Method for recording initial rotational position of rotor

Abstract

The invention relates to a method (26) for recording an initial rotational position (20) of a stationary rotor (12) of an electric motor (10) relative to a stator (14) by performing a current response recording, in which a high-frequency injection signal (22) is introduced along a recording direction (D) in a dq coordinate system of the electric motor (10), and recording the at least one current variable as a recorded current variable (I) as a current response to the injection signal (22), a first current response recording (28) is performed along a first recording direction, which is an assumed d direction (d '), in which the injection signal (22) and the first constant current value (is, 1) are superimposed in the first recording direction (D1) and the recording current variable (I) is recorded as a first current recording value (i1), and a second current response recording (30) is performed along a second recording direction (D2) opposite the first recording direction (D1) and the recording current variable (I) is recorded as a second current recording value (i2). Wherein the injection signal (22) is superimposed on a second constant current value (is, 2) in a second recording direction (D2), and the recording current variable (I) is recorded as a second current recording value (i2), and after the first current response recording (28) and the second current response recording (30), the injection signal (22) is superimposed on the second constant current value (is, 2). A 180 DEG offset between the first recording direction (D1) and the actual d-direction is determined as a function of the ratio of the first current recording value (i1) and the second current recording value (i2).

Description

Technical field

[0001] The invention relates to a method for recording an initial rotational position of a rotor of an electric motor according to the preamble of claim 1. Background art

[0002] EP 2 194 641 A1 describes a method for determining an initial rotational position of a permanent magnet rotor of an electric motor, in which the saturation behavior of ferromagnetic motor windings is used to detect and correct a 180° error when determining the initial rotational position. Before performing a 180° rotation test, a specific saturation of ferromagnetic material is tested.

[0003] From KITAMURA, Kentaro; TAKUMI, Nimura; DOKI, Shinji: Sensorless control method based on IPMSM full speed range drive using redefined extended electromotive force and its evaluation on electric vehicles. In: 29th IEEE International Symposium on Industrial Electronics (ISIE), June 17 - 19, 2020, Delft, Netherlands; 2020, P.351 - 356. ISBN 978 - 1 - 7281 - 5636 - 1. DOI: 10.1109 / ISIE45063.2020.9152459, a method for recording an initial rotational position of a rotor of an electric motor by performing a current response recording is known. A high - frequency injection signal is introduced along a recording direction, and a current variable is recorded as a current response to the injection signal. Summary of the invention

[0004] The object of the invention is to detect a 180° offset between a supposed initial rotational position and an actual initial rotational position of the rotor faster and more reliably.

[0005] At least one of these objects is achieved by a method for recording an initial rotational position having the features of claim 1. This allows for a faster and more accurate detection of a 180° offset in a supposed d - direction. This can prevent malfunctioning operation of the electric motor.

[0006] The electric motor can be arranged in a vehicle, in particular in a powertrain of the vehicle. The electric motor can have a plurality of circumferentially distributed annular windings. The annular windings can have at least one ferromagnetic core.

[0007] The recording of the initial rotational position is preferably sensorless, i.e., without using a sensor for measuring the rotational position of the rotor relative to the stator. This allows the electric motor to be constructed in a more cost - effective manner. The wiring originally required for the sensor can be omitted.

[0008] The initial rotational position is defined as the angular position of the rotor relative to the stator when the rotor is at rest, i.e., initially not rotating. The initial rotational position is preferably the angular position of the rotor before the drive power of the electric motor is established.

[0009] The electric motor can be arranged to operate at least one pump, in particular at least one pump of a vehicle. The pump can provide a fluid pressure for actuating at least one vehicle component of the vehicle and / or a fluid volume flow for cooling at least one vehicle component of the vehicle.

[0010] In the first current response record and the second current response record, the following fact is particularly utilized: Due to the direction-dependent saturation of the ferromagnetic material in the toroidal winding, in particular in the toroidal winding of the stator, the current response varies according to the direction of the constant current value.

[0011] The first current response record can be performed before or after the second current response record.

[0012] In a preferred embodiment of the present invention, it is advantageous to perform a multi-angle current variable record during the current response record, wherein, on the one hand, the current variable along a first direction offset by a first angle relative to the recording direction is detected as the first recorded current variable, and on the other hand, the current variable along a second direction offset by a second angle relative to the recording direction is detected as the second recorded current variable, and the recorded current variable is calculated based on the first recorded current variable and the second recorded current variable. Relative to the recording direction, the first angle is preferably +45°, and the second angle is preferably -45°, or vice versa. The recorded current variable can be the sum of the squares of the first recorded current variable and the second recorded current variable.

[0013] In a specific embodiment of the present invention, it is advantageous to perform a multi-angle current variable record in the first current response record, wherein the first angle and the second angle are related to the first recording direction, and the recorded current variable forms the first current record value. This allows for a more accurate determination of the first current record value. The first current record value can be the sum of the squares of the first recorded current variable and the second recorded current variable.

[0014] A preferred embodiment of the present invention is that it is advantageous to perform a multi-angle current variable record in the second current response record, wherein the first angle and the second angle are related to the second recording direction, and the recorded current variable forms the second current record value. This allows for a more accurate determination of the second current record value. The second current record value can be the sum of the squares of the first recorded current variable and the second recorded current variable.

[0015] In a preferred embodiment of the present invention, it may be provided that a possible 180° offset between the first recording direction and the actual d direction is determined based on the amplitude ratio of the first current recording value and the second current recording value. The first current recording value and / or the second current recording value may be preprocessed, in particular filtered, to calculate the amplitude ratio.

[0016] In a specific embodiment of the present invention, it is advantageous that the amplitude ratio is the amplitude difference between the magnitude of the first current recording value and the magnitude of the second current recording value. Preferably, the amplitude difference is the difference between the amplitude of the first current recording value and the amplitude of the second current recording value. The amplitude difference may also be the difference between the square of the amplitude of the first current recording value and the square of the amplitude of the second current recording value.

[0017] In a preferred embodiment of the present invention, it may be provided that if the amplitude difference is negative, an 180° offset is determined. Then the assumed d direction may be corrected by 180°.

[0018] In a preferred embodiment of the present invention, it is advantageous that if the amplitude difference is positive, the 180° offset is rejected. No correction of the assumed d direction may occur.

[0019] In a preferred embodiment of the present invention, it is advantageous that the magnitudes of the first constant current value and the second constant current value are equal. Since the second recording direction is offset by 180° relative to the first recording direction, the first constant current value may be positive and the second constant current value may be negative.

[0020] In a specific embodiment of the present invention, it is advantageous that the rotor is a permanent magnet rotor and / or the electric motor is a brushless DC motor. If the magnetic flux of the permanent magnets of the permanent magnet rotor saturates the iron core of the annular winding of the stator, a change in the alignment of the magnetic axis of the rotor relative to the annular winding results in a change in the inductive properties of the annular winding. If the magnetic flux of the permanent magnet rotor is aligned with the annular winding, the iron core is saturated to the maximum value and the coil inductance in the annular winding decreases. Therefore, the current response varies according to the rotational position of the rotor relative to the annular winding.

[0021] Furthermore, the present invention relates to an electric motor configured to perform a method having at least one of the above-mentioned features.

[0022] Other advantages and advantageous embodiments of the present invention result from the description of the figures and the drawings. Description of the Drawings

[0023] The present invention will be described in detail below with reference to the drawings. In the drawings, specifically:

[0024] Figure 1: An electric motor is shown which is used to perform a method for recording an initial rotational position in a specific embodiment of the present invention.

[0025] Figure 2 : A graph is shown which shows the execution process of the method in a specific embodiment of the present invention. Specific embodiment

[0026] Figure 1 An electric motor is shown which is used to perform the method in a specific embodiment of the present invention. The electric motor 10 includes a rotor 12 which is rotatable relative to a stator 14. The rotor 12 is preferably a permanent magnet rotor 16 which is driven by an annular winding 18 of the stator 14 according to electrical control. The annular winding 18 is simplified to a single annular winding 18 in the figure, but in fact the annular winding 18 is preferably evenly distributed around the circumference of the stator 14.

[0027] The annular winding 18 includes at least one ferromagnetic core 19 and is electrically connected to a control unit, preferably an inverter, which sets electrical operating variables, in particular the voltage and / or current on the annular winding 18. The electrical operating variables are preferably related to the dq coordinate system of the rotor 12. The dq coordinate system is a reference system of electrical operating variables which rotates together with the rotor 12 and is obtained by Park transformation.

[0028] When the rotor 12 is initially stationary relative to the stator 14, the initial rotational position 20, i.e., the rotational position of the rotor 12 relative to the stator 14, is decisive for the starting operation of the electric motor 10. In the current case, in the absence of sensors, i.e., in the absence of additional sensors, the initial rotational position 20 is recorded by recording the electrical parameters of the electric motor 10, preferably by means of current response recording, wherein a high-frequency injection signal 22 is introduced along a recording direction D in the dq coordinate system of the electric motor 10, and at least one current variable is recorded as a recorded current variable I which is the current response to the injection signal 22.

[0029] If a presumed d direction d' is determined by using current response recording, there may still be a 180° offset between the presumed d direction d' and the actual d direction. The method described in more detail below can be used to record this 180° offset.

[0030] First, perform a first current response recording along a first recording direction D1 assumed to be in the assumed d direction d'. Here, the injection signal 22 is superimposed with a first constant current value in the first recording direction D1, and the recording current variable I is recorded as a first current recording value i1. Then, perform a second current response recording along a second recording direction D2 opposite to the first recording direction D1, where the injection signal 22 is superimposed with a second constant current value in the second recording direction D2, and the recording current variable I is recorded as a second current recording value i2.

[0031] In the first current response recording, perform a multi-angle current variable recording. On the one hand, along a first direction D offset by a first angle γ1, particularly -45°, relative to the first recording direction D1 d,1 Detect the current amplitude as a first recorded current variable i d,1 and, on the other hand, along a second direction D offset by a second angle γ2, particularly +45°, relative to the first recording direction D1 d,2 Record the current variable as a second recorded current variable i d,2 and calculate the first current recording value i1 as the recorded current variable I based on the first recorded current variable i d,1 and the second recorded current variable i d,2

[0032] In the second current response recording, also perform a multi-angle current variable recording. On the one hand, along a first direction D' offset by a first angle γ'1 relative to the second recording direction D2 d,1 Detect the current amplitude as a first recorded current variable i' d,1 and, on the other hand, along a second direction D' offset by a second angle γ'2 relative to the first recording direction D1 d,2 Record the current variable as a second recorded current variable i' d,2 and calculate the second current recording value i2 as the recorded current variable I based on the first recorded current variable i' d,1 and the second recorded current variable i' d,2

[0033] Figure 2 The graph shows the execution process of the method in a specific embodiment of the present invention. The method 26 for recording the initial rotational position of the rotor is preferably performed using a stationary rotor and will be explained below using the time graphs of various parameters of the electric motor, first for a first time interval T1.

[0034] Initially, in the case of a stationary rotor, the injection signal 22 is superimposed with a first constant current value i s,1 ​​Superposition. The injected signal 22 is similar to a frequency band due to high-frequency components. Then, the injected signal 22 is superposed with the second constant current value i s,2 Superposition. The first constant current value i s,1 and the second constant current value i s,2 are equal in amount. Since the second recording direction D2 is opposite to the first recording direction D1, the first constant current value i s,1 as the constant current applied in the first recording direction is positive, and the second constant current value i s,2 is negative.

[0035] Perform the first current response recording 28 using the set first constant current value i s,1 . The first current recording value i1 is calculated using this set first constant current value as the sum of the squares of the first detection current variable and the second detection current variable recorded as multi-angle current variables. When superposed with the first constant current value i s,1 , the first current recording value i1 increases.

[0036] Perform the second current response recording 30 using the set second constant current value i s,2 . The second current recording value i2 is calculated using this set second constant current value as the sum of the squares of the first detection current variable and the second detection current variable recorded as multi-angle current variables. When superposed with the second constant current value i s,2 , the second current recording value increases.

[0037] Determine a possible 180° offset between the first recording direction and the actual d direction based on the amplitude ratio A of the first current recording value i1 and the second current recording value i2. The amplitude ratio A is a filtered signal of the amplitude difference, and the amplitude difference is calculated from the amounts of the first current recording value i1 and the second current recording value i2.

[0038] Evaluate the amplitude ratio A after the second current response recording 30 is completed, and if the amplitude ratio is negative, determine the 180° offset because the permanent magnet of the rotor is aligned along the second recording direction, and thus the actual d direction is aligned along the second recording direction. This means that the assumed d direction extending along the first recording direction can then be corrected by 180°.

[0039] In the second time interval T2, the amplitude ratio A is positive after the second current response recording 30 is performed, and the 180° offset is rejected. The assumed d direction is not corrected by 180°.

[0040] List of reference numerals

[0041] A Amplitude ratio

[0042] D Recording direction

[0043] D’d,1 First direction

[0044] D’ d,2 Second direction

[0045] D1 First recording direction

[0046] D2 Second recording direction

[0047] D d,1 First direction

[0048] D d,2 Second direction

[0049] I Record current variable

[0050] γ’1 First angle

[0051] γ’2 Second angle

[0052] γ1 First angle

[0053] γ2 Second angle

[0054] d’ Assumed d direction

[0055] i’ d,1 First recording current variable

[0056] i’ d,2 Second recording current variable

[0057] i1 First current recording value

[0058] i2 Second current recording value

[0059] i d,1 First recording current variable

[0060] i d,2 Second recording current variable

[0061] i s,1 First constant current value

[0062] i s,2 Second constant current value

[0063] 10 Electric motor

[0064] 12 Rotor

[0065] 14 Stator

[0066] 16 Permanent magnet rotor

[0067] 18 Ring winding

[0068] 19 Iron core

[0069] 20 Initial rotation position

[0070] 22 Injection signal

[0071] 26 Method

[0072] 28 First current response record

[0073] 30 Second current response record.

Claims

1. A method (26) for recording an initial rotational position (20) of a stationary rotor (12) of an electric motor (10) relative to a stator (14), wherein, a current response recording is performed, wherein a high-frequency injection signal (22) is introduced along a recording direction (D) in the dq coordinate system of the electric motor (10), and at least one current variable is recorded as a recorded current variable (I) being a current response to the injection signal (22), wherein, Perform a first current response recording (28) along a first recording direction (D1) along a supposed d direction (d'), wherein the injection signal (22) is superimposed with a first constant current value (i s,1 ) in the first recording direction (D1), and record the recording current variable (I) as the first current recording value (i1), and Perform a second current response recording (30) along a second recording direction (D1) opposite to the first recording direction (D2), wherein the injection signal (22) is superimposed with a second constant current value (i s,2 ) in the second recording direction (D2), and record the recording current variable (I) as a second current recording value (i2), and after the first current response recording (28) and the second current response recording (30), a possible 180° offset between the first recording direction (D1) and the actual d direction is determined based on a ratio of the first current recorded value (i1) and the second current recorded value (i2). It is characterized in that multi-angle current variable recording is performed during the current response recording, wherein, on the one hand, the current variable along a first direction (D’ d,1 , D d,1 ) offset by a first angle (γ’1, γ1) with respect to the recording direction (D) is detected as the first recorded current variable (i’ d,1 , i d,1 ), and on the other hand, the current variable along a second direction (D’ d,2 , D d,2 ) offset by a second angle (γ’2, γ2) with respect to the recording direction (D) is detected as the second recorded current variable (i’ d,2 , i d,2 ), and the recorded current variable (I) is calculated according to the first detected current amount (i’ d,1 , i d,1 ) and the second detected current amount (i’ d,2 , i d,2 ).

2. The method (26) for recording an initial rotational position (20) according to claim 1, characterized in that, The multi-angle current variable recording is performed in the first current response recording (28), wherein the first angle (γ1) and the second angle (γ2) are related to the first recording direction (D1), and the recorded current variable (I) forms the first current recorded value (i1).

3. The method (26) for recording an initial rotational position (20) according to claim 1 or 2, characterized in that, The multi-angle current variable recording is performed in the second current response recording (30), wherein the first angle (γ’1) and the second angle (γ’2) are related to the second recording direction (D2), and the recorded current variable (I) forms the second current recorded value (i2).

4. The method (26) for recording an initial rotational position (20) according to one of the preceding claims, characterized in that, A possible 180° offset between the first recording direction (D1) and the actual d direction is determined based on an amplitude ratio (A) of the first current recorded value (i1) and the second current recorded value (i2).

5. The method (26) for recording an initial rotational position (20) according to claim 4, characterized in that, The amplitude ratio (A) is an amplitude difference between the magnitude of the first current recorded value (i1) and the magnitude of the second current recorded value (i2).

6. The method (26) for recording an initial rotational position (20) according to claim 5, characterized in that, In the case where the amplitude difference is negative, a 180° offset is determined.

7. A method (26) for recording an initial rotational position (20) according to claim 5 or 6, characterized in that, In the case where the amplitude difference is positive, the 180° offset is rejected.

8. A method (26) for recording an initial rotational position (20) according to one of the preceding claims, characterized in that, The amount of the first constant current value (i s,1 ) and the second constant current value (i s,2 ) are equal.

9. A method (26) for recording an initial rotational position (20) according to one of the preceding claims, characterized in that, The rotor (12) is a permanent magnet rotor (16) and / or the electric motor (10) is a brushless DC motor.

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