Discom TasAlyser

The TasAlyser Measurement Program

Tas system in an end-of-line test environment

Tas system in an end-of-line test environment

The TasAlyser measurement program executes on the Discom measurement PC in combination with a TAS08 data acquisition frontend .

The frontend supplies a data stream of sensor information from accelerometers or microphones in combination with speed data or torque signals. A typical transmission application often uses one accelerometer and one speed signal.

Moreover, the TasAlyser communicates with the test stand to synchronize the test software with the test stand operation and to signal back the result of the test.

Other components of the Rotas suite can be installed on the test computer as well but are often operated in a server environment for the control of a line consisting of several test stands.

Revolution Synchronous Order Analysis

Order spectra of several rotors

Order spectra of several rotors

The TasAlyser application analyses the time domain signals from rotating parts via an revolution synchronous order analysis. This analysis is based on a highly accurate and efficient time-domain resampling algorithm, that tracks the speed of individual rotors by one or several speed inputs via a kinematic model that is supplied by the parameter database.

Order synchronous spectra have a much higher spectral resolution than their 'standard' non-synchronous counterpart, giving rise to unequaled details for gear error detection like non-uniform shapes, pitch errors and surface waviness. Using the resampled time domain signals, the presence of nicks can be tracked down to the individual part.


Separation of rotor signal components

Separation of rotor signal components

For this detailed part analysis, often a single accelerometer is sufficient. For larger assemblies several accelerometers, sometimes in conjunction with microphones, can be used. The key ingredient to all that part-specific error analysis is still the time domain signal separation due to synchronous resampling based on the kinematic model. The error analysis can then pinpoint the kind of mechanical error right to the part involved like "Runout final drive pinion".

In addition to the synchronously analyzed signals, the application also adds overall spectra, the so-called Mix signals, to the analysis. These spectra are necessary to detect bearing noise and spectral components from other noise sources than rotors. Signal processing and analysis also includes order tracking, spectrograms, modulation analysis, gear shift force analysis, and a variety of post-processing algorithms that further evaluate tracks and spectra.

Analysis and Evaluation

The Mosaic View: Critical measurement values on a glance

The Mosaic View: Critical measurement values on a glance

Starting with revolution synchronous time domain signals and order spectra, the TasAlyser prepares a set of indicators for every rotor and for the assembly as a whole. These indicators include order spectra, order tracks, Crest and Kurtosis values, the modulation content as well as the track of these single values versus a test ramp.

All this indicators can be evaluated against an individual limit, which is inherently self-learned. Every indicator has its own reject code that produces a unique error text when it limit is violated.

Self-learned limits from production measurements

Self-learned limits from production measurements

In order to specify such a variety of limits, Rotas combines self-learning with the ability of fixed limits. It is often practical to evaluate the majority of the indicators against a self-learned limit and introduce fixed limits for quantities, that are indispensible for a correct evaluation as they have a known vehicle correlation or have known limit ranges like Crest values where the limit is in the range of 10 to 16, depending on the type of assembly and the quality of the test stand.

The WebPal application gives you an easy access to single value statistics and lets you find fixed limits that are consistent with an expected reject rate and often occurring test stand differences. These limits are then transferred into the parameter database.

A TasAlyser screen shot while performing a test

A TasAlyser screen shot while performing a test

During a test run, the operator is presented with a display of the on-going test sequence. In addition to real-time spectra and time domain graphs and speed indicators, the good/reject status of the current unit is signaled by a color coded 'street light' indicator. Reject messages are shown in a separate window.