KR100301624B1 - Speed sensorless control method and apparatus for brushless dc motor - Google Patents

Abstract

The present invention relates to a speed sensorless control device and method of a brushless DC motor. In the related art, a sliding observer is frequently used when a method of estimating the speed and position by configuring the observer by looking at the speed and position as a state variable. Since the sliding observer uses a discontinuous function as a switching function, there is a problem inevitably causing high frequency chattering during estimation. Therefore, the present invention is an adder for calculating the estimation error between the actual current flowing through the brushless DC motor and the tracking current obtained from the state equation in the control device of the brushless DC motor, and the limit region of the allowable range of the estimation error obtained in the adder. A sub loop adjuster for setting the gain of the main loop adjuster so as to remain within this area if the estimated error enters the set limit region, and the output of the sub loop adjuster and the estimated error of the adder Brush the binary observer consisting of a main loop regulator that outputs a switching function, and a gain regulator that adjusts the gain of the continuous switching function output from the main loop regulator so that the error trajectory within the limit region can be converged stably to the origin. To the controller of a lease DC motor Use group follow, by so as to follow the speed and position of the brush-less DC motor, which is to obtain an improved estimation performance.

Description

SPEED SENSORLESS CONTROL METHOD AND APPARATUS FOR BRUSHLESS DC MOTOR}

The present invention applies a binary observer, a new observer that has all the advantages of a sliding observer and supplements its disadvantages, to the control of a brushless DC motor to improve the estimation performance, stability and robustness. TECHNICAL FIELD The present invention relates to an apparatus and method for speed sensorless control of a brushless DC motor, which simplifies the structure by eliminating chattering and performing brushless speed control using a continuous switching function. .

Recently, brushless DC motors have been widely used for speed control and tote control of actuators in various industries.

The brushless DC motor should have accurate current control with absolute position information of the rotor.

As a detector for obtaining position information, an electronic position detector using an magnetic encoder such as an encoder (Absolute encoder) or a resolver (Resolver), Hall element, and the like.

Such a position detector is generally expensive, complicated wiring and structure, and is limited in the use environment.

Therefore, the control of the brushless DC motor without using the position detector is preferable.

There are various speed and position sensorless control schemes of the BRISIS motors, which are classified into first, a method of obtaining speed and position information from the counter electromotive force, and a state variable of the actual system and a state variable of the model based on the second model. The method of estimating speed from error, the method of estimating from instantaneous voltage and current measurements by calculation, and the method of estimating speed and position by configuring the observer by looking at the speed and position as state variables.

However, the first method must be a 120 ° energized inverter, and at low speeds, it is difficult to drive due to hardware limitations.

The second method is difficult to detect the actual voltage, and has a problem of causing errors in speed and position due to parameter error.

The third method is sensitive to parameter fluctuations and has a problem that stability in the low speed range is not guaranteed.

Thus, since the third method has its own problems, the fourth method is to use these methods without using them.

The fourth method uses a state observer such as a slide lamp observer. Active research is underway, and among the various observers, the sliding observer is known to have the best estimation performance for parameter fluctuations, measurement noise, and disturbance. Applicable to

However, conventionally, when using the method of estimating the speed and position by viewing the speed and position as the state variables, the sliding observer is frequently used. Since the sliding observer uses the discontinuous function as a switching function, Inevitably there is a problem of causing high frequency chattering.

Therefore, an object of the present invention for solving the conventional problems as described above is to design a new observer having all the advantages of the sliding observer and to compensate for the disadvantage, and apply the designed observer to the control of the brushless DC motor. The present invention provides a speed sensorless control device and method for a brushless DC motor.

Another object of the present invention is to provide a speed sensorless control apparatus and method for a brushless DC motor, which enables accurate estimation of robust and stable location information without chattering without using a speed sensor.

It is still another object of the present invention to provide a speed sensorless control apparatus and method for a brushless DC motor, which has a simple structure and a low cost.

Still another object of the present invention is to provide a speed sensorless control apparatus and method for a brushless DC motor which can reduce the use environment and reduce the maintenance cost by eliminating the cause of failure.

1 is an explanatory diagram showing a sliding surface and an error trajectory of a sliding observer.

2 is a block diagram of a sliding observer.

3 is an explanatory diagram showing a defined region G _δ and an error trajectory of the designed binary observer;

4 is a block diagram of a binary observer.

5 is a block diagram of a speed sensorless control device of the present invention brushless DC motor.

6 is an experimental waveform diagram of an actual speed and an estimated speed of a speed sensorless control device of a brushless DC motor to which a sliding observer is applied.

7 is an experimental waveform diagram of an actual speed and an estimated speed of a speed sensorless control device of a brushless DC motor to which a binary observer is applied.

***** Explanation of symbols for the main parts of the drawing *****

10: speed commander 20: speed controller

30: current controller 40: power converter

50: current detector 60: binary observer

61: adder 62: auxiliary loop adjuster

63: main loop regulator 64: gain regulator

BLDCM: Brushless DC Motor

In order to achieve the above object, the present invention sets an adder for calculating an estimated error between the actual current flowing in the brushless DC motor and the tracking current obtained from the state equation, and sets a limit region of the allowable range of the estimated error obtained in the adder. An auxiliary loop adjuster that sets the gain of the main loop adjuster so as to remain within this range if the estimated error enters the set limit region, and outputs a continuous switching function by inputting the output of the auxiliary loop adjuster and the estimated error of the adder Brushless using a binary observer consisting of a main loop adjuster and a gain adjuster configured to adjust the gain of the continuous switching function output from the main loop adjuster so that the error trajectory within the limit region can be reliably converged to the origin. Sensorless Speed Control of DC Motors It is characterized by applying.

Hereinafter, with reference to the accompanying drawings in detail as follows.

5 is a configuration diagram of a speed sensorless control device of the brushless DC motor of the present invention. As shown in FIG. 5, a speed commander 10 for outputting a command speed set separately, and the speed commander 10 are shown in FIG. The current controller 30 outputs a voltage to follow the current command value output from the speed controller 20, the current controller 30 to follow the command speed output from the speed controller 20, and the current controller 30. A power converter 40 for converting the output voltage into a three-phase AC power source and supplying it to a brushless direct current motor (BLDCM), a current detector (50) for sensing a current flowing through the brushless direct current motor (BLDCM), and The estimated speed is provided to the speed controller 20 by estimating the speed and position of the motor rotor using the current detected by the current detector 50, and the estimated position is provided to the current controller 30. Constitute a binary observer 60.

As shown in FIG. 4, the binary observer 60 includes an adder 61 for obtaining an estimated error? Between the actual current flowing through the brushless DC motor and the tracking current obtained from the state equation, and the adder ( A sub-loop adjuster 62 which sets the limit region of the allowable range of the estimated error σ obtained in (61), and sets the gain of the main loop adjuster so as to remain without leaving this region when the estimated error enters the set limit region. A main loop regulator 63 outputting a continuous switching function by inputting the output of the auxiliary loop regulator 62 and the estimated error? Of the adder 61, and outputted from the main loop regulator 63; It consists of a gain adjuster 64 which adjusts the gain of the continuous switching function so that the error trajectory entering the limit region can be converged stably to the origin.

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

The sliding observer, currently known as the funniest estimator, is designed by applying the theory of sliding mode control to the observer theory, and thus has both advantages and disadvantages of sliding mode control.

Then, the sliding observer having the characteristics as described above, as shown in FIG. Is an discontinuous switching function of the adder 21 and A gain for estimating the estimated speed and the estimated position of the control target by adjusting a switching function 22 for determining a switching function in response to the control function and a gain K of the switching function generated in the switching function determiner 22. It consists of the adjustment part 23.

2, it is possible to calculate the estimated current I from the state equation when detecting the actual current i flowing through the brushless DC motor.

In this way, when the estimated current I is obtained, the adder 21 obtains an estimated error (σ = Ii) between the estimated current I and the actual current i and provides the switching function determiner 22 with the switching function. Determining unit 22 is a discontinuous switching function Determine.

The discontinuous switching function thus determined Is output to the gain adjusting section 23, the gain adjusting section 23 adjusts the gain of the discontinuous switching function and finds the estimated speed and the estimated position from the gain-adjusted function.

Looking at the error trajectory of the sliding observer operating as described above in Figure 1, it can be seen that the error trajectory is severely shaking around the sliding surface.

This phenomenon occurs because of the discontinuous switching function ( Is used).

By using the discontinuous switching function as described above, it is inevitable that a high frequency chattering may be generated when estimating the speed and position of the rotor.

Therefore, to eliminate the occurrence of chattering, the feedback gain (k) can be increased to infinity or the switching can be made to infinite speed.

However, such a thing is practically impossible to implement.

Accordingly, the present invention intends to design a new observer, that is, a binary observer, which has all the advantages of the sliding observer and supplements disadvantages such as a chattering phenomenon.

In the case of binary observers, the boundary layer is defined instead of the sliding plane. Set to

Where δ is Any design parameter representing the width of an area, where range is Is the estimated error.

In Equation 1, when δ is very small, the area becomes the same as the sliding surface, and thus has the same characteristics as the sliding observer.

The relationship between the region defined in the binary observer and the error trajectory is shown in FIG. 3. Where t0, t1, and t2 are is the time to reach δ / 2 and δ.

In the sliding observer, if one gain adjuster is divided into two to adjust the feedback gain well, it is possible to design an observer having excellent estimation performance without chattering as shown in FIG. 3.

Therefore, in the present invention, two regulators, that is, the main loop regulator With secondary loop regulator We want to design a binary observer with.

4 is a block diagram of a binary observer. As shown therein, an adder 61 for obtaining an estimated error σ between the actual current flowing in the brushless DC motor and the tracking current obtained from the state equation, and the adder 61 A secondary loop adjuster 62 which sets a limit region of the allowable range of the estimated error (σ) obtained in the reference value) and sets the gain of the main loop adjuster so as to remain without leaving this region when the estimated error enters the set limit region, A main loop regulator 63 for outputting a continuous switching function by inputting the output of the auxiliary loop regulator 62 and the estimated error? Of the adder 61, and the continuous output from the main loop regulator 63; The gain adjuster 64 is configured to adjust the gain of the switching function to allow the error trajectory within the limit region to converge stably at the origin.

The structure of binary observers is similar to Model Reference Adaptive Control (MRAC).

However, the two differences between the structure of binary observers and model norm adaptive control (MRAC) are that binary observers do not use certain reference models.

This structure makes binary observers easier to implement than adaptive control.

The main characteristics of binary observers are the robustness of parameter variation, insensitivity to disturbances, elimination of high frequency chattering and the finite gain of the main loop.

In addition, two types of variables are represented in FIG. 4, which are variables used in a general feedback control system such as σ (thin arrow →) and variables that change parameters of other regulators such as μ (double arrow). Indicate by dividing).

In Fig. 4, the secondary loop adjuster 62 has an algorithm as shown in Equation 2 as below, and the main loop adjuster 63 has an algorithm as shown in Equation 3.

only,

only,

Where α is a positive constant design parameter.

Equation 2 and Equation 3 are used to design a binary observer to be applied to a brushless DC motor.

The mathematical expression of the brushless DC motor modeled in the stator coordinate system (α, β) is as follows.

ω: angular velocity of the rotor [rad / s], θ _e : electrical angle between the armature and the field [rad]

: Armature resistance, : Armature inductance, : Back EMF constant

: Torque constant, J: moment of inertia, D: coefficient of viscous friction, : Load torque

When vector control is performed by speed sensorless, current and voltage are measurable variables, and speed and position are variables to be estimated. Therefore, the hyperplane of binary observer (4) is defined as the estimation error of current as follows. .

And the structure of the binary observer shown in FIG. 4 is shown as follows.

only, ,

At this time, the switching function determined by the main loop regulator 63 is determined by Equation 2 and Equation 3 as follows.

And, the control gain k and α in binary observer control Invariant ( invariant condition).

here, Invariant condition means that the estimation error (σ) Once inside, keep going It means the condition to stay in the area without leaving the area.

This relationship can be understood with the same concept as the sliding condition in the existing sliding mode control.

By designing K and α to satisfy the invariant condition, the robustness is obtained like a sliding observer.

If Equation 6 is subtracted from Equation 4, an error equation can be obtained. The linearized error equation is expressed as follows.

only, , , , , ,

Region as in sliding observer The estimated error sigma at the boundary of?

In addition, μ must satisfy the following conditions.

However, λ (t) = σ / δ, 0 ≦ h <1, h: const.

domain The condition in which? (T) has entered does not leave the area and remains in the area can be secured by appropriately selecting the gain matrix K ₁ .

σ (t) is the area If you came in Therefore, the order of Equation 9 may be reduced.

Further, the following can be obtained from the condition of Equation 10 and μ.

, t≥t ₀

domain The condition that sigma (t) entered into converges to the origin can be secured by appropriately selecting the gain matrix K ₂ .

In line 1 of Equation 9 of The constant d in the domain is called, and the v is summarized and substituted into the second row of Equation 9 to read as follows.

From Equation 13 If the eigen value of is negative, Can be gradually reduced.

therefore, The boundary of is as follows.

only,

The gain? Of the auxiliary loop adjuster is obtained by substituting μ in the auxiliary loop adjuster of Equation 3 and substituting it into Equation 11.

only,

5 is applied to the speed sensorless control operation of the brushless DC motor using the binary observer having the characteristics as described above.

When the command speed set separately from the speed commander 100 is provided to the speed controller 20, the speed controller 20 transmits a current command value to follow the command speed to the current controller 30.

Then, the current controller 30 obtains an error between the current command value transmitted from the speed controller 20 and the actual current of the brushless DC motor (BLDCM) detected through the current detector 50 and outputs the result to the power converter 40. do.

Accordingly, the power converter 40 determines a switching pattern for the current error obtained by the current controller 30, and outputs the voltage adjusted by the determined switching pattern to the brushless DC motor BLDCM.

At this time, the estimation error (σ), which is a difference between the actual current i detected by the current detector 50 and the estimated current calculated from the state equation of the brushless DC motor, is calculated by the adder 61 of the binary observer 60, and then assisted. The loop regulator 62 and the main loop regulator 63 are supplied.

Then, the secondary loop adjuster 62 uses the estimation error σ to limit the margin where the estimation error may exist. , Set this area Area is defined afterwards The main loop adjuster 63 is output by adjusting the gain of the main loop adjuster 63 so as to remain in the region without deviating.

Accordingly, the main loop regulator 63 has a switching function in which the gain α output from the auxiliary loop regulator 62 is adjusted. Is generated and provided to the gain adjuster 64.

Thus, the gain adjuster 64 is an area defined The gain k of the switching function outputted from the main loop regulator 63 is adjusted and outputted so that the error trajectory inside can converge stably to the origin.

The speed and position of the rotor are obtained from the output of the gain-adjusted switching function.

6 and 7 are waveform diagrams showing sensorless speed control using a sliding observer and a binary observer at a command speed of 900 rpm to -900 rpm, respectively, indicating that both observers show good estimation performance.

However, in the case of the sliding observer, as shown in the enlarged waveform of the estimation error, the speed error sometimes occurs in the steady state part, which is due to the discontinuity of the switching function, which is a binary using the continuous switching function. In the case of the observer, such a phenomenon does not appear.

Therefore, when the speed sensorless control of the brushless DC motor is performed using the binary observer, the discontinuity function is eliminated and thus the estimation performance is improved.

As described in detail above, the present invention obtains improved estimation performance by eliminating discontinuous functions and has only a finite control gain, and improves stability and robustness, and develops a robust and stable estimator. To simplify the structure. In addition, the present invention is to reduce the cost by reducing the expensive speed sensor, to reduce the constraints on the use environment, and also to remove one of the causes of failure to reduce the maintenance, repair costs.

In addition, the present invention can be applied to the development of the control device of various actuators of various guided weapons in the field of defense, the civilian field is effective to be applied to various industrial fields using robotics, NC machine, speed control and torque control.

Claims (2)

A speed controller for outputting a current command value to follow the command speed output from the speed commander, a current controller for outputting a current error between the current command value and the actual current flowing through the brushless DC motor, and a switching pattern for the current error. And a power converter for supplying the voltage according to the determined pattern to the DC motor, a current detector for sensing the current flowing through the DC motor, and an estimator for estimating the speed and position of the rotor of the DC motor. In the controller of a lease DC motor, an adder for calculating an estimated error between the actual current flowing in the brushless DC motor and the following current obtained from the state equation, and a limit region of the allowable range of the estimated error obtained in the adder is set. If the estimated error enters the set limit area, remove it. An auxiliary loop adjuster for setting the gain of the main loop adjuster so as to remain unabsorbed, a main loop adjuster for outputting a continuous switching function by inputting an estimated error of the output of the auxiliary loop adjuster and an adder, and an output from the main loop adjuster Speed sensorless control device of a brushless DC motor, characterized by using a binary observer composed of a gain adjuster that adjusts the gain of successive switching functions to allow the error trajectory within the limit region to converge stably to the origin. . A first step of detecting an actual current flowing through the brushless DC motor, a second step of calculating an estimated current from a state equation of the brushless DC motor, and a third step of obtaining an estimated error which is a difference between the actual current and the estimated current And a fourth step of determining a continuous switching function using the estimated error obtained above, a fifth step of setting a limit area which is an allowable range of the estimated error, and a limit when the estimated error enters the set limit area. A sixth step of setting a gain of the auxiliary loop adjuster so as not to deviate from the area; a seventh step of determining a switching function by inputting the output of the auxiliary loop adjuster whose gain is set in the sixth step; An eighth step of adjusting the gain of the switching function to stably converge the trajectory of the estimated error entering the critical region at the origin; and the eighth stage From the switching function gain adjustment BLDC Brushless DC speed sensorless control method of a motor, characterized in that comprising the steps of claim 9 so as to follow the speed and position of the electric motor in.