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EP-4739567-A1 - A STEER-BY-WIRE STEERING ASSEMBLY

EP4739567A1EP 4739567 A1EP4739567 A1EP 4739567A1EP-4739567-A1

Abstract

A steer-by-wire assembly includes a motor assembly with at least one motor mounted in a housing, and a screw actuator configured to engage with a threaded portion of a steering shaft and move the steering shaft along a longitudinal axis. It also includes a rotor carrier sleeve operatively coupled between the at least one motor and the screw actuator, configured to rotate about the longitudinal axis, and a sensor assembly comprising a sensor portion and a target portion configured to detect relative movement of the steering shaft with respect to the housing. One of the sensor portion and the target portion are mounted in a sensor housing fixed with respect to the steering shaft. The housing comprises a sensor channel for receiving the sensor housing and constrain the movement of the sensor housing and the steering shaft in a direction parallel to the longitudinal axis.

Inventors

  • MATHEWS, CHRISTIAN
  • ROJAS, Danilo
  • TÄHKÄNEN, Thomas
  • JIDETOFT, Kristoffer
  • NILSSON, PER
  • LI, THOMAS

Assignees

  • Chassis Autonomy SBA AB

Dates

Publication Date
20260513
Application Date
20241004

Claims (17)

  1. 1 . A steer-by-wire steering assembly (100) comprising: a housing (102); a motor assembly (206) comprising at least one motor (208) mounted in the housing (102); a screw actuator (232) configured to engage with a threaded portion (234) of a steering shaft (118) and move the steering shaft (118) along a longitudinal axis (104) when the screw actuator (232) rotates; a rotor carrier sleeve (216) operatively coupled between the at least one motor (208) and the screw actuator (232) and configured to rotate about the longitudinal axis (104); a sensor assembly (238) comprising a sensor portion (244) and a target portion (246) configured to detect relative movement of the steering shaft (118) with respect to the housing (102); wherein one of the sensor portion (244) and the target portion (246) are mounted in a sensor housing (316) fixed with respect to the steering shaft (118); and the housing (102) comprises a sensor channel (302) configured to receive the sensor housing (316) and constrain the movement of a sensor housing (316) and the steering shaft (118) in a direction parallel to the longitudinal axis (104).
  2. 2. The steer-by-wire steering assembly (100) according to claim 1 , wherein the sensor assembly (238) is a linear displacement sensor assembly (238).
  3. 3. The steer-by-wire steering assembly (100) according to claim 1 or 2, wherein the sensor housing (316) is configured to slide within the sensor channel (302).
  4. 4. The steer-by-wire steering assembly (100) according to any one of claims 1 to 3, wherein the sensor channel (302) is located within a housing sleeve portion (300) of the housing (102).
  5. 5. The steer-by-wire steering assembly (100) according to claim 4, further comprising a mounting assembly (306) fixed to the housing sleeve portion (300) and comprising at least one elongate rail (308) defining the sensor channel (302).
  6. 6. The steer-by-wire steering assembly (100) according to claim 5, wherein the mounting assembly (306) further comprises fasteners (310) configured to clamp the at least one elongate rails (308) to an inner surface of the housing sleeve portion (300).
  7. 7. The steer-by-wire steering assembly (100) according to any one of claims 1 to 6, wherein the sensor housing (316) comprises a shaft engagement sleeve (320) configured to mount around the steering shaft (118).
  8. 8. The steer-by-wire steering assembly (100) according to claim 7, wherein the shaft engagement sleeve (320) comprises a central bore (322) configured to receive the steering shaft (118).
  9. 9. The steer-by-wire steering assembly (100) according to any one of claims 1 to 8, wherein the sensor housing (316) comprises a first housing engagement surface (318) and a second housing engagement surface (326) configured to engage respectively with first channel and second channel engagement surfaces (304, 324) of the sensor channel (302).
  10. 10. The steer-by-wire steering assembly (100) according to claim 9, wherein the sensor channel (302) comprises a first channel engagement surface (304) configured to engage the first housing engagement surface (318) when the screw actuator (232) rotates in a first direction, and the second channel engagement surface (324) is configured to engage the second housing engagement surface (326) when the screw actuator (232) rotates in a second direction.
  11. 11. The steer-by-wire steering assembly (100) according to any one of claims 1 to 10, wherein the sensor housing (316) is mounted on the steering shaft (118) using a set screw, press fit, or welding.
  12. 12. The steer-by-wire steering assembly (100) according to any one of claims 1 to 11 , further comprising a second sensor assembly (500) comprising a second sensor portion (244b) and a second target portion (246a) configured to detect relative movement of the steering shaft (118) with respect to the housing (102).
  13. 13. The steer-by-wire steering assembly (100) according to claim 12, wherein the second sensor assembly (500)) is a linear displacement sensor assembly (238).
  14. 14. The steer-by-wire steering assembly (100) according to claim 12 or 13, wherein one of the second sensor portion (244b) and the second target portion (246b) are mounted in a second sensor housing (502) fixed with respect to the steering shaft (118).
  15. 15. The steer-by-wire steering assembly (100) according to claim 14, wherein the second sensor housing (502) is configured to slide within a second sensor channel (302) in the housing (102).
  16. 16. The steer-by-wire steering assembly (100) according to any one of claims 12 to 15, wherein the first and second sensor assemblies (238,500) are mounted at different positions on the steering shaft (118).
  17. 17. The steer-by-wire steering assembly (100) according to any one of claims 1 to 16, wherein the motor assembly (206) comprises a first motor (208) and a second motor (210), and the rotor carrier sleeve (216) is operatively coupled between the first motor (208), the second motor (210), and the screw actuator (232).

Description

A steer-by-wire steering assembly Field The technology relates to the field of automotive engineering, specifically to steering systems for vehicles. In particular, it focuses on steer-by-wire systems, which are electronic systems that replace traditional mechanical linkages between the steering wheel and the vehicle's wheels with electronic components and sensors. The automotive industry has been continuously developing technology to assist users with various driving operations in vehicles, including steering. Powered steering systems have been introduced to assist drivers or even control the steering for them. As automotive technology advances, there is a growing trend towards fully automating vehicles, eliminating the need for user input. One critical aspect of autonomous vehicular control is autonomous steering, which typically requires steer-by-wire steering systems that can be controlled by control signals from a vehicle control unit. A steer-by-wire system does not necessarily require a mechanical linkage between a user input, such as a steering wheel, and the steering linkage, such as a rack and pinion steering assembly. In some steer-by-wire implementations, no user input is needed because the system is fully controlled by an autonomous vehicle control unit. However, in the absence of user input, the vehicular systems of the autonomous vehicle need to be robust for the vehicle to be reliable. This may mean that the steer- by-wire systems have multiple redundancies to meet industrial safety standards, such as Automotive Safety Integrity Level (ASIL) C or D ISO 26262. One such steer-by-wire system is shown in EP 3 819 190, which discloses a steer-by- wire actuation system with two steering motors and two electrical control units controlling the steering motors for controlling the rotation of the two steering motors. The two steering motors are connected to a ball screw, which interacts with a cooperating ball screw nut mounted on a shaft. A problem with the current steer-by-wire systems is that the steering shaft can rotate together with the ball screw, which means that the steering shaft may not always move linearly. The steering shaft must be prevented from rotating to ensure proper linear movement and steering control. Furthermore, the steering assembly must have a compact form to be easily incorporated into new vehicle form factors, which may have limited space for components. Another problem with existing steer-by-wire systems for autonomous vehicles is that they are prototypes and have a large volume. This means that they are unsuitable for use in an industrialised manufacturing process for assembling autonomous vehicles with small form factors because the prototype steer-by-wire systems take up too much space. Additionally, existing steer-by-wire systems often involve complex mechanical components, such as ball screws and cooperating ball screw nuts, which can be bulky and contribute to the large volume of the system, making it unsuitable for industrialised manufacturing processes. Furthermore, the layout and packaging of existing steer-by- wire systems may not be optimised for space efficiency, resulting in a larger overall volume and making it difficult to integrate the system into autonomous vehicles with small form factors. A steer-by-wire assembly typically comprises two motors, each with a stator and a common rotor. The rotor is coupled to a ball screw (screw actuator) which engages a threaded portion of the steering shaft. The steering shaft moves linearly along the steering shaft axis when one or both of the motors rotate. However, a problem with such systems is that the alignment of the electrical connections to the motors can be difficult. Additionally, long wires between the motors and the controller can receive and generate interference signals, which can negatively impact the performance and reliability of the system. The prior art steer-by-wire systems, such as the one disclosed in EP 3 819 190, use wires to connect the motors to the controller. This can cause issues with electrical interference and vibrations damaging the wires. Furthermore, the alignment and assembly of the electrical connections can be challenging and time-consuming, leading to difficulties in the installation and maintenance process. In known systems the position of the steering shaft may be detected with a linear sensor. A problem with existing linear sensors is that the length of the linear sensor is quite long with respect to the actuator. This is because the linear sensor has to be the length of the full stroke (full wheel lock to full wheel lock) of the steering shaft. This increases the size of the actuator because the linear sensor needs to be mounted in protective housing. In order to ensure the reliability and safety of steer-by-wire systems, redundancy is often incorporated into the design. One common approach to achieving redundancy is to use multiple motors to actuate the steering actuator. In