JPH114974A - D.c.motor control circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the variation of responding characteristics of a d.c.motor following the fluctuation in power resource's voltage of radio control systems and such. SOLUTION: This d.c.motor control circuit is equipped with a voltage detecting part 42 to detects voltage of a power pack 40 and a control circuit part (voltage and current converting part) 43 to convert the output of this voltage detecting part 42 into current. The output of this voltage and current converting part 43 controls the gain of a stretcher circuit 44 that stretches the pulse duration of an error pulse signal. When the voltage Vcc of the power source falls away, the stretcher circuit 44 is controlled to heighten the sensitivity of the same to control the rotating speed of the motor (rotating torque of the motor) not to decrease.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC motor control circuit suitable for a radio control technology for controlling a control object at a remote point based on control data transmitted by radio waves.

[0002]

2. Description of the Related Art Radio control (hereinafter referred to as a radio control) technology is widely used as a device for controlling a device or a device that moves at a position away from a control position by carrying control information on radio waves or the like. It is common practice to steer a moving object such as a small model car or a ship as a controlled device. In particular, in the case of a high-grade radio control device that simultaneously transmits a plurality of pieces of control information, a delicate operation is required, and a DC motor that is faithfully driven in accordance with the operation is required.

FIG. 5 shows an outline of such a remote control device. Reference numeral 10 denotes a flying object 13 which is an object to be controlled.
It is a control board for manipulating, and is composed of a jog stick and various setting switches. Reference numeral 11 denotes an encoder that converts various control signals output from the control panel 10 into, for example, a pulse width, and converts these plurality of control signals into a pulse train that is completed at a predetermined frame period and outputs the pulse train. The pulse train of one frame unit completed at a predetermined cycle is constantly transmitted to the high-frequency unit 12 (transmitting unit) during steering.
, And for example, an AM-modulated or FM-modulated radio wave is transmitted to the flying object 13.

FIG. 6 shows a pattern of a pulse train completed in a frame unit as described above.
3 direction rotation control, ascent / descent control, speed control,
Other control signals are channels 1, 2, 3, 4,...
Are converted into pulse signals CH1, CH2, CH3, CH4,..., And a pulse train is repeated in one frame, for example, 14 mS to 20 mS. To describe this in more detail, the interval P of the pulse signals CH1, CH2, CH3,.
.. are arranged so as to change according to a plurality of pieces of control information. For example, ± 600 μS (a control rotation angle of about 6
0 degree), and finally a 5 mS synchronization signal (space) to indicate the end point of one frame
Is caused to occur.

[0005] Control information of this type is constantly transmitted to the flying object 13 by radio waves. The flying object 13 on the receiving side receives the received radio wave by, for example, a W superheterodyne receiver, performs processing of the received signal by a decoder, and thereby demodulates a control signal transmitted from an operator on the transmitting side. The control signal of each channel is separated and supplied to its own control servomotor or actuator.

FIG. 7 (a) shows an outline of a decoder for separating and outputting a control signal of each channel from a series of demodulated pulse train signals (PPM). A reset circuit for generating an output, 22,
23, 24, 25,... Are D flip-flop circuits (referred to as DFFs). Demodulated pulse train signal PP
M is each of the DFFs 2, 22, 2 constituting the shift register.
3, 24... Are supplied to the reset circuit 21. When detecting an L level period of about 5 ms in the pulse train signal PPM, the reset circuit 21 generates a reset signal whose output becomes high level, and the signal is output to the first-stage shift register DFF2.
2 D inputs. Then, the subsequent pulses are sequentially transferred to the shift register, and as shown in FIG.
Control pulse signals CH1, CH2, CH3, CH4,... Corresponding to the pulse intervals of the pulse train signal PPM whose pulse positions have been modulated as shown in the waveform diagram of FIG. You.

The control pulse signal of each channel detected by the decoder as described above is injected into a servo circuit of each control means (DC motor, actuator, etc.) of the controlled device, and responds to the operation by the operator. Control is performed. FIG. 8 shows a motor control circuit of a servo system, and the signal waveform of each block is shown by waveforms A, B, C, D, E, and F in FIG. As shown in this figure, the extracted control pulse signal A of channel i, for example, is output from the comparison circuit 31 every frame period.
Supplied to

The comparison circuit 31 includes a pair of inverters IN
1 and IN2, NOR circuits NR1 and NR2, and an OR gate OR1. The position pulse signal B output from the position signal generation circuit 39 is compared with the pulse width of the received control pulse A. Then, the comparison output is output from the OR circuit OR1 as an error pulse signal C, and triggers the next dead pulse signal generation circuit 32 to generate a dead pulse signal D. If the error pulse signal C1 is smaller than the dead pulse signal D, In the case of (C2), a signal is not output from the second comparison circuit 33 and the stretcher circuit 34, thereby preventing a malfunction due to noise.

The signal E output from the second comparison circuit 33
In the next stretcher circuit 34, the pulse width is expanded at a predetermined rate in the stretcher circuit 34, and the expanded drive pulse signal F forms the drive voltage of the motor M to be controlled via the rotation direction switching circuit 35, and the drive circuit 37 Supplied to The outputs of the NOR circuits NR1 and NR2 of the comparison circuit 31 are input to the S and R terminals of a flip-flop circuit (FF) 36, and the FF circuit is determined by the pulse widths of the control pulse signal A and the position pulse signal B. Invert the output of 36,
The rotation direction of the motor M is determined by opening and closing the AND gates AD1 and AD2 of the rotation direction switching circuit 35.

That is, the rotation direction switching circuit 35 changes the rotation direction of the motor according to which direction the control pulse signal A controls the current control position of the motor. When the current position pulse signal B obtained from the signal generation circuit 39 is smaller than the pulse width of the control pulse signal A, the rotation direction of the motor is rotated forward by the error pulse signal C1 in FIG. Is generated, and the AND gates AD1. Control is performed to switch AD2.

In this embodiment, the control object 38 is a DC motor M, a gear mechanism GA for reducing and transmitting the rotational torque, and a potentiometer PM for detecting a rotational position.
The potentiometer PM
Indicates the control position (rotation angle). The potentiometer P indicating the control position
The M output signal is pulse width modulated by the position signal generation circuit 39 to form a position pulse B, and the pulse width of the error pulse signal C when comparing the position pulse signal B with the control pulse signal A is expanded. Drive pulse signal F
By driving the motor, a servo motor control circuit based on the control pulse signal A is constructed.

[0012]

In the control circuit having the servo system as described above, the motor M can ideally achieve a control operation equal to the pulse width of the control pulse signal A indicating the target value. Since the power source for driving the motor M is generally a relatively small rechargeable battery or dry battery, its terminal voltage decreases with the passage of time, and the same amount of control performed on the transmitter side is performed. In different ways. In particular, in the radio control device, the rotation speed of the motor tends to decrease with the lapse of the maneuvering time with respect to the rotation speed of the motor when the initial power supply voltage is high,
There is a problem that the feeling of torque for a delicate operation near the neutral position disappears, and the maneuverability becomes uncomfortable.

[0013]

SUMMARY OF THE INVENTION A DC motor control circuit according to the present invention has been made in order to solve such a problem, and comprises a control pulse signal supplied at a predetermined cycle and a DC motor control signal. A DC motor comprising: comparing means for comparing a position pulse signal indicating a control position; a pulse stretcher for amplifying a servo error signal output from the comparing means; and means for supplying an output of the pulse stretcher to the control motor. A control circuit for controlling the pulse stretcher based on an output of the voltage detection means and a voltage detection means for detecting a power supply voltage supplied to the DC motor control circuit; The gain of the stretcher circuit is increased.

Since the present invention is configured so that the drive voltage of the motor changes in conjunction with the power supply voltage as described above, when a small battery is used as the power supply,
In a large-sized remote control device, the rotation speed and torque of a DC motor of a device that consumes a large amount of power can be prevented from greatly changing.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a circuit diagram showing a main part of the DC motor control circuit shown above related to the present invention. In this figure, reference numeral 40 denotes a battery pack made of a dry battery or a rechargeable CADNICA battery or the like. One terminal (+) of the battery pack is used as a power source for each part of the servo motor control circuit via a filter circuit 41 for removing noise. Only the stretcher circuit described above is described as a circuit related to the present invention. 42 is a voltage detecting unit for detecting the output voltage of the battery pack 40, 43 is a control circuit unit for converting the output signal of the voltage detecting unit 42 into a current and supplying a control current, and 44 corresponds to the aforementioned stretcher circuit (34). FIG.

The filter circuit 41 is a π-type low-pass filter composed of a coil Lf and a capacitor Cf, and removes high-frequency noise mixed from the outside, but this circuit is not always necessary. The voltage detector 42 includes a resistor R0 for forming a reference voltage, and a Zener diode D
Z, a reference voltage circuit, a resistor R1, and a resistor R2.
And two differential amplifiers DA1 and DA
2, and the gains of these differential amplifiers DA1 and DA2 are set by resistors R3 to R7. Then, as shown in FIG. 2, the voltage Vin divided and input by the resistors R1 and R2 is compared with the voltage VZ using the Zener diode DZ as a reference voltage. The characteristic is such as to output from DA2.

The control circuit 43 includes transistors Q1, Q
2, a voltage-current conversion circuit configured to draw the current i set by the input voltage Vout. That is, since the transistors Q2 and Q3 are in a current mirror connection, the current i = (V
out-2Vbe) / Rx is drawn from the next stretcher circuit 44. (However, Vbe is the voltage between the base and the emitter of the transistor.) The stretcher circuit 44 includes a resistor R charged by the constant current source I.
And a capacitor C, a transistor Q4 for discharging the time constant circuit of the resistor R and the capacitor C, and a transistor Q5 for outputting an output pulse having an increased pulse width, and the error pulse input to the transistor Q4. This has the effect of expanding the pulse width of the signal C.

That is, as shown in the waveform diagram of FIG. 3, when the error pulse signal C is input and the transistor Q4 is off, a voltage of about 0.7 V is applied to the base voltage VB of the transistor Q5. As for the collector voltage of the transistor Q5, a low level signal VC is output when this transistor is turned on. When the error pulse signal C turns on the transistor Q4,
When the base voltage VB of the transistor Q5 becomes zero and becomes nonconductive, its output is inverted to a high level. However, when the pulse period t of the error pulse signal C ends, the capacitor C is charged by the constant current source I. When the capacitor C is charged to a predetermined voltage, the transistor Q5 is turned on again to form a drive pulse F having an increased pulse width.

The pulse width T of the drive pulse F is set by the charging current value I0 of the capacitor C and the constant current source I. The error pulse signal C is a period when the transistor Q4 is on. Also depends on the pulse width t. That is, the pulse width t of the error pulse signal C
Is small, the decrease in the potential of the terminal voltage CV of the capacitor C discharged by the resistor R and the transistor Q4 is small. Therefore, after the discharge time is over, the potential of the capacitor C recovers earlier, but when the pulse width t of the error pulse signal C is wide, the terminal voltage CV is greatly reduced due to the discharge of the capacitor C. In addition, the time required for the transistor Q5 to recover to a potential at which the transistor Q5 is turned on becomes longer.

When the current i drawn from the control circuit 43 increases, the capacitor C and the resistor R are charged by the current obtained by subtracting the current i from the charging current I0, as shown by the dashed line. Even if the pulse width t of the error pulse signal C is the same, the pulse width of the drive pulse F increases and the sensitivity of the stretcher circuit 44 increases. Thus, the stretcher circuit 44
Has the function of expanding the pulse width of the error pulse signal C and outputting the drive pulse signal F.

As described above, according to the DC motor control circuit of the present invention, when the voltage detector 42 detects a voltage drop of the battery pack 40, the output Vout is controlled so as to increase as shown in FIG. As a result, the drawn current i of the voltage-current converter 43 increases. Then, the capacitor C is charged from the constant current source I by a current smaller by the drawn current i. As a result, when the terminal voltage Vcc of the battery pack 40 decreases, the output pulse width of the stretcher circuit 44 increases ( The sensitivity of the stretcher circuit increases)
It is possible to compensate for a decrease in the rotation speed of the motor.

The voltage detecting section 42 can be constituted by one differential amplifier DA3 as shown in FIG. 4 in addition to the embodiment. In this circuit, several mΩ to several tens mΩ for the power supply line that supplies current to the servo motor control circuit
And a potential difference AB generated between both ends of the sense resistor RS is detected by the next differential amplifier DA3 to form a detection voltage Vout. The detection voltage Vout acts to increase when the rotational load of the motor increases for some reason and the rotational speed decreases. Therefore, if the detection voltage Vout output from the voltage detection unit 42 in FIG. 4 is supplied to the voltage-current conversion unit 43 in FIG. 1 to set the sensitivity of the stretcher circuit 44, the motor Can be controlled so that the rotation speed does not decrease when the voltage drop increases due to an increase in the load on the vehicle, and the controllability of the radio control can be improved.

[0023]

As described above, the DC motor control circuit of the present invention can cover the fact that the responsiveness of the motor changes due to the fluctuation of the power supply voltage for driving the motor, by the DC motor control circuit. In addition, there is an effect that stable motor control can be performed for a relatively long time using a battery pack. Further, even when the voltage of the power supply line applied to the motor decreases for some reason, control can be performed in a direction in which the response of the motor does not change. Therefore, there is an effect that the control characteristics particularly at the time immediately after the start and at the end point are stabilized, the torque near the neutral is improved, and when used in a radio control or the like, the controllability is improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a DC motor control circuit according to the present invention.

FIG. 2 is a graph illustrating a state of voltage detection in FIG.

FIG. 3 is a signal waveform diagram showing an operation of the stretcher circuit.

FIG. 4 is a circuit diagram showing a specific example of a voltage detection unit according to another embodiment of the present invention.

FIG. 5 is a general explanatory diagram of a remote control device.

FIG. 6 is a waveform diagram of a pulse train showing a control signal for a control target of a plurality of channels.

FIG. 7 is a block diagram for encoding a received control pulse and its waveform diagram.

FIG. 8 is a block diagram of a servo system that controls a control position of a control target (motor).

FIG. 9 is a waveform chart of each part of FIG.

[Explanation of symbols]

40 battery pack, 41 filter circuit, 42 voltage detector, 43 control circuit (voltage / current converter), 44 stretcher circuit

Claims (4)

[Claims] 1. A comparison means for comparing a control pulse signal supplied at a predetermined cycle with a position signal indicating a control position of a DC motor; a pulse stretcher for amplifying a servo error signal output from the comparison means; In a DC motor control circuit comprising means for supplying the output of the pulse stretcher to the DC motor, a voltage detection means for detecting a power supply voltage supplied to the DC motor control circuit, and the pulse output from the voltage detection means. A DC motor control circuit, comprising: a control circuit for controlling a stretcher, wherein a gain of the pulse stretcher is increased when the power supply voltage is reduced. 2. The DC motor control circuit according to claim 1, wherein said voltage detection means comprises a reference voltage and a comparison circuit to which a power supply voltage is applied. 3. The DC motor control circuit according to claim 1, wherein said voltage detection means comprises a circuit for detecting a voltage drop of a sense resistor inserted in a power supply line. 4. The DC motor control circuit according to claim 1, wherein the control circuit comprises a voltage-current conversion circuit.