JPH06217587A - Servo controller for spindle motor - Google Patents

Abstract

PURPOSE:To make it possible to perform stable servo control over a wide range of load fluctuation regardless of the causes of load fluctuation in a servo controller to servo-control a spindle motor by a driving voltage corresponding to PWM signal through pulse width modulation of error signals in feedback signals. CONSTITUTION:This controller comprises a frequency selecting circuit 21 which has a current detecting circuit 19 for detecting a load current of a spindle motor 10, a frequency selecting circuit 21 for separating the fluctuation range of load current flowing to a spindle motor 10 into a plurality of level stages (21a, 21b and 21c) and outputting selection signals 'a' to 'd' corresponding to each level stage and a frequency setting circuit 22 for setting the frequency of PWM signals in accordance with the selection signals output in conformity with the level stage corresponding to the size judged by the frequency selecting circuit 21 from the load current detected by the current detecting circuit 19.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle motor provided in a recording / reproducing apparatus for recording information on a recording medium such as a magnetic disk or an optical disk and reproducing the recording.
The present invention relates to a servo control device for a computer.

[0002]

2. Description of the Related Art A recording / reproducing apparatus is used in a wide variety of fields. As an example thereof, a recording / reproducing apparatus provided in an electronic still camera will be described. The electronic still camera is equipped with a video floppy disk drive device (hereinafter referred to as VFDD) for recording image information on a magnetic disk and reproducing this recording.

In the VFDD, a disk-shaped floppy disk (magnetic disk) is rotated at high speed by a spindle motor, and a floppy disk is contacted with a magnetic head.
Image information is recorded and reproduced by moving the disk in the radial direction.

Further, this VFDD is a server for extracting the FG signal from the rotation of the spindle motor to control the speed, and to extract the PG signal from the rotation of the floppy disk to control the phase.
It has a control device. That is, the error amount between the FG signal generated by the FG coil provided in the spindle motor and the reference signal is calculated, and the error signal is fed back. Furthermore, the phase difference between the PG signal generated by the PG coil for magnetically detecting the rotation of the floppy disk and the vertical synchronizing signal from the camera circuit, and the error amount between this phase difference and the reference signal are calculated, The error signal is fed back.

The error signal fed back is converted into a pulse by a pulse width modulation circuit, and this pulse (PWM signal) is integrated by a filter and supplied as a drive voltage for the spindle motor. The frequency of the PWM signal is fixed and load fluctuations (error amount of feedback signal)
The duty ratio is changed accordingly.

That is, when the speed of the spindle motor is low, the duty ratio of the PWM signal is large, and when the speed of the spindle motor is high, the duty ratio is small. This relationship is the same for the phase control. Then, when the spindle motor is controlled so that the error amount between the speed and the phase falls within a predetermined range, a servo-lock state is established and recording on the floppy disk becomes possible.

[0007]

In the servo control device described above, the error signal relating to speed and the error signal relating to phase are actually gain-multiplied by the amplifier and then added,
Then, after being converted into a PWM signal and integrated and output as a drive voltage, a servo control that is strong against load fluctuation and a weak servo control are performed depending on how the gain of the amplifier is applied. Therefore, if the gain is increased, the servo control becomes stronger, but if the gain is not set to an optimum value, the recorded or reproduced image may be adversely affected, or an unstable region may oscillate.

In particular, since the electronic still camera must be used in cold areas or hot areas,
It is necessary to be able to sufficiently cope with load fluctuations due to environmental temperature. However, the motor load and the hardness of the floppy disk change due to changes in the environmental temperature, and the operating load of the camera becomes heavy or light.

On the other hand, the operating load of the floppy disk may change depending on the manufacturer or the rod, and the operating load of a single floppy disk may change depending on the difference in tracks. Furthermore, load fluctuations occur when the magnetic head is not in stable contact with the floppy disk.

When the operating load changes as described above, the speed of the spindle motor is affected, so that it may be out of the range where servo lock can be performed, and recording and reproduction on the floppy disk may become impossible.

For example, if the operation guarantee range of the electronic still camera is -5 ° C. to 45 ° C., the operating load may change significantly in this range, so servo lock may not be possible, and the gain may be increased. If the servo lock is extended, the recorded image will be adversely affected.

In particular, the servo lock may not be possible when the above various conditions for varying the operating load are met. At present, no servo control means has been developed that can absorb all possible load fluctuations, and a compromise has been made in obtaining a certain degree of control accuracy.

In view of the above-mentioned circumstances, the present invention stably supports a wide load variation regardless of the cause of the operating load.
The purpose is to develop a spindle motor control device capable of controlling the robot.

[0014]

In order to achieve the above object, in the present invention, the error signal obtained from the feedback signal is pulse-converted by the pulse width modulation means and corresponds to the duty ratio of the pulse. In a servo control device which outputs a driving voltage to control a spindle motor, a detection means for detecting a load current of the spindle motor and a variation range of the load current flowing through the spindle motor are preset to a plurality of levels. Current level judging means for dividing into stages and outputting a selection signal according to each level step, and the current level judging means judges the magnitude of the load current detected by the detecting means, and determines the magnitude. And a frequency setting means for setting the frequency of the pulse output by the pulse width modulation means in response to the selection signal output according to the corresponding level step. Other service - - spindle motor to propose a volume control device.

[0015]

By operating the spindle motor, the load current flowing through the motor is detected by the detecting means. Then, the current level determination means determines which level stage of each level stage the magnitude of the load current detected as described above corresponds to.

By this judgment, any one of the level stages is selected, and a selection signal corresponding to the selected level stage is output. The selection signal thus output is sent to the frequency setting means, and this frequency setting means sets the frequency of the pulse output from the pulse width modulation means so as to correspond to the selection signal, that is, the magnitude of the load current. To do.

Even if the pulses output from the pulse width modulation means have the same duty ratio, the drive voltage supplied to the spindle motor can be increased as the frequency is increased. Conversely, the lower the frequency, the lower the drive voltage.

Therefore, in addition to the conventional servo control by the feedback signal, the frequency of the pulse output by the pulse width modulation means is set according to the magnitude of the load current to control the drive voltage. As a result, servo control can be performed in a wide load variation range for load variations of all causes.

[0019]

EXAMPLE Next, a V equipped with an electronic still camera according to the present invention will be described.
An example implemented in FDD will be described with reference to the drawings.
FIG. 1 is a block diagram showing a circuit portion of a VFDD. 10 is a spindle motor, and 11 is a floppy disk rotated by the spindle motor.

The spindle motor 10 is a DC three-phase motor which is rotationally driven by three-phase power supply (U, V, W) from the motor drive circuit 12, and is for detecting the rotational speed. F
A G coil is provided, and an FG signal generated in this FG coil is input to a CPU (central processing unit) 15 via an amplifier 13 and a waveform shaping circuit 14.

The floppy disk 11 is chucked and rotated by a turntable provided integrally with the rotary shaft of the spindle motor 10. The PG coil 16 for magnetically detecting the rotation of the floppy disk 11 is provided, and the PG signal generated in the PG coil 16 is input to the CPU 15 via the waveform shaping circuit 17.

The CPU 15 uses the FG input as described above.
The error amount between the signal and the reference signal is calculated, and this speed error signal is amplified by the amplifier and multiplied by the gain. In addition, the phase difference between the input PG signal and the vertical synchronizing signal from the camera circuit is calculated, the error between the phase difference signal and the reference signal is calculated, and the phase error signal is amplified by an amplifier to multiply the gain. To do.

Thereafter, the CPU 15 adds the speed error signal and the phase error signal, pulse-width-modulates this added signal, and outputs it as a PWM signal.

This PWM signal is input to the integrating circuit 18,
The integrating circuit 18 integrates with a filter.
The integrated signal is smoothed and then sent to the motor drive circuit 12 as the drive voltage Vm.

On the other hand, the load current (consumption current) of the spindle motor 10 is detected by the current detection circuit 19, and the detected load current is converted by the voltage conversion circuit 20. Then, the voltage conversion data signal Vo of the load current thus voltage-converted is input to the frequency selection circuit (current level determination means) 21 provided in the CPU 15. In addition,
The CPU 15 is provided with an analog input port, and the voltage conversion data signal Vo is input using this input port.

The frequency selection circuit 21 is constructed as shown in FIG. That is, the reference current value is defined by dividing the range in which the load current of the spindle motor 10 varies into a plurality of level stages. For example, in this example, 50 mA, 7
0 mA, divided into 90 mA, matching voltage data of V ₁ that these matching current value and voltage conversion, V _2, V ₃ - data each level stage 21
It is set to a, 21b, and 21c.

Then, the level stages 21a, 21b, 21c
Is selected to select signals a to d corresponding to the matching current value.
Is output. The selection signals a to d are P
The frequency of the WM signal is selected. The level stage 21a outputs a selection signal for selecting the frequency f ₁ , the level stage 21b selects the frequency f ₂ , and the level stage 21c selects the frequency f ₃ or the frequency f ₄ . These frequencies are f ₁ <f ₂ <f ₃ <
There is a relationship of f ₄ .

When the voltage conversion data signal Vo of the load current is input to the frequency selection circuit 21, it is determined which level stage the data signal Vo belongs to, and the level stage to which the data signal Vo belongs. Is selected, and the selection signal of that level stage is output.

For example, if the load current of the spindle motor 10 is 60 mA, the voltage conversion data of this current is used.
Since the signal Vo is V ₁ <Vo <V ₂ , the level stage 2
1b is selected and the selection signal b is output.

On the other hand, the CPU 15 has a frequency selection circuit 21.
A frequency setting circuit 22 that changes the PWM signal into a plurality of stages of frequencies is also provided. For example, in the present embodiment, the frequency setting circuit 22 inputs the selection signals a to d output from the frequency selection circuit 21 and sets them as PWM signals of frequencies f _{1 to} f ₄ .

In the servo control device for the spindle motor constructed as described above, when the spindle motor 10 is driven to rotate, the floppy disk 11 rotates, which causes the FG signal and the PG signal. Input to CPU15,
Further, the voltage conversion data signal Vo is input to the frequency selection circuit 21 of the CPU 15 according to the load current flowing through the spindle motor 10.

As a result, the speed error signal and the phase error signal are pulse-width modulated to become the PWM signal, and the frequency setting circuit 22 selects the frequency selecting circuit 21, that is,
The frequency of the PWM signal is set according to the magnitude of the load current.

The CPU 15 outputs the PWM signal thus pulse-width modulated and frequency-set, and the PWM signal is integrated and smoothed by the integrating circuit 18 to generate the drive voltage Vm.
Is sent to the motor drive circuit 12, and this motor drive circuit 1
2 is a spindle motor 1 according to its drive voltage Vm.
0 controls power supply.

FIG. 3 is a graph showing the relationship between the drive voltage Vm and the duty ratio of the PWM signal with respect to the set frequencies f _{1 to} f _{4 of the} PWM signal. As can be seen from this graph, the driving voltage Vm increases as the frequency increases in the region where the duty ratio is large. From this, when the load becomes large, it is extremely advantageous to increase the frequency of the PWM signal to deal with it.

In the servo control device of this embodiment, the frequency of the PWM signal is set according to the magnitude of the load current of the spindle motor 10 which is proportional to the load, so the load increases,
Spindle motor - the greater the load current of the motor 10, level stage 21c of the frequency selection circuit 21 is singled out by the output of the selection signal c or d, PWM signal is set to a frequency higher f ₃ or f ₄ It

Therefore, when the load becomes large, in addition to the speed error signal and the phase error signal, the frequency P is increased.
A drive voltage Vm generated by integrating and smoothing the WM signal is generated, and strong servo control is applied to the spindle motor 10. As a result, there is no problem that the servo lock is out of the range due to a large load variation, and the servo control is weak, so that the problem of blurring in the reproduced image is solved.

Although the example of implementing the VFDD of the electronic still camera has been described above, it can also be implemented as a servo control device of a spindle motor provided in an optical disk recording / reproducing device or other equipment.

In implementing this embodiment, the CPU
A similar effect can be obtained by providing a digital filter 15 and switching the constant of this filter by the selection signals a to d output from the frequency selection circuit 21.

[0039]

As described above, the servo control device according to the present invention performs the pulse width modulation of the error signal of the feedback signal to perform the servo control. Since the frequency is set according to the magnitude of the load current flowing through the spindle motor and servo control is performed,
Irrespective of the cause of the load fluctuation of the spindle motor, stable servo control is performed in a wide range of the load fluctuation.

[Brief description of drawings]

FIG. 1 is a circuit block diagram showing an example in which the present invention is applied to a VFDD of an electronic still camera.

FIG. 2 is an explanatory diagram of a frequency selection circuit provided in the above embodiment.

FIG. 3 is a graph showing the relationship between the drive voltage of the spindle motor and the duty ratio of the PWM signal when the frequency of the PWM signal is changed.

[Explanation of symbols]

 10 Spindle Motor 11 Floppy Disk 12 Motor Drive Circuit 15 CPU 16 PG Coil 18 Integration Circuit 19 Current Detection Circuit 20 Voltage Conversion Circuit 21 Frequency Selection Circuit 22 Frequency Setting Circuit

Claims (1)

[Claims] 1. A spindle mode in which an error signal obtained from a feedback signal is pulse-converted by a pulse width modulation means and a drive voltage corresponding to the duty ratio of the pulse is output.
In the servo control device that controls the motor, the spindle motor
A detection means for detecting a load current of the spindle motor, and a current level judgment means for dividing a variation range of the load current flowing through the spindle motor into a plurality of level stages in advance and outputting a selection signal according to each level stage. , The current level determination means determines the magnitude of the load current detected by the detection means,
A spindle motor characterized by comprising frequency setting means for setting the frequency of the pulse output by the pulse width modulating means in response to a selection signal output according to a level stage corresponding to the magnitude. Servo control device.