Steer-by-wire steering system

Abstract

This invention provides a steer-by-wire steering system that ensures redundancy while reducing the overall size, weight, and cost of the system, enabling more effective use of limited in-vehicle space. [Solution] The system includes two rack position sensors 21 that detect the position of a rack that controls the steering angle of the steering wheels, two RWAs 22 that operate the rack based on the output of the rack position sensors 21, and one HWA 12 that is electrically connected to the RWAs 22 and applies an operating reaction force to the steering wheel that steers the vehicle. The output signal of one rack position sensor 21A is input to one RWA 22A via the HWA 12, and the output signal of the other rack position sensor 21B is directly input to the other RWA 22B.

Description

Technical Field

[0001] The present invention relates to a steer-by-wire steering system that steers a steering wheel while the steering wheel and the steering wheel are mechanically disconnected from each other.

Background Art

[0002] In a steer-by-wire steering system, redundancy has been conventionally provided in case a component of the system fails. For example, in the steer-by-wire steering system disclosed in Patent Document 1, two systems are provided for each of the steering side (steering angle sensor (SAS), hand wheel actuator (HWA)) and the steering side (road wheel actuator (RWA), rack position sensor (RPS)) to ensure redundancy.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, the configuration of the steering system proposed in Patent Document 1 ensures redundancy by providing two systems for the steering side and the steering side, so there is a problem of increasing the size, weight, and cost of the entire system.

[0005] The present invention has been made in view of the above points, and an object thereof is to provide a steer-by-wire steering system that can achieve miniaturization and weight reduction of the entire system, cost reduction, and more effective utilization of limited vehicle interior space while ensuring redundancy. Furthermore, this will enable the use of the freed-up space to improve safety, ultimately contributing to further improvements in traffic safety and the development of a sustainable transportation system. [Means for solving the problem]

[0006] To achieve the above objective, the steer-by-wire steering system according to the present invention comprises two rack position sensors for detecting the position of a rack that controls the steering angle of the steering wheels, two RWAs that operate the rack based on the output of the rack position sensors, and one HWA that is electrically connected to the RWAs and applies an operating reaction force to the steering wheel used to steer the vehicle, wherein the output signal of one of the rack position sensors is input to one of the RWAs via the HWA, and the output signal of the other rack position sensor is directly input to the other RWA. [Effects of the Invention]

[0007] The present invention aims to provide a steer-by-wire steering system that ensures redundancy while reducing the overall size, weight, and cost of the system, thereby enabling more effective use of the limited interior space of a vehicle. Furthermore, this will enable the use of the freed-up space to improve safety, ultimately contributing to further improvements in traffic safety and the development of a sustainable transportation system. [Brief explanation of the drawing]

[0008] [Figure 1] This diagram shows the configuration of the steer-by-wire steering system of this embodiment under normal conditions. [Figure 2] This block diagram shows the operation of the first system of the steer-by-wire steering system of this embodiment under normal conditions. [Figure 3] This block diagram shows the operation of the second system of the steer-by-wire steering system in this embodiment under normal conditions. [Figure 4] This diagram shows the configuration of the steer-by-wire steering system in this embodiment in the event of a malfunction. [Figure 5] This block diagram shows the operation of the first system in the event of a failure in the steer-by-wire steering system of this embodiment. [Figure 6] This block diagram shows the operation of the second system in the event of a failure in the steer-by-wire steering system of this embodiment. [Modes for carrying out the invention]

[0009] The steer-by-wire steering system S (hereinafter referred to as the steering system) of this embodiment of the present invention will be described in detail with reference to Figure 1-6. In the explanations, identical elements will be given the same symbols, and redundant explanations will be omitted.

[0010] The steering system S of this embodiment is positioned on a vehicle (not shown) in which the front wheels (not shown) are set to be steering wheels (see Figure 1-3). The steering system S steers the front wheels while the steering wheel (not shown), operated by the driver, is mechanically disconnected from the front wheels. The steering system S includes a steering mechanism 1 and a steering mechanism 2. In this embodiment, the steering system S is a steer-by-wire type, so the steering mechanism 1 and the steering control mechanism 2 are mechanically separated but electrically connected.

[0011] The steering mechanism 1 is configured to calculate and determine the steering angle of the front wheels according to the angle of steering wheel operation by the driver (see Figure 1-3). The steering mechanism 1 includes a steering angle sensor 11 and a handwheel actuator 12 (hereinafter referred to as HWA: Hand wheel actuator). The steering angle sensor 11 detects the angle at which the steering wheel is operated (operation angle) and outputs it as an electrical signal (steering signal).

[0012] HWA12 calculates the angle (steering angle) by which the front wheels are steered from the input steering signal via the RWA22 described later, and outputs it as an electrical signal (steering command signal) to the RWA22 described later. In addition, HWA12 calculates an operating reaction force simulating the steering reaction force during steering from the calculated steering angle, and applies the calculated operating reaction force to the steering wheel. Note that one HWA12 is arranged in the present steering system S. And HWA12 includes a sensor IF13, a steering angle calculation unit 14, a target reaction force calculation unit 15, and a torque control unit 16.

[0013] The sensor IF13 (IF: interface) is a part that receives the output signal (rack position signal) of the rack position sensor 21 described later and transmits the received rack position signal to the RWA22. The steering angle calculation unit 14 is a part that calculates the steering angle from the steering signal of the steering angle sensor 11. The target reaction force calculation unit 15 is a part that calculates the operating reaction force from the calculated steering angle. The torque control unit 16 is a part that applies the calculated operating reaction force to the steering handle.

[0014] The steering mechanism 2 includes a rack (not shown), a rack position sensor 21 (Rack position sensor), and a road wheel actuator 22 (hereinafter, RWA: Road wheel actuator) (see FIGS. 1-3). The rack is mechanically linked to the front wheels, and the front wheels are steered by operating the rack. The rack position sensor 21 detects the position of the rack in the vehicle width direction (hereinafter referred to as the "rack position") and outputs it as an electrical signal (rack position signal) to the RWA22. Based on the rack position signal and the steering command signal, RWA determines the movement amount of the rack, the movement speed of the rack, and the steering angle of the front wheels, and controls the rack based on the calculation results. RWA22 includes a sensor IF23, a rack position calculation unit 24, a target rack position calculation unit 25, and a rack position control unit 26.

[0015] The sensor IF23 is a part that receives the steering signal output from the steering angle sensor 11 and transmits the received steering signal to the HWA12. The rack position calculation unit 24 is a part that calculates the current (before steering) position of the rack from the rack position signal output from the rack position sensor 21. The target rack position calculation unit 25 is a part that calculates the movement amount of the rack and the position after movement from the steering angle calculated by the steering angle calculation unit 14. The rack position control unit 26 is a part that moves the rack to a predetermined position based on the calculated current position and movement amount of the rack, and steers the front wheels.

[0016] Note that two steering angle sensors 11, two rack position sensors 21, and two RWAs 22 are arranged in the steering system S for redundancy (see Fig. 1-3). Therefore, regarding the two steering angle sensors 11, one steering angle sensor ① is referred to as the first steering angle sensor 11A, and the other steering angle sensor 11 is referred to as the second steering angle sensor 11B, and the description will continue.

[0017] Also, regarding the two rack position sensors 21, one rack position sensor 21 is referred to as the first rack position sensor 21A, and the other rack position sensor 21 is referred to as the second rack position sensor 21B, and the description will continue. Furthermore, regarding the two RWAs 22, one RWA 22 is referred to as the first RWA 22A, and the other RWA 22 is referred to as the second RWA 22B, and the description will continue. The first RWA 22A and the second RWA 22B are electrically connected. When both the first RWA 22A and the second RWA 22B are functioning properly, either one (for example, the first RWA 22A) is prioritized to operate the rack.

[0018] And the system composed of the first steering angle sensor 11A, the first rack position sensor 21A, the first RWA 22A, and the HWA12 is referred to as the first system SA. Furthermore, the system consisting of the second steering angle sensor 11B, the second rack position sensor 21B, the second RWA 22B, and HWA 12 is referred to as the second system SB. Note that HWA12 is common to both the first system SA and the second system SB. HWA12 is connected to the first RWA22A and the second RWA22B respectively via communication methods such as CAN (Controller Area Network) and CAN FD (CAN with Flexible Data rate).

[0019] The first steering angle sensor 11A is connected to the first RWA 22A via a communication means such as SENT (Single Edge Nibble Transmission), and the second steering angle sensor 11B is connected to the second RWA 22B via a communication means such as SENT. The steering signal from the first steering angle sensor 11A is input to the HWA12 via the sensor IF23 of the first RWA22A, and the steering signal from the second steering angle sensor 11B is input to the HWA12 via the sensor IF23 of the second RWA22B. Furthermore, the power supply for the first steering angle sensor 11A is supplied from the first RWA22A, and the power supply for the second steering angle sensor 11B is supplied from the second RWA22B.

[0020] The first rack position sensor 21A is connected to HWA12 via a communication means such as SENT, and the second rudder angle sensor 11B is connected to the second RWA22B via a communication means such as SENT. The rack position signal from the first rack position sensor 21A is then input to the first RWA22A via the sensor IF13 of the HWA12. Furthermore, the power supply for the first rack position sensor 21A is supplied from HWA12. In response, the rack position signal from the second rack position sensor 21B is input to the second RWA 22B. Furthermore, the power supply for the second rudder angle sensor 11B is supplied from the second RWA 22B.

[0021] Next, the operation of the steering system S in this embodiment will be described. First, let's explain how it works in a normal, non-malfunctioning state (see Figure 1-3). The steering angle signals from each steering angle sensor 11 are input to the HWA 12 via their respective RWA 22s.

[0022] In the HWA12, the steering angle calculation unit 14 calculates the steering angle from the steering angle signal and vehicle information (such as vehicle speed) input via communication means such as CAN. Then, HWA12 outputs the calculated steering angle to each RWA22. In addition, the HWA12 calculates the target reaction force from the calculated steering angle and vehicle information, and the torque control unit 16 applies the operating reaction force to the steering wheel.

[0023] The position signal from the first rack position sensor 21A is input to the first RWA 22A via HWA 12. The position signal from the second rack position sensor 21B is directly input to the second RWA 22B. Each RWA22 calculates the current (pre-steering) rack position (initial position) from the position signal.

[0024] Furthermore, each RWA22 calculates the target rack position from the steering angle of the HWA12. The RWA22 then moves the rack according to the target rack position, and the front wheels steer as the rack moves. If both the first and second systems are functioning correctly, the rack position and target rack position are calculated using both systems. The calculation result of one of the systems (for example, the first system) is prioritized to operate the rack and apply an operating reaction force to the steering wheel.

[0025] Next, we will explain how the steering system S functions when each component fails (see Figure 4-6). The steering angle sensor 11, rack position sensor 21, and RWA 22 are each provided in pairs, so even if one of them fails, the other will continue to operate, meaning there are no functional problems.

[0026] Next, we will explain what happens if the HWA12 fails. If HWA12 fails, power will not be supplied to the first rack position sensor 21A in the first system SA. As a result, the rack position will not be detected by the first rack position sensor 21A, and the process will end here (see Figure 5). The steering angle signal from the first steering angle sensor 11A is input to the HWA12 via the first RWA22A, but because the HWA12 is malfunctioning, the steering angle and target reaction force cannot be calculated, and the process ends here. In other words, if HWA12 fails, the first system SA will cease to function. However, if HWA12 fails after IG / ON, the rack position is calculated based on the motor position sensor (not shown) in RWA22, and control continues.

[0027] If HWA12 fails, in the second system SB, the position signal from the second rack position sensor 21B is directly input to the second RWA22B (see Figure 6). The second RWA22B calculates the current (pre-steering) rack position (initial position) from the position signal. Furthermore, the steering angle signal from the second steering angle sensor 11B is input to the second RWA 22B. The second RWA22B then calculates the steering angle from the steering angle signal of the second steering angle sensor 11B and vehicle information (such as vehicle speed) input via communication means such as CAN. Next, the second RWA22B moves the rack according to the target rack position, and the front wheels are steered by the moving rack. Furthermore, because the HWA12 is malfunctioning, no counter-force is applied to the steering wheel during steering.

[0028] Next, the effects and advantages of this embodiment will be described. The steer-by-wire steering system S of this embodiment is configured to include two steering angle sensors 11, two rack position sensors 21, two RWAs 22, and one HWA 12. This configuration allows for system redundancy while simultaneously reducing the overall cost of the system. Furthermore, by connecting the output signal of the second rack position sensor 21B to the second RWA 22B, the wiring involved in the connection can be shortened, and redundancy can be provided for determining the rack position.

[0029] Furthermore, in this embodiment, the steer-by-wire steering system S is wired so that the output signal of the first steering angle sensor 11A is input to the HWA12 via the first RWA22A. Furthermore, the output signal of the second steering angle sensor 11B is wired to be input to the HWA12 via the second RWA22B. In other words, the output signals from the two steering angle sensors 11 are input to the HWA 12 via separate RWA 22s. With this configuration, even if HWA12 fails or either RWA22 fails, the output signal from the steering angle sensor 11 can still be input to RWA22. This allows for continued functionality and ensures redundancy. Furthermore, because the first rack position sensor 21A is connected to the HWA12, the rack position can be transmitted to the vehicle's external functions even if both RWA22 sensors fail. This allows the steering angle to be determined, making it possible to continue controlling the vehicle's motion.

[0030] In this embodiment, the steer-by-wire steering system S is powered by the first RWA22A for the first steering angle sensor 11A, and by the second RWA22B for the second steering angle sensor 11B. Furthermore, in the steer-by-wire steering system S of this embodiment, the power supply for the first rack position sensor 21A is supplied from HWA12, and the power supply for the second rack position sensor 21B is supplied from the second RWA22B. This configuration allows the power lines of each sensor to be aligned with their respective output signal lines. This simplifies the configuration of the wire harness, simplifies the wiring process, and prevents miswiring. [Explanation of Symbols]

[0031] S Steer-by-wire steering system SA 1st system SB 2nd system 1. Steering mechanism 11. Steering angle sensor 11A First steering angle sensor (one of the steering angle sensors) 11B Second steering angle sensor (other steering angle sensor) 12 HWA 2. Steering mechanism 21 Rack position sensor 21A First rack position sensor (one of the rack position sensors) 21B Second rack position sensor (other rack position sensor) 22 RWA 22A First RWA (one of the RWAs) 22B Second RWA (the other RWA)

Claims

1. Two rack position sensors detect the position of the rack that controls the steering angle of the steering wheels, Based on the output signal of the rack position sensor, two RWAs operate the rack, A single HWA is electrically connected to the RWA and provides an operating reaction force to the steering wheel used for steering the vehicle. Equipped with, On the other hand, the output signal of the rack position sensor is The data is input to the other RWA via the HWA, The output signal of the other rack position sensor is, The other RWA is directly input A steer-by-wire steering system characterized by the following features.

2. In the steer-by-wire steering system according to claim 1, The steering wheel is equipped with two steering angle sensors that detect the operating angle of the steering wheel, On the other hand, the output signal of the steering angle sensor is, One of the signals is input to the HWA via the RWA, The output signal of the other steering angle sensor is, The other RWA is input to the HWA via the RWA. A steer-by-wire steering system characterized by the following features.

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