# multiple uav collision avoidance with realistic uav models

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Multiple UAV Collision Avoidance with Realistic UAV Models. Joel George and Debasish Ghose Guidance, Control, and Decision Systems Laboratory (GCDSL) Department of Aerospace Engineering, Indian Institute of Science, Bangalore India 560012. Problem Description. - PowerPoint PPT Presentation

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Multiple UAV Collision Avoidance with Realistic UAV ModelsJoel George and Debasish GhoseGuidance, Control, and Decision Systems Laboratory (GCDSL)Department of Aerospace Engineering,Indian Institute of Science, BangaloreIndia 560012.Problem Description

Multiple UAVs fly to their destinations in a free flight zoneNeed to detect and avoid mid-air collisions Each UAV has a safety zoneUAVs have limited sensor rangesObjectiveObtain high efficiency with lower number of near misses

Efficiency = Near Miss

A breach into each others safety zonesAssumptionsPositions and velocities of other UAVs within the sensor range are known6 Degree of Freedom UAV model

Solution approachMultiple UAV collision avoidance by handling pair wise conflictWhen a UAV encounters multiple conflicts, it does a maneuver to avoid a near miss with the most threatful neighbor. Every UAV doing so, in a multiple UAV conflict scenario, will result in a high efficiency with lower number of near misses.The ThesisSolution approach (continued)Most threatful neighbor (of a UAV U): A UAV in the sensor range of U with which U has a projected near miss and the least time-to-go for that near miss to occur.Collision avoidance maneuver: Turn in a direction that will increase the Line-of-Sight (LOS) rate between the UAVs.

Deciding the most threatful neighbor and the desired collision avoidance maneuverPair wise collision avoidance maneuverIn this example, where , the UAVs U1 and U2 turning in the directions of lateral accelerations a1 and a2 (green arrows) will result in an increase of LOS rate between them.

Realistic UAV ModelUAV of span 1.4224 m, weighing 1.56 kgStability and control derivatives from Aviones A UAV flight simulator developed by the Brigham Young University (an open source software) Available: http://aviones.sourceforge.net/

Controller designControllers designed through successive loop closureSeparate controllers for holding altitude, attitude, and velocityPI controllers with parameters tuned manuallyController designAltitude hold controller

Similar controllers for attitude and velocity holds are designedController response

Response of UAV model (with controller) to a 3-2-1-1 bank angle commandThe plots of system state response: bank angle ( ), height (h), and velocity (V), and the control demands: aileron deflection ( ), elevator deflection ( ), and throttle ( ). Demanded bank angle is shown in dotted lines.

Test of collision avoidance

A example of collision avoidance of 5 UAVs. The test case is tailored such that the avoidance of one conflict will lead into anotherRandom flights test case

UAVs appear at random points in outer circle (radius 500 m) and fly to randomly assigned points in inner circle (radius 400 m) with a velocity of 12 m/s and a maximum turn rate capability of 10 deg/sec.The scenario is simulated for 1 hour and at any instant during the simulation, the number of UAVs in the airspace is kept constant by replacing the UAVs that reached target points by new ones. Any approach of two UAVs within 10 m is considered a near miss. An approach within 2 m is a collision.Test case of random flights for dense trafficResultsNo. of UAVswithout collision avoidancewith collision avoidanceNear MissesEfficiencyNear MissesEfficiency204060218.1899.12027.91001001000.11.61.496.1589.1789.11Results of the random flight test caseSummaryGave a collision avoidance algorithm, for multiple UAV scenarios, that gives a good performance low near misses and high efficiencyDesigned PI controllers for a realistic UAV model using successive loop closureTested the collision avoidance algorithm on this realistic UAV model augmented with the designed controllerResults showed a good performance of the algorithm

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