Development of a heading correction model for parafoil-assisted descent of a high altitude balloon system

Abstract

The University of Kansas High Altitude Balloon System (HABS) uses a parachute for descent after release from the helium balloon. The parachute descent direction is not controlled and the HABS has to be recovered from its landing site by two chase teams that follow the HABS trajectory based on GPS downlink and unreliable predictions. Also, the landing site itself can be an undesired one. Water bodies, trees, highways are some of the undesired landing spots. Thus, a dedicated subsystem for the monitoring and control of the descent of the HABS is highly desirable.

The Advanced High Altitude Balloon System (AHABS) uses a parafoil-assisted Controlled Landing Subsystem (CLS) to autonomously control the landing of AHABS at a predetermined site. The control algorithm corrects the trajectory for heading, crosswind and near-Earth features like vegetation, power lines, towers, houses etc. Here, the implementation of the heading correction algorithm is discussed. This simulation plots the trajectory of the vehicle after deployment of the parafoil taking into consideration different cross-wind velocities and headings.

A servosystem is used for changing the angle of attack of the parafoil during flight and to make crucial maneuvers. The guidance hardware, including the GPS, Differential GPS, digital compass and a microcontroller chipset, are used for acquisition of co-ordinates and other important data and to handle the operations of the CLS respectively. The flight software is stored on the microcontroller memory module. The manual control mode of the vehicle can be activated by command from the ground station. Finally, the CCTV camera cluster is useful in providing a visual window to aid the manual controller in guiding the vehicle effectively to safe landing.

The algorithm for the flight software is a generalized one and has been adopted for both the simulation program and the microcontroller program. The simulation shows the expected trajectory along with the ideal (no crosswind) and general (no correction for crosswind) trajectories. The error in the landing site can be determined from the resultant plots.

The Controlled Landing Subsystem will not only provide more predictable flight for the HABS but it can be used in several projects other than HABS. Future work in this area will open new vistas in the field of automated recovery of systems.

This work deals only with the heading correction part of the CLS and not the complete design. Here a computer simulation has been developed for predicting the descent of the vehicle using the CLS. The design of the entire system has not been done in this work.