JPS6110981A - Rotating speed controlling circuit - Google Patents

Abstract

PURPOSE:To obtain a rotating speed control circuit which is affected by the variations in a load and environmental conditions by composing a speed feedback circuit of a rotating speed loop of a rotating speed detector, a rotating speed discriminator and a voltage generator for generating a voltage rising or falling as time. CONSTITUTION:A rotating speed discriminator 4 inputs a signal 40 outputted from a rotating speed detector 3, and outputs a signal 48 when the rotating speed is the lower limit or lower of an allowable range of a reference speed, a signal 49 when in the allowable range, and a signal 50 when the upper limit or higher of the allowable range. A voltage generator 5 supplies a voltage rising as time when the signal 48 is inputted, a voltage fallings as time when the signal 50 is inputted, and the voltage at that time to a drive amplifier 1 when the signal 49 is input.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a circuit for controlling the rotation speed of a DC motor, and is applied to a rotation servo system for a small DC motor.

[Technical background of the invention and its problems]

Many small electric motors are used in various devices such as VTRs.Specially, this small DC motor is known for its excellent response, efficiency, low power consumption, and low gastric pressure. It has many advantages, such as being able to be used with a DC power source and being easily combined on semiconductor electronic circuits.

Therefore, many small DC motors are used in various types of equipment such as VTRs. These electric motors are required to rotate accurately at a rotation speed that corresponds to the reference frequency and snow pressure, or at a rotation phase that corresponds to the reference signal phase. - Rotation phase control servo (rotation is controlled by this).

The rotational speed control system is composed of 5 rotational speed loops, so even if the load on the sensor fluctuates, the rotational speed will deviate significantly from the standard rotational speed. Always make corrections so that the rotational phase does not change.Rotational phase control → In most cases, the rotational speed is 1liIJi. When things change due to unknown reasons,
It is assumed that 4 = semi-rotational speed (reduced to 1), and at startup (here, even if load fluctuation is 3, the capture range of 1 loop (capture range i: 11 )
The goal is to increase the rotational speed to a maximum of 20%.

When there is a load fluctuation in the rotational speed and the degree of rotation, a deviation occurs between the reference rotational speed and the actual rotational speed, and the deviation is inversely proportional to the open loop gain. If the open loop gain of the servo is increased by 1 over the entire band in order to suppress this deviation, the servo characteristics will enter an unstable region. It is desirable to do so.

However, changes in environmental conditions such as temperature and humidity.

Alternatively, in response to load fluctuations, sufficient open loop gain of the speed control loop is required to raise and maintain the rotational speed of the first flow section motor at a reference speed, but this is not always possible with the conventional rotational speed control loop. However, it could not be said that sufficient open loop gain was obtained.

[Purpose of the invention]

The purpose of this invention is to develop a rotational speed control circuit which has an infinite open loop gain and is unaffected by changes in load and environmental conditions, thereby improving the performance of a rotating servo system for a DC motor. Our goal is to provide the following.

[Summary of the invention]

The feature of the present invention is that the rotational speed i1+1) r of the DC electric current a
The speed feedback circuit of the wholesale circuit is composed of a rotation speed detector, a rotation speed discriminator, and a voltage generator that generates a voltage that increases with time or a voltage that decreases with time.

The rotation, 17 degree detector converts the rotational speed of the DC motor into %.This can be done using the conventional tachometer, a combination of a tachometer and a frequency discriminator, or a tachometer and a frequency-voltage conversion circuit. (F-V conversion circuit), etc. are used. Alternatively, a circuit for extracting the back electromotive force of the DC III/I machine may be used as the rotational speed detector.

The rotational speed discriminator determines whether the rotational speed of the DC motor is higher or lower than a reference speed.

In addition, when a permissible range is set for the rotational speed of the DC current #J rock, in addition to determining whether the rotational speed is high or low (2 (1σ)), it is also determined whether the rotational speed is within the permissible range.

The 1-pressure pressure generator performs the operation 3a in response to a three-value signal from the rotational speed discriminator. In other words, when the rotation speed discriminator determines that the rotation speed is low, it generates a voltage that increases over time, and when it determines that the rotation speed is high, it generates an α pressure that decreases over time. Sometimes, it works to freeze the voltage generated at that point and maintain that state.

〔Effect of the invention〕

This operation of the voltage generator is an integral operation with respect to the rotational speed information of the +M current IHb machine, which gives an extremely large open-loop gain in the low frequency range, resulting in a low sensitivity to load fluctuations and changes in environmental conditions. This makes it possible to reliably bring the rotation speed of the DC motor closer to the reference speed. When the rotational control of a DC motor is performed not only by loose rotational speed control but also by a rotational phase control loop, the rotational speed control circuit according to the present invention
Demonstrates the ability to reliably capture the rotational speed within the capture range of the phase loop.

[Embodiment 1 of the invention] FIG. 1 is a system diagram of an embodiment of the present invention.

In FIG. 1, a DC motor 2 is driven by a drive amplifier 11, and its rotational speed is converted into voltage by a rotational speed detector 3.
Combination of tachometer and frequency oscillator,
Or a tachometer and frequency-voltage conversion circuit (F'-V
conversion circuit) etc. are used. However, in this first embodiment, a circuit for extracting the back electromotive force of a DC motor, which has the simplest configuration, is used as shown in a 2 and z c. In FIG. 2, reference numeral 3 denotes a rotational speed detector which obtains rotational speed information by extracting the back-electromotive force of the DC motor. The DC motor 2 is driven by a voltage with a drive width 51 and rotates. At this time, the internal impedance 21 of the Iα current motor is set to rm.

(Resistance 33, 31.32 in combination with amplifier 34
When re, R1, and R1 are respectively expressed, a voltage of KeW proportional to the rotational speed is extracted from the output of the operational amplifier 34 under the conditions of the following formula. Here, KE is the back electromotive force constant of the DC-motor 2, and W is the rotational angular velocity.

The rotational speed detector includes two sets of voltage comparators 43, 44 and poor gate circuits 45 and 46, as shown in FIG.

Consists of 47. The voltage that determines the upper limit of the allowable range of the standard speed is applied to the non-inverting input of the load ratio i11 and the terminal 43.
Through the terminal 40, a voltage having rotational speed information obtained from the rotational speed detector is applied to the inverting input. If the rotational speed wave is higher than the upper limit of the allowable range of the reference speed, the voltage comparator 43 outputs a low level voltage, and if the rotational speed is less than the upper limit of the allowable range of the reference speed, the voltage comparator 43 A high level voltage is obtained from the output of 43.

In voltage comparator 44, a contrasting connection is made to voltage comparator 43. Immediately, a voltage determining the lower limit of the allowable range of the reference speed is applied to the inverting input through the terminal 42,
In addition, to its non-inverting input, a voltage representing the rotation speed information is applied through a terminal 40. If the rotation speed is higher than the lower limit of the allowable range of the reference speed, the voltage comparator 44
A high level voltage is applied to the output of the motor, and a low level voltage is applied to the output if the rotational speed is below the lower limit of the allowable range of the reference speed. Table 1 below shows these conditions W.

Table 1 In Table 1, the output levels of the two voltage comparators 43 and 44 are indicated by 1 for high level voltage and 0 for low level voltage. As seen from Table 1, 2
By combining the output signals of the two heavy pressure comparators 43 and 44, the state of the rotational speed can be determined and presented as three pieces of information. Nantes Gate 45, 46
, 47] w8I\L sum is the voltage comparator 43,
It receives the output of 44 and generates three pieces of information. That is, when the rotation speed is small, the output of the gate 46 is at a low level, when the rotation speed is within the allowable range of the reference speed, the output of the gate 45 is at a low level, and when the rotation speed is high, the output of the gate 47 is at a low level. Become. These three pieces of information are the terminal 48°49.50
The voltage is extracted from the voltage generator and sent to the voltage generator.

FIG. 4 is a system diagram of the voltage generator of the embodiment.

Fig. 4 shows the drive multiplier 1 which has been explained so far.
゜DC motor 22 rotation speed detector 32 rotation speed discriminator 4
In addition, part of the phase loop is also depicted.

As shown in FIG. 4, the voltage generator 5 is connected to a delay circuit 510.
, gate circuits 511, 512, 513 . counter 51D
It is composed of an A converter 52 and a current/current-voltage conversion amplifier 53. When the DC motor 2 is in a stopped state,
Counter 51 is in a loaded state, and the data applied to terminal 550 is set.

As this data, a value is selected in which 1* degree of rotation of the DC motor corresponds to the reference speed. The set state of the counter is canceled by a signal obtained by delaying the start signal of the DC motor 1 applied to the terminal 10 by the delay circuit 510, and the counter 51 becomes in a state capable of counting. A starting signal for the DC motor 1 applied to the terminal 10 is also directly connected to the drive amplifier 1, and the DC motor 1 starts rotating as soon as the signal is applied. The delay circuit 10 provides a delay time approximately equal to the time required for the DC motor 1 to reach the reference rotational speed corresponding to the data set by the counter 514 from a stopped state. The counter 51 performs three types of operations based on three status signals obtained from the terminals 48, 49, and 50 of the rotational speed discriminator 40.

First, when the rotational speed is smaller than the reference speed, a low level signal is output from the terminal 48 of the rotational speed discriminator 40, and this signal turns off the gate 512E.

In this case, the other output terminals 49 and 5 of the rotational speed discriminator 40
0 is a high level and turns on gates 511 and 513. A signal from a clock signal generator (not shown) is connected to a terminal 570 of the voltage generator 5, and this clock signal is applied to the up-count input of the counter 51 through gates 511 and 513, which are in the on state. 51 increases its data value by one each time each clock pulse is input. Further, when the rotation speed is higher than the reference speed limit, a low level signal is output from the terminal 50 of the rotation speed discriminator 1 40, and this signal turns the gate 513 into the OFF state IW. - In this case, the other output terminals 48 and 49 of the rotation speed discriminator 40 are at a high level, turning on the gate 511 and the gate 5]2. The clock signal is applied to the down-count power of the counter 51 through these gates 511 and 512 which are on rd, and the counter 51 decrements its data value by one each time each clock pulse is input. The rotation speed is the rotation speed discriminator 4.
If the voltage applied to terminals 41 and 42 of 0 is within the allowable range, output terminal 49 of rotation speed discriminator 40
is the low level l and turns off the gate 511.

As a result, the clock signal is no longer applied to the counter 511, and the counter 51 stops counting, but the immediately preceding data of the counter 51 remains held. Data output 560 of counter 51
The A converter converts it into an analog current. Note that the amplifier 53 converts the output current of the DA converter into a voltage. The output of the amplifier 53 is further amplified by the amplifier 7 and applied to the drive amplifier 1.

The configuration described above, drive amplifier 1. DC motor 2° rotation speed detector 31 rotation speed discriminator 40. Voltage generator5. forms a rotational speed ft1t control circuit, and this loop maintains the DC motor 2 regardless of load fluctuations or changes in environmental conditions.
The rotational speed of the input terminals 41 and 42 of the rotational speed discriminator 40
It has the ability to reliably draw within the permissible range determined by the voltage applied to it.

This 11. 'When the rotation howling is slow, the voltage generator 5 generates a voltage that increases with time, and vice versa (when the rotation speed is fast, it generates a voltage that decreases with time.) This is because it has an infinitely large DC open loop gain.

Note that the frequency of the clock signal applied to the terminal 570 of the voltage generator 5 is selected to be the frequency that provides the best response characteristics of the rotational speed control circuit.

FIG. 4 also shows the phase shift control loop.The phase comparator 6 has two inputs, which determine the rotational phase of the DC electric car 2, which is not shown in FIG. The signal from the basic signal generator is connected to the terminal 61i, and the DC motor 2
The rotational phase of the tachometer pulse generator 20 is added to perform a phase comparison. The phase A&i=- output of this phase comparator 6 is given to an analog switch 60. The analog switch 60 is activated when the rotational speed discriminator 40 determines that the rotational speed is within the allowable range 1111, and the output is rejected; One input of the width filter 7 is transmitted. In this case, the allowable range determined by the voltages applied to the input terminals 41 and 421 of the rotational speed discriminator 40 is set narrower than the capture range of the rotational phase loop.

As a result, even if load fluctuations or changes in environmental conditions occur, it is possible to overcome them and reliably bring the rotational speed into the capture range of the rotational phase loop.

[Brief explanation of drawings]

Fig. 1 is a system diagram of an embodiment of the present invention; Fig. 2 is a circuit diagram showing a specific example of a rotation speed detector; Fig. 3 is a circuit diagram showing a specific example of a rotation speed discriminator; FIG. 4 is a more detailed system diagram of the embodiment. 1. Drive south center": g s 2.. Direct current 'buzzer', 3
...Rotation speed detector, 4...Rotation speed discriminator, 5...
voltage generator. Proxy Bench 14 + 4 Proxy Kensuke Chika (and 1 other person) Figure 1 6/, Otsu? Figure 2 Figure 8

Claims (2)

[Claims] (1) In a rotational speed control circuit for a DC motor, which is composed of a drive amplifier, a DC motor, and a speed feedback circuit, a rotational speed detector detects the rotational speed of the DC motor, and a rotational speed of the DC motor is a reference speed. A speed feedback circuit includes a rotation speed discriminator that discriminates whether the rotation speed is lower or higher, and a voltage generator that generates a voltage that increases or decreases to drive the DC motor, and the rotation speed discriminator When the rotational speed of the DC motor is determined to be lower than the reference speed, the voltage generator generates a voltage that increases, and when the rotational speed of the DC motor is determined to be higher than the reference speed, the voltage generator generates a voltage that decreases. A rotational speed control circuit for a DC motor, characterized in that it generates. (2) A tolerance range is set for the reference speed of the DC motor, and when the rotation speed discriminator determines that the rotation speed of the DC motor is within the tolerance range, the voltage generated by the voltage generator is frozen at that point. A rotational speed control circuit according to claim 1, characterized in that: