A numerical algorithm for optimal selection of the driving mechanisms for ExoReha exoskeleton

Exoskeleton-aided motor physiotherapy raised the need to reduce the bulkiness and mass of the designed devices. It is typically realised based on an engineer's experience or numerical optimisation. However, these rarely consider an appropriate selection of drives. The paper presents the methodology of an algorithm for optimal search for driving systems. The method was initially designed for the EXOTIC exoskeleton from Aalborg University but remains universal for structures with different kinematic chains and designs. This paper includes a case study of selecting the drives with gearboxes for the ExoReha exoskeleton from ŁUKASIEWICZ Research Network – Industrial Research Institute for Automation and Measurements PIAP. The method selects the best combination from the defined database based on the inverse dynamics computation with the multibody model of the device. The selection was realised for fourteen different cases with different reduction priorities. The outcomes enabled a reduction of mass even by 85% and dimensions by up to 77.5%. Furthermore, it was possible to add two additional drives into passive joints while reducing the total mass of the driving systems by 68.5%. However, the selected drives come from different manufacturers, which can cause problems in the control of the exoskeleton. Moreover, their combination often limits the backdriveability of the systems. Hence, the possible modifications will not be implemented before redesigning the ExoReha exoskeleton into a fully wearable device.