JPH01238483A - Rotating speed controller for motor - Google Patents

Abstract

PURPOSE:To accurately control the rotating speed of a motor by calculating the real rotating speed of the motor on the basis of the output of a detector for detecting the reach of the fine predetermined part of a rotary disk secured to the rotary shaft of the motor to a predetermined position. CONSTITUTION:A rotary disk 3 is secured to the rotary shaft 2 of one revolution of a motor 1. A pore 4 is formed at the fine position of the circumference of the disk 3. A light emitting element 5 and a photodetector 7 are disposed at the front and rear of the disk 3 corresponding to the axis of the pore. Thus, each time the disk 3 is rotated one revolution, a detection signal from the photodetector 7 is input to a microcomputer 9. The microcomputer 9 counts a clock signal during the period of a detection signal from the photodetector 7, and calculates the real speed from the counted clock value. Further, it supplies the difference between the real speed and a set speed to a motor driving circuit 11.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial Application Field The present invention relates to a rotational speed control device for a motor used, for example, in a centrifugal sedimentation type particle size distribution measuring device.

(b) Conventional technology A tacho generator is attached to the motor used in a conventional centrifugal sedimentation type particle size distribution analyzer. It is designed to compensate for the difference.

(c) Problems to be Solved by the Invention Rotational speed control devices using general-purpose inexpensive tacho generators have poor linearity and accuracy, and the overall accuracy required for centrifugal sedimentation particle size distribution measuring devices is ± 0.
When it comes to a 5% tachogenerator, it is necessary to use one that is more expensive than a general-purpose product, and on top of that, there is a problem that it becomes even more expensive when the rotation speed is over 10,000 rpm. .

The present invention solves the above-mentioned problems, and provides a motor rotational speed control device for use in centrifugal sedimentation type particle size distribution measuring devices, etc., which can ensure an accuracy of ±0.5% and which can be constructed at a relatively low cost. is intended to provide.

(d) Means and Effects for Solving the Problems The motor rotational speed control device of the present invention includes a rotating disk fixed to the rotating shaft of the motor, and a minute predetermined portion of the rotating disk that is brought to a predetermined position. a detector for detecting the occurrence of a signal, a clock counting means for counting a clock signal of a constant frequency over a period from one detection output of this detector to the next detection output, and a clock counting means for counting clock signals of a constant frequency from one detection output of this detector to the next detection output, It is comprised of a calculation means for calculating the rotation speed, and a control means for controlling the motor rotation speed based on the difference between the actual rotation speed and the set rotation speed.

In this motor rotation speed control device, a rotating disk rotates in accordance with the rotation of the motor, and each time the rotating disk rotates, a small predetermined portion (for example: a hole) of the rotating disk is detected by the detector of the sensor. When it reaches the position, the detector detects this and outputs a one-rotation signal. Therefore, if the clock signal from the clock oscillator used in a microcomputer etc. is counted by the counting means between the output of this detector and the next output,
The clock value for one rotation is calculated according to the actual rotation speed, the actual rotation speed is calculated from this, and the rotation speed of the motor is further controlled based on the difference between the actual rotation speed and the set rotation speed. become.

(e) Examples The present invention will be explained in more detail with reference to Examples below.

FIG. 1 is a block diagram of a motor rotation speed control device of a centrifugal sedimentation type particle size distribution measuring device showing an embodiment of the present invention.

In the same figure, a rotating disk 3 is fixed to a rotating shaft 2 of a motor 1, and a small hole 4 is provided at a minute position on the circumference of the rotating disk 3, and corresponding to the axis of this small hole, A light emitting element 5 and a light receiving element 7 are arranged before and after the rotating disk 3, and the light emitting element 5 is driven to be turned on by a light emitting element drive circuit 6. Although not shown, a capsule containing a sample for measuring particle size distribution is attached to the rotating disk 3, and an optical device separate from the light emitting element 5 and the light receiving element 7 measures the degree of sedimentation. It is designed to be detected.

The small hole 4, the light emitting element 5, and the light receiving element 7 are originally provided for detecting the timing of sample measurement, and in this embodiment, they are also used for detecting one revolution. When the rotating disk 3 rotates according to the rotation of the motor 1, the small hole 4 is opened every rotation.
When the light reaches the optical axis of the light emitting element 5 and the light receiving element 7, the light receiving element 7 receives the optical signal from the light emitting element 5 and outputs the signal. However, at other positions of the small holes 4, the light from the light emitting element 5 is blocked by the rotating disk 3, so that the light does not enter the light receiving element 7. Therefore, every time the rotating disk 3 rotates once, a detection signal is output from the light receiving element 7, and this detection signal is taken into the microcomputer 9 through the interface circuit 8, and the microcomputer 9 uses the attached crystal oscillator 9a. The oscillating clock signal,
A function to count the period from the detection signal from the light receiving element 7 to the next detection signal, a function to calculate the actual speed from the counted clock count value, and a signal to correct the difference between the actual speed and the set speed. The corrected digital signal from the microcomputer 9 is
The A converter 10 converts it into an analog signal, and this analog signal is input to the motor drive circuit 11, so the motor drive circuit 11 moves the motor 1 closer to the set speed.
Controls the rotation speed.

Next, the operation of the rotational speed control device of the above embodiment will be explained with reference to the flowchart shown in FIG.

First, when the operation starts, the microcomputer 9
The register X within is cleared (step 5TI). Then, it is determined whether a position signal has been output from the light receiving element 7 (step 5T2).

Until the rotating disk 3 rotates and the small hole 4 comes to the position of the light receiving element 7, the judgment of Sr1 is No, and after waiting for a while, when the small hole 4 reaches the position of the light receiving element 7, the light receiving signal 7 is Since the position signal is output and input to the microcomputer 9, the determination in step ST2 becomes YES, and then in step ST3, +1 is added to the register
It is determined whether or not it has been input (step 5T4).

Then, unless the next detection signal is input, register
The clock signal is counted by +1 (step 5T3). By such an operation, in other words, from the time when a position signal is received from the light receiving element 7 to the time when the next position signal is received,
Clock signals are counted in register X during the rotation period. In step ST4, when it is determined that the next position signal is present,
In other words, when the rotating disk 3 makes one rotation, a clock signal corresponding to one rotation is stored in the register Based on this set value and the calculated rotational speed signal, a correction value for controlling the rotational speed is input to the motor drive circuit 11 through the D/A converter 10.

The above process is repeated every time the number of revolutions is detected. Generally, the execution time for the loop in the program shown in Figure 2 needs to be a fixed number of machine cycles, but if the number of machine cycles is fixed, the measurement accuracy is
It is determined by counting the value of the measurement result register by X±1 and controlling the oscillator 9a for the microcomputer 9. Since the oscillator 9a for the microcomputer normally uses a crystal oscillator, the frequency change is about ±50 ppm and the temperature stability is about ±50 ppn+/''C, so there is no problem at all.

Therefore, the practical accuracy is ±1 loop time, and if the value of register X is 200, then ±0.5%. Therefore, it is fully applicable as a motor rotation speed control device for a centrifugal sedimentation type particle size distribution measuring device that requires accuracy of ±0.5%.

Now, setting the value of register Previous rotation speed Corrected rotation speed 6, O
OOrpm 5,913 rpm 5,
997 rpm7, OOOrpm 6,906 r
pm 6,999rpra11,OOOrpm
10.84Orpm 10,997rp
m, and good control results have been obtained.

Although the above embodiment shows an example in which the measurement position signal is placed in the address space, the measurement position signal is not placed in the address space and is sent as an interrupt signal to the microcomputer 9.
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(f) Effects of the Invention According to this invention, when applied to a centrifugal sedimentation type particle size distribution analyzer, centrifugal sedimentation can be performed by software processing of a microcomputer without adding any special hardware parts. By simply using the rotating disk, detector, etc. that are essential to a type particle size distribution measuring device, highly accurate rotational speed control is possible, making it possible to perform inexpensive and highly accurate measurements.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a motor rotation speed control device showing an embodiment of the present invention, and FIG. 2 is a flow diagram for explaining the operation of the rotation speed control device. l: motor, 3: rotating plate, 4: small hole, 5: light emitting element, 7: light receiving element, 9: microcomputer, 10
: D/A converter, 11: Motor drive circuit. Patent applicant Shimadzu Corporation Representative Patent attorney Shigeru Nakamura Figure 1

Claims (1)

[Claims] (1) A rotating disk fixed to the rotating shaft of the motor, a detector that detects when a small predetermined part of this rotating disk has reached a predetermined position, and the next detection output from the detection output of this detector a clock counting means for counting clock signals of a constant frequency over a period of A motor rotation speed control device comprising a control means for controlling the motor rotation speed based on the following.