Comparison of point foot, collisional and smooth rolling contact models on the bifurcations and stability of bipedal walking. Issue 3 (3rd May 2016)

• Record Type: Journal Article
• Authors: Charles, W. G.; Mahmoodi, P.; Ransing, R. S.; Sazonov, I.; Friswell, M. I.
• Is Part Of: Revue Européenne de mécanique numérique. Volume 25:Issue 3(2016)
• Page Start: 273
• Page End: 293
• Publication Date: 2016-05-03
• Subjects: Passive walking -- gait analysis -- roll-over shape -- prosthetic foot -- foot contact -- bifurcation diagrams -- basin of attraction; Engineering mathematics -- Periodicals; Mechanics -- Data processing -- Periodicals; Finite element method -- Periodicals; Mechanics -- Mathematical models -- Periodicals; Engineering -- Statistical methods -- Periodicals; 621.05
• DOI: 10.1080/17797179.2016.1191122
• Languages: English
• ISSNs: 1779-7179

Abstract

Abstract : Traditional biped walkers based on passive dynamic walking usually have flat or circular feet. This foot contact may be modelled with an effective rocker – represented as a roll-over shape – to describe the function of the knee–ankle–foot complex in human ambulation. Mahmoodi et al. has represented this roll-over shape as a polygon with a discretised set of collisions. In this paper point foot, collisional and smooth rolling contact models are compared. An approach based on the Lagrangian mechanics is used to formulate the equations for the swing phase that conserves mechanical energy. Qualitative insight can be gained by studying the bifurcation diagrams of gait descriptors such as average velocity, step period, mechanical energy and inter-leg angle for different gain and length values for the feet, as well as different mass and length ratios. The results from the three approaches are compared and discussed. In the case of a rolling disk, the collisional contact model gives a negligible energy loss; incorporated into the double inverted pendulum system, however, reveals much greater errors. This research is not only useful for understanding the stability of bipedal walking, but also for the design of rehabilitative devices such as prosthetic feet and orthoses.