JP2804655B2 - Software servo device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a software servo device, and more particularly to a software servo device used for a servo system of a small motor such as a capstan motor of an 8 mm VTR integrated with a camera.

[0002]

2. Description of the Related Art In a conventional software servo device, phase error data is created by sequentially adding a difference between a measured value of a period of an FG signal and a theoretical value.

[0003]

[Problems to be Solved by the Invention] 8 mm V integrated with camera
When suppressing load fluctuation (disturbance) in the servo system of a motor having a low moment of inertia such as a capstan motor used in a TR, increase the sampling frequency to increase the gain of the phase error data, or It is necessary to increase the low-frequency gain of the phase error data by using the low-pass filter. However, there is a mechanical limit to the number of FG magnetizations of the motor, which cannot be increased so much that there is a limit to increasing the sampling frequency. In addition, the software of the high-order low-pass filter is complicated, and there is a problem that it is difficult to use a microcomputer that is not good at arithmetic processing (for example, an 8-bit single-chip microcomputer that cannot perform 16-bit arithmetic).

[0004] Therefore, a main object of the present invention is to provide a software servo device which can easily suppress a load change.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a software servo device for measuring a period of an FG signal from a motor and integrating speed error data obtained based on the period to generate phase error data. -1 order (N is a positive integer of 2 or more) phase error data is successively integrated for each sampling synchronized with the FG signal to create N order phase error data. It is a software servo device.

[0006]

Assuming that the measured value of the FG cycle is A and the theoretical value of the theoretically predetermined FG cycle is B, the speed error data (DSP) is created from A and the phase error data (DPH) is It is created by adding AB to the immediately preceding DPH for each sampling of the edge of the FG signal. Then, the first-order integral data (D
PH1) is created by adding the DPH to the immediately preceding DPH1 at each sampling similar to the above. Also, the second-order integral data (DPH) of the phase error data
2) is created by adding DPH1 to the immediately preceding DPH2 each time sampling is performed. That is, the Nth-order integral data of the phase error data is obtained by the immediately preceding DPHN−
It is created by adding DPHN-2 to 1 each time sampling is performed. In this manner, the use of the Nth-order phase error data makes it possible to increase the low-frequency servo gain.

The control data (DAD) of the motor is obtained from the phase error data according to Equation 1.
Here, a is a predetermined constant determined from the stability of the control system.

[0008]

DAD = DSP + 1 / aDPH + 1 / a ² DPH1 +... + 1 / a ^{N + 1} DPHN

[0009]

According to the present invention, the servo gain in the low range can be easily increased, so that the load fluctuation can be effectively suppressed even in a small motor. The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

[0010]

Referring to FIG. 2, a software servo device 10 of this embodiment is, for example, a camera-integrated 8 mm VTR.
A microcomputer that is used for mechanical control (hereinafter simply referred to as “mechanical control”)
12) and a microcomputer sharing the system control (hereinafter simply referred to as “syscon”)
14 inclusive. The mechanical controller 12 operates in response to a command from the system controller 14.
A free-run counter 16 for period measurement is built in. From the mechanical controller 12, a PWM (Pulse Width Modulation) signal for controlling the capstan motor 18 is output. The driver 20 outputs a motor voltage corresponding to the PWM signal, and outputs it to the capstan motor 1.
Give 8 And F from the capstan motor 18
The G signal is amplified by the FG amplifier 22 and input to the mechanical controller 12 as an FG pulse.

The mechanical controller 12 creates control data based on the input FG pulse and the count value of the free-run counter 16 as shown in FIG. First, in step S1, the measurement value A of the FG cycle is determined based on the count values a and b of the free-run counter 16 (FIG. 2) shown in FIG. That is, ab is set as the measurement value A.

Next, in steps S3 and S5,
The measured value A of the FG cycle is compared with a time interval indicating a change in the state of the servo data shown in FIG. This servo data is also synchronized with the FG signal shown in FIG. 3, and if the FG cycle takes a preset theoretical value B, the time interval T _S
Means that the servo is applied in the middle part of.
In step S3, it is determined whether the measured value A of the FG cycle is smaller than the time interval T _D shown in FIG.
If the measured value A of the FG cycle is smaller than T _D , the process proceeds to step S7, and the speed error data (DSP) is set to the minimum value Min (for example, 0000000000 for 10 bits). In step S3, the measured value A of the FG cycle is T
If it is not less than _D , the process proceeds to step S5, and it is determined whether or not the measured value A of the FG cycle is not less than the time interval of T _D + T _S. If A is equal to or _larger than T _D + T _S in step S5, the process proceeds to step S9, and the DSP is set to the maximum value Max (for example, 11111111111 for 10 bits).
And If the measured value A of the FG cycle is smaller than T _D + T _S in step S5, step S1
The DSP and A-T _D 1. Thus, step S
After the value of the DSP is set in 7 or S9 or S11, the process proceeds to step S13.

In step S13, a measured value A of the FG cycle
Is set as a variable C, and then, in step S15, the immediately preceding phase error data (DP
DPH is created by adding the variable C to H). Then, the process proceeds to step S17, where DPH1 is created by adding the DPH created in step S15 to the primary integral data (DPH1) of the immediately preceding phase error data. Thereafter, the process proceeds to step S19, where the second-order integral data (DP
H2) is added to DPH1 created in step S17 to create DPH2. And
Proceeding to step S21, DPH3 is created by adding the DPH2 created in step S19 to the third-order integral data (DPH3) of the immediately preceding phase error data. Then, the process proceeds to step S23, where the fourth-order integral data (DPH4) of the immediately preceding phase error data is added to step S23.
By adding the DPH3 created in 21, the DPH4 is created. That is, step S15
In step S23, the integration process of the phase error data is performed every sampling of the FG cycle. And
In step S25, motor control data (DAD) is created according to equation (2).

[0014]

## EQU2 ## DSP + 1/16 DPH + 1/16 ² DPH1
+1/16 ³ DPH2 + 1/16 ⁴ DPH3 + 1/16
⁵ DPH4 where 16-16 ⁵ is a numerical value determined from the stability of the control system. As shown in FIG. 4, when the integration order of the phase error data is increased, the low-frequency servo gain of the transfer characteristic can be increased, so that the load fluctuation can be suppressed even in a small motor having a small moment of inertia.

Since the program of FIG. 1 is not so complicated as compared with the conventional program, it can be executed even by an 8-bit single-chip microcomputer. In the above embodiment, the phase error data up to the fourth order is obtained, but higher order integration processing is possible.

[Brief description of the drawings]

FIG. 1 is a flowchart showing one embodiment of the present invention.

FIG. 2 is a block diagram showing one embodiment of the present invention.

FIG. 3 is a timing chart showing an FG signal, a count value of a free-run counter, and servo data synchronized with the FG signal.

FIG. 4 is a graph showing a transfer characteristic obtained by one embodiment of the present invention.

[Explanation of symbols]

 10: Software servo device 12: Mechanical control 16: Free-run counter 18: Capstan motor

Claims (1)

(57) [Claims] 1. A software servo device for measuring a period of an FG signal from a motor and integrating phase error data obtained based on the period to generate phase error data, wherein an N-1 order (N is 2 or more) A positive integer), the Nth-order phase error data is created by successively integrating the phase error data at each sampling synchronized with the FG signal.