Comparing passive walker simulators in Matlab and Adams

This article presents a few different methods to present a passive walker model in Adams MD R3 software and compares their simulation results to a walker model built in Matlab software. The discontinuous Matlab simulator applies manually entered mathematical equations to describe system dynamics while the Adams simulation software creates the dynamic models automatically. In the Adams simulator we apply a few different methods to present the walker models. In the first case the Adams model is built with continuous equations to describe contact events. This is in contrast to the Matlab model where these events are discontinuous. In the second case the Adams model is discontinuous applying a scripted simulation and discontinuous motion constraints. A special attention in this article is paid for modeling of knee-locks and foot contacts in the Adams simulation environment. In further experiments the Adams model combines continuous and discontinuous models for the contact events. The simulation results show that each model behaves differently and parameter tuning is needed to make each of them walk. The Matlab model and the Adams models seem to have a different dynamic response to the knee-lock event. It is not possible to completely repeat the Matlab simulation results in Adams. Reason for this is not currently known and deserves further studies. During the heelstrike event either a two-link model or a three-link model of the walker can be applied, although the general convention applies the two-link model only. The three link model at the time of heel-strike event can be made to walk passively but its applicability in practice requires further studies.