Introduction: Racing Hovercraft
We are COSMOS, coming from UM-Shanghai Jiao Tong University Joint Institute. This instructable page is made for our Vg100 course design, a racing hovercraft controlled by Arduino. Shanghai Jiao Tong University (SJTU) is one of the top universities in China, and Joint Institute (JI) is a leading engineering school in SJTU. JI locates in Shanghai Minhang district with excellent instructors from SJTU and University of Michigan.
The course Vg100 is one of the most special courses at JI. It aims at cultivating basic engineering qualities such as solving problems, cooperation and scheduling projects. The racing hovercraft is one of the two course projects of Vg100, and our course grade is tightly related to the performance on the hovercraft game day.
In total 19 groups are invited to the game day. The first part of the game day is named "time trail", in which hovercrafts run 2 laps on a winding track one by one. Our final time is 15.44s, ranked 4th. The second race is tournament, in which two groups’ hovercraft compete against each other and the slower one got knockout. Our group win the championship. Shown below is a short version of competition rules:
· No deliberate crash with other hovercrafts.
· Never take shortcuts.
· Lifting height less than 2cm.
· Self-weight less than 800g.
· Size within 30cm×30cm×30
· Battery voltage less than 12V.
· The hovercraft is required to be remote controlled.
Links below are the videos of our performance on the game day*:
*You are going to be redirected to a Chinese online video sharing website named Youku.
Step 1: Designing Concept
Shown above is the concept diagram of our design. As you can see, the core of our racing hovercraft is a Arduino Mega 2560 micro-controller, thus the hovercraft is smart. A wireless PlayStation 3 joystick is used as the remote control, so at the beginning of each race, we have to pair the joystick and the Arduino board. Since the Playstation 3 joystick is elaborately designed for good gaming experience, controlling our hovercraft is enjoyable.
The most unique part of our design is the position of the main propeller. Unlike any other traditional designs, we fix the propeller on a servo motorat the front of the body, to pull it forward rather than to push it. The ingenuity is inspired by my father's old sedan. It is steered by rotating the front wheels, so it is easily to steer when going forward but hard to do so when reversing. From that, we assume that steering gears at the front makes it easier to steer. Since the servo motor can change the direction of propeller thrust, the hovercraft can be steered easily.
You may have noticed that there are two tiny propellers fixed on both sides. Those two propellers is fixed on two auxiliary steer motors, which provides extra steering torque for the hovercraft. Since the racing track is winding, some of the turnings are even sharper than 90 degrees, good steering capacity means championship. By adding the auxiliary steering structure, our hovercraft can even turn around without going forward.
As for the lifting part, a cheap computer cooling fan is used to lift up the system. A sealed PVC apron is designed to increase the efficiency of the fan.
To inhibit self-spin when the hovercraft is lifted up, a gyro scope is used to detect the angular velocity of the base board. The detection is sent to the Arduino board, and certain correction will be made by the Arduino, so the hovercraft can go straight for long.
It may be a bit confusing that the shape of the base board shown in the diagram is different from that of the real picture. The reason is that round shape is not easy to make by hand, so we choose to use rectangle wooden boards directly.
Step 2: Materials List
Item Quantity Price RMB(USD)
Arduino Mega 2560 1 70 (11.2)
2210 Brushless Motor Kit* 1 90 (11.4)
12V Cooling Fan 1 25 (4.0)
Coreless Motor 2 14 (2.2)
955 Servo Motor 1 35 (5.6)
USB Host Shield 1 55 (8.8)
11.1V Battery Pack 1 101 (16.2)
MPU6050 Gyro Scope 1 47 (7.5)
Wooden Boards many 20 (3.2)
Total** 457 (73.2)
*The motor kit includes two 5 in propellers, an electronic speed controller and a 2210 brushless motor.
**The price of the joystick and other tools is not included.
***You may need a soldering iron to solder wires and components.
Step 3: Step by Step 1: Designing Circuit Diagram
Shown above is a brief circuit diagram. All the green wires mean 5V power supply, all the black wires mean the ground, all the red wires means the raw voltage(11.1V) supplied by the battery pack, white wires means PWM controlling wires and the two orange wires are SPI communication port, which is the bridge between the gyro and the Arduino board.
The brushless motor, works as the main propeller, is driven through a electronic speed controller, which takes PWM signal from the Arduino board and adjust the rotate speed of the motor according to the signal.
The fan is also controlled by the PWM signal. Namely, we can adjust the lift force according to the friction of the floor. If we want the hovercraft runs more steady, we just cut down the lift force and gain the friction, or we just increase the lift force and let it run faster to compete for the championship.
The two auxiliary motors are driven by a cheap motor driver, L298N motor driver. L298N has two driving channels, namely it can drive two motors simultaneously. The rotate speed is also determined by PWM signals.
The gyro scope talks with the Arduino board through the SPI port, which has already been embedded in the Arduino Mega chip. So just make sure you connect the SCL&SDA pins of the gyro to the same pins on the Arduino board respectively, then you can let them talk. That's pretty convenient, right? After been powered up, the gyro will detect the angular velocity of the hovercraft and send it to the Arduino, what you need to do is just activate auxiliary motors to inhabit the angular velocity to 0.
Pay attention that the raw voltage provided by the battery pack is around 11.1V, which is way too high for the Arduino board and other components except for motors. So make sure you connect the battery to VIN pin of the Arduino board rather than the VCC or 5V pin. The voltage regulator embedded on the board can adjust the 11.1V power to 5V power automatically.
Step 4: Step by Step 2: Constructing the Base
(1)Cut a 2 mm-thick wooden board for a 20cm×30cm rectangle for the base.
(2)Make a 8cmx8cm square hole in the middle of the base for one computer cooling fan as a lifter. The size of the hole should be a bit smaller than the fan.
(3)Fix the fan on top of the hole with four nails on every corners.
(4)Cut a 2 mm-thick wooden board for a 17cm×18cm rectangle for the platform.
(5) Drill 4 3mm round holes on the corner of the wooden platform.
(6) Drill 4 corresponding 3mm round holes on the base to fix the Arduino board firmly on top of the base.
(7) Fix the servo on the base by glue gun.
(8) Fix two coreless motors on the base by glue gun. (Hot melt glue is strong enough to hold motors.)
(9) Cut out a 20cm*30cm rectangle frame with the width of 3cm from a wooden board, glue a few bars of foamed plastics to every side.
(10) Use a PVC plastic bag to wrap the frame and the foamed plastic bars to prevent air from escaping.
(11) Drill 4 corresponding 3mm round holes on the frame, fix the frame to the base with 4 nails.
Step 5: Step by Step 3: Soldering and Connecting
(1) Solder each wire of the brushless motor to a male banana connector (you may need a high power soldering iron, 50W is recommended).
(2) Repeat step (1) for all three propellers.
(3) Solder each wire to female banana connectors.
(4) Repeat step (3) for all three wires.
(5) Change to 25W iron with sharp tip, solder tiny pads on PCB board to wires.
(6) Cut down a 4cm*2cm rectangle board from a wire-wrap board, solder the pair of wires from the battery to it and solder 4 more pairs of wires to expand those two wires, so that every components can be evenly powered. After soldering, we finished making a battery connector.
(7) Solder the wires from the connector to the fan, the electronic speed controller, the voltage regulators and the Arduino board.
(8) Since the Arduino board in sensitive to induced electricity at the tip of the soldering iron, you'd better not solder anything on the Arduino board. We use experimental connectors (with a socket on one side and a pin on the other side) to connect outer components to the Arduino board.
(9) Double-check each connection! Any tiny mistake can ruin all of your work!
Step 6: Step by Step 4: Assembling
Since some parts of the assembling process is done in first few steps (like constructing base, soldering...), this step is like some sort of summary.
(1) Cutting down a 30cm*20cm wooden board and dig holes on it.
(2) Fix the servo and the coreless motors on the board with heat melt glue, fix the fan with 4 nails.
(3) Stick a few of foamed plastic bars to a wooden frame, wrap it with a PVC plastic bag. It is called the air apron.
(4) Fix the air apron to the base with 4 nails.
(5) Fix components except for the Arduino board to the base, solder components and wires.
(6) Fix the Arduino board on a outer platform, and fix the platform to the base.
(7) Connect all the wires to the Arduino board, put on the battery pack.
(8) Here we go!
Step 7: Finished: Ready for Rush
If other hovercrafts are family sedans, our racing hovercraft is like a muscle car. Thank you for watching the document, and hope you enjoy it. More details are always available through our E-mail: Zening.Lu@sjtu.edu.cn.
