Robotic force control for flexible assembly

The authors present a complete design procedure for determining an optimal force control for assembly tasks while assuring stability. Based on a constrained motion model of the robot, including elasticity of joints and force sensor, a custom design scheme may be applied for individual types of mating tasks. The approach guarantees separation of position and force controlled cartesian directions of the robot endpoint by complementary input/output decoupling. Position feedback parameters are optimized to obtain a maximum stability reserve and force feedback parameters are optimized to minimize settling time. Controller behavior is then predicted by the simulation of the potentially unsteady system dynamics including time-varying constraints on the workpiece. The design process is illustrated for a peg-in-hole insertion and verified by experimental results from a laboratory robot