Introduction
Achieving high productivity is of main concern to the cost of the NDE process, especially in the aircraft manufacturing industry applications where large parts have to be inspected. To that purpose, systems with multiple channel configurations, driven by high speed scanning robots are frequently used (automated NDE). Usually, C-scan images are formed from the unprocessed signals, which allows a preliminary flaw assessment. This way it has been feasible to reach high inspection rates (several square meters per hour), with a good spatial resolution.
On the other hand, NDE is a field that can take advantage from the numerous Digital Signal Processing (DSP) algorithms developed over the years [1]. However, in the context of automated NDE, speed constraints have prevented the widespread use of these techniques. Furthermore, the huge data volume produced by the inspection process itself, makes the recording and post-processing of signals an impractical issue. The only valid alternative to this situation is to carry out DSP functions on the fly, simultaneously with the scanning process.
This paper addresses the subject of DSP in the hard real-time context of automated NDE by means of a hardware-based approach: the SENDAS concept. SENDAS (which stands for the Spanish "Sistema para Evaluación No Destructiva de Arquitectura Segmentada"), is a pipeline of hardware processors or Processing Modules (PM), specialized in functions relevant to the NDE applications. All the PMs configured in the pipeline perform concurrently at a fixed speed of 10 MS/s, which allow for real-time processing in most applications. SENDAS performance is evaluated by means of a set of experiments over a thick CFRP composite test piece, involving high dynamic range DAC amplification, digitalization, non linear spatial filtering for EMI noise cancellation, deconvolution, digital envelope extraction and multigated - multipeak detection.
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