Advanced precision motion control of a permanent magnet linear synchronous motor with novel disturbance estimation methods

Abstract

The precision motion control has received significant attention in modern control systems as increasing demands to achieve high-speed/high-accuracy position tracking performance. Mostly, it is accomplished by the direct-drive devices such as rotary motor driven stages and linear motor driven stages. The rotary motor-driven stages have been widely used in many applications due to its low cost and easy manufacturing. However, these stages make it difficult to achieve high-precision motion control due to the effects of contact-types of nonlinearities and disturbances such as backlash and multi-source friction forces occurred by the indirect mechanism. Therefore, demands for linear motor driven stages have been increasing more and more over recent years. Comparing with rotary motor-driven stages, they make more easily to perform tasks that require high-precision speed/position control due to eliminating mechanical transmissions such as belt, gear, ball screws and so on. Nevertheless, there exist several problems in precision motion control performed by linear motors. Linear motors are directly affected by the model uncertainties, the friction force, and the force ripple due to system characteristics of manufactured hardware structure. These problems can be improved by hardware techniques such as the use of high quality bearings or guides and skewing permanent magnets, but additional hardware options and high cost are required. As other ways to compensate for these disturbances, there are model-based/model-free identification and adaptation schemes. These methods can improve the addressed problems by software approaches. However, most existing methods require a lot of time and effort to obtain the optimal disturbance models or experimental data (tables) of disturbances under a variety of operating conditions. In this dissertation, novel methods to identify and compensate for the disturbances such as the friction force and the force ripple are proposed, which are b...