Actor-Critic-Based Constrained Control for Cable-Driven Parallel Robots: Application in Air-Bearing Satellite Simulator

Abstract

Air-bearing satellite simulators are essential ground-based platforms for testing spacecraft guidance, navigation, and control technologies. To improve their precision and agility, cable-driven parallel robots offer a promising alternative to conventional pneumatic actuators, though they pose challenges in tension constraints and coordinated control. While optimization-based methods have shown promise in cable-driven parallel robot trajectory tracking and coordination, they suffer from scalability issues in highly redundant systems and are sensitive to motion uncertainties due to heavy reliance on the Jacobian matrix. This article presents a coordinated control approach that combines a control-based positive tension strategy with an actor-critic framework. The method guarantees positive cable tensions without iterative optimization, enabling coordinated task-space trajectory tracking. Specifically, a saturation-like function is introduced to circumvent the computational burden and feasibility risks associated with iterative optimization, while contour error formulation is utilized to extend coordination from cable space to task space. The actor-critic architecture compensates for uncertainties such as Jacobian mapping errors in tension computation. The closed-loop system is rigorously proven to be semiglobally uniformly ultimately bounded based on the Lyapunov method. Finally, a cable-driven air-bearing satellite simulator is developed to address issues such as low control accuracy and poor directional control in pneumatic actuation. Experimental results on this platform validate the effectiveness of the proposed coordinated control approach.