JP2000052951A - Method and apparatus for estimating vehicle sideslip angle of vehicle - Google Patents

Abstract

(57) Abstract: A method and an apparatus for estimating a side slip angle that can improve the estimation accuracy in a low vehicle speed range and suppress the occurrence of drift when estimating a vehicle body side slip angle. When estimating A vehicle body slip angle, for example, to calculate the longitudinal direction velocity V _X based on the wheel speed, yaw rate gamma, longitudinal acceleration alpha _X and lateral acceleration alpha _Y
Detects, by feeding back the error signal between the front-rear direction velocity V _X and the estimated longitudinal direction velocity V ^ _X which is the estimated value, to calculate the estimated lateral velocity V ^ _Y is unknown amount, estimated longitudinal direction An estimated sideslip angle β ＾ is calculated from the speed V ＾ _X and the estimated lateral speed V ＾ _Y.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for estimating a vehicle body sideslip angle of a vehicle, and more particularly, to an improvement in estimation accuracy of a vehicle body sideslip angle in a low vehicle speed range.

[0002]

2. Description of the Related Art Japanese Patent Application Laid-Open No. 8-268306 (hereinafter referred to as a first conventional example) and Japanese Patent Application Laid-Open No. 8-332934 (hereinafter referred to as a second conventional example) are examples of such prior art. Is disclosed.

The first conventional example calculates an estimated sideslip angle based on an estimated sideslip angle and an estimated yaw rate calculated based on an observer's state equation and a detected front-rear speed,
The ratio between the detected lateral acceleration and the calculated estimated lateral acceleration is calculated as a correction coefficient, and the correction coefficient is multiplied by a factor relating to cornering power in the observer's state equation. When the sideslip angle is estimated based on the cornering power, since the cornering power is accurately corrected, the estimation accuracy of the sideslip angle is improved.

[0004] The second conventional example includes a vehicle speed, a yaw rate,
And a skid physical quantity calculation block for calculating a skid physical quantity of the vehicle by an integration calculation using the lateral acceleration as a parameter,
A side slip physical quantity estimation block for estimating a side slip amount of a vehicle by a vehicle model using the detected state quantity of the vehicle as an input variable, and an integration time constant setting block for increasing an integration time constant of an integration operation when the turning behavior of the vehicle is unstable. The final calculation block finally calculates the skid physical quantity of the vehicle based on the skid physical quantity calculated by the skid physical quantity calculation block and the skid physical quantity estimated by the skid physical quantity estimation block.

[0005]

Here, since the lateral force and the cornering force of the tire generally have nonlinear characteristics in a region where the tire slip angle is large, an estimation formula based on a tire model is used for the vehicle. When estimating the vehicle body side slip angle, it has been found that the estimation accuracy of the vehicle body side slip angle decreases in a region where the tire characteristics (the relationship between the tire side slip angle and the cornering force) are nonlinear.

Therefore, as in the first prior art, for example, the cornering power included in the estimation formula is corrected by using a correction coefficient corresponding to the ratio between the detected lateral acceleration and the estimated lateral acceleration, so that the vehicle body skids. It is conceivable that the estimation accuracy of the angle is not reduced. However, even with the method using such a correction coefficient, a turning motion model of the vehicle using the vehicle mass, the vehicle yawing inertia moment, the horizontal distance from the vehicle center of gravity to the front and rear axles, the vehicle front and rear speed, the cornering power, etc. is used. Therefore, there is an unsolved problem that the approximation formula is not effective in a region where the vehicle speed is low, so that the accuracy of estimating the sideslip angle deteriorates. In particular, there is a high possibility that the vehicle body slip angle increases even at low speeds, including a phenomenon called so-called power oversteer due to the driving force immediately after the vehicle that drives the rear wheels is started. It is desired to estimate.

Further, when the vehicle side slip physical quantity is calculated by the integral calculation using the vehicle speed, the yaw rate, and the lateral acceleration as parameters, as in the second conventional example, the vehicle is operated in a low vehicle speed range as in the first conventional example. Although the problem of deterioration of the estimation accuracy does not occur, there is a possibility that the estimation value deviates from the true value due to differences in dynamic characteristics between sensors and integration errors due to the use of integration processing. However, there is an unsolved problem that it is necessary to use the method together with a method using a vehicle model.

Therefore, the present invention has been made in view of the above-mentioned unsolved problems of the prior art, and a method and an apparatus for estimating a sideslip angle capable of improving the accuracy of estimating the sideslip angle of a vehicle body in a low vehicle speed range. It is intended to provide a device.

[0009]

According to a first aspect of the present invention, there is provided a method for estimating a vehicle body skid angle of a vehicle according to the first aspect of the present invention, wherein the vehicle moves about a vertical axis in a front-rear direction and a lateral direction, respectively. A motion model that describes a state in which the motion is performed. The motion model includes an estimated front-rear motion physical quantity estimated from the motion model that describes the front-rear motion, and an actually measured front-rear motion physical quantity and other estimation methods. An error signal with any of the forward and backward movement physical quantities obtained from is used as a feedback signal, and the side slip angle of the vehicle body is estimated based on the movement model.

According to a second aspect of the present invention, there is provided the vehicle body side slip angle estimating method according to the first aspect, wherein the longitudinal physical quantity is set to a longitudinal velocity.

Further, in the vehicle body side slip angle estimation method according to a third aspect, in the invention according to the second aspect, the front-rear direction speed uses one of a wheel speed and an estimated value of the wheel speed. And

Further, in the method for estimating a vehicle body skid angle according to claim 4, the larger value of the wheel speed of the drive wheel is determined by:
The vehicle body slip angle estimation method according to claim 1 is used when the wheel speed or the vehicle body speed of the front wheels is smaller than a certain value by more than a certain value or a certain ratio with respect to that of the non-driving wheels. It is characterized in that another method of estimating a vehicle body skid angle is used.

Still further, according to a fifth aspect of the present invention, there is provided a vehicle body slip angle estimating apparatus for calculating a wheel speed of each wheel of a vehicle, a yaw rate detecting means for detecting a yaw rate generated in the vehicle body, Forward / backward speed calculating means for calculating a forward / backward speed based on the wheel speed detected by the wheel speed calculating means and the yaw rate detected by the yaw rate detecting means; forward / backward speed calculated by the forward / backward speed calculating means; Speed estimating means for estimating the longitudinal and lateral speeds by feeding back an error signal from the direction velocity, and a skid angle calculating means for calculating a skid angle based on the longitudinal and lateral speeds estimated by the speed estimating means; It is characterized by having.

[0014]

According to the first aspect of the present invention, an estimated front-rear movement physical quantity estimated from a movement model describing a front-rear movement and obtained from an actually measured front-rear movement physical quantity or another estimation method. Since the error signal with the forward and backward moving object quantity is used as the feedback signal, it is possible to estimate the sideslip angle with high accuracy in the low vehicle speed range, and the estimated value is the true value for some reason such as incorrectly giving the initial value. Can be converged to the true value even when the distance is deviated, and the effect that drift does not occur unlike the second conventional example described above is obtained.

According to the second aspect of the present invention, since the longitudinal velocity is set as the longitudinal physical quantity, accurate actual measurement is possible, and a more accurate side slip angle estimation can be performed. The effect that it can be obtained is obtained.

Further, according to the third aspect of the present invention, since the longitudinal speed is calculated using either the wheel speed or the estimated value of the wheel speed, the speed is calculated as a value corresponding to the actual running state of the vehicle. It is possible to calculate, and it is possible to obtain an effect that a more accurate side slip angle estimation can be performed.

Furthermore, according to the invention of claim 4, in a low vehicle speed range at the time of starting or the like, the invention of claim 1 is applied to perform a highly accurate side slip angle estimation, and in a middle / high vehicle speed range. ,
By switching to another estimation method, it is possible to obtain an effect that high-accuracy sideslip angle estimation can be continued and the sideslip angle can be estimated with high accuracy in all vehicle speed ranges.

Further, according to the invention of claim 5, similarly to the invention of claim 1, it is possible to perform a highly accurate estimation of the sideslip angle in a low vehicle speed range, and the estimated value is set to an initial value. The true value can be converged to the true value even if the true value is deviated for some reason, such as being given by mistake, and the effect that drift does not occur unlike the second conventional example described above is obtained.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the overall configuration of a first embodiment of the present invention. A vehicle in this embodiment includes a vehicle state quantity estimating device 10 for estimating a state quantity such as a vehicle body side slip angle, and a target control system. A power setting device 20 and a braking force control device 30 are provided. The target braking force setting device 20 is a device for setting an appropriate braking force based on each value or the like supplied from the vehicle body side slip angle estimating device 10, and its specific configuration is the control to be executed. (For example, control applicable to a vehicle such as VDC, ABS, TCS, etc.), but the content is not the essence of the present invention, and a specific description thereof is omitted. . In addition, the braking force control device 30 can appropriately adopt a known configuration according to the control to be performed, and thus a specific description thereof is omitted.

The vehicle state quantity estimating apparatus 10 is actually constituted by a microcomputer, necessary interface circuits and the like, and is provided with an actual yaw rate r supplied from a yaw rate sensor 11 for detecting a yaw rate generated in the vehicle. a longitudinal acceleration alpha _X supplied from the longitudinal acceleration sensor 12 for detecting a longitudinal acceleration generated in the vehicle,
Lateral acceleration α _Y supplied from a lateral acceleration sensor 13 detecting the lateral acceleration occurring in the vehicle, and wheel speed Vw _FL supplied from a wheel speed sensor 14 detecting the wheel speed of each wheel.
A predetermined calculation process is executed based on ~ Vw _RR to estimate the sideslip angle β of the vehicle body.

That is, as shown in FIG. 2, a general two-wheel motion model that describes a state in which the vehicle is moving around a vertical axis in the front-rear direction and the lateral direction of the vehicle is a front wheel 1F having a steering mechanism. And the rear wheel 1R without a steering mechanism, the front wheel steering angle is δ, the front wheel side slip angle is β _f , the rear wheel side slip angle is β _r , the vehicle speed at the center of gravity 2 is V, and the front-rear direction speed is V
_X , lateral speed V _Y , longitudinal acceleration α _X , lateral acceleration α _Y , yaw rate γ, sideslip angle β, horizontal distance from the center of gravity to the front wheel side axle L _f , center of gravity to rear wheel Assuming that the horizontal distance to the side axle is L _r , the equation of motion is that the mass of the vehicle is M, the rotational moment of inertia of the vehicle in the yaw direction is I _Z , and the tire cornering power of the front and rear wheels is C.
If P _f and CP _r are used, they can be expressed by the following equations (1) and (2).

[0022] _{MV X (β '+ γ)} = 2CP f β f + 2CP r β r ............ (1) I Z γ' = 2L f CP f β f -2L f CP f β f ............ (2 ) in order to sideslip angle accurately describe the motion of large states, the relationship between the longitudinal acceleration alpha _X lateral acceleration alpha _Y and the longitudinal direction velocity V _X and lateral velocity V _Y of the vehicle from the motion model of Figure 2 , (3) and (4) below.

Α _X = V _X ′ + V _Y γ (3) α _Y = V _Y ′ −V _x γ (4) where V _X ′ is the differential of the longitudinal velocity V _X. The value, V _Y ', is the derivative of the lateral velocity.

The above (3) means that if the vehicle is decelerating, if the vehicle has a lateral velocity component and a yaw rate at the center of gravity, the detected value of the longitudinal acceleration sensor and the longitudinal This indicates that the differential values of the directional acceleration do not match.

The above equation (4) indicates that when a centrifugal force acts on the vehicle, the differential value V _Y 'of the lateral speed V _Y of the vehicle does not match the detection value of the lateral acceleration sensor. Is shown.

As can be seen from the equations (3) and (4), when the vehicle has a yaw rate, the vehicle movement in the front-rear direction and the lateral direction is closely related via the yaw rate.

[0027] In addition, the front-rear direction speed V _X is the lateral velocity V _Y
In situations where the vehicle motion is not large enough, it is necessary to model the motion of the vehicle with this in mind. Therefore, the expressions (3) and (4) a physical quantity which can be measured directly by sensors in the vehicle of the variables used in the formula, yaw rate gamma, a lateral longitudinal acceleration alpha and lateral acceleration alpha _Y.

Further, the speed V _X in the longitudinal direction of the vehicle, can be relatively easily measured or estimated by the speed of the wheel. Further, the above equations (3) and (4) are equations expressing the relationship between the longitudinal acceleration α _X and the lateral acceleration α _y and the longitudinal velocity V _X and the lateral velocity V _Y. it is possible to consider longitudinal direction velocity V _X and lateral velocity V _Y quantity of state was the following (5) and (6) and equation of motion of the formula.

V _X ′ = −V _Y γ + α _X (5) V _Y ′ = V _X γ + α _Y (6) Therefore, the above equations (5) and (6) are directly used. Thus, the motion of the vehicle can be described.

[0030] Thus, using the error signal as a known quantity in the longitudinal direction velocity V _X based on the above equation (5) and (6), an observer for estimating the lateral velocity V _Y is unknown amount If set, the sideslip angle can be determined with high accuracy even in a region where the sideslip angle is large.

Here, since the above equations (5) and (6) are nonlinear motion equations, the following equations (7) and (8)
Use the observer shown in the equation. _{V ^ X '= -V ^ Y} γ + α X -K 11 (V ^ X -V X) -K 12 sign (V ^ X -V X) ............ (7) V ^ Y' = V ^ X γ + α _{Y -K 21 (V ^ X -V} X) -K 22 sign (V ^ X -V X) ............ (8) where, K _11, K ₂₁ gives linear feedback with respect to the error signal The gains K ₁₂ and K ₂₂ are gains that provide feedback only for the sign of the error. These gain values can be determined from experimental results and the like.

Using the longitudinal velocity V ＾ _X and the lateral velocity V ＾ _Y estimated by the above equations (7) and (8), the final side slip angle β 角 is calculated according to the following equation (9). calculate.

Β ＾ = tan ⁻¹ (V ＾ _Y / V ＾ _X ) (9) As described above, in the first embodiment, the vehicle state quantity estimating apparatus 10 and the yaw rate sensor 11 actual yaw rate γ detected longitudinal acceleration detected by the acceleration sensor 12 before and after alpha _X, lateral acceleration alpha _Y detected by the lateral acceleration sensor 13, the wheel speed Vw _FL ~Vw detected by the wheel speed sensor 14
By performing the observer computation of the equation (7) and (8) based on the longitudinal direction velocity V _X calculated based on the _RR, actually detected the longitudinal estimated lateral velocity V _Y direction velocity V ^ _X by feeding back the error signal between the front-rear direction velocity V _X which is the estimated lateral velocity V ^ _Y is calculated, the estimated lateral slip angle beta ^ can be calculated on the basis of the this the estimated longitudinal direction velocity V ^ _X .

[0034] In this case, the equation (7) and (8) is only so as to feed back the error signal between the front-rear direction velocity V _X which actually detects the longitudinal direction velocity V ^ _X estimated equation, non Since there is no need to model linear motion in a linear fashion, the behavior of the vehicle becomes unstable when suddenly starting at low vehicle speeds, and even when the vehicle is spinning due to a large skid angle, it is more accurate. It is possible to estimate an appropriate side slip angle.

[0035] Moreover, since the fed back error signal actually the detected longitudinal direction velocity V _X and the estimated longitudinal direction velocity V ^ _X, away from the true value for any reason, such an estimate is given incorrectly initial value In such a case, the value converges to the true value, and it is possible to reliably prevent the occurrence of drift in the method using the integration processing as in the second conventional example.

Next, a second embodiment of the present invention will be described with reference to FIG. In the second embodiment, the longitudinal velocity V
_X is obtained from the wheel speed or its estimated value.

That is, since a non-drive wheel exists in a front-wheel or rear-wheel drive vehicle, it is possible to calculate the front-rear direction speed using the wheel speed of the non-drive wheel during driving.
In general, a large skid angle occurs at low speed when a rear-wheel drive vehicle or the like suddenly starts. In such a state, since no driving force or the like is generated at the front wheels, the wheel speed may be roughly considered to be the vehicle speed in the front-rear direction of the tire at that position. By using the following equation (10), it is possible to obtain the longitudinal speed at the wheel position from the rotational speed of the wheel.

Vw _X = Vw · cos δ (10) where Vw is a value obtained by converting the rotational speed of the wheel into a translation speed, and δ is a steering angle (zero or four-wheel steering system mounted on the rear wheels). Vw _X is a component of Vw in the front-rear direction of the vehicle body, and when the wheel slip is zero, it is the vehicle front-rear speed at the wheel position.

In the first embodiment, (7)
In the observer calculation of equations (8) and (8), the velocity in the front-rear direction at the position of the center of gravity is used.
It can be calculated by converting into the longitudinal velocity at the position of the center of gravity using the equation.

V _X = Vw _X + (− 1) ⁱ · γ · tr / 2 (11) where tr is a tread, i is a subscript representing a wheel position, and odd numbers are left wheels, and even numbers are right. Each represents a ring.

Then, the objects of the equations (7) and (8)
Front-rear speed V required for server calculation _X(1)
By applying equation (1), the rear-wheel drive vehicle is accelerating.
Can be calculated.

On the other hand, at the time of braking, in order to estimate the wheel speed, the braking force of one of the four wheels of the vehicle is intentionally reduced to suppress the slip. And the speed V in the front-rear direction
it is possible to calculate the w _X. Further, even in a state where the wheels are slipping due to the braking force in all the wheels, the wheel speed is estimated by other means by using, for example, a model of the rotational motion of the wheels, and the above (7) and ( 8) can be calculated longitudinal direction velocity V _X required by the observer calculation formula. Here, the friction coefficient of the tire is given by the friction coefficient estimating means.

As described above, in both the acceleration state and the deceleration state, the rotation in the forward and backward directions at the wheel position or the center of gravity can be obtained by using the rotation of the wheel. Specifically, as shown in FIG. 3, the vehicle state quantity estimating apparatus 10 includes the above-described yaw rate sensor 11, longitudinal acceleration sensor 12, lateral acceleration sensor 13, and wheel speed sensor 14 as described above.
Angle sensor 1 for detecting the steering angle of front wheel 1F
5, the master cylinder pressure MP detected by the master cylinder pressure sensor 16 for detecting the steering angle δ and the master cylinder pressure is input, and indicates whether or not the braking force control unit 30 is in the braking force control state. The braking force control state signal SB is input, and the vehicle state quantity estimation device 10
The estimated side slip angle β ＾ is calculated based on the wheel speed by executing the state quantity calculation processing shown in FIG.

This state quantity calculation processing is executed by a timer interruption processing every predetermined time (for example, 10 msec).
First read the master cylinder pressure MP detected by the master cylinder pressure sensor 16 in step S1, by which to determine whether a relatively small 1MPa about threshold MP _S above a preset, the driver on the brake pedal It is determined whether the vehicle is in the depressed braking state and MP <MP _S
When it is determined that the vehicle is not in the braking state by the driver, the process proceeds to step S2, the braking force control state signal SB from the braking force control device 30 is read, and it is determined whether or not this is the on state. It is determined whether or not the braking force control by the traction control other than the depression of the brake pedal or the yaw moment suppression control is being performed, and if the braking force control is not being performed, the process proceeds to step S3 to be the non-drive wheel. Either left or right wheel speed V of the front wheel
After setting w _FL and Vw _FR as the wheel speed Vw, the process proceeds to step S4.

In step S4, the equation (10) is calculated on the basis of the wheel speed Vw, and the longitudinal speed Vw _X
Then, the process proceeds to step S5 to read the yaw rate γ (n) detected by the yaw rate sensor 11, and then proceeds to step S6.

In this step S6, the longitudinal speed Vw
_{Based on X} and the yaw rate γ (n), the calculation of the equation (11) is performed to calculate the longitudinal acceleration V _X (n) at the position of the center of gravity.

Next, the process proceeds to step S7, and based on the longitudinal speed V _X (n) at the position of the center of gravity, the estimated longitudinal vehicle speed V ＾ of the vehicle in accordance with the following equations (12) and (13).
_X (n) and estimated lateral vehicle speed V ＾ _Y (n) are calculated.

[0048] _{V ^ X (n) = V} ^ X (n) + Δt (-A + α X (n) -B-C) ...... (12) V ^ Y (n) = V ^ Y (n) + Δt (D + α _{Y (n) -E-F)} ...... (12) A = V ^ Y (n-1) γ (n-1) B = K 11 (V ^ X (n-1) -V X (n)) _{C = K 12 sign (V ^} X (n-1) -V X (n)) D = V ^ X (n-1) γ (n-1) E = K 21 (V ^ X (n-1) −V _X (n)) F = K ₂₂ sign (V ＾ _X (n−1) −V _X (n)) Then, the process proceeds to step S8, and the estimated vehicle speed V 前後_X (n) in the front-rear direction of the vehicle is obtained. And estimated lateral vehicle speed V ＾ _Y (n)
And the estimated sideslip angle β ＾ (n) according to the above equation (9).
Then, the process proceeds to step S9, where the calculated estimated longitudinal vehicle body speed V ( _X (n) and estimated lateral vehicle speed V ＾ _Y (n) of the vehicle are set to the previous values V ＾ _X (n-1). And V ＾ _Y (n-1)
And then terminates the timer interrupt processing and returns to the predetermined main program.

On the other hand, if the result of the determination in step S1 is that the driver is depressing the brake pedal, the flow proceeds to step S10 to refer to, for example, the estimated vehicle speed used by the antilock brake control device. , This is set as the wheel speed Vw, and
Move to

If the result of the determination in step S2 is that the vehicle is performing braking force control, the flow shifts to step S11 to determine whether or not any of the non-driven wheels has a wheel capable of releasing the braking control force. If there is a wheel that can be released, the process proceeds to step S12, in which the control force of the wheel is released, the wheel speed of the wheel is set as the wheel speed Vw, and then the process proceeds to step S4. If there is not, the process proceeds to step S10.

In the side slip angle calculation processing of FIG. 4, the processing in steps S1 to S6 corresponds to the forward / backward speed calculation means, the processing in step S7 corresponds to the speed estimation means, and the processing in step S8 corresponds to the side slip angle calculation means. Yes, it is.

Therefore, when the driver has not stepped on the brake pedal and braking force control such as traction control or yaw rate control has not been performed, the wheel speed of one of the left and right wheels of the front wheel 1F, which is a non-driven wheel, is determined. Vw _FL or Vw
_The longitudinal velocity V _X (n) at the position of the center of gravity is calculated based on _FR , and this and the previous estimated longitudinal velocity V ＾ _X (n-1) and the estimated lateral velocity V ＾ _Y (n-1) are calculated as follows: calculating the estimated longitudinal direction velocity V ^ _X (n) and the estimated lateral velocity V ^ _Y (n) by an observer computation based on the longitudinal acceleration alpha _X and the lateral acceleration alpha _Y, estimated lateral slip angle in accordance with these beta ^ (n ) Is calculated.

On the other hand, when the driver does not perform the braking operation but performs the traction control or the yaw rate control, the traction control does not perform the braking force control on the front wheels that are the non-driving wheels. Any one of the wheel speeds is selected, and in the yaw rate control, the braking force control is not performed on either the inner wheel side or the outer wheel side. Therefore, this wheel is selected, and the forward / rearward speed V _X (n ) Is calculated.

When the driver is performing the braking operation or when the braking operation is not performed but all the wheels are controlled by the traction control or the yaw rate control, for example, the antilock brake control The longitudinal speed at the position of the center of gravity is calculated based on the estimated vehicle speed.

As a result, it is possible to select the wheel speed accurately representing the longitudinal speed at that time according to the braking state of the vehicle and calculate the longitudinal speed at the center of gravity based on the selected wheel speed. The sideslip angle can be estimated.

In the second embodiment, the case where the braking operation of the driver is detected by detecting the master cylinder pressure by the master cylinder pressure sensor 16 has been described. However, the present invention is not limited to this. Alternatively, it may be detected by a switch signal of a brake lamp switch that is turned on when the brake pedal is depressed.

Next, a third embodiment of the present invention will be described with reference to FIG. In the third embodiment, since the steering angle δ is not used when calculating the estimated sideslip angle in the first and second embodiments, the longitudinal acceleration α _X in the low vehicle speed range is used. When the lateral acceleration α _Y is large, the sideslip angle can be estimated with high accuracy, but in other high vehicle speed ranges, the estimation accuracy decreases. By switching to the method, it is possible to perform a highly accurate side slip angle estimation in all vehicle speed ranges.

That is, the vehicle state quantity estimating apparatus 10 executes an estimation method switching process shown in FIG. The estimation method switching process is executed as a timer interrupt process at predetermined time intervals (for example, 10 msec). First, in step S21, the estimation method used last time uses the same high-speed motion model as the first conventional example described above. It is determined whether or not the method is a side slip angle estimating method for high speed. If the method is a method for estimating a side slip angle for high speed, the process proceeds to step S22, and the rear wheel 1 as a driving wheel is determined.
A value (Vw _RH −Vw _FH ) obtained by subtracting the high wheel speed Vw _FH of the left and right wheels of the front wheel 1F as the non-drive wheel from the high wheel speed Vw _RH of the left and right wheels of R is a preset value ΔVw.
_It is determined whether or not the wheel speed Vw _FH greater than ₁ and the high speed of the front wheel 1F as the non-drive wheel is smaller than a preset vehicle speed Vw _S1 , and (Vw _RH −Vw _FH )> ΔVw ₁ and Vw _FH
When <Vw _S1 , it is determined that the driving wheel is spinning in the low vehicle speed range, and the process proceeds to step S23.

In step S23, the longitudinal velocity V according to the first or second embodiment described above is used.
By feeding back an error signal between _X (n) and the estimated longitudinal velocity V ＾ _X (n), the estimated longitudinal velocity V ＾ _X
(n) and the estimated lateral velocity V ＾ _Y (n), and the estimated sideslip angle β ＾ by the low-speed sideslip angle estimation method using the sideslip angle estimation method of calculating the estimated sideslip angle β ＾ (n) from these. After calculating (n), the process proceeds to step S24.

In step S24, since the estimated yaw rate γ ＾ (n) is used in the high vehicle speed side slip angle estimation method described later, the actual yaw rate γ (n) detected by the yaw rate sensor 11 is used as the estimated yaw rate γ ＾ (n). Then, the process proceeds to step S25, where the estimation results (γ (n), β
(n), V _X (n), and V _Y (n)) are stored as previous values, and a flag F indicating a type corresponding to the side slip estimation method used is set, and then the timer interrupt processing is terminated. Return to the predetermined main program.

On the other hand, if the result of the determination in step S22 does not satisfy the set condition, the flow shifts to step S26,
Estimated sideslip angle β ＾ (n) by sideslip angle estimation method for high speed
Then, the process proceeds to step S27, where the vehicle speed V (n) is set as the estimated front-rear direction speed V ＾ _X used in the low-speed side slip angle estimation method in step S23, and is estimated according to the following equation (13). After calculating the lateral velocity V ＾ _Y (n), the flow shifts to step S25.

V ＾ _X (n) = V (n) * tan (β ＾ (n)) (13) Also, the result of the determination in step S21 is that the previous estimation method is the low-speed sideslip angle estimation method. If there is, step S28
And the high wheel speed Vw of the left and right wheels of the front wheel 1F as the non-driving wheel from the high wheel speed Vw _RH of the left and right wheels of the rear wheel 1R as the driving wheel, similarly to the step S22.
_The value (Vw _RH -Vw _FH ) obtained by subtracting _FH is larger than the set value ΔVw _{2 which} is larger than the set value ΔVw ₁ set in advance, and the high wheel speed Vw _FH of the front wheel 1F as the non-drive wheel is set in advance to the set vehicle speed determining whether greater than Vw _S1 by large set vehicle speed _{Vw S2, (Vw RH -Vw FH} )> ΔVw
_{If 1} and Vw _FH > Vw _S2 , it is determined that the vehicle is in the high vehicle speed range or that no wheel spin has occurred in the drive wheels, and the process proceeds to step S26. Otherwise, wheel spin has occurred in the drive wheels. Then, the process proceeds to step S23.

The method for estimating the side slip angle for high speed in step S26 is based on the side slip angle β _f of the front wheel tire and the side slip angle β _{r of the} rear wheel tire based on the two-wheel motion model shown in FIG.
Can be expressed by the following equations (14) and (15).

Β _f = tan ^-1 ｛(V _Y -L _f γ) / V _X ｝ + δ (14) β _r = tan ^-1 ｛(V _Y -L _r γ) / V _X … ......... (15) further, in a state the vehicle speed V _X is large to some extent is possible linearization, a vehicle body side slip angle β and the longitudinal direction of the vehicle body speed V _X and lateral velocity V _Y represented by the following formula (16) And the following equation (1) is used instead of the equations (14) and (15).
The relations of the equations (7) and (18) are obtained, and finally, the linear two-wheel model of the following equations (19) and (20) is obtained.

Β = −V _Y / V _X (16) β _f = −β− (L _f γ / V _X ) + δ (17) β _r = −β + (L _r γ / V _X ) (18) MV _X (β ′ + γ) = 2CP _f ｛−β− (L _f γ / V _X ) + δ｝ + 2CP _r ｛−β + (L _r γ / V _X )｝ _{(19) I Z γ '=} 2L f CP f {-β- (L f γ / V X) + δ} -2L r CP r {-β + (L r γ / V X)} ...... (20) the linear The two-wheel model is as follows (2
It can be represented by the state space of 1) to (28).

[0066]

(Equation 1)

The observer is designed as shown in the following equation (30) for the vehicle models of the above equations (21) and (22). x ＾ ′ = Ax ＾ + Bu + Ly (30) where A, B, C, and D are matrices for calculating the motion of the vehicle. x ＾ is an estimated state amount, and L is a gain that determines a correction amount of the state estimated amount. Here, the error signal y〜 is obtained by the following equation (31), and the estimated state quantity x ＾ is obtained by the following equation (32).

Y〜 = y− (Cx ＾ + Du) (31)

[0069]

(Equation 2)

Therefore, step S31 in FIG.
Calculate the matrices A to D of the above equations (25) to (28),
Then, the process proceeds to step S32 to calculate the estimated yaw rate γ ＾ and the estimated side slip amount β ＾ using the above equations (29) and (30), and then proceeds to step S33.
After the calculated estimated yaw rate γ ＾ and the estimated side slip amount β ＾ are stored as the previous values, the process ends.

According to the third embodiment, the vehicle starts
Wheel spin on the rear wheel that is the driving wheel in low vehicle speed range such as time
If this occurs, the high-speed sideslip angle
Even if the setting method is selected, step S22
From step S23 to the first or second embodiment
Velocity V depending on the state_X(n) and estimated longitudinal velocity V 方向
_XBy feeding back the error signal with (n),
Estimated velocity V 前後 _X(n) and estimated lateral velocity V ＾_Y
(n) and the estimated sideslip angle β ＾ (n)
Estimation Method for Low-Speed Side-Slip Angle Using Evolving Side-Slip Angle Estimation Method
The estimated sideslip angle β ＾ (n) is calculated by the
The estimated sideslip angle β ＾ can be calculated in degrees.

From this state, if the wheel spin of the rear wheel as the driving wheel stops or the vehicle speed increases, step S
If the determination condition in step 28 is no longer satisfied, step S26
Then, the high-speed sideslip angle estimation process shown in FIG. 8 is executed, so that a highly accurate sideslip angle estimation can be performed in a high vehicle speed range.

In the third embodiment, the case where the estimated yaw rate γ ＾ and the estimated side slip angle β ＾ are calculated using the equations (25) to (31) as the high-speed sideslip estimation method will be described. However, the present invention is not limited to this, and other methods for estimating the sideslip angle, such as the first conventional example and the second conventional example described above, can be applied.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an overall configuration of a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a two-wheel motion model.

FIG. 3 is a block diagram showing an overall configuration of a second embodiment of the present invention.

FIG. 4 is a flowchart illustrating an outline of a calculation process according to the second embodiment.

FIG. 5 is a flowchart illustrating an outline of a calculation process according to a third embodiment of the present invention.

FIG. 6 is a flowchart illustrating an example of a high-speed sideslip angle calculation process according to the third embodiment.

[Explanation of symbols]

 Reference Signs List 10 vehicle state quantity estimation device 11 yaw rate sensor 12 longitudinal acceleration sensor 13 lateral acceleration sensor 14 wheel speed sensor 15 steering angle sensor 16 master cylinder pressure sensor 20 target braking force setting device 30 braking force control device

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) B62D 113: 00 137: 00

Claims (5)

[Claims] 1. A motion model that describes a state in which the vehicle is moving around a vertical axis in a front-rear direction and a lateral direction of the vehicle, wherein the motion model describes a motion in a front-rear direction. Using an error signal between the estimated longitudinal physical quantity estimated from the model and any of the actually measured longitudinal physical quantity and the longitudinal physical quantity obtained from another estimation method as a feedback signal, the vehicle body based on the motion model A vehicle side slip angle estimation method for estimating a vehicle side slip angle. 2. The method according to claim 1, wherein a longitudinal speed is set as the longitudinal physical quantity. 3. The vehicle body side slip angle estimating method according to claim 2, wherein the longitudinal speed uses one of a wheel speed and an estimated value of the wheel speed. 4. The method according to claim 1, wherein the larger value of the wheel speed of the driving wheel is larger than that of the non-driving wheel by a certain value or a certain ratio or more, and the wheel speed of the front wheel or the vehicle speed is smaller than a certain value. Using the vehicle body side slip angle estimation method of item 1,
A method for estimating a vehicle body side slip angle of a vehicle, wherein another method for estimating a vehicle body side slip angle is used in other cases. 5. A wheel speed calculating means for calculating a wheel speed of each wheel of a vehicle, a yaw rate detecting means for detecting a yaw rate generated in the vehicle body, and a wheel speed detected by the wheel speed calculating means and the yaw rate detecting means. Forward / backward speed calculating means for calculating a forward / backward speed based on the detected yaw rate; and an error signal between the forward / backward speed calculated by the forward / backward speed calculating means and the estimated forward / backward speed, fed back and forth and forward and backward. A vehicle body slip angle estimating device comprising: a speed estimating means for estimating a speed; and a skid angle calculating means for calculating a skid angle based on the longitudinal and lateral speeds estimated by the speed estimating means. .