Test device and method for operating a test device
The test setup addresses mechanical stress detection in electric motors by using a connected second motor to analyze position and current signals, allowing for stress correction and preventing equipment damage.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- DSPACE SE & CO KG
- Filing Date
- 2026-01-13
- Publication Date
- 2026-07-23
AI Technical Summary
Existing test setups for electric motors do not effectively detect mechanical stress without additional hardware, which can lead to damage during high-force and high-speed tests due to improper mechanical coupling.
A test setup that includes a second electric motor mechanically connected to the first electric motor, detecting position and current signals to determine mechanical stress without additional hardware, using a detection unit to analyze these signals and provide feedback for correcting the coupling.
Enables detection and correction of mechanical stress in the coupling, preventing damage to the test equipment by ensuring a proper mechanical connection, thus ensuring valid test conditions without additional costs.
Smart Images
Figure EP2026050662_23072026_PF_FP_ABST
Abstract
Description
[0001] 24-035 1
[0002] TESTING DEVICE AND METHOD FOR OPERATION OF A TESTING DEVICE
[0003] Technical field
[0004] The application concerns a test facility for a first electric motor and a method for operating a test facility.
[0005] background
[0006] The applicant is already known to manufacture testing equipment for electric motors. Such testing equipment is used, for example, in steering or brake test stands.
[0007] In DE202011050806U1 a steering test stand is described which is set up to test a steering control unit.
[0008] Overview
[0009] A test setup for a first electric motor is provided for testing the first electric motor. The test setup includes a second electric motor, which can be mechanically connected to the test setup. The test setup is configured to drive the second electric motor, detect a position signal from the second electric motor, detect a current signal of a torque-generating current from the second electric motor, and determine any stress in the mechanical connection as a function of the current signal and the position signal.
[0010] In a method for operating a test setup for a first electric motor, the test setup includes a second electric motor. The first electric motor is mechanically connected to the second electric motor. The method includes:
[0011] A) Driving the second electric motor,
[0012] B) Detecting a position signal from the second electric motor,
[0013] C) Detection of a current signal of a torque-generating current of the second electric motor, 24-035 2
[0014] D) Determining the tension of the mechanical connection between the first and second electric motors as a function of the current signal and the position signal.
[0015] The first electric motor to be tested could be, for example, a motor that drives an actuator, such as one in a vehicle. This first electric motor could, for instance, assist with braking or steering. The test bench can then, specifically for testing this motor, emulate the environment of the vehicle's brakes / steering system with the corresponding counterforces.
[0016] The test setup, or the corresponding operating procedure for the test setup, makes it possible to detect mechanical stress in the test setup with the first electric motor under test, without the need for additional mechanical or optical measuring instruments. In particular, it is possible to determine the stress without having to modify the test setup with the first electric motor. This allows the user to eliminate the stress and thus prevent damage to the test setup that could be caused by such stress.
[0017] By detecting the current signal of the second electric motor, counter-torques are detected during the rotation of the first electric motor, which is mechanically coupled to the second and not powered. These counter-torques result from a preload, i.e., mechanical eccentricity, between the first electric motor and the test setup. Such an eccentric mechanical coupling leads to additional, imposed, and periodic mechanical torques, the underlying energy of which originates from the elastic deformation of the intervening mechanical elements of the coupling.
[0018] For using the test setup to test the first electric motor, it is intended that the first electric motor be mechanically coupled to the test setup. By determining the stress in the mechanical coupling, errors in the setup, e.g., due to user error, can be detected. In particular, this enables the user to create valid test conditions when using the test setup by ensuring a suitable mechanical coupling. 24-035 3
[0019] This solution does not require any additional costs for hardware, especially measuring technology, and before each test procedure of potentially different first electric motors, it can be checked whether the mechanical connection is sufficiently centered.
[0020] The test device includes a sensor for the position signal of the second electric motor and a sensor for the current signal of the torque-generating current of the second electric motor. Furthermore, the test device includes a detection unit for determining the stress in the mechanical connection as a function of the current signal and the position signal. This detection unit can, for example, be designed as a computing unit or processor with a corresponding computing module and memory, and can be located, for example, in a drive unit of the second electric motor. The detection unit can then, for example, receive the current signal and the position signal via interfaces and evaluate them accordingly.
[0021] The first electric motor, the so-called Device Under (DUT), is, for example, an electric motor for driving a steering system in a vehicle. This motor is driven by the second electric motor. The test setup includes the drive unit that drives and controls the second electric motor. This drive unit can, for example, include a power converter and the processing unit or processor.
[0022] Preferably, the second electric motor is controlled via a voltage signal to adjust the phase voltages. Various electric motor technologies can be used for the second electric motor. For example, a permanent magnet or a separately excited electric motor can be used.
[0023] To carry out the test of the first electric motor, it is mechanically connected to the test equipment, more precisely to the second electric motor.
[0024] This connection can be made, in particular, by the user of the test equipment for the purpose of testing the first electric motor. For example, an incorrect connection of the first electric motor to the test equipment can lead to mechanical stress. In the course of 24-035 4
[0025] Tests of the first electric motor can involve high forces and reach high speeds. Under these conditions, stress can damage the test equipment. This should be avoided.
[0026] The test setup itself can also exhibit such stresses in its structure between the first and second electric motors. These can be detected by the test setup or the procedure. The user can then correct or release these stresses. This prevents operation in which damage could occur due to the stress. The position signal of the second electric motor can be generated, for example, by a position encoder. It may be necessary to define a zero position. This position encoder converts the rotationally detected position of the second electric motor into an electrical position signal. This signal can then be received, for example, by the drive unit or another control unit of the test setup for evaluation.
[0027] Furthermore, the current signal of the torque-generating current of the second electric motor is recorded by the test device, for example via the drive unit.
[0028] The test equipment's detection unit, for example, includes a computer to determine the stress in the mechanical coupling as a function of the current signal and the position signal. These two signals are analyzed, processed, and compared. The detection unit is located, for example, in the test equipment's drive unit. In particular, the stress can be displayed on an output unit, such as a display, so that the user can see whether stress is present.
[0029] The same applies to the procedure for operating the testing facility.
[0030] In one embodiment, the test device is configured to determine the position and / or direction of the strain. The position of the strain can be determined by processing the position signal and the current signal. Alternatively or additionally, the direction of the strain can be determined, i.e., a force vector corresponding to the strain. Optionally, the location and direction of the strain can also be output. It is also possible to graphically display the location of the strain and / or the force vector of the strain on the output unit. 24-035 5
[0031] This allows the user, for example, to locate and potentially resolve the tension. For instance, the user can be guided through an interactive and iterative process, perhaps with hints, to eliminate the tension by improving the mechanical connection.
[0032] In one embodiment, the test device is configured to transform the current signal into a frequency signal, filter it, and then transform it back into a time signal. Such a transformation into the frequency domain allows for the easier elimination of interfering frequency components through filtering. For example, the frequency caused by the voltage may be the lowest interfering signal, and all higher frequencies can then be set to zero. This lower frequency can be determined a priori, and then the frequency spectrum can be specifically searched for. The signal can then be converted back to the time domain. This time signal is then suitable for detecting the voltage.
[0033] In one embodiment, the test device is configured to determine the stress as a function of the time signal and the position signal. That is, the time signal just acquired, which was transformed from the frequency domain, is used together with the position signal to determine the stress.
[0034] In one embodiment, determining the position and / or direction of the stress involves identifying a maximum in the time signal and its corresponding time, and then determining the position in the position signal corresponding to that time. For example, a current maximum can be detected from the time signal within a given period, along with the corresponding time at which the current maximum occurs. The corresponding position in the position signal can be determined by ensuring that the time of the current maximum corresponds to the time of the greatest stress. This then reveals the stress position in the position signal. The direction of the stress can be determined from the waveforms of the position and time signals.
[0035] In one embodiment, the test device includes the position sensor and the drive unit, wherein the second electric motor can be driven by means of the drive unit. The drive unit is designed to detect the current signal 24-035 6
[0036] The system is set up, and the position sensor is configured to detect and output the position signal. The drive unit includes, for example, the power converter, which drives the electric motor—for example, a permanent magnet electric motor—via voltage signals and also detects the current signal. The position sensor is, for example, a rotary encoder, i.e., a sensor for rotational angles, which can be designed as a sensor with or without its own bearing. The position sensor is therefore mechanically connected to the second electric motor to detect the position of the electric motor and output the position signal.
[0037] In one embodiment, the test device comprises a torque measuring device and a first coupling. The first electric motor can be mechanically connected to the torque measuring device via the first coupling, particularly for the purpose of testing the first electric motor. The coupling serves to connect the first electric motor to the test device. The torque measuring device is then used to test the first electric motor during normal operation.
[0038] The second electric motor can be mechanically connected to the torque measuring device via the second coupling. The second coupling can, for example, be identical in design to the first coupling. During operation, the first coupling will be used more frequently for removal and attachment than the second coupling, as the first electric motor is intended to be exchanged more often for testing different motors.
[0039] In another embodiment, the test device is configured to switch from a first operating mode to a second operating mode depending on the voltage. During operation, the test device switches from the first to the second operating mode depending on the voltage. This allows for a separation between voltage detection and normal testing. The first operating mode can be used, for example, to detect the voltage, and the second operating mode for the normal testing of the first electric motor. If no or only a small voltage is detected in the first operating mode, the device can switch to the second operating mode. The permissible voltage can be set, for example, by a threshold value (24-035 7).
[0040] A value can be specified. Optionally, switching to the second operating mode can be blocked if the stress determined in the first operating mode is too high, e.g., above the threshold value.
[0041] In one embodiment, the second operating mode, used for testing the first electric motor, involves driving the second electric motor and thereby subjecting the first electric motor to at least one torque and / or at least one speed. The second electric motor can thus be used, for example, to simulate an environment for the first electric motor that acts on it through torques. Speeds refer, for example, to the rotational speed of the electric motors. If a pre-stress condition is present, this can lead to distorted measurement results or damage to mechanical components in the second operating mode. Therefore, switching to the second operating mode should be avoided if a pre-stress condition is present.
[0042] In one embodiment, the second operating mode provides for the application of higher torques and / or higher speeds than the first operating mode. The first operating mode serves to determine the preload. For this purpose, the application of lower torques and / or speeds may suffice. To test the first electric motor in the second operating mode, higher torques and / or speeds can then be applied as needed, depending on the test design.
[0043] Tour list
[0044] Exemplary embodiments of the invention are shown in the drawing and are explained in more detail in the following description.
[0045] They show
[0046] Figure 1 shows a schematic representation of the test setup with the first electric motor connected.
[0047] Figure 2 is a schematic representation of a torque measuring device, Figure 3 is another schematic representation of the torque measuring device,
[0048] Figure 4 shows a diagram with a frequency signal representing the current signal versus frequency, 24-035 8
[0049] Figure 5 shows the time profiles of the current signal of the torque-generating current, the time signal and the position signal.
[0050] Figure 6 shows a flowchart of the process and
[0051] Figure 7 shows a block diagram of a current signal processing circuit. The same reference symbols are used in the figures for identical or similar elements. The representations in the figures may not be to scale.
[0052] Fi urenbeschreibung
[0053] Figure 1 schematically shows a test device PE to which a first electric motor DUT is coupled. The test device PE has a first coupling FK1 via which the coupling with the first electric motor DUT can be established. The test device PE further includes a second electric motor 14 and a drive unit AE that drives it.
[0054] Optionally, a first mounting bracket (Al) can be provided to hold the first electric motor (DUT) and establish the mechanical connection with the first coupling (FK1). The first electric motor (DUT) is detachably connected to the first mounting bracket (Al). The first mounting bracket (Al) may, for example, have bores to allow the first electric motor (DUT) to be screwed to it. The first mounting bracket (Al) can be made of metal or a combination of metal and plastic.
[0055] The first electric motor DUT is axially connected to the first coupling FK 1 via its shaft. The first coupling FK1 is connected to a torque measuring device MS on the side facing away from the first mounting Al. A second coupling FK2 is then connected to the other side of the MS, which in turn establishes an axial connection to the second electric motor 14.
[0056] Optionally, the second electric motor 14 can be detachably connected to an optional second mount A2, which can be designed in the same or a similar way to the first mount Al.
[0057] The test setup PE therefore includes the mounts Al, A2, the couplings FK1, FK2 and the torque measuring device MS. About the couplings FK1, FK224-035 9
[0058] A mechanical connection is established between the electric motors DUT, 14. In the present embodiment, the mechanical connection between the first electric motor DUT and the second electric motor 14 is designed as an axial mechanical connection via the couplings FK1, FK2. It is provided that the first electric motor DUT can be inserted into the receptacle by a user as needed for testing purposes and can also be removed again.
[0059] The axial connection from the first electric motor DUT is established via the first coupling FK1, the torque measuring device MS, and the second coupling FK2 to the second electric motor 14. An eccentric connection in this process leads to undesirable stress.
[0060] The torque measuring device MS is connected to the drive unit AE in such a way that the torque measuring device MS transmits a torque signal DS to the drive unit AE. This can be implemented via wired connections, in particular electrically.
[0061] The torque signal DS is recorded during the test operation of the test device PE to test the first electric motor DUT, which is driven by the second electric motor 14 with a torque and / or speed. The test device PE also includes a position sensor PG. The position sensor PG determines the position of the second electric motor 14, converts it into a position signal PS, and transmits it to the drive unit AE. Furthermore, the drive unit AE is connected to the second electric motor 14 to receive the current signal 10 and to drive the electric motor 14 via motor voltages 12.
[0062] The drive unit AE functions as a power converter to drive the second electric motor 14. The drive unit AE also includes evaluation components such as a processor or other computer to determine stresses from the position signal PS and the current signal 10 in a first operating mode of the test device PE. In a second operating mode, the actual test operation for the first electric motor DUT is then performed. In this second operating mode, the first electric motor DUT24-035 10 can be tested using the torque signal DS.
[0063] This can be carried out. In the test operation, an environment for the first electric motor DUT can be simulated by means of moments and / or speeds generated via the second electric motor 14.
[0064] Figure 2 shows a schematic representation of the torque measuring device MS. The torque measuring device MS has a horizontal adjusting wheel JH and a vertical adjusting wheel JV to adjust the torque measuring device MS so that the shaft 20 of the first electric motor DUT and the shaft 22 of the torque measuring device MS are arranged concentrically. The mechanical connection between the first electric motor DUT and the torque measuring device MS is achieved by coupling their shafts 20 and 22. A concentric arrangement of these two shafts is desirable, resulting in no or only minimal stress and no or only minimal undesired forces.
[0065] Tension can be corrected by using the adjusting wheels JH and JV. This can be done manually or automatically, for example. The adjusting wheels JH and JV convert a rotational movement into a lateral movement, as shown in Figure 2.
[0066] Figure 3 again shows the torque measuring device MS. The adjusting wheels JH and JV are again shown, as well as the shaft 20 of the first electric motor DUT and the shaft 22 of the torque measuring device MS, which are eccentrically positioned relative to each other. This results in a preload that leads to the force vector 24. The preload can be determined, for example, by the drive unit AE by evaluating the position signal PS and the current signal 10 and displayed on a screen.
[0067] Since the first electric motor DUT is intended to be user-replaceable, it is possible that such an eccentricity could be introduced during such a replacement process. Such replacement processes are also frequently planned, so the aim should be to make correcting the eccentricity as simple as possible.
[0068] The adjusting wheels JH and JV can be used to restore the concentric arrangement of shafts 20 and 22, possibly also in an iterative process; that is, as long as a preload is indicated, adjustments can be made using the adjusting wheels JH and JV to achieve a concentric arrangement of shafts 20 and 22. 24-035 11
[0069] Figure 4 shows the torque-generating current as a frequency signal 70. The frequency diagram plots the frequency signal 70 (dotted line) and the filtered frequency signal 72 (solid line). In the frequency range 40, the influence of a cogging torque of the first electric motor DUT on the torque-generating current is visible.
[0070] The cogging torque of an electric motor, also called cogging torque, is a torque that arises from the interaction between the magnetic fields of the stator and rotor of the electric motor.
[0071] To determine the preload, this cogging torque, which is caused by the motor itself, is filtered out. The dotted line of the frequency signal 70 is set to 0 by the filtering. This means that frequencies in range 40, which show the influence of the cogging torque, and frequencies higher than that are eliminated. The frequencies in range 40 are not caused by the preload, but by the cogging torque. All other harmonics are also eliminated, simplifying subsequent signal processing. This filtering is a low-pass filter using a low-pass filter (TP).
[0072] The voltage is currently 0.0167 Hz. This frequency can be calculated in advance, and in a second step, it can be specifically searched for. It depends on the rotational speed of the electric motors DUT, 14, which are coupled.
[0073] For example, in the first operating mode used to determine the tension, a rotational speed of 1 revolution / min is used for the second electric motor 14. This corresponds to a frequency of 1 / 60 ~ 0.0167 Hz.
[0074] The transformation to the frequency domain can be achieved using a Fast Fourier Transform (FFT). An inverse Fast Fourier Transform (invFFT) can then transform the signal 72, now cleaned by the low-pass filter TP, back into the time domain as the time signal 74 of the torque-generating current. Other transformation techniques are also possible.
[0075] Figure 5 shows, for comparison, the original current signal 10 of the torque-generating current, the corrected current signal 10 as time signal 74, and the position signal PS. The original current signal 10 of the torque-generating current (24-035 12)
[0076] The current is shown in the top diagram in a current-time diagram. The corrected current signal 10 is shown as time signal 74 in the middle current-time diagram. The position signal PS is shown in the bottom diagram in a position-time diagram.
[0077] The middle diagram shows a reference time signal without voltage alongside the time signal 74. The upper diagram shows a reference current signal without voltage alongside the current signal 10, as well as the signals from the middle diagram.
[0078] Time signal 74 is examined to determine its maximum (MAX). This maximum occurs at approximately 19 seconds. At this time, position 76 of the tension is determined by a position determination (PO) in the position signal (PS), namely 113.905°.
[0079] The direction of the voltage can also be determined from the time signal 74. Figure 6 shows the flowchart of the procedure for operating a test device for a first electric motor. The procedure for the first operating mode of the test device PE is shown.
[0080] In process step A, the second electric motor 14 is controlled by the drive unit AE.
[0081] In process step B, the position signal PS of the second electric motor 14 is detected by the drive unit AE.
[0082] In process step C, the current signal 10 of the torque-generating current of the second electric motor 14 is further acquired by the drive unit AE. Process steps B and C can be carried out simultaneously.
[0083] In process step D, the tension of the mechanical connection is determined as a function of the current signal 10 and the position signal PS.
[0084] A release signal, e.g., on a display, can then be given if no significant stress is detected. After the release signal, the user can then operate the test device in the second operating mode. It is also possible to automatically switch to the second operating mode if no or only a small amount of stress is detected. 24-035 13
[0085] and / or suggest to the user that they switch to the second operating mode.
[0086] If a tension is detected in the first operating mode, the user is shown where the tension can be seen, depending on the tension, so that the user can release the tension.
[0087] Figure 7 shows in a block diagram the processing of the current signal 10 in step D.
[0088] First, the current signal 10 is subjected to a transformation from the time domain to the frequency domain in the FFT block. This transformation can preferably be performed using a Fast Fourier Transform (FFT).
[0089] The resulting frequency signal 70 is then subjected to filtering by the low-pass filter TP in order to reduce the interfering frequencies to zero and to enable the search for the maximum in the time signal.
[0090] The filtered frequency signal 72 is then transformed back into the time domain in the invFFT block, for example, using an inverse Fast Fourier Transform, resulting in the time signal 74. This time signal 74 is then subjected to the determination of its maximum MAX, so that the corresponding time on the time axis is determined along with the maximum amplitude of the time signal 74. The position of the tension can then be determined in the PO block using the position signal PS.
[0091] With this pair of values, the position of the tensioning device is then defined in the position signal 76 and can be output as the tensioning device position in the OFF block. The process steps shown in Figure 7 are executed in the drive unit AE. Reference numerals
[0092] 10 Current signal of the torque-generating current
[0093] 12 motor voltages
[0094] 14 second electric motor
[0095] 20 Wave first electric motor
[0096] 22 Shaft of the torque measuring device
[0097] 24 Force vector of tension
[0098] 40 Frequency range of the detent force torque
[0099] 70 frequency signal
[0100] 72 filtered frequency signal
[0101] 74 Time signal
[0102] 76 Position of the tension in the position signal
[0103] Al first recording
[0104] A2 second recording
[0105] AE drive unit
[0106] OFF output position of the tension
[0107] DS torque signal
[0108] DUT first electric motor
[0109] FFT Fast Fourier Transform
[0110] FK1 first clutch
[0111] FK2 second clutch
[0112] invFFT inverse fast Fourier transform
[0113] JH horizontal adjustment wheel
[0114] JV vertical adjustment wheel
[0115] MAX Determination Maximum
[0116] MS torque measuring device
[0117] PE test facility
[0118] PG Position Transmitter
[0119] PO Determination of the tension position in the position signal PS Position signal
[0120] TP low-pass filter
[0121] A, B, C, D process steps
Claims
24-035 15 REQUIREMENTS 1. Test equipment (PE) for a first electric motor (DUT), wherein the first electric motor (DUT) is mechanically connectable to a second electric motor (14) of the test equipment (PE), wherein the test equipment (PE) is configured, to drive the second electric motor (14), to detect a position signal (PS) of the second electric motor (14), to detect a current signal (10) of a torque-generating current of the second electric motor (14) and to determine a stress in the mechanical connection as a function of the current signal (10) and the position signal (PS).
2. Testing device (PE) according to claim 1, wherein the testing device (PE) is configured to determine a position and / or a direction of the tension.
3. Test device (PE) according to claim 1 or 2, wherein the test device (PE) is configured to transform the current signal (10) into a frequency domain as a frequency signal (70), filter it and transform it back into a time domain as a time signal (74).
4. Test device (PE) according to claim 3, wherein the test device (PE) is configured to determine the tension as a function of the time signal (74) and the position signal (PS).
5. Test device (PE) according to one of claims 2 to 4, wherein determining the position and / or direction of the tension comprises determining a maximum in the time signal (74) and an associated time and determining an associated position (76) in the position signal (PS).
6. Test device (PE) according to one of the preceding claims, wherein the test device (PE) comprises a position encoder (PG) and a drive unit (AE), wherein the second electric motor (14) can be driven by means of the drive unit (AE), the drive unit is configured to detect the current signal (10), and the position encoder (PG) is configured to detect and output the position signal (PS). 24-035 16 7. Test device (PE) according to one of the preceding claims, wherein the test device (PE) comprises a torque measuring device (MS) and a first coupling (FK1), wherein the first electric motor (DUT) can be mechanically connected to the torque measuring device (MS) via the first coupling (FK1).
8. Test device (PE) according to claim 7, wherein the second electric motor (14) is mechanically connected to the torque measuring device (MS) via a second coupling (FK2).
9. Test device (PE) according to one of the preceding claims, wherein the test device (PE) is configured to switch from a first operating mode to a second operating mode depending on the tension.
10. Testing device according to claim 9, wherein in the second operating mode it is provided to test the first electric motor (DUT) and to subject it to at least one torque and / or at least one speed by driving the second electric motor (14).
11. Testing device according to claim 10, wherein in the second operating mode the application of larger torques and / or larger speeds is provided than in the first operating mode.
12. Method for operating a test apparatus (PE) for a first electric motor (DUT), wherein the first electric motor (DUT) is mechanically connected to a second electric motor (14) of the test apparatus (PE), the method comprising: A) Driving the second electric motor (14), B) Detection of a position signal (PS) of the second electric motor (14), C) Detection of a current signal (10) of a torque-generating current of the second electric motor (14), D) Determining a stress in the mechanical connection as a function of the current signal (10) and the position signal (PS).
13. Method according to claim 12, wherein a position and / or direction of the stress is determined. 24-035 17 14. Method according to claim 12 or 13, wherein, depending on the tension, the test device (PE) switches from a first operating mode to a second operating mode.
15. Method according to one of claims 12 to 14, wherein in the second operating mode the first electric motor (DUT) is tested and is subjected to at least one torque and / or at least one speed by driving the second electric motor (14).