Enhancive Robotic Exoskeleton Design Methodology Based on Link Cross-section Geometry and Length Optimization for Specific Tasks

The use of exoskeletons can aid in the performance of tasks by adding strength and structural support to the human body. The usage of enhancive exoskeletons lies within search and rescue operations, heavy material handling, aiding daily activities, muscle regeneration and control of tele operated robots. The classification of exoskeletons can be made based on the purpose, control strategy and structural design of the exoskeleton; Enhancive, Assistive, Rehabilitation and Telecommunication and Force Feedback Exoskeletons.
The research shows that there is a gap in exoskeleton design methodologies which take into consideration a wider span of human motions. Specifically optimal design of the exoskeleton’s link lengths for specific tasks considering the power consumption.
The research presents the development of a design methodology for designing optimally exoskeletons to perform given tasks. By obtaining motion capture data of motions that the exoskeleton is expected to perform, computer models can be built which are faithful to the motions.
Two motions are used to verify the design methodology, ‘Object Lifting’, using predominantly the legs, and ‘Object Raising’ using predominantly the arms. The model for the exoskeleton with a rigid back is developed and it is found that the rigid back will significantly alter the hip and shoulder trajectories of the exoskeleton in comparison to the humans, when performing the same motions. The motion data of the markers used to capture data is incorporated in geometric optimizations of the rigid back structure obtain the smallest shape for the exoskeleton back structure. Furthermore the link cross-sections are optimized for minimum mass. In comparing hollow and solid cylinder links it is found that for the required external load of 90 kg, the effects of the links masses are negligible on joint torques.
Link lengths are also optimized to obtain minimum power consumption during motions. It is found that for ‘Object Lifting’ motion, the ideal leg structure is one with longer thigh and shorter shin; and for ‘Object Raising’ motion the ideal arm structure is one with longer upper arms and shorter forearms.
The work demonstrates that the optimization for the exoskeleton link geometric properties with respect to given motions is needed in order to obtain the most efficient design.