JPH01304360A - Method for detecting speed of motor - Google Patents

Abstract

PURPOSE:To detect the speed of a motor with fixed accuracy regardless of the speed of the motor whether it is high or low by providing a control signal generation circuit, counter, and CPU. CONSTITUTION:A control signal generation circuit 3 controls the 1st-3rd counters 4-6 based on the number of PG pulses in a timer period T2 upon receiving the PG pulses and one timer period T2. The time at which the number of the PG pulses is >=2 is regarded as the high-speed operating time of a motor and the counter 6 is caused to count the number (m) of the PG pulses in the timer period T2. Then the counter 4 is caused to count the number n1 of reference clock pulses from the first PG pulse in the timer period T2 to the end of the timer period T2 and the counter 5 is caused to count the number n2 of the reference clock pulses from the last PG pulse in the timer period T2 to the end of the timer period T2. A CPU 7 calculates the frequency of the PG pulses based on the count values of the counters 4-6. When the number of the PG pulses is <2, on the other hand, it is regarded as the low-speed operating time of the motor and the counter 4 counts the timer period T2 through the number n1 of the pulses and the CPU 7 calculates the frequency of the pulses based on the count value of the counter 4.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for detecting the speed of an electric motor, and particularly to a method for detecting the speed of an electric motor that digitally detects the speed using a pulse generator.

[Prior Art and Problems to be Solved by the Invention] Conventional motor speed detection methods employ either the M method or the T method.

The M method is, as shown in Fig. 4(a), in which a pulse generator (hereinafter referred to as PG
It is called. ) is used to measure the number of pulses within a certain period of time, and the disadvantage is that the slower the speed, the greater the measurement error becomes.

As shown in FIG. 4(b), the 1' method is an intra-pulse counter 1 method that measures the time between pulses d1, and has the disadvantage that the j1 measurement error increases as the speed increases.

Therefore, the technical problem of the present invention is to provide a motor speed detection method capable of detecting the speed of an electric motor with constant accuracy regardless of whether the speed is low or high. .

Means for Solving 1 Problem] According to the present invention, a PG pulse outputted from a pulse generator installed in an electric motor is received, and within one cycle of a predetermined timer generated by frequency-dividing a reference clock pulse. If the number of falling PG pulses is larger than a predetermined value, the number of I)G pulses within one timer cycle and timer 1
Count the number of reference clock pulses from the first PG pulse in a period to the end of one period of the timer, and the number of reference clock pulses from the last PG pulse in one period of the timer to the end of one period of the timer. However, if it is smaller than a predetermined value, the number of pulses per reference within one period of the PG pulse is counted, and the rotational speed of the motor is calculated based on the counted value. A detection method is obtained.

[Example] Next, embodiments of the present invention will be described with reference to the drawings.

As shown in FIG. 1, a device using the motor speed detection method of this embodiment includes a clock generating circuit 1 that generates a reference clock period 'T' (seconds) and a reference clock period 'T' (seconds). Timer 2, which divides the frequency to generate a constant timer period (seconds), and a reference period T7,
a third counter 6 that counts the number of PG pulses from a pulse generator (not shown), and a control that controls these first to third counters 4 to 6; A control signal generation circuit 3 that generates signals (clear, launch, gate) and a CPU 7 that calculates speed based on the counter values from the first to third counters 4 to 6.
It is composed of.

Below, the timing chart 1 shown in FIGS. 2 and 3 will be explained.
The operation of the present electric motor speed detection device will be explained with reference also to .

The control signal generation circuit 3 generates a PG pulse and a timer one cycle 1υ1.
'F, and controls the first to third counters 4 to 6 based on the number of PG pulses within one timer cycle '2'.

When the number of PG pulses is 2 or more, the motor is considered to be rotating at high speed, and the third counter 6 indicates that the motor is rotating at high speed.
The number m of G pulses is counted, the first counter 4 counts the number of reference clock pulses (nl) from the first PG pulse in one timer period T to the end of one timer period T2, and the second counter 5 counts the number of reference clock pulses (02) from the last PG pulse in the timer 1 cycle Go2 to the end of the timer 1 cycle T2. CF) U 7 is the first formula based on the counts obtained by the first to third counters 4 to 6.

m/ ((n+ -n2)T+ l (1-rz)
The PG pulse frequency is calculated by:

On the other hand, if the number of pulses is less than 2, the motor is considered to be rotating at a low speed, and the first counter 4 counts one cycle of the PG pulses by the number of reference clock pulses (nl). C.P.
U7 is calculated based on the count obtained by the thirteenth counter 4 using the second formula, 1/ n + T+ (7(
z) to calculate the PG pulse frequency.

[Effects of the Invention] As explained above, according to the present invention, the speed detection method can be selected from two methods depending on the rotational speed of the electric motor, so regardless of whether the motor speed is low or high, It is possible to provide a method for detecting motor speed that can be detected with certain accuracy.

[Brief explanation of the drawing]

Fig. 1 is a block diagram related to an embodiment of the present invention, Fig. 2 is a timing chart 1 to 1 during high-speed rotation of the electric motor in Fig. 1, and Fig. 3 is a timing chart during low-speed rotation of the electric motor in Fig. Timing Chart 1-1 FIG. 4 shows timing chart 1- in the conventional detection method.

Claims (1)

[Claims] 1. The number of PG pulses within one cycle of a predetermined timer, which is generated by receiving PG pulses output from a pulse generator provided in the motor and dividing the reference clock pulse, is predetermined. If the value is larger than the specified value, the number of PG pulses within one timer cycle, the number of reference clock pulses from the first PG pulse within one timer cycle to the end of the relevant timer one cycle, and the number of reference clock pulses within the relevant timer one cycle. Count the number of reference clock pulses from the last PG pulse to the end of one cycle of the timer, and if it is smaller than a predetermined value, count the number of reference clock pulses within one cycle of the PG pulse, A motor speed detection method that calculates the rotational speed of the motor based on the counted value.