JPH02206381A - Digital controller - Google Patents

Abstract

PURPOSE:To quicken response at each harmonic component detecting/correcting section and to shorten time required for correction by shifting any one of detection timing or correction output timing at a plurality of harmonic component detecting/correcting sections. CONSTITUTION:Control target is a motor M, the detecting section is constituted with an encoder E and a counter COUNT, where the controlled variable is the rotation while the manipulated variable is the current command, and a portion of the control section, discriminating section and detecting section is constituted with a digital operating unit such as a microcomputer MC. The microcomputer MC processes signals fed from a pole position detecting section PS, thus performing ON/OFF control of the switching element in a driver and regulating the magnitude of current. Any one of detection timing or correction output timing at the plurality of harmonic component detecting/correcting sections is shifted.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a digital control device, and in particular provides a digital control device with little variation in control amount and short calculation time and response time. .

[Conventional technology]

VTR (Video Tape Recorder)
) is desired to have a constant speed. If there is a speed fluctuation (uneven rotation, speed ripple), the image will be distorted, and the reliability and quality of the VTR will be significantly impaired. Conventionally, this type of device has mainly used a DC motor, but in recent years, brushless motors, which can freely and easily change the speed and are highly reliable, are increasingly being used. Brushless motors do not have mechanical brushes, so they eliminate the various drawbacks of DC machines, but 120-degree energizing brushless motors have the disadvantage that, in principle, the motor itself generates torque ripples, increasing uneven rotation. .

As a method to eliminate the above drawbacks, we devised a method to reduce rotational unevenness by detecting harmonic components in rotational unevenness and correcting the current command (torque command) with the same harmonic components.
The patent application was filed as Japanese Patent Application No. 63-39424. This main configuration consists of a controlled object (motor) that generates a controlled variable (rotational speed), a detection section (encoder, counter) that detects the controlled variable (rotational speed), and a deviation between the target value and the measured value of the detection section. It consists of a discrimination section that calculates, and a control section that determines the amount of operation (current command) to the controlled object (motor) based on the deviation, and the control section and the discrimination section are equipped with a digital computing unit such as a microcomputer. Also,
A digital control device that outputs a manipulated variable at a fixed sampling period, detects fluctuation components included in the controlled variable (rotation speed) and deviation, etc. at a fixed period, and corrects the same period as the fluctuating harmonic component. It has the principle of reducing fluctuating harmonic components included in the controlled object by acting on the manipulated variable.

[Problem to be solved by the invention]

In the above-mentioned conventional technology, there are a plurality of harmonic components in the fluctuation of the controlled variable, and it is necessary to have a plurality of harmonic component detection and correction means. In this case, it takes time to detect and correct two harmonic components within one sampling time, and
Because the correction sampling was made the same for the long-cycle harmonic component detection and correction section and the short-cycle harmonic component detection and correction section, the response time of the short-cycle harmonic component detection and correction section could not be shortened. .

An object of the present invention is to sufficiently speed up the response time of each harmonic component detection and correction section and to shorten the time required for one correction.

[Means to solve the problem]

The above object is achieved by shifting the timing of any one of the detection of a plurality of harmonic components, the detection of the correction section, or the correction output.

[Effect]

By shifting the detection timing, the number of detections within one sampling can be reduced, and the calculation time can be reduced. Furthermore, by changing the sampling periods for detection and correction, the response time for correction becomes faster.

〔Example〕

Examples of the present invention will be described below. FIG. 2 shows a digital control device to which the present invention is applied.

In this example, the controlled object is a motor, the detection section is an encoder,
An embodiment will be shown in which the control amount is the number of rotations, the operation amount is a current command, and a part of the control section, the discrimination section, and the detection section are formed by a digital arithmetic unit such as a microcomputer.

In FIG. 2, M is a motor that has a periodic torque fluctuation component within one rotation, or has a load that changes periodically, causing speed fluctuations. This motor may be either a rotary type or a linear type, and may or may not have brushes. Here, we will use an example of a brushless motor. PS is a magnetic pole position detector that detects the magnetic pole position of the motor M, especially the rotor, and is used to switch the phase current of the motor M. Although the internal structure of the motor is not shown, brushless motors are typically configured to electronically detect the rotor position and apply current to two selected phase windings depending on the rotor position. There is. E is a speed detector consisting of an encoder etc. attached to the rotating shaft of the motor M. In addition to the encoder, the speed detector employs a frequency generator, tacho generator, pulse generator, etc. INV is an inverter that is a driver that drives motor M, and normally consists of six switching elements to form three arms each for positive and negative, and flows current to two selected phase windings, and also controls the magnitude of the windings. It is something that can be changed. ACR is an automatic current adjustment circuit (Aut
o matic Current Regulator
) is configured to receive the current detection value obtained by the current transformer CT. MC is a microcomputer and has functions described later. C0UNT is a speed detection circuit, which is actually composed of a counter, and is operated by detecting the number of pulses or the pulse interval detected at a constant sampling time. The main parts of the speed control means C include the above-mentioned microcomputer MC1 automatic current adjustment circuit ACR, driver (inverter) INV, and speed detection circuit C0UNT.

Then, the speed obtained by the speed detection circuit C0UNT is transmitted to the microcomputer MC, and the signal from the magnetic pole position detection section PS is transmitted to the microcomputer MC and the driver I.
The microcomputer MC processes the signal to control the switching element of the driver on and off, and adjusts the magnitude of the current value.

Microcomputer MC has the internal functions shown in FIG. That is, the calculation unit ALU, counter CNT, D
/A converter DA and storage unit MRY. The counter CNT measures the period of the pulse signal from the encoder E, and detects the speed as the reciprocal of this period. Arithmetic unit A
The LU receives the signal from the counter and stores the R of the storage MRY.
The speed error is calculated by comparing it with the command speed stored in the OM. Next, a correction signal is created based on the speed error thus calculated. Then, this correction signal is stored in the RAM of the storage unit MRY from time to time, and is sequentially updated with new data. Furthermore, the calculation unit ALU has an element for detecting harmonic components inherent in the actual speed mode of the motor M detected above. Further, this detection of harmonic components is carried out targeting the fundamental wave component and, in particular, the third or fifth harmonic components that cause torque ripple. Although the counter CNT is shown as an external one, it may be built into the microcomputer MC.

FIG. 1 is a concrete block diagram of the speed control device. In this figure, the speed signal, which is a controlled variable, is obtained by counting the number of pulses of a reference oscillator (clock or counter internal to the microcomputer) that falls between the pulses of the speed detector (encoder) E that constitutes the detection section, and the inverse value of this is obtained. (F/V conversion), and the speed signal nt obtained thereby is taken into a microcomputer.

In the microcomputer, a software processing method is used to calculate the speed deviation signal ne from the difference between the speed command ns, which is the target value, and the speed signal n.The controller performs proportional/integral control (PI control). ) After processing, a new current command value, which is the manipulated variable, is output. The current control system is composed of hardware, and calculates the current error Ie from the current command Is given based on the speed command ns and the current detection value obtained from the current transformer CT, and calculates the current error Ie through the automatic current adjustment device ACR. The motor M is configured to apply current to the motor M to be controlled. Note that the inverter is omitted in FIG. 1.

Although their overall configuration is conventionally known, the block to which the present invention is applied has a harmonic component detection means 1°, which is a novel element, indicated by a broken line frame in FIG. That is, the speed signal nff1 or the speed deviation signal n. Calculate the arbitrary harmonic (frequency) component inherent in , and apply proportional control (
A correction signal is created by P control) or proportional/integral control (PI control), and this is added to the current command Is. IOA, IOB, and Ion are each nth
They are the 1st fire component detection means, the nZth fire component detection means, and the nhth fire component detection means. Then, each detection means has a PI
The control element is connected, and its output signal, the correction signal, is
The current command Is is added to the current command Is. The respective output signals may be given to the current command Is in parallel. Further, the arbitrary harmonic components to be detected and their number can be freely changed for each target motor.

Figure 4 shows the speed fluctuations per rotation of the motor M. The number of pulses generated by the encoder E per rotation is Nk, and the calculation for speed detection is performed once at each pulse interval. .

The speed nt can be determined by the reciprocal of the number of pulses of the reference oscillator built in the microcomputer that enters each pulse interval of the encoder E. Actually, it is measured by a speed detection counter, and the speed signal n1 is shown in FIG.

Generally, the speed ni(θ) can be expanded into each frequency component according to the following equation.

However, no...DC component, al...Sine coefficient, b.

...cosine coefficient, and n for any frequency component. The absolute value of 1an1b is expressed by the following equation.

n s P P R (Pulse Per Revol)
The speed fluctuation amount of

However, Nk...number of pulses per rotation, nfn...
The speed between the nth pulse and the n−1th pulse, and further n
The speed fluctuation N of IP PR is obtained by the following formula.

In the example of FIG. 4 using encoder E that generates nm pulses per revolution, the correction term in proportional control is CNI:K per revolution.
'ANII DN1=K o13HtK: Proportional gain Although the graph shown in FIG. 4 is for one revolution, the same fluctuation mode is shown for the next revolution, and this is repeated.

The starting point of the calculation is the reference position of the rotor. The reference position is detected using a reference signal provided by the encoder E or, in the case of a brushless motor, a rotor magnetic pole position detection signal provided by a Hall element. Incidentally, in the case of a DC machine that does not use an encoder or the like, a reference position may be separately provided and an arbitrary position may be set.

The above-mentioned method requires sine wave or cosine wave information, but this can be handled by storing it in ROM in advance. Furthermore, as will be described later, in a brushless motor that uses a drive method that supplies current to each phase in a sinusoidal manner, it already has sine wave and cosine wave information in the ROM, so it can be used as is. Available.

FIG. 4 shows a specific method of speed ripple reduction according to the present invention. The present invention is directed to systems in which there are two or more factors that cause speed ripples, and it is necessary to correct two or more ripples. In the figure, (, 1) indicates the actual speed fluctuation mode of the motor.

(b) shows that speed detection is performed once between each pulse. (c) is a speed signal (current signal) obtained at each pulse interval, which is digitally stepped. (cl) is the fundamental wave component (-fire component) of the speed signal obtained from the speed signal in (c). (e) is the n-th blowing component of the speed signal similarly obtained from (c).

The harmonic components of these (d) and (e) are as described in (5) above.
, can be obtained by frequency division calculation using equation (6).

Since the harmonic components are obtained in this way, (f) and (g
) These harmonic components are canceled out and eliminated by adding the correction signal (current) shown in (), so that the torque ripple (speed ripple) caused by this can be eliminated or reduced.

FIG. 5 shows an example of a digital system for constructing these speed control systems. In a VTR motor or the like which must be rotated at a constant speed, speed control is generally performed at intervals of a pulse period obtained from an encoder or frequency generator FG or several times that period. Said fifth
The example in the figure shows a case where the pulse period and the speed control period are made equal, and when calculating for the n-th speed control, as shown in the example of 16 pulses per encoder rotation, n-1
Information on the signal period of the second encoder or frequency generator is used as data. On the other hand, it is preferable that the sampling period of the correction control be longer than the period of the speed control.

In the figure, 16 pieces of speed information f1 to flB are obtained per rotation.In the present invention, 1 of the two speed ripples is
For example, for the second harmonic component, fz* f
3. Based on the speed information of fs and f7, ripple components ANZ and BNZ are calculated using the formulas (5) and (6). The correction term calculates CNi Dnz in (8) by multiplying this value by, for example, a proportionality constant Kc. The magnitude of the correction term can be updated twice per revolution.6On the other hand, for the first harmonic component that has one period per revolution, f zt f 41 f
eg...Based on the speed information of flB (5),
After calculating the ripple components ANI and BNI using formula (6), the correction term is calculated in the same way as for the second harmonic component.

In the case of the first harmonic component, of course, according to the 0 or more method in which the magnitude of the correction term is updated once per rotation, calculation of equations (5) and (6) for one speed control It is only necessary to perform either the first or second harmonic component, and the calculation time can be reduced.

Furthermore, the calculation time of equation (8) for creating the correction signal can also be shortened. By shifting the timing of harmonic component detection, correction detection, or correction output between the two harmonic detection means in this way, the calculation time occupied in one speed control can be reduced. As shown in FIG. 5, by making the sampling period for harmonic component detection and correction with a short period shorter than the sampling period for harmonic component detection and correction with a long period, responsiveness to short periods is improved.

FIG. 6 shows a flowchart for executing the method of the present invention described above by a microcomputer.
To explain with reference to the drawings, first, the counter is incremented by 1 at step. Next step ■,■
, ■, ■ are speed control operations, in which a speed command ns, a speed signal nf is taken in, a speed error ng, and a proportional term output (shown as an example of proportional control) P are calculated. In step (2), it is selected whether to calculate the first harmonic or the second harmonic.

Steps 1 to 2 are for calculating the sine term coefficient and cosine term coefficient AN2 + BNZ of the second harmonic component from the speed signal, and further calculating the correction term coefficients CNz and DNz. Calculation of Asz and BN2 is proceeded in steps (2) and (2), and upon confirmation of completion of calculation in (2), correction term coefficients cN, , DN2 are calculated in step [phase]. Further step 0
Initialize with . Steps @ to O relate to the first harmonic and are exactly the same as steps ① to ①. Finally, in step @, the output of the speed control system and the correction value are added and output.

In FIG. 6, as shown in FIG. 5, one-time speed control is performed by allocating every other piece of data in the speed information n1 as calculations for the first harmonic and the second harmonic, respectively. The calculation time can be shortened. In addition, separate counters are provided for the first harmonic and the second harmonic, and the correction term coefficients CN, DN
Responsiveness can be improved by increasing the number of outputs.

In the above example, the correction value for each harmonic is the same value because the counter stopped between two speed controls, but by having a separate counter and using this, it is possible to change the correction value. It is also possible to change.

In the above embodiments, a Fourier expansion method has been described as a correction calculation method, but the present method can be applied in exactly the same manner to a method of correcting speed information via a digital filter. In the above case, the speed information can be stored in the memory and calculated by recalling as many pieces as necessary, or the speed information can be corrected as shown in Figure 5 without being stored in the memory. It is also possible to introduce an arbitrary sampling time and perform the sampling at a constant constant during that time.

〔Effect of the invention〕

As described above, according to the present invention, calculation time for one speed control can be reduced, and responsiveness can also be improved.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an embodiment of the present invention, Fig. 2 is a basic block diagram, Fig. 3 is an internal structure diagram of a microcomputer, Fig. 4 is a principle diagram of harmonic component detection and correction, FIG. 5 shows a principle diagram of a harmonic component detection method, and FIG. 6 shows a flow diagram of a microcomputer according to the present invention. M...Electric motor, PS...Position sensor, E...
・Encoder, C0UNT...Speed detection circuit, MC・
...Microcomputer, ACR...Automatic current adjustment circuit, C...Control device. Figure Figure 6 To circle C Figure 4 Figure 6 Figure 5

Claims (1)

[Claims] 1. A controlled object that generates a controlled amount, a detection section that detects the controlled amount, a discrimination section that calculates a deviation from a target value and a measured value of the detection section, and a controlled object that generates a controlled amount based on the deviation. A digital control device comprising: a control unit that determines the amount of operation to be performed; the control portion and the separate valve portion each include a digital calculation unit such as a microcomputer; and,
By detecting multiple fluctuating harmonic components with a fixed period included in the controlled variable and deviation, and applying a correction having the same period as the fluctuating harmonic components to the manipulated variable, the fluctuating harmonics contained in the controlled object can be detected. What is claimed is: 1. A digital control device having a harmonic component detection and correction section for reducing components, characterized in that the timing of any one of the detection of a plurality of harmonic components, the detection of the correction section, or the correction output is shifted. 2. A digital control device according to claim 1, characterized in that the period for detecting and correcting harmonic components with a long period is longer than the period for detecting and correcting harmonic components with a short period. 3. In the first claim, the control amount data used for correcting harmonic components with different periods is at least one
A digital control device characterized by one difference. 4. A digital control device according to claim 1, wherein the object to be controlled is a linear or rotary moving body, and the controlled variable is a speed or a rotational speed.