KR100659156B1 - Speed Control Method of Brushless DC Motor Using 2 Hall Sensors and PLEL - Google Patents

Abstract

In the speed control method of a brushless DC motor using two Hall sensors and a PLL according to the present invention, a Hall sensor is installed only in an arbitrary two phases among three phases of a PM BLDC motor, and the remaining signal is detected using the detection signal of the Hall sensor. The Hall sensor signal for the phase is estimated by a separate Hall sensor estimation circuit, and is separately prepared to replace the encoder for speed control of the motor using the two actually measured Hall sensor signals and one estimated Hall sensor signal. In response to the pulses from the digital logic circuit by means of a separate PLL to generate six pulses per revolution of the rotor by the digital logic circuit, while compensating for the problem of low resolution caused by the use of two Hall sensors. Generate pulses at a denser interval than the pulses generated in the digital logic circuit, and recall the generated pulses. The speed control unit of the motor drive system finally controls the speed of the PM BLDC motor.

According to the present invention, six pulses are generated using two measured Hall sensor signals and one estimated Hall sensor signal, and 23 pulses are generated for each of the six pulses, using a total of 138 pulses. It can be used to control the speed of the motor, so it is possible to precisely control the speed without expensive encoders and resolvers, and ultimately reduce the manufacturing cost of the overall motor drive system.

Description

Method for controlling speed of brushless DC motor using two hall sensors and PLL}

1 is a view schematically showing a drive system of a PM BLDC motor employed to implement a speed control method of a brushless DC motor using two Hall sensors and a PLL according to the present invention.

2 is a diagram schematically illustrating an algorithm for estimating a signal of one phase with a hall sensor signal of two phases in a speed control method of a brushless DC motor using two Hall sensors and a PLL according to the present invention.

3 is a view showing the configuration of a general practical integrating circuit.

4 is a view showing the configuration of a Hall sensor signal estimation circuit employed in the speed control method of a brushless DC motor using two Hall sensors and a PLL according to the present invention.

5 is a view showing an estimation signal (H _C) that is integrated signal, and finally output of the Hall sensor signals (H _A), the Hall sensor signal (H _A) used as an input to the estimation circuit of Fig.

6 is a diagram schematically illustrating a speed discrimination algorithm employed for implementing a speed control method of a brushless DC motor using two Hall sensors and a PLL according to the present invention.

FIG. 7 is a diagram showing the configuration of a six-pulse digital logic circuit constructed inside an EPLD in the drive system of the PM BLDC motor of FIG. 1; FIG.

8 is a diagram illustrating a basic circuit of a PLL employed in a speed control method of a brushless DC motor using two Hall sensors and a PLL according to the present invention.

9 is a diagram showing the configuration of a signal of 6 pulses per revolution of the rotor based on two measured Hall sensor signals, one estimated Hall sensor signal, and thus the pulses generated in the PLL.

10 shows a mechanism for generating a position signal of a rotor using a PLL for precise speed control in the method of the present invention.
FIG. 11 shows actual experimental waveforms for FIGS. 9 and 10.

<Explanation of symbols for main parts of the drawings>

101 AC power supply 102 rectifier

103 ... Inverter 104 ... PM BLDC Motor

105 Hall sensor 106 Current controller

107 ... gate driver 108 ... EPLD

109 ... PLL 110 ... Counter

111 ... Proportional integral controller 112 ... D / A converter

113 ... Computer System

The present invention relates to a speed control method of a brushless DC motor, and more particularly, to performing speed control of a PM BLDC motor by using two Hall sensors (Hall-ICs) which are position detection sensors without a separate speed sensor. It is used instead of the speed sensor to determine the position of the rotor, and compensates the problem of low resolution caused by the use of two Hall sensors by using PLL (Phase Locked Loop). The present invention relates to a speed control method of a brushless DC motor using a sensor and a PLL.

Recently, the use of brushless electric motors (hereinafter referred to as PM BLDC electric motors) in which rotors are composed of permanent magnets is increasing in various industrial devices and automation devices. The PM BLDC motor removes the field and armature of the DC motor, and has the advantages of robustness, low noise, no maintenance, long service life, no rotor loss, simple control, and a wide operating range.

On the other hand, the method of controlling the speed of the PM BLDC motor as described above can be divided into a method using a speed sensor and a sensorless method without using a speed sensor.

In the case of using a speed sensor, a magnetic sensor or an optical sensor is used to detect the position of the rotor, and a speed sensor such as an encoder and a resolver is required to detect the speed. However, the encoder and the resolver are expensive and difficult to measure at high speed, and the manufacturing cost of the motor driving circuit is increased, and the volume is increased.

In the case of not using the speed sensor, since the sensor is not used, it can be used even where the sensor is not available. However, in the case of sensorless control, if the parameters of the motor to be controlled are changed, the same algorithm is difficult to apply, and complicated computations are required, which requires a high performance processor.

The present invention has been made in view of the above-mentioned matters. In performing the speed control of the PM BLDC motor, the position of the rotor is determined by using two Hall sensors, which are position detection sensors, without a separate speed sensor. It is used instead of sensor and compensates for the problem of low resolution by using two Hall sensors by using PLL to provide speed control method of brushless DC motor using two Hall sensors and PLL that can control speed more precisely. Has its purpose.

In order to achieve the above object, a speed control method of a brushless DC motor using two Hall sensors and a PLL according to the present invention,

In the speed control method of a PM BLDC motor using a Hall sensor in a system in which an AC power is supplied to the DC power supply, the DC power is supplied to a PM BLDC motor via an inverter, and the motor is driven.

The Hall sensor is installed only in any two phases of the three phases of the PM BLDC motor, and is estimated by the Hall sensor estimation circuit which separately prepares the Hall sensor signal for the other phase by using the detection signal of the Hall sensor. By using the actually measured Hall sensor signal and one estimated Hall sensor signal, 6 pulses per revolution of the rotor are generated by a digital logic circuit separately prepared to replace the encoder for speed control of the motor. In order to compensate for the problem of low resolution due to the use of the Hall sensor, a separate PLL generates pulses with a denser interval than those generated in the digital logic circuit in response to the pulses from the digital logic circuit. By providing the generated pulse to the speed control unit of the motor drive system, the speed of the PM BLDC motor is finally achieved. Its features are in controlling it.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a view schematically showing a drive system of a PM BLDC motor employed to implement a speed control method of a brushless DC motor using two Hall sensors and a PLL according to the present invention.

Referring to FIG. 1, a drive system of a PM BLDC motor, which is employed to implement a speed control method of a brushless DC motor using two Hall sensors and a PLL, according to the present invention, receives an AC power source 101 to supply a DC power source. Any of three phases of the switching rectifier 102, the inverter 103 which receives the DC power output from the rectifier 102, and outputs switching power for driving the PM BLDC motor 104, and the PM BLDC motor 104. And installed in two phases of the PM BLDC motor 104 for detecting the relative position of the permanent magnet rotor of the PM BLDC motor 104, and supplied to the PM BLDC motor 104 via the inverter 103. A current controller 106 that performs hysteresis current control on the current, and a gate driver for transmitting a gate signal for driving on / off of the device to a gate terminal of the semiconductor switching device of the inverter 103 ( 107 and a Hall sensor estimation circuit based on the position signals for the two phases detected by the Hall sensors 105 installed in any two phases of the three phases of the PM BLDC motor 104 and the two detection signals (Fig. Per one revolution of the rotor of the motor (Hall sensor detection pulse) by a digital logic circuit (see Fig. 7) configured internally for speed control of the motor based on the Hall sensor signal for the remaining phase estimated by Erasable Programmable Logic Device (EPLD) 108 for generating six pulses at 60 ° intervals per one cycle of the signal, and EPLD 108 to compensate for the problem of low resolution due to the use of two Hall sensors. Each pulse for each six revolutions of the rotor generated in EPLD 108 generates a number of pulses that are more closely spaced than pulses generated in EPLD 108 in response to pulses from Generate 23 pulses per pulse, totaling 1 The PLL 109 which generates 38 pulses, the counter 110 which counts the number of input pulses from the PLL 109 to calculate the actual speed ω of the motor, and the previously given PM BLDC motor 104 A proportional integral controller 111 which performs proportional integral control on the error between the reference speed ω _ref and the actual speed ω, and converts an output signal (digital signal) from the proportional integral controller 109 into an analog signal. On the other hand, a digital-to-analog (D / A) converter 112 for outputting a reference current signal I _ref and a reference speed ω _ref for the PM BLDC motor 104 are provided. Computer system 113 for inputting various parameters and control commands related to speed control of 104. Here, the proportional integral controller 111, the D / A converter 112, and the counter 110 may be replaced with one microprocessor (for example, 80C196KC) incorporating such functions.

Then, the speed control method of the brushless DC motor using the two Hall sensors and the PLL of the present invention based on the drive system of the PM BLDC motor as described above will be described.

FIG. 2 is a diagram schematically illustrating an algorithm for estimating a signal of one phase with a hall sensor signal of two phases in a speed control method of a brushless DC motor using two Hall sensors and a PLL according to the present invention.

As shown in FIG. 2, the Hall sensor 105 is placed on any two phases (eg, A and B phases) of three phases (eg, A, B, and C three phases) of the PM BLDC motor 104. The position detection signals (H _A , H _B ) relative to the permanent magnet rotor in the PM BLDC motor 104 are obtained by the two Hall sensors 105, and the remaining one phase (C phase) is used by the two Hall sensors 105. Estimate the position signal H _C with respect to.

In general, PM BLDC motors usually have a Hall sensor for each phase (for all three phases, for all three phases) for position determination. However, in the case of the present invention, as described above, two Hall sensors are used to estimate the position signals for the other phase, and for this purpose, a Hall sensor signal estimation circuit is introduced.

In terms of frequency, the integrating circuit has a characteristic that the gain is 1/2 for every frequency doubled, and there is a -90 ° delay with respect to the input in terms of phase. Such integrated circuits are widely used for making sawtooth waves or triangle waves, for applications to timers, and circuits for converting outputs of differential sensors to actual displacement values.

3 shows a general integrating circuit. In this integrated circuit, the input current i ₁ and the feedback current i _f are the same (i ₁ = i _f ), and the integrated circuit is analyzed using this. The integration operation uses the charging characteristic of the capacitor C. When the current i flows through the capacitor C, the voltage V charged to the C can be expressed by the following equation.

In FIG. 3, the input current i ₁ flowing by the input voltage V ₁ can be expressed by the following equation using the concept that A point is an imaginary earth.

The voltage charged in the capacitor C by the feedback current i _f can be expressed by the following equation using the concept of Equations 1, 2, and A being a virtual ground.

The output voltage V _O of the integrating circuit is related to the capacitor C as shown in Equation 3, which is influenced by the frequency as shown in Equation 4 below defining the capacitive reactance. Therefore, the integrating circuit must consider the range of the input frequency f _i , and the reference frequency thereof is referred to as the integral operating limit frequency f _C.

Here, as a precaution in circuit design, if the gain at the low frequency is not limited, the operational amplifier enters the saturation state even when the DC offset voltage becomes small. Further, if the frequency f of the input voltage V ₁ is smaller than f _C (= 1 / 2πR _S C), the operation of this circuit becomes a simple inverting amplifier circuit and V _O / V _i = -R _S / R ₁ . When f _C <f, integral operation is performed and f When <f _C , it operates as an inverting amplifier.

4 is a diagram illustrating a Hall sensor signal estimating circuit introduced in the method of the present invention including the practical integrating circuit and the zero point detecting circuit of FIG. 3.

As shown in FIG. 4, the Hall sensor signal estimating circuit includes a practical integrating circuit of FIG. 3, that is, an operational amplifier and a resistor R ₁ connected in series to a negative input terminal of the operational amplifier, In a conventional integrating circuit consisting of a capacitor (C) connected to a feedback circuit between a negative (−) input terminal and an output terminal of an operational amplifier, another resistor (R ₂ ) in parallel to the capacitor (C) of the feedback circuit is provided. ) Is connected, and the output terminal of the operational amplifier is connected to the negative input terminal of another second operational amplifier, and actually detected by the Hall sensor through the negative input terminal of the operational amplifier. The hall sensor signal H _A is input to output the hall sensor estimation signal H _C for the other phase where the hall sensor is not finally installed through the output terminal of the second operational amplifier. That is, the Hall sensor signal H _C is estimated by comparing the triangular wave output through the practical integrating circuit with the ground so that a pulse is generated at a value greater than or equal to zero. The Hall sensor signal estimation circuit as described above may be provided in the EPLD 108 (see FIG. 1), or may be provided as a separate component and installed between the Hall sensor 105 and the EPLD 108 of FIG. 1. .

FIG. 5 illustrates a Hall sensor signal H _A used as an input of the estimation circuit of FIG. 4, an integrated signal of the Hall sensor signal H _A , and an estimated signal H _C finally output.

As shown in FIG. 5, it can be seen that the estimated H _C signal actually takes the form of a square wave like the Hall sensor signal H _A detected by the Hall sensor.

Figure 6 is a schematic diagram illustrating a speed discrimination algorithm employed for implementing the method of the present invention.

In general, to measure speed, you must use a speed sensor such as an encoder or resolver. However, the method of the present invention introduces an algorithm that can replace the speed sensor with the signal of the Hall sensor, which is a position determination sensor.

As shown in FIG. 6, the Hall sensor signal is generated with a phase difference of 120 °, and each phase crosses each other by 60 °.

In this way, the circuit is implemented to generate a pulse every 60 ° in the EPLD (see FIG. 1), and generates a pulse to act as a pulse of phase A and phase B generated by a general encoder, thereby providing a kind of low resolution. The encoder is configured.

FIG. 7 is a diagram showing the configuration of a 6-pulse digital logic circuit constructed in an EPLD.

Referring to FIG. 7, the digital logic circuit uses two Hall sensor signals and the other Hall sensor signal H _C estimated by the Hall sensor signal estimating circuit of FIG. (Flip-flop) is used to generate 6 pulses as the standard for speed discrimination.

8 is a diagram illustrating a basic circuit of a PLL.

Referring to FIG. 8, the PLL compares the frequency and phase of an input signal with an oscillation frequency and phase of a voltage controlled oscillator, and generates a phase comparator 801 and a phase comparator 801 which generates a DC voltage proportional to an error caused by the comparison. A low pass filter 802 for filtering the harmonics in the error voltage signal output by the amplification voltage and amplifying the error voltage, and a VCO (Voltage generating a frequency of a predetermined value and controlling the voltage output through the low pass filter 802). Controlled Oscillator) (803).

The PLL configured as described above synchronizes with the input signal and performs a locked role. If the phase of the input signal changes, that is, the frequency changes, the output of the phase detector 801 increases or decreases so that the frequency f _o of the VCO 803 remains the same as the frequency f _i of the input signal. If the input signal frequency f _i and the frequency f _o of the VCO 803 are different, the phase angle between the two signals is also different. The outputs of the phase detector 801 and the low pass filter 802 are proportional to the phase difference of the two signals, and this proportional voltage is fed back to the VCO 803, until the two frequencies of the VCO 803 and the input signal are equal. The frequency f _o is controlled.

Is applied to the phase detector 801 the input signal (V _i) and the VCO output signal (V _O) is given by:

Here, θ _i and θ _o are the relative phase angles of the two signals and multiply the two signals so that the frequency output of the sum and the difference v _d is given by

Here, when the PLL is locked, f _i = f _o , 2πf _i t = 2πf _o t, and the frequency output v _d is

Here, the second cosine term is the second harmonic term (2 × 2πf _i t), which is filtered by a low pass filter. The control voltage at the output of the filter is expressed by the following equation.

When θ _e = θ _i -θ _o , θ _e becomes a phase error, and the filter output voltage is proportional to the phase difference between the input signal and the VCO signal and used as the control voltage of the VCO.

In general, to measure speed, you must use a speed sensor such as an encoder or resolver. However, in the method of the present invention, two Hall sensors, which are position determination sensors, are used, and when they are used, a pulse proportional to the rotor speed is generated to compensate for the problem of low resolution, that is, to perform more precise speed control. Introduce a PLL to replace the encoder. Here, I will explain more about this.
When the phase difference between voltage and current occurs or when the input frequency is shaken, the phase difference can be synchronized and the output frequency can be made constant by using PLL circuit to fix the output frequency to constant frequency. Therefore, when only the PLL is used, it may be used for the purpose of obtaining synchronization for phase difference or fixed frequency for output frequency, but in the present invention, as shown in FIG. 10 to be described later, the PLL 211 is additionally programmable. ), The counter 213 and the BCD switch 212 are used.
In FIG. 10, reference numeral 211 denotes a PLL portion referred to in the present invention, which receives a 6-pulse signal as an input, and equalizes a phase difference between an input and an output of the 6-pulse signal, and includes a programmable counter 213 and a BCD switch 212. 6 pulses, that is, to improve the low resolution.
Therefore, the output of the PLL 211 is synchronized with the six pulses coming into the input while obtaining a signal with increased resolution. In order to increase the resolution, the programmable counter 213 and the BCD switch 212 enter the circuit to adjust the portion of the BCD switch 212 and increase the frequency as shown in FIG. 9 to be described below based on the frequency coming into the input of the PLL 211. The output frequency can be obtained from the PLL output signal part.
Meanwhile, FIG. 11 shows the actual experimental waveforms of FIGS. 9 and 10, and shows that a 6-pulse input signal is obtained as an input of the PLL and a signal having an increased resolution, such as signal (3), is obtained at the PLL output. . In Fig. 11, (1) is a Hall sensor signal, (2) is a 6-pulse signal, and (3) is a PLL output signal.
Therefore, in order to compensate for the problem of the low resolution of the Hall sensor, by increasing the resolution using the circuit proposed in FIG. 10, an effect that can replace a speed sensor such as an encoder or resolver can be obtained.

FIG. 9 is a diagram showing the configuration of a signal of 6 pulses per revolution of a rotor based on two actual detection Hall sensor signals and one estimated Hall sensor signal, and thus the pulses generated in the PLL.

Referring to FIG. 9, the signal of the hall sensor is generated with a phase difference of 120 °, and each phase crosses each other by 60 °. In this way, a circuit is implemented in the EPLD 108 (see FIG. 1) such that a pulse is generated every 60 °, where six pulses are input to the PLL circuit to further refine the rotor per revolution from the PLL circuit. A plurality of pulses, for example, 138 (6 × 23 = 138) pulses are obtained, and the actual speed of the motor is calculated using the pulses.

10 is a view showing a mechanism for generating a position signal of a rotor using a PLL in the method of the present invention for precise speed control.

As shown in FIG. 10, the rotor position signal generation mechanism uses signals of the Hall sensors H _A and H _B capable of knowing the rotor position and the two Hall sensor signals H _A and H _B. EPLD section 210 that generates six pulses when the rotor makes one revolution with the estimated signal H _C obtained by the Hall sensor signal estimation circuit, and a PLL that increases the frequency of the output signal in proportion to the change in the rotor frequency. The portion 211 is largely composed. As the PLL portion 211, a PLL IC 4046B is used which stabilizes the output signal of the loop filter and also has additional functions such as synchronization signal generation. In addition, a binary code decimal (BCD) switch 212 and a programmable counter 213 (IC 4522B) are additionally used to increase the output frequency in proportion to the rotor frequency.

With the above configuration, it can be applied to the field requiring precision speed by solving the problem of low resolution when using the existing Hall sensor, and can replace the speed sensor such as encoder or resolver. You will also benefit economically.

As described above, the speed control method of the brushless DC motor using two Hall sensors and PLL according to the present invention is the position of the permanent magnet rotor with respect to any two phases of the three phases of the PM BLDC motor by the two Hall sensors Obtains the position signal relative to, and estimates the position signal for the other phase based on the two detected signals, and generates six pulses using the Hall sensor signal for the three phases thus obtained. It generates expensive pulses for each of the three pulses and calculates the speed of the motor using the generated multiple pulses, compares it with a given reference speed, and finally controls the speed of the motor. Precise speed control is possible without the need for sensors, encoders and resolvers, ultimately greatly reducing the overall manufacturing cost of the motor drive system. There is an advantage that can be reduced.

Claims (2)

In the speed control method of a PM BLDC motor using a Hall sensor in a system in which an AC power is supplied to the DC power supply, the DC power is supplied to a PM BLDC motor via an inverter, and the motor is driven. The Hall sensor is installed only in any two phases of the three phases of the PM BLDC motor, and is estimated by the Hall sensor estimation circuit which separately prepares the Hall sensor signal for the other phase by using the detection signal of the Hall sensor. By using the actually measured Hall sensor signal and one estimated Hall sensor signal, 6 pulses per revolution of the rotor are generated by a digital logic circuit separately prepared to replace the encoder for speed control of the motor. In order to compensate for the problem of low resolution due to the use of the Hall sensor, a separate PLL generates a plurality of pulses with a relatively tighter interval than the pulses generated in the digital logic circuit in response to the pulses from the digital logic circuit. By providing the generated pulse to the speed control unit of the motor drive system, the PM BLDC motor Speed control method of a brushless DC motor using two Hall sensors and PLL characterized in that the control of the speed of. The method of claim 1, Generating six pulses per revolution of the rotor by the digital logic circuit and generating a plurality of pulses further divided per pulse by the PLL in response to the six pulses. A speed control method of a brushless DC motor using two Hall sensors and a PLL, further comprising a BCD switch and a programmable counter, in order to increase the output frequency in proportion to the electronic frequency.

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