JP6106353B2 - Brushless motor drive control device, motor unit and equipment using the same - Google Patents

Description

  The present invention relates to a drive control device that controls the drive of a brushless motor.

  As a method for reducing the noise of the brushless motor, there is a so-called sine wave driving method (180 ° energization method). In this method, the current flowing through the coil is changed in a sine wave shape, thereby suppressing torque fluctuations and vibrations caused by a steep current change and realizing noise reduction. As a drive control device for driving a brushless motor by such a sine wave drive system, Patent Document 1 uses a Hall element as position detecting means for detecting the rotational position of the rotor, and is obtained from the output of the Hall element. An apparatus that utilizes changes in amplitude is disclosed. Specifically, the time between the timings of changes in the position signals of three phases (up edge and down edge) is pulse-counted, and the time width data for the 60 ° phase of the modulation waveform of the same phase in the next cycle is counted. Are used to form a modulation waveform, and the modulation waveform is output to the PWM circuit to drive the brushless motor.

JP 2012-65495 A

  However, in the drive control device disclosed in Patent Document 1, since a sinusoidal current is generated using a period of a position signal that is not in real time, the speed fluctuation with respect to a sudden load fluctuation is large.

  For this reason, it is desirable to use the output of the position signal of the real-time Hall element. However, if the three-phase Hall element has variations in sensitivity, offset in the amplitude direction, and mounting position (ripple), there is a problem that ripples are generated in the driving torque of the brushless motor and uneven rotation occurs.

  FIG. 2A shows a state in which there is no variation in the offset, sensitivity, and mounting position of the three-phase Hall elements U, V, and W, and there is no torque fluctuation. On the other hand, FIG. 2B shows a state in which the sensitivity of the three-phase Hall elements of U, V, and W varies and the torque fluctuation occurs twice during one electrical angle cycle. Yes. Further, FIG. 2 (c) shows a state in which the three-phase Hall elements U, V, and W have offset variations, and one torque fluctuation occurs during one electrical angle cycle. Even when the mounting positions of the three-phase Hall elements of U, V, and W vary, torque fluctuation similar to that shown in FIG. 2B or FIG. 2C occurs.

  The present invention provides a drive control device capable of reducing uneven rotation of a brushless motor due to variations in sensitivity, offset, and mounting position of a plurality of position detection means in driving a brushless motor using a sine wave drive method. To do.

A drive control device according to one aspect of the present invention includes a multi-phase coil, a rotor that rotates in response to energization of the coil, and a plurality of position detection units that detect rotational positions of the rotor in different phases. The driving of the brushless motor is controlled based on a first command signal generated according to an input signal from the outside . The drive control unit based on the output from the plurality of position detecting means generates a plurality of sine wave signals having a phase difference from each other, in the rotation of the brushless motor by using the square root of the square sum of the plurality of sinusoidal signals It has a signal generation part which calculates | requires a ripple component and produces | generates the 2nd command signal which added the reverse phase of this ripple component to the 1st command signal, It is characterized by the above-mentioned.

  Note that a motor unit including the brushless motor and the drive control device, and various devices including the motor unit and a driven member driven by the brushless motor also constitute another aspect of the present invention.

  According to the present invention, the ripple component in the rotation of the brushless motor is obtained in a pseudo manner by performing a predetermined calculation on the plurality of sine wave signals generated based on the output from the position detection means of the plurality of phases. The reverse phase of the ripple component is added to the command signal. As a result, variations in sensitivity, offset, and mounting position of the position detection means are canceled, and torque fluctuations and rotation unevenness of the brushless motor can be reduced.

The figure which shows the PWM output by the comparison with the sine wave signal and carrier wave in the Example of this invention. The figure explaining the subject of this invention. The block diagram which shows the whole structure of the drive control apparatus of an Example. The figure explaining the drive logic in the drive control apparatus of an Example. The figure which shows the internal structure of the control circuit in the drive control apparatus of an Example. The figure which shows the calculation result of the output from Hall element in an Example (there is offset variation), and Hall ripple. The figure which shows the result of having extracted the ripple component from the Hall ripple calculation result in an Example. The figure which shows the FFT analysis result of the rotation unevenness of an Example and a comparative example.

  Embodiments of the present invention will be described below with reference to the drawings.

  First, FIG. 3 shows an overall configuration of a motor unit including a brushless motor and a drive control apparatus according to an embodiment of the present invention.

  Reference numeral 1 denotes a rotor of the brushless motor 4. In the figure, the rotor 1 is shown as being magnetized with one N pole and one S pole, but this is because one period of electrical angle is indicated, and the rotor 1 is a two-pole magnetized type. It is not limited to. 2U, 2V, and 2W are Hall elements as a plurality of (three in the present embodiment) position detecting means for detecting the rotational position of the rotor 1, and are based on the common-mode input voltage as the rotor 1 rotates. Outputs a signal as a frequency voltage (AC voltage). These Hall elements 2U, 2V, and 2W are mounted at an electrical angle interval of 120 °, that is, at different phases.

  3U, 3V, and 3W are stator coils of a plurality of phases (in this embodiment, three phases), and 2 × N pole-3 × N slots or 4 × N pole-3 × N slots (N is Integer). Similarly to the rotor 1, the stator coils 3U, 3V, and 3W also indicate one cycle of the electrical angle. The brushless motor 4 is constituted by the rotor 1, the hall elements 2U, 2V, 2W and the stator coils 3U, 3V, 3W.

  Next, the configuration of the drive control device will be described. Reference numerals 5a to 5f denote FETs that perform On-Off switching of voltages for phase switching and PWM control. Reference numeral 6 denotes a control circuit as a signal generation unit, information on the rotation angle of the rotor 1 obtained from outputs (signals) from the Hall elements 2U, 2V, 2W, and information on the rotation speed obtained from the speed detector 8 described later. On-off timing and duty ratio of the FETs 5a to 5f, that is, energization to the stator coils 3U, 3V, 3W is controlled based on the above. Reference numeral 7 denotes a power source.

  The speed detector 8 detects the actual rotational speed of the rotor 1 and outputs the information. As the speed detector 8, if the rotational speed can be obtained, such as detecting the rotational speed from the frequency of magnetic flux change accompanying the rotation of the rotor 1 or detecting the rotational speed using an optical encoder, the speed detector 8 The configuration does not matter. The FETs 5a to 5f, the control circuit 6 and the speed detector 8 constitute a drive control device.

  The output of the brushless motor 4 is transmitted to a driven member 20 of a device on which the motor 4 and the drive control device are mounted via a transmission mechanism (not shown), and this is moved or operated. As equipment, all equipment that can be driven by a brushless motor, for example, a photocopier that drives a photosensitive drum or a fixing roller as a driven member by a brushless motor, and a paper feed roller as a driven member that is driven by a brushless motor Including printers.

  Next, the drive logic in the control circuit 6 of the present embodiment will be described with reference to FIG. The control circuit 6 has a relationship in which the magnetic flux vector of the rotor 1 and the current vectors of the stator coils 3U, 3V, and 3W are orthogonal to each other based on the hall outputs HU, HV, and HW that are outputs from the hall elements 2U, 2V, and 2W. Are generated from the hall outputs HU, HV, and HW so that a plurality of phases (three phases in this embodiment) of sinusoidal signals SINU, SINV, and SINW are delayed in electrical angle by π / 2 [rad]. To do. The three-phase sine wave signals SINU, SINV, and SINW have a phase difference of 120 electrical degrees.

  Then, as shown in FIG. 1, the control circuit 6 generates PWM signals U_PWM, V_PWM, W_PWM by comparing the sine wave signals SINU, SINV, SINW and the carrier wave, and each of the gates UHG, VHG, Control On-Off of WHG, ULG, VLG, and WLG. By changing the amplitude of the sine wave signals SINU, SINV, SINW, the amplitude of the current flowing through the stator coils 3U, 3V, 3W can be changed, whereby the torque of the brushless motor 4 can be controlled.

  Next, the internal configuration of the control circuit 6 will be described with reference to FIG. SINU, SINV, and SINW generate sine wave signals SINU, SINV, and SINW based on the outputs of the Hall elements HU, HV, and HW. U_PWM, V_PWM, and W_PWM compare the sine wave signals SINU, SINV, SINW and Carrier (carrier wave) to generate PWM signals U_PWM, V_PWM, and W_PWM. In the drawing, a part surrounded by a dotted line is a characteristic part in the present embodiment. If this part does not exist, the difference between TargetSPEED (target position) input from the outside of the drive controller and MotorSPEED (rotational speed) detected by the speed detector 8 is amplified by Gain, integrated by Integrator, Vout smoothed by the filter is output, the amplitude is adjusted by taking the product of Vout and the sine wave signals SINU, SINV, and SINW, and the torque and rotational speed are controlled.

  However, if there are variations (shifts) in the offset (see the upper diagram of FIG. 6), sensitivity, and mounting position of the three-phase Hall elements 2U, 2V, and 2W, ripples occur at unintended timing in the torque. Uneven rotation of the motor 4 occurs.

  On the other hand, in the present embodiment, the following drive control process reduces rotational unevenness due to the above-described variations in the offset, sensitivity, and mounting position of the Hall elements (hereinafter referred to as variations in Hall elements). First, the square root of the sum of squares of the sine wave signals SINU, SINV, SINW is calculated by Hall ripple (calculation unit) as shown in the following equation and the lower diagram of FIG.

The meaning of this calculation will be described. As shown in FIG. 2A, when the sinusoidal signals SINU, SINV, and SINW are not affected by variations in the Hall elements, a DC signal is obtained as a Hall ripple output corresponding to a constant torque. However, as shown in FIGS. 2B and 2C, when the influence of the variation of the Hall element is included, the output of Hall ripple includes one or two fluctuations in one electrical angle period. Become. The lower diagram of FIG. 6 shows a state in which one fluctuation appears in one period of electrical angle in Hall ripple due to variations in the offset of the Hall element.

  Next, as shown in FIG. 7, in order to extract only the torque fluctuation component (pseudo ripple component) by removing the DC portion from the Hall ripple output, an extremely flat output is obtained by the Filter (filter unit). Is removed from the Hall ripple, and a Hall ripple output consisting of only the ripple component (hereinafter referred to as an extracted Hall ripple) is obtained. Then, this extracted Hall ripple is multiplied by a coefficient HFBGain for matching with the output level of Vout (Hall ripple × HFBGain). Furthermore, since the amount of torque ripple varies depending on the magnitude of torque, MLT (multiplier) Hall ripple × HFBGain is multiplied by Vout for adjustment to obtain the output of Hout. Then, in SUB (subtraction unit), Vout ′ is generated as a command signal in which the reverse phase of the ripple component of the torque is included (added) by subtracting Hout from Vout. Thereby, the fluctuation | variation of the rotation of the brushless motor 4 can be estimated in advance and canceled.

  Since this drive control process can be executed independently of the feedback signal of the rotation speed, the rotation unevenness can be reduced without being restricted by the mechanical time constant of the inertia of the rotor 1 or the resolution of the speed detector 8. It is.

  FIG. 8 shows the case where the FFT analysis result (simulation result) of the rotation unevenness of the brushless motor is added to the reverse phase of the ripple component (hereinafter referred to as Hall output feedback) as in this embodiment. A comparative example REF that does not perform feedback of the Hall output is shown. In this simulation, an 8-pole-12-slot brushless motor was driven at 1000 [r / min]. The wow shown on the vertical axis in the graph indicates the rotation unevenness calculated by the following calculation method. In this simulation, calculation was performed in each power spectrum from 0 to 500 [Hz].

  As shown in FIG. 2C, the influence of the variation in the offset of the Hall element appears as a single torque fluctuation during one electrical angle cycle. In an 8-pole-12-slot motor, the frequency of one electrical angle cycle is (1000 ÷ 60) × 4 = 66.7 [Hz], and when the hall output is fed back as compared with REF, 65 The peak in the vicinity of [Hz] is reduced, and the rotation unevenness is improved.

  Further, as shown in FIG. 2B, the influence of variations in the sensitivity of the Hall elements appears as torque fluctuations twice during one electrical angle cycle. The frequency component of this variation is ((1000 ÷ 60) × 4) × 2 = 133.3 [Hz], which is around 130 [Hz] when the Hall output is fed back as compared with REF. The peak is reduced and the rotation unevenness is improved.

  Thus, when the Hall output feedback is performed, the effect of improving the rotation unevenness of about 70% in both cases where there is a variation in the offset of the Hall element and in a case where there is a variation in sensitivity, compared to the case where the feedback is not performed. was gotten.

  In the present embodiment, the case where a three-phase Hall element and a stator coil are provided has been described. However, the number of these elements is not limited to three, and may be two or four or more.

  In this embodiment, the Hall element is used as the position detection means. However, other position detection means that can detect the rotational position of the rotor, such as an MR sensor (magnetoresistance effect element) or an optical sensor, are used. May be.

  Each embodiment described above is only a representative example, and various modifications and changes can be made to each embodiment in carrying out the present invention.

  The present invention is useful for reducing rotation unevenness of a brushless motor driven by a sine wave driving method using the output of a position detecting means such as a Hall element.

1 Rotor 2U, 2V, 2W Hall element 3U, 3V, 3W Stator coil 4 Brushless motor 5a to 5f FET
6 Control circuit 7 Power supply 8 Speed detector

Claims (4)

The drive of a brushless motor having a multi-phase coil, a rotor that rotates in response to energization of the coil, and a plurality of position detecting means that detects the rotational position of the rotor in different phases from each other as an input signal from the outside A drive control device that performs control based on a first command signal generated in response ,
The ripple component in generating a plurality of sine wave signals, the rotation of the brushless motor by using the square root of the sum of the squares of the previous SL plurality of sine wave signals having a phase difference from each other based on an output from said plurality of position detecting means A drive control apparatus comprising: a signal generation unit that generates and generates a second command signal obtained by adding the reverse phase of the ripple component to the first command signal. The signal generator is
An arithmetic unit that calculates a square root of a sum of squares of the plurality of sine wave signals;
A filter unit that extracts only the ripple component from the output of the arithmetic unit;
A multiplier for multiplying the ripple component by the first command signal;
The drive control device according to claim 1, further comprising: a subtracting unit that subtracts an output from the multiplying unit from the first command signal. A brushless motor,
A motor unit comprising the drive control device according to claim 1. A motor unit according to claim 3;
And a driven member driven by the brushless motor.