Adaptive robust precision motion control of linear motors with high frequency flexible modes

This paper studies precision motion control of linear motors in the presence of parameter variations, disturbances and various significant nonlinearity effects. An adaptive robust control (ARC) algorithm with integrated compensation of major nonlinearities ranging from Coulomb friction and cogging force to the nonlinear electromagnetic field effect is developed. High frequency structural flexible modes and dynamics in linear motors, which are neglected in the previous researches, are explicitly identified experimentally and their effects are carefully examined. With the knowledge of those high frequency dynamics, theoretical analysis is subsequently conducted to generate a set of practically useful guidelines on the tuning of controller gains in maximizing the achievable performance in practice. Comparative experiments of the propose ARC control law with different controller gains are carried out to illustrate the usefulness of the generated guidelines. In addition, to further push the achievable control performance, explicit compensation of the known high-frequency flexible modes and dynamics using pole/zero cancelation is also investigated, and its effectiveness is evaluated through comparative experimental results as well.