A High–Precision Motion Control Based on a Multi-Rate Periodic Adaptive Disturbance Observer of a Linear Actuator for High Load Systems

This study is concerned with the problem of compensating for periodic disturbances under repetitive motion conditions. In order to achieve high precision positioning for high load systems with periodic disturbances, a practical motion control scheme based on a multi-rate periodic adaptive disturbance observer (MPADOB) is proposed. Nonlinear disturbances such as the force ripple, friction force, and cable tension force occur when linear actuators for high load systems are used on linear motors with iron-cores. These disturbances are obstacles to achieving high-precision control. In the proposed scheme, these disturbances are attenuated perfectly by using a periodic feedback loop. However, the memory size becomes large when the repetitive motions increase since the periodic feedback loop has many sample delay terms. It is a weakness in the control schemes that use a periodic feedback loop, although it can improve the control performance. In this study, the multi-rate periodic feedback loop and a predictive estimator have been proposed to improve the memory size issues for practical implementation and control performance. Using MPADOB, the control schemes that use periodic feedback loop can be applied to a variety of industrial applications practically. The effectiveness of the proposed scheme is verified by a variety of experimental tests.