Vehicle control device

Abstract

To provide a vehicle control device that can accurately estimate the vehicle body speed even when a wheel is in a slipping state.SOLUTION: A vehicle control device comprises: a slip determining part that determines whether respective wheels are in a slipping state or not on the basis of the wheel speed and the vehicle body speed; an acceleration sensor correcting part that changes a correction amount in accordance with the number of wheels determined to be in the slip state and corrects an acceleration sensor value detected by an acceleration sensor on the basis of the correction amount; and a vehicle body speed estimating part that estimates the vehicle body speed, using an integral value determined by integrating corrected acceleration corrected based on the correction amount.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a vehicle control device.

Background Art

[0002] Patent Document 1 discloses that when it is determined that any one of a plurality of wheels is in a slip state, the vehicle body speed is estimated using an acceleration sensor value detected by an acceleration sensor without using the wheel speed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When a vehicle travels on sandy or muddy roads, it is assumed that any one of the wheels will be in a slip state. Therefore, in the configuration described in Patent Document 1, when the vehicle travels on sandy ground or the like, the dependence on the acceleration sensor increases, the error influence of the low-frequency component of the acceleration sensor value appears strongly, and there is a risk that the estimation error of the vehicle body speed will increase.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide a vehicle control device that can accurately estimate the vehicle body speed even when a wheel is in a slip state.

Means for Solving the Problems

[0006] The present invention is characterized by comprising a slip determination unit that determines whether or not each wheel is in a slip state based on the wheel speed and the vehicle body speed, an acceleration sensor correction unit that changes a correction amount according to the number of wheels determined to be in the slip state and corrects an acceleration sensor value detected by an acceleration sensor based on the correction amount, and a vehicle body speed estimation unit that estimates the vehicle body speed using an integrated value obtained by integrating a corrected acceleration corrected based on the correction amount.

Effect of the Invention

[0007] In the present invention, even when a wheel is in a slip state, the vehicle body speed can be accurately estimated.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0009] Hereinafter, a vehicle control device according to an embodiment of the present invention will be specifically described. Note that the present invention is not limited to the embodiments described below.

[0010] FIG. 1 is a schematic diagram showing a vehicle in an embodiment. The vehicle Ve includes an engine 1 as a power source for the front wheels, a motor 2 as a power source for the rear wheels, and a control device 10. The vehicle Ve is a four-wheel drive vehicle, where the engine 1 drives the left and right front wheels 3L and 3R, and the motor 2 drives the left and right rear wheels 4L and 4R. The engine 1 is connected to the front wheels 3L and 3R via a differential gear mechanism 5 so as to be power-transmittable. The motor 2 is composed of a permanent magnet synchronous motor and is a motor generator that functions as an electric motor and a generator. The motor 2 is connected to the rear wheels 4L and 4R via a differential gear mechanism 6 so as to be power-transmittable. The vehicle Ve can travel in a four-wheel drive state driven by the front wheels 3L and 3R and the rear wheels 4L and 4R.

[0011] The control device 10 is a control device that controls the vehicle Ve. The control device 10 includes a processor and a memory. The control device 10 loads a program stored in a storage unit into a working area of the memory and executes it, and controls each component through the execution of the program to realize a function that meets a predetermined purpose. Signals from various sensors mounted on the vehicle Ve are input to the control device 10. Signals from a wheel speed sensor 7 that detects the wheel speed of the vehicle Ve, an acceleration sensor 8 that detects the acceleration of the vehicle Ve, and the like are input to the control device 10. The control device 10 executes various controls based on the signals input from the various sensors. The control device 10 executes a vehicle body speed estimation control that estimates the vehicle body speed of the vehicle Ve. The control device 10 is configured to accurately estimate the vehicle body speed even when the wheels are in a slip state.

[0012] As shown in FIG. 2, the control device 10 includes an LPF turning correction unit 11, a slip determination unit 12, a wheel speed selection unit 13, a wheel speed reliability index unit 14, an acceleration sensor correction unit 15, and a vehicle body speed estimation unit 16.

[0013] The LPF turning correction unit 11 removes high-frequency noise from the wheel speeds and corrects the inner and outer wheel speed differences during turning. The wheel speeds detected by the wheel speed sensor 7 are input to the LPF turning correction unit 11. The wheel speeds of the front left wheel 3L, the front right wheel 3R, the rear right wheel 4R, and the rear left wheel 4L are input to the LPF turning correction unit 11. The LPF turning correction unit 11 functions as a low-pass filter for the wheel speeds. When the vehicle Ve is turning, the LPF turning correction unit 11 corrects the inner and outer wheel speed differences for the wheel speeds of the front wheels 3L, 3R and the rear wheels 4L, 4R that have passed through the low-pass filter. The LPF turning correction unit 11 outputs the corrected wheel speeds obtained by correcting the wheel speeds of each wheel.

[0014] The slip determination unit 12 determines the slip state for each wheel based on the wheel speed and the vehicle body speed. The corrected wheel speeds are input from the LPF turning correction unit 11 to the slip determination unit 12, and the estimated vehicle body speed is input from the vehicle body speed estimation unit 16.

[0015] For example, the slip determination unit 12 calculates the difference between the corrected wheel speed and the estimated vehicle body speed for each wheel, and determines whether the difference is greater than the allowable value. If the difference is greater than the allowable value, the wheel is determined to be in a slip state, and if the difference is less than or equal to the allowable value, the wheel is determined to be a grip wheel.

[0016] Alternatively, the slip determination unit 12 calculates the difference between the acceleration calculated from the corrected wheel speed and the acceleration calculated from the estimated vehicle body speed, and determines whether the difference is greater than the threshold value. If the difference is greater than the threshold value, the wheel is determined to be in a slip state, and if the difference is less than or equal to the threshold value, the wheel is determined to be in a locked state.

[0017] The wheel speed selection unit 13 selects the minimum value among the wheel speeds of the wheels that are not slipping. When the vehicle Ve is decelerating, the wheel speed selection unit 13 selects the maximum value among the wheel speeds of the wheels that are not slipping. The corrected wheel speed is input to the wheel speed selection unit 13 from the LPF turning correction unit 11, and the slip determination result is input from the slip determination unit 12. The wheel speed selection unit 13 outputs the selected wheel speed. When the vehicle Ve is accelerating, the wheel speed selection unit 13 outputs the minimum value (wheel speed Min) among the wheel speeds. When the vehicle Ve is decelerating, the wheel speed selection unit 13 outputs the maximum value among the wheel speeds.

[0018] The wheel speed reliability index unit 14 generates a reliability index of the wheel speed according to the number of wheels determined to be in a slipping state. The slip determination result is input to the wheel speed reliability index unit 14 from the slip determination unit 12. The wheel speed reliability index unit 14 outputs the wheel speed reliability.

[0019] The acceleration sensor correction unit 15 corrects the acceleration sensor value based on the minimum value of the wheel speed input from the wheel speed selection unit 13 and the wheel speed reliability input from the wheel speed reliability index unit 14. The minimum value of the wheel speed is input to the acceleration sensor correction unit 15 from the wheel speed selection unit 13, the wheel speed reliability is input from the wheel speed reliability index unit 14, and the acceleration sensor value representing the acceleration detected by the acceleration sensor 8 is input. The acceleration sensor correction unit 15 changes the correction amount according to the number of wheels determined to be in a slipping state, and corrects the acceleration sensor value detected by the acceleration sensor 8 based on the correction amount. The acceleration sensor correction unit 15 outputs the corrected acceleration (estimated G).

[0020] The vehicle body speed estimation unit 16 estimates the vehicle body speed using the minimum value of the wheel speeds input from the wheel speed selection unit 13 and the integrated value obtained by integrating the corrected acceleration input from the acceleration sensor correction unit 15. The minimum value of the wheel speeds is input to the vehicle body speed estimation unit 16 from the wheel speed selection unit 13, the wheel speed reliability is input from the wheel speed reliability index unit 14, and the corrected acceleration is input from the acceleration sensor correction unit 15. The vehicle body speed estimation unit 16 interpolates between the minimum value of the wheel speeds and the integrated value of the corrected acceleration with the wheel speed reliability to obtain the estimated vehicle body speed. The vehicle body speed estimation unit 16 outputs the estimated vehicle body speed.

[0021] According to the control device 10 configured as described above, when the vehicle Ve travels on soft soil such as sandy soil or muddy roads, the slip frequency of the wheels is high, and there is always a situation where one of the wheels is in a slip state, and even in a situation where the acceleration sensor 8 is easily affected by the gradient change due to the off-road unevenness, it is possible to estimate the vehicle body speed with high accuracy. The control device 10 performs slip determination for each wheel, and estimates the vehicle body speed by correcting the vehicle body speed obtained from the wheel speeds according to the number of slipping wheels to the vehicle body speed obtained from the acceleration sensor 8. Further, the acceleration sensor 8 improves the accuracy of estimating the vehicle body speed when all wheels are slipping by sequentially learning and correcting the error of the low-frequency component of the acceleration sensor 8 from the acceleration calculated from the wheel speeds according to the number of slipping wheels.

[0022] As shown in FIG. 3, the control device 10 changes the correction amount based on the wheel speeds according to the number of wheels in the slip state. When there are slipping wheels during acceleration and the number of gripping wheels is small, the control device 10 reduces the correction amount based on the wheel speeds. During full-wheel slip, the corrected acceleration is used.

[0023] Further, the control device 10 includes a calculation unit that calculates two types of vehicle body speeds. This calculation unit calculates a vehicle body speed that depends on the wheel speeds and a vehicle body speed that does not depend on the wheel speeds. For example, the wheel speeds, the acceleration sensor 8, the camera, the GPS, etc.

[0024] The control device 10 includes a calculation unit that calculates two types of acceleration. This calculation unit calculates the acceleration that depends on the wheel speed and the acceleration that does not depend on the wheel speed. For example, it includes the wheel speed, the acceleration sensor 8, the camera, the GPS, etc. The control device 10 passes the acceleration calculated by this calculation unit through a filter of a certain frequency. The control device 10 passes the acceleration calculated by this calculation unit through a low-pass filter with a certain frequency or lower.

[0025] Also, the control device 10 includes a correction unit that corrects the acceleration sensor 8 according to the number of wheels determined to be in a slip state. The control device 10 performs zero-point correction on the acceleration sensor 8.

[0026] As described above, in the embodiment, even if any wheel is in a slip state, by correcting the acceleration sensor value using the wheel speed of the remaining grip wheels, the error influence of the acceleration sensor 8 can be reduced. Even in a slip state, instead of immediately switching to the acceleration sensor value, the error influence of the acceleration sensor 8 can be reduced by correcting with the wheel speed of the remaining grip wheels. When multiple wheels are slipping, since the remaining grip wheels are also near the limit, by changing the correction amount of the vehicle body speed according to the wheel speed according to the number of grip wheels, the reliability of the wheel speed can be reflected in the estimated vehicle body speed.

[0027] Also, the control device 10 sequentially learns and corrects the error of the low-frequency component of the acceleration sensor value by performing zero-point correction on the acceleration sensor 8 based on the wheel speed with the correction amount changed according to the number of grip wheels. Thereby, even when all wheels are in a slip state, the vehicle body speed can be accurately estimated.

[0028] Also, by accurately estimating the vehicle body speed by the control device 10, it is possible to accurately execute slip rate control such as TRC and ABS, and improve the off-road driving performance.

[0029] Note that the vehicle Ve may be a four-wheel drive vehicle (4WD) or an all-wheel drive vehicle (AWD), and the configuration of the power source and the power transmission device is not particularly limited. For example, the power source for the front wheels is not limited to the engine 1 and may be a motor.

[0030] Also, the vehicle Ve is not limited to a configuration in which the drive system on the front-wheel side and the drive system on the rear-wheel side are independent, and may be a common drive system for the front-wheel side and the rear-wheel side. For example, the power source may be connected to the front wheels 3L, 3R and the rear wheels 4L, 4R via a transfer so as to be capable of power transmission.

[0031] Also, when the control device 10 selects the wheel speed by the wheel speed selection unit 13, the process shown in FIG. 4 may be performed. As shown in FIG. 4, the wheel speed selection unit 13 determines whether or not there is all-wheel slip (step S1).

[0032] When there is all-wheel slip (step S1: Yes), the wheel speed selection unit 13 selects the previous value of the vehicle body speed as the wheel speed (step S2). In step S2, the wheel speed is determined to be the previous value of the vehicle body speed, and that value is output from the wheel speed selection unit 13. When the process of step S2 is performed, this control routine ends.

[0033] When there is no all-wheel slip (step S1: No), the wheel speed selection unit 13 determines whether or not the vehicle Ve is accelerating (step S3).

[0034] When the vehicle Ve is accelerating (step S3: Yes), the wheel speed selection unit 13 selects the minimum value of the non-slip wheels as the wheel speed (step S4). In step S4, the wheel speed is determined to be the minimum value among the wheel speeds of the wheels that are not slipping, and that value is output from the wheel speed selection unit 13. When the process of step S4 is performed, this control routine ends.

[0035] When the vehicle Ve is not accelerating (step S3: No), the wheel speed selection unit 13 selects the maximum value of the non-slip wheels as the wheel speed (step S5). In step S5, the wheel speed is determined to be the maximum value among the wheel speeds of the wheels that are not slipping, and that value is output from the wheel speed selection unit 13. When the process of step S5 is performed, this control routine ends.

[0036] Further, when the control device 10 corrects the acceleration sensor value by the acceleration sensor correction unit 15, the process shown in FIG. 5 may be performed. As shown in FIG. 5, the acceleration sensor correction unit 15 determines whether the vehicle Ve is stopped (step S11).

[0037] When the vehicle Ve is stopped (step S11: Yes), the acceleration sensor correction unit 15 subtracts the low frequency of the acceleration sensor 8 from the acceleration detected by the acceleration sensor 8 (step S12). When the process of step S12 is performed, this control routine proceeds to step S14.

[0038] When the vehicle Ve is not stopped (step S11: No), the acceleration sensor correction unit 15 holds the previous value (step S13). When the process of step S13 is performed, this control routine proceeds to step S14.

[0039] The acceleration sensor correction unit 15 subtracts a predetermined value from the acceleration of the acceleration sensor 8 (step S14). This predetermined value is the low frequency of the subtraction value obtained by subtracting the acceleration calculated based on the wheel speed from the acceleration of the acceleration sensor 8. In step S14, "acceleration of acceleration sensor 8 - (low frequency of (acceleration of acceleration sensor 8 - acceleration calculated from wheel speed))" is calculated. The acceleration sensor correction unit 15 outputs the value calculated in step S14 as the corrected acceleration. When the process of step S14 is performed, this control routine ends.

[0040] Further, as shown in FIG. 6, when the vehicle Ve travels on a sloped road, the acceleration sensor correction unit 15 can correct the acceleration sensor 8 using the acceleration based on the wheel speed. The sensor value of the acceleration sensor 8 always has the gradient added. Therefore, the acceleration sensor correction unit 15 performs zero-point correction on the acceleration sensor 8 using the acceleration based on the wheel speed.

[0041] Further, the control device 10 may generate a reflection rate corresponding to the number of slipping wheels as an index of the reliability of the wheel speed. The wheel speed reliability index unit 14 generates a reflection rate of 0% of the wheel speed as a reliability index when the number of wheels in the slip state is three or more. Similarly, the wheel speed reliability index unit 14 generates a reflection rate of 20% of the wheel speed as a reliability index when the number of wheels in the slip state is two, generates a reflection rate of 40% of the wheel speed as a reliability index when the number of wheels in the slip state is one, and generates a reflection rate of 50% of the wheel speed as a reliability index when the number of wheels in the slip state is zero.

[0042] Further, the vehicle body speed estimation unit 16 may calculate the estimated vehicle body speed using the formula "vehicle body speed = integral value of corrected acceleration + wheel speed × reflection rate of wheel speed + previous vehicle body speed".

Explanation of symbols

[0043] 3L, 3R Front wheels 4L, 4R Rear wheels 7 Wheel speed sensor 8 Acceleration sensor 10 Control device 11 LPF turning correction unit 12 Slip determination unit 13 Wheel speed selection unit 14 Wheel speed reliability index unit 15 Acceleration sensor correction unit 16 Vehicle body speed estimation unit Ve Vehicle

Claims

【Claim 1】 A slip determination unit that determines whether or not each wheel is in a slip state based on the wheel speed and the vehicle body speed; An acceleration sensor correction unit that changes a correction amount according to the number of wheels determined to be in the slip state and corrects the acceleration sensor value detected by an acceleration sensor based on the correction amount; A vehicle body speed estimation unit that estimates the vehicle body speed using an integrated value obtained by integrating the corrected acceleration corrected based on the correction amount A vehicle control device characterized by comprising the above.

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