JP3158734B2 - Contact load estimation device, longitudinal acceleration calculation device and lateral acceleration calculation device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ground contact load estimating device for estimating a ground contact load of each wheel of a vehicle, a longitudinal acceleration calculating device for calculating a longitudinal acceleration acting on a vehicle using the estimated ground contact load, and a lateral acceleration. The present invention relates to a lateral acceleration calculation device that calculates

[0002]

2. Description of the Related Art In order to estimate the ground contact load of a vehicle, in the prior art, a strain gauge is attached to an axle portion under a spring of a suspension, and the ground contact load is estimated from the degree of distortion. There was a way. However, this method requires a strain gauge and a strain amplifier, and is very expensive. In addition, the measuring device must be mounted under severe conditions such as the axle portion of the suspension, and there has been a major problem in terms of reliability.

[0003] As another method, in the case of a hydropneumatic vehicle, it was possible to estimate the ground contact load by measuring the oil pressure, but this method is also applicable only to a hydropneumatic vehicle. Met. Accordingly, the present invention provides a device that detects a ground contact load from a small number of detection signals that are already mounted or can be easily mounted, and a device that estimates or calculates longitudinal and lateral acceleration accompanying the ground load. Aim.

[0004]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a contact-load estimating apparatus comprising at least one of a relative displacement, a relative speed, and a relative acceleration between a vehicle sprung and a vehicle unsprung. And ground contact load calculating means for calculating the ground load of each wheel of the vehicle based on the relative displacement, relative speed, or relative acceleration detected by the detecting means.

[0005] The contact load calculating means uses at least one of the relative displacement, the relative speed, and the relative acceleration, and calculates the following contact load estimation formula:

[0006]

(Equation 2)

(Where M1 is the unsprung load, M2 is the sprung load, K2 is the spring constant of the suspension spring, C
Is the damping coefficient of the absorber, Y is the relative displacement between sprung and unsprung, dY is the same relative speed, and d ² Y is the same relative acceleration. ) May be calculated. Here, the principle of estimating the contact load by the above-described contact load estimation formula will be described.

FIG. 1 shows a one-wheel two-degree-of-freedom model corresponding to one wheel of a vehicle. Here, M1 is the unsprung load, M2 is the sprung load, K2 is the spring constant of the suspension spring, C is the damping coefficient of the absorber, K1 is the spring constant of the tire, X0 is the road surface displacement, X1 is the unsprung displacement, and X2 is the unsprung displacement. The sprung displacement, Y, is the relative displacement between sprung and unsprung.

Considering the equations of motion of the sprung mass and the unsprung mass, they are expressed by the following equations (1) and (2).

[0010]

(Equation 3)

Further, since the contact load F is expressed by the following equation (3), if the above equations (1) and (2) are substituted and deformed, the following equation (4) is obtained. Can be.

[0012]

(Equation 4)

Although there are variable parameters of M1, M2, K2, and C in this estimation formula, M1, M2, and K2 are almost constant, and the remaining C also includes the speed dY and the estimated damping force shown in FIG. Based on a graph showing the relationship with (C · dY), d
If Y is determined, it can be estimated as (C · dY). Therefore, if Y or dY or d ² Y is determined by a height sensor or a piezoelectric sensor, the grounding load F
Can be estimated.

The present invention further comprises the above-mentioned contact load estimating device, and uses the contact load estimated by the contact load estimating device,
A longitudinal acceleration calculator that calculates longitudinal acceleration acting on the vehicle based on a difference in the grounding load between the front and rear wheels of the vehicle, and a grounding load estimated by the grounding load estimating device. Lateral acceleration calculating device for calculating the lateral acceleration acting on the vehicle. With these devices, it is possible to calculate the longitudinal acceleration or the lateral acceleration without requiring the longitudinal G sensor or the lateral G sensor as in the related art.

[0015]

Embodiments of the present invention will be described below. First, a first embodiment of the contact load estimation device will be described based on the contact load estimation principle (explained with reference to FIGS. 1 and 2). The first embodiment is a case where a height sensor is used.

As shown in FIG. 3, height sensors 1a to 1a
d is the front and rear four wheels 101a to 101d and the body 1
02, which measures the distance between each of the wheels 101a to 101d and the body 102. FIG.
As shown in FIG. 1, a control device 10 is provided, and is constituted by a microcomputer having at least an interface circuit 11, an arithmetic processing device 13, and a storage device 15.
A height sensor 1 is provided on the input side of the interface circuit 11.
a to 1d are supplied, and from the output side, the calculation result Sa by the later-described grounding load estimation calculation processing
To Sd are output.

The ground load estimation calculation processing will be described with reference to the flowchart of FIG. In this calculation process, calculation is performed based on the values of the corresponding wheels 101a to 101d in accordance with signals from the height sensors 1a to 1d. Step 100 (hereinafter simply referred to as S10
Say 0. The same applies hereinafter. After the initial setting in (), S11
At 0, the relative displacement (Y) signals from the height sensors 1a to 1d are fetched, and the value of Y is stored as the memory 1. Then, in S120, the gain (K) is added to the relative displacement (Y).
2) is applied to obtain a spring force (K2 · Y) and stored as the memory 2. Here, the gain (K2) is a spring constant of the suspension spring.

In S130, the memory 1 (relative displacement Y)
Is read and differentiated to obtain a relative speed (dY), which is stored in the memory 3. In S140, the damping force estimated value (C · dY) is multiplied by the damping coefficient (C) of the absorber by the relative speed (dY). obtain. Then, in S150, the memory 2
(K2 · Y) is added to the read damping force estimated value (C · dY), and in S160, the sum is added to the gain ｛− (M1
+ M2) / M2} and store it as the memory 4. Here, M1 is the unsprung load per wheel, and M2 is the sprung load per wheel.

Next, in S170, the memory 3 (relative speed d
To give a relative acceleration (d ² Y) and read differential processing of Y), multiplied by the gain (-M1) in S180. And S
At 190, when the memory 4 is read and added to the result at S180, the following expression (5) is obtained.
The contact load (F) can be estimated.

[0020]

(Equation 5)

Finally, in S2000, the ground contact load (F) calculated in S190 is output, and this processing ends. Next, a second embodiment of the contact load estimation device will be described. In the above-described first embodiment, an example using the height sensors 1a to 1d has been described. In the second embodiment, a case in which a piezoelectric sensor using a piezo element or the like is mounted will be described.

As shown in FIG. 6, the piezoelectric sensors 3a to 3d
Are mounted on absorber rods 103a to 103d of shock absorbers provided corresponding to the four front and rear wheels 101a to 101d, respectively, for measuring the rate of change of the damping force. Further, similarly to the above-described first embodiment, a control device 20 shown in FIG.
At least the interface circuit 21 and the arithmetic processing unit 2
3. A microcomputer having a storage device 25. Signals from the piezoelectric sensors 3a to 3d are supplied to the input side of the interface circuit 21, and the output side of the interface circuit 21 calculates the calculation result S by the later-described grounding load estimation calculation processing.
a to Sd are output.

The grounding load estimating operation according to the second embodiment will be described with reference to the flowchart of FIG.
Note that this calculation process is performed in accordance with signals from the piezoelectric sensors 3a to 3d, and the corresponding wheels 101a to 101d, respectively.
The calculation is performed based on the value of

After the initial setting in S300, S310
, The rate of change of the damping force from the piezoelectric sensors 3a to 3d (C · d ²
Y) is fetched and stored as the memory 1. And S
At 320, the damping force change rate (C · d ² Y) captured at S310 is integrated, and the damping force estimated value (C · d
Y) is obtained and stored as the memory 2. In S330, the relative speed (dY) is referred to with reference to a map (not shown) based on the graph showing the relationship between dY and (C · dY) shown in FIG.
Is estimated and stored as the memory 3, and the damping coefficient (C) is further estimated from the damping force estimated value (C · dY) of the memory 2.

In S340, a relative acceleration (d ² Y) is estimated based on the memory 1 (damping force change rate (C · d ² Y)) and the damping coefficient (C) estimated in S330.
At 350, gain (−M1) to the relative acceleration (d ² Y)
And store it as the memory 4. Next, in S360, the memory 3 (relative speed dY) is read and integrated to estimate the relative displacement (Y). Then, in S370, the relative displacement (Y) is multiplied by a gain (K2) to apply a spring force (K).
After obtaining 2 · Y, the memory 2 (damping force estimated value (C · d
Y)).

Subsequently, in S380, the result of (C · dY + K2 · Y) in S370 is added to the gain ｛− (M1 + M2) /
Multiply by M2｝. Then, in S390, the memory 4
Is read, and the result in S380 is added, as shown in the following equation (6), and the contact load (F) can be estimated.

[0027]

(Equation 6)

Finally, in S400, the ground contact load (F) calculated in S390 is output, and this processing ends. In addition,
In the first embodiment, the relative displacement (Y) taken from the height sensors 1a to 1d is used, and in the second embodiment, the damping force change rate (C · d ² Y) taken from the piezoelectric sensors 3a to 3d.
An example is shown which is calculated using the relative displacement from the ground contact load estimated principle described above (Y), the relative velocity (dY), the relative acceleration (d ² Y) or values on a spring constant (K2) or attenuation coefficient ( By measuring one or more of the values multiplied by C), it is possible to estimate and calculate the contact load (F).

When the ground contact load F of each of the four front and rear wheels 101a to 101d is obtained, it is possible to judge the deceleration / acceleration state and the turning state of the vehicle accompanying this. First, the relationship between the ground load F and the front and rear G will be described. In FIG. 9A, the vehicle mass is M, the distance from the ground to the vehicle center of gravity is H, and the distance between the front axle and the center of gravity is L.
1. The wheel base is L, the ground load of the front wheels during braking at the braking deceleration α is F1, and the ground load of the rear wheels is F2. When the gravitational acceleration is g, the contact load of the front and rear wheels is F
1 and F2 are as shown in the following equations (7) and (8), respectively.

[0030]

(Equation 7)

Therefore, the difference between the ground load of the front and rear wheels (F1-F
2) is as shown in the following equation (9).

[0032]

(Equation 8)

In the equation (9), the vertical axis represents the difference in the contact load (F1
−F2), and the horizontal axis represents a graph of the deceleration α, as shown in FIG.
It is shown by a straight line as in (B), and it can be seen that the difference in the ground contact load between the front and rear wheels is proportional to the front and rear G of the vehicle. Since the front and rear load movement amount ((H / L) Mα in the above equations (7) and (8)) is proportional to the front and rear G of the vehicle, the front and rear G can be obtained by the difference in the grounding load of the front and rear wheels.

Next, the relationship between the contact load F and the lateral G will be described. 10A, the vehicle mass is M, the distance from the ground to the center of gravity of the vehicle is H, the wheel tread is T, the ground contact load of the right wheel during turning at the centrifugal acceleration β is F3, and the ground load of the left wheel is F4. I do. Assuming that the gravitational acceleration is g, the grounding loads of the left and right wheels are F3 and F4, respectively (10),
Equation (11) is obtained.

[0035]

(Equation 9)

Therefore, the difference between the ground load of the left and right wheels (F3-F
4) is as shown in the following equation (12).

[0037]

(Equation 10)

In the equation (12), the vertical axis represents the difference in contact load (F
3-F4), when the horizontal axis is represented as a graph of the centrifugal acceleration β, it is indicated by a straight line as shown in FIG. 10B, and it can be seen that the difference in the contact load between the left and right wheels is proportional to the lateral G of the vehicle. Left and right load movement amounts ((H / T) in the above equations (10) and (11))
Mβ) is proportional to the left and right G of the vehicle, so that the lateral G can be obtained from the difference in the grounding load of the left and right wheels.

The deceleration / acceleration and turning state of the vehicle can be determined based on the information on the front / rear G and the side G.
Application to ABS / TRC control is also possible. The output of the height sensors 1a to 1d of four or less wheels can be used to detect the ground contact load of each wheel or the front and rear G and side G of the vehicle, which makes it applicable to ABS / TRC devices in the following points. It becomes possible. FIG. 11 shows an ABS / TRC to which the height sensors 1a to 1d described below are applied.
FIG. 2 is a block diagram showing an embodiment of the device and the electronic control suspension device. Detailed description of each configuration is omitted.

First, a description will be given of a point that conventionally, when the vehicle crosses a step, the ABS malfunctions and braking is insufficient. FIG.
As shown in FIG. 2, the control which has conventionally been performed only with the wheel speed signal is added to the wheel speed signal and the height sensor 1 is used.
By considering the grounding load obtained from a to 1d,
For example, a step which is a temporary disconnection of the ground load is detected, and an appropriate measure is taken.

In other words, if there is a temporary sudden drop and return of the ground contact load in response to a temporary sudden drop and return of the wheel speed, the brake oil pressure reduction is stopped at the point of determination. The brake hydraulic pressure intended by the driver is immediately returned to prevent the braking force from coming off as much as possible. As a result, a large lack of braking does not occur, and the driver can brake without feeling uncomfortable even if the driver crosses a step.

FIG. 13 shows that the braking distance tends to be extended by suppressing the brake oil pressure on the outer wheel side where the braking force should be increased by the ABS at the time of turning braking.
This will be described with reference to FIG. FIG. 13 (A) shows the result of the conventional control, and an insufficient initial deceleration due to early operation is seen.

On the other hand, according to the ABS control of this embodiment, the ground load of each wheel is obtained by the output of the height sensors 1a to 1d, and the vehicle lateral G is obtained by the output difference between the left and right wheels of the height sensors 1a to 1d. , The turning state is detected, and an appropriate measure is taken. That is, FIG.
As shown in FIG. 3 (B), based on the turning degree obtained from the signals from the height sensors 1a to 1d, the braking force is suppressed early on the inner wheel side, and conversely, the braking force is applied on the outer wheel side as much as possible. The feeling of early operation can be eliminated, and the initial deceleration can be improved. Thereafter, independent control of the inner and outer wheels according to the turning state can be performed.

Thus, even if an expensive lateral G sensor is not used, the height sensors 1a to 1d originally provided for adjusting the vehicle height are generally diverted without using an expensive lateral G sensor. Can be achieved. Estimation of road surface μ at the time of ABS control and control of distribution of front and rear braking force with normal braking, which were conventionally performed by detecting the deceleration by the front and rear G sensor, can be performed by installing an air suspension as described above without using an expensive front and rear G sensor. By diverting the height sensors 1a to 1d originally provided for adjusting the vehicle height (the output difference between the front and rear wheels is equivalent to the front and rear G, or considering changes in the ground contact load of each wheel by the height sensors 1a to 1d) , Can be implemented.

Further, by using an actuator capable of quickly controlling the absolute value of the braking force in the ABS,
While estimating the road surface μ from the absolute value of the ground load and the braking force and the slip state at the wheel speed, an optimum braking force can be obtained by the ground load and the road surface μ. Then, it is possible to estimate and feedback the target braking force by applying the optimal braking force to changes in the grounding load such as running on steps, wavy roads, and gravel roads, or turning, and making small corrections. Insufficient braking of the ABS control on the road surface can be improved.

On the other hand, in the TRC as well as in the ABS,
A description will be given of a point that the TRC has malfunctioned and insufficient acceleration has occurred conventionally when the vehicle crosses a step. As shown in FIG. 14, the control which has conventionally been performed only with the wheel speed signal is considered in consideration of the ground load obtained from the height sensors 1 a to 1 d in addition to the wheel speed signal. A step which is a temporary omission is detected, and appropriate measures are taken.

In other words, if there is a temporary sudden drop and return of the ground contact load in response to a temporary rapid rise and return of the wheel speed, the brake oil pressure increase is stopped at the point of determination. The driving force is immediately returned to the driving force intended by the driver, and the driving force is prevented from falling off as much as possible. As a result, a large lack of acceleration does not occur, and the driver can accelerate without discomfort even if the driver crosses a step.

Conventionally, in the TRC, the front / rear / horizontal G
By using the sensor and the steering angle sensor, the turning acceleration and the traceability with respect to the driver's steering and acceleration intention have been improved. On the other hand, the height sensors 1a to 1d originally provided for adjusting the vehicle height of the vehicle equipped with the air suspension can be diverted without using the expensive front / rear / lateral G sensor (the output difference between the front and rear wheels is reduced by the front and rear G sensors). , The output difference between the left and right wheels corresponds to the lateral G, or the change in the ground contact load of each wheel by the height sensors 1a to 1d is taken into account).

Further, when one of the driving wheels comes off the side groove or the like, the output of only one of the wheels suddenly changes by monitoring the output of the height sensors 1a to 1d, and the contact load almost disappears. And appropriate measures can be taken for this. That is, since it is impossible to escape by the TRC controlled by the engine, a warning is issued to release the TRC, or the escape can be achieved by more actively using a function such as a differential lock.

In the TRC of the brake control,
If it is possible to escape, it is good, but if it is impossible to escape, it is preferable to provide a certain time limit, issue a warning to release the TRC, and limit the long-term load on the brake in order to protect the brake device and the TRC device. Further, by detecting the grounding load of each wheel using the outputs of the height sensors 1a to 1d of each of the four or less wheels, application to an electronically controlled suspension device is possible in the following points.

In a conventional electronically controlled suspension device,
When traveling on rough roads such as gravel roads, the tendency was to soften the damping force to improve ride comfort. However, when the damping force is made soft, there is a disadvantage that the unsprung portion flaps due to unsprung resonance and the grounding load changes greatly, so that the steering stability is deteriorated. Therefore, the height sensors 1a to 1
By performing appropriate control using the grounding load obtained from d, it is possible to achieve both stability and ride comfort.

For example, as shown in FIG. 15, a height signal is read, a ground load is estimated, a band-pass filter (for example, 10 to 15 Hz) is applied, and a flutter level (for example, a preset value is set according to a predetermined value). Level 1
3) is determined. On the other hand, the acceleration signal is read and subjected to a band-pass filter (for example, 4 to 8 Hz) to determine a rugged level (for example, levels 1 to 3 preset according to a predetermined value).

Damping force level maps (soft S, middle soft MS, middle M, middle hard MH, hard hard MH in this embodiment) set in advance corresponding to the flapping levels 1 to 3 and the lumpy levels 1 to 3 in combination. H of 5
The type has been set. ) To determine the optimal damping force and output it to the actuator.

As described above, it is possible to know the degree of deterioration of the steering stability by observing the fluctuation of the grounding load obtained from the height sensors 1a to 1d. Security can be improved.

[0055]

As described above, the apparatus for estimating the contact load according to the present invention provides a method for contacting each wheel of the vehicle based on at least one of the relative displacement or relative speed or relative acceleration between the sprung and unsprung state of the vehicle. The load can be calculated. The longitudinal acceleration calculating device and the lateral acceleration calculating device calculate the longitudinal acceleration and the lateral acceleration acting on the vehicle using the contact load estimated by the contact load estimating device. It is simpler than.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a one-wheel two-degree-of-freedom model corresponding to one wheel of a vehicle.

FIG. 2 is a graph showing a relationship between a speed dY and a damping force estimated value C · dY.

FIG. 3 is a schematic explanatory view showing a four-wheel vehicle model provided with a height sensor.

FIG. 4 is a block diagram showing a first embodiment of a contact load estimation device.

FIG. 5 is a flowchart illustrating a contact load estimation calculation process in the first embodiment.

FIG. 6 is a cross-sectional view of a shock absorber showing an arrangement of a piezoelectric sensor.

FIG. 7 is a block diagram showing a second embodiment of the contact load estimation device.

FIG. 8 is a flowchart illustrating a grounding load estimation calculation process according to the second embodiment.

FIG. 9A is an explanatory diagram showing the relationship between the contact load F and the front and rear G, and FIG. 9B is a graph in which the vertical axis represents the difference between the contact load and the horizontal axis represents the deceleration α.

10A is an explanatory diagram showing a relationship between a contact load F and a lateral G, and FIG. 10B is a graph in which a vertical axis represents a contact load difference and a horizontal axis represents a centrifugal acceleration β.

FIG. 11 is a block diagram showing an embodiment of an ABS / TRC device and an electronic control suspension device to which a height sensor is applied.

FIG. 12 is a time chart showing a result of applying the height sensor to the ABS control when the vehicle crosses a step.

FIGS. 13A and 13B are time charts showing application to ABS control at the time of turning braking. FIG. 13A shows a conventional result, and FIG. 13B shows a result in the present embodiment using a height sensor.

FIG. 14 is a time chart showing a result of applying a height sensor to TRC control when the vehicle crosses a step.

FIG. 15 is a flowchart showing a procedure in a case where a height sensor is applied to an electronic control suspension device for determining a damping force.

[Explanation of symbols]

1a to 1d: height sensor, 3a to 3d: piezoelectric sensor, 10, 20: control device, 11, 21: interface circuit, 13, 23: arithmetic processing device, 1
5, 25: storage device, 101a to 101d: wheels,
102: body, 103a to 103d: absorber rod

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hiroshi Ishikawa 1-1-1, Showa-cho, Kariya-shi, Aichi Japan Inside Denso Co., Ltd. (56) References JP-A-2-95913 (JP, A) JP-A-4- 90916 (JP, A) JP-A-2-182525 (JP, A) JP-A-2-24813 (JP, A) JP-A-62-219958 (JP, A) JP-A-62-140525 (JP, A) JP-A-4-232111 (JP, A) Patent 2565384 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01L 5/00 G01P 15/00 B60G 17/015

Claims (4)

(57) [Claims] 1. A detecting means for detecting at least one of a relative displacement, a relative speed, and a relative acceleration between a vehicle sprung and a vehicle unsprung, and based on the relative displacement, relative speed, or relative acceleration detected by the detecting means. And a contact load estimating means for estimating the contact load of each wheel of the vehicle. 2. The ground contact load estimating means uses at least one of the relative displacement, relative speed, and relative acceleration detected by the detecting means, and calculates the following contact load estimating equation: (However, M1 is the unsprung load, M2 is sprung weight, K2 is the spring constant of the suspension spring, C is the attenuation coefficient of the absorber, Y is the relative displacement between the sprung-unsprung, dY is the relative velocity, d ² The ground contact load estimating device according to claim 1, wherein the ground contact load is estimated based on Y is the same relative acceleration.). 3. A longitudinal acceleration acting on a vehicle based on a difference in grounding load between front and rear wheels of a vehicle, using the grounding load estimated by the grounding load estimating device provided with the grounding load estimating device according to claim 1 or 2. Longitudinal acceleration calculation device that calculates 4. A ground load estimating device according to claim 1 or 2, wherein the ground load estimated by the ground load estimating device is applied to a vehicle based on a ground contact difference between left and right wheels of the vehicle. A lateral acceleration calculation device that calculates a lateral acceleration.