Vibration Suppression and Disturbance Rejection for Flexible Joints of Robotic Arm Using Equivalent Input Disturbance Approach

The flexible joint of a robotic arm is sensitive to internal and external disturbances, which may cause mechanical vibration and degrade control performance. This paper proposes a strategy of vibration suppression and disturbance rejection for the flexible joint of a robotic arm based on the equivalent input disturbance (EID) approach. First, the dynamic model of the robotic arm is derived. Internal and external disturbances are treated as an EID on the control input channel. Then, the structure of an EID-based robotic arm conctrol system is developed. A state observer and an estimator are devised to produce an estimate of the EID. An inner compensation is added to reject the disturbances by using the estimate. Next, the damping coefficient of the flexible joint of the robotic arm is analyzed. It is adjusted to suppress mechanical vibration by choosing the proper parameters of the observer and estimator. The effectiveness of the method is validated by simulations.