Steer-by-wire systems and methods of operating thereof in vehicles
Described herein are steer-by-wire systems and methods of operating these systems in vehicles. A steer-by-wire system comprises a steering wheel assembly, comprising a steering wheel, sensors, and a torque generator. The system comprises a rack assembly, comprising a steering rack, sensors, and a rack actuator. The steering wheel assembly and the rack assembly are communicatively coupled by a steer-by-wire system controller, without having any direct mechanical links between the assemblies. In some examples, the controller instructs the rack assembly to control the steering rack position based on the steering input, such as changes in the steering wheel position. A steering map is used to determine the desired steering rack position based on the current steering wheel position. In some examples, a steering map is selected from a steering map set based on, e.g., the vehicle speed, vehicle direction, driver preference, and the like.
1. A method of determining a steering wheel position in a steer-by-wire system of a vehicle, the method comprising:
rotating a steering wheel in a first direction while monitoring steering wheel actuator torque, wherein the steering wheel is rotated in the first direction until the steering wheel actuator torque reaches or exceeds an actuator-side torque threshold;
registering a first temporary steering wheel position at which the steering wheel actuator torque reaches or exceeds the actuator-side torque threshold while rotating the steering wheel in the first direction;
rotating the steering wheel in a second direction opposite the first direction while monitoring the steering wheel actuator torque, wherein the steering wheel is rotated in the second direction until the steering wheel actuator torque reaches or exceeds the actuator-side torque threshold;
registering a second temporary steering wheel position at which the steering wheel actuator torque reaches or exceeds the actuator-side torque threshold while rotating the steering wheel in the second direction;
determining a temporary steering wheel position range between the first temporary steering wheel position and the second temporary steering wheel position; and
assigning the second temporary steering wheel position as the steering wheel position when the temporary steering wheel position range is within a calibrated threshold of an absolute steering wheel rotation range.
2. The method of claim 1 , further comprising rotating the steering wheel until the steering wheel position corresponds to a steering rack position of a steering rack of the vehicle.
3. The method of claim 2 , wherein the steering wheel position corresponding to the steering rack position is determined using a steering map.
4. The method of claim 1 , wherein a steering rack of the vehicle remains stationary while rotating the steering wheel in the first direction and also while rotating the steering wheel in the second direction.
5. The method of claim 1 , wherein the steering wheel is rotated in the first direction and in the second direction using a steering wheel torque generator.
6. The method of claim 5 , wherein monitoring the steering wheel actuator torque while the steering wheel is rotated in the first direction and in the second direction is performed using the steering wheel torque generator.
7. The method of claim 6 , wherein monitoring the steering wheel actuator torque comprises monitoring an electrical power drawn by the steering wheel torque generator.
8. The method of claim 1 , wherein monitoring the steering wheel actuator torque while the steering wheel is rotated in the first direction and in the second direction is performed in combination with an output from a steering wheel sensor.
9. The method of claim 1 , further comprising, before rotating the steering wheel in the first direction:
determining that the steering wheel position is not available; and
when the steering wheel position is not available, sending a steering system calibration request to a vehicle network and receiving confirmation from the vehicle network to proceed with determining the steering wheel position.
10. The method of claim 9 , wherein determining that the steering wheel position is not available comprises checking a steering wheel controller of the vehicle for availability of a steering wheel calibrated reference.
11. The method of claim 9 , further comprising immobilizing the vehicle in accordance with the steering system calibration request to the vehicle network.
12. The method of claim 9 , further comprising, after assigning the second temporary steering wheel position as the steering wheel position, sending a calibration request completion update to the vehicle network.
13. The method of claim 1 , wherein:
the first temporary steering wheel position corresponds to one of multiple absolute steering wheel limits, and
the second temporary steering wheel position corresponds to another one of the multiple absolute steering wheel limits.
14. The method of claim 1 , further comprising:
monitoring driver torque while rotating the steering wheel in the first direction and also while rotating the steering wheel in the second direction; and
when the driver torque exceeds a driver-torque threshold, warning adriver and stopping rotation of the steering wheel.
15. The method of claim 1 , further comprising, before rotating the steering wheel in the first direction, warning a driver about upcoming rotations of the steering wheel.
16. The method of claim 1 , further comprising warning a driver to remove obstacles from the steering wheel when the temporary steering wheel position range is less than the absolute steering wheel rotation range.
17. The method of claim 16 , further comprising, after warning the driver to remove the obstacles from the steering wheel:
waiting for a predetermined period or a confirmation from the driver; and
repeating the steps of rotating the steering wheel in the first direction, registering the first temporary steering wheel position, rotating the steering wheel in the second direction, registering the second temporary steering wheel position, determining the temporary steering wheel position range, and assigning the second temporary steering wheel position as the steering wheel position when the temporary steering wheel position range is equal to the absolute steering wheel rotation range.
18. The method of claim 1 , wherein the absolute steering wheel rotation range is within a calibrated threshold of a range between steering wheel absolute limits.
19. The method of claim 1 , wherein the first temporary steering wheel position and the second temporary steering wheel position are registered by a steering wheel sensor and transmitted to a steering feel actuator module controller.
20. The method of claim 1 , wherein rotating the steering wheel in the first direction and rotating the steering wheel in the second direction are performed while the vehicle is immobilized.