JP4026187B2 - Vehicle attitude control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention detects a vehicle state quantity representing a turning posture of the vehicle with respect to the traveling direction, and independently applies a braking force to each wheel according to the detected vehicle state amount, so that the turning posture of the vehicle becomes the target traveling direction. The present invention relates to a vehicle attitude control device that controls to converge toward the vehicle.
[0002]
[Prior art]
  Conventionally, as a posture control device for this type of vehicle, it is detected that either one of the front two wheels or the rear two wheels has reached the grip limit based on the side slip angle of each wheel, and the other has not lost the grip. It is known that vehicle posture control is performed by applying braking force to these two wheels (see, for example, Japanese Patent Laid-Open No. 7-232629). In this case, for example, when the front two wheels reach the grip limit and the vehicle is about to drift out, the braking force is applied to the rear two wheels to reduce the cornering force that the rear two wheels can generate. Thus, the balance between the cornering force generated on the front wheel side and the cornering force generated on the rear wheel side is maintained, thereby preventing the vehicle from drifting out.
[0003]
[Problems to be solved by the invention]
  However, in general, in order to prevent the vehicle from drifting out, it is effective and safe to reduce the centrifugal force acting on the vehicle body by decelerating the vehicle. If the braking force applied to the two wheels is made sufficiently large, the cornering force generated on the rear wheel side may suddenly decrease and the stability of the vehicle posture may be impaired. Therefore, there is an inconvenience that the vehicle cannot be sufficiently decelerated. In addition, since braking force is simultaneously applied to either the front two wheels or the rear two wheels, yaw moments around the center of gravity of the vehicle body due to these braking forces cancel each other, and the direction of the vehicle is changed. There is also an inconvenience that it is difficult to change quickly.
[0004]
  The present invention has been made in view of such circumstances, and an object of the present invention is to sufficiently decelerate the vehicle and prevent drift-out without impairing the stability of the posture of the vehicle. In addition, the vehicle orientation can be changed quickly.
[0005]
[Means for Solving the Problems]
  To achieve the above objective,This applicationThe invention includes a vehicle state detecting unit that detects a vehicle state amount that represents a turning posture of the vehicle with respect to the traveling direction, and the vehicle state amount detected by the vehicle state detecting unit is derived from the target vehicle state amount corresponding to the target traveling direction. It is assumed that the vehicle attitude control device performs control so that when the vehicle deviates by a predetermined amount or more, the state of the turning attitude of the vehicle converges to that corresponding to the target vehicle state quantity.
[0006]
  In this one,First, vehicle speed detection means for detecting the vehicle speed, steering amount detection means for detecting the steering amount by the driver,From braking means configured to be able to individually apply braking force to the front, rear, left and right wheels, attitude control means for controlling the turning attitude of the vehicle by controlling the operation of the braking means, and the vehicle state detection means An understeer determination means for determining that the detected vehicle state quantity to be output deviates from the target vehicle state quantity toward the understeer side by a set amount or more and the vehicle is in an understeer state;Attitude change determining means for determining the presence or absence of a change in attitude of the vehicle toward the inward turn of the vehicle based on the amount of change in the detected vehicle state quantity output from the vehicle state detecting means;WithTo do.
[0007]
  AndThe posture control means isAn attitude control unit that changes the direction of the vehicle to the inside of the turn by operating the braking means so that a braking force is applied to the front wheel or the front and rear wheels inside the turn of the vehicle;A deceleration control unit that decelerates the vehicle by operating the braking means so that braking force is simultaneously applied to the two wheels on the diagonal line of the front wheel outside the turning and the rear wheel inside the turning.When the output of the determination result that the vehicle is in the understeer state is received from the understeer determination means, first, the attitude control of the vehicle is performed by the attitude control unit, and thereby the inward turning to the inside When it is determined by the posture change determination means that there is no posture change, the control immediately shifts to the deceleration control by the deceleration control unit, whereas when it is determined that there is a posture change, the change in the detected vehicle state quantity corresponding to the posture change. After the amount becomes equal to or larger than a predetermined determination change amount, it is configured to shift to the deceleration control, and further, the determination change amount is decreased according to an increase in the detected vehicle speed value detected by the vehicle speed detecting means. A determination change amount correction unit that corrects and increases the determination change amount according to an increase in the detected steering amount detected by the steering amount detection unit;It is set as the structure provided.
[0008]
  In the case of the above configuration, when the understeer tendency of the turning vehicle becomes strong and the detected vehicle state quantity deviates from the target vehicle state quantity to the understeer side by a set amount or more, the judgment result that the vehicle is in the understeer state is an understeer judgment unit. The braking means is actuated by the attitude control means receiving this output,First, as a first step, a braking force is applied to the front wheel inside the turning or the front and rear wheels inside the turning. Yaw moment acting around the center of gravity of the vehicle body due to this braking force Thus, the direction of the vehicle is quickly changed to the inward turning side.
[0009]
  Then, after changing the direction of the vehicle to the inside of the turn, as the second stageThe braking force is simultaneously applied to the two wheels on the diagonal lines of the front wheel outside the turning and the rear wheel inside the turning.AndWhen the braking force is applied, the vehicle is decelerated, the centrifugal force acting on the vehicle body is reduced, and the understeer tendency is reduced. At this time, since the braking force is applied to the two wheels on the diagonal line of the front wheel outside the turning and the rear wheel inside the turning, the yaw moment around the center of gravity of the vehicle body accompanying the braking force applied to each wheel Will cancel each other, and the cornering force on the front wheel side and the cornering force on the rear wheel side will simultaneously decrease. As a result, even if the braking force is sufficiently increased, the vehicle can be safely operated without adversely affecting the posture change caused by the braking force application, that is, without deteriorating the stability of the vehicle body posture and leaving room for posture recovery. And it becomes possible to decelerate reliably and to prevent the drift-out.
[0010]
  Moreover, at the time of transition from the first-stage attitude control to the deceleration control,When it is determined by the posture change determining means that there is no change in the vehicle's inward turning direction, for example, the road surface is very slippery and a sufficient yaw moment cannot be applied to the vehicle body. When is almost unchangedInThe deceleration control is immediately performed and braking force is applied to the left and right front wheels and the rear rear wheel, thereby decelerating the vehicle. On the other hand, when it is determined by the posture change determination means that there is a posture change to the inside of the turnIsExecution of the deceleration control is delayed, and accordingly, the direction of the vehicle is changed more to the inside of the turn.
[0011]
  In other words, the vehicle attitude control can reliably prevent drift-out, while the vehicle can be immediately decelerated in a driving situation where the attitude control is difficult, thereby improving safety.
[0012]
  Also, by the above attitude controlWhen it is determined that there is a change in the attitude of the vehicle toward the inside of the turn, the deceleration control is executed after the change amount of the detected vehicle state quantity corresponding to this change in attitude exceeds a predetermined determination change amount.RutaTherefore, it becomes possible to make the change amount of the direction of the vehicle before the deceleration control sufficient for the determination change amount.
[0013]
  Furthermore, in the above configuration,The determination change amount correction unit corrects the determination change amount according to the detected vehicle speed value detected by the vehicle speed detection unit and the detected steering amount detected by the steering amount detection unit. That is, since the determination change amount is corrected to decrease when the vehicle speed increases, the transition from the posture control to the deceleration control is performed while the change amount of the vehicle state amount is relatively small, and when the driver's steering amount is large Since the determination change amount is increased and corrected, the shift from the posture control to the deceleration control is performed after the change amount of the vehicle state amount becomes relatively large.
[0014]
  In other words, when the vehicle speed is high, deceleration control is performed early, and when the amount of steering by the driver is large, the shift to the deceleration control is delayed correspondingly to increase the amount of change in the direction of the vehicle before deceleration. This makes it possible to perform appropriate control according to the vehicle speed and the driving operation of the driver..
[0015]
DETAILED DESCRIPTION OF THE INVENTION
  Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0016]
  FIG. 1 shows a vehicle to which a vehicle attitude control device (Stability Control System: hereinafter simply referred to as SCS) according to an embodiment of the present invention is applied, 1 is a vehicle body, 2, 2,. , 21FL, 21RR, 21RL, four sets of hydraulic brakes, 3 is a pressure unit for supplying pressure fluid to each of these brakes 2, 4 is supplied from this pressure unit 3 Is a hydraulic unit (hereinafter simply referred to as HU) that distributes the pressurized fluid to the brakes 2, and the brakes 2, 2,..., The pressurizing unit 3 and the HU 4 constitute braking means. 5 is an SCS controller that controls the operation of each brake 2 via the pressurizing unit 3 and the HU 4, 6, 6,... Are wheel speed sensors that detect the rotational speed of the wheels 21, and 7 is the vehicle body. 1 is a lateral G sensor that detects a lateral acceleration acting on 1, a yaw rate sensor that detects a yaw rate acting on the vehicle body 1, and 9 is a rudder as steering amount detection means that detects a steering angle of the driver. It is an angle sensor. Note that 10 is a master cylinder, 11 is an engine, 12 is an automatic transmission, and 13 is an EGI controller that adjusts the fuel injection amount in accordance with the rotational speed of the engine 11 and the intake air amount.
[0017]
  2, the brake 2 of the right front wheel 21FR and the brake 2 of the left rear wheel 21RL are connected to the master cylinder 10 by the first hydraulic line 22a, while the left front wheel The 21FL brake 2 and the right rear wheel 21RR brake 2 are connected to the master cylinder 10 by a second hydraulic line 22b different from the first hydraulic line 22a. Two independent brake systems are configured. In addition, a braking force is applied to the wheels 21FR, 21FL,... According to the driver's stepping on the brake pedal 14.
[0018]
  The pressurizing unit 3 can connect and disconnect the hydraulic pumps 31a and 31b connected to the first and second hydraulic lines 22a and 22b, and the hydraulic pumps 31a and 31b and the master cylinder 10, respectively. In this way, the cut valves 32a and 32b disposed in the first and second hydraulic pressure lines 22a and 22b, respectively, and the hydraulic pressure for detecting the hydraulic pressure between the cut valves 32a and 32b and the master cylinder 10 And a sensor 33. Then, the cut valves 32a and 32b are closed in accordance with a command from the SCS controller 5, whereby the hydraulic fluid discharged from the hydraulic pumps 31a and 31b is supplied to the HU 4 regardless of the brake operation by the driver. The brakes are supplied to the brakes 2, 2,. Further, as shown in FIG. 2, the HU 4 includes pressurizing valves 41, 41,... That pressurize the brakes 2 with the pressure fluid supplied via the first hydraulic pressure line 22a or the second hydraulic pressure line 22b. The brakes 2 are connected to a reservoir tank 42 and pressure reducing valves 43, 43,. And according to the command from the SCS controller 5, the opening of each of the pressurizing valves 41 and the pressure reducing valves 43 is increased / decreased / changed, whereby the hydraulic pressure applied to the brakes 2 is increased / decreased to It is configured to be changed.
[0019]
  The SCS controller 5 determines the turning posture of the vehicle based on input signals from the wheel speed sensors 6, 6,..., The lateral G sensor 7, the yaw rate sensor 8, and the rudder angle sensor 9, and according to the determination result. While controlling the operation of the pressurizing unit 3 and the HU 4, the brake operation of the driver is detected based on the input signal from the hydraulic pressure sensor 33, and the operation control of the pressurizing unit 3 and the HU 4 corresponding to the brake operation. Is configured to do. Specifically, as shown in FIG. 3, the SCS controller 5 includes a state quantity calculation unit 51, a target state quantity calculation unit 52, a control intervention determination unit 53 as an understeer determination unit, and a control calculation unit 54. , An understeer level determination unit 55a as an understeer level determination unit, a vehicle speed limit determination unit 55b as a vehicle speed limit determination unit, an attitude change determination unit 55c as an attitude change determination unit, and an operation control unit 56. Of these, the state quantity calculation unit 51 and the target state quantity calculation unit 52, the wheel speed sensors 6, 6,..., The lateral G sensor 7, the yaw rate sensor 8, and the steering angle sensor 9 constitute vehicle state detection means. In particular, the state quantity detection unit 51 and the wheel speed sensors 6, 6,... Constitute a vehicle speed detection unit, and the control calculation unit 54 and the operation control unit 56 constitute an attitude control unit. .
[0020]
  The state quantity calculation unit 51 is a vehicle state quantity that represents a turning posture with respect to the traveling direction of the vehicle based on input signals from the wheel speed sensors 6, 6,..., Lateral G sensor 7, yaw rate sensor 8, and rudder angle sensor 9. The vehicle body side slip angle, the vehicle body speed, and the like are calculated, and the target state quantity calculation unit 52 similarly corresponds to the vehicle state quantity that converges in the target travel direction according to the driving operation of the driver. A target side slip angle, a target yaw rate, etc. as target state quantities are calculated. Specifically, as shown in FIG. 4, a vehicle body speed Vref is calculated based on each wheel speed detected by the wheel speed sensors 6, 6,... (C1), and this vehicle body speed Vref and each wheel speed are calculated. On the basis of the lateral acceleration detected by the lateral G sensor 7, the yaw rate γ detected by the yaw rate sensor 8, and the front wheel steering angle calculated from the steering angle θH detected by the steering angle sensor 9, The angle β is calculated (C2). Further, the slip ratio and the slip angle of each tire 23 are calculated based on each wheel speed, the vehicle body speed Vref, the vehicle body side slip angle β, the yaw rate γ, and the front wheel rudder angle (C3). The vertical load at each wheel position is calculated based on the lateral acceleration and the lateral acceleration (C4). Based on the vertical load and the slip rate and slip angle, the current grip force relative to the total grip force that each tire 23 can exert is calculated. A load factor as a ratio is calculated (C5). Further, the road surface friction coefficient between the road surface and the tires 23, 23,... Is calculated based on the load factor and the lateral acceleration (C6), and the road surface friction coefficient, the vehicle body speed Vref, and the front wheel steering angle are calculated. Based on this, the target yaw rate and the target skid angle are calculated (C7).
[0021]
  The control intervention determination unit 53 calculates a vehicle body side slip angle deviation amount that is a deviation amount of the vehicle body side slip angle β with respect to the target side slip angle and a yaw rate deviation amount that is a deviation amount of the yaw rate γ with respect to the target yaw rate, and these vehicle body side slip angles. Based on the deviation amount and the yaw rate deviation amount, the SCS control intervention determination is performed.
[0022]
  The control calculation unit 54 applies a braking force to one of the left and right sides of the vehicle body 1 to apply a yaw moment around the center of gravity of the vehicle body 1 to control the vehicle posture, A deceleration control unit 54b that performs deceleration control of the vehicle by applying a braking force to the left and right sides of the vehicle body 1, and a correction calculation unit 54c that changes and corrects a first determination change amount in drift-out suppression control described later. In accordance with the determination result of the control intervention determination unit 53, the braking force applied to each wheel 21 is calculated so that the turning posture of the vehicle converges toward the target traveling direction according to the driving operation of the driver. Further, the control calculation unit 54 detects the brake operation by the driver when the brake pressure P detected by the hydraulic pressure sensor 33 becomes larger than the atmospheric pressure P0, and specifies the one of the pair of cut valves 32a and 32b. By opening one of them, the hydraulic fluid in the master cylinder 10 can be circulated through the first or second hydraulic pipelines 22a and 22b in accordance with the driver's brake operation.
[0023]
  The understeer degree determination unit 55a determines that it is difficult to change the direction of the vehicle when the understeer tendency is too strong in the drift-out suppression control described later. The vehicle speed limit determination unit 55b determines that the vehicle speed limit is high. When it is too much, it is determined that it is difficult to change the direction of the vehicle. Further, the posture change determination unit 55c determines whether or not there is a change in the direction of the vehicle by the posture control in the drift-out suppression control. And the said operation control part 56 operates cut valve 32a, 32b, pressurization valve 41, 41 ..., etc. according to the calculation result by the said control calculating part 54. FIG.
[0024]
  In addition to the control of the SCS, the SCS controller 5 is an ABS (Anti-skid) that limits the braking force applied to the wheels 21FR, 21FL,... To prevent the brakes of the wheels 21FR, 21FL,. Brake System) and TCS (Traction Control System) that controls slipping by limiting the driving torque of the wheels 21FR, 21FL,... Priority is given, and then the control of the SCS and the control of the TCS are arbitrated in a predetermined manner.
[0025]
  FIG. 5 shows the overall basic control by the SCS controller 5. In this basic control, first, when the driver gets into the vehicle and turns on the ignition key, various initial settings are made in step SA1, and in step SA2, the wheels are set. After the origin correction of the speed sensors 6, 6,... Is performed, a signal is input from the sensors to the SCS controller 5. Based on these signal inputs, the vehicle speed, vehicle deceleration, vehicle speed at each wheel position, etc. of the vehicle running in step SA3 are used as common vehicle state quantities for ABS, SCS and TCS control. Calculate. Subsequently, in step SA4, an SCS control calculation is performed. That is, in step SA41, the SCS vehicle body speed Vref, the vehicle body side slip angle β, the wheel slip rate and slip angle of each wheel, the vertical load of each wheel, the tire load factor, and the road surface friction coefficient are calculated. In step SA42, the target yaw rate is calculated. Calculate the target skid angle and target deceleration. Then, in step SA43, the vehicle side slip angle deviation amount and the yaw rate deviation amount are calculated based on the calculation result, and the SCS control intervention determination is performed based on these deviation amounts. If the control intervention is determined, step SA44 is performed. , The wheels 21, 21,... To which the braking force is applied are selected, and the braking force to be applied to each of the selected wheels 21 is calculated. Based on the calculated braking force, the valve opening of each of the pressurizing valves 41, 41,... And the pressure reducing valves 43, 43,.
[0026]
  Further, the control calculation of the ABS is performed at step SA5, the control calculation of the TCS is performed at step SA6, and the calculation results of the ABS, TCS and the SCS are arbitrated by a predetermined method at the step SA7, and the pressurizing valves 41 are adjusted. And the valve opening degree of the pressure reducing valve 43 and the like are determined. In step SA8, by changing the opening degree of each of the pressurizing valve 41 and the pressure reducing valve 43, the hydraulic fluid is supplied to each brake 2 according to the opening degree to apply a braking force to each wheel 21. To do. Finally, in step SA9, a fail-safe determination for detecting malfunctions of the wheel speed sensors 6, 6,... Is performed, and then the process returns to step SA1.
[0027]
  In the flowchart, step SA41 corresponds to the state quantity calculation unit 51, SA42 corresponds to the target state quantity calculation unit 52, step SA43 corresponds to the control intervention determination unit 53, step SA44 corresponds to the control calculation unit 54, Step SA45 corresponds to the operation control unit 56 corresponding to the understeer degree determination unit 55a, the vehicle speed limit determination unit 55b, and the posture change determination unit 55c.
[0028]
  The details of the SCS control from step SA43 to step SA45 will be described in detail below with reference to FIGS. In order to simplify the description, it is assumed that ABS and TCS are not controlled.
[0029]
  As shown in FIG. 6, the SCS control intervention determination in step SA43 compares the vehicle body side slip angle deviation amount x with a determination side slip angle deviation amount x1 preset for the SCS control intervention determination in step SB1. If the vehicle body side slip angle deviation amount x is equal to or greater than the judgment side slip angle deviation amount x1, it is determined that the vehicle is oversteered and the vehicle is about to spin, and the process proceeds to step SB2 to be described later. Perform suppression control. On the other hand, if the vehicle body side slip angle deviation amount x is smaller than the judgment side slip angle deviation amount x1, the process proceeds to step SB3. In step SB3, the yaw rate deviation amount y is set in advance for the SCS control intervention judgment. Compared with the determined yaw rate deviation y1 as a quantity. When the yaw rate deviation amount y is equal to or larger than the judgment yaw rate deviation amount y1, it is determined that the understeer tendency of the vehicle is likely to drift out, and the process proceeds to step SB4 to be described later. Perform suppression control.
[0030]
  In this drift-out suppression control, as shown in FIG. 7, when it is determined that the vehicle is about to drift out (see FIG. 8A), first, the driver does not step on the brake pedal in step SC1. After the cut valves 32a and 32b are closed under the above condition, in step SC2, the yaw rate deviation amount y is compared with a limit deviation amount ylim set in advance for determining whether or not attitude control is possible. When the yaw rate deviation amount y is equal to or larger than the limit deviation amount ylim, that is, when it is determined that the understeer tendency is too strong and the posture control is difficult, the process proceeds to step SC13, which will be described later. If it is smaller than the limit deviation amount ylim, the process proceeds to step SC3. In step SC3, the brake pressure P detected by the hydraulic pressure sensor 33 is compared with the atmospheric pressure P0. If the brake pressure P is not equal to the atmospheric pressure P0, that is, the driver is stepping on the brake, If there is a deceleration request based on the judgment, the process proceeds to step SC14 described later. On the other hand, if the brake pressure P is equal to the atmospheric pressure P0, that is, if the driver does not step on the brake, the process proceeds to step SC4. In step SC4, the vehicle body speed Vref is compared with a limit vehicle body speed Vlim set in advance to determine whether or not the vehicle speed is capable of attitude control, and the vehicle body speed Vref is equal to the vehicle body speed Vlim or If the vehicle speed is too high, that is, if it is determined that the attitude control is difficult and the deceleration is necessary because the vehicle speed is too high, the process proceeds to step SC12 described later, whereas if the vehicle body speed Vref is smaller than the limit vehicle body speed Vlim, the process proceeds. Proceed to SC5.
[0031]
  Subsequently, in step SC5, it is determined whether or not there is a margin in the grip force based on the load factor of the front wheel 21FL inside the turn. That is, if the load factor is not 1, it is determined that the grip force of the front wheel 21FL on the inside of the turn has a margin, and the process proceeds to step SC6, where the braking force corresponding to the yaw rate deviation amount y is applied to the front wheel 21FL on the inside of the turn. (See FIG. 8B). On the other hand, if the load factor is 1, it is determined that there is no margin in the grip force, and the process proceeds to step SC7, where braking force corresponding to the yaw rate deviation amount y is applied to the front wheel 21FL and the rear wheel 21RL inside the turn. Then, the process proceeds to step SC8 in order to determine whether or not there is a change in the direction of the vehicle body by using the change amount Δy of the yaw rate deviation amount y due to the braking force applied to the front wheel 21FL or the front and rear wheels 21FL, 21RL inside the turning. Compared with the preset small change amount Δy0, if the change amount Δy is smaller than the small change amount Δy0, that is, for example, the road surface is very slippery, so that the yaw rate hardly acts on the vehicle body and the direction of the vehicle changes. If not, the process proceeds to step SC12 described later. On the other hand, if the change amount Δy of the yaw rate deviation amount y is larger than the minute change amount Δy0, that is, a certain amount of yaw moment acts on the vehicle body, If has changed, the process proceeds to step SC9.
[0032]
  In step SC9, the first determination change amount Δx1 as the determination change amount for determining that the direction of the vehicle has sufficiently changed to the inside of the turn is set in accordance with the vehicle body speed Vref and the steering angle θH by the driver. After the change correction, the process proceeds to step SC10. The change correction of the first determination change amount Δx1 in step SC9 is performed by reading from a predetermined map based on the relationship between the vehicle body speed Vref and the steering angle θH. In this map, the first determination change amount Δx1 is changed. Is corrected to decrease as the vehicle body speed Vref increases, and is corrected to increase as the steering angle θH increases. In step SC10, the change-corrected first determination change amount Δx1 is compared with the change amount Δx of the vehicle body side slip angle deviation amount x, and the change amount Δx of the vehicle body side slip angle deviation amount x is greater than the determination change amount Δx1. If it is smaller, that is, if it is determined that the direction of the vehicle body has not changed sufficiently, the process returns to step SC5, while the change amount Δx of the vehicle body side slip angle deviation amount x is equal to the first determination change amount Δx1 or If it is larger, that is, if it is determined that the direction of the vehicle body has changed sufficiently, the process proceeds to step SC11.
[0033]
  In step SC11, it is determined whether or not the yaw rate deviation y is zero. If it is zero, it is determined that the attitude of the vehicle has converged to the target state, and the drift-out suppression control is terminated. On the other hand, if it is determined in step SC11 that the yaw rate deviation amount y is not zero, the process proceeds to step SC12, and the braking force corresponding to the yaw rate deviation amount y is applied to the left and right front wheels 21FR, 21FL and the turning inner rear wheel 21RL. (See FIG. 8C), the vehicle is decelerated while applying a yaw moment that suppresses the understeer tendency to the vehicle body 1, and the process returns to step SC1. That is, when it is determined in step SC2 that the attitude control is not difficult, first, in step SC6 or SC7, the direction of the vehicle is sufficiently changed to the turning inward side and then decelerated in step SC12. This vehicle drift-out (see FIG. 8D) is surely prevented. In step SC12, the braking force applied to the front wheel 21FR outside the turn is substantially equal to the braking force applied to the rear wheel 21RL inside the turn, and is therefore applied to the turning inward position of the vehicle body 1. The total braking force applied is larger than the total braking force applied to the turning outward position of the vehicle body 1, and therefore the vehicle body 1 has a yaw moment that changes the direction of the vehicle to the turning inward side. Has come to work.
[0034]
  If it is determined in step SC2 that posture control is difficult and the process proceeds to step SC13, the brake pressure P detected by the pressure sensor 33 is compared with the pump pressures Pp of the hydraulic pumps 31a and 31b in step SC13. If the brake pressure P is equal to or greater than the pump pressure Pp, that is, it is determined that the driver is depressing the brake pedal 14 and the process proceeds to step SC14. Apart from this, if the driver's brake depression operation is detected in step SC3, the process proceeds to step SC14. In this step SC14, the brake system cut valve 32a connected to the front wheel 21FR outside the turn is opened. Let it be in a state. As a result, the pressure fluid flows from the master cylinder 10 to the first pipe 22a in response to the stepping operation of the brake pedal 14 by the driver, and the driver steps on the turning outer front wheel 21FR and the turning inner rear wheel 21RL. A braking force corresponding to the operation is applied. Therefore, the driver himself can avoid the situation where the brake pedal 14 cannot be stepped on when the brake pedal 14 can be stepped on in response to the driver's stepping operation and the cut valves 32a and 32b are kept closed. Brake operation feeling can be secured. Then, the process proceeds to step SC15, the braking force corresponding to the yaw rate deviation amount y and the brake pressure P is applied to the front wheel 21FL on the inside of the turn, and the process returns to step SC1. In other words, if it is determined in step SC2 that it is difficult to control the posture and it is determined that the driver himself is fully braking (SC13), the vehicle turns to prevent drift-out due to deceleration. The outer front wheel 21FR and the turning inner rear wheel 21RL are left to the driver's own brake operation (SC14), and a predetermined braking force is applied to the turning inner front wheel 21FL (SC15).
[0035]
  Further, if the brake pressure P is smaller than the pump pressure Pp in step SC13, that is, if the driver has depressed the brake pedal 14 only slightly, the process proceeds to step SC12, where the braking force is applied to the front wheel 21FL inside the turn. The vehicle is decelerated by applying a braking force to the front wheel 21FR and the rear rear wheel 21RL inside the turn while applying a yaw moment that suppresses the understeer tendency to the vehicle body 1. That is, if it is determined in step SC2 that the vehicle attitude control is difficult and deceleration is necessary, but it is determined that the driver's brake depression operation is insufficient (SC13), the hydraulic pumps 31a, The brakes 2 and 2 of the left and right front wheels 21FR and 21FL are forcibly braked by the discharge pressure from 31b to decelerate the vehicle (SC12).
[0036]
  In the flowchart, step SC2 corresponds to the understeer degree determination unit 55a, step SC4 corresponds to the vehicle speed limit determination unit 55b, step SC6 and step SC7 correspond to the attitude control unit 54a, and step SC8 corresponds to the attitude change. The determination unit 55c corresponds to the determination unit 55c, and the step SC9 corresponds to the correction calculation unit 54c, and the step SC12 and step SC15 correspond to the deceleration control unit 54b.
[0037]
  Next, the spin suppression control is shown in FIG. When it is determined that the vehicle is about to spin (see FIG. 10A), the cut valves 32a and 32b are closed in step SD1, and then the brake detected by the hydraulic pressure sensor 33 in step SD2. When the pressure P is compared with the atmospheric pressure P0 and the brake pressure P is not equal to the atmospheric pressure P0, that is, when the driver is stepping on the brake, the process proceeds to step SD7 described later, while the brake pressure P is increased. When it is equal to the atmospheric pressure P0, that is, when the driver does not step on the brake, the routine proceeds to step SD3.
[0038]
  In step SD3, it is determined based on the load factor of the front wheel 21FR outside the turn whether or not the grip force of the wheel 21FR has a margin, and if the load factor is not 1, it is determined that the grip force has a margin. Proceeding to SD4, a braking force corresponding to the vehicle body side slip angle deviation amount x is applied to the front wheel 21FR outside the turn (see FIG. 10B). On the other hand, if the load factor is 1, it is determined that there is no margin in the grip force of the front wheel 21FR outside the turn, and the process proceeds to step SD5, where the braking force according to the vehicle body side slip angle deviation amount x is applied to the front and rear wheels outside the turn. It is given to 21FR and 21RR. That is, by applying a backward force to the vehicle body 1 turning outward position, a yaw moment that suppresses the oversteer tendency is applied to the vehicle body 1 to change the vehicle direction to the vehicle turning outward direction. Spin (see FIG. 10D) is prevented. In step SD6, it is determined whether or not the vehicle body side slip angle deviation amount x is zero. If it is zero, it is determined that the turning posture of the vehicle has converged in the target travel direction, and the spin suppression control is terminated. (See FIG. 10 (c)). On the other hand, if it is determined in step SD6 that the vehicle body slip angle deviation amount x is not zero, the process returns to step SD1.
[0039]
  On the other hand, if it is determined in step SD2 that the driver is stepping on the brake, the process proceeds to step SD7, where the vehicle body side slip angle deviation amount x is set to a boundary deviation amount x2 set in advance to determine the degree of oversteer tendency. In comparison, if the vehicle body side slip angle deviation amount x is smaller than the boundary deviation amount x2, that is, if it is determined that the degree of the oversteer tendency is low, the routine proceeds to step SD8 and is connected to the front wheel 21FL on the inside of the turn. The cut valve 32b of the brake system being opened is opened. As a result, pressure fluid flows from the master cylinder 10 to the second pipe 22b in response to the driver's stepping operation on the brake pedal 14, and the driver steps on the turning inner front wheel 21FL and the turning outer rear wheel 21RR. A braking force corresponding to the operation is applied. Therefore, the driver himself can avoid the situation where the brake pedal 14 cannot be stepped on when the brake pedal 14 can be stepped on in response to the driver's stepping operation and the cut valves 32a and 32b are kept closed. Brake operation feeling can be secured. Then, the process proceeds to step SD9, where the braking force corresponding to the vehicle body side slip angle deviation amount x and the brake pressure P is applied to the front wheel 21FR outside the turning, and the process returns to step SD1. That is, when a brake operation by the driver is detected (SD2) and it is determined that the degree of oversteer is low (SD7), one hydraulic pipe 22a or 22b is communicated with the master cylinder 10 ( SD8) enables the driver to operate the brake to ensure the operation feeling, and applies a braking force to the vehicle according to the driver's stepping operation.
[0040]
  If it is determined in step SD7 that the vehicle body side slip angle deviation amount x is equal to or larger than the boundary deviation amount x2, that is, if it is determined that the degree of oversteering is high, the process proceeds to step SD10, where the hydraulic pressure sensor 33 The detected brake pressure P is compared with the pump pressure Pp of the pumps 31a and 31b. If the brake pressure P is equal to or greater than the pump pressure Pp, the process proceeds to step SD8. That is, even when the degree of oversteering is high, if the driver's deceleration request is extremely high, the vehicle is decelerated according to the braking operation. On the other hand, if the brake pressure P is lower than the pump pressure Pp, the process proceeds to step SD11 to apply the braking force to the front wheel 21FR outside the turn to change the direction of the vehicle to the turn outward, and then to step SD12. Then, the change amount Δx of the vehicle body side slip angle deviation amount x is compared with a second determination change amount Δx2 set in advance in order to determine that the direction of the vehicle has sufficiently changed to the forward and outward side. When the change amount Δx of the vehicle body side slip angle deviation amount x is smaller than the second determination change amount Δx2, that is, when the vehicle direction has not changed sufficiently, the process returns to step SD2, while the vehicle body side slip angle deviation amount When the change amount Δx of x is larger than the second determination change amount Δx2, that is, when the direction of the vehicle has changed sufficiently, the process proceeds to step SD13 and the braking force corresponding to the vehicle body side slip angle deviation amount x and the brake pressure P is reached. Are added to the left and right front wheels 21FR and 21FL and the rear outer wheel 21RL, and the vehicle is decelerated while acting on the vehicle body 1 with a yaw moment that suppresses oversteer. That is, when the degree of oversteering is high (SD7) and the driver's request for deceleration is not so high (SD10), first, the vehicle is changed in direction (SD11), and the vehicle is decelerated after stabilizing its posture (SD11). SD12).
[0041]
  Next, operations and effects of the vehicle attitude control device according to the embodiment will be described.
[0042]
  According to the drift-out suppression control in the vehicle attitude control device, when it is determined that attitude control is not difficult (SC2), a braking force is applied to the front wheel 21FL or the front and rear wheels 21FL, 21RL inside the turn ( SC6, SC7) to sufficiently decelerate the vehicle by changing the direction of the vehicle to the inside of the turn and then applying sufficient braking force to the front wheel 21FR outside the turn and the rear wheel 21 inside the turn (SC12). Thus, the vehicle can be decelerated safely and reliably without impairing the stability of the posture of the vehicle, and the drift-out of the vehicle can be reliably prevented.
[0043]
  At this time, the amount of change Δx of the vehicle body side slip angle deviation x due to the application of braking force (SC6, SC7) to the front wheel 21FL or rear wheel 21RL inward of the turn is equal to a preset first determination change amount Δx1 or Since the braking force is applied (SC12) to the front wheel 21FR outside the turn and the rear wheel 21 inside the turn after the increase (SC10), the direction of the vehicle is made sufficiently inward of the turn. The vehicle can be decelerated after being changed. In addition, when the vehicle body speed Vref is high, the first determination change amount Δx1 is corrected to decrease (SC9), so that the vehicle can be decelerated earlier by changing the vehicle orientation to decelerating. When the driver's steering amount is large, the first determination change amount Δx1 is corrected to increase (SC9), thereby delaying the transition to deceleration of the vehicle and increasing the amount of change in the vehicle direction. Thus, appropriate control according to the speed of the vehicle and the driving operation of the driver can be performed.
[0044]
  Further, when it is determined by the understeer degree determination unit 55a that the understeer tendency is too strong and posture control is difficult (SC2), the vehicle speed limit determination unit 55b determines that the traveling speed of the vehicle is too high and first deceleration is necessary. (SC4), or when the road surface is very slippery and almost no yaw moment can be applied to the vehicle body 1, and the posture change determination unit 55c determines that the vehicle orientation does not change (SC8). In addition, the vehicle is immediately decelerated by applying braking force to the left and right front wheels 21FR and 21FL and the turning inner rear wheel 21RL (SC12), and in addition, when the driver performs a brake operation (SC3) In addition, since the vehicle is decelerated according to the stepping operation (SC14), safety can be improved.
[0045]
  On the other hand, according to the spin suppression control in the vehicle attitude control device, when it is determined that the driver does not step on the brake pair 14 (SD2), braking force is applied to the front wheel 21FR or the rear wheel 21 outside the turn. (SD4, SD5), a yaw moment that suppresses oversteer is applied to the vehicle body 1 to suppress vehicle spin. Even when it is determined that the driver is depressing the brake pedal 14 (SD2), if it is determined that the brake pressure P is not large and the driver's deceleration request is not so high (SD10), the vehicle Suppression of the spin is prioritized over the deceleration of the vehicle (SD11), thereby preventing the vehicle from spinning due to the application of the braking force. Further, when it is determined that the brake pressure is extremely high and the driver's deceleration request is extremely high (SD10), the vehicle is decelerated (SD8) in response to the driver's stepping operation, thereby the vehicle attitude. If the vehicle needs to be decelerated even if it collapses, the vehicle can be decelerated reliably.
<Other embodiments>
  In addition, this invention is not limited to the said embodiment, Various other embodiments are included. In other words, in the above embodiment, the drift-out suppression control is performed based on the yaw rate deviation amount y, while the spin suppression control is performed based on the vehicle body side slip angle deviation amount x. For example, both the drift-out suppression control and the spin suppression control may be performed based on both the yaw rate deviation amount y and the vehicle body side slip angle deviation amount x.
[0046]
  In the above embodiment, when the vehicle speed limit determination unit 55b determines that the vehicle traveling speed is too high and the vehicle needs to be decelerated first (SC4), the left and right front wheels 21FR, 21FL and the turning inner rear wheel 21RL Although the braking force is applied, the present invention is not limited to this, and the braking force may be applied to two wheels on the diagonal line of the front wheel 21FR outside the turning and the rear wheel 21RL inside the turning.
[0047]
  In the above embodiment, the hydraulic system of the vehicle brake is a so-called X piping type, but is not limited thereto, and may be a so-called H piping type, for example.
[0048]
【The invention's effect】
  As explained above,This applicationAccording to the vehicle attitude control device of the present invention, when the understeer tendency of the turning vehicle is strengthened,As the first stage, the direction of the vehicle is changed to the inside of the turn, and as the second stageBy simultaneously applying a braking force to the front wheel outside the turning and the rear wheel inside the turning of the vehicle, a sufficient braking force can be applied without impairing the stability of the posture of the vehicle. Can be safely and reliably decelerated to prevent drift-out.
[0049]
  Also,For example, the vehicle can be decelerated immediately when the road surface is very slippery and a sufficient yaw moment cannot be applied to the vehicle body, thereby improving safety.on the other hand,If the attitude control of the vehicle is possible, the direction can be sufficiently changed to the inside of the turn before the vehicle is decelerated.
[0050]
  In addition,When the vehicle speed is high, the vehicle can be decelerated early, and when the amount of steering by the driver is large, the amount of change in the direction of the vehicle before deceleration can be increased. Appropriate control can be performed.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing a vehicle to which a vehicle attitude control device according to an embodiment of the present invention is applied.
FIG. 2 is a diagram showing a hydraulic system of a brake.
FIG. 3 is a block diagram showing a configuration of an SCS controller.
FIG. 4 is a diagram showing the contents of processing in a state quantity computing unit and a target state quantity computing unit.
FIG. 5 is a flowchart showing an outline of control by an SCS controller.
FIG. 6 is a flowchart showing the contents of processing in a control intervention determination unit.
FIG. 7 is a flowchart showing drift-out suppression control.
FIG. 8 is a conceptual diagram showing prevention of vehicle drift-out.
FIG. 9 is a flowchart showing spin suppression control.
FIG. 10 is a conceptual diagram showing prevention of vehicle spin.
[Explanation of symbols]
2 Brake (braking means)
3 Pressurizing unit (braking means)
4 Hydraulic unit (braking means)
6 Wheel speed sensor (vehicle speed detection means)
7 Lateral G sensor (vehicle state detection means)
8 Yaw rate sensor (vehicle state detection means)
9 Rudder angle sensor (steering amount detection means)
21FR, 21FL, 21RR, 21RL wheels
51 State quantity calculation unit (vehicle state detection means)
52 Target state quantity calculation unit (vehicle state detection means)
53 Control intervention judgment part (understeer judgment means)
54 Control operation unit (attitude control means)
54a Posture control unit
54b Deceleration control unit
54c Correction calculation part (determination change amount correction part)
55a Understeer degree determination unit (understeer degree determination means)
55b Vehicle speed limit determination unit (vehicle speed limit determination means)
55c Posture change determination unit (posture change determination means)
56 Action Control Unit (Attitude Control Unit)
Vref Body speed (detected vehicle speed)
x Body side slip angle deviation (detected vehicle state)
Δx Change amount of side slip angle deviation (change amount of detected vehicle state)
Δx1 First judgment change amount (judgment change amount)
y Yaw rate deviation (detected vehicle state)
y1 judgment yaw rate deviation amount (set amount)
Δy Change amount of yaw rate deviation (change amount of detected vehicle state)
β Vehicle side slip angle (vehicle state quantity)
γ Yaw rate (vehicle state)
θH Steering angle (detected steering amount)

Claims (1)

Vehicle state detecting means for detecting a vehicle state quantity representing the turning posture of the vehicle with respect to the traveling direction is provided, and the vehicle state quantity detected by the vehicle state detecting means is greater than a predetermined amount from the target vehicle state quantity corresponding to the target traveling direction. A vehicle attitude control device that controls the vehicle so that the state of the turning attitude of the vehicle converges to that corresponding to the target vehicle state quantity when deviated,
Vehicle speed detection means for detecting the vehicle speed;
Steering amount detection means for detecting the steering amount by the driver;
Braking means configured to be able to individually impart braking force to the front, rear, left and right wheels;
Attitude control means for controlling the turning attitude of the vehicle by controlling the operation of the braking means;
An understeer determination unit that determines that the detected vehicle state amount output from the vehicle state detection unit deviates from the target vehicle state amount toward the understeer side by a set amount or more and the vehicle is in an understeer state;
Attitude change determining means for determining the presence or absence of a change in attitude of the vehicle toward the inward turn of the vehicle based on the amount of change in the detected vehicle state quantity output from the vehicle state detecting means;
With
The posture control means,
A posture control unit that changes the direction of the vehicle to the inside of the turn by operating the braking means so that a braking force is applied to the front wheel or the front and rear wheels inside the turn of the vehicle;
A deceleration control unit for decelerating the vehicle by operating the braking means so that braking force is simultaneously applied to the two wheels on the diagonal line of the front wheel outside the turning and the rear wheel inside the turning ; With
When the output of the determination result that the vehicle is in the understeer state is received from the understeer determination means, the posture control unit first controls the posture of the vehicle, and if the posture does not change toward the inside of the turn due to this, the posture described above When it is determined by the change determination means, the control immediately shifts to the deceleration control by the deceleration control unit. On the other hand, when it is determined that there is a posture change, a determination is made that the change amount of the detected vehicle state amount corresponding to the posture change is set in advance. It is configured to shift to the deceleration control after the change amount is exceeded.
Further, the determination change amount is corrected to decrease according to the increase in the detected vehicle speed value detected by the vehicle speed detection means, and the determination change amount according to the increase in the detected steering amount detected by the steering amount detection means. A vehicle attitude control device comprising: a determination change amount correction unit for correcting the increase of the vehicle .

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