JP2022186058A - Method for detecting rotor position of sensorless motor and sensorless motor drive method - Google Patents

Abstract

To provide a method for detecting a rotor position of a sensorless motor which is adapted for startup and low-speed rotation, and with which a position detection current, noise and vibration are reduced.SOLUTION: A sensing pulse signal in six conduction patterns of an electric angle 120° is generated and applied to a three-phase coil. An open-phase voltage immediately before the termination of a sensing pulse in two sections constituting a complementary section is measured and stored as a rotor position signal. A sign of a result of subtracting the stored two open-phase voltage values from each other is adopted as subtraction position information, and similar application, measurement and computation processing are performed on two remaining pairs of complementary sections to generate a total of three bits of subtraction position information, with logical operation performed thereupon, and a rotor position is thereby identified to be one of three pairs of complementary sections. Further, an amplitude is added to a neutral point potential of the open-phase voltage values in two sections constituting the identified complementary section and a magnetic saturation component is extracted. One section is selected from the two sections constituting the complementary section by the sign of an addition result, and the rotor position is finally identified to be one of conduction sections of the electric angle 120°.SELECTED DRAWING: Figure 7

Description

The present invention relates to a sensorless motor rotor position detecting method for detecting the rotor position of a sensorless motor and a sensorless motor driving method for starting the motor by a 120 electrical angle energization method after detecting the rotor position.

Conventionally, brushed DC motors have been used as compact DC motors, but brushless DC motors have emerged due to problems such as sliding noise, sliding resistance, electrical noise, durability, and space caused by the brushes. Recently, sensorless motors, which do not have position sensors, have attracted attention from the viewpoint of reducing size, weight, robustness, and cost, and were first used in hard disk drives in the information equipment field. However, it has started to be adopted.

FIG. 8 shows the configuration of a three-phase brushless direct current (DC) motor as an example of a sensorless motor having no position sensor. A rotor 2 rotating around a rotor shaft 1 is provided with a pair of permanent magnets 3 having an S pole and an N pole. There are various magnetic pole structures (IPM, SPM) or the number of poles of the permanent magnet field. On 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 via a neutral point (common) C. Some are delta-connected, connecting adjacent phases and having no neutral point.

FIG. 9 is a block diagram showing an example of a conventional sensorless motor drive circuit. MOTOR is a three-phase sensorless motor. The control circuit 51 (MPU) controls the gate output to the output circuit 57 according to the rotation command (RUN) from the host controller 50 (CONT). The output circuit 57 (INV) is an inverter circuit with a three-phase bridge configuration and sends out the coil output UVW to the motor. A zero-cross detection circuit (ZERO) is composed of a zero-cross comparator 59 and a dummy common generator 60 (COM). An actual sensorless motor drive circuit also requires a power supply section, a host interface section, a pre-driver circuit, etc., but they are omitted to avoid complication.

FIG. 10 shows a timing chart of energization at an electrical angle of 120° as a representative example of a three-phase brushless DC motor drive system. 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, Section 6 is energized with a rectangular wave from the W phase to the V phase. A dashed line is an induced voltage waveform. HU to HW are the output waveforms of Hall sensors incorporated in the motor, and a conventional three-phase brushless DC motor with a position sensor performs excitation switching based on these signals.

A sensorless drive system that does not use a position sensor is mainly used to detect the rotor position from the induced voltage. However, since no induced voltage is generated when stationary and the induced voltage is small even when rotating at low speed, position detection is difficult. Therefore, various methods of starting and rotating at low speed without detecting position have been put into practical use. In many DC motors, an open-loop method is often used in which a large direct current is applied for several seconds to forcibly position the rotor, and then a rotating magnetic field is generated to start the motor in forced synchronization and gradually increase the speed.

The method of forcibly initial positioning (aligning) by applying a direct current before starting in the above-mentioned open loop method requires a large current, takes a long time to complete positioning, and causes a collision stop state. There are various problems such as the inability to perform initial positioning in a restrained state. In addition, the occurrence of a start delay of several seconds significantly impairs the operability of the engine, making it unusable in many applications.

Therefore, a method was devised to detect the position of the rotor before the start and start the engine instantly. As a method of detecting the initial position before starting, there is a method of applying a plurality of high-current sensing pulses in a 120 electrical angle energization pattern to detect the magnetic saturation deviation and identify the rotor position. Alternatively, there is also a method of specifying the rotor position by simultaneous three-phase energization. (See Patent Document 1).

Japanese Patent No. 6284207

This sensing pulse method eliminates the need for initial positioning before starting, and has the effect of eliminating start delays. However, there is a problem that a large noise (click sound) and vibration are generated when a large current sensing pulse is applied. In addition, stress may be applied to the coil, which may cause insulation deterioration or burnout, thus increasing the load on the drive circuit and the DC power supply. Also, depending on the circuit configuration, a startup delay of several hundred milliseconds may occur, which may pose a problem in applications requiring instant startup.

Furthermore, since the induced voltage is small not only when the engine is stationary before starting but also when the engine is started at low speed, it becomes difficult to detect the rotor position. Since the forced synchronization method based on the open loop control described above does not detect the rotor position, there is a problem that the control may be lost if there is a load fluctuation during low speed rotation, and the starting is uncertain and the application is limited. In addition, there are many parameter settings such as forced commutation time, current value, ramp curve characteristics, etc., and it requires an excessive starting current, which is disadvantageous from the viewpoint of energy saving.

Therefore, we adopted an inductive sense method that detects the rotor position using the phenomenon that the open phase voltage changes according to the phase angle when PWM (Pulse Width Modulation) is energized between two coil leads connected to a 3-phase coil. A position closed loop system that rotates while detecting the position has also been proposed.
FIG. 11 shows an example of actual measurement of the open phase voltage of the inductive sensing method. A roughly sine wave with two periodicity is obtained by measuring the change in the open phase voltage when rotating by one electrical angle while applying the PWM current in the UV current pattern. Measurements are overwritten while changing the PWM duty ratio by 10%. In addition, for reference, the theoretical induced voltage waveform (single wave of one period) of the open phase is described. grow and become dominant.

However, the inductive sensing method can only be applied during forward rotation, and if the rotor rotates even slightly in reverse due to an external force at start-up, an induced voltage of opposite polarity is superimposed on the open phase, canceling out the voltage change due to the inductance, resulting in erroneous detection of the rotor position. There is Therefore, it is necessary to check whether the motor has been started correctly. For example, a method has been proposed in which a high-frequency sensing current is superimposed on the excitation current to check the rotor phase. becomes complicated.
Furthermore, the detection signal level of the inductive sense method depends on the PWM duty ratio as described above, and the usable range is approximately 20% to 80%. Rotor position detection is difficult. Therefore, there are restrictions on low-speed rotation, low-load operation, and high-load operation.
As described above, there are many problems with the open-loop method of sensorless driving of brushless DC motors, and improvements have been made with the sensing pulse method, the inductive sense method, and the like, but each method has its own problems.

The present invention has been made to solve the above-mentioned various problems, and its purpose is to apply it to start-up and low-speed rotation by energizing at an electrical angle of 120°, and to reduce position detection current, noise, and vibration. To provide a motor rotor position detection method and a sensorless motor drive method that reliably starts and rotates at a low speed by closed loop control using this method, and has no restrictions on the duty ratio of the excitation output and the energization method.

A rotor position detection method for a sensorless motor for sensorless driving of a brushless DC motor comprising a rotor having a permanent magnet field and a stator having a three-phase coil, comprising six energization sections in an electrical angle of 120° energization. A pair of two sections with a 180° phase difference is set as a complementary section, and a sensing command is received from the host controller to generate a sensing pulse signal for the three-phase coil, and the rotor position signal detected from the three-phase coil is input. and a three-phase bridge configuration output circuit that amplifies power and outputs a sensing pulse to a three-phase coil when a sensing pulse signal is input from the control circuit. When receiving a sensing command from the host controller, the control circuit generates sensing pulse signals of six energization patterns of 120° electrical angle energization, and applies the sensing pulses to the three-phase coils via the output circuit. a step of measuring open-phase voltages immediately before the end of the sensing pulse in the two sections forming the complementary section and storing them as rotor position signals; subtracting the stored open-phase voltage values of the two sections forming the complementary section from each other; The sign of the subtraction result is used as subtraction position information, and the same sensing pulse application, open phase voltage measurement, and arithmetic processing are performed for the remaining two pairs of complementary sections to generate subtraction position information of 3 bits in total; a step of specifying the rotor position to any one of the three pairs of complementary sections by performing a logical operation on the subtracted position information of; is added to extract the magnetic saturation component, one section is selected from the two sections constituting the complementary section according to the sign of the addition result, and finally the rotor position is set to one of the 120 electrical angle energization sections. and a step of identifying.
As a result, the control circuit has a large resistance to power supply voltage fluctuations and demagnetization, and can detect the rotor position from the stationary state to the extremely low speed rotation region. Sensing is performed instantaneously, and there is almost no delay in starting.In addition, the sensing current is small, and noise and vibration can be greatly reduced compared to the conventional high-current sensing pulse method.

The control circuit applies a sensing pulse for a predetermined time and measures the coil current at the end of the sensing pulse, or applies a sensing pulse of a predetermined current and measures the time required to reach a predetermined current value. Further, after the complementary section is identified, the control circuit generates a sensing pulse signal in the energization pattern of one section constituting the identified complementary section, and outputs the first sensing pulse through the output circuit to the three-phase coil. After a rest time corresponding to the first sensing pulse time, a sensing pulse signal is generated in the energization pattern of the other section constituting the complementary section, and the second sensing pulse is applied to three through the output circuit. For each of the sensing pulses applied to the phase coils, the control circuit detects the current value after energization for a predetermined time or the arrival time to reach the predetermined current, compares the two current values or the arrival time, and Based on this, either one of the two sections forming the complementary section may be selected, and the rotor position may be specified as one section of 120° energization.
As a result, the control circuit detects the amount of magnetic saturation with a current larger than the sensing pulse and determines the magnetic field polarity. It can be extended from the region to the slow rotation region.

When the rotor position detection is repeatedly performed, on the condition that the rotor does not rotate by one section or more between the previous position detection and the current position detection, when the previous complementary section number obtained by the previous position detection is given, the current complementary section number is given. If the section number is the same as the previous complementary section number, the current section number will be the same as the previous section number. The rotor position may be specified in one section of 120 electrical angle energization by returning one section number from the previous complementary section number when is one section back from the previous complementary section number.
As a result, the rotor position can be specified in one section of the 120° energization section only by specifying the complementary section with the subtraction position signal, and the application of the sensing pulse or the arithmetic processing for discriminating the polarity can be omitted, thereby reducing the noise. It is possible to reduce or shorten the time required for rotor position detection.

In the method of driving a sensorless motor, the energization to the three-phase coil is interrupted and the rotation speed of the rotor is detected from the induced voltage. During low speed rotation, a sensing step of performing a process of specifying the rotor position by any of the above sensorless motor rotor position detection methods, and determining an excitation pattern based on the rotor position specified in the sensing step and an energizing step of energizing for a predetermined time at an arbitrary PWM duty ratio, and alternately repeating the sensing step and the energizing step during low-speed rotation below a predetermined speed.
This enables Field Oriented Control (FOC) at startup and at low speed rotation, ensuring rotation without loss of control even when load fluctuations, stalls, and reverse rotation occur at startup and low speed rotation. be able to.

According to the sensorless motor rotor position detection method, startability and controllability are improved, and it is possible to replace brushed motors and sensored brushless motors with sensorless motors in many applications. Also, the open-loop start-up of sinusoidal drive can be changed to closed-loop start-up.
Specifically, the rotor position detection time is shortened to about one-fifth of that of the conventional method, and the rotation speed range in which the position can be detected is expanded.
Sensing current is reduced to about 1/10 of the conventional method, reducing noise and vibration.
Since the overcurrent is eliminated, the load on the power supply and the output stage can be reduced, and the coil burning accident of the small motor can be prevented.
Stable and less susceptible to fluctuations in rotation speed, coil voltage, coil current, coil temperature, magnetic flux density, etc.

In addition, since the position detection time is short, a low-speed region ON/OFF control method in which excitation is energized while periodically detecting the rotor position is possible. It reliably starts the motor, quickly returns to normal rotation even when external force is reversed, can handle extremely low speed rotation and stall operation when overloaded, and can follow sudden overloads, so-called impact loads, without losing synchronism. It is possible to construct a sensorless motor system with high robustness almost equivalent to position sensor drive, which returns to normal in one cycle even when it malfunctions due to noise or the like.
In addition, the sensing process and the energization process are independent, so there is a high degree of freedom in excitation, and the energization method and output duty ratio are arbitrary. A wide range of driving methods such as 150° electrical angle energization or 180° electrical angle energization (sine wave energization) can be supported.

FIG. 1A shows open-phase voltage simulation waveforms in complementary interval 1, FIG. 1B in complementary interval 2, and FIG. 1C in complementary interval 3. FIG. It is a subtraction simulation waveform of the open phase voltage. It is an addition simulation waveform of open phase voltage amplitude. FIG. 10 is an operation explanatory diagram of a polarity sensing pulse; FIG. 4 is an operation explanatory diagram of a low-speed region on/off control system; 1 is a block diagram of a driving circuit according to the present invention; FIG. 4 is a general flow chart of a control program; It is an explanatory view of a three-phase motor. 1 is a block diagram of a conventional drive circuit; FIG. It is a timing chart of 120-degree energization. It is an actually measured waveform of the open phase voltage by the inductive sensing method.

An embodiment of a motor driving method according to the present invention will be described below with reference to the accompanying drawings. As an example of a motor, the present invention is a brushless motor in which a rotor is provided with a permanent magnet field, windings are arranged in a stator at a mechanical angle of 120° phase difference and star-connected, and phase ends are connected to a motor output circuit. A direct current (BLDC) motor can be mentioned, and here, a position sensorless motor, which has been widely used in recent years, will be used for explanation.

An embodiment of a three-phase BLDC sensorless motor is shown with reference to FIG. As an example, a 3-phase brushless DC motor with a 2-pole permanent magnet rotor and a stator 4 with 3 slots is illustrated. The motor may be either an inner rotor type or an outer rotor type. Further, the permanent magnet type magnetic field system may be either an embedded permanent magnet (IPM) motor or a surface permanent magnet (SPM) motor.

In FIG. 8, a rotor 2 is provided integrally with a rotor shaft 1, and a two-pole permanent magnet 3 is provided as a magnetic field. On the stator 4, pole teeth U, V, W are arranged facing the permanent magnet 3 with a mechanical angle phase difference of 120°. Windings u, v, and w are provided on the respective pole teeth U, V, and W of the stator 4, and the phases are star-connected by a common C to form a three-phase brushless DC motor wired to a motor driving device, which will be described later. . Note that the common line is omitted because it is unnecessary. Also, it may be a delta connection that connects adjacent phases and does not have a neutral point.

Next, an example of a motor drive circuit for a three-phase sensorless motor will be described with reference to FIG. In order to avoid complication, the description of the power supply unit, clock generation unit, communication unit, etc. is omitted.
The host controller 50 (CONT) sends a rotation command (RUN) to the control circuit 51 . The control circuit 51 (MPU) incorporates a logic circuit 52 (LOGIC), a PWM controller 53 (PWMC), a current amplifier 54 (AMP), an AD converter circuit 55 (ADC), and the like. A pre-driver 56 (PRE) receives a gate signal from the PWM controller 53 and outputs a gate output to an output circuit 57 . The output circuit 57 (INV) receives the gate output from the pre-driver 56 and sends out the coil output UVW to the motor. The coil current flows through the shunt resistor 58 (RS) to the GND bus, and the coil current signal IM detected by the shunt resistor 58 is amplified by the current amplifier 54 and input to the AD converter circuit 55 . The coil voltage is attenuated by the voltage dividing circuit 61 (DIV), and the conditioned coil voltage signal uvw is input to the AD converter circuit 55 .

When the control circuit 51 receives a rotation command from the host controller 50, it performs a position detection operation. The logic circuit 52 stores an energization pattern of 120° electrical angle energization and sends a sensing pulse signal to the PWM controller 53 . The sensing pulse signal is a timer-controlled DC pulse signal, and PWM control is not performed. The PWM controller 53 receives the sensing pulse signal and sends out a DC gate signal to the pre-driver 56 .

The pre-driver 56 receives the gate signal and outputs a voltage-amplified gate output to the output circuit 57 . A charge pump circuit that boosts the gate output voltage and a through current prevention circuit are built in. The output circuit 57 is an inverter circuit with a three-phase bridge configuration. When the gate output is input from the pre-driver 56, the output element of the high side arm or the low side arm of each phase is driven, and power-amplified coil output U~ W is output to the motor. An FET is used as an output element, and a regenerative diode is incorporated.

The AD converter circuit 55 (ADC) selects either one of the coil current signal IM or the coil voltage signals u to w according to the designation from the logic circuit 52 (LOGIC), AD-converts the signal immediately before the end of the sensing pulse, The conversion result is sent to logic circuit 52 . The logic circuit 52 stores the AD-converted measurement data, and performs arithmetic processing on the stored measurement data to detect the rotor position.
The hardware configuration example regarding rotor position detection has been described above. Although the control circuit 51 naturally drives the motor at a high speed, any control method is allowed and a known control method can be used, so the explanation is omitted.

A rotor position detection method for a sensorless motor will be described in detail below.
(1) Complementary section detection method A complementary section is a pair of two sections having a phase difference of 180° among six energization sections in an electrical angle of 120°, and there are three pairs of complementary sections 1 to 3. .
When a square wave pulse of several tens of kHz is applied between the two wires of the coil leads connected to the coils of a three-phase BLDC motor, the open phase (non-energized phase terminal) exhibits reluctance, magnetic saturation, and induced voltage depending on the phase angle θ. generates an inductance voltage VL reflecting VL can be schematically represented by the following formula.
During forward rotation with sensing pulse of energization pattern in odd number section VL1=K1・sin2θ+K2・sinθ+K3・sin(θ-90°) Equation (1)
Reverse rotation with sensing pulse of energization pattern in odd number section VL2=K1・sin2θ+K2・sinθ+K3・sin(θ+90°) Equation (2)
Forward rotation with sensing pulse of energization pattern in even section VL3=-(K1・sin2θ+K2・sinθ)+K3・sin(θ+90°) Equation (3)
Reverse rotation with sensing pulse of energization pattern in even section VL4=-(K1・sin2θ+K2・sinθ)+K3・sin(θ-90°) Equation (4)
However, K1 = reluctance coefficient, K2 = magnetic saturation coefficient, K3 = induced voltage coefficient. is a wave. The induced voltage is a cyclic sine wave that depends on the number of rotations and the direction of rotation.

1A to 1C show simulation waveforms of the inductance voltage VL with respect to the neutral point potential when the three-phase coil is rotated by one electrical angle while applying sensing pulses in six energization patterns of 120° energization. . V1 to V6 are energization patterns in intervals 1 to 6, and are open phase voltage waveforms during sensing. The induced voltage is 0. 1A-C are superimposed representations of the two waveforms that make up the complementary interval.
The point to be noted here is the crossing point where complementary interval waveforms intersect at the zero crossing point. 1A, 30° and 210° in FIG. 1B, and 90° and 270° in FIG. 1C. These intersection points reflect the phase angle at which the field magnetic pole and the magnetic pole of the energizing magnetic field face each other, and are stable intersection points where the phase does not change even if the induced voltage is superimposed. The phase angle of the stable intersection coincides with the section switching point of 120° energization and can be used for rotor position detection. If the stable intersection is detected, it is not affected by the induced voltage, so the rotor position can be detected from the time of rest to the time of rotation.
In order to detect a stable crossing point, the signals of complementary sections should be subtracted.

FIG. 2 illustrates subtraction simulation waveforms. A signal AA (broken line) is a waveform obtained by subtracting the section 1 signal from the section 4 signal. A signal BB (thick line) is a waveform obtained by subtracting the section 2 signal from the section 5 signal. A signal CC (thin line) is a waveform obtained by subtracting the section 3 signal from the section 6 signal. Of the zero-crossing points of the subtraction waveform, the intersections (30°, 90°, 150°, 210°, 270°, 330°) that coincide with the section switching points of the 120° energization are stable intersections. From the above, it can be seen that one of the three pairs of complementary sections 1 to 3 can be specified by performing a logical operation on the sign of the subtraction waveform.

For example, under the condition that the signal BB (bold line) is positive and the signal CC (thin line) is positive, two sections of section 30° to 90° and section 210° to 270° are obtained. ). Similarly, the signal CC (thin line) is negative and the signal AA (broken line) is positive under the condition that the signal CC (thin line) is negative and the signal AA (broken line) is positive. Section 3 (section 3 and section 6) can be distinguished.
Although the open-phase voltage waveform of an actual motor changes in a complex manner depending on the stator shape and magnetization pattern, the binarization of the subtraction waveform eliminates these effects and the waveform level does not matter. It is also possible to increase the resistance to demagnetization due to temperature changes and the like. In addition, since the induced voltage is measured at almost the same time in both complementary sections, the voltage difference due to the induced voltage can be ignored at low speed rotation and does not affect the phase. Similarly, the rotor position can be detected.

(2) Section identification method 1
Hereinafter, the specification method 1 for specifying one section from two sections constituting a complementary section will be described.
The two sections forming the complementary section identified above are sections with the maximum and minimum magnetic saturation amounts. The open-phase voltage contains a magnetic saturation component, although it is small, and the magnetic saturation component can be extracted from the already measured open-phase voltage. Therefore, the amplitude of the open-phase voltage value in the complementary section with respect to the neutral point potential is added.

FIG. 3 shows an amplitude addition simulation waveform of the open phase voltage in the complementary section. Waveform signal A (solid line) is V1 amplitude+V4 amplitude, waveform signal B (broken line) is V2 amplitude+V5 amplitude, and waveform signal C (thin line) is a summed waveform of V3 amplitude+V6 amplitude. Signals V1-6 are the open phase voltage waveforms of the energization patterns of sections 1-6, which are shown in FIGS. 1A-1C.
For example, focusing on the waveform signal A (solid line), it is negative at 30° to 90° (section 1) and positive at 210° to 270° (section 4). and interval 4 can be discriminated. Similarly, sections 2 and 5 can be discriminated from the sign of the waveform signal B (broken line), and sections 3 and 6 can also be discriminated from the sign of the waveform signal C (thin line).
However, when the induced voltage is superimposed on the added signal, a maximum phase shift of ±90° occurs. Therefore, this method 1 is applicable when the number of rotations is restricted and when the vehicle is stationary or when it rotates at a very low speed.

(3) Section identification method 2
A method 2 for identifying one section from two sections forming a complementary section will be described below. Identification method 2 expands the rotation speed range of identification method 1 described above, and is capable of detecting the initial position even in a low-speed rotation range. In this method, after the complementary section is identified, a sensing pulse with a slightly large amount of current is applied to the three-phase coil in the energization pattern of the two sections that make up the complementary section to increase the amount of magnetic saturation, thereby ensuring magnetic saturation. to detect.
The control circuit 51 (MPU) applies to the three-phase coil a sensing pulse for polarity detection, the pulse time of which is several times longer than the sensing pulse for detecting the above-mentioned complementary section, and the current value immediately before the end of the sensing pulse is calculated. Measure. Alternatively, the energization time until the predetermined current is reached is measured. These measurements are performed for two sections that constitute complementary sections, and one section is specified by comparing both current values or energization times.

FIG. 4 shows an explanatory diagram of the operation when the polarity sensing pulse is applied. Sensing pulses of energization patterns I and II of two sections constituting complementary sections are applied to the three-phase coil with a pause period approximately corresponding to the sensing pulse time.
FIG. 4A shows a method of applying a sensing pulse for a predetermined time to a three-phase coil and measuring the coil current, where IM1 and IM2 are the coil currents and TS1 is the energization time. Since the current rising curve differs depending on the amount of magnetic saturation and IM1 and IM2 are different, by measuring the coil current immediately before the end of the sensing pulse with an AD converter and comparing the two, it is possible to specify one section from the two sections that constitute the complementary section.
Note that the approximate value when the coil current IM is small can be obtained by the following equation.
IM=VM·TS1/L Formula (5)
However, VM = coil voltage, L = coil inductance at magnetic saturation

FIG. 4B shows a method of applying a sensing pulse of a predetermined current to a three-phase coil and measuring the arrival time, where IM is the coil current and TS1 and TS2 are the arrival times. Since TS1 and TS2 are different because the current rising curve differs according to the amount of magnetic saturation, if the arrival times are measured by a timer and compared, two sections constituting complementary sections can be identified as one section.

(4) Section identification method 3
A method 3 for identifying one section from two sections forming a complementary section will be described below. The identification method 3 is applied not to initial position detection but to repeated position detection at the time of start-up or low speed rotation. Since the previous complementary section number is already known, it can be determined by comparing with the current complementary section number whether it is positioned in the same section as the previous one, or whether it has rotated forward or reversed by one section. If the current section number is determined based on this, continuous rotation is possible. However, since complementary section numbers are used, only changes within one section can be handled. Therefore, it is a condition that the rotor does not rotate for one section or more from the previous rotor position detection to the current rotor position detection.
According to this identification method 3, the polarity sensing pulse is not required, and the noise can be reduced. The control software is also simplified because the segment can be specified only by specifying the complementary segment.

(5) Low-speed area ON/OFF control method Since all of the various rotor position detection methods described above can detect the position in a short time of about 1 ms, it is possible to detect the position by interrupting the instantaneous output during low-speed rotation. Position closed loop control can be realized by performing excitation for a predetermined time based on the detected rotor position. That is, the low-speed rotation area can be field-oriented controlled.

FIG. 5 shows an operation timing chart of the low-speed area ON/OFF control method.
The sensing process is performed with the output turned off. First, the speed is detected from the induced voltage, and if the rotation is at a high speed equal to or higher than a predetermined speed, the present invention is abandoned and the high-speed processing program is started. If the rotor rotates at a low speed, the position of the rotor is identified by the position detection method described above.
Next, an energizing step is performed, in which an excitation pattern is selected according to the position specified in the sensing step, and energized at an arbitrary output duty ratio for a predetermined period of time.
During low-speed rotation, the sensing process and the energizing process are repeated.
This low-speed region on/off control method has limits on the upper limit of rotation speed and acceleration resistance, but it can handle stalls and reverse rotations because it is excited according to the rotor position. It can be detached, and there are no restrictions on the output duty ratio, etc., and soft start and torque control are easy, and high practicality can be realized. In addition, even if noise or malfunction occurs, it can recover normally in one cycle and is excellent in robustness to operate reliably. However, since low-frequency vibration and noise are generated when the output is turned on and off, it is not suitable for applications that require severe vibration and noise.

Next, FIG. 7 shows an example of a general flowchart of a rotor position detection program using the sensorless motor drive circuit shown in FIG. The rotor position detection operation will be described step by step based on the flow chart of FIG. Note that the control program is stored in the control circuit 51 .

When a rotation command (RUN) is given from the host controller 50, the MPU 51 first cuts off the coil output and detects the rotational speed of the rotor from the induced voltage (STEP 1). If the rotation speed is equal to or higher than a predetermined speed, the process proceeds to arbitrary high speed rotation processing (STEP 2). If the rotation speed is low, proceed to the following position detection processing.

The logic circuit 52 (LOGIC) sends a sensing pulse signal for a predetermined time to the PWM controller 53 (PWMC) in the conduction pattern of one of the complementary sections. The PWM controller 53 receives the sensing pulse signal and sends out a DC gate signal to the pre-driver 56 (PRE). The pre-driver 56 amplifies the gate output and sends it to the output circuit 57 (INV), and when the output circuit 57 receives the gate output from the pre-driver 56, it sends the coil output voltage UVW to the motor. The open-phase voltage of the coil is attenuated by the voltage dividing circuit 61 (DIV), and the conditioned coil voltage signal uvw is input to the AD converter circuit 55 . The open-phase voltage immediately before the end of the sensing pulse is AD-converted, and the conversion result is sent to the logic circuit 52 . The logic circuit 52 stores the AD-converted measurement data (STEP 3).

In addition, the logic circuit 52 applies a sensing pulse (reverse sensing pulse) to the three-phase coil for a predetermined time in the energization pattern of the other segment of the complementary segment, and measures the open-phase voltage immediately before the sensing pulse ends in the same manner as described above. Save (STEP 4). Then, a rest period of a predetermined time is provided (STEP 5). The above sensing energization is repeated until sensing is completed for three pairs of complementary sections (STEP 6).

Next, the logic circuit 52 subtracts the open phase voltage values of the two sections forming the complementary section, uses the sign as the subtraction position information, and calculates the three pairs of complementary sections to obtain 3-bit subtraction position information (STEP 7). A logical operation is performed on the 3-bit subtraction position information to identify the complementary section (STEP 8).
Also, the logic circuit 52 finds the average of the six open-phase voltage values and sets it as the neutral point voltage (STEP 9). The amplitudes from the neutral point of the open-phase voltage values of the two sections forming the identified complementary section are added (STEP 10). One section is identified from the two sections by the sign of the added value (STEP 11).
With the above procedure, the rotor position can be specified in one section of 120 electrical angle energization.

1 rotor shaft 2 rotor 3 permanent magnet 4 stator 50 host controller 51 control circuit 52 logic circuit 53 PWM controller 54 current amplifier 55 AD converter circuit 56 pre-driver 57 output circuit 58 shunt resistor 59 zero cross comparator 60 dummy common generator 61 voltage divider

Claims (4)

A rotor position detection method for a sensorless motor for sensorless driving of a brushless DC motor comprising a rotor having a permanent magnet field and a stator having a three-phase coil, comprising:
A pair of two sections having a phase difference of 180° among six energization sections in 120 electrical angle energization is defined as a complementary section,
a control circuit that receives a sensing command from a host controller, generates a sensing pulse signal for the three-phase coil, and determines the rotor position when a rotor position signal detected from the three-phase coil is input;
an output circuit having a three-phase bridge configuration that amplifies power when a sensing pulse signal is input from the control circuit and outputs a sensing pulse to a three-phase coil,
When the control circuit receives a sensing command from the host controller, the control circuit generates a sensing pulse signal of six energization patterns with an electrical angle of 120° and applies the sensing pulse to the three-phase coil through the output circuit, a step of measuring the open-phase voltage immediately before the end of the sensing pulse in the two intervals constituting the complementary interval and storing it as a rotor position signal;
The open phase voltage values of the two sections forming the stored complementary section are subtracted from each other, the sign of the subtraction result is used as subtraction position information, and the same sensing pulse application, open phase voltage measurement and arithmetic processing are performed for the remaining two pairs of complementary sections. to generate 3-bit subtraction position information;
specifying the rotor position to any one of three pairs of complementary sections by logically operating the 3-bit subtracted position information;
A magnetic saturation component is extracted by adding the amplitudes of the open-phase voltage values of the two sections forming the specified complementary section with respect to the neutral point potential, and one section is selected from the two sections forming the complementary section by the sign of the addition result. A rotor position detection method for a sensorless motor, comprising a step of selecting and finally specifying the rotor position in one of the 120 electrical angle energization sections. The control circuit applies a sensing pulse for a predetermined time and measures the coil current at the end of the sensing pulse, or applies a sensing pulse of a predetermined current and measures the time required to reach a predetermined current value. further includes
After the complementary section is identified, the control circuit generates a sensing pulse signal in the energization pattern of one section constituting the identified complementary section, and applies the first sensing pulse to the three-phase coil via the output circuit. , a sensing pulse signal is generated in the energization pattern of the other section constituting the complementary section after a pause time corresponding to the first sensing pulse time, and the second sensing pulse is applied to the three-phase coil through the output circuit. For each of the two sensing pulses, the control circuit detects the current value after a predetermined time of energization or the arrival time to reach the predetermined current, compares the two current values or the arrival time, and complements them based on the result. 2. A rotor position detection method for a sensorless motor according to claim 1, wherein either one of two sections constituting the section is selected, and the rotor position is specified as one section of 120° energization. When the rotor position detection is repeatedly performed, on the condition that the rotor does not rotate by one section or more between the previous position detection and the current position detection, when the previous complementary section number obtained by the previous position detection is given, the current complementary section number is given. If the section number is the same as the previous complementary section number, the current section number will be the same as the previous section number. 3. Rotation of the sensorless motor according to claim 1 or 2, wherein the rotor position is specified in one section of 120 electrical angle energization by returning one section number from the previous complementary section number when the number is one section back from the previous complementary section number. Child location method. The rotation speed of the rotor is detected from the induced voltage by interrupting the energization to the three-phase coil,
When rotating at a speed equal to or higher than a predetermined speed, an arbitrary high-speed rotation process is performed, and when rotating at a low speed below a predetermined speed, the rotor position is detected by the sensorless motor rotor position detection method according to any one of claims 1 to 3. A sensing step for performing identifying processing;
An energizing step of determining an excitation pattern based on the rotor position specified in the sensing step and energizing for a predetermined time at an arbitrary PWM duty ratio,
A method of driving a sensorless motor, wherein the sensing step and the energizing step are alternately repeated during low-speed rotation below a predetermined speed.

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