Ieee Transactions on Robotics and Automation 1 Robust Torque Control of Harmonic Drive Systems

In this paper the torque control of a harmonic drive system for constrained{motion and free{ motion applications is examined in detail. A nominal model for the system is obtained in each case from experimental frequency responses of the system, and the deviation of the system from the model is encapsulated by a multiplicative uncertainty. Robust torque controllers are designed using these information in an H 1 {framework, and implemented on two diierent setups. From time and frequency domain experiments, it is shown that the closed{loop system retains robust stability, while improving the tracking performance exceptionally well. To further improve the performance of the system for free-motion case, a feedforward friction{compensation algorithm is implemented in addition to the robust torque control. It is shown that friction{compensation will shrink the model uncertainty at low frequencies and hence, the performance of the closed{loop system will be improved at those frequencies.

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