HovercraftDesign and make hovercraft

Louis, Haojun Zhang

Jiacheng Shang,Ziyang Zhou,Yulin Jin,Zihao Lin,Chenxi Dong

5 July 2015

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Contents

1 Introduction 31.1 Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31.2 Principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41.3 Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41.4 Introduction of program . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

2 High level design 72.1 Mechanical part . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72.2 Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

3 Low level design 73.1 Mechanical part . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

3.1.1 Solidworks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73.1.2 Build . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

3.2 Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113.2.1 Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113.2.2 Program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

4 Future work (Next step) 144.1 Result . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144.2 Advancement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144.3 Safety issue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

5 Reference 15

6 Appendix 15

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1 Introduction

1.1 Definition

A hovercraft, also known as an air-cushion vehicle or ACV, is a craft capable of travelingover land, water, mud or ice and other surfaces. Hovercraft are hybrid vessels operatedby a pilot as an aircraft rather than a captain as a marine vessel.

Figure 1: A recreational hovercraft

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1.2 Principle

Hovercraft use blowers to produce a large volume of air below the hull that is slightlyabove atmospheric pressure. The pressure difference between the higher pressure air be-low the hull and lower pressure ambient air above it produces lift, which causes the hullto float above the running surface.

Figure 2: Work functional picture

1.3 Applications

Because of the strong functionality and practicability of hovercraft, there are a largeamount of applications of hovercraft:1. Commercial

2. Civilian non-commercial

3. Rescue

4. Military

5. Recreational/sport

6. Other uses

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Figure 3: A passenger-carrying hovercraft

Figure 4: A Formula 1 racing hovercraft

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1.4 Introduction of program

The aim of programming is to design and build a prototype of a hovercraft so that it canfloat on the ground as well as overcome a wide variety of complicated landscape rangingfrom rough land to water surface.

Due to customers needs, the hovercraft is expected to includes two mechanisms. One forpushing the hovercraft leaving the ground for a considerable distance and floating, andanother for pushing the hovercraft moving forward by using two sets of propellers. Also,a python programmed microcontroller is needed to enable user to make self-regulation asenvironment varies. Finally, a body structure including skirt with reasonable design isrequired to support these all electric and mechanical components.

Figure 5: a prototype of hovercraft

The main issues that are ought to be considered when designing and making:1. Material ranking.2. How to design a reasonable structure.3. Custom-made parts need to be designed to be integrated with the standard compo-nents and be available to get from your existing materials.4. Where to place all components including electric and custom-made . (Key:Solidworks)5. Safety requirements.

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2 High level design

2.1 Mechanical part

In mechanical part, which is further composed of design and build, a software calledsolidworks is used to design a suitable 3D sustainable structure of hovercraft and carryout making process according the 3D models dimension so that the process is efficientand reduce waste of materials.

Figure 6: 3D model

2.2 Control

This part is further divided into circuit and program. Since we are willing to design aself-regulated automatic hovercraft, so it should be capable of turning right and turn-ing left. Hence, we need a circuit to connect two motors linked to two propellers withmicrocontroller and Raspberry Pi , and compile a python (a programming language)problem in Raspberry Pi to control the microcontroller to drive two motors and is ableto change the turning direction freely so that achieving our aim of turning.Additionally, Raspberry Pi can be controlled by your computer by installing a softwarecalled tightvnc and a camera is deposited in Raspberry Pi so you can directly see thescene in front of the hovercraft.

3 Low level design

3.1 Mechanical part

There are two tasks to compose the Mechanical part, they will be explained below.

3.1.1 Solidworks

Since hovercraft is 3D, it is hard to draw and design hovercraft in paper, therefore, we im-port a software called Solidworks. Solidworks is a software regarding engineering through

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which we are able to transfer our ideas in our mind into a 3D space inside our computers.

In the initial stage , design each component needed respectively. The method of de-sign components is drawing a sketch in a 2D plane and using a function called feature todraw it up or rotate it to approach whatever shape you want.

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Figure 7: before matching-up

After finishing all the components, it is able to assemble them together to becomea entirety. In this step, a function called match-up is used to confirm the geometricrelationship among all the components. Normally, a completely defined geometric re-lationship needs 2 4 times of use of match-up. When all components are completelydefined, assembling is finished and the 3D hovercraft design is over.

Figure 8: after matching-up

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What must be mentioned is when making all single components, it is necessary tomake sure that the sizes are limited in the range of dimension of materials you have,otherwise, components are not attainable when making them!

3.1.2 Build

First of all, cut two large piece of PVC plastic boards according the Solidworks 3D mod-els size (36*[48+12]). Then draw reference lines to confirm the locality of two propellerstents, two central holders and six holders between two large piece of PVC plastic boards.After that, it is time to cut these components. Due to the thickness of PVC plastic boardis 2.5 cm; therefore, one of three dimensions should be less then 2.5 cm. One of the prob-lems I met is that I designed a 1cm*1cm*2.5cm square hole below propeller stents, so itwas quite hard to cut a regular and smooth shape. Fortunately, I cut a slightly tighter onewhich can just be filled in and the batten can be stuck inside. Making the central woodenboard supporter by using glue to stick board and batten together. Stick components withhovercraft body in a similar way. After that, mechanical part is approximately finished.

Figure 9: final product

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3.2 Control

3.2.1 Circuit

Due to the nature of the task , there is a relative high standard of electrical systemintegration. Therefore, we are not required to design the microcontroller or circuit byourselves, but we are expected to understand the principle and functions of microcontrollerand circuit.

Figure 10: layout of pins

Raspberry Pi has totally 26 pins in the top right corner of the board, as indictedabove in the figure. Different colors represent different uses.

In our circuit, no.2, 6,11,12,13,15,22 pins of Raspberry Pi are used. They have theirown functions showed below:

No.2: Power.No.6: Ground.No.11: Left motors forward output.No.12: Left motors backward output.No.13: Right motors forward output.No.15: Right motors backward output.(it will be explained more in details in 3.4.program)No.22: Main switch.

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Figure 11: circuit

On another side, they are connected to the microcontroller by female plug. Similarly,microcontroller has several pins with various functions. As indicated below.

Figure 12: layout

No.3, 6, 11, 14 of microcontroller are joint with two motors and Raspberry Pi .

Hence, it is easy to drive program in Raspberry Pi and thus control the speed, du-ration, direction of propulsion system.

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Figure 13: circuit

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3.2.2 Program

The programming language we used is called Python , which is a computer programminglanguage and is widely used in the world. There is a table showing what we needed tolearn and use:

sentence meaningimport <>: import a module.import RPi.GPIO as GPIO: import RPi.GPIO module,and name it as

GPIO to simplify following programs.GPIO.setup(< number,> GPIO.OUT ): set < number > as outputmotor=GPIO.PWM(< number >,<Hz >):

let motor to represent GPIO.PWM(,) to setthe gross output and hertz.

motor.start(< number >): set < number0 − 100 > percentage powerGPIO.output(< number >,< 0or1 >): change the state of < number > , 0 is close ,

1 is open.try:while True: a infinite loop, repeat running the program.if < condition >: if condition is true, then run the following

program;: if condition is wrong, then do not run the

following program.time.sleep(< time >): keep last state for < time > secondexcept KeyboardInterrupt: press ctrl+c to end the program compul-

sively.motor.stop(): stop all GPIO programs.GPIO.cleanup(): clear all GPIO settings.print(”Exiting now...”): print words in the screen:”Exiting now...”

(whole program is in the appendix1)

4 Future work (Next step)

4.1 Result

After testing and practicing, it is found that my hovercraft is able to float on ground,however, winds only blow through right and left sides, front and back sides have little wind,making asymmetric air flow overall, which finally lead to unbalanced pressure difference.It will bring about instability to hovercraft. It seems to be caused by wrinkled skirt,especially in its front and back, which resists flows of air. Another possibility is that theskirt is too tight.

4.2 Advancement

(1)Cut the skirt to make it more loose so that air flows can thread it more rapidly. (2)Cutthe foundation supporter to let air flows thread it more rapidly.

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4.3 Safety issue

Since buoyancy propeller moves with very high power, it is of a great necessity to designand deposit a safe fence encircling the central hole where buoyancy propeller are situatedor use a layer of cloth to cover it.

5 Reference

6 Appendix

[1]Programming codesBasic settingimport timeimport RPi.GPIO as GPIOGPIO.cleanup()GPIO.setmode(GPIO.BOARD)GPIO.setup(13,GPIO.OUT)GPIO.setup(15,GPIO.OUT)GPIO.setup(11,GPIO.OUT)GPIO.setup(12,GPIO.OUT)GPIO.setup(22,GPIO.OUT)motor=GPIO.PWM(22,50)

motor.start(100)GPIO.output(13,0)GPIO.output(15,0)GPIO.output(11,0)GPIO.output(12,0)print (”Press ctrl+c to exit...”)

Choose directiontry:while True:direction=input(”Please choose the direction...”)if direction==”8”:GPIO.output(11,0)GPIO.output(12,1)GPIO.output(13,0)GPIO.output(15,1)time.sleep(5)GPIO.output(12,0)GPIO.output(15,0)

if direction==”2”:GPIO.output(11,1)

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GPIO.output(12,0)GPIO.output(13,1)GPIO.output(15,0)time.sleep(5)GPIO.output(11,0)GPIO.output(13,0)

if direction==”4”:GPIO.output(11,0)GPIO.output(12,1)GPIO.output(13,1)GPIO.output(15,0)time.sleep(2)GPIO.output(12,0)GPIO.output(13,0)

if direction==”6”:GPIO.output(11,1)GPIO.output(12,0)GPIO.output(13,0)GPIO.output(15,1)time.sleep(2)GPIO.output(11,0)GPIO.output(15,0)

except KeyboardInterrupt:print(”Exiting now...”)motor.stop()GPIO.cleanup()

References

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