Design and locomotion analysis of two kinds of rolling expandable mobile linkages with a single degree of freedom

This study presents two kinds of rolling robots that are able to roll by deforming their outer shapes with a single degree of freedom.Each robot is an essential multi-loop planar expandable linkage constructed by a concave outer loop and several inner parallelogram loops.In this study,the mechanical design of the robots is introduced.Dynamic rolling process is further analyzed on the basis of zero moment point method,and a morphing strategy is proposed to guarantee a stable dynamic rolling process.A novel passive rolling locomotion is also developed,which enables the robots to roll and stand on a slope.To verify the design,two prototypes are manufactured,wherein the dynamic and passive rolling locomotion are carried out.