Active Disturbance Rejection Control for Grasping Force Tracking

In this paper, a robotic manipulator is developed to allow the appropriate exertion of the coupling force needed for proper implementation of Smart-touch inspection. A force feedback control system works in tandem with a load cell sensor and DC motor, which allows the manipulator to guide two fingers to grasp a bolted connection for Smart-touch inspection. The envisioned device can be mounted onto a remotely operated vehicle (ROV) and eventually a fully autonomous vehicle. The load-cell on one of the fingers senses the touching force, which provides force feedback information for the DC motor on the joint of the robotic manipulator. To reject the system's uncertainties and nonlinearities, such as dead-zone, backlash and sensing noise, a reduced-order active disturbance rejection control (R-ADRC) is developed for the robotic manipulator to maintain its grasping force at the inspection location. Experimental results have shown that the R-ADRC can actively reject the system's uncertainties and work better than proportional-integral-derivative (PID) control in terms of less steady-state error and overshoot.