Motion control of systems with nonlinear transmission couplings

Nonlinearities in transmission couplings, actuators and sensors are three types of significant nonlinearities requiring special attention when high precision motion performance is desired. Tao and Kokotovic recently proposed an interesting nonlinear compensation scheme called the adaptive inverse approach. The scheme was applied to compensate actuator and sensor nonlinearities. However, extension of the inverse compensation approach to addressing nonlinearities in transmission couplings is not straightforward due to the inherent feedback structure between the drive and the load through the couplings. In this paper, a new control scheme for compensating nonlinearities in couplings is proposed. The design is based on the ideas of the inverse approach and the feedback decoupling. The closed-loop stability of the proposed compensation scheme against uncertainties in the coupling nonlinearities is proved in the sense that all signals of interest remain bounded. The effectiveness of the proposed scheme is illustrated via computer simulation for nonlinear viscous-type (slip-type) transmission couplings.