Vehicle driving control device

Abstract

To provide a travel control device which can determine an abnormality when the abnormality that causes excessive increase in a wheel speed occurs, and avoid unnecessary wheel speed determination.SOLUTION: A travel control device for vehicle includes: multiple wheel speed detection devices which detect a wheel speed Vwi of each of the multiple wheels; and a control unit which performs travel control (anti-skid control) of the vehicle on the basis of the wheel speed detected by the wheel speed detection device. The control unit is configured to perform abnormality determination (S30) for determining whether or not the wheel speed of a first wheel is abnormal, on the basis of the relationship between the wheel speed of the first wheel at which the wheel speed is the highest and the wheel speed Vwmh of a second wheel at which the wheel speed is the second highest. In addition, the control unit does not perform abnormality determination when the increase rate of the wheel speed of the first wheel is less than an increase rate reference value (S20) in a case where the vehicle is braking.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a cruise control device for a vehicle such as an automobile. [Background technology]

[0002] In a vehicle that employs anti-skid control as a driving control, the estimated vehicle speed for calculating the braking slip ratio is set based on the highest wheel speed among a plurality of wheel speeds. If the highest wheel speed becomes excessively high due to load shifts accompanying deceleration and turning of the vehicle, the estimated vehicle speed will also become excessively high. Therefore, the estimated vehicle speed is corrected so that it does not become excessively high.

[0003] For example, Patent Document 1 listed below describes an anti-skid control method in which, when the difference between the highest wheel speed among the left and right front wheels and the rear wheels and the intermediate wheel speed is equal to or greater than a reference value, the estimated vehicle speed is changed to a value obtained by subtracting a predetermined wheel speed from the intermediate wheel speed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 60-050061 Summary of the Invention

[0005] [Problem to be solved by the invention] The wheel speed is detected by a wheel speed sensor provided on each wheel. The wheel speed sensor includes a detection unit that generates a pulse signal proportional to the rotational speed of the wheel, and an electronic control unit that calculates the wheel speed based on the pulse signal and outputs a signal indicating the wheel speed. If an abnormality occurs in the electronic circuit of the electronic control unit, the wheel speed indicated by the signal output by the wheel speed sensor may become excessively high.

[0006] When the above-mentioned situation occurs, the detected wheel speed changes more significantly than the increase caused by the load shift associated with deceleration and turning of the vehicle. The anti-skid control method described in Patent Document 1 does not take into account the rate of increase in wheel speed, and therefore is unable to determine whether the wheel speed is abnormal due to an abnormality in the wheel speed sensor, and is also unable to avoid unnecessary determinations of whether the wheel speed is abnormal.

[0007] To provide a driving control device that controls vehicle driving based on wheel speed, and that can determine an abnormality when an abnormality occurs in which the wheel speed becomes excessively high, and can avoid unnecessary wheel speed determination. [Means for solving the problems and effects of the invention]

[0008] According to the present invention, there is provided a vehicle driving control device (10) including a plurality of wheel speed detection devices (wheel speed sensors 44FL to 44RR) that detect the wheel speed (Vwi) of each of a plurality of wheels (14FL to 14RR), and a control unit (driving control ECU 10) that controls the driving of the vehicle based on the wheel speeds detected by the wheel speed detection devices.

[0009] The control unit (travel control ECU 10) is configured to perform an abnormality determination (S30) to determine whether the wheel speed of the first wheel is abnormal based on a relationship between a wheel speed (Vwmax) of a first wheel having a maximum wheel speed and a wheel speed (Vwmh) of a second wheel having a second maximum wheel speed;

[0010] Furthermore, when the vehicle (16) is braking, the control unit is configured not to make an abnormality determination if the rate of increase in the wheel speed of the first wheel is less than the reference rate of increase (S20).

[0011] If an abnormality such as an abnormality in the electronic circuit of the wheel speed detection device occurs, the wheel speed detected by the wheel speed detection device may become excessively high, and in that case the relationship between the wheel speed of the first wheel and the wheel speed of the second wheel will be different from that in normal times. Therefore, it is possible to determine whether the wheel speed of the first wheel is abnormal based on the relationship between the wheel speed of the first wheel and the wheel speed of the second wheel.

[0012] According to the above configuration, whether the wheel speed of the first wheel is abnormal is determined based on the relationship between the wheel speed of the first wheel, which has the highest wheel speed, and the wheel speed of the second wheel, which has the second highest wheel speed. Therefore, if an abnormality occurs in which the wheel speed of the first wheel becomes excessively high due to an abnormality such as an abnormality in the electronic circuit of the wheel speed detection device, the abnormality can be determined.

[0013] Furthermore, with the above configuration, when the vehicle is braking, if the rate of increase in the wheel speed of the first wheel is less than the increase rate reference value, no abnormality determination is made. Therefore, in a situation where the rate of increase in the wheel speed of the first wheel is less than the increase rate reference value, unnecessary abnormality determination is prevented, and it is possible to prevent an erroneous determination that the wheel speed of the first wheel is abnormal.

[0014] [Mode of the Invention] In another aspect of the present invention, the control unit (travel control ECU 10) is configured to determine that the wheel speed of the first wheel is abnormal when the ratio of the wheel speed (Vwmax) of the first wheel to the wheel speed (Vwmh) of the second wheel exceeds an abnormality determination reference value (1 / Ka).

[0015] When an abnormality such as an abnormality in the electronic circuit of the wheel speed detection device occurs and the wheel speed of the first wheel becomes excessively high, the ratio of the wheel speed of the first wheel to the wheel speed of the second wheel becomes higher than normal, and therefore, it is possible to determine whether the wheel speed of the first wheel is abnormal based on the ratio of the wheel speed of the first wheel to the wheel speed of the second wheel.

[0016] According to the above aspect, when the ratio of the wheel speed of the first wheel to the wheel speed of the second wheel exceeds the abnormality determination reference value, it is determined that the wheel speed of the first wheel is abnormal. Therefore, when an abnormality occurs in which the wheel speed of the first wheel becomes excessively high due to an abnormality such as an abnormality in the electronic circuit of the wheel speed detection device, the abnormality can be determined.

[0017] In one aspect of the present invention, the control unit (cruise control ECU 10) is configured to calculate an estimated vehicle body speed (Vvba) of the vehicle based on the wheel speed of the first wheel (S260) when the wheel speed (Vwmax) of the first wheel is not determined to be abnormal and the vehicle (16) is braking, and to perform anti-skid control as cruise control using the estimated vehicle body speed.

[0018] According to the above aspect, when the wheel speed of the first wheel is not determined to be abnormal and the vehicle is being braked, an estimated vehicle speed of the vehicle is calculated based on the wheel speed of the first wheel, and anti-skid control is performed as a travel control using the estimated vehicle speed. Therefore, when excessive braking slip occurs in a wheel other than the first wheel, the braking slip can be reduced by the anti-skid control.

[0019] Furthermore, in another aspect of the present invention, the control unit (cruise control ECU 10) is configured to limit (S260) the increase in the estimated vehicle speed (Vvba) at a limited increase rate (Kbu).

[0020] According to the above aspect, the increase in the estimated vehicle speed is limited by the limited increase rate, so that even if an abnormality such as an abnormality occurs in the electronic circuit of the wheel speed detection device and the wheel speed of the first wheel increases suddenly, the estimated vehicle speed can be prevented from increasing suddenly.

[0021] Furthermore, in another aspect of the present invention, the control unit (travel control ECU 10) is configured to, when it is determined that the wheel speed (Vwmax) of the first wheel is abnormal and the vehicle (16) is braking, calculate an estimated vehicle body speed (Vvba) of the vehicle based on the wheel speed (Vwmh) of the second wheel, and limit the decrease in the estimated vehicle body speed at a limited decrease rate (Kbd) (S260).

[0022] According to the above aspect, when it is determined that the wheel speed of the first wheel is abnormal, the estimated vehicle speed of the vehicle is calculated based on the wheel speed of the second wheel, and the decrease in the estimated vehicle speed is limited by the limited decrease rate. Therefore, even if an abnormality such as an abnormality occurs in the electronic circuit of the wheel speed detection device and the wheel speed of the first wheel suddenly increases, the estimated vehicle speed can be prevented from becoming excessively high. Furthermore, when the estimated vehicle speed changes from being calculated based on the wheel speed of the first wheel to being calculated based on the wheel speed of the second wheel, a sudden decrease in the estimated vehicle speed can be prevented, thereby preventing inappropriate anti-skid control.

[0023] Other objects, other features and attendant advantages of the present invention will be readily apparent from the following description of the preferred embodiments of the present invention which will be given with reference to the accompanying drawings. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a schematic diagram showing an embodiment of a vehicle travel control device according to the present invention; [Figure 2] 4 is a flowchart showing a control routine for abnormality determination in the embodiment. [Figure 3] 4 is a flowchart showing a routine for calculating and controlling an estimated vehicle speed in the embodiment. [Figure 4] 10 is a diagram illustrating an example in which the rate of increase in the wheel speed of a first wheel becomes equal to or greater than a reference rate of increase in a situation in which the wheel speed gradually decreases due to braking. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0025] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0026] A vehicle cruise control device 10 according to the embodiment shown in FIG. 1 is applied to a vehicle 16 having a cruise control electronic control device 12 and wheels 14FL, 14FR, 14RL, and 14RR. In this embodiment, the left and right front wheels 14FL and 14FR are steered and driven wheels, and the left and right rear wheels 14RL and 14RR are non-steered and driven wheels. The front wheels 14FL and 14FR are steered via a rack bar 22 and tie rods 24L and 24R by an electric power steering device 20 driven in response to operation of a steering wheel 18 by a driver. In the following description, the electronic control device will be referred to as an ECU (abbreviation for Electronic Control Unit).

[0027] The vehicle 16 has a braking device 30 that applies braking force to the wheels 14FL to 14RR. The braking device 30 includes a hydraulic circuit 32, wheel cylinders 34FR, 34FL, 34RR, and 34RL provided on the wheels 14FL to 14RR, and a master cylinder 38 that pumps brake oil in response to the driver's depression of a brake pedal 36. Although not shown in detail in Fig. 1, the hydraulic circuit 32 includes a reservoir, an oil pump, various valve devices, and the like, and functions as a brake actuator.

[0028] The braking device 30 applies braking force to the wheels 14FL-14RR in proportion to the pressure in each of the wheel cylinders 34FL-34RR. The pressure in the wheel cylinders 34FL-34RR is normally controlled in accordance with the pressure in a master cylinder 38 (master cylinder pressure Pm), which is activated in response to the driver's depression of the brake pedal 36. That is, the master cylinder pressure Pm is detected by a pressure sensor 40, and the braking ECU 42 controls the pressure in each of the wheel cylinders 34FL-34RR based on the master cylinder pressure Pm. Furthermore, the braking ECU 42 controls the oil pump and various valve devices as needed, so that the pressure in each of the wheel cylinders 34FL-34RR is controlled regardless of the amount of depression of the brake pedal 36 by the driver.

[0029] The wheels 14FL, 14FR, 14RL, and 14RR are provided with wheel speed sensors 44FL, 44FR, 44RL, and 44RR, which function as wheel speed detection devices that detect the wheel speeds Vwi (i=fl, fr, rl, and rr) of the corresponding wheels. Signals indicating the wheel speeds Vwi detected by the wheel speed sensors 44FL, 44FR, 44RL, and 44RR are input to the cruise control ECU 12.

[0030] Although not shown in FIG. 1, the vehicle 16 has an engine as a drive device that applies drive force to the left and right front wheels 14FL, 14FR, which are drive wheels. The amount of depression of the accelerator pedal 46 by the driver is detected as accelerator pedal position Acc by an accelerator position sensor 48. The engine output is normally controlled by a drive ECU 50 based on the accelerator pedal position Acc, and is controlled independently of the accelerator pedal position Acc as necessary. The drive device may be any device that can apply drive force to the drive wheels, such as an electric motor or a hybrid system. The drive wheels may be the left and right rear wheels 14RL and 14RR, or may be four wheels 14FL to 14RR.

[0031] Each ECU has a microcomputer as its main component, which includes a CPU, ROM, RAM, read / write non-volatile memory (N / M), and an interface (I / F). The CPU performs various functions by executing instructions (programs, routines) stored in the ROM. Furthermore, these ECUs are interconnected via a Controller Area Network (CAN) to enable data exchange (communication). Therefore, the detected values ​​of sensors (including switches) connected to a specific ECU can be transmitted to other ECUs.

[0032] The cruise control ECU 12 and the braking ECU 42 cooperate to function as control units that perform anti-skid control (hereinafter referred to as "ABS control") as a vehicle cruise control based on wheel speed. When the vehicle is braking, the cruise control ECU 12 calculates an estimated vehicle body speed Vvba of the vehicle 16 based on the maximum wheel speed Vwmax among the wheel speeds Vwfl, Vwfr, Vwrl, and Vwrr. Furthermore, the cruise control ECU 12 limits increases or decreases in the estimated vehicle body speed Vvba so that it does not increase or decrease excessively. The cruise control ECU 12 determines that the vehicle is braking when the master cylinder pressure Pm is equal to or higher than a reference value or when a brake lamp switch (not shown) is on.

[0033] The braking ECU 42 calculates the braking slip ratio Sbi of the wheels 14FL to 14RR based on the wheel speed Vwi and the estimated vehicle speed Vvba according to the following equation (1): Furthermore, when the braking slip ratio Sbi of any wheel exceeds a control start reference value Sbc (a positive constant), the braking ECU 42 controls the braking force in a manner known in the art so that the braking slip ratio of that wheel remains within a predetermined range until a preset control end condition is met. Sbi = (Vvba - Vwi) / Vvba ... (1)

[0034] In particular, the cruise control ECU 12 performs an abnormality determination to determine whether the wheel speed of the first wheel is abnormal based on the relationship between the wheel speed Vwmax of the first wheel, which has the maximum wheel speed, and the wheel speed Vwmh of the second wheel, which has the second highest wheel speed. When the vehicle is braking, the cruise control ECU 12 permits the abnormality determination of the wheel speed of the first wheel when it determines that the increase rate of the wheel speed Vwmax of the first wheel is equal to or greater than a predetermined increase rate reference value Vwdc (positive constant). Therefore, when the increase rate of the wheel speed Vwmax of the first wheel is less than the increase rate reference value Vwdc, the abnormality determination of the wheel speed of the first wheel is not permitted. The increase rate reference value Vwdc is set to a positive constant that the increase rate of the wheel speed cannot be when the vehicle is traveling.

[0035] In this embodiment, the cruise control ECU 12 determines that the wheel speed of the first wheel is abnormal when it determines that the ratio of the wheel speed Vwmax of the first wheel to the wheel speed Vwmh of the second wheel exceeds an abnormality determination reference value (a positive constant) for a predetermined time or more. When the cruise control ECU 12 determines that the wheel speed of the first wheel is abnormal, it activates the warning device 52 to issue a warning to the vehicle occupants that the wheel speed of the first wheel is abnormal.

[0036] When the cruise control ECU 12 determines that the wheel speed of the first wheel is abnormal, it calculates the estimated vehicle body speed Vvba of the vehicle 16 based on the wheel speed Vwmh of the second wheel. Furthermore, the cruise control ECU 12 limits the increase or decrease in the estimated vehicle body speed Vvba so that the estimated vehicle body speed Vvba does not increase or decrease excessively.

[0037] Furthermore, the cruise control ECU 12 and the drive ECU 50 cooperate with each other to function as a control unit that performs traction control (hereinafter referred to as "TRC control") as another type of vehicle cruise control. When the vehicle is being driven, the cruise control ECU 12 calculates an estimated vehicle body speed Vvda of the vehicle 16 based on, for example, the smaller wheel speed Vwd of the left and right rear wheels 14RL and 14RR, which are driven wheels. Furthermore, the cruise control ECU 12 limits the increase or decrease in the estimated vehicle body speed Vvda so that it does not increase or decrease excessively.

[0038] The drive ECU 50 calculates the drive slip ratio Sdi of the drive wheels according to the following equation (2) based on the wheel speed Vwi and the estimated vehicle speed Vvda. Furthermore, when the drive slip ratio Sdi of any drive wheel exceeds a control start reference value Sdc (a positive constant), the drive ECU 50 controls the braking force in a manner known in the art so that the drive slip ratio of that wheel remains within a predetermined range until a preset control termination condition is met. Sdi=(Vwi-Vvda) / Vvda …(2)

[0039] When the wheel speed of the first wheel is determined to be abnormal while the vehicle is in motion, the drive slip ratio of the first wheel becomes an abnormal value, and therefore braking force is not applied to the first wheel through TRC control.

[0040] In this embodiment, the ROM of the cruise control ECU 12 stores a control program corresponding to the flowchart shown in Fig. 2. The CPU of the cruise control ECU 12 controls abnormality determination for the wheel speed of the first wheel in accordance with this program. Furthermore, the ROM of the cruise control ECU 12 stores a control program corresponding to the flowchart shown in Fig. 3. The CPU of the cruise control ECU 12 calculates and controls estimated vehicle speeds Vvba and Vvda in accordance with this program.

[0041] <Control of abnormality detection> Next, the control routine for abnormality determination in this embodiment will be described with reference to the flowchart shown in Fig. 2. The control according to the flowchart shown in Fig. 2 is repeatedly executed every predetermined time ΔT when an ignition switch (not shown) is on. In particular, steps S10 to S80 are executed for each wheel in the order of, for example, the left front wheel (i=fl), the right front wheel (i=fr), the left rear wheel (i=rl), and the right rear wheel (i=rr), and steps S130 to S170 are executed for the first wheel, i.e., the wheel with the highest wheel speed.

[0042] 2 will be simply referred to as “determination control.” Prior to the start of the determination control, a flag Fai indicating whether the wheel speed of the first wheel is abnormal is reset to 0 (not abnormal).

[0043] First, in step S10, the CPU determines whether or not the flag Fai is 1, i.e., whether or not the wheel speed of the first wheel is abnormal. If the CPU makes a positive determination, the CPU proceeds to step S120, and if the CPU makes a negative determination, the CPU proceeds to step S20.

[0044] In step S20, the CPU determines whether the conditions for permitting abnormality determination of whether the wheel speed of the first wheel is abnormal are satisfied. If the CPU makes a negative determination, it proceeds to step S40, and if the CPU makes a positive determination, it proceeds to step S30.

[0045] When the vehicle 16 is not braking, it is determined that the conditions for permitting abnormality determination are met when the vehicle is in a straight-ahead traveling state. In this case, it may be determined that the vehicle is in a traveling state when the smallest wheel speed Vwmin among the wheel speeds Vwfl, Vwfr, Vwrl, and Vwrr or the estimated vehicle body speed Vvba is equal to or greater than a reference value Vwrc (positive constant) for traveling determination. It may also be determined that the vehicle is in a straight-ahead traveling state when the ratio between the wheel speeds of the left and right wheels is within a reference range.

[0046] Furthermore, when the vehicle 16 is braking, it is determined that the conditions for permitting abnormality determination are met when the rate of increase in the wheel speed Vwmax of the first wheel is equal to or greater than the increase rate reference value Vwdc and the vehicle is traveling straight ahead. In this case, it may be determined that the rate of increase in the wheel speed Vwmax of the first wheel is equal to or greater than the increase rate reference value ΔVwc (a positive constant) when the increase amount ΔVwmax from the previous time in the wheel speed Vwmax of the first wheel is equal to or greater than the increase rate reference value ΔVwc.

[0047] In step S30, the CPU determines whether Ka·Vwi is greater than the wheel speed Vwmh of the second wheel, i.e., whether the ratio of the wheel speed Vwi of the wheel in question to the wheel speed Vwmh of the second wheel exceeds the abnormality determination reference value 1 / Ka, with Ka being a positive constant coefficient of approximately 0.8 and smaller than 1. If the determination is negative, the CPU resets the count value Tai of the abnormality determination timer to 0 in step S40, and if the determination is positive, the CPU counts up the count value Tai of the abnormality determination timer by ΔT in step S50.

[0048] In step S60, the CPU determines whether the count value Tai of the abnormality determination timer is equal to or greater than a reference value Tac (a positive constant of about 1 second). If the CPU determines that the abnormality is not detected, it temporarily terminates the determination control. If the CPU determines that the abnormality is detected, it proceeds to step S70.

[0049] In step S70, the CPU determines that the wheel speed of the first wheel is abnormal, sets flag Fai to 1, and stores information that flag Fai is 1 in non-volatile memory. Furthermore, the CPU resets count value Tai of the timer for abnormality determination to 0.

[0050] In step S80, the CPU identifies which of the wheels 14FL, 14FR, 14RL, and 14RR is the first wheel based on i. Furthermore, the CPU activates the alarm device 52 to issue an alarm that the wheel speed of the first wheel is abnormal.

[0051] In step S120, the CPU determines whether or not the conditions for permitting a cancellation determination to cancel the determination that the wheel speed of the first wheel is abnormal are satisfied. If the CPU makes a negative determination, the CPU proceeds to step S140, and if the CPU makes a positive determination, the CPU proceeds to step S130. As in step S20, when the CPU determines that the conditions for permitting an abnormality determination to determine whether the wheel speed of the first wheel is abnormal are satisfied, the CPU determines that the conditions for permitting a cancellation determination to cancel the abnormality determination are satisfied.

[0052] In step S130, the CPU determines whether Kr·Vwi is equal to or less than the wheel speed Vwmh of the second wheel, i.e., whether the ratio of the wheel speed Vwi of the wheel in question to the wheel speed Vwmh of the second wheel is equal to or less than the release determination reference value 1 / Kr, with Kr set to a positive constant coefficient of approximately 0.955, which is smaller than 1 and larger than Ka. If the determination is negative, the CPU resets the count value Tri of the release determination timer to 0 in step S140, and if the determination is positive, the CPU counts up the count value Tri of the abnormality determination timer by ΔT in step S150.

[0053] In step S160, the CPU determines whether the count value Tri of the timer for determining release is equal to or greater than a reference value Trc (a positive constant of about 1 second). If the CPU determines that the count value Tri is not equal to or greater than a reference value Trc (a positive constant of about 1 second), the CPU temporarily ends the determination control. If the CPU determines that the count value Tri is not equal to or greater than a reference value Trc, the CPU proceeds to step S170.

[0054] In step S170, the CPU determines that the wheel speed of the first wheel is normal, resets the flag Fai to 0, and deletes the information indicating that the flag Fai is 1 from the non-volatile memory. Furthermore, the CPU resets the count value Tri of the timer for determining release to 0.

[0055] In step S180, the CPU deactivates the alarm device 52, thereby ending the issuance of the alarm that the wheel speed of the first wheel is abnormal.

[0056] <Calculation and control of estimated vehicle speed> Next, a calculation control routine for the estimated vehicle speeds Vvba and Vvda in this embodiment will be described with reference to the flowchart shown in Figure 3. The control according to the flowchart shown in Figure 3 is repeatedly executed at predetermined time intervals when an ignition switch (not shown) is on. In the following description, the control according to the flowchart shown in Figure 3 will be simply referred to as "calculation control."

[0057] First, in step S210, the CPU determines whether the vehicle 16 is traveling. If the CPU makes a positive determination, it advances the calculation control to step S230. If the CPU makes a negative determination, it sets the estimated vehicle body speed Vvba to 0 and sets the estimated vehicle body speed Vvda to a positive constant Vvc close to 0 in step S220. The estimated vehicle body speed Vvda is set to the positive constant Vvc to prevent the denominator of the above equation (2) from becoming 0.

[0058] In step S230, the CPU determines whether or not the vehicle 16 is being braked. If the CPU makes a negative determination, it advances the calculation control to step S280, and if the CPU makes a negative determination, it advances the calculation control to step S240.

[0059] In step S240, the CPU determines whether the flag Fai is 1, i.e., whether the wheel speed of the first wheel is abnormal, as in step S10. If the CPU makes a positive determination, it proceeds to step S260, and if the CPU makes a negative determination, it proceeds to step S250.

[0060] In step S250, the CPU sets the wheel speed Vwb, which is the basis for calculating the estimated vehicle speed Vvba, to the wheel speed Vwmax of the first wheel, and in step S260, the CPU sets the wheel speed Vwb to the wheel speed Vwmh of the second wheel.

[0061] In step S270, the CPU calculates the estimated vehicle body speed Vvba based on the wheel speed Vwb in accordance with the following equation (3): In the following equation (3), Vvbaf is the previous value of the estimated vehicle body speed Vvba, Kbd is a decrease limiting coefficient (a positive constant), and Kbu is an increase limiting coefficient (a positive constant smaller than Kbd). In the following equation (3) and equation (4) described later, MED means to select the median value of the three values ​​in parentheses. Vvba=MED(Vvbaf+Kbd·ΔT,Vwb,Vvbaf+Kbu·ΔT) …(3)

[0062] In step S280, the CPU calculates an estimated vehicle speed Vvda based on the smaller of the wheel speeds Vwrl and Vwrr of the left and right rear wheels 14RL and 14RR, using the following equation (4): Vvdaf is the previous value of the estimated vehicle speed Vvda, Kdd is a decrease limit coefficient (a positive constant), and Kdu is an increase limit coefficient (a positive constant smaller than Kdd). Vvda=MED(Vvdaf+Kdd·ΔT,Vwd,Vvdaf+Kdu·ΔT) …(4)

[0063] <Operation of the embodiment> Next, abnormality determination and calculation of estimated vehicle speed in the above embodiment will be described for the case where the vehicle is braking.

[0064] (X) All wheel speeds are normal When all the wheel speeds Vwfl, Vwfr, Vwrl, and Vwrr are normal, the flag Fai is 0, and the increase rate of the wheel speed Vwmax of the first wheel does not exceed the increase rate reference value Vwdc. Therefore, negative determinations are made in steps S10 and S20. In step S40, the count value Tai of the timer for abnormality determination is reset to 0, and a negative determination is made in step S60. Therefore, steps S30 and S70 are not executed, and the flag Fai remains 0.

[0065] Although affirmative determinations are made in steps S210 and S230, a negative determination is made in step S240. Therefore, in step S250, the wheel speed Vwb, which is the basis for calculating the estimated vehicle body speed Vvba, is set to the wheel speed Vwmax of the first wheel, and therefore the estimated vehicle body speed Vvba is calculated based on the wheel speed Vwmax of the first wheel in step S260.

[0066] (Y) When the rate of increase in the wheel speed of the first wheel is equal to or greater than the reference rate of increase. If an abnormality occurs in any of the wheel speed sensors 44FL, 44FR, 44RL, and 44RR and the rate of increase in the wheel speed Vwmax of the first wheel becomes equal to or greater than the increase rate reference value Vwdc, a negative determination is made in step S10, but positive determinations are made in steps S20 and S30. These determinations are repeated and step S50 is repeatedly executed, so a positive determination is made in step S60 and the flag Fai is set to 1 in step S70. Furthermore, the first wheel is identified in step S80, and the alarm device 52 is activated to issue an alarm indicating that the wheel speed of the first wheel is abnormal.

[0067] 4 shows an example in which the rate of increase in the wheel speed of the first wheel becomes equal to or greater than the reference increase rate value when the wheel speed Vwi gradually decreases due to braking. As shown in FIG. 4, at time t1, the rate of increase in the wheel speed Vwmax of the first wheel becomes equal to or greater than the reference increase rate value Vwdc, and at time t2, the wheel speed Vwmax of the first wheel becomes greater than (1 / Ka) × the wheel speed Vwmh of the second wheel. Furthermore, at time t3, the count value Tai of the abnormality determination timer becomes equal to or greater than the reference value Tac.

[0068] After time t1, the judgment in step S20 becomes positive, after time t2, the judgment in step S30 becomes positive, and at time t3, the judgment in step S60 becomes positive, so in step S70, flag Fai is set to 1.

[0069] Since the flag Fai is 0 until time t3, a negative determination is made in step S240. Therefore, from time t1 until time t3, the estimated vehicle body speed Vvba is calculated based on the wheel speed Vwmax of the first wheel in step S270, and the rate of increase of the estimated vehicle body speed Vvba is limited. Therefore, even if the wheel speed Vwmax of the first wheel increases suddenly, the estimated vehicle body speed Vvba increases gradually or decreases more gradually than the wheel speed Vwmh of the second wheel, which is the normal wheel speed.

[0070] After time t3, the determination in step S240 becomes positive, so that the estimated vehicle body speed Vvba is calculated based on the wheel speed Vwmh of the second wheel in steps S260 and S270, and the rate of decrease of the estimated vehicle body speed Vvba is limited. Therefore, the estimated vehicle body speed Vvba gradually decreases, and if it becomes equal to the wheel speed Vwmh of the second wheel at time t4, for example, it will become equal to the wheel speed Vwmh of the second wheel after time t4.

[0071] (Z) If the wheel speed sensor for the first wheel is replaced When the wheel speed sensor of the first wheel is replaced with a normal wheel speed sensor, affirmative determinations are made in steps S10 and S120 while the vehicle 16 is traveling straight without braking. Since the difference between the wheel speed Vwmax of the first wheel and the wheel speed Vwmh of the second wheel becomes small, affirmative determinations are repeatedly made in step S130. Therefore, a positive determination is made in step S160, so the flag Fai is reset to 0 in step S170, and issuance of the warning indicating that the wheel speed of the first wheel is abnormal is terminated in step S180.

[0072] As can be seen from the above description, according to the embodiment, even if an abnormality such as an abnormality in the electronic circuit of the wheel speed sensor occurs and the wheel speed Vwmax of the first wheel becomes excessively high, the abnormality can be determined (S30 to S70). Furthermore, when the rate of increase in the wheel speed of the first wheel is less than the increase rate reference value Vwdc (S20), no abnormality determination is made. Therefore, in a situation where the rate of increase in the wheel speed of the first wheel is less than the increase rate reference value, it is possible to prevent unnecessary abnormality determinations and to prevent the wheel speed of the first wheel from being erroneously determined to be abnormal.

[0073] Furthermore, according to this embodiment, if the wheel speed Vwmax of the first wheel is not determined to be abnormal and the vehicle is being braked (S230, S240), an estimated vehicle body speed Vvba of the vehicle is calculated based on the wheel speed of the first wheel (S250, S270), and anti-skid control is performed as a travel control using the estimated vehicle body speed. Therefore, when excessive braking slip occurs on a wheel other than the first wheel, the braking slip can be reduced by the anti-skid control.

[0074] According to the embodiment, the increase in the estimated vehicle speed is limited by the limited increase rate (S270). Therefore, even if an abnormality such as an abnormality occurs in the electronic circuit of the wheel speed detection device and the wheel speed of the first wheel increases suddenly, the estimated vehicle speed can be prevented from increasing suddenly.

[0075] Furthermore, according to this embodiment, when it is determined that the wheel speed of the first wheel is abnormal, the estimated vehicle speed of the vehicle is calculated based on the wheel speed of the second wheel, and the decrease in the estimated vehicle speed is limited by the limited decrease rate (S260, S270). Therefore, even if an abnormality such as an abnormality in the electronic circuit of the wheel speed detection device occurs and the wheel speed of the first wheel increases suddenly, the estimated vehicle speed can be prevented from becoming excessively high. Furthermore, when the estimated vehicle speed changes from being calculated based on the wheel speed of the first wheel to being calculated based on the wheel speed of the second wheel, a sudden decrease in the estimated vehicle speed can be prevented, thereby preventing inappropriate anti-skid control.

[0076] Although the present invention has been described in detail above with reference to specific embodiments, it will be apparent to those skilled in the art that the present invention is not limited to the above-described embodiments, and that various other embodiments are possible within the scope of the present invention.

[0077] For example, in the above-described embodiment, in step S30, it is determined whether the ratio of the wheel speed Vwi of the wheel in question to the wheel speed Vwmh of the second wheel exceeds the abnormality determination reference value 1 / Ka. However, this may be modified so that the higher the wheel speed Vwmh of the second wheel, the greater the reference value ΔVwc, and the determination is made as to whether the difference ΔVwi between the wheel speed Vwi and the wheel speed Vwmh of the second wheel exceeds the reference value ΔVwc.

[0078] In the above-described embodiment, when the wheel speed of the first wheel is determined to be abnormal and the vehicle is being braked (S230, S240), the estimated vehicle body speed of the vehicle is calculated based on the wheel speed of the second wheel, and the decrease in the estimated vehicle body speed is limited by the limited decrease rate (S260, S270). However, the estimated vehicle body speed may be estimated based on the wheel speed of the first wheel and the wheel speed of the second wheel, and may be gradually decreased until the contribution of the wheel speed of the first wheel to the estimated vehicle body speed becomes 0.

[0079] Furthermore, in the above-described embodiment, the vehicle running control is ABS control and TRC control, but may be any running control known in the art. [Explanation of symbols]

[0080] 10... Vehicle driving control device, 12... Driving ECU, 14FL to 14RR... Wheel, 16... Vehicle, 30... Braking device, 42... Braking ECU, 44FL to 44RR... Wheel speed sensor, 50... Driving ECU, 52... Alarm device

Claims

1. A vehicle driving control device including a plurality of wheel speed detection devices that detect the wheel speeds of a plurality of wheels, and a control unit that controls vehicle driving based on the wheel speeds detected by the wheel speed detection devices, the control unit is configured to perform an abnormality determination to determine whether the wheel speed of the first wheel is abnormal based on a relationship between a wheel speed of a first wheel having a maximum wheel speed and a wheel speed of a second wheel having a second maximum wheel speed; Furthermore, the control unit is configured not to perform the abnormality determination when the rate of increase in the wheel speed of the first wheel is less than a reference increase rate value while the vehicle is braking.

2. 2. The vehicle driving control device according to claim 1, wherein the control unit is configured to determine that the wheel speed of the first wheel is abnormal when a ratio of the wheel speed of the first wheel to the wheel speed of the second wheel exceeds an abnormality determination reference value.

3. 2. The vehicle driving control device according to claim 1, wherein the control unit is configured to, when it is not determined that the wheel speed of the first wheel is abnormal and the vehicle is being braked, calculate an estimated vehicle body speed of the vehicle based on the wheel speed of the first wheel, and perform anti-skid control as the driving control using the estimated vehicle body speed.

4. 4. The vehicle cruise control device according to claim 3, wherein the control unit is configured to limit the increase in the estimated vehicle speed at a limited increase rate.

5. 5. The vehicle driving control device according to claim 4, wherein the control unit is configured to, when it determines that the wheel speed of the first wheel is abnormal and the vehicle is being braked, calculate an estimated vehicle body speed of the vehicle based on the wheel speed of the second wheel, and limit a decrease in the estimated vehicle body speed at a limited decrease rate.

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