A new control method for kinematically redundant manipulators having the properties of local torque-optimality and singularity-robustness is developed. The proposed control method is applied to the numerical model of the SNU-ERC 3-DOF direct-drive manipulator. It is shown that the proposed control method is very effective in overcoming the singularity problem, especially in the case of using the local torque optimization control of redundant manipulators.

This paper addresses the problem of stabilizing a base-excited inverted pendulum around its upright position with a robot. The pendulum has two rotational degrees of freedom and its base point is moved in two-dimensional space by a planar direct-drive robot. The robot has three degrees of freedom and its kinematic redundancy occurring at the inverse kinematics is utilized to optimize the joint acceleration and the manipulability measure. A decentralized joint acceleration control with a software velocity/acceleration observer, is used to accelerate/decelerate each joint of the robot to balance the pendulum. Experimental results are described to show the stable and robust responses of the control system.

This paper addresses the problem of stabilizing a base-excited inverted pendulum around its upright position with a robot. The pendulum has two rotational degrees of freedom and its base point is moved in two-dimensional space by a planar direct-drive robot. The robot has three degrees of freedom and its kinematic redundancy occurring at the inverse kinematics is utilized to optimize the joint acceleration and the manipulability measure while balancing the pendulum. A decentralized joint acceleration control with a software velocity/acceleration observer, is used to accelerate/decelerate each joint of the robot to balance the pendulum. Experimental results are described to show the stable and robust responses of the control system.

The redundancy of robot manipulators plays an important role in increasing their flexibility and versatility, especially in an environment with obstacles. In this paper, the redundancy is utilized for enabling collision-free motion for a given trajectory of a manipulator end-effector. Manipulator links and obstacles are approximated by polytopes that are described by their vertices. The distance algorithm, which allows computation of the distance information between polytopes in R/sup m/, is used to obtain distance information between robot and obstacles. Three kinds of method based on the distance information-gradient projection method, obstacle avoidance force method, obstacle avoidance velocity method-are proposed to calculate the joint trajectory that enable a manipulator to perform a desired end-effector motion and avoid obstacles. A simple numerical example involving a two-dimensional five degree-of-freedom manipulator working among obstacles is described.

For PD-controlled industrial robot manipulators performing point-to-point (PTP) motion, the effect of joint flexibility grows as the cycle time for the PTP motion increases. To reduce residual vibration induced by joint flexibility, a method of generating preshaped reference trajectory command is proposed. This preshaped reference trajectory command is developed from the given PTP motion and the parameters of given PD controller. Simulations show that low overshoot and short settling time in fast PTP motion is achieved by applying the preshaped trajectory reference command, without excessive control effort. This proposed method is readily applicable to PD-controlled industrial robots which perform repetitive fast PTP motions.