This paper presents a haptic device with a simple architecture of only two limbs that can provide translational motion in three degrees of freedom (DOF) and one-DOF rotational motion. Actuation redundancy eliminates all forward-kinematic singularities and improves the motion-force transmission property. Thanks to the special structure of the kinematic chains, all actuators are close to the base and full gravity compensation is achieved passively by using springs. Force producibility analysis shows that this haptic device is able to produce long-term continuous force feedback of 15–30 N in each direction. By developing a prototype of the haptic device and a virtual three-dimensional simulator, a preliminary performance evaluation of the haptic device was conducted. In addition, a torque distribution algorithm considering a relaxed form of actuator-torque saturation was experimentally evaluated, and a comparison with other algorithms reveals that this algorithm offers several advantages.

This paper presents an underactuated robotic gripper that consists of three fingers. This gripper is driven by seven actuators and capable of grasping a wide range of objects in different working scenarios. A combination of a four-bar mechanism and parallelograms ensures that each finger can provide the basic pinch grasp and power grasp. Detailed fingertip grasping force analysis shows the large payload of this gripper. To fulfill multiple challenging grasping tasks, the fingertip orientation of each finger was designed to be decoupled from the finger flexion motion. Particular emphasis is placed on the environmental contact-based grasp and active transition from the pinch grasp to the power grasp. Detailed analysis shows that the contact-based fingertip grasp could be used to grasp thin objects lying on a flat surface with widths less than 168 mm safely and stably. To prevent over-squeezing of the grasped object in the active transition, the fingertip orientation and finger flexion motion were controlled coordinately. Moreover, a combination of the contact-based grasp and the direct power grasp was also allowed to grasp objects lying on a flat surface and having smooth surfaces robustly. Experimental results demonstrate the effectiveness of the proposed gripper in real-world applications.

A spherical two-degree-of- freedom wrist adapting the structure of the spatial parallelogram is proposed. A U type extended link out of three UU type limbs of the spatial parallelogram is selected as an output link. As a result, the wrist can be interpreted as being formed by combination of a U type limb and a (2-UU)+U type hybrid limb. Screw theory is employed to analyze its first-order kinematic model. Then a compact wrist prototype suitable for wrist module supporting the robot hand is designed and implemented. Finally, experiments with the prototype confirm that the wrist has a very high potential application for wrist modules in terms of dexterity and maximum load handling capacity.

Conventional dexterous grippers are not only heavy and complex but also task dependent. As a result, they cannot provide power, intermediate and precision grasping together. We propose usability evaluation of a novel gripper mechanism which can provide 1-Degree of Freedom (DOF) parallel grasping and 2-DOF independent pinching by using a closed chain architecture. The usability of our design and one commercial product has been evaluated based on various grasping tasks: adaptive grasping, parallel pinching grasping, independent pinching grasping and contact grasping. The success rate has been evaluated to validate the excellent usability of the proposed 3-DOF gripper.

Conventional vascular intervention radiology (VIR) procedure presents a few challenges to overcome, which are radiation exposure issue during the procedure under X-ray, physical and mental burdens to the operator in handling catheter and guidewire. We propose a robotic approach to resolve such problems. Specifically, this paper deals with usability test of master devices to control four degrees of freedom (4-DOF) robotic vascular intervention system. The usability of two master devices was measured in terms of task completion time and NASA-TLX index. Both novice and expert group participated in master-slave vascular intervention procedure based on abdominal blood vessel phantom. We found that position to velocity based master device is much effective compared to position to position based master device.

This paper presents a 3-DOF linkage-driven underactuated finger for achieving several different grasp modes. This finger mechanism is constructed by stacking one five-bar mechanism over one double parallelogram. This special architecture allows for installing all of the actuators on the base. A 2-finger robotic gripper having three actuators is developed for performing self-adaptive power grasping, parallel precision grasping, grasping during contact with the environment, and other grasping tasks through changing the orientation of the distal phalanx actively. The performance of the gripper is confirmed through both simulation and practical grasping experiment.

In this study, we aim at grasping a single target object in a cluttered environment using a robotic arm. While dexterous grasp for various shapes of objects is not considered in this work, we focus on developing the method to mitigate clutter near the target object as soon as quickly. For this purpose, we propose a method to generate nonlinear pushing motions for object singulation based on an off-the-shelf machine learning algorithm and a typical semantic segmentation algorithm. Through experiments, we show that the success rate of robotic grasping is considerably improved by the proposed pushing behavior. And notably, the nonlinear pushing trajectories allows the robot to perform singulation of the target object in a cluttered environment with fewer trials than linear pushing usually pursued in related works.

Development of an integrated gripping system for grasping various objects in different work environments is very useful in many practical applications, such as warehouse automation. In this paper, we propose a linkage-driven underactuated gripper combined with a suction mechanism. This underactuated gripper has two fingers which can be controlled independently and each finger is constructed by stacking one five-bar mechanism over one double parallelogram. The special architecture allows for installing all of the actuators on the base. The suction mechanism is used to grasp objects in narrow space and enhance the grasp stability. The ability of grasping various objects is confirmed through practical grasping experiment on a commercial robot arm.

The pathway to the maxillary sinus is anatomically curved and narrow. Thus, the conventional approach using a straight endoscope and surgical tools is difficult to diagnose and treat some blind regions of the maxillary sinus through the nostrils. Such cases are usually dealt with by an approach with an external incision that causes large invasive surgery. In order to approach the blind regions without any external incision, a new bendable device and an image-guided robotic approach for the maxillary sinus surgery are required. This work reports design, development, and validation of an image-guided dual master-slave robotic system for the maxillary sinus surgery. Initially, specifications of the robotic system for sinus surgery are decided by analysis of the anatomical structure of the sinus. A method for determining the design parameters of continuum type salve robot is also presented. Based on the specifications and the design parameter determining method, a compact design of bendable dual slave robotic system for inspection and biopsy operation of the maxillary sinus area is devised and workspace analysis for verifying the robot design is conducted. The performance of the dual master-slave system equipped with flexible devices is validated through several phantom tests. The results suggest that bendable end-effectors and navigation software are useful to navigate and treat blind regions inside general sinus areas as well as the maxillary sinus.

Purpose of this study is to propose a new robotic system equipped with a steerable catheter for percutaneous coronary intervention. Key design issues of the system are less X-ray exposure, easy sterilization, and convenient user interface.

This paper presents the robotic hammering task performed by single arm and dual arm. In order to analyze optimal hammering task, the analytical model of external and internal impulses are taken as the measure. Desired hammering task implies that the hammer simultaneously exerts maximum external impulse on nail and minimum internal impulses on robot or human joints. The advantages of dual arm manipulator with muscles over dual arm without muscles and single arm model with muscle and without muscle are presented. Moreover, the effective mass in nailing operation is experimentally obtained for two different materials and it is integrated into the external impulse model of the hammering task. Furthermore, the hammering workspace is optimized by considering the minimum internal and maximum external impulses.

This paper presents the kinematic modeling and analysis of a gravity balanced 3T1R parallel mechanism with actuation redundancy. The screw theory is employed for Jacobian derivation and singularity analysis. Actuation redundancy is introduced to eliminate forward kinematic singularities. Moreover, three load redistribution algorithms employing redundant actuation to avoid torque saturation are presented and the comparison analysis shows through simulation study that the newly suggested algorithm considering a relaxed form of torque limit has several advantageous features in comparison to other load distribution algorithms.

Flexible endoscope has been used for the diagnosis of the large intestine. This paper aims at the development of navigation software that provides the surgeon with the 2D/3D shape of flexible endoscope inside the colon real time. It helps surgeon insert the endoscope in a safe manner and locate the position of the lesion. With the information of the insertion length and the position/orientation information of the distal end, we propose a shape prediction algorithm with consideration of constrained geometry and gravity load of the flexible endoscope. To corroborate the effectiveness of the shape prediction algorithm, we perform simulation using 2D/3D flexible endoscope models and verify the result through experiments.

This paper describes design and application of a novel counter-balancing stackable parallel mechanism. The stackable mechanism is designed by combining a five-bar and a couple of parallelograms. This design allows a compact design and wide workspace as compared to prior parallel type counter-balancing mechanisms. A linear geometry of this mechanism guarantees static balancing in the whole workspace. This mechanism was successfully applied to otologic.

This paper describes a localization algorithm based on hybrid sensor system with application to an active shopping cart. For a given experimental environment, the probability localization method is applied to confirm the global coordinate of the target customer. And a hybrid sensor system combining the Zigbee and odometry is used to improve the localization performance of the active shopping cart. The shopping cart is equipped with motors for mobility and sensors for tracking person. Through experimental work, we corroborate the feasibility of the proposed localization algorithm.

Much attention has not been paid to analysis of the open-loop stability for gravity counter-balancing of parallel mechanisms or closed-chain mechanisms. The open-loop stability is crucial especially in passively counter-balanced mechanisms where no actuators are involved. Passive hands-on device is such an example. A general stiffness model is derived for general closed-chain mechanism including counter-weight model. As a measure of the open-loop stability, we employ the determinant of the stiffness matrix. A parallel mechanism having 3 translational DOF (degree of freedom) is employed as an exemplary device. An antagonistically counter-balancing is found the most stable method. We conduct dynamic simulation and experiment to confirm the open-loop stability of the system.

The pathway to the maxillary sinus area is anatomically curved and narrow. Thus, using the conventional approach based on the straight endoscope and surgical tools, there are some limitations in inspection and treatment of the target legion of the maxillary sinus. To cope with such problems, a dual master-slave system is investigated in this work for general maxillary sinus surgery. Initially, the need for dual arm operation is explained. A compact design of two 4-DOF end-effector mechanisms for acquiring the endoscopic image and performing biopsy is introduced. Next, a dual master device to control the motions of the two end-effector mechanisms is employed and a motion scheduling algorithm for a proper master-slave control is also developed. Finally, the feasibility of the dual master-slave system is verified through experimental work.

In impact dynamics, coefficient of restitution (COR) is an important parameter to calculate the impulse. Generally, COR has been assumed a constant value. However, COR varies according to the colliding condition. In order to apprehend this phenomenon, analysis of impact dynamics is conducted using a 3-DOF finger mechanism. The external impulse exerted on a wall or a cart by the mechanism is a function of the robot's geometry and dynamic parameters. In this paper, we derive an analytical model of COR with the 3DOF finger model colliding to a wall and a cart, and emphasize that the actual motion just after impact is not the same as what we expected unless the variable COR is considered. The effectiveness of proposed COR model is verified through wall and cart impact experiments using the finger mechanism.

This paper proposes an automatic lighting system using multiple 3-DOF robotic lamps. The robotic lamp is a spherical type parallel mechanism with a unique forward kinematic solution. In order to minimize the dynamic load, three motors are installed at the base frame and a counter balancing design is performed. Using the coordinate transformation between the environment coordinate and the robot coordinate, the position data of the human is converted to three output angles of the robotic lamp. Positions of people are measured by a laser scanner, and in order to track the positions of people accurately by multiple robotic lamps, the Kalman filter algorithm and a data association algorithm were applied. In experiment, three robotic lamps were employed to track three people independently. For each lamp, two tilting angles are controlled for a localized light and the zoom mechanism is employed to control the intensity of the light.

This paper presents tracking algorithms of a mobile robot that tracks a human in front. The mobile robot, which is a differential-driven wheel type, is equipped with a laser range finder to perform human tracking in front. Initially, we recommend the torso part for the robust tracking of the human body in outdoor environment by a laser range finder. To track a human in front, we define a virtual target determined by the velocity of the target human. For a more efficient movement of the mobile robot, a desired heading direction of the robot considering motion vectors of the robot and the human is proposed.

This paper deals with a design and motion planning algorithm of a caterpillar-based pipeline robot that can be used for inspection of 80-100-mm pipelines in an indoor pipeline environment. The robot system uses a differential drive to steer the robot and spring loaded four-bar mechanisms to assure that the robot expands to grip the pipe walls. Unique features of this robot are the caterpillar wheels, the analysis of the four-bar mechanism supporting the treads, a closed-form kinematic approach, and an intuitive user interface. In addition, a new motion planning approach is proposed, which uses springs to interconnect two robot modules and allows the modules to cooperatively navigate through difficult segments of the pipes. Furthermore, an analysis method of selecting optimal compliance to assure functionality and cooperation is suggested. Simulation and experimental results are used throughout the paper to highlight algorithms and approaches.

This paper deals with the impact dynamics of a soccer ball. The trajectory of the ball is decided according to its initial velocity, launch angle, and some aerodynamic effect. Specially, the initial velocity is created by an instant impulse given to the ball. The external impulse exerted on a ball by a kicking robot is a function of the robot's geometry and dynamic parameters. Here, the coefficient of restitution (COR) is an important parameter to calculate the impulse applied to the ball when the collision is occurred. Usually, COR has been assumed a constant value. We derive an analytical model of COR for the pendulum model colliding with a soccer ball, and show that COR varies according to the velocity. The drag force is taken into account in the COR model. The velocity-dependent characteristic of COR is applied to simulation of a soccer ball traveling a long distance. It is shown that the velocity-dependent COR considerably affects the traveling distance of the flying ball.

This paper presents a new pipeline inspection robot that has multiple sensors for inspection of 80-100mm pipelines. The special feature of this robot is realization of driving and steering capability by using only two wheel chains. Compared to popularly employed pipeline robots using three wheel chains, the new design allows simple robot control and easy user interface, specially at T-branch. As another advantage, the flat shape of this robot allows mounting additional sensors on the both sides of the robot. The kinematics and three control modes are described. Finally, the performance of this robot system is verified by experimentation.

This paper presents a new control scheme of JAIST Active Robotic Walker (JARoW) developed to provide elderly people with sufficient ambulatory capability. Toward its practical use, our focus is placed on how to allow easier and reliable maneuverability by creating a natural user interface. Specifically, our challenge lies in providing a well-functioning controller by detecting what the user wants to do or their intentions. A Kalman filter based tracking scheme is realized to estimate and predict the locations of the user's legs and body in real time. The feedback control can then adjust the motions of JARoW corresponding to the actual user's walking behaviors. Our experiments confirm that JARoW can autonomously adjust its motion direction and velocity without requiring any additional control inputs.

This paper presents tracking algorithms of a mobile robot that follows a human body moving at high speed in unstructured outdoor environment. The mobile robot, which is a differential-driven wheel type, is equipped with one laser range finder to perform high-speed human tracking and obstacle avoidance. Initially, the waist part of the human body is found the best part of the human body for robust tracking by a laser range finder. Next an obstacle avoidance algorithm considering the relative velocity between the robot and obstacles is proposed. It is shown that the proposed human tracking algorithms based on the Kalman filter performs well even in the case of the target occlusions and temporary losses. These tracking algorithms have been applied to a marathoner following robot that carries the marathoner's personal belongings in many different outdoor environments.

This work introduces a new endoscope robot system for general sinus surgery. The proposed endoscope can be bent in accordance with a user's intension at the time of inserting the endoscope into the sinus area, and it was designed to be bent up to 180 degrees and its diameter is about 4mm. The design of the proposed endoscope uses a spring backbone, which allows flexibility of the mechanism. A design method to determine design parameters for this device is proposed. The performance of the proposed system is verified by integration of the robot device and simulator.

Recently, quite a few practical parallel mechanisms having spatial 3-DOF and 6-DOF have been introduced and implemented. However, not many useful practical applications using low-mobility parallel mechanisms having 4-DOF and 5-DOF have been developed. In this paper, we propose a 4-DOF parallel mechanism for needle insertion application in which proper orientation and needle insertion process are required. The mechanism has four outer chains and one passive middle chain through which a needle insertion motion occurs. The kinematic modeling and kinematic analysis are performed to understand the characteristics of this mechanism. Through the singularity analysis, a singularity-free design for the desired workspace is proposed. Finally, the effectiveness of this device as a needle insertion device is shown through experimental work.

This paper proposes a new 4-Degree-of-Freedom (DOF) master-slave system for 3 dimensional needle steering. Both master and slave devices are commonly composed of a 3 DOF spherical type parallel mechanism and a 1 DOF needle insertion mechanism. This system provides users with 3 dimensional needle steering and force reflection capabilities. The real time forward solution of the master device is addressed. The design of the master-slave system is described in detail. Finally, the effectiveness of this system for 3 dimensional needle steering task is verified through experimental work.

This work presents the kinematic modeling and motion planning algorithm for an omni-directional mobile robot with kinematic redundancy. This robot consists of three wheel mechanisms each of which has one redundant joint as compared to the operational degrees. Initially, the kinematic modeling of this robot is conducted. Next, using such a kinematic redundancy of each chain, several motion planning algorithms are suggested. A localization algorithm of the mobile robot based on odometry is presented and specifically, two-leveled obstacle avoidance scheme, which simultaneously considers both large and small obstacles, is presented. The usefulness of the proposed algorithms is verified through simulation.

This paper presents a new pipeline inspection robot with a linkage type mechanical clutch, which is designed for inspection of pipelines with 100mm diameter. This robot has three powered wheel chains each of which has a mechanical clutch. The mechanical clutch is designed by using a parallel linkage mechanism. The kinematic model of the pipeline inspection robot is driven and its proto type has been developed. The performance of this robot system is verified by both simulation and experimentation.

In previous studies on 4-DOF parallel mechanisms with four sub-chains, only symmetric arrangement of those four chains connected to the top plate was considered. Such symmetric shape sometimes falls into a sort of architetural singularity. This work demonstrates that an asymmetric placement of the four chains on the top platform is desired to minimize the effect of such architectural singularity. A new 4-DOF parallel mechanism exhibiting 4-DOF motion (3-DOF translational motion and one rotational motion) is examined as an exemplary device. This device consists of a base plate, an upper plate, and four hybrid subchains connecting those two plates together. The position analysis and kinematic modeling for this mechanism are performed, and an optimal design with respect to the workspace size and the kinematic isotropic characteristic is conducted. A set of offset angles on the top platform is found, which significantly minimizes the architectural singularity problem within the valid workspace of the mechanism. Then, through the analysis of the workspace and kinematic isotropic property for the optimized mechanism, its high potential for real applications is confirmed. Finally, the mechanism was developed to verify the motion capability.

There is no prior work on exact kinematic modeling for a pipeline robot having three powered chains. This work presents the closed-form kinematic model of the pipeline inspection robot driven by three caterpillar wheel chains. Next, optimal kinematic parameters are analyzed by using isotropic index and force transmission ration. Lastly, the feasibility of the kinematic model is verified through motion simulation for a virtual pipeline equipped with elbows and T-branches.

This paper proposes a new spatial 3-DOF parallel mechanism with a unique forward kinematic solution. Using the Scott mechanism as its sub-chain, the mechanism is foldable, which is useful for design of a compact-sized master device. The kinematics of this mechanism is derived and its kinematic characteristics are analyzed in terms of workspace and kinematic isotropy. The mechanism was implemented and tested as a master device to control a virtual construction robot handling a large glass plate.

Less degree-of-freedom robots are useful for special applications. Specifically, practical application of 4-DOF parallel mechanism has been rare, though synthesis on this type has been conducted quite a few. Recently, we proposed a revolute joint-based 3T1R 4-DOF parallel mechanism having Schonflies motions whose output rotational motion is a roll motion. This work proposes another type of a new 3T1R 4-DOF parallel mechanism having Schonflies motions whose rotational motion is a pitch motion. The position analysis and kinematic modeling for the mechanism are performed, and its workspace size and kinematic characteristic with respect to the kinematic isotropic characteristic are examined. To support high potential of the mechanism for real applications, three different versions are suggested and each motion capability is verified through its simulator. Finally, a prototype is developed to verity its actual motion capability.

Humans and mammals possess their own feet. Using the mobility of their feet, they are able to walk in various environments such as plain land, desert, swamp, and so on. Previously developed biped robots and four-legged robots did not employ such adaptable foot. In this work, a biomimetic foot mechanism is investigated through analysis of the foot structure of the human-being. This foot mechanism consists of a toe, an ankle, a heel, and springs replacing the foot muscles and tendons. Using five toes and springs, this foot can adapt to various environments. A mathematical modeling for this foot mechanism was performed and its characteristics were observed through numerical simulation.

This paper deals with a new 3-degree-of-freedom (DOF) parallel mechanism for a flat-panel TV mounting device with two rotations and one translation. The most important operational requirements of this device are that it should support the heavy weight of the flat-panel TV and should be foldable to save space between the flat panel and the wall. An asymmetric parallel structure that has three kinematic chains with internal four-bar linkage is proposed to meet such requirements. Kinematic modeling was performed along with actuator sizing. Finally, the mechanism was developed and tested to show its effectiveness as a flat-panel TV mounting device.

This work deals with navigation of an omni-directional mobile robot with active caster wheels. Initially, the posture of the omni-directional mobile robot is calculated by using the odometry information. Next, the position accuracy of the mobile robot is measured through comparison of the odometry information and the external sensor measurement. Finally, for successful navigation of the mobile robot, a motion planning algorithm that employs kinematic redundancy resolution method is proposed. Through experiments for multiple obstacles and multiple moving obstacles, the feasibility of the proposed navigation algorithm was verified.

This paper deals with design and motion planning of a reconfigurable robot that can be used for inspection of 80-100 mm pipelines. This robot consists of two connecting modules and each module consists of three pairs of caterpillar, which is operated by micro DC motor. The robot is foldable by using an embedded four-bar mechanism and compression of a spring connected to the four-bar allows the robot to maintain contact with the wall of pipelines. Controlling the speed of each caterpillar independently provides a steering capability to go through elbow and T-branch. The robot system has been developed and the validity of this mechanism was proved by experimentation.

As the need of well-being life becomes popular, one of important issues is clean drinking water. Delivery of clean water from the main water fountain to the end user is very crucial. However, typical pipelines are being contaminated by rust and several chemicals. And thus the water being delivered to house is not trustful as the drinking water. Thus, cleaning and inspection of the in-house pipeline becomes an important issue. However, it is hard to find a small-sized motor adequate to the robot for the inspection of the in-house pipeline with diameter of 15 mm. Thus, this paper introduces a new semi-automatic pipeline inspection robotic system for small-sized pipelines. Three different types of inspection robot system were developed, which have different combination of sensors to realize SLAM. The robot system is carried by an extension cable, which is in advance being penetrated into the pipeline by a compressed air. The feasibility of the proposed SLAM using this semi-automatic pipeline inspection robotic system was verified through experimentation.

In tightly coupled cooperative manipulation of two arms, an interaction force control is one of the important issues. In this paper, a sensor-less interaction force control in a de-burring task using a dual-arm is introduced. The dual arm manipulation increases the motion dexterity in the de-burring task as compared to the single arm manipulation. A closed form interaction force control algorithm is proposed, which does not require any force sensor. In the motion planning, the 12 Lagrangian coordinates of the system are decomposed into 9 motion degrees and 3 constrained degrees. Then, the whole dual arm can be modeled as a kinematically redundant robot. The primary task is to control the 9 motion degrees and the secondary task is to control the interaction force and the relative motion between the two arms. The concept of virtual joints is employed to represent the constrained degrees, which include the interaction force and the relative motion between the two arms. Through the simulation results, we show that the smooth de-burring task can be accomplished by using the suggested interaction force model without force sensor.

This work introduces a modified endoscope structure that employs a spring as its backbone. This design allows backdrivability of the mechanism due to the flexibility of the spring structure. Furthermore, the full 3 DOF motion including compression and two rotational motions can be realized. The geometric analysis, kinematic modeling, and actuator sizing for this device are conducted. Both simulation and experiment have been performed to show the effectiveness of this device.

In this paper, we propose a new 3-DOF parallel mechanism for PDP TV mounting device with 2-rotation and 1-translation. The most important operational requirement of this device is that the device should support large weight of the PDP panel and be foldable to save the space between the PDP panel and the wall. An asymmetric parallel structure that has three kinematic chains with internal four-bar is proposed to meet such requirements. The special four-bar mechanism is foldable and supports large weight structurally, which allows employment of small-sized actuators for motion. The kinematic modeling and kinematic analysis was performed along with actuator sizing. Finally, this mechanism was developed and tested to show the effectiveness as the PDP TV mounting device. It is believed that this device is a successful commercialized parallel mechanism.

This work deals with a motion planning algorithm of an omni-directional mobile robot with active caster wheels. A typical problem occurred in the motion control, which has been identified through experimental experiences, is skidding of the mobile wheel. It sometimes results in uncertain rotation of the steering wheel. This is due to mismatching between the command and the mechanical hardware. To cope with this problem, a motion planning algorithm pursuing the natural configuration of the mobile wheel was mainly investigated, which resolves the skidding problem and uncertain motions of the steering wheel. Through simulations and experimentation, the feasibility of this algorithm was verified.

Two 3-DOF parallel mechanisms, a translational mechanism and a spherical mechanism, are analyzed. Each of two mechanisms commonly possesses three UPS serial sub-chains, and an additional passive 3-DOF PPP-type serial sub-chain and a passive 3-DOF RRR-type serial sub-chain are incorporated for the translational device and the rotational device, respectively. Such additional passive serial sub-chains act as constraints to restrict the output motion of the mechanism either in a 3-DOF translational space or in a 3-DOF spherical space. The position solutions of the proposed mechanisms and their first-order kinematic models are derived. Then their workspaces and kinematic characteristics are examined via the kinematic isotropic index

In this paper, we propose a new closed-form dynamic model of interaction forces between two interacting robotic modules and a methodology to control the interaction forces by using inherent kinematic redundancy of robotic systems. To show the usefulness of controlling interaction forces, two exemplary cases are introduced. The first example investigates the interaction force between a mobile platform and a serial robot mounted on the platform. The interaction force between the two modules is controlled so that the motion of the mobile platform can be controlled in a desired way. The second example deals with interaction between a serial robot and a human operator. An interaction force is controlled so that the human operator does not feel uncomfortable when the operator performs a designed trajectory motion in cooperation with the robot

This paper deals with the trajectory planning of a soccer ball driven by a kicking robot. The trajectory of a ball is function of its initial velocity, launch angle, and some aerodynamic effect. Specially, the initial velocity is created by an instant impulse given to the ball. The external impulse exerted to a ball by a kicking robot is function of robot geometry and dynamic parameters. Initially, we analyze the external impulses for several kicking postures and simulate trajectories for several different kicking conditions. Based on this observation, a trajectory-planning algorithm of a ball, in which the initial velocity and the launch angle of the ball are calculated for a desired trajectory of the ball, is proposed, and then an external impulse required for that motion is calculated and applied to the kicking simulation. The aerodynamic effect such as drag force and lift force is also incorporated into the dynamic simulation of the soccer ball. A kicking robot has been developed for experimental verification of the proposed analytical methodology. It was shown that experimental result is in good agreement with simulation result within 10% error bound.

The goal of this work is to develop a robot-assisted surgery system for spinal fusion, which is composed of a robot, a surgical planning system, and an optical tracking system. The system plays roles of assisting surgeon for inserting a pedicle screw in spinal fusion. Compared to pure navigation systems as well as conventional methods for spinal fusion, it is able to achieve better accuracy through compensating for the portending movement of the surgical area. Furthermore, the robot can position and guide needles, drills, and other surgical instruments or conducts drilling/screwing directly. In preoperative surgery, the desired entry point, orientation, and depth of surgical tools for pedicle screw insertion are determined by the surgical planning system based on CT or MR images. Intra-operatively, the position information on the surgical instruments and the targeted surgical areas are obtained by the tracking system and, using that information, a robot conducts the preplanned operation depending on its role while compensating the movement of the surgical area. Two exemplary experiments employing the developed robot-assisted surgery system are conducted.

A new spherical-type 3-degree-of-freedom parallel mechanism consisting of a two degree-of-freedom parallel module and a serial module is proposed. Two alternative designs for the serial sub-chain are suggested and compared. The first design employs RU joint arrangement for the serial sub chain structure. The second design incorporates a gear chain to drive the distal revolute joint of the serial sub-chain from the base platform of the mechanism. This modification significantly improves kinematic characteristics of the mechanism within its workspace. Firstly, the closed-form solutions of both the forward and the reverse position analysis are derived. Secondly, the first-order kinematic model with respect to three inputs which are located at the base is derived. Thirdly, it is confirmed through simulation that the modified mechanism has much more improved isotropic characteristic throughout the workspace of the mechanism. Lastly, the proposed mechanism is implemented to verify the results from this analysis.

Despite that omni-directional mobile robots have been investigated and used popularly, there are rarely useful command systems and control methods for practical applications. In this research, a command system to describe the navigation task for an omni-directional mobile robot is developed, and a motion generation method considering the robot geometry and the given trajectory is proposed. Furthermore, a control method to track the given linear and circular trajectories is proposed. A closed form kinematic model was utilized for motion generation and control as well. A redundantly actuated omni-directional mobile robot that consists of three caster-type wheel mechanisms with high performance embedded controller module was developed for the experiments. And some experiments in the real environment were carried out to verify the effectiveness of the proposed command system and the performance of the motion generation and the trajectory control method.

The human body exploits "redundant degree of freedom" to execute various motions in a suitable fashion. This work deals with development of effective redundancy resolution algorithms for the motion control of humanoid. Differently from the typical kinematically redundant robots that are attached to the fixed ground, the ZMP condition should be taken into account in the human body motion in order to guarantee the system stability. For this, a geometric constraint equation is derived by reshaping the existing ZMP equation. This constraint equation is formed like a second order kinematic equation, which enables one to plan the ZMP trajectory in a feedforward fashion. This constraint equation and the kinematic equation of the humanoid model are solved together. A sequential redundancy resolution algorithm exploiting the remaining kinematic redundancy is also proposed to optimize several secondary criteria such as joint limit index and manipulability. The feasibility of the proposed algorithms is verified by simulating a stable standing up motion and a planar walking motion though planar 5 DOF and 6 DOF humanoid models.

This paper deals with motion generation algorithm considering the external and internal impulses. Initially, we analyze the trend of the impulses with a simple 3-DOF planar robot arm in various contact positions and present a problem that is in discord with the general trend. To cope with this problem, we propose a new motion generation algorithm considering both the external and internal impulse. The gradient projection method is employed to exploit the kinematic redundancy of robot systems. Initially, the effectiveness of the proposed algorithms is verified through simulation of a 3-DOF planar robot arm model, and two application examples considering both the external and internal impulses are investigated. Through simulations for the landing of a 4-DOF planar human-body model and the sawing motion by a dual-arm model, it is shown that the posture is stable and the trend of the impulses calculated by the analytical models is coincident to the human experiences.

Some of manufacturing tasks, such as sawing, often require continuous impulsive motion. In the case of sawing, such impulsive motions can be observed between the teeth of the saw and the object. The amount of the external impulse exerted on the object has been treated as an important control parameter. At the same time, the internal impulses experienced at the joints should be taken into account to avoid serious damage or injury at the joints of robot. The purpose of this paper is to improve the efficacy of sawing by using dual arms. For this, we suggest an external impulse model, and introduce a new concept of effective mass that accounts for the hardness of the object to corroborate the effectiveness of the proposed chip model employed in the derivation of the external impulse model. Closed-form internal impulse models are also proposed for both single and dual arms. Based on these models, the paper proposes a new measure for internal impulse. A normalized impulse ellipsoid reflecting the velocity direction is employed to visualize the impact geometry. Finally, we identify the optimal sawing region, wherein there is a maximum amount of external impulse and a minimal amount of the internal impulse. Simulation and experimentation demonstrate that the dual arm exhibits a better sawing performance than a single arm, in terms of external and internal impulses.

In this paper, we deal with the kinematic and dynamic modeling of hybrid robotic systems that are constructed by combination of parallel and serial modules or series of parallel modules. Up to now, open-tree structure has been generally employed for dynamic modeling of hybrid robotic systems. However, it requires not only expensive computation as the complexity of the system increases, but also must perform dynamic modeling for the whole manipulator again even if the partial portion of the robot structure is changed. Therefore, we propose an efficient dynamic modeling methodology for hybrid robotic systems. In the proposed method, initially the local dynamics of each of modules are obtained with respect to its independent joint coordinates and then the dynamics of the hybrid robot is calculated utilizing the concept of virtual joints that are attached to the base of each module of interest The virtual joints are assigned to have the appropriate number of DOFs in the operational space to represent the motion of all the proximal modules from the module of interest to the ground. For general multiple module-based hybrid robots, a recursive dynamic formulation of the proposed method is derived and the usefulness of the method is verified by comparing the computational efficiency of both the proposed method and the existing method.

Mobility for a great portion of robot mechanisms having over-constraint and non-holonomic constraints has not been clearly identified. This work us to introduce a method of mobility analysis for such systems using the concept of representative screws and pseudo-joint. The pseudo-joint is employed to effectively represent the real motion trajectory due to the rolling contact of the wheel. To show the validity and effectiveness of the proposed method, mobility of various types of planar mobile robots having over-constraint and non-holonomic constrains are examined.

It is known that parallel type mechanisms have many singularities than serial type mechanisms. In haptic application, these singularities deteriorate the force reflecting performance. Moreover, different from general manipulators, haptic systems can't avoid the singular point, because they are operated by the user's random motion command. Although many singularity-free load distribution algorithms for kinematically redundant manipulators have been proposed, singularity-free load distribution algorithms for parallel haptic application have not been deeply discussed. In this work, various singularity-free load distribution algorithms that are appropriate to parallel haptic system are discussed. A new 6 DOF parallel mechanism equipped with four sub-chains is employed as a test device. To cope with singularity problem, four task-priority algorithms and redundant actuation algorithm are discussed and compared through simulation, and also experiments have been performed to show the effectiveness of those algorithms at the presence of singularity.

A novel action-selection-mechanism is proposed to deal with sequential behaviors, where associations between some of stimulus and behaviors would be learned by a shortest-path-finding-based reinforcement learning technique. To be specific, we define behavioral motivation as a primitive node for action selection, and then sequentially construct a network with behavioral motivations. The vertical path of the network represents a behavioral sequence. Here, such a tree for our proposed ASM can be newly generated and/or updated, whenever a new sequential behaviors is learned. To show the validity of our proposed ASM, some experimental results on a "pushing-box-into-a-goal (PBIG) task" of a mobile robot is illustrated.

In most spine surgeries, the physician directly performs the surgical operation with help of specially designed surgical tools along with off-line CT images and possibly with fluoroscopic images that provide the on-line status of current surgical operation for patient However, the surgical procedure generally requires accurate operational skills and intuition of the physician. Sometimes, trifling errors or misjudgments during surgical operation could result in unrecoverable damages to patients. To cope with these problems, robotic technology has been incorporated into the surgical operations in various levels. In this paper, a robotic system for percutaneous spine surgery, called SPlNEBOT, is developed. The expected roles of SPINEBOT are to provide the guide for the K-wire, to help the physician to locate and orient the position of surgery more accurately, and to compensate for respiration movement of the patient's body during operation. A preliminary experiment has been conducted with a mockup environment of surgical operation. The experimental results confirm that the SPINEBOT is not only able to guide by accurately pointing and orienting the specified location, but also successfully compensate the emulated respiratory movement of the patient.

Trailer type mobile robots have been studied from the viewpoint of control and design of nonholonomic mechanical systems in literature. However, researches for its detailed closed form kinematic and dynamic modeling are rarely being progressed. Though the trailer type mobile robot is shaped like a kinematically redundant system consisting of surplus joints, its actual kinematic characteristic is similar to a closed chain system since the motion of every trailer is constrained to the ground and the following trailers' motion is dependent on the leading trailer's motion. The exact kinematic relationship between the leading trailer and the following trailers is derived by the transfer method using the augmented generalized coordinates. A general dynamic model is derived using the Lagrangian approach and load distribution algorithm is suggested. It can be seen that the proposed approach facilitates distribution of the system load to all trailers. Forward dynamic simulation is conducted to verify the effectiveness of the suggested kinematic and dynamic models.

A haptic rendering system is proposed for a puncture task of a virtual vertebra model. To build a mesh model from medical images, Delaunay triangulation is applied and physical models are based on elasticity theory. Also, a redundant actuated 6 DOF parallel type haptic device is designed to display large force and to resolve the singularity problem of parallel type mechanisms. Haptic feeling of puncture task and the performance of the proposed haptic device are tested by two puncture task experiments.

Parallel-type mechanisms provide many advantages over serial-type mechanisms. However, in case of using parallel structures as a haptic device, it is sometimes hard to ensure the performance of the force reflection due to many singular points existing in workspace. In this paper, we propose a redundantly actuated parallel 3-DOF haptic device, which is singularity-free in the workspace and also has an improved force reflection capability. Using two sets of actuators with different size and different force resolution, we propose several useful load distribution algorithms considering force resolution and torque limit. We confirm the performance of the force reflection capability throughout simulation and experimentation.

Some of manufacturing tasks such as sawing task often require continuous impulsive motion. In case of sawing task, such impulsive motions can be observed between the teeth of the saw and the object being sawn. The amount of the external impulse exerted on the object is treated as an important control parameter in the sawing task. The purpose of this work is to show the efficacy of sawing task by using a dual-arm. For this, a new concept of effective mass is introduced to model the impact phenomenon in the sawing task. Using this concept, the external impulse model of sawing tasks is suggested. The optimal sawing region is identified in which the amount of external impulse is maximized. It is demonstrated through simulation and experiment that the dual-arm exhibits better sawing performance over a single arm in aspects of external impulse.

A new parallel grasper mechanism having 3-DOF spherical motions is proposed. The mechanism consists of one parallel four-bar chain and four serial sub-chains that are connected in parallel to the four-bar chain. Particularly, all joint axes of the mechanism are placed to have a common intersection point securing that all joint motion spaces of the mechanism are confined within the 3-DOF spherical motion spaces. Thus, the mechanism can not only grasp irregular shaped objects by changing configuration of its four-bar chain, but also exhibit 3 DOF spherical motions after grasping. The position analysis and kinematic analysis of the mechanism are performed. Also, its kinematic characteristics are investigated through simulation in aspects of three kinematic design indices. Lastly, a prototype was developed and tested through motion tracking and grasping experiments.

This paper deals with modeling and analysis for the landing motion of a human-body model. First, the dynamic model of a floating human body and the impact model are derived and the external impulse exerted on the ground as well as the internal impulse experienced at the joints of the human body model are investigated. Second, a motion planning algorithm exploiting the kinematic redundancy is suggested to ensure stability in terms of ZMP stability condition during a series of landing phases. Four phases of landing motion are investigated. In simulation, the external and internal impulses experienced at the human joints and the ZMP history resulting from the motion planning are analyzed for two different configurations. A desired landing posture is suggested by comparison of the simulation results.

Recently quite a few applications of an omnidirectional mobile robot have been reported. However, understanding some fundamental issues still remains as further study. One of the issues is the exact dynamic model. Previous studies very often ignore the wheel dynamics of the mobile robot and suffer from algorithmic singularity. Thus, actuator sizing or control algorithms based on the incomplete plant model does not guarantee the control performance of the system. This paper deals with the singularity-free, exact dynamic modeling and analysis of an omnidirectional mobile robot with three caster wheels. Initially, the exact dynamic model of the mobile robot including the wheel dynamics is introduced. A natural orthogonal complement approach is also introduced. The joint-space and operational-space dynamic models are derived as analytical forms. Through simulation, the discrepancy of the incomplete dynamic model is shown by comparison with the exact dynamic model. Furthermore, the useful aspect of operational dynamics in terms of impact geometry is also discussed.

In a humanoid robot system, many human-body motions such as walking, running and jumping require large power. To achieve a high power-to-weight ratio, this paper proposes a new design of the leg mechanism using parallel kinematic chains involving redundant actuators. The kinematics for the leg mechanism is derived and a kinematic index to measure force transmission ratio are introduced. It is demonstrated through simulation that incorporation of redundant actuator into the leg mechanism enhances the power of the mechanism approximately 4 times of the minimum actuation. The leg mechanism is developed and has been integrated into the biomimetic system for the purpose of payload enhancement.

A behavior-based control and learning architecture is proposed, where reinforcement learning is applied to learn proper associations between stimulus and response by using two types of memory called as short Term Memory and Long Term Memory. In particular, to cope with delayed-reward problem, a knowledge-propagation (KP) method is proposed, where well-designed or well-trained S-R(stimulus-response) associations for low-level sensors are utilized to learn new S-R associations for high-level sensors, in case that those S-R associations require same objective such as obstacle avoidance. To show the validity of our proposed KP method, comparative experiments are performed for the cases that:(1) only a delayed reward is used, (2) some of S-R pairs are preprogrammed, (3) immediate reward is possible, and (4) our KP method is applied.

A new 4 DOF parallel mechanism is proposed in this work. This device consists of four parallel kinematics chains and a foldable parallelogrammic platform that can be used to grasp any large or irregular-shaped object. Thus, out of 4-DOF motion space of the device, the one-DOF is used for gripping an irregular object and the other three-DOF is used for adjusting motion of the grasped object. Particularly, the three-DOF motion is restricted in the decoupled three-dimensional translational motion space in spite of revolute joint-based parallel structure. Thus, it is not only very compact, but also has distinctive feature of both grasping and micro-positioning that are one of important aspects required in real applications. In this work, we carry out the position and kinematic analysis for the mechanism, and develop the mechanism for experimental verification of its performance.

In this paper, a modified two-step compliance control method for robot hands is proposed: resolved interfinger decoupling solver (RIFDS) and resolved interjoint decoupling solver (RIJDS). For this, we first investigate how many fingers are necessary to successfully implement stiffness characteristics in the operational space. RIFDS is then proposed to decompose the desired compliance characteristic specified in the operational space into the compliance characteristic in the fingertip space without interfinger coupling, and RIJDS is also proposed to decompose the compliance characteristic in the fingertip space without interjoint coupling. It is found in the process of RIFDS that some nondiagonal stiffness elements specified in the operational space cannot be planned arbitrarily, due to grasping geometry. Similar to independent finger control, RIJDS aims at independent joint control. This scheme facilitates the joint servo control. To show the effectiveness of the proposed compliance control method, some experimental results are illustrated for a compliant task by using two- and three-fingered hands, which consist of five-bar finger mechanisms. It is concluded that grasping geometry and finger structure are crucial to successfully performing multifingered hands operations.

Flexure hinge has been commonly used as a substitute for mechanical joints in the design of micropositioning mechanisms. However, inaccurate modeling of flexure hinges deteriorates the positioning accuracy. In this paper, a planar 3-DOF parallel-type micropositioning mechanism is designed with the intention of accurate flexure hinge modeling. For this, a preliminary kinematic analysis that includes inverse kinematics, internal kinematics, and analytic stiffness modeling referenced to the task coordinate is presented. First, the revolute type of 1-DOF flexure hinge is considered. The simulation result based on the finite element method, however, is not coincident to the analytic result. This is due to the minor axial elongation along the link direction that keeps the mechanism from precise positioning. To cope with this problem, a 2-DOF flexure hinge model that includes this additional motion degree as a prismatic joint is employed in part, and additional actuators are added to compensate for the motion of this new model. On the basis of this model, the positional accuracy is ensured. The effectiveness of this accurate model is shown through both simulation and experimentation. This paper emphasizes that the precise modeling of a flexure hinge is significant to guarantee the positional accuracy of parallel micromechanisms using flexure hinge.

In this paper, the mobility analysis of various planar mobile robots are performed. Two different approaches are employed for that purpose. In the first approach, joint screws are used to find the size of a feasible joint motion space for each of independent loops of mobile mechanisms. Particularly, the concept of "representative screws" is introduced to represent the feasible motion spaces for subsets of joints belonging to either a loop or a sub-system consisting of several closed loops. In the second approach, imaginary joints are employed to compensate for the lack of geometric generality of mobile robots. It is confirmed that both approaches are useful in the mobility analysis for various type of planar mobile robots even in the case of lacking geometric generality.

It is known that parallel-type mechanisms have more singularities than serial-type mechanisms. In haptic application, these singularities deteriorate the system performance generating reflecting force. Moreover, different from general manipulators, haptic systems can't avoid the singular point, because they are operated by user random command. Although many singularity-free algorithms for serial mechanisms have been proposed and studied, singularity-free algorithms for parallel haptic application have not been deeply discussed. In this paper various singularity-free algorithms, which are appropriate to parallel haptic system, will be discussed. Furthermore, to overcome singularity problems, a new design including redundant actuation is proposed. The proposed mechanism has fairly large workspace and is relatively light by employing non-floating actuators.

Some of manufacturing tasks such as sawing task often requires continuous impulsive motion. In case of sawing task, such impulsive motions can be observed between the teeth of the saw and the object. The amount of the external impulse exerted on the object has been treated as an important control paramete. Also, the internal impulses experienced at the joints should be simultaneously taken into account to avoid serious damage or injury at the joints. The purpose of this work is to improve the efficacy of sawing task by using dual arm. For this, an external impulse model for sawing task is suggested. Also, the closed-form internal impulse models are proposed for both a single and dual arms. Based on these models, a new measure for internal impulse is proposed. A normalized impulse ellipsoid reflecting the velocity direction is employed to visualize the impact geometry. Finally, the optimal sawing region is identified in which the amount of external impulse is maximized and the amount of the internal impulse is minimized. It is demonstrated through simulation that the dual arm exhibits better sawing performance over a single arm in aspects of external and internal impulses.

Despite that omni-directional mobile robots have been employed popularly in several application areas, effort on optimal design of such mobile robots has been few in literature. Thus, this paper investigates the optimal design of omni-directional mobile robots. Particularly, optimal design parameters such as one or double offset distance of wheel mechanism and the wheel radius are identifed with respect to isotropic characteristic of mobile robots. In addition, the force transmission characteristics and actuator-sizing problem of mobile robots are investigated Analysis has been performed for three actuation sets. It is shown that the redundantly acruated mobile robot with three active caster wheels represents the best performance among them.

A planar 3 DOF parallel-type micro-positioning mechanism is designed with the intention of accurate flexure hinge modeling. For this, a preliminary kinematic analysis that includes inverse kinematics, internal kinematics, and analytic stiffness modeling referenced to the task coordinate is presented. First, the revolute type of a 1 DOF flexure hinge is considered. The simulation result based on FEM, however, is not coincident to the analytic result. This is due to the minor axial elongation along the link direction that keeps the mechanism from precise positioning. To cope with this problem, a 2 DOF flexure hinge model that includes this additional motion degree as a prismatic joint is employed in part. On the basis of this model, the positional accuracy is ensured. The effectiveness of this accurate model is shown through both simulation and experimentation This work emphasizes that the precise modeling of a flexure hinge is significant to guarantee the positional accuracy of parallel micro-mechanisms using flexure hinge.

This paper presents a design method of transparency optimized feedback controller with robustness for a parallel 6-DOF haptic system. A disturbance observer is employed to eliminate coupling effects that exist in a mechanically coupled structure. A performance index for the transparency is defined by admittance matching, and by solving the H/sub 2/ optimal problem. The optimal solution that minimizes the performance index is obtained.

A kinematic modeling method is proposed which uses augmenting variables to match the dimensions of the input vector and output vector of each serial subchain of the mobile robots. Firstly, kinematic models of various type of wheels are derived including skidding and sliding velocities. Then the method of augmented generalized coordinates is applied to obtain inverse and forward kinematic models. The kinematic models derived by the direct inverse of the augmented matrices provide an accurate solution, which was not achievable by the modeling method based on the pseudo-inverse method which provides an approximate solution. Lastly, two kinematic models for typical, differential-driven mobile robots are presented to show the effectiveness of the proposed modeling method.

Based on the analysis of the stiffness relation between the operational space and the fingertip space of multifingered hands, this paper provides a guideline of task-based compliance planning for multifingered hands. 2D and 3D examples are illustrated to show the characteristics of the task-based stiffness matrix. It is shown that some of coupling stiffness elements cannot be planned arbitrarily due to grasping geometry. Through the analytical results, it is concluded that the operational stiffness matrix should be carefully specified by considering the location of compliance center and the grasp geometry of multifingered hands for successful grasping and manipulation tasks.

We provide a guideline for specifying compliance characteristics in the operational space of multifingered hands. From the analysis of the stiffness relation between the operational space and the fingertip space of multifingered hands, it is shown that some of the coupling stiffness elements cannot be planned arbitrarily. An independent finger-based compliance control method to achieve the given compliance characteristics is presented. Through the analytical results, it is concluded that the operational stiffness matrix should be carefully specified by considering the grasp geometry of multifingered hands for successful grasping and manipulation tasks, and the three-dimensional compliance control can also be achieved by a five-fingered human-like hand.

In this paper, a new 6-DOF parallel haptic master device is proposed. Many existing haptic devices require large power due to having floating actuator and also have small workspaces. The proposed new mechanism is relatively light, as it employs nonfloating actuators and has large workspace. Kinematic analysis and kinematic optimal design problem is performed for this mechanism. Dexterous workspace, global isotropic index, and global maximum force transmission ratio are considered as kinematic design indices. To deal with such multicriteria optimization problem, composite design index is employed. Actuator sizing for this mechanism is also carried out.

When spacecraft dock with each other, impact will rise at the docking point. It is assumed in this paper that a docking platform having the shape of Stewart platform is attached at the one of the docking spacecraft to reduce the effect of impact. Although the impact between two spacecraft at the contact point of the upper plate of the platform is very large, the impact is absorbed by the docking platform and a negligible impact is transmitted to the spacecraft. To show this, the modeling of the internal impulses at the joints of multibody system is introduced and the internal impulses of the docking platform are analyzed by the modeling method.

When a robot system collides with its environment, unexpected position errors occur due to the effect of impact. Large actuation effort may grow up to compensate for these errors. The sudden increases of actuator torque may violate the torque limit. We propose to employ a redundant actuation mode to facilitate disturbance rejection. An optimal load distribution algorithm for redundantly actuated system is introduced to reduce the effect of shocks. This scheme distributes the compensating effort to the system actuators in consideration of the torque limit. The disturbance rejection capability of the proposed scheme is compared with those of other load distribution methods by simulation and experiment. A five-bar mechanism is employed as an exemplary plant.

This work introduces a new architecture for a parallel, six degree of freedom manipulator. The kinematic analysis of this redundant manipulator is provided. The proposed parallel mechanism allows easy implementation of redundant actuators, and has relatively large workspace in comparison to conventional six degree of freedom parallel devices. The kinematic analysis performed forms the basis for the introduction of design criteria for the manipulator. Several design criteria are introduced and their use is illustrated by example design involving an initial geometric parameter analysis of the manipulator.

In this paper, we propose and develop a spatial 3-DOF tele-micromanipulator for precise position control of micro-objects. Typical feature of this device is a one-module flexure hinge that consists of a revolute joint and a spherical joint. Based on preliminary kinematic analysis and stiffness modeling of the system, optimal design and actuator sizing for the device are performed. Furthermore, FEM analysis and resonant frequency analysis are executed to validate the results of analytic design process. The designed device was successfully implemented to tele-micromanipulation system.

For a multi-fingered hand to grasp an object, there are numerous ways to grasp it stably, and thus an optimal grasp planning is necessary to find the optimal grasp point for achieving the objective of the given task. First, we define several grasp indices to evaluate the quality of each feasible grasp. Since the physical meanings of the defined grasp induces are different from each other, it is not easy to combine those indices to identify the optimal grasping. In this paper, we propose a new generalized grasping performance index to represent all of the grasp indices as one measure based on a non-dimensional technique. Through simulations, we show that the proposed optimal grasp planning is resemblant to the physical sense of human grasping.

Underwater robotic vehicles (URV) have been employed for mobility, and robot manipulators attached to the underwater vehicle play the role of manipulation. URV motions are determined by inherent dynamic couplings between active and passive joints. Furthermore, the control problem becomes complex since there should be considered many hydrodynamic terms as well as intrinsic model uncertainties. To cope with these difficulties, we propose a disturbance observer-based robust control algorithm for underwater manipulators with passive joints. The proposed control algorithm is able to treat an underactuated system as a pseudo-active system in which passive joints are eliminated. Also, to realize a robust control method, a nonlinear feedback disturbance observer is applied to each active joint. A four-jointed underwater robotic system with one passive joint is considered as an illustrative example. Through simulation, it is shown that the proposed control algorithm has good position tracking performances even in the presence of several external disturbances and model uncertainties.

For an object grasped by a robot hand to work in the compliance control domain, we first analyze a necessary condition for successful stiffness modulation in the operational space. Next, we propose a compliance control method for robot hands which consist of two steps: the RIFDS (resolved inter-finger decoupling solver) decomposes the desired compliance characteristic specified in the operational space into the compliance characteristic in the fingertip space without inter-finger coupling; and the RIJDS (resolved inter-joint decoupling solver) decomposes the compliance characteristic in the fingertip space into the compliance characteristic in the joint space without inter-joint coupling. According to the analysis results, the finger structure should be biomimetic in the sense that either kinematic redundancy or force redundancy are required to implement the proposed compliance control scheme. Five-bar fingered robot hands are treated as illustrative examples to implement the proposed compliance control method. To show the effectiveness of the proposed compliance control method, simulations are performed for two-fingered and three-fingered robot hands.

Omnidirectional mobile robots have been popularly employed in several application areas. However, the kinematics for these systems have not been clearly identified, specially for the redundantly actuated case which is common in omnidirectional mobile robot such as Nomadic model. For such mobile robot systems, exploitation of redundant actuation as well as singularity analysis has not been extensively addressed. In light of this fact, this paper introduces two different kinematic approaches for omnidirectional mobile robots and examine singularity configurations of such systems. Then, a singular-free load distribution scheme for a redundantly actuated three-wheeled omnidirectional mobile robot is proposed. Through simulation, several advantages of the redundantly actuated mobile robot with respect to singularity avoidance and exploiting several sub-tasks, are presented.

A transparency-optimized feedback controller with robustness is designed for a multi-axis haptic device, where a disturbance observer is employed to decouple the coupling effect existing in the multi-axis haptic device. A performance index for the transparency is defined from the viewpoint of admittance matching, and the optimal solution minimizing the performance index is obtained by solving an H/sub 2/ optimal problem. To implement a stabilizing haptic controller robust to parametric uncertainties of the haptic device, a robust stable condition using an H/sub /spl infin// norm derived from small gain theorem is proposed. The effectiveness of the proposed haptic control scheme has been experimentally verified for a virtual wall characterized by stiffness and damping properties.

This paper deals with stiffness analysis for effective peg-in/out-hole tasks using multifingered robot hand without inter-finger coupling. We first observe the fact that some coupling stiffness elements cannot be planned arbitrary. Then, we analyze the conditions of the specified stiffness matrix in the operational space to successfully and more effectively achieve the given peg-in/out-hole tasks. It is concluded that the location of compliance center on the peg and the coupling stiffness element between the translational and the rotational direction play important roles for successful peg-in/out-hole tasks. Simulation results are included to verify the feasibility of the analytic results.

It is well-known that bio-systems do not calculate inverse dynamics for trajectory planning, but they move by proper modulation of the system's impedances. Inspired by bio-systems, a biomimetic trajectory planning method is introduced. This scheme is based on employment of redundant actuation which prevails in bio-systems. We explain that in the generation of the biomimetic trajectory, intelligent structure of bio-systems plays an important role to completely modulate the dynamic behaviour of a system, such as natural frequencies and damping ratios. A five-bar mechanism equipped with two redundant actuators is employed to demonstrate the feasibility of the proposed biomimetic trajectory experimentally.

Springs have been employed in a wide range of mechanical systems. This work deals with the design of multi degree-of-freedom spring mechanism. The adaptable spring is desired for enhancing performances of various mechanical systems employing springs. We demonstrate that such adaptable springs can be realized by adopting anthropomorphic musculoskeletal structures of the human upper-extremity, which possesses highly nonlinear kinematic-coupling among redundant muscles existing in its structures. We propose multi-degree-of-freedom spring mechanisms resembling the musculoskeletal structure of the human upper-extremity, and verify the applicability of these mechanisms through simulation.

A new parallel gripping mechanism is proposed in this work. This device has a parallelogramic platform which can be flexibly folded. Therefore, this mechanism not only can be used to grasp an object having irregular shape or large volume, but also can be utilized as micro-positioning device after grasping the object. Forward position analysis and platform kinematics are investigated to deal with motion tracking and force control. Pneumatic rotator is employed for actuation and a compact sized, 4/3 way proportional pressure valve is also developed to deal with feedback-based dynamic control. The pressure valve also allows indirect force control by measuring the offset pressure occurring due to contact between the grasped object and the parallel platform. In experimental work, performances of the motion tracking and indirect force control are shown satisfactory.

We discuss an inherent problem occurring in the former operational-based compliance control scheme. In order to obviate this problem, an independent joint-based compliance control scheme is proposed. This control method requires that for the adjustment of the operational compliance matrix, a manipulator should have at least the same number of joints as the number of independent components of the desired compliance matrix specified in the operational space. Types of robot structures which are appropriate to independent joint-based compliance scheme are addressed. A five-bar finger with redundant actuators is treated as an illustrative example. Our experimental results show that the proposed compliance modulation method gave satisfactory performance. We also consider an additional stiffness effect due to the antagonistic conflict between the controlled-operational force and the equilibrium joint torque vector. It is also experimentally shown that this additional term notably improved the force tracking performance of the given mechanism.

We investigate the feedforward modulation methodology of the dynamic behaviour of anthropomorphic systems which inherently possess abundant actuators. For the complete modulation of the dynamic behaviour of such systems, redundant actuation is essential since it enables the system to modulate the stiffness property or weighted stiffness property such as motion frequency, and even in the modulation of the damping ratio of the system, the stiffness property plays an important role. We also address that incorporation of active damper is necessary for complete modulation of the dynamic behaviour. The feasibility of our proposed scheme is verified through simulation for a two degree-of-freedom anthropomorphic robot resembling the human upper-extremity.

A closed-chain mechanism having redundancy in the force domain can produce a spring effect by proper internal load distribution. The so-called antagonistic stiffness is provided by redundant actuation in conjunction with nonlinear geometric constraints. In the paper, an optimal structure of a five-bar mechanism that can maximize efficiency in generation of antagonistic stiffness is evaluated and analyzed. A stiffness modulation index that represents isotropic characteristics in antagonistic stiffness generation is proposed. A gradient design index that shows rate of change of the isotropic index is also employed to distribute the isotropy of stiffness uniformly throughout the workspace. To deal with multi-criteria based design, a composite design index based on the max-min principle of fuzzy theory is used as an objective function. Two optimization results are obtained. One is optimizing the X-directional stiffness and the other corresponds to optimizing the Y-directional stiffness. The result of the former design is found suitable for antagonistic stiffness generation as well as for first-order kinematic performances.

Deals with a sawing task performed by two cooperating arms. The two-arm system under our hand consists of a four degree-of-freedom (DOF) SCARA robot and a five DOF PT200V robot. When the two arms are rigidly grasping a saw, the mobility of the system is three, which is not enough for sawing tasks. Therefore, we deliberately insert a passive joint at the end of the SCARA robot to increase the mobility up to four. A hybrid control method to regulate the force and velocity by the two arms is proposed in this work. The proposed scheme has three typical features; first, the two arms are treated as one arm in a kinematic viewpoint. Secondly, our approach is different from other acceleration-based approaches, in the sense that our hybrid control method is based on a Jacobian and an internal kinematics for a single closed-kinematic chain of the two arms to reflect the nature of the position-controlled industrial manipulator. Thirdly, the proposed scheme is not only able to operate the system even if a passive joint exists, but also is able to utilize the internal loads for useful applications such as pitch motion control. We experimentally show that the performance of the velocity and force response are satisfactory, and that one additional passive joint not only prevents the system from unwanted roll motion in the sawing task, but also allows an unwanted pitch motion to be notably reduced by an internal load control. To show the effectiveness of the proposed algorithms, we perform experimentation under several, different conditions for saw, such as three saw blades, two sawing speeds, and two vertical forces.

A five-bar finger mechanism driven by redundant actuators is given as an illustrative example. It is shown that judicial choice of the location of one redundant actuator greatly enhances the load handling capacity of the system, when compared to those of minimum actuation and more than two redundant actuators. Also, methodologies for stiffness and motion frequency modulations via redundant actuation are investigated. Internal load distribution associated with the stiffness and motion frequency modulations is further discussed. Specifically, the motion frequency of the system is modulated by employing inertial and spring-like impedance properties created by internal loading. The motion frequency as well as the amplitude of oscillation can be actively adjusted during the motion, and the equilibrium position about which the vibration occurs can also be arbitrarily changed during the motion. Furthermore, using the stiffness modulation capability, a point-to-point motion can be accomplished by a progressive movement of equilibrium posture, which is called a virtual trajectory. To show the effectiveness of the proposed algorithms, several simulation results are illustrated.

In order to develop a human hand mechanism, a 5-bar finger with redundant actuation is suggested. Optimal sets of actuator locations and link lengths for the cases of minimum actuator, one, two and three redundant actuators are obtained by employing composite design index which simultaneously consider several performance indices such as workspace, isotropic index, and force transmission ratio. Finally, several finger-configurations optimized for special performance indices are illustrated.

Typical biomechanical systems such as human body and mammals possess abundant muscles which are more than required for motion generation of such systems. The purpose of this work is to verify a biological phenomenon, the so called frequency modulation, in a mathematical manner. The frequency modulation represents simultaneous control of force and kinematic redundancies. The phenomenon of frequency modulation is explained through a human-like anthropomorphic robot. A load distribution method for frequency modulation via redundant actuation is also introduced. To show the effectiveness of the proposed algorithms, several simulation results are illustrated.

In this work, a parallel-type gripping and micro-positioning mechanism is proposed. This device has a parallelogrammatic platform which can be flexibly folded. Therefore, this mechanism not only can be used to grasp an object having irregular shape or large volume, but also can be utilized as a micro-positioning device after grasping the object. Configuration parameter for configuration control of the proposed gripping mechanism is defined. Grasping force and isotropic characteristic of the mechanism are considered as design indices for optimal design of the gripping mechanism. The proposed mechanism is expected to be used as an adaptable gripping and micro-positioning device by attaching it at the end-point of a robot.

A planar three degree-of-freedom parallel manipulator has been extensively studied as the fundamental example of parallel manipulators. It has been proven from the authors' previous work (1996) that when three identical joint compliances are attached to the three base joints of the mechanism in its symmetric configurations, this mechanism possesses a completely decoupled compliance characteristic at the object space, which is the important operational requirement for remote centre of compliance device. In this paper, we concern about the adjustability of the output compliance matrix of this mechanism by employing redundancy on either joint compliances or on actuators. Two approaches are suggested to achieve this purpose: 1) the stiffness modulation is achieved through purely, redundant passive springs or decoupled feedback stiffness gains; and 2) the stiffness modulation is achieved through antagonistic actuation of the system actuators. General stiffness models are derived for both cases. Based on these stiffness models, stiffness modulation algorithms are formulated.

Concerns a sawing task by two cooperating arms. To follow a line in a horizontal plane, three directional motions must be controlled, 2 translational and 1 rotational. A certain level of force must be controlled in the vertical direction, to keep contact with the object to be sawn. The two-arm system consists of a 4-DOF SCARA robot and a 5-DOF PT200V robot. When the two arms are rigidly grasping a saw, the mobility of the system is 3, which is not enough. Therefore, we deliberately insert a passive joint at the end of the SCARA robot to increase the mobility to 4. A hybrid control method to regulate force and position is proposed. The proposed scheme has three typical features: First, the two arms are treated as one in a kinematic viewpoint. Second, the hybrid control method is based on a Jacobian and an internal kinematics for a single closed-kinematic chain of the two arms to reflect the nature of the position-controlled manipulator. Third, the proposed scheme is not only able to operate the system even if a passive joint exists, but also is able to utilize the internal loads for useful applications such as pitch motion control. We experimentally show that the performance of the position and force response are satisfactory, and that one additional passive joint not only prevents the system from unwanted roll motion in the sawing task, but also allows an unwanted pitch motion to be notably reduced.

For a 5-bar finger mechanism with redundant actuators, it is shown that judicial choice of the location of one redundant actuator greatly enhances the load handling capacity of the system when compared to that of nonredundant systems, And, it is also shown that excessive redundant actuation enables the system to modulate the end-point stiffness or motion frequency by internal load distributions. Especially, the motion frequency modulation via internal loads in redundantly actuated closed-chain systems is believed to be fairly new. To show the effectiveness of the proposed algorithms, several simulation results are illustrated.

A biologically inspired, novel concept for an actively adjustable frequency modulator is presented. The idea of frequency modulation stems from the human body. The human body is known to be able to modulate the spring-like impedance property in a feedforward fashion using antagonistically fighting muscles. Therefore, the motion frequency of the system can be also modulated by employing the information on the inertial property and the spring-like impedance property of the human body. Based on this concept, a methodology for the motion frequency modulation via redundant actuation is investigated. A five-bar finger mechanism driven by redundant actuators is given as an illustrative example. It is shown that the motion frequency as well as the amplitude of oscillation can be actively adjustable during the motion, and that the equilibrium position about which the vibration occurs can also be arbitrarily changed during the motion. Furthermore, using the frequency modulation capability, a point-to-point motion is accomplished by a progressive movement of equilibrium posture, which is termed a virtual trajectory. To show the effectiveness of the proposed algorithms, several simulation results are illustrated.

A three degree-of-freedom planar parallel manipulator has been extensively studied as the fundamental example of parallel manipulators. In this work, we explicitly show that this mechanism possesses a completely decoupled compliance characteristic at the object space, which is the important operational requirement for RCC devices. As a first condition to have a RCC point, this mechanism should maintain symmetric configurations. As the second condition, the same magnitude of joint compliance should be symmetrically placed at the same joint location of each chain. An alternative planar configuration with more adjustable feature of compliance is introduced. We also investigate the compliance characteristics of a spherical 3-degree-of-freedom mechanism which has a similar kinematic structure as the planar mechanism. It turns out that the spherical mechanism also has a RCC point at the intersection point of all of nine joint axes in its symmetric configuration. It is expected that these two parallel mechanisms not only can be used as excellent three degree-of-freedom RCC devices, but also can be integrated into the design of a new six degree-of-freedom RCC device.

Impedance is considered to be one of the primary controlled-properties in general biomechanical systems, with the relationship between redundant actuation and impedance modulation an important issue. Primarily, this work deals with the modeling and analysis of the spring-like impedance properties inherent in the musculoskeletal structures of biomechanical systems. A stiffness model for biomechanical systems is derived, and a load distribution methodology is investigated which attempts to explain how biomechanical systems simultaneously control their impedance properties, motion, and internal loading by utilizing redundant actuation. Through examples of the human arms, the presence and the necessity for excess-redundant actuation is illustrated in terms of spring-like impedance modulation.

Previous implementations of robot force control seldom produced satisfactory results, and researchers in the past have experienced significant instability problems associated with their force controllers. When a manipulator is constrained to an environment (force-controlled), geometric stability due to the manipulator configuration and the force-controlled direction is shown to be a significant factor in overall system stability. This exploratory study points out a rather intuitive, geometrically based stability and analyzes the phenomenon both analytically and graphically. Sequential joint self-motion algorithms for kinematically redundant manipulators are suggested for reduced transitional impact and greater stability in the ensuing force-controlled operation.>

The authors derive the object-based effective stiffness of antagonistically actuated, backdrivable, parallel linkages and show how to use this result to synthesize the generalized input loads required to create a desired system stiffness. They investigate the open-loop stability characteristics of such antagonistically actuated systems as a simple four-bar linkage, a dual-arm system, and a multifingered hand. In addition, they compare object-based and joint-based load distribution schemes in terms of their effect on system stability and input load requirements for an overconstrained planar mechanism. These investigations show an extreme interdependence between system geometry, actuation mode, and stability.>

A novel approach for the control of task-space stiffness characteristics in systems consisting of a superabundance of kinematically dependent inputs is proposed. When there are more input actuations than operational degrees of freedom, internal preloads can be generated that produce effective restoring forces in the face of displacement or disturbances imposed on the system. Examples of this excessive actuation can be found in certain modes of structurally overconstrained parallel manipulators and in antagonistically structured serial manipulators. The input loads are synthesized offline (prior to operation) and entered as a feedforward component so that the desired effective loads on objects are obtained, and (simultaneously) significant disturbances at the task level can be largely rejected in an open-loop fashion. This reduces the burden and shortcomings of standard feedback schemes. Moreover, a layered feedback scheme is used to compensate for small perturbations and unmodeled dynamics. The open-loop task-based stiffness control scheme as applied to structurally parallel mechanism/robotic linkage systems is investigated. The scheme's applicability as a programmable active compliance device is also discussed.>