Title :
Frequency analysis of inertial sensor data for measuring toe clearance
Author :
Lai, Daniel T H ; Begg, Rezaul ; Charry, Edgar ; Palaniswami, M.
Author_Institution :
Centre for Ageing, Victoria Univ., Melbourne, VIC
Abstract :
The use of sensors in studies of human movement and gait is now fast gaining attention as a promising alternative to video capture systems in gait laboratories. Inertial sensors such as accelerometers and gyroscopes have been deployed to detect acceleration and angular velocities of body landmarks, from which secondary quantities such as velocity, displacement and joint angles could be inferred. The major challenge with secondary quantity derivation has been the cumulative errors arising from the integration used. While this has often been attributed to sensor measurement errors, quantification of these errors have so far been limited. In this paper, we performed frequency analysis of accelerometer and gyroscope signals to investigate the effect of sensor errors on the frequency components in motion measurements. We employ the Fast Fourier Transform (FFT) to obtain the Fourier frequency spectra of the inertial sensor signals. Comparisons were made against the frequency spectra of the same signals obtained from the Optotrak video capture system. Our analysis revealed that sensor signals contained a large DC signal which could be filtered out using a bandpass Butterworth filter with a 1-20Hz passband. This allowed us to obtain better estimates of toe displacement data without the use of strapdown integration techniques. It was also discovered that inertial sensors possessed low frequency errors which co-existed in the frequency band of gait motion making them difficult to remove with static filters. Future work will focus on adaptive filtering methods to detect and remove these sensor errors in an effort to improve displacement measurements.
Keywords :
Butterworth filters; accelerometers; biomedical measurement; distance measurement; error analysis; fast Fourier transforms; gait analysis; gyroscopes; medical signal processing; sensors; FFT; Fourier frequency spectra; Optotrak video capture system; acceleration measurement; accelerometer signal frequency analysis; accelerometers; angular velocity measurement; bandpass Butterworth filter; cumulative errors; fast Fourier transform; frequency 1 Hz to 20 Hz; gait analysis; gyroscope signal frequency analysis; gyroscopes; human motion analysis; inertial sensor data frequency analysis; motion measurement frequency components; secondary quantity derivation; sensor error effects; strapdown integration techniques; toe clearance measurement; Acceleration; Accelerometers; Angular velocity; Band pass filters; Frequency measurement; Gyroscopes; Laboratories; Sensor phenomena and characterization; Sensor systems; Signal analysis;
Conference_Titel :
Intelligent Sensors, Sensor Networks and Information Processing, 2008. ISSNIP 2008. International Conference on
Conference_Location :
Sydney, NSW
Print_ISBN :
978-1-4244-3822-8
Electronic_ISBN :
978-1-4244-2957-8
DOI :
10.1109/ISSNIP.2008.4762004