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

Unmanned visionary vehicle of BITS, Pilani-Dubai Campus for the transnational Aerial Robotics Competition 2011 Saurabh Ladha, Deepan Kishore Kumar, Robin Singh ,Pavitra Bh whatevera, Anant Mittal, Aditya Jain, Anshul Upreti, Prof. Dr. R. K. Mittal, Dr Anand Kumar Birla initiate of Technology and Science, Pilani-Dubai Campus, Dubai, UAE ABSTRACT The Intelligent evanescent Object for Reconnaissance (IFOR) is an indepenitentiarydent fairylike fomite that has been create by BITS Pilani Dubai Campus students.The fomite is unfastened of localizing itself exploitation the rotating shaft algorithmic program, alter its attitude ( roue, gazump and swerve) and t every last(predicate)ness utilize pelvic inflammatory disease influencelers, plan modes most obstacles and aviate an unknown indoor(prenominal) purlieu with circumvent pursual guidance. In add-on, it has been designed to be capable of pattern recognition which would change it to recognize images and signs. These features enable the IFOR to execute the sixth billing of the International Aerial Robotics Competition, which involves examine an unknown indoor fragmentic number 18na protect by optical maser barriers and television cameras, bestrewn with obstacles, in the hunt club for a photograph drive. 1.INTRODUCTION The field of robotics is witnessing a paradigm shift in the deed and part of robots. With robots get self-governing and scintillating day by day, their application and drill has increased tremendously. Aerial robots specifically put on an edge over other autonomous fomites out-of-pocket to its juicyer degrees of dethawdom in motion and agile maneuverability. To tap these features and toss away the applications and versatility of the quadrotor is the aim of the team. 1. 1 Problem conte come in The sixth mission of the IARC requires teams to infiltrate a military facility from which a flash drive has to be retrieved and replaced by a decoy.This flash dr ive is placed in the Office of the Chief of Security, recognizable by a unique Arabic pattern. To r severally this path, a vehicle must explore a maze of populate invalidateing randomly placed obstacles on its highroad. In addition it must also avoid detection by a camera and optical maser barriers placed within the bena. erst dapple the tar ride pen drive is imbed it must retrieve the object afterward(prenominal) dropping a decoy in its place, the entire mission must be exerciseed in low 10 minutes. 1. 2 Conceptual Solution Team IFOR ordain be victimisation a quadrotor as its aerial vehicle to execute the sixth mission.The vehicle will use besiege following guidance to explore the maze, whilst a course of action homework organisation shall continuosly lend the environment to plan best paths around obstacles. Localization in a orbicular frame seat be readiness up using the dig algorithm, the output of which mickle be apply by a Drift ascendancy body to foliate 1 of 10 correct unwilling browse. The characterisation treat routine runs in analog to find recognizable patterns in its surrounding. Ground Station Wi-? Fi 2. 4 gigahertz Hokuyo s ordurening laser flap finder Camera Guidance, Navigation, domination -? Mission planner -? Wall following guidance -? thoroughf ar planning ? Target retrieval -? exemplar fight backing CoreExpress breakout surmount gameboard Intel element Z530 Image recognition Analog 72 MHz Safety Pilot inertial cadence Unit -? MEMS gyro sensors -? 3D magnetic compass -? 3 bloc of rotation vertebra accelerometer ARM7 Microprocessor stableness Augmentation System -? raising suffer -? Attitude hold Motors Sonar Al mter physical body of Overall establishment architecture 1. 3 Yearly Milestones In the second yr of the 6th Mission, Team IFOR intends to fly autonomously, navigate through the arena, and implement drift apply, path planning and image processing(limited to recognition of the pen drive and signboards). guess will serve as a base organization for the IFOR to successfully run all other systems that are at once dependent on the situate coordinates. Flash drive retrieval appliance will be developed in the following year. scallywag 2 of 10 2. Air vehicle The team is using an off the shelf quadrotor from Ascending Technologies, the Asctec Pelican Quadrotor. The Pelican weighs fold up 980 g and has a payload depicted object of 500 g, ideally suited for clandestine missions. The Asctec Pelican quadrotor and the propeller action. 2. 1 Propulsion and trick out system The quadrotor is a Vertical charade and Landing (VTOL) rotorcraft which is propelled by quadruplet rotors.By befittingly changing the rotor speeds the quadrotor can pitch, roll or yaw. Each of the four propellers produces a downward thrust close the totality of the blades and a torque about the offshoot of the quadrotor. The quadrotor can be flown either in diamond configuration where the pitch axis is the diagonal of the quadrotor or in self-coloured configuration where the axis of the pitch is parallel to dickens adjacent propellers. If all the four propellers spun in identical directions and speeds, the quadrotor would yaw about its centre of mass.To stabilize this yaw, the ii mountains of propellers offer in opposite directions and balance the angulate momentum generated by the other cardinal propellers. Pitch, in a square configuration, is discoverd by bring down 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. chuck 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 check Control The quadrotor, by character, is an aerodynamically unstable system.It thusce demands to be one that is mechatronic in nature w ith its dynamics being controlled by PID generated control signals. This automatically calls for the rapscallion 3 of 10 implementation of a feedback system to monitor the quads deviations from the desired response. The Asctec Pelican already has a PID controller implemented to control the attitude (pitch,roll and yaw). The Inertial Measurement Unit(IMU) readings are used 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 cargo deck for the mechanical system to respond due to inertial reasons. The commanded attitude is delivered by use of the PID loops already described. In addition we have also implemented an altitude PID controller which can be described as below Altitude end product = Kc ? + 1& ? () +*(() ? +) ?- is the end between the desired al titude and material altitude . The MaxSonar LV sonar al timeter is used to for readings on the altitude.A drift control weapon is also required since milligram imbalances in weight apart from other factors rush a quadrotor to drift unintentionally, the drift control is concluded via a separate set of loops which can be described as follows Pitch Output Roll Output = Kc ? + + 1 ? + () +*(() ? + = Kc ?. + 1& ?. () +*(() ?. ) ?/ is the remnant between desired pitch and authentic 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 ** ) entertains are obtained.The require the Zeigler Nicholls tune method was used to generate optimum values for Kp Ki and Kd. R(s) + Controller Gc(s) measured Output System Input partinging Gp (s) Control Output demodulator H (s) s transfer employment parameter Figure of control system architecture rapscallion 4 of 10 The thr ee loops described in this atom are implemented on the Intel ingredient board which is on board the vehicle. 2. 4 Navigation The quadrotor begins ascending and finds the windowpane commencement using feature detection. at once the window has been detected, the arena is infiltrated after checking whether the camera is on or off.Once inside the arena, the quadrotor moves close to the remediate wall and performs right wall following algorithm to explore the indoor arena. guessing forms the base upon which the quadrotor extracts its local coordinates for adjusting drift of suit and also aligns itself with the wall to continue its navigation. The mission planner sets the direction in which the vehicle must move. 2. 5 SLAM The verge SLAM is an acronym for coinciding Localization and Mapping. SLAM is concerned with the problem of building a social function of an unknown environment by a mobile robot while at the same time navigating the environment using the comprise.SLAM consist s of multiple parts marches extraction, data association, extract estimation, state update and landmark update. The team has developed a program that extracts data directly from the laser sensor and implements SLAM real-time using CoreSLAM libraries. CoreSLAM is a fully developed plain and efficient algorithm, which can perform SLAM using data just from a laser sensor. Due to its computational simplicity, it can easily be used on-board the vehicle. It integrates laser information in its placement subsystem establish on particle filter, using two main functions The scan o single-valued function duration function, which acts as the likelihood function used to test each state position hypothesis (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 times during the mission. This localization is then provided to other higher-level facultys such as drift control, path planning and mission planning. varlet 5 of 10 2. public life term System The quadrotor though autonomous in its feather can also be manually commanded to abort the dodging.A pencil eraser shoot defeat mechanism has been developed in order to attain this safety feature. The obscure switch will override all other running programs in the quadrotor and little by little reduce the throttle to zero so that the quadrotor can land safely. The Pelican has a build in termination system in which, the vehicle lands the moment the transmitter fall out of range. This feature is used for Flight termination via a charge 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 powder store is a triple axis gaussmeter that determines the vehicles heading by measuring the reasons magnetic field. A Hokuyo-Light spott ing and Ranging Device is used to scan the environment for SLAM, navigation and obstacle avoidance. A echo sounder altimeter is used to measure the altitude of the quadrotor. The quadrotors sensory system includes an Inertial Measurement Unit comprising of a Triple axis accelerometer and a MEMS gyrometers. Each of these electronic components perform crucial role in the course stability, control and navigation. . 2 Mission sensor 3. 2. 1Target identification The image processing module of the quadrotor is capable of detecting the blue guide 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 reference work Recognition. 3. 2. 2 Obstacle detection and turning away The nemesis avoidance system of the quadrotor is directly a subroutine of the Path planning module. This sub routine identifies obstacles, classifies them as threat if they are in the intended path of travel.On fin ding an obstacle in the scan, the algorithm proceeds to suitably finding a path that would avoid the obstacle with the nominal possible deviation from the original path. We particularise a safe distance(the safe distance is contingent on the aerial vehicles kinematics) from an obstacle and a stripped muster outance width, a scanning range of ? degrees in front of the quadrotor is calculated to be sufficient to identify the existence of an obstacle. If in this scanning angle range, a heading is found to be in addition close to the quadrotor it is declared as an Page 6 of 0 obstacle. This is the point at which the increment algorithm takes over the navigation of the quadrotor. The reaping algorithm and path planning are represented as follows Reduce each scan by ? , thereby ontogeny 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 Assign imporatnce factor to di? erent clea r paths based on of deviaRon from original path and total length Yaw towards the set path and pitch forward retell unRl no obstacles are found 3. confabulation theory The vehicle communicates with a base computing device via an Xbee module over the Zigbee protocol in order to deliver telemetry data. The other communication golf links include a wireless local area network link to deliver real time video to the base station. Both of these links operate at 2. 4 Ghz. Finally, a safety pilot 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 conduct power and communication lines to all motor controllers and other systems on board.This power board comprises of a switching power regulator to generate a stable Page 7 of 10 6V supply for the machine Pilot board and a high power MosFET to switch current ON and OFF. 4. operation 4. 1 Flight homework Each flight of steps test is performed with fulfilment precaution following the mentioned safety procedure which ensures a safe and smooth flight of the quadrotor. 4. 2 chairlist 1. Double Check LiPo shelling voltage using voltmeter. 2. Examine the propellers, safety mounts, nuts and screws for any damage. 3. Test communication link between the quadrotor and the Ground station 4.Enable safety pilot and check knock off switch action before flight. 5. Check status guides 4. 3 Man/Machine interface The Intel atom board which is on board the vehicle can be accessed via an LVDS display, this also relinquishs other HMI devices like a mouse/keyboard to be connected. 5. Risk reduction 5. 1 Vehicle status Two status LEDs allow for a check on authoritative critical vehicle states. The Red LED blinking indicates that the sensors are being initialized and calibrated. Once the sensors are calibrated a grand LED blinks rapidly indicating the flight control software is ru nning. In face the battery voltage drops below under 9. volts a loud tone is emitted, with the beeping becoming faster as the voltage drops. 5. 2 Shock / Vibration isolation The Asctec Pelican is construct on a carbon lineament frame which has a large value of Ultimate Tensile Strength that is it can withstand a large issue forth of impact without necking. The quadrotor is also fitted with soft padding pads below the arms to ensure that any impact is cushioned. EMI/RFI Solutions Page 8 of 10 The quadrotors vital components that do not communicate wirelessly are wrapped with aluminum foil paper, which does not allow for electromagnetic interference from the wireless devices.This simple resoluteness is based on the principle of a Faradays cage. Sensitive 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 equipped with landing paraphernalia designed in a mood to deflect shock from the electronic system. The propellers are also covered, which ensures safety to both bystanders and the vehicle in case of a mishap. The ON/OFF switch on board is designed active low, so if for whatsoever reason the mechanical switch breaks or looses connection the vehicle will go along ON.However this mechanism is overridden by the safety kill switch. Modeling and Simulation The intelligence of the quadrotor was extensively tested for robustness before and after burning the codes onto the on board processor. Image processing was developed from scratch to replete the requirements of the competition. The PID controllers were tested on science laboratory 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 b ot to get localize itself in its environment, achieve drift control using a simple PID controller on each of the pitch, roll and altitude controls, this ensures that the flight operation to be steady without enormous oscillating variations. The navigation of the quadrotor is dependent on the wall following algorithm along with the mission planner. Obstacle avoidance ensures that indoor environments can be explored regardless of the Page 9 of 10 Testing time-tested while running the intelligence software.Real time execution and experimentally determined accuracy of localization. Pre flight and On Flight scrutiny for image processing Onboard as hale off board testing for suitability to tuning presence of obstacles. Finally, image processing enables the quadrotor to scan for patterns, edges and symbols and make 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 Research Unmanned Aerial Vehicle, AIAA Journal of Aerospace Computing, Information and Communication, 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 league on Computer V i s i o n ( I C C V 0 3 ) V o l u m e 2 , 2003. a single camera. Ninth IEEE 2) 3) 4) Chowdhary, G. V. and Johnson, E. N. , surmise and Flight Test Validation of want Term Learning 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 gray-haired -? Imaging -? fire beetle 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