ABSTRACT
Objective To solve the problem in motion signal extraction due to nonstationarity.Methods The calf angular acceleration signal was taken as an example,and the time-frequency analysis was carried out by using Hilbert-Huang transform (HHT).Then,the empirical mode decomposition (EMD) of the signal was executed to obtain some intrinsic mode functions (IMFs),and then all or some intrinsic mode functions were subjected to a Hilbert transform to obtain Hilbert spectrum of the signal.Results In the mode of stomping,walking and falling,when the test-feet touched the ground,the energy was concentrated at the frequencies of 4 Hz,3 Hz and 2 Hz,and the time-frequency resolution was higher,and the information of these behaviors was mainly focused on the high-frequency components of the intrinsic mode functions.Conclusion The time-frequency characteristics of the human body calf angular acceleration signal can be applied to other kinematic parameters of the lower limbs in order to obtain the movement characteristics of the lower limbs.
ABSTRACT
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.
ABSTRACT
Objective:To provide a criterion for determining whether a mouse's health by analyzing the time-frequency local characteristics of nonlinear and unsteady mice blood spectrum signal.Methods: Collect the blood spectrum signal of the normal and liver damage mice by infrared spectrum method, then study the mice blood spectrum signal by Hilbert - huang transform method.Results: Initially formed criterion on judge whether there is hepatic injury in mice signal.Conclusion: Analysis method based on HHT in mice blood signal spectrum analysis can accurately determine the health of the mice and it provides a new method of analysis for noninvasive blood tests.
ABSTRACT
Objective Based on the analysis of time domain of heart sound with envelop to extract the envelope character of heart sounds.Methods The envelope extraction of heart sounds based on Hilbert-Huang Transform was given.Firstly,the original heart sounds signal was preprocessed by Huang Transform.Secondly,the envelope of heart sounds was got with Hilbert Transform.Results The first heart sound and the second heart sound were extracted,and all kinds of characters in time domain of heart sound were acquired more accurately.Conclusion The envelope of heart sound is extracted correctly.The foundation for further analysis of heart sounds is established.