JPS6118433B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a type of differential minor method in which a detection signal of a speed change rate of a DC motor is matched with a deviation output from a major loop, and the DC motor is controlled based on the matching result. This invention relates to a new type of DC motor control device that employs the following.

Describing a conventional DC motor control device, in FIG. 1, 1 is a speed setting section, 2 is a first matching circuit, and this matching circuit 2
, the speed setting signal from the speed setting section 1 and the speed detection signal from the rotation speed detector 3 that detects the rotation speed of the electric motor 10 are matched, and this deviation output is applied to the speed control amplifier 4 to adjust the speed. The output signal of the control amplifier 4 and the current detection signal from the current detector 5 that detects the excitation current of the motor 10 are matched in a second matching circuit 6, and the deviation output of this matching circuit 6 is further converted into a current. Control amplifier 7
This amplified signal causes the electric motor 10 to be amplified.
The speed of the electric motor 10 is controlled so as to follow the set speed command by controlling the excitation current.

Incidentally, the equation regarding torque T, which represents the basic characteristics of a DC motor, is expressed by the following equation (1).

T=KIφ...(1) where K is a constant, I is armature current, and φ is magnetic flux. From equation (1), when the magnetic flux is constant, that is, when the field current is constant, the torque is proportional to the armature current, and therefore the rated torque at the rated current is constant, resulting in constant torque characteristics. On the other hand, when controlling the magnetic flux, that is, when performing field control, the torque changes depending on the field current even if the armature current is constant. In such a field control range, when the armature voltage is kept constant and the magnetic flux is reduced (torque reduced), the rotational speed increases, so the rated output at the rated current remains constant, resulting in constant output characteristics. Figure 2 is a characteristic diagram showing the relationship between speed and drive torque in controlling a DC motor using a Leonard device.The characteristic is a constant torque characteristic until the base speed _V1 is reached; It is a constant output characteristic until the maximum speed _V2 is exceeded.

Regarding the relationship between the characteristics of the DC motor as described above and the manner in which rotational torque (driving torque) is generated in terms of the output amount of the speed control amplifier 4 in the conventional control device shown in FIG. In a range smaller than ₁ , if the output of the speed control amplifier 4 is constant, the armature current will be constant regardless of the speed, and the driving torque will be constant. However, in the range of constant output characteristics, even if the output of the speed control amplifier 4 is constant, the driving torque will decrease extremely as the speed increases.
That is, the acceleration becomes smaller, and the response of the control system itself becomes slower.

In addition, in order to keep the excitation current of the motor constant, if a limiter 8 is provided after the speed control amplifier 4 in the configuration shown in FIG. 1, the excitation current of the motor 10 can be suppressed by the limiter 8 at any time. It is possible to realize a control operation that does not exceed the specified value (rated current value).

However, in this type of control, if the speed setting section 1 that gives the speed command is not configured with a time function generator that separately provides the speed command, if the speed command is suddenly increased or decreased, the motor 10 will not reach its full rated current. In some cases, the rate of change in rotational speed over time is too large, making it undesirable to operate the motor. Therefore, it is recommended to provide a speed command generating device such as the above-mentioned time function generator and set the speed command itself so that it changes gradually, so that the system can be configured to operate at a desired speed change rate using both of them. Although this is common, in such a case an expensive speed generator is required separately, which is uneconomical.

The present invention has been made based on the above circumstances, and when controlling in a region where the drive torque is not proportional to the armature current, it is possible to control the drive torque according to the output amount of the speed control amplifier regardless of the rotation speed. It is an object of the present invention to provide a control device for a DC motor that can keep the drive torque constant and constantly increase the response of the control system itself.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 is a diagram showing an embodiment of the present invention,
The same reference numerals as in FIG. 1 indicate the same parts. Regarding the difference in configuration between this embodiment and the conventional device shown in FIG. 1, in the embodiment shown in FIG. 3, a differential signal detector 21 is provided on the output side of the rotational speed detector, and The speed control amplifier 4 and the second
A third matching circuit 2 is connected between the matching circuit 6 and the third matching circuit 2.
2 and an acceleration control amplifier 23 are provided, and the matching circuit 22 extracts the deviation between the output signal of the speed control amplifier 4 and the output signal of the differential signal detector 21, and the deviation is outputted to the acceleration control amplifier 2. 2
3. Further, a limiter 24 is provided on the output side of the acceleration control amplifier 23 to regulate the maximum value thereof.

Next, the operation of the above embodiment will be described. The rotational speed of the DC motor 10 is detected by the rotational speed detector 3, and the deviation between the speed detection signal and the speed setting signal is extracted by the first matching circuit 2 and output via the speed control amplifier 4. be done. The output signal becomes an acceleration setting signal, and the third matching circuit 22 extracts the deviation from the acceleration detection signal from the differential signal detector 21. Given as a control input for the minor loop. Therefore, regarding the acceleration, the armature current of the DC motor 10 is controlled by the current minor loop so that the acceleration is maintained at a magnitude corresponding to the output signal of the speed control amplifier 4, that is, the acceleration setting signal. Therefore, assuming that the DC motor 10 is currently being operated within the constant output characteristic range due to field control shown in FIG. The acceleration is controlled to be constant, that is, the drive torque is controlled to be constant. Therefore, the drive torque characteristic with respect to the rotational speed becomes constant depending on the output amount of the speed control amplifier 4, as shown in FIG. In Fig. 4, straight lines A and B indicate the speed control amplifier 4, respectively.
It deals with the case where the output of is the minimum and the maximum.

According to the embodiment described above, if the output amount of the speed control amplifier 4 is constant regardless of the magnitude of the rotational speed, the acceleration is constant according to the output amount, and the driving torque is Since becomes constant,
The response of the control system itself can always be made faster.

Next, another embodiment of the present invention will be described with reference to FIG. 5 of the attached drawings. This embodiment is an embodiment that solves the problem when a limiter is provided in the speed control of an electric motor as shown in FIG. 1 mentioned above, and the same reference numerals as in FIGS. The explanation will be omitted.

The configuration of the other embodiment is characterized in that a limiter 28 is further provided at a stage subsequent to the speed control amplifier 4 in the configuration of the embodiment shown in FIG.

With the above configuration, as long as there is a deviation between the speed setting signal and the speed detection signal, a signal below a certain set value is generated in the limiter 28.
Since the signal E and the signal H are operated by the amplifier 23 so that the deviation becomes zero, as long as the value of the signal E is constant, the rate of change of the speed detection amount with respect to time is kept constant. That is, if the limiter value E of the limiter 28 is set to a value commensurate with the increase or decrease in speed, the rate of change in speed can be suppressed to a value determined by the limiter value or less in any case, and the speed setting signal R and speed detection signal C Since the limiter value E remains constant while the deviation between the values of E and E is large, the rate of change in speed is kept constant.

Furthermore, it is easy to configure the circuit so that the set value of the limiter 28 can be set to different values for positive voltage and negative voltage, and when configured in this way, the speed can be increased. It is possible to operate with different speed change rates for and descending.

Assuming that the output of the amplifier 23 becomes the signal F via the limiter 24, and that the value of F is set to a value that is different from the value of E and corresponds to the rated value of the motor, then The excitation current of the motor is maintained at any value depending on the magnitude of the load by the action of the current control amplifier 7 until it reaches the rated value. Since the amplifier 23 has a high degree of amplification, no matter how small the value of the signal E is to suppress the speed change rate of acceleration/deceleration, it still generates the value of F necessary for the excitation current of the motor to reach the rated value. be able to.

Therefore, according to the embodiment shown in FIG. 5, the maximum value of the excitation current of the motor can be suppressed no matter how large or small the set value of the limiter 28 is, and it is possible to suppress an increase or decrease in speed. The maximum value of the rate of change can be set regardless of the size of the limiter 28. In this way, this embodiment does not require a special speed command generation device, and can constantly control the speed increase/decrease gently using arbitrarily settable acceleration/deceleration torque, while keeping the speed change rate constant and constant. It is likely that the deviation will continue to rise or fall.

Note that Fig. 6 shows a limiter amplifier with a limiter set so that the limiter value is the maximum rate of change in rotational speed, and this amplifier with limiter may be used in place of the amplifier and limiter. . Here, OP is an operational amplifier, and D ₁ and D ₂ are diodes. Furthermore, although it is possible to simply apply an integral amplifier or a proportional amplifier as the amplifiers in FIGS. 3 and 5, if an integral amplifier with proportionality is used, the system as a whole performs P, I, and D operations, which improves controllability. Further improvement. Furthermore, in each of the embodiments, even if part or all of the control system is composed of digital elements instead of analog elements, it is of course possible to perform equivalent control.

As described above, the present invention provides a control system for a DC motor including a speed major loop and a current minor loop, in which the deviation between the output signal of the speed control amplifier and the acceleration detection signal is used to control the current minor loop through the acceleration control amplifier. I am trying to give it as input. Therefore, according to the present invention, the armature current is controlled so that the acceleration is maintained at a magnitude corresponding to the output amount of the speed control amplifier. Even in areas where there is no proportional relationship with torque,
Since the acceleration is constant according to the output amount regardless of the magnitude of the rotational speed, it is possible to solve the problem of the drive torque drastically decreasing as the speed increases as in conventional devices, and it is possible to always maintain the control system itself. You can respond quickly.

Furthermore, a limiter set so that the limiter value becomes the maximum acceleration is inserted between the speed control amplifier and the third matching circuit, or a limiter set so that the limiter value becomes the maximum acceleration. If an amplifier with a limiter is used in place of the speed control amplifier, the speed can be controlled gently using acceleration/deceleration torque that can be set to increase or decrease the speed at any time without the need for a special speed command generator. The deviation from the speed reference value can continue to rise or fall while the speed change rate remains constant.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a conventional device, FIG. 2 is a characteristic diagram showing the relationship between speed and driving torque in a Leonard device, FIG. 3 is a block diagram showing an embodiment of the present invention, and FIG. A characteristic diagram showing the relationship between speed and driving torque when the embodiment shown in Fig. 3 is applied, Fig. 5 is a block diagram showing another embodiment of the present invention, and Fig. 6 is a circuit showing an example of an amplifier with a limiter. It is a diagram. DESCRIPTION OF SYMBOLS 1... Speed setting part, 2... First matching circuit, 3... Rotation speed detector, 4... Speed control amplifier, 6... Second matching circuit, 21... Differential signal detector , 22...Third matching circuit, 23
...Amplifier for acceleration control.

Claims (1)

[Claims] 1. The speed setting signal and the speed detection signal of the DC motor are matched by a first matching circuit, and the deviation output from the first matching circuit is amplified by a speed control amplifier. The DC motor is controlled by the signal obtained by matching the signal generated by the current detection signal with the current detection signal of the DC motor in a second matching circuit, and amplifying the deviation output from the second matching circuit with a current control amplifier. In the control device, a third matching circuit and an acceleration control amplifier are provided between the speed control amplifier and the second matching circuit, and an output signal of the speed control amplifier is provided in the third matching circuit. and an output signal of a differential signal detector that detects the rate of change of the speed detection signal with respect to time, and the deviation output thereof is led to the second matching circuit via the acceleration control amplifier. A DC motor control device characterized by: 2. In the control device for a DC motor according to claim 1, a limiter value between the speed control amplifier and the third matching circuit is set to a maximum rate of change of the speed detection signal. A control device for a DC motor, characterized in that a limiter is further inserted, or the speed control amplifier is an amplifier with a limiter having a limiter set to the maximum rate of change of the speed detection signal.