Method for controlling permanent magnet synchronous motor

Abstract

The invention relates generally to a method for controlling a permanent magnet synchronous machine. The method simplifies the calculation required for control in order to reduce the calculation time while achieving the lowest possible deviation from the optimal d-q current point or current vector Idq. The invention further relates to a permanent magnet synchronous machine suitable for carrying out the method.

Description

Field of the Invention

[0001] The present invention generally relates to a method for controlling a permanent magnet synchronous motor. Furthermore, the present invention relates to an electronic control device adapted to carry out the method and to a braking system comprising a permanent magnet synchronous motor. Background Art

[0002] Permanent magnet synchronous motors (PMSMs) are used in a wide variety of fields and products because they have a very good ability to convert electrical parameters such as voltage and current into mechanical parameters such as rotational speed and torque and also allow for a compact design and are low-maintenance.

[0003] In modern motor vehicles, such synchronous motors are also used in various ways and in a wide variety of designs and embodiments. For example, it is known that an electric motor-driven pump (e.g., a hydraulic pump) generates pressure in a braking system.

[0004] The permanent magnet synchronous motor may include an electronic control device for control purposes, the electronic control device including a controller, an interface, and an inverter or converter. For applications in the automotive industry, the drive energy may be provided by the vehicle's internal battery or the on-board electrical network of the motor vehicle.

[0005] For the stable operation of such an on-board electrical network, it is typically necessary to achieve a balance between current generation and current consumption. This may require limiting the total power consumed in the case of a current consumer (such as the permanent magnet synchronous motor of the braking system) so as not to overload the on-board electrical network.

[0006] This power limit value can be calculated, for example, by multiplying the operating voltage of the on-board electrical network by the maximum allowable current. In particular, the maximum allowable current can also vary depending on the operating state of the on-board electrical network. This may make it necessary to adjust the operation of the permanent magnet synchronous motor so that its consumption does not exceed the maximum allowable power.

[0007] In order to operate the permanent magnet synchronous motor accordingly, control algorithms typically integrated in the controller or the electronic control device are required. The control algorithms can perform precise control of the converter, which, according to known arrangements in the automotive industry, can have, for example, a B6 bridge circuit including power semiconductor components.

[0008] For this purpose, pulse-width modulated drive signals (PWM) can be used to control the power semiconductor components, where an alternating voltage and current curve for operating the synchronous motor can be generated from a direct current (e.g., from the vehicle battery) in the converter. The voltage or current regulated in this way can be supplied to the synchronous motor and generate a rotating field or stator field at the stator, which can generate torque in the rotor.

[0009] Depending on which part is considered to be the part of the motor control, either there is a rotational speed demand which is the main input for regulation or there is directly a torque demand. In the first case, a rotational speed regulator can be used to convert the rotational speed demand into a torque demand.

[0010] Regardless of how the torque demand is generated, in order to optimally control a synchronous motor, these torque demands must be converted into corresponding currents or current demands. To further take into account the variables related to control, the three phases (U, V, W) of the synchronous motor can be transformed into a two-axis coordinate system fixed relative to the rotor and having axes d and q. Thus, the torque demand can be converted into d- and q-current demands, and then these two current demands can be controlled via appropriate control loops.

[0011] Several ways are known for converting the torque demand into this d-q current demand, and two types of ways can be distinguished among them.

[0012] On the one hand, there are rule-based ways. The rule-based ways attempt to control the voltage reserve to control the d-q currents.

[0013] The advantages of the rule-based ways are simplicity and, partly, robustness against parameter deviations. The main disadvantages are the additional control loops and their delays, and in many cases the standard system states must be taken into account. Therefore, the regulator is parameterized for certain operating states and loses control quality when leaving these states, which can be disadvantageous because, for example, the properties of the magnetic material may be different or also change due to temperature variations, for example.

[0014] Another way involves the so-called open-loop or feedforward strategies. These ways do not use the voltage reserve for the basic algorithm but perform model-based calculations for the d-q current demands.

[0015] However, with this way, on the one hand, the complexity of the required calculations must be taken into account. On the other hand, certain limiting conditions must also be observed, and these limiting conditions can relate, for example, to the DC power supply, because exceeding certain power values as described above may lead to damage to, for example, the DC power supply (such as a battery) or the wires. Summary of the Invention

[0016] Therefore, a method for controlling a permanent magnet synchronous machine is desired which does not have the disadvantages mentioned above or at least mitigates the disadvantages mentioned above.

[0017] The calculations required by this method should have as low a complexity as possible here, such that a simple implementation of the control algorithm (for example, in the microcontroller of the control device) is possible.

[0018] Furthermore, it would be helpful if this method could even be used with synchronous motors having different designs without extensive adjustment.

[0019] The inventors have set this objective.

[0020] This objective is achieved in a surprisingly simple manner by a method for controlling a permanent magnet synchronous machine (preferably as part of a braking system of a motor vehicle), an electronic control device, and a braking system comprising a permanent magnet synchronous machine as claimed in any one of the independent claims.

[0021] Preferred embodiments and improvements of the invention can be derived from the respective dependent claims.

[0022] Accordingly, in a first aspect, the invention relates to a method for controlling a permanent magnet synchronous machine, the method comprising the steps of:

[0023] - determining a first d-q current point P1 in a d-q coordinate system, at which the phase current limit and the voltage limit are observed, and wherein the first d-q current point P1 further satisfies:

[0024] - the q-component of the d-q current point P1 in the d-q coordinate system is zero (i q = 0 A), and

[0025] - the d-component of the d-q current point P1 in the d-q coordinate system is selected to be as small as possible in terms of value,

[0026] - determining a second d-q current point P2 in the d-q coordinate system, at which the phase current limit and the voltage limit are observed, and at which the maximum torque can be set,

[0027] - determining a polynomial N connecting these d-q current points P1, P2 to each other,

[0028] - determining a d-q current point P3 according to the intersection point of this polynomial N and the curve of the power boundary G L ,

[0029] - determining a d-q current point P4 according to the intersection point of this polynomial N and the curve of the required motor torque G M ,

[0030] - selecting a working point P from the d-q current points P2, P3, P4 that satisfies the following conditions B :

[0031] - the d-q current points P2, P3, P4 are admissible,

[0032] - the d-components of these admissible d-q current points P2, P3, P4 have the lowest value in terms of value.

[0033] On the other hand, the invention also relates to an electronic control device for controlling a permanent magnet synchronous motor of a motor vehicle, which permanent magnet synchronous motor is preferably part of a braking system, and which electronic control device is designed to carry out the method mentioned above.

[0034] The permanent magnet synchronous motor can be designed to operate a pump unit, in particular a hydraulic pump, of a motor vehicle braking system.

[0035] The method according to the invention makes it possible to determine a d-q current point or a target voltage vector for controlling the permanent magnet synchronous motor, which represents an optimum value under given limiting conditions, that is to say, as close as possible to the desired or predefined torque requirement and additionally also represents the lowest energy consumption.

[0036] For a further embodiment of controlling the permanent magnet synchronous motor, it is based on the d / q transformation of the three-phase system of this synchronous motor. The d-q coordinate system is generally known in the field of controlling permanent magnet synchronous motors and provides a simple representation of the operating parameters of such motors. Therefore, a detailed representation should be omitted here and only the aspects essential to the invention should be outlined. For example, the basic aspects of controlling a permanent magnet synchronous motor are described in the document DE 10 2018 213 939 A1 from the applicant, which is hereby incorporated in its entirety and made the subject of this disclosure. Therefore, the conversion of the torque requirement of the permanent magnet synchronous motor into a corresponding d-q current requirement can be considered a step of the method according to the invention.

[0037] Based on an embodiment of the invention, the sought-after current vector I for control can be determined based on the torque requirement dq . In this case, the torque requirement is generally a specification that determines the torque that the synchronous motor should generate or provide at a specific point in time. Thereby, the current vector I can generally be calculated in the d-q coordinate system dq , wherein the above-mentioned limiting conditions and optimizations are to be taken into account. The torque can be provided, for example, by a vehicle control system or a vehicle computer or an on-board computer of a higher-level vehicle electronic control device.

[0038] Therefore, the current vector I obtained according to the invention in the d-q coordinate system dq can represent the current point that is closest to the desired d-q current requirement, and through this current point, the permanent magnet synchronous motor will be controlled accordingly in order to provide the desired torque as much as possible.

[0039] Regarding the permanent magnet synchronous motor, certain limiting conditions must be observed, which can also be related to the current operating state and will be discussed below.

[0040] The boundary conditions to be observed can include the power limit of the permanent magnet synchronous machine. In this case, the maximum power of the permanent magnet synchronous machine can be specified as the product of a preset voltage and a preset maximum current intensity. Non-compliance with the given power limit may cause damage to the on-board electrical network of the motor vehicle.

[0041] The preset voltage can also be referred to as the voltage limit and in this case can correspond to the operating voltage of the on-board electrical network (e.g., the on-board electrical network of a motor vehicle). In this case, the operating voltage is typically the voltage that is desired to be maintained during normal operation. This boundary condition can also be considered a "hard" boundary because the voltage applied to the three phases to control the synchronous machine, for example, comes from the vehicle's on-board electrical network. Therefore, the voltage cannot exceed this voltage limit.

[0042] The following rules can be applied to the voltage vector in the d-q coordinate system:

[0043]

[0044] where,

[0045] U q : the q-component of the voltage vector in the d-q coordinate system,

[0046] U d : the d-component of the voltage vector in the d-q coordinate system,

[0047] U ctrl : the maximum voltage or voltage limit.

[0048] According to an embodiment of the present invention, the maximum current intensity or the maximum phase current can be another boundary condition to be observed, where, for example, when the phase voltage is applied, this boundary can also be slightly exceeded briefly. However, long-term exceeding may cause, for example, heating of the motor and / or damage to the electronic components, and should therefore be avoided.

[0049] For the phase current in the d-q coordinate system, the following rules can be adopted:

[0050]

[0051] where,

[0052] I q : the q-component of the current vector in the d-q coordinate system,

[0053] I d : the d-component of the current vector in the d-q coordinate system,

[0054] I ph,max : the maximum phase current.

[0055] The maximum power can be changed during operation, for example, according to specific operating states, such as the availability of a current generator or the operating state of other current consumers. In addition to the maximum power, a minimum power may also be required, for example, in the generator operation of an electric motor. Therefore, the power limits can advantageously be determined at the time points of torque demand.

[0056] For the minimum power and the maximum power, the following rules can be assumed:

[0057] P DC，min ≤P DC ≤P DC，max

[0058] where

[0059] P DC : the possible power,

[0060] P DC,min : the minimum power,

[0061] P DC,max : the maximum power.

[0062] Based on these boundary conditions, the sought current vector I dq can be determined by the method according to the invention such that the above-mentioned boundary conditions are complied with and the corresponding torque is as close as possible to the desired torque demand.

[0063] The inventors have understood that another boundary condition is necessary for determining the optimal target current vector I dq because the above-mentioned boundary conditions do not have a unique solution in all cases.

[0064] Therefore, a preferred embodiment of the invention provides that the operating efficiency of the synchronous motor is used as another boundary condition to be complied with. In other words, a current vector I dq is determined which complies with the current boundary conditions mentioned above, is as close as possible to the desired torque demand, and achieves the lowest possible power consumption of the synchronous motor. dq In other words, the sought current vector I dq

[0065] provides as much torque as possible for the permanent magnet synchronous motor but also consumes as little power as possible. dq

[0066] It is assumed here that in the case of a properly designed motor system, such a d-q current point or current vector I dqThe task is theoretically possible, but it is so complex that it requires a large amount of computing capacity. This makes implementation in, for example, a microcontroller almost impossible.

[0067] Against this background, the approach according to the invention provides some simplifications in order to reduce the computing time while achieving the smallest possible deviation from the "perfect" d-q current points or current vector I dq respectively.

[0068] Therefore, the method according to the invention for controlling a permanent magnet synchronous machine is also suitable for simple implementation in, for example, a microcontroller, since the method according to the invention requires less computing capacity than known methods.

[0069] The following text describes the approach according to the invention, which reduces the computational complexity by means of a model-based approximation method and allows for multiple variants depending on the available computing power and available system parameters.

[0070] In this case, the method according to the invention provides a multi-stage scheme in which, first, two d-q current points P1, P2 in the d-q coordinate system are determined independently of each other as starting points, and in which these d-q current points apply or satisfy different conditions.

[0071] Thus, a first d-q current point P1 can be determined at which the phase current limit and the voltage limit are observed, and the first d-q current point P1 should additionally satisfy:

[0072] - The q component of the current vector P1 in the d-q coordinate system is zero, such that: i q_P1 = 0 A, and

[0073] - The d component of the current vector P1 in the d-q coordinate system is selected to be as small as possible in terms of value.

[0074] Furthermore, a second d-q current point P2 can be determined at which the phase current limit and the voltage limit are likewise observed, and at which the maximum torque can be set.

[0075] Then a polynomial N connecting these two d-q current points P1, P2 to each other can be determined.

[0076] Then a d-q current point P3 resulting from the intersection of this polynomial N with the curve of the power boundary G L of the actuator can be determined.

[0077] Finally, another d-q current point P4 resulting from the intersection of this polynomial N with the curve of the required torque G M can be determined.

[0078] Therefore, the method according to the present invention proposes to determine a total of four d-q current points P1, P2, P3, and P4, where each d-q current point satisfies specific limiting conditions.

[0079] The method further proposes that then the operating point P can be determined based on the last-mentioned three d-q current points P2, P3, and P4 B of the current point, where this current point should satisfy the following rules:

[0080] - The d-q current points P2, P3, P4 are admissible,

[0081] - The d-component of this admissible d-q current point (P2, P3, P4) has the lowest value in terms of the value taken.

[0082] Associated with this operating point P B is the current vector I dq which can be used to control the permanent magnet synchronous motor. The voltage vector that can be used to operate the motor in a desired manner can be determined based on the current vector I dq .

[0083] According to a preferred embodiment of the present invention, the d-q current points, in particular the d-q current point P1 and the d-q current point P2, can be determined by calculation. The algorithms required for this can be stored in a control device, for example, in a microcontroller. The advantage of this approach is that the corresponding operating point P can also be optimally determined based on influencing factors that may change over time B . For example, parameter changes (such as parameter changes regarding the motor), or temperature changes, voltage changes in the vehicle electrical network, etc. can be considered. However, the required computing power must be provided for this purpose so that the calculation can be completed quickly.

[0084] According to another embodiment of the present invention, the d-q current points, in particular the d-q current point P1 and the d-q current point P2, or possible value ranges can be determined empirically and / or stored in a table or memory and provided for the application of the method. This can shorten the time by reducing the calculation time.

[0085] The type of polynomial N also affects the calculation time. Therefore, according to a preferred embodiment of the present invention, a first-order polynomial can be used, which enables a very good approximation of the optimal operating point P with a very low calculation workload B .

[0086] According to an improvement of the present invention, a higher-order polynomial N, in particular an nth-order polynomial, where n is 2, 3, or 4, can be used. A second-order polynomial can already further improve the result quality of the operating point P B without increasing the calculation workload too much.

[0087] In yet another aspect, the present invention further includes a braking system for a motor vehicle, the braking system having a permanent magnet synchronous motor and a control device as described above, wherein the control device can be designed to perform the method further described above.

[0088] The permanent magnet synchronous motor may include a stator having phase windings, a rotor having permanent magnets, and an inverter. A rotor position sensor may also be provided.

[0089] The permanent magnet synchronous motor can be controlled with a current vector I during motor operation while observing the boundary conditions, dq but can also be controlled during generator operation, wherein the regenerative current can be limited such that overheating or damage to the battery and / or the charging electronics or the control electronics can be avoided. BRIEF DESCRIPTION OF THE DRAWINGS

[0090] Further details of the present invention will be obtained from the description of the exemplary embodiments shown and the appended claims.

[0091] In the drawings:

[0092] Figure 1 A simplified illustration of a block diagram for controlling a permanent magnet synchronous motor is shown,

[0093] Figure 2 An exemplary embodiment for visually explaining the method steps according to the present invention is shown,

[0094] Figure 3 Another exemplary embodiment for visually explaining the method steps according to the present invention is shown, and

[0095] Figure 4 An exemplary embodiment of a flowchart is shown.

[0096] LIST OF REFERENCE NUMERALS:

[0097] 10 Controlled system

[0098] 11 Permanent magnet synchronous motor

[0099] 12 Pressure regulation module

[0100] 13 Speed regulation module

[0101] 14 Module for power demand

[0102] 15 Power regulation module

[0103] 16 Drive module

[0104] P1 Current point

[0105] P2 Current point

[0106] P3 Current Point

[0107] P4 Current Point

[0108] N Polynomial

[0109] G L Power Boundary

[0110] B L Allowable Power Range

[0111] G U Voltage Boundary

[0112] B U Allowable Voltage Range

[0113] G I Current Boundary

[0114] B I Allowable Current Range

[0115] G M Motor Torque Boundary

[0116] B M Desired Motor Torque Range Detailed Description of the Specific Embodiment

[0117] In the following detailed description of the preferred embodiments, for clarity, the same reference numerals denote substantially the same parts in these embodiments or among these embodiments. However, for better elucidation of the present invention, the preferred embodiments shown in the drawings are not always drawn to scale.

[0118] Figure 1 A simplified illustration of a block diagram is shown, taking the control system 10 for controlling the permanent magnet synchronous motor 11 as an example. The permanent magnet synchronous motor 11 is a component of the braking system of a motor vehicle (not shown) and operates together with a pump unit (such as a hydraulic pump) of the motor vehicle braking system.

[0119] The parameters of the control system 10 are pressure, speed, and current. In this exemplary embodiment, for this purpose, corresponding regulators or modules are integrated in the control system, in particular a pressure regulation module 12, a speed regulation module 13, a module 14 for determining the current vector, a power regulation module 15, and a drive module 16 with pulse width modulation. Sensors or measurement units can also be provided to detect the consumed current, position, and / or pressure. For clarity, these sensors or measurement units are not shown in Figure 1is shown. In the illustrated example of the controlled system 10, the d-q current points are determined in module 14 based on the torque demand from the speed control module 13. For this purpose, other relevant system parameters (such as rotational speed, voltage, temperature, or motor parameters) are provided to this module. Then, the power control module 15 can adjust the I dq target current accordingly.

[0120] Figure 2 An exemplary embodiment for illustratively explaining the method steps according to the present invention is shown. Figure 2 A plurality of curves or families of characteristic curves are shown, which represent the effective or allowable ranges of voltage, current intensity, power, and motor torque as a function of the d-current component or the q-current component.

[0121] For example, the reference sign B U represents the range of allowable voltage, where G U represents the boundary of this family of characteristic curves. Thus, the range represented by B U indicates the sum of the current points that satisfy the voltage limit.

[0122] Furthermore, the reference sign B I represents the range of allowable current, where G I represents the boundary of this family of characteristic curves. Thus, the range represented by B I indicates the sum of the current points that satisfy the phase current limit.

[0123] Furthermore, the reference sign B L represents the range of allowable power, where G L represents the boundary of this family of characteristic curves. Thus, the range represented by B L indicates the sum of the current points that satisfy the power limit.

[0124] Finally, the reference sign B M represents the range of required torque, where G M represents the boundary of this torque range.

[0125] The method according to the present invention for driving the permanent magnet synchronous motor 11 provides for the following steps:

[0126] 1. Determine a first d-q current point P1 in the d-q coordinate system, at which the phase current limit and the voltage limit are observed, and the first d-q current point P1 further satisfies:

[0127] - The q-component of the d-q current point P1 in the d-q coordinate system is zero (i q_P1 = 0 A), and

[0128] The d-component of the d-q current point P1 in the d-q coordinate system is selected to be as small as possible in terms of its value.

[0129] In Figure 2 the d-q current point P1 is shown and this point lies on a horizontal line where the q-component is equal to zero. Additionally, the d-q current point P1 is selected in such a way that the d-component is as small as possible but still admissible in terms of its value.

[0130] In Figure 2 the exemplary embodiment of U the d-q current point P1 is on the boundary G

[0131] of the family of characteristic curves of the voltage limit, so the voltage limit is complied with.

[0132] 2. Determine a second d-q current point P2 in the d-q coordinate system, at which the phase current limit and the voltage limit are complied with and the maximum torque can be set.

[0133] In Figure 2 the exemplary embodiment of U the d-q current point P2 lies on the boundary G I of the family of characteristic curves of the voltage limit and on the boundary G

[0134] This means that the d-q current point P2 is also within the admissible value range.

[0135] 3. Determine a polynomial N that connects these d-q current points P1, P2 to each other.

[0136] In Figure 2 the exemplary embodiment of

[0137] a polynomial N of the first degree is selected, which is regarded as a straight line passing through the two current points P1 and P2.

[0138] 4. Determine the d-q current point P3 based on the intersection points of this polynomial N with the power boundary G L curve.

[0139] In Figure 2 the exemplary embodiment of

[0140] the d-q current point P3 is approximately in the middle section between the two current points P1 and P2. The d-q current point P3 is denoted by the reference sign P3*: If a polynomial of the second degree passing through the two current points P1 and P2 is used instead of the polynomial of the first degree, this current point will be obtained. A slight deviation can be seen especially in terms of the d-component of the d-q current point.

[0141] 5. Determine the d-q current point P4 based on the intersection point of the polynomial N and the required torque G M curve.

[0142] In Figure 2 the embodiment, the d-q current point P4 is on the boundary G M of the relevant characteristic curve family.

[0143] Then perform the sixth step of the method:

[0144] 6. Select a working point P that satisfies the following conditions from the d-q current points P2, P3, and P4 B :

[0145] - The d-q current points P2, P3, and P4 are admissible,

[0146] - The d component of this admissible d-q current point P2, P3, and P4 has the lowest value in terms of the value range.

[0147] In Figure 2 the exemplary embodiment, the current point P4 withdraws from the group of possible current points P2, P3, and P4 because the current point P4 is outside the voltage limit, phase current limit, and power limit. Among the remaining current points P2 and P3, the corresponding d component of the current point has a lower value. Therefore, Figure 2 in the exemplary embodiment of B the current point P3 is the optimal working point P for operating the synchronous motor 11

[0148] This current point or the related current vector I dq satisfies the given boundary conditions and is at the same time the most effective parameter for controlling the synchronous motor 11.

[0149] Figure 3 shows another exemplary embodiment. In this exemplary embodiment, the determined current points P2 and P3 are outside the required torque range, and therefore ultimately the current point P4 is the admissible current point in the group of current points P2, P3, and P4 and is therefore selected for control.

[0150] Figure 4 shows yet another exemplary embodiment. In this exemplary embodiment, the current point P3 satisfies these limiting conditions and is selected as the optimal working point P B .

Claims

1. A method for controlling a permanent magnet synchronous motor (11), the method comprising the following steps: - determining a first dq current point (P1) in the dq coordinate system, at which the phase current limit and the voltage limit are observed, and the first dq current point (P1) also satisfies: -The q component of the dq current point (P1) in the dq coordinate system is zero (i q_P1 =0A), and - the d component of the dq current point (P1) in the dq coordinate system is selected to be as small as possible in terms of value, - determining a second dq current point (P2) in the dq coordinate system at which the phase current limit and the voltage limit are observed and the maximum torque can be set, - determining the polynomial (N) connecting these dq current points (P1, P2) to one another, -According to this polynomial (N) and the power boundary G L The intersection of the curves is used to determine a dq current point (P3), -According to this polynomial (N) and the required torque G M The intersection of the curves is used to determine a dq current point (P4), -Select the dq current point that satisfies the following conditions from these dq current points (P2, P3, P4) as the operating point (P B ): - this dq current point (P2, P3, P4) is allowed, - The d component of this allowed dq current point (P2, P3, P4) has the lowest value in terms of value.

2. The method according to claim 1, characterized in that With the working point (P B ) The associated current vector I dq Used to drive the permanent magnet synchronous motor (11).

3. The method according to any one of the preceding claims, characterized in that The phase current limit meets:

4. A method according to any one of the preceding claims, characterised in that The voltage limit meets:

5. The method according to any one of the preceding claims, characterized in that The power limit satisfies: PDC,min≤PDC≤PDC,max.

6. A method according to any one of the preceding claims, characterised in that The dq current points (P1, P2) are determined by calculation.

7. A method according to any one of the preceding claims, characterised in that The possible value ranges of the dq current points (P1, P2) are determined empirically and / or stored in a table and provided for application of the method.

8. A method according to any one of the preceding claims, characterised in that Polynomial(N) is a first-degree polynomial.

9. The method according to any one of the preceding claims 1 to 7, characterized in that Polynomial(N) is a polynomial of degree n, where n is 2, 3, or 4.

10. The method according to any one of the preceding claims, characterized in that The permanent-magnet synchronous motor (11) is designed for operating a pump unit, in particular a hydraulic pump, of a motor vehicle brake system.

11. A control device for controlling a permanent-magnet synchronous machine (11) of a motor vehicle, preferably as a component of a brake system, the control device being designed to carry out a method as claimed in any of the preceding claims.

12. A braking system for a motor vehicle, comprising a permanent magnet synchronous machine (11) and at least one control device as claimed in claim 11.

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