VCM controller design with enhanced disturbance decoupling for precise automated manufacturing processes

In this study, a controller design of a voice coil motor (VCM) with enhanced disturbance rejection (or disturbance input decoupling) performance, especially for precise automated manufacturing processes, is proposed. The proposed disturbance decoupling strategies are twofold: (1) a dynamic stiffness-enhanced position-velocity controller and (2) state-filter-based disturbance input decoupling in a force control mode. First, a state-feedback style position-velocity controller is designed to meet tracking requirements and improve disturbance rejection in VCM control. In this control structure, the conflict in requirements between command tracking and disturbance rejection can be considerably alleviated. This design property provides powerful insights into achieving precise position control. To enhance the force control accuracy, a disturbance state filter for force control is also applied to estimate and compensate for the varying dynamics of VCM systems, such as non-linearly variable loads and other uncertainties. The state filter estimation accuracy in the presence of system parameter errors is fully analysed. In addition, both disturbance decoupling methods are computationally efficient and robust to other parameter errors. The proposed algorithms are implemented in a developed VCM actuator and verified to be appropriate for a VCM drive system with unknown disturbances.