Control unit, implantable blood pump, pump system, and method

Abstract

The invention relates to a control unit (100) for a blood pump (200), to an implantable blood pump (200), to a pump system, and to a method for controlling a blood pump (200). The blood pump (200) comprises an axial flux motor (210) having a stator (220) and a rotor (240) which can be magnetically mounted and can be rotated about an axis of rotation in order to convey blood, the stator (220) comprising at least three coil groups (230), in particular exactly three coil groups, coplanarly arranged about the axis of rotation, each of the coil groups (230) comprising a plurality of adjacent coplanarly arranged coils (221). The control unit (100) is designed to determine specifications for a respective electric current flowing through each of the stator coils (221) in such a way that an axial force (501) for actively magnetically supporting the rotor (240) is exerted on the rotor (240) in the axial direction by the stator (220) and a respective tangential force (502) is exerted on the rotor (240) in the tangential direction by each of the coil groups (230), the control unit (100) being designed to determine mutually independent specifications for each of the tangential forces that can be generated by the coil groups (230) in such a way that the tangential forces result in an effective radial force (503) for supporting the rotor (240) in the radial direction.

Description

[0001] Control unit, implantable blood pump, pump system and procedure

[0002] The application relates to a control unit for a blood pump, an implantable blood pump, a pump system comprising a blood pump, and a method for controlling a blood pump.

[0003] Various bearing concepts for rotary fluid pumps designed as blood pumps, particularly for use as ventricular assist devices (VADs), are known from the prior art. For example, fully magnetically supported rotors with respect to a stator—i.e., magnetically supported in all degrees of freedom—are known for such pumps. Active and / or passive magnetic bearings can be used in the different degrees of freedom. Various requirements must be considered and weighed against each other in the design and operation of such pumps.

[0004] To avoid or minimize disadvantages, a blood pump should be as compact, lightweight, and robust as possible, as well as safe, efficient, and reliable in operation. For example, a fully magnetic bearing uses several separate magnetic assemblies (coils and / or permanent magnets) in both the stator and the rotor for bearing in their respective degrees of freedom. With active magnetic bearings (i.e., bearings using actively controllable magnetic fields) in certain degrees of freedom, sensors may also be required to detect deflections and / or tilts of the rotor relative to a target position. Both aspects (magnetic assemblies and sensors) can increase the size and / or mass of the pump and / or reduce its operational efficiency.Particularly with passive magnetic bearings, i.e., using only permanent magnet arrangements, instabilities or vibrational behavior can occur with respect to translational and / or rotational degrees of freedom. For example, when the rotor is deflected in a passively supported direction, a deflection-dependent restoring force occurs. However, the passive bearing does not dampen the rotor, so that with appropriate excitation (e.g., by flow forces and / or patient movement), oscillation can occur. Furthermore, a high (maximum) restoring force in a passively supported direction results in high stiffness in a perpendicular direction; active bearings in the latter direction then place high demands on sensors and control systems, which, as mentioned, can affect the size, mass, and / or efficiency of the pump.The effect of a passive magnetic bearing with a strong stiffness in one degree of freedom on the other degrees of freedom is a consequence of Earnshaw's theorem, which states that a three-dimensional array of multiple dipoles, such as point charges or permanent magnets, cannot stably support a dipole in all degrees of freedom. Specifically, the sum of the stiffnesses in Newtons of dipole force per meter of displacement is always greater than zero. Bearing stiffnesses greater than zero are unstable. This means that in a pure dipole arrangement, the unstable bearings outweigh the stable ones.

[0005] Accordingly, the application is based on the objective of providing solutions for the design and control of blood pumps with a magnetically steerable rotor that at least partially meet the aforementioned requirements and / or at least partially avoid or reduce the aforementioned disadvantages. The subject matter of the independent claims is proposed to solve this problem. Preferred embodiments and optional features are defined in the dependent claims.

[0006] The proposed control unit is intended for use with a blood pump, wherein the blood pump comprises an axial flux motor with a stator and a magnetically buoyant rotor rotatable about a rotational axis for pumping blood, the stator comprising at least three coil groups arranged around the rotational axis, each coil group comprising a plurality of adjacent stator coils. The coil groups are hereinafter also referred to as sector motors.

[0007] The coil groups arranged around the axis of rotation and / or the adjacent stator coils of the coil groups can be arranged coplanarly. The coil groups arranged around the axis of rotation and / or the adjacent stator coils of the coil groups can be arranged so that they intersect a common plane and are angled relative to it. The coil groups arranged around the axis of rotation and / or the adjacent stator coils of the coil groups can be arranged relative to each other so that they approximately form the shape of a conical segment.

[0008] The stator can be arranged on and / or form part of the blood pump housing. The housing preferably includes a fluid inlet and a fluid outlet that can be fluidically connected to respective blood vessels and / or a heart.

[0009] The axis of rotation can refer specifically to a principal axis of the rotor's rotation caused by the stator coils and thus not be a physical axis of the blood pump. The axis of rotation defines (in a target position of the rotor) an axial direction as well as radial and tangential directions perpendicular to it, characterized by radial and tangential vectors, where the radial vectors pass through the axis of rotation and the tangential vectors are at a distance from it. The tangential vectors pass through the magnetic center of gravity of each sector motor.The control unit is designed to determine specifications for a respective electric current through each of the stator coils in such a way that an axial force (hereinafter also referred to as lift force) is exerted on the rotor by the stator for active magnetic bearing of the rotor in the axial direction, and that a respective tangential force is exerted on the rotor in the tangential direction by each of the coil groups.

[0010] The control unit can be configured, in particular, to regulate the axial position (axial control) of the rotor relative to the stator in contactless magnetic bearings. The control unit can also be configured to regulate the tilting of the rotor about one or more axes essentially perpendicular to the axis of rotation (tilt control). For this purpose, it can be provided, in particular, that each sector motor generates a respective lift force (axial force) such that a resulting torque is obtained with respect to the one or more axes essentially perpendicular to the axis of rotation, which can be controlled to regulate the tilting.

[0011] The control unit is configured to determine independent parameters for each of the tangential forces generated by the coil groups, such that these tangential forces result in an effective radial force for radially stabilizing the rotor. The control unit thus enables radial position control of the rotor and, consequently, active magnetic radial stabilization using the sector motors of the axial flux motor. Since no additional magnetic assemblies are required specifically for radially stabilizing the rotor, the blood pump can be designed to be correspondingly compact and lightweight. Furthermore, the aforementioned disadvantages of passive radial stabilization can be counteracted. In conjunction with the aforementioned tilt control and axial stabilization, the rotor can be actively magnetically stabilized in all degrees of freedom solely by the sector motors of the axial flux motor.

[0012] Furthermore, the tangential forces preferably result in a torque with respect to the axis of rotation in order to set the rotor in rotation for pumping blood and / or to control the rotation of the rotor.

[0013] Using the example of a stator with three coil groups, the generation of an effective radial force with radial force components F can be illustrated. x , F y (perpendicular to the axis of rotation) and a torque M z with respect to the axis of rotation based on the independently specified tangential forces F ti (with i = 1, 2, 3) can be described as follows, for example:

[0014] M z — (F tl + F t2 + F t3 ) ■ r.

[0015] Here, r is the radius of the point of force application on the rotor. For example, given by control loops, F x , / and M z The three components consist of a torque component and a projection of the Cartesian force component onto the tangential force unit vectors together: 120° ■ n) ■ F x + cos(a + 120° ■ n) ■ F y with n = 1, 2, 3, and a constant a that depends on the orientation of the coordinate system. Thus, the transformation matrix in Fig. 3B for this example is:

[0016] Similarly, the axial force components F ai (with i = 1, 2, 3) also from a component that is the same for all i for F z and a coordinate system-dependent projected component for M x and M y together. The transformation matrix in Fig. 3A is then composed of the submatrices and can also be represented as two parallel matrix multiplications.

[0017] The rotor typically comprises a permanent magnet arrangement, in particular a magnetic ring, which interacts with a magnetic field generated by the stator coils, thus forming the axial flux motor. The rotor can be disc-shaped, especially such that the rotor's impeller has a radial diameter larger than its axial length. With a disc-shaped rotor of this type, the described tilt control can be particularly advantageous, as it counteracts potential instability in the tilting direction. The rotor or impeller can also have a greater axial length than its diameter; in this case, the tilt and radial control are less effective due to the reduced leverage, but still functional.

[0018] The blood pump can be, in particular, an implantable blood pump (implantable VAD), but at least partially extracorporeal designs are also conceivable. The control unit can be an external unit (in the case of the implantable blood pump, especially extracorporeal), connected to the blood pump via a driveline, or already connected to it. However, the control unit can also be fully or partially integrated into the blood pump and / or implantable with it. It is also possible for the control unit to include both components located on the blood pump and those located externally / extracorporeally.

[0019] The blood pump can be a centrifugal pump, but is not limited to this type. Since active bearings with multiple degrees of freedom, particularly six degrees of freedom, allow for precise control and thus minimization of the distance between the impeller blades and the pump housing, the flow over the impeller in an axial pump can also be kept small. Larger gaps between the impeller blades and the pump housing lead to inefficient turbomachinery more quickly than in radial pumps. Axial pumps with passive magnetic bearings in the radial direction, such as the INCOR cardiac support system from Berlin Heart GmbH, require very rigid radial bearings to prevent contact between the rotor and the pump housing. Active radial control allows for smaller passive magnetic bearing components while simultaneously keeping the impeller gap smaller and constant.

[0020] The stator coils of each coil group can be configured as phases of the respective sector motor. The control unit can be configured for the appropriate control of the sector motors, for example, by means of block commutation, sinusoidal commutation, and / or vector control (field-oriented control, FOC). Each sector motor is controlled by, for example, a vector control system, whereby the component that conventionally generates torque current (Iq) in a rotary motor generates the tangential force in the sector motor, and the component that is conventionally used for field weakening (Id) generates the local axial force in the sector motor. Analogously, each sector motor can also be understood as a local linear motor. The stator can, in particular, comprise exactly three coil groups arranged around the axis of rotation. It can be provided that each of the coil groups comprises at least three adjacent stator coils.Compared to an arrangement with, for example, only two stator coils per coil group, a tilting control of the type described can thus be implemented particularly effectively. In particular, each coil group can comprise exactly three (i.e., no more than three) adjacent stator coils, thereby avoiding unnecessary redundancies and inefficiencies. If only two coils per coil group are used, then theoretically six currents are available for controlling six degrees of freedom, which represents the minimum in terms of static controllability. However, the degrees of freedom are then coupled, meaning that, for example, the tilting moments cannot be generated independently of the radial forces in all rotor angles. From a control engineering perspective, the controllability matrix then has a rank of less than six.

[0021] The control unit can be electrically connected to any two of the three stator coils in each coil group via separate connecting leads. The control unit can also be electrically connected to the remaining stator coils in each coil group via a common connecting lead. This eliminates the need for individual driveline leads and / or power electronics components. For example, independently controlling three-phase stator coils in three sector motors requires a total of nine connecting leads in the driveline and nine half-bridges in the power electronics. However, generating any axial force and any tangential force with a sector motor requires only two independent currents; the third current is derived from these.The third coil of each sector motor can therefore be connected to a common line and routed to the power electronics, thus saving two lines and two half-bridges in this example.

[0022] In accordance with the considerations above regarding the controllable degrees of freedom, the control unit for specifying the respective electric current through each of the stator coils can be set up in such a way that the rotor is actively magnetically supported in three rotational and three translational degrees of freedom (i.e., an overall active 6-axis magnetic support is provided).

[0023] Alternatively, the blood pump may include a passive magnetic bearing arrangement for passively magnetically supporting the rotor in at least one first spatial degree of freedom. The control unit may then be configured to specify the respective electrical current through each of the stator coils such that the rotor is actively magnetically supported in the remaining spatial degrees of freedom. It may also be provided that the rotor is actively magnetically supported in only one degree of freedom, particularly in the axial direction, and passively magnetically supported in the remaining degrees of freedom.

[0024] The control unit can be configured to specify the respective electrical current through each of the stator coils such that the movement of the rotor relative to the stator is limited in at least one degree of freedom. This limitation can be achieved by actively damping the movement of the rotor relative to the stator in at least one degree of freedom and / or by limiting it to a predetermined maximum displacement and / or maximum displacement force. The limitation to a predetermined maximum displacement and / or maximum displacement force is also referred to below as position limitation. The predetermined maximum displacement force can, for example, correspond to an acceleration of at most log₀ or at most 2g.

[0025] Additional considerations regarding the properties and operation of the control unit, blood pump and pump system in the case of active or passive magnetic bearing, active damping and / or position limitation in one or more degrees of freedom are discussed below with reference to FIG. 9A to FIG. 10B.

[0026] Various controller configurations of the control unit are conceivable. The control unit can, for example, be set up to regulate the position of the rotor using separate controllers for the respective axial positions of the rotor with respect to each of the sector motors (i.e., for respective, independent lift forces), whereby the tilt angles of the rotor with respect to tilt axes perpendicular to the axis of rotation are fixed and therefore not independently controlled.

[0027] The control unit can alternatively be configured to regulate the rotor's position using a controller for the effective axial position of the rotor relative to the stator as a whole, and at least one controller for the rotor's tilt angle relative to a tilt axis perpendicular to the axis of rotation. Compared to three axial controls for sector motors, the advantage is that the controllers for tilt and axial displacement can be designed differently, thus allowing them to be optimally adapted to the mass distribution and flow force distribution of the rotor and decoupled from each other.

[0028] The control unit can be configured to determine the specifications for each of the tangential forces and / or lifting forces that can be generated by the coil groups by means of a transformation matrix of force and / or torque specifications with respect to Cartesian coordinates.

[0029] The control unit can be configured to regulate the position, in particular the translation and / or rotation and / or tilting, of the rotor by means of zero-power control. In this case, a target position is set such that external forces or moments acting on the rotor with respect to the degree of freedom to be controlled add up to a predetermined force, in particular a zero force, and / or that the power expended to maintain the target position is minimal (see, for example, document EP 3 827 852 Al).

[0030] As an alternative to the control system described above, the generation of radial or axial forces can also be used to compensate for known radial flow forces and / or tilting moments. The control unit can be configured to determine the parameters for each of the tangential forces generated by the coil groups such that an external radial force and / or an external tilting moment acting on the rotor is compensated without active control. The external radial force or tilting moment can, in particular, result from a flow force determined based on a flow measurement and / or flow estimation. Likewise, the external radial force or the corresponding tilting moment caused by the pump movement can be determined by measuring the movement of the pump housing using accelerometers, gyroscopes, and / or a positioning system.

[0031] To enable control as described above, the control unit, or the system consisting of the control unit and the blood pump, can further be configured to determine the position, in particular the radial position and / or tilt, of the rotor. Several options exist for this, some of which are explained below. The control unit can then be configured to determine the parameters for each of the tangential and / or axial forces that can be generated by the coil groups, based on the determined position.

[0032] The control unit can be configured to determine the position, in particular the radial position and / or tilt, of the rotor based on a detected back EMF and / or based on a magnetic field measurement, and to determine the parameters for each of the tangential and / or axial forces that can be generated by the coil groups based on the determined position. Position determination based on back EMF is known and described, for example, in EP3 827 852 A1. This enables position measurement without additional sensors.

[0033] The stator can include an eddy current sensor designed to determine the position, in particular the radial position and / or tilt, of the rotor. A dedicated eddy current sensor, preferably a three-phase eddy current sensor, can be used for this purpose.

[0034] Alternatively, an eddy current sensor can be formed by one or more of the stator coils, thus eliminating the need for additional components. Rotor position measurement using this approach is described, for example, in European patent application 24 153 240.7.

[0035] The rotor can form or comprise an eddy current target for such a measurement. The eddy current target can be formed by an electrically conductive structure arranged in and / or on the rotor. The electrically conductive structure can be an element specifically designed for this purpose and / or a structure or component of the rotor also designed for another purpose. Furthermore, the eddy current target can be configured to have an effective radius that differs from, and is in particular larger than, the effective radius of a rotor magnet assembly designed to interact with the stator coils. The effective radius is defined as the radius or position at which equivalent ideal components, in the case of magnets, these are dipoles, would be located.

[0036] The proposed pump system comprises a blood pump with an axial flux motor including a stator and a magnetically buoyant rotor rotatable about a rotational axis for pumping blood, the stator comprising at least three, and in particular exactly three, coil groups arranged around the rotational axis, each coil group comprising a plurality of adjacent stator coils, and a control unit of the proposed type. It is evident that the control unit in this pump system exhibits the properties and advantages discussed above.

[0037] Accordingly, a method for controlling a blood pump is also proposed, wherein the blood pump comprises an axial flux motor with a stator and a magnetically posable rotor rotatable around a rotational axis for pumping blood, wherein the stator comprises at least three, in particular exactly three, coil groups arranged around the rotational axis, each of the coil groups comprising a plurality of adjacent stator coils.

[0038] The procedure includes:

[0039] Determining specifications for a respective electric current through each of the stator coils such that an axial force is exerted on the rotor by the stator for active magnetic bearing of the rotor in the axial direction, and a respective tangential force is exerted on the rotor in the tangential direction by each of the coil groups.

[0040] Determine independent parameters for each of the tangential forces that can be generated by the coil groups such that the tangential forces result in an effective radial force for bearing the rotor in the radial direction.

[0041] The procedure can be further developed according to optional features of the control unit, the pump system and / or the blood pump, and / or vice versa.

[0042] An implantable blood pump of the proposed type comprises an axial flux motor with a stator and a magnetically posable rotor rotatable around a rotational axis for pumping blood, wherein the stator comprises at least three, in particular exactly three, coil groups arranged around the rotational axis, each of the coil groups comprising a plurality of adjacent stator coils.

[0043] As mentioned above, it may be provided that the blood pump includes a passive magnetic bearing arrangement for passively magnetically supporting the rotor in at least one first spatial degree of freedom, and that the rotor can be actively magnetically supported in at least the remaining spatial degrees of freedom by means of the stator coils.

[0044] Alternatively or additionally, it can be provided that at least one, preferably each, of the stator coils comprises a winding head angled with respect to a plane perpendicular to the axis of rotation. In this way, the sensitivity of the radial position measurement can be improved, in particular, when using the rotor as an eddy current target (as described above).

[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 blood pump in longitudinal section view,

[0047] FIG. 2A and 2B Cross-sectional views of a part of the blood pump according to FIG. 1,

[0048] FIGS. 3A and 3B show exemplary controller structures of a control unit.

[0049] FIG. 4A a cross-sectional view of part of a blood pump according to another example,

[0050] FIG. 4B shows a longitudinal sectional view of part of the blood pump according to FIG. 4A.

[0051] FIG. 5, FIG. 6 and FIG. 7 Longitudinal sectional views of parts of blood pumps according to further examples,

[0052] FIG. 8 shows a circuit diagram for part of the pump system according to FIG. 1.

[0053] FIG. 9A Time profiles of rotor positions or passively recorded bearing forces for various exemplary bearing arrangements,

[0054] FIG. 9B shows a time course of an external acceleration,

[0055] FIGS. 10A and 10B show longitudinal sectional views of parts of blood pumps according to further examples. 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.

[0056] The pump system 300 shown in FIG. 1 comprises a blood pump 200 and a control unit 100 connected to the blood pump 200 by means of a driveline 400.

[0057] The blood pump 200 comprises an axial flux motor 210 with a stator 220 and a magnetically lubricated rotor 240 that can be rotated around a rotational axis 301 for pumping blood. The stator 220 comprises a plurality of stator coils 221.

[0058] The stator 220 is arranged on a housing 201 of the blood pump 200, which forms a cavity 204 in which the rotor 240 is received. 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.

[0059] The rotation axis 301 is the main axis of a rotation of the rotor caused by the stator coils 221, which drives the fluid. As indicated in the coordinate system shown at the bottom right, the rotation axis 301 (in a desired position of the rotor) defines an axial direction Z as well as radial directions Rx and Ry perpendicular to it.

[0060] The rotor 240 comprises a rotor magnet arrangement 242, which interacts with a magnetic field generated by the stator coils 221 and thus forms the axial flux motor 210.

[0061] The blood pump 200 is a centrifugal pump in the example shown, but is not limited to that.

[0062] The Blood Pump 200 is an implantable blood pump (implantable VAD), although at least partially extracorporeal versions are also conceivable. The Control Unit 100 is an extracorporeal control unit. However, the control unit can also be fully or partially integrated into the blood pump and / or implantable with it. It is also possible for the control unit to include both components located on the blood pump and components located externally / extracorporeally.

[0063] As can be seen in FIGS. 2A and 2B, the stator comprises three coil groups 230 (sector motors or sectors 1, 2 and 3) arranged coplanarly around the axis of rotation, each coil group 230 comprising three adjacent and coplanarly arranged stator coils 221. Alternatively, the coil groups can, for example, be arranged such that they intersect a common plane and are angled relative to it, and / or such that they approximately form the shape of a conical segment.

[0064] The stator coils 221 of each coil group 230 are configured as phases of the respective sector motor. The control unit 100 can be configured to control the sector motors accordingly. The stator 220 can comprise a different number of coil groups, and each coil group can comprise a different number of stator coils, than shown in the example.

[0065] Figures 2A to 3B illustrate a method for controlling a blood pump using the example of the blood pump 200.

[0066] The method comprises determining parameters for a respective electric current through each of the stator coils 221 such that the stator 220 exerts three axial forces 501 on the rotor 240 in the axial direction Z for active magnetic bearing of the rotor 240, and that each of the coil groups 230 exerts a respective tangential force 502 on the rotor in the tangential direction. The total axial force on the rotor 240 corresponds to the average of the three axial force components 501.

[0067] The method further includes determining independent parameters for each of the tangential forces 502 that can be generated by the coil groups 230, such that an effective radial force 503 for supporting the rotor 240 in the radial direction results from the tangential forces through vector addition. In the configuration shown in FIG. 2A, the three tangential forces 502 are of equal magnitude, so that the radial components sum to zero. This situation can occur, for example, in a desired position of the rotor 240. In FIG. 2B, the tangential forces 502 have different magnitudes. The vector addition (illustrated below in the figure) therefore results in an effective radial force 503 that acts on the rotor 240. In both cases, the mean value of the tangential forces 502 results in a torque with respect to the axis of rotation 301 in order to set the rotor 240 in rotation to pump blood or to regulate the rotation of the rotor.

[0068] To execute the described procedure, the control unit 100 is configured to determine parameters for a respective electric current through each of the stator coils 221 such that each of the coil groups 230 exerts a respective tangential force 502 in the tangential direction on the rotor 240. The control unit 100 thus enables radial control of the rotor 240 and, accordingly, active magnetic bearing in the radial direction with the coil groups 230 of the axial flux motor 210.

[0069] The control unit 100 can also be configured for axial and tilt control of the rotor 240. For this purpose, each coil group generates a respective axial force 501 such that a resulting torque is obtained with respect to the axes perpendicular to the axis of rotation 301, which can be controlled to regulate the tilt. The individual axial forces 501 also result in an effective axial force for the active magnetic bearing of the rotor 240 in the axial direction. Thus, the rotor 240 can be actively magnetically held in all degrees of freedom solely by the sector motors of the axial flux motor 210.

[0070] FIG. 3A and 3B show different possible controller configurations of the control unit 100.

[0071] According to the controller configuration shown in FIG. 3A, the control unit 100 is set up to control the position and rotation of the rotor 240 by means of a controller for an effective axial position of the rotor (axial position controller) with respect to the stator 220 as a whole, two controllers for respective tilt angles of the rotor 240 (tilt controllers) with respect to respective tilt axes perpendicular to the axis of rotation 301, two radial position controllers for the two degrees of freedom perpendicular to the axis of rotation 301 and a rotational speed controller.

[0072] The control unit 100 is configured to determine the parameters for each of the tangential forces 502 and lifting forces 501 that can be generated by the coil groups 230 by means of a transformation matrix of force parameters (F_x, F_y, F_z) and torque parameters (M_x, M_y, M_z) with respect to Cartesian coordinates Rx, Ry, Rz (as shown in the respective coordinate systems in FIG. 1, FIG. 2A and FIG. 2B). The transformed parameters are applied to the respective commutators or FOC blocks, which are configured to output control signals for driving the stator coils 221 (in particular, the aforementioned parameters for a respective electric current through each of the stator coils 221). The parameters for currents can also be given as parameters for applied voltages, from which resulting currents are derived. The phase currents in the individual stator coils can be measured and adjusted using vector control.Alternatively, the currents can also be applied without feedback via measurement, particularly using sinusoidal commutation. Only during the generation of drive torque does a large back EMF occur, which inhibits the current. However, this can be compensated for in the sinusoidal commutation or the speed controller if the rotational speed is known.

[0073] Each stator coil corresponds to the phases Ui, Vi, Wi of a given sector motor (coil group) with index i (i in this case ranges from 1 to 3). As mentioned, different numbers of coil groups and / or stator coils per coil group are possible.

[0074] According to the controller configuration shown in FIG. 3B, the control unit 100 is configured to control the position of the rotor 240 by means of separate controllers for the respective axial positions of the rotor (three axial position controllers) with respect to each of the sector motors (i.e., for respective, independent lift forces). This means that the tilt angles of the rotor with respect to tilt axes perpendicular to the axis of rotation are fixed and therefore not independently controlled. With regard to radial control, rotational speed control, and the actual control via commutators / FOC blocks, the configuration corresponds to that shown in FIG. 3A. However, the transformation matrix is ​​smaller in this case, since only the two forces F_x and F_y and the torque M_z need to be transformed.

[0075] As an alternative to the control system described above, the generation of radial or axial forces can also be used to compensate for known radial flow forces and / or tilting moments. The control unit 100 can be configured accordingly to determine the parameters for each of the tangential forces that can be generated by the coil groups, such that an external radial force and / or an external tilting moment acting on the rotor is compensated without active control. The external radial force or the external tilting moment can, in particular, result from a flow force that can be determined based on a flow measurement and / or flow estimation.

[0076] To enable control as described above, determining the position of the rotor 240 is also provided. Examples of suitable arrangements, which in particular enable the determination of the radial position and / or tilt, are shown in FIGS. 4A to 6.

[0077] The stator 220 of the blood pump 200' shown in FIGS. 4A and 4B comprises an arrangement of eddy current sensors 222, which are arranged radially around the rotor 240 in the housing 201. The rotor 240 includes an annular eddy current target 242, which interacts with the eddy current sensors 222 and thus enables position determination (x and y position).

[0078] The numbers 1 to 6 indicate possible positions for the eddy current sensors 222, although – depending on the intended measurement method – only some of these positions may be occupied by eddy current sensors 222. It is important that the x and y positions of the rotor 240 can be determined in each case. For this purpose, sensor arrangements with, for example, two sensors offset by 90° or three or four sensors distributed around the circumference are conceivable.

[0079] For a single-channel measurement, eddy current sensors 222 can be arranged at positions 1 and 2. For a differential measurement, eddy current sensors 222 can be arranged at positions 1 and 4 for the y-position and 2 and 6 for the x-position. A differential measurement is characterized by better insensitivity to rotor size or interference compared to a single-channel measurement.

[0080] For a three-phase measurement, eddy current sensors 222 can be arranged at positions 1, 3, and 5. A three-phase measurement has the same advantages as a differential measurement, but additionally requires fewer sensors and is therefore particularly preferred.

[0081] As an alternative to a dedicated eddy current sensor (as shown in FIGS. 4A and 4B), an eddy current sensor can be formed by one or more of the stator coils 221, as shown in FIGS. 5 and 6. This enables position measurement without additional sensors. The blood pump 200" shown in FIG. 5 also includes an annular eddy current target 243 arranged on the rotor 240, which in this case is not arranged radially outside (as in FIGS. 4A / B), but rather towards the stator coils 221 on the rotor 240.

[0082] In addition to or as an alternative to position measurement using eddy current measurement, the control unit 100 can be configured to determine the rotor position based on a detected electromotive force (back EMF) induced in the stator coils by the rotor's rotation. A three-phase back EMF can be measured for each sector motor and transformed without loss of information into a two-dimensional vector from which the position information can be determined.

[0083] A combination of both measurement methods (back-EMF measurement and eddy current measurement with stator coils) is particularly advantageous, especially when based on the use of the eddy current target 243 with an effective radius that is larger (or at least different) than the effective radius of the rotor magnet arrangement 242. This arrangement ensures that both measurement methods react differently to x- and y-deviations, thereby improving position determination, since otherwise a tilt can only be inaccurately distinguished from a radial displacement. FIG. 5 additionally shows a passive magnetic bearing arrangement for passively magnetically supporting the rotor in the radial direction, comprising a first magnetic bearing component 244 and a second magnetic bearing component 245.The first magnetic bearing component 244 is arranged radially inside the rotor 240, and the second magnetic bearing component 245 is arranged on the stator 220 such that it projects into an axially arranged cavity of the rotor 240 and is at least partially surrounded by the rotor magnet arrangement 242. Although the passive magnetic bearing arrangement is illustrated in connection with the blood pump 200", it can also be omitted in this design and / or provided in other blood pump configurations, such as blood pumps 200, 200', and / or 200'". The passively supported degrees of freedom can be further limited by active control within the range of motion or prevented from oscillating by active damping. The integration of the passive magnetic bearing also enables zero-force control (also called zero-power control) in the passively magnetically unstable degrees of freedom.Zero-force control allows static forces, such as the weight of the rotor, to be absorbed solely by the passive magnetic bearing components. This reduces the forces that must be applied to the stator coils due to current and thus power losses.

[0084] In the blood pump 200"' shown in FIG. 6, each of the stator coils 221 comprises a winding head 221a angled axially towards the rotor 240. This increases the radial sensitivity of the eddy current measurement using stator coils. Such an arrangement can be used both in conjunction with a dedicated eddy current sensor (as in blood pump 200') and with back-EMF measurement (as in blood pump 200"). In this case, the eddy current target 243 can be arranged radially on the outside of the rotor 240. The separate eddy current sensors can optionally be connected in parallel to the stator coils to read them via the same connection lines. The drive signals of the sector motors and the back-EMF can be separated from the eddy current signal in the frequency domain.

[0085] In the blood pump 200"" shown in FIG. 7, the rotor position is determined based on a magnetic field measurement using a magnetic field sensor arrangement 260. A target magnet arrangement 264 is arranged radially inside the rotor 240. On the stator 220, the magnetic field sensor arrangement 260 is arranged such that it is located in an axially arranged cavity of the rotor 240 and is at least partially surrounded by the target magnet arrangement 264. A magnetic field 265 of the target magnet arrangement 264 is toroidal and extends along the axis of rotation 301 in the Z-direction (when the rotor 240 is in its non-tilted target position). If the rotor 240 tilts, non-zero field components are generated at a first magnetic field sensor 2361 in the x- and y-directions, from which the tilt can be determined.When the rotor 240 is radially displaced, a different field component in the z-direction is generated at the second magnetic field sensor 262 than at the third magnetic field sensor 263. If, as in the blood pump 200" in FIG. 5, a passive magnetic bearing arrangement is provided, the target magnet arrangement 264 can coincide with the first magnetic bearing component 244.

[0086] Alternatively, the magnetic field can also be measured without the target magnet arrangement 264. In this case, the field of the rotor magnet arrangement 242 itself is measured using a magnetic field sensor arrangement. However, inhomogeneities in the magnetic field can impair the measurement. Correction of such inhomogeneities is possible, as described, for example, in document EP 4 249 039 Al.

[0087] FIG. 8 shows a possible connection diagram for the stator coils in the stator 220, which are labeled here with their inductances L1-L3 (first coil group), L4-L6 (second coil group), and L7-L9 (third coil group). The driveline 400, by means of which the control unit 100 can be connected to the blood pump 200, comprises six separate connecting lines 401 and one common connecting line 402. The control unit 100 can be electrically connected to any two stator coils (here L1 / L2, L4 / L5, L7 / L8) of each coil group via the separate connecting lines 401. The control unit 100 can be electrically connected to the remaining stator coils (here L3, L6, L9) of each coil group via the common connecting line 402. Depending on the application, the Driveline 400 can optionally include additional cables besides the aforementioned connection cables 401 and 402.In the following, further considerations regarding the properties and operation of the control unit, blood pump and pump system in the case of active or passive magnetic bearing, active damping and / or position limitation in one or more degrees of freedom will be discussed.

[0088] These considerations will be based on the requirements for an exemplary implantable blood pump. These exemplary requirements are:

[0089] The rotor is to be magnetically mounted without contact.

[0090] The rotor should be efficiently supported in all positions (especially under 1 g acceleration in any direction).

[0091] The rotor should remain contact-free during dynamic accelerations up to at least 5 g (enabling sporting activities, etc.).

[0092] The release power for the rotor (= release force) 2* Detachment efficiency; detachment force in [N], detachment efficiency in [N / (W)] 0 5 )]) is to be minimized in order to keep implanted components, including components of any TET system (TET = transcutaneous energy transfer) such as coils or batteries, small.

[0093] The pump size should be minimized.

[0094] Engine efficiency should be maximized to minimize thermal blood damage.

[0095] To prevent the rotor from hitting anything even under 5g acceleration, the magnetic bearings must be able to withstand a force five times the rotor's weight at maximum deflection. For the five passive magnetic bearings of a uniaxially active-bearing pump, this means either the movement range must be large or the passive magnetic bearings must be strong, and therefore large. Both of these options increase the pump's size.

[0096] Passive magnetic bearings also behave like a spring and offer only negligible damping at the linear rotor speeds typical of VADs. The significant component of the damping is fluid damping. Since blood typically has a relatively low viscosity, the rotor motion is only weakly damped in the passive degrees of freedom. This leads to rotor overshoot during dynamic accelerations. FIG. 9A illustrates the rotor's response (solid line 601) to the jump from 1 g of external acceleration to 5 g shown in FIG. 9B.

[0097] Due to the low damping of the blood, the rotor's position oscillates beyond the point where the forces would be balanced. Only after a settling time does the rotor come to rest at this position. To prevent the rotor from striking the surface, however, the range of motion must be unobstructed up to 7 g; therefore, the pump must be statically designed for accelerations significantly exceeding 5 g. With low damping in water, air, or even a vacuum, the overshoot actually doubles the required range of motion. If additional external excitations are present, the resulting oscillation can even become unstable and increase exponentially in amplitude.

[0098] If the range of motion of the passive bearing directions is to be restricted, then the bearings must be made stronger. This in turn enlarges the magnets, so that the overall installation space is only slightly smaller and often even larger.

[0099] In a pump with at least one active magnetic bearing and zero-force control, the release force depends directly on the passive force-absorbing capacity of the active bearing. The release force corresponds at least to the maximum permissible rotor force during operation, since at this maximum permissible rotor force, the bearing must absorb the force in the opposite direction. To generate this force, the rotor is then deflected to its maximum extent. When the rotor is in this position, the bearing force corresponds to the maximum rotor force, regardless of whether a rotor force is actually acting. During operation, the rotor force is typically less than 1 g. However, the maximum bearing force must still be completely overcome for the release process. Therefore, the following should preferably apply: Release force = maximum permissible rotor force during operation + safety margin.

[0100] The release force increases proportionally with the current in the coil(s) of the active magnetic bearing. Since power loss increases quadratically with the current, the release force increases quadratically with the maximum permissible rotor force. For the example of the passive magnetic bearing, this means that the overshoot 7 2 / 5 2 = 196%, meaning it effectively has to provide double the transfer fee.

[0101] A reduction in the maximum forces that can be absorbed therefore has a very significant impact on the detachment performance and thus the size of a TET system or an implanted battery.

[0102] Active mounting allows the range of motion in the active degrees of freedom to be limited. The mounting can be used, for example, to introduce additional damping. This prevents overshoot (FIG. 9A, dashed line 602). Controlling multiple, especially all, degrees of freedom also makes it possible to dampen the primarily passively mounted degrees of freedom, thus reducing the range of motion and ultimately the release performance.

[0103] In principle, the active bearing also allows for arbitrary restriction of the movement range. However, the necessary bearing forces then come at the cost of additional power consumption and thus additional heat generation. To keep this additional heat generation within acceptable limits, it can be advantageous, for example, to passively absorb forces equivalent to 1 g of gravitational acceleration plus a safety margin, thus enabling zero-force control in any position at rest. Only larger dynamic disturbance forces are compensated for with additional power expenditure. FIG. 9A shows the pump's response with active limitation to lg + lg and simultaneous active damping (dotted-dashed line 602).

[0104] However, these measures can only be applied in actively controlled degrees of freedom. The movements in passive degrees of freedom all exhibit the weakly damped overshoots shown. Therefore, the movement spaces and the passive magnetic bearings must be designed to be correspondingly large.

[0105] Active control in all degrees of freedom enables both additional damping and position limitation in all directions. Since the passive bearings are linked via Earnshaw's theorem, a strong passive bearing also leads to destabilization in the degrees of freedom not stabilized by that bearing. In summary, all passive bearings transfer their instability to the active bearing, which consequently has to perform more work and, in particular, react much faster. This results in considerably higher demands on the sensors and the control loop of the active bearing, which directly impacts its transfer performance and controller stability.

[0106] If all degrees of freedom are actively controlled, then each passive bearing can be directly damped and its force limited. This reduces the requirements for each individual degree-of-freedom controller and sensor. Six simple sensors and controllers can potentially be more advantageous (smaller, simpler, or even feasible, more efficient, more robust) than a single sensor for a single controller with demanding requirements.

[0107] The solution space for five passive stable degrees of freedom and one unstable, actively controlled degree of freedom is significantly restricted compared to the solution space for six passively unstable degrees of freedom.

[0108] Conventionally, the following measures, for example, are conceivable to achieve sufficient tilting stability with passive bearings:

[0109] The rotor is pulled lengthwise (or widthwise, for concentric passive tilting bearings, not shown) to provide a large lever arm between the front and rear pairs of bearings.

[0110] The engine is designed with little or no iron to avoid further tilting instabilities.

[0111] However, this stability comes at the cost of the following properties:

[0112] The rotor is larger than absolutely necessary for the turbomachine. The return path at the inlet is longer than absolutely necessary and exhibits changes in direction.

[0113] Motor efficiency is inherently limited. (Iron-core motors can theoretically be made arbitrarily efficient if the stator can be made arbitrarily large; ironless motors have an optimal geometry for a given rotor and cannot be made more efficient even with more installation space.) Control in multiple, especially all, degrees of freedom enables active tilt stabilization. With active tilt stabilization, one is not dependent on passive tilt stability. This makes it possible to build the motor with return iron. Thus, there is no longer a single optimum for the motor, but rather several parameters with different efficiencies, from which the best compromise for the given application can be selected.

[0114] The resulting increase in efficiency allows the motor magnets in the rotor to be made smaller, which, with the same bearing forces, effectively increases the load-bearing capacity by several times the rotor weight force and reduces the rotor volume and thus the blood-conducting surface.

[0115] Another advantage of active tilt control is its behavior under gyroscopically induced tilting moments. The orientation of the gyroscopic moment causes the rotor to undergo precession at high speeds and with tilting. This precession is not stabilized by passive bearings, and only fluid damping keeps it within limits. With active tilt control in at least two degrees of freedom, precession can be actively suppressed. This further reduces the required range of motion. At typical VAD speeds, however, precession can generally still be managed passively. Precession also leads to the coupling of the tilting degrees of freedom. This means that kinetic or potential energy is exchanged between the degrees of freedom. This energy exchange allows precession to be damped by damping at least one of the coupled degrees of freedom.

[0116] FIG. 10 compares an example of a blood pump 200a with single-axis control (FIG. 10A) and a blood pump 200b with multi-axis control (FIG. 10B). As explained above, the rotor 240 of the blood pump 200a is axially elongated and, in addition to the outlet-side bearing magnet pair 246, includes the inlet-side bearing magnet pair 247. This latter pair is unnecessary in the blood pump 200b and is therefore omitted; here, the rotor 240 is purely disc-shaped. Besides the properties discussed above, the blood pump 200b offers additional flexibility with regard to the motor geometry. For example, the inlet geometry can be designed more flexibly. There is also greater freedom regarding the size of the bearing gaps 270, which can be made larger (for less shear force input into the blood) or smaller (for less backflow). The complexity of the sensors associated with the six-axis control,

[0117] Controllers and actuators can be reduced or compensated for in various ways. In many cases, common components can be used for the degrees of freedom, so the complexity is not increased sixfold. Active damping of multiple degrees of freedom, especially passively supported ones, as well as position limiting, can be used in all active magnetic bearings, motors, or bearingless motors where the corresponding number of degrees of freedom can be actively influenced. This includes, in particular, multiphase radial flux motors (including those with more than three phases), axial flux motors, and hybrid forms such as radial-axial flux motors with one or more stators.

[0118] List of reference symbols

[0119] 100 control units,

[0120] 200, 200', 200", 200'", 200"", 200a, 200b blood pump,

[0121] 201 cases,

[0122] 202 Fluid inlet,

[0123] 203 Fluid outlet,

[0124] 204 Cavity,

[0125] 210 Axial flux motor,

[0126] 220 Stator,

[0127] 221 Stator coil,

[0128] 221' alternative stator geometry,

[0129] 221a angled winding head,

[0130] 222 Eddy current sensor,

[0131] 230 coil group,

[0132] 240 Rotor,

[0133] 241 Blades,

[0134] 242 Rotor magnet arrangement,

[0135] 243 eddy current target,

[0136] 244 first magnetic bearing component,

[0137] 245 second magnetic bearing component,

[0138] 246 outlet-side bearing magnet pair,

[0139] 247 inlet-side bearing magnet pair, 250 impeller,

[0140] 260 Magnetic field sensor arrangement,

[0141] 261 first magnetic field sensor,

[0142] 262 second magnetic field sensor,

[0143] 263 third magnetic field sensor,

[0144] 264 Target magnet arrangement,

[0145] 265 Target magnetic field,

[0146] 270 bearing gap,

[0147] 300 pump system,

[0148] 301 Rotation axis,

[0149] 400 Driveline,

[0150] 401 separate connection cable,

[0151] 402 common connection line,

[0152] 501 Axial force, 502 Tangential force,

[0153] 503 effective radial force,

[0154] 601 Rotor position as a function of time for a passive magnetic bearing with blood damping, 602 Rotor position as a function of time for an active magnetic bearing with

[0155] Damping and zero force control

[0156] 603 Rotor position as a function of time for an active magnetic bearing with damping and position limitation.

Claims

1. Patent claims 1. Control unit (100) for a blood pump (200), in particular an implantable one, wherein the blood pump (200) comprises an axial flux motor (210) with a stator (220) and a magnetically locatable rotor (240) rotatable about an axis of rotation for pumping blood, wherein the stator (220) comprises at least three, in particular exactly three, coil groups (230) arranged around the axis of rotation, wherein each of the coil groups (230) comprises a plurality of adjacent stator coils (221), wherein the control unit (100) is configured to determine parameters for a respective electric current through each of the stator coils (221) such that an axial force (501) is exerted on the rotor (240) by the stator (220) for actively magnetically locating the rotor (240) in the axial direction, and a respective tangential force is exerted by each of the coil groups (230). (502) is exerted in the tangential direction on the rotor (240),wherein the control unit (100) is configured to determine independent parameters for each of the tangential forces that can be generated by the coil groups (230) such that an effective radial force (503) for bearing the rotor (240) in the radial direction results from the tangential forces.

2. Control unit (100) according to claim 1, wherein each of the coil groups (230) comprises at least three, in particular exactly three, adjacent stator coils (221).

3. Control unit (100) according to claim 2, wherein the control unit (100) is connected to two stator coils (221) of each coil group (230) by means of separate connections. The terminal lines (401) are electrically connectable or connected and are electrically connectable or connected to the respective remaining stator coils (221) of each coil group (230) by means of a common connecting line (402).

4. Control unit (100) according to one of the preceding claims, configured to specify the respective electric current through each of the stator coils such that the rotor (240) is actively magnetically supported in three rotational and three translational degrees of freedom.

5. Control unit (100) according to one of the preceding claims, wherein the blood pump (200) comprises a passive magnetic bearing arrangement (244, 245) for passively magnetically supporting the rotor (240) in at least one first spatial degree of freedom and the control unit (100) is configured to specify the respective electric current through each of the stator coils such that the rotor (240) is actively magnetically supported in the remaining spatial degrees of freedom.

6. Control unit (100) according to one of the preceding claims, configured to control a position of the rotor (240) by means of a controller for an effective axial position of the rotor (240) with respect to the stator (220) as a whole and at least one controller for a tilting angle of the rotor (240) with respect to a tilting axis perpendicular to the axis of rotation.

7. Control unit (100) according to one of claims 5 and 6, configured to determine the specifications for each of the tangential forces that can be generated by the coil groups (230) by means of a transformation matrix of force and / or torque specifications with respect to Cartesian coordinates.

8. Control unit (100) according to one of the preceding claims, configured to control a position, in particular a translation and / or rotation and / or tilting, of the rotor (240) by means of a zero-power control.

9. Control unit (100) according to one of the preceding claims, configured to determine the parameters for each of the tangential forces that can be generated by the coil groups (230) such that an external radial force acting on the rotor (240) and / or an external force acting on the rotor (240) The tipping moment is compensated without active control, whereby the external radial force or the external tipping moment results in particular from a flow force that can be determined based on a flow measurement and / or flow estimate.

10. Control unit (100) according to one of the preceding claims, configured to determine a position, in particular radial position and / or tilt, of the rotor (240) based on a detected electromotive back-EMF and / or based on a magnetic field measurement and to determine the parameters for each of the tangential forces that can be generated by the coil groups (230) based on the determined position.

11. Control unit (100) according to one of the preceding claims, wherein the stator (220) comprises an eddy current sensor (222) configured for determining a position, in particular radial position and / or tilt, of the rotor (240), in particular a three-phase eddy current sensor (222) and / or an eddy current sensor (222) formed from one or more of the stator coils (221), wherein the rotor (240) forms or comprises an eddy current target (243) which preferably has an effective radius that differs from, in particular is larger than, an effective radius of a rotor magnet assembly configured for interacting with the stator coils (221), and wherein the control unit (100) is configured to determine the parameters for each of the tangential forces that can be generated by the coil groups (230) based on the determined position.

12. Pump system comprising a blood pump (200), in particular an implantable one, comprising an axial flux motor (210) with a stator (220) and a magnetically posable rotor (240) rotatable about an axis of rotation for pumping blood, wherein the stator (220) comprises at least three, in particular exactly three, coil groups (230) arranged about the axis of rotation, each of the coil groups (230) comprising a plurality of adjacent stator coils (221), and a control unit (100) according to one of the preceding claims.

13. Method for controlling a blood pump (200), in particular an implantable one, comprising an axial flux motor (210) with a stator (220) and a magnetically posable rotor (240) rotatable about an axis of rotation for pumping blood, wherein the stator (220) comprises at least three, in particular exactly three, coil groups (230) arranged coplanarly around the axis of rotation, wherein each of the coil groups (230) comprises a plurality of adjacent and coplanarly arranged stator coils (221), wherein the method comprises: Determining specifications for a respective electric current through each of the stator coils (221) such that an axial force (501) is exerted by the stator (220) for active magnetic bearing of the rotor (240) in the axial direction on the rotor (240), and a respective tangential force (502) is exerted by each of the coil groups (230) in the tangential direction on the rotor (240), Determine independent parameters for each of the tangential forces that can be generated by the coil groups (230) such that the tangential forces result in an effective radial force (503) for bearing the rotor (240) in the radial direction.

14. Implantable blood pump (200) comprising an axial flux motor (210) with a stator (220) and a magnetically locatable rotor (240) rotatable about an axis of rotation for pumping blood, wherein the stator (220) comprises at least three, in particular exactly three, coil groups (230) arranged coplanarly around the axis of rotation, wherein each of the coil groups (230) comprises a plurality of adjacent and coplanarly arranged stator coils (221), wherein the blood pump (200) comprises a passive magnetic bearing arrangement for passively magnetically locating the rotor (240) in at least one first spatial degree of freedom and the rotor (240) is actively magnetically locatable in at least the remaining spatial degrees of freedom by means of the stator coils (221).

15. Implantable blood pump (200) comprising an axial flux motor (210) with a stator (220) and a magnetically posable rotor (240) rotatable about an axis of rotation for pumping blood, wherein the stator (220) comprises at least three, in particular exactly three, coil groups (230) arranged coplanarly around the axis of rotation, wherein each of the coil groups (230) comprises a plurality of adjacent and coplanarly arranged stator coils (221), wherein at least one, preferably each of the stator coils (221) comprises a winding head (221a) angled with respect to a plane perpendicular to the axis of rotation.

16. Control unit (100) according to one of claims 1 to 11, configured to specify the respective electric current through each of the stator coils such that a movement of the rotor (240) with respect to the stator (220) is limited in at least one degree of freedom by actively damping the movement and / or limiting it to a predetermined maximum deflection and / or maximum deflection force.

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