JPH08198131A - Car condition presuming device - Google Patents

Abstract

PURPOSE: To presume the car running condition accurately during its running by setting a model of the tire characteristics for the wheel load, and presuming the car condition on the basis of the set tire model. CONSTITUTION: A car condition presuming device is equipped with load sensors 16a-16d mounted on respective wheels and a free gyro 14 accommodating a lateral acceleration sensor and yawrate sensor, car speed sensor 12, and steering angle sensor, and the outputs of these sensors are supplied to an electronic unit(ECU). On the basis of the outputs from sensors, the ECU judges whether each wheel maintains proper gripping condition, and on the basis of the result therefrom a presumption is made whether the car is in stable run. Thus the gripping condition is judged on the basis of the relation to the slip angle of the characteristic value reflecting the variation of the road surface and/or wheel condition and also corresponding to the actual wheel load and the running condition of the car is presumed accurately.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle state estimating device, and more particularly, to setting a tire model corresponding to the motion state of the vehicle while the vehicle is traveling and estimating the traveling state of the vehicle based on the tire model. Vehicle state estimating device.

[0002]

2. Description of the Related Art Conventionally, for example, JP-A-5-69845.
As disclosed in the publication, there is known a device that detects whether or not the running state of a vehicle is stable from the relationship between the slip angle of the steered wheels and the restoring torque that acts on the steered wheels.

That is, the change rate ΔT / ΔG of the restoring torque T of the steered wheels with respect to the change of the lateral acceleration G acting on the vehicle.
Reaches almost "0" just before the tire reaches the skid limit. The device described in the above publication focuses on such characteristics, and tries to determine the grip state of the steered wheels based on whether or not the absolute value of ΔT / ΔG is equal to or greater than a predetermined value.

In this case, the change rate ΔT / Δ of the restoring torque T
If the absolute value of G is equal to or greater than the predetermined value, it can be determined that the steered wheels are traveling while maintaining an appropriate grip state, that is, the traveling state of the vehicle is stable, while ΔT
If the absolute value of / ΔG is less than the predetermined value, it can be determined that the steered wheels have reached the skid limit, that is, the running state of the vehicle is unstable.

[0005]

However, the above-mentioned conventional apparatus determines whether or not the steered wheels have reached the skid limit based on the relationship between the slip angle and the restoring torque preset by using a trailer tester or the like. This is a judgment device.

More specifically, after setting the condition of the steered wheels, the road surface μ, etc. to the standard condition, it is possible to judge that the steered wheels have reached the skid limit. The configuration is such that ΔG is obtained, and whether or not the steered wheels maintain an appropriate grip state is determined using the value of ΔT / ΔG as a threshold value.

Therefore, for example, the air pressure of the steered wheels, the groove depth,
The rate of change ΔT / Δ of the steering torque T that appears when the steered wheels reach the skid limit due to changes in the road surface μ, vehicle loading conditions, etc.
When the value of G fluctuates from a preset value, it becomes difficult to accurately detect the grip state of the steered wheels.

In this sense, the above-mentioned conventional vehicle state estimating device can properly estimate the vehicle state under standard driving conditions, but the actual use environment in which the state of the steered wheels, the road surface μ and the like change. Below, there is a problem that the vehicle state cannot always be estimated accurately.

The present invention has been made in view of the above-mentioned points, and a tire model is appropriately set on the basis of the motion state of a vehicle, and the tire model is used to estimate the state of the wheels, so that the tire model is always accurate. It is an object of the present invention to provide a vehicle state estimation device capable of estimating the vehicle state.

[0010]

FIG. 1 is a block diagram showing the principle of a vehicle state estimating device for solving the above problems. That is, the above-mentioned objects are, as shown in FIG. 1, steering angle detecting means M1 for detecting a steering angle, vehicle speed detecting means M2 for detecting a vehicle speed, vehicle behavior detecting means M3 for detecting a vehicle behavior,
A load detecting means M4 for detecting a wheel load, a slip angle estimating means M5 for estimating a slip angle of a wheel based on a steering angle, a vehicle speed and a vehicle behavior, and a wheel characteristic based on a steering angle, a vehicle speed and a vehicle behavior. The characteristic of the tire with respect to the wheel load based on the characteristic value estimation means M6 for estimating the value, the estimation result of the slip angle estimation means M5, the estimation result of the characteristic value estimation means M6, and the detection result of the load detection means M4. The vehicle state estimating device includes a tire model setting means M7 for setting a model of the vehicle and a vehicle state estimating means M8 for estimating the vehicle state based on the tire model set by the tire model setting means M7.

[0011]

In the present invention, the steering angle detecting means M1, the vehicle speed detecting means M2, and the vehicle behavior detecting means M3.
Detects the steering angle of the steered wheels, the vehicle speed, and the vehicle behavior, respectively.

The slip angle estimating means M5 is
Based on the steering angle, the vehicle speed, and the vehicle behavior, the slip angle, that is, the angle formed by the traveling direction of the wheel and the center plane of the wheel is estimated. Further, the characteristic value estimating means M6, based on the steering angle, the vehicle speed, and the vehicle behavior, the characteristic value representing the grip state of the wheel, that is, the cornering force,
At least one of the longitudinal force or the restoring torque is estimated.

By the way, the characteristic value of the wheel and the slip angle of the wheel are correlated with each other. The relationship between the two changes in accordance with changes in the wheel condition, road surface μ, wheel load, and the like. On the other hand, the tire model setting means M7
The slip angle estimating means M5 and the characteristic value estimating means M
Based on the estimation result of No. 6 and the detection result of the load detecting means M4, a tire model representing the relationship between the characteristic value for the wheel load and the slip angle is set.

Therefore, when the wheel condition, the road surface μ, etc. are changed while the vehicle is being used, the slip angle estimating means M5 and the characteristic value estimating means M6 are adapted to the slip angle and the characteristic value according to the situation. Then, the tire model setting means M7 sets a tire model corresponding to the changed situation.

Then, the vehicle state estimating means M8 determines the grip state of the wheels by using the tire model in which the changes in the wheel state and the road surface μ are appropriately reflected as described above, and the vehicle state is determined based on the determination result. Estimate if it is in a state.

[0016]

FIG. 2 is a perspective view showing a mounting state of various sensors constituting a vehicle state estimating device according to an embodiment of the present invention. Further, FIG. 3 shows a block configuration diagram of the vehicle state estimating device of the present embodiment.

As shown in FIGS. 2 and 3, the vehicle state estimating device according to the present embodiment has a steering angle sensor 10, a vehicle speed sensor 12,
The yaw rate sensor 14a and the lateral acceleration sensor 14b are incorporated in the free gyro 14, and the load sensors 16a to 16d provided in each wheel are provided.

The steering angle sensor 10 is a sensor for detecting the steering angle δ of the front wheels, which are the steered wheels, and is mounted on the steering rack. The vehicle speed sensor 12 is a sensor that emits a signal according to the rotation speed of the front wheels, which are the driving wheels, and is mounted near the drive shaft connected to the front wheels.

The yaw rate sensor 14a is a sensor for detecting a yaw angular velocity γ about the center of gravity of the vehicle, and the lateral acceleration sensor 14b is a sensor for detecting a lateral acceleration G acting on the center of gravity of the vehicle. Free gyro 14
Is arranged at the center of gravity of the vehicle.

The load sensors 16a to 16d are sensors for detecting the loads applied to the four wheels, respectively, and are arranged at the upper end of the shock absorber in this embodiment. The steering angle sensor 10, the vehicle speed sensor 12, the yaw rate sensor 14a, and the lateral acceleration sensor 14 described above.
Outputs of b and the load sensors 16a to 16d are supplied to an electronic control unit (ECU) 20 as shown in FIG.

The ECU 20 is a main part of the vehicle state estimating device of the present embodiment, and judges whether or not each wheel maintains an appropriate grip state based on the output supplied from each of the above-mentioned sensors, Based on the result, it is estimated whether the vehicle is traveling stably. Hereinafter, the content of the process executed by the ECU 20 to estimate the vehicle state in the present embodiment will be described.

By the way, the ECU 20 estimates the vehicle state based on the tire modeling by the magic formula, that is, the slip angle β of the wheel with respect to a specific wheel load F _Z (the traveling direction of the wheel and the wheel while the vehicle is traveling). The angle between the center plane of the wheel and the cornering force C _F is detected, and based on the detection result, the relationship between the slip angle β and the cornering force C _F established for an arbitrary wheel load F _Z ( (Hereinafter, referred to as a tire model) is set and the vehicle state is estimated based on the tire model.

FIG. 4 is an equivalent two-wheeled vehicle model of a four-wheeled vehicle used for estimating the wheel slip angle β and the cornering force C _F based on the output of each sensor when the ECU 20 performs such processing. Is. As shown in the figure, the center of gravity - front inter-axle distance L _f, the center of gravity - rear wheel axle distance of L _r, vehicle speed V, _c the traveling direction angle of the center of gravity with respect to the axle beta, the front wheel slip angle beta _f, The rear wheel slip angle is β _r , the yaw angular velocity around the center of gravity is γ, the steering angle is δ, and the front 2
When the resultant force of the cornering forces of the wheels is 2C _Ff and the resultant force of the cornering forces of the rear two wheels is 2C _Fr , the following equation of motion is established. However, m in the following formula is vehicle weight,
I is the yaw moment of inertia.

MV (dβ _c / dt + γ) = 2C _Ff + 2C _Fr ... (1) I · dγ / dt = L _f · 2C _Ff −L _r · 2C _Fr ... (2) β _f = β _c + L _f γ / V−δ (3) β _r = β _c −L _r γ / V (4) That is, the first term (mV · dβ _c / d) on the left side in the above formula (1).
t) is the translational acceleration (V · d) acting on the center of gravity of the vehicle.
β _c / dt) is the product of vehicle weight (m) and the second term (mVγ) on the left side is the centrifugal force acting on the vehicle. Therefore, the total value thereof becomes the total value of the lateral forces acting on the vehicle, and is balanced with 2C _Ff + 2C _{Fr shown on the} right side.

In addition, the left side of the equation (2) (I · dγ / dt
) Represents the torque required to rotate the object having the moment of inertia I with the angular acceleration dγ / dt. On the other hand, the first term on the right side (L _f · 2C _Ff ) is the lateral force 2C of the front two wheels.
The turning direction of the torque generated due to _ff, also represents the second term on the right side (-L _r · 2C _Fr) is anti turning direction generated due to the lateral force 2C _Fr of 2 rear wheels torque respectively . Therefore, the total value on the right side becomes the total value of the torques acting in the direction of turning the vehicle and is balanced with the left side.

Further, when the yaw angular velocity is γ as shown in FIG. 4, the velocity vector V _{f of the} front wheels is a composite vector of the vector of the size L _f γ toward the inside of the turn and the vehicle speed V,
Further, the velocity vector V _r of the rear wheel can be understood as a combined vector of the vector of the size L _r γ going outward in the turn and the vehicle speed V.

In this case, the angle formed by the direction of the vehicle speed V and the traveling direction of the front wheels and the angle formed by the direction of the vehicle speed V and the traveling direction of the rear wheels are L _f γ / V and L _r γ, respectively. / V
It can be expressed as. Accordingly, it is an angle formed in the center plane of the front wheel and the traveling direction of beta _f, and, beta _f is an angle formed in the center plane of the rear wheel and its traveling direction, each of the above (3)
It can be expressed as the formula or the formula (4).

By the way, in the above equation (1), "V (dβ _c
/ dt + γ) "is the total value of the lateral acceleration acting on the vehicle. Therefore, the value can be obtained as the output value of the lateral acceleration sensor 14b. In the following description, the above" The value of V (dβ _c / dt + γ) ”will be referred to as“ lateral acceleration G ”.

In the above equations (1) and (2), m,
I, L _f , and L _r are values determined by the specifications of the vehicle and can be treated as constants. Therefore, by substituting the vehicle speed V detected by the vehicle speed sensor 12, the yaw angular velocity γ detected by the yaw rate sensor 14a, and the lateral acceleration G detected by the lateral acceleration sensor 14b, the above equations (1) and (2) can be used as the front and rear wheels. cornering force C _Ff, become a secondary simultaneous equation for C _Fr, it is possible to obtain the C _Ff, C _Fr by solving this.

On the other hand, in the above equations (3) and (4), β _c
Can be obtained by dividing the lateral acceleration G = V (dβ _c / dt + γ) by the vehicle speed V and then integrating the value obtained by subtracting the yaw angular velocity γ from the value. Therefore, by substituting the vehicle speed V, the yaw angular velocity γ, and the lateral acceleration G, the slip angles β _f and β _r of the front and rear wheels can be obtained from the equations (3) and (4).

As described above, when the equivalent two-wheeled vehicle model of the four-wheeled vehicle shown in FIG. 4 is used, the slip angles of the front and rear wheels are made by the hardware configuration of this embodiment shown in FIGS. 2 and 3. β _f , β _r (hereinafter, simply referred to as slip angle β), and front and rear wheel cornering forces C _Ff , C _Fr (hereinafter, simply referred to as cornering force C _F) Called) can be estimated.

By the way, the cornering force C of the wheel
_F is generated by elastic deformation of the wheel contact surface due to the slip angle β. In this case, if the slip angle β is within an appropriate range, the wheel can maintain an appropriate grip state, and its elastic deformation amount is approximately proportional to β.

However, since the elastically deformable region of the wheel is finite, if β continues to increase, the amount of elastic deformation eventually reaches a saturated state, and the wheel cannot maintain an appropriate grip state. For this reason, the relationship between the wheel slip angle β and the cornering force C _F is such that if the wheel condition, wheel load, road surface μ, etc. are the same, C _F until a certain critical value is reached as shown in FIG. Is approximately proportional to β, and in the region where β exceeds the critical value, C _F exhibits a characteristic that it saturates to almost the maximum value max or the minimum value min. Therefore, if it can be determined whether or not the slip angle β of the wheel is within the proportional range of C _F , then it can be determined whether or not the wheel maintains an appropriate grip state.

The β- _CF characteristic diagram shown in FIG. 5 is a point object center of the characteristic diagram ( _CF is the maximum value max and the minimum value due to the tread pattern of the tire, the camber angle of the wheels, etc.). The point where the average value of min) is shifted from the origin is illustrated. In this case, the center of the point object is (β,
If C _F ) = (Sh, Sv), then (X,
Y) = (β-Sh, _CF- Sv) coordinate axes (X, Y)
By setting, the center of the point object can be made to coincide with the origin (0, 0) as shown in FIG. Further, when such conversion is performed, it is possible to treat the region of X> 0 and the region of X <0 equally, which is convenient for analyzing the characteristics of the wheel.

Therefore, in the present embodiment, the relationship between the slip angle β and the cornering force C _F is analyzed as described later, and the tire model regarding the relationship between them is set based on the analysis result (X, Y) = (β-S
The coordinate axes (X, Y) of h, _CF- Sv) are used.

The cornering force C _F generated on the wheel is equal to the frictional force generated between the wheel and the road surface. Therefore, even if the condition of the wheels and the road surface μ are the same,
If the wheel load F _Z changes, the relationship between the slip angle β and the cornering force C _F also changes.

On the other hand, in the vehicle state estimating device of this embodiment, the actual motion state of the vehicle is determined based on the detection results of the steering angle sensor 10, the vehicle speed sensor 12, the yaw rate sensor 14a and the lateral acceleration sensor 14b. As described above, the corresponding slip angle β and the cornering force C _F can be estimated, and the wheel load of each wheel can be detected using the load sensors 16a to 16d.

Therefore, in the ECU 20, the estimated values of the slip angle β and the cornering force C _F can be sorted and stored for each wheel load F _Z , and the stored data thereof are described above (X, Y). ) By applying the coordinates, a plurality of characteristic curves can be obtained for each wheel load F _{Z as} shown in FIG. 7. Incidentally, FIG. 7 shows the wheel load of 2KN, 4
This is an example of the case where the characteristic curves are obtained for KN and 6KN.

By the way, FIG. 8 shows a general form of a characteristic diagram showing the relationship between the slip angle β and the cornering force C _F. In the figure, D is (β, _CF )
The maximum value of Y when is expressed on the (X, Y) coordinates,
Xm is the value of X that maximizes Y, Ys is the convergent value of Y, and BC
D is the slope of the characteristic curve at X = 0.

In this case, the characteristic curve shown in the (X, Y) coordinates in FIG. 8 can be expressed by the following general formula. Y (X) = D sin [C tan ⁻¹ {B · X−E (B · X− tan ⁻¹ (B · X))}] where C = 2 / π sin ⁻¹ (Ys / D) E = {B · Xm− tan (π / 2C)} / {B · Xm− tan ⁻¹ (B · Xm)} (5) Here, the wheel slip angle β and the cornering force C
The relationship between the _F is changed in accordance with the wheel load F _Z are as defined above, B, C, D, the coefficient of E such is a value recognized as a function of the wheel load F _Z.

The coefficient C is a value that is almost uniquely determined by the characteristics of the tire to be expressed by using the above equation (5), and in this embodiment, it should be treated as a constant representing the characteristics of the cornering force C _F. You can Therefore, as shown in FIG. 7, a coefficient corresponding to each wheel load F _Z is read from a plurality of characteristic curves set for several different kinds of wheel loads F _Z , and a general formula for each coefficient is read based on the read values. 9 can be specified, a tire model representing a characteristic curve for an arbitrary wheel load F _Z can be set as shown in FIG. Note that FIG. 9 exemplifies a case where eight characteristic curves are set for a wheel load F _Z of 1 KN to 8 KN.

Then, in this way, an arbitrary wheel load F _Z
If a tire model expressing the characteristic curve of can be set, it is possible to accurately recognize the region of the slip ratio β in which the wheel can maintain an appropriate grip state in correspondence with the actual wheel load F _Z. It is possible to accurately estimate whether or not the traveling state of the vehicle is stable, based on whether or not β is within the range.

Further, the tire model as shown in FIG. 9 is a model set based on the actual motion state of the vehicle while it is running. Therefore, if the relationship between the slip angle β and the cornering force C _F with respect to the wheel load F _Z fluctuates due to changes in the wheel condition and the road surface μ, the fluctuation is appropriately reflected in the tire model, and the actual vehicle condition is always maintained. It is possible to make an appropriate estimation according to

The vehicle state estimating device of the present embodiment is a device for estimating the vehicle state by using such a method, and the contents of the processing executed by the ECU 20 to realize the above estimating method will be described below. explain. FIG. 10 shows the ECU 2.
0 shows a flowchart of an example of a characteristic curve identification routine that is executed to identify characteristic curves for a plurality of wheel loads F _Z as shown in FIG. 7. It should be noted that this routine is a timed interrupt routine that is activated every predetermined time.

When the routine shown in FIG. 10 is started, first in step 100, as data sampling,
For each wheel load F _Z = in (n = 1 to 3), an appropriate number of pairs of slip angle β and cornering force C _F are calculated. Here, in the present embodiment, i
_{1 = 2KN, i 2 = 4KN} , i 3 = a 6KN.

After the above data sampling is completed, in is set to i ₁ (= 2KN) in step 102, and then
Proceeding to step 104, (β, C for F _Z = in
_F ) read. Steps 106, 108 and 110 are
Of the data read as described above, respectively, beta is a C _F when it is the predetermined value "+ alpha" as C _{F +,} the C _F when beta is a predetermined value "-.alpha." as C _F-, also, This is a step of reading C _F when C is “0” as C _F0 .

[0047] After finishing the above processing, in step 112, C _F + stored as described above, C _F-, and using C _F0, a _{(C F + + C F-)} / 2-C F0 becomes operational Then, the calculated value is stored as Sv. That is, the ECU
In Fig. 20, when the wheel slip angle β and the cornering force C _F are estimated based on the outputs of various sensors and they are used to identify a plurality of characteristic curves as shown in Fig. 7, (β, C _F ) It is necessary to convert the data on the coordinates to the data on the (X, Y) coordinates, and for that purpose, Y
It is necessary to perform an operation of = _CF- Sv.

In this case, since Sv is the average value of the maximum value max and the minimum value min of C _F (see FIG. 5 above),
It is most appropriate to calculate and calculate max and min, but max and min are not always detected during normal traveling. Therefore, in the present embodiment, by performing the processing of steps 106 to 112, Sv is specified within the range of the slip angle β that is always detected during normal traveling.

[0049] After identifying the thus Sv, in order to identify the Sh which is obtained in response to Sv, a slip angle beta in C _F = Sv and beta ₀ in step 114, stores the beta ₀ as Sh In step 116 To do. Then, in step 118, (X, Y) = (β−Sh, C _F −
Sv) (X, Y) is stored as data at Fz = in, and in the following step 120, the characteristic curve corresponding to Fz = in is identified from the set of (X, Y).

[0050] Then, it is determined whether or not in = i ₃ at step 122, and terminates the current process if in = i _3,
If in = i _{3 is} not satisfied, n is incremented in step 124 and the processes in step 104 and thereafter are executed again. As a result, when the present routine ends, as shown in FIG. 7, three characteristic curves for F _Z = i ₁ , i ₂ , i ₃ can be identified on the (X, Y) coordinates.

FIG. 11 shows a flow chart of an example of a tire model setting routine executed by the ECU 20 to set a tire model applicable to an arbitrary wheel load F _Z from the three characteristic curves identified as described above. Less than,
The details of the processing for setting the tire model will be described in detail with reference to FIG.

When the routine shown in FIG. 11 is started, first,
In step 200, F_Z= I ₁, I₂, I₃Nitsu
Read the maximum value of Y from each characteristic curve,
Their values D₁, D₂, D₃(Hereinafter, these are collectively referred to as
In this case, it is recorded as Dn).

At step 202, each characteristic curve is
Road surface μ, that is μ₁, Μ₂, Μ ₃(Hereafter, these
When collectively called, it is described as μn). Where D above
n is the road surface μn and the wheel load F_Z= Multiplication value of in,
It can be obtained by an operation of μn = Dn / in.

By the way, it is known that the road surface μ formed between the wheel and the road surface can be expressed as the following equation as a linear function of the wheel load F _Z. μ = a ₁ F _Z + a ₂ (6) Therefore, if the value of μn and in obtained in the above step 202 are substituted into μ and F _Z in the above equation (6), two unknowns are obtained. Can be set to three equations, and by adapting the solutions of these equations, the unknowns a ₁ ,
It is possible to specify a ₂ . In this routine, step 204 is a step of calculating the coefficients a ₁ and a ₂ related to μ according to such a procedure.

Further, if a ₁ and a ₂ are found as described above, the maximum value D of Y in the characteristic curve is F _Z
Can be set as a function of. D = μ · F _Z = (a ₁ F _Z + a ₂ ) F _Z (7) Therefore, in the present embodiment, when a ₁ and a ₂ are found as described above, the calculation is performed in the following step 206. , D is set to the general formula D (F _Z ). In this case, if the wheel load F _Z is specified thereafter, D for that F _Z can be specified immediately.

At step 208, F_Z= I₁, I₂,
i₃From the characteristic curve for
Read the slope of the characteristic curve and calculate the values by BCD₁, B
CD ₂, BCD₃(Hereinafter, these are collectively referred to as BC
Dn).

It is known that the slope BCD of the characteristic curve near the origin can be expressed by the following equation using the two coefficients a ₃ and a ₄ . BCD = a ₃ sin {2 tan ⁻¹ (F _Z / a ₄ )} (8) Therefore, the BCDn obtained in the above step 208 and the corresponding in are the BCD in the above equation (8), and F _Z
By substituting into, three equations can be set for the two unknowns, and the unknowns a ₃ and a ₄ can be specified. Further, when substituting a ₃ and a ₄ found as described above, the above equation (8) is converted into the general equation BCD for BCD.
It can be treated as (F _Z ).

Therefore, in this routine, after the processing in step 208 is completed, the coefficients a ₃ and a ₄ relating to BCD are calculated in step 210, and then in step 212, the general formula BCD for BCD is calculated.
(F _Z ) is set. In this case,
If the wheel load F _Z is specified, the BCD for that F _Z
Can be identified immediately.

In step 214, F _Z = i ₁ , i ₂ ,
From the characteristic curves for i ₃ , Sh ₁ , S
A process of reading h ₂ and Sh ₃ (hereinafter, referred to as Shn when they are collectively referred to) and storing their values is performed. Here, it is known that the correction value Sh of the origin deviation of the characteristic curve can be expressed as a linear function of Fz using the two coefficients a ₅ and a ₆ as in the following equation.

Sh = a ₅ F _Z + a ₆ (9) Therefore, by substituting the Sh obtained in step 214 and the corresponding in for Sh and F _Z in the equation (9), respectively. Three expressions can be set for two unknowns, and the unknowns a ₅ and a ₆ can be specified. Furthermore, when a ₅ and a ₆ found as described above are substituted, the above expression (9) is replaced by the general expression Sh (F _Z ) for Sh.
Can be treated as

Therefore, in this routine, after the processing of step 214 is completed, the coefficients a ₅ and a ₆ relating to Sh are calculated in step 216, and then in step 218, the general formula Sh (F _Z )
Is to be set. In this case, if the wheel load F _Z is specified thereafter, Sh for that F _Z can be specified immediately.

In step 220, F _Z = i ₁ , i ₂ , i
_From the characteristic curves for ₃ , Sv ₁ , Sv ₂ ,
Sv ₃ is read (hereinafter, when these are collectively referred to as Sh,
(n), the step of storing those values. Here, the correction value Sv of the deviation of the origin of the characteristic curve is determined by the two coefficients a.
It is known that a linear function of Fz can be expressed by the following equation using ₇ and a ₈ .

Sh = a ₇ F _Z + a ₈ (10) Therefore, by substituting Svn and the corresponding in obtained in step 220 for Sv and F _Z in the above equation (10), respectively, Three expressions can be set for two unknowns, and the unknowns a ₇ and a ₈ can be specified. Further, when substituting a ₇ and a ₈ found as described above, the above equation (10) is converted into the general equation Sv (F
_Z ) can be treated.

Therefore, in this routine, after the processing of step 220 is completed, the coefficients a ₇ and a ₈ relating to Sv are calculated in step 222, and then in step 224, the general expression Sv (F _Z )
Is to be set. In this case, if the wheel load F _Z is specified thereafter, Sv for that F _Z can be specified immediately.

Next, in step 226, F _Z = i ₁ ,
From the characteristic curves for i ₂ and i ₃ , the value of X at which Y is maximum is read, and these values are set to Xm ₁ and X
m ₂ and Xm ₃ (hereinafter, these are collectively referred to as Xmn) are stored. In step 228, the Dn read in step 200 and the step 2
Using BCDn read in 08 and C preset as a constant, B = BCDn / (C · Dn) corresponding to the characteristic curves for F _Z = i ₁ , i ₂ , i ₃ is calculated,
The result is stored as B ₁ , B ₂ and B ₃ (hereinafter, these are collectively referred to as Bn).

Then, in step 230, these B
where n, C, and Xmn are shown in the proviso in the above formula (5) E =
{B · Xm− tan (π / 2C)} / {B · Xm− tan ⁻¹
(B · Xm)}, and E corresponding to each characteristic curve for F _Z = i ₁ , i ₂ , i ₃ is calculated, and the result is calculated as E ₁ , E ₂ , E ₃ (hereinafter, these When collectively called, it is recorded as En).

Here, E used in the above equation (5)
It is known that can be expressed by the following equation using three coefficients a ₉ , a ₁₀ and a ₁₁ . E = (a ₉ F _Z + a ₁₀ ) {1-a ₁₁ · sin (β + Sh)} (11) Therefore, the En obtained in step 220 above and the Shn obtained in step 214 above and corresponding in And slip angle β in Eq. (11) above, E, Sh, F _Z ,
By substituting for β, three expressions can be set for the three unknowns, and the unknowns a ₉ , a ₁₀ and a ₁₁ can be specified. In addition, a _9, which it was found as described above,
When a ₁₀ and a ₁₁ are substituted, the above formula (11) can be treated as a general formula E (F _Z ) for E.

Therefore, in this routine, when the processing of step 230 is completed, then step 23 is performed.
2, the coefficients a ₉ , a ₁₀ and a ₁₁ related to E are calculated,
Then, in step 234, the general expression E for E
(F _Z ) is set and the current processing is ended. In this case, if the wheel load F _Z is specified thereafter, E for that F _Z can be specified immediately.

As described above, when the ECU 20 executes this routine, the coefficients B, C, and
Sh, Sv used to transform D, E, and (β, _CF ) coordinates into (X, Y) coordinates can all be uniquely determined for F _Z. Thus, in the ECU 20, for any F _Z as required such characteristic curve shown in FIG. 9, i.e., by setting the tire model representing the relationship between the slip angle β and the cornering force C _F for any F _Z You can

FIG. 12 shows a flowchart of an example of a vehicle state estimation routine executed by the ECU 20 to estimate the traveling state of the vehicle using the tire model set as described above. In the routine shown in the figure, first, step 3
00, the actual wheel load F applied to the focused wheel
_{Read Z.}

Next, at step 302, by using the tire model set as described above, X where the conversion value Y of the cornering force C _F becomes maximum when the wheel load is F _Z , that is, Xm (see FIG. 8). ), And the conversion value Sh for converting the slip angle β into the conversion value X are calculated.

Then, in step 304, the slip angle β for the wheel of interest is read, and in step 306, using the Sh read in step 302, the slip angle β is a value on the (X, Y) coordinates. X = β-S
Perform processing to convert to h. In this case, if the converted value X of the actual slip angle β is Xm or less, it is determined that the cornering force C _F is in a region proportional to the slip angle β, that is, the wheel maintains an appropriate grip state. Yes, on the other hand, if X exceeds Xm, the slip angle β has reached a saturated state with respect to the cornering force C _F ,
That is, it can be determined that the wheels have reached the skid limit.

Therefore, in this routine, subsequent to the above-mentioned processing, it is judged in step 308 whether X ≦ Xm holds. Then, if the above condition is satisfied, the routine proceeds to step 310, where the fact that the running state of the vehicle is stable is output and the processing of this time is ended. On the other hand, if the above condition is not satisfied, the routine proceeds to step 312 and the vehicle is executed. The fact that the traveling state of is unstable is output and the processing of this time is ended.

In this case, since the wheel load of each wheel is reflected in the factor for estimating the running state of the vehicle, a high estimation accuracy can be always maintained even when the loading state of the vehicle changes. . Further, since the tire model set by the ECU 20 reflects the actual motion state of the vehicle, if the tire air pressure, groove depth, road surface μ, or the like changes, those changes are appropriately reflected in the tire model. To be done. Therefore, according to the vehicle state estimating device of the present embodiment,
State estimation is performed based on an appropriate tire model that fluctuates according to changes in the running conditions of the vehicle, and the vehicle state can always be estimated with high accuracy.

In the above embodiment, the cornering force C _F is focused on as the characteristic value of the wheel and the tire model is set for the cornering force C _F , but the characteristic value of the wheel is not limited to this. For example, it is possible to set the tire model for the longitudinal force of the wheel generated in the front-rear direction of the vehicle, the restoring torque for turning the wheel in the straight direction, or the like as characteristic values.

In the above embodiment, each steering sensor 10 has a vehicle speed sensor 12 in addition to the steering angle detecting means M1.
To the vehicle speed detecting means M2 described above, the free gyro 14 to the vehicle behavior detecting means M3 described above, and the load sensor 1
6a to 16d correspond to the load detecting means M4 described above.

Further, the ECU 20 estimates the slip angle β of the wheel by using the equivalent two-wheel vehicle model of the four-wheel vehicle shown in FIG. 4, and the above-mentioned slip angle estimating means M5.
However, the characteristic value estimating means M6 is realized by estimating the cornering force C _{F of the} wheel.

Further, based on those estimated values, the ECU 20
By executing the characteristic curve identifying routine shown in FIG. 10 and the tire model setting routine shown in FIG. 11 by the tire model setting means M7.
The vehicle state estimating means M8 described above is realized by executing the vehicle state estimating routine shown in FIG.

[0079]

As described above, according to the present invention, in the tire model setting means, the tire model in which the changes in the wheel condition and the road surface μ are appropriately reflected, that is, the relationship between the characteristic value and the slip angle with respect to the wheel load is calculated. Can be set.

Therefore, according to the vehicle state estimating apparatus of the present invention, the vehicle wheel load is dealt with based on the relationship between the characteristic value and the slip angle, which corresponds to the actual wheel load and reflects the variation of the wheel state and the road surface μ. You can judge the grip state of the wheel,
While the vehicle is traveling, it is possible to accurately estimate the traveling state of the vehicle.

[Brief description of drawings]

FIG. 1 is a principle configuration diagram of a vehicle state estimation device according to the present invention.

FIG. 2 is a perspective view showing a mounted state of various sensors that form the vehicle state estimation device that is an embodiment of the present invention.

FIG. 3 is a block configuration diagram of a vehicle state estimating device of the present embodiment.

FIG. 4 is an equivalent two-wheel vehicle model of a four-wheel vehicle used for estimating a wheel slip angle β and a cornering force C _F in the present embodiment.

FIG. 5: Wheel slip angle β and cornering force C
It is an example of a characteristic curve showing the relationship with _F.

[FIG. 6] Wheel slip angle β and cornering force C
It is an example of the case where the characteristic curve showing the relationship with _F is shown on the conversion coordinates.

FIG. 7 is an example of a characteristic curve identified on the basis of actual measurement values by the vehicle state estimating device of the present embodiment.

FIG. 8: Wheel slip angle β and cornering force C
It is a general form that expresses the relationship with _F.

FIG. 9 is an example of a tire model set in the vehicle state estimating device according to the present embodiment.

FIG. 10 is a flowchart of an example of a characteristic curve identification routine executed in this embodiment.

FIG. 11 is a flowchart of an example of a tire model setting routine executed in this embodiment.

FIG. 12 is a flowchart of an example of a vehicle state estimation routine executed in this embodiment.

[Explanation of symbols]

 M1 steering angle detecting means M2 vehicle speed detecting means M3 vehicle behavior detecting means M4 load detecting means M5 slip angle estimating means M6 characteristic value estimating means M7 tire model setting means M8 vehicle state estimating means 10 steering angle sensor 12 vehicle speed sensor 14 free gyro 14a yaw rate Sensor 14b Lateral acceleration sensor 16a-16d Load sensor 20 Electronic control unit (ECU)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location B62D 113: 00 137: 00

Claims (1)

[Claims] 1. A steering angle detecting means for detecting a steering angle, a vehicle speed detecting means for detecting a vehicle speed, a vehicle behavior detecting means for detecting a vehicle behavior, a load detecting means for detecting a wheel load, a steering angle and a vehicle speed. , And a slip angle estimating means for estimating the slip angle of the wheel based on the vehicle behavior, a characteristic value estimating means for estimating a characteristic value of the wheel based on the steering angle, the vehicle speed, and the vehicle behavior, and the slip angle estimating means. Based on the estimation result, the estimation result of the characteristic value estimation means, and the detection result of the load detection means, a tire model setting means for setting a model of the characteristics of the tire with respect to the wheel load, and the tire model setting means set. A vehicle state estimating device, comprising: vehicle state estimating means for estimating a vehicle state based on a tire model.