Power-Assist Controller Design Permitting Abnormality Detection by Means of DC Servomotor

Power-assist system (PAS) technology and its applications to manufacturing systems have attracted special interest recently. In such a man-machine system as PAS, the abnormality detection of the controlled mechanical part of the system, e.g., the collision detection of mechanical part, is extremely important. Some conventional studies have already proposed the collision detection methods for robots or PASs. In this study, we assume that DC servomotors are utilized as actuators. Then, this study proposes a novel power-assist controller design method. This method includes a software-based abnormality detection based on the current dynamics of motor. The controller design utilizes a two-degree-of-freedom control system structure which consists of an on-line linear simulator taking account of the current dynamics, an impedance controller and an LQI servo controller. The abnormality detection is realized by detecting the difference between the simulator's current and the real current of motor. The effectiveness of the method is verified experimentally.