Thesis
Numerical and experimental investigation of bio-inspired robot propulsion and manoeuvring
- Creator
- Rights statement
- Awarding institution
- University of Strathclyde
- Date of award
- 2024
- Thesis identifier
- T17122
- Person Identifier (Local)
- 201784977
- Qualification Level
- Qualification Name
- Department, School or Faculty
- Abstract
- Continuously growing interest in discovering, developing and exploiting offshore resources requires efficient, reliable and cost-effective robotic operations underwater. To ensure human safety and enable automated robotic intervention of offshore assets, including Inspection, Maintenance and Repair (IMR), future robotic systems will be required to be more efficient, manoeuvrable and resilient. Bio-inspired underwater vehicles are designed to mimic the excellent swimming abilities of natural swimmers. To enhance the understanding and implementation of bio-inspired locomotion and to address gaps in the knowledge of bio-inspired locomotion hydrodynamics, control and robotic design, this thesis investigates several key aspects relating to the propulsion, manoeuvrability and power of Body Caudal Fin (BCF) locomotion by means of numerical simulations, prototype design and hydrodynamic lab testing. This thesis is organised in two parts: numerical studies and experimental investigations. Numerical simulations are established through coupling a numerical fluid solver, a body dynamics model and feedback control. A single-body and a multi-body fish model, which are implemented within User Define Functions (UDF) and coupled to Ansys Fluent, are presented in detail and reference is given to a Fluid Structure Interaction (FSI) solver used to simulate elastic structures. Linear feedback control is represented by means of a Proportional, Integral and Derivative (PID) control algorithm. Adding linear feedback control to CFD simulations makes it possible to simulate unsteady swimming manoeuvres at a set point and make a comparison across parameter spaces under quasi-steady state conditions. Three control strategies are derived by defining feedback control error logics that are applied in three numerical studies. The first investigation focusses on optimal curvature distribution of a manoeuvring BCF swimmer. Results show energetic benefit for swimmers turning with greater body curvature towards the tail. The second numerical simulation considers the thrust performance of a fixed and pitching elastic plate of different material stiffnesses and pitching frequencies over a parameter space. The results provide insights into the instantaneous hydrodynamics and thrust performance of flexible appendages, such as a BCF and the differences in performance for various material properties and actuation parameters. The third numerical investigation studies the energetic performance of an actuated elastic plate swimming in front of a cylinder while holding its position. The results identify any interaction between a freely moving plate and a cylinder as well as the energetic benefit of smaller distances towards the low-pressure zone at the leading edge of the cylinder. The experimental part of the thesis introduces a new modular robotic design that incorporates a novel approach to achieve static watertight torque couplings and mechanical modularity. The key innovation lies in the application of a synchronous magnetic coupling, which replaces traditional methods, such as dynamic seals and flexible covers used in existing modular robotic designs. This magnetic coupling provides a sole magnetic connection between neighbouring body elements, eliminating the need for mechanical connections between modules and addressing potential weaknesses associated with fixed connections. The rotational degree of freedom afforded by the magnetic coupling enables the robot to form a traveling body wave within a continuum space, facilitating thrust generation and manoeuvring. All mechanical parts, including the enclosure, shaft and gears, have been custom CAD designed and created through additive manufacturing techniques including Fuse Deposition Modelling (FDM) and Stereolithography (SLA). The untethered robot can move freely in a plane just below the water surface and is controlled through Bluetooth Low Energy (BLE) communications between each module and a central pc. Extensive hydrodynamic testing has been conducted at Strathclyde University’s Kelvin Hydrodynamics Laboratory to confirm the basic swimming abilities of the robot prototype and assess its performance. Two separate investigations of thrust generation and free-swimming performance are conducted. Thrust measurements are taken applying different undulation frequencies and amplitudes with a constant amplitude envelope at a custom-made testing stand. Motion capturing is utilised to record the motion of the robot in three and six degrees of freedom during free swimming tests. Free-swimming measurements are taken with a constant amplitude envelope of the manoeuvring robot and straight forward swimming velocity with different undulation frequencies and amplitudes. Finally, experimental measurements are compared with the results of a CFD multi-body simulation.
- Advisor / supervisor
- Yue, Hong
- Xiao, Qing
- Post, Mark
- Resource Type
- DOI
Las relaciones
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PDF of thesis T17122 | 2024-10-08 | Público | Descargar |