Technical Journal Paper AUVSI SUAS 2015

Transcription

1 Technical Journal Paper ZeppelinFC-26 Unmanned Aerial Systems: ZEPHYR AUVSI SUAS 2015 ZeppelinFC-26 is a team of 10 students from Northern India Engineering College affiliated to Guru Gobind Singh Indraprastha University. The ZEPHYR Unmanned Aerial Systems a complete system designed to successfully compete in the 2015 Association for Unmanned Vehicle Systems International (AUVSI) Student Unmanned Aerial System (SUAS) 2015 Competition. Over the course of the 2014/2015 academic year, the ten member team designed, constructed, and evaluated the individual subsystems needed to create a complete UAS, which consists of an Unmanned Aerial Vehicle (UAV) and a Ground Control Station (GCS). The competition will take place in June 2015 at Naval Air Station Patuxent River, Maryland. TEAM MEMBERS: Vaibhav Gangwar Divyani Jain NipunSachdeva Siddhartha Bhatia Shivangi Mittal Nishant Rohit Sikka Rahul Kumar Krishna Kumar Sharma Rachit Mittal

2 Abstract: The AUVSI Student Unmanned Air System (SUAS) competition presents the goals of autonomous navigation, surveillance, and real-time actionable intelligence. Zephyr, the system developed by ZeppelinFC-26 for this year s competition, is able to conduct successful missions through the integration of mechanical, imagery, and navigation systems. The Unmanned Aerial Vehicle frame is a High-Wing RC plane, which has been designed and modified on Solid Works taking help from the plans available on internet and reinforced for better flight integrity and modified for carrying a payload. Turnigy HD WiFi action cam video camera is used. Image telemetry is controlled on-board by the aircraft through AOMWAY TX1000,RX04 Receiver and Transmitter which can be remotely accessed through a 5.8GHz wireless bridge. The autopilot used is the HKpilot32 Autopilot. Images are sent through the 5.8GHz wireless bridge to a ground station computer running target detection software developed by ZeppelinFC-26.The software helps recognizing and decoding the QR code target from the images captured and stored on the ground control station. Ground and flight tests have shown that this system is capable of the goals laid out by the AUVSI SUAS competition regulations. ZeppelinFC-26: ZEPHYR 2.

3 CONTENTS 1. INTRODUCTION 1.1. Competition Goals System Design Overview AIRFRAME SYSTEM DESIGN 2.0. introduction Design Methodology Modifications and payloads Power System Motor selection IMAGERY SYSTEM 3.0. introduction Camera Wireless Bridge AVIONICS AND INSTRUMENTATION DESIGN 4.1. Autopilot HKpilot MAVLink Flight sensors Inertial measurement unit(imu) Global positioning system(gps) telemetry radio systems RC controller VISION SYSTE.M 5.0. Vision System Air drop mechanism TESTING AND ANALYSIS FLIGHT SAFETY PRECAUTIONS CONCLUSION ACKNOWLEDGMENT...17 ZeppelinFC-26: ZEPHYR 3.

4 1. Introduction 1.1 Competition Goals Critical design objectives of ZeppelinFC-26 s system, as defined by the competition rules, are takeoff (rule 7.1.1), waypoint navigation (rule 7.1.3), area search (rule 7.2), landing (rule 7.1.4), and mission completion time (rule 6.2.4). Takeoff and landing are accomplished autonomously. The autopilot controls flight for waypoint navigation.the area search uses waypoints assigned by team software. A camera on board the aircraft records images of the ground and sends them to the ground station, controlled by a compact computer on the aircraft communicating with the ground station via a wireless bridge.the ground station receives these images and processes them with telemetry data from the autopilot to produce actionable intelligence, which can be facilitated through manual recognition. The on board camera also provides life video feed.since images can be received at the ground station while the aircraft is still flying, the amount of additional time needed to complete target recognition after the flight has ended is minimal, making the total mission time to fit well within 60 minutes. 1.2 System Design Overview Figure below shows the complete system structure. The autopilot is the main component of the navigation system, sending telemetry and receiving commands to and from the ground through a 5.8GHz radio. The autopilot directly controls the servos, but a switch on the safety pilot s controls triggers a manual override through software. A GPS unit developed by the ZeppelinFC-26 connects to the autopilot as the primary source of position and velocity information.the autopilot controls the flight surfaces, camera system, and speed controller through a standard servo interface, and is commanded through software running at the ground station. The vision system includes three cameras which are connected wirelessly to the ground station. A high-power radio on the aircraft and on the ground facilitates the wireless bridge formed to network the air and ground computers. The airframe is designed to easily carry the vision system and navigation system payloads for stable flight with simple setup before missions. ZeppelinFC-26: ZEPHYR 4.

5 ZeppelinFC-26: ZEPHYR 5.

6 2. Airframe System Design: The airframe selection process was the first major issue tackled by the airframe team. From the beginning, the team wanted to design a small, portable UAV instead of a larger, heavier aircraft. There were two possible routes to a viable airframe: design a custom aircraft and build it from raw material, or choose an off-the-shelf consumer Remote Controlled (RC) aircraft. In order to facilitate easy flight control and intelligence gathering, a slowflying, highly stable aircraft was needed. The aircraft also needed to be large enough to hold all the flight instruments and hardware, a camera and transmitter radio and extra batteries to extend the flight duration. The batteries would occupy the greatest amount of fuselage space. From early on, the team was in favour of an electric powered model. Electric motors require no liquid fuel and offer less vibration and engine noise than gas powered engines. Wood like Balsa, is light-weight and easy to repair. Zephyr meets all the requirements of the Academy of Model Aeronautics and the AUVSI Seafarers Chapter. 2.1 Design Methodology The High wing RC Plane built as the airframe of Zephyr is composed entirely of Balsa and Plywood. Along with a simple and efficient design, the Zephyr has a large fuselage volume, a relatively slow cruising speed and low wing loading. About 4 degrees of dihedral promotes favourable roll stability and cross-wind performance. An electric propulsion system is utilized in place of a combustion engine to reduce potential vibrations. An electric motor also does not produce any exhaust that could compromise the vision system and is much less likely to stall or stop mid-flight. These characteristics are key advantages towards Zephyr s role as a surveillance aircraft. To successfully achieve the goals of the AUVSI competition, ZeppelinFC-26 identified key mission performance parameters: flight stability, payload volume and accessibility, flight endurance, ease of (dis)assembly and overall safety. Meeting these parameters facilitates the unmanned aerial system s survivability, maintainability, and flexibility during any type of mission. Zephyr, is ZeppelinFC- 26 s air system that meets and exceeds each of these design parameters. ZeppelinFC-26: ZEPHYR 6.

7 2.2 Modifications and Payloads The critical mission payloads onboard Zephyr are the HKpilot32 autopilot, Turnigy HD WiFi Camera, GPS system and100mw Video Transmitter. The team demanded that the integration of these components into the airframe would allow for system modularity. The airframe is heavily reinforced in order to safely lift these components. For example, the wings are bolted onto the fuselage with additional support from a custom reinforcement rib and elastic bands, and the wing struts and landing gear are bolted to the fuselage using metal hardware. The motor mount firewall and forward bulkheads are reinforced to support the excessive forces from the wings and electric motor, and the electronic speed controller (ESC) is mounted inside the aircraft. The on-board computer and all batteries except the main flight pack are secured in the forward-most cavity of the plane with Velcro. This cavity is easily accessible at any time by a hinged flap and provides access to all navigation and vision system power switches. Figures below represents some of these onboard payloads. ZeppelinFC-26: ZEPHYR 7.

8 2.3 Power System With a payload takeoff weight of 5kg, Zephyr, must be equipped with a power system that can provide enough thrust to keep the aircraft aloft for at least 35 minutes with ample reserve power for emergency situations. Additionally, all payloads must be adequately powered to ensure no loss of control or communication. To meet this demand, Zephyr is powered by a brushless DC motor that runs a 12x10E propeller. This motor was chosen based on its ability to continuously deliver watts per pound nominally in cruise by a 55 amp Turnigy high voltage electronic speed controller and two two-cell, 10 amp-hour lithium polymer batteries wired together in series. After extensive analysis, the propulsion requirements of Zephyr were more efficiently (in terms of weight) met by supplying the power via current instead of voltage, as higher voltages are achieved by adding more battery cells. Following safety conventions for lithium polymer batteries, only 80% of battery capacity should be discharged to prevent permanent battery damage. 2.4.Motor Selection The required motor size is a function of the amount of payload weight the aircraft must carry. Selection of a motor then depends on choosing the proper input watts per pound rating provided by motor manufacturers. Therefore, the first step in the motor selection process was estimating the maximum weight of the UAV and for that ZeppelinFC-26 is using a 750KV motor in Zephyr. When fully assembled the Zephyr aircraft weighs 0.9kg. Since autopilots and other flight electronics are generally very small and light weight the total weight ZeppelinFC-26: ZEPHYR 8.

9 was estimated at 400gms. The vision payload was estimated to weigh less than 550gms. The most significant weight component are the batteries. To provide a flight time of up to 35 minutes it was estimated that a battery weight of 998gms was required. This brought the entire system weight to 2.9kgs. 3. Imagery System Design The overarching design requirement for the imagery system is the ability to locate, recognize, and classify targets on the ground visible from the air (rule 7.2.8,7.2.9). In addition, real-time acquisition of targets better accomplishes the mission objectives (rule 7.1 table 2). The camera is controlled by, a compact computer on-board the aircraft. The UAV itself is controlled via a wireless network with the ground station. Images taken by the camera are sent to the ground station for manual and/or automatic target recognition and are tagged with telemetry information retrieved from the navigation system Camera The camera chosen by ZeppelinFC-26 is a Turnigy HD WiFi Action Cam full HD video camera. The camera has a 170 wide-angle lens and has an image sensor of 12 mega pixels CMOS. This choice was based on the ability to control the camera and for its picture quality and high frame rate for a point and shoot camera.the significant features of our camera are: Popular form factor allowing it fit most GP3 camera gimbals Full 1080P HD video recording WiFi connectivity allowing streaming of live video and wireless menu function access Integrated 1.5" LCD screen 170 wide-angle lens 12 mega pixels CMOS sensor Lightweight at only 58g with battery installed HDMI output for playback on other devices 4X digital zoom Removable 900mAh lithium battery (rechargeable) Up to 70 minutes battery life when recording in full 1080P HD ZeppelinFC-26: ZEPHYR 9.

10 3.2. Wireless Bridge The wireless telemetry system was designed for ease of operation and reliability. Several factors influenced the radio selection: Output Power Receiver sensitivity Antenna gain Size and form factor Bandwidth The Aomway 5.8GHz 1000mW TX1000, RX04 Receiver were chosen as the radios for the aircraft and ground station respectively. These radios use the 5.8GHz 1000mW standard power and provide high transmit power (up to 29dBm) and low receiver sensitivity (as low as -96dBm) in a compact package. The TX1000 is connected to a 7dbi circular polarised antenna, while the RX04 Receiver contains a 14dBi right hand circular polarised antenna, which can be directed towards the aircraft during flight. While the Aomway has a reasonably small size. ZeppelinFC-26: ZEPHYR 10.

11 4. Avionics and Instrumentation Design The Avionics and Instrumentation team was responsible for all electronic and software systems needed for the unmanned aircraft. This included an autopilot, an inertial measurement unit (IMU), airspeed and altitude sensors, Global Positioning System (GPS) and telemetry radio system. These systems are outlined in the coming sections. 4.1 Autopilot The autopilot is the heart of the unmanned system and in the source of all autonomous behaviour. This device is what sets the UAV apart from a remote controlled aircraft. The autopilot polls all the flight sensors for information about flight status and orientation, makes any necessary control and navigation decisions, then adjusts the flight control surfaces accordingly. An overview of theautopilot system is shown in figure: The autopilot used in Zephyr is the HKpilot32 Autopilot developed by Hobbyking. Images are sent through the 5.8GHz wireless bridge to a ground station computer running targeting software developed by ZeppelinFC-26. It matches telemetry information received from Virtual Cockpit to images and can recognize and classify images through manual recognition. ZeppelinFC-26: ZEPHYR 11.

12 4.1.1 HKpilot32 The HKPilot32 is the next step in FC hardware with its powerful ST micro 32bit ARM Cortex core and massive I/O support. The HKpilot32 is one of the most advanced autopilot systems available with support for almost any type of vehicle from a moon rover or a multirotor aircraft, even a submarine! Designed by the PX4 open-hardware project, it is supported by a number of development communities making this one of the most flexible and reliable platforms for vehicle control, with many features and functions sure to be available in the future.with powerful integrated multithreading NuttX RTOS, a Unix/Linux-like programming environment, completely new autopilot functions, auto detection and configuration of peripherals and a seamless transition from a HK Pilot Mega or APM, these advanced capabilities remove the limitation to your autonomous vehicle. fig: Ground Control Station ZeppelinFC-26: ZEPHYR 12.

13 4.1.2Micro Air Vehicle Link Mavlink or Micro Air Vehicle Link is a protocol for communicating with small unmanned vehicle. It is designed as a header-only message marshalling library. It is used mostly for communication between a Ground Control Station (GCS) and unmanned vehicles, and in the inter-communication of the subsystem of the vehicle. It can be used to transmit the orientation of the vehicle, its GPS location and speed. 4.2Flight Sensors The flight sensors are needed to gather information about the aircraft s state in the air. This information includes altitude, airspeed, pitch, roll, yaw, position and heading. Taken together, this information allows for the creation of a total picture of the aircrafts state. With this picture control and navigation decisions can be made. The flight sensors outlined below are inertial measurement unit and global positioning systems Inertial Measurement Unit (IMU) The Inertial Measurement Unit (IMU) is a device capable of measuring velocity, orientation and gravitational forces, using a combination of accelerometers and gyroscopes. The information collected from this instrument is essential for providing control and navigation commands for the UAV. IMU s are commonly found on aircraft, spacecraft, water-craft and guided weapons. The IMU used here is entirely solid-state, allowing it to be sufficiently small and light-weight to be placed on the aircraft. These sensors are based on Micro- Electromechanical systems (MEMS) based technologies Global Positioning System (GPS) While the IMU provides sufficient information for dead reckoning navigation, this data is not relative to any geographical location. The Global Positioning System (GPS) provides a large deal of information including ground speed, altitude, heading, latitude, longitude and time. Many commercial GPS receivers are available and for this application the QUANUM LEA-6H GPS WITH COMPASS module was chosen. ZeppelinFC-26: ZEPHYR 13.

14 Telemetry Radio Systems While not technically a flight sensor, the telemetry radios are an essential part of the unmanned system. Without some method of transmission of the flight data to human operators, the system would not be useful for real-time applications. The telemetry radio system is main method of communication between the operators on the ground and the aircraft systems in flight.for this system two modules Aomway 1000mW TX1000 and RX04 Receiver are used respectively. One modules is placed in the aircraft while another is kept at the ground station. 4.3 RC Controller Since the aircraft must be able to be manually overridden and flown by the operator on the ground, a standard RC controller is required. Turnigy-9x 9channel TX and 8channel RX RC controller is used to fly the airplane when it is not in automatic mode. This controller is also used to change between the different flightmodes on the autopilot. The controller operates on the 5.8GHz band and features spread spectrum technology and receiver binding to prevent interference. The 5.8GHz band is avoided by all the other radios to prevent interference in the system. 5. Vision System The vision system only one of many possible payloads that could be mounted to the UAV. Its operation is independent from the operation of the unmanned system and is not required for flight. The vision system is used as the primary source of visual intelligence data. Using its camera and radio transmitter, it relays this vital information down to the operators at the ground station. The vision system consists of a video camera located on the underside of the plane, a transmitter connected to the video camera located in the fuselage of the plane, and a receiver located at the ground station. This system takes an image input from the camera and transmits it to the ground station using thetransmitter and the receiver. ZeppelinFC-26: ZEPHYR 14.

15 5.1. AIR DROP MECHANISM: A two component system is used to classify targets. First, there is a manual system that ensures identification accuracy and completeness. Second, there is an automatic system that performs autonomous classification. Together they create a system that allows for real-time classification of targets. This system is designed to survive both application and station failures through software redundancy and data preservation. The air-drop target will be a bulls-eye with at least two concentric rings. Characteristics are: Bulls eye radius; X = 5 ft. Objective radius; Y = 30 ft. Threshold radius; Z = 100 ft. and we will be using an air drop canister to hit the bull's eye target. ZeppelinFC-26: ZEPHYR 15.

16 6. TESTING AND ANALYSIS: A series of system tests were conducted for the airframe, vision and navigation systems. These test flights were a culmination of extensive ground testing on the individual components of each sub-system. Test flights were structured to systematically build up from basic analysis to more complex and integrated system tests. 50 full test flights were preformed (a photographs of a prototypes of planesmade by us ). ZeppelinFC-26 operates within rules for autonomous flight, because the aircraft is always under immediate control of the safety pilot. Fig: prototype testing ZeppelinFC-26: ZEPHYR 16.

17 7. Flight Safety Precautions Proper safety precautions must be observed while operating any aircraft, especially unmanned systems. Neglecting safety in design and testing can lead to serious personal injury and vehicular damage when operating Zephyr. For this reason, safety of the flight vehicle, payloads and most importantly, personnel, are strongly emphasized throughout all phases of ZeppelinFC-26 s systems and operations. ZeppelinFC-26 has designed a system without redundancies, it is fail-safe and has appropriate factors of safety that eliminate potential risks before testing the aircraft in the air. The team has implemented rigorous system test flight procedures and checklists that are strictly followed by all members of the team. The checklists ensure that every system is analyzed, and given the go/no-go before the airplane ever leaves the ground. Before each test flight, the entire team is briefed on mission objectives in order to assign specific roles to each member. 8. CONCLUSION: ZeppelinFC-26 will continue to test Zephyr up until the competition, responding to the lessons learned through the test flights. ZeppelinFC-26 has designed, fabricated and tested an unmanned air system, using a systems engineering approach that is capable of successfully completing the 2015 competition mission objectives set forth by AUVSI. Based on that approach and numerous system tests, ZeppelinFC-26 feels confident that autonomous waypoint navigation, area search, manual target recognition and air drop task can be accomplished at the 2015 competition. 9. Acknowledgments ZeppelinFC-26 would like to thank the following for their support to the team: Dr. Alka Das Gupta, Vice Chairperson, Northern India Engineering College Mr. S.N. Garg, CEO, Northern India Engineering College Dr. G.P. Govil, Director, Northern India Engineering College Mr. Ajit Sharma, H.O.D. of Electrical and Electronics Engineering, Northern India Engineering College. ZeppelinFC-26: ZEPHYR 17.

18 ZeppelinFC-26: ZEPHYR 18.