Method for determining the rotor position in a permanent magnet synchronous machine

Abstract

The invention relates to a method for determining a rotor position (RP2) of a three-phase permanent magnet synchronous machine (1). Each phase (u, v, w) of the permanent magnet synchronous machine (1) here corresponds to an inductance which changes as a function of the rotor position (RP2). In the method, a voltage (u(t)) is applied across the phases (u, v, w), wherein the applied voltage (u(t)) respectively causes a ripple current (i(t)) for each phase (u, v, w). The ripple current (i(t)) is determined for at least two of the three phases, and the inductance of the respective phase is determined on the basis of the determined ripple current (i(t)) for the respective phase. The rotor position (RP2) is then determined from the changing inductance. The method is also used here in a method for field-oriented regulation of the permanent magnet synchronous machine (1). Furthermore, the invention relates to a control unit (2) for carrying out such a method, and to a steering system having a steering regulator which comprises a permanent magnet synchronous machine (1) having such a control unit (2).

Description

Technical Field

[0001] This invention relates to a method for determining the rotor position of a three-phase permanent magnet synchronous motor (PMSM), wherein the PMSM has a d-axis inductance (Ld) and a q-axis inductance (Lq) deviating from the d-axis inductance (Ld) relative to a d / q coordinate system having d-axis and q-axis as a reference frame for rotor fixation, wherein each phase of the PMSM corresponds to an inductance that changes according to the rotor position, and wherein the rotor position is determined by means of the changed inductance. Furthermore, this invention also relates to a method for field-oriented adjustment of a PMSM, particularly for use in auxiliary systems in motor vehicles, wherein the rotor position of the PMSM required for field-oriented adjustment is determined by the aforementioned method for determining the rotor position.

[0002] Furthermore, the present invention also relates to a control unit for operating a permanent magnet synchronous motor, and a steering system having such a control unit. Background Technology

[0003] A permanent magnet synchronous motor (PMSM) is, in principle, a combination of an induction motor and a brushless DC motor. Like a brushless DC motor, a PMSM consists of a permanent magnet rotor and coils on the stator. However, the construction of the stator with coils results in a sinusoidal back electromotive force (EMF), also known as back EMK (elektromotorishe Kraft) or BEMF (back electromotive force), making the PMSM more similar to an induction motor in this respect. The different windings of the coils are represented by U, V, and W, as is common in motors.

[0004] Permanent magnet synchronous motors (PMSMs) are commonly used in motor vehicles, particularly as servo motors. Their use in electromechanical power steering is well-known, but they are also used in other vehicle assistance systems that incorporate motors. For example, PMSMs can also drive air conditioning compressors. Since the vehicle's electrical system provides DC voltage, PMSMs are typically controlled using PWM (Pulse Width Modulation) technology, which allows for the electronic simulation of multiphase AC systems.

[0005] For controlling permanent magnet synchronous motors, especially for field-oriented control (FOC), it is important to consider the rotor position in addition to the rotational speed. The rotor position must be determined for this purpose. It is known to use rotor position sensor units, which may include Hall effect sensors and angle sensors. For safety-related applications, particularly in the automotive field, such as in the electromechanical power steering disclosed in DE 10 2019202 142 A1, reliable operation of the synchronous motor must be ensured under all circumstances. Therefore, a third rotor position sensor is typically provided in such applications, which increases complexity and cost.

[0006] Furthermore, to determine the rotor position, a method based on inverse EMK, also known as a BEMF-based method, is known. Here, a high-frequency signal is applied to the base voltage, and the resulting current is determined, from which the rotor position is derived. A drawback is that the high-frequency signal impairs the base voltage signal. Additionally, it is disadvantageous that the current change curve caused by the applied signal needs to be detected using measurement techniques. Furthermore, this method is essentially only applicable when a predetermined rotational speed is reached.

[0007] Furthermore, it is known that the rotor position of a synchronous motor can be derived by determining the star contact voltage. This is fully utilized because the star contact voltage is related to the inductance of the corresponding phase, which in turn is related to the rotor position. Here, the PWM signal used is employed as the excitation voltage. This is based on the premise that the inductances on the d-axis and q-axis in the d / q coordinate system are different. Additionally, the motor's star contacts must be connected to the assigned control unit. Furthermore, to determine the star contact voltage under different space vector conditions, a specific DC voltage-bus compatible pulse width modulation must be employed. Summary of the Invention

[0008] Against this backdrop, the object of the present invention is to provide a low-cost solution for determining the rotor speed of a permanent magnet synchronous motor, which is preferably applicable to the entire operating range of the permanent magnet synchronous motor.

[0009] To achieve this objective, the present invention provides a method for determining the rotor position of a three-phase permanent magnet synchronous motor, a method for field-oriented adjustment of the permanent magnet synchronous motor, a control unit for operating the permanent magnet synchronous motor, and a steering system. Other advantageous designs of the invention are described in the specification and shown in the accompanying drawings.

[0010] The proposed solution specifies a method for determining the rotor position of a three-phase permanent magnet synchronous motor, wherein the permanent magnet synchronous motor has a d-axis inductance (Ld) and a q-axis inductance (Lq) deviating from the d-axis inductance (Ld) relative to a d / q coordinate system having d-axis and q-axis as a reference frame fixed to the rotor, wherein each phase of the permanent magnet synchronous motor corresponds to an inductance that changes according to the rotor position, and wherein the rotor position is determined by means of the changed inductance. According to the invention, a voltage is applied to the phase, wherein the voltage applied to each phase induces a ripple current, wherein the ripple current is determined for at least two of the three phases, and the inductance of the corresponding phase is determined based on the ripple current determined for the corresponding phase. Here, the determination of the inductance of the corresponding phase is advantageously carried out according to the known relation u(t) = L di(t) / dt, which describes the relationship between voltage u(t) and current i(t) with respect to time t in the case of inductance L. Because the proposed solution eliminates the need for sensors for rotor position detection, such as Hall effect sensors, it can be implemented more cost-effectively compared to solutions with rotor position detection sensor units. Furthermore, this solution advantageously improves system availability, as the proposed method enables rotor position detection across the entire operating range of the permanent magnet synchronous motor.

[0011] Preferably, the permanent magnet synchronous motor is a motor used in motor vehicles, especially in motor vehicles' safety-related systems, and further particularly in motor vehicles' steering systems. Specifically, the permanent magnet synchronous motor is a salient-pole rotor motor.

[0012] Furthermore, it is specifically stipulated that, in the method according to the invention, only the voltage applied to the phase for operating the permanent magnet synchronous motor is used, and no additional voltage superimposed on the applied voltage is applied. Thus, the applied voltage is advantageously unaffected by any additional voltage superimposed on it. In particular, it is stipulated that the voltage is applied as a pulse width modulation signal, also known as a PWM signal.

[0013] Advantageously, the permanent magnet synchronous motor is controlled by means of a PWM signal, wherein the PWM signal, in particular, is used to induce ripple current without being superimposed on other signals. The PWM signal here specifically has a frequency of at least 10 kHz (kHz: kilohertz). It is particularly specified that the permanent magnet synchronous motor is controlled by means of space vector modulation using a voltage space vector, wherein the applied voltage space vector is advantageously used to induce ripple current.

[0014] For a phase of a permanent magnet synchronous motor, the current caused by the ripple voltage is advantageously defined as the ripple current, wherein the ripple voltage is advantageously derived from the voltage difference between the instantaneous voltage and the average phase voltage. The instantaneous voltage is here determined by the corresponding voltage space vector.

[0015] The determination of the average phase voltage is specifically defined as being based on the phase duty cycle and / or the α-β filter and / or the dq voltage vector. Advantageously, the phase voltage corresponding to the respective harmonic current is determined as the average phase voltage.

[0016] Therefore, the ripple current is advantageously induced for each phase by an excitation voltage, which is derived as the voltage difference between the applied voltage space vector and the average phase voltage. Here, this excitation voltage originates from pulse-width modulation-based space vector modulation, which is applied to control the permanent magnet synchronous motor and thus advantageously does not need to be generated additionally. That is, the generation of additional voltage signals and the application of additional voltage signals to the existing voltages are advantageously eliminated. Due to the high frequency of space vector modulation at the converter output, particularly greater than 10 kHz, and especially due to frequencies in the range of 12 kHz to 24 kHz, the excitation voltage is advantageously also high-frequency. In particular, a frequency of 16 kHz or 20 kHz is set at the converter output. The voltage space vector here has particularly discrete voltage levels, which interact with the phase voltages.

[0017] Here, considering the inductances Lu, Lv, Lw corresponding to each winding phase U, V, W and thus to each phase, the instantaneous voltage of the corresponding phase can be advantageously determined as shown in the table below, where Ubat represents the voltage of the main voltage source. In the case of using this method in motor vehicles, especially the voltage of the motor vehicle battery, the instantaneous voltage of the corresponding phase can be determined.

[0018]

[0019] According to another advantageous design of the method, gradients of the ripple current are determined for at least two of the three phases, wherein the inductance of the corresponding phase is determined by the gradient determined for one phase and the ripple voltage derived for that phase. Specifically, gradients of the ripple current are determined for all three phases, wherein the inductance of the corresponding phase is determined by the gradient determined for one phase and the ripple voltage derived for that phase. Here, gradients of the ripple current are determined for all three phases, particularly when different voltage space vectors are applied. In this way, the inductance for each phase can be determined for each determined gradient, taking into account the ripple voltage.

[0020] An advantageous design variation of this method specifies that the gradient of the ripple current is determined for only two of the three phases, and the inductance of these two phases is determined by the gradient determined for one phase and the ripple voltage derived for that phase, wherein the inductance for these two phases is determined under the same voltage space vector. When the voltage space vector is the same, the inductance of the third phase is advantageously determined for that voltage space vector by the inductance determined for the other two phases.

[0021] According to another advantageous design of this method, the gradient of the ripple current is determined by means of phase current measurement. Another advantageous design proposes that the gradient of the ripple current be determined by means of intermediate loop current measurement. Advantageously, a microcontroller unit with an analog-to-digital converter is used to control the permanent magnet synchronous motor, wherein, in particular, the input of the analog-to-digital converter of the microcontroller used to control the permanent magnet synchronous motor is used to measure the ripple current. For the same voltage space vector, at least two gradients of the phase ripple current can be determined here by means of phase current measurement and the gradient of the ripple current can be determined by means of intermediate loop current measurement. If the ripple current gradient is obtained by means of intermediate loop current measurement or low-side current measurement, it is particularly set that the measurement is performed at a predetermined time after the switching process, wherein preferably the magnitude of the predetermined time is determined such that the signal oscillates steadily at the output of the operational amplifier. Further advantageously, the duty cycle, i.e., the ratio of pulse duration to period duration, is increased relative to the voltage space vector so that the gradient of the ripple current can be determined sufficiently well. Because the ripple current of only one phase can be determined for a given applied voltage space vector during intermediate loop current measurement, it is advantageous to use at least two different additional voltage space vectors for determining all three phases. Advantageously, the inductance of the corresponding phase is determined by the determined gradient of the ripple current and the associated voltage.

[0022] In particular, the first rotor angle is determined from the determined inductance for the corresponding phase when using the Clarke transformation. The Clarke transformation is well known and is also called the α-β transformation because it is used to transform the parameters of a multiphase motor (as in a three-phase motor with axes U, V, W) into a two-axis coordinate system with α and β axes. The determined first rotor angle here does not correspond to the actual rotor angle of the permanent magnet synchronous motor. Specifically, the first rotor angle rotates in the opposite direction at twice the rotor speed.

[0023] Therefore, it is specifically stipulated that the correction calculation used to determine the second rotor angle is applied to the first rotor angle. Preferably, the actual rotor angle is determined as the second rotor angle by means of the correction calculation. In this case, the second rotor angle rotates at half speed and in the opposite sign relative to the first rotor angle.

[0024] In particular, the periodic trend, which alternates between a first period and a second period offset by 180° relative to the first period, is considered using correction calculations. Advantageously, the periods are counted by means of a counter, which is advantageously initialized at the start of the permanent magnet synchronous motor, especially considering the current settling time.

[0025] According to an advantageous improvement of the method, the rotor position is determined using a BEMF-based method at a predetermined speed of the permanent magnet synchronous motor. Specifically, it is therefore stipulated that when the speed is below the predetermined speed, the rotor position is determined by determining the phase inductance from the corresponding gradient of the ripple current, and the method is switched to BEMF-based when the predetermined speed is reached.

[0026] Furthermore, it is specifically proposed that different PWM signals be applied to the permanent magnet synchronous motor in its unloaded static state and under its loaded state. This advantageously prevents the absence of ripple current when the instantaneous voltage is 0 V (V: volts), and thus the inductance cannot be determined. Specifically, it is specified that a modified space vector modulation is applied to generate ripple current in the static state. This advantageously takes into account that the fundamental harmonics of the phase voltage are zero in the static state, which could lead to errors in current measurement. In this regard, error correction is advantageously performed, taking into account the known value of the ripple current for each voltage space vector and further considering that the ripple current does not contribute to the fundamental harmonics of the phase current. Using this error correction, the sampling used to control the permanent magnet synchronous motor is advantageously adjusted such that when the ripple current is superimposed on the fundamental harmonics, the ripple current is not measured.

[0027] According to a particularly advantageous design of the present invention, the proposed method for determining the rotor position of a three-phase permanent magnet synchronous motor, having the aforementioned features, is used alone or in combination in methods for field-oriented adjustment of permanent magnet synchronous motors, particularly for auxiliary systems in motor vehicles. Specifically, a method for field-oriented adjustment of a permanent magnet synchronous motor, particularly for auxiliary systems in motor vehicles, is proposed, wherein the rotor position required for field-oriented adjustment of the permanent magnet synchronous motor is determined, and the rotor position is determined using the method for determining the rotor position proposed according to the present invention. According to a preferred embodiment, the determination of the rotor position is primarily performed using at least one rotor position determining sensor, and secondarily using the method for determining the rotor position proposed according to the present invention to increase fault reliability. In particular, it is specified that the method for determining the rotor position proposed according to the present invention is used instead of a third sensor, especially as a substitute function in case of rotor position determining sensor failure.

[0028] To address the aforementioned objective, the control unit is advantageously configured to field-orientedly adjust the permanent magnet synchronous motor according to the method proposed in this invention. The proposed steering system, particularly an electromechanical steering system, and especially an electromechanical power steering device, advantageously includes such a control device. Here, the steering system is configured to detect steering commands given via the steering handle and transmit them to a rack via a steering adjuster, on which wheels steerable via steering tie rods are arranged, wherein the steering adjuster includes a permanent magnet synchronous motor. Attached Figure Description

[0029] Other advantageous details, features, and design details of the invention are described in detail in conjunction with the embodiments shown in the accompanying drawings. The drawings illustrate:

[0030] Figure 1 An embodiment of a control unit configured according to the present invention for operating a permanent magnet synchronous motor, as illustrated in the same schematic diagram, is shown in a simplified schematic block diagram.

[0031] Figure 2 In the d / q coordinate system, for example, as shown below... Figure 1 An exemplary difference between the d-axis inductance and the q-axis inductance of the permanent magnet synchronous motor shown;

[0032] Figure 3 For example, in Figure 1 An exemplary view showing the variation curves of the phase inductances Lu, Lv, and Lw of the rotating rotor of a permanent magnet synchronous motor;

[0033] Figure 4a The invention is shown to be applied to, for example, such as Figure 1 An illustration of an embodiment of the voltage signal on a phase of a permanent magnet synchronous motor;

[0034] Figure 4b Shown by according to Figure 4a A diagram illustrating the current generated by the voltage signal;

[0035] Figure 5 The illustration shows an example of a PWM signal to be used in the operation of a permanent magnet synchronous motor when the average phase voltage and instantaneous voltage are approximately 0 V, in order to prevent ripple current from occurring.

[0036] Figure 6 An illustration shows an embodiment for a first rotor angle derived according to the present invention and a second rotor angle derived therefrom;

[0037] Figure 7 A simplified schematic diagram illustrates an embodiment of a motor vehicle, which has, for example, in... Figure 1The following are different applications of the permanent magnet synchronous motor according to the invention, having a control unit constructed according to the invention.

[0038] Figure 8a An embodiment of the steering system constructed according to the present invention is shown in a simplified perspective view; and

[0039] Figure 8b Another embodiment of the steering system constructed according to the present invention is shown in a simplified perspective view. Detailed Implementation

[0040] Reference Figure 1 An advantageous embodiment of the invention is described below. Figure 1 The diagram schematically illustrates a three-phase permanent magnet synchronous motor 1, which has winding phases U101, V102, and W103, wherein each winding phase U101, V102, W103, and therefore each phase, corresponds to inductances Lu, Lv, and Lw. The phase inductance of the permanent magnet synchronous motor 1 varies here as a function of the rotor angle. Relative to a d / q coordinate system with d and q axes as a reference frame fixed to the rotor, the permanent magnet synchronous motor 1 has a d-axis inductance (Ld) and a q-axis inductance (Lq) deviating from the d-axis inductance (Ld), as shown in... Figure 2 This is exemplarily shown in the d / q coordinate system. Figure 2 In this diagram, the inductance is plotted in μH (μH: microhenry) on axes Ax1 and Ay2. Phases U101, V102, and W103 are plotted here... Figure 2 The difference between Ld and Lq is drawn and modeled as an ellipse. As the rotor of the permanent magnet synchronous motor 1 rotates, this causes changes in the phase inductances Lu, Lv, and Lw.

[0041] The inductances Lu, Lv, and Lw can here be shown as sinusoidal functions of the rotor position of the permanent magnet synchronous motor 1, as exemplarily in... Figure 3 As shown in [the document / reference]. Here, in [the document / reference] Figure 3 An angle in radians (rad) is plotted on axis Ax2, and an inductance in μH (μH: microhenry) is plotted on axis Ay2.

[0042] Here, according to Figure 1The permanent magnet synchronous motor 1 of the embodiment shown is controlled by a control unit 2. The control unit 2 includes a control block 200, which includes functions known per se for controlling the permanent magnet synchronous motor, but not shown in detail, such as, in particular, an analog-to-digital converter, an SVM modulator (SVM: space vector modulation), and a PWM unit. That is, the permanent magnet synchronous motor 1 is controlled by a PWM signal, specifically by voltage space vector control using space vector modulation. The PWM signal at the converter output can, in particular, have a frequency of 16 kHz or 20 kHz.

[0043] Here, control unit 2 is configured for field-oriented adjustment of permanent magnet synchronous motor 1, wherein block 21 is used for the same known function of controlling field-oriented adjustment within block 200. For field-oriented adjustment of permanent magnet synchronous motor 1, the rotor position of the permanent magnet synchronous motor 1 must be provided to block 21 as an input parameter. In control unit 2, the rotor position RP2 is determined in block 20 without sensors by means of a method for determining the rotor position of a three-phase permanent magnet synchronous motor, wherein the rotor position is determined by means of inductances that change as the rotor rotates. This method is designed here for use in a three-phase permanent magnet synchronous motor, wherein, as in this embodiment, the permanent magnet synchronous motor has a d-axis inductance (Ld) and a q-axis inductance (Lq) deviating from the d-axis inductance (Ld) relative to a d / q coordinate system having d and q axes as a reference frame fixed to the rotor, and each phase of the permanent magnet synchronous motor corresponds to inductances Lu, Lv, and Lw, respectively, which change according to the rotor position. Here, the method for determining the rotor position is also implemented outside of block 21 by control unit 2. The correspondence with block 21 here is mainly used for Figure 1 The diagram is intuitive, but in this embodiment, the rotor position is ultimately determined in block 21. Specifically, the parameters required to determine the inductors Lu, Lv, and Lw are also input into block 21 of the control unit 2.

[0044] The method for determining the rotor position specifies that a voltage u(t) is applied to the phases via connecting wires 111, 112, and 113 of the permanent magnet synchronous motor, wherein the applied voltage induces a ripple current i(t) for each phase. Figure 4a An example of this preset voltage u(t) from time point t=0 to time point t=Ts is shown, where time t is plotted on axis Ax3. Axis Ay3 represents voltage. Here, the ripple voltage ur(t) is derived from the difference between the instantaneous voltage u(t) and the average phase voltage ua(Ts), which causes the ripple current i(t). The ripple current i(t) caused by the ripple voltage ur(t) is... Figure 4bThe diagram shows the ripple current gradient and is determined for at least two of the three phases. Here, time is plotted on axis Ax4 corresponding to axis Ax3. Axis Ay4 represents the current. The gradient of the ripple current i(t) can be determined here, in particular, by means of phase current measurement and / or by means of intermediate loop current measurement. Specifically, the input of the analog-to-digital converter of the microcontroller unit of control unit 2 can be used to determine the gradient of the ripple current. Then, the corresponding inductance is determined using the determined gradient of the ripple current through the relation u(t) = L di(t) / dt.

[0045] In this embodiment, the method for determining the rotor position specifies that different PWM signals are applied to the permanent magnet synchronous motor 1 in its unloaded static state and in its loaded state. Figure 5 The diagram shows a specific PWM signal to be applied to the corresponding connecting wires 111, 112, 113, which advantageously ensures the generation of a ripple current i(t) in a no-load static state, which would otherwise not occur with a mismatched PWM signal, thus hindering the determination of the phase inductances Lu, Lv, Lw.

[0046] If the inductances Lu, Lv, and Lw of the corresponding phase are determined in block 20 of control unit 2 by the determined gradient of the ripple current of the corresponding phase, then a two-dimensional coordinate diagram is transformed in block 20 by applying the Clarke transformation to the determined inductances, and the first rotor angle w1 is determined from the two-dimensional coordinate diagram. Here, in Figure 6 An example of a first rotor angle w1 determined in this way is shown, where a sample is shown on axis Ax5 and an angle in radians (rad) is shown on axis Ay5. A second rotor angle w2, corresponding to the actual rotor angle, is determined from the first rotor angle w1 by applying a correction calculation. Furthermore, block 20 includes a counter by which the period is counted for inclusion in the correction calculation. Here, the counter is initialized at startup of the permanent magnet synchronous motor 1, taking into account the current settling time. The rotor position RP2 determined in this way is then provided as an input parameter to block 21 for adjusting the field orientation of the permanent magnet synchronous motor 1.

[0047] According to an optional advantageous design, the rotor position RP2 is a rotor position redundantly determined relative to the rotor position RP1 determined using an optional rotor position sensor unit 3. Here, both the rotor position RP1 determined by the sensor and the rotor position RP2 determined without the sensor are transmitted to block 21, thereby advantageously allowing the permanent magnet synchronous motor 1 to continue operating even if the rotor position sensor unit 3 fails.

[0048] In particular, another alternative design proposes that the control unit 2 has a block 22 for BEMF-based rotor position determination, wherein the BEMF-based rotor position determination of block 22 is configured to replace the ripple current-based rotor position determination of block 20 at a predetermined rotor speed of the permanent magnet synchronous motor 1. Here, the rotor position RP3 determined based on BEMF is also fed to block 21 for regulating the permanent magnet synchronous motor 1.

[0049] As in Figure 1 As shown, the permanent magnet synchronous motor 1 with control unit 2 is specifically configured for use in a motor vehicle 4, as exemplarily in Figure 7 As illustrated in the figure. In particular, the permanent magnet synchronous motor 1 with control unit 2 is arranged in the steering adjuster 53 of the steering system 5. Another application is as a motor 61 in the air conditioning compressor used in the motor vehicle 4. Another application is as a servo motor 73 in the braking system 7 of the motor vehicle 4, wherein the servo motor provides braking force acting on the corresponding brake 71.

[0050] exist Figure 8a and Figure 8b An embodiment of a steering system 8 for a motor vehicle is shown. Here, in Figure 8a The electromechanical steering system 8 is shown in the figure, and... Figure 8b The diagram illustrates a steer-by-wire system 8. The steering system 8 includes a steering column 81 with a steering shaft 82 and a steering transmission 83. The steering transmission 83 includes a pinion 835 and a rack 836, which may also be referred to as a toothed coupling rod. The steering transmission 83 converts the rotational motion of the pinion 835 into the translational motion of the rack 836 along its longitudinal axis. A steering wheel 87 is fixed at the driver-facing end of the steering column 81, and thus the steering shaft 82, for inputting the driver's steering desire or steering command, which the driver can input by turning the steering wheel 87 in a known manner. The rack 836, moving linearly along its longitudinal axis, is mechanically coupled to tie rods 838 on both sides of the vehicle. The tie rods 838 are in turn mechanically coupled to the vehicle wheels 84. Figure 8a In the electromechanical steering system 8, the steering column 81 is mechanically coupled to the steering wheels 84 of the vehicle via a steering transmission device 83. According to... Figure 8b In the steer-by-wire system 8, the detected steering command is electronically forwarded from the steering column 81 to the steering adjuster 831 of the steering transmission. Here, according to... Figure 8a Steering adjuster 831 and according to Figure 8b The steering adjuster 831 includes a permanent magnet synchronous motor 1 with a control unit 2, as shown in reference. Figure 1 As stated in the text.

[0051] The embodiments shown in and described in conjunction with the accompanying drawings are used to illustrate the invention and are not intended to limit the invention.

[0052] Explanation of reference numerals in the attached figures

[0053] 1 permanent magnet synchronous motor

[0054] 101 winding phase U

[0055] 102 winding phase V

[0056] 103 winding phase W

[0057] 111 is the connecting wire for winding phase U (101).

[0058] 112 is the connecting wire for winding phase V (102).

[0059] 113 is the connecting wire for winding phase W (103).

[0060] 120Ld-Lq difference

[0061] 2 control units

[0062] 20 Block of control unit (2) for determining rotor position (RP2) based on ripple current

[0063] 21. Block of control unit (2) for field-oriented adjustment of permanent magnet synchronous motor (1)

[0064] 22 Optional block of control unit (2) for determining rotor position (RP3) based on BEMF

[0065] Blocks with known functions in control unit (2) 200

[0066] 3. Sensor unit for determining rotor position (RP1) using a rotor position determination sensor

[0067] 4 motor vehicles

[0068] 5-Steering System

[0069] 51 Steering Handle

[0070] 52 steering shaft

[0071] 53 Steering Adjuster

[0072] 54 steerable wheels

[0073] 6 air conditioner compressors

[0074] 61. Motor of air conditioning compressor (6)

[0075] 7. Braking System

[0076] 71 brake

[0077] Braking amplifier at center 72

[0078] Servo motor of braking system (7)

[0079] 8-Steering System

[0080] 81 steering column

[0081] 82 steering axle

[0082] 83 Steering Transmission

[0083] 831 Steering adjuster with permanent magnet synchronous motor (1) and control unit (2)

[0084] The pinion of the 835 steering transmission (83)

[0085] 836 rack

[0086] 838 steering tie rod

[0087] 84 steerable wheels

[0088] 87 Steering Handle

[0089] The rotor position of RP1 is determined by a rotor position determination sensor.

[0090] The rotor position of RP2 was determined using a method based on ripple current.

[0091] The position of rotor RP3 was determined using a BEMF-based method.

[0092] w1 First rotor angle

[0093] w2 Second rotor angle

[0094] i(t) ripple current

[0095] instantaneous voltage u(t)

[0096] ua(Ts) average phase voltage

[0097] ur(t) ripple voltage

[0098] Lu phase inductance

[0099] Lv phase inductor

[0100] Lw phase inductance

[0101] Ldd axis inductance

[0102] Lqq axis inductor

[0103] t time

[0104] Ts time point

[0105] Ax1x axis Figure 2

[0106] Ay1y axis Figure 2

[0107] Ax2x axis Figure 3

[0108] Ay2y axis Figure 3

[0109] Ax3x axis Figure 4a

[0110] Ay3y axis Figure 4a

[0111] Ax4x axis Figure 4b

[0112] Ay4y axis Figure 4b

[0113] Ax5x axis Figure 6

[0114] Ay5y axis Figure 6

Claims

1. A method for determining the rotor position (RP2) of a three-phase permanent magnet synchronous motor (1), wherein the permanent magnet synchronous motor (1) has a d-axis inductance (Ld) and a q-axis inductance (Lq) deviating from the d-axis inductance (Ld) relative to a d / q coordinate system having a d-axis and a q-axis, which serves as a reference frame for rotor fixation, wherein each phase of the permanent magnet synchronous motor (1) corresponds to an inductance (Lu, Lv, Lw) that changes according to the rotor position, and wherein the rotor position is determined by means of the changed inductance, characterized in that, A voltage (u(t)) is applied to a phase, wherein the applied voltage (u(t)) causes a ripple current (i(t)) for each phase, wherein the ripple current (i(t)) is determined for at least two of the three phases, and the inductance of the corresponding phase is determined based on the ripple current (i(t)) determined for the corresponding phase; in the case of applying the Clarke transform, a first rotor angle (w1) is determined from the inductance determined for the corresponding phase, and a correction calculation is applied to the first rotor angle (w1) to determine a second rotor angle (w2), the correction calculation taking into account the periodic trend having a transition between a first period and a second period offset by 180° relative to the first period.

2. The method according to claim 1, characterized in that, The cycle is counted using a counter.

3. The method according to claim 1 or 2, characterized in that, Initialization is performed when the permanent magnet synchronous motor (1) starts.

4. The method according to any one of claims 1-2, characterized in that, The permanent magnet synchronous motor (1) is controlled by a PWM signal, wherein the PWM signal is used to induce ripple current (i(t)).

5. The method according to claim 1 or 2, characterized in that, The permanent magnet synchronous motor (1) is controlled by means of space vector modulation using voltage space vector.

6. The method according to any one of claims 1-2, characterized in that, For a phase, the current caused by the ripple voltage (ur(t)) is determined as the ripple current (i(t)) by the voltage difference between the instantaneous voltage (u(t)) and the average phase voltage (ua(t)), wherein the instantaneous voltage (u(t)) is determined by the voltage space vector to which it belongs.

7. The method according to claim 6, characterized in that, Determine the gradient of the ripple current (i(t)) for at least two of the three phases, wherein the inductance of the corresponding phase is determined by the gradient determined for one phase and the ripple voltage (ur(t)) derived for that phase.

8. The method according to claim 7, wherein the gradient of the ripple current (i(t)) is determined for only two of the three phases, and the inductance of the two phases is determined by the gradient determined for one phase and the ripple voltage (ur(t)) derived for that phase, characterized in that, The inductance for the two phases is determined under the same voltage space vector, wherein the inductance for the third phase under the same voltage space vector is determined by the inductance determined for the other two phases.

9. The method according to claim 7 or 8, characterized in that, The gradient of the ripple current (i(t)) is determined by means of phase current measurement.

10. The method according to any one of claims 7 to 8, characterized in that, The gradient of the ripple current (i(t)) is determined by means of intermediate loop current measurement.

11. The method according to any one of claims 7 to 8, characterized in that, In order to control the permanent magnet synchronous motor (1), a microcontroller unit is used, wherein the input of the analog-to-digital converter of the microcontroller unit is used to determine the gradient of the ripple current (i(t)).

12. The method according to any one of claims 1-2, characterized in that, Given a predetermined rotational speed of the permanent magnet synchronous motor (1), the rotor position (RP3) is determined using a BEMF-based method.

13. The method according to any one of claims 1-2, characterized in that, Different PWM signals are applied to the permanent magnet synchronous motor (1) in its unloaded static state and in its loaded state.

14. A method for field-oriented adjustment of a permanent magnet synchronous motor (1), wherein the rotor positions (RP1, RP2, RP3) of the permanent magnet synchronous motor (1) required for field-oriented adjustment are determined, characterized in that, The rotor position is determined by the method according to any one of claims 1 to 13.

15. The method according to claim 14, characterized in that, The permanent magnet synchronous motor is a permanent magnet synchronous motor (1) used in the auxiliary system of a motor vehicle (4).

16. A control unit (2) for operating a permanent magnet synchronous motor (1), characterized in that, The control unit (2) is designed to field-orientedly adjust the permanent magnet synchronous motor (1) according to the method of claim 14 or 15.

17. A steering system (5, 8) designed to detect steering commands issued via steering handles (51, 87) and transmit them to a rack (836) via steering adjusters (53, 831), on which wheels (54, 84) capable of being steered via steering tie rods (838) are mounted, wherein the steering adjusters (53, 831) comprise permanent magnet synchronous motors (1), characterized in that, The permanent magnet synchronous motor (1) includes the control unit (2) according to claim 16.

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