JP2569658B2 - Synchronous operation of motor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a synchronous operation system for an electric motor.

[Conventional technology]

Conventionally, a control method as shown in FIG. 2 has been used as a positioning method for an electric motor. In the figure, when a position command signal is generated from a command generator 21, a signal corresponding to the difference between the position command signal and the current value of the rotational position of the electric motor 25 detected by the position detector 27 is sent to a deviation counter 22. Accumulate in The output is converted to an analog signal by the D / A converter 23, and the deviation of the speed of the motor 25 from the current value detected by the speed generator 26 is input to the speed amplifier 24, and the motor 25 is driven.

By the way, in such a control method, an electric motor is controlled based on a deviation between a position command or a speed command value and a current value.
Since the motor 25 is driven, the motor 25 cannot be operated without a deviation. Therefore, synchronous operation in a complete sense cannot be performed.

In order to reduce the deviation in this control method, as shown by a broken line in FIG. 2, a method of inputting a feedforward loop constituted by a differentiator 28 as a speed input and increasing an apparent position loop gain is known. is there. Alternatively, as shown in FIG. 3, a system is considered in which an integrator 29 is inserted to make the position loop an integral control system, and if a deviation occurs, the deviation is corrected by the integration effect.

[Problems to be solved by the invention]

However, in the former feedforward method,
There is a problem that it is difficult to adjust the feed forward gain and the like, and if the gain adjustment is not accurate, the system becomes unstable.

In the latter integral control of the position loop, a limit cycle occurs in a steady state. That is, the output of the D / A converter 23 in FIG. 3 is generated by D / A conversion of the output pulse of the deviation counter 22, and its output characteristic is
It becomes a quantized step-like output signal. In particular, the deviation is 0
In this case, the output voltage of the D / A converter 23 should be theoretically 0, but in reality, a small voltage called an offset voltage appears as an output. Since the integrator 29 integrates the output voltage by its nature, when the offset voltage is integrated, it finally reaches a voltage at which the electric motor 25 is operated. When the motor 25 moves, since the servo system is working, a command is issued to give a voltage of the opposite polarity to the offset voltage and cancel the offset voltage. Will move. Such an operation is called a limit cycle. Since a limit cycle occurs in this way, synchronous operation in a complete sense cannot be performed even in the integral control as shown in FIG.

Conventionally, as a control method used for synchronous operation such as pulse synchronization, there is a method called a PLL (phase locked loop) method as shown in FIG. Specifically, the phase of the command frequency output from the command generator 31 and the phase of the speed frequency detected by the speed detector 36 are compared by the phase comparator 32, and a voltage signal corresponding to the phase difference is output. The output is smoothed by a loop filter 33, converted into a DC voltage, and drives a motor 35 via a power amplifier 34.

This PLL system has been conventionally used for constant speed operation, but is rarely used for variable speed operation. Further, in the PLL system, basically, positioning control is impossible. The reason is that, since the phase is detected and compared, the phase information decreases at low speeds, and the control system basically becomes unstable.

Today, synchronous operation is often required as a control requirement such as a gear grinding machine. In these applications, positioning is usually required, and the conventional method cannot satisfy the requirement.

The present invention has been made to meet such a demand, and has as its object to enable synchronous operation and positioning control.

[Means for solving the problem]

In order to achieve this object, a synchronous operation method for a motor according to the present invention includes a command generator that generates a position command pulse for the motor and a position detector that detects a current position of the motor in the position control of the motor. A deviation counter that counts the deviation between the position command pulse generated by the command generator and the output pulse of the position detector, a D / A converter that converts the output of the deviation counter into an analog signal, and a D / A conversion An integrating circuit for integrating the output signal of the detector, a phase comparator for comparing the phase of the position command pulse generated by the command generator with the output pulse of the position detector, and converting the output of the in-phase comparator to DC. A loop filter that detects whether the output of the deviation counter is within a predetermined range, and a pulse comparator that detects that the output of the deviation counter is within a predetermined range. A drive signal supplied to the electric motor when the out switching to an output of said loop filter, at other times is made of a switch for switching the drive signal supplied to the electric motor to the output of the integrator circuit.

[Action]

The present inventors have switched between the conventional two control methods, the normal positioning control method and the PLL control method, under certain conditions, so that synchronous operation and positioning control in a complete sense can be realized.

In a control system in which the position loop is an integral control system as shown in FIG. 3, when a command pulse train is input, the response is as shown in FIG. That is, even though the deviation is large at first, the limit cycle is drawn within approximately ± several pulses due to the correction effect of the integration. Under the influence of this limit cycle, synchronous operation in a complete sense cannot be performed.

In the present invention, the state in which the limit cycle is drawn is monitored, and at the moment when the deviation enters a certain value, for example, within ± 1 pulse, the integral control system is disconnected, and the control is switched to the synchronous operation system of the PLL system. By doing so, perfect synchronous operation by the PLL method can be obtained at a constant speed.

In addition, even if the synchronization due to the operation of the PLL system is lost due to a sudden change in the load or the like, if the change exceeds ± 1 pulse,
By switching to the original position loop integration method, position control is performed without losing the current value. Switching to the PLL method when the speed is stabilized enables synchronous operation as before.

EXAMPLES Hereinafter, the present invention will be specifically described based on examples shown in the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a command generator. In this example,
The upper stage is an integral control system, and the lower stage is a PLL control system. It is input to the comparator 10. The output of the deviation counter 2 is converted into an analog signal by a D / A converter 3 and is integrated and compensated through an integration circuit 4. The signal is input to the power amplifier 6 via the switch 5 and the electric motor 7 is driven.

On the other hand, the output of the phase comparator 10 becomes the other input signal of the switch 5 through the loop filter 11.

In this control system, control is performed by the upper position control loop at the time of starting. When the position deviation decreases and the count pulse of the deviation counter 2 falls within, for example, ± 1 pulse, this is detected by the pulse comparator 9, the switch 5 is switched based on the output signal, and the output of the loop filter 11 is captured. . This switches to the PLL control system,
Synchronous operation is performed.

If the synchronization is lost for some reason, the output of the deviation counter 2 becomes ± 1 or more.
, And switches the switch 5 to use the output signal of the integration circuit 4 as the input signal of the power amplifier 6. The position deviation is
Even during operation under control, since the data is stored by the integration circuit 4, the switching is smoothly performed.

In a specific embodiment of the present invention, not only an analog configuration but also a digital configuration can be applied.

〔The invention's effect〕

As described above, in the present invention, the integral control method used only for positioning in the past and the PLL control method used only for speed control have a position deviation amount equal to or more than a predetermined position deviation amount. Switching is performed based on the condition of entering. For this reason, control that simultaneously satisfies the synchronous operation and the positioning control, which has been impossible in the past, has become possible. In addition, since speed control can be performed without the need for a speed generator or the like, the configuration can be simplified and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a block diagram showing a conventional positioning system, FIG. 3 is a block diagram of a positioning system with integral compensation, and FIG.
FIG. 5 is a block diagram of the L system, and FIG. 5 is a diagram showing a response when integral compensation is used in the position loop. 1: Command generator, 2: Deviation counter 3: D / A converter, 4: Integrator 5: Switch, 6: Power amplifier 7: Motor, 8: Position detector 9: Pulse comparator, 10: Phase comparison Unit 11: Loop filter

Claims (1)

(57) [Claims] In a position control of an electric motor, a command generator for generating a position command pulse for the motor, a position detector for detecting a current position of the motor, a position command pulse generated by the command generator, and the position A deviation counter for counting the deviation from the output pulse of the detector, a D / A converter for converting the output of the deviation counter into an analog signal, an integration circuit for integrating the output signal of the D / A converter, A phase comparator for comparing the phase of the position command pulse generated by the command generator with the output pulse of the position detector, a loop filter for converting the output of the phase comparator to DC, and an output of the deviation counter being a predetermined value. And a drive signal to be given to the electric motor when the pulse comparator detects that the output of the deviation counter has entered a predetermined range. It switched to the output of the loop filter,
In other cases, a synchronous operation system of the electric motor comprising a switch for switching a drive signal given to the electric motor to an output of the integrating circuit.