FI89636C - FOERFARANDE FOER BESTAEMNING AV INDUKTANS - Google Patents

Description

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The invention relates to a method for determining inductance by means of an electrical circuit or the like controlled by a control arrangement, wherein the measuring arrangement for measuring inductance measures one or more properties of electric current flowing in an electronic circuit or the like, such as force, voltage, electric motor power and / or correspondingly, the control arrangement comprising in particular at least one current-breaking control element, such as one or more transistors or the like, wherein the electric current supply to the electrical circuit or the like or at least its inductive part in the electric circuit or the like phase, depending on the at least two voltages of substantially different magnitudes.

The method according to the invention is particularly suitable for operating and / or controlling various actuators, such as motors, valves, switches, magnetic bearings or the like, their functions being based on determining the position of a moving part of the actuator, such as valve stem, motor rotor or the like. by.

A method based on determining or changing the inductance is currently used, for example, in the control of hydraulic and pneumatic valves. 35 In this case, a separate winding arrangement is placed in connection with the valve, which comprises, for example, a primary winding and two secondary windings. The position of the valve stem is then determined by a metal 8 9 6 3 o 2 indicator connected to the stem, which moves between the primary and secondary windings of the winding arrangement, respectively, as the stem moves. In this case, depending on the position of the indicator, the mutual signal amplitudes of the secondary windings differ from each other, on the basis of which the position of the spindle can be determined, for example, computationally. In principle, a method of the type described above has been utilized, for example, in the so-called LVDT sensor.

10 Correspondingly, for example, the so-called Brushless DC motors are currently commonly used for so-called hall sensor for measuring the rotor switching position and controlling the motor. The Hall sensor is a magnetic field sensor that is mounted on the motor in connection with the rotor. Naturally, in order to achieve a control effect, a certain type of rotor construction, for example an asymmetrical one, is required, with which the magnetic field is changed periodically depending on the position of the rotor.

20

In particular for brushless permanent magnet motors, a sensorless method has also been developed to measure the electric motor force generated by a rotating rotor. In this case, each pole of the motor is operated continuously in principle in two successive stages, the pole in the first stage operating in a motor-like manner and in the second stage in a generator-like manner. In this case, by using the voltage induced at the generator-like pole, i.e. the electric motor force in the control 30, the commutation station of the pole can be determined to restore its operation back to the motor-like. The problem with such a method is that at low speeds, due to the small amount of kinetic energy, the amplitude to be measured must also be very small, which is why it is not possible to apply the method at speeds below a certain limit speed. Devices applying this method therefore have to use, for example, separate starting circuits at low engine speeds, such as when starting or stopping it.

5 In addition to the Hall sensors and LVDT sensors mentioned above, other sensors that mainly measure the position are currently in use, such as inductive and capacitive sensors, eddy current sensors and pulse sensors. In summary, the disadvantages of all such 10 separate sensors are: large size, expensive cost, usually complex interface electronics, fault - increasing effect, difficulties in installing the 15 - sensor, such as tuning, susceptibility to interference and interference.

20 The use of conventional position sensors, for example those mentioned above, always requires special installation, tuning, etc., in addition to which they must be suitably placed in the actuator or the actuator or part thereof must be designed to be suitable for them. However, in many applications today, it is not possible or even possible to use methods that replace position sensors.

The method according to the present invention is intended to provide a decisive improvement over the above-mentioned drawbacks and thus to substantially increase the state of the art in the art. To achieve this purpose, the method according to the invention is mainly characterized in that the inductance is determined at least during said on and off phases by the voltages acting on the electrical circuit or the like at least in the inductive part and / or the electric currents occurring therein. based on the changes.

The most important advantages of the method according to the invention 5 are simplicity and reliability, in which case it is possible to replace the current methods requiring a certain investment or operating condition. It is possible to apply the "holistic" method according to the invention in a wide range of applications in a much more efficient way than, for example, by applying the modern technology fully automatically. The application of the method according to the invention does not significantly increase the external dimensions of the actuator or the necessary wiring arrangements, like most other similar methods currently in use. At its simplest, it is possible to arrange the method according to the invention to operate directly on the basis of the power supply circuit belonging to the actuator.

20

In the following description, the invention will be illustrated in detail with reference to the accompanying drawings, in which Figure 1 shows in principle a diagram of a simple electronic circuit applying the method according to the invention, Figure 2 shows graphs (a, b, c, d) explaining the principles of the method; As an example, a brushless DC motor, Fig. 4 shows a valve, switch or the like for a similar purpose, and Fig. 5 shows a magnetic bearing for a similar purpose.

The method according to the invention is intended for determining the inductance 5 by means of an electrical circuit 1, which is acted upon by control systems 2. To determine the inductance L, one or more properties of the electric current flowing in the electrical circuit 1, such as intensity I, voltage U, electric motor force and / or or similar. The control arrangement 2 comprises an interrupting control element 2a, such as one or more transistors or the like, whereby the current supply I, U acting in the electrical circuit 1 causes the inductive part i of the electrical circuit 1 to form a phase of the control element 2a. phase and off-phase, depending on at least two voltages U1, U2 of substantially different magnitude. In this case, according to the invention, the inductance L is determined during said on and off phases on the basis of the changes in the voltages U1, U2 and / or the electric currents d11, dI2 in the inductive part i of the electric circuit 1.

Fig. 1 shows in principle a simple electrical circuit 1, which illustrates, for example, a circuit passing through one coil 6a of one pole of an electric motor;

In the coil 6a, its winding forms an inductive element L, and the conductor used in the winding resists the resistive element R. Conventionally, in such connections, a diode indicated by reference numeral 4 is additionally used, which allows the coil 6a to bypass in one direction. As a result of the by-pass current, an inductive part i of the electrical circuit 1, operating as follows, is formed between the connection points X of the diode 4.

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The transistor 2a acting as a control element causes the inductive part i of the circuit 1 to be acted upon substantially by two alternating voltages, the first voltage U1 and the second voltage U2. According to a preferred embodiment of the invention 5, the inductance L is then computed on the basis of the mutual deviations of the first voltage U1 and the second voltage U2 and the respective rates of change of the electric current intensities d11 / dt, dI2 / dt.

As a further preferred embodiment, the transistor 2a is operated at a high frequency, at least> 1 kHz, typically> 20 kHz, whereby the electric current forces d11, dI2 change substantially linearly during said on and off phases. In this case, in order to determine the inductance L, the change in the intensity of the electric current during the on and off phases can be estimated by lines d11, dI2, whose slope coefficients of opposite signs correspond to the rates of change of intensity d11 / dt, dI2 / dt. In this case, the mutual deviation e of the rates of change can be determined as the difference of the slope coefficients.

In a further preferred embodiment, the inductance L is determined on the basis of the inverse value of the difference of the current change rates determined from the inductive part i of the electrical circuit 1: d11 / dt to dI2 / dt.

As a further preferred embodiment, the first voltage U1, the second voltage U2 and the respective rates of change of the electric current intensity d11 / dt, dI2 / dt are measured and / or determined from said inductive part i of the electric circuit 1, whereby the inductance L is determined. calculated using the equation: dll / dt - dI2 / dt 1 / L = - 5 UI - U2

Figure 2 shows graphs explaining the application of the method from two electronic circuits 1, 1, j, whose inductances differ from each other. Figures 2a 10 show the alternating first and second voltages U1, U2 during the on and off phases. Figures 2b show the corresponding linear changes in electric current intensity d11, dI2 when a sufficiently high frequency is used. Figures 2c show the rate of linear changes in time d1 / dt, dI2 / dt in the respective steps 15, which correspond to the slope coefficients of the lines shown in Figures 2b. Figures 2d compute the inverse values of the inductance L determined on the basis of the above criteria. In the 20 cases shown, the inductance L 1 of the electrical circuit ln is 2x the inductance L 1 of the electrical circuit 1.

The method according to the invention has been considered later on a theoretical basis, whereby with certain initial assumptions 25 it has been possible to prove the validity of the above-mentioned equation. The theory supporting the above equation is briefly presented below.

The initial assumption is that the switching frequency is so high that the current intensity can be assumed to change linearly in each on and off phase.

For example, when a voltage U is applied to the coil 6a in the electric circuit 1 according to Fig. 1 with a current of I and 35 with a coil resistance of R, the rate of change of the electric current intensity is dl / dt = (U - R1) / L.

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When the voltages of the inductive part i of the electrical circuit 1 in the on and off phases of the transistor 2a are U1 and U2, the respective rates of change of the current intensity are: d11 / dt = (UI - IR) / L 5 dI2 / dt = (U2 - IR) / L, where the difference between these is: dll / dt - dI2 / dt 1 / L = - UI - U2 10 Thus, when UI and U2 are assumed to be constant, the difference in current intensity derivatives is thus inversely proportional to the inductance of the coil regardless of the transistor pulse ratio and coil resistance. . Thus, the result of measurement-15 is also not affected by the change in resistance due to the heating of the coil or by the change in the resistance of the coupling element.

For typical practical applications, it is possible to apply the method according to the invention 20 in connection with a wide variety of actuators, such as electric, pressurized or similar motors, valves, switches, magnetic bearings or the like. In this case, in order to determine the inductance L, e.g. in principle as shown in Fig. 1, by means of a calculating element 5, such as a microprocessor, analog circuit or the like, the inductive part i of the electronic circuit 1 connected to the actuator 6 is fitted with at least measuring means 3a, at least for measuring and / or determining the change in electric current intensity d11, dI2 and the voltage U1, U2 with respect to time. In this case, the method according to the invention can also be applied in the same way as the above-mentioned separate position sensors, in which case an electronic circuit operating on a simple principle according to the method or a part thereof is arranged to operate in the actuator in question. Of course, an electronic circuit or a part thereof operating by the method according to the invention can also replace a sensor previously used in the actuator in question.

5

As discussed above, in many electric actuators, the inductance of the associated coil changes based on the position of the moving part. In this case, the inductance of its power supply circuit also varies as a result of a winding essentially related to the operation of the actuator, such as a solenoid, a coil or the like, directly describing, for example, the position of the moving part. Thus, it is possible to apply the method according to the invention particularly advantageously in connection with an actuator, the electrical circuit 1 of which is essentially connected to the power supply by means of a transistor 2a. In this case, the inductance L can be determined directly from the electrical circuit 1 belonging to the actuator, to which the measuring elements 3a are fitted, for example on the basis of the principle 20 described above.

Figures 3, 4 and 5 show applications of the method implemented with the above-mentioned principles.

Figure 3 shows the application of the method in connection with a reluctance motor representing a brushless DC motor. In this case, e.g. according to the principle shown in Fig. 1, the inductance L calculated by the calculation element 5 affects the motor operation via the control arrangement 2 30 and the associated control element 2b so that the calculated inductance L to be determined during the rotational movement of the rotor 7 , the polarity of the stator 8 is changed (6a, 35 -> 6a2) to maintain the rotational movement.

Fig. 4 shows, as a typical application, for example a valve or a switch, the control of the mandrel 9 89636 10 of which uses a magnetic field provided by a solenoid 6a. The method according to the invention is still very simple to apply, because the position of the spindle 9 can be determined directly from the electrical circuit 1 supplying power to the Sole-5 witch.

Figure 5 further shows, as a further preferred example, the application of the method according to the invention in connection with a movable part 10, such as a shaft or a similar, conventional magnetic bearing 10, which application corresponds in principle to the advantages described above.

It is clear that the invention is not limited to the applications presented above, but can be considerably modified within the framework of the basic idea, already due to the simplicity and general validity of the method. Of course, the method can be applied in a variety of ways in a wide variety of technical applications, of which only general examples have been presented above. Of course, the equations used or the parameters used in them may also differ from those presented in different applications. Of course, the equation used in this presentation, as well as its parameters, can be rearranged in very different forms.

Claims (7)

A method for determining inductance by means of an electrical circuit or the like, which is actuated by a control system (2), wherein for determining the inductance (L) one or more properties, such as intensity (I), are measured with a measuring device (3). ), voltage (U), electromotive force and / or the like, of the electric current in the electrical circuit (1) or the like, wherein the control system (2) comprises in particular at least one electric current cutting off actuating means (2a), such as one or more transistors or the like. , whereby by supplying (I, U) of the electrical current acting in the electrical circuit, the electric circuit (1) or the like or eating at least in its inductive part (i) at least two voltages (UI, U2) which differ substantially from each other is achieved. depending on its potential, depending on the interruption shift, ie. the on-shift and off-shift, characterized in that the inductance (L) is determined at least during said on and off switches on the basis of the voltages (UI, U2) acting in the inductive part (i) of the electrical the circuit or the like and / or the changes (dll, dI2) that precede the intensity of the electric current. 25 The method of claim 1, wherein, with the actuator (2a), as with one or more transistors or the like, affecting the control system (2) belonging to the electrical circuit (1) or the like, substantially at least two alternating voltages are provided. the first voltage (UI) and the second voltage (U2), to act at least in the inductive part (i) of the electrical circuit (1) or the like, characterized in that the inductance (I) is determined by calculating the base of each other the deviations between the at least the first voltage of the electric current (UI) and the second voltage (U2) and the corresponding rates of change (dll / dt, dI2 / dt) of the intensity of the electric current. 16? ? 6 o O. The method of claim 1 or 2, wherein the at least the inductive portion (i) of the electrical circuit (1) or the like is actuated by actuators (2a), such as one or more transistors or the like, belonging to the control system (2). , using a large hacker frequency (> 1 kHz), the intensities of the electric current (dll, dI2) changing substantially linearly during said on and off shifts, characterized in that for determining the inductance (L) the change of the intensity of the electric current is measured by straight lines (dll, dI2), whose angular coefficients with opposite directions correspond to the rates of change (dll / dt, dI2 / dt) of the intensity of the electric current, where the deviation (e) of the change velocities is determined as the difference between Method according to any of the preceding claims 1-3, characterized in that the inductance (L) is determined essentially on the basis of the mutual deviation (e) determined in the inductive part (i) of the electrical circuit (1) or the like. between at least one first current change rate (dll / dt) during the on shift and a second current change rate (dI2 / dt) during the off shift, as on the basis of the reciprocal value of their difference. Method according to any one of the preceding claims 1-4, characterized in that in the inductive part of the electrical circuit (1) or the like, a first voltage (UI), a second voltage (U2) and the the corresponding rates of change (dll / dt, dI2 / dt) of the intensity of the electrical current during the said on and off shifts, the inductance (L) being determined using the equation: dll / dt - dI2 / dt 1 / L UI - U2 17 8 9 6 5ο Method according to any one of the preceding claims 1-5, used in connection with the at least one actuator (6), such as an electric, pressure medium-actuated or similar motor, valve, coupling, magnetic bearing or the like, whose function is at least measured during operation with the measuring device (3) and actuated by the control system (2), which measuring device (3) and control system (2) at least through the 10 or more induction means (6a), such as a coil, winding or the like, in contact with the actuating device ( 6) associated with said electrical circuit (1) or the like, characterized in that in order to determine the inductance (L) by means of a calculation means (5), such as a microprocessor, analog circuit or the like, is arranged in the the inductive portion (i) of the at least one electrical circuit (1) present or disposed in connection with the actuator (6), the at least at least one of the measurement system (3) in data transmission, existing measuring means (3a), at least for calibration and / or determination of the change (dll, dI2) of the intensity of the electric current and / or voltage (UI, U2) relative to time. .25 A method according to any of the preceding claims 1-6, wherein the method is used in connection with an at least one actuator (6), such as an electric, pressurized or similar motor, valve, coupling, magnetic bearing or the like, whose function is at least 30 during operation. are measured by the measuring device (3) and actuated by the control system (2), which measuring device (3) and control system (2) at least through the one or more induction means (6a), such as a coil, winding or the like, in contact with actuators (6) associated with said electrical circuit (1) or the like, and wherein the actuator (2a), such as one or more transistors or the like, belonging to the control system (2), actuate in an electrical circuit (1) or part thereof belonging to the actuator (6), preferably substantially its power supply circuit or the like, characterized in that for determining the inductance (L) m and by means of a computing means (5), such as a microprocessor, analog circuit or the like, directly from the substantially actuator (6) of the electrical circuit (1) or part thereof, is arranged in the inductive part (i) of the actuator 10 (6) ) said electrical circuit (1) at least in data communication in connection with the calculating means (5) existing measuring means (3a), eating at least for measuring and / or determining the change (dll, dI2) of the intensity and / or voltage of the electric current (UI, U2) relative to time.