JP2012191729A - Control device of motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device for controlling a motor under PWM control by accurately performing position detection of a rotator when a voltage of a terminal connected to a coil exceeds a reference voltage.SOLUTION: The control device for a motor is caused to function as: next position detection estimation time calculation means that calculates a time from a reference time until an immediate position detection in the future; determination means that determines whether or not a next position detection estimation time as an immediate position detection estimation time in the future arrives during an ON period of a PWM signal on the basis of a calculation result by the next position detection estimation time calculation means, a control command voltage of the motor and a frequency of a carrier signal under the PWM control; and carrier waveform change means that changes a carrier waveform under the PWM control if the determination means determines that the next position detection estimation time does not arrive during the ON period of the PWM signal.

Description

  The present invention relates to a sensorless DC motor control device using PWM (Pulse Width Modulation) control, which improves the stability of rotor position detection and prevents or reduces turbulence, noise, vibration, etc. caused by position detection errors. This relates to the control device.

FIG. 4 is a circuit diagram showing a sensorless DC motor drive circuit based on PWM control.
In FIG. 4, the motor 1 is connected to an inverter 2 that generates a PWM drive signal, and the inverter 2 is connected to a PWM signal generator 9 that outputs a PWM control signal.
The PWM control signal generator 9 is connected to a control device 4 that outputs a carrier signal for generating a PWM control signal and an output voltage command signal. The control device 4 is used to obtain a position detection signal of the motor 1. The outputs of the comparators 5U, 5V, and 5W for comparing the voltages Uv, Vv, and Wv of the U-phase terminal 7U, V-phase terminal 7V, and W-phase terminal 7W of the motor 1 with the reference voltage B are connected. The positive side is connected.

  In the inverter 2, as shown in FIG. 5, a pair of switching elements 6Up and 6Un, 6Vp and 6Vn, 6Wp and 6Wn are connected between the positive side and the negative side of the DC power source 3, respectively. , 6Un, 6Vp, 6Vn, 6Wp, 6Wn are connected to the corresponding outputs of the PWM signal generator 9.

The connection point of the switching elements 6Up and 6Un constituting the inverter 2 is connected to the U-phase terminal 7U of the motor 1, the connection point of the switching elements 6Vp and 6Vn is connected to the V-phase terminal 7V of the motor 1, and the connection point of the switching elements 6Wp and 6Wn. Is connected to the W-phase terminal 7W of the motor 1.
The switching elements 6Up, 6Un, 6Vp, 6Vn, 6Wp, and 6Wn are generic names including bipolar transistors, FETs, MOS-FETs, thyristors, insulated gate bipolar transistors, and the like, which are appropriate depending on the output and specifications of the motor. Selected.

In the configuration as described above, the voltages Vu, Vv, and Vw of the U-phase terminal 7U, V-phase terminal 7V, and W-phase terminal 7W of the motor 1 are compared with the reference voltage B by the comparators 5U, 5V, and 5W. The position information of the rotor is input to the control device 4.
The control device 4 generates a PWM control signal as shown in FIG. 7 on the basis of the position information from the comparators 5U, 5V, and 5W, for example, a carrier signal and a voltage command having an appropriate period C composed of a triangular wave. The signal is output to the PWM signal generator 9.

  The PWM signal generator 9 compares the voltage command signal Vc for each phase that determines the duty ratio of the PWM drive signal that controls the rotation of the motor 1 with the carrier signal, and rises when the carrier signal becomes equal to or higher than the voltage command signal Vc. A rectangular PWM control signal as shown in FIG. 7, which falls when the voltage command signal Vc becomes lower, is output to the inverter 2.

  The inverter 2 controls the switching elements 6Up, 6Un, 6Vp, 6Vn, 6Wp, and 6Wn on / off according to the PWM control signal from the PWM signal generator 9, and the U-phase terminal 7U, V-phase terminal 7V, A PWM drive signal is output to the W-phase terminal 7W to rotate the motor 1.

Hereinafter, rotation control of the motor 1 will be described.
A PWM control signal is given to the gate of the switching element 6Up from the control device 4 via the PWM signal generator 9 in the period of electrical angle 0 to 120 degrees shown in FIG. As shown in FIG. 8B, a PWM control signal is given during a period of 120 to 240 electrical angles, and the electrical angle of 240 to 240 is applied to the gate of the switching element 6Wp as shown in FIG. 8C. A PWM control signal is given during a period of 360 degrees.

  As shown in FIG. 8 (d), a PWM control signal is given to the gate of the switching element 6Un during a period delayed by an electrical angle of 180 degrees of the switching element 6Up, and the gate of the switching element 6Vn is shown in FIG. 8 (e). As shown in FIG. 8, a PWM control signal is given in a period delayed by an electrical angle of 180 degrees of the switching element 6Vp, and the electrical angle of the switching element 6Wp is 180 degrees as shown in FIG. The PWM control signal is given during the delay period.

In the 120-degree energization method by PWM control, the PWM control signals given to the above switching elements 6Up, 6Un, 6Vp, 6Vn, 6Wp, and 6Wn have an initial electrical angle of 0 to 30 degrees and an end electrical angle of 90 to 120 degrees. A comb-like waveform in which the period repeats on and off, and a period with an intermediate electrical angle of 30 to 90 degrees is a flat plus waveform, and one of a pair of switching elements constituting a closed circuit described below is The comb-like waveform is controlled so that the other becomes a flat plus waveform.
The applied voltage is controlled by changing the duty ratio of the comb-like waveform to control the rotation speed to a desired value.

In the period of electrical angle 0 to 60 degrees, the switching elements 6Up and 6Vn become conductive and the positive side of the power source 3 → the switching element 6Up → the U phase coil 8U → the V phase coil 8V → the switching element 6Vn → the negative side of the power source 3 A closed circuit is formed and current flows.
Similarly, the switching elements 6Up and 6Wn are electrically connected in the period of 60 to 120 electrical angles, and in the direction from the U-phase coil 8U to the W-phase coil 8W, in the period of 120 to 180 electrical angles, 6Vp and 6Wn are conducted and the switching elements 6Vp and 6Un are conducted in the direction from the V-phase coil 8V to the W-phase coil 8W in the direction of the electrical angle of 180 to 240 degrees and the V-phase coil 8V to the U-phase coil 8U. In the direction of the electrical angle of 240 to 300 degrees, the switching elements 6Wp and 6Un are conducted, and in the direction of the W-phase coil 8W to the U-phase coil 8U, in the period of the electrical angle of 300 to 360 degrees, the switching element 6Wp. And 6Vn are conducted, and current flows in the direction from the W-phase coil 8W to the V-phase coil 8V.
As a result, a rotating magnetic field is generated by the coils 8U, 8V, and 8W to induce the rotor, and the motor rotates in a predetermined direction.

The rotor position detection will be described below.
A sensorless DC motor with PWM drive control using a 120-degree energization method has an induced voltage as shown in FIG. 6 applied to a stator coil to which any drive signal is not applied among U-phase, V-phase, and W-phase stator coils. V appears. The induced voltage V is compared with the reference voltage B to detect a point (points E and F in FIG. 6) that coincides with the reference voltage B, thereby detecting the position of the rotor. Based on this position information, the PWM drive signal is detected. And the motor is controlled to a desired rotational speed (Patent Document 1).

Hereinafter, the waveform of the voltage Vu appearing at the U-phase terminal 7U will be described with reference to FIG.
In the U-phase terminal 7U, an induced voltage Vu appears in a period of 120 to 180 electrical angles in which no voltage is applied and in a period of 300 to 360 degrees, but a series circuit of a V-phase coil 8V and a W-phase coil 8W. Since a voltage is applied to the three coils, a comb-like voltage is applied to the neutral point 10 of the three coils. As a result, the U-phase terminal 7U also has a comb-teeth waveform as shown in FIG. appear.
Similarly, a comb-tooth waveform that changes as shown in FIG. 8H appears in the V-phase terminal 7V in the period of electrical angle 60 to 120 degrees and the period of electrical angle 240 to 300 degrees, and in the W-phase terminal 7W. A comb-tooth waveform that changes as shown in FIG. 8 (i) appears in a period of 0 to 60 degrees electrical angle and a period of 180 to 240 degrees electrical angle.

Next, rotor position detection will be described by taking the U-phase terminal 7U as an example.
The rotor position can be detected by the induced voltage Vu appearing in the U-phase coil 8U when no driving voltage is applied to the U-phase terminal 7U. In the case of PWM control, the U-phase terminal is detected as described above. A comb-like voltage influenced by the PWM drive signal appears in the 7U voltage Vu.
The voltage Vu of the U-phase terminal 7U in which the comb-like voltage appears is compared with the reference voltage B. For example, the voltage Vu of the U-phase terminal 7U that appears in the period of the electrical angle 330 to 360 degrees in FIG. Is detected as the position of the rotor. As the reference voltage B, for example, a voltage obtained by dividing the voltage of the power source 3 by 1/2 using a resistor is used.

FIGS. 9A and 9B are partial enlarged views of the voltage Vu of the U-phase terminal 7U in the period of electrical angle 330 to 360 degrees.
The voltage Vu appearing at the U-phase terminal 7U has a comb-like voltage waveform that gradually increases.
In order to detect the position of the rotor using this, the voltage Vu appearing at the U-phase terminal 7U is compared with the reference voltage B by the comparator 5U, and the voltage Vu appearing at the U-phase terminal 7U matches the reference voltage B. Detect the point.
Further, the voltage Vu appearing at the U-phase terminal 7U has a voltage opposite in polarity to that at 330 to 360 degrees in the period of 150 to 180 degrees, and the voltage Vu and the reference voltage B are compared with the comparator 5U. And the point where the voltage Vu appearing at the U-phase terminal 7U matches the reference voltage B is detected.
Also for the V-phase terminal 7V and the W-phase terminal 7W, the same voltage is generated by shifting 120 degrees in electrical angle, position detection is performed in the same way, and position detection is performed 6 times during the electrical angle of 360 degrees. Done.

JP 59-139883 A.

  In the sensorless DC motor of the above PWM drive control, as shown in FIGS. 8G, 8H, and 8I, a comb-like waveform affected by the PWM drive signal is also applied to a terminal to which no voltage is applied. As shown in FIG. 9A, when the comb-like voltage Vu of the U-phase terminal 7U coincides with the reference voltage B during the period when it appears in the U-phase coil 8U, the position detection signal is correctly obtained. be able to.

However, during the period when the comb-like voltage Vu of the U-phase terminal 7U does not appear due to the influence of the PWM drive signal, the induced voltage Vu of the U-phase coil 8U indicated by the broken line in FIG. , The voltage Vu at the U-phase terminal 7U is 0, and that point cannot be detected.
In this case, since the voltage Vu of the U-phase terminal 7U exceeds the reference voltage B at the next rise timing when the PWM control signal is turned on, the comparator outputs a detection signal when the voltage exceeds the reference voltage B.
For this reason, when the point where the voltage Vu of the U-phase terminal 7U exceeds the reference voltage B is a period in which the voltage does not appear due to the influence of the PWM drive signal, an error occurs in the rotor position detection, resulting in turbulence, noise, There was a problem of causing vibration and the like.

  The present invention has been made in view of the above-described problems. Even when the point where the voltage Vu of each phase terminal of the motor stator exceeds the reference voltage B corresponds to the OFF period of the PWM control signal, It is an object of the present invention to provide a motor control device capable of detecting the position of a rotor with reduced error by predicting that point and preventing or reducing turbulence, noise, and vibration.

  Claim 1 of the present invention has a rotor and a stator composed of a plurality of phase coils, and sequentially applies a control voltage by PWM control to the stator to perform rotation control, and no control voltage is applied. A time when the voltage induced in the coil in the non-energized phase and the reference voltage coincide with each other is set as the rotor position detection time, and the position detection time of the rotor is fed back to the control device to perform the rotation control. In the DC motor control device, when the rotor position is detected, the motor control device acquires a leading time of a carrier signal of PWM control at the position detection time, and the reference time Based on the detection result of the detection means and the position detection time, the position detection time calculation means for calculating the time from the start of the carrier signal of PWM control to the position detection, the rotational speed of the motor, A theoretical interval time calculating means for calculating a time between two position detection times based on the number; and the reference time based on detection results of the reference time detecting means, the position detection time calculating means and the theoretical interval time calculating means. To the next position detection estimated time calculating means for calculating the time from the current position detection to the most recent position detection in the future, the calculation result by the next position detection estimated time calculating means, the frequency of the motor control command voltage and the PWM control carrier signal. Based on the next position detection estimated time which is the latest position detection estimated time in the future based on the PWM signal ON section, and the next position detection estimated time is turned on by the determination means. When it does not arrive in the section, it is made to function as a carrier waveform changing means for changing the carrier waveform of PWM control. A motor control device.

  Claim 2 of the present invention has a rotor and a stator composed of a plurality of phase coils, and sequentially applies a control voltage by PWM control to the stator to perform rotation control, and no control voltage is applied. A time when the voltage induced in the coil in the non-energized phase and the reference voltage coincide with each other is set as the rotor position detection time, and the position detection time of the rotor is fed back to the control device to perform the rotation control. In the DC motor control device, when the rotor position is detected, the motor control device acquires a leading time of a carrier signal of PWM control at the position detection time, and the reference time Based on the detection result of the detection means and the position detection time, the position detection time calculation means for calculating the time from the start of the carrier signal of PWM control to the position detection, the rotational speed of the motor, A theoretical interval time calculating means for calculating a time between two position detection times based on the number; and the reference time based on detection results of the reference time detecting means, the position detection time calculating means and the theoretical interval time calculating means. To the next position detection estimated time calculating means for calculating the time from the current position detection to the most recent position detection in the future, the calculation result by the next position detection estimated time calculating means, the frequency of the motor control command voltage and the PWM control carrier signal. A determination means for determining whether or not the next position detection estimated time which is the latest position detection time in the future arrives in the ON section of the PWM signal, and the next position detection estimated time is determined by the determining means to be the ON section of the PWM signal. If the next position detection estimation time arrives in the latter half of the center of the ON section of the PWM signal, A motor control device is characterized in that so as to function as a carrier waveform changing means for changing the Yaria waveform.

  Claim 3 of the present invention has a rotor and a stator composed of a plurality of phase coils, and sequentially applies a control voltage by PWM control to the stator to perform rotation control, and no control voltage is applied. A time when the voltage induced in the coil in the non-energized phase and the reference voltage coincide with each other is set as the rotor position detection time, and the position detection time of the rotor is fed back to the control device to perform the rotation control. In the DC motor control device, when the rotor position is detected, the motor control device acquires a leading time of a carrier signal of PWM control at the position detection time, and the reference time Based on the detection result of the detection means and the position detection time, the position detection time calculation means for calculating the time from the start of the carrier signal of PWM control to the position detection, the rotational speed of the motor, A theoretical interval time calculating means for calculating a time between two position detection times based on the number; and the reference time based on detection results of the reference time detecting means, the position detection time calculating means and the theoretical interval time calculating means. To the next position detection estimated time calculating means for calculating the time from the current position detection to the most recent position detection in the future, the calculation result by the next position detection estimated time calculating means, the frequency of the motor control command voltage and the PWM control carrier signal. A determination means for determining whether or not the next position detection estimated time which is the latest position detection time in the future arrives in the ON section of the PWM signal, and the next position detection estimated time is determined by the determining means to be the ON section of the PWM signal. If the next position detection estimation time arrives in the latter half of the center of the ON section of the PWM signal, Carrier waveform changing means for changing the carrier waveform, means for determining whether the next position detection estimated time belongs before or after the set position of the carrier, and the next position detection estimated time from the set position of the carrier In the motor control apparatus, the PWM control signal functions as a means for changing the waveform of the carrier so that the ON period of the PWM control signal becomes the trailing edge of the carrier.

  A fourth aspect of the present invention includes a rotor and a stator composed of a plurality of phase coils, and sequentially applies a control voltage by PWM control to the stator to perform rotation control, and no control voltage is applied. A time when the voltage induced in the coil in the non-energized phase and the reference voltage coincide with each other is set as the rotor position detection time, and the position detection time of the rotor is fed back to the control device to perform the rotation control. In the DC motor control device, when the rotor position is detected, the motor control device acquires a leading time of a carrier signal of PWM control at the position detection time, and the reference time Based on the detection result of the detection means and the position detection time, the position detection time calculation means for calculating the time from the start of the carrier signal of PWM control to the position detection, the rotational speed of the motor, A theoretical interval time calculating means for calculating a time between two position detection times based on the number; and the reference time based on detection results of the reference time detecting means, the position detection time calculating means and the theoretical interval time calculating means. To the next position detection estimated time calculating means for calculating the time from the current position detection to the most recent position detection in the future, the calculation result by the next position detection estimated time calculating means, the frequency of the motor control command voltage and the PWM control carrier signal. A determination means for determining whether or not the next position detection estimated time which is the latest position detection time in the future arrives in the ON section of the PWM signal, and the next position detection estimated time is determined by the determining means to be the ON section of the PWM signal. If the next position detection estimation time arrives in the latter half of the center of the ON section of the PWM signal, Carrier waveform changing means for changing the carrier waveform, means for determining whether the next position detection estimated time belongs to the first half or the second half of the carrier, and if the next position detection estimated time belongs to the second half of the carrier, The motor control device is configured to function as means for changing the waveform of the carrier so that the on period of the PWM control signal becomes the rear end of the carrier.

  According to the first and second aspects of the invention, by changing the waveform of the corresponding carrier to which the next position detection estimated time belongs, the position where the position of the rotor can be correctly detected or the error can be reduced by turning on the PWM control signal. Therefore, it is possible to reduce the error in detecting the position of the rotor and prevent or reduce turbulence, noise, vibration and the like.

  According to the third and fourth aspects of the present invention, the PWM control signal is moved to the rear end side of the carrier only when the ON period of the PWM control signal is behind or in the latter half of the set position of the carrier. The processing in the case where it is not necessary to change the carrier waveform can be reduced, and the burden on the control device can be reduced.

It is a waveform diagram of a carrier of a triangular wave that generates a PWM control signal with a high duty ratio, (a) is a waveform diagram before processing, (b) is a post-processing when the next position detection estimation time belongs to the latter half of the triangular wave Waveform diagram (c) is a waveform diagram after processing when the next position detection estimation time belongs to the first half of the triangular wave. It is a waveform diagram of a carrier of a triangular wave that generates a PWM control signal with a low duty ratio, (a) is a waveform diagram before processing, (b) is a post-processing when the next position detection estimated time belongs to the latter half of the triangular wave Waveform diagram (c) is a waveform diagram after processing when the next position detection estimation time belongs to the first half of the triangular wave. The flowchart which shows the process of moving the position of a PWM control signal, and is a main flowchart. The flowchart which shows the process of moving the position of a PWM control signal, and is a flowchart of the calculation process of theoretical area time. The flowchart which shows the process of moving the position of a PWM control signal, The flowchart of the calculation process of the number of carriers and surplus time until the next position detection. It is a flowchart which shows the process of moving the position of a PWM control signal, and is a flowchart of a carrier waveform selection process. It is a circuit diagram which shows the control circuit of the sensorless DC motor by PWM control. It is a circuit diagram which shows the detail of the inverter of FIG. In the conventional position detection of a rotor, it is a figure which shows the relationship between the position of a rotor, and an induced voltage. It is a wave form diagram which shows the carrier waveform output from the control apparatus 4 to the PWM signal generator 9. FIG. It is a wave form diagram which shows the voltage which appears in the terminal of a PWM control signal and each phase, (a) is a drive signal of switching element 6Up, (b) is a drive signal of switching element 6Vp, (c) is a drive signal of switching element 6Wp. , (D) is a drive signal for the switching element 6Un, (e) is a drive signal for the switching element 6Vn, (f) is a drive signal for the switching element 6Wn, (g) is a U-phase voltage Vu, and (h) is a V-phase. Voltages Vv and (i) are waveform diagrams of the W-phase voltage Vw. FIG. 7 is an enlarged view of a voltage waveform appearing at a terminal during a period in which the rotor position is detected by a conventional method, where (a) is a waveform diagram when position detection is normal, and (b) is a waveform diagram when position detection is abnormal. is there.

As described above, a comb-like voltage appears at each phase terminal, and an accurate detection signal can be obtained when the voltage exceeds the reference voltage B during the period in which the voltage appears. When the timing when the voltage exceeds the reference voltage B is reached during the period when the voltage does not appear, the point where the voltage appearing at the terminal exceeds the reference voltage B cannot be accurately detected.
In the present invention, when it is estimated that the position to be detected is in the OFF period of the PWM control signal, the ON period of the PWM control signal is moved by changing the carrier waveform to detect the position of the rotor. Reduce errors.

Next, examples of the present invention will be described.
The circuit of the motor control device of the present invention has a basic configuration common to that of the conventional example shown in FIG. 4, and description of portions common to this conventional example is omitted.
The motor control device of the present invention differs from the conventional circuit configuration in that the motor control device obtains the leading time of the carrier signal for PWM control at the position detection time when the rotor position is detected. Based on the detection result of the reference time detection means, the position detection time calculation means for calculating the time from the beginning of the carrier signal of PWM control to the position detection based on the detection result of the reference time detection means, and the position of the motor Based on the detection results of the theoretical interval time calculating means for calculating the time between two position detection times based on the number of revolutions and the number of poles, and the reference time detecting means, the position detection time calculating means and the theoretical interval time calculating means. The next position detection estimated time calculating means for calculating the time from the reference time to the most recent position detection in the future, and the calculation result in the next position detection estimated time calculating means, Determining means for determining whether or not the next position detection estimated time, which is the latest position detection estimated time in the future, arrives in the ON section of the PWM signal based on the motor control command voltage and the frequency of the PWM control carrier signal; If the next position detection estimated time does not arrive in the ON section of the PWM signal by the determination means, it is made to function as a carrier waveform changing means for changing the carrier waveform for PWM control.

Hereinafter, as an example of the present invention, the U phase is changed based on FIGS. 1A and 1B, FIGS. 2A and 2B, and FIGS. This will be described in detail as an example. Note that S represents a step, and the subsequent numbers represent step numbers.
Steps (S0) to (S6) are common regardless of where the estimated next position detection time belongs in the triangular wave.

(S0) When the control device 4 receives an input of the position detection signal from the comparator 5U, processing for changing the carrier waveform is started.
(S1) The position detection time Ti1, which is the time when the control device 4 receives the position detection signal from the comparator 5U, is acquired.
(S2) The control device 4 acquires the leading time (hereinafter referred to as reference time) Ti0 of the carrier in the carrier signal at the input time of the position detection signal, and the position detection time t1 from the reference time Ti0 and the position detection time Ti1. Is calculated.
(S3) The control device 4 calculates a theoretical interval time t2, which is a time interval until the next position detection estimated from the most recent position detection time Ti1.

The calculation of the theoretical interval time t2 is as shown in FIG.
(S31) Theoretical frequency = (number of revolutions × (number of poles / 2)) is calculated from the number of rotations of the motor calculated based on the time interval of the position detection signal input from the comparator 5U and the number of stations of the motor.
(S32) Theoretical electrical angle period = (1 / theoretical frequency) is further calculated from the theoretical frequency.
(S33) Theoretical interval time t2 = theoretical electrical angle period × (60/360) is calculated.

(S4) When the theoretical interval time t2 is calculated in the control device 4, the next position detection position estimation time t3 = t1 + theoretical interval time t2 from the position detection time t1 and the theoretical interval time t2 calculated so far. Is calculated.
(S5) When the next position detection estimated time t3 is calculated, the control device 4 next calculates the number of carriers from the reference time Ti0 to the next position detection estimated time Ti3 and the surplus time S described later.

The calculation of the surplus time S is as shown in FIG.
(S51) Since the period C of the carrier signal for generating the PWM signal is constant, the number of carriers N = next position detection estimated time t3 / carrier period C is calculated. The number of carriers N calculated here takes an integer value excluding the remainder.
(S52) The surplus period S = next position detection estimated time t3- (carrier cycle C × number of carriers N) is calculated. The surplus time corresponds to the remainder of the calculation result of the number of carriers N in step S51.

(S6) When the surplus time S is calculated, the waveform of the carrier at the next position detection estimated time Ti3 is selected.
The selection of the carrier waveform is as shown in FIG.
(S61) It is determined whether the surplus time S is equal to or longer than (carrier cycle C / 2).
(S62) When the surplus time S is equal to or longer than (carrier cycle C / 2) (Yes), the carrier waveform at the next position detection estimated time Ti3 is set to the back sawtooth wave shown in FIG.
(S63) If the surplus time S is not (carrier cycle C / 2) or more (No), the waveform of the carrier at the next position detection estimated time Ti3 is not changed. In this case, the reason why the waveform of the carrier is not changed will be described later.

(S7) The control device 4 determines whether or not the carrier waveform set in step S6 at the estimated next position detection time Ti3 is a back sawtooth wave. If the back sawtooth wave is not selected for the carrier waveform (No), the following carrier waveform changing process is not performed and the process ends (S13).
(S8) If a back sawtooth wave is selected as the carrier waveform (Yes), processing timer set value = (number of carriers N-1 up to next position detection time Ti3 estimated from reference time Ti0k) × carrier cycle C is calculated.
(S9) The set value calculated in step S8 is set in the processing timer.
(S10) The processing timer is started.
(S11) The processing timer ends.
(S12) When the processing timer expires, the carrier waveform next to the carrier at the time of termination is changed to a back sawtooth wave, and the process ends (S13).

Next, the steps S8 to S12 when the above steps are executed will be described separately when the duty ratio is high and when it is low.
First, a case where the duty ratio is as high as about 1/2 or more and the width of the PWM control signal ON period is wide will be described.
If the next position detection estimated time Ti3 belongs to the latter half of the carrier, it is determined in step S61 in FIG. 3 (d), and in step S62, as shown in FIG. Is changed to the back sawtooth wave, and the PWM control signal moves to the second half of the carrier cycle. Then, the estimated next position detection time Ti3 arrives during the ON period of the moved PWM control signal, and the position of the rotor can be detected correctly.

When the next position detection estimated time Ti3 belongs to the first half of the carrier, the PWM control signal does not move because the carrier is not changed as shown in FIG.
In this case, the estimated next position detection time Ti3 may arrive during the on period of the PWM control signal, or may arrive during the off period of the PWM control signal.
When the PWM control signal arrives during the ON period, the rotor position can be correctly detected. When the PWM control signal is turned off before the PWM control signal is turned on, it is detected as the position of the rotor at the next induced voltage rise that appears in response to the rise of the PWM control signal that has not moved. However, since the rise of the PWM control signal that has not moved is close, the delay of the detection point is small and there are few problems.

Next, the case where the duty ratio is as low as less than about 1/2 and the width of the PWM control signal is narrow will be described.
If the next position detection estimated time Ti3 belongs to the second half of the carrier, it is determined in step S61 in FIG. 3D, and in step S62, as shown in FIG. It is changed to a back-sawtooth wave shape, and the on period of the PWM control signal moves to the rear end side of the carrier cycle.

In this case, the next position detection time Ti3 may arrive during the off period of the PWM control signal, or may arrive during the on period of the PWM control signal.
When the PWM control signal arrives during the ON period, the rotor position can be detected correctly. However, when the PWM control signal arrives during the OFF period, the PWM control signal moved immediately after arrival. Since the ON period of is rising, the rise of the induced voltage that appears in response to the rise is detected as the rotor position.
If the next position detection time Ti3 is before the PWM control signal ON period, the rotor position cannot be detected accurately, but the error is greater than when the PWM control signal ON period is not moved. Can be reduced.

If the next position detection estimated time Ti3 is in the first half of the carrier, it is determined in step S61 in FIG. 3D, and the carrier is not changed in step S63 as shown in FIG. Does not move.
This is the same as when the duty ratio is as high as about 1/2.

The process for changing the carrier waveform described above is performed twice for the U phase, ie, position detection between the electrical angles 150 to 180 degrees and the electrical angles 330 to 360 degrees shown in FIG.
Also, the electrical phase of the V-phase terminal 8V of 90 to 120 degrees, the electrical angle of 270 to 300 degrees, the W-phase electrical angle of 30 to 60 degrees, and the electrical angle of 210 to 240 degrees respectively. Processing for changing the carrier waveform is performed.
As a result, the sensorless DC motor is driven and controlled according to the six position signals correctly or with reduced errors, thereby preventing or reducing turbulence, noise, and vibration.

In the above embodiment, when the next position detection estimated time Ti3 is the first half of the carrier, the period during which the PWM control signal is on is not moved.
This is because if the next position detection estimated time Ti3 is the first half of the carrier, the next position detection estimated time Ti3 is moved when the duty ratio is low when the PWM control signal ON period is moved to the front end side. This is because there is a case where the time is later than the period, and in this case, the next rise of ON becomes the detection position, and the error in detecting the position of the rotor becomes very large.
However, even if the next position detection time Ti3 is the first half of the carrier, if the duty ratio is as high as ½ or more and the width of the PWM control signal is wide, this is detected and the peak of the triangular wave is detected. May be moved to the front end side of the carrier, and the on period of the PWM waveform may be moved to the first half of the carrier.

  DESCRIPTION OF SYMBOLS 1 ... Motor, 2 ... Inverter, 3 ... DC power supply, 4 ... Control device, 5U, 5V, 5W ... Comparator, 6Up, 6Un, 6Vp, 6Vn, 6Wp, 6Wn ... Switching element, 7U ... U-phase terminal, 7V ... V phase terminal, 7W ... W phase terminal, 8U ... U phase coil, 8U ... V phase coil, 8W ... W phase coil, 9 ... PWM signal generator.

Claims (4)

It has a rotor and a stator composed of coils of a plurality of phases, and controls rotation by sequentially applying a control voltage by PWM control to the stator, and is induced in a coil of a non-energized phase to which no control voltage is applied. In the control device for the sensorless DC motor for performing the rotation control by returning the rotor position detection time to the control device as a time at which the detected voltage and the reference voltage coincide with each other as a rotor position detection time,
The motor control device comprises:
A reference time detecting means for acquiring a leading time of a carrier signal for PWM control at the position detection time when the position of the rotor is detected;
Position detection time calculating means for calculating the time from the beginning of the carrier signal of PWM control to position detection based on the detection result of the reference time detection means and the position detection time;
Theoretical interval time calculating means for calculating a time between two position detection times based on the number of rotations and the number of poles of the motor;
Based on the detection results of the reference time detection means, the position detection time calculation means, and the theoretical interval time calculation means, a next position detection estimated time calculation means that calculates a time from the reference time to the most recent position detection in the future;
The next position detection estimated time, which is the most recent position detection estimated time in the future, is calculated based on the calculation result of the next position detection estimated time calculating means and the frequency of the motor control command voltage and the PWM control carrier signal. A determination means for determining whether or not to arrive in the section;
A motor control apparatus, wherein when the next position detection estimated time does not arrive in an ON section of a PWM signal by the determination means, the motor control apparatus functions as a carrier waveform changing means for changing a carrier waveform for PWM control. It has a rotor and a stator composed of coils of a plurality of phases, and controls rotation by sequentially applying a control voltage by PWM control to the stator, and is induced in a coil of a non-energized phase to which no control voltage is applied. In the control device for the sensorless DC motor for performing the rotation control by returning the rotor position detection time to the control device as a time at which the detected voltage and the reference voltage coincide with each other as a rotor position detection time,
The motor control device comprises:
A reference time detecting means for acquiring a leading time of a carrier signal for PWM control at the position detection time when the position of the rotor is detected;
Position detection time calculating means for calculating the time from the beginning of the carrier signal of PWM control to position detection based on the detection result of the reference time detection means and the position detection time;
Theoretical interval time calculating means for calculating a time between two position detection times based on the number of rotations and the number of poles of the motor;
Based on the detection results of the reference time detection means, the position detection time calculation means, and the theoretical interval time calculation means, a next position detection estimated time calculation means that calculates a time from the reference time to the most recent position detection in the future;
The next position detection estimated time, which is the latest position detection time in the future, based on the calculation result of the next position detection estimated time calculating means and the frequency of the motor control command voltage and the carrier signal of PWM control is the on period of the PWM signal. Determining means for determining whether or not
When the next position detection estimated time does not arrive in the ON section of the PWM signal by the determination means and the next position detection estimated time arrives in the latter half from the center of the ON section of the PWM signal, the carrier for PWM control A motor control device characterized by functioning as a carrier waveform changing means for changing a waveform. It has a rotor and a stator composed of coils of a plurality of phases, and controls rotation by sequentially applying a control voltage by PWM control to the stator, and is induced in a coil of a non-energized phase to which no control voltage is applied. In the control device for the sensorless DC motor for performing the rotation control by returning the rotor position detection time to the control device as a time at which the detected voltage and the reference voltage coincide with each other as a rotor position detection time,
The motor control device comprises:
A reference time detecting means for acquiring a leading time of a carrier signal for PWM control at the position detection time when the position of the rotor is detected;
Position detection time calculating means for calculating the time from the beginning of the carrier signal of PWM control to position detection based on the detection result of the reference time detection means and the position detection time;
Theoretical interval time calculating means for calculating a time between two position detection times based on the number of rotations and the number of poles of the motor;
Based on the detection results of the reference time detection means, the position detection time calculation means, and the theoretical interval time calculation means, a next position detection estimated time calculation means that calculates a time from the reference time to the most recent position detection in the future;
The next position detection estimated time, which is the latest position detection time in the future, based on the calculation result of the next position detection estimated time calculating means and the frequency of the motor control command voltage and the carrier signal of PWM control is the on period of the PWM signal. Determining means for determining whether or not
When the next position detection estimated time does not arrive in the ON section of the PWM signal by the determination means and the next position detection estimated time arrives in the latter half from the center of the ON section of the PWM signal, the carrier for PWM control A carrier waveform changing means for changing the waveform;
Means for determining whether the next position detection estimated time belongs before or after the set position of the carrier;
When the next position detection estimated time belongs after the set position of the corresponding carrier, the on-period of the PWM control signal is made to function as a means for changing the waveform of the corresponding carrier so that it becomes the rear end of the corresponding carrier. The motor control device. It has a rotor and a stator composed of coils of a plurality of phases, and controls rotation by sequentially applying a control voltage by PWM control to the stator, and is induced in a coil of a non-energized phase to which no control voltage is applied. In the control device for the sensorless DC motor for performing the rotation control by returning the rotor position detection time to the control device as a time at which the detected voltage and the reference voltage coincide with each other as a rotor position detection time,
The motor control device comprises:
A reference time detecting means for acquiring a leading time of a carrier signal for PWM control at the position detection time when the position of the rotor is detected;
Position detection time calculating means for calculating the time from the beginning of the carrier signal of PWM control to position detection based on the detection result of the reference time detection means and the position detection time;
Theoretical interval time calculating means for calculating a time between two position detection times based on the number of rotations and the number of poles of the motor;
Based on the detection results of the reference time detection means, the position detection time calculation means, and the theoretical interval time calculation means, a next position detection estimated time calculation means that calculates a time from the reference time to the most recent position detection in the future;
The next position detection estimated time, which is the latest position detection time in the future, based on the calculation result of the next position detection estimated time calculating means and the frequency of the motor control command voltage and the carrier signal of PWM control is the on period of the PWM signal. Determining means for determining whether or not
When the next position detection estimated time does not arrive in the ON section of the PWM signal by the determination means and the next position detection estimated time arrives in the latter half from the center of the ON section of the PWM signal, the carrier for PWM control A carrier waveform changing means for changing the waveform;
Means for determining whether the next position detection estimated time belongs to the first half or the second half of the carrier;
When the next position detection estimated time belongs to the latter half of the carrier, the motor is made to function as means for changing the waveform of the carrier so that the ON period of the PWM control signal becomes the rear end of the carrier. Control device.

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