A functional analysis of some multi-bar linkage mechanisms in animals

• Main Author: Wang, Jiao
• Published: University of Bristol 2013
• Subjects: 591.5
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.658570

This thesis presents a functional analysis of some multi-bar linkage mechanisms in animals. In particular it investigates the effect of multi-bar linkage mechanisms on the locomotion efficiency of animals. Three case studies are presented. The first case study involves modeling the deployment of the jaw mechanism in the sling jaw wrasse. Numerical modeling of the energy required to move in water shows that the jaw mechanism can signifIcantly reduce the energy cost of locomotion. The second case study involves mode ling the effect of the pantograph mechanism in bird wings on the inertial power required for flight. Energy modeling shows that the pantograph mechanism has a small but significant advantageous effect on locomotion by reducing the inertia of wings. The energy modeling also shows that significant aerodynamic braking occurs during flapping. The third case study involves modeling the benefIts of the linkage mechanism inside insect wings. This study shows there are significant benefits in having 4-bar mechanisms because the mechanisms provide compliance that enables elastic5-storage to take place during wing flapping. The case studies show that linkage mechanisms enable complex mechanical functions to take place that lead to signifIcant energy savings. A common factor in all the case studies was that the actuator is optimally located where mass and space is not at a premium. The potential for biomimicry is discussed for each case study. The sling wrasse jaw has potential for harvesting and cleaning applications. The bird pantograph mechanism and insect wing mechanism has potential for micro air vehicle design and robotics design. There are similarities between multi-bar mechanisms in engineering and nature in terms of types of mechanism. However, there are significant differences in the detail implementation. Engineering mechanisms have pinned joints whereas in nature there are pivot points. Engineering mechanisms tend to be planar whereas in nature they are 3-dimensional. Engineering mechanisms tend to be fully constrained whereas nature's mechanisms tend to be under constrained.