This paper proposes a passivity-based nonlinear disturbance observer (DOB) design for a powered upper-limb robot control. The proposed DOB allows for the nonlinearities of the robot dynamics, whereas the typical DOB designs cannot. Moreover, by virtue of the passivity property, human operator and environmental interactions can be embedded in the control loop. As a DOB, the proposed approach has a disturbance observation property that makes the actual robot behave like a nominal model selected by the user. Performance analysis proposes a gain tuning rule. In experimental validation, actual powered upper-limb robot is used to perform unknown payload carrying applications.

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

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.

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.

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.

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.

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.

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.

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.