Benchmark of advanced structural materials for lightweight design of industrial robots

Market push for higher energy efficiency, lower total automation cost and safer automation solution has driven the lightweight design of industrial robot manipulators. Advanced structural materials like optimally designed carbon fiber reinforced plastics (CFRP) and aluminium tubes are therefore gaining increased use in achieving the lightweight design of industrial robots. A sophisticated benchmark investigation between CFRP and aluminium robot arms based on structural stiffness (flexural/bending and torsional), tube thickness and material weight is presented. The benchmark is conducted based on simulations using analytical stiffness models for CFRP and aluminium tubes. The benchmark results are presented in graphs where flexural and torsional stiffness are plotted as functions of fiber angle. For the purpose of comparison, the corresponding flexural and torsional stiffness of aluminium tubes are also presented in the same graph. Availability of this type of stiffness curves gives design engineers a full visual design space of fiber angle of CFRP tubes in comparison to aluminium tubes, in terms of both flexural and torsional stiffness. In total, six different benchmark case studies are conducted using the developed methodology and proposed stiffness curves. A quantitative design benchmark between CFRP and aluminium tubes is achieved based on the trade-offs among fiber angle, fiber E-modulus specifically, structural tube weight and design compactness represented by the tube thickness. For example, results of one case study disclose that when a fiber angle of about 22 degrees of the medium E-modulus fibers is chosen, the CFRP tube of the same mass as its aluminium counterpart may achieve a 200% increase in the torsional stiffness and more than 250% increase in flexural stiffness.