JPH0356086A - Speed controlling type of servo-motor - Google Patents

Abstract

PURPOSE:To set a servo-motor controller strong in noise and for enabling it to be miniaturized by obtaining speed signal from a potential difference between both ends of the coil of a servo-motor moving through a magnetic field. CONSTITUTION:The speed of a linear DC motor 13 is detected by a speed detecting section 14, and according to direction switching signal, polarity is switched by a signal switch 15, and is processed by a differential circuit 16, and speed signal is obtained. The signal is compared with desired speed signal by a comparing circuit 11, and by a driving circuit 12, according to this deviation, the linear DC motor 13 is controlled. The speed detecting section is determined by detecting a potential difference between both ends of a coil moving through a magnetic field in a linear DC motor 13.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a highly accurate servo motor speed control system.
In particular, a coil is placed in the magnetic field created by a permanent magnet,
The present invention relates to a servo motor speed control method in which the speed of the servo motor is detected by moving the coil as the servo motor moves, and the servo motor is controlled based on this.

The servo motor speed control method according to the present invention is applicable to recording devices used, for example, in optical card reader/writer devices and magnetic card reader/writer devices. Good results can be obtained by applying this method to controlling the motor that drives the playback head when accessing a track or when moving a card. Furthermore, it can be applied to control of general servo motors.

[Prior art] As an example of a servo motor in which a coil is provided in a magnetic field created by a permanent magnet and the coil is moved as the servo motor moves, a speed sensor is added to a linear DC motor. Fig. 4 shows a perspective view of the structure.

In Figure 4, 1 is a linear DC motor and 2 is a speed sensor. 3 is the coil that increases the speed. 4 is the center yoke.
5 is a permanent magnet. 6 is the back yoke. 7 is the sliding shaft that supports the slider, and 8 is the sliding shaft mounting base. 9 is slider, 10
is the substrate. The speed sensor 2 has a coil 3 disposed in a magnetic field created by a permanent magnet 5 and moves with the movement of the linear DC motor 1 to detect the speed of the linear DC motor 1. A drive coil is attached to the lower part of the slider 9, and the slider 9 moves by energizing the drive coil. As the slider 9 moves, the coil 3 of the speed sensor 2 moves. the result. The coil 3 moves at a certain speed at right angles to the magnetic field created by the permanent magnet 5.

At this time, an electromotive force is generated in the coil 3 as an output signal according to Fleming's right-hand rule. The output signal of the coil 3 is used as a speed signal of the linear DC motor to perform speed control by a speed control device.

A block diagram of a conventional speed control device is shown in FIG. Fifth
In the figure, 11 is a comparison circuit, 12 is a drive circuit, 13 is a linear DC motor, 14 is a speed detection section (speed sensor),
15 is a signal switching circuit.

The output signal detected by the speed detection unit 14 is switched to the signal switching path 1.
The speed signal processed in step 5 so that only the forward direction signal is outputted by the direction change signal is compared with the externally set target speed signal 1] in the comparison circuit 11, and a signal corresponding to the difference is sent to the drive circuit 12. The drive coil of the linear direct current motor 13 is energized to control the speed.

FIG. 6 shows a conventional signal switching circuit for detecting a speed signal for controlling the speed of a linear DC motor. In Fig. 6, 21 is an analog switch, 22 is an operational amplifier,
R1, R2, and R3 are resistors, and 23 is a buffer operational amplifier.

FIG. 7 shows signal waveforms at each point in FIG. 6.

The output signal V1 of the coil generated with the movement of the linear DC motor is input to an operational amplifier 2 with a gain of 1 of Rl-R2.
Invert the signal through 2. Output signal V1 and output signal V
1 is selected by an analog switch 21 or the like using a direction switching signal that reverses the moving direction of the linear DC motor using a sensor or the like, so that a constant positive direction speed signal is obtained, and then the buffer oven is selected. This speed signal is passed through the amplifier 23 as a speed signal to control the speed of the linear DC motor.

[Problems to be solved by the invention] In the conventional servo motor speed control method described above.
Since the speed signal used for control is directly used as the output signal from the speed detecting coil, if external noise enters the speed detecting coil, the signal waveform shown in Figure 7 will be generated. Does that noise directly affect the speed signal? Also. For miniaturization, a speed detection coil is often installed near the servo motor, and the noise generated when controlling the servo motor, especially when switching the direction of current, can also directly affect the speed signal and cause high noise. This hinders accurate speed control. For this reason, in the past, shielding measures such as arranging the servo motor and the coil for detecting speed separately were taken, which hindered miniaturization of the device.

Therefore, the problem of the present invention is to make it strong against noise. It is an object of the present invention to provide a servo motor speed control system that performs highly accurate speed control that allows for miniaturization of the device.

[Means for Solving the Problems] According to the present invention, a coil is provided in the magnetic rise created by a permanent magnet, and the coil is moved along with the movement of the servo motor to obtain a speed representing the speed of the servo motor. A servo motor speed control method in which a signal is obtained and the speed of the servo motor is controlled based on the speed signal, characterized in that the speed signal is obtained by taking a differential between the output signals at both ends of the coil. A servo motor speed control method is obtained.

[Example] Examples of the present invention will be described below.

FIG. 1 shows a block diagram of a speed control system for a linear DC motor according to an embodiment of the present invention. In Figure 1, 1
1 is a comparison circuit. 12 is a drive circuit, 13 is a linear DC motor, 14 is a speed detection section (speed sensor), 15 is a signal switching circuit, and 16 is a differential circuit. The signal switching circuit 15 processes the output signal detected by the speed detection section 14 using a direction switching signal and outputs it as a forward direction speed signal. A differential circuit 16 processes the differential output signal from the signal switching circuit 15 to obtain a speed signal. A comparator circuit 11 compares this speed signal with a target speed signal set from the outside, and outputs a signal corresponding to the deviation to a drive circuit 12. The drive circuit 12 controls the speed of the linear DC motor 13 by energizing the drive coil thereof.

FIG. 2 shows details of a signal switching circuit and a differential circuit for detecting a speed signal for controlling the speed of a linear DC motor.

In Figure 2, 31 is an analog switch, 32, 33
．． 34 is an operational amplifier, R1, R2, R3, R4, R5,
R6 and R7 are resistors.

FIG. 3 shows signal waveforms at each point in FIG. 2.

The output signals v1 and V2 of the coils generated with the movement of the linear DC motor are switched to V by an analog switch 31, etc.
2-The output signal is switched by a direction switching signal that reverses the moving direction of the linear DC motor using a sensor or the like so that Vl always obtains a positive speed signal. After that, manually connect the operational amplifier to the resistor Rl-R4, R2-R5 Under the conditions of R6-R7, VOUT-R6/R2・(1+2R1/R3)V2-
Vl is output as an output signal, and this output signal becomes a speed signal for controlling the speed of the linear DC motor.

In the linear DC motor speed control system explained above, the configuration of each circuit section is just an example.
Other configurations are also possible. Also. It is clear that the servo motor speed control method according to the present invention can be applied to various types of servo motors.

[Four Effects] As explained above using the embodiments, the present invention provides a servo motor speed control system that performs highly accurate speed control that is resistant to noise and allows for miniaturization of the device. It can also be applied to control of servo motors other than those mentioned above, and has great industrial value.

[Brief explanation of drawings]

Figure 1 is a block diagram of the servo motor speed control method according to the present invention. Figure 2 is a circuit diagram showing the signal switching circuit and differential circuit of the servo motor speed control method in Figure 1, and Figure 3 is a circuit diagram showing the signal switching circuit and differential circuit of the servo motor speed control method in Figure 1.
FIG. 3 is a waveform diagram showing signal waveforms of various parts in the circuit diagram shown in the figure. FIG. 4 is a perspective view of a linear DC motor in which a speed detection section (speed sensor) is attached. FIG. 5 is a block diagram of a conventional speed control system, FIG. 6 is a circuit diagram of a conventional signal switching circuit, and FIG. 7 is a waveform diagram showing signal waveforms at various parts in the circuit diagram of FIG. 1. Linear DC motor, 2: Speed sensor. 3: Coil,
4: Center yoke, 5: Permanent magnet. 6: Hack yoke, 7: Sliding shaft. 8: Sliding shaft mounting base. 9: Slider, 1
0: Board, 11: Comparison circuit, 12: Drive circuit, 13 Nilinear DC motor. 14: Speed detection section, 15: Signal switching circuit, 16: Differential circuit, 21, 31: Analog switch,
23: buffer operational amplifier, 32, 33, 34: operational amplifier. Figure 1 Figure 2 Figure 3 Figure 4 Figure 8 Figure 5 Figure 6 Figure 7

Claims (1)

[Claims] 1. Install a coil in the magnetic field created by a permanent magnet,
In the servo motor speed control method, the coil is moved in accordance with the movement of the servo motor to obtain a speed signal representing the speed of the servo motor, and the speed of the servo motor is controlled based on the speed signal. A servo motor speed control method characterized in that the speed signal is obtained by taking a differential between output signals at both ends of a coil.