Adaptive control of harmonic drives

In this paper, an adaptive control algorithm is designed for controlling the harmonic drives used to drive robot manipulators. Direct torque measurement is available by using the flexspline mounted strain-gauges. The torque error is added to the required velocity. Adaptive friction compensation and flexspline dynamics based control are the two main contributions in the paper. The L₂/L_∞ stability and the L₂-gain induced H_∞ stability are guaranteed in both joint torque and joint position control modes. Experiments conducted on two typical types of harmonic drives confirm the feasibility of the controller in both time and frequency domains. By using the virtual decomposition control approach, the independently designed joint adaptive controller for harmonic drives can be efficiently incorporated into the motion/force control systems of robot manipulators.