WO2014061982A1

WO2014061982A1 - Apparatus for determining error of sensorless motor using counter-electromotive force signal

Info

Publication number: WO2014061982A1
Application number: PCT/KR2013/009230
Authority: WO
Inventors: 김봉준
Original assignee: 콘티넨탈 오토모티브 시스템 주식회사
Priority date: 2012-10-16
Filing date: 2013-10-16
Publication date: 2014-04-24
Also published as: KR20140048581A; KR101937958B1

Abstract

The present invention relates to an apparatus for determining an error of a sensorless motor using a counter-electromotive force signal. The apparatus for determining the error of the sensorless motor using the counter-electromotive force signal, according to the present invention, can prevent a detection error for the counter-electromotive force signal according to the external environment by predicting a generation time point of the counter-electromotive force in the sensorless motor and permitting only the counter-electromotive force signal corresponding to the predicted result. In addition, the present invention predicts a generation location of the counter-electromotive force signal on the basis of the stable filtering of the counter-electromotive force signal so as to detect the location of the sensorless motor, and controlling a driving operation of the motor from the predicted result, thereby simplifying the configuration of an inverter circuit and reducing a unit cost of a system.

Description

Error Determination Device of Sensorless Motor Using Back EMF Signal

The present invention relates to a method of driving a sensorless motor, and more particularly, by detecting a counter electromotive force generation time of a sensorless motor and allowing only a counter electromotive force signal corresponding to the prediction result, thereby detecting a counter electromotive force signal according to an external environment. The present invention relates to an error determination device of a sensorless motor using a back EMF signal which can be prevented in advance.

In general, in the case of rotating a washing tank using a sensorless permanent magnet synchronous motor applied to a washing machine, there is almost no steady state region that operates at a constant speed, and the acceleration and deceleration are repeated, so that the sensorless permanent magnet is operated for stable operation. When the synchronous motor makes forward / reverse rotation, the acceleration / deceleration operation characteristics should be good. In such sensorless control, rotor position detection and control performance during low / low speed operation and acceleration / deceleration are important.

Therefore, in the related art, the rotor position and speed of the observer are determined from the current error of each axis by setting the virtual q axis and the d axis to convert the phase current of the actual system into the virtual axis, and comparing the current with the model equation in the observer. Follow the position and speed of. However, the sensorless control of the sensorless permanent magnet synchronous motor is performed only after a certain speed after the motor is started. This is because the back electromotive force of the sensorless permanent magnet synchronous motor is deteriorated as the speed decreases. This is because it is difficult to estimate the electronic position and velocity.

Thus, although the sensor-less permanent magnet synchronous motor is required to provide a current corresponding to the position of the rotor at the initial start-up and generate a proper amount of motor torque, the position and speed of the rotor are not known. Regardless of the rotor's position and speed, it will provide current based on peak load. Therefore, in the past, when the sensorless permanent magnet synchronous motor is initially started, at low loads, the inertia coefficient is not the same as the actual load, and unnecessary torque is required. Accordingly, torque is applied more than necessary to increase the starting current, and also the starting current. Increasing the increase in the heat generated by the inverter also could not be continued operation.

In order to solve such a problem, the attached patent document estimates the position of the rotor from a preset inertia coefficient and torque acceleration. That is, as shown in FIG. 1, a voltage source inverter 180 for supplying a three-phase voltage, a current estimator 110 according to a phase voltage application, and a first speed / position estimator 120 estimated based on a motor model. ), A second speed / position estimator 130 estimated based on a machine model, a mixer 140 having a crossover function that mixes positions and velocities estimated by the motor model and the machine model, respectively, measured or estimated Speed controller 150 that generates torque command by comparing speed and command, Current command converter 160 that converts torque command into current command, and Vector current controller that generates voltage by comparing command current with estimated and measured current It consists of 170.

The current estimator 110 may be configured in various forms. First, three-phase current is directly detected by using three current converters or a series shunt resistor in three phases of the motor, and second, Two current transducers or series shunt resistors to detect the current in two phases, and the other phase is obtained as a two-phase current value. Third, one series shunt resistor on the DC bus side or the lower switches of the inverter and ground It consists of estimating current reconstruction with three or three shunt resistors in series.

As a result, when the sensorless permanent magnet synchronous motor is initially started, the inertia coefficient and torque acceleration according to the actual load are used to estimate the speed and position information. By preventing the increase of heat generated by the inverter by minimizing the current, it is possible to prevent the case that continuous operation is impossible.

However, estimating the position of the sensorless motor using the inertial system and torque acceleration as described above causes an increase in the unit cost of the product since an inertial and torque acceleration sensor or the like must be added. Therefore, it is urgent to develop a system for easily estimating the position of the sensorless motor.

The present invention has been made to solve the above problems, and an object of the present invention is to predict the occurrence of back EMF of a sensorless motor and allow only back EMF signal corresponding to the prediction result, thereby detecting a detection error of the back EMF signal according to an external environment. To provide an error determination device for a sensorless motor using a back EMF signal that can prevent the in advance.

Another object of the present invention, based on the stable filtering of the back electromotive force signal for detecting the position of the sensorless motor, by predicting the generation position for the back electromotive force signal, and performing the drive control of the motor from the prediction result, The present invention provides a device for determining an error of a sensorless motor using a counter electromotive force signal that can reduce a system cost by simplifying a circuit configuration of an inverter.

An apparatus for determining an error of a sensorless motor using a back electromotive force signal according to an aspect of the present invention for achieving the above object is a device for determining an error signal when driving a sensorless motor using a back electromotive force signal, the sensorless motor driving A signal amplifier for amplifying a back-EMF (BEMF) signal generated at a predetermined level; An AD converter for converting an output signal of the signal amplifier into a digital signal; A zero crossing detector for detecting a zero-crossing point of the counter electromotive force signal based on the output signal of the AD converter; And calculating a time difference between zero crossing time points of the counter electromotive force signal based on the rotational speed of the sensorless motor, determining whether the zero crossing time point output from the zero crossing detector is included in the calculated time difference category, and outputting the AD converter. And a control unit for determining the authenticity of the counter electromotive force signal.

The calculated time difference according to the preferred embodiment of the present invention is a time difference between zero crossing points computed from the rotational speed V [rps] of the current sensorless motor, and the calculated time difference category allows for a time difference between calculated zero crossing points. It is characterized by the possible range.

In addition, the allowable range for the time difference according to a preferred embodiment of the present invention is characterized in that the ratio of 100% to 200㎲, or 10% to 20% of the time difference.

As described above, the error determination device of the sensorless motor using the back EMF signal proposed in the present invention by predicting the back electromotive force generation time of the sensorless motor, by allowing only the back EMF signal corresponding to the prediction result, according to the external environment Has an effect of preventing the detection error in advance. In addition, based on the stable filtering of the back EMF signal for detecting the position of the sensorless motor, by predicting the occurrence position of the back EMF signal, and performing the drive control of the motor from the prediction result, the circuit configuration of the inverter for driving the sensorless motor By simplifying the system cost can be reduced.

The following drawings attached in this specification are illustrative of the preferred embodiments of the present invention, and together with the detailed description of the invention to serve to further understand the technical spirit of the present invention, the present invention is a matter described in such drawings It should not be construed as limited to.

1 is a configuration diagram illustrating a conventional sensorless motor driving device.

2 is a block diagram showing an error determination device of a sensorless motor using a back EMF signal according to the present invention.

3 is a timing graph for explaining the operation of FIG. 2.

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

First, the operation of the sensorless motor proposed by the present invention predicts a zero-crossing time point of the counter electromotive force with reference to the motor rotation speed, and determines whether the currently detected back electromotive force signal is authentic based on the predicted time point. . That is, the counter electromotive force signal may be confused with noise caused by electrical or mechanical noise, and the noise of the motor control is lost due to such noise, so that the noise and the counter electromotive force signal are distinguished based on the zero crossing point of the counter electromotive force.

Here, in order to predict the counter electromotive force signal, the rotational speed of the rotor, that is, rotation per second (rps) should be recognized, and it can be predicted by calculating the time therefrom. The counter electromotive force signal generated per rotation of the sensorless motor is generated 'n × 6' times for the magnetic pole number n of the motor rotor in the case of a three-phase DC motor. This is because back EMF is generated as a positive signal and a negative signal, respectively, for the U, V, and W phases.

However, since the number of magnetic poles n is opposite to the north pole and the south pole of the rotor, and the counter electromotive force signals having different polarities are generated at the same time, the counter electromotive force signal generated per one revolution of the motor is substantially 'n / 2 ×. 6 'occurs. The number of occurrences of the back EMF signal may be assumed to be the number of zero-crossings of the back EMF signal.

Therefore, the rotational speed (V) [rps] of the rotor is calculated as "(n / 2 x 6) / t" divided by the time (t) required for one revolution of the rotor, and the period for zero crossing of counter electromotive force Is "t / (n / 2 x 6)". This represents the time difference of the counter electromotive force zero crossing, and is a means for predicting the occurrence time of the counter electromotive force.

2 is a block diagram showing an inverter for driving a sensorless motor according to the present invention. As shown, a signal amplifier 203 for amplifying a back-EMF (BEMF) signal generated when driving a sensorless motor to a predetermined level, and converts an output signal of the signal amplifier 203 into a digital signal. An AD converter 205, a zero crossing detection unit 207 for detecting a zero crossing point of the counter electromotive force signal based on the output signal of the AD converter 205, and a rotation speed of the sensorless motor. The time difference between the zero crossing points of the counter electromotive force signal is predicted, and according to the prediction result, it is determined whether the zero crossing points output from the zero crossing detection unit 207 are included in the predicted time difference category and are output from the AD converter 205. The control unit 201 determines the authenticity of the counter electromotive force signal.

Here, the rotational speed of the sensorless motor may be detected by an external sensor, and the time difference predicted from the controller 201 is a time difference between zero crossing points calculated from the rotational speed V [rps] of the current sensorless motor. Indicates. The predicted time difference category may be set to approximately 100 ms to 200 ms as an acceptable range for the time difference between the calculated zero crossing points. If necessary, the allowable range may not be set, but may be set to a certain ratio, such as 10% to 20% of the time difference.

In addition, if a zero crossing signal is detected within the time difference category, it is regarded as a normal counter electromotive force signal. When the sensorless motor rotates at constant speed, the above-described time difference category may be very small or need not be set. However, when the rotation of the sensorless motor is in an acceleration or deceleration state, the estimated time difference calculated by the controller 201 should be variable. The controller 201 recognizes that the rotation speed of the sensorless motor currently detected is variable, and the zero crossing timing detected by the zero crossing detection unit 207 is allowed as the estimated time difference between the zero crossing times is changed therefrom. To give a scope.

Therefore, when the controller 201 determines that the current back EMF signal output from the AD converter 205 is included in the predicted time difference category, the controller 201 determines that the back EMF signal output from the AD converter 205 is a normal signal. . The inverter including such a configuration ensures reliability of the control of the sensorless motor by discriminating noise and normal back EMF signal.

3 is a graph showing a back EMF signal together with a PWM signal which is a control signal of a sensorless motor according to the present invention. 3A illustrates a superimposed PWM signal and a counter electromotive force signal, and FIG. 3B illustrates a predicted time difference category of the controller 201.

As shown first, when the PWM signal for driving the sensorless motor is generated on the U phase, the counter electromotive force a is generated at the positive edge portion of the PWM signal. In addition, the counter electromotive force (d) is generated at the negative edge portion of the PWM signal on the U phase. As such, when each phase (U, V, W) PWM signal is sequentially supplied, the counter electromotive force signal corresponding thereto is generated as shown in the figures b, c, d, e, f ...

The back electromotive force (BEMF) signal is amplified by a signal amplifier 203 into a signal of a predetermined level, and is converted into a digital signal by the AD converter 205. The digital signal samples an analog counter electromotive force signal at a set frequency. The zero crossing detection unit 207 detects zero crossing of the counter electromotive force signal based on the digital signal. That is, the zero crossing detection unit 207 extracts a zero-crossing time point for each counter electromotive force signal.

At the same time, the control unit 201 receives the rotational speed information of the sensorless motor, the rotational speed information is measured by the rpm of the sensorless motor using a separate speed detector connected from the outside, the measurement result is the control unit ( 201). The controller 201 predicts a zero crossing time point for the counter electromotive force based on the currently detected rotational speed V and the number of poles n of the sensorless motor currently applied.

For example, when the pole number n of the sensorless motor is 4 poles and the rotation speed of the currently detected sensorless motor is 3000 rpm, the time difference between the counter electromotive force signals is calculated to be 1.33 msec. In addition, the controller 201 calculates an allowable range for the time difference between the counter electromotive force signals, that is, a predicted time difference category within a preset range. If the allowable time difference category is 200 ms, the controller 201 calculates the estimated time difference as 1.13 msec to 1.53 msec.

Thereafter, the controller 201 determines whether the zero crossing time point of the counter electromotive force signal detected by the zero crossing detection unit 207 is included in the predicted time difference category. Here, when the controller 201 determines that there is no zero crossing time point of the currently detected back EMF signal within the estimated time difference category, the currently detected back EMF signal is determined as noise. On the other hand, when there is a zero crossing time point of the currently detected back EMF signal within the predicted time difference category, it is recognized that the currently detected back EMF signal is a normal signal.

FIG. 3B is a diagram in which the time difference predicted by the controller 201 and the counter electromotive force signal currently detected are superimposed. When the counter electromotive force (b) signal is generated after the counter electromotive force (a) signal is generated, the controller 201 performs the counter electromotive force (a). The estimated time difference is calculated based on, and it is determined whether the counter electromotive force (b) exists in the predicted time difference category based on the calculation result. In FIG. 3B, the currently detected back EMF signal b is included in the predicted time difference category detected by the controller 201, and thus is determined to be a normal signal.

On the other hand, when the zero crossing detection unit 207 detects the current counter electromotive force c and the control unit 201 calculates the third time difference, the counter electromotive force c is not detected in the predicted time difference category. The control unit 201 regards the currently detected signal as noise.

The control unit 201 removes the signal determined as noise, thereby enabling the control of the sensorless motor. A masking method is used to remove the noise. That is, the controller 201 stores the back EMF signal (data) detected by the zero crossing detection unit 207 in the internal memory as shown in FIG. 3B and generates masking data according to the prediction time difference calculated by the controller 201.

That is, the back EMF data detected in a predetermined time unit is stored in the memory in time series, and the prediction time difference information calculated by the controller 201 is set to '1' and the remaining information is set to '0' to mask the memory. It is. Therefore, when the current counter electromotive force data '1' exists in correspondence with the predicted time difference, the predicted time difference information '1' and the counter electromotive force data '1' are outputted to the AND gate to maintain only a normal signal.

Since the memory is written as '0' during the unexpected time, when the back EMF data '1' is present at the unexpected time, it is masked as '0' by the AND gate output. Therefore, the signal determined to be noise is cleared by the masking data, and only normal back EMF data exists in the memory.

The control unit 201 removes noise according to the masking technique and extracts only normal data, thereby providing only data for accurately driving the sensorless motor.

Although described above with reference to a preferred embodiment of the present invention, those skilled in the art will be variously modified and changed within the scope of the invention without departing from the spirit and scope of the invention described in the claims below I can understand that you can.

The error determination device of the sensorless motor using the back electromotive force signal predicts the occurrence of the back electromotive force of the sensorless motor and allows only the back electromotive force signal corresponding to the prediction result, thereby preventing the detection error of the back electromotive force signal in advance according to the external environment. Has an effect. In addition, based on the stable filtering of the back EMF signal for detecting the position of the sensorless motor, by predicting the occurrence position of the back EMF signal, and performing the drive control of the motor from the prediction result, the circuit configuration of the inverter for driving the sensorless motor It can greatly improve the operation accuracy and reliability of the error determination device of the sensorless motor using the back electromotive force signal which can reduce the system cost by simplifying the system cost, and further improve the performance efficiency. It is an invention with industrial applicability, since the possibility of business is not only sufficient but also practically obvious.

Claims

An apparatus for determining an error signal when driving a sensorless motor using a back electromotive force signal,

A signal amplifier for amplifying a back-EMF (BEMF) signal generated when driving the sensorless motor to a predetermined level;

An AD converter for converting an output signal of the signal amplifier into a digital signal;

A zero crossing detector for detecting a zero-crossing point of the counter electromotive force signal based on the output signal of the AD converter; And

Based on the rotational speed of the sensorless motor, the time difference between the zero crossing points of the counter electromotive force signal is calculated, the zero crossing point output from the zero crossing detector is included in the calculated time difference category, and the counter electromotive force output from the AD converter is determined. Control unit for determining the authenticity of the signal; error determination device of a sensorless motor using a back electromotive force signal, characterized in that consisting of.
The method of claim 1,

The rotation speed of the sensorless motor is an error determination device of the sensorless motor using a back EMF signal, characterized in that detected by an external sensor.
The method according to claim 1 or 2,

The time difference calculated from the controller is a time difference between zero crossing points calculated from the rotational speed V [rps] of the current sensorless motor, and the calculated time difference category is an allowable time difference range at the zero crossing point of time calculated. Error determination device of sensorless motor using back EMF signal.
The method of claim 3, wherein

The calculated time difference is an error determination device of a sensorless motor using a back EMF signal, characterized in that calculated by Equation 1 below.

Time difference = t / (n / 2 × 6) ...

Here, t is the time required per rotation of the sensorless motor, and n is the number of poles of the motor.
The method of claim 3, wherein

The error difference apparatus of the sensorless motor using a back EMF signal, characterized in that the time difference range is 100 kHz to 200 kHz.
The method of claim 3, wherein

The time difference range is an error determination device of a sensorless motor using a back EMF signal, characterized in that the ratio of 10% to 20% with respect to the time difference.