Prescribed performance model-free hybrid force/position control for 3-DOF SEA-based manipulator under partial state constraints

In this paper, for 3-DOF series elastic actuator (SEA) -based manipulators under partial state constraints, a prescribed performance model -free hybrid force/position controller (PPMHC) is designed. The PPMHC contains an outer force and an inner position control loop. The outer force control loop is designed by impedance control. Then, the inner position control loop is proposed according to the idea of model -free control. The inner position control loop consists of the prescribed performance control, integral -barrier Lyapunov function (IBLF), time -delay estimator, and neural approximation algorithm. It can be proven that the designed PPMHC can achieve stability of the closed -loop system under the partial state constraints by the Lyapunov function. Finally, the effectiveness of PPMHC is illustrated by the simulation results.