WO2020165376A1

WO2020165376A1 - Method for detecting a fault in an electrical machine for a vehicle

Info

Publication number: WO2020165376A1
Application number: PCT/EP2020/053820
Authority: WO
Inventors: Benedikt Van Booven; Gerhard Eser
Original assignee: Vitesco Technologies GmbH
Priority date: 2019-02-14
Filing date: 2020-02-13
Publication date: 2020-08-20
Also published as: DE102019201985A1; EP3925067A1; DE102019201985B4

Abstract

The present invention relates to a method for detecting an electrical and/or mechanical fault in an electrical machine for a vehicle, which machine has a rotor shaft to which a torque sensor is applied, which torque sensor is designed to determine the torque acting on the rotor shaft. The method according to the invention comprises the steps: generating a torque signal, which indicates the torque acting on the rotor shaft, by means of the torque sensor; and detecting an electrical and/or mechanical fault in the electrical machine if the torque signal deviates from a reference torque signal by more than a torque threshold value.

Description

description

Method for detecting a fault in an electrical machine for a vehicle

The present invention relates to a method for recognizing a fault in an electrical machine for a vehicle, in particular a method for recognizing an electrical and / or mechanical fault in an electric motor for a vehicle.

The fault diagnosis of an electric drive of a vehicle is becoming more and more important and it is desirable to recognize failure of the same early and in a differentiated manner so that suitable countermeasures can be taken in good time in the event of a fault. In particular, the high dynamics of the drives with regard to the torque curve places the highest demands on future diagnoses. In addition, the desire of the operator of a vehicle is to extend the maintenance intervals of the vehicle as much as possible, but the operating times of the vehicles are constantly increasing, for example through car sharing.

Potential faults in an electrical drive can essentially be divided into two categories, namely mechanical and electrical faults. Mechanical errors relate to errors that can be assigned to the mechanics of the electric drive, such as defective bearings or plastic deformations of components of the electric machine. In contrast to this, electrical faults affect those faults in the electrical drive that affect the electronic

Components or electrical elements of the electric drive can be assigned, such as short circuits in the rotor or stator winding or defective sliding contacts.

Today's fault diagnoses are essentially based on the evaluation of the phase currents / voltages, the vibration measurement using structure-borne noise sensors or temperature measurements, which also include the speed of the rotor shaft and / or the position of the rotor can be taken into account in order to be able to infer potential faults in the electrical machine.

EP 3 034 812 A1 relates to monitoring of a gas turbine engine recorded on the basis of the measurements of a torque sensor.

US 2018/229765 A1 relates to a control unit for a servo steering unit, in which an anomaly of the servo motor unit is based on a

Torque signal is determined.

From US 2018/022379 A1 a power steering device and

Control device known for this. Further such power steering devices are known from US 2017/0274929 A1 and US 2018/032191 A1.

The present invention is essentially based on the object of detecting electrical and / or mechanical faults in an electrical drive early and reliably in a simple manner and issuing corresponding warnings to the operator of the vehicle and providing emergency running programs.

This object is achieved with a method according to independent claim 1. Preferred embodiments of the present invention are shown in

Subclaims indicated.

The present invention is essentially based on the idea of being able to determine an electrical and / or mechanical fault in an electrical machine in that the torque detected by means of a torque sensor attached to the rotor shaft of the electrical machine is compared with a reference torque and at a large deviations from this can be inferred from a specific error. The torque delivered by the electric machine via the output shaft is the final size of the entire chain of action of the electric drive train. In particular, the present invention makes use of the fact that a mechanical error of the

electric drive, such as a defective bearing, differently to the The torque curve on the rotor shaft acts as an electrical fault in the electrical machine, such as a short circuit in the rotor winding. With precise processing and analysis of the torque curve, the type of specific error can be determined and a corresponding warning can be issued to the driver of the vehicle, with the corresponding

Measures such as replacing a defective bearing can be taken.

Consequently, according to the present invention, a method for detecting an electrical and / or mechanical fault of an electrical machine for a vehicle is disclosed, which has a rotor shaft to which a torque sensor is applied, which is designed to contact the rotor shaft

To detect torque. The method according to the invention comprises generating a torque signal, which indicates the torque applied to the rotor shaft, by means of the torque sensor and recognizing an electrical and / or mechanical fault in the electrical machine if the

Torque signal deviates from a reference torque signal by more than a torque threshold value. The electric machine can be operated as an electric motor, which emits a torque via the rotor shaft, or as a generator, which receives a torque via the rotor shaft and stores it in electrical form.

The reference torque signal can be, for example, a torque signal stored in an engine control system, which is used as a drive train of the electrical machine that is newly manufactured and is therefore free of errors

Reference torque signal was generated. Alternatively, reference torque signals set in advance can be stored, which represent a faultless drive train.

In a preferred embodiment, the method according to the invention also has an analysis of the torque signal generated by the torque sensor. The detection of an electrical and / or mechanical fault in the electrical machine is based on the analyzed torque signal. Preferably analyzing the torque signal includes performing a time analysis with the torque signal and / or performing a frequency analysis with the torque signal and / or filtering the torque signal by means of a bandpass, such as a low-pass filter and / a flochpass filter, and / or performing a reference frame Theory Analysis with the torque signal and / or performing a Finite Element State Space Analysis with the torque signal.

In an advantageous embodiment of the method according to the invention, an electrical and / or a mechanical fault is detected when the

The torque signal deviates from the reference torque signal by more than a predetermined period of time by more than the torque threshold value. In particular, it can be ensured that individual

Measurement inaccuracies or isolated measurement errors do not result in an immediate one

Detection of a fault in the electrical machine. Should be

If there are mechanical and / or electrical faults, the torque applied to the rotor shaft would change permanently

Torque sensor would be detected as a torque signal.

In a further advantageous embodiment, the inventive

The method further comprises incrementing an error if the torque signal deviates from the reference torque signal by more than the torque threshold value, decrementing the counter if the torque signal does not deviate from the reference torque signal by more than the torque threshold value and recognizing the electrical and / or mechanical failure of the electrical machine when the counter has a predetermined

Counting threshold exceeded. In this case, use is made in particular of the fact that the torque sensor supplies a torque signal at constant intervals, for example every 100 ps (i.e. a sampling rate of approximately 10 kHz) and thus it can be checked that individual outliers or

Measurement inaccuracies do not immediately lead to the detection of an error. An electrical fault in the electrical machine preferably includes a line break and / or short circuit in the stator and / or rotor winding and / or an abnormal connection of the stator and / or rotor winding and / or a defect in the sliding contacts and / or a defect in the squirrel-cage rotor and / or or short-circuit ring and / or a fault in the inductive energy transfer between stator and rotor.

Furthermore, it is preferred if the mechanical fault of the electrical machine is a defect in the inner and / or outer bearing run and / or a defect in at least one rolling element of the bearing and / or a defect in the bearing and / or a defect in the bearing cage of the bearing and / or or a plastic one

Deformation of the rotor shaft and / or an abnormality in the static air gap and / or a defect in at least one of the permanent magnets of the

electrical machine and / or a de-axising of the rotor shaft, which can lead to wobbling of the rotor shaft.

It is also advantageous if the torque sensor is at least one strain gauge attached to the rotor shaft.

In a particularly preferred manner, the reference torque signal is provided for the engine control via remote access. For example, cloud services can be cited here that can be queried by the motor control unit of the electrical machine via a remote communication connection in order to be able to carry out the comparison with the torque signal generated by the torque sensor and thus also to be able to detect an electrical fault.

Alternatively or additionally, the signals detected by the torque sensor can be sent to the cloud service via the remote communication connection, in which case the evaluation can then take place in the cloud service. This has the advantage that the majority of the computing power does not take place in the vehicle, but rather away from it, whereby the need for computing power in the vehicle can be reduced.

In a further embodiment of the method according to the invention, it can be preferred to further include the steps of detecting the speed of the rotor electrical machine and / or sensing the position of the rotor of the electrical machine and / or sensing the temperature of the rotor of the electrical and / or sensing the characteristic electrical parameter applied to the electrical machine, in particular the electrical current applied to the electrical machine or the electrical voltage applied to the electrical machine, wherein the detection of an electrical and / or mechanical fault in the electrical machine is also based on at least one of the aforementioned recorded parameters.

In particular, this enables certain states of the electrical machine, such as different temperatures, different speeds, different positions of the rotor and different electrical currents and voltages when the electrical fault is detected

be taken into account so that the detection of such can be carried out even more precisely and reliably. More precisely, they can

The aforementioned parameters serve to confirm a detected error.

In particular, mechanical errors in the electrical machine are scaled with the speed, i. This means that mechanical ones can increase proportionally with increasing speed of the rotor shaft. Electrical errors are also scaled with the speed of the rotor shaft, but are also dependent on the number of pole pairs. A mechanical fault can thus be clearly distinguished from an electrical fault in the electrical machine.

Other features and advantages of the present invention will become apparent to those skilled in the art by practicing the teachings herein and viewing the accompanying drawings, in which:

1 shows a flow chart of a method according to the invention, and

FIG. 2 shows a diagram in which a torque curve is shown versus time for a faultless electrical machine and a faulty electrical machine. 1 shows an exemplary flow chart of a method according to the invention for recognizing a mechanical and / or electrical fault in an electrical machine. In particular, the method according to the invention is based on an electrical machine which is formed from an electric motor / generator with a stator and rotor and a rotor shaft. The electric machine can be operated as an electric motor and generator, so that the rotor shaft can function as an output and drive shaft.

A torque sensor, such as a strain gauge, is applied to the rotor shaft of the electrical machine and is designed to detect the torque applied to the rotor shaft. In particular, the torque sensor is designed to provide a corresponding torque signal, preferably in analog form, as a function of the torque applied to the rotor shaft, which is then transmitted in a control unit, such as

for example the engine control unit, can be processed, analyzed and evaluated.

The method of FIG. 1 starts at step 100 and then arrives at step 110, at which the torque sensor generates a torque signal indicating the torque applied to the rotor shaft and makes it available to a motor control unit for further processing. The method then arrives at a step 120 in which bandpass filtering of the torque signal takes place. In the

Bandpass filtering, in particular those signal components are filtered out in which the errors of the drive were reflected. In one

Subsequent step 130 is an absolute value formation of the difference between the original torque signal generated by the torque sensor and the filtered torque signal, whereby the disturbance or the fault of the electrical machine is filtered out.

In a subsequent step 140, the absolute value formed in step 130 is compared with a reference torque signal that is a

Torque signal for a faultless electrical machine corresponds. The reference torque signal can be stored in the engine control. Alternatively, the engine control can access the reference torque signal stored remotely from the vehicle via a telecommunication connection.

If it is determined at step 140 that the absolute value formed at step 130 of the predetermined reference torque signal by a predetermined

If the torque threshold value deviates, the method goes to step 142 and a counter is also incremented. However, if it is determined at step 140 that the absolute formed at step 130 differs from the predetermined

If the reference torque signal value does not differ by more than the torque threshold value, the method proceeds to step 144 and the counter is also decremented. The torque threshold value is approximately 20%, preferably approximately 10%, most preferably approximately 5% of the

Reference torque signal.

In a step 150 following steps 142 and 144, a query is made as to whether the count value exceeds a predetermined count threshold value. If this is the case, the method goes to step 160 and a fault in the electrical machine is recognized. If the counter value falls below the predetermined counting threshold at step 150, the method goes to step 142 and a decision is made on “no error” or “error-free electrical machine” and the method then goes back to step 110, where a new one is repeated

Torque signal is generated by means of a torque sensor.

Step 150 thus serves to ensure that individual measurement outliers or

Measurement inaccuracies are sorted out and an error is only output when the error is confirmed in a first measurement by a second measurement. Step 150 can also serve to ensure that an error is only recognized when the error has existed for a certain period of time and is therefore also a real error.

A torque signal can be generated, for example, at fixed time intervals, such as every 100 mps (or sampling rate of approximately 10 kHz). In step 160, at which an electrical and / or mechanical fault is detected, the torque signal can also be analyzed, for example a frequency analysis. In addition, FIG. 2 shows an exemplary time curve of the torque which is applied to the rotor shaft with the

Torque sensor was determined.

In FIG. 2, the solid line 200 represents the torque curve which would be expected with a fault-free electric drive. Line 200 thus shows the profile of the torque that would be applied to the rotor shaft of an electrical machine that has neither a mechanical nor an electrical fault. In contrast, the dashed line 300 represents one

Represents the torque curve that has been recorded in a faulty electric drive. From Fig. 2 it is clear that the measured

Torque curve 300 deviates significantly from the expected torque curve 200.

The method according to the invention can be carried out during normal operation of the electrical machine. In particular that is

Method according to the invention suitable for identifying electrical faults in the electrical machine.

Claims

1 . Method for detecting an electrical and / or

mechanical error of an electrical machine for a vehicle, which has a rotor shaft to which a torque sensor is applied, which is designed to detect the torque applied to the rotor shaft, the method comprising:

Generating a torque signal, which indicates the torque applied to the rotor shaft, by means of the torque sensor, and

Detection of an electrical and / or mechanical fault in the electrical machine when the torque signal from a

Reference torque signal deviates by more than a torque threshold value.

2. The method of claim 1, further comprising:

Analyzing the torque signal generated by the torque sensor,

wherein the detection of an electrical and / or mechanical fault in the electrical machine is based on the analyzed torque signal.

3. The method of claim 2, wherein analyzing the torque signal comprises:

Carrying out a time analysis with the torque signal, and / or

Performing a frequency analysis with the torque signal, and / or

Filtering the torque signal by means of a low-pass filter, and / or

Filtering the torque signal by means of a floch pass filter, and / or

Carrying out a Reference Frame Theory Analysis with the torque signal, and / or, Performing a finite element state space analysis on the torque signal.

4. The method according to any one of the preceding claims, wherein an electrical and / or mechanical error is detected when the

The torque signal deviates from the reference torque signal for more than a predetermined period of time by more than the torque threshold value.

5. The method according to any one of the preceding claims, further comprising:

Incrementing a counter if the torque signal deviates from the reference torque signal by more than the torque threshold value,

Decrement the counter when the torque signal from the reference torque signal does not exceed the

Torque threshold deviates, and

Detection of an electrical and / or mechanical fault in the electrical machine when the counter exceeds a predetermined value.

6. The method according to any one of the preceding claims, wherein an electrical fault in the electrical machine comprises:

Line break and / or short circuit of the stator and / or

Rotor winding, and / or

Abnormal connection of the stator and / or rotor winding, and / or

Defect of the sliding contacts, and / or

Defect in the squirrel-cage rotor and / or short-circuit ring and / or defect in the inductive energy transfer between the stator and

Rotor.

7. The method according to any one of the preceding claims, wherein a mechanical fault in the electrical machine comprises:

Defect of the inner and / or outer bearing race and / or defect of at least one rolling element, and / or Defect of the bearing cage, and / or

plastic deformation of the rotor shaft, and / or

Static air gap abnormality, and / or

Defect in at least one permanent magnet, n and / or

De-axising of the rotor shaft.

8. The method according to any one of the preceding claims, wherein the torque sensor is at least one attached to the rotor shaft

Strain gauge is.

9. The method according to any one of the preceding claims, wherein the reference torque signal is provided via remote access and / or an analysis of the torque signal takes place in the remote access, wherein the signals of the torque sensor are sent to the remote access.

10. The method according to any one of the preceding claims, further comprising:

Detecting the speed of the rotor of the electrical machine, and / or

Detecting the position of the rotor of the electrical machine, and / or

Detecting the temperature of the rotor of the electrical machine, and / or

Detection of the characteristic electrical parameter applied to the electrical machine, in particular the current applied to the electric motor or the voltage applied to the electric motor,

wherein the detection of an electrical and / or mechanical fault in the electrical machine is further based on at least one of the above-mentioned recorded parameters.