Chapter One Introduction

Chapter One Introduction

1

Chapter One Introduction 1.1 Introduction:

The world is looking for the most helpful things and tools in humans’ life. One of these things is vehicles. During different eras the human tried to develop vehicles. Among these, recently human developed unmanned or remotely controlled vehicles for various applications to meet different needs. This project aims to design a multi-role vehicle which can be used in the ground, in the water and in the air at the same time. The design aims to combine an unmanned marine & ground vehicle which is called a hovercraft, with an unmanned version called the quad-copter. This kind of vehicles hasn’t commonly been used in the world in a formal way till now. The scope is that, the design of the vehicle is only conceptual and typical one with a character that can be magnified to work as a manned vehicle. The project study will generally be considered from two main design view-points: 1.

Designing of unmanned marine & ground vehicle “hovercraft”, and

2.

Designing of unmanned aerial vehicle “quad-copter”.

The theories of unmanned vehicles, air-cushion vehicles and vertical takeoff and landing vehicles, represents the scientific background for this project, which are combined together and applied to the vehicle so as to achieve the multi-role design. 2

1.2

Research problem: The research problem is addressed by answering the following

questions: 1-

Can the human use one vehicle in the three ambiences, the ground, the water and the air?

2-

How to make a new combination between the three types of vehicles into one vehicle which can perform in the three ambiences effectively?

1.2.1 Research importance: The technology challenge nowadays is to find the most helpful, modern and easy ways for the human kind use. Vehicles are one of those things that play a great role to help human kind in many purposes. The research is seeking to make new generation of vehicles that can have a multi-role by working in the three different environments: ground, water, and air simultaneously.

1.3

Research objectives:

1- General objective: The general objective is to make a conceptual design of a multi-role vehicle which can work in the ground, the water and air. 2- Specific objectives: the specific objectives are: a- Conducting a conceptual design of an unmanned hovercraft system. b- Conducting a conceptual design of an unmanned quad-copter system that works up to the range of 500 meters above the ground. c- Combining the two systems in one vehicle.

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1.4

Scope of the research: The main basis of the research is the vertical takeoff and landing and

the air-cushion vehicles in the form of an unmanned vehicle. The scope of the research is to design the vehicle in two parts: as a ground vehicle; and then as a marine and air vehicle state. That should be conducted by gathering the required data & calculations of the both states. Modeling of the vehicle is the next step by using computer software and making the required tests and trying to find a suitable design which gives the vehicle the ability of working in the air, the ground and the water.

1.6 Research proposed plan: 1.6.1 Gantt chart: The research Gantt chart shown in Table (1.1):

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Table (1.1) Gantt chart

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Chapter Two Literature review & statistical study

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Chapter Two Literature review & statistical studies 2.1Hovercraft: A hovercraft, also known as an air-cushion vehicle, is a vehicle that moves along a surface on a cushion of air. The hovercraft was invented by Christopher Cockerell in 1950s

[1]

. The British aircraft and marine

engineering company Saunders-Roe built the first practical man-carrying hovercraft for the National Research Development Corporation [1]. The physical body of a hovercraft consists of - at minimum - a deck and a skirt. Lift is generated by filling a chamber between the deck, skirt, and ground surface with air. A fan mounted in the deck blows air towards the ground, creating higher air pressure below the fan than above it and lifting the deck. The skirt surrounding the deck contains the pressurized air chamber. Some of the pressure is leaked between the skirt and the ground, allowing movement of the craft [5]. Figure (2.1) explains that:

Figure (2.1): hovercraft skirt and airflow [26]

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2.1.1 Hovercraft Literature review: There are many hovercraft types according to the purpose, like racing and cruising hovercrafts. But there is no need to focus on these types because of the project requirement to make an unmanned & conceptual design of a multi-role vehicle. That leads to focusing on unmanned hovercrafts because of their differences in characters (weight – size) than the commercial or manned types. In a paper by Cean Williard, [2] the aim was to design and fabricate a radio controlled air cushion vehicle, or hovercraft, capable of transportation over land and water. The criteria of the project was divided into four focused categories: lift, thrust, control and materials under four considerations: the performance that the hovercraft must transport over land and water; the serviceability; the ease of maintenance operation; and the manufacturability the hovercraft must be constructed with limited resources and the economic with high priority to minimize cost. The main criteria governing performance was that the device must lift and transport 20 lbs (weight of the craft included). The hull was made of polystyrene which was acceptably rigid, very easy to form with rudimentary hand tools, and has a very low weight. So it was suitable for this project. A 7” x 5” fiberglass fan was used in lifting. To spin the fan two possible motors were considered, a brushless outrunner motor, and 45 turn DC motor. The brushless outrunner provides the greatest power and lowest weight for a given voltage, but also cost three times as much as the 45 turn. A bag skirt from rip-stop nylon, a material which is light, water resistant, readily available, and relatively cheap compared with custom skirt

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fabrics. Thrust for the craft is generated by a 45 turn DC motor and 7” x 5” fiberglass axial fan. Both motor and fan are similar to the ones in the lift subsystem. Control of the craft is accomplished through two rudders which divert airflow to the right and left of the craft. The rudders, cut into the shape of an airfoil, are made from balsa wood which is light, rigid, and sufficiently strong.[2] In the paper by Hassan Abdulkareem, Jassim M. Alhor and Miguel A., they presented a design which they called “Frontera hovercraft”, which was a guided hovercraft model by two vertical poles. They used Graupner motor “Speed 400” 7.2 voltage produce 120W , SlimPROP propeller Size 9x5” , a wood sheet Size 0.25x6x36 and Sanyo KR-600-AE. 8.4Volts batteries. The motor performed flawlessly but the power source (batteries) was quite Problematic, as recharging was constantly needed. The weight of the model was 226 g. [3] Jeffrey Schleigh, aimed to design and construct a physical model of a hovercraft prototype and control the motion of the constructed hovercraft prototype. There were one lift fan and two propelling fan on the rear generate the thrust. The weight of the craft was 981 g. [4] Mat Conyers, Aurora Walker and Bob Warwick,” designed a hovercraft that was lifted by using two propellers to fill a skirt with a pocket of air. This craft weighed a maximum of 1.5 Kilograms, consumed no more than 40 Watts of power (roughly 5.5A current from a 7.2 Volt power source), and

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included a combination of motors, sensors, and controllers as part of both a hovercraft and stationary base station. They made three prototypes each one was a complete design and different from the other so as to compare between them. Two lifting fans & a polystyrene frame were used in each prototype. The prototype had a semi rectangular shape, the second one was circular and the third one was rectangular shape. The comparison was in the speed, stability and ability to lift heavier loads. [5]

2.2 Quad-rotor: A quad-copter is a multi-copter that is lifted and propelled by four rotors. Quad-copters are classified as rotorcraft. Quad-copter is a vertical takeoff and landing vehicle as the helicopter but it has several advantages over helicopter: First, quad-copters do not require mechanical linkages to vary the rotor blade pitch angle as they spin. This simplifies the design and maintenance of the vehicle. Second, the use of four rotors allows each individual rotor to have a smaller diameter than the equivalent helicopter rotor, allowing them to possess less kinetic energy during flight. This reduces the damage caused should the rotors hit anything. Some small-scale quad-copters have frames that enclose the rotors, permitting flights through more challenging environments, with lower risk of damaging the vehicle or its surroundings. In 1922 a French engineer, Etienne Edmond Oemichen, built and flew his second helicopter design. This helicopter, which

was

called

"Oehmichen

No.2",

had

an

X-shaped frame with a rotor at each arm. The first complete quad-copter was made in (1956) as a result of developing many helicopter designs. The 10

maximum model weight 42,000 lb. (19 t) with a payload of 10,900 lb (4.9 t) over 300 miles and at up to 173 mph (278 km/h).[6]

2.2.1 Quad-rotors literature review: Quad-copter is a vertical takeoff and landing vehicle. Quad-copter is used for military and civilian purposes. A number of manned designs appeared in the 1920s and 1930s. These vehicles were among the first successful heavier-than-air vertical takeoff and landing (VTOL) vehicles. However, early prototypes suffered from poor performance, and latter prototypes required too much pilot work-load, due to poor stability augmentation and limited control authority. More recently Quad-copter designs have become popular in unmanned aerial vehicle (UAV) research. [7] In a paper by Inkyu Sa and Peter Corke, they described the characteristics of what they called “MikroKopter”, relevant to horizontal motion and made a control system for this quad-copter. The MikroKopter had a mass of 0.65kg and endurance of 18 minutes (with 2200mAh battery). The nominal payload was 0.25 kg, but they had lifted a payload of 0.85kg although this reduced endurance to 8.3 minutes. [8] Christopher Alexander Herda, described the full development and testing of an Arduino based, radio controlled

quad-rotor. The

motor

selected for use in his project was the Hacker Style KDA2022LBrushless Motor. The most important factors that were taken into account when selecting this motor was the kV, or rpm/V, and the weight. A motor weight of 60g with an rpm/V of 1000 and 10” x 4.7” propellers, would supply about 11

2400g of thrust at 10V, as a note; lower rpm/v carry more weight. 1000rpm/v was suitable for medium or light weight quad-copter. The frame constructed for use in this project consisted for 4 aluminum rods mounted on a fiberglass centerpiece.

The fiberglass centerpiece

consisted of three plates to which the Arduino, sensors, and battery are mounted to.[9] Nate Carlos, Ben Cole, John Cook , Jonathan Forest , Sansen Johnson, Ed Massie and Chris Rogers , competed in constructing a fully autonomous aerial robot that was able to fly and navigate in a confined environment, specifically indoors.They made two prototypes. The weight of both prototypes was 1500g. In the first prototype, the structure was from basswood, the spar length was designed to be 500 mm (0.5 m) long, yielding a maximum width including rotating propellers of less than 700 mm (0.7 m). Prototype two was constructed from carbon fiber and custom pieces of aluminum 6061. [10]

2.3 Conclusions: There are a wide range of hovercrafts which are different in weight and purpose either manned or unmanned. Quad-copters are divided into three types according to the weight: light (up to 2 kg), medium (from 2 up to 6 kg), and heavy (from 6 up to 10 kg). But, to the author knowledge, there wasn’t any previous research in heavy weight model. The parameters that needed to prove the ability of the combination between vehicles depends on mutual designing characters like speed – weight – allowable pressure- range. Table (2.1) represents that:

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Table (2.1) weight data from hovercrafts & quad-rotor

Hovercraft weight [g]

Quad-rotor weight [g]

9071.848

850

226

2400

981

1500

1500

-

10000 8000 6000 Series1

4000

Series2

2000 Series2

0 1

Series1

2 3 4

Graph (2.2) hovercraft weights vs quad-rotor weights

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Chapter Three Configuration Design

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Chapter three Configuration Design 3.1 Introduction: The vehicle mission required that the ability of performing in the water and the ground and in the air. The differences between these environments make the design process very sensitive to the variables among any environment of them. We divided the design process to three main divisions: 1- Design of the flight state as a quadcopter. 2- Design of the marine and ground state as hovercraft. 3- Choosing and adjusting the suitable parts to the two states to work in one configuration effectively. These three divisions include many operations of designing and calculations to reach the intended design. Design will depend on the basis of the unmanned vehicles (aerial, ground, marine), vertical takeoff and landing vehicles and the air cushion vehicles. These three theories are the main basis that we have to use to reach the intended design of the vehicle. 3.1.1 Quad-copter: Quad-copter till now is an unmanned aerial vehicle and also it’s vertical takeoff and landing vehicle. 3.1.1.1 Quad-copter main systems and parts: 1- Power system: The source is a rechargeable electric battery. 15

2- Thrust system: Include four brushless motors connected with propellers. 3- Control system: Include the sending and receiving parts, a microcontroller circuit and the inertial measurement unit, or IMU, which is an electronic device that measures and reports on a craft's velocity, orientation, and gravitational forces. 4- Frame: The main body of the vehicle 3.1.2 Hovercrafts: Hovercrafts are air cushion vehicles that have the ability of moving through the water and the ground in the same time. The hovercraft floats above the ground surface on a cushion of air supplied by the lift fan. The air cushion makes the hovercraft essentially frictionless. Air is blown into the skirt through a hole by the blower .The skirt inflates and the increasing air pressure acts on the base of the hull thereby pushing up (lifting) the unit. Small hole made underneath the skirt prevent it from bursting and provide the cushion of air needed. A little effort on the hovercraft propels it in the direction of the push. As soon as the assembly floats, a blower incorporated in the thrust engine blows air backwards which provides an equal reaction that causes the vehicle to move forward. Little power is needed as the air cushion has drastically reduced friction as shown in Figure (3.1):

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Figure (3.1): Hovercrafts lifting [13]

3.1.2.1 Hovercraft main systems and parts: 1- Power system: Power system in hovercraft could be internal combustion engine or in some small hovercraft electric battery. Electric battery is suitable for the small sizes of hovercraft specially the autonomous types. 2- Lift and thrust system: Includes brushless motors and the flexible skirt which is very necessary to make the air cushion that lead to hovering. 3- Main body of the hovercraft: the frame “the hull, the deck and the duct”

3.2 Minitab statistical tests: 3.2.1General information about Minitab: Minitab is a prepared statistical application that used in calculating, analyzing, testing, forecasting and simulate statistical data which inserted to it. Minitab is used for teaching statistics over a wide range of mainly scientific disciplines. It has a strong tradition of Exploratory Data Analysis 17

so there are lots of useful graphs and diagnostic charts such as the dot-plots or the combination plots. [11] it contains a wide range of statistical measurements parameters and units. Minitab has the ability to do the basic three missions of the statistics Data Description, Statistical Inference and Forecasting. 3.2.2 2-sample T test: 2-sample T test is one of the parametric tests that is used in measuring the correlation between two or more independent communities.  Our consideration is that unmanned hovercrafts and unmanned Quad-copters are in the same range of weight.  The alternative consideration is that unmanned hovercrafts & unmanned Quad-copters are not in the same range of weight.  The two communities are hovercraft weight (the left column) & Quad-copter weight (the right column).  The confidence ratio chosen was 95% 3.2.2.1 The results:-

Figure (3.2) and Figure (3.3) explain Minitab plots results for 2-sample T test:

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Figure (3.2): Minitab plot individual value plot of hovercraft vs. quad-rotor 2-sample T test

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Figure (3.3): Minitab plot Boxplot of hovercraft vs. quad-rotor weight 2sample T test

3.2.2.2 Results Discussion:  Decision making is associated with the value of the probability value (pvalue). If the probability value is bigger than the result of (1- confidence ratio), then we accept our consideration. That means there is a correlation between the two communities. If it is less than we accept the alternative consideration. That means there is no correlation between the two communities.  The probability value in the result is .564 which is bigger than .05 that’s means our consideration is true (the hovercraft and the quad-copter are in the same range of weight).

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3.2.3 One- way ANOVA test: One- way ANOVA is one of the parametric tests that used in measuring the variance between two or more communities.  Our consideration is that unmanned hovercraft & unmanned Quad-copter are in the same range of weight. -the alternative consideration is that unmanned hovercraft & unmanned Quad-copter are not in the same range of weight.  The two communities are hovercraft weight (the left column) & Quadcopter weight (the right column).  The confidence ratio chosen was 95%.

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3.2.3.1 The results:-

Figure (3.4) represents Minitab normal probability plot one way ANOVA test

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Figure (3.4): Minitab plot normal probability plot one way ANOVA test

3.2.3.2 Result Discussion:  Decision making is associated with the value of the probability value (p). If the probability value is bigger than the

result

of

(1- confidence ratio) then we accept our consideration. That means there is no variance between the two communities. If it is less, then we accept the alternative consideration. That means there is a variance between the two communities.

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 The probability value in the result is .605 which is bigger than .05 which means that our consideration is true (there is no variance in weight between the hovercraft and the quad-copter).

3.2.4 Final result:According to the two tests (2-sample T & one way ANOVA), there is convergence between the hovercraft weight and the quadcopter weight. That gives us the green light in designing a combination between the two crafts (hovercraft & quad-copter) the new combination that is obtained will be in the same range of weight, from 1kg up to 10 kg according to the recent data of the two crafts.

3.3 Hovercraft design calculations and designing estimations: As it is shown on the plan of the research, the design process of the vehicle will be divided into a marine and ground state as a hovercraft and flight state as a quad-rotor. 3.3.1Hovercraft design calculation aims to specify the following: 1. The gross weight of the vehicle. 2. The suitable dimensions and the main factor on the dimensions is the hull of the vehicle and the skirt. 3. The air flow effect including the total mass air flow on the skirt, and cushion pressure and its effect on the skirt shape details, all which causes the lifting process. 4. Required Thrust

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5. Required power. 3.3.2 Hull: The basic required characters of the hull include: 

Need to have adequate size for the total weight of craft and payload.



Need to be strong enough to support craft off cushion (on landing pads).



Need to have enough freeboard to support craft in displacement mode on water.



Need to be watertight and as smooth as possible.

The hover pressure is found to be about 0.1 pound per square inch in most crafts as in literature. [12] The Relation between width and length vs. lifting capability at 0.1 lb./ in² is as follow: (

)

[12]

(3.1)

The length of the hovercraft is mostly taken as twice of the width. [13] Previous hovercraft design characters including the hull dimensions against the lift are shown in table (3.1): [12]

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Table (3.1): Width and length vs. lifting [12]

 Lift must be equal to the weight of the vehicle.  The estimated weight of the vehicle was 10 kg or 22.046 lb. so Equation (3.2) will be : (

)

(3.2)

W=0.875feet = 0.267m Then L=2*w=2*.875=1.75feet=0.534m The hull dimensions are (0.875*1.75) feet.  Cushion area will be the total hull area.

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 Cushion pressure is a basic factor that effect on lifting process Cushion pressure is given by Equation (3.3) below; (3.3) Pcu= (10*9.81)/ (0.267*0.534) = 688.044 N/m2. 3.3.3 The skirt: Skirt is a basic part of the hovercraft. Lifting process depends on cushioning the air using the skirt which surrounds the hull of the craft so as to keep the air inside the cushion area. After some initial investigation it was found that there were three different types of hovercraft skirt which could be used: 1. Bag Skirt: The simplest skirt to design and manufacture. Best suited to multi-terrain cruising hovercraft (see Fig. (3.4). 2. Finger Skirt: This design is more complex than the bag skirt. This is best suited to light racing hovercraft due to its low coefficient of drag. Design also requires the use of an air chamber to evenly distribute the air into each finger section. 3. Bag and Finger Skirt: The most complex skirt to manufacture. This design makes the best of both the bag and finger skirts; low drag and multi-terrain capability.

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3.3.3.1 Results: After some further investigation into the vehicle under consideration, and comparing the needs with R/C hovercraft, it becomes apparent that the bag skirt was the most viable option for our hovering, because when scaling down the size of a hovercraft the advantages of a finger and bag & finger skirt become less noticeable. If the bag skirt is well designed at this small scale level it can be in-fact more efficient than finger and bag &finger skirts beside of it’s the simplest to design and manufacture. Figure (3.5) describes bag skirt:

Figure (3.5): Bag skirt [14]

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Bag pressure is the pressure inside the bag skirt as a result of inflating the skirt with air. According to the size of the bag, the pressure could be changed. The size of the bag is formed by two radiuses the inner radius which makes the shape of the inner skirt and the outer radius which makes the shape of the outer skirt. There is a radius between the cushion pressure and the bag pressure which controls the inner and the outer radius needed as shown in table (3.2). Table (3.2): Pressure differential and the radiuses factor [14]

The choice of pressure differential is based upon the degree of stability required. The higher ratio gives greater stability, but at the expense of undulating surface performance and higher skirt wear on uneven terrain. It is suggested that when designing the first hovercraft without having the ability to measure the cushion pressure for similar designs using the ratio (1.5:1), so the factor will be 3. (3.4) P bag = 1.5*688.044 = 1032.067 N/m2.

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The radius of the inner circle is calculated by multiplying the outer radius by a factor selected from the table. The outer diameter is always equal to the height of the skirt .The height can be roughly estimated as 1/8 th of the total hull width.[15] (

)

(3.5)

Skirt height = (1/8)* 0.267 = 0.033375 m. (3.6) Outer radius = 0.033375 /2 = 0.0166875 m.

Inner radius = 3 * 0.0166875 = 0.0500625 m. Figure (3.6) explains the inner and the outer radiuses.

Figure (3.6): Skirt geometry shape [2]

From Bernoulli’s theory, the velocity of air escaping under the peripheral gap Vc is given by equation (3.7) below: √(

)

(3.7)

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Where ρ is the air density. Table (3.3) contains the density values.

Table (3.3): Density and Specific Weight of Air at Standard Atmospheric Pressure in SI Units [15]

By calculating the vc for three different temperatures 1- At 15ºC , ρ =1.225 kg/m3 Vc was 33.516 m/s. 2- At 20ºC , ρ =1.204 kg/m3 Vc was 33.807 m/s. 3- At 30ºC , ρ =1.165 kg/m3 Vc was 34.37 m/s.

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The total volume flow of air from the cushion Q is given by equation (3.8): (3.8) Where h is the clearance height over the ground, Icu is the perimeter of the air cushion and Dc is the discharge coefficient. The discharge coefficient is the ratio of the mass flow rate at the end of the nozzle to what the mass flow rate would be if the nozzle were ideal. The discharge coefficient is primarily a function of the wall angle ɵ and the length of the wall. The values of Dc are as in table (3.4): Table (3.4): The angel from the horizontal and the discharge coefficient [16]

Ө

0º

45º

Dc

0.5

0.537

90 º

135 º

180 º

0.611 0.746 1.000

Icu of the hull semi rectangular shape is 1.338m, h is 20 mm, at Ө 45º Dc 0.537 and at 20 ºC Vc 33.807 m/s. The total air flow volume from the cushion Q generated is 0.4858 m3/s. But if the flow loss is taken into consideration, a flow loss C should be added, the range of which normally varies between 0.6 – 0.7

[17]

. It may

be more than this range but to be more confident about the success of the design, the minimum value of the flow factor 0.6 should be taken. (3.9) Then the total mass flow Q* will be 0.29149 m3/s. The total area of the peripheral jets holes can by calculated by equation

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(3.10): (3.10) The area of the holes will be 8.6221*10-3 m2. By estimating 4 circular holes on the skirt, the area of the any hole will be 2.1557*10-3 m2. So the diameter of the hole will be 0.05239 m or 52.39 mm. The power required to sustain the air cushion at the peripheral jets P is given by equation (3.11) below: (3.11) (3.12) The final derivation of the equation will be as shown in equation (3.13) below: (

)

( )

(3.13)

The required power P will be 336.011 W. 3.4 4wings hovercraft development web calculator results: By entering the data of the estimated design, the four wings calculator shows the results as demonstrated in table (3.5):

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Table (3.5): 4 wings calculator Hovercrafts configuration result

3.4.1 Results comparison: By comparing the manually calculated result with the results above, it can be found that the result well agrees with the previously estimated dimensions, and that the cushion pressure results are equal. The difference was on the value of the velocity and the power that difference appears as a result of the variation of the discharge coefficient and the argument factor used and the density of the air according to the variation of the temperature taken on the calculations considerations.

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This is because the estimations were based on high requirements in order to have more reliable design.

3.5 Quad-copter configuration design: The quad-copter contains four rotors; each rotor produces a thrust force as shown in Figure (3.7):

Figure (3.7): Quad-copter rotors

The summation of these forces gives the thrust produced by the quad-copters motors as shown by the equation (3.14) below: [18]

(3.14)

The total force is equal to the weight as shown in equation (3.15): [18]

(3.15)

Where m is weight of the vehicle (kg) and g is the gravity 9.81 m/s2. The required hovering power is calculated from equation (3.16): [19]

(3.16)

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Where Vi is the induced velocity on the rotor. √(

)

[19]

(3.17)

Where ρ is the density of the air A is the area of the rotor. From equation (4.4), it’s clear that increasing the rotor diameter decreases the required power. The flight time is given by equation (3.18): Flight time = battery capacity / drain amps [20]

(3.18)

The drained current is consumed by the motors. There are 4 motors on the flight state. The battery capacity is measured by the amperes per hour. 3.5.1 Model 1: Emax GT 5325 – 11 260 Kv (rpm/v), is used which have a 80 A as a maximum. 3.5.1.1 Mass estimation: Table (3.6) contains model 1 the mass estimation:

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Table (3.6): Model 1 Mass estimation

Part

Weight (Kg)

5 brushless motors Emax GT 5325 – 11

2.85

QUADROPOWER 10,000 mAh (6S) LIPO BATTERY

1.358

HOBBYWING Platinum-30A-Pro 26S Electric Speed Controller (ESC)

0.158

Frame

3_4

HobbyKing Quadcopter Control Board

0.015

Total

7.381 _ 8.381

3.5.1.2 Parts table: Table (3.7) contains model 1 parts description: Table (3.7): Model 1 parts description

Battery

motor

QUADROPOWER brushless 10,000 mAh (6S) motors LIPO BATTERY Emax GT 5325 – 11 (260 Kv)

ESC

props

Total weight

HOBBYWING Aeronaut 8.381 Platinum-30A- camcarbon Pro 2-6S 18*9 Electric Speed Controller

From equation (2.4), the total thrust for hovering equals the total weight Then TH = 8.381 * 9.81= 82.218 N 37

From equation (4.4) the induced velocity of the rotor will be: Vi = 14.297 m/s From equation (3.4) the required hovering power will be: P = 1175.5 W From equation (5.4) the flight time will be: Flight time = 10000 * 60 / (80 *4 * 1000) =1.875 min 3.5.2 Model 2: If hacker motors A50 16L 265 Kv (rpm/v) is used, which have a 60 A as a maximum drain amperes. Note: Each motor from the 4 motors should have a battery. 3.5.2.1 Mass estimation: Table (3.8) contains model 2 mass estimation:

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Table (3.8): Model 2 Mass estimation

Part

Weight (kg)

5 brushless motor hacker A50-16l-v2

2.15 3.632

4 Turnigy nano-tech 6000mah 6S 25~50C

0.16 5 Flight Power 40A Brushless ESC 3_4 Frame 0.015

HobbyKing Quadcopter Control Board

8.957 _ 9.957

Total 3.5.2.2 Parts table: Table (3.9) contains model 2 parts description:

Table (3.9): Model 2 parts description

Battery Turnigy

motor

nano- brushless

tech 6000mah 6S motor 25~50C

ESC

props

Total weight

Flight Power APC Electric Maximum 9.957

hacker 40A

E 19*10

A50-16l-v2

Brushless

(265) Kv

ESC

From equation (2.4), the total thrust for hovering equals the total weight.

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Then; TH = 9.957 * 9.81 = 97.678 N From equation (4.4) the induced velocity of the rotor will be: Vi = 14.76 m/s From equation (3.4) the required hovering power will be: P = 1442 W From equation (5.4) the flight time will be: Flight time = 6000 * 60 / 60 * 1000 = 6 min. 3.5.3 Models comparison: Model 1 had a less weight. It used 1 battery with higher mAhs (10000 mAh) for the vehicle compared with model 2 which had a higher weight because it used 4 batteries with lower mAh (6000 mAh ) and that lead to increasing the total weight of the vehicle because of the total weight of the 4 batteries. The weight of the 6000 mAh battery was lesser than the 10000mAh battery but the total weight of the 4 batteries of the 6000 mAh was higher. From this point of view, model one was better. But when studying the total flight time of the two models it can be concluded that: Model 2 is better because it had an acceptable flight time with 6 minutes. Model 1 had a lower flight time with 1.875 minutes which is too short for model to use on air and water and ground.

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According to the project objective it’s clear that it’s better to use model 2.

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Chapter Four Vehicle Control

42

Chapter Four Vehicle Control The vehicle has been divided into two parts or flight states; “quadcopter” & marine and ground state “hovercraft”, then, the control system will too be divided into two states.

4.1 hovercraft control system: The remote control will translate the human orders into signal and send it to vehicle controller. The controller controls the motors position and angle in the case that the thrust motors are on the rear of the vehicle using stepper motors that are used to change the orientation of the motor so as to change the thrust force direction. 4.1.1 Hovercraft control system including: 1. Remote control 2. Micro controller 3. Electronic speed controllers 4. 4 servo motors 5. 2 rear thrust/brake motors 6. 1 lift motor

43

4.1.2 Hovercraft block diagram:

Controller

R.C signal

Hovercraft Dynamics

Visual feedback

Figure (4.1): Hovercraft block diagram The visual feedback is done by the human who orients the vehicle in the case of marine and ground state according to observed vehicle position.

4.2 Quad-copter control system: Quad-copter control theory depends on the variation of the motors speed. As the quad-copter has 4 rotors, each one has a rotation direction and speed magnitude relative to others motors to give the vehicle the targeted flight dynamics. 4.2.1Quad-copter flight dynamics definition: Flight dynamics is the science of air vehicle orientation and control in three dimensions. The three critical flight dynamics parameters are the angles of rotation in three dimensions about the vehicle's center of mass, known as roll, pitch and yaw. [21]

44

Each one of the three parameters is oriented around one of the three axes x, y and z as shown in Figure (4.2) and Figure (4.3):

Figure (4.2): Yaw, pitch and roll around x, y and z axes

Figure (4.3): Yaw, pitch and roll on the quad-copter 45

4.2.2 Quad-copter configuration: There are two configurations for quad-copter motors positioning (X) configuration and (+) configuration as shown in Figure (4.4)

Figure (4.4): Quad-copter x & + configuration [22]

The main motions that the vehicle should perform are front, back, left and right as shown for the x configuration in figure (4.5) and for the + configuration in Figures (4.6) & (4.7):

:

46

Figure (4.5): X configuration motions

For the (+) configuration:

Figure (4.6): (+) Configuration front

47

Figure (4.7): (+) configuration rotation and liner motion right

As it’s shown below, the control theory of the quad-copter depends on the principle of rotation moment and the balance between motors to make the vehicle stable and in the needed direction. 4.2.3 Quad-copter block diagram:

R.C Signal

Controller

Quad-copter flight dynamics

Inertia measurement unit IMU

Figure (4.8): Quad-copter block diagram

48

Motor

Motor

ESC

ESC

Controller

ESC

ESC

Motor

Motor

Figure (4.9): Quad-copter control system

49

Chapter Five Conclusion and Recommendations

50

Chapter Five Conclusion and Recommendations The chapter summarizes the project overcomes in relation to the project objectives that were outlined in Section 1.3. This section concludes with recommendations for the future direction that the project should take.

5.1

Research objectives: The general objective was to make a conceptual design of a multi-role

vehicle which can work in the ground, the water and air by combining the hovercraft with the quad-copter. The research approved the possibility of combining the two vehicles into on vehicle by two statistical tests 2-sample T test and One- way ANOVA test. The results shown in table (5.1) below: Table (5.1): statistical study results

Test

Scope of the test

2-sample T One- way ANOVA

Hovercraft vs. quadcopter Hovercraft vs. quadcopter

Tested Characters Weight

pvalue 0.564

Weight

0.605

These results gave the permission to make the design of the vehicle. The design is divided into two divisions according to the states of the vehicle; the marine and ground state “Designing of the hovercraft” and the aerial state “Designing of the quad-copter” conducting the combination possibility in each design phases. The calculation needed to reach the final

51

vehicle design had been made and after many configurations testing the final parts configuration details selecting shown in the table (5.2) below: Table (5.2): vehicle parts and weights

Part

Weight (kg)

5 brushless motor hacker A50-16l-v2

2.15

4 Turnigy nano-tech 6000mah 6S 25~50C 5 Flight Power 40A Brushless ESC Frame Including hull, duct, holders and flexible skirt HobbyKing Quadcopter Control Board

3.632 0.16

3-4 0.015 8.957 _ 9.957

Total The parts selected shown in table (5.3) below: Table (5.3): parts description

Part Battery Motor ESC Ground & marine propellers Aerial state propellers Frame Flexible skirt

Description Turnigy nano-tech 6000mah 6S 25~50C brushless motor hacker A50-16l-v2 (265) Kv Flight Power 40A Brushless ESC APC Electric E 9.2*7 APC Electric E 19*10 Carbon Fiber Nylon

The calculations had been made using this configuration and the results shown in the table (5.4): 52

Table (5.4): calculation data

parameter result Thrust of hovering aerial state 97.678 N induced velocity 14.76 m/s Minimum Power required 1442 W Expected flight time 6 min

The final drafting of the vehicle from Catia is shown in figure (5.1) below:

Figure (5.1): the vehicle drafting

53

The parts and the vehicle modeling had been made using Catia and it had been attached to appendix B.

5.2

Future work: The design of the vehicle is ready for implementing now. The coming

work should be implementing the model so as to complete the experimental data required and parameters which had been mentioned on Appendix A; that can give us the ability for converting the data of the mathematical modeling of the vehicle to a simulation.

54

References: [1] http://en.wikipedia.org/wiki/Christopher_Cockerell visited at 16/9/2013 [2] Cean Williard,” The Hover Project Radio Controlled Air Cushion Vehicle”, University of Portland. Department of Mechanical Engineering. April, 2008.

[3] Hassan Abdulkareem , Jassim M. Alhor and Miguel A. “Frontera”hovercraft”, e-bookspdf.org, 2010.

[4] Jeffrey Schleigh, “Construction of a Hovercraft Model and Control of its Motion”, Institute for Systems Research ISR, 2006.

[5] Mat Conyers, Aurora Walker and Bob Warwick ,” Physical hovercraft design, Project Phase 2, University of Victoria, spring 2010.

[6] Øyvind Magnussen and Kjell Eivind Skjønhaug, “Modeling, Design and Experimental Study for a Quadcopter System Construction”, University of Agder Department of Engineering Faculty of Technology and Science, 2011. [7] http://en.wikipedia.org/wiki/Quadcopter, visited at 21/9/2013.

[8] Inkyu Sa and Peter Corke , “Estimation and Control for an Open-Source Quadcopter”, Queenslamd University of Technology, Proceedings of the

55

Australasian Conference on Robotics and Automation, Monash University, Melbourne, Vic, 2011.

[9] Christopher Alexander Herda,” Implementation Of a Quadrotor Unmanned Aerial Vehicle’, CALIFORNIA STATE UNIVERSITY, NORTHRIDGE, May 2012. [10] Nate Carlos, Ben Cole, John Cook , Jonathan Forest , Sansen Johnson, Ed Massie and Chris Rogers ,” IARC Team Quadrotor”, indabook.org, 2008-2009.

[11] http://www.ed.ac.uk/schools-departments/informationservices/research-support/research-computing/statistics/supportedpkgs/minitab/about-minitab, visited at 1/12/ 2013. [12] http://4wings.com.phtemp.com/tip/lh.html, visited at 2/3/ 2014. [13] Okafor, B.E, “Development of a Hovercraft Prototype”, International Journal of Engineering and Technology Volume 3 No. 3, March, 2013. [14] http://4wings.com.phtemp.com/tip/bag.html, visited at 3/3/ 2014. [15]http://www.engineeringtoolbox.com/air-density-specific-weightd_600.html, visited at 5/4/ 2014. [16] J. Y. Wong, “Theory of ground vehicles” 3rd edition, JOHN WILEY & SONS, INC, year. [17] G .H. Williams, “Homebuilt hovercraft, a plain man’s to ACV design and construction, Part-13”, Flight International Supplement 21, April 1966.

56

[18] Senior Designby Christopher Moy and Silver De Guzman TA, Mustafa Mukadam “Alternative Quadcopter”, Fall 2013. [19] Eva Saadé Latorre ,Universitat Politècnica de Catalunya, “Propulsion system optimization for an unmanned lightweight quadrotor”. Master in Aerospace Science & Technology,June 2011. [20] http://quadcopterproject.wordpress.com/battery-and-flight-time/, visited at 10/4/ 2014. [21] http://en.wikipedia.org/wiki/Quadcopter, visited at 28/4/ 2014. [22] http://copter.ardupilot.com/wiki/px4fmu-only-wiring/, visited at 2/5/ 2014. [23] H .J .L .M. Consten, “Control of a Model Sized Hovercraft”, THE UNIVERSITY OF NEW SOUTH WALES SYDNEY, AUSTRALIA, Report nr. : 2003 .32, April 2003. [24] P. Fitz Patrick, “Calculation of thrust in a ducted fan assembly for hovercraft”, Hovercraft club of Great Britain (S.E Branch), 2003. [25]

Tomáš

Jiinec,

Quadcopter”,CZECH

“Stabilization TECHNICAL

and

Control

of

Unmanned

UNIVERSITY

IN

PRAGUE

FACULTY OF ELECTRICAL ENGINEERING DEPARTMENT OF CYBERNETICS, Prague, May 30, 2011. [26]http://www.antonineeducation.co.uk/Image_library/Physics_2/Mechanic s/MEC_09/hover_2.gif visited at 27/10/2013

57

Appendix A Mathematical modeling

58

Appendix A: Mathematical model: Mathematical modeling of the vehicle is about studying all the parameters that effect on the vehicle and its operations by studying the statics and dynamics of the vehicle. That will guide us to find the equation of motions which represent the acceleration of the hovercraft as a result of the forces acting on it. Before all that we have to define the kind of system that we dealing with and as a result of the control studying of the vehicle it is clear that the control system is nonlinear system. We have to main states quad-copter state and hovercraft state and everyone is separate from the other so we have to make two mathematical models “hovercraft mathematical model & quadcopter mathematical model”.

A.1 hovercraft modeling: It’s necessary to define the degree of freedom of the hovercraft. It is clear that the vehicle has six degrees of freedom. Three translational: surge, sway, heave, and three rotational: roll, pitch, and yaw. That DOFs effecting on the body fixed reference which means vehicle coordinate system X o, Yo and Zo . There is other coordinate system that refers to the earth which called earth fixed reference X, Y and Z. The body fixed reference X o, Yo and Zo is defined as follow:  Xo longitudinal axis (directed from aft to fore).  Yo transverse axis (directed to starboard).  Zo normal axis (directed from top to bottom). Figure (A.1) & table (A.1) represents that: 59

Figure (A.1): Hovercraft rigid body axes and motions Table (A.1): DOF, forces & moments and velocities on axes

DOF

Forces moments

and Velocities Axes

Surge

X (linear to axes)

u

Xo

Sway

Y (linear to axes)

v

Yo

Heave

Z (linear to axes)

w

Zo

Roll (Ø)

K (around axes)

P

Xo

Pitch(θ)

M (around axes)

q

Yo

Yaw(ψ)

N (around axes)

r

Zo

60

A.1.1 Modeling estimations: 1. The hovercraft is rigid thus no forces act between individual elements of mass. 2. The mass and moment of inertia of the hovercraft are assumed to be constant: ṁ = 0, Ī = 0. 3. The earth fixed reference frame is inertial. This means that none of the forces acting on the hovercraft are a result of the movement of the earth. 4. The origin of the body-fixed reference frame is chosen to coincide with the center of gravity. A.1.2 Equations of motion: There are two kind of motion translational or rotational. From

[23]

the

equations of motion for the two types:  Translational: ( ̇

)

(A.1)

( ̇

)

(A.2)

( ̇

)

(A.3)

 Rotational: ̇

(

(

( ̇

)

(

)

̇) ̇

(

)

(

(A.4) )

( ̇

)

̇)

(

) (A.5)

61

̇

(

)

(

( ̇

)

̇)

(

) (A.6)

For the hovercraft we can neglect the heave, roll and pitch mode. The heave is not relevant since the hovercraft is operated on an even surface. Although there is some displacement in Z direction when the lift motor is turned on or off but that has no influence on the behavior of the hovercraft. The roll and pitch of the hovercraft are negligible for the same reason; the surface on which the hovercraft is operated is even. The hovercraft is very stable and therefore the roll and pitch modes are hardly present on an even surface. They can be present very shortly if the lift force is adjusted but are small very fast so they can be neglected. Only the surge, sway and yaw displacements remain in the model. Then the final equations become: ( ̇

)

(A.7)

( ̇

)

(A.8)

̇

(A.9)

Above equations was about body fixed. Now we have to find the equations that describe the motion around the earth fixed reference: From [23] ̇ ̇ ̇

(A.10) ̇

̇ [ ̇]

[

]

62

Where dll, d22 and d33 are damping coefficients. Fwl, Fw2 and Fw3 are friction forces. The forces X, Y and N can be rewritten as a function of the lift force and the back thrust force as follow: [23] (

)

(A.11)

( )

(A.12)

( )

(A.13)

Where (Fxx) is the back thrust, (a) is the arm of the force causing a moment around the z-axis and ( ) is the back thrust angel. A.1.3 Hovercraft Parameter Estimation and Identification: A.1.3.1 Mass (m): The mass of the vehicle is 10 kg. A.1.3.2 Moment of inertia (J): There are two methods to determine J experimentally and mathematically; the experimental method by the rig-test and the mathematical by calculating J for the parts of the vehicle. By using Catia as shown in Figure (A.2) for determining the vehicles moment of inertia:

63

Figure (A.2): Catia inertia measure

The result shown in table (A.2) as follow:

64

Table (A.2) Catia inertia measure results

A.1.3.3 Back thrust: The back thrust is coming from the two rear motors that are rotated 90o clockwise using servos. From [24] the net thrust equation: ( Where

)

is the back thrust,

is the air density and

(A.14) is the discharge velocity,

is the fan area,

is the free stream velocity.

Since the diameter of the propeller is known then 65

will be 0.1829 m2

A.1.3.4 Damping: From [23] the damping equation is: (

( ))

(A.15)

The mass is known and the back thrust then damping will be a function of the surge velocity

and the angel ( ). If we assume that the

angel is 0o and the surge velocity is 3 m/s,

= 16.213 N. since in the sway

direction there is no acting force there for

is 0 and

also.

A.1.3.5 Friction: To determine the friction we have to find the frictions factors. These factors depend on experimental tests. Since we haven’t experimental tests we will chose factors from previous simulations. [23] 1 = 0.100 2 = 0.010 3 = 0.004

A.2 Quad-copter modeling: Vehicle on quad-copter state has the same degree of freedom as the hovercraft state. Quad-copter has six degree of freedom. The references are the same references body fixed reference and the earth fixed reference. The different will be in the formulas that describes the motions and the positioning and the parameters effect on the vehicle.

66

A.2.1 Quad-copter references and motion definition: The basic variables that control the motion of the quad-copter and it’s positioning relative to the two coordinate references the body fixed reference and the earth fixed reference are yaw, pitch and roll. The motion is also divided into two kinds transitional and rotational as shown in Figure (A.3)

Figure (A.3): Quad-copter references and motion definition

A.2.2 Quad-copter modeling equations: The equations describing the main parematers that effect on the quadcopter and it’s dynamics. First we have to describe relationship between the quadcopter two cordinates the earth fixed cordinate and the body cordinate and the transformation between them. From [25] the Direction cosine matrix is:

[

]

(A.16) And to describe the change of position according to quadrotor's attitude in its velocity measured in the body frame: 67

̇

[ ̇] ̇

[ ]

(A.17)

Yawing and pitching and rolling give the quad-copter position and orientation that makes the angular velocities shown as follow: ̇ [ ̇] ̇

[ ]

(A.18)

Where [

]

(A.19)

Then we have to describe the forces effecting on the axes x, y and z ̇ [ ̇

[ ]

] ̇

(A.20)

If we neglect the aerodynamics forces the remain force will be the weight force on x and z axes and the resultantant of the thrust and the weight on the z axes. Then the equation becomes: ̇ [

]

[ ̇ ̇

]

(A.21)

Considering no motor dynamics the thrust of all rotors will be: (

)

(A.22) 68

Where b is a thrust coefficient and

i

is speed of each rotor.

Then the lingtunal accelaration equations will be: ̇

(A.23) ̇

(A.24) ̇

(

)

(A.25)

Then to The external torques are produced by the thrust and drag of the propellers. Neglecting the propeller's inertia and aerodynamic torques, then the external torques can be written as: (

)

(A.26)

(

)

(A.27)

( where

)

(A.28)

is the drag factor of the rotors and is the distance of the propeller

from the center of gravity. Now the rotational accelaration is described with the equations: ̇

̇

̇

(

)

(

)

(

(

)

(A.29) (A.30) )

(A.31)

69

Appendix B Parts modeling

70

Appendix B: Parts modeling This section containing the parts modeling the final vehicle assembly using Catia. B.1: Deck:

Figure (B.1): deck of the vehicle catia 3D interface

71

Figure (B.2): deck drafting

72

B.2: Lift fan duct:

Figure (B.3): lift fan duct catia 3D interface

73

Figure (B.4): lift fan duct drafting

B.3: The hull:

Figure (B.5): the hull catia 3D interface

74

Figure (B.6): the hull drafting

B.4: Lifting center motor:

Figure (B.7): lifting center motor catia 3D interface

75

Figure (B.8): lifting center motor drafting

76

B.5: Terminal motors rod:

Figure (B.9): terminal motors rod catia 3D interface

Figure (B.10): terminal motors rod drafting

77

B.6: Quad-copter rotor:

Figure (B.11): quad-copter rotor catia 3D interface

Figure (B.12): quad-copter rotor drafting

78

B.7: Rotor cage:

Figure (B.13): rotor cage catia 3D interface

Figure (B.14): rotor cage drafting

79

B.8: Terminal rotors holder:

Figure (B.15): terminal rotors holder catia 3D interface

80

Figure (B.16): terminal rotors holder drafting

B.9: The skirt:

Figure (B.17): the skirt catia 3D interface

81

Figure (B.18): the skirt drafting

82

B.10: The vehicle:

Figure (B.19): the vehicle Catia 3D interface

83

Figure (B.20): the vehicle different views catia 3D interface

84

Figure (B.21): the vehicle drafting

85