Pulse counter

Details Pulse counter Pulse counter

1999-07-06

2001-01-16

Wambach, Margaret R. (Department: 2816)

Electrical pulse counters, pulse dividers, or shift registers: c

Applications

Determining machine or apparatus operating time or...

C377S002000, C377S047000, C377S049000

Reexamination Certificate

active

06175607

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a pulse counter for counting a pulse train outputted in response to the rotation of an electric motor, and more particularly, to a pulse counter used for simultaneously controlling a plurality of electric motors in a highly accurate manner.
2. Description of the Prior Art
In an electric motor driving device which simultaneously drives two electric motors, it is usual to control revolutions of each electric motor by inputting the pulse trains outputted from the electric motors and counting the difference between the pulse numbers outputted from the electric motors with a pulse counter.
To create the pulse train from the electric motor, a pulse generator is mounted on each of the electric motors. The pulse generated by the pulse generator has a very high frequency. This leads to a problem in that there is a limitation to processing the high frequency outputted pulse.
It is usual that the number of pulses per revolution generated by the pulse generator is not fixed and changes in response to the machines which are driven by the electric motors and the applications to which those machines are subject.
When an incremental pulse generator is used, it is difficult to obtain synchronized operation of two electric motors and keep an absolute phase difference between the two electric motors at all times.
It is an object of the present invention to provide a pulse counter capable of counting high frequency pulses and easily dealing with such high frequency pulses even though the number of pulses per revolution generated from the pulse generator is different. Furthermore, the present invention detects an absolute phase difference between a plurality of the electric motors.
SUMMARY OF THE INVENTION
A pulse counter which simultaneously counts the pulse generated from a plurality of electric motors in a highly accurate manner has now been discovered. The pulse counter of the present invention counts a pulse signal outputted from an incremental pulse generator mounted on two or more electric motors.
Broadly, the pulse counter of the present invention comprises integrating counters of the number corresponding to that of the electric motors, a coefficient unit for setting a ratio, and a multiplier.
Inputted into the integrating counter from the incremental pulse generator are a pulse output in response to a rotation angle, and a zero phase pulse output outputted per revolution.
Once the pulse output in response to the rotation angle is inputted into the integrating counter, the integrating counter counts the pulse output one by one. The integrating counter resets the counted value once the zero phase pulse in inputted. The integrating counter can easily count the pulse output and the zero phase pulse output even though those outputs are at high speeds by adding only the simple function described above on the integrating counter.
A pulse number from the pulse generator can be corrected by providing the coefficient units and the multiplier for multiplying coefficients from the coefficient units by the counted value of the integrating counter. The multiplier and the coefficient unit need not be operated each time the pulse output from the pulse generator and the zero phase pulse output are inputted. The multiplier and the coefficient unit need only process arithmetic operation at the time required for control.
More specifically, the integrating counter counts the pulse output in response to the rotation angle from the pulse generator attached to the electric motor one by one as described above. Since the function is simple, it can also count the pulse output at high frequency, for example, above 1 MHz. The integrating counter is cleared with the zero phase signal. A user can be informed of the rotation angles of the pulse generator and the respective electric motor at all times by permitting the output of the integrating counter to use a zero of the pulse generator as 0.
The coefficient unit is provided, and multiplication of the coefficient from the coefficient unit and the counted value from the integrating counter accomplished in a microprocessor (hereinafter referred to as a MPU) whereby arithmetic operation is effected only at a time required for controlling the motor without following a rapid change in the signal input from the pulse generator. With the construction described above, pulse numbers per revolution of a plurality of electric motors can be made the same.
The present invention also has an arithmetic operation unit for calculating a deviation of the foregoing multiplier whereby a deviation, namely a phase difference between the output pulses from the pulse generators is calculated.
The pulse counter of the present invention also allows a user to be accurately informed of a phase difference between different electric motors, and hence two or more electric motors can be operated simultaneously in a highly accurate manner.
The phase difference between two or more electric motors may be calculated in the arithmetic operation unit at the necessary time, and hence it is not necessarily to calculate the same every time the pulse output and the zero phase pulse output from the pulse generators.


REFERENCES:
patent: 5423192 (1995-06-01), Young et al.
patent: 5929578 (1999-07-01), Atarashi

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