阅读说明：本技术 用于确定动力传动系的特征值的方法、控制装置及机动车 (Method for determining a characteristic value of a drive train, control device and motor vehicle ) 是由 M·辛特伯格 B·利布哈特 C·特布拉克 C·恩迪施 于 2020-02-19 设计创作，主要内容包括：本发明涉及一种用于确定动力传动系(11)的至少一个特征值(25)的方法,该动力传动系在安装的状态下处于借助于其部分或完全电动驱动机动车(10)中并具有含电构件(15)的电部分(12)和含机械构件(18)的机械部分(13),电部分(15)和机械部分(18)通过电机(14)耦联。本发明规定,在至少一个测量过程中,通过操控所述机械部分(13)的机械构件(18)中的至少一个机械构件和/或借助于至少一个车辆外的机械构件设定和保持用于所述电机(14)的预定的机械的边界条件(27),所述机动车(10)的控制装置(22)通过操控电部分(12)的电构件(15)中的至少一个电构件在电部分(12)中产生电的激励信号(28),借助于机动车(10)的测量装置(M)检测至少一个响应信号(29)。(The invention relates to a method for determining at least one characteristic value (25) of a drive train (11) which, in the installed state, is in a motor vehicle (10) driven by means of said drive train in a partially or fully electric manner and has an electric part (12) comprising an electric component (15) and a mechanical part (13) comprising a mechanical component (18), the electric part (15) and the mechanical part (18) being coupled by means of an electric machine (14). According to the invention, during at least one measurement process, a predetermined mechanical boundary condition (27) for the electric machine (14) is set and maintained by actuating at least one of the mechanical components (18) of the mechanical part (13) and/or by means of at least one mechanical component outside the vehicle, the control device (22) of the motor vehicle (10) generates an electrical excitation signal (28) in the electrical part (12) by actuating at least one of the electrical components (15) of the electrical part (12), and at least one response signal (29) is detected by means of the measurement device (M) of the motor vehicle (10).)

1. A method for determining at least one characteristic value (25) of a drive train (11), which is in a motor vehicle (10) in an installed state and which can be partially or completely driven electrically by means of the drive train (11), having an electrical part (12) with an electrical component (15) and a mechanical part (13) with a mechanical component (18), wherein the electrical part (15) and the mechanical part (18) are coupled by means of an electric machine (14),

it is characterized in that the preparation method is characterized in that,

setting and maintaining predetermined mechanical boundary conditions (27) for the electric machine (14) during at least one measurement by actuating at least one of the mechanical components (18) of the mechanical part (13) and/or by means of at least one mechanical component outside the vehicle, the control device (22) of the motor vehicle (10) generates an electrical activation signal (28) in the electrical part (12) by actuating at least one of the electrical components (15) of the electrical part (12), and at least one response signal (29) is detected by means of a measuring device (M) of the motor vehicle (10), the at least one response signal is generated in the drive train (11) by an excitation signal (28), and the control device (22) determines at least one characteristic value (25) on the basis of the at least one response signal (29) by means of a predetermined calculation rule (30).

2. Method according to claim 1, characterized in that during the measurement a brake system (20) of the motor vehicle (10) as a mechanical component (18) is actuated for braking at least one wheel (21) of the motor vehicle (10), whereby the rotation of the electric machine (14) is prevented as a mechanical boundary condition (27), a drive voltage (U) for the electric machine (14) is generated as an excitation signal (28), and a machine current of the electric machine (14) is measured as a response signal (29), the calculation rule (30) comprising a machine equation for a short-circuit test.

3. Method according to claim 2, characterized in that the armature resistance and/or the rotor resistance and/or the leakage inductance and/or the main inductance (14) and/or one or more further parameters of the electrical machine are determined as corresponding characteristic values (25).

4. A method according to any one of the foregoing claims, characterised in that, during the measuring, a clutch (19) of the drive train (11) as a mechanical component (18) is disengaged in order to separate the electric machine (14) from the rest of the mechanical part (13), whereby the electric machine (14) is operated without mechanical load as a mechanical boundary condition (27), and a drive voltage (U) for the electric machine (14) is generated as an excitation signal (28).

5. Method according to claim 4, characterized in that the motor current of the motor (14) is measured as the response signal (28), and in that the calculation rule (30) comprises a motor equation for a no-load test, and in that the motor constant and/or the armature inductance and/or the stator intrinsic inductance and/or one or more further parameters of the motor (14) are determined as the corresponding characteristic values (25).

6. A method according to claim 4 or 5, characterized in that the rotational speed of the electric machine (14) is measured during the start-up of the rotor (32) of the electric machine (14) as the response signal (29), and that the calculation rule (30) comprises calculating a mechanical parameter of the electric machine (14) as the characteristic value (25).

7. Method according to any one of the preceding claims, characterized in that the boundary condition is generated completely or partly by means of at least one mechanical component outside the vehicle.

8. Method according to any of the preceding claims, characterized in that during at least one inspection process the mechanical part is driven by means of at least one mechanical component outside the vehicle in order to compensate for the frictional resistance and/or the moment of inertia of the mechanical part and/or a model for evaluating the measurement signal is run, which takes into account the elasticity or bending moment of the mechanical part (13) and/or the moment of inertia of the axle and/or wheel of said mechanical part (13).

9. The method according to one of the preceding claims, characterized in that the excitation signal (28) is generated by means of power electronics (17) as an electrical component (15) of the electrical section (12), or wherein the excitation signal (28) is generated by means of switchable battery cells (34) of a battery system (16) of the motor vehicle (10), wherein the time profile of the excitation signal (28) is adjusted by successively switching on and off individual battery cells or subgroups of battery cells (34) in an electrical circuit (39) of the electrical section (12).

10. Method according to any of the preceding claims, characterized in that the mechanical boundary conditions (17) are set during a parking phase (26) of the motor vehicle (10).

11. A control device (22) for controlling a drive train (11) of a motor vehicle (10), wherein the control device (22) has a processor device (23) which is provided to carry out a method according to one of the preceding claims.

12. A motor vehicle (10) having a drive train (11) with an electrical part (12) having an electrical component (15) and a mechanical part (13) having a mechanical component (18), wherein the electrical part (12) and the mechanical part (13) are coupled by means of an electrical machine (14), characterized in that the motor vehicle (10) has a control device (22) according to claim 11.

Technical Field

The invention relates to a method for determining a characteristic value of a drive train already in a mounted state in a motor vehicle. The characteristic value relates to at least one component in an electrical or mechanical part of the drive train. The invention also relates to a control device, by means of which the method can be carried out in a motor vehicle. Finally, the invention also includes a motor vehicle having a drive train and a control device according to the invention.

Background

The drive train of an electric vehicle typically comprises an electric part with a battery system and power electronics for controlling the electric machine. In this case, the electric machine generates a mechanical torque which drives the coupled mechanical part up to the wheels of the motor vehicle.

The control of the electric machine is carried out by the targeted actuation of the power electronics by means of a control system. For this regulation, it is necessary to know the parameters of the motor, the battery and the power electronics and preferably also the mechanical part. Typically, these parameters are determined during production. However, the parameters of each component may change over time. Thus, the parameters of the component may change on the one hand as a result of aging and also as a result of the current state. On the other hand, the presence of fault defects (e.g. contact or insulation failure) may affect the parameters. Currently, many parameters cannot or cannot be determined in operation.

One common method of determining motor parameters is a short circuit test/short circuit test and a no load test/no load test. In electrical engineering, they are reliable methods for determining copper and iron losses in transformers and electrical machines. Both methods are performed to determine the characteristics of the machine after the production process or when there is a suspicion of faulty characteristics. Currently, it is not possible to carry out a diagnosis in the state of being installed in a motor vehicle, i.e. on board or online in an electric vehicle. Therefore, the motor diagnosis capability by the short circuit test and the no-load test is not currently set.

It is known from US 2017/0102425 a1 to determine a characteristic value of an electric machine in an electric vehicle in the installed state by generating a test current in an electric coil of the electric machine by means of power electronics. Here, in order to prevent the rotor of the motor from starting to rotate, it is necessary to perform a troublesome vector control. Therefore, the number of characteristic values that can be determined is limited.

DE 112012001244T 5 discloses determining the state of a mechanical part of a drive train in the installed state by means of an electric machine, which drives the mechanical part. For this purpose, the torque curve of the electric machine is measured and the harmonics are checked. The test method requires the vehicle to be driven. However, this therefore limits the choice of excitation signals for checking the mechanical parts of the drive train, due to the necessary driving safety.

It is known from DE 102011006516 a1 to electrically short the windings of an electric machine in order to determine characteristic values of the electric machine in a hybrid vehicle. This is referred to as short-circuit operation in the publication, but differs from per se known short-circuit tests. The approach described in this publication requires the provision of additional interconnectivity of the electrical windings, which increases circuit complexity.

Disclosure of Invention

The object of the invention is to determine at least one characteristic value for a drive train already installed in a motor vehicle afterwards.

This object is achieved by the subject matter of the independent claims. Advantageous embodiments of the invention are indicated by the dependent claims, the following description and the drawings.

The present invention provides a method for determining at least one characteristic value of a powertrain. The method is based on the fact that the drive train is already in the installed state in the motor vehicle. The motor vehicle is electrically drivable, i.e. the drive train has an electrical part with an electrical component and a mechanical part with a mechanical component. The electrical part and the mechanical part are coupled by an electrical machine. The electric machine is supplied with power or driven by means of the electric part, and the torque generated by the electric machine is transmitted to at least one wheel of the motor vehicle by means of the mechanical part. The electric machine is thus a connecting element between the electrical part and the mechanical part and may be an integral part of both.

In this respect, the method according to the invention now provides for at least one measurement process or measurement test or measurement to be carried out. During at least one measurement, a predetermined mechanical boundary condition for the electric machine is set by actuating at least one of the mechanical components of the mechanical part and/or by actuating at least one component outside the vehicle.

Thus, boundary conditions are set explicitly for the planned measurement process. The boundary conditions are not caused, for example, by the driver or by the autopilot during driving operation. During the measuring process, the mechanical boundary conditions, i.e. the constraining boundary conditions, are maintained by means of at least one mechanical component and/or by means of at least one component outside the vehicle. Furthermore, the control device generates an electrical excitation signal in the electrical part by actuating at least one of the electrical components of the electrical part of the drive train. The electric machine is thus excited by the excitation signal from the electrical part, but is limited or fixed in terms of the mechanical part by mechanical boundary conditions. Furthermore, the control device detects at least one response signal by means of a measuring device of the motor vehicle, which response signal can be present in the drive train, i.e. in the electrical and/or mechanical part (including the electric machine), as a result of the excitation signal. Furthermore, the control device determines at least one characteristic value from the at least one response signal by means of a predetermined calculation rule. The response signal is thus obtained by fixing the electric machine with reference to the mechanical boundary conditions and subsequently exciting the electric machine with the aid of the excitation signal, the response signal characterizing at least one characteristic value associated with the at least one characteristic value. Then, at least one characteristic value can be determined from the response signal (given the known excitation signal and the known boundary conditions of the machine) by means of a predetermined calculation rule. For this purpose, the calculation rules can generally be provided with models and/or mathematical methods and/or at least one formula and/or at least one synthetic characteristic curve.

The invention thus provides the electric machine with mechanical boundary conditions by means of the adjustability achieved by the mechanical part, for example by actuating a mechanical component of the mechanical part itself of the drive train, so that a response signal can be brought about or induced in a targeted manner by means of an excitation signal from the electrical part and in the presence of the mechanical boundary conditions, on the basis of which at least one characteristic value can be determined. The advantage is thereby obtained that the determination of the at least one characteristic value can be carried out even in the installed state of the drive train in the electrically drivable motor vehicle. Thus, at least one characteristic value can be detected and checked, for example, without going to the workplace, or used to calibrate the regulation.

The invention also includes embodiments that yield additional advantages.

In principle, any component that can withstand the torque of the electric machine can be used in order to fix the rotor of the electric machine. They may be located in the vehicle itself (e.g., in the electric machine) and/or outside the vehicle. The torque can be prevented in a non-positive manner (for example by means of a clamping connection) and/or in a positive manner (for example by means of a snap-fit) and/or in a material-fit manner (for example by welding).

In one embodiment, a brake system of the motor vehicle as a mechanical component is actuated during the measurement process in order to brake at least one wheel of the motor vehicle. As a result, the rotation of the electric machine, i.e. the rotor of the electric machine, is prevented as a mechanical boundary condition. However, a drive voltage for the motor is generated as the excitation signal. The electric machine is therefore supplied with drive voltage in the electrical part by means of the excitation signal, but cannot rotate due to the clamped brake system. The motor current of the motor is measured as a response signal, and the calculation rule includes a motor equation for a short-circuit test. The motor equations for the short-circuit test are known per se from the prior art. The short-circuit test described above is therefore simulated by means of the brake system without the electric machine having to be removed from the motor vehicle for this purpose.

In particular, it is provided that the armature resistance and/or the rotor resistance and/or the leakage inductance and/or the main inductance of the electric machine are determined as corresponding characteristic values. Thus, at least one electrical characteristic value of the electric machine is determined, which can be used to calibrate a control system for controlling the electric machine. The determination of which characteristic values may be determined according to the motor type of the motor.

In one embodiment, during the measurement, the clutch of the motor vehicle as the mechanical component is disengaged in order to disconnect the electric machine from the rest of the mechanical part. As a mechanical boundary condition, the electric machine is therefore operated without mechanical load. In other words, the electric machine is in idle operation, since the electric machine cannot output the mechanical drive torque to the mechanical part. The drive voltage for the electric machine is generated as an excitation signal. However, the electric machine is still driven, i.e. accelerated or started, by means of the excitation signal in the form of a drive voltage. In this case, the electric machine can now be measured electrically and/or mechanically by means of the unloaded operation.

For this purpose, in one embodiment, the motor current of the motor is measured as a response signal, and the calculation rule includes the motor equation for the no-load test. The test stand is otherwise required for the no-load test. The motor constant of the electric machine and/or the armature inductance and/or the stator intrinsic inductance of the electric machine are determined as corresponding characteristic values, wherein the determined characteristic values can depend on the type of electric machine. In this case, the no-load test can therefore be carried out without the motor having to be removed from the motor vehicle for this purpose.

Additionally or alternatively, according to an embodiment, the rotational speed of the electric machine during the start-up of the rotor of the electric machine is measured as a response signal. Thus, the rotor accelerates at this rotational speed. The calculation rule includes a calculation of a mechanical parameter of the electric machine. By operating the electric machine without load, the mechanical properties are determined solely by the rotor itself, and the mechanical properties can thus be determined without distortion of the remaining mechanical components of the mechanical part. The rotational speed can be determined in a manner known per se by means of a rotational speed sensor or a so-called rotational speed transmitter. By means of the starting properties, for example, the coefficient of friction and/or the moment of inertia (rotational inertia) of the electric machine can be determined.

It has been explained above how a control device of a motor vehicle sets a boundary condition by actuating at least one of the mechanical components of the mechanical part of the motor vehicle itself. In one embodiment, it is provided that, in addition or alternatively, the boundary condition is generated by means of at least one mechanical component outside the vehicle or outside the vehicle (for mechanical locking or (reduced) no-load testing), rather than, for example, by the brake of the vehicle itself. For example, a brake that can act on at least one tire of a motor vehicle can be used in the test stand. Instead of the clutch, for example, an "idling" or freewheeling operation of the rotor of the electric machine can be carried out on the test stand by at least one wheel of the motor vehicle slipping (completely slipping) or even being driven by means of the test stand, so that the frictional resistance and/or the moment of inertia are compensated by the driving of the test stand and the rotor is thus operated without resistance. In order to compensate for the still existing influence of the mechanical components of the intermediate connection, a model for evaluating the measurement signals can additionally or alternatively be provided in order to calculate the elasticity or bending moment of the mechanical part, for example in the case of a lock, and/or to calculate or take into account the moment of inertia of the axle or of the wheel, for example in the case of idle operation. Thus, according to one embodiment, the mechanical part is driven during at least one inspection process by means of at least one mechanical component outside the vehicle in order to compensate for the frictional resistance and/or the moment of inertia of the mechanical part and/or to run a digital model for evaluating the measurement signals, which takes into account the elasticity or bending moment of the mechanical part and/or the moment of inertia of the axle and/or the wheel. The model may be implemented, for example, based on a computer program.

The described measurement procedure is not the only possible implementation. For example, it can also be provided that, as in the measuring procedure described above, the brake system is activated and in this case a predetermined torque is set by means of the electric machine and it is checked whether the torque generated by the electric machine is greater than a braking torque at a predetermined and set braking pressure. This can be detected by the wheel rotation of the motor vehicle, which can be measured, for example, by means of the rotational speed. The braking characteristic curve of the motor vehicle can thus be determined for different settings of the brake pressure and the corresponding setting of the torque of the electric machine.

An electrical excitation signal is required for each measurement process. In one embodiment, the excitation signal is generated by means of power electronics, which are electrical components of the electrical section. By means of the power electronics, a variable excitation signal having a time profile can be generated on the basis of the constant direct voltage of the battery system of the motor vehicle. Alternatively, the excitation signal can be generated by means of a switchable cell of the battery system itself. In a battery system, the battery voltage can be generated more precisely by connecting a plurality of switchable battery cells in series, wherein in each switchable battery cell its cell connection can be connected on the one hand via a circuit branch containing the electricity of the actual electrochemical cell and also via the following circuit branches: the circuit branches bridge the electrochemical cells and connect the cell junctions directly to one another by short circuits. The circuit branch with the electrochemical cell is referred to herein as a cell branch, and the circuit branch for bridging the electrochemical cell is referred to as a bypass branch. In each of the circuit branches, an electrical switching element can be provided, which can be realized, for example, on the basis of a transistor, in particular a field effect transistor. The cell connections are thus interconnected with one another by the cell branches or by-pass branches depending on the switching state of the switching element. The electrochemical cells of the switchable battery cells can therefore be switched into the circuit of the electrical part by switching on the cell branch, and the battery voltage is therefore increased by the cell voltage. Conversely, if not the cell branch, but a bypass branch, is connected between the cell connections, the battery cell is disconnected from the circuit (deactivated battery cell). The time profile of the activation signal can then be set by means of the battery system itself by switching on and off the individual cells or subgroups of the cells in each case one after the other. The excitation signal can thus be generated directly in the battery system and used to check at least one characteristic value of the entire electrical part as well as of the mechanical part from the battery system. In particular, it is therefore also provided to determine a characteristic value of the power electronics and/or of an electrical component which is arranged upstream of the power electronics from the viewpoint of the battery system.

In one embodiment, the mechanical boundary conditions are set during a parking phase of the motor vehicle. The driving behavior of the motor vehicle is therefore not influenced by the setting of the mechanical boundary conditions. The corresponding measuring process is therefore not noticeable by the driver. For example, if no person is present in the motor vehicle, the measurement process can also be carried out during a parking phase of the motor vehicle, for example.

In order to carry out the method according to the invention in an electrically drivable motor vehicle, the invention also provides a control device for controlling a drive train of the motor vehicle. The control device has processor means arranged to perform an embodiment of the method according to the invention. For this purpose, the Processor device may have at least one microprocessor and/or at least one microcontroller and/or at least one FPGA (Field Programmable Gate Array) and/or at least one DSP (Digital Signal Processor), or may also be implemented by means of analog circuits. The processor means may have program code/Software (Software) with program instructions arranged to perform an embodiment of the method according to the invention when carried out by the processor means. The program code may be stored in a data memory of the processor device. The control device can be designed, for example, as a controller or as a combination of several controllers.

Finally, the invention also includes a motor vehicle which can be driven electrically and for this purpose has a drive train with an electrical part having an electrical component and a mechanical part having a mechanical component, wherein the electrical part and the mechanical part are coupled by an electric machine. In the electrical sector, battery systems and/or power electronics can be provided as corresponding components, for example, in an illustrative manner. The mechanical part may have, for example, the described clutches and/or drive shafts and/or differentials and/or brake systems as corresponding components. The motor vehicle according to the invention is characterized in that it has an embodiment of the control device according to the invention.

The motor vehicle according to the invention is preferably a motor vehicle, in particular a passenger or commercial vehicle, or a passenger car or a motorcycle. The motor vehicle can be designed as a hybrid vehicle (partially electric drive) or as an electric vehicle (fully electric drive).

The invention also comprises a combination of features of the described embodiments.

Drawings

The following describes embodiments of the present invention. Wherein:

fig. 1 shows a schematic representation of an embodiment of a motor vehicle according to the invention;

fig. 2 shows a flow chart of an embodiment of the method according to the invention.

Detailed Description

The examples set forth below are preferred embodiments of the present invention. In the examples, the illustrated components of the embodiments are respectively individual features of the invention which can be considered separately from one another, which also improve the invention independently of one another. Thus, the disclosure also includes combinations of features of the embodiments other than those shown. The embodiments described can furthermore be supplemented by further features of the invention already described.

In the drawings, like reference numbers correspondingly indicate functionally similar elements.

Fig. 1 shows a motor vehicle 10, which can be a motor vehicle, in particular a passenger or commercial vehicle, or a passenger car or a motorcycle, in the illustrated manner. The motor vehicle 10 may be partially or fully electrically driven and may have a drive train 11 for this purpose, which may be provided with an electrical part 12 and a mechanical part 13. The electrical part 12 may be coupled with the mechanical part 13 by means of an electrical machine 14, which is an electromechanical converter and may thus belong to both the electrical part 12 and the mechanical part 13.

In the electrical part 12, in addition to the electric machine 14, further electrical components 15 can be provided, wherein in fig. 1 a battery system 16 as electrical component 15 and power electronics 17 as further electrical component 15 are shown.

In the mechanical part 13, a mechanical clutch 19, a brake system 20, and at least one wheel 21, which is a mechanical load, may be provided as other mechanical components 18 in addition to the motor 14.

For controlling the electrical member 15 of the electrical part 12 and the mechanical member 18 of the mechanical part 13, a control device 22 may be provided, which may generate a control signal 23 for controlling the powertrain 11. For this purpose, the control device 22 can have a processor device 24.

In motor vehicle 10, it can be provided that at least one characteristic value 25 in motor vehicle 10, which specifies drive train 11 or characterizes drive train 11, is determined after drive train 11 has been installed in motor vehicle 10. Thus, at least one characteristic value 25 can also be determined during operation of the motor vehicle 10, for example in a parking phase 26 (for example during a stop).

The drive train 11 may have a measuring device M, by means of which at least one electrical variable and/or at least one mechanical variable in the drive train 11 may be detected or measured.

For this purpose, the method described below with reference to fig. 1 and 2 can be carried out by the control device 22.

The method can provide at least one measurement process, in which a respective predetermined measurement can be set for at least one characteristic value 25. In step S10, control device 22 may set a predetermined mechanical boundary condition 27 for electric machine 14 by actuating at least one of mechanical components 18 of mechanical part 13 and maintain or execute or maintain the boundary condition. In step S11, the control device can generate an electrical activation signal 28 in the electrical part 12 by operating at least one of the electrical components 15 of the electrical part 12.

In step S12, the control device can detect at least one response signal 29 by means of the measuring device M, which occurs in the drive train 11 as a result of the excitation signal 28. The corresponding response signal may be a measurement signal of the measurement device or a signal derived or determined from a measurement signal of the measurement device. In step S13, the control device can determine at least one characteristic value 25 by means of the at least one response signal 29 using the predetermined calculation rule 30.

The mechanical boundary condition 27 can be achieved, for example, by actuating the brake system 20, as a result of which the drive shaft 31 of the mechanical part 13 can be locked, which also prevents the rotor 32 of the electric machine 14 from rotating, even if it generates a mechanical torque 33 in the drive shaft 31. The drive voltage U can be generated as an excitation signal, for example, by the battery system 16. The drive voltage U can be generated by the battery system 16, for example, on the basis of switchable battery cells 34, which can be grouped in parallel in the battery system 16, and the groups can be connected in series for generating the voltage. Conversely, it can also be provided that a plurality of battery cells 34 are connected in series in groups and then the groups are connected together in parallel. This may be done for all cells 34 or for a portion of the cells.

Each cell 34 can be designed to be switchable in that the cell connections 35 are interconnected by a cell branch 36 containing an electrochemical cell 37, and can be interconnected by a bypass branch 38 bypassing or bridging the electrochemical cell 37. Switching elements SA, SB can be provided in the individual branches 36 and bypass branches 38, respectively, by means of which the respective circuit branch (individual branch 36 and bypass branch 38) can be switched into the circuit 39 of the electrical part 12. The battery cells 34 can be connected to a battery connection 40 of the battery system 16 by means of the protection switches S +, S ", so that the battery voltage U can be supplied to the power electronics 17.

The power electronics 17 can have, for example, a converter 41, which can generate an alternating current from the direct current of the battery system 16 in an electrical phase line 42 of the electric machine 14. For this purpose, the converter 41 may have, in a manner known per se, switching elements T1, T2, T3, T4, T5, T6, which may be provided on the basis of a respective at least one transistor. The power electronics 17 may also have an intermediate circuit capacitor 43 in a manner known per se. The alternating current generated in the phase line 42 on the basis of the battery voltage U and the converter 41 can generate a rotating magnetic field in an electric coil 44 of the electric machine 14 in a manner known per se, by means of which the rotor 32 is acted upon by the torque 33, by means of which the rotor 32 can output the torque to the drive shaft 31. However, here it is not limited to only rotating field machines with 3 phases, but there can generally be m phases, i.e. 2 phases or more than 3 phases (m is equal to or greater than 1). However, it is also possible here to use a similar or known motor of any type (e.g. dc motor, reluctance motor) in general, without being limited to only rotating field motors.

If the drive shaft 31 is locked in the described manner by means of the brake system 20 during the measurement process, a magnetic reaction of the coil 44 acting on the electricity, which can be calculated on the basis of the motor equation, is obtained, which influences the motor current of the electric motor 14 in the phase line 42 and can therefore be measured by means of the measuring device M. The motor equation itself is known in the prior art relating to short circuit tests.

In addition or as an alternative to the measuring process, the control device 22 can disengage the rotor 32 from the rest of the machine part 13 by means of the clutch 19, so that the rotor 32 and therefore the electric machine 14 are operated without load with respect to the mechanical load. Then, if the drive voltage U is provided as an excitation signal in the electric machine 14, for example by the power electronics 17, the torque 33 is completely converted into an acceleration of the rotor 32. At this point, the calculation rule 30 may calculate at least one characteristic value 25 of the electric machine 14 on the basis of the electric machine equation for the electric machine 14 for the no-load test. The motor equation is known per se from the prior art relating to no-load tests.

Thus, the brake or brake system 20 of the wheel 21 and the mechanical clutch 19 between the electric machine 14 and the mechanical part 13 can be used to perform a short circuit test and an idle test, respectively, for the electric machine 14. Furthermore, the excitation from the battery system 16 can be fed into the circuit 39 of the electrical part 12 and thus the diagnosis of the drive member is carried out in the mounted state. The components can therefore be checked by the existing hardware during the parking phase, when the entire production process is ended and during maintenance, and the fault diagnosis can be carried out in the installed state.

The technical embodiments described are only illustrated here by way of example with two specific examples. The basis of which is the schematic diagram of fig. 1. In addition to the already described electrical components 15, the respective vehicle 10 also has mechanical components 18, in which the electrical machine 14 (motor) serves as a connecting element for converting electrical energy into rotational energy.

The electric machine can be adjusted in such a way that it provides the required rotational speed with a defined torque. If the clutch 19 is present, the electric machine can be mechanically disengaged from the mechanical parts of the power train (up to the tires). The brake 20 may fix the drive shaft 31. The vehicle has a measuring device M with various sensors in order to detect, in particular, electrical and mechanical variables of the drive. For the sake of clarity, they are not shown in the schematic.

In the short-circuit test, the parameters of the electric machine can in principle be determined in such a way that the rotor is fixed. The rotational speed of the electric motor is brought to zero by means of a brake, for example a parking brake during parking. In the classical method, the connection of an electric machine is energized, the excitation depending on the respective machine type. The parameters of the equivalent circuit diagram can be calculated from the sensor values, for example the current and the voltage, by means of the motor equation. For a dc motor the parameters may be the armature impedance and for an asynchronous motor the parameters may be the rotor impedance and the leakage and main inductances. It should be noted that various excitation signals can be generated by introducing switches at each cell or via power electronics. The voltage at the motor can be set approximately variably, which provides more possibilities for determining the parameters.

The no-load test can be performed very similar to the short circuit test. In this case, the electric machine is disengaged by means of the clutch, so that no load torque is present anymore. If the motor is operated again, power is supplied by the battery. In the case of no load, the motor equation is simplified in such a way that, for a direct-current motor, the motor constant and the armature inductance can be calculated from the current value and the voltage value. For asynchronous machines, the stator intrinsic inductance can be estimated. From the starting behavior, the mechanical parameters (friction coefficient) can likewise be determined.

In general, the examples show how excitation of electrical components in a drive train and estimation of electrical machine parameters can be achieved in a motor vehicle by the invention.