Variable Speed Machine Condition Analysis via Position-Based Decimation
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Solution Overview
Problem
Existing methods for condition monitoring of machines with rotating parts, particularly those with variable speeds, face challenges in accurately detecting mechanical wear or damage due to high noise levels and low signal amplitudes, leading to inadequate early warning systems for potential failures.
Innovation Solution
A system comprising a sensor that generates an analogue electric measurement signal based on mechanical vibrations, an analogue-to-digital converter, a position signal generator, and a speed value generator that interpolates speed values, combined with a decimator and evaluator to analyze the condition of the machine, reducing smearing and improving accuracy during acceleration phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a machine operates at variable speeds, then the machine can adapt to different working conditions and maintain productivity, but the accuracy of detecting mechanical wear or damage deteriorates due to noise and signal smearing
Solution Approach 1:
The system performs preliminary actions by recording both time sequences and position sequences before analysis, and by pre-calculating speed values through interpolation. This preparation allows the system to later decimate signals accurately even during variable speed operation, preventing signal smearing that would otherwise occur during acceleration or deceleration phases.
Solution Approach 2:
The system changes parameters by using position-based decimation instead of time-based decimation. By using the position sequence to determine sampling intervals rather than fixed time intervals, the system adapts the sampling rate to the actual rotational position, maintaining measurement precision regardless of speed variations.
2Productivity
If the sampling frequency is reduced through decimation, then the data processing load is decreased and productivity is improved, but the measurement precision deteriorates due to signal smearing during acceleration phases
Solution Approach 1:
The system changes from fixed time-based sampling to position-based sampling. The decimation process uses the recorded position sequence to determine when to sample, ensuring that samples are taken at consistent angular intervals regardless of the time between them. This eliminates signal smearing while still reducing data volume for efficient processing.
Solution Approach 2:
The system performs preliminary recording of position sequences and speed value calculations before the decimation process. This preliminary action provides the necessary information to perform position-based decimation accurately, allowing data reduction without loss of measurement precision.
3Measurement precision
If interpolation is used to calculate speed values, then the accuracy of speed measurement is improved during acceleration phases, but the device complexity increases
Solution Approach 1:
The system replaces complex mechanical speed sensing mechanisms with a computational approach. Instead of using additional mechanical sensors or complex hardware, the system uses a processor to perform interpolation calculations on recorded position sequences, achieving high measurement precision through software-based methods.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system enables precise detection of mechanical wear or damage in machines with rotating parts, even at variable speeds, by reducing noise and improving the accuracy of condition analysis, thus preventing unexpected breakdowns.
Implementation Method 1
a first sensor (10) adapted to generate an analogue electric measurement signal (SEA) dependent on mechanical vibrations (VMD) emanating from rotation of said part
Data Source
AI summary
An apparatus for analysing the condition of a machine having a part rotating with a speed of rotation (fROT), comprising: a first sensor (10) adapted to generate an analogue electric measurement signal (SEA) dependent on mechanical vibrations (VMD) emanating from rotation of said part; an analogue-to-digital converter (40, 44) adapted to sample said analogue electric measurement signal (SEA) at an initial sampling frequency (fs) so as to generate a digital measurement data signal (SMD, SENV) in response to said received analogue electric measurement signal (SEA); a device (420) for generating a position signal (Ep) having a sequence of position signal values (P(i)) for indicating momentary rotational positions of said rotating part; and a speed value generator (601) being adapted for recording a time sequence of said position signal values (P(i)) such that there are angular distances (delta-FIp1-p2, delta-FIp2-p3) and corresponding durations (delta-Tp1-p2; delta-Tp2-p3) between at least three consecutive position signals (P1, P2, P3) wherein the speed value generator (601) operates to establish at least two momentary speed values (VT1; VT2) based on said angular distances (delta-FIp1-p2, delta-FIp2-p3) and said corresponding durations (delta-Tp1-p2; delta-Tp2-p3), and wherein further momentary speed values for the rotational part (8) are established by interpolation between the at least two momentary speed values (VT1, VT2).