Analysis of translational positioning of unit loads by directionally-oriented friction force fields

The objective of this study was numerical simulation and experimental examination of the process of translational positioning of a stream of unit loads (i.e. postal parcels) transported on conveyors. A system of two inversely-oriented fields of friction forces was used to perform the task of load positioning. In numerical investigations, one applied theoretical description of the positioning process based on the Karnopp's model of static friction and the dynamic friction model of LuGre. In the Karnopp's model, two classic friction coefficients were used (based on one or two parameters, respectively) and a nonlinear coefficient defined by a B-spline curve of third order (determined based on experimental results). The results of numerical investigation were verified by experiments, which consisted in translating the objects by a system of two inversely-driven belts. The analyses of numerical and experimental results indicated that the effectiveness of the positioning process is mostly influenced by nonlinearity of friction coefficient of the transported loads.