Control unit for a rotary fluid pump, pump system, and method

Abstract

The invention relates to control units (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) in order to convey fluid, and a stator (220) having a plurality of motor coils (221). An exemplary control unit (300) is designed to: generate a control signal for at least one of the plurality of motor coils (221), wherein a modulation signal is applied to the control signal; detect at least one measurement signal corresponding to a current flowing through the at least one of the plurality of motor coils (221) and / or a voltage applied to the at least one of the plurality of motor coils (221); and demodulate the at least one measurement signal in order to determine at least one variable characteristic electrical resistance of an electrical arrangement comprising the at least one of the plurality of motor coils (221) and a feed line designed to connect the at least one of the plurality of motor coils (221) to the control unit (300). The invention also relates to pump systems (100) and to methods for determining at least one variable characteristic electrical resistance of an electrical arrangement of a rotary fluid pump (200).

Description

[0001] Berlin Heart GmbH

[0002] P148762PC00 (257PCT 1823)

[0003] Control unit for a rotary fluid pump, pump system and process

[0004] The application relates to control units for rotary fluid pumps, pump systems with rotary fluid pumps, and methods for determining at least one variable characteristic electrical resistance of an electrical arrangement of a rotary fluid pump. The subject matter of the application is particularly applicable in the field of cardiac support devices and systems, whereby the rotary fluid pumps may be, in particular, blood pumps. Rotary fluid pumps, especially those designed as blood pumps, for example for use as ventricular assist devices (VADs), as well as corresponding control units and control methods, are known from the prior art.Such pumps typically comprise a stator (essentially stationary relative to the pump's installation or implantation site) and a rotor that rotates about an axis of rotation relative to the stator for pumping fluid. The rotor and stator together form an electric motor assembly (hereinafter also referred to simply as the motor). To control the desired rotation of the rotor, knowledge of its rotational position is required. Knowledge of the rotor's translational position may also be necessary, 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 particular, without contact, i.e., "floating"). Various requirements must be considered and weighed against each other in the design and operation of such pumps, and disadvantages must be avoided or mitigated.For example, a rotary fluid pump should be as compact, lightweight, robust, and safe, efficient, and reliable as possible in operation.

[0005] If, as is known from the prior art, separate sensors are provided to detect the rotational and / or translational position of the rotor, this can increase the size, mass, complexity and / or energy consumption of the pump.

[0006] Alternatively, a position determination based on the measurement of position-dependent induced voltages (so-called "back electromotive force", BEMF) generated by the rotor magnets in the stator motor coils has been proposed. Since this determination can only be carried out indirectly—in particular based on measurements of the currents and voltages on all motor leads and on an electrical model of the resulting electric motor—the most accurate possible knowledge of the model parameters of the electrical model is required.

[0007] Such model parameters can be determined through calibration, for example, a one-time calibration before installation or implantation of the pump. However, these model parameters can change over time (for example, depending on operating conditions and / or aging of the pump and / or other parts of the pump system), which can affect the accuracy in determining the induced voltages and thus the efficiency, safety, and / or reliability of the pump's operation. For example, it may be the case that determining the induced voltage based on fixed model parameters (e.g., determined by a one-time calibration) is insufficient for a floating rotor bearing, especially one that also needs to compensate for impulse input from external impacts on the pump across a range of operating conditions (e.g., at different pump temperatures).

[0008] Accordingly, the application is based on the task of providing solutions regarding the design, operation and / or control of rotary fluid pumps that at least partially meet the aforementioned requirements and / or at least partially avoid or reduce the aforementioned disadvantages.

[0009] To solve the problem, the subject matter of the independent claims is proposed. Preferred embodiments and optional features result from the features of the dependent claims.

[0010] A control unit for a rotary fluid pump is proposed, 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. The motor coils are preferably configured to generate a torque acting on the rotor with respect to the rotational axis. The rotary fluid pump can be designed as a blood pump, in particular as a vascular assisted diverter (VAD), wherein the pumped fluid is blood. In this case, the blood pump can be implantable; however, at least partially extracorporeal designs are also conceivable. The control unit can be an external (in the case of the implantable blood pump, in particular extracorporeal) control unit that can be connected to or is connected to the blood pump via a driveline. However, the control unit can also be wholly or partially integrated into the blood pump and / or implantable with it.It may also be provided that the control unit includes both parts located on the blood pump and parts located externally / extracorporeally.

[0011] The rotary fluid pump is not limited to being a blood pump and can alternatively be used, for example, to pump water, oil or another fluid.

[0012] The stator can be arranged on and / or form part of the pump housing. The housing preferably includes a fluid inlet and a fluid outlet, which, in the case of a blood pump, can be fluidically connected to respective blood vessels and / or a heart.

[0013] The control unit is designed 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.

[0014] The control unit can also be configured to:

[0015] Generating a control signal for at least one of the plurality of motor coils, wherein the control signal is subjected to a modulation signal,

[0016] Demodulating the at least one measurement signal to determine 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.

[0017] The inventors have determined that knowledge of the variable characteristic electrical resistance of the type mentioned, hereinafter sometimes also referred to as phase resistance, is crucial for determining the induced voltages with high accuracy, in particular with sufficient accuracy for reliable control of the rotation and / or position of the rotor based on the position dependence of the induced voltages. The measurement principle, involving the application of the modulation signal to the control signal and the demodulation of the at least one measurement signal, enables an accurate determination of the phase resistance, while suppressing various interfering influences – including variations in inductance, back EMF, and / or eddy current losses during motor operation.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 timescales considerably longer than a rotor rotation period and / or the inverse of a rotating field speed (as defined below) during operation (for example, over approximately 1 to 10 s at a rotating field speed of, for example, 0.1 to 1 kHz).

[0018] The control unit can be set up additionally or alternatively for:

[0019] Determine, based on 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

[0020] 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.

[0021] This additional method for determining the phase resistance also makes it possible, as explained above, to design a particularly compact, lightweight, and robust rotary fluid pump and to operate it with exceptional safety, efficiency, and reliability. 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.

[0022] 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. The described measurements can be advantageously combined: one over the first interval by demodulation, and the other over the second interval based on temperature changes. 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.

[0023] 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.

[0024] 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.

[0025] The stator may be configured to comprise a plurality of motor phases, each comprising at least one of the plurality of motor coils. The control unit may then be configured to successively specify a plurality of modulation states, wherein in each modulation state a respective set of motor phases is supplied with the modulation signal in opposite phase or phase-shifted, and wherein the measurement signal in the respective modulation state is tapped from the set of motor phases supplied with the modulation signal.

[0026] In this way, all relevant components of the measurement signal can be recorded to determine all relevant phase resistances of the motor.

[0027] The modulation frequency of the modulation signal can be less than the rotational speed of the 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.

[0028] 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.

[0029] The control unit can be configured to generate the control signal using pulse width modulation. The control unit can be 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 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.

[0030] 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.

[0031] The rotor can be magnetically supported, particularly actively magnetically supported, in at least one degree of freedom relative to the stator, for example, 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.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 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 transformation, the rotation of the rotor can be controlled via the torque current (l. q), an axial force for position control along the rotation axis is controlled via the field component (Id).

[0032] The control unit can be configured to determine the change in temperature and / or the value or change in phase resistance based on a power input to the rotary fluid pump determined from the measurement signal and / or based on an estimated thermal power output of the rotary fluid pump. The power input and / or power output can, in particular, be used as input for the thermal model.

[0033] The control unit can 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 faults (such as a broken wire in the pump and / or the supply line) cause changes in the phase resistance, which can be detected using the proposed methods. For example, detecting the connection state can replace a pull-up / down resistor in the connector, thus reducing the hardware complexity. Furthermore, in this case, the same wires and sensors are used as for pump operation, so this detection method can improve reliability compared to an approach using separate pins.Detecting defective conditions can improve the safety of the pump (for example, a warning can be issued and / or the system can switch to an alternative operating mode in response to such a detection).

[0034] Also proposed is a pump system comprising a rotary fluid pump, comprising a rotor rotatable around a rotational axis for pumping fluid, a stator with a plurality of motor coils, and a control unit of the proposed type.

[0035] In the proposed pump system, the control unit obviously unfolds its aforementioned and further effects and advantages.

[0036] Corresponding effects and advantages also unfold in a method for determining at least one variable characteristic electrical resistance of an electrical arrangement of a rotary fluid pump of the described type, wherein the method comprises:

[0037] Capturing 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,

[0038] The process may include:

[0039] Generating a control signal for at least one of the plurality of motor coils, wherein the control signal is subjected to a modulation signal,

[0040] Demodulating the at least one measurement signal to determine the at least one variable characteristic electrical resistance of the electrical arrangement, 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.

[0041] The process may include:

[0042] Determine, based on 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

[0043] Determine, based on the determined change in temperature, a value or a change in the at least one variable characteristic electrical resistance of the 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.

[0044] The process can be further developed in an easily recognizable manner according to optional features of the control unit and / or the pump system, and / or vice versa.

[0045] The drawings described below illustrate principles and exemplary embodiments of the subject matter of the application. They show, schematically,

[0046] FIG. 1 a pump system including a rotary fluid pump in longitudinal section view,

[0047] FIG. 2 shows a circuit diagram of part of the rotary fluid pump according to FIG. 1.

[0048] FIG. 3 a schematic diagram of a method according to an example,

[0049] FIG. 4 shows part of the pump system according to FIG. 1,

[0050] FIG. 5 shows a schematic diagram of a method according to another example.

[0051] Recurring and similar features in the drawings are identified by identical or similar reference numerals. These may be partially omitted if the corresponding features are already shown and described in another drawing, or if they are not mentioned with reference to a drawing.

[0052] The pump system 100 shown in FIG. 1 comprises a control unit 300 and a rotary fluid pump 200. 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. The stator 220 and rotor 240 form a motor 210, in the example shown an axial flux motor. However, the subject matter of the application is not limited to axial flux motors and also includes, for example, radial flux motors. The rotor 240 comprises a rotor magnet assembly 242, consisting of 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.

[0053] 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.

[0054] 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 respective blood vessels and / or a heart. To pump the fluid from the fluid inlet 202 to the fluid outlet 203, the rotor 240 includes a blade 241.

[0055] 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 include suitable magnet arrangements. 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).

[0056] 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.

[0057] Based on the measurement signal, the position-dependent induced voltages (BEMF voltages) generated by the rotor magnet arrangement 242 of the rotor 240 in the motor coils 221 of the stator 220 can be determined. The principle of this determination can 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.

[0058] 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, wdrop. The respective induced voltages are denoted as Uu, ind, Uv, ind, Uw, ind. The resistances R u , R v , Rw 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).

[0059] The components of the measurement signal are the total currents flowing through the motor phases u, v, w l u , l v , Iw as well as the total voltages U applied to the motor phases u, v, w u , U v , U w detectable. The following applies:

[0060] (Equations 1).

[0061] Given known inductances L u , L v , L w and phase resistances R u , R v , R w BEMF voltages U BEMFI, UBEMFZ, UBEMFS can be calculated as follows:

[0062] (Equations 2).

[0063] 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 L u , L v , Lw, Ru, Rv, Rw, lu, lv, Iw, Uu, Uv, Uw dependent.

[0064] The voltage and current measurements 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 , Rw) on:

[0065] Ä - R 20 (l + Ä Ä 1T1 with a Ctt = 3.93 • IO -3, (Equation 3). 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) can also affect the phase resistance, which is therefore considered to be time-varying and should be determined during pump operation for control purposes.

[0066] The control unit 300 is accordingly configured to determine the respective phase resistance using the methods proposed here.

[0067] In particular, the control unit 300 is designed for

[0068] Generating a control signal for each of the plurality of motor coils 221, wherein the control signal is subjected to a modulation signal,

[0069] 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.

[0070] 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).

[0071] To measure the phase resistance, R pFor 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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 of 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 an arrow in a circle).

[0078] 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.

[0079] 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.

[0080] Synchronously with the respective 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 Uuv, Uuw, and Uvw and six currents are thus measured in three steps (corresponding to the three modulation states). u i,. I v i, Iwi, Iu2, l V 2, l V 2. These satisfy the following equations:

[0081] (Equations 4).

[0082] This is 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, l V 2, l V 2 analog.

[0083] From this, the phase resistances of phases u, v, w can be calculated:

[0084] (Equations 5).

[0085] 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.

[0086] 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.

[0087] The phase resistances can then be calculated based on the following system of equations:

[0088] (Equation 6).

[0089] This is U vwi the recorded amplitude of the voltage difference between phase v and w during the first measurement step, U uwi and Uvw2 analog. I w2 is the recorded amplitude of the current in phase w during the second measurement step, Ivi, Iwi, Iv2 analogous.

[0090] The following results are obtained for the phase resistances:

[0091] (Equations 7).

[0092] 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. 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.

[0093] The control unit 300 can be configured to perform both measurement methods alternatively, i.e., differential measurement according to FIG. 5 and 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. In this way, measurement is still possible even in the event of such a failure. The control unit can issue a warning in this case, allowing the control unit to be serviced or replaced.

[0094] 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.

[0095] 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.

[0096] The control unit 300 is designed for the purpose of determining, by means of temperature changes, the following:

[0097] 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

[0098] 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.

[0099] 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.

[0100] A simple thermal model can be chosen, for example as follows, based on a thermal capacity C. t h:

[0101] (Equation 8).

[0102] 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 input power P can be precisely calculated from the current and voltage measurements. The output power E, on the other hand, is estimated, for example, by the following approximation:

[0103] (Equation 9).

[0104] 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 taken into account in the output power E.

[0105] 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.

[0106] The change AR of the phase resistance R can finally be estimated as:

[0107] (Equation 10).

[0108] R is involved othe electrical resistance at the initial temperature, AT the estimated temperature difference, and a Cu a material-dependent temperature coefficient as defined above.

[0109] 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: R — R s + ÄÄ — ; Afijp (Equation 11).

[0110] 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 T s , for example the pace of the regulation), ARi p the one between the last and penultimate update of R s Average value of AR.

[0111] 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.

[0112] 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 according to the above descriptions of these parameters. Removing the pump switches back to the fast mode. List of reference symbols:

[0113] 100 pump systems,

[0114] 200 rotary fluid pump,

[0115] 201 cases,

[0116] 202 Fluid inlet,

[0117] 203 Fluid outlet,

[0118] 204 Cavity,

[0119] 210 engine,

[0120] 220 Stator,

[0121] 221 motor coils,

[0122] 240 Rotor,

[0123] 241 Blades,

[0124] 242 Rotor magnet arrangement,

[0125] 300 control unit,

[0126] 310 virtual star point,

[0127] 400 Driveline,

[0128] 410 connector,

[0129] 420 conductive conductor, 500 rotational axis.

Claims

Berlin Heart GmbH P148762PC00 (257PCT 1823) 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 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), Demodulating the at least one measurement signal to determine 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).

2. 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: 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).

3. Control unit (300) according to claim 1, further configured for: 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 specified change in temperature, a value, or a change in at least one variable characteristic electrical resistance.

4. Control unit (300) according to claim 3, configured to repeatedly determine the at least one variable characteristic electrical resistance in normal operation of the rotary fluid pump (200) for each first measurement interval by demodulating the at least one measurement signal, and to detect a change in the at least one variable characteristic electrical resistance over a second measurement interval, which is shorter than the first measurement interval to be determined based on the specified change in temperature, in particular in response to the detection of an increased power input into the rotary fluid pump compared to normal operation (200).

5. Control unit (300) according to one of claims 1 or 3 to 4, 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 successively specify a plurality of modulation states, wherein in each modulation state a respective set of motor phases is supplied with 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 supplied with the modulation signal.

6. Control unit (300) according to one of claims 1 or 3 to 5, wherein a modulation frequency of the modulation signal is less than a rotating field speed of a rotating field causing the rotation of the rotor (240), preferably less than 50 Hz, and / or wherein at least a portion of the detected measurement signal and / or a quantity determined based on the measurement signal is time-averaged and / or cumulative for determining the at least one variable characteristic electrical resistance, in particular over an interval of at least 1 s and / or at most 10 s.

7. Control unit (300) according to one of claims 1 or 3 to 6, configured to generate the control signal using pulse width modulation and to apply the modulation signal by varying the pulse width modulation, in particular by adding a signal shape, especially a square wave signal, and / or to detect a modulation component of the measurement signal caused by applying the control signal with the modulation signal by means of synchronous demodulation.

8. Control unit (300) according to claim 2, 3 or one of claims 4 to 7, insofar as it relates to claim 2, configured to change to determine the temperature based on a power input into the rotary fluid pump (200) determined on the basis of the measurement signal and / or based on an estimated thermal power output of the rotary fluid pump (200).

9. Control unit (300) according to one of the preceding claims, further configured to detect a connection state between the rotary fluid pump (200) and the control unit (300) and / or a defect state of the rotary fluid pump (200) and / or the supply line based on the at least one variable characteristic electrical resistance.

10. 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 (300) according to one of the preceding claims.

11. Method for determining at least one variable characteristic electrical resistance of an electrical arrangement of a rotary fluid pump (200), in particular a blood pump, wherein the rotary fluid pump (200) comprises a rotor (240) rotatable for pumping fluid about a rotational axis (500) and a stator (220) with a plurality of motor coils (221), wherein the method comprises: 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), Demodulating the at least one measurement signal to determine the at least one variable characteristic electrical resistance the electrical arrangement, 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).

12. Method for determining at least one variable characteristic electrical resistance of an electrical arrangement of a rotary fluid pump (200), in particular a blood pump, wherein the rotary fluid pump (200) comprises a rotor (240) rotatable for pumping fluid about a rotational axis (500) and a stator (220) with a plurality of motor coils (221), wherein the method comprises: 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 the at least one variable characteristic electrical resistance of the electrical arrangement comprising the 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. The method of claim 11, further comprising: 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 specified change in temperature, a value, or a change in at least one variable characteristic electrical resistance.

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