JPH07120552A - Vehicle slip rate compensation device - Google Patents

Abstract

PURPOSE:To absorb each accuracy fluctuation of a Doppler sensor and the error due to slight deviation of a mounting angle by compensating a detection vehicle speed obtained from the Doppler sensor with a slip rate when the vehicle is traveling on a road as a reference. CONSTITUTION:An ultrasonic Doppler sensor 5 for detecting the ground speed is mounted to the lower part of the body of a tractor between front and rear wheels. A wheel rotation sensor 6 for detecting the rotative speed of the rear wheel is provided on the axle of the rear wheel. The sensors 5 and 6 obtains frequency by counting the number of pulses generated according to the vehicle speed or the rotative speed and then input it to a controller 8. A non-volatile memory 11 of the controller 8 stores compensation coefficients for compensating the slip rate. Since the slip rate is nearly equal to 0 when driving on an asphalt road surface, the vehicle speeds are obtained by the sensors 5 and 6 and the ratio of the vehicle speeds is calculated and compensation coefficients are determined for use as the compensation of the slip rate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to, for example, a tractor.
With regard to a Doppler sensor in a power vehicle such as the above, it is intended to reduce an error in slip rate detection.

[0002]

2. Description of the Related Art The slip ratio of a vehicle is constructed by dividing the difference between the vehicle speed obtained from the wheel rotation speed and the vehicle speed obtained from a Doppler sensor by the vehicle speed obtained from the wheel rotation speed and displaying the ratio. There is. The Doppler sensor is usually attached to the lower part of the abdomen of the body, is fixed at a predetermined angle (for example, 60 degrees) with respect to the ground, emits ultrasonic waves toward the ground, and captures the received wave.

[0003]

In the case of the above-mentioned conventional device, the mounting angle of the Doppler sensor is about 1 with respect to the set angle.
Incorrectly, an error of about 3% occurs in the calculated slip ratio. Also, the Doppler sensor itself has deviations in hole positions between the transmitter / receiver and the mounting base, and variations in the accuracy of each Doppler sensor. Considering these, the error in the slip ratio display tends to increase more and more. However, if the detection error is too large with respect to the proper slip ratio of 10 to 20% during plow work, there is a problem that this cannot be ignored in displaying the slip ratio.

[0004]

The present invention has been proposed in view of the above problems, and the following technical means have been taken. That is, in a vehicle configured to calculate the slip ratio from a Doppler sensor attached to the airframe to detect the ground speed of the airframe and a wheel rotation sensor to detect the rotational speed of the wheels, the slip ratio during road traveling The slip ratio correction device for a vehicle is characterized in that means for correcting the detected vehicle speed obtained from the Doppler sensor is provided on the basis of the above.

[0005]

Embodiments of the present invention will be described below based on the embodiments shown in the drawings. First, the structure will be explained as follows.
Is a tractor having a front wheel 2 and a rear wheel 3, and an ultrasonic Doppler sensor 5 for detecting the ground speed of the machine body is provided in the lower part of the machine body between these front and rear wheels 2, 3.

A wheel rotation sensor 6 for detecting the number of rotations of the rear wheel 3 is provided on the axle of the rear wheel 3. Both the Doppler sensor 5 and the wheel rotation sensor 6 count the pulses generated according to the vehicle speed or rotation to obtain the frequency, and these signals are controlled as shown in FIG.
It is input to LA8. The controller 8 is provided with an interface 9, a CPU 10 and a non-volatile memory 11. The non-volatile memory 11 stores a correction coefficient for correcting the slip ratio (S) as described later. is doing.

Reference numeral 12 is a data logger for displaying the slip ratio (S), which is a liquid crystal display unit 13 and a tuning switch 14.
And is connected to the controller 8 through a communication line 15. The data logger-12 is installed at an appropriate position in the tractor-1 cabin 17 and is freely removable. Next, a method of correcting the slip ratio (S) will be described based on FIGS. 3 and 4. The graph of FIG. 3 shows the actual vehicle speed on the horizontal axis and the detected vehicle speed on the vertical axis.

In the figure, the dotted line A is the speed obtained from the wheel rotation, and B is
Is a line where the actual vehicle speed and the detected vehicle speed match, and C is the speed obtained from the Doppler sensor 5. In the figure, A and B
Indicates that the wheel diameter slightly changes due to road surface hardness, tire air pressure, and the like, but the difference is small, but since the error is small, it can be considered that A = B. Therefore, the slip ratio (S) is represented by S = (A−C) / A. When traveling on an asphalt road surface without plow towing work, the slip ratio (S) is almost zero, and in this case, the slip ratio (S) calculated so that A = C.
To correct. That is, the tuning switch 14 of the data logger 12 is pressed to obtain the vehicle speed A by the wheel rotation sensor 6 and the vehicle speed C by the Doppler sensor 5 at this time,
The ratio A / C of these is calculated. Then, the calculated correction value is set as the correction coefficient α, and thereafter, α = A / C is used to correct the slip ratio (S).

Therefore, the formula for calculating the slip ratio from the next time is S = (A-Cα) / A. As described above, the correction coefficient is determined by focusing on the fact that the vehicle speed by the Doppler sensor 5 when traveling on the road and the vehicle speed by the wheel rotation sensor 6 are matched. It is possible to reduce the error of the slip ratio due to the attachment error to the, and the accuracy of the displayed contents is improved.

Next, the structure and operation of the improved device shown in FIGS. 5 and 6 will be briefly described. In this improved device, an engine rotation sensor 20 is further connected to the controller 8 shown in FIG. Since the ultrasonic Doppler sensor 5 utilizes the Doppler effect of sound waves, it has a property of being easily affected by disturbance noise such as engine sound. In a power farming machine such as tractor-1, the place where the Doppler sensor 5 is installed is limited due to the effects of pitching and rolling of the machine body, the restriction of the minimum ground clearance, etc., and this noise should be ignored because the engine noise is large. In many cases The improved device described here is one in which the Doppler sensor 5 value (vehicle speed ΔV) in a state where the aircraft stops traveling is subtracted from the traveling vehicle speed V to minimize the influence degree by the engine sound.

Since the engine speed may fluctuate when the airframe is stopped, the above-mentioned Δ
V can be updated. The updated ΔV is stored in the non-volatile memory 11 of the controller 8 and can be rewritten at any time. 7 and FIG. 8, when calculating the vehicle speed from the wheel rotation sensor 6, the wheel diameter is given as an over-all value D described in a catalog or the like.
This is a description of a configuration in which a value smaller than (catalog display value when no load is applied) is used for calculation.

The theoretical vehicle speed in this case is represented by (wheel diameter × π × rotational speed) / hour. The applicant confirmed in the field that it was 0.97 in the case of asphalt and 0.
It was found that the accuracy of the vehicle speed obtained from the wheel rotation sensor 6 can be improved by multiplying the wheel diameter, that is, the over-all value D by the coefficient of 93. If the correction coefficient is multiplied in the range of 0.93 to 0.97, there is no practical problem in the field.

9 and 10 show the slip ratio (S) which is not displayed for a certain period of time when the aircraft starts. In the vehicle speed calculation by the ultrasonic Doppler sensor 5, the received signal of the nonuniform reflected wave from the ground is subjected to averaging processing so that the detected value becomes a stable value. For this reason, a response delay occurs as compared with the vehicle speed calculation processing by the wheel rotation sensor 6, the speed by the Doppler sensor 5 may be zero immediately after the aircraft starts, and the slip ratio (S) is displayed as 100%. There is. If this is used not only for display problems but also for draft control of the plow, it will be judged that the detected slip ratio> the set slip ratio, an inadvertent draft control output will be output, and the plow will be temporarily lifted. . In this improved device, the draft control and the slip ratio display are not performed until a certain time elapses immediately after starting the vehicle.

Contrary to the above case, FIGS. 11 and 12 are for correcting the slip ratio (S) display only immediately after the machine has stopped traveling. Similar to the case described with reference to FIGS. 9 and 10, the vehicle speed is displayed after the aircraft has stopped due to the response delay of the speed calculation processing of the Doppler sensor 5,
In a state that is impossible in reality, that is, the slip ratio (S) may be displayed as a negative value. At the moment when the aircraft is likely to show such a result, the slip ratio (S)
Is zero.

13 and 14 are graphs showing the relationship between the pulse frequency corresponding to the vehicle speed and the vehicle speed. Fig. 13 shows the case of the conventional device from the low speed region to the high speed region (15 km / h or more)
The characteristics are evenly set to the same gradient, and FIG. 14 shows the characteristics changed in the middle such that the resolution is increased in the low speed range and the resolution is decreased in the high speed range. If the resolution is increased as a whole, the pulse frequency becomes high in the high-speed range, and there is a risk that the controller 8 side may not be able to cope with it. Therefore, in the improved apparatus, the necessary resolution is ensured in the low speed range, and then the controller 8 can be processed in the high speed range.

[0016]

According to the present invention, the slip ratio S is calculated from the Doppler sensor 5 attached to the body for detecting the ground speed of the body and the wheel rotation sensor 6 for detecting the rotation speed of the wheel. In such a vehicle, the means 8 for correcting the detected vehicle speed obtained from the Doppler sensor 5 is provided on the basis of the slip ratio S when the vehicle is running on the road. Even if there is some deviation in the angle, the error can be absorbed and the detection error can be reduced.

[Brief description of drawings]

FIG. 1 is a side view of a tractor.

FIG. 2 is a block diagram.

FIG. 3 is a graph showing a relationship between a detected vehicle speed and an actual vehicle speed.

FIG. 4 is a flowchart of a program for calculating a correction coefficient.
It is

FIG. 5 is a block diagram of a device that eliminates a speed error due to an engine sound.

FIG. 6 is a control flowchart thereof.

FIG. 7 is a diagram illustrating an effective diameter of a wheel.

FIG. 8 is a flowchart.

FIG. 9 is a time chart illustrating how a response is delayed when the vehicle starts moving.

FIG. 10 is a control flowchart thereof.

FIG. 11 is a time chart for explaining how the response is delayed when the machine is stopped.

FIG. 12 is a control flowchart thereof.

FIG. 13 is a graph of an unimproved device for explaining a relationship between a vehicle speed corresponding pulse frequency and a vehicle speed.

FIG. 14 is a graph of the improved device corresponding to FIG.

[Explanation of symbols]

 1 tractor 2 front wheel 3 rear wheel 5 Doppler sensor 6 wheel rotation sensor 8 controller 11 non-volatile memory 12 data logger 14 tuning switch

Claims (1)

[Claims] 1. A vehicle configured to calculate a slip ratio S from a Doppler sensor 5 mounted on the body for detecting the ground speed of the body and a wheel rotation sensor 6 for detecting the number of rotations of the wheels. A slip ratio correction device for a vehicle, comprising means 8 for correcting the detected vehicle speed obtained from the Doppler sensor 5 on the basis of the slip ratio S during traveling on the road.