Methods, systems, and computer program products for calculating a torque overlay command in a steering control system
A method, system, and computer program product for calculating a torque overlay command in a steering control system is provided. The method includes receiving a current hand wheel angle, receiving a change in vehicle yaw moment command, and calculating a lateral force in response to the change in vehicle yaw moment command. The method also includes determining a new tire side slip angle from the lateral force and calculating a commanded hand wheel angle from the new tire side slip angle. The method further includes calculating an error signal as a difference between the commanded hand wheel angle and the current hand wheel angle, and generating a torque overlay command from the error signal.
1. A system for calculating a torque overlay command in a steering control system, the system comprising:
a hand wheel angle sensor;
a yaw rate sensor;
a control system, the control system performing:
receiving a current hand wheel angle from the hand wheel angle sensor;
determining a change in vehicle yaw moment command;
calculating a lateral force in response to the change in vehicle yaw moment command;
determining a new tire side slip angle from the lateral force;
calculating a commanded hand wheel angle from the new tire side slip angle;
calculating an error signal as a difference between the commanded hand wheel angle and the current hand wheel angle;
generating the torque overlay command from the error signal;
calculating a vehicle slip angle; and
calculating a commanded road wheel angle, comprising:
summing the new tire side slip angle and the vehicle slip angle; and
converting the commanded road wheel angle into a commanded hand wheel angle.
2. The system of 1 , wherein the system further comprises:
a vehicle speed sensor; and
calculating a commanded road wheel angle further comprises:
calculating an offset value as a product of a distance between a steering axle and a center of gravity of the vehicle times a yaw rate of the vehicle;
dividing the offset value by a longitudinal velocity of the vehicle; and
adding the offset value to the summation of the new tire side slip angle and the vehicle slip angle.
3. A system for calculating a torque overlay command in a steering control system, the system comprising:
a hand wheel angle sensor;
a yaw rate sensor;
a control system, the control system performing:
receiving a current hand wheel angle from the hand wheel angle sensor;
determining a change in vehicle yaw moment command;
calculating a lateral force in response to the change in vehicle yaw moment command;
determining a new tire side slip angle from the lateral force;
calculating a commanded hand wheel angle from the new tire side slip angle;
calculating an error signal as a difference between the commanded hand wheel angle and the current hand wheel angle;
generating the torque overlay command from the error signal;
providing a steering actuator; and
adding the torque overlay command to the steering actuator output.
4. The system of claim 3 , wherein the change in vehicle yaw moment command is generated as a function of the current hand wheel angle, vehicle speed, yaw rate, and lateral acceleration.