Industrial Application

As previously introduced, the Hypostomus plecostomus, as known as Pleco fish, is known as a bottom feeder, meaning this fish’s natural habitat is at the river bed or the bottom of any aquatic environment. Evolution through time has enabled this fish to adapt to its environment more efficiently. This aspect takes reference onto its semi elliptical streamline top along with a flat underside. The elliptical topside had taken a streamline shape to better redirect the underwater current in order to minimize the force acted onto the fish’s body. According to Newton’s Third Law of Motion, “For every action, there is an equal and opposite reaction. In order for the Pleco Fish to stay stationary, it has to utilize its suction power to counteract against the current. Thus, by having a streamline body which results in lesser resistance, the Pleco Fish would require lesser energy to maintain position. Evolution such as this has enabled the fish to utilize its energy more efficiently which served as a key importance in survival.

The team’s observation had taken preference over its unique streamline shape for implication of biomimicry study. Adapting the aspects of underwater aerodynamics, the team had decided to implement it upon redesigning the Autonomous Underwater Vehicle (AUV). In summary, the AUV serves its purpose of underwater survey and observation where data collection is mostly the primary task. Subdivided into three categories, AUV are primary used under these fields;

Field	Description
Commercial	Oil and Gas industry where it is used to map the seabed in detail prior to subsea infrastructure constructions.
Research	Study and data collection on ocean, ocean floors and lakes.
Air crash investigation	Used to find and locate wreckages of missing airplanes

 

What these three fields hold in common is that an improvement in terms of energy efficiency usage would deem highly beneficial under its designated purpose. Better energy efficiency would provide;

• Operation cost reduction
• Minimize carbon emission
• Minimal maintenance requirement
• Better energy distribution towards primary objective
• Longer underwater operational period

In general, AUV’s are powered by rechargeable batteries such as lithium-ion, lithium-polymer and nickel metal hydride battery. It is common that rechargeable battery, when undergone extensive and excessive power usage would result in a significant increase of temperature internally which could potentially reduce the lifespan of the battery, as well as the connected component. Under extreme cases, it might cause damage to the sophisticated components nearby due to high temperature exposure for long period. This overall contributes to one of the factor of high maintenance cost. Thus it is believed that energy efficiency improvement would drastically benefit current AUVs. 


The proposed conceptual AUV design is as shown in figures below. 

 

The team had selected the aluminium grade 6061-T6 as the primary material for the outer hull construction as well as the support fixture. Reason being is that, aluminium weighs less; approximately 66.25% lighter and possess a better Modulus of Elasticity than stainless steel. Also, issues with material corrosion would be voided if aluminium is used. The properties of the aforementioned material would be tabulated as shown in figures below.

 

The general purpose of an AUV is to mainly take readings and monitor the condition of the environment. Sensors that are required to accomplish its task would be as listed below;

Sensor
Accelerometer	Accelerometers measure non-gravitational acceleration.
Gyroscope	Gyroscope is to measure the rate of rotation at a defined axis.
Depth, Temperature & Pressure Sensor	Determine aquatic environment status.
Side-Scan Sonar Sensor	To create images of large areas or map or aquatic floor.
Magnetometer	To determine location in referenced with earth’s magnetic pole.
Thermistor	Measuring internal change of temperature in AUV through electrical resistance fluctuation.
Conductivity Probe (EC meter)	Monitor nutrients, salt and impurities in water based on medium’s electrical conductivity.
Acoustic Doppler Velocimetry	Sensor that function detects AUV’s velocity through measuring particles velocity.
Transducer	Converts pressure and brightness into electrical signals.

Navigation
Long Baseline acoustic positioning	Highly accurate location and stability positioning system which relies on mounted baseline transponders that are deployed to at the seabed. Uses transponders as reference points for navigation.
Replaceable Antenna	Antenna serves a key importance in data transmitting thus was made replaceable.
Inertial Navigation System (INS)	Uses accelerometer and gyroscope to calculate dead reckoning positions, orientation and velocities without the requirement of external reference (transponders).

Data
Data Interface Box	Data storage and provision of simple user interface for ease of access.
Laptop with Impact & Water Resistant Casing	To avoid damage and short circuitry of the devices as it could pose a threat to user due to the wet working environment.

As for the propulsion system of the proposed AUV design, ducted propulsion is chosen as it has higher propulsive efficiency, better course stability and less vulnerability to debris when compared to the usual un-ducted propulsion. A rudder could be found behind the ducted propeller for the purpose of steering the AUV thus changing the travelling direction (left and right motion) of the AUV. Two hydroplanes could be found at each side of the AUV as it controls the pitch of the AUV. Both hydroplanes are free to rotate at its neutral axis. By changing the rotational angle of the hydroplanes, a pitching moment will be introduced to the AUV while in motion, thus making the AUV to submerge or to surface. Also, the aerodynamic outer shape of the AUV also adds value to the propulsion of the AUV as drag imposed to the surface of the AUV while in motion will be minimal, thus further improving the efficiency of the propulsion system.

It is believed that the proposed AUV would work if manufactured as there are a lots of similar AUV in the current market. The only distinguish features of the proposed AUV are such that the AUV incorporates the shape of the pleco fish with flat bottom and a fish like aerodynamic outer shape. The purpose of the design is to enables the AUV to rest at the bottom of river bed when performing its task or mission without being affected by the current.

Fund could be raised by the team for the purpose of manufacturing and testing the proposed AUV. To raise a fund, the team could contact any researchers which require an AUV for their research purposes. A detailed proposal which clearly defined the details of the design with the pros and cons will allow the sponsor to decide whether to support and fund the manufacturing process. Another method which could be used by the team to raise fund is through crowdfunding. Crowdfunding is a new method of online fund raising through the support of strangers all around the world. In order to acquire the support from the pledgers, a series of engineering simulation could be prepared to provide evidence in the feasibility of the idea. Also, as a return for their support, pledgers could be offered with rewards such as a free tour to control the AUV in testing facility.

Biomimetics is definitely one of the tool which often explored by engineers to seek solution for their design challenges in solving engineering issues. As an example, the wing design of aircrafts are often inspired by the wing shape and pattern of a flying bird. Such inspiration is considered as reductive biomimicry as only the form of the flying birds are mimicked. In the other hand, holistic biomimicry are often utilized by engineer in solving engineering challenges. Hollistic biomimicry does not only imitates the form of a natural phenomenon, but also incorporates the whole development process of the natural phenomenon into the sustainable solution.

Reference

A. Bhattacharyya and S. Steen, “Propulsive factors in waves: A comparative experimental study for an open and a ducted propeller,”Ocean Eng., vol. 91, pp. 263–272, Nov. 2014. 

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