JP2023128821A - steering system - Google Patents

Abstract

To improve practicability of a steer-by-wire type steering system.SOLUTION: A steer-by-wire type steering system includes an operation member 80 operated by a driver, a wheel turning device 12 for turning wheels according to the operation of the operation member, a reaction force application device 84 for applying operation reaction force to the operation member, and controllers 16 and 18, wherein the controller is configured to determine operation reaction force TqC to be applied, and to control the reaction force application device on the basis of the determined operation reaction force, and to determine operation reaction force including vehicle behavior-based components TqC-GY and TqC-γ depending on at least one of lateral acceleration GY generated in the vehicle and a yaw rate γ of the vehicle. The lateral acceleration and the yaw rate are indices of a vehicle turning behavior, and accordingly the operation reaction force including the component based on the indices is appropriate according to the vehicle turning behavior.SELECTED DRAWING: Figure 3

Description

TECHNICAL FIELD The present invention relates to a steer-by-wire steering system, and more particularly, to control of operational reaction force thereof.

The steering system is a system that steers the wheels, and the vehicle turns by steering the wheels. The turning behavior of a vehicle can be understood by changes in behavior indicators such as yaw rate and lateral acceleration. In view of this, for example, in the technology described in the following patent document, the yaw rate is utilized for wheel steering control.

Patent Application No. 2016-101837

The technology described in the above-mentioned patent document relates to a so-called electric power steering system, and is a technology for controlling force for assisting steering of wheels. Nowadays, systems that are different from power steering systems, more specifically, operating members such as a steering wheel and a steering device for steering the wheels, are not mechanically connected, and the driver has to Steer-by-wire steering systems (hereinafter sometimes referred to as ``steer-by-wire systems''), which use a steering device to steer wheels according to the operation of operating members without relying on operating force, are being actively developed. It is being done. In the steer-by-wire system, since the steering device and the operating member are not connected, it is necessary to give the driver a feeling of steering operation by some means. As a means for this purpose, specifically, a reaction force applying device is provided that applies a reaction force (hereinafter sometimes referred to as "operation reaction force") to the operation member against the driver's operation using, for example, an electric motor or the like. . The inventor of the present application has found that the practicality of the steer-by-wire system can be improved by using the above-mentioned behavior index to control this operation reaction force. Based on this knowledge, it is an object of the present invention to provide a highly practical steer-by-wire steering system.

In order to solve the above problems, the steering system of the present invention includes:
A steer-by-wire steering system installed in a vehicle,
An operating member operated by a driver, a steering device that steers wheels in accordance with the operation of the operating member, a reaction force applying device that applies an operating reaction force to the operating member, and a steering system that controls the steering system. Equipped with a controller that controls the
The controller,
configured to determine the operational reaction force to be applied, and to control the reaction force applying device based on the determined operational reaction force, and
The operation reaction force is configured to determine the operation reaction force including a vehicle behavior dependent component based on at least one of a lateral acceleration occurring in the vehicle and a yaw rate of the vehicle.

The above-mentioned lateral acceleration and yaw rate are indicators of the turning behavior of the vehicle, and the operation reaction force including the above-mentioned vehicle behavior dependent component based on the indicators is appropriate according to the turning behavior of the vehicle. Therefore, according to the present invention, a practical steer-by-wire system can be constructed.

Aspects of the invention

The present invention can also be applied to a system in which left and right wheels are steered by one steering device, and also to a system including two steering devices, each of which steers one of the left and right wheels independently. In other words, it can also be applied to a left and right wheel independent steering system.

Both lateral acceleration and yaw rate are behavior indicators that indicate the turning behavior of the vehicle, and the vehicle behavior-dependent component may be a component based only on either the lateral acceleration or the yaw rate, or the lateral acceleration and the yaw rate. It may be a vehicle behavior dependent component based on both. The latter can be considered to be a combination of a lateral acceleration dependent component based on lateral acceleration and a yaw rate dependent component based on yaw rate. Both lateral acceleration and yaw rate can be estimated based on the operating amount of the operating member and the vehicle's traveling speed (hereinafter sometimes referred to as "vehicle speed"), but it is also possible to estimate the lateral acceleration and yaw rate based on the operating amount of the operating member and the traveling speed of the vehicle (hereinafter sometimes referred to as "vehicle speed"). From the perspective of applying a reaction force, the lateral acceleration and yaw rate that are relied on in determining the vehicle behavior dependent component must be the lateral acceleration and yaw rate that are actually detected by the lateral acceleration sensor and yaw rate sensor mounted on the vehicle. is desirable. Considering that it is desirable to increase the operation reaction force as the turning behavior of the vehicle becomes larger (stronger), the vehicle behavior dependent component should be set to become larger as the lateral acceleration and yaw rate become larger. desirable.

The operation reaction force can include components other than the vehicle behavior dependent component. Specifically, other components include, for example, a vehicle speed turning amount dependent component that depends on the vehicle speed and the turning amount of the wheels (which can be considered as "steering angle", "wheel toe angle", etc.) , a steering load-dependent component that depends on the load of the steering device, and an operation speed-dependent component that depends on the operation speed of the operating member.

When the force for steering the wheels is defined as the steering force, the component depending on the vehicle speed and steering amount is considered to be a component corresponding to the steering force to counter the self-aligning torque acting on the wheels, for example. be able to. In order to maintain or increase the amount of wheel turning, it is necessary to overcome the self-aligning torque, and in order to make the driver aware of the self-aligning torque, the vehicle speed turning amount dependent component should be adjusted as the vehicle speed increases. , It is desirable to set the value to be larger as the amount of steering becomes larger.

The above-mentioned steering load-dependent component can be considered, for example, as a component corresponding to the steering force actually exerted by the steering device to steer the wheels. For example, steering operations when the vehicle speed is quite low, such as stationary steering operations, are greatly affected by the frictional force between the road surface and the tires, require a considerable steering force, and the load on the steering device is considerable. big. The steering load dependent component can be considered as a component for making the driver feel the load of such a steering device. Therefore, it is desirable to set the steering load dependent component to increase as the load on the steering device increases. In addition, if the steering device has an electric motor as a drive source, the load on the steering device can be considered to be roughly proportional to the current supplied to the electric motor, and the steering load The dependent component can be determined depending on the supplied current.

The operation speed-dependent component can be made to function as a component for restricting rapid operation of the operation member, for example. Simply put, it functions as a damper against operations. In order to ensure this function, it is desirable that the operation speed dependent component is set to be larger as the operation speed of the operation member is higher.

The operational reaction force to be applied may be determined by weighting and adding up each of the above-mentioned components. This weighting coefficient is the gain. In other words, this gain can be considered as the degree of contribution of each component to the operation reaction force. The present steer-by-wire system may be configured to change this degree of contribution. By changing the degree of contribution of each component, it becomes possible to optimize the operation reaction force depending on the situation in which the vehicle is placed, for example. As a supplementary note regarding the degree of contribution, changing the degree of contribution is a concept that includes setting the degree of contribution to 0 or increasing it from 0. In other words, by setting the contribution of some of the multiple components to 0, you can eliminate that part from the operation reaction force, or by increasing the contribution of some of the components from 0 to Including it in the operation reaction force also corresponds to changing the degree of contribution. Furthermore, the degree of contribution of each of the plurality of components is relative, and increasing the degree of contribution of one component means decreasing the degree of contribution of the other components.

To give a specific example of changing the degree of contribution, in the above-mentioned steer-by-wire system with left and right wheels independently steered, for example, in the case of a steer-by-wire system in which the left and right wheels are independently steered, for example, there is a steer-by-wire system in which one of the left and right wheels is steered by only one of the two steering devices. In wheel steering situations, the degree of contribution of the vehicle behavior dependent component may be increased. If the other of the two steering devices fails, one of the left and right wheels will not be able to be steered depending on the other one. In such a one-wheel steering situation, the amount of steering of the wheel steered by the other steering device may deviate from the amount of steering of the wheel steered by one steering device, and, It is considered that if the other steering device does not operate, no load will be generated on the other steering device. In such a case, it is predicted that the above-mentioned vehicle speed turning amount dependent component and steering load dependent component will not have appropriate magnitudes. In view of such a situation, in a one-wheel steering situation, it is possible to increase the contribution of the vehicle behavior-dependent component, in other words, to lower the contribution of the vehicle speed steering amount-dependent component and the steering load-dependent component. Even in wheel steering situations, it becomes possible to apply an appropriate operational reaction force.

Further, in a single-wheel steering situation, sudden wheel steering is not preferred. Therefore, in order to suppress sudden steering of the wheels, that is, to suppress sudden operation of the operating member, the degree of contribution of the operation speed dependent component may be increased.

FIG. 1 is a schematic diagram showing the overall configuration of a vehicle equipped with a steering system according to an embodiment. FIG. 2 is a perspective view showing a wheel arrangement module incorporating a wheel steering device constituting the steering system of the embodiment. FIG. 2 is a block diagram schematically showing functions related to control of the steering system of the embodiment. They are a graph showing map data for determining the steering gear ratio, and a table for explaining changes in the degree of contribution of each component of the operation reaction force. It is a graph showing map data for determining each component of operation reaction force. It is a flowchart of a target steering angle determination program and a wheel steering program that are executed to perform steering control. This is an operation reaction force control program executed to perform operation reaction force control.

EMBODIMENT OF THE INVENTION Hereinafter, as a mode for carrying out the present invention, a steer-by-wire type steering system which is an embodiment of the present invention will be described in detail with reference to the drawings. In addition to the following examples, the present invention can be implemented in various forms including the form described in the above [Aspects of the Invention] and various modifications and improvements made based on the knowledge of those skilled in the art. can.

[A] Overall configuration of a vehicle equipped with a steering system As schematically shown in FIG. ing. The left and right front wheels 10FL and 10FR are drive wheels and steered wheels. In addition, when there is no need to distinguish between the left and right front wheels 10FL and 10FR, they are collectively referred to as the front wheel 10F, and when there is no need to distinguish between the left and right rear wheels 10RL and 10RR, they are collectively referred to as the rear wheel 10R. However, if there is no need to distinguish between the front wheels 10F and the rear wheels 10R, they may simply be referred to collectively as wheels 10.

This steering system is a so-called steer-by-wire type steering system with left and right wheels independent steering. A pair of wheel steering devices (hereinafter sometimes simply referred to as “steering devices”) 12, an operating device 14 for receiving operations from the driver, and a device for controlling the pair of wheel steering devices 12, respectively. A pair of steering electronic control units (hereinafter sometimes abbreviated as "steering ECU" and shown as "S-ECU" in the figure) 16, which controls the operating device 14 and also controls the steering ECU 16. It is configured to include an operation electronic control unit (hereinafter sometimes abbreviated as "operation ECU" and expressed as "O-ECU" in the figure) 18 for controlling the operation. The configuration and control of this steering system will be described in detail later, but it can be considered that the two steering ECUs 16 and the operation ECU 18 constitute a controller of the steering system.

Further, this vehicle is equipped with a vehicle drive system that includes a pair of wheel drive units 20 that are respectively provided on the two front wheels 10F and rotated by electric motors. The vehicle drive system includes an accelerator pedal 22 as an accelerator operation member operated by a driver, an accelerator operation amount sensor 24 for detecting an accelerator operation amount ε _A that is an operation amount of the accelerator pedal 22, and the accelerator operation amount. A vehicle drive electronic control unit (hereinafter sometimes abbreviated as "drive ECU" and "A-ECU" in the figure) controls the operation of the pair of wheel drive units 20 based on the accelerator operation amount detected by the sensor 24. 26). Since the vehicle drive system has a general configuration and performs general control, a description of the configuration and control of the vehicle drive system will be omitted.

Furthermore, this vehicle is equipped with a hydraulic brake system. The brake system includes a brake pedal 30 as a brake operation member operated by a driver, a master cylinder 32 connected to the brake pedal 30, and a hydraulic pressure source such as a pump, which pressurizes the hydraulic fluid. a supply device 34 , four brake devices 36 provided on each of the four wheels 10 to brake each wheel by the pressure of the hydraulic fluid from the hydraulic fluid supply device 34 , and a brake that controls the operation of the hydraulic fluid supply device 34 . The brake system includes an electronic control unit (hereinafter sometimes referred to as "brake ECU" and is indicated as "B-ECU" in the figure) 38.The brake system is a so-called brake-by-wire type system, and the brake ECU 38 is the pressure of the hydraulic fluid supplied from the hydraulic fluid supply device 34 to the brake device 36 of each wheel 10 based on the brake operation amount ε _B , which is the operation amount of the brake pedal 30 detected by the brake operation amount sensor 40. By controlling the braking force applied to the vehicle, the brake system has a general configuration and is subject to general control, so an explanation of the configuration and control of the brake system is provided. is omitted.

The vehicle is provided with a CAN (car area network or controllable area network) 42, and two steering ECUs 16, an operation ECU 18, a drive ECU 26, and a brake ECU 38 are connected to the CAN 42. These ECUs 16, 18, 26, and 38 communicate with each other via CAN 42 and execute the control that each one should perform. Incidentally, each of the ECUs 16, 18, 26, and 38 includes a computer having a CPU, ROM, RAM, etc., and a computer for driving components (for example, electric motors, valves, pumps, etc.) based on instructions from the computer. It is configured to include a driver (drive circuit). This vehicle is provided with a lateral acceleration sensor 44 for detecting the lateral acceleration G _Y occurring in the vehicle body, and a yaw rate sensor 46 for detecting the yaw rate γ of the vehicle. A wheel speed sensor 48 is provided for detecting the wheel rotational speed (hereinafter sometimes referred to as "wheel speed") v _W of each of the wheels. The lateral acceleration sensor 46, yaw rate sensor 46, and wheel speed sensor 48 are also connected to the CAN 42.

Incidentally, the vehicle speed v, which is the traveling speed of the vehicle, is specified by the brake ECU 38. Specifically, the wheel speed v _W of each front wheel 10F is grasped by the drive ECU 26 based on the rotational speed of the electric motor that is the drive source of the wheel drive unit 20, and the information is sent to the brake ECU 38 via the CAN 42. It will be sent to you. On the other hand, the wheel speed v _W of each rear wheel 10R is detected by the wheel speed sensor 48, and the information is sent to the brake ECU 38 via the CAN 42. The brake ECU 38 specifies the vehicle speed v based on this information.

[B] Hardware configuration of steering system (a) Hardware configuration of wheel steering device Each of the pair of wheel steering devices 12 of the vehicle steering system of this embodiment is incorporated in the wheel arrangement module 50. The wheel arrangement module 50 also incorporates one of the pair of wheel drive units 20 of the vehicle drive system described above and one of the four brake devices 36 of the brake system. The wheel arrangement module (hereinafter sometimes simply referred to as "module") 50 is, as shown in FIG. 2, a module for arranging a wheel 10b on which a tire 10a is mounted on a vehicle body. Although the wheel 10b itself can be considered a wheel, in this embodiment, for convenience, the wheel 10b to which the tire 10a is attached will be referred to as the wheel 10.

To explain the wheel steering device 12 of the present steering system while explaining the configuration of the module 50, the above-mentioned wheel drive unit 20 disposed in the present module 50 includes a housing 20a and a drive unit built in the housing 20a. It has an electric motor as a source, a speed reducer (both not shown) that reduces the rotation of the electric motor, and an axle hub (not visible in the figure) to which the wheel 10b is attached. The wheel drive unit 20 is arranged inside the rim of the wheel 10b, and is a so-called in-wheel motor unit. Since the wheel drive unit 20 has a well-known structure, a description of its structure will be omitted.

The module 50 includes a MacPherson type suspension device (also referred to as a "MacPherson strut type"). In this suspension device, the housing 20a of the wheel drive unit 20 functions as a carrier that rotatably holds the wheels, and furthermore, the housing 20a functions as a steering knuckle in the wheel steering device 12, allowing vertical movement with respect to the vehicle body. be done. Therefore, the suspension device includes a lower arm 52 that is a suspension arm, a housing 20a of the wheel drive unit 20, a shock absorber 54, and a suspension spring 56.

The suspension device itself has a general structure, so to briefly explain, the lower arm 52 has a shape called a so-called L arm, and the base end is divided into two parts in the longitudinal direction of the vehicle. , is supported at its base end via a first bush 58 and a second bush 60 by a side member (not shown) of the vehicle body so as to be rotatable about the arm rotation axis LL. The housing 20a of the wheel drive unit 20 is connected to the tip of the lower arm 52 at its lower part via an arm connecting ball joint 62 (hereinafter sometimes referred to as "first joint 62"), which is a first joint. Rotatably connected.

The shock absorber 54 has a lower end fixedly supported by the housing 20a of the wheel drive unit 20, and an upper end supported by the upper part of the tire housing of the vehicle body via an upper support 64. The upper end of the suspension spring 56 is also supported by the upper part of the tire housing of the vehicle body via an upper support 64, and the lower end of the suspension spring 56 is supported by a lower support 54a provided in the shape of a flange on the shock absorber 54. ing. That is, the suspension spring 56 and the shock absorber 54 are arranged in parallel with each other between the lower arm 52 and the vehicle body.

As described above, this module 50 has the brake device 36, and the brake device 36 is configured to straddle the disc rotor 66 that is attached to the axle hub together with the wheel 10b and rotates together with the wheel 10, and the disc rotor 66. This disc brake device includes a brake caliper 68 held in the housing 20a of the wheel drive unit 20. Although detailed explanation is omitted, this brake caliper 68 has a brake pad as a friction member and a hydraulic cylinder, and the brake device 36 uses hydraulic fluid supplied from the hydraulic fluid supply device 34 to the hydraulic cylinder. By pressing the brake pad against the disc rotor 66 depending on the pressure of the brake pad, a braking force for stopping the rotation of the wheel 10 is generated.

The wheel steering device 12 is a single-wheel independent steering device for steering only one of the pair of left and right front wheels 10F independently of the other, and generally serves as a steering knuckle as described above. The housing 20a of the functioning wheel drive unit 20 (hereinafter, when treated as a component of the wheel steering device 12, may be referred to as the "steering knuckle 20a") and the lower arm 52 at a position near the base end thereof. 52, and a tie rod 72 that connects the steering actuator 70 and the steering knuckle 20a.

The steering actuator 70 is rotated by a steering motor 70a that is an electric motor as a drive source, a reducer 70b that reduces the rotation of the steering motor 70a, and the rotation of the steering motor 70a via the reducer 70b. The actuator arm 70c functions as a pitman arm. The base end of the tie rod 72 is connected to the actuator arm 70c via a rod base end connecting ball joint 74 (hereinafter sometimes referred to as "second joint 74"), which is a second joint. The tip end is connected to the knuckle arm 20b of the steering knuckle 20a via a rod tip ball joint 76 (hereinafter sometimes referred to as "third joint 76") that is a third joint.

In the present wheel steering device 12, a line connecting the center of the upper support 64 and the center of the first joint 62 is the kingpin axis KP. By operating the steering motor 70a, the actuator arm 70c of the steering actuator 70 rotates around the actuator axis AL, as shown by the thick arrow in the figure. The rotation is transmitted by the tie rod 72, and the steering knuckle 20a is rotated around the king pin axis KP. In other words, the front wheels 10F are steered as shown by the thick arrows in the figure. Due to this structure, the present wheel steering device 12 includes the actuator arm 70c, tie rod 72, knuckle arm 20b, etc., and includes a motion conversion mechanism 78 that converts the rotational operation of the steering motor 70a into the steering operation of the front wheels 10F. It is equipped with the following.

In the wheel steering device 12, a steering actuator 70 is disposed on the lower arm 52. Therefore, it becomes possible to easily assemble the module 50 to the vehicle body. Simply put, by simply attaching the base end of the lower arm 52 to the side member of the vehicle body and attaching the upper support 64 to the top of the tire housing of the vehicle body, the suspension device, brake device, and wheel steering device can be mounted on the vehicle. It is possible. In other words, the present module 50 is considered to be a module with excellent mountability in a vehicle.

Here, to briefly explain the rear wheels 10R, each of the rear wheels 10R is held on the vehicle body via a trailing arm type suspension device. Although a brake device 36 is provided for each rear wheel 10F, the wheel drive unit 20 and wheel steering device 12 are not provided because each rear wheel 10R is neither a driving wheel nor a steered wheel.

(b) Hardware configuration of operating device The operating device 14 has a general structure in a steer-by-wire type steering system, and briefly described, as shown in FIG. 1, the operating device 14 is steered by the driver. A steering wheel 80 as a steering operation member and a steering operation angle (hereinafter sometimes simply referred to as "operation angle") δ, which is a rotation angle of the steering wheel 80, are detected as an operation amount of the steering operation member from a straight-ahead state position. The steering sensor 82 is configured to include a steering sensor 82 for controlling the steering wheel 80, and a reaction force applying device 84 for applying an operation reaction force, which is a reaction force to the operation of the steering wheel 80 by the driver, to the steering wheel 80. The reaction force applying device 84 includes a reaction force motor 84 a that is an electric motor serving as a force source, and a reduction gear 84 b for transmitting the force of the reaction force motor 84 a to the steering wheel 80 .

[C] Control of Steering System (a) Functional Configuration Regarding Control Control of the steering system is executed by the above-mentioned operation ECU 18 and two steering ECUs 16. The operation ECU 18 includes a computer including a CPU, ROM, RAM, etc., and a driver (drive circuit) for the reaction force motor 84a.Similarly, the steering ECU 16 includes a computer including a CPU, ROM, RAM, etc. , and a driver (drive circuit) for the steering motor 70a. The functions of the operation ECU 18 and the steering ECU 16 will be explained below with reference to the block diagram schematically shown in FIG. 3.

i) Steering Control First, steering control, which is control related to steering of the wheels 10, will be explained. Roughly speaking, in this steering system, the operation ECU 18 determines the target steering angle θ ^* , which is the steering angle θ of the wheels 10 to be achieved, based on the steering operation angle δ, and Based on the target turning angle θ ^* , the actual turning angle θ (hereinafter sometimes referred to as "actual turning angle θ") of the corresponding wheel 10 becomes the target turning angle θ ^* . Thus, the operation of the steering motor 70a of the steering actuator 70 is controlled. Note that the steering angle θ is a rotational phase of the wheel 10 about the kingpin axis KP with reference to the posture in which the vehicle is traveling straight, and is a type of steering amount.

This steering system employs a so-called variable gear ratio system (VGRS), and in connection with steering control, the operation ECU 18 controls the steering gear ratio β, which is the ratio of the steering angle θ of the wheels 10 to the operation angle δ. It has a gear ratio determining section 100 that determines. The gear ratio determination unit 100 determines the steering gear ratio β based on the vehicle speed v and according to map data as shown in the graph of FIG. 4(a). Incidentally, as can be seen from the graph, in consideration of the running stability of the vehicle, the steering gear ratio β is generally set to become smaller as the vehicle speed v becomes higher. The operation ECU 18 has a target steering angle determination section 102, and the target steering angle determination section 102 determines the operation angle δ detected by the steering sensor 82 and the steering gear determined by the gear ratio determination section 100. Based on the ratio β, the target steering angle θ ^* is determined according to the following equation.
θ ^* = β × δ

This steering system does not have a steering angle sensor that directly detects the steering angle θ of the wheels 10. Therefore, by utilizing the fact that the motor rotation angle θ _M of the steering motor 70a and the steering angle θ of the wheels 10 have a certain proportional relationship, the steering angle θ can be determined based on the motor rotation angle θ _M. In order to obtain this, the steering ECU 16 has a steering angle conversion section 104. The steering motor 70a has a motor rotation angle sensor 70d, and the steering angle conversion unit 104 calculates the actual steering angle θ based on the motor rotation angle θ _M detected by the motor rotation angle sensor 70d. Identify.

The steering ECU 16 has a steering torque determination section 106, and the steering torque determination section 106 uses the target steering angle θ determined by the target steering angle determination section 102 of the operation ECU 18 and transmitted as information. ^* and the actual steering angle θ specified by the steering angle conversion unit 104, the steering torque Tq _S is determined as the steering force necessary for steering the wheels 10. To explain in detail, the steering torque determination unit 106 specifies the steering angle deviation Δθ which is the deviation of the actual steering force θ from the target steering angle θ ^* , and performs the PID feedback control based on the steering angle deviation Δθ. In order to perform steering control using this method, the steering torque Tq _S is determined according to the following equation.
Tq _S =K _P ×Δθ+K _I ×∫Δθdt+K _D ×dΔθ/dt
Note that the first, second, and third terms on the right side of the above equation are the proportional term, integral term, and differential term, respectively, and K _P , K _I , and K _D are the proportional term gain and the integral term gain, respectively. , is the differential term gain. Note that information about the actual steering angle θ specified by the steering angle conversion unit 104 is transmitted to the operation ECU 18.

The steering ECU 16 has a steering energization control section 108, and since the steering motor 70a is a three-phase DC brassless motor, the steering ECU 16 includes a drive circuit (driver) of the steering motor 70a. ). The steering energization control unit 108 determines a steering current I _S that is a current to be supplied to the steering motor 70a based on the steering torque Tq _S determined by the steering torque determining unit 106, and A current _IS is supplied from the inverter to the steering motor 70a.

Note that the steering ECU 16 has a current sensor 110 for detecting the supplied steering current I _S , and information on the steering current I _S detected by this current sensor 110 will be explained later. It is transmitted to the operation ECU 18 to be used for controlling the operation reaction force. Further, the steering ECU 16 has a self-diagnosis section 111 for diagnosing the operating state of the wheel steering device 12, and as will be described in detail later, information on the diagnosis, specifically, the wheel steering device Failure information DEF, which is information indicating that 12 has failed, is also transmitted to the operation ECU 18.

ii) Operation reaction force control Next, operation reaction force control, that is, control for applying an operation reaction force to the steering wheel 80, which is an operation member, in order to make the driver feel the operation feeling in response to the steering operation will be explained. . This operation reaction force control is performed by the operation ECU 18. Roughly speaking, the operation ECU 18 determines the reaction torque Tq _C as the operation reaction force by adding up a plurality of components, and controls the reaction force applying device 84 based on the determined reaction torque Tq _C. A current (hereinafter sometimes referred to as "reaction current") I _C is supplied to the reaction motor 84a.

The plurality of components include a vehicle speed turning angle dependent component Tq _Cv θ determined based on the vehicle speed v and the turning angle θ of the wheels 10, and a turning load dependent component determined based on the load of the steering device 12. A component Tq _C-IS , an operation speed dependent component Tq _Cd δ determined based on the operation speed dδ of the steering wheel 80, and a vehicle behavior dependent component determined based on the behavior of the vehicle are set. Specifically, the vehicle behavior dependent components include a lateral acceleration dependent component Tq _C-GY determined based on the lateral acceleration G _Y occurring in the vehicle body, and a yaw rate dependent component Tq _C determined based on the yaw rate γ of the vehicle. _- γ is set.

The vehicle speed turning angle dependent component Tq _Cv θ can be considered as a component corresponding to the steering force for countering the self-aligning torque acting on the wheels 10. The steering load dependent component Tq _C-IS can be considered as a component corresponding to the steering force actually exerted by the wheel steering device 12 in order to steer the wheels 10. The operation speed dependent component Tq _Cd δ can be considered as a component for restricting sudden operation of the steering wheel 80. The lateral acceleration dependent component Tq _C-GY and the yaw rate dependent component Tq _C- γ, which are vehicle behavior dependent components, can both be considered as components of the operation reaction force that take into account the actual turning behavior of the vehicle.

The operation ECU 18 includes a vehicle speed turning angle dependent component determination unit 112 that determines a vehicle speed turning angle dependent component Tq _Cv θ. Furthermore, the steering angle θ of the wheels 10, which is relied on in determining the vehicle speed turning angle dependent component Tq _Cv θ, is based on the actual steering angle θ _R of the right wheel 10, which is sent as information from each of the two steering ECUs 16. , the average turning angle θ _AVE is the average of the actual turning angle θ _L of the left wheel 10, and in order to obtain the average turning angle θ _AVE according to the following formula, the operation ECU 18 includes a turning angle averaging section 114. are doing.
θ _AVE = (θ _R + θ _L )/2
Based on the average steering angle θ _AVE and the vehicle speed v sent as information from the brake ECU 38, the vehicle speed turning angle dependent component determination unit 112 uses the average turning angle θ _AVE and the vehicle speed v as parameters. The vehicle speed turning angle dependent component Tq _Cv θ is determined according to the function shown by the following equation.
Tq _Cv θ=f(θ _AVE ,v)
This function f(θ _AVE , v) is a function set such that Tq _Cv θ becomes larger as the average steering angle θ _AVE becomes larger and the vehicle speed v becomes higher.

The operation ECU 18 also includes a steering load dependent component determination unit 116 that determines the steering load dependent component Tq _C-IS . It may be considered that the load on the wheel steering device 12 is approximately proportional to the magnitude of the steering current I _S supplied from the steering ECU 16 to the steering motor 70a, and the steering load dependent component determination unit 116 It is determined based on the rudder current _IS . Strictly speaking, the steering current I _S that is relied on in determining the steering load dependent component Tq _C-IS is the steering current I _S on the right wheel 10 side that is sent as information from each of the two steering ECUs 16. The average steering current I _S - _AVE is the average of the steering current I _S - _L on the left wheel 10 side and the steering current I S - _R , and in order to calculate the average steering current I _S - _AVE according to the following formula, the operation ECU 18 It has a load averaging section 118.
I _S - _AVE = (I _S - _R + I _S - _L )/2
The steering load dependent component determination unit 116 determines the steering load dependent component Tq _C-IS based on the average steering current I _S - _AVE and according to map data as shown in the graph of FIG. 5(a). . As can be seen from the graph, the steering load-dependent component Tq _C-IS is determined to increase as the average steering current _IS - _AVE increases.

The operation ECU 18 further includes an operation speed-dependent component determining section 120 that determines an operation speed-dependent component Tq _Cd δ. The operation speed dependent component determination unit 120 specifies the operation speed dδ of the steering wheel 80 based on the operation angle δ detected by the steering sensor 82, and based on the operation speed dδ, the operation speed dependent component determination unit 120 determines the operation speed dδ in the graph of FIG. 5(b). The operation speed dependent component Tq _Cd δ is determined according to map data as shown. As can be seen from the graph, the operation speed dependent component Tq _Cd δ is determined to be larger as the operation speed dδ is higher.

The operation ECU 18 has a vehicle behavior dependent component determining section 122 that determines a vehicle behavior dependent component, and the vehicle behavior dependent component determining section 122 includes a lateral acceleration dependent component determining section 124 and a yaw rate dependent component determining section 126. have. The lateral acceleration dependent component determination unit 124 determines the lateral acceleration dependent component Tq _C-GY based on the lateral acceleration G _Y detected by the lateral acceleration sensor 44 and according to map data as shown in the graph of FIG. 5(c). Based on the yaw rate γ detected by the yaw rate sensor 46, the yaw rate dependent component determination unit 126 determines the yaw rate dependent component Tq _C- γ according to map data as shown in the graph of FIG. 5(d). As can be seen from the graph, the lateral acceleration dependent component Tq _C-GY is determined to increase as the lateral acceleration G _Y increases, and the yaw rate dependent component Tq _C- γ increases as the yaw rate γ increases. It is determined.

The operation ECU 18 has an adder 128, and the determined components Tq _Cv θ, Tq _C-IS , Tq _Cd δ, Tq _C-GY , Tq _C- γ are added by the adder 128. However, each component Tq _Cv θ, Tq _C-IS , Tq _Cd δ, Tq _C-GY , Tq _C- γ is added after taking into account the degree of contribution, in other words, after being weighted. . Therefore, the operation ECU 18 includes a gain setting multiplication section 130. The contribution of each component Tq _Cv θ, Tq _C-IS , Tq _Cd δ, Tq _C-GY , Tq _C- γ is, respectively, vehicle speed turning angle dependent component determination gain K _v θ, steering load dependent component determination gain K _IS , operation speed dependent component determining gain K _d δ, lateral acceleration dependent component determining gain K _GY , and yaw rate dependent component determining gain Kγ. In the gain setting multiplier 130, each multiplier 132 to 140 calculates each component Tq _Cv θ, Tq _C-IS , Tq _Cd δ, Tq _C- determined by each component determining unit 112, 116, 120, 124, 126. _GY , Tq _C- γ is multiplied by each component determination gain K _v θ, K _IS , K _d δ, K _GY , K γ, and each multiplied component Tq _Cv θ, Tq _C-IS , Tq _Cd δ, Tq _C-GY and Tq _C- γ are output to adder 128. The components Tq _Cv θ, Tq _C-IS , Tq _Cd δ, Tq _C-GY , Tq _C- γ that take these contributions into consideration are added by an adder 128, and the reaction torque Tq _C to be applied is determined. Ru. The processing by the multipliers 132 to 140 and the adder 128 is expressed as the following arithmetic processing.
Tq _C =K _v θ×Tq _Cv θ+K _IS ×Tq _C-IS +K _d δ×Tq _Cd δ+K _GY ×Tq _C-GY
+Kγ×Tq _C- γ

The operation ECU 18 has a reaction force energization control section 142, and since the reaction force motor 84a is a three-phase DC brassless motor, the reaction force energization control section 142 controls the drive circuit (driver) of the reaction force motor 84a. The system includes an inverter. The reaction force energization control unit 142 determines a reaction current I _C , which is a current to be supplied to the reaction motor 84a, based on the determined reaction torque Tq _C , and supplies the reaction current I _C from the inverter. The reaction force is supplied to the motor 84a.

In this steering system, it is possible to change the degree of contribution of each of the components Tq _Cv θ, Tq _C-IS , Tq _Cd δ, Tq _C-GY , and Tq _C- γ in determining the reaction torque Tq _C. To explain in detail, for each component determined gain K _v θ, K _IS , K _d δ, K _GY , Kγ, high gain K _v θ- _H , K _IS - _H , K _d δ- _H , K _GY - _H , Kγ- _H and low gains K _v θ- _L , K _IS - _L , K _d δ- _L , K _GY - _L , Kγ- _L are set, and both wheel steering devices 12 are normal. There is a two-wheel steering situation in which both the left and right wheels 10 are properly steered, and a single-wheel steering situation in which one of the two wheel steering devices 12 fails and one of the left and right wheels 10 is not steered properly. Depending on the rudder situation, high gains K _v θ- _H , K _IS - _H , K _d δ- _H , K _GY - _H , K γ- _H and low gains K _v θ- _L , K _IS - _L , K _d δ- The component determination gains K _v θ, K _IS , K _d δ, K _GY , and K γ are switched between _L , K _GY - _L , and K γ - _L .

To explain in more detail, the vehicle speed steering angle dependent component Tq _Cv θ and the steering load dependent component Tq _C-IS are the actual steering angle θ of both the left and right wheels 10, and the steering current for both, respectively. Since it is determined based on I _S , in a single-wheel steering situation where one of the two wheel steering devices 12 has failed, the actual steering angle θ of one of the left and right wheels 10, and the actual steering angle θ of one of the left and right wheels 10, There is a possibility that the rudder current I _S cannot be accurately grasped, and the vehicle speed turning angle dependent component Tq _Cv θ and the steering load dependent component Tq _C-IS may themselves become inappropriate values. Therefore, in a single-wheel steering situation, the contributions of the vehicle speed turning angle dependent component Tq _Cv θ and the steering load dependent component Tq _C-IS are set to be low, and the operational reaction force corresponding to the actual turning behavior of the vehicle is accordingly reduced. In order to obtain this, the contributions of the lateral acceleration dependent component Tq _C-GY and the yaw rate dependent component Tq _C- γ are set high, and in order to limit sudden steering operations, the contribution of the operation speed dependent component Tq _Cd δ is set to be high. Set it high.

Specifically, as shown in the table of FIG. 4(b), in a two-wheel steering situation, the vehicle speed turning angle dependent component determination gain K _v θ and the steering load dependent component determination gain K _IS are set to high gains, respectively. K _v θ- _H , K _IS - _H are the operation speed-dependent component determination gain K _d δ, lateral acceleration-dependent component determination gain K _GY , and yaw rate-dependent component determination gain Kγ, respectively, and the low gains K _d δ- _L , K Set to _GY - _L , Kγ- _L . On the other hand, in a one-wheel steering situation, the vehicle speed steering angle dependent component determining gain K _v θ and the steering load dependent component determining gain K _IS are manipulated to low gains K _v θ- _L and K _IS - _L , respectively. The velocity-dependent component determination gain K _d δ, the lateral acceleration-dependent component determination gain K _GY , and the yaw rate-dependent component determination gain Kγ are set to high gains K _d δ- _H , K _{GY -H} , and Kγ- _H , respectively.

The gain setting multiplication unit 130 determines whether it is a two-wheel steering situation or a one-wheel steering situation based on the failure information DEF transmitted from the self-diagnosis unit 111 of each steering ECU 16, and applies Based on this, each component determination gain K _v θ, K _IS , K _d δ, K _GY , and Kγ is changed.

In addition, in this steering system, for example, by setting the low gains K _v θ- _L , K _IS - _L , K _d δ- _L , K _GY - _L , and K γ- _L to 0, in a two-wheel steering situation, Vehicle speed turning angle dependent component Tq _Cv θ, steering load dependent component Tq _C-IS Only reaction force torque Tq _C is applied, and in a one-wheel steering situation, operation speed dependent component Tq _Cd δ, lateral acceleration dependent component Tq _{C -GY} , the reaction torque Tq _C of only the yaw rate dependent component Tq _C- γ may be applied. Further, as the vehicle behavior dependent component, only one of the lateral acceleration dependent component Tq _C-GY and the yaw rate dependent component Tq _C- γ may be employed.

(b) Control flow Although the steering control and operation reaction force control described above may be performed by an electronic circuit such as an ASIC designed according to the functional blocks of FIG. 3, in this steering system, the steering control is This is carried out by the computers of the ECU 18 and the steering ECU 16 repeatedly executing a target steering angle determination program and a wheel steering program, the flowchart of which is shown in FIG. The operation reaction force control is performed by the computer of the operation ECU 18 repeatedly executing an operation reaction force control program shown in a flowchart in FIG. 7 at short time pitches (for example, several meters to several tens of milliseconds). Below, the flow of steering control and operation reaction force control according to those programs will be explained with reference to those flowcharts.

i) Steering control In the process according to the target turning angle determination program executed in the operation ECU 18, first, in step 1 (hereinafter sometimes referred to as "S1". The same applies to other steps), the brake ECU 38 Based on the transmitted information, the vehicle speed v is acquired, and in S2, the steering gear ratio β is determined based on the vehicle speed v with reference to the map data shown in FIG. 4(a). In subsequent S3, the steering angle δ is detected by the steering sensor 82, and in S4, the target turning angle θ ^* of each wheel 10 is determined based on the operating angle δ and the steering gear ratio β. Information about the determined target steering angle θ ^* is transmitted to each steering ECU 16 in S5.

In the process according to the wheel steering program executed in each steering ECU 16, first, in S11, the target steering angle θ ^* of the wheel 10 to be steered is acquired based on information transmitted from the operation ECU 18. . On the other hand, in S12, the actual steering angle θ of the wheels 10 is acquired based on the motor rotation angle θ _M detected by the motor rotation angle sensor 70d. Then, in S13, the turning angle deviation Δθ is specified based on the target turning angle θ ^* and the actual turning angle θ.

Next, in S14, the steering torque Tq _S to be applied to the wheels 10 is determined based on the steering angle deviation Δθ and according to the feedback control method. In subsequent S15, a steering current I _S to be supplied to the steering motor 70a is determined based on the steering torque Tq _S , and in S16, a current is applied to the steering motor 70a based on the steering current I _S. is supplied. Information about the acquired actual steering angle θ and the determined steering current I _S is transmitted to the operation ECU 18 in S17.

ii) Operation reaction force control In the process according to the operation reaction force control program executed in the operation ECU 18, first, in S21, based on the information transmitted from the brake ECU 38 and the information transmitted from each steering ECU 16, , vehicle speed v, and actual steering angle θ are obtained. Since the information regarding the actual steering angle θ is transmitted to each of the left and right wheels 10, as explained earlier, in S21, the actual steering angle θ is determined based on the actual rotation of the left and right wheels 10. It is obtained as the average steering angle _θAVE, which is the average of the steering angles θ. Then, in S22, the vehicle speed turning angle dependent component Tq _Cv θ is determined based on the vehicle speed v and the average turning angle θ _AVE according to the function described above.

Next, in S23, the steering current I _S is acquired based on the information transmitted from each steering ECU 16. Since the information regarding the steering current I _S is transmitted from the steering ECU 16 corresponding to each of the left and right wheels 10, as explained earlier, in S23, the steering current I _S is It is obtained as the average steering current I _{S -AVE,} which is the average of I _S . Then, in S24, the steering load dependent component Tq _C-IS is determined based on the average steering current I _S-AVE and according to the map data shown in FIG. 5(a).

In subsequent S25, the steering sensor 82 detects the operating angle δ of the steering wheel 80, and the operating speed dδ is specified based on the operating angle. Then, in S26, the operation speed dependent component Tq _Cd δ is determined based on the specified operation speed dδ and according to the map data shown in FIG. 5(b).

In S27, the lateral acceleration G _Y detected by the lateral acceleration sensor 44 is acquired, and in S28, based on the lateral acceleration G _Y , the lateral acceleration dependent component Tq _C-GY is determined according to the map data shown in FIG. 5(c). is determined. In S29, the yaw rate γ detected by the yaw rate sensor 46 is acquired, and in S30, the yaw rate dependent component Tq _C- γ is determined based on the yaw rate γ and according to the map data shown in FIG. 5(d).

In the next step S31, depending on whether the failure information DEF is transmitted from the self-diagnosis unit 111 of either of the two steering ECUs 16, the steering system is in the above-mentioned two-wheel steering condition or one-wheel steering condition. It is determined whether If it is determined that the situation is a two-wheel steering situation, in S32, the vehicle speed turning angle dependent component determining gain K _v θ is set to a high gain K _v θ- _H , and the steering load dependent component determining gain K _IS is set to a high gain. K _IS - _H , the operation speed dependent component determining gain K _d δ is a low gain K _d δ- _L , the lateral acceleration dependent component determining gain K _GY is a low gain K _GY - _L , and the yaw rate dependent component determining gain K γ is low. The gain Kγ- _L is set respectively. On the other hand, if it is determined that the situation is one-wheel steering, in S33, the vehicle speed turning angle dependent component determination gain K _v θ is changed to a low gain K _v θ- _L , and the steering load dependent component determining gain K _IS is the low gain K _IS - _L , the operation speed dependent component determining gain K _d δ is the high gain K _d δ- _H , the lateral acceleration dependent component determining gain K _GY is the high gain K _GY - _H , and the yaw rate dependent component determining gain is Kγ is set to high gain Kγ− _H , respectively.

Each component determination gain K _v θ, K _IS , K _d δ, K _GY , Kγ set above and each component determined above Tq _Cv θ, Tq _C-IS , Tq _Cd δ, Tq _C-GY , Tq Based on _C- γ, reaction torque _TqC is determined in S34. Based on the determined reaction torque Tq _C , the reaction current I C to be supplied to the reaction motor 84a is determined in S35, and in S36, the reaction force current I _C to be supplied to the reaction force motor 84a is determined based on the reaction force current I _C. Current is supplied to

10: Wheel 12: Wheel steering device 14: Operating device 16: Steering electronic control unit (steering ECU) [controller] 18: Operation electronic control unit (operation ECU) [controller] 42: CAN 44: Lateral acceleration sensor 46 : Yaw rate sensor 70: Steering actuator 70a: Steering motor [electric motor] [drive source] 70d: Motor rotation angle sensor 80: Steering wheel [steering operation member] 82: Steering sensor 84: Reaction force applying device 84a: Reaction force Motor 110: Current sensor 111: Self-diagnosis section 112: Vehicle speed turning angle dependent component determining section 114: Turning angle averaging section 116: Turning load dependent component determining section 118: Load averaging section 120: Operation speed dependent component determining section 122 : Vehicle behavior dependent component determining unit 124: Lateral acceleration dependent component determining unit 126: Yaw rate dependent component determining unit 128: Adder 130: Gain setting multiplier 132 to 140: Multiplier 142: Reaction force energization control unit G _Y : Lateral acceleration γ: Yaw rate δ: Steering operation angle [operation amount] dδ: Operation speed θ: Steering angle [steering amount]/actual turning angle θ _R : Actual turning angle of right wheel θ _L : Actual turning angle of left wheel θ _AVE : Average steering angle Tq _C : Reaction torque [operation reaction force] Tq _Cv θ: Vehicle speed steering angle dependent component Tq _C-IS : Steering load dependent component Tq _Cd δ: Operation speed dependent component Tq _C-GY : Lateral acceleration dependent component Tq _C- γ: Yaw rate dependent component I _S : Steering current I _SR : Right wheel steering current I _SL : Left wheel steering current I _S-AVE : Average steering current I _C : Reaction current K _v θ: Vehicle speed steering angle dependent component determination gain K _IS : Steering load dependent component determination gain K _d δ: Operation speed dependent component determination gain K _GY : Lateral acceleration dependent component determination gain Kγ: Yaw rate dependent component determination Gain K _v θ- _H , K _IS - _H , K _d δ- _H , K _GY - _H , K γ- _H : High gain K _v θ- _L , K _IS - _L , K _d δ- _L , K _GY - _L , Kγ- _L : Low gain DEF: Failure information

Claims (5)

A steer-by-wire steering system installed in a vehicle,
An operating member operated by a driver, a steering device that steers wheels in accordance with the operation of the operating member, a reaction force applying device that applies an operating reaction force to the operating member, and a steering system that controls the steering system. Equipped with a controller that controls the
The controller,
configured to determine the operational reaction force to be applied, and to control the reaction force applying device based on the determined operational reaction force, and
A steering system configured to determine the operation reaction force including a vehicle behavior dependent component that is based on at least one of a lateral acceleration occurring in the vehicle and a yaw rate of the vehicle. The controller,
2. The control system according to claim 1, wherein the control system is configured to determine the operation reaction force including components other than the vehicle behavior dependent component, and is configured to be able to change the degree of contribution of the vehicle behavior dependent component to the operation reaction force. steering system. The controller,
As a component other than the vehicle behavior dependent component, at least one of a vehicle speed turning amount dependent component that depends on the traveling speed of the vehicle and the turning amount of the wheels, and a turning load dependent component that depends on the load of the steering device. The steering system according to claim 2, wherein the steering system is configured to determine the operation reaction force including: The steering system is
Each of the steering devices is the steering device, and includes two steering devices that independently steer one of the left and right wheels,
The controller,
Claim 2 or Claim 3, wherein the vehicle behavior-dependent component is configured to increase the degree of contribution of the vehicle behavior-dependent component in a single-wheel steering situation in which one of the left and right wheels is steered by only one of the two steering devices. The steering system described in. The components other than the vehicle behavior dependent component include an operation speed dependent component that depends on the operation speed of the operation member,
The controller,
The steering system according to claim 4, wherein the steering system is configured to increase the degree of contribution of the operation speed dependent component in the one-wheel steering situation.

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