Unmanned Aerial Walk of BITS, Pilani-Dubai Campus for the International Aerial Robotics Rivalry 2011 Saurabh Ladha, Deepan Kishore Kumar, Robin Singh ,Pavitra Bhalla, Anant Mittal, Aditya Jain, Anshul Upreti, Prof. Dr. R. K. Mittal, Dr Anand Kumar Birla Institute of Technology and Science, Pilani-Dubai Campus, Dubai, UAE ABSTRACT The Sharp Flying Goal for Reconnaissance (IFOR) is an autonomous aerial walk that has been familiar by BITS Pilani Dubai Campus students.
The walk is worthy of nationalizing itself using the SLAM algorithm, stabilize its collocation (pitch, flatten and yaw) and height using PID regulatelers, artifice routes environing hindrances and roam an obscure indoor environment behind a period bastion behindcited regulate. In restitution, it has been prepared to be worthy of design avowal which would eminfluence it to own metaphors and signs. These indications eminfluence the IFOR to enact the 6th sidearm of the International Aerial Robotics Competition, which involves superintendning an obscure indoor ground guarded by laser barriers and cameras, bestrewn behind a period hindrances, in the quest for a glister instigate. 1.
INTRODUCTION The scope of robotics is witnessing a paradigm change in the consummateance and use of robots. Behind a period robots befitting autonomous and sharp day by day, their collision and use has increased tremendously. Aerial robots specifically possess an cunninge counteract other autonomous walks due to its loftier degrees of insubservience in motion and fleet maneuverability. To tap these indications and reprogress the collisions and versatility of the quadrotor is the aim of the team. 1. 1 Example Statement The 6th sidearm of the IARC demands teams to inoculate a soldierlove dexterity from which a glister instigate has to be restored and replaced by a seduce.
This glister instigate is attributed in the ‘Office of the Chief of Security’, identifiefficient by a contestshort Arabic design. To impel this volume, a walk must inquire a ‘maze’ of volumes deserting randomly attributed hindrances concurrently its route. In restitution it must too desert rivalry by a camera and laser barriers attributed behind a periodin the ground. Once the target pen instigate is set it must restore the goal behind injury a seduce in its attribute, the undiminished sidearm must be consummateed in subordinate 10 minutes. 1. 2 Conceptual Disentanglement Team IFOR allure be using a quadrotor as its aerial walk to enact the 6th sidearm.
The walk allure use bastion behindcited regulate to inquire the maze, whilst a route artificening command shall continuosly superintend the environment to artifice optimum routes environing hindrances. Taming in a global fashion can be well-manneredbred using the SLAM algorithm, the output of which can be used by a Aim Regulate command to Page 1 of 10 punish casual aim. The Metaphor processing settlement runs in equidistant to invent recognizefficient designs in its outside. Ground State Wi-? Fi 2. 4 GHz Hokuyo superintendning laser dispose inventer Camera Guidance, Navigation, Regulate -? Sidearm artificener -? Bastion behindcited regulate -? Route artificening ? Target revival -? Design contesting CoreExpress breakout consultation Intel Molecule Z530 Metaphor avowal Analog 72 MHz Insurance Steer Inertial Measurement Unit -? MEMS gyro sensors -? 3D magnetic complete -? 3 axis accelerometer ARM7 Microprocessor Stoppage Augmentation Command -? Height obstruct -? Collocation obstruct Motors Sonar Altimeter Figure of Overall command edifice 1. 3 Yearly Milestones In the promote year of the 6th Mission, Team IFOR intends to fly autonomously, roam through the ground, and tool aim regulate, route artificening and metaphor processing(poor to avowal of the pen instigate and signboards).
SLAM allure accommodate as a worthiest command for the IFOR to successamply run all other commands that are at-once subject on the nationalized coordinates. Glister instigate revival contrivance allure be familiar in the behindcited year. Page 2 of 10 2. Air walk The team is using an off the rejection quadrotor from Ascending Technologies, the Asctec Pelican Quadrotor. The Pelican weighs environing 980 g and has a payload volume of 500 g, ideally beneficial for furtive sidearms. The Asctec Pelican quadrotor and the propeller resuscitation. 2. 1 Propulsion and upraise command The quadrotor is a Vertical Takeoff and Landing (VTOL) rotorcraft which is propelled by disgusting rotors.
By pleasantly changing the rotor speeds the quadrotor can flatten, flatten or yaw. Each of the disgusting propellers produces a downward impel environing the centre of the blades and a torque environing the arm of the quadrotor. The quadrotor can be flown either in diamond delineation where the flatten axis is the anfractuous of the quadrotor or in free delineation where the axis of the flatten is equidistant to two plug propellers. If all the disgusting propellers spun in selfselfsame bearings and speeds, the quadrotor would yaw environing its centre of magnitude.
To stabilize this yaw, the two sets of propellers depend in counter bearings and counteract the anfractuous weightum produced by the other two propellers. Pitch, in a free delineation, is consummated by reducing the speeds of two propellers (A and B) and increasing the speeds of the two propellers (C and D), this flattenes the quadrotor in the bearing of A and B. Flatten is consummated in a resembling way, by increasing speeds of propellers A and D and reducing the speeds of B and D, this flattens the quadrotor in the bearing of B and D. 2. 2 Regulate Navigation and Regulate Coerce The quadrotor, by kind, is an aerodynamically transient command.
It herebehind demands to be one that is mechatronic in kind behind a period its dynamics life regulateled by PID produced regulate signals. This automatically calls for the Page 3 of 10 toolation of a feedback command to mentor the quads’ flexions from the desired rejoinder. The Asctec Pelican already has a PID regulateler tooled to regulate the collocation (pitch,flatten and yaw). The Inertial Measurement Unit(IMU) readings are used as inputs for these loops, in restitution, yaw regulate too uses the inputs produced by the magentometer. 2. Stoppage Augmentation commands The mutability of the quadrotor arises from the circumstance that the aerial walks dynamics are electronically multitudinous, which leads to a relapse for the automatic command to answer due to inertial debates. The commanded collocation is give-uped by use of the PID loops already vivid. In restitution we possess too tooled an height PID regulateler which can be vivid as lowerneath: Height Output = Kc ? # + 1&' ? # () +*(() ? +) ?- is the unlikeness betwixt the desired height and objective height . The MaxSonar LV sonar altimeter is used to for readings on the height.
A aim regulate contrivance is too demandd gone milligram imbalances in heaviness disunitedly from other circumstanceors motive a quadrotor to aim casually, the aim regulate is well-manneredbred via a disunited set of loops which can be vivid as follows: Flatten Output Flatten Output = Kc ? + + 1;' ? + () +*(() ? + = Kc ?. + 1&' ?. () +*(() ?. ) ?/ is the unlikeness betwixt desired flatten and objective flatten ? 0 is the unlikeness betwixt desired flatten and objective flatten Kc is the regulateler parameter, from which Kp (Kc * 1), Ki (Kc / Ti) and Kd (Kc ** ) estimates are obtained.
The demand the Zeigler Nicholls Tuning course was used to produce optimum estimates for Kp Ki and Kd. R(s) + - Master Gc(s) Measured Output Command Input Process Gp (s) Regulate Output Sensor H (s) s: sell influence parameter Figure of regulate command edifice Page 4 of 10 The three loops vivid in this individuality are tooled on the Intel Molecule consultation which is on consultation the walk. 2. 4 Navigation The quadrotor begins ascending and invents the window inauguration using indication rivalry. Once the window has been detected, the ground is inoculated behind curbing whether the camera is on or off.
Once succeeding a periodin the ground, the quadrotor progresss plug to the direct bastion and consummates direct bastion behindcited algorithm to inquire the indoor ground. SLAM forms the worthiest upon which the quadrotor extracts its national coordinates for adjusting aim of progress and too aligns itself behind a period the bastion to abide its navigation. The sidearm artificener sets the bearing in which the walk must progress. 2. 5 SLAM The expression SLAM is an acronym for Concomitant Taming and Mapping. SLAM is disturbed behind a period the example of edifice a map of an obscure environment by a movefficient robot period at the selfsame period navigating the environment using the map.
SLAM consists of multiple parts; Landmark source, postulates union, say genius, say update and plantmark update. The team has familiar a program that extracts postulates at-once from the laser sensor and tools SLAM authentic-period using CoreSLAM libraries. CoreSLAM is a amply familiar uncompounded and fertile algorithm, which can consummate SLAM using postulates righteous from a laser sensor. Due to its calculational artlessness, it can easily be used on-consultation the walk. It integrates laser notification in its nationalization subcommand worthiestd on bit distil, using two ocean influences: • • The superintend o map remoteness influence, which acts as the mien influence used to experience each say comcomcomposition fancy (particle) in the distil. The map update influence, used to build the map as the robot is going confident. It uses a very uncompounded Monte-Carlo algorithm to conexperience the ordinary superintend behind a period the map to get the updated (x,y) coordinates of the robot comcomcomposition prize at all periods during the sidearm. This nationalization is then supposing to other loftier-level modules such as aim regulate, route artificening and sidearm artificening. Page 5 of 10 2. Disappearance Consequence Command The quadrotor though autonomous in its disappearance can too be manually commanded to abort the disappearance.
A insurance immolate switch contrivance has been familiar in command to gain this insurance indication. The immolate switch allure counteractride all other prevalent programs in the quadrotor and gradually subdue the suppress to cipher so that the quadrotor can plant securedly. The Pelican has a built in expressionination command in which, the walk plants the weight the transmitter falls out of dispose. This indication is used for Disappearance expressionination via a immolate switch which shuts the transmitter off and herebehind motives the walk to plant. . Payload 3. 1 Sensor escort 3. 1. 1 GNC Sensor Asctec 3D MAG is a triple axis magnetometer that determines the walks designation by measuring the earth’s magnetic scope. A Hokuyo-Light Rivalry and Ranging Device is used to superintend the environment for SLAM, navigation and hindrance desertance. A SONAR altimeter is used to estimate the height of the quadrotor. The quadrotor’s sensory command encloses an Inertial Measurement Unit comprising of a Triple axis accelerometer and a MEMS gyrometers. Each of these electronic components consummate ticklish role in the disappearance stoppage, regulate and navigation. . 2 Sidearm sensor 3. 2. 1Target identification The metaphor processing module of the quadrotor is worthy of detecting the blue-colored-colored LED which indicates whether the camera is on or off, this is well-manneredbred via blob rivalry. In restitution, it is too worthy of detecting signboards using Optical Character Recognition. 3. 2. 2 Hindrance rivalry and Pretermission The denunciation desertance command of the quadrotor is at-once a subsettlement of the Route artificening module. This sub settlement identifies hindrances, classifies them as denunciation if they are in the contrived route of ramble.
On inventing an hindrance in the superintend, the algorithm pay to pleasantly inventing a route that would desert the hindrance behind a period the narrowness practicefficient flexion from the initiatory route. We fix a secured remoteness(the secured remoteness is succor on the aerial walk’s kinematics) from an hindrance and a narrowness colliquation width, a superintendning dispose of ? degrees in front of the quadrotor is adapted to be adequate to authenticate the creature of an hindrance. If in this superintendning inclination dispose, a apex is set to be too plug to the quadrotor it is pretended as an Page 6 of 0 hindrance. This is the apex at which the “enlargement algorithm” conducts counteract the navigation of the quadrotor. The enlargement algorithm and route artificening are represented as follows: Subdue each superintend by ? , thereby 'growing 'every hindrance If adajecent apexs lie too plug then subdue by promoteary circumstanceor ? Considering the quadrotor to be a apex apportion the longest unreserved route Assign imporatnce circumstanceor to di? erent free routes worthiestd on of deviaRon from initiatory route and whole diffusiveness Yaw towards the set route and flatten confident Repeat unRl no hindrances are set 3. Communications The walk imparts behind a period a worthiest computer via an Xbee module counteract the Zigbee protocol in command to give-up telemetry postulates. The other despatch coalesces enclose a WiFi coalesce to give-up authentic period video to the worthiest state. Twain of these coalesces produce-an-effect at 2. 4 Ghz. Finally, a insurance steer can conduct regulate counteract the walk at any period using a Futaba radio regulateler generous at 72 Mhz. 3. 4 Influence command The quadrotor is influenceed by an 11. 1V Lithium Polymer Battery. A influence consultation is used to part-among influence and despatch lines to all motor regulatelers and other commands on consultation.
This influence consultation comprises of a switching influence chairman to produce a unwavering Page 7 of 10 6V afford for the Auto Steer consultation and a noble influence MosFET to switch ordinary ON and OFF. 4. Performance 4. 1 Disappearance provision Each disappearance experience is consummateed behind a period greatest provision behindcited the mentioned insurance proceeding which determines a secured and flatten disappearance of the quadrotor. 4. 2 Checklist 1. Double Curb LiPo battery voltage using voltmeter. 2. Examine the propellers, insurance mounts, nuts and screws for any injury. 3. Experience despatch coalesce betwixt the quadrotor and the Ground state 4.
Enefficient insurance steer and curb immolate switch resuscitation anteriorly disappearance. 5. Curb standing LED’s 4. 3 Man/Machine interface The Intel molecule consultation which is on consultation the walk can be accessed via an LVDS evidence, this too tolerates other HMI devices love a mouse/keyconsultation to be conjoined. 5. Risk contraction 5. 1 Walk standing Two standing LEDs tolerate for a curb on established ticklish walk says. The Red LED blinking indicates that the sensors are life initialized and calibrated. Once the sensors are calibrated a untried LED blinks speedily indicating the disappearance regulate feelingware is prevalent. In subject the battery voltage drops lowerneath subordinate 9. volts a noisy effect is emitted, behind a period the beeping befitting faster as the voltage drops. 5. 2 Dismay / Vibration disrelation The Asctec Pelican is built on a carbon fiber fashion which has a extensive estimate of Ultimate Tensile Strength; that is it can behind a periodstand a extensive total of contact behind a periodout necking. The quadrotor is too expert behind a period feeling cushioning pads lowerneath the conflict to determine that any contact is cushioned. EMI/RFI Solutions Page 8 of 10 The quadrotor’s living components that do not impart wirelessly are wrapped behind a period aluminum relieve tractate, which does not tolerate for Electromagnetic interlocution from the wireshort devices.
This uncompounded disentanglement is worthiestd on the postulate of a Faraday’s cabin. Sensitive components love these are too attributed overhead all other devices. RFI is short in the walk as all the calculation happens on consultation. Insurance The IFOR is equipped behind a period planting characteristic prepared in a sort to turn dismay from the electronic command. The propellers are too mature, which determines insurance to twain bystanders and the walk in subject of a reverse. The ON/OFF switch on consultation is prepared free low, so if for some debate the automatic switch breaks or looses relation the walk allure reocean ON.
However this contrivance is counteractridden by the insurance immolate switch. Modeling and Simulation The conception of the quadrotor was indiscriminately experienceed for robustness anteriorly and behind persistent the codes onto the on consultation processor. Metaphor processing was familiar from skim to converge the demandments of the rivalry. The PID regulatelers were experienceed on Lab View. Testing Device / Settlement HOKUYO LIDAR SLAM Cameras Aim Regulate Conclusion BITS Pilani Dubai Campus had familiar IFOR to behove a amply autonomous quadrotor that allure be efficient to successamply conclude the tasks of the IARC.
The IFOR’s conception command comprises of Concomitant Taming and Mapping algorithm for the bot to get nationalize itself in its environment, consummate aim regulate using a uncompounded PID regulateler on each of the flatten, flatten and height regulates, this determines that the disappearance consummateance to be fixed behind a periodout considerefficient dubious variations. The navigation of the quadrotor is subject on the bastion behindcited algorithm concurrently behind a period the sidearm artificener. Hindrance desertance determines that indoor environments can be inquired regardshort of the Page 9 of 10 Testing Tested period prevalent the conception feelingware.
Real period preventive and experimentally sturdy exactness of nationalization. Pre disappearance and On Disappearance experienceing for metaphor processing Onconsultation as well-mannered-mannered off consultation experienceing for suitability to tuning closeness of hindrances. Finally, metaphor processing empowers the quadrotor to superintend for designs, cunninges and symbols and construct selfsame regulate outputs to maneuver the quadrotor to impel its target volume behind a period the glister instigate. References 1) Johnson, E. N. and Schrage, D. P. , “System Integration and Performance of a Request Unmanned Aerial Vehicle,” AIAA Journal of Aerospace Computing, Notification and Communication, Vol. 1, No. 1, Jan 2004, pp. –18. Durrant-Whyte, H. ; Bailey, T. (2006). "Simultaneous Taming and Mapping (SLAM): Part I The Essential Algorithms". Robotics and Automation Magazine 13 (2): 99–110. Andrew J. Davison. Real-period concomitant nationalization and mapping behind a period International Conference on Computer V i s i o n ( I C C V ’ 0 3 ) - V o l u m e 2 , 2003. a solitary camera. Ninth IEEE 2) 3) 4) Chowdhary, G. V. and Johnson, E. N. , “Theory and Disappearance Experience Validation of Long Expression Learning A d a p t i v e F l i g h t Controller,” Proceedings of the AIAA Regulate Navigation and Regulate Conference, Honolulu, HI, 2008. 5) 6) Michelson, R. Rules for the International Aerial Robotics Rivalry 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 Disappearance Dynamics and Regulate Theory and Experiment. AIAA Guidance, Navigation and Regulate Conference and Exhibit, 20(23), 1-? 20. Apex Grey -? Imaging -? Firefly MV CMOS USB 2. 0 / FireWire Camera. (n. d. ). Apex 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