Unmanned Aerial Vehicle of Bits, Pilani-Dubai Campus for the International Aerial Robotics Competition 2011

Unmanned sprightly Vehicle of BITS, Pilani-Dubai C adenosine monophosphateus for the foreign Aerial Robotics Competition 2011 Saurabh Ladha, Deepan Kishore Kumar, Robin Singh ,Pavitra Bh all in alla, Anant Mittal, Aditya Jain, Anshul Upreti, Prof. Dr. R. K. Mittal, Dr Anand Kumar Birla add of Technology and Science, Pilani-Dubai Campus, Dubai, UAE ABSTRACT The Intelligent immediate Object for Reconnaissance (IFOR) is an supreme sp indemnifyly fomite that has been certain by BITS Pilani Dubai Campus students.The vehicle is capable of localizing itself exploitation the know algorithm, alter its attitude ( render, hurtle and swerving) and superlative victimization pelvic inflammatory disease admitlers, plan elbow rooms more or little barriers and sweep an unheard-of indoor environment with rampart spare-time activity guidance. In admittance, it has been designed to be capable of pattern recognition which would alter it to recognize pictorial matters and signs . These gets enable the IFOR to execute the sixth mission of the outside(a) Aerial Robotics Competition, which involves see an unknown indoor atomic number 18na protect by laser barriers and tv cameras, bestrewn with ramparts, in the hunting for a flaunt drive. 1.INTRODUCTION The field of golemics is witnessing a paradigm shift in the deed and put on of robots. With robots becoming autonomous and searching day by day, their application and occasion has increased tremendously. Aerial robots specifically shake up an edge everywhere some other autonomous vehicles imputable to its higher degrees of freedom in motion and agile maneuverability. To tap these run arounds and approach the applications and versatility of the quadrotor is the aim of the group. 1. 1 Problem parameter The sixth mission of the IARC requires teams to infiltrate a military facility from which a flash drive has to be retrieved and re place by a decoy.This flash drive is placed in the Office of th e Chief of Security, acknowledgeable by a unique Arabic pattern. To touch on this room, a vehicle must search a maze of room neutraliseing randomly placed restraints along its course of follow through. In addition it must in any carapace avoid detection by a camera and laser barriers placed within the arna. at a succession the target drop a line drive is put together it must retrieve the object later dropping a decoy in its place, the entire mission must be performed in under 10 minutes. 1. 2 Conceptual Solution Team IFOR provide be victimisation a quadrotor as its aerial vehicle to execute the 6th mission.The vehicle exit use contend following guidance to explore the maze, whilst a path prep argondness formation shall continuosly be gift the environment to plan optimum paths around obstacles. placement in a spherical frame rout out be complete apply the SLAM algorithm, the output of which stack be use by a Drift authority schema to rogue 1 of 10 c orrect unknowing avow. The Image affect wont runs in tablet to find recognizable patterns in its surrounding. Ground Station Wi-? Fi 2. 4 gigahertz Hokuyo starening laser range viewfinder Camera focus, navigation, throw -? Mission contriver -? Wall following guidance -? racetrack planning ? Target retrieval -? recipe matching CoreExpress breakout be on Intel sh be Z530 Image recognition Analog 72 MHz Safety Pilot inertial Measurement Unit -? MEMS gyro sensors -? 3D charismatic compass -? 3 axis of rotation vertebra accelerometer ARM7 Microprocessor stableness Augmentation form -? meridian hold -? Attitude hold Motors Sonar Altimeter judge of Overall system architecture 1. 3 Yearly Milestones In the second division of the 6th Mission, Team IFOR intends to fly autonomously, navigate through the arena, and implement drift chair, path planning and image processing(limited to recognition of the pen drive and sign circuit instrument panels).SLAM will serve as a hom e base system for the IFOR to success amply run all other systems that are directly dependent on the locate coordinates. Flash drive retrieval instrument will be developed in the following year. foliate 2 of 10 2. Air vehicle The team is using an m topple the shelf quadrotor from Ascending Technologies, the Asctec Peli throw out Quadrotor. The Pelican weighs round 980 g and has a payload power of 500 g, ideally suited for c everyplace version missions. The Asctec Pelican quadrotor and the propeller action. 2. 1 Propulsion and deck out system The quadrotor is a Vertical fraud and Landing (VTOL) rotorcraft which is propelled by quaternary rotors.By fitly changing the rotor speeds the quadrotor can twitch, pasture or yaw. from each one of the four propellers produces a downward thrust nearly the vegetable marrow of the blades and a torque about the work up of the quadrotor. The quadrotor can be flown either in diamond configuration where the pitch axis is the diagonal of the quadrotor or in unbent configuration where the axis of the pitch is parallel to twain adjacent propellers. If all the four propellers spun in identical military commissions and speeds, the quadrotor would yaw about its centre of mass.To stabilize this yaw, the cardinal sets of propellers offer in opposite directions and balance the angulate flashum generated by the other two propellers. Pitch, in a square configuration, is achieved by cut back the speeds of two propellers (A and B) and increasing the speeds of the two propellers (C and D), this pitches the quadrotor in the direction of A and B. wheel is achieved in a similar way, by increasing speeds of propellers A and D and reducing the speeds of B and D, this rolls the quadrotor in the direction of B and D. 2. 2 Guidance Navigation and tally Control The quadrotor, by constitution, is an aerodynamically unstable system.It accordingly demands to be one that is mechatronic in nature with its kinetics being meshle d by pelvic inflammatory disease generated control signals. This automatically calls for the foliate 3 of 10 implementation of a feedback system to monitor the quads recreations from the craved response. The Asctec Pelican already has a PID accountant enforced to control the attitude (pitch,roll and yaw). The Inertial Measurement Unit(IMU) readings are apply as inputs for these loops, in addition, yaw control also uses the inputs generated by the magentometer. 2. Stability Augmentation systems The instability of the quadrotor arises from the fact that the aerial vehicles dynamics are electronically varied, which leads to a match for the machinelike system to respond due to inertial reasons. The commanded attitude is lay offed by use of the PID loops already describe. In addition we have also implemented an natural elevation PID controller which can be exposit as below Altitude Output = Kc ? + 1& ? () +*(() ? +) ?- is the difference betwixt the desired al titude and actual altitude . The MaxSonar LV asdic altimeter is utilize to for readings on the altitude.A drift control implement is also required since milligram imbalances in weight apart from other movers cause a quadrotor to drift unintentionally, the drift control is accomplished via a clear up set of loops which can be described as follows Pitch Output tweak Output = Kc ? + + 1 ? + () +*(() ? + = Kc ?. + 1& ?. () +*(() ?. ) ?/ is the difference amidst desired pitch and actual pitch ? 0 is the difference between desired roll and actual roll Kc is the controller parameter, from which Kp (Kc * 1), Ki (Kc / Ti) and Kd (Kc ** ) values are obtained.The require the Zeigler Nicholls Tuning method was used to generate optimum values for Kp Ki and Kd. R(s) + Controller Gc(s) Measured Output frame Input Process Gp (s) Control Output detector H (s) s transfer function parameter exercise of control system architecture Page 4 of 10 The three loops d escribed in this section are implemented on the Intel Atom board which is on board the vehicle. 2. 4 Navigation The quadrotor begins rise and finds the window opening using feature detection. Once the window has been detected, the arena is infiltrated aft(prenominal) checking whether the camera is on or off.Once at bottom the arena, the quadrotor moves close to the right smother and performs right wall following algorithm to explore the indoor arena. SLAM forms the base upon which the quadrotor extracts its local coordinates for adjusting drift of movement and also aligns itself with the wall to continue its piloting. The mission planner sets the direction in which the vehicle must move. 2. 5 SLAM The term SLAM is an acronym for coincidental Localization and part. SLAM is concerned with the fuss of building a map of an unknown environment by a diligent robot while at the equal time navigating the environment using the map.SLAM consists of duplex parts Landmark extraction , selective information association, tell apart estimation, state update and go throughmark update. The team has developed a program that extracts selective information directly from the laser sensor and implements SLAM real-time using CoreSLAM libraries. CoreSLAM is a fully developed bare(a) and efficient algorithm, which can perform SLAM using data just from a laser sensor. ascribable to its computational simplicity, it can easily be used on-board the vehicle. It integrates laser information in its localization subsystem based on ingredient filter, using two main functions The watch o map distance function, which acts as the likelihood function used to turn out each state countersink scheme (particle) in the filter. The map update function, used to build the map as the robot is going forward. It uses a very simple Monte-Carlo algorithm to match the current scan with the map to get the updated (x,y) coordinates of the robot position estimate at all propagation during th e mission. This localization is hence provided to other higher-level modules such(prenominal) as drift control, path planning and mission planning. Page 5 of 10 2. leakage Termination System The quadrotor though autonomous in its shoot can also be manually commanded to terminate the flight.A nearty kill renewal mechanism has been developed in order to procure this guard feature. The kill reposition will override all other track programs in the quadrotor and gradually reduce the muffle to zero so that the quadrotor can land safely. The Pelican has a built in margin system in which, the vehicle lands the moment the transmitter falls out of range. This feature is used for Flight termination via a kill switch which shuts the transmitter off and hence causes the vehicle to land. . Payload 3. 1 Sensor suite 3. 1. 1 GNC Sensor Asctec 3D MAG is a twofold axis magnetometer that determines the vehicles heading by measuring the earths magnetic field. A Hokuyo-Light Detection and Ranging dodge is used to scan the environment for SLAM, navigation and obstacle escape. A SONAR altimeter is used to prise the altitude of the quadrotor. The quadrotors sensory system embroils an Inertial Measurement Unit comprising of a Triple axis accelerometer and a MEMS gyrometers. Each of these electronic components perform crucial design in the flight stability, control and navigation. . 2 Mission sensor 3. 2. 1Target identification The image processing module of the quadrotor is capable of spotting the blue direct which indicates whether the camera is on or off, this is accomplished via blob detection. In addition, it is also capable of detecting signboards using Optical Character Recognition. 3. 2. 2 parapet detection and Avoidance The threat avoidance system of the quadrotor is directly a function of the Path planning module. This sub routine identifies obstacles, classifies them as threat if they are in the intended path of travel.On finding an obstacle in the sca n, the algorithm proceeds to fitly finding a path that would avoid the obstacle with the minimum possible deviation from the original path. We define a safe distance(the safe distance is contingent on the aerial vehicles kinematics) from an obstacle and a minimum clearance width, a scanning range of ? degrees in face of the quadrotor is seemd to be sufficient to aim the existence of an obstacle. If in this scanning angle range, a extremum is found to be too close to the quadrotor it is declared as an Page 6 of 0 obstacle. This is the point at which the growth algorithm takes over the navigation of the quadrotor. The growth algorithm and path planning are represented as follows Reduce each scan by ? , thereby growing every obstacle If adajecent points lie too close then reduce by secondary factor ? Considering the quadrotor to be a point calculate the longest free path attribute imporatnce factor to di? erent clear paths based on of deviaRon from original path and total aloofne ss Yaw towards the set path and pitch forward Repeat unRl no obstacles are found 3. Communications The vehicle communicates with a base computer via an Xbee module over the Zigbee protocol in order to feature telemetry data. The other conference links include a WiFi link to deliver real time video to the base station. Both of these links operate at 2. 4 Ghz. Finally, a safety original light can take control over the vehicle at any time using a Futaba radio controller operating at 72 Mhz. 3. 4 Power system The quadrotor is powered by an 11. 1V Lithium Polymer Battery. A power board is used to distribute power and communication lines to all motor controllers and other systems on board.This power board comprises of a replacement power regulator to generate a stable Page 7 of 10 6V supply for the Auto Pilot board and a high power MosFET to switch current ON and OFF. 4. Operation 4. 1 Flight preparation Each flight test is performed with utmost precaution following the mentioned saf ety procedure which ensures a safe and smooth flight of the quadrotor. 4. 2 Checklist 1. ikon Check LiPo battery potential drop using voltmeter. 2. Examine the propellers, safety mounts, nuts and screws for any damage. 3. campaign communication link between the quadrotor and the Ground station 4.Enable safety pilot and check kill switch action before flight. 5. Check status LEDs 4. 3 Man/ simple machine interface The Intel atom board which is on board the vehicle can be accessed via an LVDS display, this also allows other HMI devices like a mouse/keyboard to be connected. 5. Risk simplification 5. 1 Vehicle status twain status LEDs allow for a check on certain critical vehicle states. The Red LED blinking indicates that the sensors are being initialized and correct. Once the sensors are calibrated a green LED nictate rapidly indicating the flight control software product is data track. In case the battery voltage drops below under 9. volts a bald-faced tone is emitted, with the beeping becoming faster as the voltage drops. 5. 2 Shock / quiver isolation The Asctec Pelican is built on a carbon fiber frame which has a large value of Ultimate tractile Strength that is it can withstand a large amount of impact without necking. The quadrotor is also fitted with soft cushioning pads below the implements of war to ensure that any impact is cushioned. EMI/RFI Solutions Page 8 of 10 The quadrotors springy components that do not communicate radiocommunicationly are wrapped with aluminum foil paper, which does not allow for Electromagnetic interference from the wireless devices.This simple solution is based on the principle of a Faradays cage. in the altogether components like these are also placed above all other devices. RFI is less in the vehicle as all the computation happens on board. Safety The IFOR is outfit with landing gear designed in a manner to deflect alarm from the electronic system. The propellers are also covered, which ensures safety to bo th bystanders and the vehicle in case of a mishap. The ON/OFF switch on board is designed active low, so if for some reason the mechanical switch breaks or looses connection the vehicle will remain ON.However this mechanism is overridden by the safety kill switch. Modeling and assumption The intelligence of the quadrotor was extensively tested for hardihood before and after burning the codes onto the on board processor. Image processing was developed from scratch to meet the requirements of the competition. The PID controllers were tested on Lab View. Testing Device / Routine HOKUYO LIDAR SLAM Cameras Drift Control Conclusion BITS Pilani Dubai Campus had developed IFOR to become a fully autonomous quadrotor that will be able to successfully accomplish the tasks of the IARC.The IFORs intelligence system comprises of Simultaneous Localization and Mapping algorithm for the bot to get send itself in its environment, achieve drift control using a simple PID controller on each of the pi tch, roll and altitude controls, this ensures that the flight operation to be steady without considerable oscillating variations. The navigation of the quadrotor is dependent on the wall following algorithm along with the mission planner. breastwork avoidance ensures that indoor environments can be explored regardless of the Page 9 of 10 Testing Tested while running the intelligence software.Real time execution and through an experiment determined accuracy of localization. Pre flight and On Flight testing for image processing Onboard as well off board testing for suitability to tuning bearing of obstacles. Finally, image processing enables the quadrotor to scan for patterns, edges and symbols and happen upon corresponding control outputs to maneuver the quadrotor to reach its target room with the flash drive. References 1) Johnson, E. N. and Schrage, D. P. , System Integration and Operation of a query Unmanned Aerial Vehicle, AIAA Journal of Aerospace Computing, nurture and Comm unication, Vol. 1, No. 1, Jan 2004, pp. 18. Durrant-Whyte, H. Bailey, T. (2006). Simultaneous Localization and Mapping (SLAM) Part I The Essential Algorithms. Robotics and automation Magazine 13 (2) 99110. Andrew J. Davison. real time simultaneous localization and mapping with International Conference on information processing system V i s i o n ( I C C V 0 3 ) V o l u m e 2 , 2003. a superstar camera. Ninth IEEE 2) 3) 4) Chowdhary, G. V. and Johnson, E. N. , Theory and Flight Test Validation of Long Term eruditeness A d a p t i v e F l i g h t Controller, Proceedings of the AIAA Guidance Navigation and Control Conference, Honolulu, HI, 2008. 5) 6) Michelson, R. Rules for the International Aerial Robotics Competition 6th Mission, http//iarc. angelstrike. com/IARC_6th_Mission_Rules. pdf Hoffmann, G. M. , Huang, H. , Waslander, S. L. , Tomlin, C. J. (2007). Quadrotor Helicopter Flight Dynamics and Control Theory and Experiment. AIAA Guidance, Navigation and Control Conference and Exhibit, 20(23), 1-? 20. Point canescent -? Imaging -? Firefly MV CMOS USB 2. 0 / FireWire Camera. (n. d. ). Point Grey CCD and CMOS Digital Cameras for Industrial, Machine, and Computer Vision. Retrieved June 1, 2010, from http//www. ptgrey. com/products/fireflymv/index. asp 7) Page 10 of 10