JP2015040020A - Estimator of road surface friction coefficient in two-wheeled motor vehicle, and anti-lock brake controller using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a road surface μ estimator that can precisely estimate a road surface μ in the case where only one wheel is equipped with a wheel speed sensor in a two-wheeled motor vehicle.SOLUTION: A road surface μ is estimated on the basis of a return state of a wheel acceleration generated when a brake force B corresponding to a hold G is generated upon braking start, that is, depending upon whether or not the wheel acceleration increases to return. Concretely, when the wheel acceleration generated when the brake force B corresponding to a hold G is generated, decreases by an off-set amount or more of a decompression threshold corresponding to the hold G, a state is determined that a brake force B of a value corresponding to an actual road surface μ or more is generated. This process enables a road surface μ estimation that the road surface μ of a running road surface is a road surface μ corresponding to the hold G of a previous setting or more, and below a road surface μ corresponding to the hold G of a present setting.

Description

  The present invention relates to a road surface friction coefficient estimating device and an antilock brake control device using the same when a wheel speed sensor is provided only on one wheel in a motorcycle.

  2. Description of the Related Art Conventionally, a motorcycle has a wheel speed sensor for each of a front wheel and a rear wheel, and anti-lock brake (hereinafter referred to as ABS) control is performed based on a wheel speed obtained from a detection signal of each wheel speed sensor. (See, for example, Patent Document 1). Specifically, the estimated vehicle body speed is created from the wheel speeds of the front and rear wheels, and the slip of each wheel is determined based on the slip ratio represented by the deviation between the estimated vehicle body speed and each wheel speed. ABS control is executed based on the result.

JP 2002-96723 A

  However, when the ABS control device in a motorcycle is provided only for one front wheel, for example, with the aim of simplifying the device configuration, the wheel speed detected by the wheel speed sensor is also only for one wheel. The slip cannot be determined, and the ABS control cannot be executed with high accuracy. In order to determine the slip of each wheel, it is only necessary to accurately estimate the road surface friction coefficient (hereinafter referred to as road surface μ). Specifically, the estimated vehicle body speed can be accurately calculated based on the road surface μ, and the slip of each wheel can be determined based on this. It is desired that the ABS control can be performed with high precision based on the slip determination result.

  In view of the above points, it is a first object of the present invention to provide a road surface μ estimation device that can accurately estimate a road surface μ when a motorcycle has a wheel speed sensor only on one wheel. It is a second object of the present invention to provide an ABS control device that can perform ABS control with high accuracy based on the road surface μ estimated with high accuracy.

  In order to achieve the above object, according to the first aspect of the present invention, the wheel speed detecting means for detecting the wheel speed provided only for the front wheels and the front wheel braking force for applying a braking force to the front wheels in response to a deceleration request of the vehicle. A road surface μ estimation device for a motorcycle having a providing means, which holds and applies a predetermined braking force for a predetermined period at the start of braking based on a deceleration request, and the wheel acceleration of the front wheels increases and returns during the predetermined period. It is characterized by comprising friction coefficient estimating means for estimating the road surface μ of the traveling road surface of the motorcycle based on the return state indicating whether or not.

  According to this, at the start of braking, the road surface μ is estimated based on the return state of the wheel acceleration generated when a predetermined braking force is applied for a predetermined period. As described above, it is possible to estimate the road surface μ of the traveling road surface based on the return of the wheel acceleration.

  In the invention according to claim 2, the friction coefficient estimating means is a predetermined braking force applied by the front wheel braking force applying means when the wheel acceleration of the front wheel is increased and returned during a predetermined period in which the predetermined braking force is applied. And increasing the predetermined braking force again for a predetermined time, and estimating the road surface μ of the traveling road surface of the motorcycle based on the return state of the wheel acceleration of the front wheels during the predetermined period. Yes.

  As described above, when the wheel acceleration returns during the predetermined period, the predetermined braking force is increased and the holding is again applied for the predetermined time. In this way, when the wheel acceleration does not return, the road surface μ of the traveling road surface is greater than or equal to the road surface μ corresponding to the predetermined braking force generated last time and the road surface μ corresponding to the predetermined braking force generated this time. The road surface μ can be estimated.

  In the invention according to claim 3, when the friction coefficient estimating means reduces the wheel acceleration of the front wheels more than a predetermined decompression threshold more than a wheel acceleration assumed by generating the predetermined braking force during a predetermined period, The road surface coefficient corresponding to the predetermined braking force sometimes applied is estimated to be the road surface μ of the traveling road surface.

  Thus, for example, when the wheel acceleration generated when the predetermined braking force is generated is further reduced to a predetermined pressure reduction threshold or more than the wheel acceleration assumed by generating the predetermined braking force, the actual road surface μ It can be determined that a braking force greater than a value corresponding to is generated. As a result, it can be estimated that the road surface μ of the traveling road surface is equal to or greater than the road surface μ corresponding to the predetermined braking force generated last time and less than the road surface μ corresponding to the predetermined braking force generated this time, and the road surface μ can be estimated. Become.

  According to a fourth aspect of the present invention, the road surface μ estimation device according to any one of the first to third aspects is provided, which is estimated by the wheel speed detected by the wheel speed detection means and the road surface μ estimation device. Vehicle body speed calculating means for calculating an estimated vehicle body speed based on the road surface μ of the traveling road surface, and determining a slip of the front wheel based on a slip ratio represented by a deviation between the estimated vehicle body speed and the wheel speed of the front wheel, When it is determined that slip has occurred, the pressure reduction control for decreasing the pressure applied to the wheel cylinder provided to the front wheel as the braking force applying means is performed, and then the pressure increase control for increasing the pressure is performed, thereby And an ABS control means for controlling the slippage.

  Thus, based on the estimation result of the road surface μ by the road surface μ estimation device, it is possible to calculate the estimated vehicle body speed when executing the ABS control. As a result, in a motorcycle, even when a wheel speed sensor is provided on only one wheel, it is possible to provide a road surface μ estimation device that can accurately estimate the road surface μ. Then, it is possible to perform the ABS control with high accuracy based on the road surface μ estimated in this way.

  In the invention according to claim 5, there is a friction coefficient change determining means for detecting a μ jump in which the road surface μ of the traveling road surface changes during ABS control, and when the μ jump is detected by the friction coefficient change determining means, The present invention is characterized in that re-estimation means for re-estimating the friction coefficient of the running road surface by the friction coefficient estimation means is provided.

  Since it is possible that a μ jump that changes the road surface μ occurs during braking, it is determined whether or not the μ jump requirement is satisfied during ABS control after the road surface μ is estimated, and the requirement is satisfied. In this case, the road surface μ is estimated again. Thus, when a μ jump occurs during braking, it is possible to prevent the estimated vehicle body speed from being calculated based on an erroneous road surface μ estimated in the past. Based on the correct road surface μ estimated after the μ jump, the estimated vehicle body speed can be calculated with high accuracy, and ABS control can be performed with high accuracy.

1 is a diagram illustrating an overall configuration of a brake system 1 for a motorcycle in which road surface μ estimation and ABS control according to a first embodiment of the present invention are executed. FIG. It is a model figure regarding wheel motion. It is a model figure showing various parameters of a motorcycle. 5 is a flowchart showing details of a road surface μ estimation process. FIG. 6 is a μ-s characteristic diagram showing a relationship between a road surface μ and a slip ratio s. 6 is a time chart showing changes in estimated vehicle body speed and wheel speed of a front wheel FW during ABS control. FIG. 6 is a μ-s characteristic diagram showing a relationship between a road surface μ and a slip ratio s. It is a time chart at the time of performing road surface μ estimation.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, parts that are the same or equivalent to each other will be described with the same reference numerals.

(First embodiment)
A first embodiment of the present invention will be described. In the present embodiment, a road surface μ estimation device for a rear-wheel-drive motorcycle in which a driving force is generated for a rear wheel based on a driver's accelerator operation and an ABS control device using the same will be described.

  FIG. 1 shows an overall configuration of a brake system 1 for a motorcycle in which road surface μ estimation and ABS control are executed.

  The motorcycle is a vehicle having a front wheel FW located in the vehicle traveling direction and a rear wheel RW located in the reverse direction, and the brake system 1 shown in FIG. 1 brakes the front wheel FW and the rear wheel RW. It is something to hang. Although the ABS control is executed by the brake system 1, the wheels to be controlled by the ABS control are only the front wheels FW of both wheels, and the rear wheels RW are not the wheels to be controlled.

  Specifically, as shown in FIG. 1, the brake system 1 includes two piping systems, a system that generates a braking force (braking force) for the front wheels FW and a system that generates a braking force for the rear wheels RW. It is set as the structure which has.

  As shown in FIG. 1, the brake system 1 includes a brake lever 11 positioned on the right side of the handle and a brake pedal 12 positioned in front of the right footrest. The brake lever 11 and the brake pedal 12 correspond to brake operation members for generating a braking force for the front wheel FW and the rear wheel RW, respectively, and are operated independently by a driver. The brake lever 11 and the brake pedal 12 are connected to a brake circuit having first and second piping systems 14 and 15 via a front wheel master cylinder (hereinafter referred to as M / C) 13a and a rear wheel M / C 13b. Has been.

  Specifically, the brake lever 11 is connected to the first piping system 14 that generates a braking force for the front wheel FW via the front wheel M / C 13a and the like. The brake pedal 12 is connected to a second piping system 15 that generates a braking force for the rear wheel RW via the rear wheel M / C 13b and the like. When the brake lever 11 or the brake pedal 12 is operated, the front wheel FW side is passed through the first and second piping systems 14 and 15 based on the brake fluid pressure generated in the front wheel M / C 13a and the rear wheel M / C 13b. W / C pressure is generated with respect to the front wheel cylinder (hereinafter referred to as W / C) 16 and the rear wheel W / C 17 on the rear wheel RW side, thereby generating a braking force.

  A brake fluid pressure control actuator 2 is provided between the front wheel M / C 13a and the front wheel W / C16. By controlling various control valves and the like provided in the brake fluid pressure control actuator 2, the W / C pressure applied to the front wheel W / C 16 is controlled in the first piping system 14.

  The brake fluid pressure control actuator 2 is provided with a pipe line A serving as a main pipe line on the front wheel side connecting the front wheel M / C 13a and the front wheel W / C16. Through this pipe A, the M / C pressure is transmitted to generate the W / C pressure at the front wheel W / C 16.

  Further, the pipe line A is provided with a pressure increase control valve 19 for controlling an increase in brake fluid pressure to the front wheels W / C 16. The pressure increase control valve 19 is constituted by an electromagnetic valve as a two-position valve capable of controlling the communication / blocking state. When the pressure increase control valve 19 is controlled to be in the communication state, the M / C pressure is applied to the front wheel W / C16, and when the shut-off state is established, the M / C pressure is not applied to the front wheel W / C16.

  Note that, during normal braking by the operation of the brake lever 11 performed by the driver, the pressure increase control valve 19 is controlled to be always in communication. For this reason, the M / C pressure generated in the front wheel M / C 13a is directly transmitted as the W / C pressure of the front wheel W / C16. The pressure increase control valve 19 is provided with a safety valve 19a in parallel.

  A line B as a pressure reducing line is connected between the pressure increase control valve 19 and the front wheel W / C 16 in the line A, and a pressure regulating reservoir 20 is provided for the line B. In addition, a pressure reduction control valve 21 made of an electromagnetic valve is disposed in the pipeline B as a two-position valve that can control the communication / blocking state. The pressure reducing control valve 21 is always cut off during normal braking.

  Further, a conduit C serving as a reflux conduit is disposed so as to connect the pressure adjusting reservoir 20, the front wheel M / C 13 a in the conduit A, and the pressure increase control valve 19. Through this line C, when the brake is released, the brake fluid stored in the pressure regulating reservoir 20 during the ABS control is returned to the M / C 13 side.

  The pressure adjusting reservoir 20 is connected to the pipe C and returns to the front wheel M / C 13a. The reservoir hole 20a returns the brake liquid, and the reservoir hole is connected to the pipe B and receives the brake liquid discharged from the front wheel W / C16. 20b, which communicate with the reservoir chamber 20c. A valve body 20d made of a ball valve is disposed inside the reservoir hole 20a. The valve body 20d is attached to and detached from the valve seat 20e to control the communication interruption between the conduit C and the reservoir chamber 20c, and the reservoir chamber 20c is adjusted by adjusting the distance from the valve seat 20e. The pressure difference between the internal pressure and the M / C pressure is regulated. Below the valve body 20d, a rod 20f having a predetermined stroke for moving the valve body 20d up and down is provided separately from the valve body 20d. Also, in the reservoir chamber 20c, there are a piston 20g interlocking with the rod 20f, and a spring 20h that generates a force for pressing the piston 20g toward the valve body 20d to push out the brake fluid in the reservoir chamber 20c. Is provided.

  The pressure regulating reservoir 20 configured as described above is configured such that when a predetermined amount of brake fluid is stored, the valve body 20d is seated on the valve seat 20e and the brake fluid does not flow into the reservoir chamber 20c. For this reason, much brake fluid does not flow into the reservoir chamber 20c. Further, at the time of braking, the valve body 20d contacts the valve seat 20e based on the M / C pressure, so that the reservoir chamber 20c can be prevented from being filled with the brake fluid.

  On the other hand, the second piping system 15 is provided with a pipeline D serving as a main pipeline on the rear wheel side connecting the rear wheel M / C 13b and the rear wheel W / C 17. The M / C pressure is transmitted through the pipe D, so that the W / C pressure is generated in the rear wheel W / C 17. Unlike the 1st piping system 14, the 2nd piping system 15 is set as the structure which is only provided with the pipe line D and is not provided with various control valves.

  As described above, the brake circuit in the brake system 1 of the motorcycle including the first and second piping systems 14 and 15 is configured. Various control valves 19 of the brake hydraulic pressure control actuator 2 provided in such a brake circuit are driven by an electronic control device (hereinafter referred to as a brake ECU) 4 for brake control.

  The brake ECU 4 controls the control system of the brake system 1 and is constituted by a known microcomputer having a CPU, a ROM, a RAM, an I / O, and the like, and processes various calculations according to a program stored in the ROM. Execute. The brake ECU 4 corresponds to the road surface μ estimation device of the present invention and an ABS control device using the same. The brake ECU 4 inputs a detection signal from a wheel speed sensor 5 provided on the front wheel FW and a detection signal from a brake switch 6 attached to each brake lever 11 or brake pedal 12. Then, when it is detected that braking is being performed based on the detection signal of the brake switch 6, the road surface is obtained using the wheel speed of the front wheel FW based on the detection signal of the wheel speed sensor 5 and using the wheel speed. μ estimation is performed, wheel slip is determined based on the wheel speed and the estimated road surface μ, and ABS control is executed. The brake system 1 concerning this embodiment is comprised by the above structures.

  In the brake system 1 configured as described above, for example, during normal braking in which ABS control or the like is not performed, current supply from the brake ECU 4 to the various control valves 19 and 21 is not performed. For this reason, the W / C pressure corresponding to the operation amount of the brake lever 11 and the brake pedal 12 is generated in each of the W / Cs 16 and 17. As a result, a braking force corresponding to the brake lever 11 and the brake pedal 12 is generated on the front wheel FW and the rear wheel RW.

  Further, during ABS control, current is supplied from the brake ECU 4 to the various control valves 19 and 21 as necessary. For example, when the pressure reducing control valve 21 is in a communication state, the pipe A and the pressure regulating reservoir 20 are in a communication state through the pipe B, the W / C pressure generated in the W / C 16 is reduced, and wheel slip occurs. It becomes possible to avoid wheel lock by being suppressed. Further, when both the pressure increase control valve 19 and the pressure reduction control valve 21 are cut off, the W / C pressure generated by the W / C 16 is held. Then, when the pressure increase control valve 19 enters a communication state and the pressure reduction control valve 21 enters a shut-off state, the W / C pressure generated by the W / C 16 is increased. In this way, ABS control is executed by performing pressure reduction control, holding control, and pressure increase control.

  Next, the road surface μ estimation process executed by the brake system 1 configured as described above and the ABS control process based on the road surface μ estimation process will be described.

  As described above, the brake system 1 according to the present embodiment has a configuration in which the wheel speed sensor 5 is provided only on one front wheel in a motorcycle, but in the case of such a configuration, the wheel of the front wheel FW. Only speed is required. For this reason, the estimated vehicle body speed cannot be calculated by a method such as, for example, using the faster wheel speed of the two front and rear wheels as the estimated vehicle body speed. Therefore, the slip of each wheel FW and RW cannot be determined, and the ABS control cannot be executed with high accuracy.

  Therefore, in this embodiment, the road surface μ is estimated by the road surface μ estimation process. In the ABS control, the slip of the front wheel FW is determined based on the estimated road surface μ, and the ABS control is executed.

  Hereinafter, the details of the road surface μ estimation process will be described. Prior to that, the basic concept of the road surface μ estimation executed in the present embodiment will be described with reference to FIGS. 2 and 3.

  The road surface μ on the traveling road surface of the motorcycle is unknown. For this reason, when the deceleration request | requirement by a driver or vehicle control is issued, road surface micro estimation is performed. For example, the road surface μ is estimated when a braking operation is performed by the driver or when a deceleration request is issued by active cruise control or the like. Here, as an example, a case will be described in which the road surface μ is estimated when the driver performs a braking operation and the braking system 1 generates a braking force.

  As shown in the model relating to wheel motion shown in FIG. 2, the braking force generated on the wheel corresponding to the W / C pressure is B, the load is W, the wheel radius is r, the rotational inertia is I, the angular acceleration is Let ω ′ be the following equation of motion.

(Equation 1) Iω ′ = μWr−Br
If the first term shown on the right side of Equation 1 is larger than the second term, the wheel is in a grip state, and if the first term is smaller than the second term, the wheel is in a slip state. Therefore, when a predetermined braking force B is generated, the magnitude relationship between the first term and the second term in Formula 1 is switched according to the road surface μ. Further, as the magnitude relationship between the first term and the second term is switched, the positive and negative signs of Iω ′ shown on the left side in Equation 1 are also switched. That is, based on the sign of the angular acceleration ω ′, the interchange of the magnitude relationship between the first term and the second term is known. Since the angular acceleration ω ′ and its positive / negative can be grasped from the change in the wheel acceleration (deceleration), the wheel acceleration is calculated by differentiating the wheel speed, and the angular acceleration ω ′ and its positive / negative are obtained from the wheel acceleration. be able to.

  Therefore, the road surface μ is estimated by gradually increasing the braking force B and confirming whether the wheel slips or the wheel acceleration increases and the wheel speed increases and returns. For example, the brake force B is increased by temporarily setting the road surface μ to be the first predetermined value μ1 that is relatively low. Here, as the first predetermined value μ1 temporarily set as the road surface μ, a low value assumed as the road surface μ on the traveling road surface, for example, a road surface μ (= 0.4) such as a snow-capped road is applied. Since the road surface μ on the actual road surface is likely to be equal to or higher than the first predetermined value μ1 assumed when the road surface μ is low on the road surface, the first predetermined value μ1 is initially set as the road surface μ. To do. Further, the road surface μ on the road surface set as the performance guaranteed road surface of the motorcycle may be used as the first predetermined value μ1.

  Then, the braking force B is held as a predetermined braking force for a predetermined time, and it is confirmed whether the wheel acceleration increases or decreases. At this time, when the road surface μ on the actual traveling road surface is smaller than the first predetermined value μ1 (μ <μ1), Iω ′ = μWr−Br <0 and the angular acceleration ω ′ <0. For this reason, wheel acceleration decreases. Conversely, when the road surface μ on the actual traveling road surface is equal to or greater than the first predetermined value μ1 (μ ≧ μ1), Iω ′ = μWr−Br ≧ 0 and the angular acceleration ω ′ ≧ 0. For this reason, wheel acceleration increases.

  If the loads applied to the wheels FW and RW of the motorcycle are Wf and Wr, respectively, the loads Wf and Wr are basically obtained as values obtained by dividing the weight of the motorcycle by 2. The front wheel load Wf is substituted into Equation 1. However, the loads Wf and Wr applied to the wheels FW and RW vary depending on the deceleration α of the motorcycle. Specifically, as shown in the vehicle model shown in FIG. 3, when the height of the center of gravity of the motorcycle is h, the wheelbase is L, the entire load is W, and the gravitational acceleration is g, the load fluctuation ΔW is expressed by a mathematical formula. It is represented by 2. Therefore, when the road surface μ is larger than the first predetermined value μ1, the load fluctuation ΔW occurs with the deceleration α, and the load Wf of the front wheel FW becomes larger, so that the angular acceleration ω ′ becomes larger and ω '> 0.

(Expression 2) ΔW = (W × α × h) / (g × L)
Thus, when the wheel acceleration decreases, it can be estimated that the road surface μ is less than the first predetermined value μ1. When the wheel acceleration increases, the road surface μ is equal to or greater than the first predetermined value μ1, so that the braking force is set to a value corresponding to the case where the road surface μ is a second predetermined value μ2 larger than the first predetermined value μ1. Increase B. Then, the braking force B is held as a predetermined braking force for a predetermined time, and it is confirmed whether the wheel acceleration increases or decreases in the same manner as described above. If the wheel acceleration decreases, it can be estimated that the road surface μ is greater than the first predetermined value μ1 and less than the second predetermined value μ2, and if the wheel acceleration increases, it is estimated that the road surface μ is greater than or equal to the second predetermined value μ2. Can do. By repeating such an operation, the road surface μ can be estimated.

  Based on such an estimation method of the road surface μ, the road surface μ estimation process is executed. FIG. 4 is a flowchart showing details of the road surface μ estimation process. The brake ECU 4 executes various processes shown in this figure every predetermined control cycle (for example, 6 ms) when the brake operation is performed and the brake is being performed.

  First, in step 100, it is determined whether or not the brake is on, that is, whether or not braking has been started, and the process proceeds to step 105 and subsequent steps only when the brake is on. Whether or not the brake is ON is determined based on the detection signal of the brake switch 6.

  Next, in step 105, an acceleration (hereinafter referred to as “holding G”) serving as a threshold value to be held at the initial start of the road surface μ estimation is determined. The holding G here is an acceleration that defines a threshold value used for estimating the road surface μ, and a wheel acceleration that is assumed to be generated by generating the braking force B when the road surface μ of the traveling road surface is a predetermined road surface μ. It is. This holding G is appropriately changed when the actual road surface μ is different from the assumed road surface μ. Further, the holding G is a value that becomes a threshold value of the wheel acceleration generated by the brake operation, and thus basically represents the wheel deceleration and is set to a negative value. As described above, the road surface μ is estimated based on the increase / decrease of the wheel acceleration when the brake force B is gradually increased and held, but is generated when the brake force B is generated on a predetermined road surface μ. Since the wheel deceleration is almost determined, whether or not the actual road surface μ is the expected road surface μ by comparing the wheel acceleration generated by generating the braking force B and the holding G is determined. Determine. The initial holding G is set to the wheel acceleration assumed to be generated by generating the braking force B at the first predetermined value μ1 that is the lowest as the assumed road surface μ.

  Specifically, the process proceeds to step 110 to increase the W / C pressure of the front wheel FW. At this time, the W / C pressure is increased linearly over time by controlling the pressure increase control valve 19. That is, the M / C pressure generated based on the brake operation is not transmitted to the W / C of the front wheel FW as it is, but the pressure increase control valve 19 is controlled to increase the W / C pressure to a desired value. I have to. Then, the routine proceeds to step 115, where it is determined whether or not the wheel acceleration is equal to or lower than the holding G, that is, whether or not the wheel deceleration corresponding to the holding G has occurred. As described above, since the initial holding G is set to the wheel acceleration assumed when the road surface μ is the first predetermined value μ1, the holding G is not limited to the actual road surface μ. The wheel acceleration decreases. Then, the process proceeds to step 110 until the affirmative determination is made in step 115, and the process of increasing the W / C pressure is repeated.

  In step 120, the W / C pressure is maintained. Then, the process proceeds to step 125, in which it is determined whether or not the wheel acceleration is larger than the holding G, that is, whether or not the wheel acceleration has increased and the wheel speed has returned. When an affirmative determination is made here, it is considered that the actual road surface μ is larger than the first predetermined value μ1 corresponding to the initial holding G. Therefore, the process proceeds to step 130 and the holding G is increased to a value larger than the initial value. Specifically, the wheel acceleration assumed when the road surface μ is a second predetermined value μ2 larger than the first predetermined value μ1 is set as a new holding G. In this case, the process returns to step 110, and the processes after step 110 are repeated.

  On the other hand, if a negative determination is made in step 125, it is considered that the actual road surface μ is equal to or smaller than the road surface μ corresponding to the holding G set at that time. For example, if the holding G is an initial value, the actual road surface μ is considered to be equal to or less than the first predetermined value μ1, and if the holding G is increased, it corresponds to the holding G after the increase. It is considered that the road surface μ is, for example, the second predetermined value μ2 or less. In this case, the process proceeds to step 135.

  In step 135, it is determined whether or not the wheel acceleration is less than the pressure reduction threshold value. The depressurization threshold here is a value set by adding an offset to the holding G generated at that time, for example, a value obtained by adding an offset of −0.5 G to the holding G. . When the holding G set at the initial time is, for example, -0.4G, the pressure reduction threshold is -0.9G. That is, in step 135, when the wheel acceleration generated when the braking force B is generated is further decreased by a predetermined pressure reduction threshold or more than the holding G, the braking force B greater than the value corresponding to the actual road surface μ is generated. It is determined that the state has been made.

  If an affirmative determination is made here, the routine proceeds to step 140 where the increase in the W / C pressure generated for estimating the road surface μ is reduced. In step 145, the road surface μ of the traveling road surface is set to be equal to or larger than the road surface μ value corresponding to the previously set holding G and smaller than the road surface μ value corresponding to the holding G set this time. For example, if the road surface μ corresponding to the previously set holding G is the first predetermined value μ1 and the road surface μ corresponding to the holding G set this time is the second predetermined value μ2, the road surface μ of the traveling road surface is the first. It is 1 predetermined value μ1 or more and less than the second predetermined value μ2.

  By the processing so far, it is possible to estimate the road surface μ, and based on the estimation result, it is possible to calculate the estimated vehicle body speed when executing ABS control or the like. Specifically, since the deceleration assumed when the braking force B is generated based on the estimated road surface μ, that is, the decreasing gradient of the estimated vehicle speed is determined, the estimated vehicle speed is determined based on the decreasing gradient. It can be calculated. This decrease gradient (deceleration) increases as the road surface μ increases, and the estimated vehicle speed decreases with a large decrease gradient.

  Specifically, the estimated vehicle speed is calculated based on the following equation with VS0 (n) as the estimated vehicle speed in the current control cycle.

(Equation 3) VS0 (n) = MID {VS0 (n-1) + [alpha] _DW * [Delta] T, VW, VS0 (n-1) + [alpha] _UP * [Delta] T}
That is, the estimated vehicle speed VS0 (n) is set to an intermediate value between “VS0 (n−1) + α _DW × ΔT” and “VW” and “VS0 (n−1) + α _UP × ΔT”. VS0 (n-1) indicates the estimated vehicle body speed in the previous control cycle. ΔT represents a time corresponding to one control cycle. α _DW indicates a maximum value assumed as a decrease gradient of the estimated vehicle body speed during one control cycle, and α _DW = holding G. α _UP indicates a maximum value assumed as an increase in the estimated vehicle body speed during one control period, and a predetermined value corresponding to the estimated road surface μ is set.

  Then, the slip of the front wheel FW is determined based on the slip ratio represented by the deviation between the estimated vehicle body speed calculated in this way and the wheel speed of the front wheel FW, and ABS control is executed based on the determination result. That is, as the ABS control, the pressure reduction control for reducing the W / C pressure, the holding control for holding the W / C pressure, and the pressure increase control for increasing the W / C pressure are executed, so that the slip of the front wheel FW is within an appropriate range. So that braking can be performed efficiently. Specifically, when slip occurs in the front wheel FW, the decompression control valve 21 is set in a communicating state as decompression control, and the execution timing of the decompression control for reducing the W / C pressure is determined. Next, the pressure-increasing control valve 19 and the pressure-reducing control valve 21 are turned off as holding control after the pressure-reducing control so that the W / C pressure is maintained and the wheel speed is restored to approach the estimated vehicle body speed. Subsequently, when the wheel acceleration increases due to the holding control, the wheel speed returns to the estimated vehicle body speed, and the wheel acceleration switches from positive to negative as the estimated vehicle body speed decreases again, pressure increase control is started at that timing. Then, the pressure-increasing control valve 19 is brought into the communication state and the pressure-reducing control valve 21 is in the shut-off state to increase the W / C pressure again to increase the braking force B. The ABS control is executed by repeating such an operation. Since the ABS control is executed based on the accurate estimated vehicle body speed calculated using the road surface μ obtained by the above method, the ABS control can be executed with high accuracy.

  However, even if the road surface μ is estimated once, a μ jump may occur in which the road surface μ of the traveling road surface changes suddenly during braking. In this case, if the estimated value of the road surface μ is not changed, the estimated vehicle speed is calculated based on the incorrect road surface μ, which is not preferable. Therefore, the processing after step 150 is executed.

  In step 150, it is determined whether or not the road surface μ estimated in step 145 is a relatively high high μ. For example, when the value of the road surface μ is equal to or greater than a predetermined value (here, 0.6), it is determined that the road surface μ is high μ. If an affirmative determination is made here, the process proceeds to step 155, and it is determined by the first method whether or not the road surface μ of the traveling road surface satisfies the requirement of μ jump from high μ to relatively low low μ. Specifically, by determining whether or not the angular acceleration ω ′ is less than the first threshold Th1, it is determined whether or not the road surface μ satisfies the requirement of μ jump from high μ to relatively low low μ. doing. This will be described with reference to the μ-s characteristic diagram showing the relationship between the road surface μ and the slip ratio s shown in FIG.

When the road surface μ of the traveling road surface is high and uniform, as shown in FIG. 5, the brake force B (= μW) is gradually increased so that μ _A W → μ _B W → μ _P W → μ _Q When increased to W, the road surface reaction force μW changes from μ _A W → μ _B W → μ _P W → μ _c W. Basically, the braking force B and the road surface reaction force μW change in the same way, but when the braking force B is increased from μ _P W to μ _Q W, it exceeds the peak μ _{P of the} road surface μ. Therefore, the road surface reaction force μW changes from μ _P W to μ _c W.

Therefore, Formula 4 is derived based on the road surface reaction force μ _c W and the braking force μ _Q W at that time, and the angular acceleration ω ′ takes a negative value as expressed in this formula. Therefore, since the wheel slips, the pressure reduction control in the ABS control is entered and the W / C pressure is reduced. At this time, when the braking force B is reduced to the point where the road surface μ is μ _A , the angular acceleration ω ′ returns as shown in Equation 5.

(Equation 4) ω ′ = (μ _C W−μ _Q Wr) / I <0
(Equation 5) ω ′ = (μ _C W−μ _A Wr) / I> 0
On the other hand, when the braking force B is increased from μ _P W to μ _Q W, if the road surface μ of the traveling road surface jumps from high μ to low μ, the road surface μ is changed from μ _C to μ _C as shown in FIG. Decrease to _D. For this reason, as shown in Formula 6, the angular acceleration ω ′ takes a negative value. Therefore, since the wheel slips, the pressure reduction control in the ABS control is entered and the W / C pressure is reduced. At this time, when the braking force B is reduced to the point where the road surface μ is μ _A , the angular acceleration ω ′ returns as shown in Equation 7.

(Equation 6) ω ′ = (μ _D W−μ _Q Wr) / I <0
(Equation 7) ω ′ = (μ _D W−μ _A Wr) / I> 0
In this way, there is a difference in the angular acceleration ω ′ after the return, as shown in Equations 5 and 7, when the road surface μ of the traveling road surface is high and uniform and when it jumps from high to low μ. Therefore, the former is greater than the latter in terms of the return amount of the acceleration ω ′ when the braking force B is reduced from the same μ _Q Wr to μ _A Wr. Therefore, it is possible to determine a change in the road surface μ of the traveling road surface based on the amount of decrease in the W / C pressure and the angular acceleration ω ′.

  Therefore, the first threshold value Th1 for determining whether the road surface μ of the traveling road surface is high and uniform or jumps to the low μ is set based on the reduced amount of the W / C pressure, and the angular acceleration is set. If ω ′ is equal to or greater than the first threshold Th1, it can be determined that no μ jump has occurred, and if it is less than the first threshold Th1, it has been determined that a μ jump has occurred. In addition, since the pressure reduction amount of the W / C pressure becomes a value corresponding to the pressure reduction time, the first threshold value Th1 is set based on, for example, the coefficient K × pressure reduction time based on the pressure reduction time of the W / C pressure at the time of pressure reduction control. can do.

  Therefore, if an affirmative determination is made in step 155, there is a possibility that a μ jump has occurred. Therefore, the process returns to step 105 to perform re-estimation, which is a re-estimation of the road surface μ. When a negative determination is made in step 155, in the first method, the road surface μ does not satisfy the requirement for the μ jump from the high μ to the low μ, so the process proceeds to step 160.

In step 160, it is determined whether or not the road surface μ of the traveling road surface satisfies the requirement of μ jump from high μ to low μ by a second method different from step 155. Specifically, the estimated vehicle speed VS0 when the differential value DVS0 of the estimated vehicle speed VS0 changes from negative to positive, that is, the minimum value VS0 _MIN of the estimated vehicle speed VS0, and the differential value DVS0 of the estimated vehicle speed VS0 from positive. estimated vehicle speed VS0 when negatively changed, i.e. determining the difference VS0 _MAX -VS0 _MIN minus the maximum value VS0 _MAX of the estimated vehicle speed VS0. Then, by determining whether or not the difference VS0 _MAX −VS0 _MIN is equal to or greater than the second threshold Th2, it is determined whether or not the road surface μ satisfies the requirement of μ jump from high μ to low μ. . This will be described with reference to a time chart showing changes in the estimated vehicle body speed and the wheel speed of the front wheel FW during the ABS control shown in FIG.

  When the road surface μ jumps from high μ to low μ, the difference between the estimated vehicle speed calculated based on the road surface μ estimated by the above method and the actual vehicle speed increases. That is, as shown in FIG. 6, the estimated vehicle speed VS0 (solid line in the figure) calculated by assuming high μ is far from the actual vehicle speed (broken line in the figure) at the low μ from the time when the μ jump occurs. To go. In the ABS control of this embodiment, the start timing of the pressure increase control is when the wheel acceleration is switched from positive to negative, and the timing at which the wheel acceleration is switched from positive to negative is when the wheel speed returns to the actual vehicle speed. It is. Since the calculation of the estimated vehicle speed is performed based on the wheel speed, if the wheel speed is higher than the estimated vehicle speed calculated by estimating the wheel speed as high μ, a new value is calculated based on the increased wheel speed. Thus, the estimated vehicle body speed VS0 is calculated, and the estimated vehicle body speed VS0 increases following the wheel speed.

Therefore, when the traveling road surface jumps from high μ to low μ, the difference VS0 _MAX −VS0 _MIN between the maximum value VS0 _MAX and the minimum value VS0 _MIN of the estimated vehicle speed VS0 is equal to or greater than the second threshold Th2, and μ jump If not, it is less than the second threshold Th2. Based on this, it can be determined whether or not the traveling road surface has μ jumped from high μ to low μ.

  Therefore, if an affirmative determination is made in step 160, there is a possibility that a μ jump has occurred, so the process returns to step 105 to reestimate the road surface μ. If a negative determination is made in step 160, the process is terminated because the road surface μ does not satisfy the requirement of μ jump from high μ to low μ even by the second method.

  On the other hand, if a negative determination is made in step 150, that is, if it is determined that the traveling road surface is low μ, the process proceeds to step 165. Then, in step 165, it is determined whether or not the road surface μ of the traveling road surface satisfies the requirement of μ jump from low μ to high μ. Specifically, it is determined whether or not the road surface μ satisfies the requirement of μ jump from low μ to high μ by determining whether or not the return amount of the angular acceleration ω ′ is equal to or greater than the third threshold Th3. doing. This will be described with reference to the μ-s characteristic diagram showing the relationship between the road surface μ and the slip ratio s shown in FIG.

When it is estimated that the road surface μ is μ _B by the estimation of the road surface μ, the pressure reduction control is started when the braking force B exceeds a value (= μ _B W) corresponding to μ _B estimated as the road surface μ. At this time, when the brake force B becomes μ _D W larger than the brake force B corresponding to the low μ peak μ _B (= μ _B W), the pressure reduction control is started, and thereby μ smaller than μ _B W and it was lowered to _a W. In that case, when the road surface μ of the traveling road surface is low and uniform, the braking force B (= μ _B W) corresponding to the low μ peak μ _B is exceeded, so the road surface reaction force μW is μ _D It has changed from W to μ _C W. On the other hand, when the road surface μ of the traveling road surface jumps from low μ to high μ, the road surface reaction force μW becomes μ _D W. For this reason, when the road surface μ of the traveling road surface is low and uniform, the angular acceleration ω ′ is expressed as Equation 8, and when the μ jump from low μ to high μ is performed, the angular acceleration is expressed as follows. ω ′ is expressed as Equation 9.

(Equation 8) ω ′ = (μ _C Wr−μ _A Wr) / I
(Equation 9) ω ′ = (μ _D Wr−μ _A Wr) / I
In this way, there is a difference in the angular acceleration ω ′ after the return as shown in Expressions 8 and 9 between the case where the road surface μ of the traveling road surface is low and uniform and the case where μ jumps from low μ to high μ. In other words, the latter is greater than the former with respect to the return amount of the acceleration ω ′ when the braking force B is reduced from the same μ _D Wr to μ _A Wr. Therefore, it is possible to determine a change in the road surface μ of the traveling road surface based on the amount of decrease in the W / C pressure and the return amount of the angular acceleration ω ′.

  Therefore, the third threshold Th3 for determining whether the road surface μ of the traveling road surface is low and uniform or jumped to high μ is set based on the amount of decrease in the W / C pressure, and the angular acceleration is set. If ω ′ is less than the third threshold Th3, no μ jump has occurred, and if it is greater than or equal to the third threshold Th3, it can be determined that a μ jump has occurred. Since the amount of pressure reduction of the W / C pressure becomes a value corresponding to the pressure reduction time, the third threshold Th3 is set based on, for example, the coefficient K × pressure reduction time, based on the pressure reduction time of the W / C pressure at the time of pressure reduction control. can do.

  Therefore, if an affirmative determination is made in step 165, there is a possibility that a μ jump has occurred. Therefore, the process returns to step 105 in order to reestimate the road surface μ. If a negative determination is made in step 165, the process is terminated because the road surface μ does not satisfy the requirement of μ jump from low μ to high μ.

  FIG. 8 is a time chart when the road surface μ is estimated as described above. As shown in the figure, when the brake is turned on and braking is performed, the estimated vehicle body speed VS0 also decreases as the wheel speed VW decreases. The estimated vehicle speed VS0 at this time is calculated based on Equation 3 described above. When the initial holding G is determined and the W / C pressure is increased accordingly, wheel slip occurs and the wheel acceleration VW decreases. At this time, when the holding G set at the initial time is, for example, −0.4 G, even when the wheel acceleration VW becomes −0.4 G or less at the time T1, the road surface μ corresponding to the holding G is equal to the road surface μ corresponding to the holding G. If it is above, wheel acceleration VW will return.

In this case, the holding G is increased to, for example, -0.5G. Along with this, the W / C pressure is increased according to the set holding G again, and the wheel acceleration VW decreases. If the road surface μ of the traveling road surface is less than the road surface μ corresponding to the holding G set at that time, the wheel acceleration DVW further falls, and if the road surface μ falls below the decompression threshold at the time T2, the road surface μ is changed to the previous time. The road surface μ value corresponding to the set holding G is set to be equal to or larger than the road surface μ value corresponding to the currently set holding G (0.4 ≦ μ <0.5). As a result, the μ estimation period ends, and thereafter, the road surface μ estimated as described above at the time of setting α _DW used for the calculation of the estimated vehicle speed VS0, specifically, the estimated road surface μ Time G is used, and the estimated vehicle speed VS0 corresponding to the road surface μ is calculated.

  As described above, the road surface μ is determined based on the return state of the wheel acceleration generated when the braking force B corresponding to the holding G is generated at the start of braking, that is, whether or not the wheel acceleration increases. Estimation can be performed. Specifically, when the wheel acceleration generated when the braking force B corresponding to the holding G is generated falls below the offset of the pressure-reducing threshold with respect to the holding G, the brake more than the value corresponding to the actual road surface μ. It is determined that the force B is generated. Thereby, it can be estimated that the road surface μ of the traveling road surface is equal to or larger than the road surface μ corresponding to the previously set holding G and less than the road surface μ corresponding to the currently set holding G, and the road surface μ can be estimated.

  Therefore, based on the estimation result of the road surface μ, it is possible to calculate the estimated vehicle body speed when executing ABS control or the like. Thereby, in a motorcycle, even when the wheel speed sensor 5 is provided only on one wheel, it is possible to provide a road surface μ estimation device that can accurately estimate the road surface μ. Then, it is possible to perform the ABS control with high accuracy based on the road surface μ estimated in this way.

  Furthermore, since it is possible that a μ jump that changes the road surface μ occurs during braking, it is determined whether or not the μ jump requirement is satisfied during ABS control after the road surface μ is estimated. When the condition is satisfied, the road surface μ is estimated again. Thus, when a μ jump occurs during braking, it is possible to prevent the estimated vehicle body speed from being calculated based on an erroneous road surface μ estimated in the past. Based on the correct road surface μ estimated after the μ jump, the estimated vehicle body speed can be calculated with high accuracy, and ABS control can be performed with high accuracy.

(Other embodiments)
The present invention is not limited to the embodiment described above, and can be appropriately changed within the scope described in the claims.

  For example, in the above embodiment, in consideration of the occurrence of a μ jump in which the road surface μ changes during braking, the road surface μ is estimated again after the road surface μ is estimated, but this need not necessarily be performed. . Further, when the road surface μ is determined to be high μ, the requirement that the μ jump has occurred from high μ to low μ is determined using the first and second methods, but only one of them may be used. Absent. Furthermore, the various methods used for determining the requirement for the occurrence of μ jump are merely examples, and other methods may be used.

  In the above-described embodiment, the case where the road surface μ is estimated and the ABS control is executed when the braking force is generated by the deceleration request based on the driver's brake operation has been described. However, this is merely an example, and the road surface μ estimation and the ABS control based on the road surface μ according to the present invention are executed at the time of another deceleration request, for example, a deceleration request by pre-crash control or adaptive cruise control. Also good.

  In addition, the part which performs various processes in brake ECU4, for example, the step shown in each figure, etc. respond | corresponds to the various means in this invention. That is, the part for detecting the wheel speed based on the detection signal of the wheel speed sensor 5 corresponds to the wheel speed detecting means, and the part for controlling the brake fluid pressure control actuator 2 to apply the braking force corresponds to the front wheel braking force applying means. . Moreover, the part which performs the process of steps 105-145 in FIG. 4 is equivalent to a friction coefficient estimation means. Further, the part for calculating the estimated vehicle speed based on the estimated road surface μ is the vehicle body speed calculating means, the part for executing the ABS control is the ABS control means, the part for executing the processing of steps 150 to 165 is the friction coefficient change determining means, The part where the processes in steps 105 to 145 are performed again based on the determination result of the friction coefficient change determination means corresponds to the re-estimation means.

  DESCRIPTION OF SYMBOLS 1 ... Brake system, 2 ... Brake hydraulic pressure control actuator, 4 ... Brake ECU, 5 ... Wheel speed sensor, 6 ... Brake switch, 11 ... Brake lever, 12 ... Brake pedal, 16, 17 ... W / C, 19 ... Pressure increase control valve, 20 ... pressure regulating reservoir, 21 ... pressure reduction control valve

Claims (5)

Applied to a motorcycle having a front wheel located in the vehicle traveling direction and a rear wheel located in the vehicle reverse direction, a wheel speed detecting means for detecting a wheel speed provided only in the front wheel, and a request for deceleration of the vehicle A road surface friction coefficient estimating device in a motorcycle having a front wheel braking force applying means for applying a braking force to the front wheel in response,
At the start of braking based on the deceleration request, a predetermined braking force is retained and applied for a predetermined period, and the motorcycle is based on a return state indicating whether or not the front wheel acceleration increases during the predetermined period. A road surface friction coefficient estimating device comprising: friction coefficient estimating means for estimating a road surface friction coefficient of a running road surface.   The friction coefficient estimating means increases the predetermined braking force applied by the front wheel braking force applying means when the wheel acceleration of the front wheel increases and returns during the predetermined period, and the increased predetermined braking force is increased again. 2. The road surface friction according to claim 1, wherein a predetermined period of time retention is given and a road surface friction coefficient of a traveling road surface of the motorcycle is estimated based on a return state of wheel acceleration of the front wheels during the predetermined period. Coefficient estimation device.   The friction coefficient estimating means, when the wheel acceleration of the front wheel is further reduced by a predetermined depressurization threshold or more than the wheel acceleration assumed by generating the predetermined braking force during the predetermined period, The road surface friction coefficient estimating device according to claim 1 or 2, wherein the road surface coefficient corresponding to the constant braking force is estimated to be a road surface friction coefficient of the traveling road surface. The road surface friction coefficient estimating device according to any one of claims 1 to 3,
Vehicle body speed calculating means for calculating an estimated vehicle body speed based on the wheel speed detected by the wheel speed detecting means and the road surface friction coefficient of the traveling road surface estimated by the road surface friction coefficient estimating device;
Based on the slip ratio represented by the deviation between the estimated vehicle body speed and the wheel speed of the front wheel, the front wheel slip is determined, and if it is determined that the front wheel has slipped, the braking force applying means Anti-lock brake control means for controlling slip of the front wheel by performing pressure increase control for increasing the pressure after performing pressure reduction control for decreasing the pressure applied to the wheel cylinder provided in the front wheel, An anti-lock brake control device comprising:   Friction coefficient change determination means for detecting a μ jump in which the road surface friction coefficient of the traveling road surface changes during the anti-lock brake control, and when the μ jump is detected by the friction coefficient change determination means, the friction coefficient 5. The antilock brake control device according to claim 4, further comprising re-estimation means for re-estimating the friction coefficient of the traveling road surface by the estimation means.

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