JP6311546B2 - Motor drive device - Google Patents

Description

  The present invention relates to a motor driving device that drives a so-called sensorless brushless motor.

  This type of motor drive device does not include a sensor for detecting the rotational position of the rotor, and detects the zero cross point where the induced voltage induced in the non-energized phase of the motor and the reference voltage intersect. Estimate the rotational position. For example, in Patent Document 1, in a device that estimates the rotational position of a rotor based on an induced voltage induced in a non-energized phase of a motor in this way, a commanded duty ratio, a commanded motor speed, and a detected duty The rotational position is detected in a wide range from low to high rotation by increasing or decreasing the frequency of the PWM signal stepwise in accordance with any one of the ratio and detected motor rotation speed parameters. Is disclosed.

JP 2012-165603 A

  By the way, in the configuration for estimating the rotational position of the rotor based on the induced voltage induced in the non-conducting phase of the motor, noise is generated in the voltage of the non-conducting phase during the ON period of the PWM signal superimposed on the drive signal. It is necessary to prevent erroneous detection due to the noise crossing the reference voltage. Therefore, a mask period for masking the rotational position estimation process is provided in association with a period in which noise is generated in the voltage of the non-energized phase, and after this mask period and within the period in which the PWM signal is on. In addition, a technique for performing rotation position detection processing is considered. However, in this technique, when the on period of the PWM signal is shorter than the period in which noise is generated in the voltage of the non-energized phase or the mask period, there is a problem that it is impossible to detect the rotational position of the rotor. Therefore, there is a lower limit value in the on period of the PWM signal, and there is a problem that the motor cannot be driven particularly at low speed rotation.

  Therefore, in providing a mask period for masking the rotational position estimation process in association with a period in which noise occurs in the voltage of the non-energized phase, the zero cross point detection timing, which is the rotor position detection timing, is greater than this mask period. Provided is a motor drive device that can avoid a decrease in the ON period of a PWM signal and can drive a motor at a lower speed.

  According to the motor drive device of the present invention, the PWM signal output means outputs a PWM signal. The rotor rotational position estimating means estimates the rotational position of the rotor of the brushless motor based on the induced voltage induced in the non-energized phase of the brushless motor. The drive signal output means outputs a drive signal based on the PWM signal output from the PWM signal output means and the input signal from the rotor rotation estimation means. The inverter circuit unit drives the brushless motor by turning on / off the plurality of switching elements based on the drive signal output by the drive signal output means. The mask period setting means sets a mask period for masking the estimation processing by the rotor rotational position estimation means in association with the ON period of the PWM signal. The mask period setting means changes the length of the mask period to be set according to the length of the ON period of the PWM signal.

  According to this configuration, by setting a mask period shorter than the on period at the detection timing of the zero cross point according to the length of the on period of the PWM signal, the on period of the PWM signal is set to be shorter than the mask period. The reduction in size can be avoided, and the motor can be driven at a lower speed.

The figure which shows schematically the structural example of the motor drive device which concerns on one Embodiment. The figure which shows an example of the energization state of each phase of a motor Time chart for explaining an example of setting the mask period Flowchart showing an example of motor drive control by the motor drive device The figure for demonstrating the example of a setting of a time threshold value and a frequency threshold value

  Hereinafter, an embodiment according to a motor drive device will be described with reference to the drawings. As illustrated in FIG. 1, the motor drive device 10 includes an inverter circuit unit 11, an inverter drive control unit 12, and a rotor rotational position estimation unit 13. The inverter circuit unit 11 is configured by connecting six switching elements 11a in a three-phase bridge. A DC power supply 15 having a voltage Vdc is supplied between the DC power supply lines 14 a and 14 b of the inverter circuit unit 11. Each phase output terminal of the inverter circuit unit 11 is connected to each phase stator winding 16U, 16V, 16W of the brushless motor 16, respectively. Hereinafter, the brushless motor 16 is simply referred to as “motor 16”.

  The inverter circuit unit 11 is switching-controlled by the inverter drive control unit 12. The inverter drive control unit 12 includes a PWM signal output unit 21 and a drive signal output unit 22. The PWM signal output unit 21 is an example of a PWM signal output unit. The PWM signal output unit 21 generates and drives a three-phase PWM signal based on a rotational position signal input from the rotor rotational position estimation unit 13 as described in detail later. The signal is output to the signal output unit 22. The drive signal output unit 22 is an example of a drive signal output unit. Based on a rotation position signal input from the rotor rotation position estimation unit 13 and a PWM signal output from the PWM signal output unit 21 as will be described in detail later. A drive signal is generated and output to the inverter circuit unit 11. The inverter circuit unit 11 drives the motor 16 by turning on / off the plurality of switching elements 11 a based on the drive signal output from the drive signal output unit 22.

  The rotor rotation position estimation unit 13 is an example of a rotor rotation position estimation unit, and estimates a rotation position of a rotor (not shown) included in the motor 16 based on an induced voltage induced in a non-energized phase of the motor 16. That is, as illustrated in FIG. 2, the energized state of each phase of the motor 16 includes an energized state of 120 degrees in electrical angle to which a positive voltage is applied, a non-energized state of 60 degrees in electrical angle, and a negative voltage. An energization pattern having a total of 360 degrees, which is composed of an energized state of 120 degrees with an applied electrical angle and a non-energized state with an electrical angle of 60 degrees, is repeated. In the non-energized state immediately after the energized state where the positive voltage is applied, the phase voltage first decreases to near the negative voltage of the DC power supply, then the voltage increases, and then the induced voltage decreases to the right. Is induced to generate a voltage. In the non-energized state immediately after the energized state where a negative voltage is applied, the phase voltage first rises to near the voltage on the DC power supply plus side, then the voltage falls, and then the induced voltage rising to the right A voltage is generated when induced.

  Then, the rotor rotational position estimating unit 13 estimates the rotational position of the rotor of the motor 16 by detecting the zero cross point Pz where the induced voltage induced in the non-energized phase of the motor 16 and the reference voltage Va intersect in this way. To do. Then, the rotor rotational position estimating unit 13 outputs a rotational position signal indicating the detected rotational position to the inverter drive control unit 12. The rotational position detection process by the rotor rotational position estimation unit 13 is a well-known process, and as the reference voltage Va, for example, a voltage of a neutral point 16a of the motor 16 is a three-phase voltage indicated by reference numerals 17U, 17V, and 17W. And a voltage reproduced using a resistor and a voltage that is ½ of the voltage Vdc of the DC power supply 15 are set.

  The rotor rotational position estimation unit 13 includes a mask period setting unit 31. The mask period setting unit 31 is an example of a mask period setting unit, and sets a mask period for masking the rotor rotational position estimation processing by the rotor rotational position estimation unit 13. During this mask period, the rotor rotational position estimating unit 13 is configured to generate a rotational position signal by detecting the zero cross point Pz, but not to output the rotational position signal to the inverter drive control unit 12.

  In this case, the mask period setting unit 31 sets a period slightly longer than the period as the mask period in association with at least a period from when noise is generated in the voltage of the non-conduction phase until the noise converges. . Hereinafter, the “period from when noise is generated in the voltage of the non-conduction phase until the noise converges” is simply referred to as “noise generation period”. In addition, if the mask period is a length including the noise generation period, the length can be changed as appropriate. However, if the mask period is too long, the detection process of the rotational position of the rotor may be unnecessarily masked. Therefore, it is preferable that the length is as long as the noise generation period. In addition, the noise generation period is set as a noise generation period assumed when the motor 16 is driven by a general motor driving device, and can be obtained from, for example, experimental data or simulation data. The motor drive device 10 stores data information in which a duty ratio of the PWM signal is associated with a noise generation period assumed when the PWM signal is driven at the duty ratio in a storage circuit (not shown).

  When the noise generation period is shorter than the ON period of the PWM signal output from the PWM signal output unit 21, the mask period is set in association with the ON period of the PWM signal. On the other hand, when the noise generation period is longer than the ON period of the PWM signal output from the PWM signal output unit 21, the mask period is set beyond the ON period of the PWM signal. The mask period setting unit 31 is configured to be able to change the length of the ON period of the PWM signal output from the PWM signal output unit 21, and when the length of the ON period of the PWM signal is changed The length of the mask period to be set can be changed according to the ON period of the PWM signal after the change.

  Next, an example of setting the mask period by the mask period setting unit 31 will be described. That is, the non-conduction phase voltage Vn illustrated in FIG. 3B is likely to generate noise when the PWM signal Sa illustrated in FIG. 3A is switched from OFF to ON. Therefore, when this noise reaches the reference voltage Va and a zero cross point is detected, the rotor rotational position detection signal Sb is output to the inverter drive control unit 12 as illustrated in FIG. There is. Therefore, the mask period setting unit 31 sets the mask period Tm in association with the period Tn from when noise is generated in the non-energized phase voltage Vn until the noise converges.

  The motor drive device 10 is set not to output the rotational position detection signal Sb to the inverter drive control unit 12 even if a zero cross point is detected in the set mask period Tm. Therefore, by setting the mask period Tm in this way, it is possible to avoid erroneous detection due to the noise generated in the non-conducting phase voltage Vn crossing the reference voltage Va.

  However, as indicated by reference characters Pa, Pb, and Pd in FIG. 3A, for example, when the motor 16 is driven at a predetermined speed or less, that is, at low speed rotation, the PWM signal ON period Ton is shorter than the noise generation period Tn. May be smaller. In such a case, since the entire on period Ton of the PWM signal is masked by the mask period Tm, the rotation position cannot be detected during the on period Ton of the PWM signal.

  Therefore, when the noise generation period Tn is longer than the ON period Ton of the PWM signal, the mask period setting unit 31 turns on the PWM signal as indicated by a symbol Pc in FIG. The period Ton is changed to be longer than the noise generation period Tn. Then, the mask period setting unit 31 sets a period longer than the noise generation period Tn and shorter than the ON period Ton of the PWM signal after the change as the mask period Tm. Note that the noise generation period Tn may vary due to the change of the PWM signal ON period Ton. Therefore, the mask period setting unit 31 sets a new mask period Tm in consideration of fluctuations in the noise generation period Tn.

  As the predetermined condition, the condition that the occurrence of the zero-cross point Pz is approaching, that is, the condition that the zero-cross point Pz is likely to occur is set. In this case, the first condition and the second condition are set. Yes. The mask period setting unit 31 is set to execute a changing process for making the ON period Ton of the PWM signal longer than the noise generation period Tn when one of the first condition and the second condition is satisfied.

  The first condition is that, in one pulse of the PWM signal, the time when the induced voltage is lowering to the right is lower than the reference voltage, and the time when the induced voltage is rising to the right is higher than the reference voltage is a predetermined time threshold Ka or more. It is to become. That is, as illustrated in FIG. 3D, when the PWM signal is turned on, the mask period setting unit 31 causes the induced voltage to be lower than the reference voltage if the induced voltage is lowered to the right. Accordingly, it is monitored whether or not the rotational position signal has changed. Although not shown, if the induced voltage is rising to the right, it is monitored whether the rotational position signal has changed as the induced voltage becomes higher than the reference voltage. Then, when a change in the rotational position signal is detected, the mask period setting unit 31 increases the time measurement counter Ca according to the time during which the rotational position signal is changing. Then, the mask period setting unit 31 determines that the first condition is satisfied when the value of the time measurement counter Ca is equal to or greater than the time threshold Ka, and makes the ON period Ton of the PWM signal immediately after that longer than the noise generation period Tn. To do. In addition, the mask period setting part 31 will reset the time measurement counter Ca, if the detection of a zero cross is completed. Thereby, the mask period setting unit 31 is configured to measure the time during which the induced voltage is lower than the reference voltage in one pulse of the PWM signal.

  On the other hand, the second condition is that, in one pulse of the PWM signal, the number of times that the induced voltage is lower than the reference voltage when the induced voltage is lowered to the right, and the number of times that the induced voltage is higher than the reference voltage when the induced voltage is raised to the right It is to become Kb or more. That is, as illustrated in FIG. 3E, when the PWM signal is turned on, the mask period setting unit 31 causes the induced voltage to be lower than the reference voltage if the induced voltage is lowered to the right. Accordingly, it is monitored whether or not the rotational position signal has changed. Although not shown, if the induced voltage is rising to the right, it is monitored whether the rotational position signal has changed as the induced voltage becomes higher than the reference voltage. Then, when a change in the rotational position signal is detected, the mask period setting unit 31 increases the number measurement counter Cb according to the number of detections. Then, the mask period setting unit 31 determines that the second condition is satisfied when the value of the number-of-times counting counter Cb is equal to or greater than the number of times threshold Kb, and makes the ON period Ton of the PWM signal immediately after that longer than the noise generation period Tn. To do. Note that the mask period setting unit 31 resets the count counter Cb when the detection of the zero cross is completed. Thereby, the mask period setting unit 31 is configured to measure the number of times that the induced voltage becomes lower than the reference voltage in one pulse of the PWM signal.

  Next, an example of drive control of the motor 16 by the motor drive device 10 will be described. That is, as illustrated in FIG. 4, when the motor driving device 10 starts driving the motor 16 (S1), the motor driving device 10 acquires information indicating the command duty ratio of the PWM signal at that time (S2). Then, the motor drive device 10 specifies the ON period of the PWM signal based on the acquired command duty ratio, and specifies the noise generation period assumed when the motor is driven at the command duty ratio. Then, the motor drive device 10 sets a mask period in association with the identified noise generation period (S3).

  Then, the motor drive device 10 compares the magnitude relation between the ON period of the identified PWM signal and the noise generation period (S4). When the noise generation period is longer than the ON period of the PWM signal (S4: YES), the motor drive device 10 determines whether the first condition is satisfied (S5) and the second condition is satisfied. Whether or not (S6) is monitored. Then, when the first condition or the second condition is satisfied (S5: YES or S6: YES), the motor drive device 10 executes an on period change process (S7) and a mask period change process (S8).

  In the on period changing process, the motor drive device 10 makes the on period of the PWM signal longer than the noise generation period. Note that the amount of extension of the ON period can be changed as appropriate. In the mask period changing process, the motor driving apparatus 10 changes the mask period to a period that is slightly longer than the noise generation period and shorter than the ON time of the PWM signal after the change. As a result, it is possible to detect the zero cross point while avoiding erroneous detection due to noise after the mask period and within the ON period of the PWM signal.

  Then, when completing the on-period changing process and the masking period changing process, the motor drive device 10 executes a rotor rotational position estimating process (S9). When the noise generation period is equal to or less than the ON period of the PWM signal (S4: NO), the motor drive device 10 performs the rotational position estimation process (S9) without executing the on period change process and the mask period change process. Transition. Also in this case, the mask period is slightly longer than the noise generation period and shorter than the ON time of the PWM signal. Accordingly, it is possible to detect the zero cross point while avoiding false detection due to noise after the mask period and within the ON period of the PWM signal.

  In the rotational position estimation process, the motor driving apparatus 10 estimates the rotational position of the rotor by detecting the zero cross point after the mask period and within the on period of the PWM signal. The motor driving device 10 continues driving the motor 16 while outputting a driving signal based on the estimated rotational position of the rotor. When the stop command signal for stopping the driving of the motor 16 is not input (S10: NO), the motor drive device 10 repeatedly executes the processes after step S4. Then, when a stop command signal is input (S10: YES), the motor drive device 10 stops driving the motor 16 and ends this control.

  According to the motor drive device 10, when the on period of the PWM signal is changed, the length of the mask period to be set is changed according to the length of the on period of the PWM signal after the change. According to this configuration, by setting a mask period that is shorter than the ON period in accordance with the ON period of the PWM signal after the change, it is possible to avoid the ON period of the PWM signal being smaller than the mask period. The motor can be driven at a lower speed.

  Further, according to the motor drive device 10, a period that is slightly longer than the noise generation period and shorter than the ON period of the PWM signal is set as the mask period. As a result, it is possible to reliably mask the noise generated in the voltage of the non-energized phase, and to perform the rotor rotational position detection process after the mask period and within the on period of the PWM signal. Can be ensured.

  Further, according to the motor drive device 10, when the noise generation period is longer than the on period of the PWM signal, when the predetermined condition is satisfied, the on period of the PWM signal is changed to be longer than the noise generation period. Further, the mask period is changed to a period slightly longer than the noise generation period and shorter than the ON time of the PWM signal after the change. If the noise generation period is longer than the PWM signal ON period, the noise generated in the non-energized phase voltage can be masked, but after the mask period, the rotation of the rotor within the PWM signal ON period A period for performing position detection processing cannot be secured. According to the motor drive device 10, in such a case, the length of the on period of the PWM signal is changed, and the length of the mask period is changed accordingly, thereby generating a voltage in the non-conduction phase. Noise can be reliably masked, and a period for detecting the rotational position of the rotor can be reliably ensured after the mask period and within the ON period of the PWM signal.

  Moreover, according to the motor drive device 10, the first condition and the second condition that can sense that the occurrence of the zero cross point is approaching are set. As a result, on the condition that the occurrence of the zero cross point is approaching, the length of the on period of the PWM signal can be changed, and the length of the mask period can be changed accordingly, and the on period changing process It can be avoided that the mask period changing process is performed wastefully.

  Note that the present invention is not limited to the above-described embodiments, and can be applied to various embodiments without departing from the gist thereof. For example, the time threshold value Ka and the frequency threshold value Kb may be set as small as possible. That is, for example, as shown in FIG. 5A, when the gradient of the induced voltage Vn generated in the non-energized phase is steep, the time and number of times that the noise crosses the reference voltage Va immediately before the occurrence of the zero cross point Pz. Tend to be relatively low. Conversely, as shown in FIG. 5B, for example, when the gradient of the induced voltage Vn generated in the non-conduction phase is gentle, the time when the noise crosses the reference voltage Va immediately before the occurrence of the zero-cross point Pz, The number of times tends to increase. In this case, if the number of times threshold Kb is set to “3” with the state of FIG. 5B as a reference, even if the state of FIG. 5A occurs, the second condition is not satisfied, It is impossible to change the on period of the PWM signal or change the mask period. Therefore, it is preferable to set the time threshold value Ka and the frequency threshold value Kb as small as possible, for example, by setting the frequency threshold value Kb to “1” with reference to FIG.

  In the drawings, 10 is a motor drive device, 11 is an inverter circuit unit, 11a is a switching element, 13 is a rotor rotation position estimation unit (rotor rotation position estimation means), 16 is a brushless motor, and 21 is a PWM signal output unit (PWM signal output). Means), 22 is a drive signal output section (drive signal output means), and 31 is a mask period setting section (mask period setting means).

Claims (2)

PWM signal output means (21) for outputting a PWM signal;
Rotor rotational position estimating means (13) for estimating the rotational position of the rotor of the brushless motor based on the induced voltage induced in the non-energized phase of the brushless motor (16);
Drive signal output means (22) for outputting a drive signal based on the PWM signal output from the PWM signal output means and the rotational position signal input from the rotor rotational position estimating means;
An inverter circuit section (11) for driving the brushless motor by turning on / off a plurality of switching elements (11a) based on the drive signal output by the drive signal output means;
A mask period setting means (31) for setting a mask period for masking the estimation processing by the rotor rotational position estimation means in association with the ON period of the PWM signal;
With
The mask period setting means includes
According to the on period of the PWM signal, the length of the mask period to be set is changed ,
As the mask period, set a period longer than a period from when noise is generated in the voltage of the non-energized phase until the noise converges, and shorter than an ON period of the PWM signal,
When a period from when noise is generated in the voltage of the non-energized phase to when the noise converges is longer than the ON period of the PWM signal, when the predetermined condition is satisfied, the ON period of the PWM signal is A motor driving device characterized in that the duration is longer than a period from when noise is generated in a voltage of an energized phase until the noise converges . 2. The motor according to claim 1 , wherein the predetermined condition is set such that a time or the number of times that the induced voltage is lower than a reference voltage in one pulse of the PWM signal is equal to or greater than a predetermined threshold value. Drive device.

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