JPH0638563A - Motor-speed controller - Google Patents

Abstract

PURPOSE:To improve a transient response at starting in a motor-speed controller by comparing a signal from VCO in a rotational-speed setter feedback-controlled by the actual rotational speed of a motor with a signal from a reference oscillator by the use of a phase comparator and by inputting the difference signal of the comparison to the motor to feedback-control the rotational speed of the motor. CONSTITUTION:An active filter composed of a resistor RF and a circuit, in which an amplifier, capacitor C and switch are respectively connected in parallel, is connected in series with the rear stage of a phase comparator and the switch is turned off at the time of starting a motor so that the power level of the active filter is raised by a time constant determined by the resistor RF and capacitor C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor speed control device, and more particularly to a motor speed control device for improving transient response at the time of starting.

[0002]

2. Description of the Related Art There are various types of motor speed control devices for controlling the speed of a motor by feedback control, and one of them is the device shown in FIG. FIG. 4 is a block diagram showing the configuration of a conventional motor speed control device used in, for example, a medical injector, in which 1 is a reference oscillator, 2 is a phase comparator, and 4 is an LPF (L
ow-pass filter, 5 is an amplifier, 6 is a motor, 7 is an encoder, 8 is a doubler circuit, 9 is a phase comparator, 10 is an LPF, 11 is a VCO (Voltage c).
Reference numeral 12 denotes a variable frequency dividing circuit.

Next, the operation of the circuit shown in FIG. 4 will be described. Reference signals S ₁ from the reference oscillator 1 in the phase comparator 2 is compared with the signal R ₄ from VCO 11, the difference signal S ₂ is input to the LPF 4, the amplified waveform is matched with the amplifier 5 in LPF 4, the motor The rotation speed control of 6 is performed. The actual rotation speed of the motor 6 is converted into an electric signal by the encoder 7 and is input to the phase comparator 9 as a signal R ₁ via the doubling circuit 8. The other of the phase comparator 9 has a phase comparator 9-LPF10. -VCO 11-Variable frequency dividing circuit 12
-The output of the rotation speed setting device constituted by the feedback circuit of the phase comparator 9 is input, and the variable frequency dividing circuit 12
By setting the frequency division number (that is, the rotation speed of the motor 6) to, the signal R ₂ is input to the phase comparator 9, the phase comparator 9 compares the signal R ₂ and the signal R _1, and the difference Signal R
₃ controls the oscillation frequency of the VCO 11 via the LPF 10, and the output R _{4 of} this VCO 11 is input to the phase comparator 2. In this way, the rotation speed of the motor 6 is feedback-controlled at the rotation speed set in the variable frequency dividing circuit 12. If it is desired to have a sufficient variable speed range of the motor 6, the frequency division number N of the variable frequency divider 12 may be fixed and the oscillation frequency of the reference oscillator 1 may be changed.

[0004]

Since the conventional motor speed control device as described above is constructed and operates as described above, the transient response at the time of starting the motor cannot be avoided, that is, the constant response at the time of starting the motor. There is a problem that it is inevitable that the rotation speed of the time motor becomes abnormally higher than the set value. That is, as shown in FIG. 3B, the signal R ₄ is not input to the phase comparator 2 at the time of starting, the value of the signal S ₂ becomes abnormally large, and the motor 6 overrotates.
When the motor 6 over-rotates, the difference signal S ₂ becomes negative by that amount, and the motor 6 operates so as to rapidly decelerate to the set rotation speed. Therefore, transient response at the time of start causes abnormal rotation or vibration. There were problems such as occurrence.

The present invention has been made to solve the above problems, and an object of the present invention is to obtain a motor speed control device having a simple structure and greatly improving the transient response at the time of starting.

[0006]

A motor speed control device according to the present invention comprises a resistor 33, an amplifier 30, and a capacitor 3.
1, the active filter 3 including a circuit in which the switch 32 is connected in parallel is inserted in series after the phase comparator 2.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention, in which 1 is a reference oscillator, 2 is a phase comparator, and 3 is a reference oscillator.
Is an active filter, 4 is an LPF, 5 is an amplifier, 6
Is a motor, 7 is an encoder, 8 is a doubler circuit, 9 is a phase comparator, 10 is an LPF, 11 is a VCO, and 12 is a variable frequency divider circuit. The conventional circuit shown in FIG. Since it is the same as the above, the duplicate description is omitted here.

FIG. 2 is a diagram showing an example of the configuration of the active filter 3 shown in FIG. 1, in which 30 is an amplifier,
Reference numeral 31 is a capacitor, 32 is a switch, and 33 and 34 are resistors. The active filter 3 as shown in FIG.
Resistor 33, amplifier 30, capacitor 31, switch 3
2 is connected in parallel to each other, and the resistance value of the resistor 34 is set so that the output signal level becomes zero level when the motor 6 is stopped and the switch 32 is turned on.

Next, the operation will be described. At the time of starting the motor 6, the switch 32 is automatically turned off. Therefore, the output signal level rises with a time constant determined by the resistor 33 and the capacitor 31, and when the motor 6 reaches the set rotation speed, the output signal level is settled. Therefore,
After the rotation speed of the motor 6 reaches the set rotation speed, the output signal level depends on the gain of the amplifier 30. As described above, as shown in FIG. 3 (A), the transient response at the time of starting is prevented to prevent over-rotation and vibration. The switch 32 is generally a logic circuit switch, and is configured to operate in conjunction with a start start switch (not shown) of the motor 6.

[0010]

As described above, the present invention can provide a motor speed control device having a simple structure and greatly improving the transient response at the time of starting. Further, since it can be configured by a simple circuit and the V-F conversion IC can be used for the VCO, there are effects such as a low cost configuration.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration example of the active filter shown in FIG.

FIG. 3 is a diagram showing a comparison between the device of the present invention and a conventional device.

FIG. 4 is a block diagram showing a conventional device.

[Explanation of symbols]

 1 Reference Oscillator 2 Phase Comparator 3 Active Filter 6 Motor 7 Encoder 9 Phase Comparator 11 VCO 12 Variable Frequency Divider 30 Amplifier 31 Capacitor 32 Switch 33, 34 Resistance

Claims (1)

[Claims] 1. A phase comparator compares a signal from a reference oscillator with a signal from a VCO in a rotation speed setting device which is feedback-controlled by an actual rotation speed of the motor, and inputs a difference signal to the motor. In a motor speed control device for feedback controlling the rotation speed of a motor, an active filter including a resistor R _F , a circuit in which an amplifier, a capacitor C, and a switch are connected in parallel is connected in series after the phase comparator. When the motor starts, turn off the above switch to activate
A motor speed control device for increasing the output level of a filter with a time constant determined by the resistor R _F and the capacitor C.