JP4671128B2 - Suspension control device - Google Patents

Description

  The present invention relates to a suspension control device that can be used in a vehicle to improve its steering stability and ride comfort, and can contribute particularly to shortening of a braking distance.

  2. Description of the Related Art Conventionally, for example, an active suspension system has been used to achieve both good riding comfort and handling stability of an automobile. In this active suspension system, for example, an actuator such as a hydraulic cylinder capable of supplying and discharging hydraulic pressure is interposed between the vehicle body and the wheel side member, and a force is generated in this actuator to actively control the vehicle motion. By doing this, the attitude of the vehicle is kept flat, and both good ride comfort and steering stability are realized.

Further, regarding braking of a vehicle, it is considered that the braking distance is shortened by using an active suspension system. As an example of this, there is a suspension control device disclosed in Patent Document 1.
The suspension control device disclosed in Patent Document 1 determines the tendency of a tire (wheel) to lock from the slip ratio, and determines the vertical acceleration in the direction of increasing the wheel load (ground load) as at least one of sprung mass and unsprung mass. Generate either one.
Japanese Patent Laid-Open No. 10-315736

By the way, the suspension control device disclosed in Patent Document 1 described above determines whether or not it is necessary to generate vertical acceleration in the direction of increasing the wheel load (determination of wheel locking tendency) using only the slip ratio. For this reason, the determination accuracy of the wheel locking tendency, and hence the accuracy of the vertical acceleration to be generated, is lowered, and the control accuracy of the apparatus is inferior.
Further, since the wheel load is controlled only in the increasing direction in accordance with the slip ratio, the wheel load cannot be increased when the actuator is gradually extended and fully extended. As a result, there is a problem that the braking performance is not improved thereafter. Further, at this time, since the vehicle height is high, there is a problem that the center of gravity is high and the vehicle becomes unstable.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a suspension control device capable of ensuring a long braking performance improvement during sudden braking by increasing a wheel load while maintaining an actuator stroke. And

  According to the first aspect of the present invention, there is provided a motion state detection means for detecting a motion state of a vehicle, an actuator that is interposed between the vehicle body and the wheel side member, and changes a relative distance between the two, and the motion state detection means. A suspension control device comprising: a control unit that controls the actuator based on a control signal obtained from a detection result; a braking state detection unit that detects a braking state of the vehicle; and a wheel that detects a rotation speed of the wheel. Speed detection means, vehicle speed detection means for detecting the traveling speed of the vehicle, slip speed calculation means for obtaining a slip ratio based on a wheel speed detection value obtained by the wheel speed detection means and a vehicle speed detection value obtained by the vehicle speed detection means And the control means calculates the slip ratio when the braking state of the vehicle detected by the braking state detection means indicates a sudden braking state. When the slip ratio obtained by the means is larger than a preset target slip ratio, the control signal is corrected so as to increase the relative distance in the vertical direction between the vehicle body and the wheel side member, and the slip ratio When the slip ratio obtained by the calculating means is smaller than a preset target slip ratio, the control signal is corrected so as to decrease the vertical relative distance between the vehicle body and the wheel side member, and is obtained by this correction. The new control signal is used for controlling the actuator.

According to a second aspect of the present invention, in the suspension control device according to the first aspect, the control signal is corrected based on a slip ratio change rate obtained by the slip ratio calculating means.
According to a third aspect of the present invention, in the suspension control device according to the first or second aspect, an anti-lock brake device is provided that performs an anti-lock operation of the wheel according to the slip ratio during sudden braking. To do.

According to a fourth aspect of the present invention, in the suspension control device according to the third aspect, the target slip ratio is set smaller than a slip ratio at which the antilock brake device operates.
According to a fifth aspect of the present invention, in the suspension control device according to any one of the first to fourth aspects, the brake state detection means detects the braking state of the vehicle using an operation amount of a brake pedal provided in the vehicle. It is characterized by being performed.

  According to the first to fifth aspects of the present invention, when the braking state of the vehicle detected by the braking state detecting unit indicates the sudden braking state, the control unit presets the slip ratio obtained by the slip ratio calculating unit. The control signal is corrected so as to increase the vertical relative distance between the vehicle body and the wheel side member, and the slip ratio calculated by the slip ratio calculating means is preset. When the slip ratio is smaller than the target slip ratio, the control signal is corrected so as to decrease the relative distance in the vertical direction between the vehicle body and the wheel side member, and the new control signal obtained by this correction is used for controlling the actuator. In the sudden braking state, the actuator is extended and operated to increase the wheel load and increase the frictional force against the road surface of the wheel to improve the braking performance and shorten the braking distance. Can. In addition, by controlling not only the direction in which the wheel load is increased but also the direction in which the wheel load is reduced (contraction direction), the actuator can be prevented from being fully extended, and the stroke can be maintained accordingly. As a result, braking performance can be improved over a long period of time.

The control signal for actuator control is corrected based not only on the slip ratio but also on the comparison result of the slip ratio calculated by the slip ratio calculation means with the target slip ratio, so that the accuracy of the control signal and hence the braking performance of the device can be improved. High accuracy can be achieved.
When not in the sudden braking state, the actuator is controlled in a state where the control signal is not corrected, and good riding comfort and steering stability can be ensured.

Hereinafter, a suspension control apparatus according to a first embodiment of the present invention will be described with reference to FIGS.
In FIG. 1, four wheels 3 of a vehicle 2 such as an automobile on which the suspension control device 1 is mounted are supported on a vehicle body 6 by suspension arms 4 and 5 (wheel side members) so as to be movable up and down. The wheels 3 are provided with rubber tires (not shown). Hereinafter, the wheel 3 including the rubber tire is referred to.
Since the wheels 3 are provided with rubber tires, as shown in FIG. 6, when the frictional force with the road surface of the traveling road is slightly slipped (slip ratio ≠ 0), the slip is not slipped (slip The ratio becomes larger than that in the case of (ratio = 0). That is, as shown in FIG. 6, in the slip ratio / friction force characteristic indicated by the solid line 8, the value Fmax at which the friction force is the maximum with a value (for example, value s in FIG. 6) where the slip ratio A / B is not “0”. Will show.

Between the suspension arms 4 and 5 and the vehicle body 6, there are provided a damper 10, a spring 11, and a hydraulic cylinder 13 (actuator) that expands and contracts by oil supply / discharge control of a suspension controller 12 described later. FIG. 1 shows only one of the four wheels 3 provided on the vehicle 2. The suspension arms 4 and 5, the damper 10, the spring 11, and the hydraulic cylinder 13 are also displayed in the same manner.
The hydraulic cylinder 13 is controlled by a control signal (control command value) from the suspension controller 12 to change the vertical relative distance between the vehicle body 6 and the wheels 3.

The vehicle 2 includes a sprung vibration detection means 15 (motion state detection means) that detects vertical vibrations of the vehicle body 6, a vehicle height detection means 16 (motion state detection means) that detects the vehicle height, and a braking state of the vehicle 2. Braking state detecting means 17 for detecting the vehicle speed, wheel speed detecting means 18 for detecting the rotational speed of the wheel 3, and vehicle speed detecting means 19 for detecting the traveling speed of the vehicle 2 are provided. For example, an optical vehicle speed sensor that optically observes a road surface that moves relative to the vehicle 2 to obtain the vehicle speed is used as the vehicle speed detection means 19.
Moreover, in this embodiment, it has ABS21 and can also estimate a vehicle speed from a wheel speed. The estimation of the vehicle speed from the wheel speed will be described later.
For example, a brake pedal sensor that detects an operation amount of a brake pedal (not shown) is used as the braking state detection unit 17. Further, as the braking state detecting means 17, a hydraulic pressure sensor that detects the brake hydraulic pressure of a brake braking device (not shown) that generates a braking force on the wheel 3 by the brake hydraulic pressure may be used.

The vehicle 2 is further provided with an ABS 21 (anti-lock brake device) and an ABS control device 22 for controlling the ABS 21 to prevent the wheels 3 from locking during sudden braking (full braking). The posture of the vehicle 2 is stabilized so that the effectiveness of the steering wheel can be secured.
In this case, the slip ratio A / B obtained using the wheel speed C obtained by the wheel speed detection means 18 and the vehicle speed B obtained by the vehicle speed detection means 19 is a predetermined numerical value (hereinafter referred to as an antilock operation slip ratio G). If it exceeds, it operates to prevent the wheel 3 from being locked. That is, when sudden braking (full braking) is applied, the slip ratio A / B of the wheel with respect to the road surface increases, and when the slip ratio A / B exceeds the antilock operation slip ratio G, the ABS 21 is operated by the operation of the ABS controller 22. Actuate and release the brake. As a result, the slip ratio A / B decreases, and the difference in speed between the wheel 3 and the road surface becomes small. When the speed difference between the wheel 3 and the road surface becomes small, the ABS 21 brakes again. By repeating the above operation, the vehicle 2 can be stopped without creating a state in which the wheels 3 are locked.

Along with the above repeated operation, the wheel speed C decreases in a step-like manner to the speed 0 with time. If time is taken on the horizontal axis and the wheel speed C is taken on the vertical axis, the wheel speed C is expressed by a stepped waveform. Here, since the vehicle speed B should be substantially equal to the wheel speed C in a state where the speed difference between the wheel 3 and the road surface is small, the vehicle speed B is expressed by a line segment connecting the apexes of the waveform indicating the wheel speed C. Thus, the vehicle speed B can be estimated from the wheel speed C as described above.
If the wheel speed C for all four wheels is used as the data of the wheel speed C, the timing at which the ABS 21 releases the brake is different for each wheel 3. Therefore, if the waveforms corresponding to each wheel 3 are superimposed on the same graph, the top of the waveform Therefore, the accuracy of the estimation of the vehicle speed B is increased accordingly.

  In the present embodiment, as shown in FIGS. 3 and 4, a slip ratio calculation unit 24 included in a braking control controller 23 described later uses a wheel speed obtained by the wheel speed detection unit 18 from a vehicle speed B obtained by the vehicle speed detection unit 19. The difference A (A = B−C) is obtained by subtracting C, and the slip ratio A / B is obtained by dividing the difference A by the vehicle speed B.

  A suspension controller 12 is connected to each detection means and the hydraulic cylinder 13. The suspension controller 12 has a function of controlling the hydraulic cylinder 13 based on the detection signals of the detection means. The suspension controller 12 will be described as including a normal control suspension controller (hereinafter referred to as a normal control controller 25) for controlling the hydraulic cylinder 13 and a brake control suspension controller (the brake control controller 23).

The normal controller 25 generates a control signal (hereinafter referred to as a normal control signal 26) for the hydraulic cylinder 13 based on the detection results of the sprung vibration detection means 15 and the vehicle height detection means 16. When the brake controller 23 does not generate a brake control signal 27 (described later), the suspension controller 12 inputs the normal control signal 26 to the hydraulic cylinder 13 to cause the hydraulic cylinder 13 to expand and contract, thereby providing good riding comfort and good maneuvering. Stability is ensured.
In addition, when the brake controller 23 generates the brake control signal 27, the suspension controller 12 adds the brake control signal 27 to the normal control signal 26 to correct the normal control signal 26 to generate a new control signal (hereinafter, for convenience). The correction normal control signal 28 is obtained), and the correction normal control signal 28 is input to the hydraulic cylinder 13 to extend and contract the hydraulic cylinder 13 to achieve good riding comfort and good steering stability. The braking distance during braking is shortened.

As shown in FIGS. 3 and 4, the braking controller 23 detects the slip ratio A / S determined by the slip ratio calculating unit 24 when the braking state of the vehicle 2 detected by the braking state detecting unit 17 indicates the sudden braking state. A slip ratio deviation D (D = M−A / B) between B and a preset target slip ratio M is obtained, and the slip ratio deviation D is amplified by a gain Kp to generate a braking control signal 27 (braking control command). To do. As described above, the braking control signal 27 is obtained by correcting the normal control signal 26 (addition correction in the present embodiment), and further correcting the normal control signal 28 [(normal control signal 26) + (brake control signal 27)]. Used for calculation.
In the present embodiment, as shown in FIG. 6, the target slip ratio M is a friction force in a slip ratio / friction force characteristic (indicated by a solid line 8) obtained in advance for the traveling path of the wheel 3 and the vehicle 2. The slip ratio s corresponds to the point having the maximum Fmax. The slip ratio / friction force characteristics and the slip ratio s obtained as described above are stored in a memory (not shown).
The target slip ratio M is not limited to the slip ratio s, and may be a slip ratio in the vicinity of the slip ratio s.

The suspension controller 12 executes a control algorithm having the contents shown in FIG. The processing contents of the control algorithm of the suspension controller 12 will be described with reference to FIG.
First, the braking state of the vehicle 2 is obtained by the braking state detection means 17 (step S1).
Next, it is determined whether or not the braking state of the vehicle 2 is sudden braking (step S2).
The determination regarding the sudden braking by the braking state detection means 17 may be performed using the rate of change of the brake fluid pressure, or may be performed using the brake pedal operation amount. In addition, when performing using a brake pedal operation amount, compared with another example, it becomes possible to control at an early stage.

When it is determined in step S2 that the braking is sudden, the normal control controller 25 and the braking control controller 23 obtain the normal control signal 26 and the braking control signal 27, respectively.
At this time, the braking controller 23 obtains the slip ratio A / B from the wheel speed C and the vehicle speed B as shown in FIG. Further, as described above, the slip ratio deviation D between the slip ratio A / B and the preset target slip ratio M is obtained, and this slip ratio deviation D is multiplied by the gain Kp to obtain the braking control signal 27 (command value). .

Subsequently, the braking control signal 27 (command value) and the normal control signal 26 (command value) are added to obtain the corrected normal control signal 28 (control command value) (step S3).
The corrected normal control signal 28 obtained in step S3 is output to the hydraulic cylinder 13 to generate thrust (step S5). In this step S5, the wheel load is increased or decreased when thrust is generated by the control of the hydraulic cylinder 13 based on the corrected normal control signal 28 obtained in step S3.

By controlling as described above, if the slip ratio A / B is less than the target slip ratio M (value s) (left side in FIG. 6), the hydraulic cylinder 13 is controlled in the contraction direction to suppress the suspension from being fully extended. Further, if the slip ratio A / B is equal to or greater than the target slip ratio M (value s) (right side in FIG. 6), the wheel load is increased by controlling the hydraulic cylinder 13 in the extending direction, whereby the slip ratio A / B is increased. B is controlled to be the target slip ratio M (slip ratio A / B corresponding to the value Fmax at which the frictional force of the wheel 3 is maximized). For this reason, a frictional force becomes large and a braking distance can be shortened.
If NO is determined in step S2 (the braking state of the vehicle 2 is sudden braking), a normal control signal 26 is obtained (step S4), and the normal control signal 26 obtained in step S4 is converted to the hydraulic cylinder 13 in step S5. To generate thrust.

As described above, when control using only the normal control signal 26 (referred to as normal control for convenience) is performed, control using the corrected normal control signal 28 (normal control signal 26 + brake control signal 27) (for convenience, braking). For each of the cases where control is performed), the distance (braking stop distance L) from the position at the start of braking (braking start position) to the stop position of the vehicle 2 is measured. As shown in FIG. The stop distance L was 30 to 40 m. The braking stop distance L when the braking control is performed is 15 to 20 cm shorter than the braking stop distance L when the normal control is performed.
As a result of the above measurement, the braking control (using the corrected normal control signal 28 (normal control signal 26 + braking control signal 27)) is performed as compared to the normal control (using only the normal control signal 26). Thus, it was verified that the braking performance could be improved.

In the first embodiment, as shown in FIGS. 3 and 4, the braking control signal 27 and thus the corrected normal control signal 28 (normal control signal 26 + braking control signal 27) are calculated using the slip ratio A / B. . On the other hand, as shown in FIGS. 7 and 8, the braking control signal 27 and the corrected normal control signal are used by using the rate of change of the slip ratio deviation D (slip ratio deviation rate of change E) in addition to the slip ratio A / B. 28 (normal control signal 26 + brake control signal 27) may be calculated (second embodiment).
In the second embodiment, the slip ratio deviation D is differentiated in parallel with the process of “multiplying the slip ratio deviation D by the gain Kp to obtain the braking control signal 27” performed in the first embodiment (FIG. 3). 40, the slip ratio deviation D change rate (slip ratio deviation change rate E) is obtained, and the amplifier circuit 41 multiplies the slip ratio deviation change rate E by the gain Kd to amplify the slip ratio deviation change rate signal 42. Processing to calculate is performed. Then, the adding unit 43 adds the slip ratio deviation change rate signal 42 to the braking control signal 27 to obtain a new braking control signal. This new braking control signal includes a slip ratio deviation change rate signal 42, and hereinafter referred to as a corrected braking control signal 44 in order to distinguish it from the braking control signal 27. The corrected braking control signal 44 is a signal for controlling the hydraulic cylinder 13 during sudden braking, as in the braking control signal 27 in the first embodiment [corresponding to the corrected normal control signal 28 in the first embodiment. ] And used. As is apparent from the calculation, the slip ratio deviation change rate signal 42 reflects the change state of the slip ratio deviation D, and hence the braking state change.
According to the second embodiment, since the slip ratio deviation change rate E is included in the signal used to control the hydraulic cylinder 13, when the slip ratio A / B has a tendency to lock rapidly, the braking control signal As a result, the corrected normal control signal 28 (normal control signal 26 + brake control signal 27) can be suddenly increased. For this reason, the lock tendency of the wheel 3 can be effectively suppressed.

  For the second embodiment, when the normal control is performed and the braking control is performed in the same manner as in the first embodiment (FIG. 5), the braking stop distance L is measured. The result shown in 9 was obtained. In this case, the braking stop distance L was 30 to 40 m. The braking stop distance L when the braking control is performed is 40 to 50 cm shorter than the braking stop distance L when the normal control is performed. When the slip ratio deviation change rate E is used for the calculation of the braking control signal 27 and the corrected normal control signal 28 (normal control signal 26 + brake control signal 27), the slip ratio deviation change rate E is not used. It was verified that braking performance could be improved compared to

  In the above embodiment, the case where the actuator is the hydraulic cylinder 13 (hydraulic type) is taken as an example. However, the present invention is not limited to this, and an electromagnetic actuator or a pneumatic actuator may be used.

  In the above-described embodiment, the normal control signal 26 is corrected by adding the braking control signal 27 to the normal control signal 26, whereby a new control signal (a new control signal in the above-described embodiment is described for convenience. Correction normal control signal 28.). On the other hand, the normal control signal 26 is corrected so as to replace the normal control signal 26 with the braking control signal 27 to obtain a new control signal (substantially, the braking control signal 27 is used for controlling the actuator). May be used).

  In the above embodiment, as shown in FIGS. 10 and 11, the road surface state detecting means 30 for detecting the road surface state such as a good road and a bad road is provided, and the detection result of the road surface state detecting means 30 is obtained. It is possible to change the value of the target slip ratio M to a value at which the frictional force is always maximized (third embodiment). In the third embodiment, the optimum target slip ratio M can be selected according to the road surface condition. In this case, as shown in FIG. 11, a map indicating a slip ratio / friction force characteristic in advance (referred to as a road surface condition corresponding slip ratio / friction force characteristic map 31) as shown in FIG. )). In the present embodiment, slip ratio / friction force characteristics for both good and bad roads are included. In the slip ratio / friction force characteristic for the good road, the value (slip ratio) at which the friction force becomes the maximum (Fmax1) is s1, and in the slip ratio / friction force characteristic for the bad road, the friction force The value (slip ratio) at which becomes the maximum (Fmax2) is s2.

In the third embodiment, as shown in FIG. 10, first, the road surface state of the traveling road is detected and road surface state information indicating the detection result is obtained (step S31). Next, referring to the road surface state corresponding slip ratio / friction force characteristic map 31 of FIG. 11 from the road surface state information, a value at which the frictional force becomes maximum is set as the target slip ratio M (step S32). When the road surface state information indicates a good road, the value of the target slip ratio M is s1. Further, when the road surface state information indicates a bad road, the value of the target slip ratio M is set to s2.
According to the third embodiment, at the time of sudden braking, the braking distance is not controlled by controlling the wheel load to set the slip ratio A / B of the wheel 3 to a value at which the frictional force of the wheel 3 is maximized. Can be shortened. For this reason, it can contribute to a dramatic improvement in safety.
In each of the above-described embodiments, when the oil liquid is discharged from the hydraulic cylinder and contracted, the vehicle becomes unstable if it is contracted rapidly, so the direction of contraction is more limited by limiting the control amount. Stable braking can be obtained. This can be achieved by suppressing the upper limit value of the control amount.

It is a figure showing typically the suspension control device concerning a 1st embodiment of the present invention. It is a flowchart which shows the control content of the suspension controller of FIG. It is a block diagram which shows the braking control controller of FIG. FIG. 4 is a waveform diagram showing a slip ratio and a corrected normal control signal (control command value) 28 obtained by the braking control controller of FIG. 3. It is a figure which shows the difference in the braking distance in the case where it does not use with the case where the braking control signal of FIG. 1 is used. It is a figure which shows a slip ratio and a frictional force characteristic. It is a block diagram showing typically a braking control controller used for a suspension control device concerning a 2nd embodiment of the present invention. FIG. 8 is a waveform diagram showing a slip ratio and a corrected normal control signal (control command value) 44 obtained by the braking control controller of FIG. 7. It is a figure which shows the difference in the braking distance in the case where it does not use with the case where the braking control signal of FIG. 1 is used. It is a flowchart which shows the action | operation content of the suspension controller of the suspension control apparatus which concerns on 3rd Embodiment of this invention. FIG. 11 is a map showing slip ratio / friction force characteristics obtained in advance by a suspension controller executing the flowchart of FIG. 10. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Suspension control apparatus, 15 ... Spring-spring vibration detection means (motion state detection means), 16 ... Vehicle height detection means (motion state detection means), 17 ... Braking state detection means, 18 ... Wheel speed detection means, 19 ... Vehicle speed Detection means, 23 ... braking control controller, 24 ... slip ratio calculation means.

Claims (5)

The movement state detection means for detecting the movement state of the vehicle, the actuator that is interposed between the vehicle body and the wheel side member, and changes the relative distance in the vertical direction between them, and the control signal obtained from the detection result of the movement state detection means A suspension control device comprising: control means for controlling the actuator based on:
Braking state detecting means for detecting the braking state of the vehicle;
Wheel speed detecting means for detecting the rotational speed of the wheel;
Vehicle speed detection means for detecting the traveling speed of the vehicle;
Slip ratio calculation means for obtaining a slip ratio based on a wheel speed detection value obtained by the wheel speed detection means and a vehicle speed detection value obtained by the vehicle speed detection means;
With
The control means, when the braking state of the vehicle detected by the braking state detection means indicates a sudden braking state, when the slip ratio obtained by the slip ratio calculation means is greater than a preset target slip ratio, When the control signal is corrected so as to increase the vertical relative distance between the vehicle body and the wheel side member, and when the slip ratio calculated by the slip ratio calculation means is smaller than a preset target slip ratio Suspension control, wherein the control signal is corrected so as to reduce a vertical relative distance between the vehicle body and the wheel side member, and a new control signal obtained by the correction is used for controlling the actuator. apparatus.   2. The suspension control device according to claim 1, wherein the control signal is corrected based on a slip ratio change rate obtained by the slip ratio calculation means.   3. The suspension control device according to claim 1, further comprising an anti-lock brake device that performs an anti-lock operation of the wheel according to the slip ratio during sudden braking.   4. The suspension control device according to claim 3, wherein the target slip ratio is set smaller than a slip ratio at which the antilock brake device operates. 5. The suspension control device according to claim 1, wherein the braking state of the vehicle is detected by an operation amount of a brake pedal provided in the vehicle. Suspension control device.