METHOD AND DEVICE FOR CALIBRATING A CONTROL SYSTEM OF AN ELECTRICAL MACHINE

Description

[0001] The present invention relates to a method for calibrating a control of an electrical machine and a device for calibrating a control of an electrical machine. State of the art

[0002] Electric drive systems have a wide range of applications, whether in households, vehicles or industry.

[0003] Drive systems comprise electrical machines controlled by a controller. With field-oriented control, torque control is decoupled from flux control. This allows for good speed and positioning accuracy. For this purpose, a dq coordinate system is advantageously considered, which moves with the rotor of the electrical machine.

[0004] The d and q axes are perpendicular to each other. The q value corresponds to the torque of the electric machine, and the d value corresponds to the magnetic flux density. The q and d values ​​can be controlled by the controller using a PI controller, just like a DC motor. In particular, the torque of the electric machine can be influenced by a predefined q reference value.

[0005] Precise control of electrical machines requires precise knowledge of the rotor angle at all times. To determine the rotor angle, angle sensors can be mounted on the rotor shaft to measure angles.

[0006] Sensorless drive systems are also known, which do not require an angle encoder. This can reduce system costs and improve robustness and space requirements.

[0007] To determine the rotor position in such sensorless drive systems, the anisotropy of the electric machine can be determined. For example, the position and angle dependence of the electric machine can be determined using high-frequency excitation. An exemplary method for identifying the magnetic anisotropy of an electric rotating field machine is known from DE 10 2015 / 217986 A1. Further methods and devices for this purpose are known from the publications EP 3 288 179 A1, DE 10 2014 209603 B3, DE 103 11 028 A1, DE 10 2012 205540 A1, DE 10 2005 045835 A1, US 2005 / 127857 A1, and DE 10 2014 212383 A1.

[0008] Technical defects can occur during operation of the electric machine, such as the determination of an incorrect rotor offset angle, incorrect phase sequence, and the like. This can lead to the actual direction of rotation of the electric machine not being correctly determined. This can result in an unintended direction of rotation of the electric machine during control and, as a result, in the incorrect direction of movement of a vehicle controlled by the electric machine. To avoid such safety-relevant malfunctions, it is necessary to reliably determine the direction of rotation of the electric machine.

[0009] There is therefore a need for methods for the precise calibration of the control of an electrical machine. Disclosure of the invention

[0010] The invention provides a method for calibrating a control of an electrical machine with the features of patent claim 1 and a device for calibrating a control of an electrical machine with the features of patent claim 8.

[0011] Preferred embodiments are the subject of the respective subclaims. Advantages of the invention

[0012] The invention makes it possible to reliably determine the direction of rotation of the electrical machine by applying the electrical test signal. For this purpose, the electrical test signal is applied with a predetermined direction in the dq coordinate system. The exact direction itself does not have to be known initially. Rather, it is sufficient for the test signal to have a fixed direction in the dq coordinate system rotating with the rotor. According to one embodiment, the position of the axes of the dq coordinate system can be known, but the exact orientation not yet. In particular, the direction in which the q-axis is oriented may not yet be known. If, for example, a test signal with a predetermined direction along the q-axis is applied, the direction of rotation can be determined based on the measured change in the rotor angle.If the rotor angle changes in a positive direction, it can be determined, for example, that the test signal was applied in a positive direction along the q-axis.

[0013] The invention thus makes it possible to determine the orientation of the dq coordinate system. The control of the electric machine can thus be calibrated. This can be understood as meaning that the control signals with which the electric machine is controlled by the controller are calculated and applied to the electric machine, taking into account the determined orientation of the dq coordinate system.

[0014] According to one embodiment of the method for calibrating a control of an electrical machine, a hypothesis regarding an orientation of the dq coordinate system can be verified. It is assumed that a specific direction corresponds to a positive q-direction in the dq coordinate system. If, when an electrical test signal is applied along the positive q-axis, a corresponding change in the rotor angle in the positive direction is also measured, the hypothesis is confirmed. However, if, when the electrical test signal is applied along the positive q-axis, a change in the rotor angle in the negative direction is measured, the hypothesis is refuted. Instead, it is recognized that the specific direction corresponds to the negative q-direction in the dq coordinate system.

[0015] The invention thus makes it possible to prevent an incorrect direction of rotation of an electrical machine.

[0016] According to one embodiment of the method for calibrating a control system of an electrical machine, an offset angle of the rotor of the electrical machine is determined before applying the electrical test signal. This determines whether the software angle, i.e., the angle used in the control by the controller, corresponds to the actual rotor position angle.

[0017] According to one embodiment of the method for calibrating the control of an electrical machine, the offset angle of the rotor of the electrical machine is determined based on a measurement of an anisotropy of the electrical machine. The determination or calibration of the offset angle of the rotor of the electrical machine can be carried out within a certain measurement accuracy. For example, the direction of the flux axis can be determined with an accuracy of + / - 20°. However, after determining the offset angle, a remaining 180° uncertainty may still exist. In other words, the direction of the flux along the flux axis is still unknown. Whether this is a positive or negative direction is determined based on the method for calibrating the control of the electrical machine.

[0018] According to one embodiment of the method for calibrating a control system of an electrical machine, a plurality of electrical test signals are applied to the electrical machine, wherein the predetermined directions of the test signals differ from one another in the dq coordinate system. If the determination of the orientation of the dq coordinate system is not unambiguous based on a single test signal, a unique orientation can be determined by using several additional electrical test signals.

[0019] According to one embodiment of the method for calibrating a control of an electrical machine, applying the at least one electrical test signal with a predetermined direction in a dq coordinate system to the electrical machine comprises applying a first test signal with a first predetermined direction in the dq coordinate system to the electrical machine. If applying the first test signal does not cause a change in the rotor angle of the rotor of the electrical machine, a second test signal with a second direction deviating from the first predetermined direction in the dq coordinate system is applied to the electrical machine. For example, components of the electrical machine can be biased so that applying the first test signal does not cause any significant movement of the rotor.The second test signal can cause a larger change in the rotor angle of the rotor of the electric machine, so that the orientation of the dq coordinate system can be determined.

[0020] According to one embodiment of the method for calibrating a control of an electrical machine, the second direction is opposite to the first direction in the dq coordinate system.

[0021] According to one embodiment of the method for calibrating a control system of an electrical machine, the electrical test signal is a voltage signal or a current signal. The signal can have any desired signal shape. In particular, the signal can be step-shaped, sinusoidal, pulse-shaped, or the like.

[0022] According to one embodiment of the method for calibrating the control of an electric machine, a maximum voltage or a maximum current of the electrical test signal is successively increased until a change in the rotor angle of the rotor of the electric machine is measurable. By increasing the value in steps, excessive deflection, i.e., an excessive change in the rotor angle of the rotor of the electric machine, can be prevented. In particular, it can be achieved that a wheel angle of the motor vehicle driven by the electric machine remains unchanged during application of the method for calibrating the control of the electric machine. Due to the gear ratio and the limited rigidity of the drive train, the slight change in the rotor angle of the rotor of the electric machine does not lead to a movement of the vehicle itself.

[0023] According to one embodiment of the method for calibrating a control of an electrical machine, the electrical machine is at a standstill when the electrical test signal is applied. Short description of the drawings

[0024] They show: Figure 1 shows a schematic block diagram of a device for calibrating a control of an electrical machine according to an embodiment of the invention; and Figure 2 shows a schematic flow diagram of a method for calibrating a control of an electrical machine according to an embodiment of the invention.

[0025] The numbering of procedural steps is for clarity and generally does not imply a specific chronological order. In particular, several procedural steps can be performed simultaneously. Description of the embodiments

[0026] Figure 1shows a schematic block diagram of a device 1 for calibrating a control of an electrical machine 6.

[0027] The device 1 comprises a signal generator 2, a measuring device 3, and a calibration device 4. The electric machine 6 comprises a rotor and a stator and is controlled by a controller 5 (control device). The signal generator 2 generates an electrical test signal, which is applied to the electric machine 6 by the controller 5.

[0028] The electrical test signal can be a voltage signal or a current signal that has a predetermined direction in a dq coordinate system. This means that the direction does not change in the coordinate system that rotates with a rotor of the electric machine 6. However, the orientation of the dq coordinate system does not need to be known.

[0029] It can be provided that the electrical test signal is only applied to the electrical machine 6 when the electrical machine is stationary. Sensors can be provided for this purpose. If the electrical machine is driving a vehicle, it can be determined, for example, that the vehicle is stationary.

[0030] Furthermore, it can be provided that an offset angle of the rotor of the electric machine 6 is determined before applying the electrical test signal. The offset angle of the rotor of the electric machine is preferably determined by measuring an anisotropy of the electric machine. The anisotropy can be measured by the measuring device 3.

[0031] The measuring device 3 is further designed to measure a change in the rotor angle of the rotor of the electric machine 6 as a function of the applied electrical test signal. In particular, the measuring device 3 can determine the direction in which the rotor of the electric machine 6 rotates. The measuring device 3 outputs a corresponding measurement signal.

[0032] Calibration device 4 evaluates the measurement signal from measuring device 3 to determine the orientation of the dq coordinate system. For example, if the position of the d and q axes is known by determining the rotor's offset angle, but the exact orientation of the d and q axes is not yet known, the orientation of the d and q axes can be determined based on the direction of rotation of the electric machine's rotor, which results from applying the electrical test signal.

[0033] For example, signal generator 2 can apply an electrical test signal in a first direction along a q-axis. If the rotor angle of the rotor changes in a positive direction, it can be recognized that the first direction is a positive direction of the q-axis.

[0034] The calibration device 4 calibrates the controller 5, i.e. transmits the orientation of the dq coordinate system to the controller 5. The controller 5 carries out the further control of the electric machine 6 taking into account the transmitted orientation of the dq coordinate system.

[0035] If the measuring device 3 measures no or only an insignificant change in the rotor angle of the rotor of the electric machine 6, the signal generator 2 can apply a further electrical test signal to the electric machine 6 via the controller 5. The further electrical test signal can have a direction in the dq coordinate system that is opposite to the direction of the first electrical test signal.

[0036] Furthermore, the signal generator 2 can be configured to successively increase the strength of the electrical test signal, such as a voltage or current. Thus, an electrical test signal is applied to the electrical machine 6 in each case to measure the change in the rotor angle of the rotor of the electrical machine 6. If the change in the rotor angle is smaller than a predetermined threshold value, the strength of the electrical test signal is increased.

[0037] Figure 2shows a schematic flow diagram of a method for calibrating a control of an electrical machine.

[0038] In a first method step S1, it is ensured that the electric machine 6 is at a standstill.

[0039] Furthermore, an offset angle of the rotor of the electric machine 6 is optionally determined. The offset angle can be determined by measuring an anisotropy of the electric machine 6. As a result, the direction of a flux axis can be determined with a certain accuracy, approximately + / - 20°. Thus, the position of the axes of the dq coordinate system is known. However, the exact orientation of the dq coordinate system does not have to be determined yet.

[0040] In a second method step S2, an electrical test signal with a predetermined direction in the dq coordinate system is applied to the electrical machine 6. For example, the electrical test signal can correspond to a first direction along a q-axis.

[0041] In a third method step S3, a change in a rotor angle of a rotor of the electric machine 6 is measured, which is caused by the applied electrical test signal.

[0042] In a further method step S4, the orientation of the dq coordinate system is determined based on the measured change in the rotor angle of the rotor of the electric machine 6. If, for example, an excitation in a positive direction along the q-axis results in a change in the rotor angle in a positive direction, it can be concluded from measuring a change in the rotor angle in a positive direction that the test signal was also oriented in a positive direction along the q-axis.

[0043] The control of the electric machine 6 by the controller 5 is subsequently carried out taking into account the determined orientation of the dq coordinate system. The controller 5 has thus been calibrated.

[0044] Furthermore, it can be provided to apply a plurality of electrical test signals to the electrical machine 6, which differ by the predetermined directions in the dq coordinate system.

[0045] Thus, a first test signal with a first predetermined direction in the dq coordinate system can first be applied to the electric machine 6. If the resulting change in the rotor angle of the rotor of the electric machine 6 is not measurable or has only a small value that falls below a predetermined threshold, a second test signal with a second direction deviating from the first predetermined direction can be applied to the electric machine 6. Preferably, the second direction can be opposite to the first direction. Furthermore, provision can be made to apply further test signals with further directions in the dq coordinate system in order to improve the accuracy of the measurements.

[0046] Finally, it may also be provided to successively increase a maximum voltage or a maximum current of the electrical test signal until a change in the rotor angle of the rotor of the electrical machine can be measured, ie the friction of the rotor and gear is overcome.

Claims

1. Method for calibrating the control of an electric machine (6), having the following steps: applying (S2) at least one electrical test signal with a predefined direction along the q-axis in a d-q coordinate system to the electric machine (6); measuring (S3) a change in a rotor angle of a rotor of the electric machine (6) depending on the applied at least one electrical test signal; and calibrating (S4) the control of the electric machine (6), wherein the control takes place using the d-q coordinate system, and wherein an orientation of the d-q coordinate system is determined on the basis of the measured change in the rotor angle of the rotor of the electric machine (6), characterized in that the direction of rotation of the rotor of the electric machine is determined on the basis of the measured change in the rotor angle; the plausibility of a hypothesis regarding the orientation of the d-q coordinate system is verified by means of the calibration of the control of the electric machine; the application of the at least one electrical test signal with a predefined direction along the q-axis in a d-q coordinate system to the electric machine (6) includes the application of a first test signal with a first predefined direction in the d-q coordinate system to the electric machine (6); and, if the application of the first test signal does not cause a change in the rotor angle of the electric machine rotor (6), a second test signal with a second direction that is different to the first predefined direction in the d-q coordinate system is applied to the electric machine (6), where the second direction is opposite to the first direction in the d-q coordinate system.

2. Method according to Claim 1, wherein an offset angle of the rotor of the electric machine (6) is determined (S1) before the electrical test signal is applied.

3. Method according to Claim 2, wherein the offset angle of the rotor of the electric machine (6) is determined on the basis of a measurement of an anisotropy of the electric machine (6).

4. Method according to any one of the preceding claims, wherein a plurality of electrical test signals are applied to the electric machine (6), wherein the predefined directions of the test signals in the d-q coordinate system differ from one another.

5. Method according to any one of the preceding claims, wherein the electrical test signal is a voltage signal or a current signal.

6. Method according to Claim 7, wherein a maximum voltage or a maximum current strength of the electrical test signal is increased successively until a change in the rotor angle of the rotor of the electric machine (6) can be measured.

7. Method according to any one of the preceding claims, wherein the electric machine (6) is at a standstill when the electrical test signal is applied.

8. Apparatus (1) for calibrating the control of an electric machine (6), having: a signal generator (2) designed to apply at least one electrical test signal with a predefined direction along the q-axis in a d-q coordinate system to the electric machine (6); a measuring device (3) designed to measure a change in a rotor angle of the rotor of the electric machine (6) on the basis of the applied at least one electrical test signal; and a calibration device (4) designed to calibrate the control of the electric machine (6), wherein the control is carried out using the d-q coordinate system, and wherein the calibration device (4) is designed to determine an orientation of the d-q coordinate system on the basis of the measured change in the rotor angle of the electric machine rotor (6), characterized in that the calibration device is designed to determine the direction of rotation of the rotor of the electric machine on the basis of the measured change in the rotor angle; to verify the plausibility of a hypothesis regarding the orientation of the d-q coordinate system by means of the calibration of the control of the electric machine; the application of the at least one electrical test signal with a predefined direction along the q-axis in a d-q coordinate system to the electric machine (6) includes the application of a first test signal with a first predefined direction in the d-q coordinate system to the electric machine (6); and, if the application of the first test signal does not cause a change in the rotor angle of the electric machine rotor (6), a second test signal with a second direction that is different to the first predefined direction in the d-q coordinate system is applied to the electric machine (6), where the second direction is opposite to the first direction in the d-q coordinate system.