Robust electro-hydraulic control for aircraft anti-skid systems with full validation from test bench to flight

In modern aviation, anti-skid systems are fundamental in preventing wheel-locking conditions and maximizing braking performance. To achieve airworthiness, these systems must be robust, fault-tolerant, and comply with existing standards and regulations. Existing solutions fall short in addressing important aspects for a successful practical implementation, as testified by the lack of flight testing verification in the literature. This paper proposes a novel aircraft anti-skid system that leverages robust control techniques to enhance safety and performance. The proposed architecture integrates a fault-tolerant design that accounts for measurement noise, hydraulic system asymmetries, and pressure transducer faults, while maintaining stability despite uncertainties in the electro-hydraulic brake dynamics. A cascaded control structure combining robust pressure regulation with wheel deceleration control and supervisory logic enables resilient performance under varying operating conditions. The pressure controller's stability is verified by a Kharitonov-type stability check, whereas the proposed gain-scheduled deceleration controller is analyzed under a Linear Parameter-Varying system formulation, checked for stability by a collection of Linear Matrix Inequalities under assumptions of rate-bounded variability of the involved parameters. The approach is validated on a hydraulic test bench, an aeronautic dynamometer, and flight test experiments, demonstrating practical applicability and alignment with the demands of modern hydraulic control systems.