JP7006513B2 - Motor control device - Google Patents

Description

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

The following Patent Document 1 describes a technique for detecting the rotor position of a brushless motor using three Hall ICs. Specifically, a hardware timer possessed by a microcomputer (hereinafter referred to as a microcomputer) is used to measure a cycle count value Cyy representing the electrical angular cycle of one Hall IC signal, and for each preset processing cycle. Acquires the instantaneous count value Cin, which represents the instantaneous value of the hardware timer. Then, the electric angle θ [deg] representing the rotor position is calculated using the following equation.

θ = Cin ÷ Cy × 360 [deg]

Japanese Patent No. 5709693

However, as a result of detailed studies by the inventor, in the prior art described in Patent Document 1, there is a problem that the rotor position cannot be estimated accurately when the rotor is operating at a low speed that is 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 rotation speed and the lower limit of the measurable rotor rotation speed (hereinafter referred to as the lower limit rotation speed) are determined by the frequency of the clock that operates the hardware timer. It will be decided. In practice, the lower limit of revolutions is determined by setting the clock frequency so that the required resolution is obtained.

When the rotor is operating at a rotation speed lower than the lower limit rotation speed (hereinafter, low-speed operation), the count value of the hardware timer is saturated before the measurement of one cycle is completed, so that the cycle 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 a rough accuracy of 60 [deg] intervals from the pattern of the signals output from the three Hall ICs. That is, in the prior art, the estimation accuracy of the rotor position deteriorates at low speed operation, and the performance of motor control is impaired.

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

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

The pattern generation unit generates a detection pattern corresponding to a plurality of rotation positions that can be taken during the electric angle period. The electric angle period is a period during which the rotor makes one rotation at the electric angle.
The first period measuring unit calculates the first period value representing the electric angle period by using the first timer (3c). The first timer has a preset bit width, performs a counting operation according to a clock signal whose period is set according to the resolution of the rotation speed of the rotor, and resets the count value for each electric angle period according to a detection pattern. It is a hardware timer.

The second cycle measuring unit uses the second timer to calculate the second cycle value representing the cycle in which the detection pattern changes. The second timer performs a counting operation every count cycle set longer than the clock signal cycle, and resets the count value every time the detection pattern changes.

The equivalent value calculation unit acquires the second timer value, which is the count value of the second timer, and converts the second timer value into a timer equivalent value using the detection pattern and the second cycle value. The timer equivalent value corresponds to the value counted in the count cycle from the timing which is the base point of the electric angle cycle to the timing when the second timer value is obtained.

The low speed determination unit determines whether or not the rotation speed of the rotor is smaller than the lower limit rotation speed. The lower limit rotation speed is the rotation speed of the rotor in which the first timer value is saturated during the electric angle cycle, 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 rotor rotation speed is equal to or higher than the lower limit rotation speed, and corresponds to a timer when it is determined that the rotor rotation speed is smaller than the lower limit rotation speed. Select a value.

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

Therefore, even when the rotation speed of the rotor is lower than the lower limit rotation speed that cannot be measured by the first timer, the rotor position can be measured accurately. A hardware timer is used as the first timer that requires high speed, but a 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 restricted by the hardware, so it can be set to any size, which greatly improves the lower limit of the measurable rotation speed. can do.

Further, 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 used as an instantaneous value according to the rotation speed of the rotor. Since the selection is made, the reference electric angle can be calculated by the same calculation regardless of which one is selected.

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

It is a block diagram which shows the structure of the motor control device, and the brushless motor to be controlled. It is a list which shows the relationship between a plurality of detection patterns and a 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 device. It is a timing diagram which illustrates the operation of each part of a control part. It is a graph which illustrates the rotation speed and the detected reference electric angle.

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

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

The stator 52 is arranged around the rotor 51 at equal angular intervals, and windings are wound around the stator 52. The stator 52 is wound around any of the U-phase, V-phase, and W-phase windings. In the present embodiment, the case where the number of stators 52 is 3 is illustrated, but the present invention is not limited to this, and the number of stators 52 may be a multiple of 3.

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

The three hole ICs 53 are arranged at positions separated by 120 [deg] in terms of electrical angle. The electric angle represents an angle when one cycle of the detection signal output by 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), they are arranged at positions separated by 24 (= 120/5) [deg] in terms of mechanical angle. However, the arrangement interval at the machine angle is not limited to 24 [deg], and may be, for example, 96 (= 120/5 + 360/5) [deg]. 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, I / F) unit 2, a control unit 3, and a drive circuit 4.
The I / F unit 2 inputs 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 the reference electric angle θ that expresses the rotation position with higher accuracy from the low-precision rotation position expressed in units of electric angles 60 [deg] by the detection signals Su, Sv, and Sw, and this reference. A PWM signal having a duty ratio corresponding to the electric angle θ is generated and output to the drive circuit 4.

The drive circuit 4 energizes the windings of the stator 52 of each phase at a predetermined cycle according to the PWM signal, and rotates the rotor 51 by the attractive force and the repulsive force generated between the windings and the magnetic poles. ..

The control unit 3 includes a microcomputer having a CPU 3a, a semiconductor memory such as RAM or ROM (hereinafter, memory 3b), 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 substantive recording medium. In this example, the memory 3b corresponds to a non-transitional substantive recording medium in which a program is stored. In addition, when this program is executed, the 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 a detection pattern (U, V, W) and a limit value associated with the detection pattern (U, V, W). The detection pattern (U, V, W) is a combination pattern of signal levels expressed by the detection signals Su, Sv, Sw. It should be noted that the clockwise direction of the rotor 51 shown in FIG. 1 is expressed as CW and the counterclockwise direction is expressed as CCW, and the detection pattern (U, V, W) changes when the rotation direction of the rotor 51 is CW. It is memorized 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 so that the difference between the two is 60 [deg], and the upper limit angle of the first detection pattern arranged in the forward direction and the lower limit angle of the later detection pattern match. Here, it is assumed that the high level Hi of the detection signals Su, Sv, and 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 the 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 cycle by using the detection signal from any one of the hall IC 53s, here the rising edge of the U-phase detection signal Su, as a trigger. Save as the value Cr and reset the measurement counter.

The frequency fhwt [Hz] of the clock CK that drives the hardware timer 3c can obtain a rotation speed accuracy of ± Nerror [rpm] or less when the rotation speed of the rotor 51 (hereinafter, rotor rotation speed) is Nrated [rpm]. Is set to. Specifically, the count value when the electric angle period corresponding to the rotor rotation speed Nrated is counted at the frequency fhwt is obtained, and the change in the rotor rotation speed becomes Nerror or less when the count value is changed by 1 count. , Set the frequency fhwt. However, as the frequency fhwt, the minimum frequency satisfying the above conditions 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 16 bits described above.

When the frequency is ^fhwt , the time required from the start of counting to the saturation of the count value of the hardware timer 3c is 216 / fhwt [s]. Further, the lower limit rotation speed, which is the lower limit of the rotor rotation speed that can be detected by the hardware timer 3c, is 60 ÷ pole pair number ÷ (216 / ^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 arbitration unit 37, an electric angle calculation unit 38, and a signal generation unit 39 are provided. The method for realizing the functions of each unit included in the control unit 3 is not limited to software, and some or all of the functions may be realized by using one or a plurality of hardware. For example, when the above function is realized by an electronic circuit which is hardware, the electronic circuit may be realized by a digital circuit, an analog circuit, or a combination thereof.

The instantaneous value arbitration unit 37, the electric angle calculation unit 38, and the signal generation unit 39 execute processing at each preset processing cycle Tp. The processing cycle Tp is set to Tp = 1 / fp [s], for example, as fp [Hz]. Further, the second cycle measurement unit 32, the rotation determination unit 33, the low speed determination unit 34, and the equivalent value calculation unit 36 execute processing 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 levels of the detection signals Su, Sv, and Sw are high level or low level for each processing cycle Tp, and stores the detection pattern (U, V, W) as the 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, determines whether or not the current pattern has changed from the previous pattern, and determines that determination. 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 cycle measuring unit 32. The stored contents of the buffer are input to the second cycle measurement unit 32, the rotation determination unit 33, and the equivalent value calculation unit 36.

The second period measuring unit 32 has a second timer which is a timer realized by software. The second cycle measurement unit 32 executes the count operation of the second timer for each count cycle Tc, and resets the count value according to the switching signal Sx, triggered by the change in the detection pattern (U, V, W). The second cycle measurement unit 32 outputs the count value obtained immediately before the reset as the second cycle value Cpt representing the cycle Tpt at which the pattern changes. Further, the second cycle measurement 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 compares the previously acquired detection pattern with the newly acquired detection pattern with reference to the pattern table shown in FIG. 2, and changes the detection pattern (U, V, W). Therefore, the rotation direction of the rotor 51 is determined, and the 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 to be CW, and when it changes from the bottom to the top, it is determined to be CCW. The rotation determination signal Sr is input to the equivalent value calculation unit 36 and the electric 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 value, and outputs a low-speed determination signal Sv indicating 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 rotation speed of the rotor rotation speed by the count cycle Tc. That is, when the second cycle value Cpt exceeds the low speed threshold value, the low speed determination unit 34 reduces the rotor rotation speed to less than the lower limit rotation speed, that is, the rotation speed that cannot be measured by the hardware timer 3c. It is determined that there is. Further, the low speed determination unit 34 determines that the rotor rotation speed does not reach the lower limit rotation speed even when the count value C2 is not reset even if it exceeds the low speed threshold value.

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

The periodic 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 Cyy representing the electric angle period of the rotor 51. Output as periodic data Dcy. Specifically, when the low speed determination signal Slow indicates that the rotor rotation speed is lower than the lower limit rotation speed, the second data [max] is selected as the periodic data Dcy. When the rotor rotation speed is equal to or higher than the lower limit rotation speed, the first data [n] is selected as the periodic data Dcy. The selected periodic data Dcy is input to the electric angle calculation unit 38.

The equivalent value calculation unit 36 includes a signing unit 361, a limit setting unit 362, and a conversion unit 363.
The coding unit 361 acquires the count value C2 and the second period value Cpt from the second period measurement unit 32 for each count cycle Tc, and according to the equation (1), the coded count value SC representing the phase in the pattern period. Is calculated.

SC = Sign × (C2 ÷ Cpt) × ([max] × 60 ÷ 360) (1)
That is, the signing 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, as the pattern cycle (that is, 60 [deg]). The signed count value SC is calculated by multiplying the value converted into the minute value and further assigning the sign Sign according to the rotation determination signal Sr. Specifically, the symbol Sign is a plus sign when the rotation direction indicated by the rotation determination signal Sr is CW, and is a minus sign when the rotation direction is CCW.

The limit setting unit 362 acquires a detection pattern (U, V, W) from the pattern generation unit 31, refers to the pattern table, and has a lower limit angle αL and an upper limit corresponding to the acquired detection pattern (U, V, W). The angle αU is acquired, and the lower limit CL and the upper limit CU are calculated according to the 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, by multiplying the result by the saturation value [max] which is the upper limit of the count value of the hardware timer 3c. , Lower limit CL and upper limit CU are calculated. The lower limit value CL and the upper limit value CU represent a range of values that the timer equivalent value Ce can take 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. Further, the conversion unit 363 adds the signed count value SC from the signing unit 361 to the selected reference value Cf. Specifically, when the rotation direction is CW, the addition of the lower limit value CL which is the reference value Cf and the count value of the plus sign is executed, and when the rotation direction is CCW, the upper limit value CU which is the reference value Cf is executed. And the count value of the minus sign are added, that is, the count value is subtracted from the upper limit value CU. Further, 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. If the addition result is out of the permissible range, the conversion unit 363 outputs the 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 which is a guard value is set as the timer equivalent value Ce, and when the value is smaller than the lower limit value CL, the lower limit value CL which 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 rotation position of the rotor 51) within the range of 60 [deg] with the electric angle specified by the detection pattern (U, V, W), and further. Using the detection pattern (U, V, W), the value converted into a value representing the phase within the range of 360 [deg] in the electric angle (that is, one cycle) is output as the timer equivalent value Ce.

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

The electric angle calculation unit 38 sets the periodic data Dcy as the first periodic value Ccy, and based on the first periodic value Ccy, the instantaneous value Cin, and the rotation determination signal Sr, when the rotation determination signal Sr is CW (4). ), When the rotation determination signal Sr is CCW, the reference electric angle θ is calculated according to the equation (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 ÷ Cy × 360 [deg] (4)
θ = -Cin ÷ Cy x 360 + 180 [deg] (5)
Here, the periodic data Dcy is used as it is as the first periodic value Ccy, but the present invention is not limited to this. For example, assuming that the period data Dcy for the past N cycles is represented by D1 to DN, as shown in Eq. (6), the period data D1 to DN for N cycles with the electric angle corresponding to one cycle in the mechanical angle. The average value may be used as the first cycle value Cy. 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 winding of the stator 52 according to the reference electric angle θ.

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

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

Although not shown, the first cycle value Ccy is acquired every processing cycle Tp or every count cycle Tc, and the value changes every one cycle of the electric angle. The second cycle value Cpt is acquired for each count cycle Tc, and the value changes every 60 [deg] of the electric angle. The timer equivalent value Ce is calculated for each count cycle Tc.

The reference electric angle θ is calculated for each processing cycle Tp.
The rotation determination signal Sr is confirmed for each processing cycle Tp, and changes at the timing when the detection pattern (U, V, W) changes. The low speed determination value Sv is confirmed for each 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 count cycle Tc based on the cycle data Dcy, and the reference electric angle θ is calculated for each processing cycle Tp using the instantaneous value Cin and the first cycle value Ccy. Will be done.

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

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

At low speed operation, the second data [max] is selected as the periodic data Dcy. That is, the saturation value representing the period at the lower limit rotation speed is used as the period data Dcy, and by extension, the first period value Ccy.

FIG. 4 shows a timing diagram when the rotor 51 is in non-low speed operation, but 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 diagram is the same except that the instantaneous value Cin (that is, the timer equivalent value Ce) calculated by using the second timer operated by the software instead of the hardware timer 3c is used.

FIG. 5 illustrates a guard value set from a reference electric angle θ calculated based on a timer equivalent value and 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 electric angle θ, the alternate long and short dash line is the guard value, and the broken line is the theoretical value of the reference electric angle θ.

During low-speed operation, the count value [max] representing the cycle at the lower limit rotation speed is used to calculate the first cycle value Ccy. Therefore, as the rotation speed approaches zero, the first cycle value Ccy is higher than the actual value. It will be underestimated, and the reference electric angle θ will be calculated to be larger than the theoretical value. However, since the guard value is set for each pattern cycle in which the detection pattern (U, V, W) changes and the value of the reference electric angle θ is limited by the guard value, an error is accumulated 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, but it is necessary to compare the detection patterns over a plurality of pattern cycles to determine the rotation direction. , There is a delay with respect to the actual situation. Due to this effect, in the vicinity of time 6 in FIG. 5, there is a deviation that the basic electric angle θ increases even though the electric angle actually decreases. However, the deviation of the basic electric angle θ after the determination of the rotation direction is correctly reflected from the theoretical value 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 rotation speed is lower than the lower limit rotation speed that cannot be measured by the hardware timer 3c, the reference electric angle θ is calculated using the second timer that operates at a slower count cycle Tc. do. Therefore, even when the rotor rotation speed is lower than the lower limit rotation speed, the rotor position can be estimated accurately. Specifically, in the hardware timer 3c that operates with the clock of fhwt [Hz], the lower limit rotation speed that can be measured is 60 ÷ the number of pole pairs ÷ (216 / ^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 logarithm ÷ (216 / (1 /). Tc)) It can be reduced to [rpm].

(2) When the second timer is used, the phase within the electrical angle cycle is not directly measured, but the pattern cycle in which the detection pattern (U, V, W) changes and the phase within the pattern cycle are measured. However, this is converted into a timer-equivalent value that represents the phase within the electrical angle period. Therefore, the reference electric angle can be estimated in a shorter time as compared with the case of directly measuring the phase within the electric angle period. Further, since the timer equivalent value Ce is the same value as the first timer value HC, the reference electric angle θ can be calculated by the same calculation regardless of which value is selected as the instantaneous value Cin, which is the conventional configuration. Can be used effectively.

(3) By setting a guard value according to the detection pattern (U, V, W) when measuring the phase in the pattern cycle, the error in the pattern cycle is accumulated across the pattern cycle. It is designed not to happen. Therefore, during low-speed operation, although the contribution of disturbance to the change in rotation speed is large, the influence can be limited to within each pattern period, and the estimation accuracy of the reference electric 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 the hardware, so that the lower limit of the measurable rotation speed is greatly reduced. Can be improved.

[4. Other embodiments]
Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments, and can be variously modified and implemented.

(A) In the above embodiment, one count equivalent value Ce is calculated using one second timer, but a plurality of counts are calculated using a plurality of second timers having different count cycles Tc. It may be configured so that the equivalent value Ce is calculated. That is, the longer the count cycle Tc, the lower the resolution of the rotation speed while the lower speed can be measured. That is, by using a plurality of count equivalent values Ce that realize the resolution according to the rotation speed to be measured, the lower limit of the measurable rotation speed can be further lowered while maintaining the required resolution.

(B) In the above embodiment, the equivalent value calculation unit 36 adds a signed count value SC based on a value determined by the detection pattern (U, V, W) and the rotation direction to obtain a 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 the value obtained at the end of the immediately preceding pattern cycle as a reference. In this case, even if the determination of the rotation direction is incorrect, the value at the start of the pattern cycle is always the value at the end of the immediately preceding pattern cycle. Therefore, when the determination of the rotation direction is incorrect, the timer equivalent value Ce in the pattern cycle becomes a constant value from the start to the end, but the timer equivalent value Ce is in the direction opposite to the actual phase change. You can prevent it from changing.

(C) A plurality of functions possessed by one component in the above embodiment may be realized by a plurality of components, or one function possessed by one component may be realized by a plurality of components. .. Further, a plurality of functions possessed by the plurality of components may be realized by one component, or one function realized by the plurality of components may be realized by one component. Further, a part of the configuration of the above embodiment may be omitted. Further, at least a part of the configuration of the above embodiment may be added or replaced with the configuration of the other above embodiment. It should be noted that all 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 above-mentioned motor control device, a system having the motor control device as a component, a program for operating a computer as the motor control device, a non-transitional actual record of a semiconductor memory or the like in which this program is recorded, etc. The present disclosure can also be realized in various forms such as a method for estimating a medium and a rotor position.

1 ... Motor control device, 2 ... Interface unit, 3 ... Control unit, 3a ... CPU, 3b ... Memory, 3c ... Hardware timer, 4 ... Drive circuit, 5 ... Brushless motor, 31 ... Pattern generation unit, 32 ... Second 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 ... signing unit, 362 ... limit setting unit, 363 ... conversion unit.

Claims (4)

A motor control device (1) that drives a brushless motor (5).
It is configured to generate a detection pattern (U, V, W) corresponding to a plurality of rotation positions that can be taken during the electric angle cycle, with the period during which the rotor (51) makes one rotation at the electric angle as the electric angle cycle. Pattern generation unit (31) and
A hardware timer that has a preset bit width, performs a count operation according to a clock signal whose period is set according to the resolution of the rotation speed, and resets the count value for each electric angle period according to the detection pattern. A first cycle measuring unit (35) configured to measure a first cycle value (Ccy) representing the electric angular cycle using a first timer (3c), and a first cycle measuring unit (35).
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 each time the detection pattern changes. A second period measuring unit (32) configured to measure a second period value (Cpt) representing
The second timer value (C2), which is the count value of the second timer, is acquired, and the second timer value corresponds to the value counted in the count cycle using the detection pattern and the second cycle value. The equivalent value calculation unit (36) configured to convert to the timer equivalent value (Ce) to be used, and
The rotation speed of the rotor is determined by setting the count value of the first timer as the first timer value (HC) and the rotation speed of the rotor at which the first timer value is saturated during the electric angle cycle as the lower limit rotation speed. A low-speed determination unit (34) for determining whether or not the rotation speed is smaller than the lower limit rotation 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 to be smaller than the lower limit rotation speed, it corresponds to the timer. An instantaneous value arbitrator (37) configured to select a value,
Using the instantaneous value (Cin), which is the value selected by the instantaneous value arbitration unit, and the first period value, the reference electric angle (θ) representing the electric angle within the electric angle period is calculated. A motor control device including a configured electric angle calculation unit (38). The motor control device according to claim 1.
The equivalent value calculation unit is a motor control device configured to generate the timer equivalent value within a range from a lower limit value set in advance for each detection pattern to an upper limit value. The motor control device according to claim 1 or 2.
The first cycle measuring unit is an average value of the count values over a plurality of the electric angle cycles when the change of the count value acquired for each electric angle cycle is within a preset allowable range. Is set as the first cycle value, and when the change of the count value exceeds the permissible range, the latest count value is set as the first cycle value.
Motor control device. The motor control device according to any one of claims 1 to 3.
The first cycle measuring unit is configured to set the saturation value of the first timer as the first cycle value when the rotation speed of the rotor is smaller than the lower limit rotation speed.
Motor control device.

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