RESUMO
Objective To propose a method for analyzing the hip joint signals during human walking based on Hilbert-Huang transform (HHT) method and verify its feasibility. Methods First, the hip joint angles of one healthy subject were measured by using the hip joint measuring platform composed of acceleration sensors and gyroscopes. Second, all intrinsic mode functions (IMFs) at different scales, which could be further analyzed and combined, were obtained by applying the ensemble empirical mode decomposition (EEMD) to original signals. Finally, the Hilbert spectrum of original signals were plotted and analyzed. Results The signals representing different motion modes as well as gait characteristics indicated by rotating track of the hip joint were obtained. The Hilbert spectrum could show the intra-wave frequency modulation in the main motion mode and the characteristics of walking frequencies. Conclusions This method can be used in rehabilitation and treatment of patients with gait diseases. By using this method, the characteristic signals of the hip joints at different frequency scales can be effectively decomposed, and the post-processing signals can be filtered and centrally corrected, so as to adaptively analyze gait signals of the patients.
RESUMO
Los potenciales evocados auditivos del tronco cerebral (PEATC) son frecuentemente usados para fines diagnósticos; sin embargo, su procesamiento se hace difícil porque están inmersos en una gran cantidad de ruido proveniente no solo de fuentes externas sino también fisiológicas. Hasta ahora el método más utilizado y aceptado para obtener un registro confiable es la promediación coherente, aunque presenta algunos inconvenientes. La descomposición modal empírica (EMD) es una técnica relativamente nueva que se usa para el procesamiento de señales no estacionarias como la mayoría de señales fisiológicas. Este método separa una señal, extrayendo la energía asociada a diferentes escalas de tiempo intrínsecas, en una suma finita de modos oscilatorios. El propósito de este trabajo fue evaluar la EMD como una herramienta para mejorar el desempeño de la promediación coherente de PEATC buscando reducir la cantidad de épocas necesarias para obtener un registro confiable. Para tal fin se analizó la reconstrucción de ocho registros usando solamente los modos 2, 3 y 4 resultantes de la EMD, los estudios determinaron que una reconstrucción de 800 épocas es aceptable.
The brainstem auditory evoked potentials (BAEPs) are commonly used for diagnostic purposes; however, processing becomes difficult because they are immersed in a large amount of noise coming not only from external sources but also from other physiological sources. So far the most widely used and accepted method to obtain reliable recording is the coherent averaging, but this type of processing presents some drawbacks. The empirical mode decomposition (EMD) is a relatively new technique which is used for processing of non-stationary signal like almost physiological signals. This method separates a signal, xextracting the energy associated with various intrinsic time scales, into a finite set of oscillatory modes. The purpose of the study was to asssess the EMD as a tool for improving the performance of the averaging coherent BAEPs seeking to reduce the amount of epochs needed to obtain a reliable register. To this end, we have analyzed the reconstruction of eight registers using only modes 2, 3 and 4 resulting from the EMD, the studies found that a reconstruction of 800 epochs is acceptable.