Monitoring concentricity
Patent Information
- Application Number
- CN202410872955.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2023-06-29
- Filing Date
- 2024-07-01
- Publication Date
- 2024-12-31
AI Technical Summary
Existing methods for monitoring the concentricity of electric motors are inadequate in detecting early signs of bearing wear and potential failures, which can lead to sudden motor malfunction and production downtime.
A method using an encoder ring and two measuring sensors to monitor the concentricity of a rotor in a stator, determining an operating state metric and comparing it against predetermined conditions to detect deviations, with the option to account for inherent inaccuracies during commissioning.
Enables early detection of bearing wear and potential failures, allowing for timely maintenance and preventing unexpected motor shutdowns and component damage.
Smart Images
Figure CN119231845A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a method for monitoring the concentricity of an electric motor, a control device for implementing the method, and a detector having the control device. Background Art
[0002] A detector for determining the position of an electric machine having a rotor rotatable in a stator about an axis of rotation is known from publications US 2023 / 022341 A1 and US 2023 / 142572 A1. The detector comprises an encoder ring and two measuring sensors, wherein the measuring sensors are at a rotational angular distance from one another when viewed with respect to the axis of rotation and are arranged to each output a piece of position information related to the rotational orientation of the encoder ring, which is dependent on the angular position of the rotor relative to the stator. Summary of the invention
[0003] The object of the invention is to improve the use of known position sensors.
[0004] This object is achieved by the features of the independent claim. Preferred embodiments are the subject matter of the dependent claims.
[0005] According to one aspect of the invention, a method for monitoring the concentricity of a rotor rotating in a stator about an axis of rotation in an electric machine using a detector having an encoder ring and two measuring sensors, wherein the measuring sensors are at a rotational angular distance from one another when viewed about the axis of rotation and are arranged to each output a piece of position information related to the rotational orientation of the encoder ring, which is dependent on the angular position of the rotor relative to the stator:
[0006] - a working position detection step, in which, at the working angular position of the rotor relative to the stator, in the working state of the motor, each measuring sensor detects a piece of working position information;
[0007] - an operating state metric determination step, in which an operating state metric characterizing the distance between two measuring sensors is determined based on the detected operating position information; and
[0008] - A monitoring step, in which the concentricity error is output if the working condition metric satisfies a predetermined condition.
[0009] This designation method is based on the fact that, in electric motors, the wear of bearing elements, such as ball bearings and linear bearings, is a critical factor in their service life. The raceways or rolling elements are subject to normal wear. This wear will be greater without regular maintenance and relubrication. If a failure of a bearing element is not detected in time, the motor suddenly no longer functions properly, and this can lead to a complete failure of the system, with correspondingly costly production interruptions. In some cases, a sudden stop of the motor can also lead to mechanical collisions in the system, which can damage other components. Therefore, early detection of impending motor failures is very important in plant engineering.
[0010] One way to detect impending failure is to monitor the concentricity of the motor, which enables the condition of the bearing elements to be monitored and possible failures to be predicted. By continuously monitoring and analyzing measurement data (such as vibration or temperature), impending failure of bearings or other components can be detected. This means that replacement can be planned and implemented in a timely manner before a failure occurs. Predicting wear and failure by monitoring concentricity is an effective way to improve the reliability of motors and prevent production downtime.
[0011] Until now, concentricity has been monitored via vibration, temperature or acoustics.
[0012] In contrast, this designation method is based on the consideration that rotating shafts with positioning capabilities are usually equipped with incremental or absolute measuring systems. The measuring sensors scan an encoder ring in the form of a circular measuring disk to detect the angular position of the motor. If the encoder ring has more than one measuring sensor, the offset of the rotor pivot point relative to the stator can be detected. In this way, even the smallest displacement of the shaft to the center can be detected.
[0013] The encoder ring and the measuring sensor can be based on any measuring principle, such as an optical principle or a magnetic principle. In principle, it is not important whether the encoder ring is mounted on the rotor and the measuring sensor is mounted on the stator or vice versa. However, for practical reasons, the encoder ring is mounted on the rotor.
[0014] In the context of a given method, the term metric is a value used to describe the relative distance or ratio between two measuring sensors. The metric may describe the distance directly or indirectly using information from which the distance can be derived.
[0015] In another embodiment of the specified method, under the working state of the motor, a working position detection step and a working state metric determination step are performed at different working angle positions of the rotor relative to the stator, and a working state metric series is established relative to different working angle positions, wherein the predetermined state includes the maximum change of the working state metric within the working state metric series.
[0016] This embodiment is based on the consideration that, in the case of ideal concentricity, the distance between the two measuring sensors and therefore the working state metric remains constant. By considering the working state metric at different working angle positions, the change of the working state metric at different working angle positions can be used to directly infer insufficient concentricity.
[0017] In an additional embodiment, the designation method further comprises:
[0018] - a reference position detection step, in which reference position information is acquired using various measuring sensors at a reference angular position of the rotor relative to the stator and in a reference state of the motor;
[0019] - a reference state metric determination step, in which a reference state metric characterizing the distance between the two measuring sensors is determined based on the acquired reference position information; and
[0020] - Determining a predetermined state based on a reference state metric.
[0021] This embodiment is based on the consideration that concentricity inaccuracies may not only be caused by signs of wear, but also by other factors that are, for example, production-related and therefore do not affect the service life of the motor. These concentricity inaccuracies, which are therefore not important for monitoring the motor, can be taken into account together with the reference state metric and calculated outside the predetermined state so that they are no longer taken into account during monitoring.
[0022] In a further specific embodiment of the specified method, the reference position detection step and the reference state metric determination step are performed at various reference angular positions of the rotor relative to the stator in a reference state of the motor, and a reference state metric sequence is established relative to the various reference angular positions, wherein the predetermined state is created based on the reference state metric sequence. In this way, the concentricity can be defined under a condition determined to be fault-free (such as after delivery from the factory) and taken into account when monitoring the concentricity accuracy.
[0023] During this process, reference metrics and / or reference state metric series may be stored.
[0024] To record the reference state metric series, the reference metric and / or the reference state metric series can be recorded in a learning run before the operating state, in which the rotor of the electric motor rotates around the stator. The learning run can then define the reference state and distinguish it from the operating state.
[0025] In another embodiment of the specified method, two measuring sensors are arranged at a distance between 45° and 135°, preferably between 75° and 105°, particularly preferably 90°. In the optimal arrangement, with the best possible detection of the axial displacement, the measuring sensors are spaced 90° apart. The further this arrangement deviates from 90°, the less the influence of concentricity inaccuracies in the operating state metric, which ultimately influence the accuracy.
[0026] Particularly preferably, the operating state measure describes an angular offset of the two measuring sensors relative to the axis of rotation in the operating state.
[0027] According to another aspect of the invention, a control device is arranged to implement one of the specified methods.
[0028] In another embodiment, the designation device has a memory and a processor. The designation method is stored in the memory in the form of a computer program, and the processor is provided to execute the method when the computer program is loaded from the memory into the processor.
[0029] According to another aspect of the present invention, a computer program comprises program code means for executing all the steps of a specified method when the computer program is executed on one of an electronic device or a specified device.
[0030] According to another aspect of the invention, a computer program product comprises a program code which is stored on a computer-readable data carrier and which, when executed on a data processing device, carries out a specified method.
[0031] According to another aspect of the invention, a detector for an electric motor, wherein the electrode has a rotor rotatable around a rotation axis in a stator, the detector comprising: an encoder ring; two measuring sensors, wherein the measuring sensors are spaced apart from each other by a rotational angular distance when viewed with respect to the rotation axis and are arranged to each output a piece of position information related to the rotational orientation of the encoder ring that depends on the angular position of the rotor relative to the stator; and one of the designated control devices for implementing one of the above-mentioned methods. BRIEF DESCRIPTION OF THE DRAWINGS
[0032] The above characteristics, features and advantages of the present invention and their implementation will become more clear in conjunction with the following description of the embodiments, which will be explained in more detail in conjunction with the accompanying drawings, in which:
[0033] Figure 1 shows an exploded view of a motor with a detector,
[0034] Figure 2 Shows that there is Figure 1 A cross-sectional view of the detector motor,
[0035] Figure 3 Shown for use Figure 1 and Figure 2 A structural diagram of a method of monitoring concentricity in a motor using a detector,
[0036] Figure 4 shows the measurement without concentricity inaccuracy. Figure 1 and Figure 2 A schematic diagram of the detector, and
[0037] Figure 5 shows the possibility of making measurements with concentricity inaccuracies Figure 1 and Figure 2 Schematic diagram of the detector.
[0038] In the figures, identical technical elements have the same reference numerals and are described only once. The figures are purely schematic and in particular do not reflect actual geometric proportions. DETAILED DESCRIPTION
[0039] refer to Figure 1 , which shows an electric machine 2 having a detector 3 in a space spanning a radial direction 4 , an axial direction 6 at right angles to the radial direction 4 , and a tangential direction 8 extending around the axial direction 6 and at right angles to the radial direction 4 .
[0040] The motor 2 is arranged with the detector 3 around the rotation axis 10 arranged in the axial direction 6, and has a stator 12. A rotor 14 is rotatably arranged in the stator. The stator 12 serves as a motor housing, in which the detector 3 is also accommodated. The rotor 14 is designed as a rotating flange and is driven by a drive device not further shown in a manner known per se (such as an electric field) to rotate around the rotation axis 10.
[0041] In principle, the rotor 14 can be slidably mounted in the stator 12. To reduce friction, the rotor 14 in this embodiment is mounted in the stator 12 via an anti-friction bearing 16, for example in the form of a ball bearing or a roller bearing.
[0042] An encoder ring 18 as part of the detector 3 is held on the rotor 14 and is rotationally symmetrical with respect to the axis of rotation. The encoder ring 18 is designed to excite a variable encoder field in the tangential direction 8, which encoder field can be a magnetic field, an optical field, an electric field, etc., depending on the operating principle of the position sensor. This structure is well known and does not need further explanation for the sake of brevity.
[0043] A printed circuit board 22 is held on the stator 12 at an axial distance 20 from the encoder ring 18, on which two measuring sensors 26 are arranged at an angular distance 24. Each measuring sensor 26 is arranged to detect a variable encoder field of the encoder ring 18 and thus a rotational orientation 27 of the encoder ring and convert it into position information, which contains the position or orientation of the encoder ring 18 and thus the position or orientation of the rotor 14 relative to the stator 12.
[0044] The measuring sensors in such motors work separately from one another and generate two independent pieces of position information. These pieces of information can then be processed by the motor control unit and the safety control unit. A key feature of such motors is their position redundancy. If one of the measuring sensors fails, the motor can keep running and system failures are avoided. In this case, the control unit can issue a warning. If the motor is operating normally, the control and regulation results obtained from the position information of the first measuring sensor should be roughly the same as those of the second measuring sensor. A difference can be seen as an indication of a problem and the safety control unit can stop the motor.
[0045] the following, Figure 3 A method is described which extends the concept of using two redundant measuring sensors for fault finding by monitoring the concentricity of an electric machine.
[0046] First, consider that the motor 2 is in a working state. The working state is a state in which the motor 2 achieves its intended purpose when installed in a robot application, a machine tool or automation technology. The position information of each measuring sensor 26 output in this state is hereinafter referred to as working position information and is Figure 3 It is marked with reference numeral 28 in the figure.
[0047] A metric is determined based on the working position information 28, which characterizes the distance between the two measuring sensors 26 in the tangential direction 8. In the following, this metric is referred to as the working state metric and is Figure 3 30. In order to determine the operating state measure 30, a filter 32 is first used to determine the sensor angle position 34 of the respective measuring sensor 26 relative to a specific zero position on the stator 12 from the operating position information 28 of the respective measuring sensor 26. This zero position can be chosen arbitrarily and is irrelevant for a further understanding of the method.
[0048] In the present embodiment, the sensor angular positions 34 are then simply subtracted from one another in a subtraction element, whereby the distance of the two measuring sensors 26 in the tangential direction 8 is directly obtained and thus an example of an operating state measure 30 is determined. Therefore, the subtraction unit which determines this measure is referred to below as operating state measure determination and is referred to in Figure 3 The reference number 36 is provided in FIG.
[0049] Finally, the operating condition metric 34 is plotted in the recorder 38 along with the angular position 40 of the rotor 14 relative to the stator 12 to form an operating condition metric series 42. The individual values of the operating condition metric series 42 can then be compared with at least one predetermined state 46 in the monitoring device 44 to monitor the concentricity. Depending on the design of the algorithm, the monitoring device 44 can output a warning signal 48 if the predetermined state 46 is met or is no longer met, and therefore the concentricity of the motor 2 is no longer ensured.
[0050] For this purpose, in the simplest case, the predetermined state 46 can be designed as a fixed value which specifies the operating state metric 34 with certainty and thus in this example the distance and the correct concentricity between the two measuring sensors 26. As soon as the operating state metric 30 deviates from this predetermined distance within a certain tolerance, a decision about the concentricity inaccuracy can be made and a warning signal 48 can be output.
[0051] However, this type of monitoring is relatively inaccurate, since the entire distance between the two measuring sensors 26 is always considered as the information to be monitored. It is better to focus on the information of interest, in this case the change in the distance between the two measuring sensors 26. For this purpose, the currently determined operating state metric 30 can be delayed using a buffer element 50, and the delayed operating state metric 30' can be plotted again in another recorder 38 via the angular position 40 of the rotor 14 relative to the stator 12 to form a delayed operating state metric series 42'. In this way, the monitoring device 44 can monitor the change of the operating state metric 30, and the predetermined state must then be adjusted accordingly to the maximum change in the change of the operating state metric 30.
[0052] To further improve the method, the concentricity may also be taken into account in a reference state of the electric machine 2 and taken into account when specifying the predetermined state 46. For example, during commissioning of a higher-level system using the electric machine 2, such a reference state may be assumed.
[0053] In principle, position information is recorded again in this reference state, but here as reference position information 52, from which the sensor angle position 34 is then determined again in the corresponding filter 32 in order to determine the reference state measure 54 in a subtractor-like reference state measure determination 56 similarly to the operating state measure 30. The reference state measure 54 is then plotted again in the recorder 38 similarly to the operating state measure 30 to form a reference state measure sequence 58, whereby a delayed reference state measure sequence 58' can optionally also be formed here via the buffer element 50.
[0054] However, in contrast to the case of monitoring the operating state measure 30, the evaluation device 60 now determines the predetermined state 46 as a basis for the monitoring 44 based on the reference state measure series 58 and optionally on the delayed reference state measure series 58′. In this way, inherent concentricity inaccuracies that are already present during the aforementioned commissioning can be taken into account and suppressed from the predetermined state.
[0055] In order to set the accuracy of the monitoring, the type of reference variable 62 of the evaluation device 60 can be specified for the predetermined state.
[0056] Use below Figure 4 and Figure 5 The effect of the method using the detector 3 in the case of operation of the motor 2 with and without concentricity inaccuracies is illustrated.
[0057] Figure 4 The operation of the motor 2 without concentricity inaccuracy is shown in FIG. Figure 4 3 shows the trajectory of the operating state measure 30 relative to the angular position 40 and thus shows the operating state measure series 42. For better classification, the predetermined state 46 is plotted relative to the angular position 40 using a dashed line.
[0058] exist Figure 4 As can be clearly seen in FIG. 4 , the operating condition metric series 42 always remains within the limits specified by the predetermined state 46, so that trouble-free operation without concentricity inaccuracies can be clearly distinguished from trouble-free operation, which is shown in FIG. Figure 5 The comparison is shown in FIG.
[0059] Reference numerals list
[0060] 2 Motor
[0061] 3 Detector
[0062] 10 Axis of rotation
[0063] 12 Stator
[0064] 14 Rotor
[0065] 16 Wear-resistant bearings
[0066] 18 Encoder ring
[0067] 20 Axial distance
[0068] 22. Printed Circuit Board
[0069] 24 Rotation angle distance
[0070] 26 Measuring sensors
[0071] 27 Rotation direction
[0072] 28 Work location information
[0073] 30 Work Status Measurement
[0074] 32 Filters
[0075] 34 Sensor angular position
[0076] 36 Work status measurement determination
[0077] 38 Recorder
[0078] 40 Angular position
[0079] 42 Work Status Measurement Series
[0080] 44 Monitoring Device
[0081] 46 Booking Status
[0082] 48 warning signs
[0083] 50 Buffer element
[0084] 52 Reference location information
[0085] 54 Reference state metrics
[0086] 56 Reference state measurement determination
[0087] 58' Reference State Metrics Series
[0088] 60 Evaluation Device
[0089] 58' Delayed Reference State Metric Series
Claims
1. A method for monitoring the concentricity of a rotor (14) rotating in a stator (12) about an axis of rotation (10) in an electric machine (2) using a position sensor (3), the position sensor having an encoder ring (18) and two measuring sensors (26), wherein: The measuring sensors (26) are located at a rotational angular distance (24) from one another when viewed about the rotation axis (10) and are arranged to each output a piece of position information relating to a rotational orientation (27) of the encoder ring (18) depending on an angular position (40) of the rotor (14) relative to the stator (12), the method comprising: - a working position detection step, in which, at the working angular position of the rotor (14) relative to the stator (12), in the working state of the motor (2), each measuring sensor (26) detects a piece of working position information (28); - an operating state metric determination step (36), in which an operating state metric (30) characterizing the distance between the two measuring sensors (26) is determined based on the acquired operating position information (28); and - a monitoring step (44) in which, if the operating condition metric (30) satisfies a predetermined condition (46), a concentricity error (48) is output.
2. The method according to claim 1, wherein: In the working state of the motor (2), the working position detection step and the working state metric determination step (36) are performed at different working angle positions (40) of the rotor (14) relative to the stator (12), and a working state metric series (42) is established relative to the different working angle positions (40), wherein the predetermined state (46) includes the maximum change of the working state metric (30) within the working state metric series (42).
3. The method according to claim 1 or 2, comprising: - a reference position detection step, in which, at a reference angular position of the rotor (14) relative to the stator (12), each measuring sensor (26) detects a piece of reference position information (52) in a reference state of the motor (2); - a reference state metric determination step (56), in which a reference state metric (54) characterizing the distance between the two measuring sensors (26) is determined based on the acquired reference position information (52); and - determining said predetermined state (46) based on said reference state metric (54).
4. The method according to claim 3, wherein: In the reference state of the motor (2), the reference position detection step and the reference state metric determination step (56) are performed at different reference angular positions (40) of the rotor (14) relative to the stator (12), and a reference state metric series (58) is established relative to the different reference angular positions (40), wherein the predetermined state (46) is determined based on the reference state metric series (58).
5. The method according to claim 4, wherein: The reference state metric (54) and / or the series of reference state metrics (58) are stored.
6. The method according to any one of the preceding claims 3 to 5, wherein: The reference state is part of a learning operation preceding the operating state, during which a rotor (14) of the electric machine (2) rotates in the stator (12).
7. A method according to any one of the preceding claims, wherein: The two measuring sensors (26) are arranged at a distance of between 45° and 135°, preferably between 75° and 105°, particularly preferably 90°.
8. A method according to any one of the preceding claims, wherein: The operating state metric (54) describes an angular offset of the two measuring sensors (26) about the rotation axis (10) in the operating state.
9. A control device designed to carry out the method as claimed in one of the preceding claims.
10. A detector (3) for an electric motor (2), wherein: The electric machine has a rotor (14) rotatable about a rotation axis (10) in a stator (12), and the detector comprises: - encoder ring (18); - two measuring sensors (26), wherein the measuring sensors (26) are located at a rotational angular distance (24) from one another when viewed about the rotation axis and are arranged to each output a piece of position information relating to the rotational orientation (27) of the encoder ring (18) depending on the angular position (40) of the rotor (14) relative to the stator (12); and - A control device as claimed in claim 9.