Anti-singular control of a hybrid-motion vehicle and experimental validations for its applicability in micro-sized transportation scenarios

Ground vehicles are vital in modern transportation systems due to their mobility and accessibility. This paper focuses on how to utilize control techniques to achieve economical and efficient transportation at the micro-sized level. Our main goal is to achieve smooth and precise motion tracking for our hybrid-motion vehicle to further make it applicable for micro-sized transportation scenarios. To enhance the tracking precision of the Ackermann steering mode, we first propose a disturbance estimator design that provides knowledge of the model uncertainty within a fixed time. To avoid having excessively large steering angles when there is a lack of proper speed, a new auxiliary variable that describes the steering tendency is defined to handle input saturation when there is speed-steering coupling. The concept of steering singularity is then defined to illustrate when it is necessary to perform inter-mode switching. Adaptive algorithms are developed to quantify the steering singularity issue and provide smooth commands for Ackermann-differential transitions. To validate the control scheme’s capability in micro-sized transportation, hardware-in-the-loop experiments are conducted for transportation-related tasks including fixed-point tracking (cargo delivery), dual circles tracking (constant speed following for pedestrians and cyclists) and complex nonlinear trajectories (last-mile delivery in complex environments). The results demonstrate that the hybrid-motion vehicle can be a reliable part of micro-sized transportation, and provided insights for how to model the vehicle’s behavior in practice.