JP2009219288A - Motor driving device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor driving device compatible with positive/negative voltage command signals by a circuit scale smaller than that of the conventional one. <P>SOLUTION: The motor driving device 10 includes a comparator 11 for comparing signals with each other, an error amplifier 12 for amplifying an output signal of the comparator 11, a PWM conversion means 20 for converting a voltage signal into a pulse width signal, a PWM drive part 13 for PWM-driving a motor, a switching element part 14 for performing switching operation, a resistance element 15, an ADC 16 for converting an analog signal into a digital signal, and a polarity switching part 17 for switching the signal polarity. The PWM conversion means 20 has an integration part 21 to output an error integrated value Vint, and a nonlinear conversion part 22 that performs nonlinear conversion so as to exclude a prescribed range from the input error integrated value Vint and outputs a PWM command signal PWMin, in which the prescribed range is excluded, to the PWM drive part 13. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a motor driving device that drives a motor.

  Conventionally, the PWM (Pulse Width Modulation) drive system that switches the power supply voltage with a pulse duty ratio proportional to the applied voltage command signal is generally used when operating the motor by passing a current through the armature coil of the motor. Used. In addition, a drive system has been proposed in which a motor current is detected based on a potential difference between resistors connected to the ground side or the power supply side of the switching element, and the detected current is fed back to control the current.

However, if the applied voltage command signal is small and the pulse width is short, the time during which the resistance potential difference can be detected is short, and normal current detection cannot be performed. In order to avoid this, it is preferable to limit the pulses having a certain width or less. However, simply limiting the pulse width causes a problem that the motor current is distorted. In view of this, there has been proposed a technique in which a reverse pulse (reverse vector) is appropriately selected to adjust an average voltage to reduce current distortion (see, for example, Patent Document 1).
Republished patent WO2003 / 030348

  However, although there is no detailed description in the method disclosed in Patent Document 1, if the absolute value of the voltage command signal is small when the voltage command signal is negative, the polarity of the pulse that limits the time width or the inverse vector It was necessary to reverse the sign relationship between the direction and the error integrated value for selecting them. Therefore, the technique disclosed in Patent Document 1 has a problem that the circuit scale becomes large in order to deal with positive and negative voltage command signals.

  The present invention has been made in order to solve the conventional problems, and an object of the present invention is to provide a motor drive device that can cope with positive and negative voltage command signals with a circuit scale smaller than that of the prior art.

  The motor drive device of the present invention is a motor drive device that applies a voltage by applying a drive pulse to a motor coil, and converts a voltage command signal into a pulse width command signal, and a response to the pulse width command signal. Drive pulse output means for outputting the drive pulse to the motor coil, and the signal conversion means integrates the difference between the voltage command signal and the pulse width command signal and outputs an error integrated value; An output exclusion unit that excludes and outputs an output in a predetermined range from the error integrated value, and outputs a pulse width command signal corresponding to the output of the output exclusion unit. Yes.

  With this configuration, the motor drive device of the present invention can limit pulses having a certain width or less by excluding the output in a predetermined range from the error integrated value, and is appropriate for positive and negative voltage command signals. A simple pulse width command signal can be output to the motor coil. Therefore, the motor drive device of the present invention does not require a separate circuit for responding to the positive and negative voltage command signals, and can therefore correspond to the positive and negative voltage command signals with a circuit scale smaller than that of the prior art.

  Further, the motor drive device of the present invention has a configuration in which the output excluding unit performs quantization for converting an input value in a predetermined range into a constant output value.

  With this configuration, the motor drive device of the present invention can perform voltage error compensation by excluding short pulses with a simpler configuration.

  Furthermore, in the motor drive device of the present invention, the output excluding unit is based on a predetermined reference input value and a reference output value, and has an input / output characteristic indicating a relationship between the input value and the output value of the output excluding unit. The input / output characteristics are offset in the positive / negative direction of the reference output value by a predetermined offset amount with the reference input value as a boundary.

  With this configuration, the motor drive device of the present invention can simplify the processing of the output exclusion unit, and can further simplify the circuit, program, and the like.

  Furthermore, the motor drive device of the present invention has a configuration in which the output exclusion unit reduces the offset amount as the difference between the input value and the reference input value increases.

  With this configuration, the motor driving device of the present invention can reduce the difference between the input value and the output value for a large voltage instruction while excluding the predetermined range of the input value from the output. The distortion of the flowing current can be reduced.

  Also, with this configuration, the motor drive device of the present invention can avoid output saturation, overflow, etc. for large voltage instructions.

  Furthermore, the motor drive device of the present invention includes a current detection means for detecting a current flowing through the motor coil when the drive pulse is in an on state, a detected current value detected by the current detection means and a predetermined current command. The voltage command signal is output in accordance with a difference from the signal value, and current control means for controlling the current flowing in the motor coil to a value in accordance with the current command signal is provided.

  With this configuration, the motor driving device according to the present invention can generate the target current command signal without fluctuation of the motor current even if there is fluctuation of the power supply voltage, fluctuation of the resistance of the switch element, fluctuation of the coil resistance or the like due to current feedback. The motor can be driven with a corresponding current. Therefore, the motor drive device of the present invention can perform stable and precise motor drive control.

  The present invention can provide a motor drive device having an effect of being able to cope with positive and negative voltage command signals with a circuit scale smaller than that of the prior art.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

(First embodiment)
First, the configuration of the motor drive device according to the first embodiment of the present invention will be described. FIG. 1 is a block diagram showing a configuration of a motor drive device according to the present embodiment.

  As shown in FIG. 1, the motor drive device 10 according to the present embodiment converts a comparator 11 that compares signals, an error amplifier 12 that amplifies the output signal of the comparator 11, and a voltage signal into a pulse width signal. The PWM conversion means 20, the PWM drive part 13 which carries out PWM drive of the motor, the switching element part 14 which performs switching operation | movement, the resistive element 15, and the converter (henceforth "ADC") which converts an analog signal into a digital signal. 16 and a polarity switching unit 17 for switching the polarity of the signal. The motor drive device 10 is constituted by a microcomputer, for example.

  The comparator 11 compares a target current command signal Icmd predetermined as a current to be passed through the motor coil 100 with a detected current value Idet output from a polarity switching unit 17 described later, and outputs a difference signal indicating the difference. It is like that. The comparator 11 constitutes current control means according to the present invention.

  The error amplifier 12 amplifies the difference signal output from the comparator 11 and outputs the amplified difference signal to the PWM conversion means 20 as a voltage command signal Vcmd. Here, the voltage command signal Vcmd is a signal corresponding to a voltage to be applied to the motor coil 100. The error amplifier 12 constitutes current control means according to the present invention.

  In motor driving apparatus 10 in the present embodiment, current is feedback controlled so that difference between target current command signal Icmd and detected current value Idet is reduced by error amplifier 12 outputting voltage command signal Vcmd. It is like that. Here, by increasing the gain of the error amplifier 12, a current proportional to the target current command signal Icmd can be passed through the motor coil 100. Only with the voltage command signal Vcmd, the motor current fluctuates due to power supply voltage fluctuations, fluctuations in the resistance of the switching element unit 14, fluctuations in coil resistance, etc., but these effects can be compensated for by current feedback. In the present embodiment, the voltage command signal Vcmd is described as a digital value, but an analog value may be used.

  The PWM conversion means 20 includes an integration unit 21 and a non-linear conversion unit 22. The PWM converter 20 constitutes a signal converter according to the present invention.

  The integrating unit 21 includes a subtractor 21a, a memory 21b, an adder 21c, and a memory 21d.

  The subtractor 21a subtracts the PWM command signal PWMin one sample before from the voltage command signal Vcmd, and calculates the difference between the voltage command signal Vcmd and the PWM command signal PWMin.

  The memory 21b stores the PWM command signal PWMin value one sample before. For example, the memory 21b samples and updates the current PWM command signal PWMin every PWM cycle.

  The adder 21c and the memory 21d integrate the output signals of the subtractor 21a for each sample (for example, PWM cycle) and output an error integrated value Vint to the non-linear conversion unit 22.

  The non-linear conversion unit 22 performs non-linear conversion so as to exclude a predetermined range from the input error integrated value Vint, and outputs a PWM command signal PWMin excluding the predetermined range to the PWM drive unit 13. This PWM command signal PWMin is a signal corresponding to a pulse width for PWM driving the motor coil 100. The nonlinear conversion unit 22 constitutes an output exclusion unit according to the present invention, and details thereof will be described later.

  The PWM drive unit 13 turns on and off the switching element unit 14 (switching signals UH and UL) so that the motor coil 100 can be subjected to switching control with a pulse width corresponding to the input PWM command signal PWMin value and can be PWM driven. , VH, VL). The PWM drive unit 13 constitutes drive pulse output means and current detection means according to the present invention.

  The switching element unit 14 includes switching elements 14a to 14d configured by, for example, FETs or transistors. In the present embodiment, the switching elements 14a to 14d have logic that turns on when the switching signals UH, UL, VH, and VL are at a high level, respectively. The motor coil 100 is H-bridge connected between a connection point a between the switching elements 14a and 14b and a connection point b between the switching elements 14c and 14d.

  The resistance element 15 is for generating a potential difference signal Isns proportional to the current flowing through the motor coil 100. The resistance element 15 is inserted between a ground point of the switching elements 14b and 14d on the ground side of the motor coil 100 and the ground. For this reason, the resistance element 15 can detect the current (or the current in the opposite direction) flowing from the power source to the ground side through the motor coil 100 when the PWM pulse is on-duty. Yes. On the other hand, the current when the PWM pulse is off duty (OffDuty) is not detected by the resistance element 15 because it is regenerated by the motor coil 100 and the switching element section 14 without passing through the resistance element 15.

  The ADC 16 samples the potential difference signal Isns and converts it into a digital value. The sampling timing will be described later.

  The polarity switching unit 17 inverts the polarity of the sampled potential difference signal Isns in accordance with the polarity instruction signal inv and outputs the signal to the comparator 11.

  The resistive element 15, the ADC 16, and the polarity switching unit 17 constitute a current detection unit according to the present invention.

  Next, PWM driving in the present embodiment will be described with reference to FIG.

  As shown in FIG. 2, the PWM drive unit 13 outputs a pulse that turns on and off with a pulse width on-duty that is proportional to the absolute value of the PWM command signal PWMin for each fixed period Tpwm.

  When the PWM command signal PWMin is a positive sign, UH and UL are complementarily outputted (with logic that UL is inverted from UH), VH is fixed at a low level, and VL is fixed at a high level. That is, the switching element 14c is always off, the switching element 14d is always on, and when the PWM is on, the switching element 14a is on and the switching element 14b is off. Therefore, a voltage is applied to the motor coil 100 from the switching elements 14a to 14d, and a current flows from the power source to the ground side. When the PWM is off, the switching element 14a is off, the switching elements 14b and 14d are on, a regenerative current flows through the motor coil 100, and does not flow to the ground side.

  On the other hand, when the PWM command signal PWMin has a negative sign, VH and VL are complementarily outputted (with logic that VL is inverted from VH), UH is fixed at a low level, and UL is fixed at a high level. That is, the switching element 14b is always on, and when the PWM is on, the switching element 14c is on and the switching element 14d is off. Therefore, a voltage opposite to the above is applied to the motor coil 100 from the switching elements 14c to 14b, and a current flows from the power supply to the ground side. When the PWM is off, the switching element 14c is off, the switching elements 14a and 14b are on, a regenerative current flows through the motor coil 100, and does not flow to the ground side.

  FIG. 2 also shows a case where the absolute value of the PWM command signal PWMin is small and the pulse width is narrow, but pulses shorter than the predetermined width are excluded as described below, so the PWM drive unit 13 is actually A thin pulse command signal is not input.

  The PWM drive unit 13 outputs a polarity instruction signal inv = 0 when the PWM command signal PWMin has a positive sign, and outputs a polarity instruction signal inv = 1 when the PWM instruction signal PWMin has a negative sign.

  When the PWM command signal PWMin has a positive sign, the direction of the voltage applied to the motor coil 100 is the direction from the connection point a to b shown in FIG. 1, but when the PWM command signal PWMin has a negative sign, it is described above. As described above, the direction of the voltage applied to the motor coil 100 is reversed (the direction from the connection point b to the point a in FIG. 1). However, the direction of the current flowing through the resistance element 15 is the same (the direction from the power supply to the ground in FIG. 1). Therefore, when the PWM command signal PWMin is negative, the current detection is performed correctly by inverting the polarity of the current flowing through the resistance element 15. Polarity is obtained.

  As described above, when the PWM command signal PWMin is negative, the polarity switching unit 17 inverts the result of sampling the potential difference signal Isns in the ADC 16, and the polarity switching unit 17 outputs the detected current value Idet.

  The sampling timing of the ADC 16 is preferably a point indicated by a white circle in the potential difference signal Isns waveform of the waveform example shown in FIG. This corresponds to the final part of the on-duty of the PWM pulse. The sampling signal smpl may be output from the PWM drive unit 13 to the ADC 16 at this timing.

  As described above, the potential difference signal Isns appears in the positive direction even when the PWM command signal PWMin is negative. However, the potential difference signal Isns has the correct polarity by inverting the polarity instruction signal inv = 1 to obtain the detected current value Idet. Although the short PWM pulse is not excluded in FIG. 2, as will be described later, in practice, the non-linear converter 22 does not generate a pulse within a predetermined range. This facilitates sampling of the potential difference signal Isns, and enables stable current detection.

  Next, the non-linear conversion unit 22 will be described in detail.

  First, FIG. 3 shows an example of the input / output relationship of the non-linear converter 22. A program example of internal processing of the non-linear conversion unit 22 in this example is shown below as steps s101 to s104.

s101: if (input <mt) then output = input;
s102: else if (input <h) then output = mt;
s103: else if (input <pt) then output = pt;
s104: else output = input;

  In this example, when the input value (input) of the non-linear converter 22 is smaller than the predetermined parameter mt (that is, larger in the negative direction) or larger than the predetermined parameter pt (that is, larger in the positive direction). The non-linear conversion unit 22 outputs the input value as it is (output = input), and outputs mt or pt with a predetermined parameter h as a boundary when the input value is in the range from mt to pt. That is, the non-linear conversion unit 22 quantizes the input value in the range from mt to pt into two levels of mt and pt. In the above-described s101 to s104 and FIG. 3, the parameters are mt = −20, pt = + 20, and h = 0.

  Next, the process of converting the voltage command signal Vcmd into the PWM command signal PWMin is written in the form of a program that operates every sampling period, for example, as follows. However, it is assumed that the function NL is defined as output = NL (input) in the processing of the non-linear conversion unit 22 (s101 to s104 described above). The output values of the memories 21d and 21b are z1 and z2, respectively.

Processing for converting the voltage command signal Vcmd into the PWM command signal PWMin:
Vint = (Vcmd-z2) + z1
PWMin = NL (Vint)
z1 = Vint
z2 = PWMin

  Next, FIG. 4 shows a waveform example of the PWM command signal PWMin and the coil current Current of the motor coil 100 when the voltage command signal Vcmd is input as a sine wave due to the input / output relationship shown in FIG. FIG. 5 shows an enlarged view of the portion from the horizontal axis “80” to “120” in FIG. 4 and 5, the unit of the horizontal axis is the PWM cycle number. For example, “80” means the 80th PWM cycle. The unit of the vertical axis is arbitrarily set so that the amplitudes are the same, but in actuality, a physical quantity (voltage, current, digital value, PWM duty ratio, or the like) is appropriately added with a coefficient.

  Next, the actual data that is the basis of the graph of FIG. 5 is shown in FIG. In FIG. 6, n represents the PWM cycle number on the horizontal axis. Vint [n] in the nth PWM cycle is obtained by the following equation.

Vint [n] = (Vcmd [n]-PWMin [n-1]) + Vint [n-1]
For example, at the timing of n = 93, the calculation is performed as follows.

Vint [93] = (Vcmd [93]-PWMin [92]) + Vint [92]
= (10-(-20)) + (-7)
= 23
PWMin = NL (23) = 23

  As shown in FIG. 5, with respect to the voltage command signal Vcmd, the PWM command signal PWMin is converted so as to exclude the range from mt (= −20) to pt (= + 20), and the value outside thereof is appropriately set. You can see that it is output. For this reason, the PWM pulse width becomes a predetermined value or more, and current detection becomes easy. Further, as shown in the figure, the coil current Current is smooth because smoothing is performed by inductance, and the sine wave waveform of the input voltage command signal Vcmd can be substantially maintained. Therefore, the motor can be operated smoothly and without distortion by the non-linear converter 22 in this configuration.

  The processing described above is simple with fewer conditional branches and signal selection than the conventional example, and the circuit scale and program scale can be kept small. Further, the positive / negative voltage command signal Vcmd can be appropriately converted into the PWM command signal PWMin, and a normal positive / negative current can be passed.

  In the above description, the quantization level of the non-linear conversion unit 22 is two, but the present invention is not limited to this. For example, as shown in FIG. Also good.

  FIG. 7 is a diagram illustrating an example in which the quantization level is set to only −20 with respect to −20 to +20 in the input range. Similarly to the case where the number of quantization levels is two, the response of the PWM command signal PWMin and the coil current Current when the voltage command signal Vcmd is input as a sine wave is shown in FIG. As shown in FIG. 8, although the PWM command signal PWMin converted in the case of one quantization level changes more greatly than in the case of two quantization levels (see FIG. 5), the coil current Current is There is almost no distortion. Therefore, the motor can be operated smoothly and without distortion by the non-linear converter 22 in this configuration. Further, by making the quantization level of the nonlinear conversion unit 22 one, the circuit can be further simplified.

  Next, the operation of the motor drive device 10 in the present embodiment will be described with reference to FIGS. FIG. 9 is a flowchart showing the operation of the motor drive device 10 in the present embodiment.

  First, the PWM conversion means 20 inputs the voltage command value Vcmd (step S11). This voltage command value Vcmd is a signal obtained by amplifying the differential output from the comparator 11 by the error amplifier 12.

  Subsequently, the integrating unit 21 generates an error integrated value Vint based on the input voltage command value Vcmd (step S12). Specifically, in the integrating unit 21, the subtractor 21a inputs the PWM command signal PWMin one sample before from the memory 21b, for example, for each sample, and subtracts the input PWM command signal PWMin from the voltage command signal Vcmd, The result is output to the adder 21c. The adder 21c and the memory 21d, for example, integrate the results of the subtractor 21a for each sample and output the error integrated value Vint to the non-linear conversion unit 22.

  Subsequently, the non-linear conversion unit 22 excludes an output in a predetermined range from the input error integrated value Vint, and outputs a PWM command signal PWMin to the PWM drive unit 13 (step S13). For example, when the input of the non-linear conversion unit 22 is smaller than the parameter mt or larger than the parameter pt by the above-described steps s101 to s104, it is output as it is, and when the input is in the range from mt to pt, the parameter h is set. Output mt or pt to the boundary.

  Then, the PWM drive unit 13 outputs switching signals UH, UL, VH, and VL corresponding to the input PWM command signal PWMin to the switching element unit 14 to drive the motor in PWM (step S14).

  Here, the resistance element 15 generates a potential difference signal Isns proportional to the current flowing through the motor coil 100 and outputs it to the ADC 16. The ADC 16 receives the potential difference signal Isns and the sampling signal smpl from the PWM drive unit 13, converts the potential difference signal Isns into a digital signal based on the sampling signal smpl, and outputs the digital signal to the polarity switching unit 17. The polarity switching unit 17 switches the polarity of the output signal of the ADC 16 according to the polarity instruction signal inv value from the PWM driving unit 13 and outputs the polarity to the comparator 11 as the detected current value Idet.

  As described above, according to the motor drive device 10 in the present embodiment, the integrating unit 21 integrates the difference between the voltage command signal Vcmnd and the PWM command signal PWMin to output the error integrated value Vint, and performs nonlinear conversion Since the unit 22 excludes the output in the predetermined range from the error integrated value Vint and outputs the excluded signal to the PWM drive unit 13 as the PWM command signal PWMin, the output in the predetermined range is the error. By excluding from the integrated value Vint, pulses having a certain width or less can be limited, and current detection when the PWM is on-duty can be easily and accurately performed.

  Therefore, the motor drive device 10 in the present embodiment does not require a separate circuit for corresponding to the positive and negative voltage command signals, and the motor coil 100 is supplied with an appropriate PWM command signal PWMin for the positive and negative voltage command signals. Since it can output, it can respond to a positive / negative voltage command signal with a circuit scale smaller than before.

  In addition, since the motor drive device 10 in the present embodiment compensates for the voltage error due to the short pulse exclusion by error integration, the distortion of the current flowing through the motor coil 100 can be reduced.

  In addition, since the motor driving apparatus 10 according to the present embodiment can reduce the condition judgment by directly converting the error integration result as it is, voltage error compensation can be performed with a simpler configuration than the conventional one.

  In addition, the motor driving device 10 in the present embodiment can perform voltage error compensation without changing the configuration according to the sign of the voltage command signal Vcmnd.

  Further, in the motor drive device 10 according to the present embodiment, the non-linear converter 22 is configured to perform quantization so as to convert the input within a predetermined range into a constant output value. Voltage error compensation by exclusion can be performed.

  In addition, since the motor drive device 10 according to the present embodiment can set the quantization level number and the boundary value as parameters in the non-linear converter 22, the voltage error compensation characteristics can be adjusted by simply changing the setting. Flexible voltage error compensation is possible at low cost.

  In addition, the motor driving device 10 according to the present embodiment is configured such that the non-linear converter 22 is driven by excluding short pulses among PWM driving pulses, so that current sampling detection is easy and precise current control is performed. Can be realized.

  In addition, the motor drive device 10 according to the present embodiment has a PWM drive unit 13, a resistance element 15, an ADC 16, and polarity switching as current detection means for detecting a current flowing through the motor coil 100 when the drive pulse is in an on state. Current control for providing a voltage command signal Vcmnd according to the difference between the detected current value Idet detected and the target current command signal Icmnd and controlling the motor coil current to a value according to the target current command signal Icmnd. Since the comparator 11 and the error amplifier 12 are provided as means, the motor current does not fluctuate even if there are fluctuations in power supply voltage, switch element resistance, or coil resistance due to current feedback. The motor can be driven with a current corresponding to the current command signal. Therefore, the motor drive device 10 can perform stable and precise motor drive control.

(Second Embodiment)
The configuration of the motor drive device according to the second embodiment of the present invention is different from the motor drive device 10 according to the first embodiment in the function of the non-linear converter 22. Accordingly, the non-linear conversion unit 22 will be described with the same reference numerals as those of the motor drive device 10 in the first embodiment, and redundant description will be omitted.

  The non-linear conversion unit 22 in the present embodiment switches the offset in order to exclude an output within a predetermined range from the error integrated value Vint, and will be described with reference to FIG.

  FIG. 10 is a diagram illustrating an example of input / output characteristics when the non-linear conversion unit 22 switches the offset to either −20 or +20 with the input 0 as a boundary. The processing of the non-linear conversion unit 22 in the example shown in FIG. 10 is described as a program as follows.

s301: if (input <h) then output = input + c1;
s302: else output = input + c2;

  That is, the non-linear conversion unit 22 adds the offset c1 or c2 to the input value with the input predetermined value h as a boundary. In the example shown in FIG. 10, h = 0, c1 = −20, and c2 = + 20.

  As a result, the non-linear converter 22 can prevent the output PWM command signal PWMin from including values from c1 to c2, and can prevent short pulses from occurring. Even if the offset changes to c1 or c2, the PWM command signal PWMin is converted into the voltage command signal Vcmd by feedback that integrates the difference between the PWM command signal PWMin and the voltage command signal Vcmd to make a non-linear conversion to the PWM command signal PWMin. And the offset is cancelled.

  Next, FIG. 11 shows a response example of the PWM command signal PWMin and the coil current when the same voltage command signal Vcmd as described in FIGS. 6 and 9 is input as a sine wave. The change for avoiding the range of the PWM command signal PWMin from −20 to +20 is larger than that shown in FIGS. 6 and 9, but the coil current is almost smooth and undistorted. Therefore, the motor can be operated smoothly and without distortion by the non-linear converter 22 in this configuration. In this example, the processing of the non-linear conversion unit 22 can be greatly simplified, so that the circuit and program can be further simplified.

  Next, another aspect of the non-linear conversion unit 22 in the present embodiment will be described with reference to FIGS. FIG. 12 shows an example of input / output characteristics of the non-linear conversion unit 22 in another aspect.

  In this example, the offset is changed with the input 0 as a boundary, and the slope is changed so that the output and the input coincide with each other at the maximum input value and the minimum input value (here, +100 and −100). As a result, the difference between the input value and the output value becomes smaller as the voltage instruction becomes larger while excluding the predetermined range (from -20 to +20 in this case) from the output, so that the distortion of the coil current can be reduced. Also, output saturation and overflow can be avoided for large voltage instructions.

  Next, FIG. 13 shows a response example of the PWM command signal PWMin and the coil current Current when the same voltage command signal Vcmd as described in the first embodiment is inputted as a sine wave. The change for avoiding the PWM command signal PWMin from −20 to +20 is larger than that in the first embodiment (in the case of the characteristics shown in FIGS. 4 and 8), but the simple offset addition shown in FIG. Smaller than the case. The coil current Current is almost smooth and has no distortion. Therefore, the motor can be operated smoothly and without distortion by the non-linear converter 22 in this configuration.

  Next, a processing example of the non-linear converter 22 that can obtain the input / output characteristics shown in FIG. 12 is shown in the form of a program as follows.

s201: if (input <h) then output = a1 * input + b1;
s202: else output = a2 * input + b2;

  In this example, the inclination and the intercept (offset) are switched between (a1, b1) and (a2, b2) with the input predetermined value h as a boundary. In the characteristic example of FIG. 12, h = 0, a1 = a2 = 80/100, b1 = −20, and b2 = + 20.

  As described above, according to the motor drive device of the present embodiment, the non-linear conversion unit 22 is configured to change the offset with a predetermined input value as a boundary. Therefore, the processing of the non-linear conversion unit 22 is very simple. In addition, the circuit and the program can be simplified.

  As described above, the motor drive device according to the present invention has an effect of being able to deal with positive and negative voltage command signals with a circuit scale smaller than the conventional one, and is useful as a motor drive device for PWM driving a motor. is there.

The block diagram which shows the structure in 1st Embodiment of the motor drive device which concerns on this invention. Explanatory drawing of the PWM drive in 1st Embodiment of the motor drive device which concerns on this invention The figure which shows an example of the input / output relationship of a non-linear conversion part in 1st Embodiment of the motor drive device which concerns on this invention. The figure which shows the waveform example of voltage command signal Vcmd, PWM command signal PWMin, and coil current Current in 1st Embodiment of the motor drive device which concerns on this invention. FIG. 4 is an enlarged view of the portion from the horizontal axis “80” to “120” in FIG. 4 in the first embodiment of the motor drive device according to the present invention. FIG. 5 is a diagram showing actual data of FIG. 5 in the first embodiment of the motor drive device according to the present invention. The figure which shows the example which made the quantization level of the non-linear transformation part one in 1st Embodiment of the motor drive device which concerns on this invention. In the first embodiment of the motor driving device according to the present invention, waveform examples of the voltage command signal Vcmd, the PWM command signal PWMin, and the coil current Current when the quantization level of the non-linear conversion unit is one are shown. Figure The flowchart which shows operation | movement of 1st Embodiment of the motor drive device which concerns on this invention. The figure which shows the input-output characteristic example in case the nonlinear conversion part switches offset in 2nd Embodiment of the motor drive device which concerns on this invention. The figure which shows the waveform example of voltage command signal Vcmd, PWM command signal PWMin, and coil current Current in 2nd Embodiment of the motor drive device which concerns on this invention. The figure which shows the input-output characteristic example of the non-linear transformation part in the other aspect of 2nd Embodiment of the motor drive device which concerns on this invention. The figure which shows the waveform example of voltage command signal Vcmd, PWM command signal PWMin, and coil current Current in the other aspect of 2nd Embodiment of the motor drive device which concerns on this invention.

Explanation of symbols

10 motor drive device 11 comparator (current control means)
12 Error amplifier (current control means)
13 PWM drive section (drive pulse output means, current detection means)
14 switching element part 14a-14d switching element 15 resistance element (current detection means)
16 ADC (current detection means)
17 Polarity switching part (current detection means)
20 PWM conversion means (signal conversion means)
21 accumulator 21a subtractor 21b memory 21c adder 21d memory 22 non-linear converter (output exclusion unit)
100 motor coil

Claims (5)

A motor driving device for applying a voltage by applying a driving pulse to a motor coil,
A signal conversion means for converting a voltage command signal into a pulse width command signal, and a drive pulse output means for outputting a drive pulse corresponding to the pulse width command signal to the motor coil,
The signal conversion means integrates a difference between the voltage command signal and the pulse width command signal and outputs an error integrated value, and outputs the error integrated value by excluding an output in a predetermined range. And a motor drive device that outputs a pulse width command signal corresponding to the output of the output exclusion unit. The motor drive apparatus according to claim 1, wherein the output excluding unit performs quantization for converting an input value in a predetermined range into a constant output value. The output excluding unit is configured to input / output characteristics indicating a relationship between the input value and the output value of the output excluding unit based on a predetermined reference input value and a reference output value. 3. The motor driving apparatus according to claim 1, wherein the output characteristic is offset in a positive / negative direction of the reference output value by a predetermined offset amount. The motor drive device according to claim 3, wherein the output exclusion unit is configured to reduce the offset amount as a difference between the input value and the reference input value increases. Current detection means for detecting a current flowing through the motor coil when the drive pulse is on, and the voltage according to a difference between a detected current value detected by the current detection means and a predetermined current command signal value 5. The apparatus according to claim 1, further comprising a current control unit that outputs a command signal and controls a current flowing through the motor coil to a value corresponding to the current command signal. 6. Motor drive device.

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