JPH0745018A - Motor controller - Google Patents

Abstract

PURPOSE:To perform feedback control with accuracy at low cost by compensating an offset due to a resistance value error of a detecting value of a driving current of a motor, etc. CONSTITUTION:At the time of deciding a compensating value of an offset, a multiplexer 13 is instructed by an offset compensating circuit 11 to select and output a positive current signal so that a driving current Im of the motor 5 is made to be a positive set current of 0.1A, and an offset is detected from a difference between an output Vo of a current detector 6 and a correct output for 0.1A to decide a compensating value in the case of Im>0. Then, a negative current signal is selected and outputted, so that from an output Vo of the current detector 6 with a negative set current of -0.1A, a compensating value in the case of Im<0 is decided in a similar manner. At the usual time, a control signal to be inputted from a host machine is selected and outputted by the multiplexer 13, and the compensating value to be outputted by the offset compensating circuit 11 in response to whether the driving current Im to be inputted from a PWM modulation circuit 2 is positive or negative is added to an output of the current detector 6 by an adder 12 to compensate the offset.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor control device for controlling a motor by pulse-width modulating a predetermined voltage.

[0002]

2. Description of the Related Art Generally, in order to rotate a motor in both forward and reverse directions or to suddenly stop a rotating motor, the polarity of applied voltage is often reversed. In addition, a method of analogly controlling the voltage or current applied to control the number of rotations of the motor is widely known, but recently, in order to control more accurately, digital control, particularly digital pulse width modulation is used. The number of things to do is increasing.

In the case of performing pulse width modulation control (hereinafter referred to as "PWM control"), if two positive and negative power supplies having the same voltage can be selectively used according to the polarity, a current detection value offset as described below There is no such thing, and the configuration is relatively simple. However, preparing two constant voltage power supplies that require a relatively large current capacity has a problem of high cost.

For that purpose, an example of a conventional PWM control type motor control device using one positive or negative power source is shown in FIG.
Shown in. In the illustrated motor control device, the PWM modulation circuit 2b to which the digital control signal for instructing the drive current of the motor is input via the subtractor 1, generates the PWM signal of the duty according to the absolute value of the input signal, If the input signal is positive, the PWM signal is output to the PWM amplifier 3 and the PWM amplifier 4
Off, and vice versa if negative.

That is, if positive, the drive current I of the motor 5
m flows from the PWM amplifier 3 to the PWM amplifier 4, and if negative, flows in the opposite direction. At that time, voltages V1 and V2 are generated with respect to the ground at both ends of the resistor R0, and the current detector 6 inputs the voltages V1 and V2 and outputs a detection value Vo (voltage signal) corresponding to the drive current Im. To do. The detection value Vo is converted into a digital detection signal by the A / D converter 7 and output to the subtractor 1.

Feedback control is performed by the subtracter 1 subtracting the detection signal from the control signal and outputting it to the PWM modulator 2b, so that the drive current Im of the motor 5 accurately corresponds to the control signal input to the motor control device. It becomes the corresponding value.

[0007]

However, there is no problem if the components of the current detector 6, especially the resistance value of the resistor are accurate, but if there is a slight error in the resistance value, it will be detected as described later. An offset (a deviation due to an error) occurs in the value Vo, and the feedback control cannot be performed correctly.

Since this offset often becomes a value that cannot be ignored, its correction (compensation) is necessary. Therefore, a variable resistor is provided at each position in the circuit to check whether the drive current Im accurately corresponds to the input control signal or whether the detected value Vo is the correct value for the drive current Im. While making adjustments, I compensated for the offset to be zero.

However, the adjustment in the case of the PWM control is more difficult than the analog control, and requires a considerable number of man-hours for adjustment with a skilled worker, and the cost is high in spite of using only one power source. There was a problem that it did not fall as much as I expected.

The present invention has been made in view of the above points, and reduces the cost of the motor control device without compensating for the offset of the detected value of the drive current of the motor, and further, it is accurate. The purpose of this is to ensure accurate feedback control.

[0011]

In order to achieve the above object, the present invention provides a pulse width modulator for pulse width modulating a predetermined voltage and outputting the pulse voltage to a motor, and a current detector for detecting a drive current flowing through the motor. And a motor control device that controls the drive current flowing in the motor by feeding back the detection value detected by the current detector, and is configured as follows.

That is, according to the value detected by the current detector when the pulse width modulator outputs a voltage pulse-width modulated by the pulse width modulator corresponding to the preset drive current value of the motor, the current detector detects the current. An offset compensating means for compensating the value offset is provided.

Alternatively, in accordance with each detection value by the current detector when the pulse width modulator outputs a voltage pulse-modulated by the pulse width modulator corresponding to the preset positive and negative drive current values of the motor, An offset compensating means for compensating the offset of the detection value of the current detector is provided.

Each of the above-mentioned offset compensating means detects each current by the current detector when the pulse width modulator outputs a voltage pulse-modulated by the pulse width modulator corresponding to the preset positive and negative drive current values of the motor. It is preferable to provide means for setting the average value of the absolute values of the offset values obtained according to the value as the absolute value of the compensation value when a positive or negative drive current is applied to the motor.

Alternatively, the positive drive current is output according to the value detected by the current detector when the pulse width modulator outputs a voltage pulse-modulated by the pulse width modulator corresponding to the preset positive drive current value of the motor. The offset of the detection value of the current detector when the current is flown is determined according to the detection value by the current detector when the pulse width modulator outputs the voltage pulse-modulated by the pulse width modulator corresponding to the negative drive current value. Offset compensation means for compensating for the offset of the detection value of the current detector when a negative drive current is supplied.

Alternatively, in order to prevent the current from flowing through the motor, the current is detected according to the value detected by the current detector when the voltage pulse-modulated in the same phase by the pulse width modulator is output to both terminals of the motor. An offset compensating means for compensating the offset of the detection value of the detector is provided.

[0017]

In the motor control device constructed as described above, the pulse width modulator outputs the voltage pulse-width-modulated by the pulse width modulator corresponding to the preset drive current value for detecting the offset, and the voltage is supplied to the motor at that time. The current detector detects the drive current and outputs the detected value. The offset compensation means compares the output detection value with a value corresponding to a preset drive current value to obtain an offset value, and determines a compensation value such that the offset becomes zero. After that, during normal motor operation, the offset compensating means can compensate the detected value output by the current detector by the determined compensation value and feed back the value at which the offset becomes zero.

Further, the offset compensating means compensates for each detected value of the current detector when the pulse width modulated voltage corresponding to the preset positive and negative drive current values is output to the motor. By determining the value and compensating the detected value thereafter, the offset can be compensated more accurately.

In that case, the average value of the absolute values of the offset values obtained by the offset compensating means according to the respective detected values,
By providing means for setting the absolute value of the compensation value when a positive or negative drive current is passed, the compensation value can be obtained relatively easily.

Further, the offset compensating means obtains a compensation value obtained according to the detected value of the drive current flowing through the motor in correspondence with the preset positive drive current value, and a motor corresponding to the negative drive current value. The offset can be more accurately compensated by compensating the detected value when a positive or negative drive current is respectively applied thereafter by the compensation value obtained according to the detected value of the flowing drive current.

Alternatively, the offset compensating means compensates for the offset according to the value detected by the current detector when the voltage pulse-modulated by the pulse-width modulator in the same phase is output to both terminals of the motor. Determine the value. In this case, since the drive current flowing through the motor is zero, offsets at zero drive currents when the drive current is positively and negatively applied are accurately compensated. Therefore, needless to say, when the polarity of the drive current value flowing through the motor is suddenly changed, the drive current flowing through the motor can be smoothly changed according to the change of the drive current value even when gradually changing.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be specifically described below with reference to the drawings. FIG. 7 is a waveform diagram showing an example of a drive current of a seek motor, which is a linear motor that drives an optical pickup device of an optical disk device, as an example of a motor used under the most severe conditions.

The seek motor accelerates by sending the maximum drive current as shown in FIG. 7 in order to send the optical pickup device to the target track position as quickly as possible from its application. When approaching a truck, the movement to suddenly switch to the maximum drive current of the opposite polarity and suddenly stop is frequently repeated in either direction.

In addition, when reading or writing a desired track, in order to accurately track the track, the track is always bidirectional in accordance with the high-speed left / right fine movement of the track due to eccentricity of the optical disk or the like. Since the minute movement is repeated, the polarity inversion is performed with a driving current smaller than the maximum driving current.

FIG. 1 is a circuit diagram showing a configuration of a motor control device according to a first embodiment of the present invention for controlling a seek motor and a motor used under severe conditions as well.
The same parts as those in the conventional example shown in FIG.

The first embodiment shown in FIG. 1 is a subtracter 1, a PWM modulation circuit 2 and a PWM amplifier 3 on the positive side, a PWM amplifier 4 on the negative side, and a PWM amplifier 4 on the negative side, each of which constitutes a pulse width modulator, and a drive current detecting element. In addition to the configuration including the resistor R0 and the current detector 6 and the A / D converter 7, an offset compensating circuit 11 and an adder 12, which respectively constitute offset compensating means, and a digital multiplexer 13 are provided. .

At the input terminals of the multiplexer 13, in order to detect a control signal which is a digital signal for instructing the drive current of the motor 5 from the main body device (not shown) and an offset of the detection value output from the current detector 6, Instruct each preset drive current value to ± 0.1 A +
The current signal and the-current signal are input.

The multiplexer 13 selects any one of the three input signals in accordance with the instruction from the offset compensation circuit 11 and outputs it to the subtractor 1. The subtractor 1 subtracts a feedback signal, which will be described later, from the signal selected by the multiplexer 13, converts the signal into a current signal, and outputs the current signal to the PWM modulation circuit 2.

The PWM modulation circuit 2 generates a PWM signal having a duty corresponding to the absolute value of the input current signal. If the polarity of the current signal is positive, the PWM modulation circuit 2 outputs an ON signal (12V) to the PWM amplifier 3 and outputs a negative signal. Output a logical PWM signal to the PWM amplifier 4, and if the polarity is negative, turn off the signal (0V) to PW.
The PWM signal of positive logic is output to the PW while being output to the M amplifier 3.
Output to the M amplifier 4.

At the same time, the PWM modulation circuit 2 outputs to the offset compensation circuit 11 an amplifier selection signal indicating whether the PWM amplifier 3 is outputting an ON signal or an OFF signal.

FIG. 2 is a circuit diagram showing an example of the configuration of the PWM amplifier 3 (same for 4). NPN type transistor Q1 and PNP type transistor Q2 connected in series
And reverse-voltage preventing diodes D1 and D2 connected in parallel to the transistors Q1 and Q2, respectively.

The collector of the transistor Q1 is DC12V
, The collector of the transistor Q2 is connected to the ground, the bases of the transistors Q1 and Q2 are connected to each other, and the PWM signal is input to the transistor Q1.
The connection point between the emitter of the transistor Q2 and the emitter of the transistor Q2 is the output terminal of the PWM amplifier 3.

In the first embodiment, since the series circuit of the motor 5 and the resistor R0 is connected between both output terminals of the PWM amplifiers 3 and 4, the polarity of the current signal is positive and the PWM
When the ON signal is input to the amplifier 3 and the PWM signal of the negative logic is input to the PWM amplifier 4, the positive drive current Im is PW as indicated by an arrow according to ON / OFF of the PWM signal.
It flows from the M amplifier 3 through the motor 5 to the PWM amplifier 4.

On the contrary, when the polarity of the current signal is negative and the OFF signal is input to the PWM amplifier 3, the PW of positive logic is input to the PWM amplifier 4.
When the M signal is input, the negative drive current Im is PWM
Depending on the ON / OFF of the signal, the PWM amplifier 4 to the motor 5
Through to the PWM amplifier 3.

FIG. 3 is a waveform diagram showing an example of the output voltages of the PWM amplifiers 3 and 4 and the drive current Im of the motor 5 depending on the polarity of the current signal. When the current signal is positive, (A) in Fig. 3
As shown in, the output voltage of the PWM amplifier 3 remains 12V in response to the ON signal, and the output voltage of the PWM amplifier 4 is 0V when the negative logic PWM signal is ON and 12V when it is OFF. Become. Therefore, the drive current Im flows in the positive direction shown by the arrow in FIG.

However, in general, the frequency of PWM modulation is as high as about 10 KHz to 100 KHz, and the impedance of the motor 5 is much larger than the resistance, so that the difference between the output voltages of the PWM amplifiers 3 and 4 is 0. Since the current flows even at times, the drive current Im is smoothed as shown in FIG. 3 (A) and has a value including a slight ripple and proportional to the duty ratio of the PWM modulation.

When the current signal is negative, as shown in FIG. 3B, the output voltage of the PWM amplifier 3 does not change to 0V according to the off signal, and the output voltage of the PWM amplifier 4 is positive logic. The PWM signal of 12V is 12V when it is on, and 0V when it is off. Therefore, the drive current Im flows in the negative direction contrary to the direction shown by the arrow in FIG.

A positive or negative drive current Im flows through the motor 5 depending on whether the current signal is positive or negative, and (R0 × I) is applied across the resistor R0.
m) and the output voltage of the PWM amplifier 3 is 12 V when the drive current Im is positive and 0 V when the drive current Im is negative. Therefore, the terminal of the resistor R0 on the PWM amplifier 3 side and the motor 5 are connected.
Voltage of V1 and V2 with respect to the ground, respectively, is generated at the terminal on the side, and the voltages V1 and V2 are respectively detected by the current detector 6
Is output to.

The detection value Vo (analog voltage signal) output from the current detector 6 is the drive current Im, as will be described later.
Vo = 6V when = 0, and decreases when Im> 0, Im
When <0, it is set to increase. That is,
When Im = 0.1A, Vo = 5V, and when Im = -0.1A, Vo = 7V.

The A / D converter 7 inputs the detection value Vo, and with the digital value corresponding to Vo = 6V (Im = 0) as the central value, Vo <6V (Im>
In the case of 0), a decidal value that increases when Vo> 6V (Im <0) decreases is output.

That is, when the digital value is described as a decimal number without a dimension, for example, the digital value when Vo = 6V is 600, and Vo = 5V (Im = 0.1).
In the case of A), 700 is output as a detection signal, and in the case of Vo = 7V (Im = -0.1A), 500 is output as a detection signal.

During normal operation, the offset compensation circuit 11
Responds to the amplifier selection signal input from the PWM modulation circuit 2 and selects a compensation value which is determined in advance so that the offset becomes zero and is stored, and outputs it to the adder 12. The adder 12 adds the compensation value input from the offset compensation circuit 11 to the detection signal input from the A / D converter 7, converts it into a feedback signal in which the offset is compensated, and outputs the feedback signal to the subtractor 1.

The subtractor 1 subtracts the feedback signal from the control signal selected and output by the multiplexer 13 during normal operation, and outputs the subtracted feedback signal to the PWM modulator 2 as a current signal having positive and negative values. In this way, feedback
A loop is formed and the motor 5 is supplied with a drive current Im that exactly corresponds to the control signal.

FIG. 4 is a circuit diagram showing an example of the configuration of the current detector 6. The current detector 6 includes an operational amplifier 14 and two ripple removing capacitors C connected in parallel to the resistors R1, R2, R3 and R4 and the resistors R2 and R4.
It consists of and.

The voltages V1 and V2 across the resistor R0 are input to the − input terminal and the + input terminal of the operational amplifier 14 via the resistors R1 and R3, respectively, and the analog detection value Vo is output from the output terminal of the operational amplifier 14. To be done. The resistor R2 connects the output terminal and the-input terminal of the operational amplifier 14 to form a feedback circuit, and the reference voltage Vr is input to the other end of the resistor R4 connected to the + input terminal of the operational amplifier 14.

[0046]

[Equation 1]

The detection value Vo output from the current detector 6 is given by
It is obtained by the formula shown in. The expression shown in (A) of Equation 1 is an expression when the resistors R1 to R4 have independent resistance values, and the resistors R3 and R4 are respectively R3 = R.
1, R4 = R2 or R3 / R4 = R1 / R2
If it is set so as to be as shown in FIG.

In the equation (B), if the reference voltage Vr is set to zero, the formula of a normal differential amplifier is obtained. In this embodiment, however, the A / D conversion by the A / D converter 7 in the next stage is easy. As described above, when the drive current Im is zero, that is, when V1 = V2, the reference voltage Vr is set so that the detected value Vo takes a positive value instead of zero, and when the drive current Im reaches the maximum negative value. The detection value Vo ≧ 0.

[0049]

[Equation 2]

Since the expression 2 is V2 = V1−R0 × Im, it is substituted into the expression of the expression 1 to eliminate V2 and change the order of the array, and the expressions (A) and (B) of the expression 2 are obtained. Is the number 1
It corresponds to (A) and (B). In the equation (A) of the equation 2, the term of V1 remains, but R3 = R1, R4 =
In the equation (B) in which R2 or R3 / R4 = R1 / R2 is set, it can be seen that the term of V1 disappears.

In the current detector 6 shown in FIG. 4, the resistance values and the reference voltage values are R1 = R3 = 1KΩ and R, respectively.
2 = R4 = 10KΩ, R0 = 1Ω and Vr = 6V are set, and the unit of current and voltage is A and V, respectively.
Substituting into the equation (B), the R0 = 1Ω disappears and the equation shown in the equation (B) is obtained, and Vr = 6V.
When m = 0.1A, 0A, -0.1A, the detected value V
o = 5V, 6V, 7V.

[0052]

[Equation 3]

If the resistors R1 to R4 are accurate and the error is zero, the detected value Vo changes according to the drive current Im as shown in the formula (B) of the equation 3, and according to the polarity of the current signal. Even if V1 changes to 12V or 0V, there is no effect and no offset occurs.

However, there is a slight error in the resistance value, for example ± 1%, and for example, R1 = 1.01 KΩ, R
2 = 9.9KΩ, R3 = 0.99KΩ, R4 = 10.1K
If Ω is obtained, those values are substituted into the equation (A) of the equation 2 to obtain the equation (A) of the equation 3.

That is, the coefficient of Vr is not 1 but 0.9.
643, the coefficient of V1 is 0.0357 instead of 0
And the Im coefficient becomes −9.838 instead of −10. Therefore, the influence of V1 appears on the detected value Vo, V1 = 12V when the drive current Im is positive, and V1 = when the drive current Im is negative.
It becomes 0. Substituting the value of V1 and Vr = 6V into (A) of Equation 3 and arranging Im> 0 and Im <0 separately,
The Vo calculation formula shown in Formula 4 is obtained.

[0056]

[Equation 4]

That is, in the expression (Im> 0) of the equation 4, the first term 5.786V on the right side of the first row is a variation of Vr = 6V, and the second term 0.428V is V1 =. 12V
It was caused by the influence of. Therefore, the constant term shown in the 2nd row becomes the sum of both, 6.214V. on the other hand,
Since the constant term on the right side of the expression (Im <0) in the equation 4 is V1 = 0, 0.428V disappears, and Vr = 6V holds 5.7.
Only 86V.

Depending on the polarity of the current signal (the polarity of the drive current Im is also the same), Vo when the resistors R1 to R4 have no error and when there is an error are expressed by the equation (3) and the equation (4).
Table 1 shows the values calculated for Im = 0.1A and −0.1A by the equation (1) and the values obtained by extending the equation to Im = 0A.

[0059]

[Table 1]

FIG. 5 shows the detected value Vo (V) with respect to the drive current Im (A) obtained by plotting the values shown in Table 1.
FIG. 4 is a diagram showing an example of changes in the above, where a rough broken line shows the case where there is no error in the resistance value, and a solid line shows the case where there is an error.

If there is no error in the resistance value, the slope (Vo / Im) is -10 regardless of whether the drive current Im is positive or negative, as shown by the broken line in FIG.
It is one straight line that coincides at = 6V. However, if there is an error as illustrated in the resistance value, the slope is −9.838 as shown by the solid line, and V at Im = 0.
Positive and negative errors, that is, respective offsets are generated with respect to o = 6V, and one straight line is not formed.

As shown in Equation 4, Im> 0, Im <0
In any of the expressions, the Im coefficient does not become -10, but -9.8.
However, since the transfer function of the feedback changes only -0.14 decibels, this does not mean that the match between the control signal or the current signal and the drive current Im changes, and there is a particular problem. I won't.

Further, even if there is a straight line disagreement due to an offset of about ± 0.21 V at Im = 0, the motor 5 has a maximum drive current in both forward and reverse directions as shown in FIG. When accelerating and decelerating, there is no problem at all.
However, when performing control such that the drive current Im gradually changes from positive to negative or from negative to positive, discontinuity at Im = 0 due to an offset becomes a serious problem, and the motor 5 should be kept stationary. Becomes difficult.

In the first embodiment, the offset compensation circuit 11 detects the offset value prior to the normal operation and determines the compensation value for making the offset zero,
The compensation value is stored. During normal operation, the offset compensation circuit 11 selects a compensation value according to the amplifier selection signal input from the PWM modulation circuit 2, that is, according to V1 = 12V or 0V, and the adder 12 adds the compensation value to the detection signal. Zero the effect of offset.

Therefore, the offset compensation circuit 11 instructs the multiplexer 13 to select and output the + current signal instructing Im = 0.1A. At this time, since the digital value 677 corresponding to the detected value Vo = 5.23V output from the current detector 6 is input, the offset compensation circuit 1
1 is a value 23 obtained by subtracting the input value 677 from the digital value 700 corresponding to the correct value 5V with no offset, Im>
It is stored as a compensation value when it is 0.

Next, the offset compensation circuit 11 instructs the multiplexer 13 to instruct Im = -0.1A-
Select and output a current signal. At this time, since the digital value 523 corresponding to the detected value Vo = 6.77V output from the current detector 6 is input, the offset compensation circuit 11 outputs the digital value 5 corresponding to the correct value 7V with no offset.
The value -23 obtained by subtracting the input value 523 from 00 is Im <0.
It is stored as a compensation value at the time of.

To be precise, as shown in Table 1, Im> 0
, And Im <0, when Im = 0, the compensation values are 21 (-0.21V) and -21 (+ 0.21V), respectively. Therefore, in both cases, the absolute value of the offset is 2 (0.02V). It remains, but practically it makes little difference. However, in order to obtain a correct compensation value as much as possible, it is better to set the driving current Im at the time of detecting the offset to a minimum value.

The compensation value 23 in the case of Im> 0 and the compensation value -23 in the case of Im <0 thus obtained are stored, and the amplifier selection input from the PWM modulation circuit 2 in the normal operation is stored. If the signal indicates that the PWM amplifier 3 is on, the offset compensation circuit 11 selects the compensation value 23 of Im> 0 and outputs it to the adder 12, and the PWM amplifier 3
Is OFF, the compensation value of Im <0-2
Select 3 and output.

The adder 12 adds the selected compensation value to the detection signal output from the A / D converter 7 to obtain a feedback signal in which the influence of the offset is zero or minimized, and the subtractor 1 receives the feedback signal. Can be output.

As described above, in the first embodiment, the compensating values when Im> 0 and Im <0 have opposite positive and negative values when Im has the same absolute value. Equal to each other, but in the general case, the absolute value of the offset, ie, the absolute value of the compensation value, is not necessarily equal.

However, as in the first embodiment, the reference voltage Vr is V1 = 12 when the PWM amplifier 3 is on.
If set to 1/2 of V, the formula is omitted, but
Ideal detection value Vo without resistance error shown in (B) of
And the detected value Vo when there is an error shown in (A) of Equation 2.
It can be proved that the absolute value of the difference, that is, the absolute value of the offset or the compensation value is equal when the absolute value of Im is the same.

Therefore, by setting Vr = 6 V, even if the compensation value is not determined for ± 0.1 A, if the compensation value is determined for either one,
As for the other, the inverted value of the sign can be used as the compensation value. Practically, even if it is not exactly halved, it may be used as the other compensation value as long as it is in the vicinity thereof.

Even if it is out of the vicinity of 1/2, ±
The PWM modulation circuit 2 uses the average value of the absolute values of the compensation values determined for each case of 0.1 A as the absolute value of the compensation values.
According to the amplifier selection signal input from, the value is output to the adder 12 as it is or the value whose polarity is inverted,
The offset compensation circuit 11 can be simplified and the cost can be reduced.

As described above, when the polarity of the drive current Im is rapidly switched by setting the influence of the offset to zero or minimum, the motor is driven with a small drive current Im or the polarity is slowly inverted. Even if it does, control can be performed smoothly.

FIG. 6 is a circuit diagram showing the structure of a motor control device according to a second embodiment of the present invention. The same parts as those of the first embodiment shown in FIG. Omit it.

The second embodiment shown in FIG. 6 is different from the first embodiment in that the multiplexer 13a has two input terminals instead of three, and two input signals for offset detection +
Instead of the current signal, −current signal, one current signal indicating zero current has become the 0 current signal.

The second embodiment is based on the offset compensation circuit 1
When 1 determines a compensation value, the multiplexer 13a is instructed to select and output the 0 current signal designating the drive current Im = 0, and the PWM modulation circuit 2 causes the PWM amplifiers 3 and 4 to output.
The signals having the same phase, that is, the ON signal and the OFF signal, are output to. The offset compensation circuit 11 receives the PWM amplifiers 3, 4 according to the amplifier selection signal input from the PWM modulation circuit 2.
When both are on, a compensation value of Im> 0 is determined, and when both are off, a compensation value of Im <0 is determined.

That is, both when Im> 0 and Im <0, the PWM amplifiers 3 and 4 are both on and the output voltage is 12
Since either V or both are off and the output voltage is 0 V, the voltage difference applied to both ends of the motor 5 becomes zero, and the drive current does not flow in either case.

Therefore, since the offset at Im = 0 can be detected and the compensation value can be determined, as shown in (A) and (4) of the equation 3, the coefficient of the drive current Im depends on the error of the resistance value. 5 is not affected by the change in the offset compensation value, unlike the case where the drive current is passed to determine the offset compensation value as in the first embodiment.
Im> 0 straight line and Im with error shown by solid line in
The straight line <0 matches exactly at Im = 0, and smooth motor control can be performed.

[0080]

As described above, the motor control device according to the present invention does not require manpower for compensating the offset of the detection value of the drive current of the motor, reduces the cost of the motor control device, and is accurate. Feedback control can be performed.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of a motor control device according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing an example of a configuration of the PWM amplifier shown in FIG.

FIG. 3 is a waveform diagram showing an example of the output voltage of the PWM amplifier and the drive current of the motor in the first embodiment.

FIG. 4 is a circuit diagram showing an example of the configuration of the current detector shown in FIG.

5 is a diagram showing an example of changes in the detected value with respect to the drive current of the current detector shown in FIG.

FIG. 6 is a circuit diagram showing a configuration of a motor control device according to a second embodiment of the present invention.

FIG. 7 is a waveform diagram showing an example of drive current of a seek motor used under the most severe conditions.

FIG. 8 is a circuit diagram showing a configuration of a conventional example of a motor control device.

[Explanation of symbols]

1: Subtractor 2: PWM modulation circuit 3, 4: PWM amplifier 5: Motor 6: Current detector 7: A / D converter 11: Offset compensation circuit 12: Adder 13: Multiplexer Im: Motor drive current Vo: Drive Current detection value

Claims (5)

[Claims] 1. A detection value detected by the current detector, comprising: a pulse width modulator for pulse-width-modulating a predetermined voltage to output to a motor; and a current detector for detecting a drive current flowing in the motor. In a motor control device that controls the drive current flowing to the motor by feeding back the voltage, when the pulse width modulated voltage is output to the motor by the pulse width modulator corresponding to a preset drive current value of the motor. 2. A motor control device comprising: an offset compensating means for compensating an offset of a detection value of the current detector according to the detection value of the current detector. 2. A pulse width modulator for pulse-width modulating a predetermined voltage and outputting it to a motor, and a current detector for detecting a drive current flowing through the motor, and a detection value detected by the current detector. In a motor control device that controls the drive current flowing to the motor by feeding back the voltage, the voltage that the pulse width modulator respectively pulse-width-modulates in accordance with preset positive and negative drive current values of the motor A motor control device comprising an offset compensating means for compensating an offset of a detection value of the current detector according to each detection value of the current detector when output to the motor. 3. The motor control device according to claim 2, wherein the offset compensating means applies a pulse width modulated voltage to each of the pulse width modulators corresponding to preset positive and negative drive current values of the motor. , The average value of the absolute value of the offset value obtained according to each detection value by the current detector when output to the motor, the absolute value of the compensation value when a positive or negative drive current is passed through the motor A motor control device comprising: 4. A detection value detected by the current detector, comprising: a pulse width modulator for pulse-width modulating a predetermined voltage and outputting the pulse voltage to a motor; and a current detector for detecting a drive current flowing through the motor. In a motor control device that controls the drive current flowing in the motor by feeding back the voltage to the motor, a voltage pulse-width modulated by the pulse width modulator corresponding to a preset positive drive current value of the motor is supplied to the motor. The offset of the detection value of the current detector when a positive drive current is passed according to the detection value of the current detector when outputting is pulsed by the pulse width modulator corresponding to the negative drive current value. Offset of the detection value of the current detector when a negative drive current is passed according to the detection value of the current detector when the width-modulated voltage is output to the motor, respectively. Motor control device is characterized by providing an offset compensating means for amortization. 5. A detection value detected by the current detector, comprising: a pulse width modulator for pulse-width-modulating a predetermined voltage and outputting it to a motor; and a current detector for detecting a drive current flowing through the motor. In a motor control device that controls the drive current flowing in the motor by feeding back the voltage, voltage that is pulse-width modulated in the same phase by the pulse-width modulator so that current does not flow in the motor is applied to both terminals of the motor. The motor control device is provided with an offset compensating means for compensating for an offset of the detection value of the current detector according to the detection value of the current detector when the current is outputted to.