JP2538358B2 - Motor servo device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a servo device for a motor, and in particular, for example,
The present invention relates to a motor servo device that controls an 8 mm VTR cylinder motor.

[Prior art]

For example, the Technical Report of the Television Society, ITEJ Technical R
eprot Vol.12, No.17, PP37-42, VR'88-13 (May, 1989)
In "Development of software servo system in VTR", a recursive comb filter realized by software is proposed. With such a digital notch filter, as shown in FIG. 8, the gain in the ultra-low frequency region becomes small. Therefore, it is not possible to apply such a digital notch filter to a signal that combines velocity error and phase error. This is because the direct current component of the added signal is lost and the cylinder servo system does not function. Therefore, the conventional software-based cylinder servo system in a VTR is configured as shown in FIG. Note that, also in FIG. 7 and the description of the embodiments below, each block is referred to as a “circuit” for convenience, but it has been pointed out in advance that the functions of these blocks are processed by software in the servo microcomputer. I'll do it.

In the servo device 1 shown in FIG. 7, the speed error detection circuit 2
Detects a speed error based on a frequency (FG) signal of a cylinder motor (not shown). The speed error data from the speed error detection circuit 2 is given to the weighting circuit 4 through the digital notch filter 3. The weighting circuit 4 gives a predetermined weight to the velocity error data passed through the digital notch filter 3 and gives it to the adding circuit 5. On the other hand, a phase error is detected by the phase error detection circuit 6 based on the phase (PG) signal from the motor and the reference frequency signal, and the phase error data from this circuit 6 is given to the addition circuit 5 via the weighting circuit 4. To be Therefore, in the adder circuit 5, the speed error data that has passed through the digital notch filter 3 and the phase error data that does not pass through the digital notch filter are added at a predetermined ratio, whereby a motor control signal is obtained.

[Problems to be Solved by the Invention]

In the prior art shown in FIG. 7, since the phase error data is not filtered by the digital notch filter, when the phase error is sampled at a frequency equal to or higher than the notch frequency, as shown in FIG. A periodic fluctuation component remains. That is, even if the velocity error data is filtered by the digital notch filter 3 as shown in FIG. 9 (A), the periodic fluctuation occurring in the phase error data at the same frequency as the notch frequency is shown in FIG. 9 (B). As shown, it is added to the phase error data as it is.

Therefore, a main object of the present invention is to provide a servo device for a motor, which can more completely eliminate periodic fluctuation components.

[Means for solving the problem]

The present invention is a speed error detecting means for detecting a speed error in response to a frequency signal whose frequency changes according to the number of rotations of a motor, and a phase signal whose phase changes according to the rotation phase of the motor and N times the frequency signal. A first phase error detecting means for detecting a first phase error based on a first reference signal (N is an integer of 1 or more), a speed error from the speed error detecting means and a first phase error detecting means from the first phase error detecting means. 1st addition means for adding 1 phase error at a predetermined ratio, a notch filter which receives the output from the 1st addition means and has a predetermined reference notch frequency, a phase signal and 1 / M (M of the reference notch frequency) Second phase error detection means for detecting a second phase error based on a second reference signal of 1 or more),
And a second adding means for adding the output of the notch filter and the second phase error from the second phase error detecting means at a predetermined ratio to obtain a motor control signal for controlling the motor.

[Action]

The first adding means adds the speed error and the first phase error that do not pass through the digital notch filter at a predetermined ratio, and the output of the first adding means is filtered by the digital notch filter. On the other hand, the second phase error detected by the second phase error detecting means at the sampling frequency of 1 / M of the notch frequency of the digital notch filter is added to the output of the digital notch filter by the second adding means. The sampling of the second phase error causes the gain of the digital notch filter at the reference notch frequency and its higher order frequencies to become infinite. This second phase error is not filtered by the digital notch filter. Therefore, in the second phase error given to the second adding means together with the output of the digital notch filter, the gain is not lowered in the extremely low frequency range. On the other hand, since the first phase error is filtered by the digital notch filter, the gain is reduced in the ultra-low frequency range. Gain reduction at low frequencies is compensated.

〔The invention's effect〕

According to the present invention, the first phase error is filtered by the digital notch filter, and the second phase error is sampled at a frequency of 1 / M of its reference notch frequency, so that the notch frequency components are not included and they are added. Therefore, the notch frequency component can be completely removed from the phase error component included in the motor control signal. Therefore, the motor control signal does not fluctuate periodically, and more stable servo characteristics can be obtained.

The above-mentioned objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of the embodiments with reference to the drawings.

〔Example〕

FIG. 1 is a functional block diagram showing an embodiment of the present invention. The servo device 10 of this embodiment includes a speed error detection circuit 12 that detects a speed error based on a frequency (FG) signal from a motor (not shown), and the speed error detection circuit 12 samples each FG signal. The speed error data thus obtained is given to the adding circuit 16 through the weighting circuit 14.

Further, in the first phase error detection circuit 18, the first reference frequency signal Ref1 that is N times (N is an integer greater than or equal to 1; however, “1” in this embodiment) the phase (PG) signal and the FG signal from the motor.
The first phase error is detected based on The first phase error detection circuit 18 is supplied with the above-mentioned FG signal. Therefore, the first phase error is sampled in response to the FG signal and supplied to the addition circuit 16 through the weighting circuit 14.

When applied to the cylinder servo system of 8 mm VTR, the sampling frequency in the speed error detection circuit 12 is 360 Hz, and the sampling frequency in the first phase error detection circuit 18 is also 360 Hz.

In the weighting circuit 14, the speed error data and the first phase error data are given to the adding circuit 16 at a ratio of 8: 1, for example, so that the speed error data is processed by "× 8". Then, the adder circuit 16 adds the speed error data and the first phase error data at 8: 1, and the output is given to the digital notch filter 20.

As the digital notch filter 20, the above cyclic comb filter is used. Then, the output of the digital notch filter 20 passes through the weighting circuit 22 and the adding circuit 24
Given to. When applied to the cylinder servo system of 8 mm VTR, the basic frequency of the digital notch filter 20 is 30 Hz.

The second phase error detection circuit 26, based on the aforementioned PG signal and the second reference frequency signal Ref2 of 1 / M (M is an integer greater than or equal to 1; however, "1" in the embodiment) of the reference notch frequency, Detect a two-phase error. This second phase error detection circuit
The sampling frequency of 26 is set to 30 Hz, which is the same as the fundamental frequency of the digital notch filter 20 when applied to the cylinder servo system of 8 mm VTR. And this second
The output of the phase error detection circuit 26 is given to the addition circuit 24 via the weighting circuit 22 described above.

The weighting circuit 22 applies a predetermined weight to the output of the digital notch filter 20 and the output of the second phase error detection circuit 26, and gives the weighted output to the adding circuit 24. In the case of this embodiment, the weighting circuit 22 performs weighting so that the output of the digital notch filter and the second phase error are added at a ratio of 1: 1. Then, the adder circuit 24 adds both input data,
Obtain the motor control signal (data). The function of each circuit shown in FIG. 1 is actually achieved by software of a servo microcomputer as shown in FIG.

The servo routine of FIG. 5 is configured as an interrupt routine that responds to the FG signal. And the first step
In S1, a speed error is created and stored in an appropriate area DSP of RAM (not shown). Then, in step S2, the first phase error is created and the error data is stored in RAM.
Store it in the appropriate area DPH1. Then, in step S3, the data in the areas DSP and DPH1 are added at a predetermined ratio. That is, the speed error data of the area DSP is
8 ”, and the result is added to the first phase error data in the area DPH1 and the result is stored in the area DAD of the RAM. Then, step S4
In, the data of the area DAD, that is, the addition result of the velocity error data and the first phase error data is filtered. The result is stored in the area DAD '.

In the next step S5, an appropriate area RAM of RAM is incremented. This area RAM is cleared by interrupt processing of the PG signal. That is, this area RAM is cleared at 30 Hz. In the next step S6, the area RAM is "1".
To determine if. If it is "1", in the next step S7, the second phase error data is created,
Store it in an appropriate area DPH2 of RAM. Area RAM is
It counts "1 to 12" and is reset by the PG signal. Therefore, if the second phase error data is created when the area RAM is "1", the second phase error data will be the result of the PG signal. It means that it was sampled at the frequency of 30Hz.

In the next step S8, the data of the area DAD ′ and the area DPH2
The data of the area DAD ″ is stored in the area DAD ″.
It is output as a WM motor control signal.

According to the embodiment shown in FIG. 1, that is, FIG. 5, the second phase error data shown by the solid line in FIG. 3 is added to the output of the digital notch filter shown by the dotted line.

Since the speed error data and the first phase error data are filtered by the digital notch filter 20 as shown in FIGS. 4 (A) and 4 (B), they include, for example, a 30 Hz component due to motor eccentricity and a motor. Periodic fluctuations such as 120Hz component due to jumping into the drive magnet FG coil are completely eliminated. On the other hand, since the second phase error data is sampled at the reference notch frequency of 30 Hz, similarly, it does not include this 30 Hz and its harmonic components, and becomes the one shown in FIG. 4 (B '). Therefore, as shown in FIG. 4 (C), no periodic fluctuation component appears in the motor control signal, and thus the servo characteristic is very good.

Further, since the second phase error data is not filtered by the digital notch filter, there is no gain decrease in the ultra low frequency region as shown by the solid line in FIG. Even if the gain is reduced, the gain reduction is compensated, so that the response of the phase servo in the high range is not deteriorated.

FIG. 6 is a concrete functional block diagram when the embodiment of FIG. 1, that is, FIG. 5 is applied to a cylinder servo system of 8 mm VTR. In FIG. 6, the same or similar functions as those in FIG. 1 described above are designated by the same or similar reference symbols, and duplicated description will be omitted.

The output of the adder circuit 24 included in the servo microcomputer 100 shown in FIG. 6 is “× 4” by the optimum gain circuit 28 and is given to the PWM circuit 30. Therefore, P
A PWM motor control signal is output from the WM circuit 30, and the motor control signal is passed through a low pass filter 32 to a driver.
Given to 34. The driver 34 controls the cylinder motor 36, and the cylinder motor 36 supplies the FG signal and the PG signal to the microcomputer 100.

The FG signal and the PG signal are given to the RFSW creating circuit 38, and the head switching signal PFSW from this RFSW creating circuit 38 is given to the head control circuit (not shown) and also to the second phase error detecting circuit 26. The head switching signal PF
The SW is created by using the FG signal input as the phase signal from the motor 36 to the first phase error detection circuit 18. That is, the second phase error detection circuit 26 operates based on the FG signal. Also, the microcomputer 10
A vertical synchronizing signal Vsync is given to 0 from a synchronizing circuit (not shown), and this vertical synchronizing signal Vsync is given to the 360 Hz reference creating circuit 40, and also to the recording (Rec) side of the switch 46 via the 1/2 frequency dividing circuit 42. Given. The reference signal from the 30 Hz reference creating circuit 44 is applied to the reproduction side of the switch 46.

The reference frequency signal (reference) Refl of the first phase error detection circuit 18 is a 360 Hz reference creation circuit 40.
Is given from 360Hz. Further, 30 Hz is given as the reference frequency signal Ref2 of the second phase error detection circuit 26. During recording, the switch 46 switches to the Rec side, so the vertical sync signal Vsync is divided by the 1/2 divider circuit 42.
Hz signal is given. At the time of reproduction, the 30 Hz signal from the 30 Hz reference creating circuit 44 is given.

[Brief description of drawings]

FIG. 1 is a functional block diagram showing an embodiment of the present invention. FIG. 2 is a graph showing the characteristic of the second phase error in the embodiment of FIG. FIG. 3 is a graph showing the characteristics of the motor control signal of the embodiment shown in FIG. FIG. 4 is a waveform diagram showing each error signal and motor control signal in the embodiment of FIG. FIG. 5 is a flow chart of software for achieving the embodiment of FIG. FIG. 6 is a functional block diagram showing a concrete application example of the embodiment shown in FIG. 1 and FIG. FIG. 7 is a functional block diagram showing an example of a conventional cylinder servo. FIG. 8 is a graph showing the characteristics of the digital notch filter. FIG. 9 is a waveform diagram showing the operation of the conventional example of FIG. In the figure, 12 is a speed error detection circuit, 16 and 24 are addition circuits, 18 is a first phase error detection circuit, 20 is a digital notch filter, 26 is a second phase error detection circuit, 36 is a motor, and 100 is a servo micro. Indicates a computer.

Claims (1)

(57) [Claims] 1. A speed error detection means for detecting a speed error in response to a frequency signal whose frequency changes according to the number of rotations of a motor, a phase signal whose phase changes according to the rotation phase of the motor, and the frequency signal. A first phase error detecting means for detecting a first phase error based on a first reference signal that is N times (N is an integer of 1 or more) a speed error from the speed error detecting means and the first phase error detection First addition means for adding the first phase error from the means at a predetermined ratio, a notch filter receiving the output from the first addition means and having a predetermined basic notch frequency, the phase signal and the basic notch Second phase error detecting means for detecting a second phase error on the basis of a second reference signal having a frequency of 1 / M (M is an integer of 1 or more); and an output of the notch filter and the second Second obtaining a motor control signal for by adding the second phase error from the phase error detecting means at a predetermined ratio and controls the motor
A servo device for a motor, which comprises an adding means.