Study and implementation of a simplified and robust position digital controller for a PM synchronous actuator

This paper presents a fully digital position control system for small power surface mounted PM synchronous actuators. The control algorithm relies on a simplified decoupling state feedback in order to obtain field orientation. There is no current measurement, and the current values needed to compute the control algorithm are predicted from a model. This makes it possible to use a fully digital position controller by using low cost 8 bit microprocessors with only a position sensor. Moreover, it is shown in this paper that it is preferable to use, in the decoupling state feedback, an estimated, instead of a measured, value of the current to ensure stability and to improve the robustness of the system regarding parameter uncertainties. Furthermore, as the actuator model is linearized by a decoupling state feedback, the robustness of the system has been further improved by using appropriate techniques evolved for linear systems to synthesize the position controller. The performance of the proposed control system is analyzed by a theoretical study and digital simulations. It has been implemented around two 8 bit MCS 8051 microcontrollers and tested on a 2 kW machine