Nonlinear basic stability concept of the hybrid position/force control scheme for robot manipulators

The basic stability characteristics of the nonlinear hybrid control system are clarified by using Lyapunov´s method in relation to autonomous systems. The fundamental stability condition of hybrid control is evaluated by using a hybrid control scheme, the friction effect, an additional phase lag (dead time), and the digital control effect. The sampling delay (dead time) causes a large additional phase lag, which in turn causes instability. Moreover, the stability results confirm that the hybrid control scheme and digital control effect adversely affect hybrid control stability even if the fundamental stability condition is satisfied