On Switching between Motion and Force Control

TLDR: A simple yet robust hysteresis-relay-based switching strategy is shown to be suitable for such type of motion control applications and the hybrid automaton, as most general tool, is used for exploring and analyzing the transients.

Abstract: In motion control technologies, an automatic switching between trajectory following and set reference force, upon the impact, is a frequently encountered requirement. Despite both, motion and force controls, are something of well-understood and elaborated in the control theory and engineering practice, a reliable switching between them is not always self-evident. It can lead to undesired deadlocks, limit cycles, chattering around switching point and, as consequence, to wearing or damages in the controlled plant and its environment. This paper contributes to analysis and understanding of the autonomous switching from the motion to force control and vice versa. Simple output and state feedback controllers are assumed, and the conditions to be held in vicinity to the switching state are explored. A simple yet robust hysteresis-relay-based switching strategy is shown to be suitable for such type of motion control applications. The hybrid automaton, as most general tool, is used for exploring and analyzing the transients. A multiple Lyapunov function approach is applied for stability analysis of the switched control system. A second-order system, with uncertain nonlinear dynamics, is demonstrated as an illustrative numerical example.