Optimal guidance for airborne cable pickup system

Abstract

A computer simulation study has been made to examine the feasibility of improving the utility and capabilities of cable pickup systems. It was proposed that a vehicle with wings and control surfaces be attached to the hook at the end of the cable and the system towed by an aircraft. The towed vehicle was assumed to have a sensor package for precise tracking to the payload to be picked UP.A lumped mass, variable cable length, three-degree-of-freedom simulation program was used to explore the dynamics for the cable pickup maneuver. The measurements available to the guidance system were assumed to be angles plus range and a Kalman filter was used to estimate the state information. The information from the estimation algorithm is the input to the control system which is of the optimal linear digital regulator type. A nominal trajectory is established at target acquisition and the equations of motion are 1 inearized about the nominal trajectory. Perturbations from the nominal are driven to zero at intercept so that the hook-up is performed in a manner which requires the least control power.The simulation study showed that the guidance system was capable of very small miss distances(<lft.) under ideal conditions. The optimal guidance system limited the miss distance degradation due to the imposition of large, varying cable loads upon the vehicle.The guidance system stablilzed the towed vehicle and allowed complex obstacle avoidance maneuvers to be executed when approaching the payload target. The down lift on the towed vehicle depressed the cable to an angle in excess of 60 deg.The trajectory angle of the payload after hook engagement was approximately 45 deg. and peak accelerations were less than 4 6's.

Event-triggered anti-disturbance control for aerial recovery drogue stabilization with guaranteed transient performance constraints

“…Then, by making some related modifications to the fixed-wing UAV driving forces, 7,12,14 the six DOF affine nonlinear dynamics can be formulated.where mNV=mN+mnormald, Snormald is the drogue’s cross-sectional area; [QNxI,QNyI,QNzI], [GNxI,GNyI,GNzI], and [TNxI,TNyI,TNzI] are the external aerodynamic forces, gravity, and cable tensions in the inertial frame, respectively; GyW,GzW are the gravity components in the winding frame; TNyW…”

“…In the air-ground pick-up scenario, a linear quadratic digital regulator trajectory controller is proposed to pick up an immobile target on the ground. 14 The retrieval docking of the ground targets via cable-towed body has also been researched by Trivailo et al 15 In a circular orbit aerial recovery scenario, the drogue’s trajectory is regulated by utilizing the drag coefficient as the control input, 3 which also cannot ensure disturbance rejection capability and high control accuracy. Until now, no specific work has been done to deal with the aerial recovery drogue stabilization subject to airflow disturbances, unmeasurable cable tensions, limited computation capacity, and actuating power resources.…”