2018 Volume 7 Issue 2 Pages 117-126
In order to realize force sensorless fine force control, this paper proposes a new notch-type friction-free disturbance observer (DOB) and a new notch-type friction-free reaction force observer (FFRFO). Generally, a force sensorless force control system is always influenced by the static friction phenomenon. In order to suppress the estimation error due to static friction, a force sensorless force control system uses a dither signal, and a friction free reaction force observer (FFRFO) is used to consider this dither signal. Since the high frequency gain charactheristics of conventional FFRFO are significantly higher than 0dB, the entire force control system sometimes becomes unstable or produces oscillating responses. To overcome this problem, this paper proposes a new force sensorless control system using the notch-type friction free reaction force observer, whose inner system is the proposed acceleration control based on the notch-type friction free disturbance observer. The effectiveness of the proposed system is confirmed by experiments using an actual industrial robot.
