This paper describes a trajectory generation technique for stair-ascent walking. The knee, hip and ankle joint trajectory during stair ascent are generated using mutually coupled, nonlinear oscillators. The parameters of the oscillators are tuned using the harmonic balance method, which converts the nonlinear differential equations to a set of algebraic equations. Fourier analysis of data generated by stair-ascent walking is performed to extract the amplitude and the phase of the dominant frequency components for each joint trajectory. The solution for the oscillator is assumed to be a sinusoidal wave and then by harmonic balance method the parameters of the oscillator are found. Each oscillator is responsible for generating a single frequency component with a specific phase and amplitude. The complete trajectory is obtained by summing the output of the oscillators that are relevant to one joint and the coupling maintains the phase relationship between the oscillators.
Afzal, T.; Wright, Andrew B.; and Iqbal, Kamran
"Trajectory Generation for Stair Ascent Walking using Rayleigh Oscillator,"
Journal of the Arkansas Academy of Science: Vol. 67
, Article 6.
Available at: http://scholarworks.uark.edu/jaas/vol67/iss1/6