Optimal terrain-following for towed-aerial-cable sensors

Towed-aerial cable systems are often used for towing decoys from aircraft and for collecting electromagnetic data from low altitudes. Airborne cable systems are typically controlled by maneuvering the aircraft, which can limit the safe altitude of the towed-sensor package. In this paper, a real-time optimal control strategy for controlling a towed-cable system is proposed that uses cable winch control to control the altitude of the towed-body. The controller is based on a receding horizon control approach, where the aircraft senses the terrain profile ahead of the towed-body with a relatively short time horizon. This information is sent to the controller, which updates the cable winch reel acceleration to safely avoid colliding with the terrain, while keeping the towed-sensor close to the desired altitude for obtaining good measurements. The controller is developed for a simplified system model and implemented in a multibody cable system model that incorporates cable flexibility and elasticity.

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