Nonlinear Control For Harmonic Drives

With the continuous improvement of industrial automation, much higher theaccuracy and response of mechanical systems are required. To fulfill these requirements,harmonic drive systems are widely applied. Because of its excellent transmissionproperties, harmonic drive systems are widely used in various applications, especially inhigh-precision control field.Considering the kinematic error is the main problem in nonlinear transmissions,the high precision motion control of a harmonic drive system is studied, using therecently developed nonlinear control techniques.First, two state feedback controls including position control and trajectory trackingcontrol are studied, and then a class of nonlinear proportional plus derivative (NP-D)controller and nonlinear proportional plus derivative and feed-forward dynamic model(NP-D+) controller are proposed for further improvement of the performance. Second,because it is hard to take a measure of the velocity in the output, output feedbackposition controllers and trajectory tracking controllers are developed with positionmeasurements only. Finally, both state feedback controls and output feedback controlsare restudied taking into account the actuator saturation. The Lyapunov stabilitytheorem is used to show the asymptotic stability of the closed-loop systems resultingfrom the proposed various controllers. Simulation results are presented to demonstratethe effectiveness and performance improvements of the proposed approaches.