JPH03212182A - Servo circuit - Google Patents

Abstract

PURPOSE:To avoid overshoot and to realize quick rising by comparing the current value of error in the rotational period of a control target with a preceding sample error value multiplied by a predetermined value, and then switching from quick starting acceleration to steady state. CONSTITUTION:A servo object, e.g. a drum motor S, is started and accelerated quickly according to a rising characteristic 34 and then a rotational speed signal FG is provided to a servo circuit 3. A rotational period detecting means 30 in the servo circuit 3 determines the differences TER(i), TER(i-1) between a target rotational period and the rotational periods of current and preceding samples, which are then provided to a judging circuit 31. An operating circuit incorporated in the judging circuit 31 multiplies thus determined two differences by 3 and 5, for example, and then the differences are determined thus predicting the time when the rotational speed of the motor 8 exceeds a target speed. The judging circuit 31 produces a signal at the predicted time and turns a switch 32 to a steady feedback characteristic 36. By such arrangement, overshoot is avoided and the drum motor rises quickly and reliably.

Description

[Detailed description of the invention] The present invention will be explained in the following order.

A. Industrial field of application B. Overview of the invention C. Conventional technology Problems to be solved by the invention (Fig. 5) E. Means for solving the problems (Figs. 1 and 3) F. Effects (Fig. 3) 1 and 3) G Embodiment (G1) First embodiment (FIGS. 1 to 4) (G2) Other embodiments H Effects of the invention A Industrial field of application The present invention relates to servo circuits. For example, the present invention can be applied to a digital audio recorder that records and plays back digital audio signals.

B. Summary of the Invention The present invention provides a servo circuit in which a periodic error is multiplied by a predetermined value, and based on the result of comparison with the periodic error of one sample before multiplied by the predetermined value, after rapidly accelerating a controlled object, By switching and controlling the state, overshoot can be effectively avoided and startup can be performed rapidly.

C. Prior Art Conventionally, in digital audio recorders, a servo circuit is used to rotate a rotating drum at a predetermined speed and to run a magnetic tape at a predetermined speed.

As a result, in the digital audio tape recorder, recording tracks are sequentially formed diagonally on the magnetic tape wound diagonally around the rotating drum, and digital audio signals are recorded at high density.

D Problems to be Solved by the Invention By the way, in this type of digital audio recorder, if the rotational speed of the rotating drum and the running speed of the magnetic tape can be quickly started up at the time of startup,
It is believed that the usability of the digital audio chip recorder can be improved.

However, as shown in Figure 5, in this type of servo circuit, the occurrence of overshoot is unavoidable, and if the servo characteristics are set so that the overshoot is small,
In the steady state after startup, the response characteristics to disturbances begin to deteriorate.

Therefore, even if the rise is made faster, it takes time to settle, making it difficult to shorten the rise time.

One possible method for solving this problem is to configure a servo circuit using an arithmetic processing circuit.

That is, the speed of the controlled object relative to the target speed is detected, and control data is generated based on the detection result.

Furthermore, the control data is converted into an analog signal by a digital-to-analog conversion circuit to drive the controlled object.

Furthermore, when starting up, it accelerates rapidly and starts up, and when the rotational speed of the controlled object approaches the target speed, it switches to normal servo operation.

In this way, it is considered that overshoot can be effectively avoided and the controlled object can be quickly brought up to the target speed.

However, when switching the operation based on the rotational speed in this way, there is a problem that the calculation process becomes complicated.

Furthermore, there is also the problem that it is difficult to select the timing to switch from a state of sudden acceleration to normal servo operation.

The present invention has been made in consideration of the above points, and aims to propose a servo circuit that can effectively avoid overshoot and start up quickly.

E Means for Solving the Problem In order to solve this problem, in the present invention, the rotation period T (i-1), T (i), . . . of the controlled object 8 is
. . . are sequentially detected and the period errors T□(i-1), Tt, (i), . . . with respect to the target rotation period 'ritr are detected
The rotation period detection means 20.22.24.26 detects the period error T□(i) and the circumference of one sample before [Xl]E%
Comparing means 20 that multiplies the difference Tt*(i 1) by a predetermined value and outputs a comparison result, and based on the comparison result,
A switching means 20 and 28 for switching the controlled object 8 to a steady state after rapidly accelerating the controlled object 8 is provided.

F action period error T□(i) and period error TEt before one sample
By multiplying (it) by a predetermined value to obtain a comparison result, it is possible to easily predict whether the rotational speed of the controlled object 8 will exceed the target speed.

Therefore, if the controlled object 8 is rapidly accelerated and then switched to a steady state based on the prediction result, overshoot can be effectively avoided and the system can be started up quickly.

G example An embodiment of the present invention will be described in detail below with reference to the drawings.

(G1) First Embodiment In FIG. 2, 1 indicates a digital audio chip recorder as a whole, and its operation is switched based on control data output from a system control circuit 2.

That is, the servo circuit 3 drives the reel motor 4, capstan motor 6, and drum motor 8 based on the control data, thereby causing the magnetic tape 12 wound around the rotary drum 10 to run at a predetermined speed, thereby driving the magnetic heads 14A and 14B. scanning loci are sequentially formed diagonally on the magnetic tape 10.

Further, the servo circuit 3 rapidly accelerates the drum motor 8 at startup, and then switches to normal servo characteristics when the drum motor 8 approaches the target speed, thereby starting up the rotational speed of the rotating drum 10 at a higher speed than before. is being done.

That is, as shown in FIG. 3, the servo circuit 3 provides the control data DCOHT output from the system control circuit 2 to the arithmetic processing circuit 20 via the bus BUS, thereby switching the operation of the servo circuit 3. being done.

Further, the servo circuit 3 generates a switching pulse signal SWP whose signal level is switched at the time when the magnetic heads 14A and 14B start scanning, based on the output signal FC from the rotational speed detection means attached to the drum motor 8.

The edge detection circuit 22 detects the switching pulse signal S
An edge detection signal SA whose signal level rises at the timing when the signal level of WP falls is generated.

The latch circuit 24 latches the count value C0NT of the counter circuit 26 that cyclically counts the predetermined clock signal CK at the rising timing of the edge detection signal S1, and transfers the latched count value C0NT to the bus BUS.
Output to.

In this manner, the arithmetic processing circuit 20 can detect the rotation period of the rotary drum 10 based on the count value output to the bus BUS.

Therefore, in the arithmetic processing circuit 20, the period error with respect to the target rotation period can be detected based on the detection result of the rotation period, and the control data D C (1
By outputting 1, the rotational speed of the rotary drum 10 is increased at a higher speed than before, and then the rotary drum 10 is driven at the target speed.

By detecting the period error with respect to the target rotation period in this way and driving the drum motor 8 based on the detection result, the calculation processing work of the calculation processing circuit 20 can be reduced compared to the case where the rotation speed is detected and controlled. It can be simplified.

That is, in this type of drum motor 8, it can be assumed that it is accelerated almost linearly at the time of startup, so that the count values C0NT, , C output to the bus BUS are
By sequentially inputting and subtracting 0NTz, .

On the other hand, the rotational speed Wd can be expressed by the following equation, and in order to detect the rotational speed Wd and control the drum motor 8, in addition to the calculation process of equation (1), the calculation of equation (2) must be performed. Division will be required.

Therefore, if the period error with respect to the target rotation period is detected based on the rotation period T and the drum motor 8 is driven based on the detection result, the calculation process of equation (2) can be omitted, and the calculation process The arithmetic processing work of the circuit 20 can be simplified.

Incidentally, the acceleration Acc can be expressed from the rotational speed Wd obtained by the arithmetic processing of equations (1) and (2) as follows. Here, Wd (i) and Wd (i-1) represent the rotational speeds of the i and i-1 samplings, respectively.

Therefore, when the drum motor 8 is linearly accelerated as described above, the rotational speed W of the subsequent i+1st sampling is
d(i+1) is calculated by the following formula% formula% (4) However, as shown by the broken line in Fig. 4, in reality, at the i-th sampling speed Wd (i), (1
) and (2), the count value C0NT of i-1 and i-th sampling is obtained (Fig. 4 (A
)).

Therefore, the rotating drum 10 actually rotates at the rotational speed W (i + 1) expressed by the following formula (5) at the i+1 sampling.

That is, based on the count values of i-1 and i-th sampling, the true rotational speed W of the subsequent i+1-th sampling
It turns out that (i + 1) can be predicted.

Therefore, the drum motor 8 is accelerated in the maximum acceleration state until the predicted value W(i+1) of the rotational speed is predicted to rise to the target rotational speed W□2 or more, and then the drum motor 8 is switched to the steady servo state. For example, overshoot can be effectively avoided and the time required for startup can be shortened.

In other words, by switching from the maximum acceleration state to the steady servo state when the following relationship holds true, overshoot can be effectively avoided and the time required for startup can be shortened. .

Here (6) ceremony, The following formula () %formula% (7) can be transformed into Equation (2) is The following formula Because it can be transformed into (8) to (7) expression Put it in, The following formula %formula%() (9) The following formula As shown in , the target rotation period T @tr Expressed as, (9) ceremony, The following formula (11) Sort this out, The following formula The following formula 2T (i)T (i-1) It can be expressed as

Therefore, (13) Transforming the formula, The following formula %formula%() relationship can be obtained.

Here, the target rotation period T0. The rotation period T (i
) and T(i-1) as the periodic error T ) 3 (T□(i) +T*tr ) 〉2 (TEN(1) +Tmtr ) (16) Here, the right side can be expressed as %() (1) () () () ( 1) ) (17) If we rearrange equation (16) by transforming it as follows, we get the following equation: %(1) () () ) (18) The following equation: 5Tt+*(i 1) 3T□(i) T■r +27□(i) +27□(i-1) (19) From the following formula % formula %) () (20) Here, if the rotation speed of the rotating drum 10 is near the target rotation speed, the following formula % Since the relationship of (21) ) ( (22) holds, the right side of equation (20) can be expressed as the following equation (23), and thus equation (20) becomes It can be expressed as the following formula 3T□(i-1)-57□(i)>0 (24), and by transforming this, we can obtain the relationship of the following formula%(1) () (25) I can do it.

That is, the periodic error T□(i
-1) and T□(i), and obtain the periodic error T□(i-1
) and T□(i) by 3 and 5, respectively, and obtain the comparison results, it is possible to easily predict whether the target rotation speed will be exceeded in the subsequent i+1th sample.

Based on this detection principle, the arithmetic processing circuit 20 outputs maximum acceleration control data to the digital-to-analog conversion circuit (D/A) 2B at the time of startup (Fig. 4 (B)), thereby causing the drum motor 8 to Apply acceleration voltage MAX.

Furthermore, the arithmetic processing circuit 20 takes in the count values C0NT, , C0NTx that are sequentially output to the bus BUS (1
) equation (i.e. rotation period T (i-1), T
After obtaining (i), ...), the period error Ttl (i 1), T□ (i), ... is obtained from the subtraction result.
Detect...

Furthermore, the arithmetic processing circuit 20 calculates the obtained periodic error 'rEa
(i) is multiplied by 5, and the periodic error 'rEt(t-t) obtained one sample before is multiplied by 3 to obtain a comparison result, (2
5) When the relationship in the equation holds true, the control data is switched and the state of maximum acceleration is switched to steady servo operation.

That is, when the relationship in equation (25) is established, the arithmetic processing circuit 20 sends control data so that a control voltage proportional to the periodic error is applied, thereby effectively avoiding overshoot and controlling the drum motor 8. The rotation speed is rapidly increased.

Thus, as shown in FIG.
is the rotation period T (i
-1), T (i), . . . are sequentially detected, and the period errors T
□Rotation period detection means 3 for detecting (i),...
Configure 0.

Furthermore, the arithmetic processing circuit 20 constitutes a discrimination circuit 31 and a selection circuit 32, and multiplies the periodic error T□(i) and the periodic error T□(i-1) one sample before by predetermined values 5 and 3, respectively. The present invention comprises a comparison means for outputting a comparison result, and a switching means for switching to a steady state after rapidly accelerating the controlled object based on the comparison result.

Furthermore, the arithmetic processing circuit 20, together with the digital-to-analog conversion circuit 28, has a rise characteristic 34 that rapidly starts up the drum motor 8 at the time of start-up, and in a steady state, periodic errors T□(i-1), T□(i), . A drive circuit is configured to set the steady feedback characteristic 36 for driving the drum motor 8 based on the following.

In the above configuration, when the drum motor 8 starts up, the maximum acceleration voltage MAX is applied and the rotational speed rapidly increases.

At this time, after the count value of the counter circuit 26 is latched at the timing when the switching pulse signal SWP falls, the arithmetic processing circuit 20 sequentially obtains the subtraction results, thereby increasing the rotation period T (i-1) of the drum motor 8. ,
After T (i), ...... are detected, the period errors 'rtt(i-1), 'rtm from the target rotation period T□,
(i), . . . are detected.

The periodic error T
A comparison result is obtained with i), and based on this, it is predicted whether or not the rotational speed of the drum motor 8 will exceed the target rotational speed in the subsequent (i+1)th sample.

If it is predicted that the rotational speed of the drum motor 8 exceeds the target rotational speed, the drum motor 8 will be operated at a maximum acceleration voltage M
A steady-state drive voltage is applied from AX, which causes rapid acceleration and then quickly settles to the target speed.

According to the above configuration, by detecting a period error from the rotation period of the drum motor 8, multiplying the period error by a predetermined value, and multiplying the period error one sample before by a predetermined value to obtain a comparison result, It is possible to easily predict whether the rotational speed of the drum motor 8 will exceed the target value.

Therefore, by switching the drive of the drum motor based on the comparison result, overshoot can be effectively avoided and the rotation speed can be rapidly increased.

(G2) Other Embodiments In the above-mentioned embodiments, a case was described in which the periodic error was multiplied by five times and a comparison result was obtained between the periodic error of one sample before and multiplied by three times. The present invention is not limited to this, and the multiplication value may be changed as necessary.

That is, in the above embodiment, the case where the drum motor accelerates linearly was described, but in the case where the drum motor accelerates non-linearly, the equation can be calculated by multiplying the acceleration AC in equation (4) by a predetermined coefficient. By transforming, it is possible to easily obtain a judgment formula for whether or not the target rotational speed is exceeded, and by switching to a steady state based on the judgment formula,
It is possible to effectively avoid overshoot and start up quickly.

Further, in the above-described embodiment, a case was described in which a drum motor was driven in a digital audio chip recorder, but the present invention is not limited to this, but can be widely applied to cases where a capstan motor and a reel motor are driven. can.

Further, in the above-described embodiment, the case where the present invention is applied to a digital audio recorder is described, but the present invention is not limited to this, and can be applied to a video tape recorder, etc.
It can be widely applied to servo circuits that control various motors.

H Effects of the Invention As described above, according to the present invention, the periodic error of the controlled object is detected and the periodic error of one sample before is multiplied by a predetermined value to obtain a comparison result, thereby easily detecting the periodic error of the controlled object. It is possible to predict whether or not the rotation speed exceeds the target rotation speed.

Therefore, by switching and driving the controlled object based on the comparison result, it is possible to obtain a servo circuit that can effectively avoid overshoot and start up rapidly.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a servo circuit according to an embodiment of the present invention, Fig. 2 is a block diagram showing a digital audio tape recorder, Fig. 3 is a block diagram showing the servo circuit, and Fig. 4 shows its operation. Characteristic curve diagram for explanation;
FIG. 5 is a characteristic curve diagram for explaining the problem. 1...Digital audio chip recorder,
3...Servo circuit, 8...Drum motor, 10...Rotating drum, 20...Arithmetic processing circuit, 22...Edge detection circuit, 24・
...Latch circuit.

Claims (1)

[Claims] Rotation period detection means that sequentially detects the rotation period of a controlled object and detects a period error with respect to a target rotation period; A servo circuit comprising: comparing means for outputting a comparison result based on the comparison result; and switching means for rapidly accelerating the controlled object and then switching it to a steady state based on the comparison result.