JP2635686B2 - Vehicle body speed measuring device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle body speed measuring device for estimating a vehicle running speed from a wheel rotation speed of an automobile, and is particularly preferably applied to an anti-skid control device.

2. Description of the Related Art Wheel rotation speed (hereinafter referred to as "wheel speed")
That. ) Is substantially zero, and an anti-skid control device that hydraulically controls each wheel speed in order to keep the braking force between the wheels and the road surface at a maximum is to detect the wheel speed and to accurately detect the wheel speed. It is necessary to detect the traveling speed of the vehicle body (hereinafter, referred to as "vehicle speed").

2. Description of the Related Art Conventionally, in consideration of the safety of a braking operation, two piping systems are provided to hydraulic cylinders provided on each wheel. Generally, two piping systems are located diagonally when the vehicle is viewed from above. Piping with one wheel as one system is performed. Therefore, in an anti-skid control device having such a brake system, the wheel speeds of two diagonally located wheels are obtained, the vehicle speed is calculated and estimated from these wheel speeds, and the speed between the wheels and the road surface is calculated. It is desirable to control the wheel speed of each wheel so that the frictional force between them becomes maximum.

As means for estimating the vehicle speed from the two wheel speeds, a means for estimating the larger one of the two wheel speeds as the vehicle speed is used. However, when the accelerator pedal is rapidly depressed, the wheels on the driving wheel side are used. If the wheel slips sharply and the wheel speed rises sharply, a large estimation error will occur.

BOSCHTECHNIS is a means to solve the above problems
CHE BERICHTE (issued in February 1982, P.81, paragraph 7.3.5). According to this document, when the wheel speed of the drive wheel is higher than the wheel speed of the non-drive wheel by a predetermined value, it is determined that the drive wheel is causing a slip phenomenon due to acceleration, and the wheel speed of the non-drive wheel is reduced. Means for estimating the vehicle speed is disclosed. By making such an estimation, it is possible to prevent the vehicle body speed from being estimated to an abnormally large value even when the driving wheels slip during acceleration and the wheel speeds of the driving wheels become abnormally high.

SUMMARY OF THE INVENTION A conventional method for determining a slip state from a wheel speed difference between a driven wheel and a non-driven wheel and estimating a wheel speed of a non-driven wheel as a vehicle speed when a slip occurs. In some cases, it may not be possible to distinguish between a case where a wheel degree difference occurs between the outer peripheral wheel and the inner peripheral wheel due to the slip of the drive wheel during acceleration and the turning of the vehicle. is there. That is, for example, when the front wheel drive vehicle makes a turn, the wheel speed of the front wheels becomes faster than the wheel speed of the rear wheels, and when the wheel speed of the rear wheels is estimated as the vehicle speed, the speed lower than the actual vehicle speed is regarded as Presumed. Therefore, even if sudden braking is performed at the time of turning, even if the vehicle speed is set low, the start of control is delayed even if the wheels start to lock, and the drop in wheel speed becomes large, which affects the steering performance.

Also, if the criterion for slip at the time of acceleration of the wheel is set to a large wheel speed difference that does not occur in the turning state, the result of the determination as to whether or not the slip occurs will be delayed. If the brake operation is performed before this determination is made, the vehicle speed is estimated to be a high value, so that the wheel cylinder, which is the first operation of the anti-skid control performed to prevent the wheels from locking, is performed. The decompression operation may be performed excessively.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problems, and it is an object of the present invention to provide a vehicle body for estimating an accurate vehicle body speed even when a large wheel speed difference occurs between a driven wheel and a non-driven wheel. An object of the present invention is to provide a speed measuring device.

Means for Solving the Problems The present invention provides one of the left and right front wheels and the left and right rear wheels as a drive wheel, and the other as a non-drive wheel, and includes a left front wheel, a right front wheel, a left rear wheel, and a right rear wheel. A wheel speed sensor for detecting each wheel speed; a first processing circuit responsive to outputs from a wheel speed sensor for the right front wheel and a wheel speed sensor for the left rear wheel; a wheel speed sensor for the left front wheel and a wheel for the right rear wheel A second processing circuit responsive to an output from a speed sensor, wherein each of the processing circuits estimates a larger wheel speed as a vehicle body speed when a speed difference between a driven wheel and a non-driven wheel is less than a predetermined value. Means, when the speed difference between the wheel speeds is equal to or greater than the predetermined value and the wheel acceleration of the larger wheel speed of the two wheel speeds is less than the predetermined value, the average value of the two wheel speeds is set as the vehicle speed. First estimating means for estimating, the wheel speed Is greater than or equal to the predetermined value and the wheel acceleration of the larger one of the two wheel speeds is greater than or equal to the predetermined value, the smaller one of the two wheel speeds is estimated as the vehicle speed. A vehicle body speed measuring device for an automobile, comprising: a second estimating means.

Further, the present invention is characterized in that the second estimating means is executed prior to the first estimating means.

Further, the present invention is characterized in that the first estimating means and the second estimating means are not executed when the speed difference between the wheel speeds is less than a predetermined value.

In the present invention, if the speed difference between the driven wheels and the non-driven wheels is less than a predetermined value, the larger wheel speed is estimated as the vehicle speed. When the speed difference between the driven wheel and the non-driven wheel is equal to or greater than a predetermined value, the wheel acceleration of the larger one of the two wheel speeds is calculated, and the wheel acceleration is less than the predetermined value. At this time, the average value of the two wheel speeds is estimated as the vehicle speed. Further, the speed difference between the driving wheel and the non-driving wheel is equal to or greater than a predetermined value, and
When the wheel acceleration of the larger one of the two wheel speeds is equal to or greater than a predetermined value, the smaller one of the two wheel speeds is estimated as the vehicle speed.

Also, in the present invention, the second estimating means is executed prior to the first estimating means.

Further, in the present invention, when the speed difference between the wheel speeds of the two wheels is less than a predetermined value, the first estimating means and the second estimating means are not executed.

Embodiment FIG. 1 is an electric block diagram in a case where a vehicle body speed measuring device according to an embodiment of the present invention is used for an anti-skid control device. The anti-skid control circuit 1 is provided, for example, in a vehicle compartment or in a rear trunk. The wheel speed sensors 2a to 2d are provided for each wheel, and are sensors for detecting the rotation speed of the wheel. Wheel speed sensor 2a
2d is an electromagnetic pickup provided near a circumference of a detection plate made of a ferromagnetic material having a large number of notches and projections formed at equal intervals in a circumferential direction and fixed to a wheel axle, for example. For example, a wheel speed signal having a frequency proportional to the wheel speed is extracted. The wheel speed signals detected by the wheel speed sensors 2a to 2d are shaped into pulse signals by waveform shaping circuits 3a to 3d, and then processed by processing circuits 4a and 4b realized by a microcomputer or the like. Given.

The switch 2e is, for example, a brake switch that sends out a signal indicating the depressed state of the brake pedal, and the like.
The output of the switch 2e is provided to a level conversion circuit 3e. The level conversion circuit 3e converts the output of the switch 2e to a voltage level suitable for the anti-skid control circuit 1 and a post-processing circuit 4e.
a, 4b.

The processing circuit 4a calculates the respective wheel speeds based on the wheel speed signals from the wheel speed sensors 2a mounted on the right front wheel and the wheel speed sensors 2b mounted on the left rear wheel. The difference between the two wheel speeds is a wheel speed determined in advance (hereinafter referred to as "slip reference speed"), for example, 2-3 km / H.
If it is less than it is determined that the car is traveling straight ahead,
The larger one of the two wheel speeds is estimated as the vehicle speed.

When the difference between the wheel speeds is equal to or greater than the slip reference speed, a wheel acceleration, which is a change rate of the larger wheel speed, is calculated, and the wheel acceleration is a predetermined value (hereinafter referred to as "slip reference acceleration"). If the vehicle speed is less than the vehicle speed, it is determined that the vehicle is turning and the average value of the two wheel speeds is estimated as the vehicle speed.

Further, when the wheel acceleration is equal to or higher than the slip reference acceleration, it is determined that the drive wheel is generating a slip (hereinafter referred to as “acceleration slip”) by the acceleration operation of the accelerator pedal, and the two wheel speeds are determined. The smaller wheel speed is estimated as the vehicle speed. The vehicle speed obtained as described above is transferred to the processing circuit 4b via the signal line sl1. In the processing circuit 4b, the same processing as that of the processing circuit 4a is performed, and the obtained vehicle speed is transferred to the processing circuit 4a via the signal line sl2.

The control signals output from the processing circuits 4a and 4b are power-amplified by solenoid driving circuits 5a to 5d, and then applied to solenoid coils provided in the actuators 6a to 6d. Solenoid relay drive signals from the processing circuits 4a and 4b are applied to an AND circuit 7, and the output thereof is amplified by a relay drive circuit 8 and then applied to a relay coil 9a of a solenoid relay 9. When the contact 9b conducts, the other end of the solenoid coil incorporated in the actuators 6a to 6d is supplied with the battery voltage of the battery 11 via the connection point 10.

The motor 12 is a motor for driving the hydraulic pump. When the motor relay 13 is turned on, electric power is supplied from the battery 11 to generate a control hydraulic pressure. The motor drive signals from the processing circuits 4a and 4b are given to the OR circuit 14, and the processing circuits 4a and 4b
When any one of the motor drive signals becomes a high level, the motor relay drive circuit 15 is turned on and the motor relay 13 is also turned on.

When a lamp signal from the processing circuit 4a or 4b is given to the lamp driving circuit 16, the alarm lamp 17 is turned on. The alarm lamp 17 is turned on when an abnormality occurs in the anti-skid control device to give the driver's attention.

The positive terminal of the battery 11 is connected to the power circuit via the power switch 18.
Connected to 19. After converting the battery voltage to a desired voltage, the power supply circuit 19 supplies the converted voltage to each circuit in the anti-skid control circuit 1.

FIG. 2 is a block diagram for explaining a hydraulic path of an anti-skid control device using the vehicle body speed measuring device according to one embodiment of the present invention. Brake pedal 20
The hydraulic pressure generated in the master cylinder 21 by the depressing operation of the wheel cylinder is transmitted to the wheel cylinders via the actuators 6a to 6d.
22a to 22d. The actuators 6a to 6d are controlled by the anti-skid control circuit 1 to control the wheel cylinders 22a to 22d.
Of the wheels 23a to 23d is controlled. P valves 24b and 24d are wheel cylinders 2 for rear wheels
This is a valve for limiting the braking oil pressure applied to 2b and 22d so as not to exceed a certain value.

FIG. 3 is a plan view of the automobile viewed from above to explain a wheel speed difference between the outer peripheral wheel and the inner peripheral wheel during turning. Outer wheel 23c and inner wheel 23d of automobile 25
When the vehicle turns in the directions of the trajectories 26c and 26d, the outer wheel 2
3c has a longer traveling distance per unit time than the inner wheel 23d, so the wheel speed of the wheel 23c is considered to be faster than the wheel speed of the wheel 23d, and the outer wheel 23c is the true body of the automobile 25. It is considered that the wheel 23d rotates faster than the wheel speed corresponding to the speed, and the wheel speed of the wheel 23d on the inner peripheral side slips (hereinafter, referred to as "turning slip") so as to rub the road surface and is rotating slowly.

Therefore, when the vehicle 25 is turning, it is considered that the average wheel speed of the wheel speed of the outer peripheral wheel 23c and the wheel speed of the inner peripheral wheel 23d becomes a wheel speed corresponding to the true vehicle body speed. . In addition, when turning, the outer wheels 23
It is considered that the difference between the wheel speed of the wheel c and the wheel speed of the wheel 23d on the inner peripheral side occurs gradually in time. Therefore, when the wheel speed difference exceeds the slip reference speed and the wheel acceleration of the wheel having the higher wheel speed is equal to or less than the slip reference acceleration, it can be determined that the vehicle is turning.

FIG. 4 is a time chart for explaining the means for obtaining the vehicle speed during turning. Car 25 from time t1
Starts turning, a line l1 representing the wheel speed of the outer peripheral wheel 23c and a line l representing the wheel speed of the inner peripheral wheel 23d
There is a wheel speed difference between the two.

The line l3 is a line representing the vehicle body speed estimated from the wheel speed of the wheels 23c and 23d, and until the time t2 exceeding the line l4 representing the slip reference speed, the outer peripheral wheel 23c having the higher wheel speed is used.
Is estimated as the vehicle speed. Then, at time t2, when the wheel speed of the outer peripheral wheel 23c exceeds the line l4, the wheel acceleration of the outer peripheral wheel 23c at time t2 is determined.If the wheel acceleration is equal to or less than the slip reference acceleration, Therefore, the average value of the wheel speed of the outer wheel 23c and the wheel speed of the inner wheel 23d is estimated as the vehicle speed.

FIG. 5 is a time chart for explaining the means for obtaining the vehicle speed during acceleration. As a result of strongly depressing the accelerator pedal, at time t3, the driving wheel starts to slip, and the line l5 representing the wheel speed of the driving wheel rapidly rises,
A wheel speed difference is generated between the non-driven wheel and a line 16 representing the wheel speed. Until time t4 when the wheel speed of the drive wheel reaches the line 17 representing the slip reference speed, the vehicle speed is estimated from the wheel speed on the drive wheel side. During the period from time t3 to time t4,
Since the wheel speeds of the drive wheels rapidly increase, a certain limiting operation (a type of filter) performed in estimating the vehicle speed is performed, and the vehicle speed does not always match the wheel speed of the drive wheels.
The increase in vehicle speed is suppressed.

Then, when the wheel speed of the drive wheel exceeds the slip reference speed at time t4, the wheel acceleration at time t4 is calculated. If the wheel acceleration is greater than the slip reference acceleration, it is determined that the drive wheel is slipping. , The wheel speed of the non-driven wheels is estimated as the vehicle speed. Therefore, after time t4, the line 18 representing the vehicle speed is on the same line as the line 16 representing the wheel speed of the non-driven wheels.

FIG. 6 is a flowchart of a process performed to determine an acceleration slip or a turning slip. At step a1, it is determined whether or not the anti-skid control circuit 1 is performing the anti-skid control. If the anti-skid control is being performed, the following processing is not performed. When the anti-skid control is not being performed, the process proceeds from step a1 to step a2, and in step a2, the acceleration slip determination flag AF that is set when it is determined that the driving wheel has caused the acceleration slip has already been set. Is determined. If the acceleration slip determination flag AF, which is set when it is determined that an acceleration slip has occurred, is not performed, the following processing is not performed.

If the acceleration slip determination flag AF is not set, the process proceeds to step a3, where the difference between the two wheel speeds, for example, the wheel speed V of the front wheel which is the driving wheel in a front wheel drive vehicle
The difference ΔV between _WF and the wheel speed V _{WR of the} rear wheel that is not driven is calculated. In step a4, the wheel speed difference ΔV calculated in step a3 is determined whether it exceeds the slips reference speed KV, the flow proceeds to step a5 if exceeds, the front wheel acceleration A _WF is slips reference acceleration It is determined whether it exceeds KG. If the slip reference acceleration KG is exceeded, proceed to step a6, where the acceleration slip determination flag is set.
AF is set. Front wheel acceleration A _WF in step a5 is if it is less than slips reference acceleration KG is turning slips determination flag CF representing that the wheel speed difference ΔV occurs connexion by the turning is excisional.

FIG. 7 is a flowchart of a process performed to cancel the determination of the acceleration slip or the turning slip. The acceleration slip determination flag is determined by the processing shown in FIG.
When the AF or turning slip judgment flag CF is set, the judgment flag is held until the acceleration slip judging flag AF or the turning slip judgment flag CF is canceled by the processing shown in FIG.

In step b1, it is determined whether or not the anti-skid control circuit 1 is performing anti-skid control. If the anti-skid control is being performed, steps b2 and b2 are performed.
Step b3 is executed, and the acceleration slip determination flag AF and the turning slip determination flag CF are reset. If it is determined in step b1 that the anti-skid control is not being performed, the process proceeds to step b4, in which the wheel speed V _{WF of the} front wheel, which is the driving wheel, is determined.
And the difference ΔV between the wheel speed V _{WR of the} rear wheel which is a non-drive wheel is calculated. Then, in step b5, the wheel speed difference ΔV calculated in step b4 is equal to the predetermined wheel speed (for example, 1 km / H).
In which is less than the end criterion speed KV ₂ is step b
Proceeding to step 2 and step b3, the judgment flag is reset.

FIG. 8 is a flowchart for calculating the vehicle speed. Acceleration slip judgment flag in step c1
It is first determined whether or not AF is set. If it is determined that the vehicle is set, it is determined that the front wheel, which is the driving wheel, has an acceleration slip.
In c2, the wheel speed V _{WR of the} rear wheel that is a non-drive wheel is estimated as the vehicle speed V _S.

If it is determined in step c1 that the acceleration slip determination flag AF has not been set, the process proceeds to step c3.
It is determined whether the turning slip determination flag CF is set. If the turning slip determination flag CF is set, the process proceeds to step c4, and it is determined that the vehicle is running in a turning state.Therefore, the average of the front wheel speed _VWF and the rear wheel speed _VWR is obtained. The wheel speed is estimated as the vehicle speed V _S.

Next, in step c3, the turning slip determination flag is set.
If it is determined that CF is not set, the process proceeds to step c5, and the larger one of the front wheel speed V _WF and the rear wheel speed V _WR is estimated as the vehicle speed V _S. You.

In step c2, c4, vehicle speed V _S estimated in c5 are step c6, the so-called software filtering is performed. The software filtering, based on the vehicle speed determined in example certain time t _n, then a limit a range of the vehicle speed at time t _{n + 1} to calculate the vehicle speed, exceeding the limit In the case where the vehicle speed is obtained, the upper limit or the lower limit of the range is estimated as the vehicle speed. By performing such a filtering process, it is possible to prevent a sudden change in the vehicle speed due to, for example, noise.

FIG. 9 is a functional block diagram for explaining the calculation of the vehicle body speed performed in the processing circuit 4a. The driving wheel speed detected by the wheel speed sensor 2a and the non-driving wheel speed detected by the wheel speed sensor 2b are given to the wheel speed difference calculating means 401, and the wheel speed difference between the two wheels is calculated. The difference between the wheel speeds is provided to the comparing means 402. In the comparing means 402, the wheel speed difference is compared with the slip reference speed stored in the first memory 403, and the result is sent to the acceleration slip turning determining means 404.

Further, the driving wheel speed is given to the wheel acceleration calculating means 405, and the wheel acceleration of the driving wheel is calculated, and the result is given to the comparing means 406. The comparing means 406 compares the wheel acceleration of the driving wheel with the slip reference acceleration stored in the second memory 407, and the result of the comparison is given to the acceleration slip turning determining means 404.

The acceleration slip turning determination means 404 is based on the output of the comparison means 402, and when the wheel speed difference exceeds the slip reference speed stored in the first memory 403, the wheel speed difference is determined based on the output result of the comparison means 406. It is determined whether the cause of the occurrence is based on the slip of the drive wheels or whether the vehicle is turning. That is, the wheel acceleration of the drive wheel
If the slip reference acceleration stored in the memory 407 is exceeded, it is determined that the driving wheel is slipping into an acceleration slip state, and if it is less than the slip reference acceleration, it is determined that the vehicle is turning. The result of the determination is given to the vehicle speed calculating means 408, and the vehicle speed is estimated. That is, when the wheel speed difference is less than the slip reference speed, the larger one of the driving wheel speed and the non-driving wheel speed is estimated as the vehicle speed. When it is determined that the vehicle is in the acceleration slip state, the vehicle speed calculating means 408 estimates the non-drive wheel speed as the vehicle speed. Further, when it is determined that the vehicle is turning, the vehicle speed calculating means 408 estimates the average wheel speed of the drive wheel speed and the non-drive wheel speed as the vehicle speed.

The vehicle speed estimated by the vehicle speed calculating means 408 is supplied to the vehicle speed comparing means 409, and is compared with the vehicle speed estimated and transferred by another processing circuit 4b. The vehicle speed comparing means 409 sends the larger one of the two vehicle speeds as the control vehicle speed to the anti-skid control means 410, performs an anti-skid control calculation, and gives the result to the solenoid drive circuit.

The acceleration slip turning judgment canceling means 411 inputs the driving wheel wheel speed and the non-driving wheel wheel speed, and when the difference between the wheel speeds is less than the end judgment reference, sends the result to the acceleration slip turning judging means 404, and outputs the acceleration slip and the acceleration slip. The determination of the turning is ended.

Although the processing circuit 4a has been described above, the processing circuit
Similar processing is performed in 4b.

As described above, according to the present embodiment, when a wheel speed difference occurs between the driving wheel side wheel speed and the non-driving wheel side wheel speed, the acceleration slip state and the turning state can be distinguished, and more accurate Since anti-skid control can be performed based on a proper vehicle speed, malfunction of the anti-skid control can be prevented.

Effects of the Invention As described above, according to the present invention, when a speed difference occurs between two wheel speeds on which the vehicle speed is estimated, if the speed difference is smaller than a predetermined value, the larger wheel is used. When the speed is high, the vehicle speed estimating means is switched by the wheel acceleration of the larger wheel speed, so that a more accurate vehicle speed can be calculated.

[Brief description of the drawings]

FIG. 1 is an electric block diagram when an automobile body speed measuring apparatus according to an embodiment of the present invention is used for an anti-skid control device, and FIG. 2 is an electric vehicle body speed measuring apparatus according to an embodiment of the present invention. FIG. 3 is a block diagram for explaining a hydraulic path of an anti-skid control device to be used, and FIG. 3 is a plan view of an automobile viewed from above to explain a wheel speed difference between an outer peripheral wheel and an inner peripheral wheel during turning. FIG. 4 is a time chart for explaining means for obtaining the vehicle speed during turning, FIG. 5 is a time chart for explaining means for obtaining the vehicle speed during acceleration, and FIG. 6 is a diagram for judging an acceleration slip or a turning slip. FIG. 7 is a flowchart of a process performed to cancel the determination of an acceleration slip or a turning slip, and FIG.
The figure shows a flow chart for calculating the vehicle speed, ninth
The figure is a functional block diagram for explaining the calculation of the vehicle body speed performed in the processing circuit 4a. 1. Anti-skid control circuit, 2a-2d ... Wheel speed sensor, 3a-3d ... Waveform shaping circuit, 4a, 4b ... Processing circuit, 5a
... 5d ... solenoid drive circuit, 6a-6d ... actuator, 8 ... solenoid relay drive circuit, 11 ... battery, 12 ... motor, 13 ... motor relay, 15 ... motor relay drive circuit, 18 ... Power switch, 19 ... Power circuit

Claims (3)

(57) [Claims] 1. One of the left and right front wheels and the left and right rear wheels is a driving wheel, and the other is a non-driving wheel, and the respective wheel speeds of a left front wheel, a right front wheel, a left rear wheel, and a right rear wheel are detected. A first processing circuit responsive to outputs from a wheel speed sensor, a right front wheel speed sensor, and a left rear wheel speed sensor; and outputs from the left front wheel speed sensor and the right rear wheel speed sensor. A second processing circuit responsive to the wheel speed, wherein each of the processing circuits estimates a larger wheel speed as a vehicle speed if a speed difference between a driven wheel and a non-driven wheel is less than a predetermined value; The first speed estimating means for estimating the average value of the two wheel speeds as the vehicle speed when the wheel speed difference between the two wheel speeds is equal to or greater than the predetermined value and the wheel acceleration of the larger one of the two wheel speeds is smaller than the predetermined value. And the speed difference between the wheel speeds is determined in advance. Second estimating means for estimating the smaller one of the two wheel speeds as the vehicle speed when the wheel acceleration of the two wheel speeds is greater than a predetermined value. An apparatus for measuring the speed of a vehicle body of an automobile. 2. The apparatus according to claim 1, wherein said second estimating means is executed prior to said first estimating means.
The vehicle body speed measuring device according to claim 1. 3. The vehicle body speed according to claim 1, wherein said first estimating means and said second estimating means are not executed when the speed difference between said wheel speeds is less than a predetermined value. measuring device.