Sensorless control of servo motor based on adaptive amplitude-phase square wave injection

Existing sensorless control methods are constrained by the convergence rate and estimation accuracy, and is difficult to be directly applied to high dynamic electro-mechanical servo systems. To improve the estimation accuracy of sensorless control under high dynamics, this paper proposes a novel sensorless control method for the permanent magnet synchronous motor based on amplitude-phase adaptive square wave injection. By injecting high-frequency square wave voltage signals and demodulating the high-frequency response current of the q-axis, high dynamic rotor position estimation is achieved. At the same time, the amplitude and phase of the injected voltage are adaptively adjusted according to the real-time operating status of the motor. Therefore, the estimation errors caused by inverter nonlinearity and motor cross-saturation effect are effectively reduced. Finally, the performance of the method proposed is experimentally verified on a 2 kW servo motor platform. The experimental results show that the proposed method can enhance the accuracy of rotor position estimation, while achieving high dynamic characteristics of sensorless control.