DEVICE FOR DETECTING THE DIRECTION OF ROTATION OF A ROTOR, ASSOCIATED CONTROL AND DRIVE SYSTEMS, AND ASSOCIATED METHOD

A device (17) for detecting the direction of rotation of a rotor for a magnetic bearing includes comparing means (100), first determining means (105), and second determining means (107). The comparing means (100) compares the speed of rotation of the rotor with a predefined speed threshold (Se). The first determining means (105) determines the speed of rotation gradient of the rotor. The second determining means (107) determines the direction of rotation of the rotor from the result of the comparison of the speed of rotation of the rotor with the predefined speed threshold (Se) and the value of the determined parameter representative of the kinetics of the rotor.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to French Application No. 2301931, filed Mar. 2, 2023, the entirety of which is hereby incorporated by reference.

FIELD

The present disclosure relates to the control of magnetic bearings.

The present disclosure more particularly relates to a device for detecting the direction of rotation of a rotor of a magnetic bearing, to a system for controlling a magnetic bearing comprising such a device, to a drive system having such a system and a magnetic bearing, and to a method for detecting a change in the direction of rotation of the rotor.

BACKGROUND

Conventionally, magnetic bearings are implemented in systems having a rotor operating at a high rotational speed.

A magnetic bearing supports the rotor by magnetic levitation in a stator of the system.

The magnetic bearings are controlled by a control system generally comprising a synchronous filter implementing algorithms for controlling the magnetic bearing.

The synchronous filter comprises a modulation module which changes the reference system from a stator reference system to a rotor reference system, an algorithm for controlling the magnetic bearing which performs operations in the rotor reference system in order to simplify said operations, and a demodulation module which changes the reference system from the rotor reference system to the stator reference system.

The operations for changing the reference system implement trigonometric functions that depend on the direction of rotation of the rotor.

When the control system is started up, the direction of rotation of the rotor is defined and input in the modulation and demodulation modules manually by an operator.

If the direction of rotation that was input is not representative of the direction of rotation of the rotor, the modulation module supplies a zero value after filtering.

The operator can make an error regarding the direction of rotation that is liable to adversely affect the system in which the bearing is implemented.

Moreover, when it is necessary to modify the direction of rotation, an operator must intervene to manually change the direction of rotation of the rotor.

It is therefore proposed to overcome all or some of these drawbacks.

SUMMARY

In light of the above, the present disclosure proposes a method for detecting a change in the direction of rotation of a rotor of a magnetic bearing, comprising:determining the speed of rotation gradient of the rotor,comparing the speed of rotation of the rotor with a predefined speed threshold, anddetecting a change in the direction of rotation of the rotor from the result of the comparison of the speed of rotation of the rotor with the predefined speed threshold and the determined speed of rotation gradient of the rotor.

The change in the direction of rotation of the rotor is detected from the speed of rotation of the rotor and from the speed of rotation gradient of the rotor in order to adapt the algorithms for controlling the magnetic bearing autonomously and automatically without manual intervention by an operator.

Advantageously, when the rotor revolves in a first direction of rotation, the method comprises:detecting a first reversal of the direction of rotation of the rotor in a second direction of rotation that is counter to the first direction of rotation, when the absolute value of the speed of rotation of the rotor is less than the speed threshold and when the speed gradient is negative, anddetecting a second reversal of the direction of rotation of the rotor in the first direction of rotation following the first reversal when the speed gradient is greater than or equal to zero, and when the absolute value of the speed of rotation of the rotor is less than the speed threshold.

What is also proposed is a device for detecting a change in the direction of rotation of a rotor for a magnetic bearing, comprising:comparing means configured to compare the speed of rotation of the rotor with a predefined speed threshold,first determining means configured to determine the speed of rotation gradient of the rotor, andsecond determining means configured to detect the change in the direction of rotation of the rotor from the result of the comparison of the speed of rotation of the rotor with the predefined speed threshold and the determined speed of rotation gradient of the rotor.

Preferably, the second determining means are configured to:detect a first reversal of the direction of rotation of the rotor in a second direction of rotation that is counter to the first direction of rotation, when the absolute value of the speed of rotation of the rotor is less than the speed threshold and when the speed gradient is negative, anddetect a second reversal of the direction of rotation of the rotor in the first direction of rotation following the first reversal when the speed gradient is greater than or equal to zero, and when the absolute value of the speed of rotation of the rotor is less than the speed threshold.

What is also proposed is a control system for a magnetic bearing comprising a device as defined above, and a synchronous filter including at least one algorithm for managing the magnetic bearing, the algorithm comprising a variable gain managed by said device depending on the direction of rotation of the rotor.

The synchronous filter preferably comprises a modulation module and a demodulation module, the modulation module comprising a first algorithm comprising at least one variable gain managed by said device depending on the direction of rotation of the rotor, and the demodulation module comprising a second algorithm comprising at least one variable gain managed by said device depending on the direction of rotation of the rotor.

Advantageously, the synchronous filter also comprises a control module connected on the one hand to the modulation module and on the other hand to the demodulation module, the control module implementing an algorithm for correcting the imbalance of the rotor.

What is also proposed is a drive system comprising a magnetic bearing having a rotor and a stator having coils distributed evenly in the stator forming at least one servocontrol spindle, a power converter supplying power to the servocontrol spindle, and a control system as defined above managing the power converter.

DETAILED DESCRIPTION

Reference is made toFIG.1, which illustrates a drive system comprising a magnetic bearing1, a power converter2and a control system3.

As is known per se, the magnetic bearing1comprises a stator4and a rotor5positioned in the stator4, and a direct orthogonal reference system R(O, V, W) having two aces V, W and an origin O centred on the axis of rotation of the rotor5.

The stator4comprises coils6distributed evenly in the circumferential direction of the inner side of the stator4, two diametrically opposite coils being connected to one another so as to be supplied with power at the same time by the power converter2.

Two diametrically opposite stator coils define a servocontrol spindle of the magnetic bearing and make it possible to manage this spindle.

The stator4comprises for example four coils6a,6b,6c,6dforming four pairs of poles P1, P2, P3, P4connected to the power converter2.

The stator4also comprises two position sensors7,8for the rotor5that measure the position of the rotor5.

A first position sensor7is disposed on a first axis V of the reference system R(O, V, W) and a second position sensor8is disposed on the second axis W of the reference system R(O, V, W).

The stator4also comprises a speed sensor9that measures the speed of rotation of the rotor5.

The measurements generated by the position sensors7,8are sent to the inputs10,11of the control system3and the measurements generated by the speed sensor are sent to a third input12of the control system3.

The control system3also comprises two outputs14,15connected to the power converter2.

FIG.2schematically illustrates an exemplary embodiment of the control system3.

The control system3comprises a synchronous filter16, a device17for detecting a change in the direction of rotation of the rotor5, and means18for determining the angular position of the rotor5from the measurements supplied by the speed sensor9.

The control system3also comprises a processing unit19implementing the synchronous filter16, the detection device17, and the means18for determining the angular position connected to the third input12.

The angular position determining means18determine, in a known manner, the angular position of the rotor5from the data generated by the speed sensor9by estimating the duration needed for the rotor5to perform one revolution over a first period of rotation of the rotor5, then carries out a linear interpolation over the estimated duration to estimate the position of the rotor5over a second period following the first period of rotation.

The synchronous filter16comprises a modulation module20, a control module21and a demodulation module22.

The modulation module20comprises a first input23connected to a first input10of the control system3, a second input24connected to the second input11of the control system3, a first output25connected to a first input26of the control module21, and a second output27connected to a second input28of the control module2.

The modulation module20also comprises a third input29connected to the angular position determining means18, and a control input30connected to an output31of the detection device17.

The detection device17comprises an input170connected to the third input12of the control system3.

The control module21comprises a first output32connected to a first input33of the demodulation module22, and a second output34connected to a second input35of the demodulation module22.

The demodulation module22also comprises a first output36connected to the first output14of the control module3, and a second output37connected to a second output15of the control module3.

The demodulation module22also comprises a third input38connected to the angular position determining means18, and a control input39connected to an output31of the detection device17.

As is known, the modulation module20filters the sinusoidal signals supplied by the position sensors7,8such that the first output25supplies a first continuous value indicative of the amplitude of the sinusoidal signal supplied by the first position sensor7, and such that the second output27supplies a second continuous value indicative of the amplitude of the sinusoidal signal supplied by the second position sensor8.

The modulation module20implements a low-frequency filtering algorithm allowing frequencies to pass that are equal to the frequency of rotation of the rotor5to within a threshold so as to also make it possible to change the basis of the reference system R(O, V, W) to a direct orthogonal reference system R1of the rotor5of which the origin is a point on the axis of rotation of the rotor5.

The threshold is for example equal to 10 Hz.

The control module21implements an algorithm for correcting the imbalance determined by the modulation module20and the demodulation module22changes the reference system R1linked to the rotor5to the reference system R linked to the stator4.

As the modulation module20and demodulation module22have similar structures, only one exemplary embodiment of the modulation module20and one exemplary embodiment of the processing module21are presented below.

FIG.3schematically illustrates an exemplary embodiment of the modulation module20.

The modulation module20comprises four multipliers40,44,52,48each comprising a first input41,45,49,53, a second input42,47,50,52, and an output43,46,51,55.

The modulation module20comprises a sine operator56comprising an input57connected to the third input29of the modulation module20and an output58connected to the second inputs47,50of a second and a third multiplier44,48.

The modulation module20also comprises a cosine operator59comprising an input60connected to the third input29of the modulation module20and an output61connected to the second inputs42,54of a first and a fourth multiplier44,52.

The first inputs41,54of the first and the second multiplier40,44are connected to the first input23of the modulation module20, and the first inputs49,53of the third and the fourth multipliers48,52are connected to the second input24of the modulation module20.

The modulation module20also comprises a first variable gain62comprising an input63connected to the output46of the second multiplier44, an output64, and a management input65connected to the control input30of the modulation module20.

The modulation module20comprises a first adder66comprising an addition input67connected to the output55of the fourth adder52, a subtraction input68connected to the output64of the first gain62, and an output69connected to an input71of a saturator70of the module20.

The saturator70also comprises an output72connected to the second output27of the module20.

The modulation module20also comprises a second variable gain73comprising an input74connected to the output51of the third multiplier48, an output75, and a management input76connected to the control input30of the modulation module20.

The module comprises a second adder77comprising a first addition input78connected to the output43of the first adder40, a second addition input79connected to the output75of the second gain73, and an output80connected to an input82of a second saturator81of the module20.

The second saturator81also comprises an output83connected to the first output25of the module20.

The saturators70,81make it possible to avoid the reversals of variables relating to the fixed-point algorithms.

The first and second gains62,73are managed such that they multiply the value received at their input63,74by a multiplying coefficient which takes the numerical value 1 or −1 depending on the direction of rotation of the rotor5.

If the direction of rotation of the rotor5is oriented from the axis V to the axis W in the reference system R (reverse direction), the multiplying coefficient is for example equal to 1, and if the direction of rotation of the rotor5is oriented from the axis W to the axis V in the reference system R (forward direction), the multiplying coefficient is equal to −1.

The value of the multiplying coefficient is determined by the detection device17, as described below.

It is assumed that the first position sensor7supplies a sinusoidal signal Vcos and that the second position sensor8supplies a sinusoidal signal Vsin such that:

where A is the amplitude of the signals and θ is the angular position of the rotor5.

When the rotor5revolves in the forward direction, the coefficient of the gains62,73is equal to 1. A signal S25at the first output25and a signal S27at the second output27are equal to:

When the rotor5revolves in the reverse direction, the coefficient of the gains62,73is equal to −1. The signal S25at the first output25and the signal S27at the second output27are equal to:

The first and second non-zero continuous values supplied at the outputs25,27are representative of the spacing between the axis of rotation of the rotor5and the centre of gravity of the rotor5, and make it possible to quantify the imbalance of the rotor5.

The module20makes it possible to filter the signals generated by the position sensors independently of the direction of rotation of the rotor5by selecting the gain of the gains73,62to be equal to the multiplying coefficient, the selection being performed by the detection device17.

The gain of the variable gains73,62is representative of the direction of rotation of the rotor5.

FIG.4schematically illustrates an exemplary embodiment of the control module21that makes it possible to compensate the imbalance of the rotor5determined by the modulation module20.

The modulation module20has two identical regulating loops84,85each having an input86and an output87.

The input86and the output87of a first regulating loop84are connected to the first input26and to the first output32, respectively, of the control module21.

The input86and the output87of the second regulating loop85are connected to the second input28and to the second output34, respectively, of the control module21.

Since the regulating loops84,85are identical, only the first loop84is described in detail.

The first loop84comprises an adder88, an integrator89, a gain91and a saturator92.

The adder88comprises an addition input93connected to the input86, a subtraction input94connected to an output95of the saturator92, and an output96connected to an input97of the integrator89.

An output98of the integrator is connected to the output87and to an input99of the gain.

An output100of the gain91is connected to an input101of the saturator92.

FIG.5discloses an exemplary embodiment of the detection device17.

The device17comprises comparing means1000comprising a first input1001connected to the input170of the device17, a second input1002connected to a memory103, and an output104.

The memory103may be disposed in the device17as shown or disposed outside the device17.

The device17also comprises first determining means105having an output106, and second determining means107having a first input108connected to the output104of the comparing means1000, a second input109connected to the output106of the first determining means105, and an output110connected to the output31of the detection device17.

The device17also comprises a second processing unit111implementing comparing means1000, the memory103, and the first and second determining means105,107.

The memory103contains a predefined speed threshold Se representative of the minimum speed of rotation of the rotor5measured by the speed sensor9, the sensor9measuring for example a minimum frequency of 10 Hz, that is 600 revolutions per minute.

It is assumed below that the speed measured by the speed sensor9is the absolute value of the speed such that the measured speed is positive or zero.

The first determining means105determine the speed of rotation gradient of the rotor5.

The speed gradient is for example sent to the first determining means105by a computer (not shown) for controlling the drive system.

The speed gradient may for example be determined from the calculation of the derivative of the speed of rotation of the rotor.

In a variant, the speed gradient is provided by a controller for controlling rotor rotating means, the rotor rotating means comprising for example an electric motor.

The comparing means100compare the absolute value of the speed of rotation (2of the rotor with the speed threshold Se.

At present, an implementation example for the exemplary embodiment of the detection device17is illustrated inFIG.5.

FIG.6illustrates an example of the change over time of the speed of rotation (2of the rotor5, a signal S106supplied at the output106of the first determining means105, and a signal S31supplied at the output31of the detection device17representative of the direction of rotation of the rotor5.

It is assumed that, before the instant t1, the rotor5revolves in the reverse direction at a speed of rotation having an absolute value greater than the threshold Sc.

The speed gradient determined by the first determining means105is zero. The signal S106is zero, and the comparing means1000supply a signal S104at the output104representative of the comparison, for example the signal S104is equal to “1” when the absolute value of the speed of rotation is greater than the threshold Se, and “0” otherwise. In the present case, the signal S104is equal to “1”.

As the signal S104is equal to “1” and the signal S106is zero, the second determining means107supply a signal representative of the value of the multiplying coefficient of the gains62,73equal to “1” such that the signal S31is equal to “1” such that the multiplying coefficient of the gains62,73is equal to “1”.

At the instant t1, the speed of rotation of the rotor5decreases. The speed gradient determined by the first determining means105is negative. The signal S106is negative and takes for example a value of SN.

As the absolute value of the speed of rotation Ω is greater than the threshold Se between the instants t1and t2, the signal S31remains at “1”.

The second determining means107supply a signal representative of the value of the multiplying coefficient of the gains62,73that is equal to “1” such that the signal S31is equal to “1”.

The multiplying coefficient of the gains62,73is equal to “1”.

At the instant t2, as the absolute value of the speed of rotation Ω of the rotor is less than the threshold Se, the comparing means1000supply a signal S104equal to “−1”. Moreover, as the speed gradient is negative, the signal S106is equal to a value SN indicative of a negative gradient.

The second determining means107detect a reversal of the direction of rotation of the rotor5from the reverse direction to the forward direction counter to the reverse direction, and supply a signal representative of the value of the multiplying coefficient of the gains62,73equal to “−1” such that the signal S31is equal to “−1”. The multiplying coefficient of the gains62,73is equal to “−1”.

Between the instants t2and t3, the speed of rotation Ω continues to decrease and becomes negative since the rotor5revolves in the reverse direction. The absolute value of the speed of rotation Ω remains less than the threshold Se.

The signal S31remains at “−1”.

Between the instants t3and t4, the negative speed of rotation Ω continues to decrease.

The absolute value of the speed of rotation Ω is greater than the threshold Se and the gradient remains negative.

The signal S31remains at “−1”.

At the instant t4, the speed of rotation Ω is negative and increases such that the speed gradient becomes positive.

The first determining means105supply the signal S106equal to a value Sp indicative of a positive or zero gradient.

The absolute value of the speed of rotation is greater than the threshold Se. The signal S31remains at “−1”.

Between the instants t4and t5, the negative speed of rotation2continues to increase.

The absolute value of the speed of rotation22is greater than the threshold Se and the gradient remains positive.

The signal S31remains at “−1”.

At the instant t5, the absolute value of the speed of rotation22is less than the threshold Se, the comparing means1000supply a signal S104equal to “−1”. Moreover, as the speed gradient is positive or zero, the signal S106is equal to the value Sp indicative of a positive or zero gradient.

The second determining means107detect a reversal of the direction of rotation of the rotor5from the forward direction to the reverse direction, and supply a signal representative of the value of the multiplying coefficient of the gains62,73equal to “1” such that the signal S31is equal to “1”.

The multiplying coefficient of the gains62,73is equal to “1”.