Intro: Hovercraft for Summer 2014 Introduction to Engineering Competition
1. Introduction to Joint Institute
Hello! We are students from Joint Institute from Shanghai JiaoTong University in China. This beautiful school is located in the southwest of Shanghai and Picture1 is the view of our fantastic campus.
Joint Institute (JI) is the engineering college constructed by Shanghai JiaoTong University and University of Michigan USA. Although JI was founded in 2006, it has made great achievements in cultivating talents in engineering. The goal of JI is to become a top engineering college all over the world. Picture2 is the logo of JI.
2. Hovercraft competition
There are two parts in the hovercraft competition. The first is time trial. In this part, we need to finish the track in 3 minutes to get the full mark. There are two ways of finishing the track for us to choose. The first is that the hovercraft runs only one lap and the time for this lap will be served as our grade. The second choice is that we can run for two laps. However, only the time for lap 2 will be graded.
According to the time in the time trial, four fastest groups will be viewed as seeds in the second parts: knockout tournament. Four seeds will be divided into four different groups. In the tournament, each team should run two laps to finish the race. The track will have outer lap and inner lap and two teams need to finish both of these laps alternately. The team which first goes across the finish line will win and get to the next round.
1) Rules for time trial
Finish the trial in 3 minutes.
Run one lap or two lap.
If get troubles before the begining of the trial can request for a change time, the time should be less than 3 minutes.
2) Rules for tounament 1
Use the way of Coin Flip to choose the lap.
Collision should be less than 3 times.
Our group finished the time trial for 16.87s and get the third place in the tournament.
3) Competition regulation Mechanism: Any method that can help to reduce the friction force between “ hovercraft” and race-track surface will be acceptable.
Lifting Height: <2cm, applying for some design involving lifting mechanism like a helicopter.
Maximum Mass: 800g
Maximum Size 30 cm,30cm,30cm
Power Supply: Maximum two portable Power Supply (for each battery Voltage ≤ 12V)
Motor specifications: <12V.
Central Control Circuit: Arduino series(Required for Programming & Can Be Omitted)
Remote Control: Mandatory. Any form(BlueTooth, infrared, etc)you want to apply will be accepted.
Here is the link of the video record, which shows the excellent performance of this hovercraft:
4. Material list
1) Arduino mega 92 RMB($15.06 USD)
2) Fan 270RMB($43.23 USD)
3) Electronic speed controller 183RMB($29.29 USD)
4) Battery 99RMB($15.84 USD)
5) PS2 controller 52RMB($8.32 USD)
6) 2-cm thick and 1-cm thick PVC boards ($4.80 USD)
7) Plastic bag($0.05 USD)
8) Wires ($3.65 USD)
9) Polyurethane foam sealing agent($3.68 USD)
10) Silica gel (this may be substitude by other convenient bonds) ($0.80 USD)
11) Electric solding iron together with solding tin ($3 USD)
Step 1: Circuit Diagram
The connections between circuit components are shown in the diagram.
The second one is the detailed connection between the arduino board and the ps2 signal receiver. It is demonstrated isolately to prevent possible confusion due to the so many wires .
 2013. arduino学习笔记24 - PS2无线手柄实验, online, available ftp: http://www.arduino123.com/a/jiaocheng/jichu/2012/0412/221.html
Step 2: Cut PVC Boards
Cut a piece of 2-cm thick PVC board, 20cm im width and 30cm in length to make the hull of the hovercraft. For the skirt, we need to cut other 4 2-cm thick boards and two of them are 20cm in length, 6cm in width and the others 30cm in length, 6cm in width. Here we don't choose flexible material to make the skirt because the brushless motor is quite long and the skirt should be able to support the whole hovercraft in case the bottom of the motor collides with the ground.
Step 3: Dig a Hole for the First Motor.
The radius of the bottom proportion of the largest motor is 7cm. Dig a hole with a radius of 3.5cm at the middle of the hull board so that the motor can be inserted into the hole.
Step 4: Install the First Motor
Insert the motor into the hole for 2cm which is the thickness of PVC board and use polyurethane foam sealing agent to stablize it. The polyurethane foam sealing agent can be used as a strong and light bond.
Step 5: Make the Skirt
Attach the rest 4 boards cut in step 1 to the hull. Match them with respective sides according to the length.
Step 6: Wrap Up the Skirt With an Airbag
In order to hold the air below the hovercraft to povide the hovercraft with more strong and balanced lift force, we need an airbag to wrap up the skirt. Cut the plastic bag into the shape of a rectangular but leave some spare spaces to apply glue. Dig 4 symmetric holes on the plastic rectangular to let out the floating air then bond it to the skirt.
Step 7: Prepare for the Installation of the Other 2 Motors
The other 2 smaller motors are used to produce horizontal thrust.
Since the radius of the former part of a brushless motor is larger than that of the latter part, here we cut a thin piece of PVC board to lift the latter parts of the two motors. This board can make sure the produced thrust is horizontal and make it easier to stablize the motors.
The size of the board is 20cm*3cm*1cm.
To stablize the motors, polyurethane foam sealing agent is again applied.
Step 8: Install the Two Motors
Attach the rest motors together with the lifting board to the end of the hull.
Step 9: Install Arduino Mega Board, Battery and PS2 Signal Receiver
Install other components including arduino mega board, battery and PS2 signal receiver. Do not fix them to a specific position in this step because their weight may not be balanced and need adjustments.
Step 10: Connect the Wires and Electronic Speed Controller
Connect these components according to the circuit diagram given in step 1. Use electric solding iron and solding tin to connect two different wires. To arrange the mussy wires, bend the wires that connect the same pair of components together. It can also make it easier to examine and repair the circuit.
Step 11: Test & Adjust
Finish the programming work and transmit the prgram to the arduino mega board. Then repeatedly test the hovervraft and adjust the program and the components.
Possible problems and solutions:
1. The hovercraft fails to go along a straight line.
(1) The weight of the hovercraft is imbalanced so the frictions are inequal in different directions.
Solution: Change the positions of some of the components such as battery and electronic speed controller to balance the weight.
(2) The thrusts produced by the two propelling motors at the back are inequal.
Solution: Check the directions to which the motors are pointing. Are they pointng straight forward? Or are they parallel to each other? Also check the statues of these two motors to make sure that they all work properly.
2. The hovercraft turns too sharply at the turnings.
(1) The difference between the thrusts produced by the twp propelling motors are too large at the turning.
Solution: Adjust the program to reduce the difference between the thrusts.
Another solution: Reduce the lift force when turning directions. This can provide the hovercraft with more frictions to help stablize the craft.
3. One of the motors suddenly stopped while running.
(1) The circuit is disconnected at some joint points.
Solution: Use a multimeter to find the disconnected points and re-connect them.
(2) The motor breaks down.
Solution: Actually this is not likely to happen. Examine the circuit and the program carefully. If there is still no problem with the circuit and the program, disconnect some of the joint points and re-arrange the wires to power the troublesome motor with the partial circuit that used to power a properly working motor. See if the motor is brought back to life and examine the circuit again. If all these mehods fail, then it is determined that the motor is broken and you need a another one.
Step 12: Finished.