Control of robot arms using joint torque sensors

Describes a basic study of vibration control, disturbance rejection, and friction compensation in robots with flexible drive systems. First, the system gain characteristic at the antiresonance frequency is introduced to evaluate the vibratory behavior of the control system. Secondly, joint torque negative feedback is discussed. While it is shown that joint torque negative feedback has a good effect on vibration suppression, the property of disturbance rejection is easily deteriorated when a high-gain joint torque feedback is used. Based on the assignment of pole-distribution, the relationships between vibration suppression and disturbance rejection are analyzed. Thirdly, a feedforward compensation control based on a friction observer is proposed. It is shown that the tracking error is effectively decreased by this friction compensation.