In the industrial world, not only autonomous machinery as industrial robots but also manmachine cooperative systems as power-assist systems have attracted special interest recently. Kondo, et al. proposed the scheme of Man-Machine Collaborated Robotic Systems (MMCRSs) and its application to some assembling work. In MMCRSs, efficient mode switching from human-oriented operation to machine-oriented operation is important. However, its issue has not been fully addressed yet. This study discusses a

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... mode switching control method for MMCRSs. Especially, we treat the switching from a power-assist mode (PAM) to an automatic positioning mode (APM) for a simple robotic system. To obtain a smooth switching, this study utilizes a two-degree-of-freedom control system structure which consists of an on-line impedance control simulator and an LQI servo controller. Some smooth reference generation for APM is also introduced. No input saturation and/ or stopping appear at the switching in this method. The effectiveness of the method is verified experimentally.