JP2014101074A - Behavior control system of vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a behavior control system that suppresses a spinning behavior of a vehicle using a spinning state quantity, which is calculated based on a vehicle body slip angle, a derivative of the slip angle, and a second-order derivative thereof, as a control quantity, and avoid degradation of an effect of spin suppressing due to contribution of the second-order derivative of the vehicle body slip angle when a steering angle is retained after abrupt steering is performed once.SOLUTION: A system of the present invention is characterized in that after a second-order derivative of a vehicle body slip angle exceeds a predetermined value because a vehicle is steered in one of left-hand and right-hand directions, if an averaged value of steering angular velocities falls below a predetermined value, contribution of the second-order derivative of the vehicle body slip angle to a spinning state quantity is reduced.

Description

  The present invention relates to a vehicle behavior control device that stabilizes the behavior of a vehicle such as an automobile during travel, and more specifically, a control amount given using a vehicle body slip angle, a differential value thereof, and a second-order differential value thereof. The present invention relates to an apparatus for controlling a behavior so as to suppress a vehicle's spin behavior (side slip behavior).

  In the field of motion control of vehicles such as automobiles, VSC (Vehicle Stability Control) which improves the stability of the behavior of the vehicle in the yaw direction during turning by electronically controlling the operation of the braking / driving system or the steering system Many behavior control technologies such as VDIM (Vehicle Dynamic Integrated Management) have already been proposed (for example, Patent Documents 1 and 2). In a typical VSC, if there is a possibility that the behavior of the vehicle becomes unstable, the tire slip rate or slip amount (hereinafter referred to as “slip rate”) or the wheel steering angle of each wheel. Adjustments are made, or engine or motor power is reduced or limited to limit vehicle acceleration. As is well known, when a braking / driving force difference is generated between the left and right wheels of a vehicle or a wheel rudder angle is adjusted, a yaw moment is generated around the center of gravity of the vehicle, thereby changing the turning direction of the vehicle. Further, when the vehicle speed is reduced, the lateral force required for turning is reduced. Therefore, by adjusting the slip ratio of each wheel or the wheel rudder angle and limiting or decelerating the acceleration of the vehicle, the spin of the vehicle is reduced. Such an unstable behavior of the vehicle is suppressed, and the behavior of the vehicle in the yaw direction is stabilized.

  In the behavior control as described above, more specifically, a turning state amount representing a turning state of the vehicle, for example, a spin state amount or a skid state amount which is a function of a vehicle body slip angle, an oversteer state amount, an understeer state. The quantity is referred to as an index value of the vehicle behavior, and based on these index values, the behavior stabilization control, that is, the generation of the yaw moment (behavior stabilization yaw moment) that stabilizes the behavior or the acceleration of the vehicle is determined. Limiting or deceleration is performed. In addition, the time delay in adjusting the slip ratio of each wheel for wheel stabilization control corresponding to changes in the amount of turning state (wheel slip control), automatic control of the wheel rudder angle, or control of the braking / driving device In order to speed up control responsiveness and to suppress the tendency of vehicle behavior instability more quickly, a turning state quantity or a partial differential value thereof is further added to the vehicle behavior index value. Sometimes.

By the way, when the behavior stabilization control is executed based on the vehicle behavior index value obtained by adding the differential value to the turning state quantity for the purpose of speeding up the control response as described above, the rapid steering is repeated. If the differential value or a part of the change is too early, the action of the behavior stabilization control may be reduced at an early stage and the spin suppression effect may be impaired. For example, in the vehicle behavior control as described above, in the control for suppressing the spin of the vehicle (spin suppression control), the spin state which is an amount corresponding to the yaw moment necessary for returning the vehicle body slip angle to 0 Amount (linear sum of body slip angle and its differential value)
K1 · β + K2 · dβ / dt (A)
(K1 and K2 are predetermined weighting factors.)
Linear sum obtained by adding the second-order differential value d ² β / dt ² of the vehicle body slip angle,
K1 · β + K2 · dβ / dt + K3 · d ² β / dt ² (B)
(K3 is a predetermined weighting factor)
When the control is executed with reference to, when the response of the second derivative d ² β / dt ² of the vehicle body slip angle is fast and the behavior stabilization control is started, the control effect starts to appear. The second-order differential value of the slip angle catches the sign, which may cause a phenomenon that the action of the behavior stabilization control is reduced early and the spin suppression effect is impaired. Therefore, some of the inventors of the present invention reduced the contribution of the second-order differential value of the vehicle body slip angle after the sudden steering was executed twice in Patent Document 2, and thereby the turning state We proposed a configuration that can avoid the early reduction of the action of the spin suppression control caused by the response of the differential value of the quantity being too early.

JP 2005-206075 A Japanese Patent No. 4535178

  As described above, the behavior to be executed based on the vehicle behavior index value obtained by adding the second-order differential value of the vehicle body slip angle to the turning state amount consisting of the vehicle body slip angle and its differential value as the control amount. In the stabilization control, according to further research by the inventors of the present invention, after the sudden steering is executed only once, the behavior stabilization control is performed by the contribution of the second-order differential value of the vehicle body slip angle. When the effect is quickly demonstrated, after that, when the steering in the reverse direction is not performed and the steering angle is maintained, the control effect of the behavior stabilization is caused by the contribution of the second-order differential value of the vehicle body slip angle. It has also been clarified that a phenomenon may occur in which is reduced. This phenomenon is attributed to the fact that the second-order differential value of the vehicle body slip angle captures a sign that the vehicle body slip angle stops increasing due to the steering angle being maintained after sudden steering. Therefore, in order to avoid such a reduction in the spin suppression effect, the situation in which the steering angle is maintained after the sudden steering is executed only once is detected, and the second floor of the vehicle body slip angle in the vehicle behavior index value is detected. It is necessary to adjust the contribution of the differential value accordingly.

  Thus, one object of the present invention is to perform behavior control for executing behavior stabilization control so as to suppress the spin behavior of a vehicle based on a vehicle slip angle, its differential value, and an amount calculated based on the second-order differential value. The device is configured to prevent the spin suppression effect from being impaired due to the contribution of the second-order differential value of the vehicle body slip angle when the steering angle is maintained after sudden steering is performed only once. Is to provide a device.

  In order to solve the above-mentioned problem, it is necessary to determine whether the rudder angle is maintained as it is or steered in the reverse direction after the first sudden steering. However, such a determination cannot be achieved by referring to the second-order differential value of the vehicle body slip angle or the steering angular velocity. This is because whether or not sudden steering is executed can be determined by referring to the second-order differential value of the vehicle body slip angle or the change in the magnitude of the steering angular velocity. In any case of turning in the direction, the change of the steering angle is temporarily stopped, and at that stage, the second-order differential value of the vehicle body slip angle starts to change quickly in the reverse direction, and the steering angular velocity is This is because there is no difference in the second-order differential value of the vehicle body slip angle or the steering angular velocity between the case where the steering angle is maintained as it is and the case where the steering is turned in the reverse direction. However, according to the research of the inventors of the present invention, whether the steering angle is maintained as it is after the first sudden steering or whether it is steered in the reverse direction is determined by the smoothing value of the steering angular velocity or the primary regression filter processing. It was found that the above differences appear when referring to the magnitude of the later values. Such knowledge is used in the present invention.

  According to the present invention, the above-described problem is solved by the vehicle that suppresses the spin of the vehicle based on the control amount calculated from the vehicle body slip angle, the differential value of the vehicle body slip angle, and the second-order differential value of the vehicle body slip angle. The behavior control device, in which steering is performed in one of the left and right directions of the vehicle, and the magnitude of the smoothing value of the steering angular velocity after the magnitude of the second-order differential value of the vehicle body slip angle exceeds a predetermined value This is achieved by a device characterized in that the contribution of the second-order differential value of the vehicle body slip angle in the control amount is reduced when is below a predetermined magnitude. The vehicle behavior control device is of a type that suppresses the spin of the vehicle by generating a yaw moment that suppresses the spin based on the control amount or by limiting the acceleration of the vehicle. It may be.

  In the above configuration, “after steering is performed in one of the left and right directions of the vehicle and the magnitude of the second derivative of the vehicle body slip angle exceeds a predetermined value” This corresponds to a case where the program is executed once from left to right or from left to right. As understood by those skilled in the art, when sudden steering is performed during normal vehicle travel, the size of the slip angle of the vehicle body increases rapidly. Since it changes before the slip angle of the vehicle body and its differential value, sudden steering can be detected by detecting that the second-order differential value of the vehicle body slip angle has greatly fluctuated. Then, “when the smoothing value of the steering angular velocity falls below a predetermined value” after the detection of the sudden steering corresponds to the case where the state is maintained after the sudden steering. As will be described later in the description of the embodiment of the invention, the magnitude of the smoothing value of the steering angular velocity is 0 when the state is maintained after the sudden steering. In contrast, when the vehicle is steered in the reverse direction after the sudden steering, the value gradually decreases, but increases immediately with the start of the steer in the reverse direction. That is, it is possible to distinguish between the case where the rudder angle is maintained as it is and the case where it is steered in the reverse direction depending on whether or not the magnitude of the smoothing value of the steering angular velocity falls below a predetermined value after detection of sudden steering. It becomes possible. Note that the magnitude of the steering angular velocity smoothing value may be an absolute value of a value obtained by smoothing the steering angular velocity, or may be a value obtained by smoothing the absolute value of the steering angular velocity.

  Thus, in the above-described configuration of the device of the present invention, the vehicle spin is suppressed based on the control amount calculated from the vehicle body slip angle, the differential value of the vehicle body slip angle, and the second-order differential value of the vehicle body slip angle. When the vehicle behavior control is executed, the sudden steering is executed once, and when the steering angle is maintained as it is, this is detected and the contribution of the second-order differential value of the vehicle body slip angle is detected. It will be reduced. As already mentioned, in general, when the spin suppression control is executed based on the control amount including the second-order differential value of the vehicle body slip angle, the second-order differential value of the vehicle body slip angle is quickly obtained even if there is a sudden steering. In response to such sudden steering, a spin suppression effect is exhibited, whereby the slip angle or yaw rate of the vehicle body of the vehicle is rapidly converged. However, if sudden steering is performed only once and then the steering angle is maintained, before the slip angle or yaw rate converges, the second-order differential value of the vehicle body slip angle responds early in response to the tendency. Therefore, the action of the spin suppression control generated based on the control amount may be reduced (for a specific example, see the description of the embodiment). Therefore, in the apparatus of the present invention, as described above, sudden steering is executed only once to detect whether or not the rudder angle is maintained, and when the hold of the rudder angle is detected, the vehicle body slip angle is detected. The contribution of the second-order differential value is reduced, and the early reduction of the action of the spin suppression control is avoided.

  It should be noted that “the steering angular velocity has a predetermined magnitude after the steering is executed in one of the left and right directions of the vehicle and the second-order differential value of the vehicle body slip angle exceeds a predetermined value. In the case where the contribution of the second derivative of the vehicle body slip angle to the control amount is reduced when the steering angle is maintained after one sudden steering is executed. The contribution of the second-order differential value of the vehicle body slip angle may be ignored, and the vehicle body slip angle and its differential value (slip angle changing speed) may be quickly converged. Further, the smoothing value of the steering angular velocity referred to for detecting whether or not the steering angle is maintained after one sudden steering is executed is obtained by, for example, subjecting the steering angular velocity to a primary regression filter process. It may be a value.

In the embodiment, the controlled variable includes the vehicle body slip angle β, the vehicle body slip angle differential value dβ / dt, the vehicle body slip angle second-order differential value d ² β / dt ² , and predetermined coefficients K1, K2. , Using K3,
K1 · β + K2 · dβ / dt + K3 · d ² β / dt ²
May be given by In this case, when the control amount increases, a yaw moment that suppresses spin is generated, or the acceleration of the vehicle is limited, thereby suppressing the spin. Reduction of the contribution of the second-order differential value of the vehicle body slip angle in the control amount may be performed by setting the value of the coefficient K3 to zero.

  Thus, generally speaking, in the configuration of the apparatus of the present invention, in the vehicle spin suppression control, the contribution of the second derivative value of the vehicle body slip angle for speeding up the operation effect of the control depends on the vehicle steering conditions. By adjusting appropriately, when the contribution of the second-order differential value of the vehicle body slip angle is unnecessary, it can be said that the action is excluded. According to the configuration of the present invention, since the contribution of the second-order differential value of the vehicle body slip angle is effective at the time when the sudden steering is started, the vehicle body slip angle and the differential value can be quickly brought to convergence. On the other hand, when the rudder angle is maintained after the sudden steering, it becomes possible to prevent the control action from terminating early. In other words, the configuration of the present invention can be used only when the contribution of the second-order differential value of the vehicle body slip angle in the control amount is valid, and is more effective in suppressing the spin than before. There is expected.

  Other objects and advantages of the present invention will become apparent from the following description of preferred embodiments of the invention.

FIG. 1A is a schematic view of a vehicle on which a preferred embodiment of the behavior control device of the present invention is mounted, and FIG. 1B is a diagram of a vehicle incorporating the preferred embodiment of the behavior control device according to the present invention. It is a control block diagram of an electronic control unit. FIG. 2 shows the steering angle (a), the amount of spin state, and the components (b) constituting the steering, when the steering angle is maintained after the steering angle is changed to the right by sudden steering. The absolute value SSA (c) of the angular velocity is shown. In FIG. 5B, the solid bold line represents a change in the value when the calculation process of the spin state quantity according to the present invention is not corrected, and the round dotted line represents the vehicle body slip angle when the correction according to the present invention is performed. The change of the value of the term of a 2nd-order differential value and the amount of spin states is shown. Further, in (b), the settings of the flags F1 and F4 used in the calculation processing of the spin state quantity according to the present invention are shown superimposed. Further, in (c), the dotted line SSA is the magnitude (absolute value) of the steering angular velocity, and the solid thick line SSA_Fd is the magnitude (absolute value) of the steering angular velocity. FIG. 3 is a flowchart showing the calculation process of the spin state quantity in the preferred embodiment of the behavior control apparatus according to the present invention. FIG. 4 shows the steering angle (a), the amount of spin state, and the terms (b) constituting the steering when the steering angle is changed to the left after the steering angle is changed to the right by the sudden steering. The absolute value SSA (c) of the angular velocity is shown. In FIG. 5B, the solid bold line represents a change in the value when the calculation process of the spin state quantity according to the present invention is not corrected, and the round dotted line represents the vehicle body slip angle when the correction according to the present invention is performed. The change of the value of the term of a 2nd-order differential value and the amount of spin states is shown. Further, in (b), the settings of the flags F1, F2, and F3 used in the calculation processing of the spin state quantity according to the present invention are shown superimposed. Further, in (c), the dotted line SSA is the absolute value of the steering angular velocity, and the solid thick line SSA_Fd is the absolute value of the smoothed value of the steering angular velocity.

DESCRIPTION OF SYMBOLS 10 ... Vehicle 12FL-RR ... Wheel 28 ... Differential device 30 ... Steering device 34 ... Booster, steering angle sensor 36L, R ... Tie rod 40 ... Braking device 42FL-RR ... Each wheel wheel cylinder 46 ... Hydraulic circuit 50 ... Electronics Control device 62 ... Lateral acceleration sensor 64 ... Yaw rate sensor 66 ... Steering angle sensor

Vehicle Configuration FIG. 1A schematically shows an automobile in which a preferred embodiment of the behavior control device of the present invention is incorporated. In the figure, the vehicle 10 having the left and right front wheels 12FL and 12FR and the left and right rear wheels 12RL and 12RR is arranged in a normal manner according to the depression of the accelerator pedal by the driver (in the illustrated example, Since it is a rear wheel drive vehicle, a drive system device (only part of which is shown) that generates braking / driving force on the rear wheels, and a steering device 30 for controlling the steering angle of the front wheels (further, steering for the rear wheels) And a braking system device 40 that generates a braking force on each wheel. The drive system is configured so that the drive torque or the rotational force is transmitted from the engine and / or electric motor (not shown) to the rear wheel 12RL via the transmission (not shown), the differential gear device 28, and the like in a normal manner. , 12RR. The vehicle may be a front-wheel drive vehicle or a four-wheel drive vehicle, and in that case, the rotational force of the drive train device is transmitted to the front wheels or all the wheels. Further, the steering device transmits the rotation of the steering wheel 32 operated by the driver to the tie rods 36L and 36R while boosting the rotational force by the booster 34, and steers the front wheels 12FL and 10FR. It may be.

  The braking system device 40 includes a wheel cylinder 42i (i = FL, FR, RL) mounted on each wheel by a hydraulic circuit 46 that communicates with a master cylinder 45 that is operated in response to the driver depressing the brake pedal 44. , RR, and so forth.) Is an electronically controlled hydraulic brake device in which the brake pressure in the wheel, that is, the braking force in each wheel, is adjusted. In the hydraulic circuit 46, various valves (master cylinder cut valve, hydraulic pressure holding valve) for selectively communicating the wheel cylinder of each wheel to a master cylinder, an oil pump or an oil reservoir (not shown) in a normal manner. In a normal operation, the pressure of the master cylinder 45 is supplied to each wheel cylinder 42i in response to the depression of the brake pedal 44. However, in the case where the braking force of each wheel is adjusted individually or independently in order to execute the behavior control according to the present invention or any other braking force distribution control, based on the command of the electronic control unit 50, Various valves are operated, and the brake pressure in the wheel cylinder of each wheel is controlled to match each target pressure based on the detection value of the corresponding pressure sensor. The braking system device 40 may be of a type that applies a braking force to each wheel pneumatically or electromagnetically, or any other type for those skilled in the art.

  The behavior control and the operation control of the braking system device 40 of the present invention are executed by the electronic control device 50 as already mentioned. The electronic control unit 50 may include a microcomputer having a CPU, a ROM, a RAM, and an input / output port device, which are connected to each other by a bidirectional common bus, and a driving circuit. In the figure, the electronic control unit 50 receives the brake pedal depression amount θb, the steering angle δ, the wheel speed Vwi, the pressure Pbi in the wheel cylinder of each wheel, and the lateral acceleration Gy from sensors provided in each part of the vehicle. The detection value such as the yaw rate γ is illustrated as being input. However, various parameters necessary for various controls to be executed in the vehicle of the present embodiment, for example, various detection signals such as the front and rear G sensor values. May be entered.

Configuration and Operation of Electronic Control Device FIG. 1B shows an electronic control device 50 that realizes the behavior control device of the present invention in the form of a control block. It should be understood that the configuration and operation of the illustrated control device are realized by processing operations of the CPU or the like in the electronic control device 50 during operation of the vehicle.

  With reference to the figure, the control device 50 for executing the behavior control of the present embodiment may be similar to any known type of VSC or VDIM device in its basic configuration. Generally speaking, the control device 50 calculates a turning state amount (turning state index value) representing the behavior of the vehicle during turning, and based on the turning state amount, the target slip ratio Si of each wheel and the drive of the drive device. A hydraulic circuit for controlling the brake pressure of each wheel by referring to the VSC unit 50a for determining the torque down rate Td for reducing the output, the brake pedal depression amount θb from the brake pedal sensor 44, and the target slip rate Si for each wheel. And a drive control device 50c for controlling the engine torque with reference to the accelerator opening θa and the torque down rate Td from the accelerator opening sensor 16.

In such a configuration, first, the VSC unit 50a calculates the spin state amount SP by the following equation as a turning state amount (turning state index value) representing the behavior of the vehicle during turning. :
SP = K1 · β + K2 · dβ / dt + K3 · d 2 β / dt 2 ... (1)
Here, β, dβ / dt, and d ² β / dt ² are the vehicle body slip angle, the differential value of the vehicle body slip angle, and the second order differential value of the vehicle body slip angle, respectively, and K1, K2, and K3 are experimental values. Is a weighting factor determined by (usually a constant). The amount of spin state is an index value of the spin state or side slip amount of the vehicle that is turning. Generally speaking, the sum of the first term and the second term is necessary to return the vehicle body slip angle to 0 (stable The term corresponding to the magnitude of the yaw moment and the second-order differential value (third term) of the vehicle body slip angle are further added to speed up the control response.

In the above equation (1), the differential value dβ / dt of the vehicle body slip angle is obtained by using the lateral acceleration Gy, the vehicle speed Vx, and the yaw rate γ.
dβ / dt = Gy / Vx−γ (2a)
Given by. The vehicle speed Vx may typically be determined by the vehicle speed determination unit 50d in any known manner from the wheel speed value Vwi of each wheel from the wheel speed sensor, but a vehicle speed sensor is provided. If it is, the detected value may be used. The vehicle body slip angle is obtained by integrating the equation (2a)
β = ∫ (Gy / Vx−γ) dt (2b)
Given by. And the second order differential value of the vehicle body slip angle is obtained by differentiating the equation (2a).
d ² β / dt ² = d (Gy / Vx−γ) / dt (2c)
Given by.

A so-called “dead zone” may be provided for the second-order differential value of the vehicle body slip angle. That is, when the second-order differential value d ² β / dt ² of the vehicle body slip angle is calculated from the differential value dβ / dt of the vehicle body slip angle, the absolute value of the value obtained by differentiating (dβ / dt) is smaller than a predetermined value. Forcibly, the second derivative of the vehicle body slip angle is set to 0 (d ² β / dt ² ← 0). However, in order to avoid that the value of the spin state quantity changes discontinuously, in the calculation of the linear sum of Equation (1), the body slip that takes a value obtained by differentiating (dβ / dt) or 0. A value obtained by applying a first-order regression filter process (smoothing process) to the second-order differential value d ² β / dt ² of the corner is adopted.

  Thus, when the spin state quantity is calculated according to the equation (1), the VSC unit 50a further generates the yaw moment for correcting the turning behavior of the vehicle so that the spin state quantity becomes zero. A target value Si of the slip ratio (tire force) is determined, and the target slip ratio Si is transmitted to the braking control device 50b. In the braking control device 50b, taking into consideration the depression amount of the brake pedal 44, control commands (commands for various valves and pumps in the circuit) are sent to the hydraulic circuit 46 of the braking system device so that the target slip ratio Si of each wheel is achieved. ) And actuate the braking device (wheel cylinder) of each wheel. Typically, the target slip ratio Si of the front wheel outside the turn is selectively increased according to the magnitude of the spin state quantity, thereby generating a yaw moment in the direction of turning the vehicle body outside the turn. Thus, the spin of the vehicle (slip to the outside at the rear of the vehicle) is suppressed. [Typically, instead of generating a yaw moment sufficient to correct the behavior, when the spin state quantity exceeds a threshold value, an appropriate amount of yaw moment depends on the magnitude of the spin state quantity. Each wheel slip ratio is distributed and controlled in the direction in which the slippage is generated, and the slip ratio is adjusted by feedback control so that each turning state amount settles below a predetermined value. ]

  In addition, when the amount of spin state is large, the lateral force necessary for turning cannot be generated in the vehicle, or the tire force of the rear wheel may reach the limit. In order to limit the speed increase, the drive output may be limited (if the vehicle speed is reduced, the lateral force required for turning is reduced and the vehicle behavior is stabilized). Specifically, first, in the VSC unit 50a, the torque down rate Td that increases as the magnitude of the spin state amount increases is determined and transmitted to the drive control device 50c. The drive control device 50c refers to the torque down rate Td and the driver request torque determined based on the driver's accelerator pedal depression amount (accelerator opening), and the requested drive to be given to the drive device. Torque is determined and converted into a control command for each part of the drive device that realizes the value (the control command is a throttle opening or the like in the case of a gasoline engine) and is given to each part of the drive device. Thus, the drive output of the drive device is limited while the torque state Td is greater than zero.

It should be noted that the above-described behavior stabilization control such as the generation of the yaw moment by the slip ratio control of each wheel tire and / or the limitation of the acceleration of the vehicle should be executed only when the vehicle behavior is disturbed. The VSC unit 50a may permit the execution of the behavior stabilization control only when the degree of disturbance of the vehicle behavior is large. Specifically, for example, when the deviation of the actual yaw rate γ from the target yaw rate γt determined from the steering angle δ, the vehicle body speed Vx, etc. is large, that is, when the following equation is established, Based on the behavior stabilization control may be executed.
| Γ−γt |> γ_th (2d)
Here, the target yaw rate γt may be given as follows, for example, depending on the turning model of the vehicle.
γt = Vx · δ / N · L-Gy · kh · Vx (2e)
N, L, and kh are the steering wheel gear angle ratio (δ / N is the front wheel steering angle), wheel base, and vehicle turning characteristic values (constants), respectively. γ_th is an arbitrarily set threshold value.

  In the above behavior control device, in addition to the spin state quantity, in any known form, an index indicating that it has fallen into, or is likely to fall into, a drift-out state, an understeer state, or an oversteer state. The turning state quantity is calculated together, and the target slip ratio Si and the torque down rate Td are calculated using the turning state quantity as variables, and the brake pressure of each wheel braking device and the drive output of the driving device are adjusted. You may be supposed to. In that case, when it is detected that the vehicle is in an oversteer state or is likely to fall, each wheel brake pressure is controlled in a manner similar to the above-described spin suppression. On the other hand, when it is detected that the vehicle has entered or is likely to fall into a drift-out state or an understeer state, the target slip ratio Si of the front wheels and both rear wheels on the inside of the turn is selectively increased. As the vehicle is decelerated, a yaw moment that turns the vehicle body inward is generated. When it is detected that the behavior of the vehicle is unstable as described above, in any case, the drive output may be limited in a manner similar to spin suppression. .

Correction in Calculation of Spin State Quantity As described above, the VSC unit 50a calculates the spin state quantity and adjusts or drives the slip ratio (ie, braking force) of each wheel so that these values converge to zero. Output restriction is performed. In such control, according to the research of the inventor of the present invention, first, as described in Patent Document 2, in the vehicle, the vehicle turns to the left turn after the right turn or the left turn. Later, when the right steering is repeated twice in different directions, the response of the second derivative value of the vehicle slip angle in the spin state quantity is too early, so the vehicle slip angle or yaw rate is It has been found that the amount of spin state is reduced early before convergence, and thereby the braking force for spin suppression to be applied to each wheel is reduced early. FIG. 4 shows the steering angle (a), the spin state amount, and the amount of spin state when sudden steering is executed twice in different directions (when the steering angle is changed to the right and then to the left). Each item (b) that constitutes is illustrated. In FIG. 4, the steering angle and yaw rate are defined as positive in the left turn direction, and the vehicle body slip angle is defined as the angle in the direction of the speed vector as viewed from the longitudinal axis of the vehicle. Therefore, when the vehicle turns right, the vehicle body slip angle changes in the + direction. (The same applies to FIG. 2.)

Referring to FIG. 4, when sudden steering is executed twice in different directions, the term of the second derivative value of the vehicle body slip angle (K3 · d ² ) at the first turn (right turn). β / dt ² : solid thin line) first increases, and then the derivative of the vehicle slip angle (K2 · dβ / dt: one-dot chain line) and the vehicle slip angle (K1 · β: broken line) It increases in order (FIG. 2B). Next, when the direction is changed and a left turn is made, the term of the second derivative value of the vehicle body slip angle responds quickly to the change, and this time, the convex shape changes downward in the figure, As a result, the spin state quantity is changed to the lower side, and when the differential value term of the vehicle body slip angle starts to decrease from the upper peak value, the second-order differential value term of the vehicle body slip angle is transiently held at substantially zero. Period exists. This is because a dead zone is provided for the second-order differential value of the vehicle body slip angle, as already described. The same applies below. Corresponding to the magnitude of the spin state quantity, the vehicle is given a yaw moment that turns the vehicle outward (rightward), and the spin begins to be suppressed. However, when the magnitude of the derivative value of the vehicle body slip angle starts to decrease (beginning to increase from the lower peak) due to the effect of the yaw moment, the second derivative value of the vehicle body slip angle is In response to the change, the differential value of the vehicle body slip angle and the term of the vehicle body slip angle converge again in the figure before the convergence. Then, as shown in the figure, the magnitude of the spin state amount is temporarily reduced (the region indicated by the white arrow in the figure), and the control action for spin suppression is correspondingly reduced.

Therefore, in the invention described in Patent Document 2, in the calculation process of the spin state quantity SP, the second-order differential value term of the vehicle body slip angle is monitored, and the second-order differential value term of the vehicle body slip angle is different. When the direction deviates from the threshold range, it is determined that sudden steering has been performed twice in different directions (as understood by those skilled in the art, when the vehicle starts turning, the vehicle body slip angle changes. However, the second-order differential value term of the vehicle body slip angle first changes following the change of the steering angle.) After such a determination is made, the sign of the second-order differential value term of the car body slip angle is inverted. After that (in the figure, after F3 ← ON), the contribution of the term of the second derivative value of the vehicle body slip angle in the spin state quantity SP is indicated by a round dotted line marked with K ₃ = 0 in the figure It was decided to reduce or disregard as shown in. As a result, the spin state quantity SP does not temporarily decrease as indicated by the dotted dotted line with the corrected SP in the figure, and the spin state is suppressed accordingly. The reduction of the control action is avoided.

  On the other hand, in the configuration in which the term of the second-order differential value of the vehicle body slip angle is included in the spin state quantity as described above, the case where the steering angle is maintained after the sudden steering is executed only once is seen. While maintaining the rudder angle, before the vehicle body slip angle or yaw rate converges, the amount of spin state is reduced early, thereby reducing the braking force for spin suppression to be applied to each wheel at an early stage. A phenomenon was found. FIG. 2 exemplifies the steering angle (a), the spin state quantity, and the respective items (b) constituting the steering angle (a) when the steering angle is maintained after the sudden steering is executed only once.

Referring to the figure, when the steering angle is suddenly changed (FIG. 2 (a)), as in the example of FIG. 4, the term of the second derivative value of the vehicle body slip angle (K3 · d ² β / dt ² : solid thin line) first increases rapidly, and the magnitude of the spin state quantity SP (FIG. 2 (b) solid thick line) changes substantially following the change in the steering angle. Thus, the control action for rapid spin suppression is exhibited. However, after the change in the steering angle has generally stopped, the second-order differential value of the vehicle slip angle corresponds to the reduction in the size of the differential value of the vehicle slip angle (K2 · dβ / dt: one-dot chain line). Accordingly, the magnitude increases in the opposite direction, and therefore, the magnitude of the spin state amount SP decreases early as shown by the white arrow in the figure, and before the vehicle body slip angle or yaw rate converges, The control action for spin suppression will be reduced. That is, since the response of the second-order differential value term of the vehicle body slip angle is fast, the control action for suppressing the spin after the rudder angle is maintained is reduced early. An early decrease in the spin suppression control action when the steering angle is maintained after such one sudden steering is as follows: K ₃ = 0 in FIG. 4B when the steering angle is maintained after the sudden steering. This can be avoided by reducing or ignoring the contribution of the second-order differential value term of the vehicle body slip angle, as indicated by the dotted dotted line. Therefore, it is necessary to detect that the steering angle is maintained after sudden steering.

However, it is difficult to determine whether the steering angle is maintained after one sudden steering or whether the steering is started in the opposite direction by monitoring the second-order differential value term of the vehicle body slip angle. It is. The steering angle is maintained as understood with reference to the change in the second-order differential value (K3 · d ² β / dt ² : solid thin line) of the vehicle body slip angle in FIGS. 2 (b) and 4 (b). Whether the vehicle is steered or the vehicle is steered in the reverse direction, the second-order differential value of the vehicle body slip angle has changed in the reverse direction after one sudden steering operation. Cannot be used. Such a determination is also difficult to achieve with reference to a change in steering angle or a steering angular velocity. The change in the steering angle or the steering angular velocity is steered in the opposite direction even when the steering angle is maintained after the sudden steering, as illustrated in the SSA (dotted line) in FIGS. 2 (c) and 4 (c). In this case, since the vehicle is once stopped or gradually decreased to 0, even if these values are referred to, it is still impossible to distinguish between the case where the steering angle is maintained and the case where the steering is turned in the reverse direction.

  Accordingly, as a result of various studies by the inventors of the present invention regarding the above determination, the steering angle is maintained after sudden steering when the smoothing value of the steering angular velocity or the magnitude of the primary regression filter processing value is referred to. It was found that it is possible to distinguish between the case and the case of turning in the opposite direction. Specifically, as illustrated in SSA_Fd (bold solid line) in FIGS. 2 (c) and 4 (c), the magnitude of the smoothing value of the steering angular velocity is maintained after the sudden steering. In both cases, when turning in the reverse direction, the response is slow compared to the second-order differential value of the vehicle body slip angle or the steering angular velocity when gradually decreasing from the middle of the first sudden steering. If the value is 0, the increase starts before the value converges to 0. On the other hand, when the rudder angle is maintained, the magnitude of the smoothing value of the steering angular velocity converges to zero. Therefore, the steering angle is maintained after the sudden steering or is steered in the reverse direction by referring to whether or not the smoothing value of the steering angular velocity is less than the predetermined threshold ths after the sudden steering. It will be possible to determine whether or not.

  Thus, in the embodiment of the present invention, when the steering angle is maintained after the sudden steering, the contribution of the second-order differential value term of the vehicle body slip angle in the spin state quantity can be reduced or ignored. Therefore, after it is detected that the sudden steering is performed in any one direction, it is monitored whether or not the smoothing value of the steering angular velocity is below a predetermined threshold ths. Then, when the magnitude of the smoothing value of the steering angular velocity falls below the predetermined threshold ths, a process of reducing or ignoring the contribution of the second-order differential value term of the vehicle body slip angle in the spin state quantity is performed. When the angular velocity smoothing value does not fall below the predetermined threshold ths and the second sudden steering is performed, the second-order differential value term of the vehicle body slip angle is subsequently applied, as in Patent Document 2. Until the value approaches 0 or the sign is reversed, the calculation process of the spin state quantity is corrected so that the contribution of the second-order differential value term of the vehicle body slip angle in the spin state quantity is maintained.

  FIG. 3 shows, in the form of a flowchart, the calculation process of the spin state quantity that achieves the above control configuration. The illustrated process is repeatedly executed at a predetermined processing cycle time by the VSC unit 50a according to the computer program stored in the memory while the vehicle is running.

  Referring to the figure, in the illustrated arithmetic processing, first, the vehicle body slip angle, the differential value of the vehicle body slip angle and the second order differential value of the vehicle body slip angle represented by the above equation (1) are calculated. The weighting factors K1, K2, and K3 in the linear sum are each determined in an arbitrary manner, usually using data obtained experimentally in advance (step 10).

Next, it is determined whether or not the vehicle is suddenly steered in any of the left and right directions. Specifically, when the term K3 · d ² β / dt ² of the second-order differential value of the vehicle body slip angle exceeds a predetermined threshold th1, that is,
K3 · d ² β / dt ² > th1 (3)
Is established (step 20), the vehicle is suddenly steered to the right, so that the flag F1 is turned on to store the fact (step 30). On the other hand, when the term K3 · d ² β / dt ² of the second-order differential value of the vehicle body slip angle is below a predetermined threshold value −th1, that is,
K3 · d ² β / dt ² <−th1 (4)
Is established (step 40), the vehicle is suddenly steered in the left direction, so that the flag F2 is turned on to store this fact (step 50).

  That is, when one of the flags F1 and F2 is turned ON in the processing of steps 20 to 50 while the processing cycle of FIG. 3 is repeated, the first sudden steering is performed in either of the left and right directions. Is detected. This state corresponds to the state (ii) in FIGS. 2B and 4B.

Thus, after only one of the flags F1 and F2 in the above state (ii) is turned on, if both the flags F1 and F2 are turned on (steps 60 and 110), the first sudden After the steering is executed, the sudden steering is executed in the reverse direction (state (iii) in FIG. 4B). Therefore, in that case, as described in Patent Document 2, when the value of the second-order differential value K3 · d ² β / dt ² of the vehicle body slip angle becomes small, or such value When the sign of is reversed, the second-order differential value term of the vehicle body slip angle is reduced or ignored. Specifically, when the absolute value of the term K3 · d ² β / dt ² of the second-order differential value of the vehicle body slip angle is below a predetermined threshold th2, that is,
| K3 · d ² β / dt ² | <th2 (5)
Is satisfied (step 120), the flag F3 is set to ON (step 130), and the value of the coefficient K3 is forcibly set to 0 while the flag F3 remains ON.

However, the steering angle may be maintained as it is after only one of the flags F1 and F2 in the above state (ii) is turned on. Before the magnitude of the second derivative value changes in the opposite direction, reduction or neglect of the magnitude of the second derivative value term of the vehicle body slip angle should be performed. Therefore, in the processing cycle of this embodiment, in order to determine whether or not the steering angle is maintained when only one of the flags F1 and F2 is turned on, as described above, the steering angular velocity It is monitored whether the size of the annealing value has decreased. In particular,
[Magnitude of steering angular velocity] SSA_Fd <ths (6)
Is determined (step 70). Here, ths is a threshold that may be set arbitrarily. Further, the magnitude of the smoothing value of the steering angular velocity may be an arbitrary value that changes later with respect to the absolute value of the steering angular velocity. Typically, the absolute value of the steering angular velocity is subjected to linear regression filtering. May be obtained. Thus, as illustrated in FIG. 2C, when SSA_Fd falls below the threshold ths (state (v)), it is determined that the rudder angle is maintained, and in order to store that, The flag F4 is turned on (step 80). When the flag F4 is set to ON, thereafter, the value of the coefficient K3 is forcibly set to 0 (step 100). [As described above, when the sudden steering is performed in the reverse direction after the first sudden steering is performed, since the equation (6) is not satisfied, the vehicle body slip angle is reduced by the rapid steering in the reverse direction. The value of the coefficient K3 is not forcibly set to 0 before the magnitude of the second-order differential value changes in the reverse direction. ]

Thus, after the series of processes described above, the spin state quantity SP is calculated using the equation (1) using the coefficients K1 to K3 given in accordance with the processes so far. At that time, when K3 is forcibly set to 0, the second-order differential term K3 · d ² β / dt ² of the vehicle body slip angle is ignored, and the spin state quantity SP is
SP = K1 · β + K2 · dβ / dt (1 ')
It will be given by.

  As described above, when the spin state quantity is calculated, it is further determined whether or not the behavior stabilization control based on the calculated spin state quantity is actually executed. As described above, this determination is made by determining whether the equation (2d) is established, that is, referring to the yaw rate, whether or not the behavior is in an unstable state or whether there is a risk thereof. May be done by When equation (2d) holds, behavior stabilization control such as generation of yaw moment by slip rate control of each wheel tire and / or limitation of vehicle acceleration is executed based on the spin state quantity. . On the other hand, when the equation (2d) is not established, the behavior is stable, and thus the behavior stabilization control is not performed. When it is determined that the behavior is stable, the flags F1 to F4 are reset to OFF.

  The above processing is organized as follows in accordance with the steering state of the vehicle illustrated in FIGS. 2B and 4B.

State (i) When sudden steering is not executed or before execution-
The term K3 · d ² β / dt ² of the second-order differential value of the vehicle body slip angle does not depart from the predetermined threshold range th1 to -th1, and F1 and F2 are all OFF. Therefore, it is determined NO in Steps 60 and 110, and the spin state quantity is calculated using the term K3 · d ² β / dt ² of the second-order differential value of the vehicle body slip angle as it is. (However, in this case, since the behavior is normally stable, the behavior stabilization control is not executed.)

State (ii) When sudden steering is performed on either side-
The term K3 · d ² β / dt ² of the second-order differential value of the vehicle body slip angle deviates from one side of the predetermined threshold range th1 to -th1 (in FIG. 2 (b) and FIG. 4 (b), th1 Only one of F1 or F2 is set ON. If it does so, it will determine with Yes in step 60, and it will be determined in step 70 whether the magnitude | size SSA_Fd of the smoothing value of a steering angular velocity is less than threshold value ths. Since SSA_Fd has not fallen below the threshold ths for a certain period of time immediately after the sudden steering is executed, it is determined NO in step 70, and the spin state quantity is equal to the vehicle body slip angle. The second-order differential value term K3 · d ² β / dt ² is used as it is. Therefore, the behavior stabilization control is executed in a state where the second-order differential value term of the vehicle body slip angle is reflected.

State (iii) After sudden steering is performed in one direction, when the magnitude SSA_Fd of the steering angular velocity does not fall below the threshold ths, and sudden steering is performed in another direction (FIG. 4B) —
The term K3 · d ² β / dt ² of the second derivative value of the vehicle body slip angle deviates from the other side of the predetermined threshold range th1 to -th1 while the flag F4 is OFF (FIG. 4B). Then, the deviation from the -th1 side), both F1 and F2 are set to ON, and the determinations in steps 60 and 110 are YES. However, at this stage, the absolute value of the second-order differential term K3 · d ² β / dt ² of the vehicle body slip angle is still larger than the predetermined value th2, and the flag F3 remains OFF. No is determined, and the spin state quantity is calculated using the term K3 · d ² β / dt ² of the ^second derivative of the vehicle body slip angle as it is.

State (iv) When the sign of the second-order differential value K3 · d ² β / dt ² of the vehicle body slip angle is reversed (FIG. 4B) −
While the flags F1 and F2 remain ON, the absolute value of the second-order differential value K3 · d ² β / dt ² of the vehicle body slip angle becomes smaller than the predetermined value th2, and the flag F3 is turned ON (step 120, 130). If so, the determination in step 140 is yes, K3 is set to 0, and the spin state quantity is calculated ignoring the term K3 · d ² β / dt ² of the second-order differential value of the vehicle body slip angle.

State (v) When the steering angle is maintained after the first sudden steering (FIG. 2 (b))-
Since only one of F1 and F2 is set to ON, the determination in step 60 is YES, and the determination in step 70 is YES because the magnitude SSA_Fd of the steering angular velocity is less than the threshold ths. Thus, the flag F4 is turned ON (step 80). If so, the determination in step 90 is yes, K3 is set to 0, and the spin state quantity is calculated ignoring the term K3 · d ² β / dt ² of the ^second derivative of the vehicle body slip angle.

Thus, according to the configuration of the above processing, when the sudden steering is executed only once and the steering angle is maintained thereafter, the second-order differential value of the vehicle body slip angle is calculated in the calculation of the spin state amount thereafter. The term K3 · d ² β / dt ² will be ignored. Then, the spin state quantity is affected by an increase in the opposite direction of the term K3 · d ² β / dt ² of the second-order differential value of the vehicle body slip angle in a state in which the steering angle is maintained after sudden steering. That is, without making an early reduction, the transition is as shown by the round dotted line labeled “SP after correction” in FIG. It is expected that the correction of the spin state quantity does not cause an early reduction in the control action for suppressing the spin, thereby eliminating the convergence delay in the yaw rate.

  While the present invention has been described in detail with respect to one embodiment thereof, it will be apparent to those skilled in the art that various modifications can be made within the scope of the present invention.

For example, in this embodiment, when the contribution of the term K3 · d ² β / dt ² of the second-order differential value of the vehicle body slip angle is reduced in the calculation of the spin state quantity, the value of the term is completely Instead of ignoring, the value of the term may be made smaller, for example, half the value of the term or less. Further, the spin state quantity is not limited to the linear sum in the form of the expression (1), and is expressed in other forms that are reduced early due to the change in the second derivative value of the vehicle body slip angle described above. It should be understood that such cases are also within the scope of the present invention. Furthermore, in this embodiment, the yaw moment for suppressing the spin is given by the difference in braking force between the left and right wheels, but the vehicle is equipped with a device that can automatically adjust the wheel steering angle. In this case, a yaw moment for suppressing spin may be generated by adjusting the wheel steering angle.

Claims (7)

  A vehicle behavior control device for suppressing vehicle spin based on a control amount calculated from a vehicle body slip angle, a differential value of the vehicle body slip angle, and a second-order differential value of the vehicle body slip angle, When steering is executed in one of the directions and the magnitude of the second-order differential value of the vehicle body slip angle exceeds a predetermined value, and the magnitude of the smoothing value of the steering angular velocity falls below the predetermined value The apparatus is characterized in that the contribution of the second derivative of the vehicle body slip angle to the control amount is reduced.   The apparatus according to claim 1, wherein the steering angular velocity is smoothed after steering is executed in one of the left and right directions of the vehicle and a magnitude of a second-order differential value of the vehicle body slip angle exceeds a predetermined value. The apparatus is characterized in that the contribution of the second derivative of the vehicle body slip angle in the control amount is ignored when the magnitude of the value falls below a predetermined magnitude.   3. The apparatus according to claim 1, wherein the smoothing value of the steering angular velocity is a value obtained by subjecting the steering angular velocity to a linear regression filter process. 4. The apparatus according to claim 1, wherein the control amount includes a vehicle body slip angle β, a vehicle body slip angle differential value dβ / dt, and a vehicle body slip angle second-order differential value d ² β / dt ^2. And using predetermined coefficients K1, K2, and K3,
K1 · β + K2 · dβ / dt + K3 · d ² β / dt ²
A device characterized by being given by:   5. The apparatus according to claim 4, wherein the value of the coefficient K3 is set to 0 when the contribution of the second-order differential value of the vehicle body slip angle in the control amount is reduced.   The apparatus according to claim 1, wherein a yaw moment that suppresses spin of the vehicle is generated based on the control amount.   The apparatus according to claim 1, wherein acceleration of the vehicle is limited based on the control amount.

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