Road surface friction estimation device

Abstract

A road surface friction estimation device is provided with a first estimation unit (11) that repeatedly calculates a provisional maximum friction value, a range determination unit (16), and a second estimation unit (22). On the basis of an average value ([mu] pmdav) and a standard deviation ([sigma] pmd) obtained from the plurality of provisional maximum friction values ([mu] pmd) that have been repeatedly calculated, a range determination unit determines a determination range (Rj) including the average value. When the provisional maximum friction value is within the determination range, the second estimation unit determines the provisional maximum friction value as an estimated maximum friction value ([mu] p). When the provisional maximum friction value deviates from the determination range, the second estimation unit determines, as an estimated maximum friction value, a correction value that is a value within the determination range. Thus, when the provisional maximum friction value fluctuates aperiodically, the correction value becomes the estimated maximum friction value, and thus the estimated maximum friction value can be obtained while suppressing the influence of aperiodic external disturbance.

Description

Technical Field

[0001] The present disclosure relates to a road surface friction estimating device that estimates a maximum value of a friction coefficient between a road surface and tires of a vehicle. Background Art

[0002] Patent Document 1 describes a driving assistance system having a control device for controlling the driving of a vehicle. The control device of the driving assistance system estimates the maximum value of the friction coefficient between the road surface and the tires of the vehicle, and calculates the upper limit acceleration that does not cause the tires to spin based on the estimated maximum value of the friction coefficient.

[0003] Prior Art Literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2020-124998 Summary of the invention

[0006] In the driving assistance system of Patent Document 1, the maximum value of the friction coefficient is estimated, but the estimated maximum value of the friction coefficient, that is, the estimated maximum value of friction, is a value calculated based on various physical quantities obtained during vehicle driving. Furthermore, the physical quantity that is the basis of the estimated maximum value of friction is affected by external disturbances, so the estimated maximum value of friction obtained by the driving assistance system of Patent Document 1 is also calculated to be affected by external disturbances.

[0007] However, if the estimated maximum friction value is calculated under the influence of non-periodic external disturbances, the deviation of the estimated maximum friction value will become too large when the estimated maximum friction value is used for vehicle driving control, etc. The inventors have conducted detailed research and found the above-mentioned problem. In addition, as non-periodic external disturbances, for example, the tires of the vehicle run over small stones, the tires of the vehicle sink into depressions on the road surface, etc. can be cited.

[0008] The present disclosure has been made in view of the above-mentioned points, and an object of the present disclosure is to provide a road surface friction estimating device capable of obtaining an estimated friction maximum value while suppressing the influence of non-periodic external disturbances.

[0009] In order to achieve the above-mentioned purpose, a road surface friction estimation device based on one viewpoint of the present disclosure estimates the maximum value of the friction coefficient between the road surface on which a vehicle is traveling and the tire of the vehicle, and obtains the estimated maximum value of the friction coefficient as an estimated friction maximum value, wherein the road surface friction estimation device comprises: a first estimating unit, which repeatedly calculates a provisional friction maximum value as a provisional value of the estimated friction maximum value based on a physical quantity associated with the friction between the road surface and the tire and detected during the driving of the vehicle; a range determination unit, which determines a determination range of the provisional friction maximum value including the average value based on an average value and a standard deviation of the provisional friction maximum values ​​obtained based on a plurality of provisional friction maximum values ​​calculated by the first estimating unit; and a second estimating unit, which determines the provisional friction maximum value as the estimated friction maximum value when the provisional friction maximum value is within the determination range, and determines a correction value of the value within the determination range as the estimated friction maximum value when the provisional friction maximum value deviates from the determination range.

[0010] According to this, when the provisional maximum friction value fluctuates aperiodically, the second estimating unit determines the correction value obtained by removing the aperiodic fluctuation as the estimated maximum friction value. Therefore, the estimated maximum friction value can be obtained while suppressing the influence of aperiodic external disturbance.

[0011] In addition, a road surface friction estimation device based on another viewpoint of the present disclosure estimates the maximum value of the friction coefficient between the road surface on which the vehicle is traveling and the tire of the vehicle, and obtains the estimated maximum value of the friction coefficient as an estimated friction maximum value, wherein the road surface friction estimation device comprises: a first estimating unit, which repeatedly calculates a provisional friction maximum value as a provisional value of the estimated friction maximum value based on a physical quantity associated with the friction between the road surface and the tire and detected during the driving of the vehicle; a range determination unit, which determines a determination range of the provisional friction maximum value including the average value based on an average value and a standard deviation of the provisional friction maximum values ​​obtained based on a plurality of provisional friction maximum values ​​calculated by the first estimating unit; and a second estimating unit, which determines the provisional friction maximum value as the estimated friction maximum value when the provisional friction maximum value is within the determination range, and determines the median of a plurality of provisional friction maximum values ​​that will serve as the basis for the average value as the estimated friction maximum value when the provisional friction maximum value deviates from the determination range.

[0012] According to this, when the provisional maximum friction value fluctuates aperiodically, the second estimating unit determines the median value obtained by reducing the influence of the aperiodic fluctuation of the provisional maximum friction value as the estimated maximum friction value. Therefore, the estimated maximum friction value can be obtained while suppressing the influence of the aperiodic external disturbance. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1FIG. 1 is a diagram schematically showing a vehicle equipped with a road surface friction estimating device according to the first embodiment.

[0014] Figure 2 1 is a block diagram showing the functional structure of the road surface friction estimating device in the first embodiment.

[0015] Figure 3 : is a flowchart showing a control process executed by the road surface friction estimating device in the first embodiment.

[0016] Figure 4 It means in Figure 3 Flow chart of the subroutine executed in step S103.

[0017] Figure 5 is Figure 3 The friction coefficient map used in step S101 to calculate the provisional friction maximum value.

[0018] Figure 6 In the first embodiment, Figure 2 A block diagram of the functional structure of the scope determination unit.

[0019] Figure 7 (a) schematically shows a timing chart of a provisional friction maximum value repeatedly calculated at a predetermined calculation cycle in the first embodiment, and (b) schematically shows an appearance frequency distribution of a plurality of repeatedly calculated provisional friction maximum values.

[0020] Figure 8 The first embodiment schematically shows the estimated friction maximum value using a timing chart. Figure 3 FIG. 5 is a diagram of the processing contents of step S105.

[0021] Fig. 9 The first embodiment schematically shows the estimated friction maximum value using a timing chart. Figure 3 FIG. 5 is a diagram of the processing contents of step S106.

[0022] Fig.10 It is used to explain the first embodiment Figure 3 , Figure 4 Timing diagram of the control process.

[0023] Fig.11 is a flowchart showing the control process executed by the road surface friction estimation device in the second embodiment, and is related to Figure 3 Quite a picture.

[0024] Fig.12 In the second embodiment, Fig.11 The flowchart of the subroutine executed in step S111 is Figure 4Quite a picture.

[0025] Fig.13 In the second embodiment, Figure 2 The functional structure of the scope determination unit is as follows: Figure 6 Quite a picture.

[0026] Fig.14 It is used to explain the second embodiment. Fig.11 , Fig.12 A timing diagram of the average value of the provisional friction maximum value which is successively updated during the control process.

[0027] Fig.15 In the third embodiment, Fig.11 The flowchart of the subroutine executed in step S111 is Figure 4 Quite a picture.

[0028] Fig.16 It is used to explain the third embodiment. Fig.11 , Fig.15 A timing diagram of the average value of the provisional friction maximum value updated in the control process.

[0029] Fig.17 It is used to explain the third embodiment Fig.11 , Fig.15 The timing diagram of the control process is Fig.10 Quite a picture.

[0030] Fig.18 is a flowchart showing the control process executed by the road friction estimating device in the fourth embodiment, and is related to Figure 3 Quite a picture.

[0031] Fig.19 It is used to explain the fourth embodiment Fig.15 , Fig.18 The timing diagram of the control process is Fig.10 Quite a picture.

[0032] Fig. 20 is a block diagram showing the functional structure of the road surface friction estimation device in the fifth embodiment, and is Figure 2 Quite a picture.

[0033] Fig.21 is a flowchart showing the control process executed by the road friction estimating device in the fifth embodiment, and is related to Figure 3 Quite a picture.

[0034] Fig. 22 It means that in the fifth embodiment, Fig.21 The flowchart of the subroutine executed in step S111 is Fig.12 Quite a picture.

[0035] Fig.23 It is used to explain the fifth embodiment Fig.21 , Fig. 22 The timing diagram of the control process is Fig.10 Quite a picture.

[0036] Fig.24 is a block diagram showing the functional structure of the road surface friction estimation device in the sixth embodiment, and is Figure 2 Quite a picture.

[0037] Fig.25 This is a timing chart for explaining a problem that may occur in a comparative example compared with the sixth embodiment.

[0038] Fig.26 is a timing chart for explaining how the sixth embodiment solves the problem that may occur in the above-mentioned comparative example, and is Fig.25 Quite a picture.

[0039] Fig. 27 is a flowchart showing the control process executed by the road surface friction estimation device in the sixth embodiment, and is related to Fig.11 Quite a picture.

[0040] Fig.28 It means that in the sixth embodiment, Fig. 27 The flowchart of the subroutine executed in step S111 is Fig.15 Quite a picture.

[0041] Fig.29 It is a block diagram schematically showing a functional configuration of a road surface determination unit in the sixth embodiment.

[0042] Fig.30 is a timing chart for explaining the control process executed in the above comparative example compared with the sixth embodiment, and is Fig.17 Quite a picture.

[0043] Fig.31 It is used to explain the sixth embodiment. Fig. 27 , Fig.28 The timing diagram of the control process is Fig.30 Quite a picture. DETAILED DESCRIPTION

[0044] Hereinafter, each embodiment will be described with reference to the drawings. In addition, in the following embodiments, the same or equivalent parts are denoted by the same reference numerals in the drawings.

[0045] (First Embodiment)

[0046] like Figure 1 As shown, the road surface friction estimation device 10 according to the present embodiment is mounted on a vehicle 80 which is, for example, an electric vehicle, and is used in a vehicle control system for controlling the travel of the vehicle 80 .

[0047] in addition, Figure 1 The double-headed arrows in FIG. 1 and FIG. 2 respectively indicate the direction of the vehicle 80 equipped with the road friction estimation device 10. Figure 1 In FIG. 8 , a vehicle front-rear direction DR1 which is a front-rear direction of the vehicle 80 and a vehicle up-down direction DR2 which is an up-down direction of the vehicle 80 are respectively indicated by double-headed arrows.

[0048] like Figure 2 As shown, the road friction estimation device 10 is an electronic control device having a structure as an on-board microcomputer, wherein the on-board microcomputer has a CPU, RAM, ROM, non-volatile rewritable memory, etc., which are not shown. That is, the road friction estimation device 10 reads out a computer program stored in a ROM or non-volatile rewritable memory as a non-temporary tangible storage medium to execute. By executing the computer program, the method corresponding to the computer program is executed. For example, the road friction estimation device 10 executes the following method according to the computer program. Figure 3 Various control processing such as control processing.

[0049] like Figure 1 , Figure 2 As shown, the road surface friction estimation device 10 estimates the maximum value μmx of the friction coefficient μ between the road surface 84 on which the vehicle 80 is traveling and the tire 81 as the driving wheel of the vehicle 80 (see the following description). Figure 5 ), and the maximum value μmx of the estimated friction coefficient μ is obtained as the estimated friction maximum value μp. To this end, the road surface friction estimation device 10 includes a first estimation unit 11, a range determination unit 16, and a second estimation unit 22. In addition, the first estimation unit 11 includes a slip calculation unit 12, a friction calculation unit 13, and a provisional value calculation unit 14.

[0050] In addition, the road friction estimation device 10 is electrically connected to the detection unit SR composed of multiple sensors, and can obtain various physical quantities detected by the detection unit SR. In addition, the vehicle 80 has multiple drive wheels, but in this embodiment, the road friction estimation device 10 calculates the estimated friction maximum value μp for each wheel of the tire 81 serving as the drive wheel.

[0051] The detection unit SR is a sensor group for detecting various information related to the behavior of the vehicle 80, especially various information related to the friction between the road surface 84 and the tire 81 when the vehicle 80 travels on the road surface 84, and is provided in the vehicle 80. Specifically, the detection unit SR includes a vehicle speed sensor for detecting the speed of the vehicle 80, that is, the vehicle body speed, a wheel speed sensor for detecting the rotation speed of the tire 81, that is, the driving wheel speed, and a steering angle sensor for detecting the rotation angle of the steering wheel, that is, the steering angle. In addition, the detection unit SR includes a yaw rate sensor for detecting the rotation angular velocity in the yaw direction of the vehicle 80, that is, the yaw rate, and an acceleration sensor for detecting the acceleration of the vehicle 80. In addition, the detection unit SR includes a torque sensor for detecting the output torque of the driving motor, that is, the motor torque, and a load sensor for detecting the load in the vertical direction generated on the tire 81, that is, the tire load. The detection unit SR sends a detection signal corresponding to the detection values ​​detected by the above-mentioned various sensors to the road friction estimation device 10.

[0052] The road friction estimation device 10 repeatedly performs the calculation at a predetermined calculation cycle Tc while the vehicle is traveling. Figure 3 The control process is performed by successively calculating the estimated maximum friction value μp. Figure 3 : is a flowchart showing the control process executed by the road surface friction estimation device 10. Figure 4 It means in Figure 3 Flow chart of the subroutine executed in step S103.

[0053] exist Figure 3 In step S101, first, the slip calculation unit 12 and the friction calculation unit 13 obtain physical quantities Xa and Xb that are associated with the friction between the road surface 84 and the tire 81 and detected during the travel of the vehicle 80 from various sensors of the detection unit SR. And, the slip calculation unit 12 calculates the slip ratio S between the tire 81 and the road surface 84 based on the associated physical quantity Xa, and the friction calculation unit 13 calculates the friction coefficient μ between the tire 81 and the road surface 84 based on the associated physical quantity Xb. The slip ratio S calculated by the slip calculation unit 12 is referred to as the calculated slip ratio Sc, and the friction coefficient μ calculated by the friction calculation unit 13 is referred to as the calculated friction coefficient μc. The slip ratio S refers to the degree of slip of the rotating tire 81 relative to the road surface 84.

[0054] Specifically, the related physical quantity Xa obtained by the slip calculation unit 12 is the vehicle body speed, drive wheel speed, steering angle, yaw rate of the vehicle 80, and acceleration of the vehicle 80. The related physical quantity Xb obtained by the friction calculation unit 13 is the motor torque, tire load, and acceleration of the vehicle 80.

[0055] In addition, in the present embodiment, the calculated slip ratio Sc and the calculated friction coefficient μc are calculated by taking into account the side slip of the vehicle 80. Therefore, the associated physical quantity Xa obtained by the slip calculation unit 12 includes the steering angle, the yaw rate of the vehicle 80, and the acceleration of the vehicle 80, and the associated physical quantity Xb obtained by the friction calculation unit 13 includes the acceleration of the vehicle 80. In addition, for example, the motor torque obtained from the detection unit SR is converted into the drive wheel torque applied to one tire 81 and is used for calculating the friction coefficient μc.

[0056] Furthermore, in step S101 , when the calculated slip ratio Sc and the calculated friction coefficient μc are calculated, the provisional value calculation unit 14 calculates a provisional friction maximum value μpmd which is a provisional value of the estimated friction maximum value μp based on the calculated slip ratio Sc and the calculated friction coefficient μc.

[0057] Various methods of calculating the provisional friction maximum value μpmd are conceivable. In the present embodiment, the provisional value calculation unit 14 uses Figure 5 The friction coefficient diagram MPm is used to calculate the provisional maximum friction value μpmd. Figure 5 The friction coefficient map MPm is a map obtained by experimentally measuring the relationship between the slip rate S and the friction coefficient μ under various road conditions in advance. The friction coefficient map MPm is represented by a coordinate system with the slip rate S and the friction coefficient μ as coordinate axes, and is composed of a plurality of relationship curves Lm representing the relationship between the slip rate S and the friction coefficient μ. Furthermore, these plurality of relationship curves Lm are relationship curves obtained from different road conditions, respectively, and represent different maximum values ​​μmx of the friction coefficient μ.

[0058] For example, when the calculated slip ratio Sc and the calculated friction coefficient μc are calculated, the provisional value calculation unit 14 determines the relationship point Pc representing the calculated slip ratio Sc and the calculated friction coefficient μc in the friction coefficient map MPm. Furthermore, the provisional value calculation unit 14 determines whether the relationship point Pc is located on which relationship curve Lm among the plurality of relationship curves Lm, and calculates the maximum value μmx of the friction coefficient μ represented by the relationship curve Lm where the relationship point Pc is located as the provisional friction maximum value μpmd.

[0059] For example Figure 5 As illustrated, when the relationship point Pc representing the calculated slip ratio Sc and the calculated friction coefficient μc is located on the relationship curve L1m among the plurality of relationship curves Lm, the maximum value μmx of the friction coefficient μ represented by the relationship curve L1m is calculated as the provisional friction maximum value μpmd. Figure 3 After step S101, proceed to step S102.

[0060] In step S102, the range determination unit 16 determines whether Figure 4In step S204 and step S205, the average value μpmdav and the standard deviation σpmd of the provisional friction maximum value μpmd have been calculated. In short, the range determination unit 16 determines whether the average value μpmdav and the standard deviation σpmd have been calculated.

[0061] For example, in this Figure 3 When the above-mentioned step S204 and step S205 have not been executed after the start of the flowchart, the range determination unit 16 determines that the average value μpmdav and the standard deviation σpmd of the provisional friction maximum value μpmd have not been calculated. On the other hand, when the above-mentioned step S204 and step S205 have been executed after the start of the flowchart, the range determination unit 16 determines that the average value μpmdav and the standard deviation σpmd of the provisional friction maximum value μpmd have been calculated.

[0062] If it is determined in step S102 that the average value μpmdav and the standard deviation σpmd of the provisional friction maximum value μpmd have not been calculated, the process proceeds to step S103 . On the other hand, if it is determined that the average value μpmdav and the standard deviation σpmd of the provisional friction maximum value μpmd have been calculated, the process proceeds to step S104 .

[0063] In step S103, the range determination unit 16 executes Figure 4 And, if Figure 6 As shown, the range determination unit 16 has Figure 4 The storage device 17 is used as a memory in the subroutine of the embodiment. The storage device 17 is composed of, for example, a flash memory or a RAM, and the provisional value calculation unit 14 functions as a data storage unit that sequentially accumulates the provisional friction maximum value μpmd each time the provisional friction maximum value μpmd is calculated in step S101.

[0064] In addition, in step S103, Figure 4 If the subroutine ends and processing returns to Figure 3 Flow chart of Figure 3 The flowchart ends. And, Figure 3 The flowchart starts from step S101 again.

[0065] exist Figure 4 In step S201, the range determination unit 16 shifts the provisional friction maximum value μpmd, ie, the memory data, which has been stored in the storage device 17, toward the old memory data side by one data address.

[0066] Here, if Figure 6The storage device 17 is described below. The storage device 17 is configured to store N provisional friction maximum values ​​μpmd as memory data, and a data address is assigned to each memory data storage location. That is, the storage device 17 has N memory data storage locations.

[0067] Furthermore, in the storage device 17, the provisional maximum friction value μpmd is stored in order along the time series. Specifically, Figure 6 D 1 , D 2 、···、D N The subscripts "1, 2, ..., N" of D represent data addresses, and the smaller the subscript value, the newer the stored provisional maximum friction value μpmd.

[0068] Since the storage device 17 is structured in this way, Figure 4 The execution of step S201, for example, the memory data D N-1 Becomes memory data D N , memory data D 2 Becomes memory data D 3 , memory data D 1 Becomes memory data D 2 . And, the memory data D 1 The storage location becomes free. In addition, the initial state of the storage device 17 is a state where no provisional friction maximum value μpmd is stored. When the storage device 17 is in the initial state, it is meaningless even if the range determination unit 16 shifts the memory data, so nothing is done in step S201. Figure 4 After step S201, proceed to step S202.

[0069] In step S202, the range determination unit 16 determines Figure 3 The provisional maximum friction value μpmd calculated in step S101 is stored in the storage device 17. Specifically, the provisional maximum friction value μpmd calculated in step S101 is stored in the storage location of the latest provisional maximum friction value μpmd among the plurality of storage locations of the storage device 17. That is, the provisional maximum friction value μpmd calculated in step S101 is stored as the memory data D 1 The data is stored in the storage device 17 . Figure 4 After step S202, proceed to step S203.

[0070] In step S203, the range determination unit 16 determines whether the provisional friction maximum value μpmd is stored in all storage locations of the storage device 17. Figure 6As shown, since the storage device 17 has N storage locations, the range determination unit 16 determines whether or not N provisional friction maximum values ​​μpmd are stored in the storage device 17 .

[0071] If it is determined in step S203 that the provisional maximum friction value μpmd is stored in all storage locations of the storage device 17, the process proceeds to step S204. On the other hand, if it is determined that the provisional maximum friction value μpmd is not stored in all storage locations of the storage device 17 and there is still free storage space in the storage device 17, Figure 4 The subroutine ends and returns to Figure 3 Flowchart of the process.

[0072] like Figure 6 As shown in FIG. 1 , the range determination unit 16 includes an average value calculation unit 18 and a standard deviation calculation unit 19 in addition to the above-mentioned storage device 17. Figure 4 In step S204, the average value calculation unit 18 calculates the average value based on the plurality of provisional friction maximum values ​​μpmd stored in the storage device 17, that is, the memory data D 1 ~D N , the average value μpmdav of the provisional friction maximum value μpmd is calculated according to the following formula F1. In short, the average value calculation unit 18 calculates the plurality of memory data D stored in the storage device 17 1 ~D N The average value μpmdav.

[0073] [Formula 1]

[0074]

[0075] In the next step S205, the standard deviation calculation unit 19 calculates the standard deviation based on the plurality of provisional friction maximum values ​​μpmd stored in the storage device 17, that is, the memory data D 1 ~D N The average value μpmdav calculated by the above formula F1 is used to calculate the standard deviation σpmd of the provisional friction maximum value μpmd by the following formula F2. In short, the average value calculation unit 18 calculates the standard deviation σpmd of the plurality of memory data D stored in the storage device 17. 1 ~D N The standard deviation σpmd.

[0076] [Formula 2]

[0077]

[0078] In addition, the variable i in the above formula F1 and formula F2 represents the data address of the storage device 17. That is, the variable i represents Figure 6The subscripts of the memory data D are "1, 2, ..., N". Therefore, the provisional maximum friction value μpmd in the above formulas F1 and F2 is set as the memory data D i The provisional friction maximum value μpmd is stored in the storage device 17. This also applies to the calculation formulas described later that correspond to the above formula F1 or formula F2, for example, the formulas F9 and F10 described later. Figure 4 After step S205, proceed to step S206.

[0079] In step S206, the range determination unit 16 determines a determination range Rj of the provisional friction maximum value μpmd based on the average value μpmdav of the provisional friction maximum values ​​μpmd calculated in step S204 and the standard deviation σpmd of the provisional friction maximum values ​​μpmd calculated in step S205. The determination range Rj is relative to the periodic external disturbance and the non-periodic external disturbance. Figure 7 The provisional maximum friction value μpmd fluctuates as shown in (a), as Figure 7 The determination range Rj is formed as a range including the average value μpmdav in the determination range Rj.

[0080] For example, in this embodiment, the determination range Rj is set to the range of “μpmdav±3·σpmd.” Therefore, in step S206 , the range determination unit 16 calculates the upper limit μpp of the determination range Rj according to the following equation F3 and calculates the lower limit μmp of the determination range Rj according to the following equation F4.

[0081] μpp=μpmdav+3·σpmd···(F3)

[0082] μmp=μpmdav-3·σpmd···(F4)

[0083] When step S206 is finished, Figure 4 The subroutine ends and returns to Figure 3 Flowchart of the process.

[0084] Back to Figure 3 In step S104, the second estimating unit 22 determines whether the provisional friction maximum value μpmd calculated in step S101 is within the determination range Rj. In other words, the second estimating unit 22 determines whether the following inequality F5 holds. In addition, when the second estimating unit 22 determines that the provisional friction maximum value μpmd is within the determination range Rj, the provisional friction maximum value μpmd is determined to be within the determination range Rj. On the other hand, when the second estimating unit 22 determines that the provisional friction maximum value μpmd is not within the determination range Rj, the provisional friction maximum value μpmd is determined to be within the determination range Rj.

[0085] μmp≤μpmd≤μpp···(F5)

[0086] If it is determined in step S104 that the provisional friction maximum value μpmd is within the determination range Rj, the process proceeds to step S105 . On the other hand, if it is determined that the provisional friction maximum value μpmd is outside the determination range Rj, the process proceeds to step S106 .

[0087] For example, the idea is that the range of variation of the provisional maximum friction value μpmd caused by periodic external disturbance is set within the judgment range Rj, and the range of variation of the provisional maximum friction value μpmd caused by non-periodic external disturbance is set outside the judgment range Rj, thereby dividing the range of variation of the provisional maximum friction value μpmd.

[0088] In step S105, the second estimating unit 22 determines the provisional friction maximum value μpmd as the estimated friction maximum value μp. Figure 8 As shown, in step S105 , since the provisional friction maximum value μpmd falls within the determination range Rj, the estimated friction maximum value μp is set to the same value as the provisional friction maximum value μpmd.

[0089] In step S106, the second estimating unit 22 determines the correction value, which is the value within the determination range Rj, as the estimated friction maximum value μp. In the present embodiment, the correction value is set to be the value of the estimated friction maximum value μp as the determination range Rj is repeatedly executed. Figure 3 The previous value of the estimated friction maximum value μp is repeatedly determined according to the flowchart.

[0090] For example Fig. 9 As shown in FIG. 1 , in step S106, since the provisional friction maximum value μpmd deviates from the determination range Rj, the provisional friction maximum value μpmd is not adopted. In addition, the estimated friction maximum value μp determined in step S106 this time, in other words, Fig. 9 The current value of the estimated friction maximum value μp indicated by the point Pa is set to the same value as the previous value of the estimated friction maximum value μp indicated by the point Pb.

[0091] When step S105 or step S106 is finished, Figure 3 The flowchart ends. And, Figure 3 The flowchart starts again from step S101. Figure 3 According to the flowchart of FIG. 1 , each time the second estimating unit 22 calculates the provisional friction maximum value μpmd in step S101 , it repeatedly determines the estimated friction maximum value μp in step S105 or step S106 .

[0092] The second estimating unit 22 outputs the estimated maximum friction value μp determined in step S105 or step S106 to an external control device. Examples of the external control device include a traction control device and an ABS control device. ABS is an abbreviation for Anti-lock Braking System.

[0093] In addition, the above Figure 3 , Figure 4 The processing in each step constitutes a functional unit that realizes each function. This is also the same in the flowchart described later.

[0094] Next, use Fig.10 The timing diagram above illustrates Figure 3 , Figure 4 Control processing. Fig.10 In the timing diagram, the black dots represent Figure 3 The value obtained in each operation cycle Tc of the control process.

[0095] in addition, Fig.10 The periodic external disturbances and non-periodic external disturbances recorded are all external disturbances that affect the calculated provisional maximum friction value μpmd. Fig.10 As shown, when the motor torque fluctuates due to external disturbance, the detected values ​​of the physical quantities that are the basis for calculating the calculated friction coefficient μc and the calculated slip ratio Sc also fluctuate, and thus the calculated friction coefficient μc and the calculated slip ratio Sc also fluctuate.

[0096] As periodic external disturbances, for example, repeated changes in the road surface 84 during driving on gravel roads or sandy beaches can be cited. In addition, as non-periodic external disturbances, for example, the tire 81 of the vehicle 80 runs over a small stone, the tire 81 of the vehicle 80 sinks into a depression in the road surface 84 can be cited.

[0097] exist Fig.10 In the timing chart of , a plurality of provisional friction maximum values ​​μpmd obtained in the accumulation period PDx before the time point ta1 are sequentially stored and accumulated in the storage device 17. Then, based on the plurality of provisional friction maximum values ​​μpmd stored in the storage device 17, an average value μpmdav and a standard deviation σpmd of the provisional friction maximum values ​​μpmd are calculated.

[0098] exist Fig.10 At the ta1 time point, Figure 3 The judgment result of step S102 is switched from the judgment that the average value μpmdav and the standard deviation σpmd of the provisional friction maximum value μpmd have not been calculated to the judgment that the average value μpmdav and the standard deviation σpmd have been calculated. Figure 3 The determination in step S104, that is, the determination as to whether the provisional friction maximum value μpmd is within the determination range Rj.

[0099] For example, at time points ta2, ta3, and ta4, Figure 3 In step S104, it is determined that the provisional friction maximum value μpmd deviates from the determination range Rj. As a result, the provisional friction maximum value μpmd is not adopted as the estimated friction maximum value μp, and the previous value of the estimated friction maximum value μp is maintained as it is.

[0100] As described above, according to the present embodiment, the range determination unit 16 specifies the determination range Rj including the average value μpmdav based on the average value μpmdav and the standard deviation σpmd obtained from the multiple tentative friction maximum values ​​μpmd repeatedly calculated. Furthermore, when the tentative friction maximum value μpmd is within the determination range Rj, the second estimation unit 22 determines the tentative friction maximum value μpmd as the estimated friction maximum value μp. On the other hand, when the tentative friction maximum value μpmd deviates from the determination range Rj, the second estimation unit 22 determines the correction value as the value within the determination range Rj as the estimated friction maximum value μp.

[0101] Therefore, when the provisional maximum friction value μpmd fluctuates non-periodically, the second estimating unit 22 determines the correction value after removing the non-periodic fluctuation as the estimated maximum friction value μp. Therefore, the estimated maximum friction value μp can be obtained while suppressing the influence of non-periodic external disturbances. As a result, even when driving on gravel roads where non-periodic external disturbances are likely to occur, malfunctions such as traction control can be avoided.

[0102] (1) In addition, according to the present embodiment, the second estimating unit 22 repeatedly determines the estimated friction maximum value μp each time the provisional friction maximum value μpmd is calculated. In short, the second estimating unit 22 repeatedly determines the estimated friction maximum value μp as time passes. And, the correction value is the previous value of the estimated friction maximum value μp. Therefore, if the previous value of the estimated friction maximum value μp is temporarily stored in advance, the estimated friction maximum value μp can be determined, so that memory saving can be easily achieved. In addition, the previous value of the estimated friction maximum value μp has already been calculated, and the calculation load for obtaining the correction value does not occur, so high-speed calculation can be achieved.

[0103] (2) In addition, according to the present embodiment, the first estimating unit 11 calculates the friction coefficient μ and the slip ratio S of the tire 81 based on the related physical quantities Xa and Xb, and calculates the provisional maximum friction value μpmd based on the calculated friction coefficient μ and slip ratio S. Therefore, the related physical quantities Xa and Xb that are the basis for calculating the provisional maximum friction value μpmd can be obtained from sensors generally provided in the vehicle 80.

[0104] (Second Embodiment)

[0105] Next, the second embodiment is described. In this embodiment, the differences from the first embodiment are mainly described. In addition, the description of the same or equivalent parts as the above-mentioned embodiment is omitted or simplified. This is also the case in the description of the embodiments described later.

[0106] In this embodiment, the first embodiment Figure 3 The flowchart is replaced by Fig.11 The flowchart of the first embodiment Figure 4 The flowchart is replaced by Fig.12 In addition, in this embodiment, as in the first embodiment, the road friction estimation device 10 repeatedly executes the calculation cycle Tc during vehicle travel. Fig.11 The control process is performed to successively calculate the estimated friction maximum value μp.

[0107] exist Fig.11 In the flowchart, there is no Figure 3 Instead of step S103, step S111 is set between step S101 and step S102. Therefore, Fig.11 After step S101, proceed to step S111.

[0108] exist Fig.11 In step S111, the range determination unit 16 executes Fig.12 And, in step S111, execute Fig.12 When the subroutine ends, the processing is sent to Fig.11 When the flowchart returns, it enters step S102 from step S111.

[0109] In addition, Fig.11 The flowchart is not set as above Figure 3 Step S103. Therefore, Fig.11 If it is determined in step S102 that the average value μpmdav and the standard deviation σpmd of the provisional friction maximum value μpmd have not been calculated, Fig.11 The flowchart ends and starts again from step S101.

[0110] exist Fig.12 In step S211, the range determination unit 16 shifts the provisional friction maximum value μpmd, i.e., the memory data, which has been stored in the storage device 17, to the old memory data side by one data address. Fig.12 Step S211 and Figure 4 The same is true for step S201.

[0111] Here, in the first embodiment, if the provisional friction maximum value μpmd is stored in all the storage locations of the storage device 17, the subsequent Figure 4 In contrast, in this embodiment, even if the provisional friction maximum value μpmd is stored in all storage locations of the storage device 17, there is still a need to execute the following steps. Fig.12 The situation of steps S211 and S202.

[0112] Therefore, in Fig.12 In step S211, Figure 4 The difference from step S201 is that the range determination unit 16 Fig.13 The earliest (oldest) memory data D stored in the plurality of memory locations of the memory device 17 is shown. N The provisional maximum friction value μpmd at the storage location is deleted from the storage device 17. The range determination unit 16 deletes the oldest memory data D N The data deletion at the storage location is performed together with the shifting of the above-mentioned memory data to the old memory data side.

[0113] Therefore, through Fig.12 The execution of step S211, for example, converts the earliest memory data D N Delete the memory data D from the storage device 17 N-1 Becomes memory data D N , memory data D 2 Becomes memory data D 3 , memory data D 1 Becomes memory data D 2 . And, the memory data D 1 The storage location becomes free.

[0114] In addition to the above, Fig.12 Step S211 and Figure 4 The same is true for step S201.

[0115] In addition, since the provisional maximum friction value μpmd is sequentially stored in the storage device 17 as described above, once the storage device 17 is in a state where the provisional maximum friction value μpmd is stored in all storage locations of the storage device 17, Fig.11 , Fig.12 Therefore, in step S203, once it is determined that the provisional maximum friction value μpmd is stored in all storage locations of the storage device 17, as long as Fig.11 , Fig.12 As long as the control process continues, the result of the determination will be maintained.

[0116] In this embodiment, by repeatedly executing the above Fig.11 The control process, therefore, Fig.13 , Fig.14 As shown, the range determination unit 16 sequentially stores a plurality of provisional friction maximum values ​​μpmd obtained within the accumulation period PDx as a predetermined period in the storage device 17. The accumulation period PDx is shifted toward the time elapsed side Atp each time the provisional friction maximum value μpmd is calculated.

[0117] In addition, if Fig.12 As shown, the range determination unit 16 determines the determination range Rj of the provisional friction maximum value μpmd based on the average value μpmdav and the standard deviation σpmd obtained from a plurality of provisional friction maximum values ​​μpmd calculated during the accumulation period PDx each time the provisional friction maximum value μpmd is calculated. In this way, the range determination unit 16 updates the determination range Rj of the provisional friction maximum value μpmd each time the provisional friction maximum value μpmd is calculated.

[0118] The road surface friction estimating device 10 according to the present embodiment has the following operational effects.

[0119] (1) According to the present embodiment, each time the provisional friction maximum value μpmd is calculated, the determination range Rj of the provisional friction maximum value μpmd is repeatedly determined based on the average value μpmdav and the standard deviation σpmd obtained from the plurality of provisional friction maximum values ​​μpmd calculated within the accumulation period PDx. Furthermore, the accumulation period PDx is shifted toward the time elapsed side Atp each time the provisional friction maximum value μpmd is calculated. In other words, the accumulation period PDx shifts toward the time elapsed side Atp as time elapses.

[0120] Therefore, it is possible to avoid the determination range Rj of the provisional friction maximum value μpmd from changing suddenly as the determination range Rj is updated, and to continuously update the determination range Rj based on the latest provisional friction maximum value μpmd.

[0121] Except for the above-described contents, this embodiment is the same as the first embodiment. Also, in this embodiment, the effects obtained by the configuration common to the first embodiment described above can be obtained in the same manner as in the first embodiment.

[0122] (Third Embodiment)

[0123] Next, a third embodiment will be described. In this embodiment, points different from the first embodiment described above will be mainly described.

[0124] In this embodiment, the first embodiment Figure 3 The flowchart is replaced by Fig.11 The flowchart of the first embodiment Figure 4 The flowchart is replaced by Fig.15 In addition, in this embodiment, as in the first embodiment, the road friction estimation device 10 repeatedly executes the calculation cycle Tc during vehicle travel. Fig.11 The control process is performed to successively calculate the estimated friction maximum value μp.

[0125] In this embodiment, the Fig.11 The flowchart is the flowchart described in the second embodiment described above. In this embodiment, different from the second embodiment, Fig.11 In step S111, the range determination unit 16 executes Fig.15 In addition, in this embodiment Fig.11 The flowchart is the same as that described in the second embodiment.

[0126] In this embodiment Fig.15 In the flowchart of the first embodiment, Figure 4 The flowchart of FIG. 1 adds step S227 and step S228. In addition, the structure of the range determination unit 16 of this embodiment is the same as that of the first embodiment. Figure 6 As shown.

[0127] Fig.15 The process of the flowchart of goes to step S227 when step S206 is finished. Fig.15 In step S227, the range determination unit 16 Figure 6 The storage device 17 of the storage device 17 performs memory data clearing. That is, the range determination unit 16 deletes the provisional maximum friction value μpmd stored therein from all the storage locations of the storage device 17. As a result, the storage device 17 is restored from the state where the provisional maximum friction value μpmd is stored in all the storage locations of the storage device 17 to the initial state where the provisional maximum friction value μpmd is not stored at all. Therefore, in the next step S203 after the storage device 17 is restored to the initial state, it is determined again that there is still free space in the storage location of the storage device 17. At the end of step S227, Fig.15 The subroutine ends and returns to Fig.11 Flowchart of the process.

[0128] exist Fig.15 In step S203, when it is determined that the provisional maximum friction value μpmd is not stored in all the storage locations of the storage device 17 and there is still free space in the storage location of the storage device 17, the process proceeds to step S228.

[0129] Furthermore, in step S228, when the average value μpmdav, standard deviation σpmd, and judgment range Rj of the provisional friction maximum value μpmd have been calculated or determined, the range determination unit 16 maintains the average value μpmdav, standard deviation σpmd, and judgment range Rj as they are. Furthermore, when the average value μpmdav, standard deviation σpmd, and judgment range Rj of the provisional friction maximum value μpmd have not been calculated or determined, the range determination unit 16 maintains the state of not being calculated or determined as they are. In short, the range determination unit 16 does nothing in this step S228. At the end of step S228, Fig.15 The subroutine ends and returns to Fig.11 Flowchart of the process.

[0130] By repeatedly executing the above Fig.11 Flowchart of Figure 6 , Fig.16 As shown, the range determination unit 16 updates the average value μpmdav, the standard deviation σpmd, and the determination range Rj of the provisional friction maximum value μpmd each time the provisional friction maximum value μpmd is accumulated a predetermined number of calculations Nc in the storage device 17. The updated average value μpmdav, the standard deviation σpmd, and the determination range Rj are calculated or determined based on the provisional friction maximum value μpmd accumulated in the storage device 17 at the time of the update.

[0131] In addition, the above-mentioned predetermined number of calculations Nc is the same number as the number of storage locations of the storage device 17, so "the number of calculations Nc=N".

[0132] In addition, since the provisional friction maximum value μpmd is sequentially stored in the storage device 17 at a predetermined calculation cycle Tc, the above-mentioned predetermined number of calculations Nc can be converted into time. Therefore, the above-mentioned "each time the provisional friction maximum value μpmd is accumulated in the storage device 17 for a predetermined number of calculations Nc" can be changed to each accumulation period PDx corresponding to the predetermined number of calculations Nc. In this case, the accumulation period PDx in the present embodiment is defined as a predetermined period for continuously accumulating the provisional friction maximum value μpmd in the storage device 17.

[0133] Furthermore, after the average value μpmdav, the standard deviation σpmd, and the determination range Rj are updated, the range determination unit 16 deletes all the provisional maximum friction values ​​μpmd stored in the storage device 17, and then starts to store the provisional maximum friction values ​​μpmd in the storage device 17 again. Fig.16 As shown in FIG. 1 , the above-mentioned accumulation period PDx shifts toward the time-lapse side Atp as time passes.

[0134] Next, use Fig.17 The timing diagram above illustrates Fig.11 , Fig.15 Control processing. Fig.17 In the timing diagram, the black dots represent Fig.11 The value obtained in each operation cycle Tc of the control process. In addition, Fig.17 The timing diagram is the same as the above Fig.10 The equivalent timing diagram is Fig.10 Similarly, examples of periodic external disturbance and aperiodic external disturbance that affect the provisional friction maximum value μpmd are shown.

[0135] exist Fig.17 At the tb1 time point, Fig.15 In step S203, from Fig.11 , Fig.15 At the start of the control process, it is first determined that the provisional friction maximum value μpmd is stored in all the storage locations of the storage device 17. Thus, the average value μpmdav and the standard deviation σpmd of the provisional friction maximum value μpmd are calculated, and the determination range Rj is determined based on them. The average value μpmdav, the standard deviation σpmd, and the determination range Rj at the time point tb1 are moved to the next update time point, that is, the time point tb5, and are updated at the time point tb5.

[0136] In addition, Fig.17 In the timing diagram, for example, at time points tb2, tb3, and tb4, Fig.11 In step S104, it is determined that the provisional friction maximum value μpmd deviates from the determination range Rj. As a result, the provisional friction maximum value μpmd is not adopted as the estimated friction maximum value μp, and the previous value of the estimated friction maximum value μp is maintained as it is.

[0137] The road surface friction estimating device 10 according to the present embodiment has the following operational effects.

[0138] (1) According to the present embodiment, the storage device 17 sequentially accumulates the provisional friction maximum value μpmd each time the provisional value calculation unit 14 calculates the provisional friction maximum value μpmd in step S101. The range determination unit 16 updates the average value μpmdav, standard deviation σpmd, and determination range Rj of the provisional friction maximum value μpmd each time the provisional friction maximum value μpmd is accumulated in the storage device 17 for a predetermined number of calculations Nc. And, the updated average value μpmdav, standard deviation σpmd, and determination range Rj are calculated or determined based on the provisional friction maximum value μpmd that has been accumulated in the storage device 17 at the time of the update. In addition, the range determination unit 16 starts to accumulate the provisional friction maximum value μpmd for the above-mentioned number of calculations Nc in the storage device 17 again after the average value μpmdav, standard deviation σpmd, and determination range Rj are updated.

[0139] That is, each time the provisional friction maximum value μpmd accumulates a prescribed number of calculations Nc in the storage device 17 , the range determination unit 16 determines the determination range Rj based on the average value μpmdav and the standard deviation σpmd obtained from a plurality of provisional friction maximum values ​​μpmd accumulated in the storage device 17 for the prescribed number of calculations Nc.

[0140] Therefore, compared with the case where the determination range Rj is updated every time the provisional friction maximum value μpmd is calculated, the calculation load can be suppressed and the determination range Rj can be appropriately updated without being affected by the old provisional friction maximum value μpmd calculated in the past.

[0141] Except for the above-described contents, this embodiment is the same as the first embodiment. Also, in this embodiment, the effects obtained by the configuration common to the first embodiment described above can be obtained in the same manner as in the first embodiment.

[0142] (Fourth Embodiment)

[0143] Next, a fourth embodiment will be described. In this embodiment, points different from the third embodiment described above will be mainly described.

[0144] In this embodiment, the third embodiment Fig.11 The flowchart is replaced by Fig.18 In addition, in this embodiment, as in the third embodiment, the road friction estimation device 10 repeatedly executes the calculation cycle Tc during vehicle travel. Fig.18 The control process is performed by successively calculating the estimated friction maximum value μp. Fig.18 The subroutine executed in step S111 of the third embodiment adopts the same Fig.15 Flowchart of the process.

[0145] In this embodiment Fig.18 In the flowchart of the third embodiment, Fig.11 Step S106 of the flowchart is replaced by step S136. Fig.18 If it is determined in step S104 that the provisional friction maximum value μpmd deviates from the determination range Rj, the process proceeds to step S136 .

[0146] In step S136, the second estimating unit 22 determines the correction value, which is the value within the determination range Rj, as the estimated friction maximum value μp. In the present embodiment, the correction value is set to Fig.15 The average value μpmdav of the provisional friction maximum values ​​μpmd calculated in step S204.

[0147] When step S136 is finished, Fig.18 The flowchart ends and starts again from step S101.

[0148] Next, use Fig.19 The timing diagram above illustrates Fig.15 , Fig.18 Control processing. Fig.19 In the timing diagram, the black dots represent Fig.18 The value obtained in each operation cycle Tc of the control process. In addition, Fig.19 The timing diagram is the same as the above Fig.17 Comparable timing diagram.

[0149] exist Fig.19 The tc1 time point, and Fig.17 At the time point tb1, the average value μpmdav and the standard deviation σpmd of the provisional friction maximum values ​​μpmd are similarly calculated, and the determination range Rj is determined based on them.

[0150] In addition, Fig.19 In the timing diagram, at the time points tc2, tc3, and tc4, respectively Fig.17 The tb2, tb3, and tb4 time points are also Fig.18 In step S104 , it is determined that the provisional friction maximum value μpmd deviates from the determination range Rj.

[0151] As a result, in Fig.19 At the time points tc2, tc3, and tc4 of the timing diagram, the provisional maximum friction value μpmd is not adopted as the estimated maximum friction value μp. Fig.17 The time points tb2, tb3, and tb4 are the same as those of Fig.17 The difference between the tb2, tb3, and tb4 time points is that Fig.19At time points tc2, tc3, and tc4, the average value μpmdav of the provisional friction maximum values ​​μpmd is adopted as the estimated friction maximum value μp.

[0152] The road surface friction estimating device 10 of the present embodiment has the following operational effects.

[0153] (1) According to this embodiment, Fig.18 In step S136, the second estimating unit 22 will Fig.15 The average value μpmdav of the provisional friction maximum values ​​μpmd calculated in step S204 is determined as the estimated friction maximum value μp.

[0154] Here, for example, in the case of large periodic external disturbances, the motor torque fluctuations are as follows: Fig.19 As shown in the range B1, the result is that Fig.19 As shown by the arrow B2, the deviation of the provisional friction maximum value μpmd also increases. In this case, for example, if a value that is within the determination range Rj of the provisional friction maximum value μpmd but is located near the end of the determination range Rj continues to be used as the estimated friction maximum value μp, the effect of removing external interference from the estimated friction maximum value μp is weakened.

[0155] In the present embodiment, as described above, the average value μpmdav becomes the estimated friction maximum value μp in step S136, so it is difficult for the value near the end of the determination range Rj to continue to be the estimated friction maximum value μp. Therefore, compared with, for example, the case where the previous value of the estimated friction maximum value μp is maintained as it is, the estimated friction maximum value μp can be determined to reduce the influence of the large deviation of the provisional friction maximum value μpmd. In addition, as a case where the periodic external disturbance is large, for example, the road surface 84 on which the vehicle 80 is traveling is a rough gravel road, a road with fresh snow, etc.

[0156] Except for the above-described contents, this embodiment is the same as the third embodiment. Also, in this embodiment, similarly to the third embodiment, the effects obtained by the configuration common to the third embodiment described above can be obtained.

[0157] In addition, the present embodiment is a modified example based on the third embodiment, but the present embodiment may be combined with the first embodiment or the second embodiment described above.

[0158] (Fifth Embodiment)

[0159] Next, a fifth embodiment will be described. In this embodiment, points different from the above-described second embodiment will be mainly described.

[0160] In this embodiment, the second embodiment Figure 2 The block diagram is replaced by Fig. 20 The block diagram of the second embodiment Fig.11 The flowchart is replaced by Fig.21 The flowchart of the second embodiment Fig.12 The flowchart is replaced by Fig. 22 Flowchart of the process.

[0161] In the present embodiment, similarly to the second embodiment, the road surface friction estimation device 10 repeatedly performs the calculation at a predetermined calculation cycle Tc while the vehicle is traveling. Fig.21 The control process is performed by successively calculating the estimated friction maximum value μp. Fig.21 The subroutine executed in step S111 is Fig. 22 In addition, the structure of the storage device 17 of this embodiment is similar to Fig.13 The same is true for the storage device 17 of the second embodiment shown.

[0162] exist Fig. 22 In the flowchart, after step S206, the process proceeds to step S247. Fig. 20 The range determination unit 16 includes a median calculation unit 161. Fig. 22 In step S247, a plurality of provisional friction maximum values ​​μpmd stored in the storage device 17, that is, the memory data D 1 ~D N The median μpmid of the multiple provisional friction maximum values ​​μpmd stored in the storage device 17 is the memory data D 1 ~D N In other words, these are a plurality of provisional friction maximum values ​​μpmd that are the basis for the average value μpmdav calculated in step S204 .

[0163] At the end of step S247, Fig. 22 The subroutine ends and returns to Fig.21 Flowchart of the process.

[0164] In this embodiment Fig.21 In the flowchart of the second embodiment, Fig.11 Step S106 of the flowchart is replaced by step S146. Fig.21 If it is determined in step S104 that the provisional friction maximum value μpmd deviates from the determination range Rj, the process proceeds to step S146 .

[0165] In step S146, the second estimating unit 22 will Fig. 22The median μpmid of the provisional friction maximum values ​​μpmd calculated in step S247 is determined as the estimated friction maximum value μp. In short, the estimated friction maximum value μp is set as the median μpmid of the provisional friction maximum values ​​μpmd.

[0166] At the end of step S146, Fig.21 The flowchart ends and starts again from step S101.

[0167] Next, use Fig.23 The timing diagram above illustrates Fig.21 , Fig. 22 The control process. Fig.23 The timing diagram is the same as that of the fourth embodiment described above. Fig.19 Equivalent timing diagram. Fig.23 In the timing diagram, the black dots represent Fig.21 The value obtained in each operation cycle Tc of the control process.

[0168] exist Fig.23 The td1 time point, and Fig.19 Similarly, at the time point tc1, the average value μpmdav and the standard deviation σpmd of the provisional friction maximum values ​​μpmd are calculated, and the determination range Rj is determined based on them.

[0169] In addition, Fig.23 In the timing diagram, at the td2 time point, Fig.19 The tc2 time point is also at Fig.21 In step S104 , it is determined that the provisional friction maximum value μpmd deviates from the determination range Rj.

[0170] As a result, in Fig.23 At the time point td2 of the timing diagram, the provisional maximum friction value μpmd is not adopted as the estimated maximum friction value μp. Fig.19 However, Fig.19 The difference between the tc2 time point is that Fig.23 At the td2 time point, Fig.21 In step S146, the median μpmid of the provisional friction maximum values ​​μpmd is adopted as the estimated friction maximum value μp.

[0171] The road surface friction estimating device 10 of the present embodiment has the following operational effects.

[0172] (1) According to this embodiment, Fig.21 In step S146, the second estimating unit 22 will Fig. 22 The median μpmid of the provisional friction maximum values ​​μpmd calculated in step S247 is determined as the estimated friction maximum value μp.

[0173] Therefore, when the provisional maximum friction value μpmd fluctuates aperiodically, the second estimating unit 22 determines the median μpmid with the influence of the aperiodic fluctuation of the provisional maximum friction value μpmd reduced as the estimated maximum friction value μp. Thus, the estimated maximum friction value μp can be obtained while suppressing the influence of the aperiodic external disturbance.

[0174] Here, for example, when the vehicle 80 is traveling at high speed and immediately experiences a non-periodic external disturbance such as a headwind, Fig.23 As shown in the range B3 of FIG. 1 , there is a case where the motor torque changes greatly temporarily and the average value μpmdav is strongly affected by external disturbance as shown by the arrow B4. In addition, if the value that is within the determination range Rj of the provisional friction maximum value μpmd but is located near the end of the determination range Rj continues to be used as the estimated friction maximum value μp, the external disturbance removal effect of removing the external disturbance from the estimated friction maximum value μp is weakened.

[0175] Therefore, in this embodiment, as described above, Fig.21 In step S146, the estimated maximum friction value μp is set to the median μpmid of the provisional maximum friction value μpmd. Thus, compared with the case where the estimated maximum friction value μp is set to, for example, the previous value of the estimated maximum friction value μp or the average value μpmdav of the provisional maximum friction value μpmd, the temporary influence of the external disturbance on the estimated maximum friction value μp immediately after the non-periodic external disturbance is superimposed can be reduced. In addition, Fig.23 The range B5 shown shows the determination range Rj of the provisional friction maximum value μpmd obtained in the absence of a non-periodic external disturbance or after the non-periodic external disturbance subsides for a period of time.

[0176] Except for the above-described contents, this embodiment is the same as the second embodiment. Also, in this embodiment, similarly to the second embodiment, the effects obtained by the configuration common to the second embodiment described above can be obtained.

[0177] In addition, the present embodiment is a modified example based on the second embodiment, but the present embodiment may be combined with the above-mentioned first embodiment or third embodiment.

[0178] (Sixth Embodiment)

[0179] Next, a sixth embodiment will be described. In this embodiment, points different from the third embodiment described above will be mainly described.

[0180] In the present embodiment, the determination range Rj of the provisional friction maximum value μpmd is determined taking into account the change in the road surface 84 on which the vehicle 80 is traveling. Fig.24 As shown, the road surface friction estimating device 10 of the present embodiment includes a road surface determination unit 24 that determines whether a switch of the road surface 84 has occurred.

[0181] Here, for comparison with the present embodiment, it is assumed that Fig.24 A road surface friction estimating device of a comparative example that does not take into account the switching of the road surface 84 on which the vehicle 80 is traveling.

[0182] For example Fig.25 As shown, taking the case where the road surface 84 is switched at the time point tx during the travel of the vehicle 80 as an example, in the first period PD1 before the time point tx, the distribution of the provisional maximum friction value μpmd becomes the distribution diagram Dsa. In addition, in the second period PD2 across the time point tx, the distribution of the provisional maximum friction value μpmd becomes the distribution diagram DSB, and in the third period PD3 after the time point tx, the distribution of the provisional maximum friction value μpmd becomes the distribution diagram DSc.

[0183] In the above comparative example, since the switching of the road surface 84 is not taken into consideration, even if the distribution diagram DSb of the second period PD2 shows a distribution in which a plurality of provisional friction maximum values ​​μpmd have a plurality of occurrence frequency peaks, the average value μpmdav and the standard deviation σpmd are calculated based on the plurality of provisional friction maximum values ​​μpmd. Thus, an inappropriate determination range Rj of the provisional friction maximum value μpmd is temporarily set. That is, in the above comparative example, the calculation process for determining the determination range Rj is temporarily wrong.

[0184] In this embodiment, if Fig.26 As shown, at the time point txa immediately after the time point tx at which the road surface 84 is switched, the road surface determination unit 24 determines that the road surface 84 is switched. In the present embodiment, based on this determination, the average value μpmdav and the standard deviation σpmd are calculated based on one or more provisional friction maximum values ​​μpmd obtained before the road surface 84 is switched by removing the provisional friction maximum value μpmd.

[0185] exist Fig.26 In the example, the period of the excluded period PDn and the adopted period PDy together becomes Fig.25The second period PD2. Although the excluded period PDn includes the tx time point, the adopted period PDy does not include the tx time point and becomes a period starting after the tx time point. Moreover, in the present embodiment, the provisional maximum friction value μpmd of the excluded period PDn in the second period PD2 is not used for the calculation of the average value μpmdav and the standard deviation σpmd, and the provisional maximum friction value μpmd of the adopted period PDy is used for the calculation of the average value μpmdav and the standard deviation σpmd. Thus, the distribution of the provisional maximum friction value μpmd of the second period PD2 used for the calculation of the average value μpmdav and the standard deviation σpmd is the same as after the switching of the road surface 84, as shown in the distribution diagram DSby, so that it is possible to avoid temporarily setting an inappropriate determination range Rj.

[0186] In order to perform the above-mentioned processing, in this embodiment, the Fig.11 The flowchart is replaced by Fig. 27 The flowchart of the third embodiment Fig.15 The flowchart is replaced by Fig.28 In addition, in this embodiment, as in the third embodiment, the road friction estimation device 10 repeatedly executes the calculation cycle Tc during vehicle travel. Fig. 27 The control process is performed by successively calculating the estimated friction maximum value μp. Fig. 27 The subroutine executed in step S111 is Fig.28 Flowchart of the process.

[0187] In this embodiment Fig. 27 In the flowchart of , steps S151 to S156 are provided between step S101 and step S111. Fig. 27 In the flowchart, after step S101, the process proceeds to step S151.

[0188] exist Fig. 27 In step S151, the road surface determination unit 24 Fig.29 As shown, first, the time differential value dμc / dt of the calculated friction coefficient μc and the time differential value dSc / dt of the calculated slip ratio Sc calculated in step S101 are calculated. Then, the road surface determination unit 24 calculates the determination parameter μdiff according to the following equation F6.

[0189] μdiff=dμc / dSc=(dμc / dt) / (dSc / dt)···(F6)

[0190] When the road surface determination unit 24 calculates the determination parameter μdiff, the determination parameter μdiff is stored in a determination storage device 241 included in the road surface determination unit 24. The determination storage device 241 is basically connected to Fig.13 Specifically, the determination storage device 241 is a storage device for determining the Fig.13 The storage device 17 of the embodiment is different in that the stored memory data is the determination parameter μdiff and the number of storage locations of the memory data is NN. Fig.13 The storage device 17 has the same structure.

[0191] Therefore, a plurality of determination parameters μdiff are stored in the determination storage device 241 in a time-series order. Specifically, Fig.29 D 1 , D 2 、···、D NN The subscripts "1, 2, ..., NN" of D represent data addresses, and the smaller the subscript value, the newer the stored determination parameter μdiff is.

[0192] For example, memory data D 1 Each time the determination parameter μdiff is calculated, it is updated to the latest determination parameter among the successively calculated determination parameters μdiff. NN Each time the judgment parameter μdiff is calculated, it is updated to the memory data D 1 The judgment parameter μdiff is calculated a certain time before the calculation time point. Fig. 27 After step S151, proceed to step S152.

[0193] In step S152, the road surface determination unit 24 first uses the determination parameter μdiff stored in the determination storage device 241 and calculates the road surface determination unit 24 according to the following equation F7: Fig.29 The determination parameter difference Δμdiff is calculated as shown.

[0194] Δμdiff=┃(μdiff[NN]-μdiff[1])┃···(F7)

[0195] Here, μdiff[1] in the above formula F7 is the determination parameter μdiff stored in the first storage location of the determination storage device 241, that is, the latest determination parameter μdiff stored in the determination storage device 241. Fig.29 is represented as memory data D 1 In the above formula F7, μdiff[NN] is the determination parameter μdiff stored in the NNth storage location of the determination storage device 241, that is, the earliest determination parameter μdiff stored in the determination storage device 241. Fig.29is represented as memory data D NN .

[0196] like Fig. 27 , Fig.29 As shown, if the determination parameter difference Δμdiff is calculated in step S152, the road surface determination unit 24 determines whether the determination parameter difference Δμdiff is greater than a predetermined road surface change determination value μdiffth. Thus, the road surface determination unit 24 determines whether a state change of the road surface 84 has occurred in which the friction condition between the road surface 84 and the tire 81 has changed beyond a predetermined limit, that is, whether the road surface 84 on which the vehicle 80 is traveling has changed. That is, the road surface change determination value μdiffth is set corresponding to the predetermined limit for the friction condition, and is experimentally set in advance so that the change of the road surface 84 during traveling can be clarified.

[0197] If it is determined in step S152 that the determination parameter difference Δμdiff is greater than the road surface change determination value μdiffth, the process proceeds to step S154 . On the other hand, if it is determined that the determination parameter difference Δμdiff is less than the road surface change determination value μdiffth, the process proceeds to step S153 .

[0198] In addition, at the beginning Fig. 27 At the beginning of the control process, there will be a period of uncertainty in μdiff[NN] in the above formula F7. Fig. 27 From the start of the control process until the determination parameter μdiff is stored in all the storage locations of the determination storage device 241, the determination in step S152 is not performed, and the process proceeds to step S153 after step S152.

[0199] exist Fig. 27 In step S153, the road surface determination unit 24 Fig. 27 , Fig.29 As shown, the flag variable Rmem is set to "Rmem = 0". Fig. 27 In step S154, the road surface determination unit 24 sets the flag variable Rmem to "Rmem=1". After step S153 or step S154, the process proceeds to step S155.

[0200] exist Fig. 27In step S155, the road surface determination unit 24 determines whether the flag variable Rmem is switched from "Rmem = 0" to "Rmem = 1". The switching of the flag variable Rmem from "Rmem = 0" to "Rmem = 1" means that the friction between the road surface 84 and the tire 81 has changed beyond a predetermined limit, that is, the above-mentioned state of the road surface 84 has changed. In other words, the case where the flag variable Rmem is switched from "Rmem = 0" to "Rmem = 1" means that the previous value of the flag variable Rmem is 0 and the current value of the flag variable Rmem is 1.

[0201] If it is determined in step S155 that the flag variable Rmem is switched from "Rmem = 0" to "Rmem = 1", the process proceeds to step S156. On the other hand, if it is determined that the flag variable Rmem is not switched from "Rmem = 0" to "Rmem = 1", the process proceeds to step S111. The case where the flag variable Rmem is not switched from "Rmem = 0" to "Rmem = 1" means that the flag variable Rmem remains "Rmem = 0" or "Rmem = 1", or the flag variable Rmem is switched from "Rmem = 1" to "Rmem = 0".

[0202] exist Fig. 27 In step S156, the road surface determination unit 24 first reads Figure 6 The number of free storage locations Nyt that have not yet stored the provisional maximum friction value μpmd among all the storage locations of the storage device 17, that is, the remaining number of storage locations Nyt. Furthermore, the road surface determination unit 24 determines the number of calculation objects M based on the remaining number of storage locations Nyt and according to the following formula F8. When the number of calculation objects M is compared with the total number of storage locations N of the storage device 17, it is always "M≤N".

[0203] M=Nyt-1···(F8)

[0204] The number of calculation objects M is a variable used in the later-described formula F9 for calculating the average value μpmdav of the provisional friction maximum value μpmd and the later-described formula F10 for calculating the standard deviation σpmd. The initial value of the number of calculation objects M is set to the total number of storage locations of the memory data of the storage device 17, that is, N. Therefore, unless step S156 is executed, the number of calculation objects M maintains "M=N". After step S156, the process proceeds to step S111.

[0205] In this embodiment Fig.28 In the flowchart of the third embodiment, Fig.15 Step S204 of the flowchart is replaced by step S254. Fig.15Step S205 of the flowchart is replaced by step S255. Fig.28 In the flowchart of Fig.15 The flowchart of FIG. 1 adds step S257, and step S257 is set as the next step of step S227.

[0206] In step S254, the average value calculation unit 18 calculates the average value μpmdav of the provisional friction maximum value μpmd according to the following formula F9 based on the plurality of provisional friction maximum values ​​μpmd stored in the storage device 17. In the next step S255, the standard deviation calculation unit 19 calculates the standard deviation σpmd of the provisional friction maximum value μpmd according to the following formula F10 based on the plurality of provisional friction maximum values ​​μpmd stored in the storage device 17 and the average value μpmdav calculated according to the following formula F9. Fig.28 After step S255, go to step S206.

[0207] [Formula 3]

[0208]

[0209] [Formula 4]

[0210]

[0211] Here, the above formula F9 is a formula obtained by replacing the constant N in the above formula F1 with the number of calculation objects M, and is the same as the above formula F1 except this point. In addition, the above formula F10 is a formula obtained by replacing the constant N in the above formula F2 with the number of calculation objects M, and is the same as the above formula F2 except this point. In addition, when the number of calculation objects M becomes "M≤0", the above formulas F9 and F10 cannot be calculated, so, for example, in steps S254 and S255, the average value μpmdav and the standard deviation σpmd are not updated and the previous values ​​are maintained as they are.

[0212] Therefore, if the number of calculation objects M remains at N as the initial value, in this embodiment, similarly to the third embodiment, based on Figure 6 All the provisional friction maximum values ​​μpmd stored in the storage device 17, that is, the memory data D 1 ~D N To calculate the average value μpmdav and the standard deviation σpmd. In summary, in this case, in step S254, the memory data D is calculated according to the above formula F9. 1 ~D N The average value μpmdav is calculated in step S255 according to the above formula F10. 1 ~D N The standard deviation σpmd.

[0213] In contrast, Fig. 27 In the case where the number of calculation objects M is set to "M < N" in step S156, based on all the memory data D stored in the storage device 17 1 ~D N The memory data D on the side that is later (newer) in terms of time series 1 ~D M The average value μpmdav and the standard deviation σpmd are calculated. In addition, the memory data D is not used in the calculation of the average value μpmdav and the standard deviation σpmd. 1 ~D N The memory data D on the earlier side in terms of time series M+1 ~D N In summary, in this case, in step S254, the memory data D is calculated according to the above formula F9. 1 ~D M The average value μpmdav is calculated in step S255 according to the above formula F10. 1 ~D M The standard deviation σpmd.

[0214] exist Fig.28 In step S257 following step S227, the road surface determination unit 24 sets the number of calculation objects M to "M=N". In short, the road surface determination unit 24 returns the number of calculation objects M to N, which is the initial value. When step S257 is completed, Fig.28 The subroutine ends and returns to Fig. 27 Flowchart of the process.

[0215] Next, in order to explain the effects of this embodiment, Fig.30 The control process in the above-mentioned comparative example in which the determination range Rj is determined without considering the switching of the road surface 84 during driving is explained with reference to the timing chart. This comparative example is the same as the present embodiment except that the determination range Rj is determined without determining whether the switching of the road surface 84 has occurred. Fig.30 Examples and the following Fig.31 In the example of , the total number of storage locations of the storage device 17, that is, N, is "N=8".

[0216] like Fig.30As shown, in the comparative example, the average value μpmdav of the provisional maximum friction value μpmd is calculated at the te1 time point based on the multiple provisional maximum friction values ​​μpmd calculated during the accumulation period PDx at the switching time point across the road surface 84, i.e., the tx time point and accumulated in the storage device 17. That is, the average value μpmdav adopted from the te1 time point is calculated based on the provisional maximum friction value μpmd obtained before the tx time point and the provisional maximum friction value μpmd obtained after the tx time point. Therefore, the deviation between the average value μpmdav and the actual maximum value μmx of the friction coefficient μ on the road surface 84 being traveled becomes larger due to the switching of the road surface 84, and the deviated state continues until the average value μpmdav is updated next time. In addition, the change in the actual maximum value μmx of the friction coefficient μ is Fig.30 It is represented by a single-dot chain line Lmx.

[0217] Next, use Fig.31 The control process in this embodiment is explained by the timing diagram. Fig. 27 , Fig.28 Control processing. Fig.31 , Fig.28 As shown, the determination range Rj of the provisional friction maximum value μpmd of the present embodiment is repeatedly determined based on the average value μpmdav and the standard deviation σpmd obtained from the plurality of provisional friction maximum values ​​μpmd calculated within the predetermined period, i.e., the accumulation period PDx. Thus, the determination range Rj is updated successively. This is also the case in the above-mentioned comparative example and the aforementioned third embodiment. In addition, the plurality of provisional friction maximum values ​​μpmd calculated within the accumulation period PDx is equivalent to Figure 6 Memory data D in 1 ~D N , sometimes referred to as provisional values ​​over multiple periods.

[0218] The road surface friction estimation device 10 of this embodiment is different from the above-mentioned comparative example in that it includes a road surface determination unit 24 for determining whether the state of the road surface 84 during travel has changed. Fig.31 As shown, in this embodiment, at the time point tf1 immediately after the time point tx, which is the switching time point of the road surface 84, the flag variable Rmem is switched from "Rmem=0" to "Rmem=1", thereby Fig. 27 In step S155, it is determined that the state of the road surface 84 on which the vehicle is traveling has changed.

[0219] The result of this judgment is Fig. 27 In step S156, the number of calculation objects M is determined according to the above formula F8. Specifically, Fig.31At the time point tf1, the remaining number of storage locations Nyt obtained in step S156 is "Nyt = 4", so according to the above formula F8, the number of calculation objects M is determined to be "M = 4-1 = 3". The calculation result of "M = 3" is maintained until the number of calculation objects M is Fig.28 Until "M=N" is set in step S257.

[0220] Therefore, in Fig.31 The average value μpmdav of the provisional maximum friction value μpmd calculated at the time point tf2 is when “M=3” is set as described above. Fig.28 The standard deviation σpmd of the provisional maximum friction value μpmd calculated at the time point tf2 is calculated in accordance with the above formula F9 in step S254. Fig.28 Calculated in step S255 according to the above formula F10.

[0221] That is, the mean μpmdav and standard deviation σpmd are based on the values ​​stored in Figure 6 The three provisional friction maximum values ​​μpmd on the later side in terms of time series in the storage device 17 are the memory data D 1 ~D 3 The memory data D 1 ~D 3 exist Fig.31 The words in Fig.31 The three provisional friction maximum values ​​μpmd calculated during the adoption period PDy in the accumulation period PDx across the time point tx are not used in the calculation of the average value μpmdav and the standard deviation σpmd at the time point tf2. In addition, the five provisional friction maximum values ​​μpmd earlier in the time series stored in the storage device 17, that is, the memory data D 4 ~D 8 The memory data D 4 ~D 8 exist Fig.31 The words in Fig.31 The five provisional friction maximum values ​​μpmd calculated in the exclusion period PDn of the accumulation period PDx extending over the time point tx include the provisional friction maximum value μpmd obtained before the time point tx when the state of the road surface 84 changes.

[0222] Then, at the time point tf2, the determination range Rj of the provisional friction maximum value μpmd is determined based on the average value μpmdav and the standard deviation σpmd obtained from the three provisional friction maximum values ​​μpmd calculated during the adoption period PDy.

[0223] In this way, when it is determined that the state of the road surface 84 has changed in a certain accumulation period PDx, the average value μpmdav and the standard deviation σpmd are calculated based on the provisional friction maximum value μpmd in the adoption period PDy after removing the five provisional friction maximum values ​​μpmd in the exclusion period PDn from the provisional values ​​in the above-mentioned multiple periods. And, the determination range Rj of the provisional friction maximum value μpmd is determined based on the average value μpmdav and the standard deviation σpmd obtained from the provisional friction maximum value μpmd in the adoption period PDy.

[0224] Therefore, in this embodiment, compared with the above-mentioned comparative example, it is possible to suppress Fig.31 The average value μpmdav of the provisional maximum friction value μpmd in the example deviates from the actual maximum value μmx of the friction coefficient μ represented by the single-dot chain line Lmx. That is, compared with the above-mentioned comparative example, it is possible to suppress the inappropriate determination range Rj of the provisional maximum friction value μpmd temporarily set due to the switching of the road surface 84. Fig.31 In the example, the number of calculations of the provisional friction maximum value μpmd within the period PDy is three, but it may be one depending on the size of the number of calculation objects M.

[0225] Except for the above-described contents, this embodiment is the same as the third embodiment. Also, in this embodiment, similarly to the third embodiment, the effects obtained by the configuration common to the third embodiment described above can be obtained.

[0226] In addition, the present embodiment is a modification example based on the third embodiment, but the present embodiment may be combined with any of the second, fourth, and fifth embodiments described above.

[0227] (Other embodiments)

[0228] (1) In each of the above-mentioned embodiments, Figure 1 The vehicle 80 equipped with the road friction estimation device 10 is, for example, an electric vehicle that does not have an engine and uses a running motor as a driving force source, but this is an example. The vehicle 80 may be a hybrid vehicle or an engine vehicle that does not have a running motor.

[0229] (2) In each of the above-mentioned embodiments, the road friction estimating device 10 calculates the estimated friction maximum value μp for each wheel of the tire 81 serving as the driving wheel, but this is only an example. For example, the road friction estimating device 10 may calculate the estimated friction maximum value μp for a structure in which all the tires 81 are put together or a structure in which a pair of left and right tires 81 are put together.

[0230] (3) In each of the above embodiments, for example Figure 2As shown in FIG. 1 , the slip ratio Sc is calculated based on the vehicle body speed, the drive wheel speed, the steering angle, the yaw rate of the vehicle 80, and the acceleration of the vehicle 80, but this is an example. The physical quantity that is the basis for calculating the slip ratio Sc is not limited to the above, and can be appropriately selected. The same is true for the physical quantity that is the basis for calculating the friction coefficient μc. The physical quantity that is the basis for calculating the friction coefficient μc is not limited to Figure 2 The physical quantities shown can also be selected appropriately.

[0231] In addition, the calculation method of the provisional friction maximum value μpmd is not limited to the method disclosed in the first embodiment, and the provisional friction maximum value μpmd may not be calculated using Figure 5 The friction coefficient map MPm is used for calculation. For example, a tire model formula may be pre-set by computer simulation, and the provisional friction maximum value μpmd may be calculated according to the tire model formula. Furthermore, the provisional friction maximum value μpmd may be calculated based on other parameters instead of using the slip ratio S and the friction coefficient μ in the calculation of the provisional friction maximum value μpmd.

[0232] (4) In each of the above embodiments, for example Figure 4 As shown, the determination range Rj of the provisional friction maximum value μpmd is set to the range of “μpmdav±3·σpmd”, but this is an example. For example, the determination range Rj may be the range of “μpmdav±σpmd” or the range of “μpmdav±2·σpmd”.

[0233] (5) In the sixth embodiment described above, Fig. 27 In step S156, the calculation object number M is calculated according to the above formula F8, but this is an example. For example, the calculation object number M may also be set to "M = Nyt".

[0234] (6) In the sixth embodiment described above, if Fig. 27 As shown, the determination of whether the state of the road surface 84 has changed is performed using the difference of "dμc / dSc", but this is an example. For example, the determination may be performed based on an image of the road surface 84 taken by a vehicle-mounted camera instead of the difference of "dμc / dSc".

[0235] (7) In each of the above embodiments, for example, Figure 2 As shown in the figure, the road surface friction estimation device 10 is described as an independent device, but it can also be a control unit included in the electronic control device as a part of the functionality of the vehicle-mounted electronic control device.

[0236] (8) In addition, the present disclosure is not limited to the above-mentioned embodiments, and can be implemented in various modifications. In addition, the above-mentioned embodiments are not mutually unrelated embodiments, and can be appropriately combined except for the case where it is obvious that they cannot be combined.

[0237] In addition, in the above-mentioned embodiments, the elements constituting the embodiments are not necessarily necessary elements, except for the cases where they are specifically stated to be necessary and the cases where they are considered to be necessary in principle. In addition, in the above-mentioned embodiments, when referring to the number, value, amount, range and other numerical values ​​of the structural elements of the embodiments, except for the cases where they are specifically stated to be necessary and the cases where they are limited to a specific number in principle, they are not limited to the specific number. In addition, in the above-mentioned embodiments, when referring to the material, shape, positional relationship and the like of the structural elements, etc., except for the cases where they are specifically stated to be necessary and the cases where they are limited to a specific material, shape, positional relationship and the like in principle, they are not limited to the material, shape, positional relationship and the like.

[0238] In addition, the control unit and method described in the present disclosure can be implemented by a special-purpose computer, which is provided by constituting a processor and a memory programmed in a manner to execute one or more functions embodied by a computer program. Alternatively, the control unit and method described in the present disclosure can also be implemented by a special-purpose computer as follows, which is provided by constituting a processor using one or more special-purpose hardware logic circuits. Alternatively, the control unit and method described in the present disclosure can also be implemented by one or more special-purpose computers consisting of the following combination, which refers to a combination of a processor and a memory programmed in a manner to execute one or more functions and a processor consisting of one or more hardware logic circuits. In addition, the computer program can also be stored as an instruction executed by a computer in a non-temporary tangible storage medium that can be read by the computer. In addition, the road friction estimation device 10 of each embodiment is equivalent to the above-mentioned control unit.

Claims

1. A road surface friction estimating device, which estimates the maximum value of the friction coefficient between the road surface on which a vehicle is traveling and the tires of the vehicle, and obtains the estimated maximum value of the friction coefficient as an estimated friction maximum value, characterized in that: The road surface friction estimating device comprises: a first estimating unit that repeatedly calculates a provisional friction maximum value as a provisional value of the estimated friction maximum value based on a physical quantity associated with the friction between the road surface and the tire and detected during travel of the vehicle; a range determination unit that determines a determination range of the provisional friction maximum value including the average value based on an average value and a standard deviation of the provisional friction maximum values ​​obtained from a plurality of the provisional friction maximum values ​​calculated by the first estimating unit; as well as The second estimating unit determines the provisional friction maximum value as the estimated friction maximum value when the provisional friction maximum value is within the determination range, and determines a correction value that is a value within the determination range as the estimated friction maximum value when the provisional friction maximum value deviates from the determination range.

2. The road surface friction estimating device according to claim 1, characterized in that: The second estimating unit repeatedly determines the estimated friction maximum value as time passes. The correction value is a previous value of the estimated maximum friction value.

3. The road surface friction estimating device according to claim 1, characterized in that: The correction value is the average value.

4. A road surface friction estimation device, which estimates the maximum value of the friction coefficient between the road surface on which a vehicle is traveling and the tires of the vehicle, and obtains the estimated maximum value of the friction coefficient as an estimated friction maximum value, characterized in that: The road surface friction estimating device comprises: a first estimating unit that repeatedly calculates a provisional friction maximum value as a provisional value of the estimated friction maximum value based on a physical quantity associated with the friction between the road surface and the tire and detected during travel of the vehicle; a range determination unit that determines a determination range of the provisional friction maximum value including the average value based on an average value and a standard deviation of the provisional friction maximum values ​​obtained from a plurality of the provisional friction maximum values ​​calculated by the first estimating unit; as well as a second estimating unit that determines the provisional friction maximum value as the estimated friction maximum value when the provisional friction maximum value is within the determination range, and determines the median of a plurality of provisional friction maximum values ​​that serve as a basis for the average value as the estimated friction maximum value when the provisional friction maximum value deviates from the determination range.

5. The road surface friction estimating device according to any one of claims 1 to 4, characterized in that: The range determination unit determines the determination range based on the average value and the standard deviation obtained from a plurality of the provisional friction maximum values ​​calculated within a predetermined period each time the provisional friction maximum value is calculated. The predetermined period is shifted toward a time elapsed side each time the provisional friction maximum value is calculated.

6. The road surface friction estimating device according to any one of claims 1 to 4, characterized in that: The range determination unit includes a data storage unit that accumulates the provisional friction maximum value each time the provisional friction maximum value is calculated by the first estimation unit. The range determination unit determines the determination range based on the average value and the standard deviation obtained from the plurality of provisional friction maximum values ​​accumulated in the data storage unit, each time the provisional friction maximum value is accumulated a predetermined number of times in the data storage unit.

7. The road surface friction estimating device according to any one of claims 1 to 4, characterized in that: The road surface friction estimation device includes a road surface determination unit that determines whether a state change of the road surface occurs in which a state of friction between the road surface and the tire changes beyond a predetermined limit. The range determination unit repeatedly determines the determination range based on the average value and the standard deviation obtained from provisional values ​​within a period, wherein the provisional values ​​within a period are a plurality of provisional friction maximum values ​​calculated within a prescribed period that shifts toward a side of time as time passes, When the road surface determination unit determines that a change in the state of the road surface has occurred, the range determination unit determines the determination range based on the average value and the standard deviation obtained based on one or more of the provisional friction maximum values, wherein the one or more provisional friction maximum values ​​are provisional friction maximum values ​​obtained by removing the provisional friction maximum values ​​obtained before the change in the state of the road surface has occurred from multiple provisional values ​​within the period.

8. The road surface friction estimating device according to any one of claims 1 to 4, characterized in that: The first estimating unit calculates the friction coefficient and the slip ratio of the tire based on the physical quantity, and calculates the provisional friction maximum value based on the friction coefficient and the slip ratio.

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