DE102020124933A1 - Method of monitoring a wave - Google Patents

Abstract

The invention relates to a method for monitoring a shaft equipped with a rotary encoder, the rotary encoder detecting a rotation of the shaft mounted in at least one rotary bearing. The method includes acquiring sine and cosine signals of the rotary encoder, deriving a quantity to be analyzed from the sine and cosine signals, defining size tolerances, analyzing the quantity during operation of the rotary encoder, outputting a signal when analyzing the quantity defined size tolerances have been exceeded. In order to provide a simplified method with which a shaft equipped with a rotary encoder can be monitored, it is proposed that the analysis of the size includes a frequency analysis of the size values per defined time or signal unit and that anomalies in the rotary bearing are detected from the frequencies determined, with a Anomaly exists when a defined size tolerance is exceeded.

Description

The invention relates to a method for monitoring a shaft equipped with a rotary encoder, the rotary encoder detecting a rotation of the shaft mounted in at least one rotary bearing, with the steps: detecting sine and cosine signals of the rotary encoder, deriving a variable to be analyzed from the sine and cosine signals; define size tolerances; Analyzing the size in operation of the rotary encoder; Outputting a signal when analyzing the size has revealed that defined size tolerances are exceeded.

Such generic methods are for example from DE 102010051873 A1 famous. The correctness of the sine and cosine signals of a rotary encoder is monitored using vector length monitoring. The rotary encoder itself is thus monitored. In order to monitor functions or events outside of the rotary encoder, separate sensors are provided according to the prior art. For example, after EP 1597714 B1 separate acceleration sensors are provided with which unwanted movements such as shock or vibrations can be detected and monitored. Such monitoring is necessary, for example, to uncover bearing damage to a shaft bearing or the like.

Proceeding from this prior art, it is the object of the invention to provide a simplified method with which a shaft equipped with a rotary encoder can be monitored.

This object is achieved by a method having the features of claim 1.

• - Erfassen von Sinus- und Kosinussignalen des Drehgebers;
• - Ableiten einer zu analysierenden Größe aus den Sinus- und Kosinussignalen;
• - Definieren von Größentoleranzen;
• - Analysieren der Größe im Betrieb des Drehgebers;
• - Ausgeben eines Signals, wenn das Analysieren der Größe eine Überschreitung von definierten Größentoleranzen ergeben hat, wobei erfindungsgemäß
• - das Analysieren der Größe eine Frequenzanalyse der Größenwerte pro definierter Zeit- oder Signaleinheit umfasst und aus den ermittelten Frequenzen Anomalien des Drehlagers erkannt werden, wobei eine Anomalie vorliegt, wenn eine definierte Größentoleranz überschritten ist.

The method according to the invention for monitoring a shaft equipped with a rotary encoder, with the rotary encoder detecting a rotation of the shaft mounted in at least one rotary bearing, comprises the following steps:

• - Acquisition of sine and cosine signals of the rotary encoder;
• - Deriving a quantity to be analyzed from the sine and cosine signals;
• - define size tolerances;
• - Analyzing the size in operation of the rotary encoder;
• - Outputting a signal when analyzing the size has shown that defined size tolerances are exceeded, according to the invention
• - the analysis of the size includes a frequency analysis of the size values per defined time or signal unit and anomalies of the rotary bearing are detected from the determined frequencies, with an anomaly being present when a defined size tolerance is exceeded.

The essential advantage of the invention is that no additional components such as acceleration sensors are necessary and the analysis is based solely on the evaluation of the sine and cosine signals of the rotary encoder. The inventors have found that a frequency analysis of the size of the raw values of the encoder signals can be used to detect bearing defects in the rotary bearing of the shaft, because these defects induce periodic changes that are reflected in the raw signals and are revealed by the frequency analysis. This procedure is not only cost-efficient, but also saves installation space for the otherwise additional components, parts and sensors.

It is particularly advantageous and simple if the size is a vector length of a vector formed from the sine and cosine signals and the size tolerances are vector tolerances. Vector lengths are already used in known encoders to monitor the sine and cosine signals. These existing vector lengths can then also be used for the method according to the invention.

Advantageously, when an anomaly is detected, a bearing defect is inferred and the signal is output as an error signal, since anomalies in a rotary bearing are normally based on bearing errors.

In a development of the invention, the size tolerances include tolerance values for frequency values from the frequency analysis. A found frequency is therefore checked to see whether it is within a certain tolerance or not. A wide variety of frequency analysis methods can be used to determine the anomalies in the frequency bands, for example FFT (Fast Fourrier Transform) or similar algorithms, including their pre- and post-processing methods. Depending on this, the error signal is output.

In a development of the invention, the classic vector length monitoring, ie the absolute values of the vector length, is retained, so that the rotary encoder signals can be checked in a known manner.

The size or vector length is advantageously recorded several times per signal period.

In a development of the invention, the defined time unit corresponds to a communication cycle a cyclic communication between the rotary encoder and an evaluation unit. The evaluation unit does not have to be provided in the rotary encoder, but is usually provided in a higher-level controller.

In a further embodiment, the defined time unit corresponds to the sampling cycle of a cyclic sampling of the sine and cosine signals.

The method according to the invention is advantageously carried out on an integrated circuit which also generates the sine and cosine signals, so that no additional installation space is required to implement the invention.

In a further development of the invention, several pivot bearings located on the shaft are monitored simultaneously and/or the pivot bearing of the rotary encoder itself is monitored.

• 1 ein Antriebssystem mit Motor, Motor-Feedback-System und Steuerung;
• 2 Sinussignal des Motor-Feedback-System;
• 3 Kosinussignal des Motor-Feedback-System;
• 4 Vektordarstellung der Signale des Motor-Feedback-System;
• 5 ein Ablaufdiagramm des erfindungsgemäßen Verfahrens;
• 6 eine Welle, mit Drehgeber und Steuerung.

The invention is explained in detail below using an exemplary embodiment with reference to the drawing. Show in the drawing:

• 1 a propulsion system with motor, motor feedback system and controller;
• 2 Sine signal of the motor feedback system;
• 3 cosine signal of the motor feedback system;
• 4 Vector representation of the signals of the motor feedback system;
• 5 a flowchart of the method according to the invention;
• 6 a shaft, with rotary encoder and controller.

The method according to the invention is used to monitor any shaft 18 whose rotation is detected with a rotary encoder 12 ( 6 ). The shaft 18 has at least one rotary bearing 20, which can also be located in the encoder 12 itself. The rotary encoder 12 is connected to an evaluation unit 16 .

The method according to the invention can also be applied to a drive system and is then used to monitor a drive system 10, which includes a motor feedback system 12, a motor 14 and a motor controller 16 ( 1 ). The motor 14 is used to drive a shaft 18 whose rotation is detected by the motor feedback system 12 . The shaft 18 has at least one pivot bearing 20, which can also be located in the motor feedback system 12 itself.

The rotary encoder 12 is constructed in a known manner and is used, for example, to detect changes in angle, particularly in automation technology. Particularly high accuracies can be achieved with so-called sine encoders, which typically have two tracks and deliver a corresponding sine and cosine signal as output signals, ie two identical sine signals that are phase-shifted by 90°, which are generated when the shaft 18 coupled to the rotary encoder 12 rotates will. Such sine and cosine signals are in the 2 and 3 with the reference numerals 50 and 52 as an example and result, for example, in an optical motor feedback system due to periodic markings of a material measure that is scanned optically.

The sine and cosine signals 50 and 52 of the motor feedback system 12 are recorded and evaluated by a signal evaluation unit 22 . Capture is in 5 indicated with step 100. The signal evaluation unit 22 can be an integral part of the engine control 16 . In most cases, however, the signal evaluation unit 22 is an integral part of the rotary encoder 12 itself. This can be the vector length L of a two-dimensional vector 54 (step 102 in 5 ) be. Other sizes up to the sine and cosine signals themselves are conceivable. In the further course of this description, only the example with the vector 54 is described for better illustration. However, the method described with vector length L as variable L can also be used for a different variable.

If a vector 54 is formed, the vectorial sum of the sine and cosine signals 50 and 52 is referred to as the vector length L of the vector 54, whose x and y components are formed by the amplitude of the sine and cosine signals.

The vector length L can be used in a known manner to check the operation of the motor feedback system 12 by examining the sine and cosine signals 50 and 52, for example by defining vector tolerances within which the vector can move. This should start with step 104 in 5 be shown, where the vector tolerances are denoted by ΔL. A vector property can be the vector length L, which does not change in the ideal motor feedback system with ideal sine and cosine signals and in the real case must be at least within a defined tolerance range ΔL. In operation, the vector length L is then analyzed and an error signal is output (step 110 from 5 ) when analyzing the vector length L an overrun of the defined vector length tolerances ΔL (step 106).

The invention now proceeds in the analysis of the vector length L. Specifically, it is provided that the analysis of the vector length L includes a frequency analysis of the vector length values per defined time unit. This takes place in a step 108. The defined time unit can correspond to a cycle time, wherein the cycle time can correspond to a communication cycle in a communication between the rotary encoder 12 and the evaluation unit (e.g. motor control) 16, within which position values and the like from the rotary encoder 12 or the signal evaluation unit 22 be transmitted to the evaluation unit (e.g. engine control)16.

Ideally, the vector length will not exhibit any oscillations or changes during trouble-free operation. In the event of a malfunction, for example if the system is subjected to a mechanical shock or the rotary bearing 20 is defective, this will affect the sine and cosine signals 50 and 52 and thus the vector length L. The invention provides for detecting this , that a frequency analysis of the vector length L takes place. This can be, for example, an FFT analysis (Fast Fourrier Transform) or also an OTF (Order Tracking Filter) or comparable analysis methods.

Bearing defects of the rotary bearing 20 can be recognized from the determined frequencies, because bearing defects will have a periodic effect and thus lead to periodic changes in the vector length L. If determined frequencies deviate too much from permissible frequencies, this is interpreted and recognized as a bearing defect of pivot bearing 20 and an error signal is output. The permissible frequencies are the frequencies that exist in the case of no interference. These can be determined beforehand in a learning process, for example.

Deviations of the ascertained frequencies from the permissible frequencies are determined by comparison with frequency tolerance values Δf in step 108. The comparison mechanisms can also turn out to be very complex. A visualization of the data determined in this way is also conceivable. In addition, the pure forwarding of the frequency components of the vector length to the evaluation unit 16 or additional computing units is also conceivable in order to carry out the analysis of this data and its visualization there.

In order to be able to reliably detect oscillations of the vector length L with the frequency analysis, it is preferably provided that the vector length is detected several times per signal period. The sampling rate must be correspondingly high.

The angular position is determined by rotary encoder 12 and the sine and cosine signals 50 and 52 are evaluated preferably on an integrated circuit, which can be provided in rotary encoder 12 itself or in the evaluation unit (e.g. a motor controller) 16.

QUOTES INCLUDED IN DESCRIPTION

This list of the documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 102010051873 A1 [0002]
• EP 1597714 B1 [0002]

Claims (13)

Method for monitoring a shaft (18) equipped with a rotary encoder (12), the rotary encoder (12) detecting a rotation of the shaft (18) mounted in at least one rotary bearing (20), with the steps: - detecting sine and cosine signals (50 and 52) of the encoder (12); - Deriving a variable (L) to be analyzed from the sine and cosine signals (50 and 52); - define size tolerances (ΔL); - Analyzing the quantity (L) in operation of the rotary encoder; - Outputting a signal if the analysis of the variable (L) has revealed that defined tolerances (ΔL) are exceeded, characterized in that - the analysis of the variable (L) includes a frequency analysis of the variable values per defined time or signal unit and from the determined frequencies anomalies of the pivot bearing (20) are detected, with an anomaly being present when a defined size tolerance (ΔL) is exceeded. procedure after claim 1 , characterized in that the quantity is a vector length of a vector (54) formed from the sine and cosine signals (50 and 52). procedure after claim 1 , characterized in that when a bearing defect is detected, the signal, in particular as an error signal, is output. Method according to one of the preceding claims, characterized in that the anomalies are detected in the frequency bands by means of frequency analyses, for example FFT or similar algorithms, including pre- and post-processing methods. Method according to one of the preceding claims, characterized in that the size tolerances include tolerance values for frequency values and the error signal is output if the tolerances are exceeded by the determined frequencies. Method according to one of the preceding claims, characterized in that the absolute values of the variable (L) are monitored. Method according to one of the preceding claims, characterized in that the variable is recorded several times per signal period. Method according to one of the preceding claims, characterized in that the defined time unit corresponds to a communication cycle of a cyclical communication between a motor feedback system and a motor controller. Method according to one of the preceding claims, characterized in that the defined time unit corresponds to a communication cycle of a cyclical communication between the rotary encoder and an evaluation unit. Method according to one of the preceding claims, characterized in that the defined time unit corresponds to the sampling cycle of a cyclic sampling of the sine and cosine signals. Method according to one of the preceding claims, characterized in that it is carried out on an integrated circuit which also generates the sine and cosine signals. Method according to one of the preceding claims, characterized in that several pivot bearings located on the shaft are monitored. Method according to one of the preceding claims, characterized in that the rotary bearing of the rotary encoder (12) is monitored.

Images