Modeling review of structures and locomotion systems for mobile robots: Four case studies

This paper reviews the mathematical models of four commonly encountered designs for wheeled mobile robots (WMR). These designs belong to two generic classes of wheeled robot structures: differential-drive and omnimobile. First, the two wheel differential-drive model is presented to show how zero turning radius is achieved with only bidirectional movement. Three particular designs are addressed: the popular two-active-fixed wheels and one-passive-caster wheel, a simple belt-drive, and sprocket-chain system. Next, the model for omnimoble robots with Swedish wheels is presented to illustrate holonomic omnidirectional motion. All four models are based on physical parameters easily measured and are useful to understand the internal dynamics of these WMR and to accurately visualize their motion in 2D environments. They can be therefore used as a practical reference to predict the accessibility of physical prototypes to selected places and to test different algorithms for control, path planning, guidance, and obstacle avoidance.