JP2015220928A - Motor control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid irregularity in rotational speed of a motor.SOLUTION: A microcomputer 31 calculates a duty ratio on the basis of a speed command received from an air-conditioner ECU 82. In a case where an error between the calculated duty ratio and a reference duty ratio that is the closest to the duty ratio is within a predetermined range, the reference duty ratio is used as a command duty ratio. In a case where the error is larger than an upper limit value of the predetermined range, a reference duty ratio higher by one level than the reference duty ratio is used as the command duty ratio. In a case where the error is smaller than a lower limit value of the predetermined range, a reference duty ratio smaller by one level than the reference duty ratio is used as the command duty ratio. A target rotation number of a motor 16 is calculated on the basis of the command duty ratio. An inverter circuit 41 switches FETs 41A-41F on the basis of the target rotation number to convert a DC power supplied from a battery 80 into an AC power and to supply the AC power to the motor 16.

Description

  The present invention relates to a motor control device.

  A brushless DC motor has a rotor composed of permanent magnets provided in the circumferential direction of an output shaft that outputs rotational force, and a plurality of stators that are a kind of electromagnet are provided in the vicinity of the circumferential direction of the rotor. ing. The brushless DC motor generates a so-called rotating magnetic field in which the magnetic field polarity and magnetic flux density of each of the electromagnets constituting the stator change in a predetermined rotation direction by changing the voltage applied to each stator coil. To rotate the rotor.

  The voltage applied to the coil of the stator is generated, for example, by an inverter circuit composed of a switching element such as a FET (Field Effect Transistor), which is the power of a battery that is a DC power supply. The inverter circuit generates a voltage to be applied to a stator coil of a brushless DC motor (hereinafter referred to as “motor”) by turning on and off the switching element based on a duty ratio command output by a control circuit such as a microcomputer.

  However, in addition to determining the duty ratio of the voltage applied to the motor coil, the microcomputer, which is the control circuit, performs feedback of the voltage output from the inverter circuit or reading of the signal from the Hall element that detects the rotor position. Execute by interrupt processing. Due to such interruption processing, the duty ratio calculation processing is delayed, and as a result, there is a problem that the calculated duty ratio varies and an irregularity called so-called rotation ripple occurs in which the rotation speed of the motor fluctuates little by little.

  Patent Document 1 discloses a fan that avoids an irregular rotation speed of a motor by reducing a duty ratio of a voltage applied to a motor coil to a predetermined level when electric power supplied to the motor becomes an overcurrent. A motor control device is disclosed.

  Patent Document 2 discloses a control of a brushless motor that eliminates noise present in a signal indicating a rotor position obtained by digitizing an induced voltage signal generated by rotating the rotor, thereby avoiding irregular rotation speed of the motor. An apparatus is disclosed.

JP 2008-263668 A JP 2013-13279 A

  However, since the fan motor control device described in Patent Document 1 reduces the duty ratio of the voltage applied to the motor coil to avoid irregular rotation of the motor, the motor is stabilized at a desired rotational speed. There is a problem that there is a difficulty in rotating.

  Since the brushless motor control device described in Patent Document 2 excludes a part of the signal corresponding to the edge of the signal indicating the rotor position as noise, it is difficult to accurately calculate the rotor position. When the rotational speed is changed, the rotational speed may be irregular.

  The present invention has been made in view of the above, and an object of the present invention is to provide a motor control device capable of avoiding irregular rotation speeds.

  In order to solve the problem, the motor control device according to claim 1, wherein the target rotational speed is divided into a plurality of target rotational speed ranges when the target rotational speed is divided into a plurality of continuous target rotational speed ranges. Representing each target rotational speed in the rotational speed range and storing a reference duty ratio corresponding to each of a plurality of representative target rotational speeds set in stages, and a duty corresponding to the input rotational speed command If the degree of difference between the calculated duty ratio and the reference duty ratio closest to the calculated duty ratio is within a predetermined range, the closest reference duty ratio is used as the command duty ratio. If the degree of the difference is greater than the upper limit value of the predetermined range, a command duty ratio that is one step higher than the nearest reference duty ratio is set. A setting unit that sets a reference duty ratio that is one step smaller than the nearest reference duty ratio as a command duty ratio when the degree of difference is smaller than a lower limit value of the predetermined range; A target rotational speed setting unit that sets a representative target rotational speed corresponding to a duty ratio and a plurality of switching elements, and a direct current supplied from a battery by turning on and off the plurality of switching elements based on the representative target rotational speed A power conversion supply unit that converts electric power into AC power and supplies it to the motor.

  The motor control device uses the reference duty ratio as the command duty ratio when the degree of difference between the duty ratio calculated according to the command rotational speed and the reference duty ratio closest to the duty ratio is within a predetermined range. As a result, irregularities in the rotational speed of the motor can be avoided.

  The motor control device also provides a reference duty ratio that is one step higher than the reference duty ratio when the degree of difference is larger than the upper limit value of the predetermined range, and the degree of difference is smaller than the lower limit value of the predetermined range. In this case, by setting the reference duty ratio one step lower than the reference duty ratio as the command duty ratio, it is possible to avoid irregularities in the rotational speed of the motor even if an error occurs in the calculation of the duty ratio. .

  The motor control device according to claim 2 is the motor control device according to claim 1, wherein the degree of the difference is a difference obtained by subtracting the nearest reference duty ratio from the calculated duty ratio, or the nearest reference duty ratio. Is the ratio of the calculated duty ratio.

  According to this motor control device, the error of the calculated duty ratio is determined based on the difference between the reference duty ratio and the calculated duty ratio, or the ratio of the calculated duty ratio to the reference duty ratio, and according to the determined error. Select an appropriate reference duty ratio. As a result, even if an error occurs in the calculation of the duty ratio, it is possible to avoid an irregular rotation speed of the motor.

  A motor control device according to a third aspect is the motor control device according to the first or second aspect, wherein each of the plurality of representative target rotation speeds is a center value of each of the plurality of target rotation speed ranges.

  According to this motor control device, by setting the reference duty ratio to a value corresponding to the center value of the target rotational speed range, even if there is a slight fluctuation in the rotational speed command, the target rotational speed is changed stepwise. It is possible to avoid irregularities in the rotational speed of the motor.

It is the schematic which shows the structure of the motor unit using the motor control apparatus which concerns on embodiment of this invention. It is a figure which shows the outline of the motor control apparatus which concerns on embodiment of this invention. It is a block diagram which shows an example of the flow of the control signal in the motor control apparatus which concerns on embodiment of this invention. It is the schematic which showed the production | generation of the rotation speed command signal which is a digital signal. It is the schematic which shows calculation of command duty ratio from the rotation speed command signal in the motor control apparatus concerning embodiment of this invention. It is a flowchart which shows an example of the duty ratio determination process in the motor control apparatus which concerns on embodiment of this invention. It is the schematic which showed an example when the error arises in calculation of duty ratio by interruption processing, such as reading of the signal output from the Hall element which detects the position of the voltage output from the inverter circuit, or a rotor. It is the schematic which shows an example of the error correction of the command duty ratio in the motor control apparatus which concerns on embodiment of this invention. It is a table | surface which shows an example of the correspondence of the instruction | command rotation speed and reference | standard duty ratio in the motor control apparatus which concerns on embodiment of this invention.

  FIG. 1 is a schematic diagram showing a configuration of a motor unit 10 using a motor control device 20 according to the present embodiment. The motor unit 10 according to the present embodiment in FIG. 1 is a so-called blower motor unit used for blowing air from an in-vehicle air conditioner as an example.

  The motor unit 10 according to the present embodiment relates to a three-phase motor having an outer rotor structure in which a rotor 12 is provided outside a stator 14. The stator 14 is an electromagnet in which a lead wire is wound around a core member, and constitutes three phases of a U phase, a V phase, and a W phase.

  Each of the U-phase, V-phase, and W-phase of the stator 14 generates a so-called rotating magnetic field by switching the polarity of the magnetic field generated by the electromagnet under the control of the motor control device 20 described later.

  A rotor magnet is provided inside the rotor 12 (not shown), and the rotor magnet rotates the rotor 12 by responding to the rotating magnetic field generated by the stator 14.

  The rotor 12 is provided with a shaft 11 and rotates integrally with the rotor 12. Although not shown in FIG. 1, in this embodiment, the shaft 11 is provided with a multi-blade fan such as a so-called sirocco fan, and the multi-blade fan rotates together with the shaft 11 so It becomes possible.

  The stator 14 is attached to the motor control device 20 via the upper case 13. The motor control device 20 includes a substrate 22 of the motor control device and a heat sink 21 that dissipates heat generated from elements on the substrate 22.

  A lower case 50 is attached to the motor unit 10 including the rotor 12, the stator 14, and the motor control device 20.

  FIG. 2 is a diagram schematically showing the motor control device 20 according to the present embodiment. The motor control device 20 shown in FIG. 2 includes an inverter circuit 41 that generates a voltage to be applied to the coils 14U, 14V, and 14W of the stator 14 of the motor 16, and a microcomputer 31 that controls the inverter circuit 41.

  The inverter circuit 41 includes FETs 41A to 41F that are switching elements. The inverter circuit 41 turns the FETs 41 </ b> A to 41 </ b> F on and off based on the command duty ratio output from the microcomputer 31, thereby converting DC power supplied from the battery 80 into AC power and supplying the AC power to the motor 16. For example, the FETs 41A and 41D switch the power supplied to the U-phase coil 14U, the FETs 41B and 41E switch to the V-phase coil 14V, and the FETs 41C and 41F switch the power supplied to the W-phase coil 14W.

  The drains of the FETs 41A, 41B, and 41C are connected to the positive electrode of the on-vehicle battery 80 via a noise removing coil 43. The sources of the FETs 41D, 41E, and 41F are connected to the negative electrode of the battery 80 through the reverse connection prevention FET 44.

  In the present embodiment, a reverse connection prevention FET 44 and a noise prevention coil 43 are provided between a battery 80 as a power source and the inverter circuit 41. The reverse connection prevention FET 44 is a circuit for protecting elements constituting the motor control device 20 when the positive electrode and the negative electrode of the battery 80 are connected in reverse to the case shown in FIG. As an example, the reverse connection prevention FET 44 is configured by a so-called diode-connected FET having its drain and gate connected. The coil 43 is an element for suppressing noise generated by switching of the inverter circuit 41.

  In the present embodiment, the Hall element 12B detects the magnetic field of the sensor magnet 12A provided coaxially with the shaft 11. The microcomputer 31 detects the position (rotational position) of the rotor 12 based on the detected magnetic field, and controls switching of the inverter circuit 41 according to the rotational position of the rotor 12.

  Further, the microcomputer 31 receives a control signal from the air conditioner ECU 82 for controlling the air conditioner and a resistance value signal from the thermistor 46, and controls the switching of the inverter circuit 41 based on the input signals. In the present embodiment, a voltage sensor 48 that measures the voltage of the battery 80 is provided on the circuit.

  FIG. 3 is a block diagram showing an example of the flow of control signals in the motor control device 20 according to the present embodiment. As shown in FIG. 3, the command duty ratio calculation unit 52 in the microcomputer 31 calculates a command duty ratio based on the input rotation speed command signal. A target rotational speed calculation unit 54 in the microcomputer 31 calculates a target rotational speed of the motor 16 based on the command duty ratio.

  The rotation speed of the motor 16 is detected by the hall element 12B. The motor rotation speed calculation unit 56 in the microcomputer 31 calculates the actual rotation speed of the motor 16 based on the signal output from the Hall element 12B.

  The PID controller 58 in the microcomputer 31 feeds back the actual rotational speed of the motor 16 to the target rotational speed calculated by the target rotational speed calculating section 54 and outputs it as a motor output duty to the inverter circuit 41 which is a three-phase inverter. The inverter circuit 41 applies a voltage generated by turning on and off the FETs 41 </ b> A to 41 </ b> F that are switching elements based on the motor output duty to the motor 16.

  FIG. 4 is a schematic diagram showing generation of a rotation speed command signal which is a digital signal. As shown in the upper part of FIG. 4, the command value 202 input from the air conditioner ECU 82 is compared with the triangular wave carrier signal 200 using a circuit such as a comparator. As a result of the comparison, if the command value 202 is less than the carrier signal 200, a high level signal is output, and if the command value 202 is a PWM carrier signal 200 or more, a low level signal is output, the generated rotation The number command signal 204 is as shown in the lower part of FIG. The pulse width of the rotation speed command signal 204 varies depending on the command value 202 input from the air conditioner ECU 82.

FIG. 5 is a schematic diagram showing calculation of the command duty ratio from the rotation speed command signal in the motor control device 20 according to the present embodiment. FIG. 5 shows a case where the rotation speed command signal is a command for keeping the rotation speed of the motor constant. In the present embodiment, DOWN Edge when the rotation speed command signal changes from high level to low level and DOWN UP when the rotation speed command signal changes from low level to high level are detected, respectively, and DOWN Edge and DOWN The time when UP appears is measured with a free-run timer, and the command duty ratio is calculated from the measured time. For example, DOWN Edge appeared in time T _1, DOWN UP appeared in time T _2, when the re-DOWN Edge time T ₃ has occurred, the command duty ratio indicated by following equation (1) It becomes like this.
Command duty ratio = (T ₂ −T ₁ ) × 100 / (T ₃ −T ₁ ) (1)

Hereinafter, based on the measured times T _{3 to} T ₁₃ , the command duty ratio is calculated as shown in the lower part of FIG. If there is no error described later in the calculated command duty ratio, the calculated command duty ratio is used as a command, and the target rotational speed of the motor 16 is calculated based on the command.

FIG. 6 is a flowchart showing an example of the duty ratio determination process in the motor control device 20 according to the present embodiment. In step 300, DOWN Edge is measured stores the time T ₁ appeared in free-run timer rotational speed command signal.

In step 302, the time DOWN UP appeared in rotational speed command signal T ₂ measured by the free-run timer is stored, in step 304, the time again DOWN Edge to the rotational speed command signal appeared T ₃ free run timer Measure and memorize.

In step 306, calculates the duty ratio Dc using the equation (1) described above, in step 308, calculates an error △ _{D k,} in step 310, the error caused by the interrupt processing △ _{D k} is either a predetermined range not Determine whether.

  FIG. 7 shows an example in which an error occurs in the calculation of the duty ratio due to interrupt processing such as feedback of the voltage output from the inverter circuit 41 or reading of a signal from the Hall element 12B that detects the position of the rotor 12. It is the shown schematic. The change in the signal level of the rotation speed command signal is constant, and even when the motor is rotated at a constant speed, the time measurement by the free-run timer is delayed due to the influence of interrupt processing, and is calculated as a result. There is an error in the command duty ratio.

FIG. 8 is a schematic diagram showing an example of command duty ratio error correction in the motor control device 20 according to the present embodiment. In the present embodiment, reference duty ratios D _{1 to} D _n that are reference values of the command duty ratio are set stepwise. FIG. 9 is a table showing an example of a correspondence relationship between the target rotational speed and the reference duty ratio in the motor control device 20 according to the present embodiment. In the present embodiment, the target rotational speed is divided into a plurality of continuous ranges, and for each of the plurality of ranges, a plurality of representative target rotations that represent each target rotational speed of the plurality of ranges and that are set in stages. A reference duty ratio corresponding to each of the numbers is set. Each of the plurality of representative target rotational speeds is a center value of each of the plurality of ranges.

In Figure 8, _{V M1} as the center value of the target rotational speed _V 1, _{V 2, V M2} as the center value of the target rotational speed _V 2, _{V 3, V Mn} as the central value of the target rotational speed _{V n-1, V n -1} is shown as the representative target rotational speed. As an example, the representative target rotation speed _VMK-1 is calculated by the target rotation speeds _Vk , _Vk-1 and the following equation (2). Here, k is 1, 2, 3,..., N.
V _Mk−1 = (V _k + V _k−1 ) / 2 (2)

In FIG. 9, the reference duty ratio D ₁ corresponds to the range of the target rotational speeds V _{1 to} V ₂ , and the reference duty ratio D ₂ corresponds to the range of the target rotational speeds V _{2 to} V _3. The duty ratio is set stepwise corresponding to the change in the rotational speed. Each reference duty ratio than those corresponding to the representative target rotational speed of each, as shown in FIG. 8, the reference duty ratio D ₁ Representative target speed V _M1, the reference duty ratio D ₂ Representative target speed V _The reference duty ratio D _n−1 corresponds to _M2 and the representative target rotational speed V _Mn−1 .

  Further, in the present embodiment, the difference between the duty ratio calculated according to the command rotational speed and the reference duty ratio closest to the duty ratio, as shown by the colored area in FIG. If it is within the range, the reference duty ratio is set as the command duty ratio. When the error is larger than the upper limit value of the predetermined range, the reference duty ratio is one step higher than the reference duty ratio. When the error is smaller than the lower limit value of the predetermined range, the reference duty ratio is lower by one step. The reference duty ratio is set as the command duty ratio. The degree representing the difference is the difference between the calculated reference duty ratio closest to the calculated duty ratio and the calculated duty ratio, or the ratio of the calculated duty ratio to the closest reference duty ratio.

For example, to determine the difference between the calculated duty ratio D closest reference duty ratio _c D _k the calculated duty ratio, calculate the △ D _k as in the following formula (3), △ D _k Is determined to be within a predetermined range. When ΔD _k is within a predetermined range, the reference duty ratio D _k is set as the command duty ratio. △ D _k is a one-step higher reference duty ratio D _{k + 1} than the reference duty ratio D _k if larger than the upper limit of the predetermined range, △ D _k is the reference duty ratio D and if smaller than the lower limit of the predetermined range _The reference duty ratio D _k−1 that is one step lower than _k is set as the command duty ratio.
ΔD _k = D _c −D _k (3)

The predetermined range varies depending on the interval of each reference duty ratio, the motor specification, the purpose of use of the motor, and the like. In the present embodiment, the predetermined range is -4% to + 4%, for example. Alternatively, the lower limit value and the upper limit value of the predetermined range may be specifically calculated and set regardless of ΔD _k as described above. The correspondence relationship between the command rotational speed and the reference duty ratio, the numerical value of the predetermined range, the lower limit value and the upper limit value of the predetermined range may be stored in a ROM (Read Only Memory) in the microcomputer 31 or separately on the substrate 22. You may memorize | store in memory | storage devices, such as provided ROM or flash memory.

In step 310, the calculated duty ratio D _c is, for example, approximates the reference duty ratio D _k, and the error △ D _k with respect to the reference duty ratio D _k makes an affirmative determination in the case of a predetermined range. If the determination in step 310 is affirmative, in step 312, the reference duty ratio _Dk is output as a command duty ratio (k) to the target rotational speed calculation unit 54, and the process returns.

If the determination in step 310 is negative, it is determined in step 314 whether or not the error ΔD _k is a positive error. If the determination is affirmative, in step 316, the reference duty ratio D _{k + 1} is set as the command duty ratio (k + 1). It outputs to the target rotation speed calculation part 54, and a process is returned. If the determination in step 314 is negative, in step 318, the reference duty ratio _Dk-1 is output as the command duty ratio (k-1) to the target rotational speed calculation unit 54, and the process returns. The target rotational speed calculation unit 54 sets the representative target rotational speed corresponding to the command duty ratio output by the target rotational speed calculation unit 54 as the target rotational speed.

  As described above, in this embodiment, even when an error occurs in the duty ratio calculated due to the influence of the interrupt process, if the error is within a predetermined range with respect to the reference duty ratio, the reference duty ratio Is the command duty ratio. As a result, even when an error occurs in the calculation of the duty ratio due to the influence of the interrupt process, it is possible to avoid an irregular rotation speed of the motor.

DESCRIPTION OF SYMBOLS 10 ... Motor unit, 11 ... Shaft, 12 ... Rotor, 12A ... Sensor magnet, 12B ... Hall element, 13 ... Upper case, 14 ... Stator, 14U, 14V, 14W ... Coil, 16 ... Motor, 20 ... Motor controller, DESCRIPTION OF SYMBOLS 21 ... Heat sink, 22 ... Board | substrate, 31 ... Microcomputer, 41 ... Inverter circuit, 41A, 41B, 41C, 41D, 41E, 41F ... FET, 43 ... Coil, 44 ... Reverse connection prevention FET, 46 ... Thermistor, 48 ... Voltage sensor, DESCRIPTION OF SYMBOLS 50 ... Lower case, 52 ... Command duty ratio calculation part, 54 ... Target rotation speed calculation part, 56 ... Motor rotation speed calculation part, 58 ... PID controller, 80 ... Battery, 82 ... Air-conditioner ECU, 200 ... Carrier signal, 202 ... Command value, 204... Rotational speed command signal

Claims (3)

For each of the plurality of target rotation speed ranges when the target rotation speed is divided for each of a plurality of continuous target rotation speed ranges, the target rotation speed is set in a representative and stepwise manner for each of the plurality of target rotation speed ranges. A storage unit storing a reference duty ratio corresponding to each of the plurality of representative target rotation speeds;
When the duty ratio corresponding to the input rotational speed command is calculated, and the degree of the difference between the calculated duty ratio and the reference duty ratio closest to the calculated duty ratio is within a predetermined range, The closest reference duty ratio is set as the command duty ratio, and if the degree of the difference is larger than the upper limit value of the predetermined range, a reference duty ratio that is one step larger than the nearest reference duty ratio is set as the command duty ratio. A setting unit that sets a reference duty ratio that is one step smaller than the nearest reference duty ratio as a command duty ratio when the degree of the difference is smaller than a lower limit value of the predetermined range;
A target rotational speed setting unit for setting a representative target rotational speed corresponding to the command duty ratio;
A power conversion supply unit that includes a plurality of switching elements, converts DC power supplied from the battery to AC power by turning on and off the plurality of switching elements based on the representative target rotation speed, and supplies the AC power to the motor;
Including a motor control device.   The motor control device according to claim 1, wherein the degree of difference is a difference obtained by subtracting the closest reference duty ratio from the calculated duty ratio, or a ratio of the calculated duty ratio to the closest reference duty ratio.   3. The motor control device according to claim 1, wherein each of the plurality of representative target rotation speeds is a center value of each of the plurality of target rotation speed ranges.