Fault Tolerant Sliding Mode Control Design with Piloted Simulator Evaluation

This paper considers sliding mode allocation schemes for fault tolerant control. The schemes allow redistribution of the control signals to the remaining functioning actuators when a fault or failure occurs. The paper analyzes the schemes and determines conditions under which closed–loop stability is retained for a certain class of faults and failures. It is shown that faults and even certain total actuator failures can be handled directly without reconfiguring the controller. The results obtained from implementing the controllers on the SIMONA research flight simulator, configured to represent a B747 aircraft, show good performance in both nominal and failure scenarios even in wind and gust conditions. NOMENCLATURE 6–DOF = 6 degree of freedom EPR = engine pressure ratio cmd = command signal ru, rl = upper and lower rudders sp = spoiler air, ail, aor, aol = inner right, inner left, outer right and outer left ailerons p, q, r = roll, pitch and yaw rate (rad/sec) Vtas = true air speed (m/s) α, β = angle of attack and sideslip angle (rad) φ, θ, ψ = roll, pitch and yaw angle (rad) he, xe, ye = geometric earth position along the z (altitude), x and y axis (m) λ̄(·), λ(·) = largest and smallest eigenvalues ∥ · ∥ = Euclidean norm (vectors) or induced spectral norm (matrices) u(t) = control input ν(t) = virtual control input IR, IR+ = field of real numbers and the set of strictly positive real numbers s = Laplace variable Subscript lat, long = lateral and longitudinal axis