Design and Development of a Quad Copter (UMAASK) Using CAD/CAM/CAE Irfan Anjum Manarvi, Muhammad Aqib, Muhammad Ajmal, Muhammad Usman, Saqib Khurshid, Usman Sikandar Department of Mechanical Engineering, HITEC University, Taxila Education City, Taxila, Pakistan
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aerial vehicles (UAVs) weights ranging from hundreds of grams to thousands of kilograms [1]. Quad rotor design is one of such vehicles which has two main advantages over comparable vertical takeoff and landing UAVs, such as helicopters. First, quad rotors do not require complex mechanical control linkages for rotor actuation, relying instead on fixed pitch rotors and using variation in motor speed for vehicle control. It could be used for indoor flight application in obstacle-dense environments, with low risk of damaging the vehicle, its operators, or its surroundings [2]. Researchers at Berlin University of Technology, designed and manufactured. Major challenge was a completely different flight dynamics compared to a normal helicopter. Initially flight behavior was tested for its hovering in controlled environment. Then they developed a suitable computer model for higher flight dynamics [3]. Another Quad rotor helicopter called Dragonflies X-Pro was also designed which differed from traditional helicopters such that it had four horizontal rotors and no vertical rotors. Only variable that could be adjusted in flight was the rotational speed of the rotors [4]. At University of new south Wales School researchers developed Dragonfyer a simple remote control helicopter and its Flight Control Unit (FCU). The new control unit was equipped with gyroscopes, accelerometers, a magnetometer and an ultrasonic range finder. These sensory devices gave enough information that could be used for autonomous control [5]. At Worcester Polytechnic Institute a miniaturized autonomous quad-rotor capable of taking off from a landed position, maneuvering to a point determined by a programmed iRobot, hovering, and landing at its take off point was designed. Its structure was of quad-rotor configuration powered by battery. The team designed and machined a frame to hold all the components of the quad-rotor in a balanced and efficient manner [6]. Columbia Accident Investigation Board proposed NASA to develop and implement a comprehensive inspection plan to determine the structural integrity of all Reinforced Carbon-Carbon (RCC) system components prior to re-entry. Inspection plan was expected to take advantage of advanced non-destructive inspection technology comprising of a micro-flying robot to continuously monitor inside a space vehicle for any stress related fissures, cracks, foreign material embedded in walls and tubes. A helicopterlike flying robot “Pixelito” with 6.9 gram, two-bladed rotor of 148 mm of diameter was developed [7]. Its infra-red
Abstract—Micro flying vehicles (MFV) have become a
popular area of research due to economy of production, flexibility of launch and variety of applications. A large number of techniques from pencil sketching to computer based software are being used for designing specific geometries and selection of materials to arrive at novel designs for specific requirements. Present research was focused on development of suitable design configuration using CAD/CAM/CAE tools and techniques. A number of designs were reviewed for this purpose. Finally, rotary wing Quadcopter flying vehicle design was considered appropriate for this research. Performance requirements were planned as approximately 10 meters ceiling, weight less than 500grams and ability to take videos and pictures. Parts were designed using Finite Element Analysis, manufactured using CNC machines and assembled to arrive at final design named as UMAASK. Flight tests were carried out which confirmed the design requirements.
TABLE OF CONTENTS 1. INTRODUCTION .................................................................1 2. METHODOLOGY ................................................................2 3. QUAD COPTER DESIGN PROCESS.......................................2 4. POWER THRUST AND SPEED CALCULATIONS ...................6 5. ELECTRONIC SYSTEM .......................................................6 6. SPECIFICATIONS OF COMPONENTS...................................7 7. FINAL ASSEMBLY ..............................................................8 8. PERFORMANCE TESTING AND FINDINGS ..........................9 9. CONCLUSIONS ...................................................................9 10. REFERENCES ...................................................................9 11. BIOGRAPHY ...................................................................10 1. INTRODUCTION A research was conducted at NASA Rotorcraft Division &NASA Ames Research Center, for the development of a rotary-wing micro air vehicle (MAV). Technology trends involving microelectronic miniaturization, vehicle autonomy systems, electric propulsion and power electronics has enabled the design of rotary-wing micro air vehicles (MAVs) to larger sized, rotorcraft uninhabited 1
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control device enabled the pilot to have full 4-axis control in the space dimensions. It further lead to the development of ProxflyerMicron, a 6.9 gram very silent and aerodynamically stable flying robot with a coaxial-rotor diameter of 128 mm [7]. A research was conducted to develop Small Semi-Autonomous Rotary-Wing Unmanned Air Vehicle (UAV) which could be deployed at the front lines of combat to provide situational awareness to small units of troops through real-time information about surrounding areas [8]. The concept of micro-sized Unmanned Aerial Vehicles (UAVs) or micro Air Vehicles (µAVs) has gained increasing interest with the principal aim of carrying out surveillance missions. Primary payload of these tiny aircraft (~15 centimeters or 6 inches wingspan) is usually a miniature image sensor. Operating in an approximate radius of 600 meters from the launch point, µAVs are used to acquire real-time visual information for a wide range of applications [9]. A study revealed that development of functional micro aerial vehicles (MAVs) has been hindered by a limited understanding of the aerodynamics of small aircraft flying at low speeds. Classical aerodynamic theory provides reasonably accurate performance predictions for airplanes flying at Reynolds numbers larger than approximately one million (typically found in full scale aircraft)[10]. A focus on improving the efficiency of flapping-wing MAVs by using material with high strength and low weight to increase the overall stiffness of the MAV, producing a MAV with a total weight of 10 g and a payload capacity of approximately 20 g was investigated leading to a vehicle of 3.35 g. It was capable of providing sufficient lift force to hover and generate forward thrust using differential steering of two flapping-wings [11]. Requirements of unmanned retrieval of a remote object from hazardous environment lead to the development of a multi-agent system of quad copters (MASQ) which could be capable of autonomous retrieval of a user specified payload[12]. Control methods require accurate information from the position and attitude measurements performed with a gyroscope, an accelerometer, and other measuring devices, such as GPS, and sonar and laser sensors. Therefore components such as PID controllers, back stepping control, nonlinear H1 control , LQR controllers , and nonlinear controllers with nested saturations have also been the subject of research in this area [13]. Estimation and Control for an Open-Source Quad copter was studied [14]. MIQA was developed as a part of a research at HITEC University Taxila, Pakistan [15].
(2) Conceptual sketches to be made (3) Use of CAD/CAM and CAE tools (4) Standard parts selection (5) Carryout detailed design & analysis (6) Manufacturing of parts and assemblies (7) Final assembly and systems integration. (8) Flight testing and performance analysis 2. METHODOLOGY A conceptual design of Quad Copter was made based on review of designs from past literature. A wooden prototype was prepared to gain appreciation of components and working of the integrated system. A comparative analysis of composites and aluminum materials for the final manufacturing was carried out. Finally aluminum was considered as an appropriate material due to its easy availability and low cost. FEA analysis of geometric design was carried out to establish the stress, strain and deformation in base structure. Four propellers, electrical power and control systems were designed to achieve the required performance parameters. The standard parts were procured from local markets. Individual mechanical parts were manufactured and assembled with the standard parts to arrive at the final assembly. Finally performance testing was carried out to establish the capabilities of the Quad Copter. Software including AUTOCAD, CREO and ANSYS were used in design and analysis process and mechanical parts were manufactured on a CNC machine. Details of all the design and manufacturing processes are discussed in subsequent paragraphs. 3. QUAD COPTER DESIGN PROCESS A deep insight to possibilities of designing a fixed or rotary wing micro flying vehicle through literature showed that a quad copter design could be sufficiently challenging due its unique requirements of synchronization of four rotors and stability during flight. A detailed design process was started in which a number of pencil sketches were prepared. These physical models were created to assess the size of various components. Finally the dimensions of components were adjusted through visualization of physical models. Then 3 D geometric model was designed using CREO. Its simulation was run to ascertain the selected dimensions were suitable for a functional prototype. The pencil sketch, a wooden physical model and CREO 3 D model are shown in Figure 1.0(a), (b) and (c) below:
Present research was focused on taking this project further to the development of Quad Copter (UMAASK) using CAD /CAM and CAE for ease of design as well as possibilities of evaluating its structural performance prior to development of a prototype. A comprehensive methodology is used for its design which typically consist of following steps. (1) Knowledge of design specification
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Lift of propellers L Elastic Modulus E Length of Strip L Bending Moment M Moment of Inertia I Centroid y Bending stress σb Deflection Y Bolt diameter Mass of plate Mass of each motor Total Moment Total Weight C.G
(a) Pencil Sketch
= 2.94 N = 70GPa = 10.4cm = 0.3410 N.m = 12.8x10-11 m4 = 2mm = 5.32 MPa = 0.0005665mm = 2.8 mm = 100g = 19g = 0.15713N.m = 1.3537N = 0.1159m
FEA for various parts comprised of application of constraints and loads to arrive at the results of deformation, stress and Strain distributions for structural parts. Following figure shows application of constraints and loads for Bar. Loads
Aluminium Bar Constraint
(b) Model made using CNC Lathe and Milling
Fig 2.0 Load and constraints on Bar Bar
Base Plate
Displacement,Von Misses and shear stress distributions on bar are shown in Fig 3.0 (a) to (e) below.
Motor
(c) 3 D Geometric Model in CREO Fig 1.0 Sketching to 3D Modelling
(a) Bar Deformation
Basic design consisted of two links attached together in a cross formation. These were reinforced at the center by plates. Motors were to be mounted at the end of the bars. At this stage Finite Element Analysis (FEA) needed to be carried out. Therefore selection of a suitable material was to be based on parameters such as durability, strength, machining ability, light weight, availability and cost. Aluminum was selected for final design and its properties such as density of 2560kg/m³, Ultimate Tensile Strength 70MPa and Modulus of Elasticity 70GPa were used. Theoretical design calculations results are shown below: Angle of attack
θ
=16.60
(b) Displacement of Bar 3
(c) Von Mises stress distribution (a) Shear Stress Figure 5.0 Behavior of bar under applied forces The following observations could be made from the above results: (1) Maximum displacement of 0.105mm approximately was observed near the edge of Bar which may not have a significant influence on the stability of quad copter. (2) Maximum Von Mises stress value was observed as 360MPa at a location which was to be attached with the Base Plate. It was therefore expected that Base plate support could give required strength and rigidity at this location hence prevent failure.
(d) Von Mises stress on Bar
(3) Maximum shear stress was also observed at the same locations where Max Von Mises stress appeared. Similar analysis was carried out for Base Plate after the Bar. Its results are shown in figure 4.0 (a), (b) and (c) as follows.
(e) Shear Stress distribution Figure 3.0 FEA Results of bar FEA results showed an increase in deformation of Bar increased due to an increase in applied stresses as it may be seen from Figure 6.0(a),(b) and (c) below:
(a) Displacement distribution
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(2) Maximum Von Mises stress value was observed as 280 MPa at the central location of Base plate and was also expected not to have a significant influence on the flight performance as well as structural failure. (3) Maximum shear stress was also observed at the same locations where Max Von Mises stress appeared. However it was of a substantially low value. After analyzing various parameters on Bar and base plate, it was realized that the weight of structure needed to be reduced even further. Therefore slots were cut in the four Bars and FEA analysis of the complete assembled structure was again carried out. Its results are shown in Figure 5.0 (a) to (f) below. (b) Displacement along length
(c) Von Mises stress (a) Displacement behavior
(d) Shear stress distribution Figure 4.0 FEA results over Base Plate The following observations could be made from the above results:
(b) Displacement over length
(1) Maximum displacement of 0.002mm approximately was observed near the edge of Base plate which could be considered insignificant to have any influence on the performance of the quad copter.
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(f) Shear stress distribution over length
(c) Von Mises stress distribution
Figure 5.0 FEA results over complete structure Following observations were made from these results (1) Maximum displacement of 0.0198mm approximately was observed at the location where motor and propeller were to be fitted. It was considered insignificant to have any influence on the performance of the quad copter. (2) Maximum Von Mises stress value was observed as 0.95 MPa at the central location of Base plate and was also expected not to have a significant influence on the flight performance as well as structural failure. (3) Maximum shear stress was observed on Bars near edges of Base plate. Its value was however 0.55MPa and could be considered insignificant to have any influence on the structure.
(d) Stress distribution along length
4. POWER THRUST AND SPEED CALCULATIONS Standard relationships were used for these parameters and following results were obtained:Battery = 11.5 v Current= 7.2 A Thrust = 337g Speed = 18570 rpm Air density ρ = 1.225 kg/m3 Propeller dia d = 0.127 m Max velocity at 90% efficiency of motor = 12m/s 5. ELECTRONIC SYSTEM This system was considered as most important for a stable flight of the Quad Copter. Its major parts and systems components were procured from open market sources with known specifications. Basic circuit configuration and selected parts are shown in Figure 6(a) and (b).
(e) Shear stress distribution
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(e) AX 1806N 2100kv Brushless Micro Motor (a) Electronic System Circuit diagram
(a) Fei Yu Tech FY-90Q Quadcopter Flight Stabilization System
(f) Lithium-ion polymer batteries Figure 6.0 Electronic system circuit and parts 6. SPECIFICATIONS OF COMPONENTS Fei Yu Tech FY-90Q Quadcopter Flight Stabilization System—The FY-90 Controller is purpose built for Quad copter use. It has an Attitude flight stabilization system (AFSS), which is an integrated 3-axis gyroscope and 3-axis accelerometer. AFSS forms a comprehensive inertial based navigation platform that calculates 3D flight attitude. When in full balance mode, the AFSS detects any changes to the models horizontal attitude. If an attitude change is detected, the unit will send out controlling signals to change the rotational speed of the Quad copters motors to maintain stability.
(c) Speed controller SS Series 8-10A ESC
Speed controller SS Series 8-10A ESC— It has a limited range of programming functions and is designed to be plugn-play with properties of simple to use and economic. Its specifications were as follows:
(d) Control unit HK6S 2.4 Ghz FHSS 6 Ch Tx& Rx (Mode 2)
Weight: 6g Size: 30x18x2mm Cells: 2-3S (Auto Detect) Max Current: 8A
(d) Propellers(Standard and counter rotating) 5x3 7
Control Unit HK6S 2.4 Ghz FHSS 6 Ch Tx& Rx (Mode 2)— It is an entry level 6 channel transmitter, used for models that require 6ch operation. It has a retract switch and proportional flap dial in easy reach, the transmitter also features elevon and V-tail mixing and servo reversing. Its key features were as follows: (1) (2) (3) (4) (5) (6) (7)
6-channel 2.4GHz transmitter Servo reversing function Elevon and V-tail mixing available Features build-in antenna Easy to use control for basic models FHSS 2.4 GHz Technology Includes 6-channel receiver
(a) Assembly of systems Base Plate
Propeller (Standard and counter rotating) 5x3— Propellers provide thrust force by taking power from motor. Diameter and pitch are important parameters of propeller. We used propeller having five inch diameter and 3 inch pitch. AX 1806N 2100kv Brushless specifications were as follows:
Micro
Motors
Motor—Its
Lipo Battery
Factory Specifications (1) Kv: 2100rpm/v (2) Lipo Range: 2-3 cell (3) Suggested prop: 5x3 ~ 6x3 (4) Best current range: 3~7A (5) Weight: 19g (6) Shaft: 3mm (7) Stator:18x6mm
(1) (2) (3) (4) (5)
Bar
Connector
(b) Parts and structure sub assemblies
Test Data Battery: 11.5v Current: 7.2A Propeller: 5x3 Thrust: 337g Speed: 18570rpm
(c) Sub Assembly of parts and systems
Lithium-ion polymer batteries—Lithium-ion polymer batteries, (LiPo) batteries are usually composed of several identical secondary cells in parallel to increase the discharge current capability, and are often available in series "packs" to increase the total available voltage. It has three cells in series (giving 11.1 volts) and 2 of these 3-cell packs are wired in parallel is commonly referred to as a 3S, 2P (3 series, 2 parallel). The batteries selected satisfied the above mentioned requirements of the motor power. 7. FINAL ASSEMBLY After complete structural design and its FEA analysis, the parts were manufactured using CNC milling and lathe machines. The standards parts and assemblies of electronic systems were purchased from open market sources to start the sub and final assembly of the quad copter in following groups as shown in Figure 7.0 (a) to (d) below.
(d) Final Assembly of parts and systems All parts were assembled to make sub assemblies of various systems. These sub assemblies were put togather to arrive at the final assembly of quad copter. During this process take
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off weight was also measured for individual components and final assembly as shown in following table.
9. CONCLUSIONS
STRUCTURE
100G
4 MOTORS
76G
4SPEED CONTROLLERS
24G
4 PROPELLERS
16G
BATTERY
50G
Present research was focused on developing a new MFV based on the knowledge available through literature. Exhaustive design process was carried out and ultimately a quad copter configuration MFV was designed and manufactured. It had a capability of carrying out surveillance from 20 meters height for a duration of 20 minutes. Its primary application was to hazardous or toxic environment which was unsuitable for humans. CAD/CAM and CAE tools were extensively used to arrive at an optimized design of this vehicle.
GYROSCOPE
30G
10. REFERENCES
4 ADAPTER
50G
TOTAL WEIGHT
346G
[1] L.A. Young, E.W. Aiken Et al, “New Concepts and Perspectives on Micro-Rotorcraft and Small Autonomous Rotary-Wing Vehicles,” 20th AIAA Applied Aerodynamics Conference, St. Louis, MO, June 24-27, 2002
COMPONENT
WEIGHT
Table. 2.0 Take off mass of vehicle Final mass of UMAASK quad copter was observed to be 346g. The thrust of motors and propellers was expected to be sufficient for lifting it to over 10 meters height for which it was initially designed.
[2] Gabriel M. Hoffmann, Haomiao Huang, Steven L. Waslander, Claire J. Tomlin, “Quadrotor Helicopter Flight Dynamics and Control:Theory and Experiment.” American Institute of Aeronautics and Astronautics.
8. PERFORMANCE TESTING AND FINDINGS
[3] L. Klauske, T. Lorenz, N. Colberg, M. Janke, U. M¨onich, N. Nothing, L. Thiele, F. Venzke, T. Wernicke S. Zeiler and R. Kusch, “DSP-Copter - A Quadrotor Helicopter Controlled by a Digital Signal Processor,” ELITE-Project Report Summary
UMAASK quad copter was finally put to test flight to see its performance on takeoff, landing, image capture and transmission to ground station, time of flight on fully charged batteries and following results were achieved: (4) A maximum controllable height of 10 meters approximately was achieved.
[4] Christian FinkPetersen, Henrik, Hansen, Steffen Larsson, Lars Bo Theilgaard Madsen, Michael Rimestad, “Autonomous Hovering with a Quadrotor Helicopter,” AALBORG University, June 2, 2008.
(5) Maximum flight time was 20 minutes. (6) Takeoff and landing weights(masses) were 0.346kg.
[5] Muhammad Esa Attia, Nawid Jamali, “Control of A 4Rotor Blade Helicopter,” Thesis report, The University of New South Wales, November 3, 2004.
(7) It could fly in three degrees of freedom only, the rolling motion was not achievable due to the type of flight systems i.e. coaxial rotor assembly (8) The vehicle was able to capture images as well as transmit video successfully with in the envelop of its controllable height of 10 meters.
[6] Mark Dupuis, Jonathan Gibbons, Maximillian HobsonDupont, Alex Knight, Artem Lepilov, Michael Monfreda, George Mungai, “Design Optimization of a Quad-Rotor Capable of Autonomous Flight,” Project Report, Worcester Polytechnic Institute, April 24, 2008
(9) A better quality of control unit could help in achieving higher maneuverability of the vehicle, the present controller however gave satisfactory performance in straight and level flight conditions as well as during climb and decent operations.
[7] Jorge Bardina, Rajkumar Thirumalainambi, “MicroFlying Robotics in Space Missions,” 2005-01-3405, 2005 SAE International. [8] Scott D. Hanford, Lyle N. Long, Joseph F. Horn, “A Small Semi Autonomous Rotary-Wing Unmanned Air Vehicle (UAV),” American Institute of Aeronautics and Astronautics,” Infotech@Aerospace Conference, Paper No. 2005-7077.
From the results, it was established that UMAASK was able to meet the design and performance characteristics of a typical Coaxial rotor design type MFV. However further design and manufacturing iterations could be performed to improve and optimize its design and payload capacity by changing the material type from metals to composites for main body structures.
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[9] Mr T. Spoerry1, Dr K.C. Wong, “Design and Development of a Micro air vehicle (μav) concept: project bidule,” University of Sydney, NSW 2006. [10] Gabriel Torres and Thomas J. Mueller, “Micro Aerial Vehicle Development: Design, Components, Fabrication, and Flight-testing,” 117 Hessert Center, University of Notre Dame. [11] Mark Whitty, Lin Chi Mak, Derek Taprell, Anselm Ma, Steven Lee, Cho Ying Ng, Nicholas Robinson, Harry Xiao, “Development of the MAVSTAR Micro Aerial Vehicle and Base Station for IMAV09” The University of New South Wales NSW 2052, Australia, 22 May 2009. [12] “Multi-Agent System of Quad copters,” The University of Texas, Sep 2011. [13] Teppo Luukkonen, “Modelling and control of quadcopter,” Independent research project in applied mathematics, Aalto University, August 22, 2011. [14] Inkyu Sa and Peter Corke, “Estimation and Control for an Open-Source Quadcopter.” Queensland University of Technology, Australia 11. BIOGRAPHY Dr Irfan Anjum Manarvi is an Aerospace Engineer. He graduated from PAF College of Aeronautical Engineering Risalpur and did his M Phil and PhD from Department of Design Manufacture and Engineering Management, University of Strathclyde, Glasgow, United Kingdom. He is currently a Professor at HITEC University Taxila Education city, Taxila, Pakistan Muhammad Aqib is a Mechanical Engineer. He graduated from Department of Mechanical Engineering HITEC University Taxila, Pakistan Saqib Khurshid is a Mechanical Engineer. He graduated from Department of Mechanical Engineering HITEC University Taxila, Pakistan Muhammad Usman is a Mechanical Engineer. He graduated from Department of Mechanical Engineering HITEC University Taxila, Pakistan Muhammad Ajmal is a Mechanical Engineer. He graduated from Department of Mechanical Engineering HITEC University Taxila, Pakistan Usman Sikandar is a Mechanical Engineer. He graduated from Department of Mechanical Engineering HITEC University Taxila, Pakistan
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