Analysis of the maximum finite time Lyapunov exponent in time domain using data from torso stability tests

WCU Author/Contributor (non-WCU co-authors, if there are any, appear on document)
Chaoke Dong (Creator)
Western Carolina University (WCU )
Web Site:
Martin Tanaka

Abstract: Low back pain (LBP) is a common health problem that affects most people during their life. The goal of this research is to track the dynamics of seated stability through the falling region and determine how the maximum finite time Lyapunov exponent (FTLE) changes over time. The FTLE describes how quickly two initially close points in state space diverge. Human torso stability tests were conducted using an unstable sitting apparatus capable of attaining large deflection angles. Angle data was collected using a gyroscopic sensor and Matlab was used to calculate the FTLE in the time domain. The analysis results for the Lyapunov exponent in the time domain were consistent with the results found in state space. Deterministic behavior of the dynamical system was also detected. A suite of parameters were investigated in the data analysis. The Lyapunov exponent was found to be sensitive to changes in evolution time but not sensitive to the cutoff frequency of the low pass filter when it was above 3.2 Hz. A key point of this research was to understand how the Lyapunov exponent changed with time as it approached a critical event. Tracking the Lyapunov exponent in the time domain may be a useful indicator to predict a future event. Moreover, this approach may be generalizable to other dynamic systems that have critical transitions. This research helps to better understand torso stability and build onto the foundation of knowledge to diagnose and prevent LBP.

Additional Information

Language: English
Date: 2015
Finite time Lyapunov exponent, Low back pain, Torso stability
Backache -- Prevention

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