Method and device for controlling vehicle

Abstract

When controlling a behavior control device capable of controlling the behavior of a vehicle, this method sets a feedforward control amount of the behavior control device corresponding to a target vehicle behavior state amount that is a target value of the behavior of the vehicle, sets a feedback control amount of the behavior control device for correcting the deviation between the target vehicle behavior state amount and a state amount of the behavior of the vehicle, calculates and sets a correction coefficient larger than 1 when it is determined that a cornering force of a tire is in a non-grip area which is not proportional to an operation input of a driver, corrects the target vehicle behavior state amount by the correction coefficient, and sets the feedforward control amount of the behavior control device corresponding to the corrected target vehicle behavior state amount.

Description

Vehicle control method and apparatus

[0001] This invention relates to a vehicle control method and apparatus.

[0002] Patent Document 1, described below, discloses a system that calculates a feedforward control amount for a behavior control device from a target vehicle behavior state variable calculated based on the steering angle, and also calculates a feedback control amount for the behavior control device to correct the discrepancy between the target vehicle behavior state variable and the actual vehicle behavior state variable. The larger the feedback control amount, the smaller the feedforward control amount is corrected, and the target yaw rate is set as the target vehicle behavior state variable.

[0003] Japanese Patent Publication No. 2021-8197

[0004] In the above-mentioned Patent Document 1, the feedforward control amount acts as a disturbance to the feedback control for achieving the target yaw rate, so the target characteristics cannot be achieved unless the feedforward control amount is completely set to zero. However, if the feedforward control amount is completely set to zero, the target characteristics will be achieved by feedback control alone, resulting in poor responsiveness. In other words, there is a need for a technology that can quickly stabilize the disturbance of vehicle behavior during cornering in the non-grip region, where vehicle behavior is prone to becoming disturbed during cornering. The present invention aims to provide a vehicle control method and apparatus that can quickly stabilize the disturbance of vehicle behavior during cornering in the non-grip region.

[0005] One aspect of the present invention involves controlling a vehicle behavior control device with a processing unit, wherein the processing unit sets a feedforward control amount for the behavior control device according to a target vehicle behavior state quantity that is a target value for the vehicle's behavior, and also sets a feedback control amount for the behavior control device to correct the discrepancy between the target vehicle behavior state quantity and the vehicle's behavior state quantity. The gist of the invention is to determine whether the cornering force of the vehicle's tires is in a non-grip region that is not proportional to the driver's input, calculate a correction coefficient greater than 1 if it is determined to be in a non-grip region, and use this correction coefficient to correct the target vehicle behavior state quantity.

[0006] According to one aspect of the present invention, a correction coefficient greater than 1 is calculated and set in the non-grip region, the target vehicle behavior state quantity is corrected with this correction coefficient, and the feedforward control quantity of the behavior control device is set according to this corrected target vehicle behavior state quantity, thereby enabling rapid stabilization of disturbances in vehicle behavior during cornering in the non-grip region. The objects and advantages of the present invention are embodied and achieved using the elements and combinations thereof set forth in the claims. Both the above general description and the following detailed description are merely illustrative and explanatory and should be understood not to limit the present invention as in the claims.

[0007] This is a plan view showing the schematic configuration of an example of a vehicle equipped with the vehicle control system of the embodiment. This is a block diagram of an example of the functional configuration of the motor controller. This is a functional block diagram of the vehicle behavior feedforward control unit built within the processor of the chassis controller. This is a functional block diagram of the vehicle behavior feedback control unit built within the processor of the chassis controller. This is a control map of proportionality coefficients used to calculate the target yaw rate and target vehicle slip angle, which are target vehicle behavior state quantities. This is a calculation block diagram for calculating the rear motor torque correction value, which is a feedforward control quantity to achieve the target vehicle slip angle. This is a calculation block diagram for calculating the correction yaw moment, which is a feedback control quantity, from the yaw rate difference value. This is a control map of proportional and differential gains used in the calculation process of Figure 7. This is a calculation block diagram for calculating the rear motor torque correction value, which is a feedback control quantity, from the yaw rate difference value. This is a control map of proportional and differential gains used in the calculation process of Figure 9.

[0008] The vehicle of the embodiment shown in Figure 1 is equipped with a front motor 2F that drives the front wheels 1FL and 1FR (front axle 10F) and a rear motor 2R that drives the rear wheels 1RL and 1RR (rear axle 10R). Both the front motor 2F and the rear motor 2R are three-phase AC electric motors. Therefore, the vehicle of this embodiment is an electric four-wheel drive vehicle in which the front wheels 1FL and 1FR and the rear wheels 1RL and 1RR are each driven by separate electric motors. This vehicle is equipped with a drive battery 4 that supplies power to the front motor 2F and the rear motor 2R. The battery 4 is a DC storage battery that generates high voltage and high current power. The vehicle is equipped with a front inverter 3F and a rear inverter 3R, respectively, to convert the DC power from the battery 4 into three-phase AC power and apply it to the front motor 2F and the rear motor 2R. The front inverter 3F and the rear inverter 3R also have the function of regenerating the front motor 2F and the rear motor 2R to charge the battery 4. When the front motor 2F and rear motor 2R perform regenerative braking, braking force (braking torque) is applied to the front wheels 1FL, 1FR and the rear wheels 2RL, 2RR. The front inverter 3F and rear inverter 3R can adjust the operating state of the front motor 2F and rear motor 2R, such as the drive torque and braking torque, by adjusting the applied power or regenerative power to the front motor 2F and rear motor 2R. The drive torque and braking torque of the front motor 2F and rear motor 2R by the front inverter 3F and rear inverter 3R can be controlled according to the command signal from the motor controller 11. In other words, the front motor 2F and rear motor 2R can adjust the driving force or braking force of the front wheels 1FL, 1FR and the rear wheels 1RL, 1RR, respectively, according to their operating state. Here, the driving force or braking force is collectively referred to as the braking force. The motor controller 11 is an electronic control unit that controls the operating state of the front motor 2F and the rear motor 2R, in particular the braking and driving force (braking and driving torque) applied to the front wheels 1FL, 1FR and the rear wheels 1RL, 1RR.

[0009] Furthermore, the front wheels 1FL, 1FR and the rear wheels 2RL, 2RR are equipped with hydraulic brake devices 17 that allow each wheel to be braked individually, similar to existing vehicles. These hydraulic brake devices 17 apply braking force to each wheel using the hydraulic pressure of the brake fluid. The vehicle is also equipped with a brake controller 18 that can individually control the braking force of each wheel provided by the hydraulic brake devices 17 on the front wheels 1FL, 1FR and the rear wheels 2RL, 2RR, and a hydraulic unit 19 that adjusts the hydraulic pressure to the hydraulic brake devices 17 of each wheel in accordance with the control signals from the brake controller 18. The hydraulic unit 19 consists of a hydraulic pressure adjustment circuit that can not only maintain and reduce the hydraulic pressure of the hydraulic brake devices 17 of each wheel, but also increase it. The brake controller 18 can perform anti-skid control, which maintains or reduces the hydraulic pressure of the hydraulic brake system 17 for wheels whose wheel speed is too low relative to the vehicle speed (vehicle speed) during hydraulic braking. In addition, it can also perform control such as increasing the hydraulic pressure of the hydraulic brake system 17 for wheels whose wheel speed is too high relative to the vehicle speed (vehicle speed), such as during vehicle acceleration (electronically controlled braking force distribution). This brake controller 18 is an electronic control unit that individually controls the braking force of each wheel and can also control the yaw motion of the vehicle. In this embodiment, when a correction yaw moment command to match the actual yaw rate to the target yaw rate is given to the brake controller 18 from the chassis controller 12 (described later), it outputs a control signal to the hydraulic unit 19 to control the hydraulic pressure of the hydraulic brake system 17 so that this correction yaw moment is achieved. For example, the input correction yaw moment is divided by the distance from the vehicle center to the tire position (tread / 2) to convert it into braking force, and the hydraulic pressure of each hydraulic brake system 17 is calculated and the control signal is set so that this braking force is achieved. In other words, this brake controller 18 constitutes a part of the behavior control device of the present invention. Alternatively, an electric brake system that applies braking force to each wheel using an electric motor can also be applied instead of this hydraulic brake system. When using an electric brake system, hydraulic pressure should be read as braking force.

[0010] Furthermore, this vehicle is equipped with an accelerator pedal position sensor 5 for detecting the amount the accelerator pedal is pressed, and a brake pedal force sensor 6 for detecting the amount the brake pedal is pressed (pressure). This vehicle is also equipped with a steering angle sensor 7 for detecting the amount of steering wheel operation (including the direction of operation). This vehicle is also equipped with a yaw rate sensor 8 for detecting the yaw rate occurring in the vehicle, and a wheel speed sensor 16 for detecting the rotational speed (wheel speed) of the front wheels 1FL, 1FR and the rear wheels 1RL, 1RR. In addition, this vehicle is equipped with a driving characteristic selection switch 9 that allows the driver to select the driving state of the vehicle, for example, the driving characteristics when the vehicle is turning. This driving characteristic selection switch 9 allows the driver to select, for example, a sport mode that provides nimble turning characteristics on winding roads, an eco mode that suppresses the power consumption of the battery 4, and a snow mode that provides stable driving characteristics on slippery surfaces such as snowy roads.

[0011] The chassis controller 12 is an electronic control unit (ECU) that performs calculations to control the behavior of the vehicle and outputs command signals to the motor controller 11 and brake controller 18. Therefore, the motor controller 11 is equipped with a computer system that has advanced calculation capabilities. This computer system, like well-known computer systems, has a processor 13 that has advanced calculation functions. The processor 13 includes a ROM (Read Only Memory) in which a program is stored, a CPU (Central Processing Unit) that executes the program stored in the ROM, and a RAM (Random Access Memory) that functions as an accessible storage device. The storage device consists of a semiconductor storage device, a magnetic storage device, and an optical storage device. The storage device may further include registers, a cache memory, and a memory used as main memory. The calculations performed by the chassis controller 12 are realized, for example, by the CPU executing a computer program stored in the storage device within the processor 13 of the chassis controller 12. Similarly, each of the functional units described later is realized by the CPU executing a computer program stored in the storage device within the processor 13 of the chassis controller 12.

[0012] Figure 2 shows the logic of the calculation process executed by the motor controller 11, which calculates the command values ​​for the front motor torque and rear motor torque to be requested from the front motor 2F and rear motor 2R, and outputs a command signal. In this calculation process, the target front and rear motor torque calculation unit 14 calculates the target front motor torque and target rear motor torque, while the front and rear motor torque correction value calculation unit 15 calculates the front motor torque correction value and rear motor torque correction value. Then, the value obtained by adding the front motor torque correction value to the target front motor torque is output as the front motor torque command value, and the value obtained by adding the rear motor torque correction value to the target rear motor torque is output as the rear motor torque command value. The target front motor torque and target rear motor torque are reference values ​​that take into account the front motor torque correction value and rear motor torque correction value. In this embodiment, the driver-requested driving force requested by the driver is calculated based on the amount of accelerator pedal depression detected by the accelerator opening sensor 5 and the amount of brake pedal depression (pitch force) detected by the brake pedal force sensor 6. Filtering may be applied as appropriate during the calculation. The driving force portion of this driver-requested driving force corresponds to the driving torque obtained by operating the front motor 2F and rear motor 2R in power mode. Similarly, the braking force portion of this driver-requested driving force corresponds to the braking torque obtained by operating the front motor 2F and rear motor 2R in regenerative mode. When the driver-requested driving force is calculated and set, for example, at a predetermined sampling period, the amount of increase or decrease from the previous setting is adjusted according to the driving mode selected by the driving characteristic selection switch 9. The driver-requested driving force calculated and set in this way is distributed to the front axle 10F and rear axle 10R, for example, at a preset braking and driving force distribution ratio between the front and rear wheels, and the target front motor torque for the front motor 2F to achieve the front axle driving force and the target rear motor torque for the rear motor 2R to achieve the rear axle driving force are calculated and set. When a rear motor torque correction value is input by the calculation process in the chassis controller 12 described later, the front motor torque correction value is calculated using that rear motor torque correction value, and the front motor torque command value and rear motor torque command value are calculated and output using these.Of these, the vehicle body slip angle is feedforward controlled by a rear motor torque correction value input from the feedforward control unit 20, which will be described later. In other words, this motor controller 11 constitutes a part of the behavior control device of the present invention.

[0013] Next, an overview of the functional units built into the processor 13 of the chassis controller 12 will be described. The vehicle behavior state variables controlled in this embodiment are the yaw rate and the vehicle body slip angle. To control these vehicle behavior state variables, the processor 13 of the chassis controller 12 is equipped with a vehicle behavior feedforward control unit 20 shown in Figure 3 and a vehicle behavior feedback control unit 21 shown in Figure 4. In this embodiment, the vehicle behavior feedback control unit 21 only provides feedback control for the vehicle's yaw rate. The vehicle behavior feedforward control unit 20 shown in Figure 3 includes: a reference yaw rate calculation unit 22 that calculates a reference yaw rate to be achieved by the vehicle on a normal road surface; an actual yaw rate acquisition unit 23 that acquires the yaw rate (actual yaw rate) detected by the yaw rate sensor 8; a reference yaw rate difference value calculation unit 24 that calculates a reference yaw rate difference value consisting of the difference between the reference yaw rate and the actual yaw rate; a correction coefficient calculation unit 25 that calculates a correction coefficient for calculating a target yaw rate as a target value for the yaw rate on any road surface by correcting the reference yaw rate from the reference yaw rate difference value; a target yaw rate calculation unit 26 that calculates the target yaw rate by correcting the reference yaw rate with the correction coefficient; and a correction yaw moment calculation unit that calculates the correction yaw moment necessary to calculate the target yaw rate. The system includes a yaw moment calculation unit 27, a corrected yaw moment output unit 28 that outputs a command value of the corrected yaw moment to the brake controller 18, a target vehicle slip angle calculation unit 29 that calculates the target vehicle slip angle using a correction coefficient as a target value for the vehicle slip angle on any road surface, an estimated vehicle slip angle calculation unit 30 that calculates the vehicle slip angle currently occurring in the vehicle body as an estimated vehicle slip angle based on the front wheel steering angle, a slip angle difference value calculation unit 31 that calculates a vehicle slip angle difference value consisting of the difference between the target vehicle slip angle and the estimated vehicle slip angle, a rear motor torque correction value calculation unit 32 that calculates a rear motor torque correction value from the vehicle slip angle difference value, and a rear motor torque correction value output unit 33 that outputs the rear motor torque correction value to the motor controller 11.

[0014] The vehicle behavior feedback control unit 21 shown in Figure 4 includes: a target yaw rate acquisition unit 34 that acquires the target yaw rate calculated by the target yaw rate calculation unit 26 of the vehicle behavior feedforward control unit 20; an actual yaw rate acquisition unit 35 that acquires the yaw rate (actual yaw rate) detected by the yaw rate sensor 8; a yaw rate difference value calculation unit 36 ​​that calculates a yaw rate difference value consisting of the difference between the target yaw rate and the actual yaw rate; a yaw rate difference differential value calculation unit 37 that calculates the time derivative of the yaw rate difference value (yaw rate difference derivative value); and a reference yaw rate and actual yaw rate. A reference yaw rate difference calculation unit 38 calculates a reference yaw rate difference value consisting of the difference in yaw rates; a proportional gain calculation unit 39 for yaw moment calculation calculates a proportional gain multiplied by the yaw rate difference value according to the reference yaw rate difference value in order to calculate the yaw moment required to match the actual yaw rate to the target yaw rate; and a differential gain calculation unit for yaw moment calculation calculates a differential gain multiplied by the differential value of the yaw rate difference according to the reference yaw rate difference value in order to calculate the yaw moment required to match the actual yaw rate to the target yaw rate. The unit 40 includes a corrected yaw moment calculation unit 41 that calculates a corrected yaw moment from the yaw rate difference value and the yaw rate difference derivative value using proportional gain and differential gain for calculating yaw moment, a corrected yaw moment output unit 42 that outputs the corrected yaw moment toward the brake controller 18, a rear motor torque correction proportional gain calculation unit 43 that calculates a proportional gain multiplied by the yaw rate difference value according to the reference yaw rate difference value in order to calculate a rear motor torque correction value to match the actual yaw rate to the target yaw rate, a rear motor torque correction differential gain calculation unit 44 that calculates a differential gain multiplied by the yaw rate difference derivative value according to the reference yaw rate difference value in order to calculate a rear motor torque correction value to match the actual yaw rate to the target yaw rate, a rear motor torque correction value calculation unit 45 that calculates a rear motor torque correction value from the yaw rate difference value and the yaw rate difference derivative value using proportional gain and differential gain for calculating the rear motor torque correction value, and a rear motor torque correction value output unit 46 that outputs the rear motor torque correction value toward the motor controller 11.

[0015] Before detailing the configuration and functions of the vehicle behavior feedforward control unit 20 and the vehicle behavior feedback control unit 21, it should be noted that the phrases "normal road surface" and "all road surfaces" were used in the previous chapter. Needless to say, friction between the wheels (tires) and the road surface is crucial for controlling the behavior of a vehicle. The yaw rate and vehicle slip angle, which will be discussed later, are based on the premise that there is sufficient friction between the wheels and the road surface, in other words, that the tires are gripping. "Grip" means "to hold firmly" in English, and in light of the above, it means that the tires are firmly gripping the road surface. Generally, in the grip region, the cornering force of the tires is said to be proportional to the vehicle's slip angle (the region where the vehicle slip angle is small), and this proportionality constant is called the cornering power. The vehicle's slip angle depends on the front wheel steering angle (steering angle), the vehicle's speed, and the vehicle's acceleration / deceleration state, and therefore the cornering force of the tires in the grip region is proportional to the driver's input. Therefore, the grip region is also called the linear region. Conversely, in the non-grip region, the cornering force of the tires is not proportional to the driver's input. Therefore, the non-grip region is also called the non-linear region. The aforementioned "normal road surface" refers to a road surface that can be considered a grip region, and "all road surfaces" refers to road surfaces including the non-grip region. A road surface in the non-grip region generally refers to a road surface with a small coefficient of road friction, but even if the coefficient of road friction is somewhat large, it can become a non-grip region if the vehicle's speed is high or if there is a large acceleration or deceleration. Therefore, in this embodiment, the yaw rate desired for the vehicle on a road surface in the grip region is set as the reference yaw rate, and if the absolute value of the difference between this reference yaw rate and the actual yaw rate is greater than or equal to a predetermined threshold, it is determined to be a non-grip region (in practice, this is addressed by setting the correction coefficient to be greater than 1 or setting the gain to be greater than 0). Note that "vehicle body slip angle" refers to the angle between the direction of the vehicle body and the direction of the vehicle's velocity vector.

[0016] Next, the configurations and functions of the vehicle behavior feedforward control unit 20 and the vehicle behavior feedback control unit 21 will be described in sequence. The following describes the configuration and functions of the vehicle behavior feedforward control unit 20. First, the front wheel steering angle δ Ｆ The yaw rate (estimated yaw rate) γ generated in the vehicle is given by the following Equation 1 according to the well-known two-wheel model, and the vehicle body slip angle (estimated vehicle body slip angle) β is given by the following Equation 2, respectively. Front wheel steering angle δ Ｆ is generally proportional to the steering angle θ. In the equations, M is the vehicle mass, V is the traveling speed of the vehicle, I is the yaw moment of inertia radius, L is the wheelbase, L Ｆ is the distance from the vehicle center of gravity to the front axle 10F, L Ｒ is the distance from the vehicle center of gravity to the rear axle 10R, K Ｆ is the equivalent cornering power of the front wheels 1FL and 1FR, K Ｒ is the equivalent cornering power of the rear wheels 1RL and 1RR. For this yaw rate γ and vehicle body slip angle β, a reference yaw rate γ as a reference value of the vehicle behavior desired for the vehicle Ｒ and a reference vehicle body slip angle β Ｒ are set by the following Equation 3 and Equation 4. The gain k in Equation 3 １ is a proportional gain for adjusting the magnitude of the reference yaw rate γ Ｒ , k ２ is a phase gain for adjusting the response speed of the reference yaw rate γ Ｒ , k ３ is a damping gain for adjusting the convergence of the response of the reference yaw rate γ Ｒ . The gain k in Equation 4 ４ is a proportional gain for adjusting the magnitude of the reference vehicle body slip angle β Ｒ , k ５ is a phase gain for adjusting the response speed of the reference vehicle body slip angle β Ｒ , k ３ is a damping gain for adjusting the convergence of the response of the reference vehicle body slip angle β Ｒ . Since the denominators of Equation 3 and Equation 4 set from the two-wheel model (even in Equation 1 and Equation 2) are the same, the damping gain is unified as k ３ . As is well known, by setting the proportional gains k １ and k ４ to large values, the reference yaw rate γＲ or standard vehicle body slip angle β Ｒ This can be increased. On the other hand, in this example, the gain k adjusts the responsiveness. ２ , k ３ , k ５ The two are set to be large at the same time. If the goal is simply to increase the responsiveness, the molecular phase gain k ２ , k ５ It would be good to increase it, but if we do that the reference yo-rate γ Ｒ or standard vehicle body slip angle β Ｒ This causes an overshoot, and simultaneously, the convergence deteriorates. To suppress this, the damping gain k in the denominator is increased. ３ By also increasing the reference yaw rate γ Ｒ or standard vehicle body slip angle β Ｒ This suppresses the overshoot and further improves convergence. In this way, each gain k １ ~k ５ The reference yaw rate γ is set by tuning it. Ｒ and standard vehicle body slip angle β Ｒ If this can be achieved on a normal road surface by the brake controller 18 and the motor controller 11, then the desired vehicle behavior can be realized.

[0017]

[0018] This reference yaw rate γ Ｒ and standard vehicle body slip angle β Ｒ Using correction coefficients a to e, the target value of yaw rate γ for all road surfaces is determined. Ｔ , and the target value of the vehicle body slip angle β on all road surfaces, which is the target vehicle body slip angle β. Ｔ Set the following. The correction coefficients a to e are the respective gains k mentioned above. １ ~k ５ It is used in a form that is further multiplied by the target yaw rate γ Ｔ The following five formulas are used, with a target vehicle slip angle β. Ｔ This is expressed by the following six equations. The correction coefficients a to e are set, for example, from the control map in Figure 5. In this control map, the horizontal axis is the reference yaw rate difference value Δγ. ＲThe vertical axis represents the correction coefficients a to e. The reference yaw rate difference value Δγ Ｒ This is the reference yorate γ Ｒ Since this is the difference value obtained by subtracting the actual yaw rate γ (the yaw rate detected by the yaw rate sensor 8, which is different from the estimated yaw rate) from the reference yaw rate difference value Δγ, here it is referred to as the reference yaw rate difference value Δγ. Ｒ If the value is positive, it indicates understeer (US in the diagram), and the reference yaw rate difference value is Δγ. Ｒ If the value is negative, it is defined as oversteer (OS in the diagram). And this reference yaw rate difference value Δγ Ｒ If the absolute value of is less than a predetermined threshold (in this case, 2.5 deg / s), it is determined to be in the grip region; if it is greater than or equal to the predetermined threshold, it is determined to be in the non-grip region. If it is in the grip region, the reference yaw rate γ Ｒ and standard vehicle body slip angle β Ｒ Since there is no need to change or adjust them, all correction coefficients a to e are set to 1, and the reference yaw rate γ Ｒ = Target yaw rate γ Ｔ , standard vehicle body slip angle β Ｒ = Target vehicle slip angle β Ｔ Make it so that it becomes like this.

[0019]

[0020] In contrast, the reference yaw rate difference value Δγ Ｒ If the value is greater than +2.5 deg / s or less than -2.5 deg / s, it is determined to be a non-grip region, and the correction coefficients a to e are set to a value greater than 1. Specifically, the reference yaw rate difference value Δγ Ｒ If it is +2.5 deg / s or more, the reference yaw rate difference value Δγ Ｒ As the value increases, the correction coefficients a to e are set to gradually (linearly) larger, and the reference yaw rate difference value Δγ Ｒ In the region where the value is +5.0 deg / s or higher, the correction coefficients a to e are kept constant. Similarly, the reference yaw rate difference value Δγ Ｒ If the value is -2.5 deg / s or less, the reference yaw rate difference value Δγ Ｒ As the decrease in , the correction coefficients a to e are gradually (linearly) increased, and the reference yaw rate difference value Δγ ＲIn the region below -5.0 deg / s, the correction coefficients a to e are kept constant. These correction coefficients a to e are based on the reference yaw rate γ. Ｒ and standard vehicle body slip angle β Ｒ Since it is multiplied by the proportional gain, phase gain, and damping gain in the equation, the target yaw rate γ is obtained by multiplying by correction coefficients a to e that are greater than 1. Ｔ and target vehicle slip angle β Ｔ This is the reference yorate γ Ｒ and standard vehicle body slip angle β Ｒ In contrast, a large magnitude and fast responsiveness (and convergence) are set. The target yaw rate γ is such that it is large and fast responsive. Ｔ and target vehicle slip angle β Ｔ Once these settings are configured and achieved by the brake controller 18 and motor controller 11, the vehicle will turn in the direction in which the steering wheel is turned. At this time, since the vehicle is in a non-grip area, it is possible to quickly stabilize the vehicle's behavior (and any disturbances) by turning the vehicle as quickly as possible in the direction of the steering wheel, i.e., the direction desired by the driver.

[0021] While there are definitions for "oversteer" and "understeer" in terms of vehicle behavior, in this embodiment, the objective is to quickly stabilize the disturbance in vehicle behavior, therefore the reference yaw rate difference value Δγ is used. Ｒ If it is a positive value, i.e., the reference yaw rate γ Ｒ Understeer occurs when the absolute value of the actual yaw rate γ is small relative to the absolute value of the reference yaw rate difference Δγ. Ｒ If it is a negative value, i.e., the reference yaw rate γ Ｒ By defining oversteer as occurring when the absolute value of the actual yaw rate γ is large relative to the absolute value of , it becomes possible to respond quickly whether it is "oversteer" or "understeer". In this case, for example, if understeer occurs in the non-grip region, the target yaw rate γ Ｔis set to a large value, and it is inferred that the vehicle turning in the direction to eliminate understeer due to this is intuitively easy to understand. On the other hand, in this embodiment, even when oversteer occurs in the non-grip region, the target yaw rate γ Ｔ is set to a large value. This assumes a case where the driver of a vehicle that has oversteered in the non-grip region operates so-called countersteering (reverse steering) to eliminate the oversteer (countersteering is almost certainly performed in the event of oversteer), and for this countersteering, the target yaw rate γ Ｔ is set to a large value, whereby "the vehicle can be directed in the direction desired by the driver". In the control map of FIG. 5, the correction coefficients a to e are shown to be set to the same value for the reference yaw rate difference value Δγ Ｒ , but in practice, even if the numerical value trends are the same, these correction coefficients a to e may have different numerical values for each coefficient.

[0022] In this way, the target yaw rate γ Ｔ is set, then the front wheel steering angle δ achieved by the vehicle without control Ｆ corresponding yaw rate (yaw rate calculated by Equation 1 = estimated yaw rate) and the corrected yaw moment Y achieved by the brake controller 18 Ｍ the sum of the yaw rates by means of is defined as the target yaw rate γ Ｔ , and the following Equation 7 is established. This Equation 7 is solved for the corrected yaw moment Y Ｍ to obtain Equation 8. The corrected yaw moment Y calculated in this manner Ｍ is output to the brake controller 18, whereby the vehicle yawing motion corresponding to the target yaw rate γ Ｔ is achieved. At this time, if the vehicle is in the grip region, the target yaw rate γ equivalent to the reference yaw rate γ Ｒ and the target yaw rate γ Ｔ is achieved, whereby the desired yawing motion for the vehicle is achieved. This means that on a normal traveling road surface (grip region), the vehicle has the reference yaw rate γ Ｒmeans that the yawing motion is controlled to be achieved, however, a deviation occurs from the actual yaw rate γ generated in the vehicle, that is, the reference yaw rate difference value Δγ Ｒ If the absolute value of is large, it can be regarded as being in the non-grip region. Also, if the vehicle is in the non-grip region, a large and highly responsive target yaw rate γ Ｔ is achieved, the vehicle is oriented in the direction desired by the driver. On the other hand, for the target vehicle body slip angle β Ｔ as shown in the arithmetic block diagram of Fig. 6, a predetermined proportional gain is multiplied to the vehicle body slip angle difference value Δβ obtained by subtracting the estimated vehicle body slip angle β from this target vehicle body slip angle β, so that the rear motor torque correction value as the feedforward control amount is calculated. By outputting the rear motor torque correction value calculated in this way to the motor controller 11, the front-rear braking / driving force distribution corresponding to the target vehicle body slip angle β Ｔ is achieved. As is clear from Fig. 6, the rear motor torque correction value is a positive added value, and the larger the difference value from the target vehicle body slip angle β Ｔ , the larger it is. As is also clear from the transfer function of the vehicle body slip angle in the two equations, the cornering power of the rear wheels is present in the denominator of the transfer function, and the cornering power decreases when a front-rear force is applied to the wheels. Therefore, when the braking / driving force distribution is biased toward the rear wheels, the vehicle body slip angle decreases. In the non-grip region, a larger target vehicle body slip angle β Ｔ than in the grip region is set, so a larger rear motor torque correction value is set, and as a result, the target vehicle body slip angle β Ｔ can be achieved more quickly. Ｔ

[0023]

[0024] Next, the configuration and function of the vehicle behavior feedback control unit 21 will be described. The corrected yaw moment output function in the vehicle behavior feedback control unit 21 can be represented by the block diagram of Fig. 7. That is, in the adder-subtractor 47, the target yaw rate γ Ｔ ​The yaw rate difference value Δγ is calculated by subtracting the actual yaw rate γ from the reference yaw rate difference value Δγ. This yaw rate difference value Δγ is divided into two sequences, one of which is input to the proportional gain multiplier 48, and the other to the differential gain multiplier 50 via the differentiator 49. The proportional gain multiplier 48 and the differential gain multiplier 50 process the reference yaw rate difference value Δγ according to the control map in Figure 8. Ｒ The proportional and differential gains are set accordingly, and these are multiplied by the yaw rate difference value Δγ and the yaw rate difference differential value Δγ', respectively. The products of these are then added by the adder 51 to output the corrected yaw moment. In the control map of Figure 8, the horizontal axis is the reference yaw rate difference value Δγ. Ｒ The vertical axis represents the proportional gain and the differential gain, and the reference yaw rate difference value Δγ is used. Ｒ The settings for understeer and oversteer are the same as in the control map in Figure 5. Here again, the reference yaw rate difference value Δγ Ｒ If the absolute value of is less than a predetermined threshold (here, 2.5 deg / s), it is determined to be in the grip region; if it is greater than or equal to the predetermined threshold, it is determined to be in the non-grip region. If it is in the grip region, it is determined that there is no need to perform feedback control on the yaw rate difference value Δγ and the yaw rate difference derivative value Δγ', and both the proportional gain and the differential gain are set to 0. On the other hand, the reference yaw rate difference value Δγ Ｒ If it is +2.5 deg / s or more, the reference yaw rate difference value Δγ Ｒ As the value increases, the proportional gain and differential gain are gradually (linearly) increased, and the reference yaw rate difference value Δγ Ｒ In the region where the gain is +5.0 deg / s or higher, the proportional gain and differential gain are kept constant. Similarly, the reference yaw rate difference value Δγ Ｒ If the value is -2.5 deg / s or less, the reference yaw rate difference value Δγ Ｒ As the decrease in , the proportional and differential gains are gradually (linearly) increased, and the reference yaw rate difference value Δγ Ｒ In the region below -5.0 deg / s, the proportional and differential gains are kept constant. Thus, in the non-grip region, the corrected yaw moment is set using large proportional and differential gains for the yaw rate difference value Δγ and the yaw rate difference differential value Δγ', resulting in a larger and faster target yaw rate γＴ Feedback control is implemented to achieve this. The reason the yaw rate difference derivative Δγ' is used to set the corrected yaw moment is to improve the responsiveness of the feedback control.

[0025] On the other hand, the rear motor torque correction value output function in the vehicle behavior feedback control unit 21 can be represented by the block diagram in Figure 9. That is, the target yaw rate γ is calculated by the adder / subtractor 52. Ｔ The yaw rate difference value Δγ is calculated by subtracting the actual yaw rate γ from the reference yaw rate difference value Δγ. This yaw rate difference value Δγ is divided into two sequences, one of which is input to the proportional gain multiplier 53, and the other to the differential gain multiplier 55 via the differentiator 54. The proportional gain multiplier 53 and the differential gain multiplier 55 process the reference yaw rate difference value Δγ according to the control map in Figure 10. Ｒ The proportional and differential gains are set accordingly, and these are multiplied by the yaw rate difference value Δγ and the yaw rate difference differential value Δγ', respectively. The products of these are then added together in the adder 56 to output the rear motor torque correction value. In the control map of Figure 10, the horizontal axis is the reference yaw rate difference value Δγ Ｒ The vertical axis represents the proportional gain and the differential gain, and the reference yaw rate difference value Δγ is used. Ｒ The settings for understeer and oversteer are the same as in the control map in Figure 5. Here again, the reference yaw rate difference value Δγ Ｒ If the absolute value of is less than a predetermined threshold (here, 2.5 deg / s), it is determined to be in the grip region; if it is greater than or equal to the predetermined threshold, it is determined to be in the non-grip region. If it is in the grip region, it is determined that there is no need to perform feedback control on the yaw rate difference value Δγ and the yaw rate difference derivative value Δγ', and both the proportional gain and the differential gain are set to 0. On the other hand, the reference yaw rate difference value Δγ Ｒ If it is +2.5 deg / s or more, the reference yaw rate difference value Δγ Ｒ As the value increases, the proportional gain and differential gain are gradually (linearly) increased, and the reference yaw rate difference value Δγ Ｒ In the region where the value is +5.0 deg / s or higher, the proportional gain and differential gain are kept constant. Also, the reference yaw rate difference value Δγ Ｒ If the value is -2.5 deg / s or less, the reference yaw rate difference value Δγ ＲAs the value decreases, the proportional and differential gains are gradually (linearly) reduced, and the reference yaw rate difference value Δγ is used. Ｒ In the region below -5.0 deg / s, the proportional gain and differential gain are kept constant. Therefore, the reference yaw rate difference value Δγ Ｒ If the value is +2.5 deg / s or greater, a positive rear motor torque correction value is calculated and set, and the reference yaw rate difference value Δγ Ｒ If the value is -2.5 deg / s or less, a negative rear motor torque correction value is calculated and set. As a result, in an understeer state in the non-grip region, the braking and driving force of the rear wheels increases, reducing understeer, and in an oversteer state, the braking and driving force of the rear wheels decreases, meaning that the braking and driving force of the front wheels increases relatively, reducing oversteer. In this case, in the non-grip region, the larger the absolute values ​​of the yaw rate difference value Δγ and the yaw rate difference derivative value Δγ', the larger the absolute value of the rear motor torque correction value is set using proportional and derivative gains with larger absolute values, thus enabling a larger and faster-responding target yaw rate γ Ｔ Feedback control is implemented to achieve this. The reason the yaw rate difference derivative value Δγ' is used to set the rear motor torque correction value is to improve the responsiveness of the feedback control.

[0026] In vehicles equipped with this vehicle control system, understeer is quickly resolved by a large and responsive target yaw rate set for feedforward control when understeer occurs in a non-grip area. Furthermore, if oversteer occurs in a non-grip area and the driver performs a counter-steer operation, the oversteer is quickly resolved by a large and responsive target yaw rate set for feedforward control in response to this counter-steer—that is, a target yaw rate that changes the direction of the vehicle in a direction that eliminates the oversteer. In addition, the corrective yaw moment and rear motor torque correction value of the feedback control, which are set to achieve this target yaw rate, effectively suppress overshoot when understeer or oversteer is resolved, resulting in excellent understeer and oversteer resolution.

[0027] The vehicle control system according to the embodiment has been described above, but the present invention is not limited to the configuration described in the above embodiment, and various modifications are possible within the scope of the gist of the present invention. For example, in the above embodiment, feedback control is performed only on the difference between the target yaw rate and the actual yaw rate, but feedback control may also be performed on the difference between the target vehicle slip angle and the actual vehicle slip angle. The outline of this vehicle slip angle feedback control is the same as the outline of the yaw rate feedback control. In addition, in the above embodiment, the manner of vehicle behavior control may be changed and adjusted according to the driving characteristics (mode) selected by the driving characteristics selection switch 9. For example, when sport mode is selected, the target yaw rate may be set to be larger and the target vehicle slip angle to be set to be smaller in order to achieve nimble vehicle behavior. Also, when eco mode is selected, the braking of each wheel 1FL to 1RR by the hydraulic brake device 17 may be reduced in order to prevent the vehicle's speed from decreasing unintentionally. Also, when snow mode is selected, the rate of change of the corrected yaw moment and the rear motor torque correction value may be suppressed.

[0028] Furthermore, in the above embodiment, a brake controller 18 capable of individually controlling the braking force of each wheel was applied as a yawing motion control device to control the yaw rate occurring in the vehicle. However, various yaw rate control devices can be applied instead of this brake controller 18. Examples of such yaw rate control devices include a front wheel steering angle control device that controls the steering angle of the front wheels, and a rear wheel steering angle control device that can control the steering angle of the rear wheels and controls the steering angle of these rear wheels. Vehicle behavior can be controlled in the same manner as in the above embodiment with these yawing motion control devices as well.

[0029] Thus, in the vehicle control system of this embodiment, when a behavior control device capable of controlling the behavior of the vehicle is controlled by the processor 13, the processor 13 sets a feedforward control amount of the behavior control device according to a target vehicle behavior state quantity which is a target value of the vehicle's behavior, and also sets a feedback control amount of the behavior control device to correct the discrepancy between the target vehicle behavior state quantity and the vehicle's behavior state quantity. When it is determined that the cornering force of the tires is in a non-grip region that is not proportional to the driver's input, a correction coefficient greater than 1 is calculated and set, the target vehicle behavior state quantity is corrected with this correction coefficient, and a feedforward control amount of the behavior control device is set according to this corrected target vehicle behavior state quantity. As a result, it becomes possible to quickly stabilize the disturbance of the vehicle's behavior during cornering in the non-grip region.

[0030] Furthermore, by setting a target yaw rate and target vehicle slip angle as target vehicle behavior state variables, calculating correction coefficients to change the magnitude and response of the target yaw rate and target vehicle slip angle, and correcting the target yaw rate and target vehicle slip angle using these correction coefficients, the disturbance of vehicle behavior during cornering in the non-grip region can be quickly stabilized. In addition, by setting a feedback control amount based on the yaw rate difference value, which is the difference between the target yaw rate as a target vehicle behavior state variable and the actual yaw rate generated by the vehicle, and by greatly correcting the yaw rate difference value when it is determined to be in a non-grip region, the disturbance of vehicle behavior during cornering in the non-grip region can be stabilized. Furthermore, by setting a feedback control amount based on the yaw rate difference derivative value, which is the derivative of the yaw rate difference value, and by greatly correcting the yaw rate difference derivative value when it is determined to be in a non-grip region, the disturbance of vehicle behavior during cornering in the non-grip region can be quickly stabilized.

[0031] Furthermore, by setting the correction coefficient to 1 when it is determined that the area is not a non-grip area, and by multiplying the reference vehicle behavior state quantity, which is the reference value for the desired behavior of the vehicle, by the correction coefficient, the target vehicle behavior state quantity is set without a time lag in setting the target vehicle behavior state quantity in the grip area and the non-grip area, and without any step-like differences in the set values. In addition, by determining that the area is a non-grip area when the absolute value of the reference yaw rate difference value, which is the difference between the reference yaw rate as the reference vehicle behavior state quantity and the actual yaw rate generated by the vehicle, is greater than or equal to a predetermined threshold, it is possible to quickly determine that the area is a non-grip area, and there is no time lag in setting the target vehicle behavior state quantity in the grip area and the non-grip area.

[0032] Furthermore, by calculating a correction coefficient that increases with increasing absolute value of the reference yaw rate difference, it becomes possible to set a larger target vehicle behavior state variable the greater the discrepancy between the reference yaw rate and the actual yaw rate, thereby quickly stabilizing the vehicle's behavior during cornering in the non-grip region. Additionally, by setting predetermined thresholds for cases where understeer occurs when the absolute value of the actual yaw rate is smaller than the absolute value of the reference yaw rate, and oversteer occurs when the absolute value of the actual yaw rate is larger than the absolute value of the reference yaw rate, it is possible to quickly determine whether understeer or oversteer is occurring, and to quickly and reliably determine the non-grip region for each steering characteristic.

[0033] 1FL, 1FR...Front wheels, 1RL, 1RR...Rear wheels, 2F...Front (for front wheels) motor, 2R...Rear (for rear wheels) motor, 5...Accelerator opening sensor, 6...Brake pedal force sensor, 7...Steering angle sensor, 8...Yaw rate sensor, 9...Driving characteristic selection switch, 10F...Front axle, 10R...Rear axle, 11...Motor controller, 12...Chassis controller, 13...Processor, 14...Target front and rear motor torque calculation unit, 15...Front and rear motor torque 16...Correction value calculation unit, 17...Wheel speed sensor, 18...Hydraulic brake device, 19...Brake controller, 20...Hydraulic unit, 21...Vehicle behavior feedforward control unit, 22...Vehicle behavior feedback control unit, 23...Reference yaw rate calculation unit, 24...Actual yaw rate acquisition unit, 25...Reference yaw rate difference value calculation unit, 26...Correction coefficient calculation unit, 27...Target yaw rate calculation unit, 28...Correction yaw moment output unit, 29...Target vehicle body 30...Slip angle calculation unit, 31...Estimated vehicle body slip angle calculation unit, 32...Slip angle difference value calculation unit, 33...Rear motor torque correction value calculation unit, 34...Target yaw rate acquisition unit, 35...Actual yaw rate acquisition unit, 36...Yaw rate difference value calculation unit, 37...Yaw rate difference derivative value calculation unit, 38...Reference yaw rate difference value calculation unit, 39...Proportional gain calculation unit for yaw moment calculation, 40...Derivative gain calculation unit for yaw moment calculation, 41... 42... Corrected yaw moment calculation unit, 43... Corrected yaw moment output unit, 44... Rear motor torque correction proportional gain calculation unit, 45... Rear motor torque correction value calculation unit, 46... Rear motor torque correction value output unit, 47... Adder / subtractor, 48... Proportional gain multiplier, 49... Differentiator, 50... Differential gain multiplier, 51... Adder, 52... Adder / subtractor, 53... Proportional gain multiplier, 54... Differentiator, 55... Gain multiplier, 56... Adder

Claims

1. A vehicle control method comprising controlling a vehicle behavior control device with a processing unit, wherein the processing unit includes: a feedforward control unit that sets a feedforward control amount for the behavior control device according to a target vehicle behavior state quantity which is a target value of the vehicle's behavior; a feedback control unit that sets a feedback control amount for the behavior control device to correct the discrepancy between the target vehicle behavior state quantity and the vehicle's behavior state quantity; a non-grip region determination step that determines whether the cornering force of the vehicle's tires is in a non-grip region that is not proportional to the driver's input; a correction coefficient calculation step that calculates a correction coefficient greater than 1 if it is determined to be in a non-grip region; and a target vehicle behavior correction step that corrects the target vehicle behavior state quantity using the correction coefficient.

2. The vehicle control method according to claim 1, characterized in that the feedforward control unit sets a target yaw rate and a target vehicle slip angle as the target vehicle behavior state quantities, the correction coefficient calculation step calculates a correction coefficient that changes the magnitude and response of the target yaw rate and the target vehicle slip angle, and the target vehicle behavior correction step corrects the target yaw rate and the target vehicle slip angle using the correction coefficient that changes the magnitude and response.

3. The vehicle control method according to claim 2, characterized in that the feedback control unit sets the feedback control amount based on a yaw rate difference value which is the difference between the target yaw rate as the target vehicle behavior state quantity and the actual yaw rate generated by the vehicle, and greatly corrects the yaw rate difference value when it is determined that the vehicle is in a non-grip region.

4. The vehicle control method according to claim 3, characterized in that the feedback control unit sets the feedback control amount based on the yaw rate difference derivative value, which is the derivative of the yaw rate difference value, and greatly corrects the yaw rate difference derivative value when it is determined that the vehicle is in a non-grip region.

5. The vehicle control method according to claim 1, characterized in that, if it is determined that the vehicle is not in the non-grip region, the correction coefficient calculated in the correction coefficient calculation step is 1, and the target vehicle behavior state quantity is set by multiplying the reference vehicle behavior state quantity, which is a reference value of the desired behavior for the vehicle, by the correction coefficient.

6. The vehicle control method according to claim 5, characterized in that the non-grip region determination step determines that a non-grip region exists when the absolute value of the reference yaw rate difference, which is the difference between the reference yaw rate as a reference vehicle behavior state quantity and the actual yaw rate generated by the vehicle, is greater than or equal to a predetermined threshold.

7. The vehicle control method according to claim 6, characterized in that the correction coefficient calculation step calculates a correction coefficient that is larger the larger the absolute value of the reference yaw rate difference value.

8. The vehicle control method according to claim 6, characterized in that the non-grip area determination step determines understeer when the absolute value of the actual yaw rate is smaller than the absolute value of the reference yaw rate, and oversteer when the absolute value of the actual yaw rate is larger than the absolute value of the reference yaw rate, and sets a predetermined threshold in each of these cases.

9. A vehicle control device that controls a vehicle behavior control device capable of controlling the behavior of a vehicle using a processing unit, wherein the processing unit sets a feedforward control amount for the behavior control device according to a target vehicle behavior state quantity which is a target value of the vehicle's behavior, and sets a feedback control amount for the behavior control device to correct the discrepancy between the target vehicle behavior state quantity and the vehicle's behavior state quantity, and determines whether the cornering force of the vehicle's tires is in a non-grip region that is not proportional to the driver's input, calculates a correction coefficient greater than 1 if it is determined to be in a non-grip region, and corrects the target vehicle behavior state quantity using the correction coefficient.

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