Constructive Safety Control

TL;DR

This paper introduces a constructive safety control method for nonlinear cascade systems with multiple constraints, ensuring safety and stability through a unified approach and validated on a VTOL vehicle.

Contribution

It presents a novel constructive safety control framework with a unified safety-stability characterization and a reshaping technique for feasible sets, enabling systematic design for complex nonlinear systems.

Findings

Guarantees Lipschitz continuity of virtual control laws.

Employs a refined nonlinear small-gain synthesis for uncertain interconnections.

Validated experimentally on a VTOL vehicle in narrow spaces.

Abstract

This paper proposes a constructive approach to safety control of nonlinear cascade systems subject to multiple state constraints. New design ingredients include a unified characterization of safety and stability for systematic designs of safety controllers, and a novel technique of reshaping the feasible sets of quadratically constrained quadratic programming induced from safety control. The proposed method guarantees Lipschitz continuity of virtual control laws, enabling a stepwise constructive design. A refined nonlinear small-gain synthesis is employed to address the nonlinear uncertain interconnections between the resulting subsystems corresponding to different virtual control laws, and to guarantee the achievement of the safety control objective. When the safety constraints are removed, the proposed approach coincides with the standard constructive nonlinear control. The proposed safety-control algorithm is experimentally validated in a testbed involving a vertical takeoff and landing (VTOL) vehicle taking off in narrow spaces.