JPH08223949A - Motor starter circuit - Google Patents

Abstract

PURPOSE: To suppress time lag fluctuation due to mechanical backlash before actual start of the operation of an object to be driven when rotation of a motor is started. CONSTITUTION: The motor starter circuit comprises a polarity inversion detecting circuit 10 for storing two switches 1, 2 in respective drive directions and a switch being turned ON last and making a decision whether the switch coincides with a switch currently turned ON, a timer circuit 7 for delivering a signal upon elapse of a predetermined time after turn ON of any one switch and applying a normal drive voltage when coincidence of switches is detected, and motor drive voltage selection circuits 11-24 for applying a start voltage higher than the normal drive voltage until a signal is delivered from the timer circuit when coincidence of switch is not detected and applying the normal drive voltage until the switch currently turned ON is turned OFF after a signal is delivered from the timer circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor start circuit, and more particularly to a motor start circuit used for moving and adjusting a sample stage of an electron microscope.

[0002]

2. Description of the Related Art A sample adjusting mechanism such as an electron microscope converts the rotation of a motor into a linear motion through a gear train such as a worm gear or a screw, and adjusts the sample stage in, for example, XY directions. It is a thing. Various adjustment mechanisms are known for this purpose.

[0003]

Such a conventionally known movement adjusting mechanism using a motor has a gear train, screws and the like interposed therebetween, so that the motor is switched on by backlash, friction and the like. There was a time lag from when the sample actually started moving. Therefore,
Even if the sample or the like is to be moved quickly to the desired position, there is a gap between the sample and the operation, and the operator feels uncomfortable. Moreover, since this time lag depends on the previous rotation direction of the motor, it cannot be predicted, and an extra sense of discomfort is felt. That is, if the moving direction this time is the same as the previous time, the time lag is small, and if the direction is opposite, the time lag until the actual movement starts due to backlash becomes long.

The present invention has been made in view of the above problems of the prior art, and an object thereof is to change the voltage applied at the time of starting the rotation of the motor in accordance with the previous rotation direction. By doing so, the variation in the time lag until the start of the actual operation of the drive target due to mechanical backlash or the like is reduced. It is another object of the present invention to make it possible to adjust the rotation speed of the motor according to the magnification of the electron microscope.

[0005]

A motor start circuit of the present invention for achieving the above object is a motor start circuit for a motor capable of bidirectionally driving by changing the polarity of an applied voltage. Whether or not the switch that has been turned on is the same as the switch that has been turned on by storing any one of the two switches that have been turned on and the one that has been turned on closest in the past. The polarity reversal detection circuit that determines whether or not the switch and the time reversal detection circuit that generates a signal after a predetermined period of time from the turning on of either of the two switches and the polarity reversal detection circuit detect that the switches match. In this case, from the time the current switch is turned on to the time it is released, a predetermined normal drive voltage with a polarity corresponding to the closing switch is applied, and the polarity reversal detection circuit confirms that the switches do not match. In the case where the timing circuit is turned on, a start-up voltage higher than the normal drive voltage, which is a voltage of the polarity corresponding to the closing switch is applied after the current switch is turned on until the timing circuit generates a signal, A motor drive voltage selection circuit for applying the normal drive voltage having the polarity corresponding to the closing switch from the generation of the signal to the current release of the closing switch.

In this case, it is desirable to be able to adjust the time until the timing circuit outputs a signal. It is also desirable to be able to adjust the normal drive voltage applied by the motor drive voltage selection circuit.

[0007]

In the present invention, the start-up voltage higher than the normal drive voltage is applied for a predetermined period only when the motor is driven in the opposite direction to the previous drive direction, so that a mechanical voltage is applied. It is possible to reduce the time lag until the actual operation of the drive target starts due to backlash or the like. In addition, the startup voltage application time and the normal drive voltage are adjusted according to the magnification of the electron microscope so that the drive speed of the motor can be adjusted to the magnification so that the observer does not feel uncomfortable with the adjustment speed. Can be

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A motor start circuit according to the present invention will be described in detail below based on embodiments. FIG. 1 is a circuit diagram of a motor start circuit according to one embodiment of the present invention, and FIG. 2 is a timing chart showing its operation. In FIG. 1, 1
Is a + direction switch, 2 is a-direction switch, 3, 4 is an inverter circuit (or NOT circuit), 5 is an OR circuit, 6 is a first switch, 7 is an integrator, 8 is an inverting amplifier, 9 is a comparator, 10 is Polarity inversion detection circuit, 11 is a first AND circuit, 12 to 15 are second to fifth AND circuits, 16 respectively.
Is an inverter circuit (or NOT circuit), 17 is a CPU,
18 is a digital-analog converter, 19 is an amplifier, 20
Is an inverting amplifier, 21 to 24 are second to fifth switches, 25 is a drive amplifier, 26 is a motor drive circuit, and 27 is a motor.

The + direction switch 1 and the-direction switch 2 are
This is a switch for rotating the motor 27 for forward and reverse rotations for adjusting the movement of the sample table and the like in two directions opposite to each other, and one of the switches is selected and turned on by the operator. Each of the switches 1 and 2 is connected to a positive power supply, and when any one of them is turned on, a rectangular wave voltage corresponding to the turning-on period is generated. The outputs from the + direction switch 1 and the-direction switch 2 are input to the inverter circuits 3 and 4, respectively, inverted, and input to the input terminal of the OR circuit 5. The outputs of the inverter circuits 3 and 4 are connected to the input terminal of the polarity inversion detection circuit 10. As will be described later, the polarity inversion detection circuit 10 stores the switch 1 or 2 that has been turned on closest in the past, and if the switch that has been turned on and the switch in the past match with each other. When the output is "L" (low) and different, the circuit is "H" (high) only while the switch is pressed. The output of the OR circuit 5 is connected to the first switch 6, and the first switch 6 is turned off when the output of the OR circuit 5 is “H”,
The switch is turned on when the output of the OR circuit 5 is "L". The output of the integrator 7 is the first switch 6
Is charged to -15V when is off, and is connected to 0V when the first switch 6 is on. The output of the integrator 7 is inverted by the inverting amplifier 8 and connected to the negative terminal (point A) of the comparator 9.

On the other hand, information that determines the drive voltage of the motor 27 in the normal state, such as magnification information, is input to the CPU 17. Then, the digital information that determines the motor drive voltage via the CPU 17 becomes the normal drive positive voltage + V via the digital / analog converter 18 and the amplifier 19, and the digital information is stored in the digital / analog converter 18 and the inverting amplifier 20. After that, the normal driving negative voltage becomes -V. Among these, the normal drive positive voltage + V is the positive terminal (point B) of the comparator 9.
Connected to.

The output (point C) of the comparator 9 is the AND
The output of the polarity inversion detection circuit 10 is connected to the other input of the AND1 circuit 11, and the output of the AND1 circuit 11 (point D) is
The outputs are directly connected to one input of the AND2 circuit 12 and the AND3 circuit 13, and the output thereof is inverted by the inverter circuit 16 and connected to one input of the AND4 circuit 14 and the fifth AND circuit 15.

Further, the output of the + direction switch 1 passing through the inverter circuit 3 is the AND3 circuit 13 and the AND4 circuit 1
The output of the-direction switch 2 which is connected to the other input of the AND circuit 4 via the inverter circuit 4 is the AND2 circuit 12, A
It is connected to the other input of the ND5 circuit 15.

The outputs of the AND2 circuit 12, the AND3 circuit 13, the AND4 circuit 14 and the AND5 circuit 15 are:
The switches are connected to the fifth switch 24, the fourth switch 23, the second switch 21, and the third switch 22, respectively, and turn on the respective switches when the output of each AND circuit is “H”.

An amplifier 19 is connected to the second switch 21, and the normal drive positive voltage + is supplied in accordance with the output of the AND4 circuit 14.
V can be applied to the drive amplifier 25, the inverting amplifier 20 is connected to the third switch 22, and AND
The normal drive negative voltage −V can be applied to the drive amplifier 25 according to the output of the five circuits 15. Further, AND3 is applied to the fourth switch 23 and the fifth switch 24, respectively.
Depending on the outputs of the circuit 13 and the AND2 circuit 12, the startup positive voltage + V _REF, which is a predetermined voltage close to or the highest voltage that can be applied to the motor 27 at a voltage higher than the normal driving positive voltage + V and the normal driving negative voltage −V. The start-up negative voltage −V _REF can be applied to the drive amplifier 25.

Further, the output of the drive amplifier 25 is applied to the motor 27 via the motor drive circuit 26, and is rotated in a direction according to its polarity and at a speed according to its size.

Now, the operation of this motor start circuit will be described with reference to FIGS. As an initial condition, it is assumed that in the closest past, the-direction switch 2 was operated to drive in the-direction.

First, when the + direction switch 1 is turned on,
The output of the OR circuit 5 becomes "H", the first switch 6 is turned off, and the first switch 6 is opened. Then, the output of the integrator 7 is −
It is charged in the direction of 15V. The output of the integrator 7 is charged to + 15V through the inverting amplifier 8 and the potential at the point A becomes as shown in FIG.

The potential at the point A is connected to the minus terminal of the comparator 9 while gradually increasing after the + direction switch 1 is turned on. On the other hand, the normal drive positive voltage + V set based on the magnification information and the like is input to the + terminal (point B) of the comparator 9, the potential at point A and the potential at point B are compared, and after the power of the device is turned on. Until the potential at point A reaches the potential at point B,
The potential of the point C which is the output of the comparator 9 is "H",
After the potential at point A reaches the potential at point B, the potential at point C becomes "L".

On the other hand, the output of the polarity inversion detection circuit 10 is −
Since the directional switch 2 is switched to the + direction switch 1, it becomes "H" immediately after the + direction switch 1 is pressed, and "H" continues during that period. Therefore, as shown in FIG. 2, the potential at the point D, which is the output of the AND1 circuit 11 that ANDs the potential at the point C and the output of the polarity reversal detection circuit 10, is immediately after switching from the − direction switch 2 to the + direction switch 1. To A
It becomes "H" only for a certain period until the potential at the point reaches the potential at the point B. During this fixed period, the OP of the integrator 7
By adjusting the value of the resistor VR1 connected to the input of the amplifier, it can be adjusted to absorb the backlash variation of each device. It can also be adjusted according to the magnification of the electron microscope.

While the + direction switch 1 is on and the output of the AND1 circuit 11 is "H", the output of the AND3 circuit 13 is "H", and the startup positive voltage + V _REF is applied to the drive amplifier 25 of the motor 27. .

When the potential at point A exceeds the potential at point B, the potential at point C becomes "L" and the potential at point D also becomes "L". Therefore, this time, the output of the AND4 circuit 14 becomes "H" until the + direction switch 1 is turned off, and the normal drive positive voltage + V set based on the magnification information and the like is applied to the drive amplifier 25 of the motor 27.

Next, when the + direction switch 1 is turned off and the + direction switch 1 is pressed again, this time the same switch is pressed twice in succession, so the output of the polarity reversal detection circuit 10 is "L". However, the potential at the point D remains “L”. Therefore, while pressing the + direction switch 1, AN
The output of the D4 circuit 14 becomes "H", and the normal drive positive voltage + V is applied to the drive amplifier 25 of the motor 27.

Next, when the-direction switch 2 is pushed, the potential at the point A rises immediately after the-direction switch 2 is pushed, and the potential at the point C becomes "H" until the potential at the point B is reached.
Since the output of the polarity reversal detection circuit 10 is switched from the + direction switch 1 to the − direction switch 2, the output becomes “H” immediately after the − direction switch 2 is pressed, and “H” continues during that period. Therefore, as shown in FIG. 2, the potential at point D is +
It becomes "H" only for a certain period from immediately after switching from the direction switch 1 to the-direction switch 2 until the potential at the point A reaches the potential at the point B. Therefore, this time, the output of the AND2 circuit 12 becomes "H", and the drive amplifier 2 of the motor 27
A start-up negative voltage -V _REF is applied to 5.

When the potential at point A exceeds the potential at point B, the potential at point C becomes "L" and the potential at point D also becomes "L". Therefore, this time, the output of the AND5 circuit 15 becomes “H” until the −direction switch 2 is turned off, and the normal drive negative voltage −V set based on the magnification information or the like is applied to the drive amplifier 25 of the motor 27. .

Next, when the minus direction switch 2 is turned off and the minus direction switch 2 is pushed again, the same switch is pushed twice this time, so that the output of the polarity reversal detection circuit 10 is "L". However, the potential at the point D remains “L”. Therefore, while pressing the-direction switch 2, AN
The output of the D5 circuit 15 becomes "H", and the normal drive positive voltage + V is applied to the drive amplifier 25 of the motor 27.

Now, another example of the polarity inversion detection circuit 10 which operates as shown in FIG. 2 will be described. FIG.
Is a circuit diagram of an example thereof, and FIG. 4 is a timing chart showing its operation. 3, 31 and 32 are inverter circuits (or NOT circuits), 33 and 36 are commercially available flip-flops called 74HC74, and FIG.
It has an equivalent circuit as shown in FIG. 5A and a truth table as shown in FIG. 5B (“transistor technology”).
(May 1986) pp. 362-364). 34 is E
An XOR circuit, 35 is a delay circuit, and 37 is an OR circuit.

Outputs from the positive direction switch 1 and the negative direction switch 2 of FIG. 1 which have passed through the inverter circuits 3 and 4 are connected to the preset terminal P and the reset terminal CR of the flip-flop 33 via the inverter circuits 31 and 32, respectively. Therefore, +5 is applied to the data terminal D of the flip-flop 33.
It is connected to the V power supply and its clock terminal CK is grounded. The output Q of the flip-flop 33 is branched into two, one of which is connected to one input of the EXOR circuit 34, and the other of which is connected to the other input of the EXOR circuit 34 via the delay circuit 35. The output of the EXOR circuit 34 is connected to the clock terminal CK of another flip-flop 36.
On the other hand, the output from the + direction switch 1 and the − direction switch 2 via the inverter circuits 3 and 4 is connected to the input of the OR circuit 37, and the output of the OR circuit 37 is connected to the reset terminal CR of the flip-flop 36. The preset terminal P and the data terminal D of the flip-flop 36 are connected to the + 5V power source. The output Q of the flip-flop 36 is connected to one input of the AND1 circuit 11 shown in FIG.

Therefore, as shown in FIG. 4, the -direction switch 2 is pressed in the closest past, and the flip-flop 3
When "L" is input to the reset terminal CR of the flip-flop 33 and the output Q (point) of the flip-flop 33 is "L", the + direction switch 1 is pressed this time and the preset terminal P of the flip-flop 33 is " When L "is input, the output Q (point) of the flip-flop 33 changes to" H ". This output is divided into two, and one is directly input to the EXOR circuit 34,
The other one passes through the delay circuit 35 and after a little delay, the EXOR circuit 34.
Input to the output Q (
When the point) changes from “L” to “H”, the delay circuit 3
A pulse having a time width corresponding to the delay time of 5 is generated at the output (point) of the EXOR circuit 34 and input to the clock terminal CK of the flip-flop 36. At this time, the "H" output of the + direction switch 1 is input to the reset terminal CR of the flip-flop 36 via the OR circuit 37 (point), so that the output pulse of the EXOR circuit 34 rises at the instant when the output pulse of the flip-flop 36 rises. The output Q (point) changes from "L" to "H". The "H" state continues while the + direction switch 1 is continuously pressed. Then +
When the direction switch 1 is released, "L" is input to the reset terminal CR of the flip-flop 36, so that the output Q (point) of the flip-flop 36 becomes "L".

Next, when the + direction switch 1 is pressed again, the output Q (point) of the flip-flop 33 remains in the "H" state, and this time the output of the EXOR circuit 34 (
No pulse is generated at (point), and the output Q (point) of the flip-flop 36 remains "L".

Then, when the-direction switch 2 is pushed, the output Q (point) of the flip-flop 33 is "H" till then.
Since the state changes to the “L” state, a pulse is generated at the output (point) of the EXOR circuit 34 at the moment of the change and is input to the clock terminal CK of the flip-flop 36. At this time, the "H" output of the-direction switch 2 is the OR circuit 37.
(Point) reset terminal C of flip-flop 36
Since the signal is input to R, the output Q () of the flip-flop 36 is output at the moment when the output pulse of the EXOR circuit 34 rises.
Point) changes from "L" to "H". Then, the "H" state continues while the negative direction switch 2 is continuously pressed. After that, when the −direction switch 2 is released, “L” is input to the reset terminal CR of the flip-flop 36, so that the output Q (point) of the flip-flop 36 becomes “L”.

Next, when the-direction switch 2 is pressed again, the output Q (point) of the flip-flop 33 remains in the "L" state, and this time the output of the EXOR circuit 34 (
No pulse is generated at (point), and the output Q (point) of the flip-flop 36 remains "L".

As described above, according to the motor start circuit of the present invention, the start-up voltage V that is higher than the normal drive voltage V for a predetermined period is provided only when the motor is driven in the opposite direction to the previous drive direction. _{Since REF} is applied, it is possible to reduce the time lag until the start of the actual operation of the drive target due to mechanical backlash or the like. In addition, the normal drive voltage V is adjusted according to the magnification of the electron microscope so that the rotation speed of the motor can be adjusted to the magnification, so that the drive speed is relatively slow when the magnification is high and low when the magnification is low. It is possible to make the observer feel a sense of incongruity in the adjustment speed by making it relatively faster than.

Although the motor start circuit of the present invention has been described based on the embodiments, the present invention is not limited to the embodiments and various modifications can be made. Further, the motor start circuit of the present invention can be used not only as a motor drive circuit for moving and adjusting a sample stage of an electron microscope but also as a start circuit for other motors.

[0034]

As is apparent from the above description, according to the motor start circuit of the present invention, the normal drive voltage is kept higher than the normal drive voltage for a predetermined period only at the rising time when the motor is driven in the direction opposite to the previous drive direction. Since a high start-up voltage is applied, it is possible to reduce the time lag until the start of the actual operation of the drive target due to mechanical backlash or the like. In addition, the startup voltage application time and the normal drive voltage are adjusted according to the magnification of the electron microscope so that the drive speed of the motor can be adjusted to the magnification so that the observer does not feel uncomfortable with the adjustment speed. Can be

[Brief description of drawings]

FIG. 1 is a circuit diagram of a motor start circuit according to an embodiment of the present invention.

FIG. 2 is a timing chart showing the operation of the motor start circuit of FIG.

FIG. 3 is a circuit diagram of an example of a polarity inversion detection circuit.

FIG. 4 is a timing chart showing the operation of the polarity inversion detection circuit of FIG.

5 is a diagram showing an equivalent circuit of the flip-flop used in FIG. 3 and a truth table.

[Explanation of symbols]

 1 ... + direction switch 2 ...- direction switch 3,4 ... inverter circuit (or NOT circuit) 5 ... OR circuit 6 ... first switch 7 ... integrator 8 ... inversion amplifier 9 ... comparator 10 ... polarity inversion detection circuit 11 ... AND1 Circuits 12-15 ... AND2-5 circuits 16 ... Inverter circuit (or NOT circuit) 17 ... CPU 18 ... Digital / analog converter 19 ... Amplifier 20 ... Inversion amplifier 21-24 ... Second to fifth switch 25 ... Drive amplifier 26 ... Motor drive circuit 27 ... Motor 31, 32 ... Inverter circuit (or NOT circuit) 33, 36 ... Flip-flop 34 ... EXOR circuit 35 ... Delay circuit 37 ... OR circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuo Nakagawa 3-1-2 Musashino, Akishima-shi, Tokyo Nippon Electric Co., Ltd. (72) Inventor Yu Ishibashi 3-1-2 Musashino, Akishima-shi, Tokyo Japan Electronic Co., Ltd.

Claims (3)

[Claims] 1. A motor start circuit for a motor capable of bidirectionally driving by changing the polarity of an applied voltage, comprising two switches for driving each direction, and the above-mentioned two switches that have been turned on in the nearest past. One of the two switches, and a polarity reversal detection circuit that stores any one of the two switches and determines whether or not the currently turned-on switch and the stored switch match. When the timing circuit that generates a signal after a predetermined period of time after the switch is turned on and the polarity reversal detection circuit detect that the switches match, the closing switch is turned on after the current switch is turned on until it is released. When a predetermined normal drive voltage of the corresponding polarity is applied and the polarity reversal detection circuit detects that the switches do not match, the clock circuit generates a signal after the current switch is turned on. Until that time, a startup voltage having a polarity corresponding to the closing switch and higher than the normal drive voltage is applied, and the closing switch is released after the signal is generated by the timing circuit. And a motor drive voltage selection circuit for applying the normal drive voltage having a polarity corresponding to the motor start circuit. 2. The motor start circuit according to claim 1, wherein the time until the time counting circuit outputs the signal is adjustable. 3. The motor start circuit according to claim 1, wherein the normal drive voltage applied by the motor drive voltage selection circuit is adjustable.