Control unit and method for determining the flow rate and the differential pressure of a rotary fluid pump

Abstract

The invention relates to a method for determining the flow rate and / or the differential pressure of a rotary fluid pump and to a control unit (300) for a rotary fluid pump (200), in particular a blood pump, wherein the rotary fluid pump (200) comprises a rotor (240), which is rotatable about an axis of rotation (500) for the purpose of conveying fluid, and a stator (220), which has a plurality of motor coils (221), and the control unit (300) is designed to: generate electrical drive signals which are applied to the motor coils; detect and / or determine phase current values and phase voltage values for one or more motor coils; determine the mutual induction voltage from the phase current values and the phase voltage values; detect and / or determine the rotational speed of the rotor; determine a mutual induction coefficient kv from the mutual induction voltage and the rotational speed; determine the torque of the rotor from the mutual induction coefficient and the phase current values; and determine the flow rate and / or the differential pressure of the rotary fluid pump taking into account the rotational speed and the torque of the rotor.

Description

[0001] Berlin Heart GmbH

[0002] 1.221 PCT / P150057PC00

[0003] Control unit and method for determining the flow rate and differential pressure of a rotary fluid pump

[0004] The application relates to a control unit for a rotary fluid pump, as well as a method for determining the flow rate and / or differential pressure of a rotary fluid pump, in particular a blood pump for a ventricular assist device. Rotary fluid pumps, especially those designed as blood pumps, for example for use in a ventricular assist device (VAD), as well as corresponding control units and control methods, are generally known. Such pumps typically comprise a stator and a rotor that can be driven around a rotational axis to pump fluid relative to the stator, with the rotor and stator forming an electric motor assembly (hereinafter also referred to as the motor). Knowledge of the rotor's angular position is required to control or regulate its rotation as desired.In some cases, knowledge of the axial and / or radial position of the rotor with respect to its axis of rotation can also be helpful, for example, for position control of a rotor that is actively magnetically supported in at least one degree of freedom relative to the stator (where the rotor is supported in a contactless, i.e., "floating" manner). To determine the flow rate and / or differential pressure of the pump, the current draw of the motor and the speed of the pump are determined in most cases.

[0005] Various requirements must be considered and weighed against each other in the design and operation of such pumps, and disadvantages must be avoided or minimized. For example, a rotary fluid pump should be as compact, lightweight, and robust as possible, as well as safe, efficient, and reliable in operation. In many cases, it should also allow, among other things, the determination of the flow rate and / or a differential pressure.

[0006] It is known from the prior art to provide separate sensors for detecting the rotational and / or translational position of the rotor, such as Hall sensors. This often increases the size, mass, complexity and / or energy consumption of the pump.

[0007] Alternatively, it is known to determine the position-dependent back electromotive force (BEMF) for position determination and speed measurement. This BEMF is generated by the rotor's magnets in the stator's motor coils through the generator effect during rotation. This requires the most accurate possible knowledge of the electrical model's parameters.

[0008] To determine the flow rate of a pump, it is known in the art to determine the current consumption of the pump's drive motor and its rotational speed as accurately as possible, and to estimate the flow rate or differential pressure from these values ​​using characteristic curves. These characteristic curves are based on fixed assumptions about the motor geometry, in particular the coil geometry, rotor magnet geometry, and magnetic material parameters of the rotor magnets.

[0009] Against the background of the prior art, the invention is based on the objective of determining the flow rate and / or differential pressure of a rotary fluid pump as reliably and accurately as possible with minimal effort using a control unit and a method.

[0010] The problem is solved by the invention with the features of the independent claims. The dependent claims present possible further developments of the invention.

[0011] The invention thus relates to a control unit for a rotary fluid pump, in particular a blood pump, wherein the rotary fluid pump comprises a rotor rotatable around a rotational axis for pumping fluid and a stator with a plurality of motor coils, wherein the control unit is configured to:

[0012] Generating electrical drive signals that are applied to the motor coils,

[0013] Recording and / or determining phase current and phase voltage values ​​for one or more motor coils,

[0014] Determination of the back EMF voltage from the phase current values ​​and the phase voltage values,

[0015] Capturing and / or determining the rotational speed of the rotor

[0016] Determination of a mutual induction coefficient kv from the mutual induction voltage and the rotational speed,

[0017] Determining the rotor torque from the back-inductance coefficient and the phase current values, as well as

[0018] Determination, in particular estimation, of the flow rate and / or differential pressure of the rotary fluid pump, taking into account the rotational speed and torque of the rotor.

[0019] As explained in more detail below, the back-EMF constant kv is the quotient of the motor speed and the back-EMF voltage, (w / motorThis corresponds to the torque constant kM, which is the quotient of the torque and the motor current (M / Imotor). Therefore, if kv is determined from the motor speed and the back EMF, the motor torque can subsequently be calculated from the measured motor current, or more precisely, from the measured phase currents, using kM. From this, the torque transmitted to the fluid by the rotor can then be determined, and from this, the pump flow rate and / or the differential pressure can be calculated.

[0020] The kM value remains constant only as long as the strength of the rotor magnets and the rotor position, particularly the axial position of the rotor in its bearings, remain constant. In the short term, the strength of the rotor magnets depends primarily on the material temperature of the magnets, which can be considered largely constant, especially if the pump is a blood pump and the rotor is bathed in the pumped blood at a largely constant temperature. Furthermore, the strength of the rotor magnets depends on component variations and the age of the magnets. These dependencies, which do not change in the short term, can be compensated for by calibration measurements and the inclusion of appropriate parameters in an estimation model.

[0021] The pump rotor can be magnetically supported, particularly actively magnetically supported, in at least one degree of freedom relative to the stator, for example, in the axial direction along the axis of rotation. The rotor can also be fully magnetically supported, i.e., magnetically supported in all degrees of freedom. For a fully magnetic support, for example, several separate magnetic assemblies (coils and / or permanent magnets) are provided in both the stator and the rotor for support in their respective degrees of freedom. The motor coils themselves can—in addition to generating the torque for rotation—also be provided for the magnetic support of the rotor in at least one degree of freedom, particularly along the axis of rotation. Alternatively or additionally, separate coils or coil groups can be provided for the magnetic support.

[0022] The dependence of kM on the rotor position is automatically taken into account when determining kv, since both parameters exhibit the same dependence on the rotor position. However, the rotor position can also be determined from this dependence after kv has been calculated. This position, particularly the rotor's axial position, influences the rotor's hydrodynamic efficiency during fluid transfer. By additionally considering the rotor position, especially its axial direction, the pump's flow rate and / or differential pressure can be determined even more precisely, also taking into account the instantaneous hydrodynamic efficiency.

[0023] To determine the flow rate and / or differential pressure with particular accuracy, additional disturbances can be taken into account, as described in more detail below.

[0024] In one possible implementation of the invention, the control unit can be configured to repeatedly, and in particular regularly, determine the back EMF coefficient kv from the back EMF voltage and the rotational speed during operation. This allows for the consideration of changes in motor efficiency, rotor position, rotor temperature, rotor magnet aging, and / or manufacturing-related component variations that affect motor efficiency when determining rotor torque. Further influences on system efficiency that do not directly affect motor efficiency, such as variable resistances of the power supply or plug connectors, are also taken into account when determining torque via kv.

[0025] The mutual induction coefficient kv can be determined, for example, at least 6 times per minute or at least 3 times per minute.

[0026] By repeatedly determining the mutual induction coefficient kv during operation, the essential, short-term variable parameters that influence the determination of the pump flow rate and / or differential pressure can be continuously taken into account. This also facilitates precise control of the pump's flow rate and / or differential pressure. Furthermore, a time-averaged rotor position can be reliably determined, which is more stable over the long term and significantly more sensitive than when the rotor position is determined using eddy current sensors or magnetic field sensors, which are often used for rotor control. As described above, the rotor's hydrodynamic efficiency can thus be continuously determined and considered in a simple and drift-free manner.

[0027] It may further be provided that the control unit is set up to determine a motor coil starting torque from the back-induction coefficient and the phase currents, and from this, by taking into account non-hydrodynamic braking torques, in particular eddy current losses and / or hysteresis losses, to determine the torque actually acting on the fluid to be pumped.

[0028] The torque determined from the mutual induction coefficient and the phase currents is the total torque acting between the stator coils and the rotor. While this corresponds approximately to the torque acting on the fluid, parasitic forces or torques, such as braking torques due to eddy current effects (e.g., in the housing wall or in the pump's eddy current sensors), and / or hysteresis losses are not taken into account. These parasitic torques can be determined as a function of the other parameters, particularly the phase currents and / or the axial position of the rotor and / or the rotational speed, and can be considered when determining the flow rate and / or the differential pressure. Eddy current losses are not limited to eddy currents in the stator, for example, in the windings or the return iron. Eddy currents in the pump housing, and especially in the fluid partition between the rotor and stator, can also be considered and subtracted.

[0029] It may also be provided that

[0030] the control unit is set up for:

[0031] Generating a control signal for at least one of the plurality of motor coils, wherein the control signal is subjected to a modulation signal; acquiring at least one measurement signal corresponding to a current flowing through the at least one of the plurality of motor coils and / or a voltage applied to the at least one of the plurality of motor coils; demodulating the at least one measurement signal to determine at least one variable characteristic electrical resistance of an electrical arrangement comprising the at least one of the plurality of motor coils and a supply line provided for connecting the at least one of the plurality of motor coils to the control unit. The supply line or...Each supply line designed to connect a respective motor coil to the control unit typically comprises at least one conductive conductor (optionally several conductive conductors) and preferably at least one contact, such as a plug connector, for connecting the conductor to the pump and / or the control unit. The contacts can be fixed and / or detachable.

[0032] It has been found that knowledge of the variable characteristic electrical resistance of the type mentioned, hereinafter sometimes referred to simply as phase resistance, is useful for accurately determining the induced voltages, particularly with sufficient accuracy for precisely determining the rotor torque or for reliably controlling the rotation and / or position of the rotor based on the position dependence of the induced voltages. The measurement principle, involving applying the modulation signal to the control signal and demodulating the resulting measurement signal, enables an accurate determination of the phase resistance, while suppressing various interferences – including variations in inductance, back EMF, and / or eddy current losses during motor operation – during this measurement.The proposed control unit, therefore, makes it possible, according to the considerations above, to provide a particularly compact, lightweight, and robust rotary fluid pump and to operate it with exceptional safety, efficiency, and reliability. Applying the modulation signal to the control signal and demodulating the at least one measurement signal is particularly suitable for accurately determining the phase resistance or changes in phase resistance over time scales considerably longer than a rotor rotation period and / or the inverse of a rotating field speed (as defined below) during operation, for example, over time intervals greater than one second, such as approximately 1 to 10 s at a rotating field speed of, for example, 0.1 to 1 kHz.

[0033] The control unit can be configured to generate the control signal using pulse-width modulation. The control unit can then be further configured to apply the modulation signal to the control signal by varying the pulse-width modulation, in particular by adding a waveform, especially a square wave. The control unit can also be configured to detect a modulation component of the measurement signal caused by applying the modulation signal to the control signal by means of demodulation, in particular synchronous demodulation.

[0034] It may further be provided that the control unit is configured to detect at least one measurement signal, corresponding to a current flowing through at least one of the plurality of motor coils and / or a voltage applied to at least one of the plurality of motor coils; to determine, based on the at least one measurement signal and a thermal model, a change in the temperature of at least one part of the rotary fluid pump, comprising at least one of the plurality of motor coils, over a measurement interval; and

[0035] Determine, based on the determined change in temperature, a value or a change in at least one variable characteristic electrical resistance of an electrical arrangement comprising at least one of the plurality of motor coils and a supply line provided for connecting the at least one of the plurality of motor coils to the control unit.

[0036] This additional method for determining the phase resistance also makes it possible to design a particularly compact, lightweight, and robust rotary fluid pump and to determine its flow rate and / or differential pressure as accurately as possible. Determining the temperature change based on at least one measurement signal and the thermal model is particularly suitable for accurately determining the phase resistance or changes in phase resistance over shorter timescales than those mentioned above for the demodulation-based method; such changes can be caused, for example, by sudden impulse input, such as from external shocks or pump accelerations. Due to the necessary control processes, such an impulse input can cause the temperature of the motor coils to rise significantly in the short term, thus changing the phase resistance accordingly.Even during the motor start-up process, which in the case of a magnetically levitated and appropriately pre-tensioned rotor involves the rotor detaching from a housing wall, a rapid temperature increase can occur due to the high power required.

[0037] The change in phase resistance due to short-term temperature changes can be taken into account when determining the back-induction constant and the torque of the pump rotor, and thus when estimating the flow rate or differential pressure of the pump in the short term.

[0038] Furthermore, the control unit can be configured to

[0039] to determine the at least one variable characteristic electrical resistance in normal operation of the rotary fluid pump repeatedly for each first measurement interval by demodulating the at least one measurement signal, and

[0040] to determine a change in at least one variable characteristic electrical resistance over a second measurement interval, which is shorter than the first measurement interval, based on the determined change in temperature, in particular in response to a detection of an increased power input into the rotary fluid pump compared to normal operation.

[0041] The control unit can be configured to repeatedly determine the at least one variable characteristic electrical resistance for each initial measurement interval by demodulating the at least one measurement signal, particularly during normal operation of the rotary fluid pump. Normal operation represents a standard operating state without any momentarily increased power input. The control unit can also be configured to determine a change in the at least one variable characteristic electrical resistance over a second measurement interval based on a specific temperature change, for example, in response to the detection of increased power input to the rotary fluid pump compared to normal operation (hereinafter also referred to as exceptional operation). Repeated determinations based on the temperature change over the second measurement interval can also be performed during normal operation.The second measurement interval is preferably shorter than the first. Particularly advantageously, the described measurements can be combined: one over the first interval by demodulation and the other over the second interval based on the temperature change. This allows for a highly accurate determination of the phase resistance and its changes over both shorter and longer timescales, enabling appropriate responses to slower and faster changes.

[0042] The measurement signal preferably comprises – as a vectorial measurement signal – components corresponding to the currents flowing through each of the plurality of motor coils and the voltages applied to each of the plurality of motor coils. The control unit can be configured to acquire these components sequentially and / or simultaneously.

[0043] It should be noted that the signal referred to as the modulation signal can be a signal constant in amplitude, frequency, and / or phase, meaning that it contains no superimposed information on itself. Amplitude and phase modulation of the control signal, which is subjected to the modulation signal, then results from the motor itself, which thus acts as a modulator. The measurable signal is therefore a modulated signal from which information, particularly about the phase resistance, can be extracted by demodulation in the manner described.

[0044] It may be provided that the stator comprises a plurality of motor phases, each comprising at least one of the plurality of motor coils, and that the control unit is configured accordingly.

[0045] to specify a plurality of modulation states successively, wherein in each modulation state a respective set of motor phases is applied to the modulation signal in opposite phase or phase shift, and wherein the measurement signal in the respective modulation state is tapped from the set of motor phases applied to the modulation signal.

[0046] In this way, all relevant components of the measurement signal can be recorded to determine all relevant phase resistances of the motor.

[0047] The modulation frequency of the modulation signal can be less than the rotational speed of a rotating magnetic field causing the rotor's rotation, preferably less than 50 Hz. The rotational speed can be represented, in particular, as the product of the rotor's rotational frequency and the number of rotor pole pairs. By choosing such a modulation frequency—especially in conjunction with a sufficiently low amplitude of the modulation signal—interference from the modulation signal to the control signal can be avoided or minimized. The rotational speed can, for example, be in the range of 0.1 to 1 kHz.

[0048] At least a portion of the acquired measurement signal and / or a quantity determined based on the measurement signal (in particular a voltage and / or current value) can be time-averaged and / or accumulated to determine the at least one variable characteristic electrical resistance, particularly over an interval of at least 1 s and / or at most 10 s. This allows for an improved signal-to-noise ratio and a correspondingly accurate measurement of the phase resistance. The interval can be adjusted to the current requirements during operation; for example, a fast, short-term measurement with a reduced interval and increased modulation amplitude can be performed.

[0049] For example, it may also be provided that the control unit is designed to determine a bearing position of the rotor in its axial direction, also called axial position of the rotor, from the back-induction coefficient and to take this into account in particular when determining or estimating the flow and / or the differential pressure of the rotary fluid pump and / or when controlling the bearing.

[0050] As explained above, the axial position of the rotor influences its hydrodynamic efficiency in fluid transfer. Deviations in the rotor position in directions other than axial, such as radially, can also affect its hydrodynamic efficiency and must therefore be determined and taken into account. By considering the rotor position, particularly its axial direction, and in some cases also its radial direction or rotor tilt, the flow rate and / or differential pressure of the pump can be determined even more precisely.

[0051] Another embodiment may provide that the control unit has an assignment unit which is configured to assign a flow rate and / or a differential pressure of the rotary fluid pump to a determined torque and a rotational speed of the rotor, in particular taking into account a bearing position of the rotor and / or a viscosity value of the pumped fluid, based on an assignment model, wherein the assignment model in particular comprises an assignment table, an assignment function, an observer or a self-learning system, in particular a neural network.

[0052] To calibrate and / or train a mapping model, test measurements can be performed under varying conditions to determine reference values. The mapping model can then be trained on these values ​​or combinations of values. During operation, the control unit can provide the mapping model with the determined values, whereupon an operating point is determined in real time that best matches the measured values. A differential pressure and / or fluid flow rate is then assigned to these measured values. This assignment can also take into account temporal trends in the form of the most recently determined operating points.

[0053] A model can be fitted to measurement data, and data can also be interpolated if necessary. The model can also represent complex relationships if, for example, Kalman filters, observers, or neural networks are used.

[0054] The control unit can be configured to detect, and preferably also control, the rotation of the rotor and / or a rotational and / or translational position of the rotor based on the measurement signal and a model of at least a part of the rotary fluid pump, wherein the model particularly includes the at least one variable characteristic electrical resistance. Control is defined here as closed-loop control. The control unit can be configured for appropriate control of the motor coils, for example by means of block commutation, sinusoidal commutation, space vector modulation, and / or field-oriented control (FOC). For example, when controlled by means of vector control using a dq system obtained by Park transform, or when using sinusoidal commutation by means of an inverse Park transform, the rotation of the rotor can be controlled via the torque current (l). qAn axial force for position control along the rotational axis can be regulated via the field component (Id). The control unit can also be configured to detect a connection state between the rotary fluid pump and the control unit and / or a fault state of the rotary fluid pump and / or the supply line, based on at least one variable characteristic electrical resistance. Making or breaking the connection (i.e., changing the connection state) or defects (such as a broken wire in the pump and / or the supply line) result in changes in the phase resistance, which can be detected using the proposed methods. Detecting the connection state can, for example, replace a pull-up / down resistor in the connector, thus reducing the hardware complexity.Furthermore, in this case, the same wiring and sensors are used as for the pump's operation, so this monitoring method can improve reliability compared to an approach using separate pins. Detecting fault conditions can improve the pump's safety (for example, a warning can be issued and / or the system can switch to an alternative operating mode in response to such a detection).

[0055] The invention further relates to a pump system comprising a rotary fluid pump, comprising a rotor rotatable about a rotational axis for pumping fluid, and a stator with a plurality of motor coils, and a control unit of the type described above.

[0056] In the proposed pump system, the control unit unfolds its aforementioned effects and further advantages, and by training or setting up the mapping model on the specific rotor and stator of the pump, it allows for precise determination of the flow rate and / or differential pressure of the rotary fluid pump. The pump system can be used, in particular, as a blood pump system with a VAD, offering significant advantages.

[0057] The invention further relates to a method for determining a flow rate and / or a differential pressure of a rotary fluid pump, in particular a blood pump, wherein the rotary fluid pump (200) comprises a rotor rotatable about a rotational axis for pumping fluid and a stator with a plurality of motor coils, by means of a control unit, wherein the control unit

[0058] generates electrical drive signals that are applied to the motor coils,

[0059] Phase current and phase voltage values ​​for one or more motor coils are recorded or determined,

[0060] A counter-induction voltage is determined from the phase current values ​​and the phase voltage values.

[0061] the rotational speed of the rotor is detected or determined,

[0062] a mutual induction coefficient kv is determined from the mutual induction voltage and the rotational speed,

[0063] the rotor torque is determined from the back-inductance coefficient and the phase current values, as well as

[0064] The flow rate and / or differential pressure of the rotary fluid pump is determined, in particular estimated, taking into account the rotational speed and torque of the rotor.

[0065] The advantages and possible applications of such a procedure result from the advantages that have already been described above in connection with a control unit submitted for this procedure.

[0066] The method can be further developed, for example, by having the control unit repeatedly, and especially regularly, determine the back EMF coefficient kv from the back EMF voltage and the rotational speed during operation, thereby taking into account changes in motor efficiency and / or rotor position and / or rotor temperature and / or the aging of the rotor magnets when determining the rotor torque. The advantages of this version of the method have already been described above.

[0067] Another possible implementation could involve that

[0068] the control unit

[0069] generates a control signal for at least one of the plurality of motor coils, wherein the control signal is subjected to a modulation signal, acquires at least one measurement signal representing a current flowing through the at least one of the plurality of motor coils and / or a voltage applied to the at least one of the plurality of motor coils, demodulates at least one measurement signal for determining at least one variable characteristic electrical resistance of an electrical arrangement, wherein the arrangement comprises at least one of the plurality of motor coils and a supply line provided for connecting the at least one of the plurality of motor coils to the control unit, and / or, that the control unit:

[0070] at least one measurement signal is acquired, representing a current flowing through at least one of the plurality of motor coils and / or a voltage applied to at least one of the plurality of motor coils, and, based on the at least one measurement signal and a thermal model, a change in the temperature of at least one part of the rotary fluid pump is determined over a measurement interval, wherein the at least one part comprises at least one of the plurality of motor coils; and

[0071] based on the specified change in temperature, a value or change of at least one variable characteristic electrical resistance of an electrical arrangement is determined, wherein the electrical arrangement comprises at least one of the plurality of motor coils and a supply line provided for connecting the at least one of the plurality of motor coils to the control unit.

[0072] The method may also include the control unit repeatedly determining the at least one variable characteristic electrical resistance during normal operation of the rotary fluid pump for each initial measurement interval by demodulating the at least one measurement signal, and

[0073] a change in at least one variable characteristic electrical resistance over a second measurement interval, which is shorter than the first measurement interval, based on the determined change in temperature, in particular after detecting an increased power input into the rotary fluid pump compared to normal operation.

[0074] Furthermore, the method can be implemented by the stator comprising a plurality of motor phases, each comprising at least one of the plurality of motor coils, and the control unit

[0075] a plurality of modulation states are specified successively, wherein in each modulation state a respective set of motor phases is applied to the modulation signal in opposite phase or phase shift, and wherein the measurement signal in the respective modulation state is tapped from the set of motor phases applied to the modulation signal.

[0076] The method can be further implemented by having the control unit determine a bearing position of the rotor in its axial direction from the counter-induction coefficient and taking this into account, in particular, when determining or estimating the flow and / or the differential pressure of the rotary fluid pump and / or when controlling the position.

[0077] The embodiments of the method described above, along with the advantages of such methods, have already been discussed in connection with the control unit designed for such methods. The invention is now illustrated and subsequently described using exemplary embodiments shown in figures of a drawing. These figures show, schematically,

[0078] FIG. 1: A pump system including a rotary fluid pump in longitudinal section view,

[0079] FIG. 2: a circuit diagram of part of the rotary fluid pump according to FIG. 1,

[0080] FIG. 3: a schematic diagram of a method according to an example,

[0081] FIG. 4: Part of the pump system according to FIG. 1,

[0082] FIG. 5: a schematic diagram of a method according to another example,

[0083] FIG. 6: a method for determining the flow rate and / or differential pressure,

[0084] FIG. 7: A special embodiment of the method shown in Figure 6, taking into account further influencing factors,

[0085] FIG. 8: A first schematic representation of a device according to the prior art for determining a flow rate,

[0086] FIG. 9: a second, somewhat more detailed illustration of a prior art method for determining a differential pressure and a flow rate, as well as

[0087] FIG. 10: a schematic representation of a process sequence according to the invention for the more precise determination of a differential pressure and a flow rate, wherein the process sequence finds its equivalent in the control unit according to the invention.

[0088] Identical reference numerals in the drawings denote identical or at least functionally equivalent parts. Reference numerals may be omitted in some cases if the corresponding features are already shown and described in another drawing.

[0089] Figure 1 shows a pump system 100. This system comprises a control unit 300 and a rotary fluid pump 200. The rotary fluid pump 200 has a rotor 240 rotatable about a rotational axis 500 for pumping fluid, and a stator 220 with a plurality of motor coils 221. The stator 220 and rotor 240 are components of a motor 210, in the example shown an axial / radial flux motor. However, the subject matter of the application is not limited to such motors and also includes, for example, radial flux motors. The rotor 240 has a rotor magnet assembly 242 with one or more permanent magnets, which is configured to interact with the motor coils 221 of the stator 220 to generate a torque about the rotational axis 500.

[0090] The rotary fluid pump 200 is designed as an implantable blood pump, specifically as a VAD or part of a VAD system, with blood being the pumped fluid. At least partially extracorporeal configurations are also conceivable. The control unit 300 is an external (especially extracorporeal) control unit 300 that can be connected to the blood pump 200 via a driveline 400. However, the control unit 300 can also be fully or partially integrated into the blood pump 200 and / or implantable with it. It is also possible for the control unit 300 to include both components located on the blood pump 200 and components located externally / extracorporeally. The rotary fluid pump 200 is not limited to pumping blood and can alternatively be used, for example, to pump water, oil, or another fluid.The pump 200 shown as an example is a centrifugal pump, however the subject matter of the application is not limited to this and also includes, for example, radial pumps or hybrid forms of the pump types mentioned.

[0091] The stator 220 is arranged on a housing 201 of the pump. The housing 201 includes a fluid inlet 202 and a fluid outlet 203, which can be fluidically connected to a blood vessel and / or a heart. To convey the fluid from the fluid inlet 202 to the fluid outlet 203, the rotor 240 includes a blade assembly 241, for example with individual conveying elements in the form of blades.

[0092] The rotor 240 is magnetically supported without contact within a cavity 204 of the housing 201. For this purpose, the stator 220 and rotor 240 comprise suitable magnetic arrangements or magnetic bearings. For example, a ring-shaped rotor magnet arrangement 242 in the rotor 240 can interact with the motor coils 221 of the stator 220 to support the rotor 240 along an axial direction defined by the axis of rotation, wherein the motor coils 221 can be controlled to regulate the rotational and / or translational position of the rotor 240 (e.g., by vector control as described above).

[0093] The control unit 300 is configured to acquire a multi-component (vector) measurement signal, comprising components corresponding to the currents flowing through each of the plurality of motor coils 221 and the voltages applied to each of the plurality of motor coils 221. The control unit 200 can be configured to acquire the aforementioned components sequentially and / or simultaneously.

[0094] Based on the measurement signals, the position-dependent back EMF voltages (BEMF voltages) generated during rotor rotation in operation by the rotor magnet arrangement 242 of the rotor 240 in the motor coils 221 of the stator 220 can be determined. The back EMF voltages are used, among other things, to determine the back EMF constant KV, from which the torque constant kM is derived. This can then be used to determine the rotor torque using the measured phase currents.

[0095] The principle of this determination of the mutual induction voltage will be explained with reference to the circuit diagram shown in FIG. 2. The circuit diagram shows, by way of example, a motor 210 with three motor phases u, v, w. More generally, a plurality of motor phases, each comprising at least one of the plurality of motor coils 221, can be provided.

[0096] The motor phases u, v, w are determined by their inductances L u , L v , L w and their resistances R u , R v , R w shown, at which the respective voltages U L , u , UR, U , U L , V, UR, V , U L , W, UR, w fall off. The respective induced voltages are called U. u , ind, U v , ind, U w , in d is designated. The resistances R u , R v , R wThese correspond to the resistances of the respective arrangements, each comprising one of the plurality of motor coils 221 and a supply line provided for connecting the respective motor coil 221 to the control unit 300 (phase resistances).

[0097] The components of the measurement signal are the total currents flowing through the motor phases u, v, w l u , l v , l w as well as the total voltages U applied to the motor phases u, v, w u , U v , U w detectable. The following applies:

[0098] dl u dl v

[0099] 4«. + 14+"^ + - AÄ - Ü» - = o dl..

[0100] + + ^w.inü ~ — ~ -j— £, u — Unjnd = 0

[0101]

[0102] (Equations 1).

[0103] For known self-inductances L u , L v , L w and phase resistances R u , R v, Rw BEMF voltages (back-induction voltages due to rotor magnets) UBEMFI, UBEMF2, UBEMFS can be calculated as follows: = Uu.md — Uvjnd

[0104] ^BEMF2 t4,nw! ~ Uw,ind

[0105]

[0106] = ^IWMÄ ~ Wu.tnd'

[0107] (Equations 2).

[0108] The magnetic coupling between the coils can be taken into account using further mutual induction terms ( (dlv / dt) * Luv for induction of phase v into phase u). However, the stator coils of many stator geometries can be arranged and connected symmetrically in such a way that the mutual induction terms cancel each other out; therefore, these terms were eliminated in Equation 1.

[0109] The mutual induction coefficient k can be calculated from the measurable back EMF voltages and the rotor speed, which can also be measured. v and thus the torque constant k MDetermine from the torque constant k M The torque can then be determined from the phase currents, and from this and the rotational speed the flow rate and / or the differential pressure of the pump can be estimated to a first approximation.

[0110] For many applications, such a determination of the mutual induced voltage is sufficient. However, for particularly accurate determination of the mutual induced voltage and, above all, a determination that is insensitive to temperature changes, as well as a mutual induced voltage coefficient k, a different method is required. v and thus the torque constant k M It may be useful to also consider the ohmic resistances R u , R v and R wDuring operation, the mutual induction voltage should be continuously determined to ensure sufficient accuracy. Furthermore, it is advisable to repeatedly, and especially regularly, determine the mutual induction coefficient kv during operation, for example at constant time intervals or even continuously in adjacent time intervals, in order to continuously account for disturbances such as a changing rotor position.

[0111] The following section will first describe how ohmic resistances R u , Rv and R w These values ​​are continuously determined during operation. In some cases, this is useful for increasing the measurement accuracy of the back EMF. In other cases, it may also be possible to forgo determining, or at least continuously determining, the resistances R. u , R v and R wto dispense with it if, for example, a constant temperature of the arrangement, in particular of the supply lines, can be assumed during operation.

[0112] Further below, a method for determining the flow rate and / or differential pressure of the rotary fluid pump based on precise measurement of the electrical quantities will be discussed.

[0113] Based on the BEMF stresses, the rotational position (angle of rotation) of rotor 240 with respect to the axis of rotation 500 can be calculated. For this purpose, the three BEMF stresses are transformed into a two-dimensional representation using a Clark transformation, and the angle of rotation is calculated using the arctangent function. This calculation is therefore dependent on Lu, Lv, L w , Ru, Rv, Rw, lu, lv, Iw, Uu, Uv, Uw dependent.

[0114] The voltage and current measurements here are subject to only minor errors. In this example (air-core coils), the inductances are approximately temperature-independent and nearly constant in the frequency range relevant for control. In contrast, the phase resistance R (i.e., R) exhibits a significant temperature dependence. u , R v , R w ) on:

[0115] R

[0116]

[0117] = Ä 20 (l + niit a Cu — 3.93 * IO -3 , (Equation 3).

[0118] where R20 is the resistance at a reference temperature of 20 °C, AT is a temperature difference, and acu is a material-dependent temperature coefficient (here for coil windings and supply conductors made of copper). For example, a 10 K temperature difference changes the resistance by approximately 4%. Other factors (e.g., drift, corrosion, breakage of a redundant driveline conductor, thermal influences, variable contact resistances in connectors) can also affect the phase resistance, which is therefore considered to be time-varying and should be determined during pump operation for control purposes.

[0119] The control unit 300 is accordingly configured to determine the respective phase resistance using the methods proposed here.

[0120] In particular, the control unit 300 is configured to generate a control signal for one or more of the motor coils 221, wherein the control signal is subjected to a modulation signal,

[0121] Demodulating the measurement signal to determine a variable characteristic electrical resistance of an electrical arrangement (phase resistance), comprising the respective plurality of motor coils and a respective supply line for connecting the respective plurality of motor coils 221 to the control unit 300.

[0122] An example of the method described above is illustrated in FIG. 3. The determination of the phase resistances is implemented here as a continuous background measurement during pump operation. The control signal corresponds to a respective controller output for the phases u, v, w. The voltage corresponding to the control signal is provided as a PWM signal by pulse width modulation (PWM).

[0123] To measure the phase resistance, R p For a given motor phase (p = u, v, w), the control unit 300 is configured to apply the control signal with the modulation signal by varying the pulse width modulation, here by adding a signal shape, in particular a square wave, to the PWM signal. This can be done sequentially for each phase or phase-shifted (by 120°), as shown in FIG. 3. The corresponding motor coils 221 are then supplied with the modified control signal by means of a driver.

[0124] The amplitude of the modulation signal is variable and is preferably selected to avoid or minimize interference with motor operation (e.g., as the smallest PWM resolution). The frequency of the modulation signal is also preferably selected to avoid interference, for example, with regard to the pump speed and / or heart rate. A modulation frequency of the signal can, for example, be less than the rotational speed of the motor, preferably less than 50 Hz. For example, a frequency of 10 Hz can be selected. The rotational speed of the motor can, for example, be in the range of 0.1 to 1 kHz.

[0125] The control unit 300 is designed to detect a modulation component of the measurement signal caused by applying the modulation signal to the control signal by means of demodulation and to determine the phase resistance from the demodulated signal.

[0126] The measurement signal (l p , U p (with p = u, v, w) the measurement signal is taken from the respective set of motor phases 221 that are subjected to the modulation signal in the respective modulation state. The individual measurement points of the measurement signal can be weighted with the modulation signal or a sine wave of the respective phase. Additionally or alternatively, a window function can be applied for weighting in order to capture more frequency components for the current and voltage measurement, which can result in a better signal-to-noise ratio.

[0127] The (possibly weighted) measurement signal is summed (i.e., accumulated, or alternatively averaged) over N periods. The N periods correspond, for example, to an interval of at least 1 s and / or at most 10 s. As mentioned, the interval can be adjusted to the current requirements; for example, a fast, short-term measurement can be performed with a reduced interval and increased modulation amplitude.

[0128] From the cumulative signal for the currents and voltages (l p , U p The phase resistance is then calculated. An additional filter can be applied to smooth the obtained values ​​or remove disturbed values.

[0129] FIG. 4 illustrates exemplary components of the pump system 100 for the method illustrated in FIG. 3. The motor 210 and the control unit 300 are connected to each other by means of the driveline 400 and a detachable plug connector 410. The driveline 400, in conjunction with the plug connector 410, includes leads for connecting each of the motor coils 221 to the control unit 300. Each lead comprises one or more conductive conductors 420 and a contact, here a plug contact of the plug connector 410, for connecting the conductor 420 to the control unit 300. The contacts can alternatively be permanently installed. The phase resistance of each phase p = u, v, w includes a resistance R. m , P the respective motor coil(s), a resistance Rd, P of the respective wire(s) of the driveline and a resistance R c , Pof the respective contact. The control unit includes means for detecting the voltage drop U across the respective arrangements. p and the currents flowing as a result l p (respective circuit symbols with arrow in a circle).

[0130] FIG. 5 illustrates another example of the proposed method. The starting point is the consideration that in the example according to FIG. 3 / 4, a virtual voltage measurement is performed (with virtual neutral point 310 of the voltage measurement as shown in FIG. 4), which is only accurate if the phase resistances of all phases are approximately equal. A significant deviation of one phase resistance from the others leads to a distortion of the values ​​on the other phases. In order to nevertheless be able to perform an accurate measurement, the neutral points can be galvanically connected. Since this solution requires an additional conductor, the alternative method variant described below is provided.

[0131] A differential measurement method is used here. The modulation takes place, for example, out of phase on two phases, while the third phase is not excited. The control unit 300 is thus configured to successively specify a plurality of modulation states (in the example according to FIG. 5, designated as mode uv / uw / vw), whereby in each modulation state a respective set of motor phases 221 is supplied with the modulation signal out of phase or with a phase shift.

[0132] Synchronously with each modulation state, a difference in the voltages and currents applied to the corresponding motor coils is measured using a sine wave detector in control unit 300. The measurement is repeated and accumulated over N periods as described above, after which the phase pair is changed. In this example, three differential voltages U are thus measured in three steps (corresponding to the three modulation states).uv , Uuw, U vw and six streams l u i, Ivi, Iwi, Iu2, Iv2, Iv2 were captured. These satisfy the following equations:

[0133] = Ru * + Re ' 4i

[0134] = A w * / ya + '

[0135]

[0136] t / pw — Rp ■ 4a + * 4?a

[0137] (Equations 4). Here, U uv the measured amplitude of the voltage difference between phase u and v, Uuw and U vw analog. I ui is the measured amplitude of the current in phase v during the uv modulation state, l v i, Iwi, Iu2, Iv2, l V 2 analog.

[0138] From this, the phase resistances of phases u, v, w can be calculated:

[0139] , _ ^inv ' A?; ' hi 2 tfuw ' ul ' ^v2 ^hiv ' hi2 '

[0140] W hv: ' ha ' h<2 + ' h'l ' ha

[0141] D - «W *

[0142] h>2

[0143] K n —

[0144]

[0145] « = * j«.. “"'7 *l™t2

[0146] (Equations 5).

[0147] The differential measurement method according to FIG. 5 is characterized by a particularly high accuracy, since, as mentioned, a change in one phase resistance is not coupled to the measurement of the other phase resistances.

[0148] The following describes some alternative variations of the measurement methods described above. In the differential method described above, one (third) motor phase is not excited, and consequently, no corresponding measurement signal is recorded. It is also possible to actively supply the third phase with a current and record the measurement signal corresponding to that current. In this case, the differential measurement method can be performed in two steps instead of the three described above, with the respective third phase being supplied with different currents in each step.

[0149] The phase resistances can then be calculated based on the following system of equations:

[0150] Upwl \ f Rtr w 0

[0151] I — I ~ R n 0 ^w2 / 0 0 R v

[0152]

[0153] (Equation 6).

[0154] This is Uvwi the recorded amplitude of the voltage difference between phase v and w during the first measurement step, U uwi and U VW 2 analog. I W 2 is the recorded amplitude of the current in phase w during the second measurement step, Ivi, Li, Iv2 analogously.

[0155] The following results for the phase resistances:

[0156] «t.

[0157] ~ l v J wi - QT w t

[0158] D — ^VWl r^W ' r I — II

[0159]

[0160] %1 J W2. J lX2 J Wl (Equations 7).

[0161] In a vector control system for rotor rotation with a two-dimensional dq system, the d and q components can also be directly modulated. In this case, a measurement signal of voltage differences and currents is generated, mixed with the rotation. This signal can be directly acquired with appropriate detectors and / or separated from the rotation before acquisition. This ensures that the applied measurement signal only affects either the drive torque or the bearing force, thus interfering with only one controller.

[0162] Regardless of the specific measurement method chosen, a different signal waveform can be used instead of the aforementioned square wave modulation. Examples include sine waves, noise, or pseudorandom sequences, such as gold codes. All measurement methods are illustrated here for three motor phases but can obviously be generalized to other numbers of motor phases. The control unit 300 can be configured to perform both measurement methods alternatively: the differential measurement according to FIG. 5 and the single-phase measurement according to FIG. 3. In particular, the control unit 300 can be configured to switch from differential measurement to single-phase measurement if a detector for the measurement signal of one phase fails. This ensures that measurement is still possible even in the event of such a failure.In this case, the control unit can issue a warning, allowing the control unit to be serviced or replaced.

[0163] Regardless of the specific measurement method chosen, the control unit 300 is preferably configured to detect and control the rotation of the rotor 240 as well as at least one translational position of the rotor 240 (in particular along the axis of rotation) based on the measurement signal and a model of at least a part of the rotary fluid pump 200, wherein the model includes the phase resistance. Additionally, translational and / or rotational positions can be controlled in further degrees of freedom.

[0164] The control unit 300 is configured to repeatedly determine the phase resistances for each initial measurement interval by demodulating the at least one measurement signal according to the procedures described above. The control unit can also be configured to determine a change in the phase resistance over a second measurement interval (in particular, also repeatedly for each second measurement interval) based on a temperature change in at least one of the motor coils. The second measurement interval is shorter than the first. Thus, measurements over the first measurement interval by demodulation and over the second measurement interval based on the temperature change can be combined, enabling a determination of the phase resistance or its changes with good accuracy over both shorter and longer timescales. The control unit 300 is configured for the purpose of determination by means of temperature change to:

[0165] Determine, based on the at least one measurement signal and a thermal model, a change in the temperature of at least one part of the rotary fluid pump 200, comprising at least one of the plurality of motor coils 221 (hereinafter referred to as motor temperature), over the second measurement interval; and

[0166] Determine, based on the specified change in motor temperature, a value or change in phase resistance for at least one of the plurality of motor coils 221.

[0167] This allows for a rapid estimation of the phase resistance during temperature changes caused by brief power inputs. Such heating occurs in fractions of a second; accordingly, the second measurement interval is chosen to be short.

[0168] A simple thermal model can be chosen, for example as follows, based on a thermal capacity C. t h:

[0169] dT.

[0170] =

[0171]

[0172] at

[0173] (Equation 8).

[0174] Here, Q is the heat input, P the power input, E the power dissipated to the environment, and T the motor temperature. The control unit 300 is therefore configured to determine the change in motor temperature (and thus ultimately the change in phase resistance) based on a power input to the rotary fluid pump 200, determined from the measurement signal, and based on an estimated thermal power output of the rotary fluid pump 200. The power input P can be precisely calculated from the current and voltage measurements. The power output E, on the other hand, is estimated, for example, by the following approximation:

[0175]

[0176] E= T<- T ~ r '>

[0177] (Equation 9).

[0178] Here, Rk is a thermal contact resistance (representable in units of K / W), T e The temperature of a contact material. In one variant, the power transferred to the rotor can also be included in the output power E. During pump operation, there is normally an equilibrium between the motor temperature and the temperature of the contact material. If the power P suddenly becomes very high, the motor temperature changes rapidly. eIn contrast, the change will generally be significantly slower, particularly in the case of an implanted blood pump due to its greater heat capacity and active cooling by the blood. This change depends on numerous influencing factors (including flow conditions in the pump as well as blood and body temperature) and therefore cannot be precisely estimated. However, the previously described (slow) determination of the phase resistance over the first measurement interval by modulation provides an approximate information about a mean T. e Included, since T is also precisely known along with the resistance. Based on the assumption that T e If the thermal capacity is constant, the model can be linearized.

[0179] The change AR of the phase resistance R can finally be estimated as:

[0180] 1 Apples

[0181] AR R0a o . AT, with AT = — -,, Ul

[0182]

[0183] (L + (Equation 10).

[0184] R is involved o the electrical resistance at the initial temperature, AT the estimated temperature difference, and a Cu a material-dependent temperature coefficient as defined above.

[0185] The measurements over the first measurement interval by demodulation and over the second measurement interval based on the temperature change can be combined approximately as follows:

[0186] R

[0187]

[0188] = R s + AÄ —

[0189] (Equation 11).

[0190] Here, R is the phase resistance, R s the value estimated by means of modulation / demodulation (“background measurement”) (determined with the slower clock according to the interval Ti), AR the difference estimated due to the temperature change (determined with the faster clock according to the interval Ts , for example the pace of the regulation), ARi p the one between the last and penultimate update of R s Average value of AR.

[0191] Equation 11 was chosen based on the following considerations. Rapid resistance changes due to power input should be immediately reflected in the total resistance. However, heating also affects the background measurement. Therefore, with each update, the average resistance change caused by power is subtracted, as this is reflected in the new value R. s is included in the background measurement.

[0192] The control unit 300 can additionally be configured to detect a connection status between the rotary fluid pump 200 and the control unit 300 and / or a fault status of the rotary fluid pump 200 and / or the driveline 400 based on the phase resistance (as described above due to corresponding changes in phase resistance). For detecting the connection status, a high-amplitude resistance measurement with a short integration time can be performed when the connection is disconnected, thus enabling a rapid measurement. When the connection is re-established (detectable as a sudden change in resistance), the amplitude can then be reduced and the integration time increased, as described above regarding these parameters. Removing the pump triggers a return to the fast mode.

[0193] The following describes the procedure for determining the flow rate and / or differential pressure of the rotary fluid pump from recorded electrical measurements, based on Figures 6 and 7.

[0194] A key parameter for determining the flow rate and / or differential pressure of a rotary fluid pump is the rotor torque acting on the fluid being pumped, particularly the liquid. This can be determined from the motor current using the equation

[0195] M = I * KM

[0196] as the product of the torque current 1 = I q_measurement and the torque constant KM. I q_measurement can be determined from the phase currents and the rotor angle, for example, using the Clarke-Park transformation. It is known from the fundamentals of electrical engineering that the torque constant KM is equal to the back EMF constant Kv. This back EMF constant Kv can be determined from the measurement of the motor speed and the back EMF voltage as the quotient of the motor's induced voltage Uind and the rotor's angular velocity ω according to the equation: Kv = U|nd / W

[0197] The torque of the pump rotor can therefore be calculated from:

[0198] M=l* Uind / W.

[0199] Depending on the accuracy requirements and environmental conditions, the back EMF can be determined with or without considering the lead resistances as described in detail above. The rotational speed w can also be determined, for example, from the time-dependent behavior of the back EMF.

[0200] The two constants K M and K v their dependence on the rotor position (for example, specifically the axial position of the rotor in its bearing), the magnetic strength of the rotor magnets, the aging of materials, component variation and temperature largely coincide, so that changes in these quantities are compensated for when determining the torque without further measures.

[0201] However, to determine the flow rate and / or differential pressure as accurately as possible, it can be useful to additionally consider the hydrodynamic efficiency of the pump, which depends on the rotor position, as well as parasitic braking torques that act on the rotor independently of the fluid being pumped, and the viscosity of the fluid being pumped, especially if it is a liquid such as blood.

[0202] Since the determined constants KM and K exhibit a clear dependence on the rotor position, the rotor position can be determined very accurately from these constants. The dependence of these two constants on the rotor position is, for example, significantly stronger than the dependence of the measured values ​​of eddy current sensors previously used for rotor position measurement. For this reason, the rotor position can be determined very accurately using the constants KM and K.

[0203] Parasitic braking torques on the rotor can arise, for example, from the eddy current braking effects generated by the rotor magnets in the material of the pump housing or other pump components. Once these parasitic braking torques have been determined, they can be taken into account when calculating the torque acting on the fluid.

[0204] The determined torque and rotational speed values ​​are fed into an assignment unit, which determines a flow rate and / or differential pressure of the pump. The assignment unit contains an assignment model, which can be implemented, for example, as a self-learning model, particularly as a trained neural network, or simply as a characteristic curve array or lookup table. It can also include a so-called "observer" that maps the applicable mathematical relationships for determining the desired quantities. Alternatively, approximate mapping functions can be fitted to the measured quantities to estimate a flow rate and / or differential pressure.

[0205] To increase the accuracy and reliability of the estimates, it is advantageous to continuously determine and consider the line resistance when calculating the back EMF using the method described above, as well as the rotor position, particularly in the axial direction, to account for the hydrodynamic efficiency of the rotor or, more precisely, the pump geometry. The rotor position can be determined separately from the constants kv and KM and entered into the assignment unit. Parasitic torques that can arise from eddy current losses can also be considered in the model by training it with these quantities or by incorporating these additional dependencies, such as temperature and phase currents, into the model.

[0206] Figure 6 schematically illustrates the method for determining the flow rate and / or differential pressure of a rotary fluid pump by means of process steps.

[0207] The electric motor 210 of the pump, which can be an implantable or extracorporeal blood pump, is supplied with electrical drive signals via a motor driver 1 through its drive windings. Additionally, magnetic forces are generated in the motor's magnetic bearings by bearing currents via a bearing control 210a. The motor driver 1 draws its electrical energy from a power source 2, which can be a rechargeable battery. The phase voltages are measured in the voltage measurement module 3, and the phase currents are measured in the current measurement module 4. In the back-EMF module 5, the back-EMF voltage is determined as a function of time from the time course of the phase currents and their time derivative, as well as the measured phase voltages.In this step, the ohmic resistance of the supply lines can be determined by modulating electrical signals onto the motor's drive signals as described above, and by the measurements described. This resistance can then be taken into account when accurately determining the back EMF. Furthermore, the motor's rotational speed and absolute angle of rotation can be determined very precisely from the time course of the back EMF. From the determined values ​​of the back EMF and the rotational speed, the back EMF constant Kv, and thus also KM, is determined in module 8. The motor's rotational speed is also provided in module 6.

[0208] Module 7 provides the measured phase currents. These are further processed in Module 9 to calculate the total electrical torque generated by the motor. For this purpose, Module 9 receives not only the current but also the torque constant K determined in Module 8.M = K v transmitted.

[0209] This means that the motor speed and the total torque are available for further calculations in modules 6 and 9.

[0210] It should be noted that the electrical torque of the rotor is not fully transferred to the fluid being pumped, as there are other braking torques that mechanically brake the rotor, such as eddy current braking effects, which will be discussed further below in connection with Figure 7.

[0211] The rotational speed and torque are transmitted to the calculation modules 11 and 12 of the control unit, where module 11 can estimate a flow rate and module 12 a differential pressure.

[0212] Modules 11 and 12 can be configured as a trained, self-learning system, for example in the form of neural networks, or as observers. Module 11 outputs a flow rate to output unit 11a, and module 12 outputs a differential pressure of the pump to output unit 12a.

[0213] The determination of the flow rate and differential pressure depends, among other things, on the viscosity of the fluid being pumped. For this reason, the viscosity can be measured, entered, or otherwise determined in module 13, so that it can be transmitted to modules 11 and 12 for a more precise determination of the flow rate and / or differential pressure.

[0214] Since the dependencies of Kv and KM are identical with respect to the pump conditions, temperature, and rotor position, changes in these quantities are automatically compensated for by determining KM from Kv. However, because both constants exhibit a sensitive dependence on the rotor position, particularly in the axial direction, the rotor position, especially in the axial direction, can be determined sensitively, with high accuracy, and with long-term stability from these constants. The step of determining the axial position of the rotor from the constants K / K is denoted by 10.

[0215] Once the axial position of the rotor has been determined, it can be transmitted to calculation modules 11 and 12 in steps 10a and 10b to determine the flow rate and differential pressure more accurately, since the hydrodynamic efficiency of the rotor depends relatively strongly on its position, especially its axial position. The influence of the various measured variables on the flow rate and differential pressure to be determined can be taken into account by prior training of a self-learning unit or by using stored characteristic curves, tables, or functions in modules 11 and 12. However, a first approximation of the flow rate and differential pressure is also possible without considering, for example, the rotor position.

[0216] The modules mentioned can each be designed as processing steps in an investigation process that can be implemented and carried out using a computer unit.

[0217] The definition of the mutual induction constant kv is not always uniform in the literature. Kv can be defined, as in the present application, as the induced voltage per angular velocity, but the scaled reciprocal in thousands of revolutions per minute per induced voltage is also quite common. In both cases, the relationship to K m different, however km can always be uniquely determined from K v determine.

[0218] In addition to the processing structures and processing steps shown in Figure 6, Figure 7 shows further correction possibilities by considering and processing additional disruptive factors.

[0219] Some modules from Figure 6 have been omitted from Figure 7 for clarity, although they are also included in the calculation there. Module 9 is of central importance for determining the rotor torque from the phase currents. Module 8 is also important, as it contains the mutual inductance constant k. v and thus the torque constant kM is determined. These constants, as well as the measured phase currents, are transmitted to module 9.

[0220] The rotor position is continuously determined in module 10 based on the aforementioned constants. This rotor position is then transmitted via transmission paths 10a and 10b to modules 11 and 12 to determine a corrected flow rate and differential pressure, taking into account the hydrodynamic efficiency of the rotor or pump.

[0221] In addition, the precisely determined axial position and / or a radial position of the rotor is transmitted to the bearing control 210a of the magnetic bearings for precise control of the rotor position.

[0222] In Module 9, the torque determination aims to ascertain the actual torque acting on the fluid being pumped. To achieve this, the torque losses caused by parasitic braking torques resulting from eddy currents and hysteresis losses are subtracted from the theoretical, electrically generated torque, which is calculated from the phase currents and the torque constant. The eddy currents, generated by the rotor magnets in nearby metallic elements, such as parts of the pump housing, depend on the motor speed, the rotor position, and the temperature of the metallic elements in which the eddy currents are generated.For this reason, to accurately determine the braking torques, the temperature of the pump housing is measured using a temperature sensor in module 14 and transmitted, together with the rotor position and the rotor speed determined in module 6 (represented by arrow 16), to module 15 for determining the braking torques. The braking torque is then continuously transmitted to module 9, which can then determine the actual torque acting on the fluid.

[0223] The torque thus corrected is then transmitted to modules 11 and 12 to determine a corrected flow rate and a corrected differential pressure.

[0224] Figure 8 illustrates the operation of a flow estimation method as it was commercially available for implanted mechanical circulatory support systems at the time of application. The pump 200 is driven by the motor 220, which is controlled by the motor driver 1. The motor driver requires information about the rotor position, which is provided via a phase voltage measurement and a back EMF zero-crossing detector 603. The detector 603 can detect two zero crossings per revolution and phase, resulting in a total of six detections per motor revolution. A stepwise continuous rotor angle CD can be assigned to these detections. At each rotor angle step, the motor driver 1, operating in block commutation mode, switches the three motor phases to the next commutation state. For the flow estimation, the motor driver 1 and the motor 220 are considered as a single unit.At the connection point of this unit to the power supply 2, the power consumption is determined in the investigation unit 600 after a voltage and current measurement.

[0225] The simple flow estimation unit 604 assigns an estimated flow Q to a rotational speed n and a power input PDC. The actual flow depends on other parameters, which are assumed to be constant in the simple flow estimation. The viscosity q of the pumped fluid, which is usually set manually by the pump operator, has a significant influence. Other parameters, such as the motor efficiency, are permanently stored in the flow estimation unit 604. Disturbances 602 acting on the motor 220 or the motor driver 1, which affect the efficiency, reduce the accuracy of the flow estimation unit 604. These disturbances 602 can include, for example, changes in coil temperature, magnet temperature, or the position of the rotor magnets. The efficiency of the motor driver can also vary due to temperature or aging.

[0226] Figure 9 shows an improvement over the embodiment of Figure 8. The accuracy of the flux estimation unit 11 no longer depends on the efficiency of the motor driver 1. This is achieved by measuring the phase currents of the motor and using a Clarke-Park transform 604 to determine the current fraction l that is actually converted into torque. q (Torque current) is determined. To ensure accurate determination of the torque current lq, it is advantageous to operate the motor driver and the motor in sinusoidal commutation or with field-oriented control. In this case, the motor is driven continuously rather than in blocks. This allows the back EMF detector 606 to determine a more accurate and continuous rotor angle CD, particularly when the phase currents are also taken into account in the back EMF detector 606 in addition to the phase voltages.

[0227] From the measured torque current l qIn step 611, the motor output torque M is determined by multiplying it by the torque constant kM. The torque constant kM is usually fixed. Advantageously to a fixed efficiency as shown in Figure 8, the embodiment shown in Figure 9 compensates not only for the efficiency of the motor driver but also for some motor disturbances 602, such as changes in coil temperature. Other disturbances, such as deviations of the rotor position or rotor magnet position from an ideal position, further reduce the accuracy of the flux estimation. A pressure estimation unit 12 can also be supplied with the necessary information from the same input values ​​of the flux estimation unit 11.

[0228] Figure 10 shows a further improvement over the embodiment shown in Figure 9, with which all disturbances 602 can be compensated and thus the motor output torque of the motor 220 can be determined more accurately. This is achieved by exploiting the fact that the torque constant k MThe mutual interference voltage can be determined during operation from the rotational speed and the mutual interference voltage. This requires a particularly precise measurement of the mutual interference voltage, especially with varying phase resistances or phase inductances. The method for determining the mutual interference voltage by tracking the phase impedance, described above and illustrated in Figures 3, 4, and 5, is implemented in Block 5. An amplitude |VEMF| can be determined from the mutual interference voltages of all phases, for example, by vector addition and magnitude calculation, in the EMF magnitude detector 607. The rotational speed n can be determined by the time derivative of the measured phase angle CD in step 601. The mutual interference constant kv can be determined from the ratio of n and |VEMF| in step 608. There is a unique relationship between the mutual interference constant kv and the torque constant kM, which is shown in Figure 609.All effects and disturbances 602 that influence the back EMF of the motor 220, such as rotor position or rotor magnet strength, can thus be compensated. The output torque emanating from the motor coils can therefore be determined precisely. The estimation units 11 and 12 can now start from a precisely determined motor output torque and thus increase their accuracy. The HQ characteristic curves of the turbomachine are stored in the processing units / estimators 11 and 12. The viscosity q influences the HQ characteristic curves not only with respect to position, but also to a lesser extent with respect to shape. The precise torque determination thus also makes it possible to estimate and adjust the viscosity q instead of having to enter it manually. The dashed line 610 summarizes some components that differ the arrangement according to Figure 10 from the solution shown in Figure 9.

[0229] The described control unit and the method for a rotary fluid pump enable an accurate, reliable and long-term stable determination of the flow rate and / or the differential pressure.

Claims

Berlin Heart GmbH 1.221 PCT / P150057PC00 Patent claims 1. Control unit (300) for a rotary fluid pump (200), in particular a blood pump, wherein the rotary fluid pump (200) comprises a rotor (240) rotatable about a rotational axis (500) for pumping fluid and a stator (220) with a plurality of motor coils (221), wherein the control unit (300) is configured to: Generating electrical drive signals that are applied to the motor coils, Recording and / or determining phase current and phase voltage values ​​for one or more motor coils, Determination of the back EMF voltage from the phase current values ​​and the phase voltage values, Capturing and / or determining the rotational speed of the rotor Determination of a mutual induction coefficient kv from the mutual induction voltage and the rotational speed, Determining the rotor torque from the back-inductance coefficient and the phase current values, as well as Determination, in particular estimation, of the flow rate and / or differential pressure of the rotary fluid pump, taking into account the rotational speed and torque of the rotor.

2. Control unit according to claim 1, characterized in that the control unit (300) is configured to repeatedly, in particular regularly, determine the back-induction coefficient kv from the back-induction voltage and the rotational speed during operation, and thus in particular to take into account changes in motor efficiency and / or rotor position and / or rotor temperature and / or aging of the rotor magnets and / or production-related component variations affecting motor efficiency when determining the rotor torque.

3. Control unit according to claim 1 or 2, characterized in that the control unit (300) is configured to determine a motor coil starting torque from the back-induction coefficient and the phase currents, and to determine from this, by taking into account non-hydrodynamic braking torques, in particular eddy current losses and / or hysteresis losses, the torque actually acting on the fluid to be pumped.

4. Control unit according to claim 1, 2 or 3, characterized in that the control unit (300) is set up for: Generating a control signal for at least one of the plurality of motor coils (221), wherein the control signal is supplied with a modulation signal, Capturing at least one measurement signal corresponding to a current flowing through at least one of the plurality of motor coils (221) and / or a voltage applied to at least one of the plurality of motor coils (221), Demodulation of at least one measurement signal to determine at least one variable characteristic electrical resistance of an electrical arrangement comprising at least one the plurality of motor coils (221) and a supply line provided for connecting at least one of the plurality of motor coils (221) to the control unit (300) and / or the control unit (300) is configured for: Capturing at least one measurement signal corresponding to a current flowing through at least one of the plurality of motor coils (221) and / or a voltage applied to at least one of the plurality of motor coils (221), Determine, based on the at least one measurement signal and a thermal model, a change in the temperature of at least one part of the rotary fluid pump (200), comprising at least one of the plurality of motor coils (221), over a measurement interval; and Determine, based on the determined change in temperature, a value or a change in at least one variable characteristic electrical resistance of an electrical arrangement comprising at least one of the plurality of motor coils (221) and a supply line provided for connecting the at least one of the plurality of motor coils (221) to the control unit (300).

5. Control unit (300) according to claim 4, configured for this purpose, to determine the at least one variable characteristic electrical resistance in normal operation of the rotary fluid pump (200) repeatedly for each first measurement interval by demodulating the at least one measurement signal, and to determine a change in at least one variable characteristic electrical resistance over a second measurement interval, which is shorter than the first measurement interval, based on the determined change in temperature, in particular in response to a detection of an increased power input into the rotary fluid pump compared to normal operation (200).

6. Control unit (300) according to one of claims 1 to 5, wherein the stator (220) comprises a plurality of motor phases, each comprising at least one of the plurality of motor coils (221), and the control unit (300) is configured to to specify a plurality of modulation states one after the other, whereby in each modulation state a respective set of motor phases is subjected to the modulation signal in opposite phase or phase shift and wherein the measurement signal is tapped in the respective modulation state at the set of motor phases that are subjected to the modulation signal.

7. Control unit according to one of claims 1 to 6, characterized in that the control unit is configured to determine a bearing position of the rotor in its axial direction from the counter-induction coefficient and to take this into account in particular when determining or estimating the flow and / or the differential pressure of the rotary fluid pump and / or when controlling the bearing.

8. Control unit according to one of claims 1 to 7, characterized in that the control unit has an assignment unit which is configured to assign a flow rate and / or a differential pressure of the rotary fluid pump to a determined torque and a rotational speed of the rotor, in particular taking into account a bearing position of the rotor and / or a viscosity value of the pumped fluid, based on an assignment model, wherein the assignment model in particular comprises an assignment table, an assignment function, an observer or a self-learning system, in particular a neural network.

9. Pump system (100), comprising a rotary fluid pump (200) comprising a rotor (240) rotatable about a rotational axis (500) for pumping fluid and a stator (220) with a plurality of motor coils (221), and a control unit according to one of claims 1 to 8.

10. Method for determining a flow rate and / or a differential pressure of a rotary fluid pump (200), in particular a blood pump, wherein the rotary fluid pump (200) comprises a rotor (240) rotatable about a rotational axis (500) for pumping fluid and a stator (220) with a plurality of motor coils (221), by means of a control unit (300), wherein the control unit generates electrical drive signals that are applied to the motor coils, Phase current and phase voltage values ​​for one or more motor coils are recorded or determined, A counter-induction voltage is determined from the phase current values ​​and the phase voltage values. the rotational speed of the rotor is detected or determined, a mutual induction coefficient kv is determined from the mutual induction voltage and the rotational speed, the rotor torque is determined from the back-inductance coefficient and the phase current values, as well as The flow rate and / or differential pressure of the rotary fluid pump is determined, in particular estimated, taking into account the rotational speed and torque of the rotor.

11. Method according to claim 10, characterized in that the control unit (300) repeatedly, in particular regularly, calculates the mutual induction coefficient kv from the mutual induction voltage during operation. the rotational speed is determined, and thus changes in motor efficiency and / or rotor position and / or rotor temperature and / or the aging of the rotor magnets are taken into account when determining the rotor torque.

12. Method according to claim 10 or 11, characterized in that the control unit (300) a control signal for at least one of the plurality of motor coils (221) is generated, wherein the control signal is subjected to a modulation signal, at least one measurement signal is captured that represents a current flowing through at least one of the plurality of motor coils (221) and / or a voltage applied to at least one of the plurality of motor coils (221), at least one measurement signal is demodulated for determining at least one variable characteristic electrical resistance of an electrical arrangement, wherein the arrangement comprises at least one of the plurality of motor coils (221) and a supply line provided for connecting the at least one of the plurality of motor coils (221) to the control unit (300), and / or , that the control unit (300): at least one measurement signal is captured that represents a current flowing through at least one of the plurality of motor coils (221) and / or a voltage applied to at least one of the plurality of motor coils (221), based on the at least one measurement signal and a thermal model, a change in the temperature of at least one part of the rotary fluid pump (200) is determined over a measurement interval, wherein the at least one part comprises at least one of the plurality of motor coils (221); and based on the determined change in temperature, a value or change of at least one variable characteristic electrical resistance of an electrical arrangement is determined, wherein the electrical arrangement comprises at least one of the plurality of motor coils (221) and a supply line provided for connecting the at least one of the plurality of motor coils (221) to the control unit (300).

13. Method according to claim 12, characterized in that the control unit (300) the at least one variable characteristic electrical resistance in normal operation of the rotary fluid pump (200) is repeatedly determined for each first measurement interval by demodulating the at least one measurement signal, and a change in at least one variable characteristic electrical resistance over a second measurement interval, which is shorter than the first measurement interval, based on the determined change in temperature, in particular after detecting an increased power input into the rotary fluid pump compared to normal operation (200).

14. Method according to any one of claims 10 to 13, wherein the stator (220) comprises a plurality of motor phases, each comprising at least one of the plurality of motor coils (221), and the control unit (300) specifies a plurality of modulation states in succession, whereby in each modulation state a respective set of motor phases is subjected to the modulation signal in opposite phase or phase shift and wherein the measurement signal is tapped in the respective modulation state at the set of motor phases that are subjected to the modulation signal.

15. Method according to one of claims 10 to 14, characterized in that the control unit determines a bearing position of the rotor in its axial direction from the counter-induction coefficient and takes this into account in particular when determining or estimating the flow and / or the differential pressure of the rotary fluid pump and / or when controlling the position.

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