Developing High Performance Linear Carangiform Swimming

This thesis examines the linear swimming motion of Carangiform fish, and investigates how to improve the swimming performance of robotic fish within the fields of kinematic modeling and mechanical engineering, in a successful attempt to replicate the high performance of real fish. Intensive research was conducted in order to study the Carangiform swimming motion, where observational studies of the common carp were undertaken. Firstly, a full-body length Carangiform swimming motion is proposed to coordinate the anterior, mid-body and posterior displacements in an attempt to reduce the large kinematic errors in the existing free swimming robotic fish. It optimizes the forces around the centre of mass and initiates the starting moment of added mass upstream therefore increasing performance, in terms of swimming speed. The introduced pattern is experimentally tested against the traditional approach (of posterior confined body motion). A first generation robotic fish is devised with a novel mechanical drive system operating in the two swimming patterns. It is shown conclusively that by coordinating the full-body length of the Carangiform swimming motion a significant increase in linear swimming speed is gained over the traditional posterior confined wave form and reduces the large kinematic errors seen in existing free swimming robotic fish (Achieving the cruising speeds of real fish). Based on the experimental results of the first generation, a further three robotic fish are developed: (A) iSplash-OPTIMIZE: it becomes clear that further tuning of the kinematic parameters may provide a greater performance increase in the distance travelled per tail beat. (B) iSplash-II: it shows that combining the critical aspects of the mechanical drive system of iSplash-I with higher frequencies and higher productive forces can significantly increase maximum velocity. This prototype is able to outperform real Carangiform fish in terms of average maximum velocity (measured in body lengths/ second) and endurance, the duration that top speed is maintained. (C) iSplash-MICRO: it verifies that the mechanical drive system could be reduced in scale to improve navigational exploration, whilst retaining high-speed swimming performance. A small robotic fish is detailed with an equivalent maximum velocity (BL/s) to real fish

An holistic bio-inspired approach for improving the performance of unmanned underwater vehicles

PhD ThesisThis research, as a part of the Nature in Engineering for Monitoring the Oceans (NEMO) project, investigated bio-inspiration to improve the performance of Unmanned Underwater Vehicles (UUVs). Initially, the capabilities and performance of current AUVs were compared with Biological Marine Systems (BMSs), i.e. marine animals (Murphy & Haroutunian, 2011). This investigation revealed significant superiority in the capabilities of BMSs which are desirable for UUVs, specifically in speed and manoeuvring. Subsequently, an investigation was carried out on BMSs to find means to make use of their superior functionality towards engineering improved UUVs. It was discovered that due to a mismatch between the purpose of each species evolution and the desired mission of an UUV, all desired characteristics are not evident in a single species. Moreover, due to the multi-functionality of biological systems, it is not possible to independently study each configuration. Therefore, an holistic approach to study BMSs as a system with numerous configurations was undertaken. An evolutionary search and selection algorithm was developed to obtain the myriad of biological information and adjust them to engineering needs (Haroutunian & Murphy, 2012). This Optimum System Selector (OSS) was implemented to output aspects of the appropriate design combination for a bio-inspired UUV, based on its specified mission. The OSS takes into account the energetic cost of the proposed combination as well as the trade-off between size, speed and manoeuvrability. Appreciating the uncertainty in existing measured biological data, the developed code was successfully verified in comparison with BMSs data. Energetic cost of transport is a key factor in selecting a design combination based on desired missions. This is key to the accuracy of the algorithm. Therefore, in another essential research theme, a sophisticated study has been carried out on the understanding, calculating, predicting and comparison of various biological and engineered underwater systems energetics (Phillips et al., 2012). The results of the OSS compared with existing AUVs, showed improvements in the overall capabilities. Therefore, this method is an excellent guide to transform complex biological data for the future design and development of UUVs.EPSRC