A method automatically tuning the parameters in a digital controller is proposed for a DC servomotor. In this method, the system parameters are identified and the controller parameters are then tuned every sampling period. The features of the proposed method are summarized as follows: (1) The structure of controller is similar to the conventional one. (2) An approximate discrete-time model is introduced to simplify controller design and system identification. (3) Arbitrary closed-loop poles can be prescribed in advance for tuning. The zeros depending on the identified system-parameters and the tuned controller-parameters are not introduced. (4) For the case of using the difference of the angular position measured by an encoder instead of the real angular velocity, the influence on the control system is clarified. (5) The identification method is modified for this case. (6) The approximate discrete-time model is guaranteed to be valid in the control and identification. In order to illustrate the effectiveness of the nronosed method, experimental results are given.
