JPH01101439A - Detecting device for road surface friction coefficient - Google Patents

Abstract

PURPOSE:To adjust the response and stability of road surface coefficient estimation properly by calculating a road surface friction coefficient according to a driving state and then integrating the calculated value and varying its integral time constant according to the traveling conditions of a vehicle. CONSTITUTION:When a vehicle turns, a friction coefficient arithmetic means 39 calculates the road surface friction coefficient mu according to the stability factor of the vehicle stored in a storage means 31 and variables such as the lateral acceleration of the gravity center of the vehicle, front and rear steering angles, and vehicle speed detected by a motion state detecting means 51, a steering state detecting means 37, and a vehicle speed detecting means 53. Then an integration processing means 40 integrates the value, so variation in the road surface friction coefficient mu is smoothed. In this case, a time constant varying means 41 varies the integral time constant at the time of integration processing according to the traveling conditions of the vehicle.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a friction coefficient detection device that detects a road surface friction coefficient between a vehicle tire and a road surface, and particularly relates to a friction coefficient detection device that detects a road surface friction coefficient between a vehicle tire and a road surface. This relates to a device that detects the coefficient of friction.

(Prior Art) Conventionally, as a friction coefficient detection device for detecting a road surface friction coefficient between a vehicle tire and a road surface, for example, Japanese Patent Application Laid-Open No. 1986-
As disclosed in Japanese Patent No. 148769, a plurality of values of the road surface friction coefficient are predicted according to the steering angle of the front wheels, lateral acceleration corresponding to each of the predicted friction coefficients is calculated, and the calculated lateral acceleration is calculated. By comparing the actual lateral acceleration and selecting the predicted friction coefficient corresponding to the closest value,
A known vehicle attempts to estimate an actual friction coefficient and use this estimated friction coefficient to control the rear wheel steering angle during cornering.

(Problems to be Solved by the Invention) However, normally, disturbances due to the operation of various devices and driving conditions are added to a vehicle control device, and there are also variations in the detected values of each sensor.

Furthermore, since the grip force of the road surface on the tires fluctuates greatly intermittently, the lateral acceleration of the vehicle often fluctuates greatly. In such a case, the error in the calculated value of the road surface friction coefficient, especially its fluctuation, becomes large.

Therefore, the conventional method described above has a problem in that it is not possible to perform sufficiently stable control under conditions where such factors occur.

The present invention has been made in view of the above, and its purpose is to reduce fluctuations in the calculated value of the road surface friction coefficient during cornering, etc. by providing a means for leveling the calculated value of the road surface friction coefficient. It is an object of the present invention to provide a road surface friction coefficient detection device that is useful for smoothing and performing smooth running control.

(Means for Solving the Problems) To achieve the above object, the present invention provides a road surface friction coefficient detection system that detects the friction coefficient μ between the tires of a vehicle and the road surface, as shown in FIG. The device includes a motion state detection means 51 for detecting the motion state of the vehicle such as the lateral acceleration of the center of gravity of the vehicle, a steering state detection means 37 for detecting the steering state such as the front and rear wheel steering angles, A vehicle speed detection means 53 for detecting the running speed, a storage means 31 for storing the stability factor of the vehicle, and the detected values of the motion state detection means 51, the steering state detection means 52 and the vehicle speed detection means 53 and the storage means 31. a friction coefficient calculation means 39 that calculates a road surface friction coefficient μ according to the stored contents; an integration processing means 40 that performs an integration process on the value of the road surface friction coefficient μ calculated by the friction coefficient calculation means 39; A time constant changing means 41 is provided for changing the integration time constant during the integration processing by the integration processing means 40 according to running conditions.

(Function) With the above configuration, the present invention can detect the stability factor of the vehicle stored in the storage means 31, the motion state detection means 51, the steering state detection means 37, and the vehicle speed when the vehicle is turning or the like. Depending on variables such as the lateral acceleration of the vehicle center of gravity, front and rear wheel steering angles, and vehicle speed detected by the means 53,
The friction coefficient calculating means 39 calculates the road surface friction coefficient μ. Then, the integration processing means 40 integrates the value of the road surface friction coefficient μ calculated by the friction coefficient calculation means 39, so that fluctuations in the road surface friction coefficient μ during that time are equalized and smoothed.

In that case, the time constant changing means 41 changes the integration time constant during the integration process according to the vehicle running conditions, thereby improving the responsiveness and stability of the estimation of the road surface friction coefficient μ to changes in the vehicle running conditions. Adjusted appropriately. For example, in driving conditions where the vehicle's driving condition becomes unstable, by changing the integration time constant to a smaller value, the response delay associated with the integration process can be suppressed, and it is possible to quickly follow changes in driving conditions. . Further, under conditions such as stable running conditions, by greatly changing the integral time constant, fluctuations in the estimated value of the road surface friction coefficient μ are suppressed.

Therefore, by using the road surface friction coefficient μ value estimated in this way for vehicle turning control, etc., it is possible to perform stable and accurate driving control while ensuring safety, for example, when turning on a snow-packed road. be able to.

(Example) Hereinafter, an example of the present invention will be described based on the drawings from FIG. 2 onwards.

FIG. 2 shows the overall configuration of a four-wheel steering system for a vehicle to which the present invention is applied, where 2 and 2 are left and right front wheels of the vehicle, and 3.3 are left and right rear wheels of the vehicle. Reference numeral 5 denotes a front wheel steering mechanism that adjusts the steering angle δF of the front wheels 2, 2. The front wheel steering mechanism 5 includes front wheels 2,
A pair of left and right knuckle members 6, 6 which rotatably support 2 and are supported by the vehicle body via a joint portion 6a, and knuckle arm portions 6b, 8b of the knuckle members 6.6.
A pair of left and right tie rods 8. with one end connected to each other.
8, a rack shaft 9 formed by connecting the other ends of the pair of tie rods 8.8 to each other at both ends, and a rack shaft 9 that controls the rotation of the handle 4 via a pinion and a rack (none of which are shown). The main component is a steering gear mechanism 10 that converts the left and right movement.

In the front wheel steering mechanism 5, when the handle 4 is rotated at a constant steering angle θ, the steering gear mechanism 10
The tie rods 8, 8 are moved in the left and right direction via the rack shaft 9, and due to this movement, the knuckle members 6, 6 are rotated around the joint parts 5a, 5a, respectively.
The front wheels 2.2 are steered at a front wheel steering angle δF corresponding to a front gear ratio Z (-θ/δF).

Furthermore, a rear wheel steering mechanism 12 is provided on the rear wheel 3.3 side for steering the left and right rear wheels 3.3 in accordance with the steering of the front wheels 2.2 by the front wheel steering mechanism 5. ing. The rear wheel steering mechanism 12 includes elements having the same functions as the front wheel steering mechanism 5, that is, a pair of knuckle members 13.13,
A pinion shaft 16 which has a tie rod 14, 14 and a rack shaft 15, and which meshes with the rack portion 15a of the rack shaft 15 at a pinion portion 16a at the tip, and a bevel gear 18 attached to the other end of the pinion shaft 1B. and the bevel gear 18
The main component is a pulse motor 20 having a bevel gear 19 attached to an output shaft that meshes with the motor.

When the pulse motor 20 is driven by the control unit 21 (described later) in accordance with the adjustment of the front wheel steering angle δF by the front wheel steering mechanism 5, the rotational driving force of the pulse motor 20 is transmitted to the two bevel gears 19, 18, and the pinion. The movement is converted into a horizontal movement of the rack shaft 15 via the portion 16a and the rack portion 15a.

Further, a power cylinder 23 is disposed on the rack shaft 15 of the rear wheel steering mechanism 12 to assist in its reciprocating movement in the vehicle width direction.
A piston 23a integrally attached to the rack shaft 15, and two hydraulic chambers 2 partitioned by the piston 23a.
3b and 23c. Moreover, the hydraulic chamber 23b,
23c communicate with the control valve 26 via hydraulic passages 24, 25, respectively. The control valve 2δ is communicated with a hydraulic pump 29 that is rotationally driven by a pump drive motor 30 via an oil supply passage 27 and an oil return passage 2.8.

The control valve 26 controls the hydraulic chambers 23b, 23 of the power cylinder 23 depending on the rotational direction of the pinion shaft 16.
This controls the supply of hydraulic pressure to c. That is, when the steering shaft 15 is moved in the vehicle width direction via the bevel gears 18 and 19 and the pinion shaft 16 in order to steer the rear wheels 3, 3 by the rotational driving force of the pulse motor 2o, the rear wheels According to the steering direction of 3°3, the communication relationship between the hydraulic supply passage 27, the hydraulic return passage 28, each hydraulic passage 24, 25, and each hydraulic chamber 23b, 23c is switched, and the hydraulic chamber 23b of the power cylinder 23 is switched. , '23c assists the movement of the rack shaft 15 in the vehicle width direction, and steers the rear wheels 3 by a predetermined rear wheel steering angle -δR.

Next, 21 is a control unit that controls the pulse motor 20 and the pump drive motor 30, and signals from the following sensors 51 to 53 are input to the control unit 21. That is, 51 is a lateral force sensor as a motion state detecting means for detecting lateral acceleration ay from a lateral force acting on the vehicle body in the vehicle width direction when the vehicle is turning, etc., and 52 is a lateral force sensor for detecting the steering wheel steering angle θ. A steering angle sensor 53' is a vehicle speed sensor serving as vehicle speed detection means for detecting vehicle speed V based on the rotation speed of the left front wheel 2.

Then, as shown in FIG.
Distance Rb1 between the center of gravity on the 11th side and the rear wheel Tire cornering power KF, K of the front wheel and rear wheel in the standard state
A storage unit 31 as a storage means for storing data necessary for control such as vehicle stability factors such as the yaw moment of inertia ■ of the R1 vehicle, a calculation formula for the road surface friction coefficient μ to be described later, and steering ratio characteristics, and an external switch. The switching of the SW is detected, and it is determined whether or not the side skidding bucket β of the vehicle is on the side that performs zero control, and the road surface friction coefficient μ set in the storage unit 31 is determined according to the determination result. A switch 32 switches the calculation formula of the road surface friction coefficient between the road surface and the tires according to the output of each of the above-mentioned sensors based on the determination result of the switch 32 and the calculation formula of the selected road surface friction coefficient μ. a friction coefficient calculation unit 33 that calculates μ; a steering ratio characteristic selection unit 34 that selects an appropriate steering characteristic from the steering characteristics stored in the storage unit 31 according to the output of the friction coefficient calculation unit 33; A rear wheel steering angle calculation section 35 that calculates the steering ratio R, that is, the rear wheel steering angle δR, based on the steering ratio R selected by the steering ratio characteristic selection section 34, and an output of the rear wheel steering angle calculation section 35. and a pulse signal forming unit 36 that generates pulse signals for driving the pulse motor 20 and the pump drive motor 30, and a pulse signal forming unit 36 that generates pulse signals for driving the pulse motor 20 and the pump drive motor 30 based on the pulse signals obtained from the pulse signal forming unit 36. It is composed of a drive section MC that drives the drive 30. The above steering angle sensor 5
2 and the rear wheel steering angle calculating section 35 constitute a steering state detection means 37 that detects the steering state such as the front and rear wheel steering angles.

Here, as a feature of the present invention, an arithmetic expression for the road surface friction coefficient μ determined as follows is set in the storage unit 31.

In other words, as shown in Figure 4, from the balance of the forces acting on the tires when the vehicle turns, the basic equation of motion is shown below. FF and FR are the cornering forces of front wheel 2 and rear wheel 3, respectively, and γ is the yaw rate). the above(
FF, FR, β, γ from equations 1) to (5).

If we eliminate Te, we get [m-1-V'-s'+ 2 p-V im (a”K
F+ b"KR) +1-Kl -s + 4 c'K
F-KR-μ"-2μmm-V' (a-KF-b-
KR) ] av- 2μ 10V' (KF4 F 10Kr: r6 R) ・s
"+ 4 μ'V・KF-KR-C(b・δ(:+a-
δR)・S+4μ1vIKF・KR-C(δF-δR)
Obtain [6] (where S is the Laplace operator, K-KF+kR, c-a+b).

Here, the square term of S is the high frequency component of the transient response,
Since it can usually be ignored, we set it to zero, and by dividing both sides of the above equation by μ, we get 11-[V (m (a'KF+b'KR) + l
-K1・s -mV'(a-KF-b-KR)], a
v/2 C-KF・KR(v(b・δF+a・δR)−
8+V'(δF-δR) -c-avl
We obtain (7).

In addition, especially in the case of control such as four-wheel steering where β is set to zero, if β-0 is set in the above equations (1) to (5), a simpler formula, μ=m-ay/2 ( KF・δF+KR”δR−(
ay/V”) (a-K F-b-KR))
(8) is obtained.

In this example, control is performed so that the sideslip angle β becomes zero by four-wheel steering, and by transforming the above equation (8) into Kira, u, -m
-aY/ ((KF +R:KR) (θ/2)-(
a Y/ V''') (a-KF-b-KR)) (
9) is obtained.

That is, the road surface friction coefficient μ is determined by vehicle speed V, heavy vehicle inertial mass m, distance a between the vehicle center of gravity and the front wheel axle, distance between the vehicle center of gravity and the rear wheel axle, and cornering of the front wheels 2 and rear wheels 3 in the standard state. Force KF.

KR, yaw moment of inertia! and stability factors such as front gear ratio 2, and lateral acceleration a of the vehicle center of gravity.
It is determined from variables such as y, steering angle θ, steering ratio R, and vehicle speed V.

The storage unit 31 also includes the steering ratio characteristic selection unit 34.
The steering ratio characteristics to be selected are set. That is,
As shown in Fig. 6, this steering ratio characteristic basically changes the steering ratio R continuously so that it is on the opposite phase side when the vehicle speed V is small, and on the same phase side when the vehicle speed V is large. In addition to changing the road surface friction coefficient μ,
This allows switching to three types of steering ratio characteristics. For example, when the road friction coefficient μ is a standard value, the curve r2 in the figure appears, whereas when the road friction coefficient μ is relatively small, the steering ratio R shifts to the same phase side as the curve r1 in the figure. When the value of the vehicle speed for reversal ■1 is lower than the same vehicle speed v2 of the above-mentioned standard characteristic, and conversely, the road surface friction coefficient μ is relatively large, the vehicle speed value V3 for the phase reversal is set to the higher side, as shown by the curve r3 in the figure. ing.

Next, FIG. 5 shows a procedure for calculating the road surface friction coefficient μ, which is performed at a predetermined sampling period in the friction coefficient calculating section 33. First, in step S1, the vehicle speed sensor 53,
From the signals of the lateral force sensor 51, the steering angle sensor 52, and the rear wheel steering angle calculating section 35, the vehicle speed V1, the lateral acceleration aY of the vehicle center of gravity, the steering wheel steering angle θ, and the steering ratio R are read, and steps 82 to S4
It is sequentially determined whether the vehicle speed V2 steering angle θ and the lateral acceleration ay are each greater than a predetermined set value, and if each determination is YES, it is determined that the driving conditions are appropriate and the process proceeds to step S5. Based on the above formula (9), the road surface friction coefficient μ
After calculating, the process proceeds to step S7.

On the other hand, if any of the determinations in steps 82 to S4 above is NO1, that is, the value of the vehicle speed V, the absolute value of the steering wheel angle θ, and the absolute value of the vehicle lateral acceleration aY are lower than the set values, then the above (9 ) Since there is a risk that the denominator on the right side of the equation approaches zero and the error increases, the value of μ calculated in the previous sampling is set as μ in step S6 without calculating the road surface friction coefficient μ. The process moves to S7.

In this step S7, it is determined whether the road surface friction coefficient μ is negative or not, and if the determination is YES that μ is 0, the road surface friction coefficient μ
This is unreasonable considering the characteristics of μm0 in step S8.
On the other hand, the determination in step S7 is that μ≧0.
If the answer is No, the process directly advances to step S9.

Then, in step S9, in order to perform control smoothly, μ'-μ/(1+τ・s) Go)(
Here, μ' is a new integrated friction coefficient obtained by integrating μ, τ is an integral time constant, and S is a Laplace operator). ′ Below, to explain the procedure, first convert the above equation (10) into a discrete system using the bilinear transformation formula %) (where T is the sampling time), then u' /u= (1+Z )/l(1+Z)+a(
1-Z)l Cl2)(
However, α-2τ/T) is obtained. Furthermore, when this equation is converted into a differential equation that can be processed within the friction coefficient calculation section 33, y'(n)-iμ(n)+(α-1)・y'(n
-1)) /(α+1)03)u'(n)-y'
(n)+y' (n-1) (14).

Therefore, in step S9, the sampling time for estimating the road surface friction coefficient μ is determined in step S5.
First, for μ of the calculation result in
) (Yo and y+ indicate the calculated values from the previous and current sampling, respectively, and are stored in separate RAMs (not shown) in the storage unit 31), Yl is calculated. , Next, the formula μ'-YO+Y corresponding to the above formula 04), , (16
) is used to calculate the integrated road surface friction coefficient μ'. That is, the estimation of the road surface friction coefficient μ ends. Then, the Yl value calculated in the current sampling is set as Yo in the next sampling, and the integration process is finished, and step SIO
Proceed to.

In step SIO, it is determined whether the value of the road surface friction coefficient μ estimated in step S9 (hereinafter referred to as the integrated road surface friction coefficient μ') has changed from a high μ value to a low μ value. Then, in step So, if the road surface friction coefficient μ is high μ
It is determined whether the μ value has changed from the value to the low μ value. If both of these determination results are No, it is determined that the driving conditions are standard and the process directly proceeds to step S+2, where the constant α in the next sampling process is set as
Constant α0 (α0−2
After setting τo /T), the process proceeds to step SI5.

On the other hand, the discrimination in the above step SIO is from high μ to low μ
If Y″'E S has changed to
The constant value α1 (α
1-2τ1/T).

Also, if the determination in step S11 is from low μ to high μ
If the answer is YES, it is determined that the vehicle is in a stable running state, and the process moves to step SI4, where a time constant value τ2 larger than the standard time constant value τ0 is set as the value of the constant α in the next sampling. Constant value α2 (α2
-2τ2/T). With the above, the control ends.

Therefore, in step S5, the lateral force sensor (motion state detection means) 51. A friction coefficient calculation means 39 calculates a road surface friction coefficient μ according to the detected values of the steering angle sensor (steering state detection means) 52 and the vehicle speed sensor (vehicle speed detection means) 53 and the stored contents of the storage section (storage means) 31. configured,
Furthermore, step S9 constitutes an integration processing means 40 that performs an integration process on the value of the road surface friction coefficient μ calculated by the friction coefficient calculation means 39. Furthermore, step S'
10=S+4 constitutes a time constant changing means 41 that changes the integration time constant during the integration processing by the integration processing means 40 according to the running conditions of the vehicle.

Then, when the vehicle is turning, etc., the friction coefficient calculation unit 33 calculates the road surface friction coefficient μ estimated as described above in response to the outputs of the sensors 51 to 53.
The steering ratio characteristic selection unit 34 selects the sixth value set in advance in the storage unit 31 according to the magnitude of the road surface friction coefficient μ.
One of the steering ratio characteristic curves r1 to r3 shown in the figure is selected.

Next, the rear wheel steering angle calculation section 35 calculates the steering ratio R1 selected by the steering ratio selection section 34, the steering wheel steering angle θ detected by the steering angle sensor 52, and the steering angle θ detected by the vehicle speed sensor 53. An appropriate rear wheel steering angle δR is calculated according to the value of the vehicle speed V. Further, the pulse signal forming section 36 outputs a pulse signal according to the calculated value, and the driving section MC drives the pulse motor 20 and the pump drive motor 30 according to the pulse signal, so that the rear wheels 3, 3 is driven to a predetermined steering angle δR.

Therefore, in the above embodiment, when the vehicle is turning, the road surface friction coefficient μ between the tires and the road surface is measured by each of the detection means 51'-
After calculation is performed based on equation (9) derived from the basic equation of motion according to the lateral acceleration aY of the vehicle center of gravity, the steering angle θ, and the vehicle speed V detected at step 53, the integration processing means 40 calculates Since the calculated values are subjected to integration processing, large fluctuations from each detection means are smoothed out.

For example, the lateral acceleration of the vehicle detected by the lateral force sensor 51 varies intermittently because the grip force of the tires on the road surface usually fluctuates. For this purpose, when calculating the road surface friction coefficient μ according to the output of each detection means,
Although the calculated value changes violently in an oscillatory manner, since the calculated value is subjected to integration processing by the integration processing means 40, the fluctuations therebetween are smoothed out.

In addition, when the value of the road surface friction coefficient μ calculated by the sampling changes from high μ to low μ, the time constant changing means 41 changes the value of the integration time constant τ during the integration process from the standard value. The integration time constant is set to a small value, and when the value changes from low μ to high μ, the integral time constant τ is set to a large value. The responsiveness and stability of estimating the road surface friction coefficient μ to changes can be appropriately adjusted.

That is, when the road surface friction coefficient μ changes from a high μ value to a low μ value, the vehicle may fall into a dangerous driving state. For example, when performing 4WS control as in the above embodiment, as shown in FIG. If this is maintained, there is a risk that the steering ratio R will become too large on the opposite phase side, causing the vehicle to spin. Furthermore, by applying the present invention to a so-called anti-lock brake system used when driving on a road surface with a low coefficient of friction,
When controlling the brake force in response to changes in the actual road friction coefficient μ during cornering, etc., it is necessary to control the braking force in response to changes in the actual road friction coefficient μ, even though the actual road friction coefficient μ has changed to a low μ. If the control state is maintained, there is a risk that the brakes will be locked due to a sudden difference between the rotational speed of the wheels and the speed of the vehicle body. In the above case, by changing the integration time constant τ in the integration process to a small value, it is possible to improve the responsiveness of estimating the road surface friction coefficient μ and perform control corresponding to the change.

Furthermore, when the road surface friction coefficient μ changes from low μ to high μ, the vehicle is in a relatively stable state. In such a case, it is possible to largely change the integral time constant τ to suppress fluctuations in the estimated value of the road surface friction coefficient μ.

Therefore, by applying the road surface friction coefficient μ estimated in this way to a vehicle running control device, etc., safety can be ensured even when turning on a road surface with a low road surface friction coefficient μ value, such as a snow-packed road. It is possible to perform stable and accurate driving control at the same time.

Next, an experimental example in which the control device of the above embodiment performs cornering control such that β becomes zero in a JWS vehicle will be described with reference to FIG. FIGS. 7(A) to 7(C) are data obtained when turning driving control was performed on a compacted snow road (a so-called low μ road with an average road surface friction coefficient of μm estimated to be 0.2 to 0.3). Figure (a) shows the change in steering wheel angle θ over time.
The same (b) shows the change characteristics of the road surface friction coefficient μ when the integration process is performed with a very small time constant value τ1 after the calculation in response to the change in the steering wheel angle θ. is the above time constant τ after calculation corresponding to the same change in steering wheel angle θ.
The change characteristics of the road surface friction coefficient μ when the integration process is performed with a time constant value τ2 considerably larger than 1 is shown. When the integration process is performed with a small time constant value τ1, it responds well to changes in the steering wheel angle, while on the other hand, when a large time constant value τ2 is used,
It has been shown that very stable μ estimates can be obtained when the integration process is performed using Therefore, by changing the integral time constant τ according to the driving conditions, it is possible to estimate the road surface friction coefficient μ corresponding to the driving conditions.

In the above embodiment, the integral time constant τ is changed in accordance with the change in the road surface friction coefficient μ, but the configuration of the present invention is not limited to the above embodiment. For example, when the vehicle speed V detected by the vehicle speed sensor 53 is high, the time constant τ may be decreased, and when the vehicle speed V is low, the time constant τ may be changed greatly. Further, when the steering wheel steering angle θ is large, the time constant τ may be changed to a small value, and when the steering wheel steering angle θ is large, the time constant τ may be changed to a large value. In either case, the same effects as in the above embodiment can be obtained.

Further, the application of the present invention is not limited to the control of four-wheel steering as in the above embodiments, but can also be applied to, for example, the control of two-wheel steering. In that case, the road surface friction coefficient μ detected by the road surface friction coefficient detection device of the present invention can be applied to the above-mentioned anti-lock brake system to improve the control effect.

Furthermore, as shown in the above example, when deriving the formula for calculating the road surface friction coefficient μ from the basic equations of motion (1) to (5) of the vehicle, the formula (7) or (8) described above, that is, the following In addition to transforming into the general formula % formula %), it also transforms into μ−G' (s) ・γ/H(s) ・θ
As in G8), it can also be a function of the yaw rate γ and the steering wheel angle θ. Alternatively, it can be transformed into a function of sideslip angle β and steering wheel steering angle θ, such as p-G'(s)・β/H(S)・θ09), and these variables γ, θ or It is also possible to adopt a configuration in which the road surface friction coefficient μ is detected according to the values of β and θ.

Note that the present invention is limited to calculating the road surface friction coefficient μ based on the calculation formula expressed by the above general formula (+9) derived from the basic equation of motion of the vehicle as in the above embodiment. It is not something that will be done. In other words, it can be applied to the above-mentioned conventional devices and those in which the road surface friction coefficient μ is calculated and estimated from the state of light reflection on the road surface.
In these cases as well, smooth travel control can be provided by smoothly integrating fluctuations in the estimated μ value due to fluctuations in sensors. Further, such various road surface friction coefficient μ detection devices may be used together, and the smallest value among the road surface friction coefficient μ values obtained by each device may be used as the estimated value. In that case, there is an advantage that risks such as slipping can be most reliably prevented.

(Effects of the Invention) As explained above, according to the road surface friction coefficient detection device of the present invention, the tire and road surface After calculating the road friction coefficient between By appropriately adjusting the responsiveness and stability of the vehicle, it is possible to provide accurate and stable vehicle turning control while ensuring safety.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of the present invention. Figure 2 and subsequent figures show embodiments of the present invention. Figure 2 is an overall configuration diagram of the vehicle, Figure 3 is a configuration diagram of the vehicle control device, and Figure 4 shows the relationship of forces that act when the vehicle turns. 5 is a flowchart showing the control in the road surface friction coefficient calculation section, FIG. 6 is a diagram showing the steering ratio characteristics to be selected set in the storage section, and FIG. 7 is experimental data on a snow-complowed road. FIG. 2 is a graph showing experimental results. 31... Storage unit (storage means), 39... Friction coefficient calculation means, 37... Steering state detection means, 40... Integration processing means, 41... Time constant changing means, 51... - Lateral force sensor (motion state detection means), 52... Rudder angle sensor, 53... Vehicle speed sensor (vehicle speed detection means). Patent applicant Mazda Motor Corporation representative
Person Patent Attorney Front 1) Hiro° Figure 2 Figure 1 U41 Figure 6 Seijisuri

Claims (1)

[Claims] (1) A road surface friction coefficient detection device that detects the friction coefficient μ between the vehicle tires and the road surface, and a motion state detection means that detects the motion state of the vehicle such as the lateral acceleration of the vehicle center of gravity;
Steering state detecting means for detecting a steering state such as front and rear wheel steering angles; vehicle speed detecting means for detecting the traveling speed of the vehicle; storage means for storing a stability factor of the vehicle; the motion state detecting means; and the steering state detecting means. road surface friction coefficient μ according to the detection value of the vehicle speed detection means and the memory contents of the storage means.
friction coefficient calculation means for calculating the value of the road surface friction coefficient μ calculated by the friction coefficient calculation means; and integration processing means for performing integration processing by the integration processing means according to the driving conditions of the vehicle. A road surface friction coefficient detection device comprising: time constant changing means for changing an integral time constant during processing.