WO2009129684A1

WO2009129684A1 - An apparatus and method for measuring inductance parameter of permanent magnet motor

Info

Publication number: WO2009129684A1
Application number: PCT/CN2008/073662
Authority: WO
Inventors: 罗晓
Original assignee: 奇瑞汽车股份有限公司
Priority date: 2008-04-24
Filing date: 2008-12-23
Publication date: 2009-10-29
Also published as: CN101261294B; CN101261294A

Abstract

An apparatus for measuring inductance parameter of permanent magnet motor includes a rotor position monitoring device, detecting the rotor pole position angle of the motor to be tested, a rotation fixing device, locating the rotor of the motor to be tested so as to make the rotor position angle arrive at predetermined position, a test signal generating unit, applying a voltage pulse signal of stated magnitude to the motor to be tested, a signal acquiring unit, recording separately the total current, phase voltage and sampling time of the motor to be tested when the rotor position angle arrives at predetermined position, an inductance computing unit, computing the alternate axis and direct axis inductance of the motor to be tested according to the total current, phase voltage and sampling time acquired by the signal acquiring unit.

Description

Permanent magnet motor inductance parameter measuring device and method

This application is submitted to the Chinese Patent Office on April 24, 2008, and the application number is

200810027647.8, the entire disclosure of which is hereby incorporated by reference in its entirety in its entirety in its entirety in the the the the the the the the the

Technical field

The invention belongs to the field of automatic control, and in particular to a motor control system.

Background technique

The direct-axis and cross-axis inductance parameters of permanent magnet synchronous motors have a great influence on the steady-state and dynamic performance of permanent-magnet synchronous motors. The accuracy of the direct-axis and cross-axis inductance parameters is critical to predicting motor torque and weak magnetic properties, as well as designing the maximum efficiency of the motor, power factor, and other control system parameters. Therefore, it is very important to determine the direct-axis and cross-axis inductance parameters of a permanent magnet synchronous motor.

Since the permanent magnet synchronous motor is excited by a permanent magnet, the excitation mode is quite different from that of the electric excitation synchronous motor. Therefore, the test methods and test requirements for the AC and DC shaft inductance parameters of the electric excitation synchronous motor are no longer applicable to the permanent magnet synchronous motor.

At present, there are no specific provisions in the national and international standards for the test methods for the inductance parameters of the permanent magnet synchronous motor. At the same time, due to the variety of shapes and positions of permanent magnets in permanent magnet synchronous motors, the magnetic circuit of the rotor's AC and DC axes is extremely complicated. The inductance parameters are not only related to the saturation of the magnetic circuit, but also the cross-saturation between the magnetic circuits of the AC and DC axes. phenomenon. Therefore, the measurement of the inductance parameters of the permanent magnet synchronous motor's cross-axis and straight-axis is very complicated.

In the prior art, the finite element analysis method is generally used to determine the inductance parameters of the perpendicular and synchronous axes of the permanent magnet synchronous motor. However, the finite element analysis method must ensure that the magnetic saturation of the permanent magnet synchronous motor is obvious. At the same time, it is necessary to analyze the distribution of multiple currents in the motor winding. The calculation process is complicated and cumbersome, and the calculation amount is large. Summary of the invention

The primary object of the present invention is to provide a permanent magnet motor inductance parameter measuring device and method, which can easily realize the measurement of the inductance parameters of the permanent magnet synchronous motor between the horizontal axis and the straight axis.

The invention provides a permanent magnet motor inductance parameter measuring device, the device comprising: a rotor position monitoring device, a rotation fixing device, a test signal generating unit, a sample signal acquiring unit, and an inductance calculating unit;

The rotor position monitoring device is configured to detect a rotor pole position angle of the motor to be tested; the rotation fixing device is configured to position the rotor of the motor to be tested according to the rotor pole position angle, so that the rotor position angle reaches a preset Location

The test signal generating unit is configured to apply a voltage pulse signal of a certain magnitude to the motor to be tested; and the signal acquiring unit is configured to record the total current and phase voltage of the motor to be tested when the rotor position angle reaches a preset position, respectively. U, and the sampling time t;

The inductance calculation unit is configured to calculate the intersection axis and the direct axis inductance of the motor under test according to the total current i, the phase voltage u, and the sampling time t obtained by the sampling signal acquiring unit.

Preferably, the preset position is: when any two phases of the stator of the motor to be tested are short-circuited, the angle between the pole d-axis and the phase of the stator not short-circuited is 0 degree or 90 degree.

Preferably, when the rotor position angle is positioned at an angle of 0 degrees between the magnetic pole d-axis and the phase where the stator is not short-circuited, the inductance calculation unit calculates the direct-axis inductance of the motor to be tested by the following formula:

ψ _ά (t) = ^ _d (t - i) + [ u(t) - R χ i(t)]At

Wherein R is the electric resistance is not short-circuited phase _winding, ψ Λ, ^ is the linear axis of the stator winding and the quadrature axis flux, i _d , _q are the stator winding straight axis and the intersecting axis current, L _d , J _q are the stator winding straight axis and the intersecting axis inductance respectively, and the sampling time t is less than or equal to 0.1 millisecond.

Preferably, when the rotor position angle is located at an angle of 90 degrees between the magnetic pole d-axis and the phase where the stator is not short-circuited, the inductance calculation unit calculates the cross-axis inductance of the motor to be tested by the following formula:

W _q (t) = w _q (t - l) + [|u(t) - Rxi(t)]At

Where R is the resistance of the winding that is not shorted, ψ _、, ^ is the stator winding straight axis and the cross-axis magnetic flux, i _d , _q is the stator winding straight and cross-axis current, L _d , J _q are the stator winding respectively Straight axis and cross-axis inductance, the sampling time t is less than or equal to 0.1 milliseconds.

Preferably, the rotor position monitoring device comprises a detector, a target disk and a rotor position monitoring unit; the target disk is fixed on the rotor by a rotor bracket, and rotates around the rotor support shaft together with the rotor; the detector passes the detector bracket Fixed on the stator, outputting a sinusoidal signal and a cosine signal of the rotor magnetic pole position angle to the rotor position monitoring unit;

The rotor position monitoring unit receives and processes test data from the detector and outputs information on the magnetic pole position angle of the rotor.

Preferably, the rotation fixing device comprises a slide bar, an adjustment fixing block, and an end plate;

One end of the sliding rod is fixed to the rotor shaft, and the other end is circularly moved in a circular groove of the end plate at a center fixed to the rotor shaft;

When the rotor shaft turns to the desired rotor pole position, adjust the two adjustment blocks to position the rotor shaft in the preset position.

The invention also provides a method for measuring an inductance parameter of a permanent magnet motor, the method comprising: Shorting any two phases of the stator of the motor to be tested;

Fixing the rotor magnetic pole at a position where the magnetic pole d-axis and the stator are not short-circuited at an angle of 0 degree or 90 degrees; applying a voltage pulse signal to both ends of the series circuit composed of the unshorted phase and any remaining phase of the stator And respectively recording the total current i, the voltage U, and the sampling time t information at both ends of the series circuit when the angle between the magnetic pole d-axis and the stator not short-circuited is 0 degree or 90 degree;

According to the total current, voltage, and sampling time information, the direct-axis inductance and the cross-axis inductance of the stator winding of the motor under test at time t are respectively calculated.

Preferably, when the angle between the d-axis of the magnetic pole and the stator is not short-circuited is 0 degree, the straight-axis inductance of the stator winding at time t is calculated by the following formula:

¥ _d (t) = ^d (t - l) + [| (t) - xi(t)]At

_{Li(t) =} Ml ₌ Ml

, _d (t) i(t)

Where R is the resistance of the winding that is not shorted, ψ _、, ^ is the stator winding straight axis and the cross-axis magnetic flux, i _d , _q is the stator winding straight and cross-axis current, L _d , J _q are the stator winding respectively Straight axis and cross shaft inductance.

Preferably, when the angle between the d-axis of the magnetic pole and the stator is not short-circuited by 90 degrees, the cross-axis inductance of the stator winding at time t is calculated by the following formula:

¥ _q (t) = ^ _q (t - l) + [| (t) - R xi(t)]At

Preferably, the sampling time t is less than or equal to 0.1 milliseconds.

Through the technology provided by the invention, the direct axis and the cross-axis inductance parameters of the permanent magnet synchronous motor can be realized. It is indeed measured, and the measuring device used is simple in structure, convenient to use, less in measuring parameters, simple in operation, and does not require a large amount of computing resources.

DRAWINGS

1 is a schematic diagram of connection of a measurement signal generating unit and a measuring circuit;

Figure 2 is a schematic view showing the installation of the rotor position monitoring device;

Figure 3 is a schematic view of the rotating fixture.

detailed description

The invention provides a method for measuring the inductance parameter of a permanent magnet motor, which can easily realize the determination of the direct axis and the cross shaft inductance parameters of the permanent magnet motor.

The method for measuring the inductance parameter of the permanent magnet motor according to the first embodiment of the present invention includes the following steps: Step S101: Short-circuit the two phases of the stators 8 and C of the motor to be tested.

Step S102: The rotor magnetic pole of the motor to be tested is fixed at a position where the magnetic pole d-axis and the stator A are at an angle of 0 degrees by the rotor position monitoring device and the rotation fixing device.

Step S103: applying a voltage pulse signal to the series circuit composed of the stator and the B phase of the motor to be tested, recording the total current i flowing through the phase A of the series circuit, the series circuit (AB phase) voltage U, and the sample Time t.

Step S104: Calculate the direct-axis inductance of the stator winding of the motor under test at time t.

When the rotor pole is fixed at the 0-degree angle between the d-axis and the phase A of the magnetic pole, the direct-axis inductance of the stator winding at time t is calculated according to the following formula:

Ψ _ά (t) = (t - 1) + [ u _ab (t) - R xi _a (t)] At z _{(t) =} ) ₌ ) ( 2 ) "t) _a (t) Where R is the resistance of the A-phase winding, ψ _Λ , ^ is the stator winding straight axis and the cross-axis magnetic flux, _d , i _q are the stator winding straight axis and the intersecting axis current, J _d , J _q are the stator winding straight axis and the intersection The shaft inductance, the sample time t is less than or equal to 0.1 milliseconds.

Step S105: Fix the rotor magnetic pole of the motor to be tested at a position where the magnetic pole d-axis and the stator A are at an angle of 90 degrees.

Step S106: Apply a voltage pulse signal to the series circuit composed of the stator and the B phase of the motor to be tested, and record the total current i, the AB voltage U, and the sampling time t flowing through the phase A of the series circuit.

Step S107: Calculate the cross-axis inductance of the stator winding of the motor under test at time t.

When the rotor pole is fixed at a position where the angle between the d-axis and the phase A of the magnetic pole is 90 degrees, the cross-axis inductance of the stator winding at time t is calculated according to the following formula:

¥ _q (t) = ^ _q (t -l) + [|u _ab (t) - Rxi _a (t)]At ₍ 3 ) z _{(t) =} ) ₌ l ( 4 ) where R is the phase A winding The resistance, _Ψά , _q are the stator shaft straight axis and the cross-axis magnetic flux, _d , i _q are the stator winding straight axis and the cross-axis current, J _d , J _q are the stator winding straight axis and the cross-axis inductance respectively, and the sampling time t is smaller than Or equal to 0.1 milliseconds.

The method for measuring the inductance parameter of the permanent magnet motor according to the second embodiment of the present invention differs from the first embodiment in that: the stators 8 and C of the motor to be tested are short-circuited, and the rotor poles of the motor to be tested are respectively fixed on the magnetic pole d-axis and The angle between the stator B phases is 0 degrees and 90 degrees, and a voltage pulse signal is applied to the series circuit composed of the stators 8 and C of the motor to be tested, and the positions of the magnetic pole d-axis and the stator B are recorded at 0 degree and 90 degree respectively. The total current i, the BC phase voltage U, and the sampling time t of the phase B of the series circuit are calculated, and the direct-axis inductance and the cross-axis inductance of the stator winding of the motor under test at time t are respectively calculated. When the rotor pole is fixed at a position where the angle between the d-axis of the magnetic pole and the phase B is 0 degree, the direct-axis inductance of the stator winding at time t is calculated according to the following formula:

¥ _d (t) =

+ [| _bc (t) - R xi _b (ΐ)] Δΐ ₍ 5 ) z _(t)= ) ₌ ) (6) "t) , _b (t)

When the rotor pole is fixed at a position where the angle between the d-axis and the B-phase of the magnetic pole is 90 degrees, the cross-axis inductance of the stator winding at time t is calculated according to the following formula:

¥ _q (t) = W _q (tl) + [|u _bc (t)-Rxi _b (ΐ)] Δΐ ₍ 7 ) z _(t)= ) ₌ (8) where R is the resistance of the B-phase winding, ψ _Λ , ^ is the stator winding straight axis and the cross-axis magnetic flux, _d , i _q are the stator winding straight axis and the intersecting axis current, J _d , J _q are the stator winding straight axis and the cross-axis inductance respectively, and the sampling time t is less than or equal to 0.1 milliseconds.

The method for measuring the inductance parameter of the permanent magnet motor according to the third embodiment of the present invention is different from the first embodiment in that: the stators 8 and B of the motor to be tested are short-circuited, and the rotor poles of the motor to be tested are respectively fixed on the magnetic pole d-axis and The angle between the phases of the stator C is 0 degrees and 90 degrees, and a voltage pulse signal is applied to the series circuit composed of the stator A and the phase A of the motor to be tested, and the positions of the d-axis of the magnetic pole and the stator C are recorded at positions of 0 and 90 degrees, respectively. The total current i, the CA phase voltage U, and the sampling time t flowing through the phase C of the series circuit are calculated, and the direct-axis inductance and the cross-axis inductance of the stator winding of the motor under test at time t are respectively calculated.

When the rotor pole is fixed at a position where the angle between the d-axis and the C-phase of the magnetic pole is 0 degree, the direct-axis inductance of the stator winding at time t is calculated according to the following formula: ψ _ά (t) =

+ [| _ca (t) - xi _c (t)]At ₍ 9 ) z _(t)= ) ₌ ) ( io)

"t) _c (t)

When the rotor pole is fixed at a position where the angle between the d-axis and the C-phase of the magnetic pole is 90 degrees, the cross-axis inductance of the stator winding at time t is calculated according to the following formula:

q (t) = ^ _q (t - 1) + [ u _ca (t) - R xi _c (t)]At

j 111 /

z _(t)= ) ₌ l _{( 12} ) where R is the resistance of the C-phase winding, ψ _Λ , _q is the stator winding straight and cross-axis flux, _d , i _q is the stator winding straight and cross-axis current, J _d J _q is the stator winding straight axis and the cross-axis inductance, respectively, and the sampling time t is less than or equal to 0.1 millisecond.

By using the method of the invention, the accurate measurement of the direct-axis and cross-axis inductance parameters of the permanent magnet synchronous motor can be realized, and the measuring process is simple and convenient, the measuring parameters are small, the operation is simple, and a large amount of computing resources are not required. The invention also provides a permanent magnet motor inductance parameter measuring device.

The device includes: a rotor position monitoring device, a rotation fixing device, a test signal generating unit, a sample signal acquiring unit, and an inductance calculating unit.

The rotor position monitoring device is configured to detect the rotor magnetic pole position angle of the motor under test.

The rotation fixing device is configured to position the rotor of the motor to be tested according to the rotor magnetic pole position angle detected by the rotor position monitoring device, so that the rotor magnetic pole position angle reaches a preset position.

When the stator of the motor to be tested is short-circuited by any two phases, the preset position is that the magnetic pole d-axis and the stator are not short-circuited. The angle of the phase is 0 or 90 degrees.

The test signal generating unit is configured to apply a voltage pulse signal of a certain magnitude to the motor to be tested.

The signal acquisition unit is configured to record the total current 1, the phase voltage U, and the sampling time t of the motor to be tested when the rotor magnetic pole position angle reaches the preset position.

The inductance calculation unit is configured to calculate the intersection axis and the direct axis inductance of the motor under test according to the total current 1, the phase voltage U, and the sampling time t obtained by the signal acquisition unit.

1 is a structural diagram of a test signal generating unit according to the present invention.

The test signal generating unit comprises: a regulated power supply and a three-phase inverter bridge. By controlling the turn-on and turn-off of each of the three-phase inverter bridges, a pulse voltage test signal is generated by the regulated power supply and output to the motor under test.

Specific methods for controlling a three-phase inverter bridge include:

The PWM signal is sent to the base of each triode in the three-phase inverter bridge to control the turn-on and turn-off of each triode. By adjusting the duty cycle and frequency of the PWM signal, the length of time each transistor is turned on and the frequency of the switching are adjusted to generate the voltage pulse signal required for the test.

Referring to Figure 2, there is shown a schematic view of the installation of the rotor position monitoring device of the present invention.

The rotor position monitoring device includes a target disk 1, a detector 2, and a rotor position monitoring unit (not shown).

The target disk 1 is a structured target disk, and the detector 2 is a sensor element, which together form a position sensor based on the eddy current effect.

The target disk 1 is fixed to the rotor 4 via a rotor holder 7 and rotates around the rotor support shaft 6 together with the rotor 4. The detector 2 is fixed to the stator 3 via a probe holder 5.

Detector 2 outputs the sine and cosine signals of the rotor pole position angle to the rotor position monitoring list Two AD channels of the element (not shown).

The rotor position monitoring unit receives and processes the test data from the detector and outputs information on the magnetic pole position angle of the rotor.

Preferably, in order to cooperate with the detector 2, the outer side of the target disk 1 has a sinusoidal or cosine shape perpendicular to the disk surface direction, and is made of a metal material such as aluminum or iron.

Preferably, the rotor position monitoring unit uses a DSP chip of the type TMS320 808.

Referring to Figure 3, there is shown a structural view of the rotating fixture of the present invention.

The rotation fixing device includes a slide bar 10, adjustment fixing blocks 11, 12, 13, and an end plate 8.

One end of the sliding rod 10 is annular, and can be integrally fixed with the rotor shaft 16 by meshing or other means, and the other end of the sliding rod 10 can be circularly fixed in the arcuate groove 9 of the end plate 8 at one end fixed to the rotor shaft. motion.

The adjustment fixed block is divided into a fine adjustment fixed block 11 and a coarse adjustment fixed block 12, 13. When the rotor shaft 16 is turned to a position close to the desired rotor pole position, the rotor shaft 16 can be rotated only in a relatively small range by adjusting the two coarse adjustment blocks 12 and 13, and the fine adjustment block 11 can be adjusted by adjustment. The rotor shaft 16 is positioned at a desired position.

The process of measuring the inductance parameters of the intersecting axis and the straight axis using the permanent magnet motor inductance parameter measuring device of the present invention is as follows:

Step S1: Connect the stator winding to the first bridge arm of the three-phase inverter bridge of the three-phase winding of the stator of the motor according to the wiring shown in Figure 1. The phase B and phase C are short-circuited and the three-phase inverse The second bridge arm of the transformer bridge is connected, and the third bridge arm of the three-phase inverter bridge is suspended.

Step S2: The rotor is slowly rotated, the rotor position detection value is obtained by the rotor position monitoring device, and the rotor position angle is calculated. -li- 转子Use TI's DSP chip as the rotor position monitoring unit to perform rotor position detection. Run the rotor position detection code, slowly rotate the rotor, and use the test data from the detector 2 shown in Figure 2 to calculate the rotor position angle. The rotor position is continuously adjusted by the rotation fixture shown in Fig. 3 until the rotor position angle reaches a predetermined position, such as a 0 position (or a 90 degree position). The angle referred to herein refers to the angle between the d-axis and the phase A of the synchronous rotating coordinate system, and the rotor shaft 16 is positioned at a predetermined position by adjusting the coarse adjustment fixed speeds 12, 13 and the fine adjustment fixed block 11.

Step S3: generating a test signal by using the measured motor unit A, B with a voltage pulse signal is applied to a certain size, records A, B line voltage _{_¾ (Wfle)} and phase current. And calculate the straight-axis inductance J _d and the cross-axis inductance L _{q of the} stator winding of the motor under test. When the rotor position angle is positioned at 0 degrees, i _d = i _a = = 3/

Uab ~Uac ~ /2 U d The d-axis inductance L _d (0) which varies with the d-axis current can be obtained by the equations (1) and (2).

¥ _d (t) _ab (t) - Rxi _a (t)]At ( 1 )

d(t) (2)

0 , _a (t) When the rotor position angle is positioned at 90 degrees, i _q

By the formula and (4;), the q-axis inductance L _d (. _q (t) = W _q (tl) + [ u _ab (t) - Rxi _a (t)] At (3) can be obtained as a function of the q-axis current. )

(4)

' _q (t) -' (t) where R is the resistance of the A-phase winding. _ψ Λ, ^ stator windings direct and quadrature axis magnetic fluxes, _d, i _q of the stator windings direct and quadrature axis currents, J _d, J _q are stator windings direct and quadrature axis inductance, preclude the injection time t is less than or Equal to 0.1 milliseconds.

Similarly, in step S1, the phase B or phase C of the three-phase winding of the stator of the motor under test can be reversed. The first bridge arms of the variable bridge are connected. Correspondingly, the eight or C phases are short-circuited or 〇, the B-phase is short-circuited, and then connected to the second bridge arm of the three-phase inverter bridge, and the third bridge arm of the three-phase inverter bridge Suspended. The other steps are analogous.

Through the technology provided by the invention, the accurate measurement of the direct-axis and cross-axis inductance parameters of the permanent magnet synchronous motor can be realized, and the measuring device used is simple in structure, convenient to use, less in measuring parameters, simple in operation, and does not need to occupy a large amount of computing resources.

Claims

Claim

A permanent magnet motor inductance parameter measuring device, characterized in that: the device comprises: a rotor position monitoring device, a rotation fixing device, a test signal generating unit, a sample signal acquiring unit, and an inductance calculating unit;

2. The device according to claim 1, wherein the preset position is: when the stator of the motor to be tested is short-circuited by any two phases, the magnetic pole d-axis and the stator are not short-circuited The angle is 0 or 90 degrees.

3. The apparatus according to claim 2, wherein the inductance calculation unit is used when the rotor position angle is positioned at an angle of 0 degrees between the magnetic pole d-axis and the phase where the stator is not short-circuited. The formula calculates the direct-axis inductance of the motor under test:

ψ _ά (t) = ^ _d (t - l) + [ u(t) - R χ i(t)]At

z _{(t) =} ) ₌ )

, _d (t) i(t)

Wherein R is the resistance of the winding is not shorted _phase, ψ Λ, ^ is the linear axis of the stator winding and the quadrature axis flux - i _d , _q are the stator winding straight axis and the intersecting axis current, L _d , J _q are the stator winding straight axis and the intersecting axis inductance respectively, and the sampling time t is less than or equal to 0.1 millisecond.

4. The apparatus according to claim 2, wherein the inductance calculation unit is used when the rotor position angle is positioned at an angle of 90 degrees between the magnetic pole d-axis and the phase where the stator is not short-circuited. The formula calculates the cross-axis inductance of the motor under test:

W _q (t) = W _q (t - l) + [|u(t) - R xi(t)]At

5. The apparatus according to claim 1, wherein said rotor position monitoring device comprises a detector, a target disk and a rotor position monitoring unit;

The target disk is fixed on the rotor by a rotor bracket, and rotates around the rotor support shaft together with the rotor; the detector is fixed on the stator through the detector bracket, and outputs a sinusoidal signal and a cosine signal of the rotor magnetic pole position angle to the rotor position monitoring Unit

6. The device according to claim 1, wherein the rotation fixing device comprises a slide bar, an adjustment fixing block, and an end plate;

One end of the sliding rod is fixed to the rotor shaft, and the other end is circularly moved in a circular groove of the end plate at a center fixed to the rotating shaft of the rotor; When the rotor shaft is turned to approach the desired rotor pole position, the two adjustment blocks are adjusted to position the rotor shaft in a preset position.

A method for measuring an inductance parameter of a permanent magnet motor, the method comprising: shorting any two phases of a stator of the motor to be tested;

8. The method according to claim 7, wherein when the angle between the d-axis of the magnetic pole and the stator is not short-circuited is 0 degree, the straight-axis inductance of the stator winding at time t is calculated by the following formula: :

¥ _d (t) = ^d (t - l) + [| (t) - xi(t)]At

_{Li(t) =} Ml ₌ Ml

, _d (t) i(t)

9. The method according to claim 7, wherein when the angle between the d-axis of the magnetic pole and the stator is not short-circuited is 90 degrees, the cross-axis inductance of the stator winding at time t is calculated by the following formula: :

¥ _q (t) = ^ _q (t - l) + [| (t) - R xi(t)]At

Wherein R is the electric resistance is not shorted winding _phase, ψ ά, ^ is the linear axis of the stator winding and the quadrature axis flux, i _d , _q are the stator winding straight axis and the intersecting axis current, and L _d and J _q are the stator winding straight axis and the intersecting axis inductance respectively.

10. Method according to any one of claims 7 to 9, characterized in that the sampling time t is less than or equal to 0.1 milliseconds.