JP6383128B1 - Method for estimating inductance electromotive force of motor and field position estimating method - Google Patents

Abstract

The present invention provides a method for estimating an inductance electromotive force estimated value VLr with the same program from zero speed to the maximum rotational speed, and using the inductance electromotive voltage estimated value VLr, the motor performs a field operation from zero speed to the maximum rotational speed. There is no need to switch the position detection method, field position detection error can be reduced and smooth rotation can be realized, and only a single field position detection program is required. provide. An MPU 51 uses a property that an inductance electromotive voltage VL changes according to a field position and is proportional to an effective voltage, and a corresponding stationary time from a look-up table 56 according to a PWM duty ratio during operation. The inductance electromotive voltage VLs value is selected and read, and the read inductance inductance electromotive voltage VLs value is multiplied by the effective voltage ratio to estimate the inductance electromotive voltage estimated value VLr at a predetermined rotation angle. [Selection] Figure 8

Description

  The present disclosure relates to a method for estimating an inductance electromotive voltage and a field position estimating method for a motor such as a brushless DC motor.

  Conventionally, DC motors with brushes have been used as small DC motors, but brushless DC motors have appeared due to problems with brush sound, electrical noise, durability, and the like. Recently, sensorless motors that do not have a position sensor have attracted attention from the viewpoints of miniaturization, weight reduction, cost reduction, etc., and were first adopted for hard disk drives in the information equipment field. But it started to be adopted.

  FIG. 10 shows a configuration of a three-phase brushless direct current (DC) motor as an example of a sensorless motor not provided with a position sensor. A rotor 2 that rotates about the rotor shaft 1 is provided with a pair of permanent magnets 3 of S and N poles. The magnetic pole structure (IPM, SPM) or the number of poles of the permanent magnet field varies. In the stator 4, armature windings (coils) U, V, W are arranged on pole teeth provided with a phase difference of 120 °, and are star-connected through a neutral point (common) C.

  FIG. 11 shows a block diagram of a conventional sensorless driving circuit example. MOTOR is a three-phase sensorless motor. The MPU 51 is a microcontroller (control unit). INV 52 is an inverter circuit (output unit) having a three-phase half-bridge configuration. ZERO is a zero cross comparator 54 and a dummy common generator 55. Note that an actual drive circuit requires a power supply unit, a host interface unit, and the like in addition to this, but is omitted to avoid complication.

  FIG. 12 shows a timing chart of 120 ° energization as a typical example of the driving method of the three-phase brushless DC motor. Section 1 is from U phase to V phase, Section 2 is from U phase to W phase, Section 3 is from V phase to W phase, Section 4 is from V phase to U phase, Section 5 is from W phase to U phase, In the section 6, rectangular wave energization is performed from the W phase to the V phase. A broken line is an induced voltage waveform. HU to HW are output waveforms of a hall sensor built in the motor, and a conventional brushless DC motor with a position sensor performs excitation switching based on this signal.

  The illustrated sensorless driving method with 120 ° energization is driven by detecting the induced voltage zero cross point to detect the field position, but the induced voltage is not generated at zero speed, so the field position cannot be detected. Therefore, a method for estimating the field position by reading the electromotive voltage generated by the inductance deviation between the energized phases from the open phase terminal in the zero speed and low speed rotation regions is known, and the following documents are available as prior art.

Japanese Patent No. 5634963

Patent Document 1 described above is pulse-driven by a 120 ° energization method, and detects an electromotive voltage (hereinafter referred to as VL) generated by an inductance deviation between energized two phases in the zero speed and low speed regions to estimate the position. However, it does not correspond to the change of the VL value and the induced voltage at the time of rotation, and the error increases as the rotational speed increases from zero speed, and cannot be applied to the medium-high speed range.
Therefore, at about 10% of the maximum rotation speed, the above-described VL detection method is switched to a method of detecting an induced voltage (hereinafter referred to as VE) generated in the open phase by the linkage magnetic flux, and medium / high speed operation is performed. Regarding the field position detection after switching, VL = 0 is considered and only VE detection is performed. However, VL is generated even during the middle / high-speed rotation, and since it is set to 0, a field position detection error also occurs. Yes.

Therefore, since the VL value at rest is used in spite of the rotation in the low speed range, and in the middle and high speed range, it is set to 0 despite the occurrence of the VL value. There is a problem that field position detection errors occur in the region.
In addition, the error is particularly large near the detection method switching speed, and the control characteristics change greatly at the time of switching, which is not preferable. In addition, multiple field position detection programs must be prepared for low speed and medium / high speed. There is also a problem that the control software becomes complicated, for example, it is necessary to set a binary value at the time of increase and decrease to prevent vibration at the time and to give a hysteresis characteristic to the switching operation.

  Disclosures applied to some embodiments described below are made to solve the above-described problems, and the purpose of the disclosure is to generate an inductance electromotive voltage VL with the same program from the zero speed to the maximum rotational speed. A method for estimating the value is provided, and it is not necessary for the motor to switch the field position detection method from zero speed to the maximum rotational speed by using the inductance electromotive voltage estimated value VLr, thereby reducing field position detection error and smooth rotation. It is an object of the present invention to provide a field position estimation method for an electric motor that can be realized, requires only a single field position detection program, and realizes reduction of software development load.

  A method of estimating an inductance electromotive force of an electric motor including a rotor having a permanent magnet field and a stator having a three-phase coil, which is supplied with a constant voltage DC power source and started by energization at 120 ° by a pulse width modulation method. , PWM control of the coil output in accordance with a command from the host controller, an output unit that bi-directionally energizes the coil via the half-bridge inverter circuit, a measurement unit that A / D converts the coil voltage and sends it to the control unit, The energization angle information and the energization pattern information in units of 60 ° energization sections capable of continuous rotation are stored, and based on this, the output unit is switched to switch the energization state, and the measurement value is input from the measurement unit. ° the control section for determining the field position in the energization section, the permanent magnet field is previously stopped at a predetermined angle in the energization section, and PW is applied at a predetermined voltage. When energized, the potential difference from the energized phase voltage / 2 that appears at the open phase terminal due to the inductance deviation between the energized two phases is set as the inductance electromotive voltage VL, and the static inductance electromotive voltage VLs value corresponding to the PWM duty ratio is obtained by actual measurement, Pre-operation preparatory step for storing in the storage unit in the control unit in association with the PWM duty ratio, storing the energization phase voltage at the time of measurement of the stationary inductance electromotive voltage VLs as an initial voltage, and storing the induced voltage constant; The rotational speed of the rotor is detected, the induced voltage of the energized two phases at the predetermined rotation angle is determined from the rotational speed N and the induced voltage constant KE, and the sum is set as the energized phase induced voltage VE, and the energized interphase voltage VS is measured. Dividing the difference between the energized phase voltage VS and the energized phase induced voltage VE by the initial voltage to obtain an effective voltage ratio; The control unit uses the property that the inductance electromotive voltage VL changes according to the field position and is proportional to the effective voltage, and from the storage unit according to the PWM duty ratio during operation, The inductance electromotive voltage VLs value is selected and read, and the inductance electromotive voltage VLr estimated value at the predetermined angle is estimated by multiplying the read inductance electromotive voltage VLs value by the effective voltage ratio.

Among the three-phase coils, the voltage appearing in the open phase is composed of two electromotive voltages, and one is an electromotive voltage due to an inductance deviation between energized two phases (hereinafter referred to as “inductance electromotive voltage VL”), and an open-phase induced voltage ( Hereinafter, “open phase induced voltage VEz”) is superimposed. The inductance electromotive voltage VL changes according to the field position and is substantially proportional to the effective voltage. When attention is paid to the rotational speed, the effective voltage is [interphase voltage-energized phase induced voltage]. As the rotational speed increases, the effective voltage decreases and the inductance electromotive voltage VL decreases. On the other hand, the induced voltage increases as the rotational speed increases, and therefore the open phase induced voltage VEz increases.
In this way, the inductance electromotive voltage VL during rotation changes in accordance with the field position and is further proportional to the effective voltage, so that the detection position of the inductance electromotive voltage VL is set to a predetermined value within the energization section of the 120 ° energization method. Limiting the angle to an angle (for example, the end point of the section), using the stationary inductance electromotive voltage VLs value at a predetermined angle as a reference value, detecting the rotation speed and estimating the inductance electromotive voltage according to the energized interphase voltage, the rotation speed, and the PWM duty ratio The value VLr can be estimated. Although the induced voltage needs to be calculated in the process of estimating the inductance induced voltage estimated value VLr, it can be calculated because the detection angle is determined. It should be noted that the estimation calculation of the inductance electromotive force estimated value VLr is preferably performed immediately after the rotation speed is detected at the starting point of the energization section.
In addition, since the polarity of the inductance electromotive force estimated value VLr and the open phase induced voltage VEz value is inverted for each energization interval, it is necessary to invert the sign for each energization interval to match the sign with the stationary inductance electromotive voltage VLs value.

A method for estimating a field position of an electric motor that estimates a field position using the estimated inductance electromotive voltage value VLr during rotation, wherein the rotational speed N of the rotor and an induced voltage constant at a section start point of a predetermined energization section during operation. A step of obtaining an open-phase induced voltage VEz at a predetermined angle in the current energization section from KE by (Equation A), and VE = KE × N × SIN (θ) × 1.5 (Equation A) (KE = Induced voltage constant, N = Number of rotations, θ = Field angle when the excitation section intermediate point is 0 ° (or 180 °)) The open-phase induced voltage VEz is set to the inductance induced voltage estimated value VLr (formula B And Vth = VLr + VEz (Formula B) The control unit periodically generates neutral points. Against potential The comparison threshold Vth and magnitude measures the Hosho voltage VZ, the determining a section end point When exceeding the threshold value Vth, and switches the excitation interval.
Thus, it is preferable to perform the estimated value calculation of the open phase induced voltage VEz value and the inductance induced voltage estimated value VLr immediately after detecting the rotation speed at the starting point of the energizing section, etc. The open phase voltage can be estimated. Therefore, the end point of the section can be detected by measuring the open phase voltage VZ periodically (for example, PWM period) and comparing it with the threshold value Vth. If the section end point is detected, the excitation can be switched to the energization pattern of the next section. Can rotate continuously.

The upper limit of the duty range of the PWM duty ratio is set in the control unit in advance, and when a PWM duty ratio larger than the upper limit of the usage range is specified during operation, energization control is performed with a PWM duty ratio of 100%, and an estimated inductance electromotive force value VLr may be set to 0, and the open-phase voltage measurement period may be made asynchronous with the PWM carrier period and shorter than the PWM carrier period.
Pulse driving is normally performed at a PWM duty ratio of about 20% to 80%, but a value larger than the upper limit can be designated, and when a PWM duty ratio larger than the upper limit is designated, 100% energization is performed. When the PWM duty ratio is 100%, DC drive is used instead of pulse drive, so that an inductance electromotive voltage estimated value VLr is not generated and VLr = 0. Therefore, the threshold value is the open phase induced voltage VEz, and the field position is detected only by the open phase induced voltage VEz.
At that time, since the three-phase coil is energized continuously, there is no need to measure the open-phase induced voltage VEz in synchronization with the PWM carrier cycle. If the measurement cycle is shorter than the PWM carrier cycle, the upper limit of the rotation speed by PWM drive High-speed rotation that exceeds the limitations of The factor that limits the measurement time is almost the conversion time of the A / D converter. If a high-speed A / D converter is used, the maximum rotational speed can be increased several times in terms of control.
For example, in a 2-pole motor, the energization time per section at 100 kmin- ¹ o'clock is 100 us, and if the PWM carrier frequency is 20 kHz, there are only two PWM pulses per section, and it is difficult to control energization by PWM. However, if the PWM duty is 100%, that is, DC drive is performed and the open-phase voltage is measured at a cycle of 10 us, for example, the number of field position detections per section is 10, and controllability is improved and high-speed rotation of 200 kmin ⁻¹ is possible. Furthermore, since this method does not require detection of the zero-cross point, this point is also advantageous for high-speed rotation. Naturally, it is necessary to flow more coil current in a short time, and the power supply voltage must be increased.

When the section numbers 1 to 6 are assigned in order of the 120 ° energization method energization sequence, and the static inductance electromotive voltage VLs value in the odd section or even section is stored as a reference value in the lookup table, and when the lookup table is read out during operation In the even section (or odd section), the static inductance electromotive voltage VLs value is corrected by multiplying the correction coefficient set appropriately, or two look-up tables are prepared for the odd section and the even section, and the odd section and the even section are prepared. May be stored, and during operation, a look-up table may be selected for each energizing section to estimate the estimated inductance electromotive voltage VLr that is different between the odd-numbered section and the even-numbered section.
The polarity of the inductance electromotive voltage VL value is reversed in each section, and depending on the motor characteristics, the inductance electromotive voltage VL value may be smaller in the positive section than in the negative section, and the same inductance in the negative section and the positive section. When the estimated electromotive voltage value VLr is applied, a section with a short period and a section with a long period appear alternately and a minute vibration with a period of two sections is generated, which is not preferable.
Therefore, in order to reduce the two-period periodic field position detection error and suppress the vibration, the inductance electromotive force estimated value VLr may be different between the negative section (odd section) and the positive section (even section). As a correction method, for example, the inductance electromotive force estimated value VLr in the positive side section may be multiplied by the correction coefficient with the inductance electromotive voltage estimated value VLr in the negative side section as a reference. The correction coefficient can be determined at the motor design stage or the prototype stage.
Alternatively, two lookup tables are prepared for the negative section and the positive section, and the static inductance electromotive voltage VLs values are measured in both the negative section and the positive section and stored in the respective lookup tables. May select a look-up table for the negative interval and the positive interval.

If the above-described method for estimating the inductance electromotive voltage of the electric motor is used, the inductance electromotive voltage estimated value VLr can be estimated by the same program from the zero speed to the maximum rotational speed of the motor. In addition, it is not necessary for the motor to switch the field position detection method from zero speed to the maximum number of rotations using the estimated inductance electromotive voltage VLr, so that the field position detection error can be reduced and the field position detection method can be switched. Thus, it is possible to provide a field position estimation method for an electric motor that can realize a smooth rotation with no need for a single field position detection program and can reduce a software development load.
In addition, the method for estimating the inductance electromotive force of the electric motor and the method for estimating the field position can be used regardless of the IPM motor / SPM motor and have a wide range of applications.
In addition, since the open phase induced voltage VEz at the end point of the section is estimated at the start point of the energized section, detection of the zero cross point is not necessary, which is suitable for high speed rotation.
Further, since the field position can be accurately detected in the entire speed range of the motor, the efficiency and the noise are reduced.
Furthermore, the calculation load on the control unit is small and high-speed processing can be performed with a low-speed CPU, resulting in low cost and low power consumption.

It is explanatory drawing of the inductance electromotive voltage VL with respect to rotation speed, and the open phase induced voltage VEz. It is an example of the inductance electromotive voltage VLs approximate waveform of 1 electrical angle 6 section at the time of a rotor stationary. It is an example of an inductance electromotive voltage VL approximate waveform when changing the amount of magnetic saturation. It is an inductance electromotive voltage VL measurement waveform of an IPM motor. It is an inductance electromotive voltage VL measured waveform of the SPM motor. It is an example of actual measurement of inductance electromotive voltage VL when the power supply voltage is changed. It is a block block diagram of a motor drive circuit. It is a flowchart of the operation preparation process which estimates the inductance electromotive voltage VL. It is a flowchart of the driving | running process after a motor start. It is a block diagram of a sensorless motor. It is a block block diagram of the conventional motor drive circuit. It is a 120 degree electricity supply timing chart.

  Hereinafter, an embodiment of a field position detection method for an electric motor will be described with reference to the accompanying drawings. As an example of an electric motor, the present invention provides a sensorless motor having a permanent magnet field in a rotor, windings arranged in a stator with a 120 ° phase difference, star-connected, and phase ends connected to a motor output unit. It explains using.

  Hereinafter, as an example, a method for estimating an inductance electromotive voltage and a method for detecting a permanent magnet field position of a sensorless motor that sensorlessly drives a three-phase DC brushless motor will be described together with the configuration of the sensorless motor driving device. An embodiment of a three-phase brushless DC motor according to the present invention will be described with reference to FIG. As an example, a three-phase brushless DC motor including a stator 4 having a two-pole permanent magnet rotor and three slots is illustrated. The motor may be either an inner rotor type or an outer rotor type. The permanent magnet type field may be any of a permanent magnet embedded type (IPM type) motor and a surface permanent magnet type (SPM type) motor.

  In FIG. 10, a rotor 2 is integrally provided on a rotor shaft 1, and a two-pole permanent magnet 3 is provided as a field magnet. In the stator 4, pole teeth U, V, W are arranged to face the permanent magnet 3 with a 120 ° phase difference. A three-phase brushless DC motor is provided in which windings u, v, and w are provided on the pole teeth U, V, and W of the stator 4 and the phases are star-connected with a common C and wired to a motor driving device described later. . The common line is omitted because it is unnecessary.

Next, an example of a three-phase sensorless motor drive circuit is shown with reference to FIG.
As a driving method, 120 ° energization bipolar rectangular wave excitation is assumed.
MOTOR is a three-phase sensorless motor. The MPU 51 is a microcontroller (control unit). The MPU 51 stores field position information for designating six energization patterns for the three-phase coil (U, V, W) and 120 ° energization excitation switching sections (section 1 to section 6) corresponding to the respective energization patterns. In accordance with the rotation command RUN from the host controller 50, the output unit is switched to arbitrarily switch the excitation state.

The inverter circuit 52 (INV: output unit) energizes the three-phase coil and performs switching operation such as excitation phase switching or PWM control in order to control the motor torque. The inverter circuit 52 includes a diode connected in reverse parallel to the switching element, and half-bridge switching circuits that can be arbitrarily connected to the positive power supply line and the ground power supply line are provided for three phases.
The A / D conversion circuit 53 (ADC: measurement unit) is connected to the coil output terminals U, V, W, and simultaneously samples the coil voltages of the three phases by the conversion start signal from the MPU 51, and sequentially performs analog / digital conversion. The conversion result is sent to the MPU 51. Normally, the ADC 53 is built in the MPU 51. When the built-in ADC 53 is used, it is desirable to provide a voltage dividing circuit 57 using a resistor because the maximum input voltage is low. Thus, according to this proposal, the motor drive circuit can be configured very simply.
As will be described later, the lookup table 56 (LUT: storage unit) stores a static inductance electromotive voltage VLs value obtained by actual measurement in association with a PWM duty ratio, and between energized phases when measuring the static inductance electromotive voltage VLs. The voltage VS is stored as the initial voltage, and the induced voltage constant KE is stored.

(Description of inductance electromotive voltage)
Of the three-phase coils, the voltage appearing in the open phase that is not the energized phase is composed of two electromotive voltages, one is the inductance electromotive voltage VL due to the inductance deviation between the energized two phases, and the open phase induced voltage VEz is superimposed on it. The inductance electromotive voltage VL changes according to the field position and is substantially proportional to the effective voltage. When attention is paid to the rotational speed, the effective voltage is [interphase voltage-energized phase induced voltage]. As the rotational speed increases, the effective voltage decreases and the inductance electromotive voltage VL decreases. On the other hand, the induced voltage increases as the rotational speed increases, and therefore the open phase induced voltage VEz increases.

FIG. 1 shows the relationship between the rotational speed RPM, the inductance electromotive voltage VL, and the open phase induced voltage VEz at a predetermined angle (for example, the end point of the section) in the energization section. The sum of both is the estimated open phase voltage VZ, which is indicated by a thick solid line. In addition, an estimated value of the open phase voltage VZ ′ of the conventional method (low speed region is VL only, middle high speed region is VE only) is indicated by a broken line. The difference between VZ (thick solid line) and VZ ′ (broken line) is considered to be an error in the conventional method, and the error is large near the switching point N ′.
The inductance electromotive voltage VL will be described using a coil current equation.
I (t) = (V / R) · (1-e ^{−t · R / L} ) (Formula 1)
Here, I = coil current, t = pulse energization time, V = coil voltage, R = coil resistance, L = coil inductance. From the above equation (1), when I (t) is constant, V changes as L changes.

On the other hand, the coil inductance L changes according to the field phase angle, and the voltage change ΔV in the ideal state can be approximated by the following equation.
ΔV = cos (2θ) −m · sin (θ) (Formula 2)
Where θ = field phase angle, m = magnetic saturation coefficient. The first term on the right side is a spatial harmonic component, and the second term on the right side is a magnetic saturation component.
Since each phase is arranged with a phase difference of 120 °, an inductance deviation occurs between the two energized phases. Therefore, a difference occurs in the phase voltage, and the common potential (common connection point voltage) is neutral point potential (interphase voltage / 2). ). It is considered that this shift potential difference appears in the open phase due to the mutual induction action as an inductance electromotive voltage VL.
The voltage change ΔV becomes 6 patterns due to the 120 ° phase difference of each phase and the 180 ° phase difference due to reverse energization. The inductance electromotive voltage VL at the time of two-phase energization is a combination of the voltage changes ΔV of the two energization phases, and there are six patterns of the inductance electromotive voltage VL depending on the six energization patterns. Switch.

  FIG. 2 shows an example of an approximate waveform of the static inductance electromotive voltage VLs in one electrical angle 6 section. Inductance electromotive voltage VL approximate waveform when energized with a corresponding energization pattern for each section, section 1 is U-V energization, section 2 is U-W energization, section 3 is V-W energization, and section 4 is V- -U energization, section 5 is W-U energization, and section 6 is W-V energization. As can be seen from FIG. 2, the value of the inductance electromotive voltage VL is reversed between the sections.

The one-periodic change represented by the second term on the right side of (Equation 2) described above is considered to reflect the amount of magnetic saturation. By changing the coefficient m, the voltage change ΔV approximate waveform changes from two-periodic to one period. It is possible to approximate motors with various characteristics.
FIG. 3 shows an approximate waveform of the quiescent inductance electromotive voltage VLs for one electrical angle when the energization pattern is fixed to the U-V energization corresponding to the section 1 and the m value is changed to 0-3. Since it is UV energization, the detection range of the VL value is a 60 ° section from 30 ° to 90 °.
A permanent magnet embedded (IPM) motor has a small amount of magnetic saturation and corresponds to m = 0. A surface permanent magnet (SPM) motor has a relatively large amount of magnetic saturation and corresponds to m = 3. From the figure, it can be seen that the waveform of m = 1 shifts the phase of the zero cross point from 60 ° due to the inductance electromotive voltage VL, and when m = 2 to 3, the zero cross point does not exist in the energized section. In other words, it is considered that the SPM motor often cannot detect the zero cross point from the zero speed to the low speed due to the influence of the inductance electromotive voltage VL, and when the zero cross point detection method is adopted, the rotational speed at which a considerable induced voltage is generated. It can be understood that it is necessary to rotate by open loop control.

FIG. 4 shows an actually measured waveform of the inductance electromotive force VL of the IPM motor for the robot. It is a plot of 360 electrical data for one electrical angle measured by rotating in 1 ° steps while applying U-V excitation with PWM energization and measuring the open phase voltage.
FIG. 5 shows a measured waveform of an inductance electromotive voltage VL of an SPM motor for a hard disk drive. The measurement method is the same as in FIG. It can be seen that the zero-cross point does not occur in the energized section with approximately one periodicity.

  From FIG. 3 to FIG. 5, the inductance electromotive voltage VL approximate waveform has various gradients and zero-cross point phases even at rest, and the induced voltage at the time of rotation is superimposed on this, so that the field is highly versatile and stable. It turns out that position detection is not easy. In order to detect a practical field position, it is indispensable to grasp and correct the variation factor of the inductance electromotive voltage VL. Next, the variation factor of the inductance electromotive voltage VL will be described.

(Inductance voltage fluctuation factor)
The effective voltage is first mentioned as a factor of fluctuation of the VL value, and the inductance electromotive voltage VL value is proportional to the effective voltage. FIG. 6 shows a measured waveform of the inductance electromotive voltage VL when the power supply voltage Vdd (≈effective voltage) is changed while the PWM duty ratio and temperature are kept constant in a stationary state. It can be seen that the inductance electromotive voltage VL is proportional to the power supply voltage Vdd (≈effective voltage).
The effective voltage at the time of rotation is the difference between the interphase voltage and the induced voltage (interphase voltage-induced voltage). Therefore, an effective voltage can be obtained by detecting the rotation speed, calculating the induced voltage at the predetermined angle, and subtracting it from the interphase voltage. Since the operation preparation process for measuring the inductance electromotive voltage VLs at rest before operation, etc., is in a stationary state, the inductance electromotive voltage VLs value at rest can be obtained, and no induced voltage is generated. The effective voltage remains as it is, and the inductance electromotive voltage VL becomes the maximum value.
During operation, if the ratio of the effective voltage during the operation preparation process and the operation stroke (effective voltage ratio) is multiplied by the inductance electromotive voltage VLs value at rest, fluctuations in the inductance electromotive voltage VL due to the effective voltage can be corrected. That is, the voltage between energized phases is measured, and the effective voltage ratio is obtained by calculating (energized phase voltage−energized phase induced voltage) / (the initial voltage) by calculation. For example, when the measurement is performed at 12 V during the operation preparation process and 6 V during the operation process, the estimated inductance electromotive voltage VLr during operation can be estimated as 6/12 of the static inductance electromotive voltage VLs value.

Further, the value of the inductance electromotive voltage VL fluctuates in a complicated manner depending on the PWM duty ratio. On the other hand, the static inductance electromotive voltage VLs values based on a plurality of PWM duty ratios are stored in a lookup table (LUT: storage unit) at the time of initial measurement, and the operation corresponds to the lookup table according to the PWM duty ratio. By reading out the static inductance electromotive voltage VLs value, an inductance electromotive voltage estimated value VLr reflecting the fluctuation of the PWM duty ratio can be obtained. For example, if the interval width of the PWM duty ratio to be measured is set to 10% increments, 7 data of 20%, 30%, 40%, 50%, 60%, 70%, and 80% can be as little as possible, and the initial measurement time can be shortened. And saves memory.
Alternatively, a mathematical model for obtaining the inductance electromotive force estimated value VLr according to the PWM duty ratio is created, and the static inductance electromotive voltage VLs is measured at one or two points by changing the PWM duty ratio in the operation preparation process, and the parameters are specified and the mathematical model. Can be obtained by calculating the inductance electromotive force estimated value VLr having an arbitrary PWM duty ratio during the operation stroke. If the mathematical model is simplified, the inductance electromotive voltage VL value can be obtained only by integer calculation without using a SIN function or the like, and the calculation time can be reduced to several us or less.
The coil temperature varies depending on the ambient temperature, energizing current, energizing time, etc., and the coil resistance value varies greatly. However, the temperature resistance deviation between the coils is structurally small, and it is confirmed that the temperature dependence is very small even in actual measurement. doing.
As described above, the inductance electromotive force estimated value VLr can be estimated with high accuracy for various motors in a wide temperature range.

(Explanation of rotation operation)
By adding the open phase induced voltage VEz at a predetermined angle to the above-described inductance electromotive voltage estimated value VLr, the open phase voltage VZ at the predetermined angle can be estimated. The open phase induced voltage VEz at a predetermined angle is
VEz = KE × N × SIN (θ) × 1.5 (Formula A)
(KE = induced voltage constant, N = rotational speed, θ = field angle when the excitation section midpoint is 0 ° (or 180 °))
It is calculated by computing.
Further, the open-phase induced voltage VEz is added to the inductance induced voltage estimated value VLr (formula B).
Vth = VLr + VEz (Formula B)
The open-phase voltage with respect to the neutral point potential obtained by the addition is stored as the threshold value Vth.
Therefore, for example, the open phase induced voltage VEz at the end point of the 120 ° energization method section is calculated by calculating the induced voltage constant (known) × the number of rotations × SIN 30 ° × 1.5 with θ = 30 ° in (Formula A). Desired. Therefore, if the threshold Vth of the section end point is calculated at the section start point, the open phase voltage VZ is repeatedly measured at the PWM cycle, and it is determined whether the threshold value Vth is exceeded, the section end point can be detected, and the excitation pattern of the next section is switched. Can rotate continuously.

According to the motor field position estimation method described above, the inductance electromotive voltage estimated value VLr is estimated according to the rotational speed, and the induced voltage can be uniquely estimated according to the rotational speed, so that the field position detection error is eliminated. Highly accurate field position detection is possible with the same algorithm from zero speed to the maximum speed.
Furthermore, the conventional zero-cross point detection method requires a zero-cross point detection process and takes a long time to detect, but this method does not need to detect the zero-cross point and can instantaneously estimate the open phase voltage at the end point of the zone at the start point of the zone. Therefore, if the PWM duty ratio is set to 100% and the open phase voltage is read out in a cycle shorter than the PWM cycle, ultra-high speed rotation is possible. When the PWM duty ratio is 100%, the speed can be adjusted by pulse amplitude modulation (PAM) control.

  Hereinafter, an example of an operation procedure using the motor drive circuit shown in FIG. 7 will be described. The section end point is detected, and the power supply voltage and the PWM duty ratio are constant in the energization section. There are two operation modes. There are an operation preparation step for measuring the inductance electromotive voltage VLs at rest before the operation in advance and an operation step for continuous rotation after starting, and each step will be described with reference to a flowchart.

  FIG. 8 is a flowchart of an operation preparation process for estimating the inductance electromotive voltage VL. The permanent magnet field is positioned and stopped at the starting point of the energizing section. For example, the U phase is connected to +, the V phase is connected to GND, and self-excitation is stopped at 150 °. Alternatively, there is a method of stopping at the start point of the section by external force (STEP 1).

  The PWM duty ratio of the MPU 51 is set to the lower limit value of the use range (STEP 2). Next, PWM energization is performed for several cycles (for example, about 10 cycles) with an energization pattern corresponding to the start point of the energized section that has been stopped (STEP 3). At the end of the on-cycle of the final PWM energization cycle, the three-phase coil voltage is measured (STEP 4). Then, self-excitation is stopped for a short time (for example, about 100 ms) to prevent the field position shift, and positioning is performed so as to stop again at the section start point (STEP 5).

Next, the MPU 51 calculates a static inductance electromotive voltage VLs value.
The static inductance voltage VLs = VZ (open phase voltage) − (VS (energized phase voltage) / 2) is calculated (STEP 6).
The calculated static inductance electromotive voltage VLs is stored in a lookup table (LUT) 56 in association with the PWM duty ratio (STEP 7). Next, the PWM duty ratio is set to a larger value with a predetermined step width (for example, an increase of 10%) (STEP 8).
Here, it is determined whether or not the reset PWM duty ratio exceeds the use range upper limit (STEP 9), and if it is less than the use range upper limit, the process returns to STEP 3. If the PWM duty ratio is larger than the upper limit of the use range in STEP 9, the energized inter-phase voltage VS is stored as an initial voltage (STEP 10). Also, the induced voltage constant KE is stored (known at the design trial stage: STEP11).

  In addition, you may memorize | store the static inductance electromotive voltage VLs of both the odd-numbered area and the even-numbered area as needed. In that case, two look-up tables 56 may be prepared, and when the above measurement is completed, positioning to the start point of the next section and the same measurement may be performed. Thereafter, it is possible to shift to motor operation.

FIG. 9 is a flowchart of the operation process after starting the motor.
First, after the motor is started, when the excitation is switched, the rotation speed is calculated from the previous section time or the like (STEP 21). Then, the energized phase induced voltage VE is calculated by calculating the induced voltage of the energized two phases at the end of the energized section and adding the induced voltages of the two phases (STEP 22). The energized phase induced voltage VE is obtained as KE × N × 0.5 × 1.5 × 2 phase with θ = 30 ° in (Formula A). Similarly, the induced voltage of the open phase at the end point of the section is calculated and set as the open phase induced voltage VEz. The open-phase induced voltage VEz can be obtained by setting KE × N × 0.5 × 1.5, that is, the induced voltage of the energized two phases by 1/2, with θ = 30 ° in (Formula A) (STEP 23).

  Next, it progresses to STEP24 and the phase voltage of energized two phases is measured. Next, the effective voltage ratio is calculated using the measured energized interphase voltage VS. Effective voltage ratio = (energized phase voltage VS−energized phase induced voltage VE) / initial voltage is calculated (STEP 25). Next, the MUP 51 reads the value of the static inductance electromotive voltage VLs from the lookup table 56 according to the current PWM duty ratio (STEP 26). Then, the read value of the static inductance electromotive voltage VLs is multiplied by the effective voltage ratio to obtain an inductance electromotive voltage estimated value VLr (STEP 27). The inductance induced voltage estimated value VLr and the open phase induced voltage VEz are added and stored as the threshold value Vth (STEP 28).

  Next, proceeding to STEP 29, a three-phase coil voltage is measured for each PWM ON cycle. If the interphase voltage does not fluctuate at this time, only the voltage measurement of the open phase may be performed. Next, the open phase voltage with respect to the neutral point potential (energized phase voltage / 2) is calculated and set as the open phase voltage VZ (STEP 30). Here, it is determined whether or not the open phase voltage VZ exceeds the threshold value Vth (STEP 31). If the open phase voltage VZ is less than the threshold value Vth, the process returns to STEP 29. If the open phase voltage VZ is greater than or equal to the threshold value Vth in STEP 31, it is determined that the current-carrying section end point (STEP 32). When detecting the end point of the energization section, the MPU 51 switches the excitation, outputs the energization pattern of the next section through the inverter circuit 52, and continuously rotates.

  During high speed rotation, the PWM duty ratio can be set to 100%, that is, when the DC current is applied, the inductance electromotive voltage VL = 0, so that the VL calculation can be omitted. Therefore, the field position detection operation can be performed by calculating the open phase induced voltage VEz estimated value at the end point of the energization section and then periodically repeating the measurement of the open phase voltage VZ and the open phase induced voltage VEz estimated value. It becomes. Since the time required for the above field position detection is shorter than the PWM carrier cycle, the field position detection throughput can be increased and high-speed rotation is possible. Note that speed control when the PWM duty ratio is 100% can be realized by PAM control (detailed description of PAM control is not directly related to the present method and is omitted).

The procedure when the PWM duty ratio is 100% will be described below.
During operation, the following calculation is performed during the spike period when switching the energized section. The rotational speed is calculated from the previous energizing section time, and the open phase induced voltage VEz at the end point of the section is calculated from the rotational speed and the induced voltage constant to obtain a threshold value. In the subsequent excitation interval, the open phase voltage VZ is measured, and the measurement is repeated until the obtained open phase voltage VZ matches or exceeds the threshold value.

  Furthermore, when the section intermediate point must be detected by a motor that has a large magnetic saturation and does not generate a zero cross point during low-speed rotation, the section intermediate point, that is, the position of the 30 ° phase from the start point may be designated as the predetermined angle. According to this method, since the value of the inductance electromotive voltage estimated value VLr at the midpoint of the section can be estimated and detected, the zero cross point can be correctly detected even if the motor does not generate a zero cross point during low speed rotation. The implementation procedure is the same as that in the section end point detection operation described above.

  According to the above-described method for estimating the inductance electromotive force and the method for estimating the magnetic field position of the motor, it is possible to estimate the inductance electromotive force estimated value VLr with the same program from the zero speed to the maximum rotational speed of the motor. In addition, using the estimated inductance voltage VLr, it is not necessary for the motor to switch the field position detection method from zero speed to the maximum number of rotations, and field position detection errors can be reduced and smooth rotation can be realized. A single program is sufficient, and the software development load can be reduced.

  Various configurations of the motor drive circuit and control program are conceivable, and the present invention is not limited to the mode disclosed in the present embodiment, and an electronic circuit engineer or a programmer (a person skilled in the art) does not depart from the scope of the present invention. The change of the circuit configuration and the change of the program configuration, which can be naturally performed if there are, are included.

  DESCRIPTION OF SYMBOLS 1 Rotor shaft 2 Rotor 3 Permanent magnet 4 Stator 50 Host controller 51 MPU 52 Inverter circuit (INV) 53 A / D converter (ADC) 56 Look-up table (LUT) 57 Voltage divider circuit VE Energized phase induced voltage VEz Open Phase induced voltage VL Inductance voltage VLs Inductive voltage at rest VLr Estimated value of inductance voltage VS Interphase voltage VZ Open phase voltage Vth threshold

Claims (4)

Method for estimating inductance electromotive force of an electric motor including a rotor having a permanent magnet field and a stator having a three-phase coil and supplying a constant voltage DC power source and starting by energizing 120 ° in a pulse width modulation (PWM) method In addition, an output unit that bidirectionally energizes the coil via a half-bridge type inverter circuit, a measurement unit that performs A / D conversion of the coil voltage and sends the coil voltage to the control unit, and a coil output in accordance with a command from the host controller. The storage unit stores energization angle information and energization pattern information in units of 60 ° energization sections that can be controlled and continuously rotated, and based on this, the output unit is switched to switch the energization state, and measurement is performed from the measurement unit And a controller for determining a field position in the 60 ° energization section when a value is input,
When the permanent magnet field is previously stopped at a predetermined angle in the current-carrying section and PWM power is supplied at a predetermined voltage, the potential difference from the current-phase voltage / 2 that appears at the open-phase terminal due to the inductance deviation of the current-carrying two-phase is determined as the inductance voltage. As VL, a static inductance electromotive voltage VLs value corresponding to the PWM duty ratio is obtained by actual measurement, stored in the storage unit in association with the PWM duty ratio, and an energization phase voltage VS at the time of measuring the static inductance electromotive voltage VLs is obtained. A pre-operation preparation step of storing as an initial voltage and storing an induced voltage constant KE;
The rotational speed of the rotor is detected during operation, the induced voltage of the energized two phases at a predetermined rotation angle is determined from the rotational speed N and the induced voltage constant KE, and the sum is set as the energized phase induced voltage VE, and the energized interphase voltage VS is measured. Dividing the difference between the energized phase voltage VS and the energized phase induced voltage VE by the initial voltage to obtain an effective voltage ratio,
The control unit uses the property that the inductance electromotive voltage VL varies depending on the field position and is proportional to the effective voltage, and the corresponding static inductance electromotive voltage from the storage unit according to the PWM duty ratio during operation. A method for estimating an inductance electromotive force of a motor, wherein a VLs value is selected and read, and the inductance electromotive voltage estimated value VLr at the predetermined angle is estimated by multiplying the read inductance electromotive voltage VLs value by the effective voltage ratio. . A field position estimation method for an electric motor that estimates a field position using the rotation inductance electromotive force estimated value VLr obtained in claim 1,
A step of obtaining an open phase induced voltage VEz at a predetermined angle in the current energization section by calculation according to (Equation A) from the rotational speed N of the rotor and the induced voltage constant KE at the section start point of the predetermined energization section during operation;
VEz = KE × N × SIN (θ) × 1.5 (Formula A)
(KE = induced voltage constant, N = rotational speed, θ = field angle when the excitation section midpoint is 0 ° (or 180 °))
Storing the open-phase voltage estimated value for the neutral point potential obtained by adding the open-phase induced voltage VEz to the rotational inductance electromotive voltage estimated value VLr by (Equation B) as a threshold value Vth,
Vth = VLr + VEz (Formula B)
The controller estimates an open phase voltage VZ at a predetermined energization interval end point at a predetermined energization interval start point, periodically measures the open phase voltage VZ with respect to the neutral point potential, and compares the open phase voltage VZ with the threshold value Vth. A field position estimation method for an electric motor, wherein when the threshold value Vth is exceeded, it is determined that the end point of the section is reached, and the excitation section is switched. The upper limit of the PWM duty ratio is set in advance in the control unit,
When a PWM duty ratio larger than the upper limit of the use range is specified during operation, energization control is performed at a PWM duty ratio of 100%, the inductance electromotive voltage estimated value VLr is set to 0,
The field position estimation method for an electric motor according to claim 2, wherein the measurement period of the open phase voltage is made asynchronous with the PWM carrier period and shorter than the PWM carrier period.   When section numbers 1 to 6 are assigned in order of the 120 ° energization sequence in the energization sequence, the inductance electromotive voltage VLs value at rest in the odd or even period is stored in the lookup table as a reference value, and the lookup table is read out during operation In the even section (or odd section), the static inductance electromotive voltage VLs value is corrected by multiplying the correction coefficient set appropriately, or two look-up tables are prepared for the odd section and the even section, and the odd section and the even section are prepared. The inductive electromotive voltage VLs value at rest is stored in each, and during operation, a look-up table is selected for each energizing section to estimate the estimated inductance electromotive force value VLr in the odd section and the even power section. The method for estimating a field position of an electric motor according to claim 3.

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