Model Free Extended State Observer Based Sliding Mode Prescribed Time Control for Series Elastic Actuator-Based Manipulator

In this paper, a force position hybrid control method based on model free prescribed time control is proposed for the control of a 4-DOF series elastic actuator (SEA). The controller is based on the idea of admittance control and has a dual loop control structure with inner and outer loops. The outer control loop used adaptive laws to estimate environmental stiffness and admittance models integrated with reference trajectories for force control in position correction. In the inner loop control loop, based on the idea of simplifying complex systems using ultra-local model, a prescribed time extended state observer (PTESO) is designed to observe lumped disturbances. Then, the observer output is combined with periodic delay feedback sliding mode (PDFSM) to form a composite control law, achieving high-precision force/position hybrid control. The simulation experiment results show that the algorithm performs well in terms of stability and fast response.