KR19980058230A - Driving Circuit of Sensorless SM Motor - Google Patents

Abstract

The present invention relates to a driving circuit of a Seserith SLM motor. In the related art, when a non-excited phase is used, a very small current of a relatively high frequency must be flowed regardless of the rotation for sensing, and thus, the resulting braking torque is generated. High-precision current sensor is needed to sense small currents. Also, 4-phase SRM is mainly used to secure enough non-excitation section, which is a major obstacle in reducing the gap which is the biggest advantage of SRM. As a factor, and as shown in Figure 2, the operational amplifier 9OPAMP for sensing is in direct contact with each other, a special element is required to solve this problem, and a problem of separately requiring a frequency / voltage converter for switching frequency and voltage. have. Therefore, the present invention

Description

Driving Circuit of Sensorless SM Motor

The present invention is for driving a switched reluctance motor (SRM), in particular, by measuring the current of the initial phase of the excited current flowing in the excited phase without attaching a mechanical sensor to the rotor to determine the timing of the next excited phase to drive the srm during sensor up It relates to a drive circuit of the sensorless SM motor for.

In the conventional non-excited phase inductance measuring circuit, as shown in FIG. 2, a difference is obtained by comparing a voltage determined according to phase inductance L _ph with a reference voltage set by a resistance, and obtaining the difference to a predetermined level. A first operational amplifier (OP1) for amplifying and outputting the amplified output; Comprising a second operational amplifier (OP2) for comparing the output voltage of the first operational amplifier (OP1) and the voltage fed back from the output terminal to find the difference and amplified to a predetermined level to detect the position of the rotor. .

Referring to the prior art configured in this way in detail as follows.

Switched relucatance motor (SRM) does not have a permanent magnet inside the motor, so it does not actively form a voltage for the rotor's decay for the realization of the sensorless algorithm. The position of the rotor is detected using a method or the like.

That is, in the rotor position detection method of the sensorless SRM motor, as shown in FIG. 1, when the inductance and the sensing pulse for the rotation of the A phase are applied, the sensing current ΔI increases.

For example, if phase C is excited by four-phase motors (phase A, phase B, phase C, phase D), the phase A senses. In other words, when an image is excited, the corresponding images (A↔C, B↔C) are sensed to find out the inductance and find the position of the rotor from the next image.

This method is to detect the inductance of the unexcited phase.

In another rotor position detection method, as shown in FIG. 2, an op amp is connected to output the frequency according to the inductance of the phase, and the L _ph value according to the inductance of the motor rotation. When the voltage is different and the corresponding voltage is input to the inverting terminal (-) of the first operational amplifier OP1, the voltage is adjusted by the resistors R1 and R2 to the non-inverting terminal (+) thereof, and the two voltages are compared. After obtaining, amplify to a predetermined level and output.

Then, the output voltage of the first operational amplifier OP1 is input to the inverting terminal (-) of the second operational amplifier OP2 and the voltage fed back from the output terminal is divided through the resistors R4 and R5 and the divided voltage. Is input to the non-inverting terminal (+), the difference is obtained by comparing the two voltages, and the resulting voltage is measured as the voltage due to inductance.

The position of the rotor is detected using the inductance value detected in the same way as described above.

Knowing the position of the rotor allows the user to rotate the motor in the desired direction.

However, in the case of using the non-excited phase in the prior art as described above, a very small current of relatively high frequency must be flowed regardless of the rotation for sensing, and thus a fixed torque for sensing the small current and the breaking torque generated therefrom. In order to secure a high degree of current sensor, and to secure a sufficient non-excitation section, four-phase SRM is mainly used, which is a major obstacle to reducing the gap, which is the biggest advantage of SRM, and FIG. 2. Op amps for sensing are in direct contact with each other, so there is a problem in that a special element is required to solve this problem and a frequency / voltage converter for switching between frequency and power is required separately.

Therefore, an object of the present invention for solving the problems as described above is to determine the position of the rotor by the current increase in the initial stage after the phase excitation, so that the position of the rotor can be easily determined, and can operate in any three or four phase To provide a driving circuit of a sensorless SM motor.

Another object of the present invention is a sensorless SM motor that handles measurements of current with relatively large values, thereby eliminating the need for costly current sensors compared to other algorithms that are extremely resistant to electromagnetic noise and require very small current measurements. To provide a driving circuit of.

1 is a waveform diagram showing an increase in sensing current when an inductance for rotation of phase A and a sensing pulse thereto are applied thereto.

2 is an inductance measurement circuit diagram of a conventionally unexcited phase.

Figure 3 is a drive circuit diagram of the sensorless SM motor of the present invention.

4 is a current waveform diagram according to four-phase inductance and turn-on angles.

5 is a characteristic diagram showing the actual motor inductance actual measurement value used in the present invention and the proper traveling angle for the motor speed.

6 is a pulse waveform diagram for phase adjustment when sensorless malfunction is detected during operation;

Figure 7 is a waveform diagram of the current according to the inductance put-on angle for explaining one embodiment of the present invention.

Explanation of symbols for the main parts of the drawings

10: microcomputer 20: switching unit

30,40: current sensor 50: amplifier

60: switching control signal generator

The driving circuit of the sensorless SM motor of the present invention for achieving the above object, as shown in Figure 3, the smoothing capacitor (C) for supplying a smooth voltage to the AC power input; A switching unit 20 for driving an SRM motor by switching according to a switching control signal when the output voltage of the flat capacitor C is supplied; First and second current sensors 30 and 40 for respectively detecting two phase currents when the initial current increases when the phase is excited; Amplifying part 50 which amplifies the current detected by the second current sensor 30 and 40 to a recognizable level; Recognize each phase according to the output value of the current transmitted through the amplification unit 50, and adjust the inclination of the current in accordance with the change of the DC voltage output from the smoothing capacitor (C) to advance the motor rotation speed A microcomputer (10) for giving a command to operate in accordance with; The switching control signal generator 60 is configured to control the operation of the switching unit 20 by executing current control according to the output value according to the recognition of each phase of the microcomputer 10.

When described in detail with respect to the operation and effect of the present invention configured as described above.

When the DC voltage generated by smoothing the smoothing capacitor C with respect to the AC power input AC is supplied to the switching unit 20, the microcomputer 10 generates a gate signal to drive the SRM motor. In this case, the signal is turned on or off through the switching control signal generator 60 to drive the motor.

The phase is then excited and the initial current increases accordingly.

Accordingly, the first current sensor 30 and the second current sensor 40 are locked to the current flowing during the excitation, and thus the analog / digital conversion terminal A / D1 (A / A1) of the microcomputer 10 through the amplification unit 50. / D2) respectively.

At this time, if the SRM motor is three-phase, each phase is treated with a current sensor, but in the case of four-phase, two current sensors are used to reduce the price of the current sensing part or to simplify the system. Phase, B, and D phases are tied together and sensed.

Therefore, the first current sensor 30 detects a current flowing in phases A and C, and the second current sensor 40 detects and outputs a current flowing in phases B and D.

The microcomputer 10 reads data input from the analog / digital conversion terminals A / D1 and A / D2. The reading time is read after a predetermined time T as shown in FIG. This is to minimize the effect on the magnetic flux saturation by finishing current sensing earlier than the magnetic flux saturation occurs in the motor.

The current speed is determined by averaging the previous four values, including the current value read after a certain time (T) and the current gate signal interval, and the next phase from the time measured at the current speed. Determine the excitation timing.

That is, the current speed is connected to the sensorism algorithm inside the microcomputer 10, and the current speed is calculated through the sensorless algorithm.

Here, the voltage equation of SRM is expressed as follows.

Excluding the influence of the self saturation caused by the current, the voltage method of Equation (1) can be simplified as follows.

Where ω _m is the rotational speed of the motor.

Looking at Equation (2), in order to know the current measured value i _{swnse, it} is necessary to know the inductance value (dl (θ) / dθ).

Therefore, based on FIG. 5, FIG. 5 shows the actual inductance measurement of the motor and the proper propagation angle with respect to the speed of the motor. The inductance increase rate is 0.2 mH from 0 to 12 degrees, and 2.4 mH above 12 degrees. It has a constant value of, and if the value is measured around 30 degrees to the position where the rotor is arranged to apply the sensing pulse as shown in Figure 6 to synchronize.

As shown in FIG. 5, the value of inductance for the traveling angle is stored in a memory not shown in the microcomputer 10.

As described above, when the value of the inductance with respect to the advancing angle is known, the current value i _sense is measured, and when the current value is known, the position of the rotor is known.

By the way, the inversion of the voltage supplied after smoothing through the smoothing capacitor C changes the slope of the current flowing in the phase itself.

Therefore, in order to use the current _sense (i _sense ) shown in Equation (2), the voltage output from the ring capacitor C of FIG. 2 is divided through the resistors R1 and R2, and the divided voltage is micro-controlled. When read through the analog-to-digital conversion terminal (A / D3) of the computer 10 can be operated in accordance with the advancing angle at the operation speed in equation (2).

Next, a method of determining the excitation timing of the next phase may be generated by using the average of the previous four phase signal intervals and the current measured current value as follows.

T = (T (T-1) + T (k-2) + T (k-3) + T (k-3) / 4 + (iref-isense) * h ......... ( 3)

Where iref is the reference current value after t hours of velocity, isense is the current measured current value, and h is the proportional control gain.

In this way, the current physically measured current value is calculated from the reference value that has already been considered for the advancing angle, and the current amount is corrected at the next phase excitation.

Through the above operation, the microcomputer 10 detects the position of the rotor using a sensorless algorithm when inputting a current value and determines the current speed by averaging the previous four values including the current value and the current gate signal interval. The excitation timing of the next phase is determined.

When the excitation timing of the next phase is determined, the comparison unit of the switching control signal generator 60 transmits a digital value for executing current control in accordance with the timing through the digital / analog conversion terminal D / A1 (D / A2). 60a). The value generated at this time becomes the reference voltage Vref.

Then, the first comparator COMP1 and COMP2 of the comparator 60a receive a reference voltage Vref from the microcomputer 10 and a current value input to the microcomputer 10 through the amplifier 50. The two values are compared and output to the logic combination unit 60b.

The AND gates AD1 -AD4 constituting the logic combination unit 60b perform an AND combination of gate signals of the microcomputer 10 and output signals of the first and second comparators COMP1 and COMP2. The transistor QA-QB of the switching unit 20 is turned on and off with the generated switching control signal.

IGBT is used as the switching element of the switching unit 20 to reduce the on-resistance loss.

In Fig. 6, the current increase detection time T for determining the position of the rotor is determined to be 150-sec, and the determination of this time is such that the operating speed of the motor, the flux density, and the conditions before the current limit occur. do.

Fig. 6 shows bridging after sensing the momentary position of the rotor by applying continuous sensing pulses to the ground without restarting from the standstill when the syncronus is out of synch due to external shock or other reasons when applying the sensorless algorithm. Enter the algorithm to perform the sensorless algorithm of the present invention.

The bridging speed at this time becomes a higher speed than the bridging speed performed at startup.

When the position of the rotor is detected through the same process as described above, and the position of the rotor is detected, the motor can be rotated in a desired direction.

Fig. 7 is an example of the silencing of the present invention. Here, the inductance on the surface can be known by measuring the time to reach after the fixed current level is fixed, and the position of the rotor can be detected as well.

In other words, if the voltage is lower than the current level at which magnetic flux saturation occurs, and the voltage of the comparator is determined in consideration of the operating speed of the motor, the time to reach this level is a reference to determine the current excitation timing.

In FIG. 7, when T3 is a reference point to be excited, when the time T1 or T2 shorter than this time is measured, the excitation timing of the next phase becomes longer than the previous one, and becomes longer (T4 or T5). In the case of, the next woman is shorter than before.

As described above, the necessary sensor is removed from the SRM to overcome the shortcomings caused by the degradation of reliability due to temperature, dust, and oil, which can be caused by the sensor in most applications including the compressor.

As described above, the present invention discriminates the position of the rotor by the initial current increase after the excitation, thus eliminating the influence of saturation due to the magnetic flux generated in the iron part of the motor, thereby eliminating the nonlinear element, thereby simplifying the position of the rotor. It can be determined, and only one current is detected at one time of excitation, so the processing load is not much, so the speed can be increased, and the measured value of the current is processed with a relatively large value. The small current needs to be measured, so there is no need to select an expensive current sensor, which is advantageous in terms of price.

Claims (5)

A smoothing capacitor for supplying a smooth voltage to the input AC power; A switching unit which drives an SRM motor by switching according to a switching control signal when the output voltage of the smoothing capacitor is supplied; First and second current sensors for detecting two phase currents, each of which increases an initial current during phase excitation; An amplifier for amplifying the current detected by the first and second current sensors to a recognizable level; Recognize each phase according to the output value of the current delivered through the amplifier, determine the current motor speed and the excitation timing of the next phase by using the interval between the current value and the gate signal, the current voltage output from the smoothing capacitor A microcomputer for making a command to operate in accordance with the advancing angle of the motor rotational speed by adjusting the inclination of the current according to the change of; And a switching control signal generator for controlling the operation of the switching unit by executing current control according to the output value according to the recognition of each phase of the microcomputer. 2. The apparatus of claim 1, wherein the switching control signal generator comprises: comparing means for comparing an output value of the amplifying means and a reference value; And a logic combination unit configured to output a switching control signal generated by logically combining the comparison output of the comparison unit and the gate signal of the microcomputer. 3. The driving circuit of a sensorless SM motor according to claim 2, wherein the logic combination portion comprises a NAND gate. The driving circuit of a sensorless SM motor of claim 1, wherein the first and second current sensors collectively sense A and C phases and B and D phases corresponding to each other. 2. The drive circuit of a sensorless SM motor according to claim 1, wherein the microcomputer determines the current increase detection time to be 150 sec to determine the position of the rotor.