Legged systems are capable of locomotion in a far wider range of environments compared with wheeled or tracked vehicles. Man-made legged locomotion systems are currently economically inferior to wheeled vehicles, tracked vehicles, and legged locomotion systems which exist in nature. In previous research, trajectory optimisation has been applied to legged locomotion systems of a certain design to improve economy, however there has been little work in which the economy of legged locomotion systems is improved through design. This thesis describes the search for economically optimal designs of legged locomotion systems using parametric analysis. An abstract mathematical model of a legged locomotion system was constructed which included an imperfect spring element and electromagnetic actuator. Several actuation strategies were developed which allowed the model to be controlled to perform continuous locomotion. Six performance metrics were identified whose reduction in value implied an increase in economy. The model was simulated performing four locomotion exercises of increasing complexity, beginning with a system oscillating in the absence of gravity and ending with a planar locomotion system. Across these four locomotion exercises, the effect of system architecture, actuation strategy and key system parameters upon economy was determined. Two prototype legged locomotion systems were also constructed for comparison with simulation. It was not possible to simultaneously minimise all performance metrics because minimisation of some performance metrics required choices of system architecture, actuation strategy or system parameter which prevented minimisation of other performance metrics. The economically optimal design of a legged locomotion system was one which minimised the maximum force and peak power requirements of the locomotion system's actuator. Parallel compliance was economically superior to series compliance, which is particularly noteworthy given the comparative rarity of parallel compliance in current man-made legged locomotion systems.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:687425 |
| Date | January 2015 |
| Creators | Helps, Timothy Nicolas |
| Publisher | University of Bristol |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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