JPS59109867A - Speed detection system - Google Patents

Abstract

PURPOSE:To attain a speed detecting system where the influence of noise is eliminated and a high resolution can be held in a low-speed region, by comparing speed detection signals based on a pulse train counting system and a cycle counting system with each other and selecting and outputting one of them. CONSTITUTION:The cycle of speed detection pulses passing through a speed generator 2 is measured by a cycle measuring circuit 3, and a speed based a frequency counting system is detected by a reciprocal arithmetic circuit 4. Meanwhile, clocks are counted in a pulse integrating circuit 6 during the time of speed detection pulses of the generator 2 to detect a speed based on the pulse train counting system. These detects speed are selected by a comparator 8 and a selecting circuit 7; and the generation of a wrong pulse due to noise is decided to select the detected speed based on the pulse train counting system which is difficult to be affected by noise if the difference between both speeds is larger than a set value, and the detected speed based on the frequency counting system of a high resolution is selected if said difference is smaller. Thus, the speed detecting system is attained where the influence of noise is eliminated and a high resolution is held in a low-speed region.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a speed detection method for detecting the rotational speed of a rotating machine to be detected.

BACKGROUND ART Conventionally, a speed detection device for a rotating machine to be detected has a method of counting a pulse train of a speed detection signal obtained from a speed generator or the like attached to a rotating machine such as an electric motor for a predetermined period. In this method, even if an incorrect pulse is input for any reason, it has little effect on the detected data. That is, it has the advantage of being resistant to noise and the like, but on the other hand, it has the disadvantage that the number of pulses of the speed detection signal of the speed generator decreases in the low speed region of the motor, making it impossible to obtain the desired resolution.

On the other hand, in the low speed region of the electric motor, a method is used in which the period of the speed detection signal is measured and the inverse value of the period data is calculated to obtain speed data. However, in this period measurement method, if an incorrect input pulse signal is introduced due to noise or the like, period data will be incorrectly measured. FIG. 1 is an explanatory diagram showing an erroneous measurement state in this periodic measurement method, and in the same figure, the pulse time series Pl
.

P2. If an incorrect pulse Px is mixed into the state where Pa is measured and the period T is measured, the period will measure V2, and as a result, the output speed data will be twice or more than the actual speed. This period measurement method has the disadvantage that it is more easily affected by noise etc. than the above-mentioned pulse train counting method.

This invention was made to eliminate such conventional drawbacks, and by combining the advantages of the pulse train counting method described above and the advantages of the period measurement method, it eliminates the influence of noise etc. It is an object of the present invention to provide a speed detection method that can maintain high resolution in a low speed region.

This invention will be explained below with reference to the drawings.

FIG. 2 shows a block diagram of a speed detection method according to an embodiment of the present invention. In the figure, 1 is an electric motor serving as a rotating machine to be detected, 2 is a speed generator for speed detection, 3 is a period measuring circuit, and 4 is a reciprocal calculation circuit. A first speed calculation unit A is formed by both. On the other hand, 5id oscillator 6 is a pulse integration circuit, and this oscillator 5 and pulse integration circuit 6
A second speed calculation unit B is formed by both. Furthermore, 7 is a comparison circuit, and 8 is a selection circuit. Further, 9 is an output terminal for outputting output speed data, and a and b indicate respective output speed data of the second and second speed calculation units A and B, respectively.

The operation of the speed detection method with such a configuration will be described.

Speed detection signal V of electric motor 1 output from speed generator 2
are the first and second speed calculation units A;

B is supplied. Therefore, in the first speed calculation unit A, the period counting circuit 3 counts the speed detection signal V, and
An output cycle data signal of the counting result is output. Furthermore, this output periodic data signal is input to the reciprocal calculation circuit 4,
This data signal is subjected to reciprocal calculation and output as first speed data a.

On the other hand, in the second speed calculation unit 1-B, the pulse train output signal of the oscillator 5 that generates a pulse train output signal of a predetermined period and the speed detection signal V mentioned above are supplied to the pulse integration circuit 6. . Therefore, this pulse integration circuit 6 is
By integrating the speed detection signal (2) which does not occur in the period between two pulse signals of the pulse train output signal from the oscillator 5, the integrated value is output as second speed data b.

On the other hand, the first speed data a of the first speed calculation unit A
and the second speed data b of the second speed calculation unit B.
and are input to the comparison circuit 7, respectively. Comparison circuit 7,
When a significantly large difference occurs between the first speed data a and the second speed data b, it is assumed that an incorrect pulse Px has occurred, and the second speed calculation unit B, which is resistant to the influence of noise etc. A designation output signal is sent to the selection circuit 8 so as to designate the second speed data b from . Therefore, the selection circuit 8 to which the speed data a and b are input selects and outputs only the speed data b in response to the above designated output signal, and the speed data b is output to the output terminal 9. Further, when the difference between the first speed data a and the second speed data b is small, the speed data a of the first speed calculation unit A that can obtain speed data with higher resolution is selected by the selection circuit 8. and is configured to be output to the output terminal 9. In particular, when the second speed data b mentioned above is selected as the output signal, it is when the illegal pulse Px is generated, so it is mainly selected in the low speed region.

As described above, according to the speed detection method of the present invention, as explained earlier, the method of measuring the period and the method of counting the detected pulses are incorporated, and the advantages of each method are exploited according to the speed range of the detected speed data. Since the output speed data signal is selected and secured as the output speed data signal, there is no possibility of outputting an erroneous measurement signal in the low speed range, unlike conventional methods, and it also has high resolution and noise etc. in the entire speed range. There is an advantage that speed detection with less influence can be achieved.

[Brief explanation of the drawing]

FIG. 1 is an operation explanatory diagram showing the state of a pulse human signal in a conventional period measurement type speed detection device, and FIG. 2 is a block configuration 1 of a speed detection method according to an embodiment of the present invention.
Each of them is showing. DESCRIPTION OF SYMBOLS 1... Rotating machine or electric motor to be detected, 2... Speed generator, 3... Period measuring circuit, 4... Reciprocal calculation circuit, 5... Oscillator, 6... Pulse integration circuit, 7
... Comparison circuit, 8... Selection circuit.

Claims (1)

[Claims] a first speed calculation unit that receives a speed detection signal obtained from a speed generator or the like attached to a rotating machine and calculates speed data by measuring the period of the speed detection signal; a second speed calculation unit that calculates speed data by integrating the number of pulses of the speed detection signal for a predetermined period; and a comparison circuit that compares the respective speed data output from the first and second speed calculation units. and a selection circuit that outputs speed data of either the first or second speed calculation unit based on the output signal of the comparison circuit.