JPH0225908A - Arithmetic unit for rotational speed of rotor - Google Patents

Abstract

PURPOSE:To operate an accurate rotational speed of a rotor in a wide range even though a difference is detected between the duty ratios of a pulse waveform by operating the rotational speed based on the measurement of the time covering the 1st-3rd pulse edge emerging within a prescribed time of a pulse train signal. CONSTITUTION:A time (t) covering the 1st- 3rd pulse edges emerging within a reference time T for speed operation of a pulse train signal converted by a waveform shaping circuit 5 is measured. Then the speed of a well is operated from the time (t). While the time (t) is obtained from the mean value between the time t1 covering the 1st-3rd pulse edges and the time t2 covering the 2nd-4th pulse edges in case the pulse edges subsequent to the 4th one emerge within the time T. Thus an accurate rotational speed of a rotor is operated even in case a tone wheel 2 having a small quantity of information is used or a difference is detected between the duty ratios of a pulse waveform.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a rotation speed calculation device for a rotating body suitable for use in wheel speed calculation processing in anti-lock control of automobiles, for example.

(Prior Art) The most basic process in anti-lock control, traction control, constant speed driving control, steering control, etc. of automobiles is calculation of wheel speed, and the calculation accuracy and calculation time greatly affect control accuracy. Particularly in anti-lock control and traction control, it is necessary to accurately detect wheel speeds that change from moment to moment, so the wheel speed sensors used there are required to be highly accurate. Normally, this wheel speed sensor consists of a gear-shaped rotor called a tone wheel that rotates synchronously with the wheel, and a pickup coil wound around a permanent magnet installed close to the rotor. By changing the air gap between the tone foil and the pickup coil, an alternating current voltage having a frequency proportional to the rotation speed can be obtained from the pick amplifier coil. Then, the AC voltage is waveform-shaped and converted into a pulse train signal as shown in FIG. 6, and the time from the first rising edge to the next rising edge within each speed calculation reference time T of this pulse train signal, that is, one cycle. Measure the elapsed time t around one edge! tII reading), speed calculation is performed based on this time t.

Incidentally, the number of teeth of the tone wheel is set to a relatively small number in order to avoid the frequency generated from the pick amplifier coil being too high in a high speed range and making speed detection impossible. Therefore, in the case of one-edge periodic reading as described above, as is clear from FIG. 7, the measurement period also deviates from the speed calculation reference time T in the low speed range, making it impossible to calculate the speed for each reference time T. A period occurs. For example, if the frequency of the tone foil teeth is 15 Hz/ka/h,
And when the speed calculation reference time T is 8 mS, the frequency of the AC voltage generated in the pickup coil is 250 + (z
(The wheel speed is 16.6 km/h) or less, the above phenomenon occurs.

On the other hand, as shown in FIG. 8, the time t' from the first pulse edge to the next pulse edge within the speed calculation reference time T
The measurable speed range can be shifted to a lower speed side by performing a half-cycle reading to measure the If the period of "1" and the period of "0" are different, an error will occur in speed calculation.

(Objective of the Invention) Therefore, the present invention provides accurate speed calculation in a wide speed range even when using a tone foil with a small number of teeth, that is, a small amount of information, and even when there is a difference in the duty ratio of the pulse waveform. The purpose of the present invention is to provide a rotational speed calculation device for a rotating body that enables the following.

(Structure of the Invention) In the present invention, the time t from the first pulse edge to the third pulse edge appearing within each speed calculation reference time T of the pulse train signal obtained from the output of the rotational speed sensor is measured,
The present invention is characterized in that the rotational speed is calculated based on this measurement.

(Embodiments) Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention, in which a speed sensor 1
is a pickup coil 4 wound around a tone foil 2 and a permanent magnet 3 attached to an automobile axle hub rotor.
Therefore, the AC voltage generated in the pickup coil 4 as the tone wheel 2 rotates is converted into a pulse train signal by the waveform shaping circuit 5, and the pulse train signal is sent to the microprocessor (MPU) 6.
given to. The MPU 6 includes an edge detection section 7 comprising an input capture register, an oscillation circuit 8 comprising a floating counter, and a memory 1 comprising a RAM.
- A central processing unit 9 including a memory 4, and the edge detection section 7 outputs a detection signal and latch data to the central processing unit 9.

In the present invention, as shown in FIG. 2, the time t from the first pulse edge to the third pulse edge within the speed calculation reference time T of the pulse train signal converted by the waveform shaping circuit 5 is measured, and from this time t The wheel speed Vw is calculated by the following formula.

VW=1/(txK) Here K is a constant.

In addition, if the fourth pulse edge and subsequent pulse edges occur within the speed calculation reference time T, as shown in FIG. 3, the time t1 from the first pulse edge to the third pulse edge and the second
Calculate the time t from the average value of the time t2 from the pulse edge to the fourth pulse edge (t-(tl+t2)/2)
, improving measurement accuracy.

4 and 5 are flowcharts of the measurement of the time t and the calculation process of the wheel speed Vw based on the measurement of the time t, which is executed by the central processing unit 9.

First, in step S1 of FIG. 4, the speed calculation reference time T
It is determined whether or not time has elapsed, and if it is within time T, it is determined in step S2 whether or not a pulse edge has been detected.

If a pulse edge is detected and the pulse edge is determined to be the first pulse edge in step S3, the process advances to step S4, where the timer value of the first pulse edge is stored in the memory 1, and the process returns to step S1. Further, when the determination in step S3 is rNOJ, the process advances to step S5;
If it is determined that it is the second pulse edge, the timer value of the second pulse edge is stored in the memory 2 in step S6, and the process returns to step s1. Further, when the determination in step S5 is rNOJ, the process advances to step S7, and if it is determined here that it is the third pulse edge, the timer value of the third pulse edge is stored in the memory 3 in step s8, and step S
Return to 1. Further, when the determination in step S7 is rNOJ, the process advances to step S9, and if it is determined here that it is the fourth pulse edge, the timer value of the fourth pulse edge 7 is stored in the memory 4 in step 310, and the timer value of the fourth pulse edge 7 is stored in the memory 4. When a pulse edge after the fifth pulse edge is detected, the process immediately returns to step S1.

On the other hand, if it is determined in step S1 that the reference time T has elapsed, the process proceeds to step S11, where it is determined whether or not up to the third edge has been input. III. Execute the speed calculation process shown in FIG.

In the flow of the fifth review, first, in step 312, it is determined whether or not up to the fourth pulse edge has been input. If this determination is rNOJ, in step 313, the memory
The time t from the first pulse edge to the third pulse edge is obtained by subtracting the value of memory 1 from the value of
4, the wheel speed VW is calculated using the formula Vwx1/(LXK), and in the next step S15, each counter and memory are cleared, and the process returns to step S1.

Next, if it is determined in step S12 that the input has been made up to the fourth pulse edge, in the next step 316, the value in memory 1 is subtracted from the value in memory 3, and from the first pulse edge to the third pulse edge. Find the time t1 and subtract the value of memory 2 from the value of memory 4,
Time from 2nd pulse edge to 4th pulse edge [2
In the next step S17, the time [ is determined by the average value of the times tl and t2, and the process proceeds to step S14 to calculate the wheel speed VW.

(Effects of the Invention) The above explanation has clarified the configuration and operation of the embodiment of the present invention.According to the present invention, since both edge periods of the pulse waveform are read, the duty ratio of the pulse waveform is Even if there is a difference in speed, it is not affected by the difference (and similar to the half-cycle reading in FIG. 8 described above, high-precision measurement up to extremely low speeds is possible.

Although the above-mentioned embodiment is a wheel speed calculation device used for vehicle anti-lock control and treadmill control, the present invention is not limited to this, and can be applied to all devices for measuring the speed of a rotating body. It can be applied to

[Brief Description of the Drawings] Fig. 1 is a block diagram showing the configuration of an embodiment of the present invention;
3 are timing charts for explaining the operation, FIGS. 4 and 5 are flowcharts, and FIGS. 6 to 8 are timing charts for explaining the operation of the conventional device. l・-Speed sensor 2-・Tone foil 4-
Pick-up coil 5--Waveform shaping circuit 6--Microprocessor 7--Edge detection section 9--Central processing unit 8--Oscillation circuit

Claims (1)

[Scope of Claims] A device that calculates the rotational speed of the rotating body by measuring the cycle of a pulse train signal obtained from the output of a rotational speed sensor provided on the rotating body at predetermined time intervals, comprising: The first to appear in time
A rotational speed calculation device for a rotating body, characterized in that the time from a pulse edge to a third pulse edge is measured, and the rotational speed is calculated based on this measurement.