Leveling of the AMBLER Walking Machine: A Comparison of Methods

Abstract

For orthogonally-decoupled machines, such as the AMBLER, power efficiency is contingent upon keeping the body level. There are several ways of accomplishing this, which trade-off approximations of the complete phenomena versus simplicity of the implementation. In this report the effectiveness of four different strategies are evaluated for body attitude control. One of these uses vertical actuations to level the body ignoring the secondary geometric effects. Two alternate methods actuate only the vertical axes, but additionally utilize part of the horizontal kinematic information to calculate the required vertical displacements. Another method actuates both the horizontal and vertical joints in order to obtain ideally correct kinematic motion, but at the cost of higher energy expenditure. In this document the simulation of these methods and their implementation on the AMBLER are reported. This research shows that leveling methods that use only the vertical axes are most appropriate. The Simple Z-axes leveling method works satisfactorily to level using only six concurrent motions, ignoring the complexity of higher order kinematic calculations. The Z-axes method that is derived from the All-axes method has the consequence that the body drops when these equations are used to tilt the body. The Isoaltitude method performs slightly better than the Simple Z-axes method, by maintaining constant body height during both leveling and tilting maneuvers.