Analysis of Vertical Walking Force of Single Footstep

Abstract

The traditional vertical walking force model does not take account of the variations of intro-subject and inter-subject, this paper aims at analyzing the characteristics of vertical walking force of single footstep. Using a test platform, two single footstep traces are collected. Force shape pa rameters including characteristic time and shape amplitudes, as well as contact time and n ormalized impulse of single footstep are investigated. The contact time and normalized impulse are all fitted as functions of step frequency. Finally, based on the statistical results, a new concept equivalent force is put forward to describe the single footstep walking force. I ntroduction Interest ha s been aroused to investigate the dynamic loads due to walking because of excessive human-induced vibrations of footbridges (1, 2, 3). The traditional vertical walking force model is pe rfectly periodic and it i s represented as a sum of Fourier harmonics. However, this model ignores t he variability of successive footsteps in real walking. The left footstep and right footstep have different walking parameters from a long observation of human walking, while these differences can cause notable departure between real walking forces and perfectly periodic load s (4). The n arrow band randomness of real walking forces indicates that the old- fashioned model needs to be revised to meet the demands of designing and predicting in engineering (5). Hence, it is very necessary to investigate the single footstep walking force and obtain its characteristics. T he work in this paper is aimed at providing fundamental data and giving a basis to motivate the r esearch for human walking forces. The outline is as follows. Section 2 briefly describes the experimental measurements. In Section 3, the walking force shape parameters of single footstep, i ncluding characteristic time and shape amplitude, as well as contact time and normalized impulse are dealt with, the variability between continuous walking forces of single footsteps is presented. Finally a few inherent drawbacks of the experiment design i.e. reasons causing errors are discussed.