EP2553694A1

EP2553694A1 - Electromagnetic actuator comprising position control means and method using such an actuator

Info

Publication number: EP2553694A1
Application number: EP11709999A
Authority: EP
Inventors: Charles Blondel
Original assignee: Schneider Electric Industries SAS
Current assignee: Schneider Electric Industries SAS
Priority date: 2010-04-01
Filing date: 2011-02-21
Publication date: 2013-02-06
Anticipated expiration: 2031-02-21
Also published as: CN102934179A; EP2553694B1; FR2958444B1; WO2011121188A1; FR2958444A1; CN102934179B

Abstract

Electromagnetic actuator (100) having a processing unit (2) designed to act on control means (21) generating a control voltage (U_pwm) across the terminals of an actuating coil (3). The processing unit (2) includes first memory means (M1) for storing a first derivative (di₁/dt_on) during a supply period (t_on), second memory means (M2) for storing a second derivative (di₂/dt_off) during a non-supply period (t_off) and computing means (23). Said computing means determine, in succession, a first computing coefficient (A) dependent on the supply bus voltage (U_bus), first and second derivatives (di₁/dt_on, di₂/dt_off) and an operating position (x) on the basis of a first correlation between the operating position (x), the first computing coefficient (A) and the electric current (I).

Description

ELECTROMAGNETIC ACTUATOR HAVING POSITION CONTROL MEANS AND METHOD USING SUCH ACTUATOR

TECHNICAL FIELD OF THE INVENTION

The invention relates to an electromagnetic actuator having a processing unit for acting on control means generating a PWM-type amplitude-modulated control voltage. The actuator comprises at least one actuating coil connected to the control means, means for measuring the electric current flowing in the actuating coil and drifting means calculating the value derived from the electric current. The invention also relates to a method for determining an operating position of an electromagnetic actuator as defined above.

STATE OF THE PRIOR ART

Knowledge of certain operating parameters of the electromagnetic actuators makes it possible to guarantee optimum operation of said actuator. The operation of an electromagnetic actuator is related to its conditions of use. Certain external conditions depend in particular on the nature and / or number of equipment to be operated and / or temperature conditions in which the actuator is used and / or the supply voltage range of said actuator. Other internal conditions depend in particular on the state of aging of the actuator. Since operating conditions may change during use, it may be useful to know the closing and / or opening speeds. A knowledge of the position and / or the speed of the moving armature then makes it possible to adapt the value of the electric current in the excitation coil to minimize the impact forces of the moving parts against the fixed parts and / or for optimize the amount of electric current consumed during the closing phase or the holding phase.

Some solutions are to use additional sensors to know the values of the operating parameters of the actuator. For example, some solutions use position and / or speed sensors. However, the use of sensors is sometimes complex given the limited space available and a more or less hostile environment related for example to high temperatures.

Document FR2745913 describes a method for measuring the position of a mobile core of an electromagnet without the use of additional sensors. The measurement of the position is made from the measurement of the voltage and the current flowing in the excitation coil of this electromagnet. However, in this method, it is assumed that the inductance of the magnetic circuit is constant when the magnetic circuit is in the open position and in the closed position, that is to say that it is assumed in particular that the magnetic circuit is saturated in the closed position. However, in many contactor or contactor-breaker type switchgear devices, the magnetic circuit is not completely saturated in the closed position, so as to make full use of the performance of the magnetic circuit. Thus, the inductance in the closed position is not constant but varies widely as a function of the current flowing in the excitation coil. Therefore, such a method is not suitable.

Other solutions as described in documents FR2835061, US5424637, also describe methods for measuring the position of the moving armature of an electromagnet without the use of additional sensors. These solutions use the measurement of voltage and electric current in the excitation coil to determine the position of the moving armature.

The document US5424637 describes a method of estimating the position thanks to a complete use of electrical, mechanical and magnetic (force) equations. It is then necessary to know all the electrical, mechanical and magnetic parameters of the system. However the modification of the mechanical parameters related in particular to the wear is not taken into account which reduces the precision of the estimate. Document US5481187 calculates the operating position based on the derivative of the flux with respect to the electric current (D (flux) / Di). However, since the flux variation is also dependent on the saturation level, it is difficult to accurately determine the position using only this formula.

Documents EP1069284 and FR2835061 describe a method for determining the position of an armature of an electromagnet using the value of the inductance. The principle consists in carrying out the calculation of the inductance according to the following formula:

U - RI

L =

I

A position table then makes it possible to provide a correlation between the calculated or measured values of the electric current I and the induction L and the position of an armature. This method, although satisfying in theory, has some disadvantages. Indeed, the calculation of the inductance L depending on an integration operation, promotes a certain amount of error in each program cycle. For example, an error of 5% on the value of the inductance can induce errors of 20 to 30% on the calculation of the position. However, when the coil is powered by an amplitude modulated voltage such as a PWM type modulation, there is in this case a mismatch between the generation of the control voltage and the measurement system. Conventional PWM type modulation operates at frequencies between 20 and 40 KHz. The cycle times corresponding to such frequencies are between 50ps and 25ps. An accuracy of one percent then implies a measurement less than one microsecond. The working frequency of the processing unit commonly used for this type of application is of the order of 100 s. Thus, since the working time period of the processing unit is much greater than the cycle time of the PWM modulation, it becomes difficult under these conditions to make an accurate measurement of the voltage applied to the coil. To overcome this problem, it should use processing units with faster microcontrollers but generally too expensive for this type of application. The use of the resistance value of the coil in the calculations makes it necessary to measure this parameter regularly. Indeed, the temperature significantly affects the latter.

SUMMARY OF THE INVENTION

The invention therefore aims to overcome the disadvantages of the state of the art, so as to provide an electromagnetic actuator having precise position control means.

The processing unit of the electromagnetic actuator according to the invention comprises first storage means of a first value derived from electric current during a voltage supply period of the actuating coil, second storage means a second value derived from electric current during a period of non-voltage supply of said coil. The processing unit comprises calculation means for successively determining a first calculation coefficient dependent on the supply bus voltage, first and second values derived from electric current and comprises calculation means and an operating position of the electromagnetic actuator from a first correlation between the operating position, the first calculation coefficient and the value of the electric current.

According to a preferred embodiment, the first and second memory means are connected to the control means so that the memorizations of the first and second derived values are respectively synchronized with the duration of the power supply and the duration of non-power supply. tension of the actuating coil.

Preferably, the first correlation between the operating position, the first calculation coefficient and the value of the electric current is represented from a specific equation setting.

The first correlation between the operating position, the first calculation coefficient and the value of the electric current is represented from a first surface curve giving the operating position as a function of the first calculation coefficient and the value of the electric current. . Preferably, the processing unit comprises storage means storing the first curve in the form of one or more equations.

Preferably, the processing unit comprises storage means storing the first curve in the form of a data table containing a plurality of operating position values of the actuator, first calculation coefficients and values of the electric current. .

According to a development mode of the invention, the processing unit comprises means for measuring a total resistance of the actuating coil from an electrical reference current and / or a reference voltage. The unit further comprises calculating means for determining a second calculation coefficient depending on the first calculation coefficient, the total resistance of the coil, the second derived value and the electric current, and calculation means for determining a speed of rotation. operating the electromagnetic actuator from a second correlation between the operating speed, the second calculation coefficient and between the partial derivative value of the inductance with respect to the displacement at a constant current.

The second correlation between the partial derivative of the inductance with respect to the operating position at a constant current and the operating position and the electric current is shown from a second surface curve.

Preferably, the processing unit comprises storage means storing the second curve in the form of a data table containing a plurality of operating points giving the correspondence between the partial derivative of the inductance with respect to the operating position. at a constant current depending on the operating position and the electric current.

The method according to the invention consists in measuring the electric current flowing in the actuating coil, calculating the value derived from the electric current, storing a first value derived from electric current during a voltage supply period of the coil of actuation, memorize a second value derived from electric current during a period of non-voltage supply of said coil, determining a first calculation coefficient dependent on a supply bus voltage, first and second values derived from electric current and determining an operating position of the electromagnetic actuator from a first correlation between the operating position, the first calculation coefficient and the value of the electric current.

According to a development mode of the invention, the method consists in measuring a total resistance of the actuating coil from a reference electric current and / or a reference voltage, to determining a second calculation coefficient. depending on the first calculation coefficient, the total resistance of the coil, the second derived value and the electric current and determining an operating speed of the electromagnetic actuator from a second correlation between the operating speed, the second coefficient of calculation and between the partial derivative value of the inductance with respect to displacement at a constant current.

BRIEF DESCRIPTION OF THE FIGURES

Other advantages and features will emerge more clearly from the following description of particular embodiments of the invention, given by way of non-limiting examples, and represented in the accompanying drawings in which:

FIG. 1 represents a schematic view of an electromagnetic actuator according to one embodiment of the invention;

FIG. 2 represents a diagram of the processing means of an electromagnetic actuator according to FIG. 1;

FIG. 3 shows a first surface curve representative of the air gap of an electromagnetic actuator as a function of a first calculation coefficient of said actuator and of the electric current flowing in the coil; FIG. 4 shows a second surface curve representative of the partial derivative of the inductance with respect to the operating position at a constant current as a function of the operating position and the electric current. DETAILED DESCRIPTION OF AN EMBODIMENT

According to a first preferred embodiment, the electromagnetic actuator 100 comprises processing means 2 intended to act on at least one actuating coil 3. As an example embodiment such as represented in FIG. 1, the actuator electromagnetic circuit 100 comprises a magnetic circuit 1 having a fixed yoke 11 and a movable armature 12. The movable armature 12 is mounted in the fixed yoke 11. The movable armature 12 and the fixed yoke 11 thus form a deformable magnetic circuit having a gap variable. Said movable armature 12 is movable between an open position K1 and a closed position K2.

The processing means are powered by a Ubus supply bus voltage continuous. The processing means 2 comprise control means 20 generating a PWM modulated amplitude-modulated control voltage UPWM. As an exemplary embodiment, the control means 20 are connected to the actuating coil 3 via a control transistor T1. The control transistor T1 is controlled by its base by a voltage pulse generator 21. As an exemplary embodiment, the pulse generator 21 sends a succession of pulses during which the actuating coil 3 is energized during a so-called supply period T _on . The duration of supply T _on are interspersed with so-called non-feeding duration T ₀ ff. The cycle frequency between the T _on and non-power supply times T ₀ ff is equal to 40 kHz. The corresponding cycle time is equal to 25ps.

The processing means 2 further comprise means for measuring the electric current I flowing in the actuating coil 3. The measuring means may comprise in particular a shunt 24 connected in series with the actuating coil 3. The shunt 24 authorizing a continuous measurement of the electric current is connected to diverter means 25 continuously calculating a derived value di / dt of the electric current I.

According to a preferred embodiment of the invention, the processing unit 2 comprises storage means M1, M2 of the derived value di / dt of the electric current I.

M1 of the first memory means is for storing a first value derived di-i / dt _is electric current I during the feeding time t _on voltage of the actuator coil 3. second storage means M2 of a second value derived di ₂ / dt ₀ ff of electric current during the duration of non-supply t ₀ ff voltage of said actuator coil 3.

The first and second memory means M1, M2 are connected to the control means 20 and their respective operation is synchronized with the pulse generator 21 of the PWM type. In other words, each first value derived dii / dt _one recorded at a time T is then replaced by another first value recorded at a time T + Τ ₀ "and each second value derived di ₂ / dt ₀ ff recorded at a time T is then replaced by another second value recorded at a time T + T _on . Thus, the first and second memory means of the first and second derived values dii / dt _on , di ₂ / dt ₀ ff are respectively synchronized with the supply and non-power supply times ton, t ₀ ff under voltage of the actuating coil 3.

The processing means 2 comprise calculation means 23 for determining a first calculation coefficient A depending on the supply bus voltage U _U s, first and second derived values di ₁ / dt _on , di ₂ / dt ₀ ff of current electric. The first calculation coefficient A is calculated from the following equation (1):

^ ^ di _x di ₂

dt _on dt _off

Where Ubus is the supply bus voltage of the processing means 2. This first calculation coefficient A is periodically determined, in particular according to a working frequency of the processing means 2. By way of example, the processing means comprise calculation means 23 having a microprocessor pC having an equal working frequency. kHz is a corresponding cycle time equal to 100ps.

The processing means 2 comprise calculation means 23 for determining an operating position x of the electromagnetic actuator 100 from a first correlation between the operating position x, the first calculation coefficient A and the current value. The first correlation between the operating position x, the first calculation coefficient A and the value of the electric current I is represented from a first surface curve 10 as shown in FIG. 3 giving the operating position. x as a function of the first calculation coefficient A and the value of the electric current I. The processing unit 2 comprises storage means 22 storing the first surface curve 10 in the form of a data table containing a plurality of values operating position x of the actuator, first calculation coefficients A and values of the electric current I.

Indeed, the first calculation coefficient A is a variable which depends directly on the inductance L and the current I. Indeed, the value of the first calculation coefficient A can be expressed in the form of equation (2) next :

Knowing that the inductance L and the partial derivative of the inductance L with respect to the current I at a constant operating position x are dependent on the operating position x of the actuator and the current I of the coil, the first calculation coefficient A is therefore a variable which depends on the operating position x and the current I.

To determine a correspondence between the value of the first coefficient of calculation A, the operating position x and the current I, two methods are possible to calculate a table of operating points.

A first method consists in using computer modeling software such as, in particular, finite element method modeling. This method involves knowing perfectly the design parameters of the actuator, including the geometry of the different parts, as well as their magnetic properties such as permeability. This solution makes it possible to obtain for a given operating point (a gap and a coil current) the magnetic variables (induction, flux), mechanical (force) and electrical (inductance) variables. From these variables, it is possible to reconstruct the partial derivatives of the inductance as a function of the evolution of the current and / or the operating position x. As shown below in Table 1, it is then possible to obtain a table of operating points giving the correspondence between the first calculation coefficient A, the operating position x and the current I.

Table 1

By a search of points and an interpolation, it is then possible to calculate a new table of operating points giving the correspondence between the first calculation coefficient A, the current I and the operating position x. As shown below in Table 2, operating position values x are associated with values of the first calculation coefficient A and the current I:

According to an improved embodiment of the first method, the first correlation between the operating position x, the first calculation coefficient A and the value of the electric current I is represented from a setting in specific equations. We obtain these equations from computer programs that will "interpolate" the tables above. The processing unit 2 can then comprise storage means 22 memorizing the first curve 10 in the form of one or more equations.

A second method consists in using the analytical method based in particular on the analysis of the reluctant schemes. This solution requires a rather complex definition of the equation linking the operating position to the current and to the inductance. Indeed, the electromagnetic type actuators has many phenomena of leakage and saturation.

The processing means 2 comprise calculation means 23 for determining a second calculation coefficient B dependent on the first calculation coefficient A, the total resistance R of the coil, the second derived value di2 / dt ₀ ff and the electric current. I. The second calculation coefficient B is calculated from the following equation (3):

Where R is the resistance of the actuating coil 3 calculated from a reference electric current Iref and / or a reference voltage Uref.

This second calculation coefficient B is determined periodically, in particular according to the working frequency of the processing means 2.

The processing means 2 comprise calculation means 23 for determining an operating speed V of the electromagnetic actuator 100 from a second correlation between the operating speed V, the second calculation coefficient B and the partial derivative of the electromagnetic actuator. inductance with respect to the operating position x at a constant current. The correlation between the partial derivative of the inductance L with respect to the operating position x at a constant current and the operating position x and the current is represented from a second surface curve 9 as shown in FIG. 4. The processing unit 2 comprises storage means 22 storing the second surface curve 9 in the form of a data table containing a plurality of values of the partial derivative of the inductance L with respect to the operating position. x at a constant current and the operating position x and the electric current I. Indeed, the second calculation coefficient B is a measured value and is a variable which depends directly on the speed V and the partial derivative of the inductance L with respect to the operating position x at a constant current. The second calculation coefficient B can be written in the form of the following equation (4):

From the above equation (4), the value of the speed V can be calculated. Speed can be expressed as the following equation (5):

One method is to use computer modeling software such as finite element modeling. This method involves knowing perfectly the design parameters of the actuator, including the geometry of the different parts, as well as their properties. magnetic such as permeability. This solution makes it possible to obtain the magnetic variables (induction, flux), mechanical (force) and electrical (inductance) variables for a given operating point (an air gap and a coil current). From these variables, it is possible to reconstitute the partial derivatives of the inductance as a function of the evolution of the current and / or the operating position x. As shown below in Table 3 below, it is then possible to obtain a table of operating points giving the correspondence between the partial derivative of the inductance L with respect to the displacement x at a constant current according to of position x and current I.

Knowing the partial derivative value of the inductance L with respect to the operating position x at a constant current as well as the value of the second calculation coefficient B, it is possible to determine the velocity value from the equation ( 5).

According to one embodiment of the invention, the control means 20 connected and controlled by the processing unit 2 deliver in the actuating coil 3 an electric current I controlled according to the calculated operating position x and / or the speed V of the actuator.

The invention also relates to a method for determining an operating position x of an electromagnetic actuator 100 according to the embodiments of the invention as defined above.

According to a first mode of operation, the method consists of

measuring the electric current I flowing in the actuating coil 3;

- calculate the derived value di / dt of the electric current I; - storing a first value derived dii / dt _is electric current during a feeding time t _on voltage of the coil

actuator 3;

- memorize a second value derived from 2 dt ₀ ff of electric current

during a period of non-supply t ₀ ff voltage of said coil;

- Determine a first calculation coefficient A depending on the supply bus voltage U _bU s. first and second values derived dii / dt _on , d2 / dt ₀ ff electric current;

- determine an operating position x of the actuator

electromagnetic system 100 from a first correlation between the operating position x, the first calculation coefficient A and the value of the electric current I.

According to a particular mode of operation, the method consists of:

- Measure a total resistance R of the actuating coil 3 from a reference electric current Iref and / or a reference voltage Uref.

determining a second calculation coefficient B depending on the first

calculation coefficient A, total resistance R of the coil, the second value derived from 2 / dt ₀ ff and the electric current I;

determine an operating speed V of the actuator

electromagnetic system 100 from a second correlation between the operating speed V, the second calculation coefficient B and the partial derivative value of the inductance L with respect to the position of

operation x at a constant current.

Claims

An electromagnetic actuator (100) having a processing unit (2) for acting on control means (21) generating a PWM-type amplitude-modulated control voltage (Upwm), the actuator comprising:

at least one actuating coil (3) connected to the control means (20),

measuring means (24) for the electric current (I) flowing in the

actuating coil (3);

- Derivative means (25) calculating the derived value (di / dt) of the electric current (I);

actuator, characterized in that the processing unit (2) comprises:

first storage means (M1) of a first derived value (d / dton) of electric current during a power supply period (t _on ) of the actuating coil (3);

second storage means (M2) of a second derived value (d2 / dt ₀ ff) of electric current during a non-supply period (t ₀ ff) in voltage of said coil;

calculating means (23) for successively determining:

a first calculation coefficient (A) depending on the bus voltage

power supply (Ut> _U s). first and second derived values (dii / dt _on , di ₂ / dt ₀ ff) of electric current;

an operating position (x) of the electromagnetic actuator (100) from a first correlation between the position of

operation (x), the first calculation coefficient (A) and the value of the electric current (I).

2. Electromagnetic actuator according to claim 1, characterized in that the first and second storage means (M1, M2) are connected to the control means (20) so that the memorizations of the first and second derived values (dii / dt _on , d2 / dt ₀ ff) are respectively synchronized with the supply duration (t _on ) and the duration of no power supply (toff) in voltage of the actuating coil (3). supply duration (t _on ) and the duration of non-supply (t _0ff ) in voltage of the actuating coil (3).

An electromagnetic actuator according to claim 1 or 2, characterized in that the first correlation between the operating position (x), the first calculation coefficient (A) and the value of the electric current (I) is represented from a setting in specific equations.

An electromagnetic actuator according to claim 1 or 2, characterized in that the first correlation between the operating position (x), the first calculation coefficient (A) and the value of the electric current (I) is represented from a first surface curve (10) giving the position of

operation (x) according to the first calculation coefficient (A) and the value of the electric current (I).

5. Electromagnetic actuator according to claim 4, characterized in that the processing unit (2) comprises storage means (22) storing the first curve (10) in the form of one or more equations.

Electromagnetic actuator according to claim 4, characterized in that the processing unit (2) has storage means (22) storing the first curve (10) in the form of a data table containing a plurality of position values of operation (x) of the actuator, first calculation coefficients (A) and values of the electric current (I).

Electromagnetic actuator according to one of the preceding claims, characterized in that the processing unit comprises:

means for measuring a total resistance (R) of the coil

actuating circuit (3) from an electric reference current (Iref) and / or a reference voltage (Uref).

calculating means (23) for successively determining:

- a second calculation coefficient (B) dependent on the first calculation coefficient (A), the total resistance (R) of the coil, the second derived value (di2 / dt ₀ ff) and the electric current (I); an operating speed (V) of the electromagnetic actuator (100) from a second correlation between the speed of

operation V, the second calculation coefficient B and between the partial derivative value of the inductance L with respect to the displacement (x) at a constant current.

Electromagnetic actuator according to claim 7, characterized in that the

second correlation between the partial derivative of the inductance with respect to the operating position (x) at a constant current and the operating position (x) and the electric current (I) is represented from a second surface curve (9).

An electromagnetic actuator according to claim 8, characterized in that the processing unit (2) has storage means (22) storing the second surface curve (9) in the form of a data table containing a plurality of data points. operation giving the correspondence between the partial derivative of the inductance (L) with respect to the operating position (x) at a constant current as a function of the operating position (x) and the electric current (I).

10. A method for determining an operating position (x) of an electromagnetic actuator (100) according to the preceding claims, the actuator comprising:

a processing unit (2) intended to act on control means

(20) generating a PWM-type amplitude modulated control voltage (U _pwrtl ),

at least one actuating coil (3) connected to the control means

(21),

measuring means (24) for the electric current (I) flowing in the actuating coil (3),

- Derivative means (25) calculating the derived value (di / dt) of the electric current;

characterized in that it consists of: - measuring the electric current (I) flowing in the actuating coil (3);

- calculate the derived value (di / dt) of the electric current (I);

storing a first derived value (di-i / dton) for a duration

energizing (t _on ) voltage of the actuating coil (3);

storing a second derivative value (d 2 / dt ₀ ff) during a non-supply period (t ₀ ff) in voltage of said coil;

- determining a first calculation coefficient (A) dependent on a supply bus voltage (Ub _U s), first and second derived values (dh / dton, di ₂ / dt ₀ ff) of electric current;

- determine an operating position (x) of the actuator

electromagnetic (100) from a first correlation between the operating position (x), the first calculation coefficient (A) and the value of the electric current (I).

11. Process according to claim 10, characterized in that it consists of:

- measure a total resistance (R) of the actuating coil (3) from an electric reference current (Iref) and / or a reference voltage (Uref).

- determining a second calculation coefficient (B) dependent on the first calculation coefficient (A), total resistance (R) of the coil, the second derived value (d2 / dt ₀ ff) and the electric current (I);

- determine an operating speed (V) of the actuator

electromagnetic (100) from a second correlation between the operating speed (V), the second calculation coefficient (B) and between the partial derivative value of the inductance (L) with respect to the displacement (x) at a constant current.