Dr Bill Crowther CEng MRAES
Research>Flight dynamics>Perched landing |
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Background Wing borne flight necessarily involves motion of a body with respect to the surrounding air mass. If this air mass is fixed with respect to the ground then it is necessary to perform transition manoeuvres between ground and air states at either end of flight; these are commonly known as take off and landing. For runway-based landing, the kinetic energy associated with any differential velocity between an object and ground at the point of touchdown is absorbed through frictional dissipation during translation along the runway. A perched landing, by definition, involves no translation following touch down, and any excess kinetic energy must be absorbed through internal dissipation within the body. Thus the key problem for perched landing is the delivery of a body to a fixed point in space with minimum velocity. For landing on a runway either wheels or skids are required to allow for the differential velocity during the ground/water/snow roll. For a perched landing, it is necessary to be able to establish mechanical contact with the landing perch via some sort of foot arrangement. Furthermore, by placing this foot on the end of an extensible and controllable leg, it is possible to relax the flight control requirements by enabling the leg to correct for small errors in the landing approach. The inclusion of a controllable leg also allows reorientation once on the perch, and relaunch via a suitable jumping manoeuvre. Publications Nagendran, A., Richardson, R.C., Crowther, W.J., 'Bell shaped impedance control to minimise jerk while capturing delicate moving objects', 4th international conference in Informatics in Control, Automation and Robotics , Angers, France, May 2007 Crowther, W.J. ‘Perched landing and takeoff for fixed wing UAVs’, NATO AVT Symposium on Unmanned Vehicles for Aerial, Ground and Naval Military Operations 9-13 October 2000 in Ankara, Turkey. Crowther, W.J., Prassas, K., ‘Post-stall landing for field retrieval of unmanned air vehicles’, 14th Bristol International unmanned air vehicle systems conference, UK, April 1999.
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