A novel model-following scheme with simple structure for electrical position servo systems

A novel model-following scheme with a simple structure for electrical position servo systems is proposed. It is quite different from and much simpler than existing model-following control (MFC) schemes. The nominal model of a plant is used as the reference model in this scheme. The common external input to the reference model and to the plant is not fed from the reference command but from a model controller which is designed for the nominal model of the plant to ensure a satisfactory reference output trajectory. The following of the plant to the reference model with the expected output trajectory is guaranteed using a correction signal from an adaptive mechanism which has a simple linear PID structure, taking only the generalized output error as its input. Conditions for asymptotic model-following are first developed rigorously and then implemented. The system design method is described. Simulation and experimental results show that the proposed MFC scheme is effective and robust against both parameter variations and load disturbance of the actual plant. The comparison of the MFC system with position PI and PID control systems illustrates the superiority of the proposed MFC scheme over the conventional PI/PID control scheme.