JPS63184811A - Error correcting system for speed control system - Google Patents

Abstract

PURPOSE:To execute a speed control at a high speed and stably, even if an error is contained in a position signal, by predicting a speed and a position of a movable body of a control object in each sample period, and executing a control by using a predicted speed, in case when an abnormal speed has been detected. CONSTITUTION:The present speed is calculated by a speed calculating part 10, based on a digital position signal outputted from an A/D converter 9 of an output side of a sampling circuit 7. Also, in a predicted value calculating part 11, a predicted speed and a predicted position at the time of sampling of the next time are calculated in accordance with the variation quantity of the inputted present speed signal and the digital position signal, and stored temporarily in a storage part 12. In case when an abnormal speed detecting part 13 has detected a normal speed, an output of the speed calculating part 10 is inputted to a subtracting part 2 through a speed selecting part 14, and in case when said part has detected and abnormal speed, the predicted speed of the previous time stored in the storage part 12 is read out, inputted to the subtracting part 2 through the speed selecting part 14, and also, a predicted position signal and a predicted speed signal at the time of sampling of this time, stored in the storage part 12 are corrected to those of the previous time.

Description

[Detailed Description of the Invention] [Summary] In a speed control system using sample value control, in order to prevent abnormal operation due to an error in the current speed signal obtained by differentiating the sample value of the position signal, the movement of the controlled object in each sample period is The speed and position of the body are predicted, and when an abnormal speed is detected, control is performed using the predicted speed without using the abnormal value.

[Industrial application field]

The present invention relates to a magnetic disk drive, and more particularly to high speed and high precision head positioning control system.

In achieving the above control system using digital control using a microprocessor, accurate demodulation of the speed signal is important, but accurate speed control can be achieved even if an error occurs in reading the head position signal, which causes a speed error. It is desired to develop such an error correction method.

[Conventional technology]

FIG. 3 is a block diagram of a conventional speed control system.

In the figure, reference numeral 1 denotes a speed control device (for example, a device used in a head positioning control system in a magnetic disk device) which has a function of outputting a target speed necessary for moving the movable body 5 to a desired position in a digital value.

2 is a subtracter, and one of the input terminals receives the target speed of the speed control device 1, and the other input terminal receives a current speed signal, which will be described later, and the difference between the two is output as an error signal. . A D/A converter 3 converts the error signal into an analog value, and moves the movable body via a drive circuit 4.

A position signal detector 6 (for example, a servo head in a magnetic disk drive) detects the moving position of the movable body 5 and outputs a position signal. Reference numeral 8 denotes a speed signal conversion circuit, which uses, for example, a differentiation circuit, and converts the position signal into a current speed signal by differentiating it.

7 is a sampling circuit that samples the current speed signal at a predetermined timing, converts it into a digital value using an A/D converter 9, and feeds it back to the subtracter 2, so that the error signal output from the subtracter 2 approaches zero. This constitutes a closed-loop servo control system that controls the speed to the target speed.

Here, the position signal input and error signal output are at a certain period Δt
The control system can be achieved by a microprocessor.

FIG. 2 shows a flowchart by the microprocessor. In step A, the output of the position signal detector 6 is A/D converted to output a position signal as a digital value, and the values Pi, Pi-, (the subscript i represents each sample time) at each sample time are determined. In step B, the current speed signal Vi calculated at each sample period is a differential (difference) of the position signal Pi, and Vi= (Pi-Pi-+)/Δt ------...-
It is calculated as (1).

In step C, the subtracter 2 is used to find the difference (error signal) between the target speed and the current speed.

In step D, the error signal is D/A converted as a momentum and sent to the drive circuit 4 to move the movable body 5.

[Problem that the invention seeks to solve]

Here, if the position signal output by the position signal detector 6 is not an accurate value, the current speed signal, which is its differential value, will naturally also be inaccurate, and not only will accurate position control become impossible, but also Depending on the situation, it may run out of control and cause damage to the device.

By the way, depending on the movable object to be controlled, the observed position signal may contain errors.For example, if the sample input operation and the position signal demodulation circuit system are not synchronized for some reason, the obtained position The disadvantage is that the signal is intermittently inaccurate.

The present invention was created in view of the above-mentioned drawbacks of the prior art, and an object of the present invention is to provide an error correction method for a speed control system that is capable of high-speed and stable speed control even when a position signal contains an error.

[Means for solving problems]

The error correction method of the speed control system of the present invention is based on the speed control system of the movable body 5 which is instructed by a digital value from the speed control device l of the movable body 5.
The target velocity of is D/A converted through a subtracter 2, and the movable body 5 is moved through a drive circuit 4, and the output of a position signal detector 6 that detects the moving position is sent through a sampling circuit 7. In the speed control system, the output signal of the sampling circuit 7 is A/D converted and fed back to the subtracter 2, and servo control is performed so that the output of the subtracter 2 approaches zero. A forecast is inputted to the speed calculating section 10 which calculates the current speed through the speed calculating section 10, and calculates the expected speed and expected position at the time of the next sample from the output of the speed calculating section 10 and the output of the A/D converter 9. A value calculation section 11, a storage section 12 for temporarily storing the output of the predicted value calculation section 11, and an abnormal speed detection section 13 for determining an abnormality in the output of the speed calculation section 10, the abnormal speed detection section A speed selection section 14 is provided which switches the output of the speed calculation section 10 to the predicted speed of the previous sample period stored in the storage section 12 in response to the abnormality detection signal No. 13, and the output of the speed selection section 14 is input to the subtracter 2. We have adopted a configuration that

(Function) Based on the digital position signal output from the A/D converter 9 on the output side of the sampling circuit 7, the speed calculation section 10 calculates the current speed as before. The predicted speed and predicted position at the next sampling time are calculated in accordance with the amount of change in the speed signal and the digital position signal, and the results are temporarily stored in the storage unit 12.

When the abnormal speed detection section 13 detects a normal speed, the output of the speed calculation section IO is changed to the speed selection section 14 based on the normal signal.
When an abnormal speed is detected, the previous expected speed stored in the storage section 12 is read out using the abnormal signal, and the subtracter 2 is inputted via the speed selection section 14.
At the same time, the predicted position signal and predicted speed signal at the time of the current sample stored in the storage unit 12 are corrected to the predicted position signal and predicted speed signal at the time of the previous sample. As a result, abnormal speeds are not adopted and are converted to expected values, resulting in high speeds,
Stable speed control can be performed.

〔Example〕

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

Note that, in order to make the explanation of the configuration and operation easier to understand, the same parts are given the same reference numerals throughout all the figures, and repeated explanation thereof will be omitted.

FIG. 1 is a block diagram of the speed control system of the present invention. In the figure, reference numeral 10 denotes a speed calculation section which performs the same calculation as step B in the conventional example shown in FIG. be done.

In addition to the current speed signal, the predicted value calculation section 11 receives a position signal for each sampling from the A/D converter 9. In each sample period (L), predict the expected speed vX,L (the angle line indicates the expected value) in the next period (i.,), and calculate the expected position signal ■ Yu Calculate 0 For example, if uniform motion is predicted from the amount of change in speed, calculate the current speed Vi and the next speed Vi
and are the same, so ■mu=Vi= (Pi Pi−+) /Δt −・・
--(2) Pi, L-P i+Δt-...
...(3), and ■1 and ■yu are calculated.

In the storage unit 12, the predicted calculation value stored at the time of the previous sample is stored.
, the expected calculation value when Pi is sampled this time.

Update each plate and temporarily store it.

Reference numeral 13 denotes an abnormal speed detection unit, in which a limit amount of the rate of speed change (acceleration) is set in advance as a threshold value, and as a result of comparing this dark value with the current speed signal, if it exceeds the dark value, it is determined to be abnormal. It can be detected by If the abnormal speed detection section 13 compares the current speed Vi actually calculated by the speed calculation section 10 at each sample time with the threshold value and determines that it is a normal speed, the abnormal speed detection section 13 changes the output of the speed calculation section 10 to the speed based on the normal signal. It is input to the subtracter 2 via the selection section 14.

In addition, when an abnormal speed is detected, the previous predicted speed stored in the storage unit 12 is read out based on the abnormality signal, inputted to the subtracter 2 via the speed selection unit 14, and the current predicted speed stored in the storage unit 12 is read out. The estimated values of velocity and position at the time of sampling are corrected to the estimated values at the time of the previous sample.

As a result, even if the current position signal that is next input to the speed calculation section 10 is accompanied by an error, it will be corrected and demodulated by the same routine as long as it is within the range where the abnormal speed detection section 13 detects an abnormality. A stable speed control system is achieved without the speed taking an abnormal value.

FIG. 2 is a flowchart of the speed control system of the present invention, in which each calculation section is operated using a microprocessor.

Step (2) is the same as step A in FIG.

Step (2) is a calculation of the predicted speed at the next sampling time in the predicted value calculation unit 11, and is calculated using the above-mentioned equation (2).

Step (2) is a predicted position calculation for the next sample in the predicted value calculation section 11, and is calculated using the above equation (3) based on the predicted speed signal obtained in step (2).

In step (2), the same calculation as in step B in FIG. 4 is performed in the speed calculating section 10.

In step ■, the abnormal speed detection unit 13 compares the current speed signal with a predetermined threshold value to determine whether the current speed signal obtained in step ■ is normal or abnormal. If normal, proceed to step ■; if abnormal, proceed to step ■. Move each.

In step (2), based on the abnormal signal detected by the abnormal speed detection section 13, the expected speed signal at the time of the previous sample stored in the storage section 12 is read out, transferred to the speed selection section 14, and inputted to the subtracter 2. At this time, the current speed signal (abnormal value) inputted from the speed calculation section 10 to the speed selection section 14 is not selected by the abnormal signal, but is shifted and disappears when the current speed data at the next sample time is inputted. .

In step (2), the predicted value calculation unit ll is determined by the abnormal signal.
The expected values of velocity and position at the time of the current sample stored in the storage unit 12 are corrected to the expected values 'L Pi at the time of the previous sample, respectively.

Step ■ and step ■ are respectively step A in Figure 4.
, same as step B.

Through the above procedure, even if an abnormal speed is detected, speed control can be performed using the predicted speed, so abnormal operation of the movable body 5 can be prevented.

〔Effect of the invention〕

As explained in detail above, according to the error correction method of the speed control system of the present invention, it is possible to avoid demodulating an abnormal speed even from position information that may cause a reading error, and to achieve a high-speed and stable speed control system. is achieved.

[Brief explanation of the drawing]

Figure 1 is a block diagram of the speed control system of the present invention, Figure 2 is a flowchart of the speed control system of the present invention, and Figure 3 is a block diagram of the conventional speed control system. Flowchart Figure 2 tj-h Transfer A't"J Go r-17077m Figure 3 Flowchart 70-Chart Figure 4

Claims (1)

[Scope of Claims] The target speed of the movable body (5), which is indicated by a digital value from the speed control device (1) of the movable body (5), is D/A converted via a subtracter (2), and the drive is performed. A sampling circuit (7) moves the movable body (5) via a circuit (4) and outputs the output of a position signal detector (5) that detects the moving position.
In a speed control system, the output of the sampling circuit (7) is A/D-converted and fed back to the subtracter (2), and performs servo control so that the output of the subtracter (2) approaches zero. A speed calculation unit (10) that calculates the current speed from the signal via the A/D converter (9)
and an expected value calculating section (11) which calculates the expected speed and expected position at the time of the next sample from the output of the speed calculating section (10) and the output of the A/D converter (9).
), a storage unit (12) for temporarily storing the output of the predicted value calculation unit (11), and an abnormal speed detection unit (13) for determining abnormality in the output of the speed calculation unit (11), A speed selection section (14) is provided for switching the output of the speed calculation section (10) to the predicted speed of the previous sampling period stored in the storage section (12) in response to the abnormality detection signal of the abnormal speed detection section (13). An error correction system for a speed control system, characterized in that the output of the speed selection section (14) is input to the subtracter (2).