Longitudinal Wheel Slip Control for Flexible Landing Gear: a Second-Order Sliding Mode Approach

This work studies an anti-skid controller design for Landing Gear (LG) with flexible strut. The wheel axle and fuselage are connected by a longitudinal linear spring that accounts for the relative displacement between the wheel and the fuselage due to the landing gear deformability. Lift force and tire deflection due to the change in vertical load are also considered into the models. First and second order Sliding Mode Controls (SMC) are used to stabilize the system around the optimal braking equilibrium points. The second order SMC proves to outperform the first order control; in particular, it leads to a greatly reduced chattering and to a smaller control effort than those obtained with the first order control. The controlled variables are the relative wheel motion with respect to the fuselage and the tire slip. The simulations are demonstrating the success of SMC as anti-skid controller for main LG with flexible strut.