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.

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.

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.

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.

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.

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.

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.

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 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.

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.

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.

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.

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 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.

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 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.

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.

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.

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.

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.

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.

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.

A closed-form solution of both forward and reverse position analyses for a 6 degree-of-freedom parallel mechanism of general geometry is derived. The mechanism consists of a top plate, a base, three PPSP serial subchains connecting these two plates. In the position analysis, it is assumed that the first two prismatic joints of each of the three serial subchains are actuated and that the last passive prismatic joint of each of the three subchains are constrained to move in parallel to the top plate, and axes of those three prismatic joints intersect at a common point. Then, the workspace variations of mechanism with respect to joint limitations are investigated. It is concluded that the mechanism studied in this paper has a great advantage over the other parallel mechanism in aspects of analytical simplicity.

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 paper, the kinematic analysis for a 6 degree-of-freedom parallel manipulator with 3-PPSP type serial subchains is performed and its kinematic characteristics are investigated via isotropic index of the first-order kinematic influence matrix. Also, dynamic analysis of the manipulator is performed and its dynamic characteristics is examined via the isotropic characteristics of the output effective inertial matrix. From the analysis results, it can be concluded that the manipulator has an excellent kinematic and dynamic characteristics required for high precision manipulators. Lastly, a prototype manipulator system is implemented and the joint position servo-controller is applied to the system. Noting the manipulator has closed-form forward/reverse position solutions, it is expected that more advanced controller requiring heavy computational burden can be applied to the system in real time to further enhance the performance of the system.

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.

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.