A speed loop autotuning method based on signal injection for electrical drives

This paper presents an auto-tuning technique for the speed controller in electrical drives. The method is based on the model reference approach, where a perturbation frequency is injected into the speed control loop and superimposed to the torque reference signal. The tuning is performed by a simple signal processing elaboration before and after the injection point and the controller parameters are adjusted so as to satisfy the specified bandwidth and phase. The method is based on the Goertzel single-tone Direct Fourier Transform (DFT), enabling low computational complexity, ease of application and high immunity to noise uncorrelated to the perturbation frequency. Thus, the amplitude of the injected signal can be very small, practically comparable to the sensor resolution, without relevant interference of the normal drive operation, enabling break-through applications of the on-line controller auto-tuning. The effectiveness and validity of the proposed approach is extensively verified by simulations and experiments on a 3-kW÷1500-rpm induction motor drive.