Presents simple but effective nonlinear friction compensation methods for a 3-PRPS (prismatic-revolute-prismatic-spherical joints) in-parallel 6-DOF manipulator. It is well known that an integral action in the feedback controller can remove the steady-state error due to constant disturbance. Thus, the integral-action can compensate coulomb friction, which is the DC-component of the total friction and viscous friction in some degrees. When the direction of position command reverses, the integrator output can not change the sign of its output instantaneously, due to friction at zero velocity, i.e. stiction resulting tracking errors. To overcome this problem we attempt to reverse the sign of the integrator output as the sign of velocity changes. The effectiveness of this approach is demonstrated by experiments on a 3-PRPS in-parallel manipulator. Also discussed are disturbance observer and velocity observer approaches for friction compensation.

This paper presents a kinematic analysis of a parallel manipulator for the probing task application that requires high bandwidth, active compliance, anal high precision. Based on the concept of macro/micro manipulators, the parallel manipulator serves as a wrist of a macro manipulator. The developed manipulator is a class of in-parallel platforms with 3 prismatic-revolute-prismatic-spherical (PRPS) joints chain geometry. The main advantages of this manipulator, compared with the typical Stewart platform type, are the capability of pure rotation generation and the easy prediction of the moving platform motion. The purpose of this paper is to develop an efficient kinematic model which can be used for real-time control and to propose systematic methods to design the manipulator considering the workspace, manipulability, resistivity, and existence conditions of the forward kinematic solution. A series of simulation have been carried out to show the kinematic characteristics and performance of the mechanism. A prototype manipulator has been built based on the kinematic design analysis.

This paper presents a kinematic analysis of the parallel manipulator developed for micro-positioning application that requires high control bandwidth and high precision. The manipulator is a class of in-parallel platforms with 3 PRPS (prismatic-revolute-prismatic-spherical) joints chain geometry. The main advantage of this manipulator, compared with the typical Stewart platform type, is the ability to produce pure motion. The purpose of this paper is to develop an efficient kinematic model which can be used for real-time control and to propose systematic design methods that considers the existence conditions of the forward kinematic solution, singularity, manipulability, and resistivity. A series of simulations was carried out to show the kinematic characteristics and performance of the mechanism. The proposed manipulator has potentials in a wide range of applications from micro-surgery robots to a highly dextrous wrist mechanism of assembly robots.

A new probing mechanism and an active compliance control algorithm have been developed for the in-circuit test of a PCB. Commercially available robotic probing devices are incapable of controlling contact force generated when a rigid probe contacts with a solder joint at high speed. This uncontrollable excessive contact force makes some defects on the surface of the solder joint, which is plastically deformable over some limited contact force. This force also makes unstable contact motions resulting in unreliable test data To overcome these problems, the authors propose that serially connected macro and micro actuators with active compliance provide the best potential for the safe and reliable in-circuit test. Moreover, the depth of penetration on a solder joint can be regulated after contact. This paper describes the design characteristics, modeling, and control scheme about the newly proposed devices. The comparison of conventional passive compliance and force feedback control methods with the proposed control scheme for the contact force control is presented. The experimental results clearly show the effectiveness of the proposed system.