Robust position servo system based on vibration suppression control for industrial robotics

This paper proposes two vibration suppression control systems for industrial robots. Industrial robots often occur vibration phenomenon which is caused by the resonant frequency and nonlinear interference force from various joints of the robot. The compact high-gear reduction without backlash, such as the harmonic gear is frequently used in the driving system for the sake of high load-to-weight performance. Generally, the industrial robots have used the sensors mounted to actuator-side because hardware setting using load-side sensor is very difficult to mount signal lines. At first, this paper proposes a new vibration suppression control system uses the estimated load information due to repress the effect of external disturbance force and nonlinear inertia variation due to posture change of robot. The robust position servo system is designed based on the state, disturbance observer and robust speed control system using coprime factorization controller. Next, a zero-phase notch filter is very useful for suppressing the resonant phenomenon. However, as the design method of zero-phase notch filter is more difficult than that of the zero-phase low-pass filter, the high-performance zero-phase notch filter cannot be realized in motion control field. In order to overcome this problem, this paper proposes a new design method of the zero-phase notch filter which has no phase delay for fast robot motion control reference. The effectiveness of both proposed systems is confirmed by experimental results and numerical simulation results.