Postural stability of wheeled mobile manipulators with flexible suspension considering tire friction model

The mobility requirements on a rough terrain make a suspended wheeled mobile robot (SWMR) with multiple dexterous manipulators an appropriate choice. In this study, dynamics modeling and stability appraisal of SWMRs will be discussed. First, based on Newton-Euler´s formulation for a chain of rigid bodies, the closed-form dynamics model of such complicated systems in three dimensional maneuvers is developed. To this end, a twenty two degree-of-freedom SWMR is considered as a benchmark system. The studied system includes both sprung and unsprung elements. Also, the developed model involves both ride and handling analysis. Considering pneumatic tires, Dugoff tire friction model is adopted to describe the longitudinal and lateral forces produced at the contact patch of the wheels. Then, using the obtained dynamics, the effect of frictional effects on postural stability of such systems will accurately be investigated. It is shown that dynamic balance of the system decreases as the friction between the base and the ground increases. Finally, the new dynamic tip-over Moment-Height Stability (MHS) measure will be exploited to vigorously investigate the dynamic balance of a SWMR even after toppling down.