Auto disturbance rejection control for beam magnetic suspension system of gantry-moving type numerical control machine tool

Aim to adverse effects resulted from external disturbances, system internal parameters variations and unmodeled dynamics during the operation of gantry moving type numerical control (NC) machine tool, The paper presented that suspension air-gap of beam suspension system was controlled by using auto-disturbance-rejection control technology. Auto-disturbances-rejection controller can regard system model parameter variations and external disturbance effect of system as comprehensive disturbance, automatic online estimation and compensation. First the state variables were chosen based on the mathematical model of beam suspension system, nonlinear state equation of system was obtained; then coil voltages was regarded as controlled variable, double-loop (position loop and current loop) auto-disturbances-rejection controller of the suspension air-gap was designed, nonlinear control of the beam suspension system was realized. The simulation results show that the auto-disturbances-rejection controller can adapt well to the nonlinearity of suspension system and has strong robustness to system´s parameter variations and the system´s disturbances. The beam friction-free stable suspension can be realized.