JP2013185840A - Road surface friction coefficient estimation device and road surface friction coefficient estimation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a road surface friction coefficient estimation device that prevents a reduction in response speed even when a road surface friction coefficient suddenly changes and improves detection performance, and to provide a method thereof.SOLUTION: A road surface friction coefficient estimation device 1 includes: a road surface friction coefficient sudden change determination part 2 that outputs a road surface friction coefficient sudden change signal when a sudden change of the road surface friction coefficient is determined on the basis of a change in road surface condition; a convergence correction function setting part 3 that changes and sets a convergence correction function on the basis of the road surface friction coefficient sudden change signal; a tire deformation state amount detection part 4 that detects a state amount of tire deformation indicative of a tire deformation condition; and an estimated road surface friction coefficient value calculation part 6 that estimates a road surface friction coefficient on the basis of the tire deformation state amount and the convergence correction function, to calculate an estimated road surface friction coefficient value. When a road surface friction coefficient sudden change signal indicates a sudden change in road surface friction coefficient, a convergence correction function is set so as to reduce the ease of converging to a first target convergence value as a normal target convergence value.

Description

  The present invention relates to a road surface friction coefficient estimation device and a road surface friction coefficient estimation method for estimating a friction coefficient between a tire and a road surface.

  Conventionally, Patent Document 1 has been disclosed as an apparatus for estimating the road surface friction coefficient, and the value of the road surface friction coefficient is accurately estimated by suppressing the influence of model error and noise included in the sensor measurement value. ing. The road friction coefficient estimation device disclosed in Patent Document 1 is a device that estimates a road friction coefficient so that an error between a slip ratio calculated using a model and a measured slip ratio is reduced. In this apparatus, when the road surface friction coefficient is estimated, the robustness against the model error is improved by adding a correction term having a function of converging the calibration parameter around a preset value.

JP 2001-133391 A

  However, in the conventional road surface friction coefficient estimating device described above, it is not easy to set the magnitude of the variable gain multiplied by the correction term. If the setting of the variable gain is too large, the friction coefficient may change suddenly or acceleration / deceleration may occur. Even if the slip ratio increases in the running scene where the vehicle has started, there is a possibility that the change in the friction coefficient cannot be detected accurately and the detection performance is deteriorated.

  Therefore, the present invention has been proposed in view of the above-described circumstances, and a road surface friction coefficient estimation device and a road surface that can prevent a decrease in response speed and improve detection performance even when the road surface friction coefficient changes suddenly. An object of the present invention is to provide a friction coefficient estimation method.

  The present invention provides a road surface friction coefficient sudden change determination unit that outputs a road surface friction coefficient sudden change signal when it is determined that the road surface friction coefficient suddenly changes based on a change in the road surface state, and a road surface friction coefficient converges to a predetermined convergence target value. A convergence correction function setting unit that changes and sets a convergence correction function that is a function for correction based on a road surface friction coefficient sudden change signal, and a tire deformation state amount detection that detects a tire deformation state amount that represents a tire deformation state And a road surface friction coefficient estimated value calculation unit that calculates the road surface friction coefficient estimated value by estimating the road surface friction coefficient based on the tire deformation state quantity and the convergence correction function. The convergence correction function setting unit reduces the ease of convergence to the first convergence target value, which is the normal convergence target value, when a sudden change in the road surface friction coefficient is indicated by the road surface friction coefficient sudden change signal. It is characterized by setting a convergence correction function.

  According to the road surface friction coefficient estimation apparatus and the road surface friction coefficient estimation method according to the present invention, when it is determined that the road surface friction coefficient changes suddenly, the ease of convergence to the first convergence target value, which is the normal convergence target value, is reduced. Thus, since the convergence correction function is set, it is easy to converge to the convergence target value at the time of sudden change, and even when the road surface friction coefficient changes suddenly, the response speed can be prevented from decreasing and the detection performance can be improved.

It is a block diagram which shows the structure of the road surface friction coefficient estimation apparatus which concerns on one Embodiment of this invention. It is a figure which shows the structure of the vehicle carrying the road surface friction coefficient estimation apparatus which concerns on one Embodiment of this invention. It is a flowchart which shows the procedure of the calculation process of the road surface friction coefficient estimated value by the road surface friction coefficient estimation apparatus which concerns on one Embodiment of this invention. It is a figure which shows an example of the convergence correction function set by the road surface friction coefficient estimation apparatus which concerns on one Embodiment of this invention. It is a figure which shows an example of the convergence correction function set by the road surface friction coefficient estimation apparatus which concerns on one Embodiment of this invention. It is a figure which shows an example of the convergence correction function set by the road surface friction coefficient estimation apparatus which concerns on one Embodiment of this invention. It is a figure which shows the relationship between the tire deformation state quantity and the tire slip angle in the road surface friction coefficient estimation apparatus which concerns on one Embodiment of this invention.

  Hereinafter, an embodiment to which the present invention is applied will be described with reference to the drawings.

[Configuration of road friction coefficient estimation device]
FIG. 1 is a block diagram showing a configuration of a road surface friction coefficient estimating apparatus according to the present embodiment. As shown in FIG. 1, the road surface friction coefficient estimation device 1 according to the present embodiment outputs a road surface friction coefficient sudden change signal that outputs a road surface friction coefficient sudden change signal when it is determined that the road surface friction coefficient changes suddenly based on a change in road surface state. 2, a convergence correction function setting unit 3 that changes and sets a convergence correction function based on a road surface friction coefficient sudden change signal, a tire deformation state amount detection unit 4 that detects a tire deformation state amount that represents a tire deformation state, A tire slip angle detecting unit 5 for detecting a tire slip angle, a road surface friction coefficient estimated value calculating unit 6 for estimating a road surface friction coefficient based on a tire deformation state quantity and a convergence correction function, and calculating a road surface friction coefficient estimated value; And a storage unit 7 for storing the calculated road surface friction coefficient estimated value.

  A road surface friction coefficient estimation device 1 shown in FIG. 1 is mounted on a vehicle, and vehicle motion control is performed using the detected road surface friction coefficient estimation value. Here, an example of a vehicle equipped with the road surface friction coefficient estimating apparatus 1 according to the present embodiment will be described with reference to FIG. As shown in FIG. 2, the vehicle 100 includes a drive motor 101 as a driving force generation source, and the power shaft is connected to the rear wheels 104RL and 104RR to drive the left and right rear wheels.

  The drive circuit 102 drives the drive motor 101 by controlling the electric power from the lithium ion battery 103 so that the output torque of the drive motor 101 matches the torque command value commanded from the integrated controller 130.

The integrated controller 130 includes an accelerator opening signal APO detected by an accelerator pedal sensor 123, a steering angle signal of a steering wheel detected by a steering angle sensor 121 attached to a rotation shaft of the steering wheel 111, and each wheel. The wheel speeds detected by the attached wheel speed sensors 105FL, 105FR, 105RL, and 105RR, the yaw rate detected by the yaw rate sensor 108, the longitudinal acceleration and the lateral acceleration detected by the acceleration sensor 109 are input.

  The steering wheel 111 is connected to a reaction force motor 115, and a reaction force torque corresponding to a self-aligning torque generated in the tire at the time of turning is generated and applied by the reaction force motor 115. The front wheels 104FL and 104FR are steered in the same phase on the left and right sides when the steering motors 113L and 113R displace the steering rack in the vehicle width direction according to the angle detected by the steering angle sensor 121 attached to the steering wheel 111. ing. The steered motors 113L and 113R transmit the output torque of the motor and the rotation speed of the motor to the integrated controller 130, respectively. The road surface friction coefficient estimation device 1 according to this embodiment is mounted on the integrated controller 130.

  Next, each part which comprises the road surface friction coefficient estimation apparatus 1 shown in FIG. 1 is demonstrated.

  First, the road surface friction coefficient sudden change determination unit 2 detects a sudden change in the road surface friction coefficient based on a change in the road surface state other than the deformation state of the tire. For example, the road surface friction coefficient sudden change determination unit 2 analyzes the image of the camera that captures the road surface. Is detected from dry to wet or snowy, and a sudden change in the road surface friction coefficient is determined. Also, based on acceleration detected by an acceleration sensor installed in a suspension that actively controls vibration using a hydraulic or electric actuator, for example, when the high frequency component of the acceleration detection value increased in a short time, it entered the gravel road It may be determined that the road surface friction coefficient has suddenly changed. Alternatively, when the ABS (anti-lock brake system) is activated, or when slip is detected in the tire longitudinal direction when a driving force is applied by a TCS (traction control system) or the like, it is determined that the road surface friction coefficient has suddenly changed. It may be. In addition, when the detection value of the lateral G sensor or yaw rate sensor installed in the vehicle changes faster than the degree estimated from the change in the steering angle and the vehicle speed, it is determined that the road surface friction coefficient has changed suddenly. It is good. When it is determined that the road surface friction coefficient changes suddenly in this way, the road surface friction coefficient sudden change determination unit 2 outputs a road surface friction coefficient sudden change signal.

  The convergence correction function setting unit 3 changes and sets the convergence correction function based on the road surface friction coefficient sudden change signal. The convergence correction function is a function for correcting the road surface friction coefficient so as to converge to a preset convergence target value. In the present embodiment, the convergence correction function setting unit 3 is set in advance separately with a normal convergence correction function and a convergence correction function when the road surface friction coefficient suddenly changes, so that switching is performed according to the road surface friction coefficient sudden change signal. It has become a structure. However, the present invention is not limited to such a configuration, and any other configuration may be used as long as the convergence correction function can be changed and set according to the road surface friction coefficient sudden change signal.

  The tire deformation state quantity detection unit 4 detects a tire deformation state quantity that is a detectable state quantity that occurs in accordance with tire deformation. Examples of the tire deformation state quantity include tire lateral force, self-aligning torque (hereinafter referred to as SAT), tire longitudinal force, and slip ratio. In the present embodiment, a case where SAT is a tire deformation state amount will be described as an example. However, when another amount is a tire deformation state amount, SAT may be read as another amount.

  The tire slip angle detection unit 5 detects the tire slip angle by calculating from the rudder angle and the vehicle speed using a vehicle model such as a two-wheel model (vehicle movement and control second edition, written by Sankaido and Masato Abe). To do. Alternatively, the tire slip angle may be obtained by detecting the lateral speed of the vehicle body relative to the road surface using GPS and converting the lateral speed.

  The road surface friction coefficient estimated value calculation unit 6 calculates a tire deformation state amount error by multiplying the difference between the tire deformation state amount and the tire deformation state amount estimated value estimated from the tire model by a tire deformation state amount gain. The road surface friction coefficient estimated value is calculated by time integration of the sum of the deformation state quantity error and the convergence correction function. Further, the road surface friction coefficient estimated value calculation unit 6 calculates a tire deformation state quantity estimated value according to the tire slip angle and the road surface friction coefficient estimated value.

The storage unit 7 stores the road surface friction coefficient estimated value μ ^{^} _{k + 1} calculated by the road surface friction coefficient estimated value calculation unit 6, and the road surface friction coefficient estimated value μ ^{^} _{k + 1} is used when the next calculation step is executed. Is read as the road surface friction coefficient estimated value μ ^{^} _k in the previous calculation step.

[Calculation of estimated road friction coefficient]
Hereinafter, with reference to the flowchart shown in FIG. 3, the procedure of the calculation process of the road surface friction coefficient estimated value by the road surface friction coefficient estimation apparatus which concerns on this embodiment is demonstrated.

As shown in FIG. 3, in the road surface friction coefficient estimated value calculation process according to this embodiment, first, in step S101, the tire deformation state amount detection unit 4 detects the SAT detection value T _sat as the tire deformation state amount. As a detection method of the SAT detection value T _sat , for example, it can be calculated from the driver torque sensor installed in the existing electric power steering and the current of the assist motor. It is also possible to directly measure the amount corresponding to SAT by installing a strain sensor on the steering tie rod.

Next, when the tire slip angle detection unit 5 detects the tire slip angle in step S102, the road friction coefficient estimated value calculation unit 6 reads the road surface friction coefficient estimated value μ ^{^} _k in the previous calculation step in step S103.

  In step S104, the road surface friction coefficient sudden change determination unit 2 determines whether or not the road surface friction coefficient has suddenly changed based on the change in the road surface state. If the road surface friction coefficient has changed suddenly, the road surface friction coefficient A sudden change signal is output. As described above, as a method for determining whether or not the road surface friction coefficient has suddenly changed, the determination is made by analyzing the camera image, changing the high frequency component of acceleration, or the like.

  Next, in step S105, the convergence correction function setting unit 3 refers to the road surface friction coefficient sudden change signal to recognize whether or not the road surface friction coefficient has suddenly changed. If the road surface friction coefficient has not suddenly changed, the step is performed. In S106, a normal convergence correction function is set.

The normal convergence correction function can be expressed as the following equation using the road surface friction coefficient estimated value μ ^{^} _k in the current calculation step as a variable.

^{_{f corr (μ ^ k) =}} K s g 1 (μ ^ k) (1)
Here, K _s represents the magnitude of the absolute value of the convergence correction function as a correction gain, and is appropriately determined by the designer. The function g ₁ (μ ^{^} _k ) is a function set based on a sine function, and is a function having the shape shown in FIG. 4, for example.

The convergence correction function shown in FIG. 4 is a function based on a sine function and a road surface friction coefficient estimated value μ ^{^} as a variable. The convergence target value is 0.3 or 1.0, and the value becomes 0. The values are switched between +1 and −1 before and after. Since the purpose of this convergence correction function is to determine whether the road friction coefficient is high or low, the first convergence target value μ ₁ corresponding to a high friction coefficient such as a paved road is set to 1.0, and the frozen road surface. The second convergence target value μ ₂ corresponding to such a low friction coefficient is set to 0.3. Here, the first convergence target value μ ₁ is a normal convergence target value at which the vehicle can normally travel, and the second convergence target value μ ₂ is a convergence target value when the road surface friction coefficient suddenly changes.

  On the other hand, when the road surface friction coefficient changes suddenly in step S105, a convergence correction function when the road surface friction coefficient changes suddenly is set in step S107.

The convergence correction function at the time of sudden change can be expressed as the following equation using the road surface friction coefficient estimated value μ ^{^} _k at the current calculation step as a variable.

^{_{f corr (μ ^ k) =}} K s g 2 (μ ^ k) (2)
Here, K _s represents the magnitude of the absolute value of the convergence correction function as a correction gain, and is appropriately determined by tuning. The function g ₂ (μ ^{^} _k ) is a function set based on a sine function, for example, a function having the shape shown in FIG.

  As shown in FIG. 5, the convergence correction function at the time of sudden change brings the position of the intermediate zero point where the value is 0 between the first convergence target value and the second convergence target value closer to the direction of the first convergence target value. Yes. In the normal convergence correction function shown in FIG. 4, the intermediate zero is set to 0.6. However, in the convergence correction function during sudden change shown in FIG. It is close to the target value.

Further, the function g ₂ (μ ^{^} _k ) may be shaped as shown in FIG. In the convergence correction function shown in FIG. 6, the absolute value of the convergence correction function in the section near the first convergence target value (the section where μ ^{^} _k is 0.6 to 0.9) is the section near the second convergence target value ( μ ^{^} _k is set to be smaller than the absolute value of the convergence correction function in the interval of 0.3 to 0.6. In the normal convergence correction function shown in FIG. 4, the absolute value is set to 1 in every section. However, in the convergence correction function in the sudden change shown in FIG. 6, the absolute value is set to 1 in the section near the first convergence target value. A small value is set, and a value larger than 1 is set in the vicinity of the second convergence target value.

  If the convergence correction function at the time of sudden change is set as shown in FIG. 5 and FIG. 6 as described above, the ease of convergence to the first convergence target value, which is the normal convergence target value, is reduced and suddenly changed. It is possible to increase the ease of convergence to the second convergence target value that is the convergence target value at that time. Thereby, it is possible to improve the detection performance by preventing the responsiveness from deteriorating when the road surface friction coefficient changes suddenly. In addition, you may set the convergence correction function which applied both the convergence correction function shown in FIG. 5, and the convergence correction function shown in FIG.

  In addition, it is not necessary to set the convergence correction function for normal time and the convergence correction function for sudden change separately in advance, and the convergence correction function is changed according to the road surface friction coefficient sudden change signal. The configuration may be such that the convergence correction function can be changed and set as appropriate.

When the convergence correction function at the time of normal or sudden change is set in this way, in step S108, the road surface friction coefficient estimated value calculation unit 6 next calculates the tire deformation state quantity estimated value T ^{^} _sat (μ ^{^} , α estimated from the tire model. _f ) is obtained. Here, α _f is the tire slip angle detected by the tire slip angle detection unit 5, and the tire deformation state estimated value T ^{^} _sat (μ ^{^} , α _f ) is obtained experimentally in advance and stored as a map or the like. by storing in the section 7, it can be obtained appropriately according to the road surface frictional coefficient estimated value mu ^{^} and tire slip angle alpha _f.

The difference between the tire deformation state quantity T _sat (μ, α _f ) detected by the tire deformation state quantity detection unit 4 and the tire deformation state quantity estimated value T ^{^} _sat (μ ^{^} , α _f ) is added to the tire deformation state quantity. By multiplying the gain K _sat , the tire deformation state error K _sat {T ^{^} _sat (μ ^{^} , α _f ) −T _sat (μ, α _f )} is calculated, and this tire deformation state amount error and the convergence correction function f _The following equation is obtained by calculating the sum of _corr (μ ^{^} ).

Equation (3) is a differential equation, and the first term of Equation (3) is that the error between the estimated value T ^{^} _sat of the tire deformation state estimated by the tire model and the measured value T _sat of the tire deformation state amount is reduced. In this way, the road surface friction coefficient is estimated. The second term is a convergence correction function, which has the effect of converging the road surface friction coefficient estimated value in the vicinity of a convergence target value set in advance for various road surface conditions.

  Then, the road friction coefficient estimated value in the next calculation step is calculated based on the following expression by integrating the expression (3) with time.

_{^{μ ^ k + 1 = [K}} sat {T ^ sat (μ ^ k, α fk) -T sat (μ k, α fk)} + f corr (μ ^ k)] Δt + μ ^ k (4)
Here, k represents a calculation step, and Δt represents a sampling time, that is, a time interval in each calculation step. By implementing Equation (4) in the digital calculator, the next value can be calculated based on the current value of the road surface friction coefficient estimated value.

The tire deformation state gain (SAT error compensation gain) K _sat may be a constant value appropriately determined in advance by tuning or the like, but the noise intensity included in the SAT measurement value using the Kalman filter algorithm May be determined according to the estimated value of the road surface friction coefficient or the tire slip angle. At this time, when the tire deformation state gain K _sat is changed according to the tire slip angle, as shown in FIG. 7, the tire deformation state gain K _sat is rapidly increased as the tire slip angle α approaches zero. Set to decrease. By doing so, it is possible to expect an effect of preventing the estimated value of the road surface friction coefficient from becoming unstable when the tire slip angle in which the road surface friction coefficient information is not included in the SAT detection value is near zero.

When the next value μ ^{^} _{k + 1} of the road surface friction coefficient estimated value is calculated in this way, the road surface friction coefficient estimated value calculation unit 6 stores the next value μ ^{^} _{k + 1} of the road surface friction coefficient estimated value in the storage unit 7 in step S109. The calculation process of the road surface friction coefficient estimation value by the road surface friction coefficient estimation device 1 according to the present embodiment ends.

[Effect of the embodiment]
As described above, according to the road surface friction coefficient estimation device according to the present embodiment, when it is determined that the road surface friction coefficient changes suddenly, the ease of convergence to the first convergence target value, which is the normal convergence target value, decreases. Thus, since the convergence correction function is set, it is easy to converge to the convergence target value at the time of sudden change, and even when the road surface friction coefficient changes suddenly, the response speed can be prevented from decreasing and the detection performance can be improved. Furthermore, by using the calculated estimated value of the road surface friction coefficient for vehicle motion control, even when the road surface friction coefficient suddenly decreases, stabilization control can be performed before the behavior of the vehicle is disturbed, and spin can be prevented. Such effects can be expected.

  Moreover, according to the road surface friction coefficient estimating apparatus according to the present embodiment, when it is determined that the road surface friction coefficient changes suddenly, the ease of convergence to the second convergence target value that is the convergence target value at the time of sudden change increases. Since the convergence correction function is set, it is easy to converge to the convergence target value at the time of sudden change, and even when the road surface friction coefficient changes suddenly, the response speed can be prevented from decreasing and the detection performance can be improved.

  Furthermore, according to the road surface friction coefficient estimation apparatus according to the present embodiment, a function that has a value of 0 when the road surface friction coefficient estimated value is a convergence target value and whose sign is switched before and after the convergence target value is used as a convergence correction function. Therefore, the road surface friction coefficient estimated value can be converged to the convergence target value, and the road surface friction coefficient estimated value can be calculated robustly with respect to the tire model error.

  Further, according to the road surface friction coefficient estimating apparatus according to the present embodiment, the absolute value of the convergence correction function in the vicinity of the first convergence target value is obtained when the road surface friction coefficient sudden change signal is indicated by the road surface friction coefficient sudden change signal. Since it is smaller than the absolute value of the convergence correction function in the vicinity of the target value, the road surface friction coefficient estimated value can be estimated faster when the road surface friction coefficient changes suddenly.

  Furthermore, according to the road surface friction coefficient estimating device according to the present embodiment, when the road surface friction coefficient sudden change signal is indicated by the road surface friction coefficient sudden change signal, the value is between the first convergence target value and the second convergence target value. Since the position of the intermediate zero point that becomes 0 is brought closer to the direction of the first convergence target value, the road surface friction coefficient estimated value can be estimated faster when the road surface friction coefficient changes suddenly.

  Further, according to the road surface friction coefficient estimating apparatus according to the present embodiment, the tire deformation state amount error is calculated by multiplying the difference between the tire deformation state amount and the tire deformation state amount estimated value by the tire deformation state amount gain, The road surface friction coefficient estimated value is calculated by time integration of the sum of the tire deformation state quantity error and the convergence correction function, thus reducing the time calendar vibration of the road surface friction coefficient estimated value caused by the noise included in the tire deformation state quantity. can do.

  Furthermore, according to the road surface friction coefficient estimating device according to the present embodiment, since the tire deformation state amount estimated value is calculated according to the tire slip angle and the road surface friction coefficient estimated value, the self-aligning torque or the tire deformation state amount is calculated as the tire deformation state amount. When the tire lateral force is selected, the tire deformation state quantity estimated value can be calculated with high accuracy, and the estimation accuracy of the road surface friction coefficient can be improved.

  Further, according to the road surface friction coefficient estimating device according to the present embodiment, the tire deformation state amount gain is set so as to decrease as the tire slip angle decreases, so that the tire deformation state such as when the tire slip angle is small. Therefore, it is possible to prevent the estimated value of the road surface friction coefficient from becoming unstable when information on the road surface friction coefficient cannot be extracted from the road surface.

  In addition, according to the road surface friction coefficient estimating device according to the present embodiment, the tire output is because the tire deformation state quantity is any one of the tire lateral force, the tire longitudinal force, the self-aligning torque, and the slip ratio. The estimated value of the road surface friction coefficient can be calculated directly from the characteristic amount, and responsiveness and accuracy can be ensured.

  As mentioned above, although the road surface friction coefficient estimation apparatus of the present invention has been described based on the illustrated embodiment, the present invention is not limited to this, and the configuration of each part is an arbitrary configuration having the same function. It is possible to replace it.

DESCRIPTION OF SYMBOLS 1 Road surface friction coefficient estimation apparatus 2 Road surface friction coefficient sudden change determination part 3 Convergence correction function setting part 4 Tire deformation state amount detection part 5 Tire slip angle detection part 6 Road surface friction coefficient estimated value calculation part 7 Memory | storage part

Claims (10)

A road surface friction coefficient sudden change determination means for outputting a road surface friction coefficient sudden change signal when it is determined that the road surface friction coefficient changes suddenly based on a change in the road surface state;
A convergence correction function setting means for changing and setting a convergence correction function, which is a function for correcting the road surface friction coefficient so as to converge to a predetermined convergence target value, based on the road surface friction coefficient sudden change signal;
Tire deformation state quantity detecting means for detecting a tire deformation state quantity representing a tire deformation state;
Road surface friction coefficient estimated value calculating means for calculating a road surface friction coefficient estimated value by estimating a road surface friction coefficient based on the tire deformation state quantity and the convergence correction function,
The convergence correction function setting means reduces the ease of convergence to the first convergence target value, which is a convergence target value in a normal state, when a sudden change in the road surface friction coefficient is indicated by the road surface friction coefficient sudden change signal. A road surface friction coefficient estimating apparatus, wherein the convergence correction function is set.   When the road surface friction coefficient sudden change signal indicates an abrupt change in the road surface friction coefficient, the convergence correction function setting means can easily converge to a second convergence target value that is a convergence target value when the road surface friction coefficient suddenly changes. The road surface friction coefficient estimating device according to claim 1, wherein the convergence correction function is set so as to increase the height.   The convergence correction function is a function that changes according to the road surface friction coefficient estimated value. When the road surface friction coefficient estimated value is the convergence target value, the value becomes 0, and the sign is before and after the convergence target value. The road friction coefficient estimation device according to claim 1 or 2, wherein the function is a function to be switched.   When the road surface friction coefficient sudden change signal indicates a sudden change in the road surface friction coefficient, the convergence correction function setting unit calculates an absolute value of the convergence correction function in the vicinity of the first convergence target value in the vicinity of the second convergence target value. 4. The road surface friction coefficient estimating device according to claim 2, wherein the road friction coefficient estimating device is set smaller than an absolute value of the convergence correction function.   When the road surface friction coefficient sudden change signal indicates a sudden change in the road surface friction coefficient, the convergence correction function setting means is an intermediate zero that has a value of 0 between the first convergence target value and the second convergence target value. The road surface friction coefficient estimating apparatus according to any one of claims 2 to 4, wherein the position of the road surface is brought closer to the direction of the first convergence target value.   The road surface friction coefficient estimated value calculation means calculates a tire deformation state amount error by multiplying a difference between the tire deformation state amount and a tire deformation state amount estimated value estimated from a tire model by a tire deformation state amount gain, The road surface friction coefficient estimation value according to any one of claims 1 to 5, wherein the road surface friction coefficient estimation value is calculated by time-integrating a sum of a tire deformation state quantity error and the convergence correction function. apparatus. A tire slip angle detecting means for detecting the tire slip angle;
7. The road surface friction coefficient estimation according to claim 6, wherein the road surface friction coefficient estimated value calculation means calculates the tire deformation state quantity estimated value according to the tire slip angle and the road surface friction coefficient estimated value. apparatus.   The road surface friction coefficient estimating device according to claim 7, wherein the tire deformation state amount gain is set so as to become smaller as the tire slip angle becomes smaller.   The road surface according to any one of claims 1 to 8, wherein the tire deformation state quantity is any one of tire lateral force, tire longitudinal force, self-aligning torque, and slip ratio. Friction coefficient estimation device. A road surface friction coefficient sudden change determination step for outputting a road surface friction coefficient sudden change signal when it is determined that the road surface friction coefficient changes suddenly based on a change in the road surface state;
A convergence correction function setting step for changing and setting a convergence correction function, which is a function for correcting the road surface friction coefficient to converge to a predetermined convergence target value, based on the road surface friction coefficient sudden change signal;
A tire deformation state amount detecting step for detecting a tire deformation state amount representing a tire deformation state; and
A road surface friction coefficient estimated value calculation step for calculating a road surface friction coefficient estimated value by estimating a road surface friction coefficient based on the tire deformation state quantity and the convergence correction function,
In the convergence correction function setting step, when a sudden change in the road surface friction coefficient is indicated by the road surface friction coefficient sudden change signal, the ease of convergence to the first convergence target value, which is the normal convergence target value, is reduced. A method for estimating a road friction coefficient, wherein the convergence correction function is set.

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