Safety-Augmented Operation of Mobile Robots Using Variable Structure Control

Abstract

The design process and complexity of existing safety controls are heavily determined by the geometrical properties of the environment, which affects the proof of convergence, design scalability, performance robustness, and numerical efficiency of the control. Hence, this paper proposes a variable structure control to isolate the environment's geometrical complexity from the control structure. A super-twisting algorithm is used to achieve accurate trajectory tracking and robust safety control. The safety control is designed solely based on distance measurement. First, a nominal safety model for obstacle avoidance is derived, where realistic system constraints are considered. The nominal model is well-suited for safety control design for obstacle avoidance, geofencing, and border patrol with analytically proven stability results. The safety control utilizes distance measurement to maintain a safe distance by compensating the robot's angular velocity. A supervisory logic is constructed to guarantee the overall stability and safety of the system. Operational safety and precision tracking are proven under parametric uncertainty and environmental uncertainty. The proposed design is modular with minimal tuning parameters, which reduces the computational burden and improves the control scalability. The effectiveness of the proposed method is verified against various case studies.