Collinear mecanum drive: modelling, analysis, partial feedback linearisation, and nonlinear control

The Collinear Mecanum Drive (CMD) is a novel robot locomotion system, capable of generating omnidirectional motion whilst simultaneously dynamically balancing, achieved using a collinear arrangement of three or more Mecanum wheels. The CMD has a significantly thinner ground footprint than existing omnidirectional locomotion methods, which does not need to be enlarged with increasing robot height as to avoid toppling during acceleration or external disturbance. This combination of omnidirectional manoeuvrability and a thin ground footprint allows for the creation of tall robots that are able to navigate through much narrower gaps between obstacles than existing omnidirectional locomotion methods. This allows for greater manoeuvrability in confined and cluttered environments, such as that encountered in the personal service and automated warehousing robotics sectors.

This article derives the kinematics and dynamics models of the CMD, analyses controllability and accessibility, and determines the degree to which a CMD can be linearised by feedback. A partial feedback linearisation is then performed, and three practically useful nonlinear controllers are derived using a backstepping design approach, all with convergence and stability guarantees for the fully-coupled nonlinear model. These are demonstrated both in simulation and on a real-world CMD experimental prototype.