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 vehicle comprising:
a steering wheel assembly comprising a steering wheel;
a steering rack assembly comprising a steering rack and a rack actuator configured to change a position of the steering rack, wherein the vehicle lacks a direct mechanical link between the steering wheel assembly and the steering rack assembly;
redundant control paths electrically coupling the steering wheel assembly and the steering rack assembly;
a steering wheel controller comprising first and second steering wheel electronic control units (ECUs) and a steering wheel internal-communication bus (ICB) coupling the first and second steering wheel ECUs, each redundant control path associated with a different one of the first and second steering wheel ECUs; and
a steering rack controller comprising first and second steering rack ECUs and a steering rack ICB coupling the first and second steering rack ECUs, each redundant control path associated with a different one of the first and second steering rack ECUs.
2 . The vehicle of claim 1 , wherein the redundant control paths are configured to enable continuous control of the rack actuator based on the steering wheel such that the same rack actuator is controlled regardless of which control path or control paths are used to provide the continuous control of the rack actuator.
3 . The vehicle of claim 2 , wherein the redundant control paths comprise:
a first communication link communicatively coupling the first steering wheel ECU and the first steering rack ECU; and
a second communication link communicatively coupling the second steering wheel ECU and the second steering rack ECU.
4 . The vehicle of claim 3 , wherein:
the first and second steering wheel ECUs are further configured to communicate with each other over the first and second communication links; and
the first and second steering rack ECUs are further configured to communicate with each other over the first and second communication links.
5 . The vehicle of claim 4 , further comprising:
a first steering wheel position sensor communicatively coupled to the first steering wheel ECU;
a first steering wheel torque sensor communicatively coupled to the first steering wheel ECU;
a second steering wheel position sensor communicatively coupled to the second steering wheel ECU; and
a second steering wheel torque sensor communicatively coupled to the second steering wheel ECU.
6 . The vehicle of claim 5 , wherein:
the first steering wheel ECU is configured to communicate with the second steering rack ECU using the first communication link, the first steering rack ECU, and the steering rack ICB; and
the second steering wheel ECU is configured to communicate with the first steering rack ECU using the second communication link, the second steering rack ECU, and the steering wheel ICB.
7 . The vehicle of claim 6 , wherein:
the first steering wheel ECU and the steering wheel ICB are configured to provide measurement data from the first steering wheel position sensor or the first steering wheel torque sensor to the second steering wheel ECU; and
the second steering wheel ECU and the steering rack ICB are configured to provide measurement data from the second steering wheel position sensor or the second steering wheel torque sensor to the first steering wheel ECU.
8 . The vehicle of claim 7 , wherein the redundant control paths are configured to:
switch between using different ones of the first and second steering wheel ECUs and switch between using different ones of the first and second steering rack ECUs without switching between using different ones of the first and second communication links; and
switch between using different ones of the first and second communication links without switching between using different ones of the first and second steering wheel ECUs and without switching between using different ones of the first and second steering rack ECUs.
9 . The vehicle of claim 8 , wherein at least one of the first and second steering wheel ECUs or the first and second steering rack ECUs is configured to obtain data over one of the first and second communication links when that data is missing or unreliable on another of the first and second communication links without requiring an ECU switch and without requiring a communication link switch for other data communications.
10 . A method comprising:
operating redundant control paths electrically coupling a steering wheel assembly of a vehicle and a steering rack assembly of the vehicle, the steering wheel assembly comprising a steering wheel, the steering rack assembly comprising a steering rack and a rack actuator, the vehicle lacking a direct mechanical link between the steering wheel assembly and the steering rack assembly,
wherein the redundant control paths comprise:
a steering wheel controller comprising first and second steering wheel electronic control units (ECUs) and a steering wheel internal-communication bus (ICB) coupling the first and second steering wheel ECUs, each redundant control path associated with a different one of the first and second steering wheel ECUs; and
a steering rack controller comprising first and second steering rack ECUs and a steering rack ICB coupling the first and second steering rack ECUs, each redundant control path associated with a different one of the first and second steering rack ECUs; and
changing a position of the steering rack using the rack actuator.
11 . The method of claim 10 , further comprising:
enabling continuous control of the rack actuator based on the steering wheel using the redundant control paths such that the same rack actuator is controlled regardless of which control path or control paths are used to provide the continuous control of the rack actuator.
12 . The method of claim 11 , wherein the redundant control paths comprise:
a first communication link communicatively coupling the first steering wheel ECU and the first steering rack ECU; and
a second communication link communicatively coupling the second steering wheel ECU and the second steering rack ECU.
13 . The method of claim 12 , wherein:
the first and second steering wheel ECUs are further configured to communicate with each other over the first and second communication links; and
the first and second steering rack ECUs are further configured to communicate with each other over the first and second communication links.
14 . The method of claim 13 , further comprising:
operating a first steering wheel position sensor communicatively coupled to the first steering wheel ECU;
operating a first steering wheel torque sensor communicatively coupled to the first steering wheel ECU;
operating a second steering wheel position sensor communicatively coupled to the second steering wheel ECU; and
operating a second steering wheel torque sensor communicatively coupled to the second steering wheel ECU.
15 . The method of claim 14 , wherein:
the first steering wheel ECU is configured to communicate with the second steering rack ECU using the first communication link, the first steering rack ECU, and the steering rack ICB; and
the second steering wheel ECU is configured to communicate with the first steering rack ECU using the second communication link, the second steering rack ECU, and the steering wheel ICB.
16 . The method of claim 15 , wherein:
the first steering wheel ECU and the steering wheel ICB are configured to provide measurement data from the first steering wheel position sensor or the first steering wheel torque sensor to the second steering wheel ECU; and
the second steering wheel ECU and the steering rack ICB are configured to provide measurement data from the second steering wheel position sensor or the second steering wheel torque sensor to the first steering wheel ECU.
17 . The method of claim 16 , wherein the redundant control paths are configured to:
switch between using different ones of the first and second steering wheel ECUs and switch between using different ones of the first and second steering rack ECUs without switching between using different ones of the first and second communication links; and
switch between using different ones of the first and second communication links without switching between using different ones of the first and second steering wheel ECUs and without switching between using different ones of the first and second steering rack ECUs.
18 . The method of claim 17 , wherein at least one of the first and second steering wheel ECUs or the first and second steering rack ECUs is configured to obtain data over one of the first and second communication links when that data is missing or unreliable on another of the communication links without requiring an ECU switch and without requiring a communication link switch for other data communications.