Amplitude-Saturated Nonlinear State Feedback Position Control for Flexible Joint Robots

To achieve position control of flexible joint robot (FJR), an amplitude-saturated nonlinear state feedback controller (ASNSFC) is designed along with friction compensation. The controller uses only position and velocity of motor side to achieve position control of FJR, and residual vibration can be well suppressed. Specifically, some deficiencies of traditional PD (proportional-differential) controller are analyzed based on FJR's dynamics model. Subsequently, an ASNSFC is designed according to safety requirements in the field of tri-co (coexisting-cooperative-cognitive) robots, and the stability of the proposed closed-loop system is proven theoretically by Lyapunov stability theory. Performance of the proposed approach is evaluated on a self-built FJR platform, and experiment results illustrate that the proposed scheme can achieve better performance, including one-tenth overshoot and half settling time.