JP2003312465A - Device for estimating gripping degree for wheel, and motion controller for vehicle provided with the device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To precisely estimate a gripping degree expressing a lateral gripping degree for a wheel, and to properly control motion of a vehicle, based on the gripping degree. <P>SOLUTION: Self-aligning torque for front wheels is estimated based on steering torque and steering force by a self-aligning torque estimating means 6, and side force for the front wheels is estimated based on a vehicular state quantity by a side force estimating means 9 (or a slip angle for the front wheel is estimated). The gripping degree for the front wheels is estimated based on a change of the self-aligning torque with respect to the side force (or the front wheel slip angle), in a gripping degree estimating means M12. When the change of the self-aligning torque is judged, a reference self-aligning torque is preferably set, and the gripping degree is preferably estimated based on a comparison result of the self-aligning torque with the reference self-aligning torque. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wheel grip degree estimating device, and more particularly to a device for estimating a grip degree indicating a degree of lateral grip of a wheel in front of a vehicle. Further, the present invention relates to a vehicle motion control device including the grip degree estimating device.

[0002]

2. Description of the Related Art In order to maintain vehicle stability, there is known a device for detecting and determining the state quantity of the vehicle and independently controlling the braking force of each wheel, for example, Japanese Patent Laid-Open No. 6-99800. Is disclosed in. In this publication, a yaw rate target value is formed from the vehicle speed and the steering angle, and oversteer or understeer is determined by the time derivative of the deviation from the actual yaw rate value. In the case of oversteer, the braking slip of the front wheel on the outside of the turn is increased, that is, the braking force of the front wheel on the outside of the turn is increased, and in the case of understeer, the brake slip of the rear wheel on the inside of the turn is increased. Further, Japanese Patent Application Laid-Open No. 62-146754 discloses a device which sets a target value of a front wheel speed difference, a lateral acceleration or a yaw rate from a steering angle and a vehicle speed, and controls an output of a brake and / or an engine. .

Further, Japanese Laid-Open Patent Publication No. 11-99956 discloses a variable steering angle ratio steering device for a vehicle for the purpose of preventing excessive turning of steering wheels. The lateral force utilization ratio or the lateral G utilization ratio is disclosed. Is used. That is, according to the device described in the publication, first, the road surface friction coefficient μ
Is estimated, and the lateral force usage rate is obtained. Since the cornering power Cp of the tire decreases as the road surface friction coefficient μ decreases, the rack shaft reaction force received from the road surface at the same steering angle decreases according to the road surface friction coefficient μ. Therefore, it is possible to estimate the road surface friction coefficient μ by actually measuring the front wheel steering angle and the rack shaft reaction force and comparing the actual rack shaft reaction force with respect to the front wheel steering angle and the reference rack shaft reaction force preset as an internal model. It is supposed to be possible. Further, an equivalent friction circle is set based on the road surface friction coefficient μ, the frictional force used by the longitudinal force is subtracted, the maximum generated lateral force is obtained, and the ratio with the currently generated lateral force is taken as the lateral force usage rate. Alternatively, it is also possible to provide a lateral G sensor and set the lateral G usage rate based on the detected lateral G.

[0004]

Since there is a limit to the friction between the road surface and the tires, when the vehicle reaches the friction limit and is in an excessive understeer state, the turning radius intended by the driver is maintained. In order to do so, it is necessary not only to control the yaw motion of the vehicle, that is, the vehicle attitude on the vehicle traveling surface, but also to decelerate the vehicle. However, in the device and the like described in the above-mentioned JP-A-6-99800, since the vehicle behavior is discriminated after the tire reaches the friction limit, when the vehicle is decelerated in this situation, the cornering force decreases and the understeer is promoted. Is concerned. further,
Since the actual control system has the control dead zone, the above control is executed after a certain amount of vehicle behavior occurs.

Further, the curve shape of the road is constituted by a clothoid curve, and when the driver tries to trace the curve of the road, the steering wheel (steering wheel) is gradually cut in. Therefore, when the speed of entering the curve is high, the side force generated on the wheels does not balance with the centrifugal force, and the vehicle tends to bulge outside the curve. In such a case, the above-mentioned JP-A-6-9
Although the devices described in Japanese Patent Laid-Open No. 9800 and Japanese Patent Laid-Open No. 62-146754 operate, control may be started at the turning limit, and this control may not sufficiently reduce the vehicle speed. It may happen that the outward bulge cannot be prevented.

By the way, Automotive Technology Handbook <First
Separate Volume> pages 179 to 180 of the Basic and Theoretical Edition (published by the Society of Automotive Engineers of Japan on December 1, 1990)
The state in which the tire rolls while sliding with the sideslip angle α is described as shown in FIG.

That is, in FIG. 2, the tread surface of the tire indicated by the broken line contacts the road surface at the front end of the ground contact surface including point A in FIG. 2, adheres to the road surface up to point B, and moves in the tire traveling direction. Then, at the point where the deformation force due to the lateral shear deformation becomes equal to the frictional force, it slides off, and at the rear end including point C, it leaves the road surface and returns to the original state. At this time, the force Fy (side force) generated on the entire ground contact surface is the product of the lateral deformation area of the tread portion (hatched portion in FIG. 2) and the lateral elastic constant of the tread portion per unit area. As shown in FIG. 2, the force application point of the side force Fy is behind the point directly below the tire center line (point O) by e _n (pneumatic trail) (leftward in FIG. 2). Accordingly, moment Fy · e _n at this time is self-aligning torque (Tsa), it will act in a direction to decrease the slip angle alpha.

Next, the case where the tire is mounted on the vehicle will be described with reference to FIG. 3 which is a simplified version of FIG. In a steering wheel of a vehicle, in order to improve the return of the steering wheel (steering wheel), a caster angle e is usually provided to provide a caster trail e _c . Therefore, the ground contact point of the wheel becomes the point O ′, and the moment for restoring the steering wheel becomes Fy · (e _n + e _c ).

The lateral grip of the tire deteriorates,
When the slip region expands, the lateral deformation of the tread portion changes from the ABC shape in FIG. 3 to the ADC shape. As a result,
The force application point of the side force Fy moves forward (from point H to point J in FIG. 3) with respect to the vehicle traveling direction. That is, the pneumatic trail e _n becomes smaller. Therefore, even if the same side force Fy acts, when the adhesion area is large and the slip area is small (that is, when the lateral grip of the tire is high), the pneumatic trail e _n is large and the self-aligning torque is large. Tsa increases. On the contrary, when the lateral grip of the tire is lost and the slip area increases, the pneumatic trail e _n becomes smaller and the self-aligning torque Tsa decreases.

As described above, the pneumatic trail e
Focusing on the change in _n , it is possible to detect the degree of grip in the tire lateral direction. Since the change of the pneumatic trail e _n appears in the self-aligning torque Tsa, based on the self-aligning torque Tsa,
It is possible to estimate a grip degree (hereinafter, referred to as a grip degree) indicating a degree of lateral grip with respect to a wheel in front of the vehicle. Further, the grip degree can be estimated based on the margin degree of the side force with respect to the road surface friction, as described later.

The above-mentioned grip degree is the same as the above-mentioned JP-A-11-.
The lateral force usage rate or the lateral G usage rate disclosed in the 99995 publication is different as follows. In the device described in the publication, the maximum lateral force that can be generated on the road surface is obtained from the road surface friction coefficient μ. The road surface friction coefficient μ is estimated based on the road surface friction coefficient μ dependence of the cornering power Cp (definition is the value of the side force at a slip angle of 1 deg). However, the cornering power Cp is not limited to the road surface friction coefficient μ, but also the shape of the tire contact surface (contact surface length,
And width) and elasticity of the tread rubber. For example, when there is water on the tread surface, or
When the elasticity of the tread rubber changes due to tire wear and temperature, the cornering power Cp changes even if the road surface friction coefficient μ is the same. As described above, the technology described in the publication does not consider the characteristics of the tire of the wheel.

Therefore, the present invention provides a grip degree estimating device capable of accurately estimating the grip degree indicating the degree of lateral grip on a wheel, and notifies the driver, for example, when the grip degree becomes less than a predetermined value. The task is to be able to do so.

Further, the present invention provides a vehicle motion control device capable of accurately estimating the grip degree and appropriately controlling the motion based on the grip degree when the grip degree falls below a predetermined value. This is an issue.

[0014]

In order to solve the above-mentioned problems, the wheel grip degree estimating device of the present invention is, as described in claim 1, a steering applied to a steering system from a steering wheel of a vehicle to a suspension. Steering force index detecting means for detecting at least one steering force index among the steering force indexes including torque and steering force, and a self-appearance generated in a wheel in front of the vehicle based on a detection signal of the steering force index detecting means. Self-aligning torque estimating means for estimating the lining torque, vehicle state quantity detecting means for detecting the state quantity of the vehicle, and side force and front wheels for the wheels in front of the vehicle based on the detection signal of the vehicle state quantity detecting means. Front wheel index estimation means for estimating at least one front wheel index among front wheel indexes including slip angles, and front wheels estimated by the front wheel index estimation means For target, based on said change in self-aligning torque self-aligning torque estimating unit has estimated, it is at least that the comprise a grip degree estimating means for estimating a grip degree with respect to the vehicle front wheels.

Thus, for example, the self-aligning torque of the front wheels is estimated based on the steering torque by the steering wheel or the steering force applied to the suspension, and the side force or the front wheel slip angle of the front wheels is estimated based on the vehicle state quantity. And the grip degree of the front wheels can be estimated based on the change in the self-aligning torque with respect to the side force or the front wheel slip angle. still,
The state quantity of the vehicle includes indexes relating to the vehicle in motion, such as vehicle speed, lateral acceleration, yaw rate, steering angle, and the like.

Further, as described in claim 2, the reference self-aligning torque is set based on the front wheel index estimated by the front wheel index estimating means and the self-aligning torque estimated by the self-aligning torque estimating means. A reference self-aligning torque setting unit is provided, and the grip degree estimating unit estimates the reference self-aligning torque set by the reference self-aligning torque setting unit and the self-aligning estimated by the self-aligning torque estimating unit. Based on the comparison result with the torque, the grip degree for the wheel in front of the vehicle may be estimated at least.

The reference self-aligning torque setting means has a characteristic of the self-aligning torque estimated by the self-aligning torque estimating means with respect to the front wheel index estimated by the front wheel index estimating means. Can be configured to set a reference self-aligning torque characteristic that is linearly approximated including at least the origin, and set the reference self-aligning torque based on the reference self-aligning torque characteristic.
Further, the reference self-aligning torque setting means,
As set forth in claim 4, a linear reference self-aligning torque characteristic having a gradient set based on a brush model for the front wheel of the vehicle is set, and the reference self-aligning torque characteristic is set based on the reference self-aligning torque characteristic. It can also be configured to set the lining torque.

Further, as described in claim 5, the grip degree estimated by the grip degree estimating means is compared with a predetermined value, and when the grip degree is less than the predetermined value, the driver of the vehicle is notified. It may be provided with an informing means.

According to the sixth aspect of the present invention, the vehicle motion control device of the present invention has at least one of the steering force indexes including the steering torque and the steering force applied to the steering system from the steering wheel of the vehicle to the suspension. A steering force index detecting means for detecting one of the steering force indexes, and a self-aligning torque estimating means for estimating a self-aligning torque generated in the wheel in front of the vehicle, based on a detection signal of the steering force index detecting means, Vehicle state quantity detecting means for detecting the state quantity of the vehicle, and based on a detection signal of the vehicle state quantity detecting means, at least one of front wheel indexes including a side force and a front wheel slip angle with respect to a wheel in front of the vehicle. Front wheel index estimating means for estimating a front wheel index, and the self-aligning torque for the front wheel index estimated by the front wheel index estimating means Based on the change in the self-aligning torque estimated by the determining means, a wheel grip degree estimating device having a grip degree estimating means for estimating a grip degree for a wheel in front of the vehicle is provided, and at least the vehicle state quantity. When the grip degree estimated by the grip degree estimating means is less than a predetermined value, the control means controls at least one of the braking force for the vehicle, the engine output, and the shift position according to the detection signal of the detecting means. The control means controls at least one of a braking force, an engine output, and a shift position for the vehicle to decelerate the vehicle.

According to a seventh aspect of the present invention, in the vehicle motion control device, the reference self is calculated based on the front wheel index estimated by the front wheel index estimating means and the self aligning torque estimated by the self aligning torque estimating means. A reference self-aligning torque setting means for setting an aligning torque is provided, and the grip degree estimating means estimates the reference self-aligning torque set by the reference self-aligning torque setting means and the self-aligning torque estimating means. Based on the result of comparison with the self-aligning torque, it is preferable to estimate the grip degree for the wheel in front of the vehicle.

The reference self-aligning torque setting means may be the self-aligning torque estimating means for the front wheel index estimated by the front wheel index estimating means. The self-aligning torque characteristics estimated by
It is possible to set a reference self-aligning torque characteristic that is linearly approximated to include at least the origin, and set the reference self-aligning torque based on the reference self-aligning torque characteristic. Further, the reference self-aligning torque setting means sets a linear reference self-aligning torque characteristic having a gradient set based on a brush model for the wheel in front of the vehicle, as set forth in claim 9, The reference self-aligning torque may be set based on the reference self-aligning torque characteristic.

Further, as described in claim 10, when the grip degree estimated by the grip degree estimating means becomes less than a predetermined value during the braking operation by the driver of the vehicle, the control means causes the Regardless of the braking operation by the driver of the vehicle, it is preferable to control so that the braking force for at least one wheel of the vehicle becomes a predetermined braking force or more.

The predetermined braking force in the braking force control by the control means is, as described in claim 11, the brake pedal operation amount in the vehicle, the grip degree, the road surface friction coefficient for the wheel, and the load on the wheel. Can be set based on at least one of these. Further, as described in claim 12, when the road surface friction coefficient is less than a predetermined value, the control means may perform control so as to prohibit an increase in the braking force on the wheel behind the vehicle.

Further, in the apparatus according to claim 10,
As described in claim 13, the control means determines whether the vehicle is understeer tendency or oversteer tendency based on the detection signal of the vehicle state amount detection means, and when the vehicle is understeer tendency, The braking force may be controlled so that the generated yaw moment of the vehicle is different when the vehicle tends to oversteer.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings. 1 is a block diagram showing a main configuration of a grip degree estimating device for estimating a grip degree from a side force and a self-aligning torque according to an embodiment of a grip degree estimating device of the present invention. First,
An example of grip degree estimation will be described with reference to FIGS. 2 to 4.

As is apparent from FIGS. 2 and 3 described above,
The characteristic of the self-aligning torque with respect to the front wheel side force with respect to the front wheel of the vehicle is as shown by Tsaa in FIG. As described above, when the actual self-aligning torque and Fyf the front wheel side force and Tsaa, Tsaa = are the _{Fyf · (e n + e c} ), the front wheel side force of the actual self-aligning torque Tsaa Fyf
The non-linear characteristic for represents a direct change of the pneumatic trail e _n . Therefore, the inclination K of the actual self-aligning torque Tsaa with respect to the front wheel side force Fyf in the vicinity of the origin 0 (here, the front wheel is in the grip state).
1 is identified, that is, the self-aligning torque characteristic (reference self-aligning torque T
sao). It should be noted that the inclination K1 is preferably a predetermined value obtained experimentally as an initial value, and is identified and corrected during normal traveling with a high degree of grip.
The actual self-aligning torque Tsaa is obtained by the calculation described later.

The reference self-aligning torque T
The grip degree ε of the front wheel is estimated based on the actual self-aligning torque Tsaa with respect to sao. For example, when the front wheel side force is Fyf1, the value Tsao1 (= K1 · Fyf1) of the reference self-aligning torque Tsao,
Based on the value Tsaa1 of the actual self-aligning torque Tsaa, the grip degree ε can be obtained as ε = Tsaa1 / Tsao1.

As described above, the grip of the wheel is determined by the self-aligning torque (actual self-aligning torque Tsa) with respect to the side force (front wheel side force Fyf).
Although it can be estimated based on the change of a), this can be realized by configuring as shown in FIG. 1, and its specific configuration is shown in FIGS. 11 and 12. First, in FIG. 1, at least one steering force index (a steering force index including a steering torque and a steering force applied to a steering system from a steering wheel (not shown) to a suspension (not shown) of a vehicle ( For example, steering torque detecting means M1 and assist torque detecting means M2 are provided as steering force index detecting means for detecting (steering torque). The reaction torque is detected by the reaction torque detection means M3 based on these detection results.

In this embodiment, an electric power steering device (EPS) is provided, and is constructed as shown in FIG. 11, for example. Since a detailed description will be given later with reference to FIG. 11, an outline will be described here. The electric power steering apparatus according to the present embodiment detects the steering torque Tstr acting on the steering shaft 2 by the operation of the steering wheel 1 by the driver by the steering torque sensor TS, and the electric motor according to the value of the detected steering torque Tstr. 3 to control the wheels FL and FR in front of the vehicle through the reduction gear 4 and the rack and pinion 5 to reduce the steering operation force of the driver. Also,
The steering angle is detected by the steering angle sensor SS of FIG. 11, which is the steering angle detecting means M4, and the steering friction torque is estimated by the steering friction torque estimating means M5 based on this. Note that this will also be described later.

Then, based on the detection results of the reaction force torque detecting means M3 and the steering friction torque estimating means M5, the self-aligning torque estimating means M6 causes the actual self-aligning torque Tsaa generated on the wheels FL and FR in front of the vehicle. Is estimated.

On the other hand, as the vehicle state quantity detecting means for detecting the state quantity of the vehicle, in this embodiment, the lateral acceleration detecting means M is used.
7 and yaw rate detection means M8 are provided, and based on these detection signals, at least one front wheel index (in FIG. 1, front wheel index including side force and front wheel slip angle for wheels FL and FR in front of the vehicle). The front wheel side force Fyf) is estimated by the side force estimating means M9 which is a front wheel index estimating means.

The front wheel side force Fyf is Fyf = (Lr.m.Gy + Iz.dγ / dt) / L based on the output results of the lateral acceleration detecting means M7 and the yaw rate detecting means M8.
Is estimated according to. Here, Lr is the distance from the center of gravity to the rear wheel axis, m is the vehicle mass, L is the wheel base, Iz is the yaw moment of inertia, Gy is the lateral acceleration, and dγ / dt is the time derivative of the yaw rate.

Further, the actual self-aligning torque Tsaa estimated by the self-aligning torque estimating means M6.
Then, based on the front wheel side force Fyf estimated by the side force estimating means M9, the reference self-aligning torque setting means M11 sets the reference self-aligning torque. For example, the self-aligning torque origin gradient estimating means M10 estimates the gradient of the self-aligning torque near the origin, and based on this gradient and the front wheel side force, the reference self-aligning torque setting means M is provided.
At 11, the reference self-aligning torque is set.
Then, the reference self-aligning torque setting means M11
The grip degree estimator M12 estimates the grip degree ε with respect to the front wheel based on the result of comparison between the reference self-aligning torque set in step 1 and the self-aligning torque estimated by the self-aligning torque estimating means M6.

That is, in FIG. 1, in the vicinity of the origin of FIG. 4, based on the actual self-aligning torque Tsaa estimated by the self-aligning torque estimating means M6 and the front wheel side force Fyf estimated by the side force estimating means M9. The self-aligning torque gradient K1 is obtained. Based on this gradient K1 and the front wheel side force Fyf, the reference self-aligning torque Tsao is Tsao = K1.
Calculated as Fyf, actual self-aligning torque Tsa
Compared with a. Based on this comparison result, the grip degree ε
Is calculated as ε = Tsaa / Tsao.

As described above, the present embodiment is provided with the electric power steering device (EPS), and the EPS motor drive current is proportional to the assist torque. Therefore, the assist torque and the detection result of the steering torque detecting means M1 are detected. It is possible to easily estimate the reaction torque based on the above (this will be described in detail later). Further, although it is necessary to compensate the torque due to the friction of the steering system, in the steering friction torque estimating means M5, the difference between the reaction torque maximum value when the steering wheel is increased and the reaction torque when the steering wheel is returned is the friction. Calculated as torque,
Since the friction torque is sequentially corrected (this will also be described later in detail), the self-aligning torque (actual self-aligning torque Tsaa) can be properly estimated. However, the present invention is not limited to this. For example, a load cell or the like is attached to the steering shaft (not shown), or a strain gauge is provided in the suspension member, and the self-aligning torque is measured from the detection signal. It is also possible to do so.

Next, FIGS. 5 to 10 relate to another embodiment of the grip degree estimating device of the present invention, in which the front wheel slip angle is used as the front wheel index of the present invention. FIG. 5 is a block diagram of a grip degree estimation device that estimates the grip degree from the front wheel slip angle and the self-aligning torque. Blocks M1 to M6 are the same as those in FIG. 1, and the reaction torque,
The steering system friction torque is calculated and the self-aligning torque is estimated. On the other hand, since the front wheel slip angle is obtained from the steering angle, yaw rate, lateral acceleration, and vehicle speed, the detection signals of the steering angle detecting means M4, the lateral acceleration detecting means M7, and the yaw rate detecting means M8 are the vehicle speed, as in FIG. It is input to the front wheel slip angle estimating means M9y together with the detection signal of the detecting means M9x.

In the front wheel slip angle estimating means M9y, first, the vehicle body slip angular velocity dβ / dt is obtained from the yaw rate, the lateral acceleration and the vehicle speed, and this is integrated to obtain the vehicle body slip angle β. This body slip angle β
The front wheel slip angle αf is calculated from the vehicle speed, the steering angle, and the vehicle specifications based on the above. The vehicle body slip angle β may be calculated based on a vehicle model or a combination of this and an integration method other than the integration method.

Based on the self-aligning torque and the front wheel slip angle αf estimated as described above, the self-aligning torque origin gradient estimating means M10 identifies the origin gradient of the self-aligning torque. Based on the angle, the reference self-aligning torque setting means M11 sets the reference self-aligning torque. Then, based on the comparison result of the reference self-aligning torque set by the reference self-aligning torque setting means M11 and the self-aligning torque estimated by the self-aligning torque estimating means M6, the front wheel in the grip degree estimating means M12. The grip degree ε is estimated.

The estimation of the grip factor ε in the embodiment shown in FIG. 5 will be described in detail below with reference to FIGS. 6 to 10. The relationship between the front wheel side force Fyf and the self-aligning torque Tsa with respect to the front wheel slip angle (hereinafter referred to as front wheel slip angle) αf, particularly the front wheel slip angle αf, has a nonlinear characteristic as shown in FIG. Becomes Self-aligning torque Tsa is the fact that the product of the front wheel side force Fyf and trail e (= e _n + e _c), when the wheel (front wheel) is in a grip state, that is, the pneumatic trail e _n is the full grip state The self-aligning torque characteristic in a certain case is a non-linear characteristic as shown by Tsar in FIG.

However, in the present embodiment, the self-aligning characteristic in the perfect grip state is assumed to be linear, and as shown in FIG. 8, the slope K2 of the self-aligning torque Tsa with respect to the front wheel slip angle near the origin is determined and used as a reference. The self-aligning torque characteristic (shown by Tsas in FIG. 8) is set. For example, the front wheel slip angle is α
If it is f1, the reference self-aligning torque is Tsas1
= K2 · αf1 Then, the grip degree ε is
It is calculated as ε = Tsaa1 / Tsas1 = Tsaa1 / (K2 · αf1).

In the method of setting the reference self-aligning torque in FIG. 8, since the reference self-aligning torque characteristic is assumed to be linear, the error in estimating the grip becomes large in the region where the front wheel slip angle αf is large, There is a concern that the estimation accuracy of the grip degree will decrease. Therefore, as shown in FIG. 9, at a predetermined front wheel slip angle or more, the self-aligning torque gradient is set to K3, and the non-linearity of the reference self-aligning torque characteristic is linear as shown by OMN in FIG. It is desirable to set the values approximately. In this case, the self-aligning torque gradient K3
It is desirable to experimentally obtain in advance and set, and to identify and correct the slope K3 during traveling. Further, the point M may be set based on the inflection point (point P) of the actual self-aligning torque. For example, the inflection point P of the actual self-aligning torque is obtained, and the front wheel slip angle αm that is larger than the front wheel slip angle αp of the inflection point P by a predetermined value is set as the point M.

Further, since the reference self-aligning torque with respect to the front wheel slip angle is influenced by the road surface friction coefficient μ, the actual self-aligning torque T as shown in FIG.
By setting the reference self-aligning torque based on the inflection point P of saa, it is possible to set the highly accurate reference self-aligning torque characteristic. For example, when the road surface friction coefficient becomes low, the characteristic of the actual self-aligning torque Tsaa changes from the solid line to the broken line in FIG. That is, when the road friction coefficient μ decreases, the inflection point of the actual self-aligning torque Tsaa changes from the point P to the point P ′. Therefore, it is necessary to change the reference self-aligning torque characteristic (Tsat) from OMN to OM'N '. In this case, since the point M ′ is set based on the inflection point P ′ as described above, even if the road surface friction coefficient changes, the reference self-aligning torque characteristic can be set by following the change. It will be possible.

FIG. 11 shows an embodiment of a vehicle motion control device equipped with the above grip degree estimating device, which is equipped with an electric power steering device. An electric power steering device is already on the market, and a steering torque sensor TS detects a steering torque Tstr acting on a steering shaft 2 by a driver's operation of a steering wheel 1, and an EPS is detected according to a value of the detected steering torque Tstr. The motor (electric motor) 3 is controlled to steer the wheels FL and FR in front of the vehicle via the reduction gear 4 and the rack and pinion 5 to reduce the steering operation force of the driver.

The engine EG of this embodiment is an internal combustion engine equipped with a throttle control device TH and a fuel injection device FI.
In the throttle control device TH, the main throttle opening of the main throttle valve MT is controlled according to the operation of the accelerator pedal 6. Further, according to the output of the electronic control unit ECU, the sub-throttle valve ST of the throttle control unit TH is driven to control the sub-throttle opening, and the fuel injection device FI is driven to control the fuel injection amount. It is configured. The engine EG of this embodiment includes a shift control device GS and a differential gear D.
Although it is connected to the wheels RL and RR on the rear side of the vehicle via F to form a so-called rear wheel drive system, the drive system in the present invention is not limited to this.

Next, in the braking system of the present embodiment, the wheel cylinders Wf are respectively attached to the wheels FL, FR, RL, RR.
1, Wfr, Wrl, Wrr are mounted, and the brake fluid pressure control device B is attached to these wheel cylinders Wfl and the like.
C is connected, which will be described later with reference to FIG. The wheel FL indicates the wheel on the front left side as viewed from the driver's seat, hereinafter the wheel FR indicates the front right side, the wheel RL indicates the rear left side, and the wheel RR indicates the rear right side wheel.

Wheel speed sensors WS1 to WS4 are provided on the wheels FL, FR, RL, and RR, which are connected to an electronic control unit ECU, and the rotational speed of each wheel, that is, the number of pulses proportional to the wheel speed. Is inputted to the electronic control unit ECU. Furthermore, the stop switch ST that is turned on when the brake pedal BP is depressed, and the steering angle θ of the wheels FL and FR in front of the vehicle
Steering angle sensor SS for detecting h, longitudinal acceleration Gx of the vehicle
Longitudinal acceleration sensor XG for detecting the
Lateral acceleration sensor YG for detecting the yaw rate, yaw rate sensor YS for detecting the yaw rate γ of the vehicle, steering torque sensor T
A rotation angle sensor RS that detects the rotation angle of S and the EPS motor 3 and the like are connected to the electronic control unit ECU.

FIG. 12 shows the system configuration of the present invention. The steering control system (EPS), the brake control system (ABS, TRC, VSC), the throttle control (SL).
The T) system, the shift control system (ATM), and the notification system are connected via a communication bus, and are configured so that the system information can be shared between the systems. In the steering control system, a steering torque sensor TS and a rotation angle sensor RS are connected to a steering control unit ECU1 including a CPU, a ROM and a RAM for electric steering control (EPS), and an EPS is provided via a motor drive circuit AC1. The motor 3 is connected.

Further, the brake control system includes anti-skid control (ABS), traction control (TRC),
A vehicle speed control (VSC) is performed, and a wheel speed sensor (typically represented by WS) and a hydraulic pressure sensor (typically) are provided in a brake control unit ECU2 including a CPU, a ROM, and a RAM for these brake controls. , PS), stop switch ST, yaw rate sensor YS,
The longitudinal acceleration sensor XG, the lateral acceleration sensor YG, and the steering angle sensor SS are connected to the solenoid drive circuit A.
Solenoid valve via C2 (typically represented by SL)
Are connected.

As described above, the notification system estimates the grip degree and notifies the grip degree when it is less than the predetermined value, and displays it on the notification control unit ECU3 equipped with the CPU, ROM and RAM for notification control. An informing device AC3 that outputs an indicator, a voice, or the like is connected. Further, in the throttle control (SLT) system, a throttle control actuator ECU 4 is connected to a throttle control unit ECU 4 including a throttle control CPU, ROM and RAM. Similarly, the shift control system is used for automatic transmission (AT
An actuator AC5 for shift control is connected to the shift control unit ECU5 including the CPU, ROM and RAM for shift control of M). In addition, these control units ECU1 to 5 respectively include a communication CPU and an RO.
It is connected to the communication bus via a communication unit having M and RAM. Thus, information required for each control system can be transmitted from other control systems.

FIG. 13 shows an example of the brake fluid pressure control device BC in this embodiment, which is a so-called brake-by-wire configuration. Specifically, for example, since it is described in Japanese Patent Laid-Open No. 2000-62597,
The operation will be briefly described. During normal operation, the hydraulic circuits of the master cylinder MC and the wheel cylinders Wfr, Wfl, Wrr, Wrl are disconnected. A driver's braking request is detected by a brake pedal operation amount detecting means such as a brake pedal stroke sensor SR, a pedaling force sensor, and a master cylinder hydraulic pressure sensor, and a target braking force of each wheel is determined based on the operation amount. The braking hydraulic pressure is controlled by the linear solenoid valves (SL1 to SL8).

During braking, the ON / OFF type solenoid valves SLa, SLb, SLc are excited, the solenoid valve SLa is in the open position, and the solenoid valves SLb, SL.
c becomes the closed position. As a result, the master cylinder MC
Is separated from the wheel cylinders Wfr, Wfl, Wrr, Wrl and communicates with the stroke simulator SM via a solenoid valve SLa. The braking fluid pressure of each wheel is controlled independently of each wheel by controlling the linear solenoid valve on the accumulator side (eg SL1) and the linear solenoid valve on the reservoir side (eg SL2) using the high pressure accumulator ACC as a pressure source. Controlled.
Note that the hydraulic circuit configuration in FIG. 13 is an example, and the present invention is not limited to this, and any hydraulic circuit configuration capable of automatically pressurizing may be used.

In the vehicle motion control device having the clipping degree estimating device constructed as described above, various controls are performed as follows. First, FIG. 14 is a flowchart showing a process for notifying the driver of a decrease in grip. First, initialization is performed in step 101, and various sensor signals are read in step 102. Next, in step 103, the actual self-aligning torque Tsaa is estimated based on the read sensor signal as follows.

In this embodiment, an electric power steering device is provided as shown in FIG. 11, and as described above,
The steering torque Tstr acting on the steering shaft 2 by the steering operation is detected by the steering torque sensor TS, and E is calculated according to the value of the detected steering torque Tstr.
The PS motor 3 is controlled, and the steering operation force of the driver is reduced. In this case, the self-aligning torque generated in the tires of the front wheels is balanced with the torque obtained by subtracting the friction component of the steering system from the sum of the steering torque by the steering operation and the torque output by the electric power steering device.

Therefore, the actual self-aligning torque Tsa
a can be calculated as Tsaa = Tstr + Teps-Tfrc. Here, Tstr is the torque that acts on the steering shaft by the driver's steering operation, and is detected by the steering torque sensor TS as described above.
Teps is the torque output by the electric power steering device. This is because, for example, the motor current value of the EPS motor 3 that constitutes the electric power steering device and the motor output torque have a predetermined relationship (the motor output torque is substantially proportional to the motor current value), and therefore, based on the motor current value. Can be estimated.

The above-mentioned Tfrc is the friction component of the steering system, that is, the torque component caused by the friction of the steering system. In the present embodiment, this is corrected by subtracting it from the sum of (Tstr + Teps), and the actual self-aligning is performed. The torque Tsaa is determined. Hereinafter, this correction method will be described with reference to FIG. When the vehicle is traveling straight ahead, the actual reaction torque (Tstr + Teps) is zero. When the driver starts steering operation and starts to cut the steering wheel (steering wheel), actual reaction torque starts to be generated. At this time, first, a torque for canceling the Coulomb friction of the steering mechanism (not shown) is generated, and then the front wheels FL, FR (tires) start to break and self-aligning torque is generated.

Therefore, in the initial stage of the steering operation from the straight running state, the self-aligning torque is not yet generated with respect to the increase of the actual reaction torque, as in the area between O and A in FIG. The estimated value of the self-aligning torque has a slight inclination with respect to the actual reaction force torque. The actual self-aligning torque Tsaa (This is a corrected value and is an estimated value, but the term of estimated value is omitted. Is output). When the steering wheel is further increased and the actual reaction torque exceeds the friction torque range, the actual self-aligning torque Tsaa is AB in the figure.
It is output along. When the steering wheel is turned back and the actual reaction torque decreases, B- in FIG.
The actual self-aligning torque Tsaa is output in a form having a slight inclination such as between C. When the actual reaction torque exceeds the friction torque region, as in the case of the additional cut, the actual self-aligning torque Tsaa is C in FIG.
It is output so as to extend between -D.

Returning to FIG. 14, in step 104, the reference self-aligning torque (Tsao) is calculated by the above method, and in step 105, the grip degree ε is estimated by the above method. Then, in step 106, the grip degree ε is compared with a predetermined value ε0. When the grip degree ε is less than the predetermined value ε0, the process proceeds to step 107, and the driver is notified of that fact. As the notification means, a means for displaying on an indicator or emitting a sound is used. Furthermore, it may be configured to output a voice prompting the accelerator operation to be loosened or the brake operation.

FIG. 15 shows a process in which braking force control for decelerating the vehicle, throttle control, and / or shift control are added to the above process, and step 2
Since 01 to 207 are the same as steps 101 to 107 of FIG. 14, description thereof will be omitted. In step 206, the grip degree ε is determined to be less than the predetermined value ε0, and step 20
7. After the driver is notified, step 208 is further executed.
At, the grip degree ε is compared with a predetermined value ε1 (<ε0). In step 208, the grip degree ε is the predetermined value ε
When it is determined that it is less than 1, the routine proceeds to step 209, where at least one of braking force control, throttle control, and shift control is executed.

For example, in the braking force control, even if the driver does not perform the braking operation, the braking force is applied to at least one wheel in order to decelerate the vehicle.
Since the throttle control also decelerates the vehicle, it is controlled to close the throttle. Further, also in the shift control, the shift position is switched to the deceleration direction, and downshifting is performed.

FIG. 16 is a flow chart showing an example of the braking force control of the above controls. First, step 3
In step 01, the grip degree ε is read, and in step 302, the driver's brake pedal operation amount (detection value of the stroke sensor SR in FIG. 13) is read. next,
In step 303, the road surface friction coefficient μ is estimated.
Here, the braking force control based on the grip degree is described above (see FIG. 1).
Similar to 5), it is executed when the degree of grip is lowered to some extent. Therefore, it is possible to estimate the road surface friction coefficient μ using the inflection point (point P in FIG. 9) of the actual self-aligning torque. The road surface friction coefficient can be estimated from any one of the state quantities such as the self-aligning torque when the actual self-aligning torque inflection point occurs, the front wheel slip angle, the side force, and the lateral acceleration.

Next, in step 304, the vertical load (wheel load) of each wheel is calculated from the lateral acceleration (detection value of the lateral acceleration sensor YG) and the longitudinal acceleration (detection value of the longitudinal acceleration sensor XG). Based on the above estimation and calculation results, that is, based on the driver's brake pedal operation amount, grip degree ε, road friction coefficient μ, and wheel load, step 3
At 05, the target braking force increment of each wheel is set. Then, in step 306, the solenoid valve (representatively represented by SL) in FIG. 13 is controlled based on the target braking force obtained by adding the above-described target braking force increment, and the following braking force control is performed.

FIG. 17 shows a block diagram of the braking force control based on the grip degree. The increment of the braking force based on the grip degree is the driver's brake pedal operation amount or the driver's target braking force, the estimated value of the grip degree, It is set based on the estimated value of the road surface friction coefficient, the estimated value of the wheel load, the vehicle behavior determination result, and the steering operation speed of the driver. The grip degree is estimated by the grip degree estimating means M12 (similar to FIG. 1), and the road surface friction coefficient is determined by the friction coefficient estimating means M13, as described above, at the inflection point of the actual self-aligning torque (point P in FIG. 9). ). The wheel load is determined by the wheel load estimating means M14 as described above (step 304).
The vehicle behavior is estimated and estimated by the vehicle behavior determination means M15 as described later. Further, the steering operation speed of the driver (steering wheel operation speed) is detected by the steering operation speed means M16. For example, the time change amount of the detected steering angle signal of the steering angle sensor SS of FIG. 11 is calculated. Then, the brake pedal operation amount of the driver is detected by the brake pedal operation amount detection means M17 (for example, the stroke sensor SR in FIG. 13).

Further, the brake pedal operation amount detecting means M1
Based on the detection output of No. 7, the driver target braking force setting means M1
8, the driver target braking force is set, and the target braking force increment setting means M19 sets the target braking force increment based on the setting result and the detection results of the respective means M12 to M16. Then, the target braking force setting means M20 determines the target value of the braking force of each wheel so that the target braking force increment is added to the driver's target braking force. Further, the braking force control based on the grip degree is executed even when the driver does not perform the braking operation. Therefore, even when the vehicle enters the curve at a speed exceeding the turning radius, the vehicle can pass through the curve while maintaining the turning radius by automatically braking based on the grip of the front wheels.

The target braking force increment in the braking force control based on the above-mentioned grip degree is set under the following conditions. FIG. 18 is a map of target braking force increments according to the driver's brake pedal operation amount (or driver target braking force). If the driver has already performed a brake operation of a predetermined amount (Kd) or more, either the brake operation is performed according to the necessity of braking, or the degree of grip is reduced due to braking, so the brake pedal When the operation amount (or the driver's target braking force) is equal to or more than the predetermined amount (Kd), the target braking force increment is set to zero.

FIG. 19 shows the grip degree ε of the target braking force increment.
Is a map for, and is set such that the target braking force increment increases as the grip degree ε decreases. However, if the grip factor ε becomes too low, the increase in the braking force causes a further decrease in the grip factor. Therefore, if the grip factor is less than the predetermined grip factor (ε2), the target braking force increment is set to be suppressed. When the road surface friction coefficient μ is low (Fig. 19)
(Indicated by a solid line in Fig. 1), when the road surface friction coefficient μ is high (Fig. 1).
9) (shown by a broken line in FIG. 9), the threshold value of the grip degree ε for starting the braking force control is set higher, and the control is set to start from the state where the grip degree ε is larger. Further, when the road surface friction coefficient μ is low, it is desirable to set the change rate of the target braking force increment with respect to the grip degree ε to be low so that the behavior change occurs gently.

FIG. 20 shows the road surface friction coefficient μ of the target braking force increment.
21 is a map for the wheel load of the target braking force increment. As is clear from FIGS. 20 and 21, the target braking force increment is set to increase as the road surface friction coefficient μ and the wheel load increase. The braking force characteristic of the wheel is determined by the wheel load and the road surface friction coefficient, but the braking force control is performed within the predetermined range of the "slip area" (see Fig. 2) of the wheel slip, that is, the "adhesion area". As is done, an upper limit value is set for the target braking force increment.

FIG. 22 is a map based on the driver's steering operation speed and grip of the target braking force increment. The steering operation speed of the driver (steering wheel operation speed) is determined by the steering angle signal (steering angle sensor SS) as described above.
It is obtained by calculating the amount of change over time of the detection signal). That is, when the steering operation speed is high, it is predicted that the vehicle is in an emergency such as obstacle avoidance. Therefore, the braking force control is set to start from a higher grip degree, and further sufficient deceleration is obtained. Thus, the value of the target braking force increment is also set high.

By the way, a normal vehicle is designed to have a weak understeer characteristic, and the limit is approached from the front wheels. Therefore, when performing the braking force control, while maintaining the total side force that can maintain the yaw moment and the turning radius that act inward in turning,
It is preferable to control the braking force of at least one wheel so that the vehicle can decelerate. As an example of braking force control,
It is also conceivable to increase the number of wheels that actuate the brake in accordance with the degree of grip, in the order of the turning inner rear wheel, the turning outer rear wheel, and the turning outer front wheel. Alternatively, the turning inner rear wheel, the turning outer rear wheel, and the turning outer front wheel may be simultaneously controlled. On a road surface having a high road surface friction coefficient, sufficient deceleration can be obtained, and therefore only the rear wheels may be controlled. However, when the road surface friction coefficient is extremely low, it may suddenly change to an oversteer tendency. Therefore, it is desirable to prohibit braking force control (increase in braking force) to the rear wheels.

Further, in the steady state, the vehicle has an understeer characteristic, but when the steering steering such as slalom or lane change or the road surface friction coefficient changes, there is a case where it tends to oversteer, and the control corresponding to this case may be performed. It shows in FIG. Since steps 401 to 404 are the same as steps 301 to 304 in FIG. 16, description thereof will be omitted. In step 405, the vehicle behavior is determined to determine whether the vehicle is understeered or oversteered. If it is determined in step 406 that oversteer is based on this determination result, the process proceeds to step 407, in which an oversteer control parameter is set so that the outward yaw moment of the turning can be generated and decelerated by increasing the braking force. . Step 40
If it is not determined that the steering is oversteer in step 6, the process proceeds to step 408, in which the understeer control parameter that allows deceleration while maintaining the inward turning yaw moment capable of tracing the turning radius is set. Then, in step 409, the target braking force increment is determined based on these control parameters, and braking force control is performed in step 410.

In the above embodiment, the grip degree ε is determined based on the self-aligning torque by paying attention to the change of the pneumatic trail of the tire. However, the side force with respect to the road surface friction is as follows. Grip degree that indicates the degree of lateral grip on the wheel based on the margin of
And) can be estimated.

First, according to the theoretical model of tire generation force (brush model), the relationship between the side force Fyf of the front wheel and the self-aligning torque Tsaa is expressed by the following equation. That is, ξ = 1- {Ks / (3 · μ · F
z)} · λ, Fyf = μ · Fz · (1−ξ ³ ) ... (1) when ξ> 0, Fyf = μ · Fz (2) when ξ ≦ 0 , Ξ> 0, Tsaa = (l · Ks / 6) · λ · ξ ³ (3) When ξ ≦ 0, Tsaa = 0 (4). Here, Fz is the ground contact load, l is the ground contact length of the tire ground contact surface, Ks is a constant corresponding to the tread rigidity, λ is the lateral slip (λ = tan (αf)), and αf is the front wheel slip angle.

Generally, in the region of ξ> 0, the front wheel slip angle αf is small, so that it can be treated as λ = αf. As is clear from the above formula (1), since the maximum value of the side force is μ · Fz, if the road surface friction utilization factor η is the ratio of the side force to the maximum value according to the road surface friction coefficient μ, η = 1 It can be expressed as −ξ ³ . Therefore, εm = 1-η is the road surface friction margin,
Letting εm be the grip of the wheel, εm = ξ ³ . Therefore, the above equation (3) can be expressed as follows. Tsaa = (l · Ks / 6) · αf · εm (5)

The above equation (5) shows that the self-aligning torque Tsaa is proportional to the front wheel slip angle αf and the grip degree εm. Therefore, grip degree εm = 1
When the characteristic at (the frictional utilization factor of the road surface is zero, that is, the friction allowance is 1) is set as the reference self-aligning torque characteristic, the following is obtained. Tsau = (l · Ks / 6) · αf (6)

Therefore, from the above equations (5) and (6),
The grip degree εm can be obtained as εm = Tsaa / Tsau (7). As is clear from the expression (7), in which the road surface friction coefficient μ is not included as a parameter, the grip degree εm can be calculated without using the road surface friction coefficient μ. In this case, the gradient K4 of the reference self-aligning torque Tsau (= l.
Ks / 6) can be set in advance using the above-mentioned brush model. It is also possible to obtain it experimentally. Further, if the initial value is first set, and the inclination of the self-aligning torque when the front wheel slip angle is near zero during traveling is identified and corrected, the detection accuracy can be improved.

For example, in FIG. 25, when the front wheel slip angle is αf2, the reference self-aligning torque is T
It is calculated by sau2 = K4 · αf2. And grip degree ε
m is εm = Tsaa2 / Tsau2 = Tsaa2 / (K4 · αf2)
Is required as.

Thus, instead of the grip degree ε based on the pneumatic trail shown in FIGS. 14 to 23, the grip degree εm based on the road surface friction allowance can be used. The grip degree ε and the grip degree εm described above have the relationship shown in FIG. Therefore, the grip degree ε can be obtained and converted into the grip degree εm, and conversely, the grip degree εm can be obtained and the grip degree εm can be obtained.
It can also be converted to.

[0077]

Since the present invention is configured as described above, it has the following effects. That is, according to the wheel grip degree estimating device of the first aspect, the self-aligning torque of the front wheels is estimated based on the steering force index such as the steering torque or the steering force, and the side force of the front wheels is determined based on the vehicle state quantity. Alternatively, the front wheel index such as the front wheel slip angle can be estimated, and the grip degree indicating the degree of lateral grip with respect to the front wheel can be accurately estimated based on the change in the self-aligning torque with respect to the front wheel index. It is possible to deal with the characteristics as well.

Further, by providing the reference self-aligning torque setting means as in claim 2, when the change of the self-aligning torque is judged, the self-aligning torque estimating means estimates the self-aligning torque. The grip degree can be easily and accurately estimated based on the result of comparison between the aligning torque and the reference self-aligning torque. The reference self-aligning torque setting means can be easily configured as described in claim 3 or claim 4.

Further, if the notifying means is provided as in claim 5, it is possible to notify the driver that the grip degree is less than the predetermined value, so that the driver excessively lowers the grip degree. Appropriate actions can be taken before taking action.

According to the vehicle motion control apparatus of the sixth aspect, the grip degree can be accurately estimated by the grip degree estimating apparatus, and when the grip degree falls below a predetermined value, the front wheel It is possible to perform appropriate motion control taking into consideration the characteristics of the tire as.

Further, by providing the reference self-aligning torque setting means as in claim 7, based on the comparison result of the reference self-aligning torque and the self-aligning torque estimated by the self-aligning torque estimating means. The grip degree can be estimated easily and accurately. The reference self-aligning torque setting means can be easily configured as described in claim 8 or claim 9.

Further, in the case of the construction according to the tenth aspect, when the grip degree becomes less than the predetermined value during the braking operation by the driver, at least regardless of the braking operation by the driver. Since the braking force for one wheel is controlled to be equal to or greater than the predetermined braking force, it is possible to appropriately decelerate the vehicle before it becomes unstable. The predetermined braking force in the braking force control at this time is set on the basis of at least one of the brake pedal operation amount, the grip degree, the road surface friction coefficient, and the wheel load, as described in claim 11. You can

Further, according to the twelfth aspect, when the road surface friction coefficient is less than the predetermined value, the increase of the braking force to the wheel behind the vehicle is prohibited, so that the sudden change to the oversteer tendency occurs. Can be dealt with appropriately and maintain a stable operating state.

Further, according to the thirteenth aspect, the braking force is controlled so that the generated yaw moment is different when the vehicle is understeered and when it is oversteered. Even if the understeer characteristic in the steady state causes an oversteer tendency due to a change in the road surface friction coefficient or the like, a stable driving state can be maintained by appropriate braking force control.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a grip degree estimating device of the present invention.

FIG. 2 is a graph showing a relationship between a self-aligning torque and a side force in a state in which a tire rolls while a tire rolls on a general vehicle.

FIG. 3 is a graph showing a simplified relationship between the self-aligning torque and the side force in FIG.

FIG. 4 is a graph showing characteristics of self-aligning torque with respect to front wheel side force according to the embodiment of the present invention.

FIG. 5 is a block diagram of a grip degree estimation device according to another embodiment of the present invention.

FIG. 6 is a graph showing the relationship between front wheel side force and self-aligning torque with respect to the front wheel slip angle in another embodiment of the present invention.

FIG. 7 is a graph showing the relationship between the front wheel slip angle and the self-aligning torque in another embodiment of the present invention.

FIG. 8 is a graph showing the relationship between the front wheel slip angle and the self-aligning torque in another embodiment of the present invention.

FIG. 9 is a graph showing the relationship between the front wheel slip angle and the self-aligning torque in another embodiment of the present invention.

FIG. 10 is a graph showing the relationship between the front wheel slip angle and the self-aligning torque in another embodiment of the present invention.

FIG. 11 is a configuration diagram showing an embodiment of a vehicle motion control device of the invention.

FIG. 12 is a block diagram showing a system configuration according to an embodiment of the motion control device of the present invention.

FIG. 13 is a configuration diagram showing a brake fluid pressure control device provided in an embodiment of the present invention.

FIG. 14 is a flowchart showing a process for notifying a driver of a decrease in grip degree in an embodiment of the present invention.

FIG. 15 is a flowchart showing a process in the case of performing a braking force control or the like in addition to the notification when the grip degree is lowered in the embodiment of the present invention.

16 is a flowchart showing an example of braking force control in FIG.

FIG. 17 is a block diagram showing braking force control based on a grip degree in the embodiment of the present invention.

FIG. 18 is a graph showing a map of target braking force increments according to a driver's brake pedal operation amount according to the embodiment of the present invention.

FIG. 19 is a graph showing a map of a target braking force increment with respect to a grip degree in the embodiment of the present invention.

FIG. 20 is a graph showing a map of road surface friction coefficient of target braking force increment in one embodiment of the present invention.

FIG. 21 is a graph showing a map of a target braking force increment with respect to a wheel load according to the embodiment of the present invention.

FIG. 22 is a graph showing a map based on a driver's steering operation speed and grip degree of a target braking force increment in one embodiment of the present invention.

FIG. 23 is a flowchart showing another example of braking force control according to the embodiment of the present invention.

FIG. 24 is a graph showing the characteristic of the friction component of the steering system used for correction when estimating the self-aligning torque in the embodiment of the present invention.

FIG. 25 is a graph showing the relationship between the front wheel slip angle and the self-aligning torque in still another embodiment of the present invention.

FIG. 26 is a graph showing a relationship between a grip degree ε based on a pneumatic trail and a grip degree εm based on a road surface friction allowance in the present invention.

[Explanation of symbols]

1 steering wheel, 2 steering shaft, 3 EPS motor, TS steering torque sensor,
SS steering angle sensor, ECU electronic control unit, YS
Yaw rate sensor, XG longitudinal acceleration sensor, YG
Lateral acceleration sensor, BP brake pedal, ST stop switch, FR, FL, RR, RL wheels, WS
1-WS4 Wheel speed sensor Wfr, Wfl, Wrr, Wrl
Wheel cylinder, BC Brake fluid pressure controller

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B60R 16/02 661 B60R 16/02 661Z B62D 6/00 B62D 6/00 F02D 29/00 F02D 29/00 H // B62D 101: 00 B62D 101: 00 111: 00 111: 00 113: 00 113: 00 119: 00 119: 00 137: 00 137: 00 (71) Applicant 301065892 Advics Co., Ltd. 2 Asahi-cho, Kariya city, Aichi prefecture 1-chome (72) Inventor Yoshiyuki Yasui 2-chome, Asahi-cho, Kariya-shi, Aichi Aisin Seiki Co., Ltd. (72) Wataru Tanaka 2-chome, Asahi-cho, Kariya-shi, Aichi Aisin-seiki Co., Ltd. (72) Inventor, Eiichi Ono, Nagakute-cho, Aichi-gun, Aichi Prefecture 1 41, Yokosuka, Yokouchi Central Research Institute Co., Ltd. (72) Inventor, Yuji Muragishi Nagakute-cho, Aichi-gun, Aichi Prefecture 1 in 41 Chuo Yokoido, in the Central Research Institute of Toyota Co., Ltd. (72) Inventor Katsuhiro Asano 1 in 41, Nagakute-cho, Aichi-gun, Aichi Prefecture 1 in Chuo Research Center, Toyota (72) Inventor, Mine Kashiyama 1-1-1 Asahi-machi, Kariya city, Aichi prefecture, Toyota Koki Co., Ltd. (72) Inventor, Ogawa 2-1-1, Asahi-cho, Kariya city, Aichi prefecture, Toyota machine Co., Ltd. (72) Kenji Asano Aichi prefecture Kariya City, Asahi-cho 2-chome, Advics Co., Ltd. (72) Inventor Yuzo Imoto 2-chome, Asahi-cho, Kariya-shi, Aichi F-term in Advics Co., Ltd. 3D032 DA03 DA15 DA23 DA29 DA33 EB21 EB30 FF01 FF02 FF07 3D041 AA47 AA80 AB01 AC01 AC14 AC28 AD41 AD50 AD51 AE02 AE30 AE41 AE45 AF01 3D046 BB21 GG02 HH02 HH08 HH16 HH21 HH25 HH26 HH35 HH36 3G093 AA04 BA01 DB02 DB05 DB11 DB15 FA17 EA04 EB02

Claims (13)

[Claims] 1. Steering force index detecting means for detecting at least one steering force index of a steering force index including a steering torque and a steering force applied to a steering system from a steering wheel of a vehicle to a suspension, and the steering force. Self-aligning torque estimating means for estimating a self-aligning torque generated in a wheel in front of the vehicle based on a detection signal of the index detecting means, vehicle state quantity detecting means for detecting the state quantity of the vehicle, and the vehicle state quantity Based on the detection signal of the detection means, the front wheel index estimation means for estimating at least one front wheel index among the front wheel indexes including the side force and the front wheel slip angle for the wheel in front of the vehicle, and the front wheel index estimation means estimated. Based on the change in the self-aligning torque estimated by the self-aligning torque estimating means with respect to the front wheel index, A grip degree estimating device for a wheel, comprising: a grip degree estimating means for estimating a grip degree for a wheel in front of the vehicle. 2. A reference self-aligning torque setting means for setting a reference self-aligning torque based on the front wheel index estimated by the front wheel index estimating means and the self-aligning torque estimated by the self-aligning torque estimating means. However, the grip degree estimating means, based on the comparison result of the reference self-aligning torque set by the reference self-aligning torque setting means and the self-aligning torque estimated by the self-aligning torque estimating means, at least the aforesaid The grip degree estimating device for a wheel according to claim 1, wherein the grip degree estimating apparatus is configured to estimate a grip degree for a wheel in front of the vehicle. 3. The reference self-aligning torque setting means includes a characteristic of the self-aligning torque estimated by the self-aligning torque estimating means with respect to the front wheel index estimated by the front wheel index estimating means, at least linearly including an origin. 3. The wheel grip according to claim 2, wherein a reference self-aligning torque characteristic that is approximated to is set, and the reference self-aligning torque is set based on the reference self-aligning torque characteristic. Degree estimation device. 4. The reference self-aligning torque setting means sets a linear reference self-aligning torque characteristic having a gradient set based on a brush model for a wheel in front of the vehicle, and the reference self-aligning torque characteristic. The reference self-aligning torque is set based on the above.
The wheel grip degree estimating device described. 5. A notifying means for comparing the grip degree estimated by the grip degree estimating means with a predetermined value and notifying the driver of the vehicle when the grip degree is less than the predetermined value. The grip estimation device for a wheel according to claim 1 or 2. 6. Steering force index detecting means for detecting at least one steering force index of a steering force index including a steering torque and a steering force applied to a steering system from a steering wheel of a vehicle to a suspension, and the steering force. Self-aligning torque estimating means for estimating a self-aligning torque generated in a wheel in front of the vehicle based on a detection signal of the index detecting means, vehicle state quantity detecting means for detecting the state quantity of the vehicle, and the vehicle state quantity Based on the detection signal of the detection means, the front wheel index estimation means for estimating at least one front wheel index among the front wheel indexes including the side force and the front wheel slip angle for the wheel in front of the vehicle, and the front wheel index estimation means estimated. Based on the change in the self-aligning torque estimated by the self-aligning torque estimating means with respect to the front wheel index, The vehicle includes a wheel grip degree estimating device including a grip degree estimating means for estimating a grip degree for a vehicle front wheel, and at least a braking force for the vehicle according to a detection signal of the vehicle state quantity detecting means, A control means for controlling at least one of an engine output and a shift position, and when the grip degree estimated by the grip degree estimating means is less than a predetermined value, the control means causes the braking force and the engine output to the vehicle. And a motion control device for a vehicle configured to control at least one of a shift position and decelerate the vehicle. 7. A reference self-aligning torque setting means for setting a reference self-aligning torque based on the front wheel index estimated by the front wheel index estimating means and the self-aligning torque estimated by the self-aligning torque estimating means. However, the grip degree estimating means, based on the comparison result of the reference self-aligning torque set by the reference self-aligning torque setting means and the self-aligning torque estimated by the self-aligning torque estimating means, at least the aforesaid 7. The vehicle motion control apparatus according to claim 6, wherein the vehicle motion control apparatus is configured to estimate a grip degree with respect to a wheel in front of the vehicle. 8. The reference self-aligning torque setting means includes a characteristic of the self-aligning torque estimated by the self-aligning torque estimating means with respect to the front wheel index estimated by the front wheel index estimating means, and a linear characteristic including at least an origin. The grip of the wheel according to claim 7, wherein the reference self-aligning torque characteristic approximated to is set, and the reference self-aligning torque is set based on the reference self-aligning torque characteristic. Degree estimation device. 9. The reference self-aligning torque setting means sets a linear reference self-aligning torque characteristic having a slope set based on a brush model for a wheel in front of the vehicle, and the reference self-aligning torque characteristic. The reference self-aligning torque is set based on the above.
The wheel grip degree estimating device described. 10. The braking operation by the driver of the vehicle is performed by the control means when the grip degree estimated by the grip degree estimating means is less than a predetermined value during the braking operation by the driver of the vehicle. The control is performed so that the braking force for at least one wheel of the vehicle is irrelevant regardless of the predetermined braking force regardless of the braking force.
The vehicle motion control device described. 11. The predetermined braking force in the braking force control by the control means includes a brake pedal operation amount in the vehicle, the grip degree, a road surface friction coefficient for the wheel,
11. The vehicle motion control device according to claim 10, wherein the load is set based on at least one of the loads on the wheels. 12. The vehicle according to claim 11, wherein, when the road surface friction coefficient is less than a predetermined value, the control means controls so as to prohibit an increase in a braking force applied to a wheel behind the vehicle. Motion control device. 13. The control means determines whether the vehicle is understeer tendency or oversteer tendency on the basis of a detection signal of the vehicle state amount detection means, and when the vehicle is understeer tendency and when the vehicle is oversteer. 11. The vehicle motion control device according to claim 10, wherein the braking force is controlled so that the generated yaw moment of the vehicle is different when the vehicle is in a tendency.