JP2535944B2 - Stationary encoder - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a static encoder, and more particularly to a static encoder for an open loop controller of a synchronous motor.

B. SUMMARY OF THE INVENTION In the present invention, in open loop control of a synchronous motor by an inverter, a frequency pulse proportional to a speed command is counted by a reversible counter, and the direction of the forward and reverse rotations of the motor is determined from the lower 2 bits of the phase. By obtaining the pulse for determining the rotation angle position, the distributor that detects the rotation phase of the electric motor is unnecessary.

C. Conventional technology One of the AC (alternating current) servo systems is to drive a synchronous motor with an inverter. In a synchronous motor driven by an inverter in such a system, the inverter equivalently corresponds to the commutator portion of the DC motor,
It has exactly the same characteristics as a DC machine, and it does not require a troublesome mechanical commutator on the motor side. Therefore, the mechanism assembled in this way is called a so-called brushless DC motor.

Here, an example of the brushless DC motor will be described with reference to FIG. In the figure, an AC converter 2 output from a three-phase AC power supply 1 converts the DC power into a DC power, which is supplied to a three-phase inverter 3. A three-phase AC is supplied to the armature winding of the permanent magnet synchronous motor 4 by the three-phase inverter 3, and the synchronous motor 4 is thereby driven to rotate. The rotation speed and the rotation angle position of the rotor of the synchronous motor 4 are detected by the distributor 5 such as a resolver or an encoder. The controller 6 is the distributor 5
Signal is processed to determine the rotational speed and rotational angle position of the rotor of the synchronous motor 4 to control the position of the load and trigger pulse so that the three-phase inverter 3 operates at a frequency always synchronized with the determined rotational speed. Output P. On the other hand, by changing the phase of the trigger pulse P and changing the frequency of the three-phase inverter 3, the rotational speed of the synchronous motor 4 can be made variable.

D. Problems to be Solved by the Invention In the conventional control method, a distributor 5 coupled to the electric motor is provided in order to detect the rotational speed and the rotational angle position of the synchronous motor 4, and the synchronous motor 4 has a distributor. Machining for mounting 5 is required, and this machining is also complicated and expensive for a structure that eliminates the influence of heat and vibration of the electric motor and a structure that secures the environment resistance of the electric motor. Further, it is necessary to lay a signal cable between the control device and the distributor, and this signal cable has a problem in space and price in order to have a structure having good noise resistance and the like.

E. Means and Actions for Solving Problems The present invention has been made in view of the above problems, and counts pulses having a frequency proportional to the speed command of the synchronous motor, and adds or subtracts by the forward / reverse command of the synchronous motor. The reversible counter that can be switched to and the phase between the lower 2 bits of this counter and the positive and negative 90 ° to the upper bit output.
And a logic circuit that obtains pulses of different phases,
The pulse output phase of the logic circuit is associated with the forward and reverse rotation directions of the synchronous motor, and the integrated value of the pulse output is associated with the rotation angle position of the synchronous motor. That is, the synchronous motor is
When a rotating magnetic field is applied by an AC power source, the rotor rotates in synchronization with the rotating magnetic field, and when the rotating magnetic field stops, the rotor stops at that position, so a reversible counter for generating an AC magnetic field in the inverter. By utilizing the fact that the change in the count value of the counter corresponds to the speed of the rotor of the synchronous motor, the speed of the rotor is obtained from the change in the count value of the counter, and the rotational position is obtained by integrating the same. The same speed as the configuration with a distributor while eliminating the need for
Enables position detection and control.

F. Embodiment FIG. 1 is a circuit diagram showing an embodiment of the present invention, which is applied to a synchronous motor control device using an inverter. In the figure, 1 is a three-phase AC power supply, 2 is a converter, 3 is a three-phase inverter, 4 is a permanent magnet synchronous motor, and these are equivalent to those shown in FIG.

In FIG. 1, the host controller 10 gives a speed command to a speed command voltage converter 11, and this converter 11 obtains a voltage output of a speed pattern having an acceleration range, a constant speed range, and a deceleration range corresponding to the speed command. The voltage-frequency converter 12 configured as a voltage controlled oscillator or the like generates a pulse having a frequency proportional to the speed pattern voltage from the converter 11. Sine wave generator 13
The output pulse of the converter 12 is used as the count input of the reversible counter 14, and the count value of this counter 14 is output as a pair of sine wave data whose phase is written in the ROM 15 and is 120 ° out of phase as the address data of the ROM 15. . The control unit 16 obtains a sine wave signal for three phases from the sine wave data from the sine wave generation circuit 13, and obtains a gate pulse that determines the output frequency of the three-phase inverter 3 according to this signal. The control unit 16 also includes a current control system.

Here, as an encoder for detecting the rotation speed and the rotation angle position of the synchronous motor 4, the lower two of the reversible counter 14 are used.
A logic circuit 17 using a bit signal is provided. This logic circuit 17 has a counter 14 as shown in FIG.
A signal having a phase shown in FIG. 2 (c) is obtained by logical processing from the lower 2 bits (a and b in FIG. 2), and the signals (b) and (c) are used as the rotational angle position signal of the synchronous motor 4 in the upper order. Output as a feedback signal to the controller 10. These signals (b) and (c) have a phase difference of 90 ° in electrical angle with each other, and the frequency output to the synchronous motor 4 is the output of a pulse train composed of the number of pulses corresponding digitally. If the speed command is 0, the electric motor 4 continuously generates the braking force, but if a speed command that is not 0 is input, the inverter output is output to the electric motor 4 and, at the same time, the feedback to the host controller 10 is started through the logic circuit 17. .

In FIG. 2, a period T _F shows when the synchronous motor 4 is in forward rotation, and a period T _R shows when the electric motor 4 is in reverse rotation. That is, the counter 14 is switched to the addition or subtraction mode in accordance with the forward / reverse rotation command from the upper controller 10 and counts the output pulse of the converter 12. In this counting, the phase between the lower 2 bits is the addition of the counter 14. Depending on the mode and the subtraction mode, the periods T _F and T _R of FIG. 2 are different from each other, and the phase difference of FIG. 2 (c) with respect to the waveform of FIG. The phase relationship between both signals in FIGS. 2B and 2C corresponds to the rotation direction of the sine wave output of the ROM 15, that is, the forward / reverse direction of the synchronous motor 4.

Therefore, the host controller 10 determines the forward and reverse rotation directions of the electric motor 4 from the pair of signals of the logic circuit 17, and also determines the rotational angle position of the electric motor 4 by integrating the number of pulses of one of the signals, and further, per unit time. The number of revolutions can be determined by counting the number of pulses. These determination results are used for position control and speed control of the load driven by the electric motor 4, for example.

Although the embodiment shows the case where it is applied to the control circuit of the permanent magnet synchronous motor, the drive power supply frequency of the synchronous motor is changed to that of the reversible counter such as a synchronous motor of another type or a control method of another type. It can be applied to those associated with the count value to obtain an equivalent effect.

G. Effects of the Invention As described above, according to the present invention, pulses having a frequency proportional to the speed command are counted by the reversible counter, and the forward / reverse rotation direction and rotation angle position of the electric motor are determined from the phase of the lower 2 bits of this counter. Since I got the pulse to judge,
It is realized as a circuit incorporated in the control device by eliminating the need for a conventional distributor, and a small number of circuits can be added by using the counter of the control device.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG.
FIG. 3 is a time chart of the counter 14 and the logic circuit 17 in the figure, and FIG. 3 is a control circuit diagram of a conventional synchronous motor. 3 ... Three-phase inverter, 4 ... Permanent magnet synchronous motor, 10
...... Host controller, 11 …… Speed command voltage converter, 12
...... Voltage-frequency converter, 13 ...... Sine wave generation circuit, 14 ・ ・ ・
… Reversible counter, 16 …… Control unit, 17 …… Logic circuit.

Claims (1)

(57) [Claims] 1. A control device for controlling an output frequency of an inverter according to a speed command, and driving a synchronous motor with an output of the inverter, counts pulses having a frequency proportional to the speed command and adds them by a forward / reverse command of the synchronous motor. Or a reversible counter which can be switched to subtraction, and a logic circuit which obtains a pulse having a phase different from each other by 90 ° between the lower two bits of the counter with respect to the upper bit output of the counter. Type encoder.