JP4710634B2 - Motor control device - Google Patents

Description

  The present invention relates to a motor control device having rotational position detection means using a resolver.

  Conventionally, a robust resolver has been used as a position detection means for a motor used in a poor environment. This resolver generally has one excitation winding and two secondary windings that are 90 degrees out of phase, and a resolver / digital converter based on the output signal of the secondary winding and the excitation signal of the excitation winding. A method of detecting the rotational position using the is used.

  The general method of this resolver / digital converter uses a closed loop circuit that makes the difference between the actual rotor angle θ and the angle θp generated by the resolver / digital converter zero. Specifically, the detection signals output from the two secondary windings are respectively multiplied by the cosine value and the sine value of the estimated value θp of the rotation angle, and passed through the adder circuit to thereby obtain the sine value of the phase difference θ−θp. A signal in the form of being modulated with an excitation signal is generated.

  This signal is rectified in synchronization with the period of the excitation signal, and then the sine value of the phase difference θ−θp is generated as a DC voltage by removing the excitation signal component. The DC voltage integrated by an integrator is input to a voltage controlled oscillator, and the number of pulses output from the voltage controlled oscillator is counted to obtain an estimated rotation angle θp as digital data.

  By feeding back θp, the output of the integrator is balanced in a state where θp matches θ, and θ can be detected as θp.

  However, this method uses a lot of analog circuits, so it is easily affected by temperature drift, etc., and it is difficult to improve accuracy. In addition, the optimum gain of the closed-loop circuit changes depending on the rotation speed, so it has high performance over a wide range. It has become difficult to maintain.

  As a method for solving this, there is a method in which the signal of the secondary winding is directly AD converted and processed with digital data (see, for example, Patent Document 1).

  In this method, the secondary winding signal is rectified in synchronization with the excitation signal, then digitized by an AD converter, and the same processing as a conventional general method is performed digitally, which solves the problems of analog circuits. is doing.

However, also in this method, as in the conventional method, the spatial harmonic component of the secondary winding and the mechanical accuracy of the resolver greatly affect the angle detection accuracy. In addition, when considering the anti-noise performance of the wiring, the secondary windings must be wired independently for the purpose of eliminating the influence of common impedance, so twice the number of windings is required. However, in the recent trend of reducing the wiring of encoders, there is a problem that six or more wires are required in total including the primary winding and the secondary winding.
JP 2002-54948 A

  The problems to be solved are the high required mechanical accuracy of the resolver, the complexity of the winding method, and the number of wirings, and the complexity of the system, the difficulty of adjustment, and the influence of disturbance.

  In conventional systems, the quality of the output signal of the resolver occupies a large part of the angle detection accuracy, so its mechanical accuracy, mounting accuracy to the motor shaft, complex winding methods to reduce spatial harmonics, etc. are important Therefore, the resolver was made expensive.

  In addition, since it has a closed loop system inside, it is necessary to adjust the gain in order to operate the system stably. In addition, there is a problem that more wiring is required than the encoder.

  The present invention solves the above-mentioned conventional problems, and aims to provide an inexpensive and highly reliable motor control device that improves the complexity of rotational position detection using a resolver and suppresses the influence of disturbance. And

In order to solve the above problems, the present invention provides an excitation signal generating means for generating an excitation signal of a resolver connected to a rotating shaft of a motor, and a rotational position detecting means for detecting the rotational position of the motor from the output signal of the resolver. And PWM inverter driving means for driving the motor based on the rotational position signal output from the rotational position detecting means. The rotational position detecting means is star-connected with a phase difference of the resolver of 120 degrees. consists of a rotation angle calculating means for calculating an AD converting means for converting the line voltage of the three-phase secondary windings on three digital data, the rotation angle of the motor on the basis of the three digital data, further the rotation The angle calculation means includes an average value calculation means for calculating an average value of three digital data, and three neutral points by subtracting the average value from the three digital data. Neutral point correction means for calculating positive data, and normalization calculation for calculating three normalized data by dividing the three neutral point correction data by the square root of the sum of squares of the three neutral point correction data It consists of a means, among the three normalized data, a motor control equipment having a configuration for obtaining the rotation angle by using a preset table smallest absolute value.

  According to the motor control device of the present invention, since the secondary winding of the resolver has three phases and the rotation angle is determined from the line voltage, the harmonic component of the winding is suppressed, In addition to simplifying the configuration of the windings, the use of the line voltage suppresses the adverse effect of the common impedance between the signals, so the number of wires can be reduced by one.

  Further, by converting the voltage of the secondary winding as it is into digital data, it is possible to suppress the influence such as temperature drift of the analog circuit.

  In addition, since the rotation angle is calculated with a table using the data with the largest change amount with respect to the angle change and the smallest absolute value among the detected three-phase data, the amount of digital calculation is also reduced. This eliminates the need for complicated gain setting and adjustment.

  In addition to correcting the neutral point of the three digital data and correcting the amplitude by normalization, the required mechanical accuracy of the resolver can be lowered, and the influence on disturbance noise can be suppressed. it can.

Incidentally, it carried out AD conversion at the timing when the switching of the inverter is not implemented Then, it is possible to eliminate the influence of switching noise generated in the self.

  Therefore, the required mechanical accuracy of the resolver can be reduced, the winding method can be simplified and the number of wirings can be reduced, and an inexpensive and highly reliable motor control device that is resistant to disturbance and easy to adjust can be obtained.

  An excitation signal generating means for generating an excitation signal of a resolver connected to a rotating shaft of the motor, a rotational position detecting means for detecting the rotational position of the motor from the output signal of the resolver, and output from the rotational position detecting means PWM inverter driving means for driving the motor based on a rotational position signal, wherein the rotational position detecting means is a line voltage of a three-phase secondary winding that is star-connected with a phase difference of the resolver of 120 degrees. Are converted into three digital data by AD conversion means and rotation angle calculation means for calculating the rotation angle of the motor based on the three digital data, and the rotation angle calculation means is an average value of the three digital data. Average value calculating means for calculating the neutral point correction means for calculating three neutral point correction data by subtracting the average value from the three digital data, and Normalization calculation means for calculating three normalized data by dividing the three neutral point correction data by the square root of the sum of squares of the two neutral point correction data, and among the three normalized data, The rotation angle is obtained using a table having the smallest absolute value and set in advance.

  FIG. 1 is an overall view showing the configuration of the motor control device of the present invention. In FIG. 1, a resolver 2 is connected to the shaft of a motor 1, and a primary winding 3 of the resolver 2 is excited by an excitation signal from an excitation signal generating means 4.

  The excitation signal generation means 4 generates an excitation signal so as to synchronize with the switching carrier based on the switching carrier information output from the PWM inverter 5.

  The three-phase secondary windings 6 a, 6 b, 6 c of the resolver 2 are arranged with a phase difference of 120 degrees from each other, and the output signals thereof are input to the rotational position detection means 7.

  In the rotational position detecting means 7, differential amplifiers 8a, 8b, 8c for inputting line data of output signals and AD converting means 9a, 9b, 9c for converting the output into digital data are arranged and converted. The digital data is input to the rotation angle calculation means 10 and the rotational position information of the motor is output.

  The rotational position information of the motor detected by the rotational position detection means 7 is input to the PWM inverter 5, and the motor 1 is driven based on the information.

  Generally, in order to increase the accuracy of position detection, the output voltage of the resolver 2 needs to be a sine wave. However, in the present invention, since position detection is performed based on the line voltage of the three-phase output voltage, Harmonic components of integer multiples of 3 contained in the output voltage expected to have the highest content are removed.

  The output signal of the secondary winding 6 of the resolver 2 has a waveform obtained by modulating the sine value of the rotation angle with the excitation signal as shown in FIG.

  Since the excitation signal is synchronized with the carrier cycle of the PWM inverter, the relationship between the switching pattern of the PWM inverter, the excitation signal, and the output signal is as shown in FIG.

  In FIG. 3, td is a phase shift caused by wiring or a resolver, and the peak of the output signal comes at a timing when switching is not performed by shifting the oscillation phase in advance.

  The digital data obtained as a result of AD conversion is expressed by Equation 1 when the rotation angle of the rotor is θ. Here, K is the conversion gain of the resolver, and offset is the offset of the differential amplifier.

これらのデータの平均値は、Ｖｍｅａｎ＝（Ｖａ＋Ｖｂ＋Ｖｃ）／３で求められ、これを減算すると、中性点補正データとして式２が得られる。

The average value of these data is obtained by Vmean = (Va + Vb + Vc) / 3, and when this is subtracted, Equation 2 is obtained as neutral point correction data.

すなわち、オフセットの影響が除去される。

That is, the effect of offset is removed.

  Next, if the resolver conversion gain is not equal in each phase or a harmonic component is included due to the influence of poor resolver mounting accuracy, the AD converted digital data is expressed by Equation 3. .

この場合でも、式４および式５によって各データを正規化すれば、図４に示す様に大幅にデータを補正することができる。

Even in this case, if each data is normalized by Expression 4 and Expression 5, the data can be corrected significantly as shown in FIG.

上記により得られた３つのデジタルデータの内、絶対値の一番小さなデータが、図５に示すように、角度に対する変化率が最も大きく、このデータをテーブルに当てはめることにより角度を求めれば、複雑な演算を行わなくても、最も効率良く角度を検出することができる。

Of the three digital data obtained as described above, the data having the smallest absolute value has the largest rate of change with respect to the angle as shown in FIG. 5. If the angle is obtained by applying this data to a table, The angle can be detected most efficiently without performing a complicated calculation.

  Thereby, the complexity of rotational position detection using a resolver can be improved, and an inexpensive and highly reliable motor control device that suppresses the influence of disturbance can be obtained.

  The motor control device of the present invention is optimal for simplification of the rotational position detection system, and is also useful for applications such as conventional industrial brushless motors.

The principal part block diagram of the motor control apparatus in Example 1 of this invention Explanatory drawing of the output signal of the secondary winding in Example 1 Relationship diagram between switching pattern, excitation signal and output signal in embodiment 1 Explanatory drawing before and after correction of normalization in the first embodiment Explanatory drawing of digital data used in Example 1

DESCRIPTION OF SYMBOLS 1 Motor 2 Resolver 3 Primary winding 4 Excitation signal generator 5 PWM inverter 6a, 6b, 6c Secondary winding 7 Rotation position detection means 8a, 8b, 8c Differential amplifier 9a, 9b, 9c AD conversion means 10 Rotation angle calculation means

Claims (1)

An excitation signal generating means for generating an excitation signal of a resolver connected to a rotating shaft of the motor, a rotational position detecting means for detecting the rotational position of the motor from the output signal of the resolver, and output from the rotational position detecting means PWM inverter driving means for driving the motor based on a rotational position signal, wherein the rotational position detecting means is a line voltage of a three-phase secondary winding that is star-connected with a phase difference of the resolver of 120 degrees. an AD converter that converts the three digital data, is composed of a rotation angle calculating means for calculating a rotation angle of the motor on the basis of the three digital data, further the rotation angle calculation means, the three digital data Mean value calculating means for calculating an average value, and neutral point correction for calculating three neutral point correction data by subtracting the average value from the three digital data And normalization calculation means for calculating three normalized data by dividing the three neutral point correction data by the square root of the sum of the squares of the three neutral point correction data. Motor control apparatus comprising a configuration for obtaining a rotation angle using a preset table having the smallest absolute value among the data.

Images