Integrated control of brake and steer by wire system using optimal control allocation methods

A method of selectively inhibiting wheel rotation and lateral displacement of a vehicle during brake or steer failure, the vehicle having axles, tires coupled to the axles, a brake system including a brake pedal to control brake actuators to brake the tires, and a steer system coupled to the axles including a steering wheel to control steering actuators, comprising:

• determining desired values of state variables describing the vehicle motion in a yaw plane using driver steering and brake inputs;
• determining tire normal forces of the vehicle;
• determining values of tire and axle cornering stiffness;
• calculating a vehicle system matrix function;
• calculating a control influence matrix;
• calculating a corrective term;
• sensing a non-operating actuator;
• determining actuator limits for each actuator including setting upper and lower position limits of the non-operating actuator to the failure position;
• performing dynamic inversion by subtracting the vehicle system matrix function and the corrective term from the determined desired values of state variables to determine a solution at a particular time;
• using the determined solution to find a vector of control inputs such that the control influence matrix times the vector of control inputs is equal to the determined solution of the dynamic inversion step;
• and
• controlling the speed and direction of the vehicle by optimally controlling the remaining operating actuators using the vector of control inputs.