Abstract

This paper presents an observer-based active fault-tolerant control scheme for leader–follower formations of differential-drive unmanned ground vehicles under the Separation-Bearing Control framework. The relative pose is described by inter-vehicle distance, bearing angle, and heading difference, which are kinematically coupled, so a single actuator fault propagates through all three Separation-Bearing Control channels at once. The nonlinear kinematics are linearized about the rigid-formation operating point; for a constant-speed reference, this operating point is stationary and the resulting fault-augmented error model is linear time-invariant, explicitly accounting for additive actuator faults and bounded external disturbances. A joint estimation observer reconstructs the unmeasured fault signal and filters the measured state with a guaranteed disturbance-attenuation level obtained from a single convex linear matrix inequality, and a state-feedback law with online fault compensation is derived. The linear closed loop is certified asymptotically stable with a prescribed H∞ attenuation bound, which establishes local asymptotic stability of the corresponding equilibrium of the nonlinear formation. Numerical simulations on a three-vehicle circular convoy, together with Monte Carlo, fault-variation, measurement-noise, model-mismatch, and trajectory-change studies, and comparisons against non-fault-tolerant, passive, and integral-action baselines, delineate the specific benefit of online fault reconstruction and active compensation.

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