JPH047673Y2 - - Google Patents

Description

[Detailed description of the invention] "Industrial application field" This invention relates to an automatic braking device for a motor when a DC motor without a speed generator is used in place of a servo motor equipped with a speed generator. .

"Prior Art" Servo motors are roughly divided into two types: when the drive motor is a DC motor, it is called a DC servo motor, and when the drive motor is an AC motor, it is called an AC servo motor. All of these servo motors are always equipped with a speed generator on the rotating shaft of the DC motor or AC motor, and the rotational speed signal sent from this speed generator is fed back to the servo amplifier, and this feedback signal is used to perform rapid braking at the target position. It has a structure that allows it to stop accurately at the target position without hunting.

FIG. 4 shows a conventional servo motor drive circuit.
This example shows the case of a recorder that records changes in the voltage _VX of the voltage source MV to be measured on a recording paper PA.

In the figure, SVM indicates a servo motor. As mentioned above, the servo motor SVM includes a drive motor M (which may be a DC motor or an AC motor) and a speed generator TG directly connected to the output shaft of this drive motor M.
It is composed of

A recording pen is attached to the output shaft of the drive motor M as a load.
PN and a comparison voltage generator RV are connected. The comparison voltage generator RV generally uses a slip resistor called a potentiometer, and generates a comparison voltage from the potentiometer to balance the measured voltage _V
Generate _VR .

The measured voltage V _X and the comparison voltage V _R are deviation amplifiers.
Input to DAMP and find deviation voltage V ₀ . The deviation voltage V ₀ is applied to the power amplifier PAMP through the analog adder circuit ALU, and the drive motor M is driven by the output of the power amplifier PAMP.

In other words, the drive motor M operates the comparison voltage generator RV so that the deviation voltage _V0 is always balanced at zero, records the operation amount on the recording paper PA, and records the change in the voltage to be measured _VX . works.

Here, the operation of the speed generator TG will be explained. The speed generator TG generates a voltage signal V _G which is proportional to the drive speed of the drive motor M and whose polarity is reversed depending on the direction of rotation. This voltage signal V _G is fed back to the analog adder circuit ALU as a negative feedback signal,
It is used as a braking signal for the drive motor M.

That is, when the drive motor M is rotating, the speed generator TG outputs a voltage signal V _G having a voltage value proportional to its rotation speed and a polarity determined by the rotation direction. This voltage signal V _G has a polarity that causes the drive motor M to rotate in the reverse direction, and the analog adder circuit ALU
given to. At this time, the voltage signal V _G and the deviation signal
A damping resistor DUP is inserted so that the level of V ₀ becomes V ₀ >V _G. Therefore, the rotation direction of the drive motor M is determined depending on the polarity of the deviation signal _V0 ,
The comparison voltage generator RV is operated in a direction approaching a voltage value that is balanced with the voltage to be measured _VX .

When the comparison voltage V _R approaches _the measured voltage V _X and reaches _{V R} ≒ _V continues to rotate due to inertia, so it is a speed generator
TG continues to output voltage signal V _G. Therefore, at this time, only the voltage signal V _G is supplied to the voltage amplifier PAMP, and a braking current is applied to the drive motor M to cause it to rotate in the opposite direction. The speed of the drive motor M is rapidly reduced by this braking current and is stopped almost instantaneously.

In this way, the speed generator TG is provided to give a braking signal to the drive motor M. If there is no speed generator _TG and no _braking signal is given to the drive motor _M , even if the measured voltage _V Overtravel (stopping at a position beyond the target position) occurs, and this overtravel generates a deviation voltage V ₀ in the opposite direction in the deviation amplifier DAMP, causing the drive motor M to be driven in the reverse direction.
This reverse drive causes further overshoot, and a deviation voltage is generated again with polarity V ₀ in the forward rotation direction, and this is repeated until it gradually converges to the target value (this operation is called hunting).

Therefore, in order to instantaneously stop the drive motor M at the target position, the speed generator TG is an essential component.

``Problems to be solved by the invention'' As mentioned above, the servo motor is expensive because it is equipped with a speed generator. It also has the disadvantage of being large in size. Furthermore, in order to downsize and construct a battery-driven servo device, it is conceivable to use a DC motor without a speed generator instead of a servo motor. Small-sized DC motors are also called micromotors, and small-sized DC motors are easily available at low cost. Further, since the starting torque is large, there is an advantage that a relatively large operating body can be operated.

However, if a DC motor without a speed generator is used in place of the servo motor, there is a problem that braking cannot be applied at the target position because a feedback signal from the speed generator cannot be obtained. In other words, overtravel occurs at the target position, the inversion signal causes the rotor to rotate in the opposite direction, and further overtravel occurs, causing so-called hunting to be repeated, which is not practical in this state.

``Means for solving the problem'' This invention consists of an object to be operated, a DC motor that operates the operating section of the object to change the electrical signal output from the object, and an electric signal output from the object. A comparator that compares the electrical signal and a reference signal, a differentiating circuit provided on the output side of the comparator that differentiates the deviation signal output from the comparator, and a differential output signal of the differentiating circuit and the difference signal output from the comparator. The automatic braking device is constituted by an adding circuit that adds the difference signals of the adding circuit, and a DC amplifier that amplifies the added output signal of the adding circuit and drives a DC motor using the amplified output.

According to the automatic braking device according to this invention, when the state of the operated object approaches the target value due to the drive of the DC motor, a signal obtained by differentiating this comparison output signal is added to the comparison output signal output from the comparator. It is configured to apply braking using a differential signal.

Therefore, according to this invention, braking can be applied to a DC motor simply by adding an adding circuit and a differentiating circuit.

``Example'' Figure 1 shows an example of this invention. This embodiment shows an example in which this invention is applied to an automatic tuning circuit in a direction finder, for example.

That is, 1 is a high frequency tuning circuit, 2 is a frequency mixer,
Reference numeral 3 indicates a local oscillator, and reference numeral 4 indicates an intermediate frequency amplifier, which constitute a receiving device. The local oscillator 3 is composed of a synthesizer-type oscillator, and by inputting a desired frequency value to be received from the input keyboard 5, the local oscillator 3 oscillates at a frequency higher than the desired reception frequency by an intermediate frequency.

Reference numeral 6 indicates a servo circuit that controls the tuning frequency of the high frequency tuning circuit 1. The servo circuit 6 operates to operate the operated body 7 so that the state of the operated body 7 matches the state of the local oscillator 3. In other words, this example shows a case where the operated object 7 is a variable frequency oscillator. A variable frequency element (varicon) of this variable frequency oscillator is operated by a DC motor 8 to match its oscillation frequency with the oscillation frequency of the local oscillator 3.

For this purpose, the servo circuit 6 compares the phases of the oscillation signal of the local oscillator 3 and the oscillation signal of the operated object 7 using a phase comparator 8, and smoothes the phase-compared deviation output using a reducing pass wave filter 9, thereby producing a DC signal. The preamplifier 11 performs saturated amplification, and the saturated amplified output is supplied to an adding circuit 12 and a differentiating circuit 13.

In other words, the adder circuit 12 performs an operation of adding the signal output from the preamplifier 11 and a signal obtained by differentiating this signal. The addition result of the adder circuit 12 is given to a DC amplifier 14 to drive a DC motor 15. The shaft output of the DC motor 15 is coupled to the frequency variable element of the operated object 7 and the frequency variable element of the high frequency tuning circuit 1 via a suitable speed reduction mechanism, so that the oscillation frequency of the operated object 7 and the frequency variable element of the high frequency tuning circuit 1 are adjusted. The tuning frequency is varied, the tuning frequency of the high frequency tuning circuit 1 is tuned to a frequency lower than the oscillation frequency _R of the local oscillator 3 by an amount of the intermediate frequency, and the structure is automatically tuned to receive that frequency.

(Operation) When the relationship between the oscillation frequency _R of the local oscillator 3 and the oscillation frequency _O of the operated object 7 is _R < _O , the phase comparator 8 outputs a positive pulse as shown in FIG. 2A, and _R The pulse width of the positive pulse gradually narrows as it approaches = _O , and when _R = _O , the output signal becomes zero.

On the other hand, when the relationship _R > _O exists, a negative pulse is output as shown in Figure 2B, and the pulse width of the negative pulse increases as the frequency approaches _R = _O. It gradually narrows and when _R = _O , the output signal becomes zero.

The preamplifier 11 outputs 0 volts when the voltage of the deviation signal output from the low-pass waveformer 9 is 0 volts, and in this state, the servo circuit 6 maintains a balanced state, but the low-pass waveform If 9 outputs even a slight positive or negative deviation signal (a signal obtained by smoothing the phase detection output), it saturates and amplifies the deviation signal, and applies a constant voltage close to the voltage of the power supply supplying the preamplifier 11 to its output. Output.

In other words, for example, the positive polarity deviation signal is transmitted to the preamplifier 1.
1, the preamplifier 11 outputs a constant voltage of +5V, and when a negative deviation signal is input to the preamplifier 11, the preamplifier 11 outputs a constant voltage of -5V.

This constant saturated amplified output voltage is supplied to the DC amplifier 14 through the differentiator circuit 13 and the adder circuit 12, where it is amplified to the rated drive voltage of the DC motor 15 and applied to the DC motor 15.
Therefore, while the preamplifier 11 is outputting a constant saturated amplified output voltage, the DC motor 15 is driven to rotate at the rated, that is, maximum rotational speed.

Therefore, in a certain reception state, if the oscillation frequency of the local oscillator 3 is changed to a lower frequency than the frequency at which it has been oscillating, the relationship _R < _O will result. For this reason, the phase comparator 8 outputs a pulse of positive polarity as shown in FIG. The signal is saturated and amplified and supplied to the adder circuit 12 and the differentiator circuit 13. Figure 3 shows preamplifier 1.
1 output signal A and differential output signal B of the differential circuit 13
An example is shown below. When the oscillation frequency _R of the local oscillator 3 is changed to a lower frequency ( _R < _O ) than the previously oscillating frequency at time t ₀ shown in FIG. 3, the preamplifier 11 changes to the positive polarity shown in FIG. A voltage signal A is output.

The rise of this positive voltage signal A drives the DC motor 15 at the rated voltage. Here, the differentiating circuit 13 outputs a differentiating pulse C that rises sharply immediately after time t ₀ . This differential pulse C is added to the voltage signal A, and is passed through the DC amplifier 14 to the DC motor 1.
given to 5. Differential pulse C is DC motor 15
It is added to the voltage signal A as a starting voltage to help start the DC motor 15.

In a state where the relationship between the oscillation frequency _R of the local oscillator 3 and the oscillation frequency _O of the operated object 7 is _R < _O , the preamplifier 11 receives a constant positive voltage (for example, +
5V) continues to be output. As a result, the differentiating circuit 13
The output of is at zero while voltage signal A is maintained at a constant voltage. Therefore, in this state, the DC motor 15 is driven to rotate at the rated rotational speed.

When the oscillation frequency _O of the operated object 7 approaches _R ≒ _O due to the rotational drive of the DC motor 15, the preamplifier 1
The output voltage A of 1 begins to gradually decrease.

When the output voltage A begins to decrease, the differentiating circuit 13 generates a negative differential voltage B as shown at time _t1 to _t2 . As the differential voltage B is generated in the negative polarity direction, the differential voltage B is subtracted from the voltage A in the adding circuit 12, so that the driving voltage applied to the DC motor 15 decreases rapidly, and the DC motor 15 is suddenly braked.

Even if the output signal A of the preamplifier 11 decreases, the DC motor 15 continues to rotate due to inertia, so the output signal A of the preamplifier 11 crosses the zero point corresponding to _R = _O . In other words, the DC motor 15 is _R
= It has passed _{the O} position and the direction of rotation is reversed at time t ₂ .
The point _R = _O is approached again, and at this time, the differential output signal B has a polarity opposite to that of the output A at the shaded area, thereby suppressing the overshoot of the DC motor 15. In this way, the differential output B cancels the original drive signal A in the shaded area in FIG. 3, suppresses the overshoot of the DC motor 15, and rapidly returns to the point _R = _O In other words, it converges to the target position.

At time _t3 , the oscillation frequency _R of the local oscillator 3 is set to a higher frequency than the current oscillation frequency. In this case, the output signal A of the preamplifier 11 is generated in the negative polarity direction, and the differential output signal B is damped so that the shaded portion has the opposite polarity to the signal A.

"Effect of the invention" As mentioned above, according to this invention, the DC motor 1
A differentiator circuit 13 and an adder circuit 12 are provided before the DC amplifier 14 that drives the motor 5, and by adding the differential signal B to the original drive signal A, hunting of the DC motor 15 is suppressed and the target position is converged in a short time. can be done.

Since the differentiator circuit 13 and the adder circuit 12 have simple configurations, the cost increase for adding these circuits is small. However, since braking characteristics equivalent to those obtained using a normal servo motor can be obtained using the DC motor 15, it is possible to obtain a servo circuit that is inexpensive overall and has the same performance as when using an expensive servo motor. Obtainable.

In the above description, a case has been described in which this invention is applied to an automatic tuning device, but it is easy to understand that it can also be applied to other servo systems.

[Brief explanation of the drawing]

Figure 1 is a block diagram for explaining an embodiment of this invention, Figures 2 and 3 are waveform diagrams for explaining the operation of this invention, and Figure 4 is a diagram for explaining the conventional technology. It is a block diagram. 1... High frequency tuning circuit, 2... Frequency mixer,
3...Local oscillator, 4...Intermediate frequency amplifier, 5...
...Input keyboard, 6... Servo circuit, 7...
Operated object, 8... Phase comparator, 9... Low pass wave generator, 11... Preamplifier, 12... Addition circuit,
13...Differential circuit, 14...DC amplifier, 15...
...DC motor.

Claims (1)

[Claims for Utility Model Registration] A: An operated object; B: A DC motor that operates the operating section of the operated object to change the electrical signal output from the operated object; and C: An electrical signal output from the operated object. a comparator that compares the electrical signal with a reference signal; D a preamplifier that saturates and increases the comparison output voltage output from this comparator; E provided on the output side of this preamplifier and output from the preamplifier. a differentiating circuit for differentiating the saturated amplified output voltage signal; An automatic braking device comprising: a DC amplifier that amplifies an output signal and drives the DC motor using the amplified output.