US 12,275,466 B2
Providing assist torque in steering systems operating without a torque sensor
Tejas M. Varunjikar, Troy, MI (US); Anthony J. Champagne, Saginaw, MI (US); Michael S. Wyciechowski, Grand Blanc, MI (US); and Rangarajan Ramanujam, Saginaw, MI (US)
Assigned to Steering Solutions IP Holding Corporation, Saginaw, MI (US)
Filed by STEERING SOLUTIONS IP HOLDING CORPORATION, Saginaw, MI (US)
Filed on Apr. 19, 2019, as Appl. No. 16/389,222.
Prior Publication US 2020/0331520 A1, Oct. 22, 2020
Int. Cl. B62D 5/04 (2006.01); B60W 40/103 (2012.01); B60W 50/00 (2006.01); B62D 6/00 (2006.01); G07C 5/08 (2006.01)
CPC B62D 5/0463 (2013.01) [B60W 40/103 (2013.01); B60W 50/00 (2013.01); B62D 5/049 (2013.01); B62D 6/00 (2013.01); G07C 5/0808 (2013.01); B60W 2050/0031 (2013.01); B60W 2510/20 (2013.01); B60W 2520/10 (2013.01); B60W 2520/12 (2013.01); B60W 2520/14 (2013.01); B60W 2552/40 (2020.02)] 14 Claims
OG exemplary drawing
 
1. A method of controlling an electric power steering system, the method comprising:
determining that one or more hand wheel torque sensors of an electric power steering system are not operational;
in response, generating an assist torque command, the generating comprises:
estimating, using a bicycle model modified using a nonlinear tire model, a front slip angle based on a motor angle of a motor of the electric power steering system and a vehicle speed, wherein the bicycle model includes a dynamic bicycle model and wherein the nonlinear tire model is a function of surface friction, tire lateral force, a cornering stiffness parameter, and an inverse of a maximum lateral tire force, wherein the inverse of the maximum lateral tire force is determined based on a product of the surface friction and a vehicle load of at least one axle associated with the electric power steering system;
computing, using the bicycle model modified using the nonlinear tire model, a front axle lateral force using the front slip angle;
converting the front axle lateral force to the rack force using a product of the front axle lateral force and a pneumatic trail value associated with a pneumatic trail model comprising one of an empirical model and an equation-based model;
determining an amount of assist torque based on the rack force;
determining an estimated lateral acceleration based on the motor angle and the vehicle speed;
determining a lateral acceleration error based on the estimated lateral acceleration and a measured lateral acceleration;
in response to the lateral acceleration error exceeding a first threshold, setting the assist torque to 0; and
in response to the lateral acceleration error exceeding a second threshold;
estimating a yaw rate using the bicycle model modified using the nonlinear tire model;
receiving a measured yaw rate;
determining a yaw rate error based on a difference between the estimated yaw rate and the measured yaw rate; and
scaling down the assist torque based at least on the yaw rate error and the lateral acceleration error; and
controlling the electric power steering system using the generated assist torque command.