JP2005210839A - Apparatus and method of controlling motor and computer program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for controlling a motor which can realize a rotating position detection using a resolver with a constitution having a low cost and good controlling response. <P>SOLUTION: A microcomputer 21 outputs a clock signal S1 having a period of double as large as a conveying period in a PWM modulation. A synchronous excitation signal forming circuit 11 forms a sine wave-like excitation signal S2 by low-pass filtering the clock signal S1. And, when the microcomputer 21 performs A/D conversion by synchronizing a cosine signal S3 and a sine signal S4 outputted by the resolver 2 disposed in the motor 1 with a carrier period, cosine data Dx and sine data Dy are obtained as a difference of the continuous twice A/D conversion results, and the rotary position Θ of a rotor is calculated by using a function arctan. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a motor control device and a control method for detecting the rotational position of a motor and controlling the current supplied to the motor winding by PWM modulation, and a program for causing a computer to execute such control.

In the case of a motor control device that controls energization of a brushless motor, it is necessary to detect the rotational position of the brushless motor in order to optimize the energization phase. In general, a Hall IC is used as a means for detecting the rotational position, but a resolver may be used when it is desired to suppress torque fluctuation during one rotation as much as possible or when the stop position of the brushless motor is controlled. Is appropriate.
When a resolver is used as a means for detecting the rotational position, a conversion means is required to obtain the rotational position from the output signal of the resolver. As this means, a dedicated resolver / digital conversion IC (for example, manufactured by Tamagawa Seiki) “AU6802”) is well known. A configuration example in the case of using this conversion IC is shown in FIG.

  An excitation signal from the oscillator 14 built in the conversion IC 16 constituting the control device 30 is input to the excitation coil of the resolver 2 attached to the brushless motor 1 via the amplifier 12. Output signals from the cosine coil and the sine coil, which are output coils of the resolver 2, are input to the resolver / digital (R / D) converter 15 via the differential amplifier 13 built in the conversion IC 16, where, for example, 12 bits are input. Converted to a digital signal. The microcomputer 31 obtains rotational position information of the motor 1 by reading these digital signals from the input port.

FIG. 8 shows a configuration disclosed in Patent Document 1 as a technique for detecting a rotational position without using a dedicated conversion IC. The control device 40 is provided with an excitation signal generator 14 and an amplifier 12, and the excitation coil of the resolver 2 is excited. The output signals of the cosine coil and sine coil are input to the analog / digital converter (hereinafter referred to as A / D converter) 22c of the microcomputer 41 through the differential amplifier 13 and then through the synchronous detection circuit 17 and the low-pass filter 18. Is done. At this time, the output signals of the cosine coil and the sine coil including AC components are converted into DC components by the synchronous detection circuit 17 and the low-pass filter 18. The microcomputer 41 detects the rotational position of the motor 1 based on these A / D conversion results and the conversion table.
JP 2001-264114 A

As shown in FIG. 7, in the configuration using the dedicated conversion IC, it is possible to obtain highly accurate position information, but there is a problem that the conversion IC is expensive. Moreover, in the structure disclosed by patent document 1, since the low pass filter 18 is used, there exists a problem that the responsiveness of motor control worsens.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a motor control device capable of realizing the rotational position detection of a motor using a resolver with a low-cost and good control response configuration. And a motor control method and a computer program.

In order to achieve the above object, the motor control device of the present invention detects the rotational position of the motor, and performs PWM modulation to control the current supplied to the winding of the motor.
Forming and outputting an excitation reference signal synchronized with a control cycle, and supplying a reference signal forming means for supplying to a resolver disposed on the motor side;
The sine wave signal and the cosine wave signal output by the resolver are analog / digital converted in synchronization with the control period and at a period faster than the period of the excitation reference signal, and the conversion result is calculated, And an arithmetic means for obtaining a rotational position of the motor.

  That is, the amplitudes of the sine wave signal and cosine wave signal output by the resolver change according to the rotational position of the motor (rotor). Therefore, the excitation reference signal to be supplied to the resolver is formed in synchronization with the cycle for controlling the energization to the motor winding, and the calculation means is synchronized with the control cycle and more than the cycle of the excitation reference signal. If analog / digital conversion is performed on the sine wave signal and the cosine wave signal at a fast cycle and the conversion result is calculated, a value reflecting the AC amplitude change of the sine wave signal and the cosine wave signal can be obtained. And if those calculation results are used, the rotational position of the rotor can be obtained.

  Note that “synchronized with the control cycle” does not necessarily mean that the control cycle is matched, but also means that the timing at which the level of the excitation reference signal changes coincides with any processing time point in the control. Used to include.

  According to the motor control device of the present invention, an IC for converting the output signal of the resolver is not used, and unlike the patent document 1, the output signal of the resolver is not passed through a low-pass filter and is low in cost. The rotational position of the rotor can be detected with a configuration having good control response.

  An embodiment of the present invention will be described below with reference to FIGS. In FIG. 1 showing the configuration of the motor control device, the control device 20 includes a current detection circuit 5 for detecting a current flowing in the winding of the brushless motor 1, and an output terminal of the current detection circuit 5 is a microcomputer ( (Microcomputer, calculation means) 21 is connected to an A / D converter 22a built in. The current detection circuit 5 is configured to detect a terminal voltage of a shunt resistor inserted between the lower arm of the inverter main circuit 3 and the ground, for example.

  The inverter main circuit 3 is configured by, for example, six MOSFETs connected in a three-phase bridge. The six output terminals of the PWM circuit 23 built in the microcomputer 21 are connected to the gates of the FETs constituting the inverter main circuit 3 via the gate drive circuit 4. The inverter main circuit 3 supplies the PWM voltage to the three-phase winding of the brushless motor 1.

The microcomputer 21 outputs a clock signal S1 synchronized with a current control process to be described later, and the clock signal S1 is given to a synchronous excitation signal forming circuit (reference signal forming means) 11 for forming an excitation signal S2 (excitation reference signal). It has been. The excitation signal S2 is supplied to the excitation coil of the resolver 2 attached to the brushless motor 1 via the amplifier 12.
The cosine coil and sine coil, which are output coils of the resolver 2, are connected to the input terminals (+, −) of the differential amplifier 13, respectively. The output signals of the differential amplifier 13 are a cosine signal S3 and a sine signal S4. The A / D converter 22c of the microcomputer 21 is given. The microcomputer 21 stores a control program (computer program) 25 in an internal memory 24, and executes processing based on the program 25.

  FIG. 2 shows the configuration of the synchronous excitation signal forming circuit 11. The input clock signal S1 is supplied to an amplifier 54 after passing through low-pass filters 50, 51, 52 composed of resistors and capacitors for removing harmonics and a buffer operational amplifier 53. The capacitor C1 in the amplifier 54 is inserted in order to remove a direct current component with respect to the reference potential Vr. The amplitude and phase of the excitation signal S2, which is an output signal, are adjusted by the resistors R1, R2 and the capacitor C2.

  Next, the operation of this embodiment will be described with reference to FIGS. FIG. 3 is a flowchart showing a PWM interrupt process executed by the microcomputer 21 in synchronization with the operation of the PWM circuit 23. The PWM interrupt process is executed, for example, at a cycle of 50 μsec. The microcomputer 21 counts the number of interrupt processing in step S1, and in subsequent step S2, the process is branched into two paths depending on whether the count value is odd or even.

  When the count value is an odd number in step S2, the process proceeds to step S3 and the clock signal S1 output to the synchronous excitation signal forming circuit 11 is set to the high level. In step S4, the A / D converter 22c reads the cosine signal S3 and the sine signal S4. At this time, the A / D conversion results are stored in the memory 24 as data D1 and D2, respectively. In the next step S5, the detection result of the current detection circuit 5 is read by the A / D converter 22a. Thereby, the winding currents Iu, Iv, Iw of each phase of the brushless motor 1 are recognized.

In this embodiment, the control device 20 controls the current by so-called vector control. In step S6, the winding currents Iu, Iv, Iw are set to d (direct) based on the rotational position calculation result described later. Conversion into currents Id and Iq of the axis and q (quadrature) axis. In step S7, proportional-integral (PI) control is performed based on the difference between the converted currents Id and Iq and the current commands Idr and Iqr to determine the voltages Vd and Vq. In step S8, the voltages Vu, Vv, Vw of each phase applied to the brushless motor 1 are calculated from the voltages Vd, Vq based on the rotational position calculation result to be described later, and output to the PWM circuit 23.
That is, the current control operation in which the motor current is detected and the voltage is determined based on the comparison result with the command value is executed by the processing in steps S5 to S8. That is, while the flowchart of FIG. 3 is executed in the PWM carrier wave period, the current control is executed in twice that period.

  On the other hand, if the count value is a treatment number in step S2, the process proceeds to step S9. In step S9, the clock signal S1 output to the synchronous excitation signal forming circuit 11 is set to a low level. That is, in steps S3 and S9, the clock signal S1 is inverted for each carrier period of the PWM modulation, and thus becomes a signal having a period twice that of the carrier period. In the subsequent step S10, data reading of the cosine signal S3 and the sine signal S4 by the A / D converter 22c is executed. Also in this case, the A / D conversion results are stored in the memory 24 as data D3 and D4, respectively.

In the next step S11, first, a difference between A / D conversion results, which is data corresponding to the amplitudes of the cosine signal S3 and the sine signal S4, is obtained. The details will be described below. First, the difference between the data D1 and D2 acquired in step S4 and the data D3 and D4 acquired in step S9 is obtained and set as cosine data Dx and sine data Dy.
Dx = D1-D3
Dy = D2-D4
Next, based on the relationship between these data Dx and Dy, the rotational position Θ of the motor 1 is obtained by performing different operations by distinguishing them into eight patterns as shown in FIG.
[Pattern 1] Dx ≧ 0 and Dy ≧ 0 and | Dx | ≧ | Dy |
Rotation position Θ = arctan (Dy / Dx)
[Pattern 2] Dx ≧ 0 and Dy ≧ 0 and | Dy | ≧ | Dx |
Rotation position Θ = π / 2-arctan (Dx / Dy)
[Pattern 3] Dx <0 and Dy ≧ 0 and | D | y ≧ | Dx |
Rotation position Θ = π / 2 + arctan (Dx / Dy)
[Pattern 4] Dx <0 and Dy ≧ 0 and | Dx | ≧ | Dy |
Rotation position Θ = π-arctan (Dy / Dx)
[Pattern 5] Dx <0 and Dy <0 and | Dx | ≧ | Dy |
Rotation position Θ = π + arctan (Dy / Dx)
[Pattern 6] Dx <0 and Dy <0 and | Dy | ≧ | Dx |
Rotation position Θ = -π / 2-arctan (Dx / Dy)
[Pattern 7] Dx ≧ 0 and Dy <0 and | Dy | ≧ | Dx |
Rotation position Θ = -π / 2 + arctan (Dx / Dy)
[Pattern 8] Dx ≧ 0 and Dy <0 and | Dx | ≧ | Dy |
Rotation position Θ = -arctan (Dy / Dx)
Here, as shown in FIG. 4, the unit circle in the two-dimensional coordinates of Dx and Dy is divided into ½ quadrants (π / 4) and divided into 8 patterns. The function arctan (arc tangent) This is because the calculation accuracy near π / 2 is deteriorated in the calculation, and the calculation is performed using only the range of 0 to π / 4 while avoiding the region.

  That is, the microcomputer 21 performs A / D conversion on the output signal of the resolver in the PWM cycle in steps S10 and S11, and calculates the rotational position Θ by calculation based on two consecutive A / D conversion results in steps S1 and S9. It has gained. FIG. 5 shows the relationship between cosine data Dx, sine data Dy, and rotational position Θ. The rotational position Θ can be uniquely determined by referring to the values of these two data Dx and Dy.

  Next, the rotational position detection operation based on the flowchart of FIG. 3 will be described with reference to the timing chart of FIG. FIG. 6A shows an example of a PWM signal output by the PWM circuit 23, and the interrupt processing of the microcomputer 21 is generated as shown in FIG. 6B in synchronization with the carrier wave cycle of the PWM signal. In the interrupt process, as described above, the clock signal S1 is output by the processes in steps S1 and S9 (see FIG. 6C). In addition, since the current control is performed with a period twice the PWM carrier period, the pulse width of the PWM signal shown in FIG. 6A changes every other time.

  The excitation signal S2 shown in FIG. 6D is formed by the synchronous excitation signal forming circuit 11, but here, a delay of time t1 is given. This is to make the A / D conversion timing described later coincide with the maximum amplitude timing of the cosine signal S3 and the sine signal S4. The excitation signal S2 is applied to the excitation coil of the resolver 2 through the amplifier 12. A cosine signal S3 and a sine signal S4 (see FIG. 6 (f)) are supplied from the output coil of the resolver 2 to the microcomputer 21 via the differential amplifier 13.

  In steps S4 and S10 in the interrupt processing, an A / D conversion operation is performed at the timing shown in FIGS. 6E, 6F, and 6G, and data D1 and D3 are fetched as shown in the figure for the cosine signal S3. The difference becomes cosine data Dx (see FIG. 6H). As for the cosine signal S4, the data D2 and D4 are taken as shown in the figure, and the difference becomes the sine data Dy (see FIG. 6 (h)).

  As described above, according to the present embodiment, the microcomputer 21 outputs the clock signal S1 having a period twice the carrier wave period in PWM modulation, and the synchronous excitation signal forming circuit 11 performs low-pass filtering on the clock signal S1. Thus, a sinusoidal excitation signal S2 is formed. When the microcomputer 21 performs A / D conversion on the cosine signal S3 and the sine signal S4 output by the resolver 2 disposed in the motor 1 in synchronization with the carrier wave period, the difference between the two consecutive A / D conversion results is obtained. Thus, cosine data Dx and sine data Dy are obtained, and the rotational position Θ of the rotor is calculated using the function arctan.

  That is, in this case, since the period in which the microcomputer 21 performs the A / D conversion is equal to the PWM modulation carrier period, the period of the excitation signal S2, the cosine signal S3, and the sine signal S4 is ½. A / D conversion can be performed in the vicinity where the AC amplitude change of the signal S3 and the sine signal S4 shows the maximum value and the minimum value. Therefore, a dedicated IC for converting the output signal of the resolver 2 is not used, and unlike the patent document 1, the output signal of the resolver 2 is not passed through a low-pass filter, and the cost is low and the control response is good. The rotational position Θ can be detected with the configuration.

  Since the microcomputer 21 outputs the clock signal S1 synchronized with the PWM control cycle and the synchronous excitation signal forming circuit 11 forms the excitation signal S2, the microcomputer 21 performs current control processing, A / D conversion processing, and rotational position. Since the detection calculation can be executed by a series of operations, the synchronization control is facilitated and the burden on the program can be reduced. In addition, the microcomputer 21 performs the calculation using the function arctan with high accuracy because the calculation is performed by distinguishing the pattern into eight different patterns depending on the sign of the sine wave data and cosine wave data obtained by A / D conversion. can do.

The present invention is not limited to the embodiments described above and shown in the drawings, and the following modifications or expansions are possible.
The excitation reference signal may be formed so as to have a period n (n is a natural number) times the PWM control period. On the other hand, the period for A / D converting the cosine signal and the sine signal is n / of the PWM control period. Just double it.

In addition, when the excitation reference signal is set to a cycle that is n (n is a natural number) times the current control cycle as a reference, the A / D conversion cycle may be set to n / 2 times the current control cycle.
A circuit that outputs a clock signal serving as a synchronization reference for current control processing may exist outside the microcomputer 21.
When high calculation accuracy is not required, it is not necessary to perform the calculation using the function arctan in eight patterns.

The figure which is one Example of this invention, and shows the structure of a motor control apparatus The figure which shows the constitution of the synchronous excitation signal formation circuit Flowchart showing PWM interrupt processing executed by the microcomputer in synchronization with the operation of the PWM circuit The figure which shows eight patterns which switch the computing equation for detecting a rotation position on the two-dimensional coordinate of Dx and Dy The figure which shows the relationship between the value of cosine data Dx, sine data Dy, and rotational position (theta). FIG. 3 is a timing chart showing a change state of each signal corresponding to the processing content according to the flowchart of FIG. FIG. 1 equivalent diagram showing the prior art (part 1) FIG. 1 equivalent diagram showing the prior art (No. 2)

Explanation of symbols

  In the drawings, 1 is a brushless motor, 2 is a resolver, 11 is a synchronous excitation signal forming circuit, 12 is an amplifier, 21 is a microcomputer, 23 is a PWM circuit, and 25 is a control program.

Claims (13)

In the motor control device that detects the rotational position of the motor and controls the current applied to the winding of the motor by PWM modulation,
Forming and outputting an excitation reference signal synchronized with the control cycle, and supplying a reference signal forming means for supplying to the resolver disposed on the motor side;
The sine wave signal and the cosine wave signal output by the resolver are analog / digital converted in synchronization with the control period and at a period faster than the period of the excitation reference signal, and the conversion result is calculated, A motor control device comprising: a calculation means for obtaining a rotational position of the motor. The reference signal forming means forms an excitation reference signal synchronized with n times the current control period (n is a natural number),
The calculation means performs analog / digital conversion on the sine wave signal and cosine wave signal output by the resolver at n / 2 times the current control period, and calculates two consecutive analog / digital conversion results. The motor control device according to claim 1, wherein the rotational position of the motor is obtained. The reference signal forming means forms an excitation reference signal synchronized with n times the carrier wave period used for the PWM modulation (n is a natural number),
The calculation means performs analog / digital conversion on the sine wave signal and cosine wave signal output by the resolver at n / 2 times the PWM carrier wave period, and calculates two consecutive analog / digital conversion results. The motor control device according to claim 1, wherein a rotational position of the motor is obtained. The arithmetic means outputs a clock signal synchronized with the control cycle,
4. The motor control device according to claim 1, wherein the reference signal forming unit is configured to form an excitation reference signal synchronized with the clock signal.   5. The calculation means according to claim 1, wherein the calculation means performs calculation by distinguishing into eight different patterns according to the positive / negative and magnitude relationship of sine wave data and cosine wave data obtained by analog / digital conversion. The motor control device described in 1. In the motor control method for detecting the rotational position of the motor and controlling the current applied to the winding of the motor by PWM modulation,
Form an excitation reference signal synchronized with the control cycle, and supply it to the resolver arranged on the motor side,
The sine wave signal and the cosine wave signal output by the resolver are analog / digital converted in synchronization with the control period and with a period faster than the period of the excitation reference signal,
A motor control method characterized in that the rotational position of the motor is obtained by calculating the conversion result. An excitation reference signal that is synchronized with n times the current control period (n is a natural number) is formed,
The sine wave signal and the cosine wave signal output by the resolver are converted from analog to digital at n / 2 times the current control period,
The motor control method according to claim 6, wherein the rotational position of the motor is obtained by calculating a result of two consecutive analog / digital conversions. Forming an excitation reference signal synchronized with n times (n is a natural number) of a carrier wave period used for the PWM modulation;
The sine wave signal and the cosine wave signal output by the resolver are converted from analog to digital at n / 2 times the PWM carrier wave period,
The motor control method according to claim 6, wherein the rotation position of the motor is obtained by calculating a result of two consecutive analog / digital conversions.   9. The motor control according to claim 6, wherein the calculation is performed by distinguishing into eight different patterns according to the positive / negative and magnitude relationship of sine wave data and cosine wave data obtained by analog / digital conversion. Method. A program that is executed by a computer that detects the rotational position of the motor and controls the current applied to the winding of the motor by PWM modulation,
An excitation reference signal synchronized with the control cycle is formed and supplied to the resolver arranged on the motor side,
The sine wave signal and the cosine wave signal output by the resolver are analog / digital converted in synchronization with the control period and with a period faster than the period of the excitation reference signal,
A computer program for processing to obtain the rotational position of the motor by calculating the conversion result. An excitation reference signal synchronized with n times the current control period (n is a natural number) is formed,
A sine wave signal and a cosine wave signal output by the resolver are analog / digital converted at n / 2 times the current control period,
11. The computer program according to claim 10, wherein the computer program is processed so as to obtain a rotational position of the motor by calculating two consecutive analog / digital conversion results. An excitation reference signal synchronized with n times (n is a natural number) of a carrier wave period used for the PWM modulation is formed,
The sine wave signal and the cosine wave signal output by the resolver are converted from analog to digital at n / 2 times the PWM carrier period,
11. The computer program according to claim 10, wherein the computer program is processed so as to obtain a rotational position of the motor by calculating a result of two consecutive analog / digital conversions. The computer according to any one of claims 10 to 12, wherein the calculation is performed by distinguishing into eight different patterns according to the positive / negative and magnitude relationship of the sine wave data and cosine wave data obtained by analog / digital conversion. program.

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