Super Twisting Sliding Mode Control-Based Impedance Control for Teleoperated Virtual Robot Arm End-Effector Force Tracking

In this research, a virtual simulator (slave system) of an eight-degrees-of-freedom robot (two-DOF crane, one-DOF prismatic (telescopic mast), and five-DOF robot manipulator) is developed and teleoperated by an external hardware haptic device (master system) for nuclear power plant’s (NPP) reactor vessel internals (RVI) dismantling operations. For operations such as cutting, the robot end-effector with a laser cutter should maintain a constant distance from the physical wall of RVI. So, a virtual wall near the physical wall is assumed. The end-effector should remain on the virtual wall for optimal cutting which is achieved through force tracking impedance control. In this paper, initially sliding mode control (SMC) was implemented but resulted in chattering in force tracking response. Therefore, super twisting sliding mode control (STSMC)-based force tracking impedance control is designed and implemented for enhanced end-effector force tracking. The control input of the STSMC is composed of a continuous and discrete component. Continuous control input regulates control performance against uncertainties, whereas discrete provides a switching algorithm. STSMC then eliminates the chattering effect and reduces the force tracking error. The performance of SMC-based and STSMC-based impedance control is compared, and the comparison shows that the STSMC-based impedance control provides enhanced performance.