JPH0245260B2 - SOKUDOSHINGOGOSEIKAIRO - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a speed signal synthesis circuit, and more particularly to a speed signal synthesis circuit used in a head positioning servomechanism of a magnetic disk device.

Recent magnetic disk drives use a two-phase servo system that uses two position signals that are 90 degrees out of phase with each other. By selecting and connecting each /4 period, one continuous speed signal is obtained. Since the speed signal obtained by differentiating this position signal does not have a sufficient signal-to-noise ratio (S/N) to be used as is for speed control, the current detection signal that detects the drive current of the servo motor is used as the speed signal obtained by differentiating the position signal. The signal is added to the signal and passed through a low-pass filter to improve the S/N ratio. The reason why the current detection signal is added is to compensate for the high frequency component of the speed signal being lost in the low pass filter. That is, the drive current I of the servo motor, the force constant K _F ,
The relationship between the mass M of the moving part and the acceleration A is A=IK _F /
It is represented by M. Furthermore, since the acceleration A is a derivative of the velocity V, if the differential operator is S, the equation A=SV holds true. Furthermore, the cut-off frequency of the low-pass filter
The characteristics of the fc low-pass filter are 1/(1+S/
2πfc). Drive current I as K _F /M/
Multiplying by 2πfc and adding it to the speed V gives V+IK _F /M/2πfc=V+A/2πfc=V(1+S/
2πfc), so this can be expressed as the characteristic 1/(1+S/
When passed through a low pass filter of (2πfc), (1+S/
2πfc) are canceled and the velocity V is synthesized. The S/N is improved as the cut-off frequency fc of the low-pass filter is lowered. Therefore, as the cutoff frequency fc is lowered, the current component that occupies the composite speed signal increases, and the position signal differential component decreases, so in the limit where the cutoff frequency fc is lowered, position signal differentiation is not used and the current is integrated. A circuit that generates a speed signal is associated with this. Since velocity is the integral of acceleration, and acceleration is proportional to current as described above, the velocity signal should be obtained by integrating current.

However, the speed signal based on current integration has poor accuracy and has not been used because it causes problems such as the polarity of the speed signal being reversed with respect to the true speed at low speeds. This is caused by external forces such as the wind generated in the moving parts of the head due to the rotation of the magnetic disk, the bending force of the flexible cable that connects the head and the circuit, and the spring that returns the head to a predetermined position when the head is stopped. The reason is that current and acceleration are not exactly proportional. Therefore, conventionally, the cut-off frequency fc of the low-pass filter has been selected to be several hundred Hz as a compromise between the S/N ratio of the speed signal and the accuracy.

The purpose of the present invention is to solve the above-mentioned problems by devising a circuit configuration, improve S/N without impairing accuracy, and more stably control the seek operation speed of a magnetic disk device with high precision. The object of the present invention is to provide a speed signal synthesis circuit that is previously unknown.

According to the present invention, a speed signal synthesis circuit for a head positioning servo mechanism of a magnetic disk device that synthesizes a second speed signal from a first speed signal and a current detection signal of a servo motor includes an integrator and an error amplifier. A signal obtained by subtracting the output signal of the error amplifier from the current detection signal is input to the integrator, and a signal obtained by subtracting the output signal of the error amplifier from the current detection signal is input to the error amplifier. A speed signal synthesis circuit is obtained which is characterized in that the error obtained by subtracting the speed signal is input and amplified.

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram showing part of a servo mechanism in an embodiment of a magnetic disk device using the speed signal synthesis circuit of the present invention. In the same figure,
A servo motor 1 with a force constant K _F is driven by a servo motor drive current I ₀ . The servo motor 1
The displacement of the movable head of the movable head portion 2 of the integral element 1/S and the mass M connected to is denoted by X ₀ . the displacement
The gain of the means 3 which inputs X ₀ and performs position signal differentiation etc. to obtain the first velocity signal V ₁ is denoted by Gv·S.
Further, the gain of the current detection means 4 which detects the drive current I ₀ and outputs the current detection signal I ₁ is indicated by Gc.
The speed signal synthesis circuit 5 is an integrator 5 with a gain of 1/TS.
0, an error amplifier 51 with a gain Ge, and two hybrids 52 and 53, and the first speed signal
A second speed signal V ₂ is synthesized from V ₁ and the current detection signal I ₁ . The integration time constant T of the integrator 50 is such that the output of the second speed signal _V2 is the same as the first speed signal.
to be at the same level as V ₁ , that is, T = (M/
_The integrator 50 integrates the signal obtained by subtracting the output of the error amplifier 51 from the current detection signal _I1 .
Furthermore, the error amplifier 51 amplifies the error obtained by subtracting the first speed signal V ₁ from the combined second speed signal V ₂ . Furthermore, mixers 52 and 53 mix the current detection signal I ₁ and the output of the error amplifier 51, and mix the first and second speed signals V ₁ ,
Perform _V2 mixing.

According to this embodiment, the synthesized second speed signal
Since V ₂ is the output of the integrator 50, high-frequency noise components are compressed, so it is clear that the S/N is good, and it is always compared with the first speed signal V ₁ to eliminate the error. Since it is fed back to the integrator 50 input, the accuracy does not deteriorate. This accuracy is determined by the accuracy of the first speed signal V ₁ , the magnitude of the external force, and the cane Ge of the error amplifier 51 .

Next, FIG. 2 is a circuit diagram showing a specific example of the speed signal synthesis circuit in FIG. 1. In the same figure,
The circuits including operational amplifiers 500 and 520 correspond to integrator 50 and mixer 52, and the circuit including operational amplifier 510 corresponds to error amplifier 51 and mixer 53, respectively. Both circuits are common ones, and the operation of the speed signal synthesis circuit of this embodiment is clear from the explanation of the operation in FIG. 1, so the explanation thereof will be omitted.

Note that the specific example of the speed signal synthesis circuit of the present invention is not limited to that shown in FIG. 2, and various similar circuits can be designed. For example, it is clear that an input signal may be applied to the + side of each operational amplifier.

As explained above, the present invention is configured to integrate a current detection signal to obtain a speed signal, compare it with a speed signal obtained by differentiating a position signal, and correct the error, thereby providing a speed signal with good S/N and accuracy. It has the effect of synthesizing.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a part of a servo mechanism in an embodiment of a magnetic disk device using the speed signal synthesis circuit of the present invention, and FIG. 2 shows a specific example of the speed signal synthesis circuit in FIG. 1. It is a circuit diagram. In the figure, 1... servo motor, 2... movable head section, 3... means for obtaining a first speed signal, 4...
... Current detection means, 5 ... Speed signal synthesis circuit, 5
0... Integrator, 51... Error amplifier, 52, 53
... Mixer, 500, 510, 520 ... Operational amplifier, I ₀ ... Servo motor drive current, I ₁ ... Current detection signal, V ₁ , V ₂ ... First and second speed signals,
X ₀ ...displacement.

Claims (1)

[Claims] 1. A speed signal synthesis circuit for a head positioning servo mechanism of a magnetic disk device that synthesizes a second speed signal from a first speed signal and a current detection signal of a servo motor, which comprises an integrator and an error amplifier, and comprises an integrator and an error amplifier. inputting a signal obtained by subtracting the output signal of the error amplifier from the current detection signal to the device;
The speed signal synthesis circuit is characterized in that the error amplifier is configured to input and amplify an error obtained by subtracting the first speed signal from the second speed signal that is the output of the integrator.