A nonlinear bang-bang impact force control

Abstract

For stabilization of a robot manipulator upon collision with a stiff environment, a nonlinear bang-bang impact controller is developed. It uses a robust impedance/time-delay control algorithm with negative force feedback to absorb impact forces and stabilize the system. This control input alternates with zero when no environment force is sensed due to loss of contact. This alternation of control action repeats until the impact transient subsides and steady state is established. After impact transient, the proportional-derivative force control is used. The bang-bang control method provides stable interaction between the robot with severe nonlinear joint friction and a stiff environment and achieves rapid response while minimizing force overshoots. It is shown via simulations that overall controlled performance is comparable or superior to existing techniques of impact force control.