Aspects of Control for a Parafoil and Payload System

Abstract

A parafoil controlled by parafoil brake dee ection offers a lightweight and space-efe cient control mechanism for autonomous placement of air-dropped payloads to specie ed ground coordinates. The work reported here investigates control issues for a parafoil and payload system with left and right parafoil brakes used as the control mechanism.Itisshownthatparafoilandpayloadsystemscanexhibittwobasicmodesoflateralcontrol,namely,roll and skidsteering.Thesetwo modesoflateralsteeringgeneratelateralresponseinoppositedirections.Forexample, a roll steer cone guration turns left when the right parafoil brake is activated, whereas a skid steer cone guration turnsright under the samecontrol input. In transition between roll and skid lateral steering, the lateral responseis zero, and the system becomes uncontrollable. Angle of incidence, canopy curvature of the parafoil, and magnitude of brake dee ections are important design parameters for a controllable parafoil and payload system and greatly effect control response, including whether the basic lateral control mode is roll or skid steering. It is shown how the steering mode switches when fundamental design parameters are altered and as the magnitude of the brake dee ection increases. The mode of directional control transitions toward roll steering as the canopy curvature decreases or the angle of incidence becomes more negative. The mode of directional control transitions away from the roll steering mode as the magnitude of the brake dee ection increases, and for “ large” brake dee ections most parafoils will always skid steer.