JPS58215980A - Controller for motor - Google Patents

Abstract

PURPOSE:To enable a smooth control of a motor by suppressing the variation of a torque command due to the variation in the computed speed or acceleration using a pulse counted value. CONSTITUTION:A CPU701 of a microcomputer board 7 takes the difference between the speed command and the motor speed, proportionally controls or integrates the difference, or functionally varies the proportional gain in response to the magnitude of the speed deviation to generate torque command. Further, the torque command is compared with the loaded current value, and a firing command is applied to a thyristor 5 to cancel the deviation. The variation in the torque command can be suppressed by using means for varying the proportional gain as described above, and the motor can be smoothly controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to control of an electric motor, and more particularly to an electric motor control device suitable for digitally detecting the speed or acceleration of an electric motor and performing feedback control using the detected speed or acceleration.

When controlling the speed of an electric motor, generally all speed feedback is performed,
The control system (As) is configured so that the deviation from the speed command is zero. Conventionally, a speed generator was used as a means of speed detection, and the feedback control described above was performed in an analog manner, but in recent years, inexpensive microprocessors have been used to
A method of controlling these digitally is being adopted. There are two methods of speed detection in this case: one is to obtain the speed directly by converting the output of the analog speed generator from analog to digital, and the other is to use a pulse generator (for example, a pulse encoder) to generate a pulse train according to the speed. This method calculates the speed indirectly from the relationship between time and the number of pulses by counting all the outputs of the pulse.

By the way, when a moving body is driven by an electric motor, the amount of movement or position of this moving body may be required.

For example, in an elevator or the like, the position of the corner is a very important control element, and highly accurate detection is desired. For this reason, in elevators and the like, a method is being adopted in which the car position is detected by counting all the pulses of the pulse generating means, and in such elevators, the latter speed detection method described above is convenient. Moreover, the latter method is also excellent in economical efficiency, so it can be adopted in various fields.

However, when the motor is feedback-controlled using the speed detected by this latter method, subtle torque fluctuations occur.
It was found that the influence is particularly large at low speeds or steady speeds. Therefore, when this method is used for elevator control, for example, it is desirable to investigate the cause of the problem and improve it without impairing ride comfort.

Although the above description has been about speed detection, it has also been found that a similar phenomenon occurs when the above-mentioned pulses are counted to calculate the total acceleration of the motor, and when the calculated acceleration is fully feedback-controlled in response to an acceleration command.

An object of the present invention is to count all the pulses corresponding to the rotation of an electric motor, calculate the speed or acceleration of the electric motor using this count value, and control the electric motor based on a torque command according to the deviation from the command. An object of the present invention is to provide a control device for an electric motor that can elucidate the cause of the torque fluctuation, suppress the torque fluctuation, and perform smooth control.

By the way, in the case of digital control, results can only be obtained in integer numbers, unlike in the case of analog control.

Therefore, for example, as shown in FIG.
Consider the case where 10.1 (rlXl) is constant between 0100(
Assuming that 10 speed calculations are performed during rns-), 9 of them will point to 10(rlXl)k and 1 will point to 11(IP), resulting in an average of 10.1rIxli. .

Therefore, for the command 10.1 (rflll), in the case of digital control, the average value is controlled to 10.1 (IF), which is correct, but microscopically, the actual #i! It was found that the current command was generated to follow the jump as shown in A, and instantaneous fluctuations in torque occurred.

This kind of problem is relatively less of a problem for controlled objects that focus only on speed, but for controlled objects that have some kind of restriction on the speed change rate, that is, torque fluctuation, such as the elevator mentioned above. This problem has become noticeable and has come to the fore in control objects that place emphasis on riding comfort.

Therefore, one way to solve these problems unique to digital control is to increase the number of rotary encoder output pulses per revolution and increase the accuracy of microcomputer calculations, for example from 8 bits to 16 bits. However, with this method, there is a limit to the accuracy of pulse counting when the speed is high due to the relative relationship between tolerance to noise and the minimum pulse width that does not cause counting errors. The problem is that it is expensive.

Furthermore, in order to reduce the influence of the speed deviation ripple mentioned above, it is possible to set the proportional gain KpO value r which is multiplied by the deviation small, but the required control response time may not be obtained (the response will become slow). ), which is undesirable in elevators and the like that require highly accurate control.

A feature of the present invention is that the fluctuation itself of the torque command due to the fluctuation of the speed or acceleration calculated using the pulse count value corresponding to the rotation of the electric motor is suppressed.

Hereinafter, details of this invention will be explained using illustrated embodiments.

As mentioned above, the present invention is also effective in the case of controlling an electric motor by generating a torque command based on the deviation between the acceleration command and the acceleration of the electric motor, but in the following explanation, in the case of speed control, Let me explain using an example. From this explanation,
In the case of acceleration control FIG. 2 shows a configuration diagram of an embodiment of a motor control device according to the present invention. In the diagram, 1 is the armature, 2
is a pulse encoder that generates all pulses according to rotation, 3
is a field, 4 is a current detector, 5 is a thyristor bridge group,
6 is thyristor bridge, 7 is microcomputer, 701
is the CPU (Cen
tral Process TJnit), 7
02 is a counter that counts the output of the rotary encoder, 703 is a read-only memory element that stores programs, etc., 704 is a digital-to-analog conversion element that outputs a firing signal to the thyristor, and 705 is capable of reading and writing. The storage element 706 is an analog-to-digital conversion element that takes in all analog quantities and converts them into digital quantities. A feature of this configuration is that it uses a digital method in which the output pulses of the rotary encoder 2 are counted by a counter 702 in order to detect the speed of the electric motor 1.

FIG. 3 shows a basic configuration diagram of the software of the present invention. This motor control program 800 is an O8 (not shown).
Qperation System) is a task that is started periodically by the program.

This motor control is roughly divided into five subroutines. That is, a subroutine 810 detects the rotational speed of the motor, a subroutine 820 that inputs the armature current value f-q to the microprocessor, a subroutine 830 that generates a speed command, and a proportional control or proportional integral that calculates the difference between the speed command and the motor speed. A subroutine 84 that performs control and generates a torque command by performing processing such as changing the proportional gain functionally according to the magnitude of the speed deviation.
Components include a current command generation subroutine 850 that compares the torque command with the current value taken in, and generates a thyristor firing command to turn off all the deviation lights.

Next, the torque command generation subroutine 840, which is directly related to the present invention, will be explained in detail with reference to chart 70 in FIG. Note that this invention is not directly influenced by the contents of other subroutines, so a well-known method may be used, and detailed explanation will be omitted. Furthermore, in this motor control program, the torque command generation subroutine 830 and the flow command generation subroutine 850 are at the same task level, but if the task level is changed so that the current command generation process is performed more frequently, The essence of the invention remains intact.

A detailed explanation of the torque command generation portion, which is a feature of this embodiment, will be given with reference to FIGS. 4 and 5. When the torque command generation subroutine is called from the motor control program 800, the procedure shown in FIG. 4 is executed. That is, in step 841, the deviation Δvi between the speed command and the actual speed is calculated, and in step 842, it is determined whether this deviation ΔV is larger than a predetermined value α, and if Yes, in step 843, it is set as the proportional gain Kp. Relatively thick constant values Kp and 'e are used. If NO, step 844
All calculations are performed so that the proportional gain Kp is proportional to the value of ΔV, that is, K p tx1×ΔV/α, and as the deviation ΔV becomes smaller, the KpO value is changed proportionally from the constant value K p a s. so that it decreases to

The relationship between the deviation ΔV and the proportional gain Kp in this case is shown in FIG. 5(a). As shown in the figure, the deviation ΔV is a predetermined value α,
The proportional gain Kp decreases in proportion to below. Note that the slope of the proportional gain Kp is step-like because
This is because ΔV is processed as an integer.

Incidentally, in the above example, the proportional gain Kpk is decreased in proportion to the speed deviation ΔV, but the present invention is not limited to this. Figure 5 (as shown in Figure 5, the slope Kp/Δ
It is also easy to change the value of V midway through, and it can be arbitrarily selected depending on the characteristics of the control system including the electric motor.

Based on the proportional gain Kp'ffi obtained according to the value of the speed deviation in this way, in step 845, the deviation Δvi
The process creates a torque command Tc by adding or subtracting from the initial value TL of the torque command, and ends the torque command generation subroutine.

Next, the effects of this embodiment will be explained with reference to FIGS. 6 and 7. Both figures are oscillograms obtained using experimental equipment; FIG. 6 shows the conventional method, and FIG. 7 shows the case where the method of the present invention is applied. In both figures, (a) is the speed command, (s) is the actual speed calculated by counting the output of the rotary encoder inside the microcomputer and performing all processing, and (C)
(d) shows the actual speed obtained by directly calculating the motor speed using an analog speed generator, and (d) shows the torque command when the deviation between the speed command and the actual speed is taken and the proportional control is normally performed. Note that the digitally determined actual speed and torque commands are calculated moment by moment at predetermined time intervals, and the results have a certain range of values, so the results of monitoring are as shown in the figure. Comparing both figures, it goes without saying that the actual speed determined inside the microcomputer (b) has almost the same waveform. However, the waveforms of the torque command (d) and the actual speed (C) generated by the analog generator are clearly different.

The conventional torque command (d) shown in Figure 6 is processed by simply multiplying the deviation between the speed command and the actual speed by a proportional gain, so the actual speed (b) determined inside the microcontroller is not smooth. The torque command also lacks smoothness (especially the parts from ■ to ■).

As a result, the motor speed (C) including torque fluctuation (
Especially the parts from ■ to ■).

On the other hand, as shown in the experimental results in Fig. 7, in this embodiment, the proportional gain Kpk is changed according to the magnitude of the deviation between the command and the actual speed, so that the initial response time of the speed is Although there is almost no change from the results in Figure 6,
In a steady state, even if a deviation based on the pulse count occasionally occurs, sudden changes in the torque command (d) can be suppressed.

As a result, the unpleasant sudden change phenomenon in the motor speed (■) detected by the analog speed generator is reduced, and smooth control becomes possible.

Therefore, the present invention does not provide control to the extent that it is sufficient to simply match the motor speed to a required speed command;
This experimental result shows that it is particularly effective in applications where sufficient attention must be paid to torque fluctuations, such as elevator control and rolling mill control. Recognize.

Other embodiments of the present invention are shown in FIGS. 8 and 9. In this embodiment, the proportional gain KpO value is set to the fifth value according to the deviation ΔV.
It is changed in the same way as in the case shown in the figure, but differs from the previous embodiment in that a second predetermined value α2 is set, and this α and υ are also set as a dead zone in a region where ΔV is small. That is, step 844 in FIG. 4 is changed to steps 846 to 848 in FIG. 8, and the proportional gain Kpf in this case is shown in FIG. 9(a).
Shown below. Although this method can tolerate a certain degree of steady-state deviation, it is more effective for controlled objects where it is desired to suppress torque fluctuations as much as possible.

Moreover, by further expanding this idea, as shown in FIG. 9(b), the second predetermined value α and the first predetermined value fi [α1 are made extremely close to or coincident with each other, as if the proportional gains KptO and Kp ex 1 In other words, the speed deviation ΔV
Needless to say, a considerable effect can be achieved even if all the values below a predetermined value are insensitive.

However, according to experiments, instead of creating a sudden cine feeling when the speed deviation ΔV is below a predetermined value, the proportional gain Kpk
In the above-mentioned embodiment in which the torque is decreased gradually or in multiple stages, torque fluctuations are smaller and smoother characteristics can be obtained.

Further, another embodiment of the present invention is shown in FIG.

In this embodiment, the speed detection subroutine 810 is modified in order to realize the above-mentioned idea, and the value of the proportional gain Kp in the torque command generation subroutine 840 in FIG. 3 is independent of the value of the deviation ΔV. is controlled at a constant level.

The innovation added to the speed detection subroutine 810 is that in addition to the speed detection steps 811 to 815, which are the basic operations, 8
16 to 819 are added and processed.

That is, after determining in steps 816 and 817 that the speed command value has reached a steady state and a predetermined time has elapsed, the current speed obtained in steps 811 to 814, the average previous speed up to that point, and all steps 818 If the speed calculated this time is slightly different from the previous value, proceed to step 8.
19 is executed, and the average value up to the previous time is used as the actual speed.In the speed detection process, factors that are likely to cause torque fluctuations are removed in advance. In this way, fluctuations in the detected speed due to pulse counting can be suppressed, and there is an effect of suppressing torque fluctuations. In addition, in the case of Figure 10, an example was explained in which when the current speed is not used as the actual speed, the previous average value is used as is, but instead of using it as is, the average value with the current speed is taken. Even if all the components are used, torque fluctuations caused by pulse counts can be suppressed.

Furthermore, so far we have explained speed deviation as an example of deviation, but when performing acceleration control, by considering the deviation as total acceleration deviation, it can be carried out in the same way, and the same effect 1 can be obtained. I can do it.

Furthermore, in the above description, methods for suppressing fluctuations in the torque command include a method of varying the proportional gain and a method of suppressing fluctuations in the output speed and acceleration themselves, but the present invention is not limited to these methods.

According to the present invention, in a control method in which a feedback value of velocity or acceleration is compared with a command value digitally, a discrete digital quantity 1 [pulse count can be processed as a continuous quantity] This has the effect of suppressing as much as possible torque loss due to variations in speed or acceleration calculated by the method, and realizing smooth motor control.

Therefore, if the present invention is applied to elevator control, the ride comfort can be significantly improved.

[Brief explanation of drawings]

FIG. 1 is a speed detection waveform diagram to help understand the present invention.
Fig. 2 is a block diagram of an embodiment of a motor control device to which the present invention is applied, Fig. 3 is a basic block diagram of motor control software according to the present invention, and Fig. 4 is a torque command generation subroutine that is a feature of the present invention. FIG. 5 is a diagram of the relationship between speed deviation and proportional gain according to the present invention, FIG. 6 is a conventional signal waveform diagram, FIG. 7 is a signal waveform diagram according to the present invention, and FIGS. 8 to 10 are diagrams according to the present invention. It is an explanatory diagram of another example. 1... Armature, 2... Rotary encoder, 3...
...Field, 4...Current detector, 5.6...Sirisk device, 7...Micompode, 701...Central processing unit, 702...Programmable timer module, 704...Digital -Analog converter, 800-850...Program and subroutine, Kp...Proportional gain, ΔV...Speed deviation, α1
．． α. ...Predetermined value of deviation. '-1♀su11' Active q diagram

Claims (1)

[Claims] 1. An electric motor, a means for generating pulses according to the rotation of the electric motor, a speed or acceleration of the electric motor calculated using a counter Nu of the generated pulses, and a commanded speed or acceleration. means for calculating a torque command for the electric motor using a deviation of the torque, and controlling the electric motor according to the torque command, wherein the torque due to fluctuations in speed or acceleration calculated using the pulse count value. A control device for an electric motor, characterized in that it is provided with means for suppressing fluctuations in commands. 2. In claim 1, the control of the electric motor is provided with a proportional gain for calculating a torque command based on the deviation, and the fluctuation suppressing means is configured to vary the proportional gain in accordance with the deviation. Device. 3. The electric motor control device according to claim 2, wherein the proportional gain is configured to vary functionally in accordance with the value of the deviation. 4. In claim 3, the functional change means that the proportional gain is set to a substantially constant large value in a region where the deviation is above a predetermined value, and is proportional to the deviation in a region below a predetermined value. A control device for an electric motor, characterized in that: 5. In claim 3, the above-mentioned functional change means that the proportional gain tJt is set to a large constant value in a region where the deviation is above a first predetermined value, and when the deviation is below the first predetermined value, the A control device for an electric motor, characterized in that the proportional gain is reduced in proportion to the deviation in a region exceeding the second predetermined value, and a dead zone is provided in the proportional gain in the region smaller than the second predetermined value. 6. In claim 1, the suppression variation means is an electric motor configured to suppress a change in the calculated speed or acceleration when the initial speed or acceleration differs from the immediately preceding calculated speed or acceleration. control device. 7. A control device for an electric motor according to claim 6, which is configured to suppress changes in the calculated speed or acceleration at least when the electric motor is in a steady speed state.