System for controlling a steering wheel feel of a vehicle steering wheel assembly

#The present invention relates to a system and method of controlling a steering wheel of a vehicle steering wheel assembly for simulated steering feel in a steer-by-wire system.

#Steer-by-wire systems are known and continue to be improved. Steer-by-wire systems replace some mechanical linkages between the steering wheel and the vehicle road wheels with electrical wires and electronic components which send electrical signals through the wires to link the steering wheel to the road wheels of the vehicle. In order to provide a realistic feel to a steer-by-wire system, mechanisms are placed along and adjacent a steering wheel and steering shaft of the vehicle to generate resistive torque on the steering wheel. This simulates for the driver a realistic feel to the vehicle steering wheel as though the driver was driving a vehicle having a conventional mechanical steering assembly.

#Although current systems and methods of providing simulated steering feel are adequate, improvements can be made thereto. When a driver of a vehicle having conventional mechanical steering gears, e.g., rack-and-pinion or recirculating ball, rotates the steering wheel to turn the vehicle in a corresponding direction, the driver experiences resistive torque especially if the steering gear assembly is without power steering. Moreover, after the turn is made, the driver typically releases torque in the direction of the turn and allows the steering gear to rotate the steering wheel back toward a center position of the vehicle. In this situation, the driver typically maintains hand position over the steering wheel, but allows the steering wheel to freely turn back toward the center position.

#FIG. 1 is a schematic diagram of a steering wheel control assembly having a steer-by-wire system with a torque control mode and a return center control mode in accordance with the present invention;

#FIG. 2 is a control logic diagram of the steer-by-wire system for the steering wheel control assembly of FIG. 1;

#FIG. 3 is a flow chart illustrating one method of the steer-by-wire system in accordance with one method of the present invention; and

#FIG. 1 illustrates a steering wheel feel control assembly 10 of a vehicle having a steer-by-wire control system for simulating a steering feel on a steering wheel 13. As shown, steering wheel 13 is attached to a steering shaft 16. A sensor 20 is mounted to steering wheel 13 for sensing actual torsion and actual angular velocity of the steering wheel during normal operation of the vehicle. A controller 23 is in electrical communication with sensor 20 for receiving torque signals and velocity signals from sensor 20. An actual or input torque and actual angular velocity is applied to the steering wheel 13 by a driver during normal operation of the vehicle. As controller 23 receives angular velocity signals and torque signals from the sensor 20, controller 23 determines velocity error and torque error. Controller 23 also compares each of the errors to threshold values (as will be described in greater detail below). Controller 23 is further configured to switch between a torque control and a return to center control modes based on the actual angular velocity and the actual torsion on the steering wheel.

#In the torque control mode, the system generates a simulated steering feel torque on the steering wheel to simulate hydraulic friction as the driver inputs torque on the steering wheel or rotates the steering wheel. In the return center control mode, the system returns the steering wheel to a center position at a specified angular velocity as the driver releases the steering wheel after a vehicle turn.

#As shown in FIG. 1, an actuator 26 is in electrical communication with controller 23. Actuator 26 receives control signals indicative of velocity and torque errors from the controller 23 and applies a torque to the shaft to simulate a “traditional steering feel” based on the actual angular velocity and the actual torsion on the steering wheel.