Vehicle motion control system and vehicle motion control method

Abstract

To provide vehicle motion control by which, when there is a driving force difference between the right and left wheels of a vehicle, a steering reaction force not reflecting a yaw moment caused by the driving force difference is applied to a steering wheel.SOLUTION: A vehicle motion control system used in a vehicle in which at least two front wheels or two rear wheels have in-wheel motors and driving forces of the respective wheels can be independently controlled, includes: a yaw moment detection unit that detects generation of a yaw moment caused by a driving force difference between right and left wheels, based on motor information received from the in-wheel motors of the respective wheels; a steer-by-wire control unit that, when the yaw moment detection unit detects the generation of the yaw moment, generates a steering wheel reaction force command, based on a steering reaction force in which an influence of the yaw moment is restricted; and a steering wheel unit that applies a steering reaction force based on the steering wheel reaction force command, to a steering wheel.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to a vehicle motion control system and a vehicle motion control method used in a vehicle capable of independently controlling the driving force of each wheel.

Background Art

[0002] As a device for applying a steering reaction force to a steering wheel (steering handle), an electric power steering device of Patent Document 1 is known. As described in paragraph 0008 of this document, this electric power steering device aims to "appropriately control the control of the electric power steering device capable of applying a steering reaction force when a vehicle behavior control device that generates a yaw moment on the vehicle body and controls the vehicle behavior, such as a rear control device, fails, and make it easier to cancel the yaw moment." Further, in paragraph 0048 of the same document, it is described that "even when the rear control device 11 fails, the steering reaction force of the electric power steering device 21 is appropriately controlled with emphasis on the driver's steering intention, and the driver can easily perform a corrective steering to cancel the yaw moment caused by the failure."

[0003] That is, the electric power steering device of this document applies a steering reaction force to the steering wheel with the idea of appropriately transmitting the failure of the vehicle behavior control device to the driver, so that when a yaw moment caused by the failure occurs, it is easier to perform a corrective steering to cancel the yaw moment.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In recent years, electric vehicles that can independently control the driving force of each wheel by incorporating in-wheel motors in each wheel have been increasingly popular. In this type of electric vehicle, by intentionally creating a difference in the driving force of each wheel and appropriately generating roll, pitch, and yaw moments, it is possible to improve the vehicle's maneuverability and stability during turning and other maneuvers. Also, in this type of electric vehicle, due to a failure of some in-wheel motors or the like, some wheels may become substantially non-driven wheels, resulting in a difference in the driving force of each wheel. Regardless of the cause, when a yaw moment corresponding to the difference in driving force between the left and right wheels occurs, the steering wheel may be steered in a direction unintended by the driver due to this yaw moment.

[0006] Under such circumstances, when applying a steering reaction force corresponding to the steering to the steering wheel using the technology of Patent Document 1, there was a possibility that the driver who received an unexpected steering reaction force from the steering wheel would feel discomfort, or that the driver who received a strong steering reaction force from the steering wheel would be forced to hold the steering wheel and the vehicle would move in an unintended direction.

[0007] Therefore, an object of the present invention is to provide a vehicle motion control system and a vehicle motion control method that can apply a steering reaction force that does not reflect the yaw moment caused by the difference in driving force to the steering wheel when there is a difference in driving force between the left and right wheels of the vehicle, regardless of whether the difference in driving force between the left and right wheels is intentionally provided.

Means for Solving the Problems

[0008] To solve the above problems, the present invention provides a vehicle motion control system for use in a vehicle in which at least two front wheels or two rear wheels have in-wheel motors and the driving force of each wheel can be independently controlled, comprising: a yaw moment detection unit that detects the occurrence of a yaw moment caused by the difference in driving force between the left and right wheels based on motor information received from the in-wheel motors of each wheel; a steer-by-wire control unit that generates a steering reaction force command based on a steering reaction force that suppresses the influence of the yaw moment when the yaw moment detection unit detects the occurrence of the yaw moment; and a steering unit that applies a steering reaction force to the steering wheel based on the steering reaction force command. [Effects of the Invention]

[0009] According to the vehicle motion control system or vehicle motion control method of the present invention, regardless of whether the difference in driving force between the left and right wheels is intentionally created or not, when there is a difference in driving force between the left and right wheels of a vehicle, a steering reaction force that does not reflect the yaw moment caused by that difference in driving force can be applied to the steering wheel.

[0010] As a result, according to the present invention, it is possible to avoid situations in which the driver feels discomfort due to an unexpected steering reaction force from the steering wheel, or situations in which the driver loses control of the steering wheel due to a strong steering reaction force from the steering wheel, causing the vehicle to move in an unintended direction. [Brief explanation of the drawing]

[0011] [Figure 1] A plan view showing an example of the vehicle structure of Example 1. [Figure 2] Diagram illustrating the self-aligning torque (MSA) when the steering wheels are non-driven wheels. [Figure 3] Figure 2 shows a graph illustrating the relationship between steering angle and steering torque. [Figure 4] An explanatory diagram of the self-aligning torque (MSA) when the steering wheels are also the drive wheels. [Figure 5] Figure 4 shows a graph illustrating the relationship between steering angle and steering torque. [Figure 6] A schematic diagram showing the components of the vehicle motion control system of Example 1. [Figure 7] Functional block diagram of the main components of the vehicle motion control system of Example 1. [Figure 8] Figure 7 shows a functional block diagram of the yaw moment component remover. [Figure 9] Figure 8 shows a functional block diagram of the first steering force calculator. [Figure 10] A graph showing the frequency characteristics of various steering forces and LPF gain. [Figure 11] A graph showing the relationship between steering force under normal conditions and when a yaw moment occurs. [Figure 12] Functional block diagram of the yaw moment component remover in Example 2. [Figure 13] Functional block diagram of the yaw moment component remover in Example 3. [Modes for carrying out the invention]

[0012] Hereinafter, embodiments of the vehicle motion control system 100 of the present invention will be described with reference to the drawings. [Examples]

[0013] First, the vehicle motion control system 100 according to Embodiment 1 of the present invention will be described using Figures 1 to 11. Hereinafter, the vehicle motion control system 100 is described in detail, assuming that it is a system mounted on a four-wheel drive electric vehicle (hereinafter simply referred to as "vehicle 1") with in-wheel motors incorporated in each wheel, and that vehicle 1 is a vehicle that can appropriately control the driving force of each wheel during cornering and other driving, thereby appropriately applying roll, pitch, and yaw moments to enhance motion performance and stability.

[0014] <Example of Vehicle 1 Structure> Figure 1 is a plan view showing an example of the structure of vehicle 1. As shown in Figure 1, below, the left front wheel of vehicle 1 is tire 8FL, the right front wheel is tire 8FR, the left rear wheel is tire 8RL, the right rear wheel is tire 8RR, and the distance between the front wheels is tread d.F , the tread d of the rear wheel distance R , the length from the center of gravity of the vehicle 1 to the front axle is the distance L F , the length from the center of gravity to the front axle is the distance L R , the moment around the z-axis at the center of gravity position is the yaw moment M z is referred to as. In the xyz coordinate system in the figure, the forward direction of the vehicle 1 is the positive direction of the x-axis, the left direction is the positive direction of the y-axis, and the upward direction is the positive direction of the z-axis, which is an orthogonal coordinate system.

[0015] <Self-aligning torque> Next, the self-aligning torque generated on the steering wheels of the vehicle 1 will be described separately for the case where the driving force is not considered and the case where it is considered. The self-aligning torque is the torque that acts in the direction of reducing the slip angle θ when the tire travels in a state of a predetermined slip angle θ. Therefore, when it is desired to maintain the desired traveling direction at the steering wheels, the driver needs to continuously apply a steering wheel torque to the steering wheel that resists the self-aligning torque generated at the steering wheels.

[0016] <<Self-aligning torque M when the driving force is not considered SA >> FIG. 2 is a plan view for explaining the self-aligning torque M when the driving force on the steering wheels is not considered SA . When the slip angle θ is within a predetermined range, a cornering force Fy that is substantially proportional to the slip angle θ acts on the steering wheel (tire 8) during turning travel.

[0017] Here, if the pneumatic trail ξ is the radial distance of the tire from the steering center of the tire 8 to the origin of the cornering force Fy n , the self-aligning torque M generated by the non-driven wheels SA is calculated by the following (Equation 1). That is, a self-aligning torque M of a magnitude substantially proportional to the slip angle θ acts on the steering wheel, which is a non-driven wheel SA .

[0018]

Equation

[0019] Figure 3 is a graph showing the relationship between steering angle and steering torque, without considering the driving force to the steering wheels. Considering only the reaction force due to self-aligning torque, the steering angle shown on the horizontal axis is proportional to the slip angle θ of the steering wheels, and the steering torque shown on the vertical axis is the torque that must be applied to the steering wheel to maintain the current direction of travel. As is clear from this figure, since the steering angle and steering torque are proportional, the driver applies a steering torque to the steering wheel that is proportional to the magnitude of the slip angle θ, thereby achieving self-aligning torque M SA This prevents the steering wheels from turning and allows the vehicle to continue traveling in the desired direction.

[0020] <<When considering driving force>> Figure 4 shows the self-aligning torque M when there is driving force applied to the steering wheels. SA This is a plan view illustrating the mechanism. When the slip angle θ is within a predetermined range, the steering wheel (tire 8) during turning is subjected not only to a lateral force Fy that is approximately proportional to the slip angle θ, but also to a predetermined driving force Fx. When the driving force Fx is applied, the tire 8 and the suspension flex, and due to the influence of the suspension geometry, the steering center of the tire 8 on the contact surface is located at the position on the contact surface illustrated in Figure 4, relative to the steering center of the mechanism illustrated in Figure 2.

[0021] Here, if we define the distance in the tire width direction from the steering center in Figure 4 to the starting point of the driving force Fx as the trail ξ, then the self-aligning torque M generated in the drive wheel is... SA ' is calculated by the following (Equation 2). That is, the steering wheels, which are the drive wheels, have a self-aligning torque M which is the sum of a torque proportional to the slip angle θ and a torque proportional to the driving force Fx. SA This will have an effect.

[0022]

number

[0023] Figure 5 is a graph showing the relationship between steering angle and steering torque when the steering wheels are driven. As is clear from this figure, when the driving force Fx of the steering wheels is in the positive direction (see Figure 4), the solid line graph for the case where the driving force Fx is zero is shifted downward in accordance with the magnitude of the driving force Fx, resulting in a dotted line graph. On the other hand, when the driving force Fx of the steering wheels is in the negative direction, the solid line graph for the case where the driving force Fx is zero is shifted upward in accordance with the magnitude of the driving force Fx, resulting in a dashed line graph. Therefore, by applying an appropriate steering torque to the steering wheel as exemplified in Figure 5, the driver can achieve self-aligning torque M SA This prevents the steering wheels from turning due to ', allowing the vehicle to continue traveling in the desired direction.

[0024] <Yaw moment M caused by the difference in driving force between the left and right wheels z > In this embodiment, vehicle 1 controls the driving force Fx of each wheel individually and dynamically to enhance maneuverability and stability during cornering and other maneuvers. In vehicle 1, the driving force of some tires 8 may be lost or reduced due to failure of some in-wheel motors, etc.

[0025] If a difference in driving force occurs between the left and right wheels of vehicle 1 for any of the reasons mentioned above, then driving forces of different magnitudes will be generated in the left and right steering wheels. In that case, vehicle 1 will have a yaw moment M calculated by the following (Equation 3). z This occurs. Note that in (Equation 3), Fx FL Fx FR Fx RL Fx RR These represent the driving force for tires 8FL, 8FR, 8RL, and 8RR, respectively.

[0026]

number

[0027] The yaw moment M calculated using (Equation 3) zThis causes a slip angle in the vehicle body, and the resulting lateral force changes the self-aligning torque acting on the steering wheels. This occurs independently of the driver's steering intentions and is therefore unexpected for the driver.

[0028] In summary, the steering wheel is affected by changes in self-aligning torque resulting from changes in the driving force to the steering wheels, and also by changes in self-aligning torque resulting from the yaw moment caused by the difference in driving force between the left and right wheels. When the steering reaction force changes due to these factors, it not only causes the driver to feel uncomfortable, but if the sudden steering reaction force is stronger than the driver's steering input, the steering wheel may be pulled to one side, potentially causing the vehicle's course to change in a direction unintended by the driver.

[0029] Therefore, in the vehicle motion control system 100 of this embodiment, the yaw moment M caused by the difference in driving force between the left and right wheels is controlled by the following configuration. z Even if this occurs, the design ensures that its effect is not reflected in the steering response force of the steering wheel.

[0030] <Components of the vehicle motion control system 100> Here, the components of the vehicle motion control system 100 in this embodiment will be explained using the schematic configuration diagram in Figure 6. As shown in this figure, the vehicle 1 is equipped with the following components of the vehicle motion control system 100: a vehicle motion control device 2, a vehicle motion sensor 3, an accelerator pedal 4, a brake pedal 5, a steering system 6 (steering wheel unit 61, steering unit 62, steer-by-wire control unit 63), in-wheel motors 7 (7FL, 7FR, 7RL, 7RR), tires 8 (8FL, 8FR, 8RL, 8RR), and a controller area network 9. The details of each part will be explained in order below.

[0031] The vehicle motion control device 2 is a control device that controls vehicle motion by controlling various parts of the vehicle 1 in accordance with the driver's operations, and controls the yaw moment M caused by the difference in driving force between the left and right wheels. zIt also has the function of detecting the occurrence of and calculating its magnitude. Specifically, this vehicle motion control device 2 is a computer such as an ECU (Electronic Control Unit) equipped with hardware such as a CPU and other arithmetic units, a memory device such as semiconductor memory, and a communication device. The arithmetic units then execute predetermined programs to realize the functions described later, but in the following explanation, such well-known technologies will be omitted as appropriate.

[0032] The storage device of the vehicle motion control device 2 contains vehicle information determined by the specifications of the vehicle 1 (for example, the tread d in Figure 1). F d R , distance L F , L R (etc.) are pre-registered, and this vehicle information can be provided as needed to the relevant parts of the vehicle.

[0033] The vehicle momentum sensor 3 is a sensor that detects information regarding the momentum of vehicle 1. The momentum detected here includes, for example, the acceleration Gx in the longitudinal direction (x-axis direction), the acceleration Gy in the lateral direction (y-axis direction), the acceleration Gz in the vertical direction (z-axis direction), and the yaw rate γ at the center of gravity of vehicle 1.

[0034] The accelerator pedal 4 is the pedal that the driver presses when accelerating the vehicle 1. When the accelerator pedal 4 is pressed, the vehicle motion control device 2 controls the drive system (such as the in-wheel motors 7 during driving) so that the vehicle 1 accelerates according to the amount the pedal is pressed.

[0035] Brake pedal 5 is the pedal that the driver presses when decelerating vehicle 1. When brake pedal 5 is pressed, vehicle motion control device 2 controls the braking system (regenerative in-wheel motor 7, brakes, etc.) so that vehicle 1 decelerates according to the amount the pedal is pressed.

[0036] The steering system 6 is a steer-by-wire system that steers the steering wheels according to the driver's steering wheel operation without mechanically connecting the steering wheel and the steering wheels, and includes a steering wheel unit 61, a steering unit 62, and a steer-by-wire control unit 63.

[0037] The steering unit 61 detects the steering angle and speed operated by the driver and transmits them to the vehicle motion control device 2, and also applies steering reaction force to the steering wheel in accordance with the reaction force generated by road information (such as ruts and bumps on the road surface).

[0038] The steering unit 62 is a unit that steers the steering wheels, tires 8FL and 8FR, by generating a steering force in accordance with the steering angle and operating speed of the steering wheel detected by the steering unit 61 using a steering actuator (not shown).

[0039] The steer-by-wire control unit 63 controls the steering actuator and calculates an appropriate steering reaction force according to the situation, transmitting it to the steering unit 61 as a steering reaction force command. Further details of the steer-by-wire control unit 63 will be described later.

[0040] The in-wheel motors 7 are motors installed for each tire 8, and under the control of the vehicle motion control device 2, they generate independent driving force for each tire 8. The actual vehicle 1 is also equipped with an inverter (not shown) that supplies power to the in-wheel motors 7, and a battery (not shown) that powers the inverter.

[0041] The controller area network 9 is a bus for the in-vehicle network that interconnects the vehicle motion control device 2, vehicle motion sensor 3, accelerator pedal 4, brake pedal 5, steering system 6, and in-wheel motor 7. In the following description, this embodiment will be explained while omitting the relay processing by the controller area network 9 as appropriate.

[0042] <Details of the vehicle motion control system 100> Next, using Figures 7 to 9, we will explain the details of the vehicle motion control in this embodiment, focusing on the main components of the vehicle motion control system 100, namely the vehicle motion control device 2 and the steering system 6.

[0043] Figure 7 is a functional block diagram of the main components of the vehicle motion control system 100: the vehicle motion control device 2, the steering wheel unit 61, and the steer-by-wire control unit 63. Although the steer-by-wire control unit 63 is shown externally to the vehicle motion control device 2, its functions may be integrated into the vehicle motion control device 2.

[0044] As shown in Figure 7, the yaw moment detection unit 21, which is a functional unit of the vehicle motion control device 2, receives four motor information IMs (IMs) from the four in-wheel motors 7 (7FL, 7FR, 7RL, 7RR) for each wheel. FL , IM FR , IM RL , IM RR The following information is input. This motor information IM includes torque information indicating the output torque value that each in-wheel motor recognizes, and fault information indicating whether or not each in-wheel motor is faulty. Note that even when each in-wheel motor outputs fault information indicating a fault, it may still output meaningful torque information (objectively false information).

[0045] When the yaw moment detection unit 21 receives motor information IM for all four wheels, it converts the torque information within each motor information into the driving force for each wheel, and then uses the above-mentioned (Equation 3) to calculate the yaw moment M z The magnitude is calculated. Then, the yaw moment M is greater than or equal to a predetermined threshold. z If a yaw moment is calculated, the yaw moment generation flag and the calculated yaw moment value are output to the steer-by-wire control unit 63.

[0046] Furthermore, if any of the input fault information indicates a fault in the in-wheel motor 7, the yaw moment detection unit 21 outputs a yaw moment generation flag and the calculated yaw moment value to the steer-by-wire control unit 63 based on the yaw rate γ acquired by the vehicle momentum sensor 3.

[0047] As shown in Figure 7, the steer-by-wire control unit 63 includes a yaw moment component remover 63a and a steering reaction force calculator 63b. The yaw moment component remover 63a also includes a separation unit 63a1 and a steering force determination unit 63a2.

[0048] The separation unit 63a1 is a functional unit that generates steering force for normal conditions (when no yaw moment is generated) and steering force for when a yaw moment is generated in parallel. As shown in Figure 8, it includes a first steering force calculator, a second steering force calculator, and a low-pass filter (LPF).

[0049] The first steering force calculator is a calculator that calculates the first steering force by emphasizing steering actuator information. This steering actuator information is information output by the steering unit 62 and is information that has a strong correlation with the driver's steering operation and road information, such as the torque generated by the steering motor and the operating speed of the steering actuator. In Figure 8, the first steering force calculator has inputs for yaw moment, vehicle information, and steering actuator information, but inputs of information other than steering actuator information may be omitted.

[0050] Figure 9 shows an example of a functional block diagram of the first steering force calculator. The first steering force calculator illustrated here performs the following processing based on the steering motor torque and the operating speed of the steering actuator, which are obtained from the steering actuator information. Specifically, it first calculates the torque consumed by the steering actuator itself based on the steering motor torque and the operating speed of the steering actuator. Then, it subtracts the calculated torque from the steering motor torque, performs a coordinate transformation (conversion from the force in the thrust direction of the steering actuator to the torque in the rotation direction of the steering wheel) on the torque after the subtraction, and outputs the steering force after the coordinate transformation as the first steering force.

[0051] The second steering force calculator is a calculator that calculates the second steering force by emphasizing vehicle information. This vehicle information includes, for example, information that has a weak correlation with the driver's steering input or road information, such as yaw rate γ, acceleration Gx, Gy, and Gz detected by the vehicle momentum sensor 3, or the inertia I around the z axis, which is determined by the specifications of the vehicle 1. z , distance L F , L R This information is unrelated to the driver's steering input or road information. Note that the second steering force calculator in Figure 8 has inputs for yaw moment, vehicle information, and steering actuator information, but input of information other than vehicle information may be omitted.

[0052] This second steering force calculator uses the vehicle information and mathematical model of vehicle 1 described above to calculate the second steering force. For example, if we use (Equation 4), which is the equation for the rotational motion of vehicle 1 around the z-axis, as a simplified mathematical model, first we calculate the vehicle information (inertia I z , yaw rate γ, distance L F , L R Vehicle longitudinal speed v x , vehicle lateral speed v y Using (Equation 4), (Equation 5), and (Equation 6), the cornering force Fy(F) of each wheel is calculated. yFL F yFR F yRL F yRRNext, calculate the self-aligning torque M of each wheel using (Equation 1) or (Equation 2) described above. SA M SA The system calculates the ' self-aligning torque, performs a coordinate transformation (conversion from torque around the steering axis of the steering wheels to torque in the direction of steering wheel rotation) on the obtained self-aligning torque, and outputs the steering force after the coordinate transformation as a second steering force.

[0053]

number

[0054]

number

[0055]

number

[0056] The low-pass filter (LPF) receives the difference between the first steering force and the second steering force as input, and the low-frequency component of this difference is the yaw moment M z This component is output. Furthermore, at the output side of the low-pass filter (LPF), the low-frequency component, which is the output of the low-pass filter (LPF), is subtracted from the first steering force and output to the steering force determination unit 63a2. The significance of this processing near the low-pass filter (LPF) will be explained later.

[0057] As shown in Figure 8, the steering force determination unit 63a2 determines the output of the steering force based on the presence or absence of a yaw moment generation flag from the yaw moment detection unit 21. The significance of this processing in the steering force determination unit 63a2 will be explained later.

[0058] As shown in Figure 7, the steering reaction force calculator 63b generates a steering reaction force command to be transmitted to the steering unit 61 based on the steering force output by the yaw moment component remover 63a. The steering reaction force command generated here is basically proportional to the value of the steering force output by the yaw moment component remover 63a, but appropriate modifications are made so that the steering reaction force is stronger when the vehicle speed is high and weaker when the vehicle speed is low.

[0059] <Effects of this embodiment> Next, the effects of the vehicle motion control system 100 in this embodiment will be specifically explained with reference to the graphs in Figures 10 and 11.

[0060] Figure 10 is a graph showing the frequency characteristics of various steering forces and the frequency characteristics of the LPF gain, with the horizontal axis representing frequency and the vertical axis representing steering force or LPF gain. In this figure, (a) the solid line represents the first steering force calculated by the first steering force calculator mainly based on steering actuator information. (b) the dashed line represents the second steering force calculated by the second steering force calculator mainly based on vehicle information. (c) the dotted line represents the steering force caused by road information (contact conditions with road surface ruts, bumps, etc.). (d) the dashed line represents the yaw moment M z This is the steering force caused by (e). The dashed line in (e) shows the frequency characteristics of the LPF gain applied to the low-pass filter (LPF) to extract the steering force component in (d).

[0061] Comparing (c) steering force and (d) steering force based on this figure, it can be seen that the frequency characteristics of both steering forces overlap in some bands but do not overlap for most of the time. Therefore, by using a low-pass filter (LPF) with an LPF gain that has the characteristic of zero gain in the frequency band where only (c) steering force exists, low gain in the frequency band where both (c) and (d) steering forces are present, and high gain in the frequency band where only (d) steering force exists, it is possible to remove the frequency component of the steering force caused by (c) load information while removing (d) yaw moment M zIt can be seen that the frequency components of the steering force caused by this can be extracted.

[0062] Figure 11 is a graph showing the frequency characteristics of the two types of steering forces output by the separation unit 63a1 when the (e)LPF gain shown in Figure 10 is applied to the low-pass filter LPF.

[0063] Yaw moment M z If no yaw moment occurs, the yaw moment detection unit 21 does not input a yaw moment generation flag to the steering force determination unit 63a2. Therefore, the steering force determination unit 63a2 selects and outputs (f) the normal steering force ((a) the first steering force), as shown by the solid line in Figure 11 (see Figure 8). Consequently, in this case, (f) the steering force becomes the output of the yaw moment component remover 63a.

[0064] On the other hand, yaw moment M z If this occurs, the yaw moment detection unit 21 inputs a yaw moment generation flag to the steering force determination unit 63a2. The steering force determination unit 63a2 then selects and outputs the steering force at the time of yaw moment generation (g), as shown by the dashed line in Figure 11. Therefore, in this case, the steering force (g), with the frequency band corresponding to the steering force (d) in Figure 10 attenuated, becomes the output of the yaw moment component remover 63a.

[0065] Here, the yaw moment detection unit 21 of this embodiment detects the yaw moment M z The output state of the yaw moment generation flag can be instantly switched depending on the occurrence conditions. Therefore, the yaw moment component remover 63a can instantly switch the selected steering force when the reception state of the yaw moment generation flag changes.

[0066] Therefore, the difference in driving force between the left and right wheels results in a yaw moment M z If this occurs, the steering force input from the yaw moment component remover 63a to the steering reaction force calculator 63b is the yaw moment M z (f) From the steering force that reflects this, the yaw moment M z(g) Because the steering force instantly switches to a steering force that does not reflect this, the steering reaction force calculator 63b always calculates the yaw moment M caused by the difference in driving force between the left and right wheels. z It is possible to calculate the steering reaction force command after removing the influence of [unspecified factor].

[0067] As a result, even if the steering unit 61 applies a steering reaction force to the steering wheel based on the steering reaction force command when a difference in driving force occurs between the left and right wheels, the driver may feel an unnatural sensation in the steering reaction force, or the yaw moment M z This system helps to avoid situations where the steering wheel is pulled to one side by the steering reaction force, causing vehicle 1 to move in a direction unintended by the driver. [Examples]

[0068] Next, the vehicle motion control system 100 according to Embodiment 2 of the present invention will be described using Figure 12. Note that common points with Embodiment 1 will be omitted from the explanation.

[0069] Figure 12 is a functional block diagram of the yaw moment component remover 63a in this embodiment. As is evident from a comparison with Figure 8 of Embodiment 1, the yaw moment component remover 63a in this embodiment has an amplifier G added to the output side of the low-pass filter LPF.

[0070] The yaw moment component remover 63a in this embodiment is used in situations where one of the four in-wheel motors 7 of the vehicle 1 has failed, and the vehicle is traveling in a straight line using the remaining three in-wheel motors 7, that is, when there is no yaw moment caused by turning and the yaw moment M caused by the difference in driving force between the left and right wheels is removed. z This is particularly effective in situations where only [this] exists.

[0071] In order to calculate the appropriate steering reaction force under these circumstances, it is ideally necessary to use highly accurate vehicle information and a highly accurate mathematical model in the second steering force calculator of the yaw moment component remover 63a to calculate a highly accurate second steering force. However, in this embodiment, to enable the calculation of a steering reaction force with a reasonable degree of accuracy even when the second steering force is calculated using a simple mathematical model such as (Equation 4), (Equation 5), and (Equation 6), an amplifier G is added to the output side of the low-pass filter LPF, thereby reducing the yaw moment M caused by the difference in driving force between the left and right wheels. z We have made it possible to more reliably eliminate the effects of [the problem].

[0072] Thus, according to this embodiment, the yaw moment M extracted by the low-pass filter LPF is z The steering force resulting from this is amplified and subtracted from the first steering force, thereby increasing the yaw moment M z This can further reduce the influence on steering force when (g) yaw moment is generated. [Examples]

[0073] Next, the vehicle motion control system 100 according to Embodiment 3 of the present invention will be described using Figure 13. Note that common points with the above embodiment will be omitted from the explanation.

[0074] Figure 13 is a functional block diagram of the yaw moment component remover 63a in this embodiment. As is obvious from a comparison with Figure 12 of Embodiment 2, the yaw moment component remover 63a in this embodiment is configured so that the second steering force can be directly used as the output of the separation unit 63a1, and if information indicating a malfunction of the in-wheel motor 7 is input to the steering force determination unit 63a2, the second steering force can be directly used as the output of the yaw moment component remover 63a.

[0075] As a result, if some of the tires 8 become effectively non-driven wheels, the steering reaction force can be determined based on a second steering force calculated based on the output of the vehicle momentum sensor 3 and a mathematical model of the vehicle 1, thereby avoiding the situation in which an inappropriate steering reaction force is generated based on erroneous information from the in-wheel motor 7. [Explanation of Symbols]

[0076] 100 Vehicle motion control system 1 vehicle 2. Vehicle motion control system 21 Yaw moment detection unit 3. Vehicle motion sensor 4. Accelerator pedal 5. Brake pedal 6. Steering System 61 Handle Unit 62 Steering Unit 63. Steer-by-wire control unit 63a Yaw moment component remover 63a1 Separation section 63a2 Steering force determination unit 63b Steering reaction force calculator 7 In-wheel motor 8 tires 9. Controller Area Network

Claims

1. A vehicle motion control system used in a vehicle in which at least two front wheels or two rear wheels have in-wheel motors and the driving force of each wheel can be independently controlled, A yaw moment detection unit detects the generation of a yaw moment caused by the difference in driving force between the left and right wheels, based on motor information received from the in-wheel motors of each wheel. When the yaw moment detection unit detects the occurrence of the yaw moment, a steer-by-wire control unit generates a steering reaction force command based on a steering reaction force that suppresses the influence of the yaw moment, A steering unit that applies a steering reaction force to the steering wheel based on the aforementioned steering reaction force command, A vehicle motion control system characterized by comprising the following:

2. In the vehicle motion control system according to claim 1, The steer-by-wire control unit is A first steering force calculator calculates a first steering force based on steering actuator information from a steering actuator that steers the steering wheel, A second steering force calculator calculates a second steering force based on vehicle information from a vehicle momentum sensor that detects vehicle momentum, It includes a low-pass filter that extracts the low-frequency component of the difference between the first steering force and the second steering force, A vehicle motion control system characterized in that, when the yaw moment detection unit detects the occurrence of the yaw moment, it calculates the steering reaction force based on the steering force obtained by subtracting the low-frequency component from the first steering force.

3. In the vehicle motion control system according to claim 1, The steer-by-wire control unit is A first steering force calculator calculates a first steering force based on steering actuator information from a steering actuator that steers the steering wheel, A second steering force calculator calculates a second steering force based on vehicle information from a vehicle momentum sensor that detects vehicle momentum, A low-pass filter that extracts the low-frequency components of the difference between the first steering force and the second steering force, It includes an amplifier that amplifies the low-frequency components, A vehicle motion control system characterized in that, when the yaw moment detection unit detects the occurrence of the yaw moment, it calculates the steering reaction force based on the steering force obtained by subtracting the amplification value of the low-frequency component from the first steering force.

4. In the vehicle motion control system according to claim 3, A vehicle motion control system characterized in that, when the yaw moment detection unit detects a failure of the in-wheel motor based on the motor information, it calculates the steering reaction force based on the second steering force.

5. In the vehicle motion control system according to any one of claims 2 to 4, A vehicle motion control system characterized in that the second steering force calculator calculates the second steering force based on the vehicle information and the mathematical model of the vehicle.

6. A vehicle motion control method used in a vehicle that incorporates in-wheel motors in at least two front wheels or two rear wheels, and in which the driving force of each wheel can be independently controlled, The steps include detecting the generation of a yaw moment caused by the difference in driving force between the left and right wheels, based on motor information received from the in-wheel motors of each wheel, When the occurrence of the yaw moment is detected, the step of generating a steering reaction force command based on a steering reaction force that suppresses the effect of the yaw moment, The steps include: applying a steering reaction force to the steering wheel based on the steering wheel reaction force command; A vehicle motion control method characterized by comprising the following:

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