Cooperative Encirclement of Heterogeneous Mobile Robots under Faults and Positioning Restrictions

This paper investigates the challenge of distributed fault-tolerant control for formation of heterogeneous mobile robots engaged in encirclement tasks. The system is subjected to unknown actuator faults and positioning constraints caused by limited signal coverage. A novel switching control strategy based on Adaptive Sliding Mode Control (ASMC) is proposed, which is implemented within a dual-layer hierarchical framework. In the outer layer, a consensus algorithm is employed by the robotic system to progressively align the virtual center of the formation with the escaping target’s position for tracking, and the real-time desired state for each robot is computed from the virtual center position. In the inner control layer, outside positioning-restricted regions, the dynamically updated desired state is tracked by mobile robots utilizing an ASMC strategy. Within positioning-restricted regions, the control strategy is reconfigured by inversely deriving the reference control input from the desired state based on the original kinematic model, which is then applied as the actual control input. Upon exiting the restricted region, ASMC is reinstated, effectively mitigating the impact of actuator faults and positioning constraints on the formation. The effectiveness of the algorithm in managing complex fault scenarios during the encirclement task is validated through the physical experiment results.