Week 4 — Specification Report
Project Statement & Proposal
Two weeks ago, our group received our project statement:
Sensors and vehicles to be deployed in oceans or lakes require manpower and logistics such as boats. Often this requires to carry heavy equipment to a jetty and loaded on a boat. To carry out simple measurements of water temperature at the surface and air quality can be done at the known locations.
Can we design an autonomous vehicle that can travel on land and directly get into water without any modifications to collect data such as temperature and air humidity?
which require us to create an amphibious unmanned surface vehicle (USV) that collects data such as surface water temperature and air humidity at known locations. The USV must autonomously be able to operate on land and water without any modification by human. Our group expect this USV to be deployed in Singapore’s reservoirs and shallow sea (beaches) which have calm waters and ramps or gentle slope for launching/recovering the USV.
After conducting research on amphibious vehicle design, our group comes up with two amphibious USV designs.
Firstly, an amphibious tank that use tracks that mimic caterpillar leg. The track are made out of dense foam block that naturally float and propels like a paddle on water. This design will enable us to carry heavy load and move through mud, sand, and swamps and big obstacles when ashore.
Secondly, a hovercraft. Hovercraft are capable to travel on land, water, mud, sand and even ice due to it being an air-cushioned vehicle (ACV). Using it turbines, Hovercraft produces a small lift, which causes the hull to float above the surface. Hovercraft are able to move over small obstacles without damage due to the flexible skirt-air cushion.
After judging the pros and cons of both designs, we decided that hovercraft will be a better design for our project. The hovercraft experienced minimal drag on water which make it faster when travelling compared to the amphibious tank. The USV only need to carry a light load (sensors, fuel/battery, etc) and operate in calm to moderate environment which are better suited for the hovercraft. The tank design will perform better if we required to carry heavy load and operate in more extreme environment (disaster affected area). Hence, we chose the hovercraft for our amphibious USV design.
Sketch & Specification
Our group propose to create a radio-controlled (RC) hovercraft with the following specifications & parts:
- Dimensions: approx. 500mm (length) x 300mm (width)
- Weight: approx. 1 kg
- Base Material: 25 mm extruded polystyrene foam (XPS/blue foam). This material is chosen for it strength and toughness while being easy to shape. XPS also float on the water and it will enable the hovercraft to stay afloat in an event of power loss to the main lift motor.
- Structural Material: 3mm Foam board. This material is chosen due to it’s good strength to weight ratio and ease of construction.
- Skirt Material: Butyl rubber (tyre inner tube). This material is chosen as it is light, flexible and able to trap air.
- Lift & Propulsion: 2 x Brushless DC motor. The DC motors will be attached to different type of propeller. For the lift motor, a propeller that is optimized for high airflow will be chosen whereas the thrust motor will use a standard 8"x3.8 propeller.
- Yaw: Servo motor attached to rudders.
- Controls: hobby grade wireless transmitter and receiver.
- Sensors: temperature, air humidity, GPS.
- Electronics: 2 x 30 amps ESC, Arduino uno, Bluetooth module, LED light(Beacon).
- Batteries: 9V battery (Arduino), 2 x Lithium Polymer battery (motors)
Function Analysis
Figure 3 shows detailed function analysis of the RC Hovercraft. The solid lines represent the flow of energy in wired connection while the dotted lines represent the wireless connection. To start, user switch on the RC Hovercraft. Then, user will control the hovercraft using a wireless transmitter (remote). The transmitter have 3 signals output to control the servo and two dc motors separately. The two brushless DC motors are connected to two different Electronic Speed Controllers (ESC). The ESC will control the amount of energy drawn by the motors from the Lithium Polymer batteries according to the user input and thus, varying the speed of the motors. The servo motor will operate the rudder that control the yaw of the RC Hovercraft. 9V battery are used to power the receiver module, sensors and Arduino. The Bluetooth module connected to the Arduino is used to send location and data back to the user.
— ERICK,SHONG JIAN,VOO
