Introduction: Hovercraft by D.O.E
We are D.O.E, which means “dream of engineering”. We come from UM-Shanghai Jiao Tong University Joint Institute(JI). Shanghai Jiao Tong University(SJTU) is one of the top universities in China. It is also famous all over the world. As a leading engineering institute in SJTU, JI is on its way towards a world-class institute with the excellent instructors from SJTU and University of Michigan.
This is a hovercraft we made as a project of the Vg100 course. The main idea of this course is to give us an opportunity to form an interest of engineering and gain some basic knowledge about technology and technical communication for our future engineering career.
The competition consist of a timing part(a track defined by pillars) and four challenges including a 1.5 m rough straight track, a 90 degree angle track, a ramp lower than 30 degrees, and a jumping from the ramp. The timing part weighs 50 points according to the speed of our hovercraft during the race. Each challenge weighs 10 points. The design of our hovercraft also weighs 50 points.
On the first game day which contained only timing part, we ran 68 seconds and ranked fifth. On the second game day which contained all the parts, our hovercraft used 34 seconds to finish the timing part and finally finished three challenges including the rough track, the 90 degree angle, and the ramp. As a result, our group gained 90 points which helped us win the first place in all 15 groups.
Shown below are the rules for the design of hovercraft:
· The lifting height should be less than 3 cm.
· The budget should be less than 450 RMB (battery,Arduino board and materials for structure not included).
· The hovercraft should weigh no more than 800 g.
· The hovercraft should have less than two power supplies.
· The size of the hovercraft should be less than 30 cm×30 cm×30 cm.
· Each battery voltage should be less than 12 V.
· The hovercraft should be remote controlled.
Shown below are the rules for the competition:
· No deliberate crash with other hovercrafts.
· Never take shortcuts.
Shown below is the link of the video of our performance in the game day.
Video: Game day (the video is available on Youku, a Chinese video sharing website)
Step 1: Concept Diagram & Designing
The diagram above shows our design of our hovercraft.
The main controlling system of our hovercraft is an arduino board Arduino Mega 2560, which can receive and send out signals by the program we write for it. A six-channel remote control is our controller for the driver. Since the six channel remote control can send continuous digital signals, the driver can control the hovercraft perfectly with continuous operation.
We use a brush motor to provide the lifting fan for our hovercraft. When the motor works, the airflow first inflate the gasbag through the holes around the base under the hovercraft. After the gasbag is filled, airflow comes out of the hovercraft through the center holed on the under base. When the airflow run out, it hit the ground and gives a impulse straightly to the flat under base rather than the wounding gasbag, which makes the hovercraft very stable. When the airflow goes around out of the gas bag, the flow between the gasbag and the ground makes the friction rather small so that the hovercraft can run in a very high speed. Also this design solves the problem of self-spinning since our gasbag is closed.
A servo with rudders connected to it and a brushless motor provide the propulsion and the ability to change direction. The motor is fixed on the upper base of the hovercraft. The rudders are fixed right behind it. When the rudders change its position, the airflow hit the rudders and gives them a impulse which cause the hovercraft connected with the rudder to change its direction. This device is rather sensitive for changing the direction and easy to control the degrees we turn due to the controlling over the rudder.
Since our remote control is able to provide three channels of continuous digital signals, we can control the servo , the lifting fan, and the propulsion motor at the same time. We can decrease the speed of the lifting fan when we go on smooth ground and increase it when running on rough surface. In this way, we are able to face any possible challenges in the tournament.
Step 2: Material List
Shown below is our material list. The hyperlinks of the components will be shown in the appendix at the end of our manual. You can buy them on Taobao if you want.
Item Price RMB (USD)
Brushless Motor 85 (13.9)
Brush motor 22 (3.6)
Propellers 19 (3.1)
Brushless Electrical Speed Controller 48 (7.8)
Brush Electrical Speed Controller 45 (7.4)
6 channel remote control 145 (23.7)
9g Servo Motor 18 (2.9)
Total 382 (62.5)
Above is the materials in budgets of our racing rules. To complete the hovercraft, you also need some other components. Shown below are the rest of the components you need. The hyperlinks are also shown in the appendix at the end of our manual.
Arduino Mega 2560
11.1 V Battery Pack
Also, some other basic tools for assembling are needed if you want to make the whole hovercraft. They are shown in the picture attached.
Step 3: Design the Circuit
The diagram above shows our circuit.
We use a 9 V battery to supply power for the Arduino board and the servo and receiver connected to it. (The arduino board can adjust the voltage to 5 V automatically. ) We use a 11.1 V Li-Po package to supply power for the two motors.
The brush motor which works as the lifting fan and the brushless motor which provides the propulsion are both connected to a electrical speed controller. The electrical speed controllers are connected to the PMW pins on the Arduino board. When we give the servo a digital signal between 0 and 180, it can change its position for 180 degrees. When we give the motors a digital signal between 1000 and 2000, it can work between its lowest power and highest power. Pay attention, the increasing of the speed might not be linear, which should be taken consideration when programming.
The receiver, which receive signals from three channels on the remote control, is connected to three pins on the Arduino board. Pay attention, since the function for transferring the signals is a interrupt one, we should connect the receiver to the int pins on the Arduino board. For Arduino Mega 2560, we choose Pin 2, Pin 3, and Pin 22 as the pins for this part. (Precise information for this can be referred on the official website of Arduino. ) When the controller move the rocker on the remote control, we can get a digital signal between 1000 and 2000 from the receiver.
The voltage of the battery packaged should be higher than 11 V to make the electronic components work properly. For the 11.1V battery pack, the safety voltage is about 12.6 V and you shouldn't charge it too frequently, which may cause the battery's irreparable damage.
Step 4: Process the Raw Materials
1. Cut the a 1 cm-thick plastic board and two 2.0 cm-thick plastic boards for a 20.0 cm × 30.0 cm rectangle for the base.
2. Dig out a 9.0cm × 9.0cm hole in the centre of the 1 cm-thick plastic board to fix the lifting fan.
3. Cut two 6.5 cm ×3.8 cm right triangles on these three boards.
4. Cut one of the 2 cm boards into a frame with 2.5 cm border-width.
5. Cut out one 11.5 cm ×7.5 cm ×3.0 cm plastic board to make the frames of the pushing fan.
6. Cut some plastic board to make the frame of the rudder. Cut a 13.0 cm × 4.8 cm x 1.5 cm plastic board to support the board.
7.Make some 1.0 cm × 1.0 cm holes on the cm-thick plastic board to inflate the skirt and discharge the air.
8.Cut a plastic board to make a rim of the hovercraft.
These are the components of the main frame of our hovercraft.
Step 5: Assemble All the Components(Structures and Electronic Components)
1. Make the gasbag
- Cut the rain coat to make it a certain shape as it’s showed in the figure.(There is a 17.5cm × 8.0cm hole in the center) It’s used to make the gasbag.
2. Construct the main frame
- Stick the components made in the former step together to create the main frame of the hovercraft.
3. Stick motors
- Stick the lifting fan to the plastic board base for it.
- Stick the lifting fan base to the base board. Weld the wire of the lifting fan and pushing fan together.
- Stick the pushing fan to the plastic frame for pushing fan.
4. Stick the servo
- Assemble and stick the frame of the rudder and the rudder together.
- Connect it with the servo
- Stick the frame and the servo on the base and make it move smoothly.
5. Stick other electronic components
- Stick the Mega Arduino Board to the base board of the hovercraft.
- Stick the 9V battery and receiver to the base board as it’s showed in the picture.
- Stick the 11.1V battery to the base board.
6. Build the circuit
- Parallel the power line of the motors to make it possible to connect to one battery pack.
- Use Dupont wire to connect all the electrical components together.(receiver, arduino board, pushing fan, lifting fan, electrical speed controller).
- Connect the motors to the 11.1 V battery pack.
- Connect the Arduino board to the 9 V battery.
The assembling of the hovercraft is finished then.
Step 6: Programming
Programming is one of the most important parts in our hovercraft. We program to connect the signals sent out by the remote control and the electronic components which work under certain controlling signals. The programming is based on the Arduino Board programming, which can be learned and referred on the official website.
The hovercraft programming mainly involves two parts:
1. Get the signals from the remote control and transfer it into the forms that motors and servos can recognize.
2. Send the signals to the electronic components to make it work as we want.
To make our controlling continuous, we choose the six channel remote control designed for model airplanes rather than a PS2 controller. This controller can give a continuous signal, which makes it easier to control the direction of the hovercraft and adjust the speed more convenient.
The arduino program can be divided into two parts。 First we transfer the signal from the remote control to the digital ones. Then we map the numbers to the range that the motors need, as an example, 0-180 for the servo. Then we send the signal to the motors and the servo. Pay attention, when we control the motors, we consider them as servos. We can either send them digital signals in the range 0-180 or send microsecond signals between 1000 and 2000.
In this way, we are able to control the speed, the direction, and the lifting force of the hovercraft.
By the way, both the model programs about the transferring part and the controlling of motors and servos can be found on the official website or other technical websites. You can also e-mail me if you have any questions while programming.
Step 7: Adjust the Hovercraft
The controlling over the heading direction of the hovercraft is one of the most difficult questions we meet in this project. Once the airbag is filled and the lifting fan starts to work, the friction between the hovercraft and the ground become rather small. A slight force applied on the hovercraft can make the hovercraft spin or head to a wrong direction. As a consequence, adjusting the hovercraft becomes rather important.
One major objective is to adjust the center of gravity of the hovercraft. By moving the battery which weighs the most among all the components, we are able to move the center of gravity and test if the hovercraft can go in a straight line when the servo stays still every time we adjust it.
After several hours' adjustment, our hovercraft becomes a good boy under our controller's hand and can go right in the direction that the controller want it to go into.
Step 8: Final System View & Ready to Race!
After several steps' hard work and days of adjusting, our hovercraft is finally done and ready to fight in the tournament!
Step 9: Appendix
Hyperlinks of our components are shown below.
Electrical Speed Controllers
11.1 V Battery Pack
Arduino Mega 2560
You can also search them on the Internet by yourself and try to find some better alternative ones to these materials.
Thank you for reading our manual. If you have questions and want to know more about our hovercraft, please feel free to contact us through E-mail: Lingfeng_Sun_TToTM@sjtu.edu.cn
We hope you enjoy our manual.
Participated in the
First Time Author Challenge