Modeling and control of the Mitsubishi PA-10 robot arm harmonic drive system

The purpose of this paper is to present our results in developing a dynamic model of the Mitsubishi PA-10 robot arm for the purpose of low-velocity trajectory tracking using low-feedback gains. The PA-10 is ideal for precise manipulation tasks because of the backdrivability, precise positioning capabilities, and zero backlash afforded by its harmonic drive transmission (HDT). However, the compliance and oscillations inherent in harmonic drive systems, and the lack of any technical information on the internal dynamics of the transmission, make the development of an accurate dynamic model of the robot extremely challenging. The novelty of this research is therefore the development of a systematic algorithm to extract the model parameters of a harmonic drive transmission in the robot arm to facilitate model-based control. We have modeled all seven joints of the Mitsubishi PA-10, and we have done several experiments to identify the various parameters of the harmonic drive system. We conclude with a sample trajectory-tracking task that demonstrates our model-based controller for the Mitsubishi PA-10 robot arm.