JP2019213376A - Motor controller - Google Patents

Abstract

To expand a range, where a position of a rotor can be estimated more accurately, to a range of the lower number of revolutions.SOLUTION: A first period measurement section 35 measures a first cycle value Ccy representing an electric angle cycle, by using a hardware timer 3c. A second period measurement section 32 and a corresponding value calculation part 36 generate a timer correspondence value Ce by using a second timer performing count operation with a count period Tc longer than a processing period Tp. An instantaneous value arbitration section 37 selects a first timer value HC, i.e., the count value of the hardware timer 3c as an instantaneous value Cin when equal to or larger than the lower limit number of revolutions, and selects the timer correspondence value Ce as the instantaneous value Cin when equal to or smaller than the lower limit number of revolutions. An electrical angle calculation part 38 calculates a reference electrical angle θ representing the electrical angle in the electrical angle cycle, by using the instantaneous value Cin and the first cycle value Ccy.SELECTED DRAWING: Figure 2

Description

  The present disclosure relates to a technique for estimating a rotor position of a brushless motor.

  Patent Document 1 listed below describes a technique for detecting the rotor position of a brushless motor using three Hall ICs. Specifically, using a hardware timer of a microcomputer (hereinafter referred to as a microcomputer), a cycle count value Ccy representing an electrical angle cycle of one Hall IC signal is measured, and at each preset processing cycle. An instantaneous count value Cin representing an instantaneous value of the hardware timer is acquired. And electric angle (theta) [deg] showing a rotor position is calculated using the following Formula.

    θ = Cin ÷ Ccy × 360 [deg]

Japanese Patent No. 5709963

  However, as a result of detailed studies by the inventors, the conventional technique described in Patent Document 1 cannot accurately estimate the rotor position when the rotor is operating at a low speed outside the measurement range of the timer. Was found.

  That is, since the bit width of the hardware timer is a fixed value, the resolution of the rotor rotational speed and the lower limit of the measurable rotor rotational speed (hereinafter referred to as the lower rotational speed) depend on the clock frequency for operating the hardware timer. Determined. In practice, the lower limit rotational speed is determined by setting the clock frequency so as to obtain the required resolution.

  When the rotor is operating at a speed lower than the lower limit speed (hereinafter referred to as low speed operation), the count value of the hardware timer is saturated before the measurement of one period is completed, and therefore the period cannot be measured accurately. . As a result, the rotor position cannot be estimated from the count value of the hardware timer, and the rotor position is estimated with rough accuracy of 60 [deg] intervals from the pattern of signals output from the three Hall ICs. In other words, in the prior art, at the time of low speed operation, the estimation accuracy of the rotor position deteriorates and the performance of motor control is impaired.

  One aspect of the present disclosure is to provide a technique for expanding a range in which the position of the rotor can be accurately estimated to a range with a lower rotational speed.

  A motor control device (1) according to an aspect of the present disclosure drives a brushless motor. The motor control device includes a pattern generation unit (31), a first cycle measurement unit (35), a second cycle measurement unit (32), an equivalent value calculation unit (36), and an instantaneous value arbitration unit (37). And an electrical angle calculation unit (38).

The pattern generation unit generates detection patterns corresponding to a plurality of rotational positions that can be taken during the electrical angle period. The electrical angle period is a period during which the rotor makes one electrical revolution.
A 1st period measurement part calculates the 1st period value showing an electrical angle period using the 1st timer (3c). The first timer has a preset bit width, performs a count operation in accordance with a clock signal whose cycle is set according to the resolution of the rotational speed of the rotor, and the count value is reset for each electrical angular cycle in accordance with the detection pattern. Hardware timer.

  The second cycle measuring unit calculates a second cycle value representing a cycle in which the detection pattern changes using the second timer. The second timer performs a count operation every count cycle set longer than the cycle of the clock signal, and the count value is reset every time the detection pattern changes.

  The equivalent value calculation unit obtains a second timer value that is a count value of the second timer, and converts the second timer value into a timer equivalent value using the detection pattern and the second period value. The timer equivalent value corresponds to a value obtained by counting the period from the timing serving as the base point of the electrical angle cycle to the timing when the second timer value is obtained in the count cycle.

  The low speed determination unit determines whether or not the rotational speed of the rotor is smaller than the lower limit rotational speed. The lower limit rotational speed is the rotational speed of the rotor at which the first timer value is saturated during the electrical angle period, with the count value of the first timer as the first timer value.

  The instantaneous value arbitration unit selects the first timer value when the low-speed determination unit determines that the rotation speed of the rotor is equal to or higher than the lower limit rotation speed, and corresponds to the timer when it is determined that the rotation speed is smaller than the lower limit rotation speed. Select a value.

The electrical angle calculation unit calculates a reference electrical angle representing an electrical angle within the electrical angle cycle, using the instantaneous value that is the value selected by the selection unit and the first cycle value.
According to such a configuration, when the rotational speed of the rotor is equal to or higher than the lower limit rotational speed, the reference electrical angle that is the phase within the electrical angle cycle is calculated using the first timer value. Further, when the rotational speed of the rotor is smaller than the lower limit rotational speed, the phase within the period in which the detection pattern changes can be calculated within the electrical angular period using the count value of the second timer that operates at a slower count period. A reference electrical angle is calculated using a timer equivalent value converted into a phase.

  For this reason, even when the rotational speed of the rotor is lower than the lower limit rotational speed that cannot be measured by the first timer, the rotor position can be accurately measured. A hardware timer is used as the first timer requiring high speed, but the slower second timer can be configured by software. When the second timer is configured by software, the bit width of the count value is not limited by hardware, so it can be set to an arbitrary size, which greatly improves the lower limit of measurable rotation speed. can do.

  In addition, the measurement result using the second timer is converted into a timer equivalent value equivalent to the first timer value, and either the first timer value or the timer equivalent value is set as an instantaneous value according to the rotational speed of the rotor. Since either one is selected, the reference electrical angle can be calculated by the same calculation.

  Note that the reference numerals in parentheses described in this column and in the claims indicate the correspondence with the specific means described in the embodiment described later as one aspect, and the technical scope of the present disclosure It is not limited.

It is a block diagram which shows the structure of the motor control apparatus and the brushless motor used as control object. It is a list which shows the relationship between a some detection pattern and the limit value in each detection pattern. It is a functional block diagram which shows the functional structure of the control part of a motor control apparatus. It is a timing diagram which illustrates operation of each part of a control part. It is a graph which illustrates rotation speed and the standard electric angle detected.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.
[1. Constitution]
A motor control device 1 shown in FIG. 1 is a device that controls the drive of a brushless motor 5. The brushless motor 5 is a three-phase motor, and includes a rotor 51, a plurality of stators 52, and three Hall ICs 53.

  The rotor 51 rotatably supports a plurality of magnetic pole pairs. A permanent magnet is used for the magnetic pole pair. The magnetic pole pairs are arranged so that the N poles and the S poles are alternately and evenly arranged on the outer periphery of the rotor 51. In the present embodiment, the case where N = 5 is exemplified, where N is the number of magnetic pole pairs, but the present invention is not limited to this, and the number of magnetic pole pairs may be arbitrary.

  The stator 52 is disposed around the rotor 51 at equal angular intervals, and a winding is wound around it. The stator 52 is wound with any of the U-phase, V-phase, and W-phase windings. In the present embodiment, the case where the number of stators 52 is three is exemplified, but the present invention is not limited to this, and the number of stators 52 may be a multiple of three.

  Each of the three Hall ICs 53 is an integrated circuit in which a Hall element is incorporated, and detects the magnetic poles of a permanent magnet that rotates integrally with the rotor, and has detection signals Su and Sv having signal levels corresponding to the polarities of the magnetic poles. , Sw are output. The signal levels of the detection signals Su, Sv, Sw are, for example, a high level Hi when the magnetic pole facing the Hall IC 53 is an N pole, and a low level Lo when it is an S pole.

  The three Hall ICs 53 are arranged at positions separated by 120 [deg] in electrical angle. The electrical angle represents an angle when one cycle of a detection signal output from each Hall IC 53 is 360 [deg]. Here, since the rotor 51 has five magnetic pole pairs (that is, the number of magnetic poles is 10), the mechanical angles are arranged at positions separated by 24 (= 120/5) [deg]. However, the arrangement interval at the mechanical angle is not limited to 24 [deg], and may be 96 (= 120/5 + 360/5) [deg], for example. The mechanical angle represents an angle when one rotation of the rotor 51 is 360 [deg]. As a result, the three detection signals Su, Sv, and Sw have different phases by 120 [deg] as shown in FIG.

The motor control device 1 includes an interface (hereinafter referred to as I / F) unit 2, a control unit 3, and a drive circuit 4.
The I / F unit 2 receives three detection signals Su, Sv, and Sw, performs amplification processing, waveform shaping processing, and the like on these signals, and outputs them to the control unit 3.

  The control unit 3 estimates a reference electrical angle θ that expresses the rotational position with higher accuracy from the low-accuracy rotational position expressed in units of electrical angle 60 [deg] based on the detection signals Su, Sv, and Sw. A PWM signal having a duty ratio corresponding to the electrical angle θ is generated and output to the drive circuit 4.

  The drive circuit 4 rotates the rotor 51 by the attractive force and the repulsive force generated between the windings and the magnetic poles by energizing the windings of the stators 52 of the respective phases with a predetermined period corresponding to the PWM signal. .

  The control unit 3 includes a microcomputer having a CPU 3a, a semiconductor memory (hereinafter, memory 3b) such as RAM or ROM, and a hardware timer 3c. Each function of the control unit 3 is realized by the CPU 3a executing a program stored in a non-transitional tangible recording medium. In this example, the memory 3b corresponds to a non-transitional tangible recording medium that stores a program. Also, by executing this program, a method corresponding to the program is executed. The control unit 3 may include one microcomputer or a plurality of microcomputers.

  In addition to the program, the memory 3b stores a pattern table as data necessary for realizing the function of the control unit 3. As shown in FIG. 2, the pattern table stores detection patterns (U, V, W) and limit values associated with the detection patterns (U, V, W). The detection pattern (U, V, W) is a combination pattern of signal levels expressed by the detection signals Su, Sv, Sw. The detection pattern (U, V, W) changes when the rotation direction of the rotor 51 is CW, assuming that the clockwise rotation of the rotor 51 shown in FIG. 1 is expressed as CW and the counterclockwise rotation is expressed as CCW. Stored in order. The limit value of each detection pattern has an upper limit angle and a lower limit angle, respectively. The upper limit angle and the lower limit angle are set such that the difference between the upper limit angle and the lower limit angle is 60 [deg], and the upper limit angle of the previous detection pattern aligned in the forward direction coincides with the lower limit angle of the subsequent detection pattern. Here, the high level Hi of the detection signals Su, Sv, Sw is represented by 1 and the low level Lo is represented by 0. Then, the lower limit angle when the detection pattern (U, V, W) is (1, 0, 1) is set as a reference (that is, 0 [deg]).

  The hardware timer 3c corresponds to a first timer. The hardware timer 3c has a count value represented by 16 bits. The hardware timer 3c is driven by a clock CK having a predetermined frequency. The count value of the hardware timer 3c is output as the first timer value HC, and the count value is set to the first period with the detection signal from any one of the Hall ICs 53, here, the rising edge of the U-phase detection signal Su as a trigger. Save as value Cr and reset the counter for measurement.

  The frequency fhwt [Hz] of the clock CK for driving the hardware timer 3c can provide a rotational speed accuracy of ± N error [rpm] or less when the rotational speed of the rotor 51 (hereinafter referred to as the rotor rotational speed) is Nrated [rpm]. Is set as follows. Specifically, the count value when the electrical angular period corresponding to the rotor speed Nrated is counted at the frequency fhwt is obtained, and when the count value is changed by 1 count, the change in the rotor speed becomes Nerror or less. The frequency fhwt is set. However, for the frequency fhwt, the minimum frequency satisfying the above condition is selected from the frequencies obtained by dividing the clock prepared for driving the hardware timer 3c. The number of bits of the hardware timer 3c is not limited to the above 16 bits.

When the frequency is fhwt, the time required until the count value of the hardware timer 3c saturates from the start of counting is 2 ¹⁶ / fhwt [s]. Further, the lower limit rotational speed that is the lower limit of the rotor rotational speed that can be detected by the hardware timer 3c is 60 ÷ number of pole pairs ÷ (2 ¹⁶ / fhwt) [rpm].

As shown in FIG. 3, the control unit 3 includes a pattern generation unit 31, a second cycle measurement unit 32, a rotation determination unit 33, a low speed determination unit 34, a first cycle measurement unit 35, and an equivalent value calculation unit. 36, an instantaneous value adjuster 37, an electrical angle calculator 38, and a signal generator 39. The method of realizing the functions of the respective units included in these control units 3 is not limited to software, and some or all of the functions may be realized using one or a plurality of hardware. For example, when the function is realized by an electronic circuit that is hardware, the electronic circuit may be realized by a digital circuit, an analog circuit, or a combination thereof.

  Note that the instantaneous value arbitration unit 37, the electrical angle calculation unit 38, and the signal generation unit 39 are executed at a preset processing cycle Tp. The processing period Tp is set to Tp = 1 / fp [s], for example, as fp [Hz]. In addition, the second cycle measuring unit 32, the rotation determining unit 33, the low speed determining unit 34, and the equivalent value calculating unit 36 are processed every count cycle Tc set longer than the processing cycle Tp. The count cycle Tc has a length that is an integral multiple of the processing cycle Tp.

  The pattern generation unit 31 determines whether the signal level of the detection signals Su, Sv, Sw is high level or low level for each processing cycle Tp, and stores the detection pattern (U, V, W) as a determination result in the buffer. . The pattern generation unit 31 compares the current pattern, which is the current detection pattern, with the previous pattern, which is the detection pattern stored in the buffer, and determines whether or not the current pattern has changed from the previous pattern. A switching signal Sx representing the result is generated. The pattern generation unit 31 updates the stored contents of the buffer when the current pattern changes from the previous pattern. The switching signal Sx is input to the second period measurement unit 32. The stored contents of the buffer are input to the second period measuring unit 32, the rotation determining unit 33, and the equivalent value calculating unit 36.

  The second period measuring unit 32 includes a second timer that is a timer realized by software. The second cycle measuring unit 32 performs the count operation of the second timer every count cycle Tc, and the count value is reset by using the change of the detection pattern (U, V, W) as a trigger according to the switching signal Sx. The second period measuring unit 32 outputs the count value obtained immediately before the reset as the second period value Cpt representing the period Tpt at which the pattern changes. The second cycle measuring unit 32 outputs the count value C2 as a value corresponding to the elapsed time from the reset time. The second period value Cpt is input to the low speed determination unit 34 and the equivalent value calculation unit 36, and the count value C2 is input to the equivalent value calculation unit 36.

  The rotation determination unit 33 refers to the pattern table shown in FIG. 2, compares the detection pattern acquired in the past with the newly acquired detection pattern, and changes the detection pattern (U, V, W). From the way, the rotation direction of the rotor 51 is determined, and a rotation determination signal Sr indicating the determination result is output. That is, when the detection pattern (U, V, W) changes from the top to the bottom of the pattern table, it is determined as CW, and when it changes from the bottom to the top, it is determined as CCW. The rotation determination signal Sr is input to the equivalent value calculation unit 36 and the electrical angle calculation unit 38.

  The low speed determination unit 34 determines whether or not the second cycle value Cpt measured by the second cycle measurement unit 32 exceeds a preset low speed threshold, and outputs a low speed determination signal Sv representing the determination result. The low speed determination signal Sv is input to the first period measurement unit 35 and the instantaneous value arbitration unit 37. The low speed threshold value is set to a value obtained by dividing the pattern period Tpt corresponding to the lower limit rotational speed of the rotor rotational speed by the count period Tc. That is, when the second cycle value Cpt exceeds the low speed threshold, the low speed determination unit 34 decreases the rotor rotational speed to a lower limit rotational speed, that is, a rotational speed that cannot be measured by the hardware timer 3c. It is determined that The low speed determination unit 34 also determines that the rotor rotational speed does not reach the lower limit rotational speed even when the count value C2 exceeds the low speed threshold and is not reset.

The first cycle measurement unit 35 includes a cycle buffer 351 and a cycle arbitration unit 353.
The hardware timer 3c stores the count value Cr immediately before the reset in the period buffer 351 every time the hardware timer 3c is reset according to the detection signal Su. Buffering is performed by software. The period buffer 351 stores at least count values Cr for the past five times that are the same number as the magnetic pole pairs of the rotor 51. In FIG. 3, [n] represents the latest count value Cr stored in the buffer. [Max] represents a saturation value that is the upper limit of the count value of the hardware timer 3c. The cycle buffer 351 outputs [n] as the first data and [max] as the second data.

  The period arbitration unit 353 selects either the first data [n] or the second data [max] according to the low speed determination signal Slow, and is necessary for calculating the first period value Ccy that represents the electrical angular period of the rotor 51. Output as period data Dcy. Specifically, when the low speed determination signal Slow indicates that the rotor rotational speed is lower than the lower limit rotational speed, the second data [max] is selected as the period data Dcy. When the rotor rotational speed is equal to or higher than the lower limit rotational speed, the first data [n] is selected as the period data Dcy. The selected cycle data Dcy is input to the electrical angle calculation unit 38.

The equivalent value calculation unit 36 includes a sign assigning unit 361, a limit setting unit 362, and a conversion unit 363.
The sign assigning unit 361 acquires the count value C2 and the second period value Cpt from the second period measuring unit 32 for each count period Tc, and according to the expression (1), a signed count value SC that represents a phase within the pattern period. Is calculated.

SC = Sign × (C2 ÷ Cpt) × ([max] × 60 ÷ 360) (1)
That is, the sign assigning unit 361 divides the count value C2 by the second cycle value Cpt, and sets the saturation value [max], which is the upper limit of the count value of the hardware timer 3c, to the pattern cycle (ie 60 [deg]). The signed count value SC is calculated by multiplying the value converted into the minute value and adding a sign Sign according to the rotation determination signal Sr. Specifically, the sign Sign is a plus sign when the rotation direction indicated by the rotation determination signal Sr is CW, and a minus sign when the rotation direction is CCW.

  The limit setting unit 362 acquires the detection pattern (U, V, W) from the pattern generation unit 31, refers to the pattern table, and sets the lower limit angle αL and the upper limit according to the acquired detection pattern (U, V, W). The angle αU is acquired, and the lower limit value CL and the upper limit value CU are calculated according to equations (2) and (3).

CL = αL ÷ 360 × [max] (2)
CU = αU ÷ 360 × [max] (3)
That is, the limit setting unit 362 divides the acquired lower limit angle αL and upper limit angle αU by 360 [deg], respectively, and multiplies the saturation value [max] that is the upper limit of the count value of the hardware timer 3c. The lower limit value CL and the upper limit value CU are calculated. The lower limit value CL and the upper limit value CU represent a range of values that can be taken by the timer equivalent value Ce while the state of the acquired detection pattern (U, V, W) is maintained.

According to the rotation determination signal Sr, the conversion unit 363 selects the lower limit value CL as the reference value Cf when the rotation direction is CW, and selects the upper limit value CU as the reference value Cf when the rotation direction is CCW. In addition, the conversion unit 363 adds the signed count value SC from the sign providing unit 361 to the selected reference value Cf. Specifically, when the rotation direction is CW, addition of the lower limit value CL, which is the reference value Cf, and the plus sign count value is executed, and when the rotation direction is CCW, the upper limit value CU, which is the reference value Cf. And the minus sign count value, that is, the count value is subtracted from the upper limit value CU. Furthermore, when the addition result is within the allowable range from the lower limit value CL to the upper limit value CU, the conversion unit 363 outputs the addition result as it is as the timer equivalent value Ce. In addition, when the addition result is outside the allowable range, the conversion unit 363 outputs a value limited by the guard value as the timer value Ce. Specifically, if the addition result is a value larger than the upper limit value CU, the upper limit value CU that is a guard value is set as the timer equivalent value Ce, and if the addition result is smaller than the lower limit value CL, the lower limit value CL that is a guard value. Is output as a timer equivalent value Ce. The timer equivalent value Ce is input to the instantaneous value arbitration unit 37.

  That is, the equivalent value calculation unit 36 estimates the phase (that is, the rotational position of the rotor 51) within the range of 60 [deg] with the electrical angle specified by the detection pattern (U, V, W). Using the detection pattern (U, V, W), a value converted into a value representing a phase within a range of 360 [deg] in electrical angle (that is, one cycle) is output as a timer equivalent value Ce.

  In accordance with the low speed determination signal Sv, the instantaneous value arbitration unit 37 selects the first timer value HC when the rotor rotational speed is equal to or higher than the lower limit rotational speed, and when the rotor rotational speed is lower than the lower limit rotational speed, Ce is selected, and the selected value is output as an instantaneous value Cin. The instantaneous value Cin is input to the electrical angle calculation unit 38.

  The electrical angle calculation unit 38 sets the cycle data Dcy as the first cycle value Ccy, and when the rotation determination signal Sr is CW based on the first cycle value Ccy, the instantaneous value Cin, and the rotation determination signal Sr (4). ), When the rotation determination signal Sr is CCW, the reference electrical angle θ is calculated according to the expression (5). Equations (4) and (5) mean that the relationship between the rotor position and the rising edge changes by 180 [deg] depending on the rotation direction.

θ = Cin ÷ Ccy × 360 [deg] (4)
θ = −Cin ÷ Ccy × 360 + 180 [deg] (5)
Here, the cycle data Dcy is used as it is as the first cycle value Ccy, but is not limited to this. For example, assuming that the cycle data Dcy for the past N cycles is represented by D1 to DN, as shown in the equation (6), the cycle data D1 to DN of the N cycles with an electrical angle corresponding to one cycle in mechanical angle. The average value may be used as the first period value Ccy. Note that the number of data to be averaged is not limited to N.

Ccy = (D1 + D2 +... + DN) / N (6)
The signal generation unit 39 generates three types of PWM signals used for energization control of the windings of the stator 52 according to the reference electrical angle θ.

[2. Operation]
As shown in FIG. 4, the detection signals Su, Sv, and Sw change when the signal level changes at a timing shifted by 120 deg in electrical angle and the rotation direction is constant, during the electrical angle period (ie, 360 deg). Six detection patterns (U, V, W) appear.

  The first timer value HC is acquired every processing cycle Tp. The second timer value C2 is acquired every count cycle Tc. The second timer value C2 changes more slowly than the first timer value HC.

  Although illustration is omitted, the first cycle value Ccy is acquired every processing cycle Tp or every count cycle Tc, and the value changes every cycle of the electrical angle. The second cycle value Cpt is acquired every count cycle Tc, and the value changes every 60 [deg] of the electrical angle. The timer equivalent value Ce is calculated every count cycle Tc.

The reference electrical angle θ is calculated every processing cycle Tp.
The rotation determination signal Sr is confirmed every processing cycle Tp, and changes at the timing when the detection pattern (U, V, W) changes. The low speed determination value Sv is confirmed every count cycle Tc.
The low speed determination is performed every count cycle.

The first cycle value Ccy is calculated for each processing cycle Tp or the count cycle Tc based on the cycle data Dcy, and the reference electrical angle θ is calculated for each processing cycle Tp using the instantaneous value Cin and the first cycle value Ccy. Is done.

  As the instantaneous value Cin, the first timer value HC is used during non-low speed operation where the rotor rotational speed is equal to or higher than the lower limit rotational speed, and the timer equivalent value Ce is used during low speed operation where the rotor rotational speed is lower than the lower limit rotational speed.

  During the non-low speed operation, the first data [n] is selected as the cycle data Dcy. That is, the first data [n], which is the count value of the electrical cycle obtained from the hardware timer 3c, is used as the cycle data Dcy, and thus the first cycle value Ccy.

  During the low speed operation, the second data [max] is selected as the cycle data Dcy. That is, the saturation value representing the cycle at the lower limit rotational speed is used as the cycle data Dcy, and hence the first cycle value Ccy.

  FIG. 4 shows a timing chart when the rotor 51 is in non-low speed operation. However, in the case of low speed operation, the detection signals Su, Sv, Sw and the detection pattern (U, V, W) are in the time axis direction. The timing chart is the same except that the extended value and the instantaneous value Cin (that is, the timer equivalent value Ce) calculated using the second timer operated by software instead of the hardware timer 3c are used.

  FIG. 5 illustrates a reference electrical angle θ calculated based on a timer equivalent value and a guard value set from a detection pattern during low-speed operation that occurs before and after the rotation speed becomes zero when the rotation direction changes. It is a graph. In the lower graph of FIG. 5, the solid line is the reference electrical angle θ, the alternate long and short dash line is the guard value, and the broken line is the theoretical value of the reference electrical angle θ.

  During the low speed operation, the count value [max] representing the cycle at the lower limit rotational speed is used for the calculation of the first periodic value Ccy. Therefore, as the rotational speed approaches zero, the first periodic value Ccy is greater than the actual value. As a result, the reference electrical angle θ is calculated to be larger than the theoretical value. However, since a guard value is set for each pattern cycle in which the detection pattern (U, V, W) changes, and the value of the reference electrical angle θ is limited by the guard value, errors accumulate across the pattern cycle. There is no.

  Since the guard value is set according to the detection pattern (U, V, W), it is set correctly with good responsiveness. However, the determination of the rotation direction requires comparison of detection patterns over a plurality of pattern periods. , There will be a delay with respect to the actual situation. Due to this influence, in the vicinity of time 6 in FIG. 5, there is a deviation that the basic electrical angle θ increases although the electrical angle actually decreases. However, the deviation from the theoretical value of the basic electrical angle θ after the determination of the rotation direction is correctly reflected is sufficiently suppressed.

[3. effect]
According to the first embodiment described in detail above, the following effects are obtained.
(1) In the motor control device 1, when the rotor rotational speed is lower than the lower limit rotational speed that cannot be measured by the hardware timer 3c, the reference electrical angle θ is calculated using the second timer that operates at a slower count cycle Tc. To do. For this reason, even when the rotor rotational speed is lower than the lower limit rotational speed, the rotor position can be accurately estimated. Specifically, in the hardware timer 3c that operates with a clock of fhwt [Hz], the lower limit rotational speed that can be measured is 60 / pole pair number / (2 ¹⁶ / fhwt) [rpm]. On the other hand, by using a second timer corresponding to operating with a clock having a count cycle Tc (> 1 / fhwt), the lower limit rotation speed that can be measured is 60 ÷ pole pair ÷ (2 ¹⁶ / (1 / Tc)) [rpm].

  (2) When the second timer is used, the phase within the electrical angle period is not directly measured, but the pattern period in which the detection pattern (U, V, W) changes and the phase within the pattern period are measured. This is converted into a timer equivalent value representing the phase within the electrical angle period. For this reason, the reference electrical angle can be estimated in a shorter time compared to the case where the phase within the electrical angle cycle is directly measured. Further, since the timer equivalent value Ce is a value equivalent to the first timer value HC, the reference electrical angle θ can be calculated by the same calculation regardless of which value is selected as the instantaneous value Cin. Can be used effectively.

  (3) When measuring the phase within the pattern period, by setting a guard value according to the detection pattern (U, V, W), an error within the pattern period is accumulated across the pattern period. There has been no such thing. Therefore, at the time of low speed operation, although the contribution of disturbance to the rotation speed change is large, the influence can be kept only within each pattern period, and the estimation accuracy of the reference electrical angle θ as a whole is improved. be able to.

  (4) Since the second timer is realized by software, the bit width of the count value can be set to an arbitrary size without being restricted by hardware, so the lower limit value of the measurable rotation speed is greatly increased. Can improve.

[4. Other Embodiments]
As mentioned above, although embodiment of this indication was described, this indication is not limited to the above-mentioned embodiment, and can carry out various modifications.

  (A) In the above embodiment, one count equivalent value Ce is calculated using one second timer. However, a plurality of counts using a plurality of second timers having different count periods Tc are used. The equivalent value Ce may be calculated. In other words, the longer the count cycle Tc, the lower the resolution, while the lower the speed can be measured. In other words, by using a plurality of count equivalent values Ce that realize a resolution corresponding to the number of rotations to be measured, it is possible to further lower the lower limit of the measurable rotation speed while maintaining the necessary resolution.

  (B) In the above embodiment, the equivalent value calculation unit 36 adds the signed count value SC with reference to a value determined by the detection pattern (U, V, W) and the rotation direction, thereby obtaining the timer equivalent value Ce. However, the present disclosure is not limited to this. For example, the timer equivalent value Ce may be calculated by adding the signed count value SC with reference to the value obtained at the end of the immediately preceding pattern cycle. In this case, even when the determination of the rotation direction is incorrect, the value at the start time of the pattern cycle is always the value at the end time of the immediately preceding pattern cycle. For this reason, when the determination of the rotation direction is incorrect, the timer equivalent value Ce in the pattern cycle is a constant value from the start to the end, but the timer equivalent value Ce is opposite to the actual phase change. It can be prevented from changing.

  (C) A plurality of functions of one constituent element in the above embodiment may be realized by a plurality of constituent elements, or a single function of one constituent element may be realized by a plurality of constituent elements. . Further, a plurality of functions possessed by a plurality of constituent elements may be realized by one constituent element, or one function realized by a plurality of constituent elements may be realized by one constituent element. Moreover, you may abbreviate | omit a part of structure of the said embodiment. Further, at least a part of the configuration of the above embodiment may be added to or replaced with the configuration of the other embodiment. In addition, all the aspects included in the technical idea specified from the wording described in the claims are embodiments of the present disclosure.

  (D) In addition to the motor control device described above, a system including the motor control device as a component, a program for causing a computer to function as the motor control device, and a non-transitional actual record such as a semiconductor memory storing the program The present disclosure can also be realized in various forms such as a medium and a rotor position estimation method.

  DESCRIPTION OF SYMBOLS 1 ... Motor control apparatus, 2 ... Interface part, 3 ... Control part, 3a ... CPU, 3b ... Memory, 3c ... Hardware timer, 4 ... Drive circuit, 5 ... Brushless motor, 31 ... Pattern generation part, 32 ... 2nd Period measurement unit 33 ... Rotation determination unit 34 ... Low speed determination unit 35 ... First cycle measurement unit 36 ... Equivalent value calculation unit 37 ... Instantaneous value arbitration unit 38 ... Electric angle calculation unit 39 ... Signal generation unit , 51, rotor, 52, stator, 53, Hall IC, 351, periodic buffer, 353, periodic arbitration unit, 361, sign assigning unit, 362, limit setting unit, 363, conversion unit.

Claims (4)

A motor control device (1) for driving a brushless motor (5),
A period in which the rotor (51) rotates by an electrical angle is defined as an electrical angular period, and detection patterns (U, V, W) corresponding to a plurality of rotational positions that can be taken during the electrical angular period are generated. Pattern generation unit (31),
A hardware timer that has a preset bit width, performs a count operation according to a clock signal whose cycle is set according to the resolution of the rotation speed, and resets the count value for each electrical angular cycle according to the detection pattern A first period measuring unit (35) configured to measure a first period value (Ccy) representing the electrical angular period using a first timer (3c);
A cycle in which the detection pattern changes using a second timer that performs a count operation every count cycle (Tc) set longer than the cycle of the clock signal and resets the count value every time the detection pattern changes. A second period measurement unit (32) configured to measure a second period value (Cpt) representing
A second timer value (C2) that is a count value of the second timer is acquired, and the second timer value is equivalent to a value counted in the count cycle by using the detection pattern and the second cycle value. An equivalent value calculation unit (36) configured to convert the timer equivalent value (Ce)
With the count value of the first timer as the first timer value (HC), the rotation speed of the rotor at which the first timer value is saturated during the electrical angle period as the lower limit rotation speed, the rotation speed of the rotor is A low speed determination unit (34) for determining whether or not it is smaller than the lower limit rotational speed;
When the low-speed determination unit determines that the rotation speed of the rotor is equal to or higher than the lower limit rotation speed, the first timer value is selected, and when it is determined that the rotation speed is lower than the lower limit rotation speed, the timer corresponds An instantaneous value mediator (37) configured to select a value;
A reference electrical angle (θ) representing an electrical angle within the electrical angle period is calculated using an instantaneous value (Cin) that is a value selected by the instantaneous value arbitration unit and the first period value. A motor control device comprising: an electrical angle calculation unit (38) configured. The motor control device according to claim 1,
The equivalent value calculation unit is configured to generate the timer equivalent value within a range from a lower limit value to an upper limit value set in advance for each detection pattern. The motor control device according to claim 1 or 2,
The first period measurement unit, when the change of the count value acquired for each electrical angle period is within a preset allowable range, an average value of the count values over a plurality of the electrical angle periods When the change in the count value exceeds the allowable range, the latest count value is configured as the first cycle value.
Motor control device. The motor control device according to any one of claims 1 to 3, wherein
The first cycle measuring unit is configured to set a saturation value of the first timer as the first cycle value when the rotational speed of the rotor is smaller than the lower limit rotational speed.
Motor control device.

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