Ground Collision Avoidance Using a Variable Incidence Altitude Measurement System for the A-7 Aircraft.

摘要

This study examines the use of a forward looking sensor in the implementation of an automatic terrain following system. The effect of the incidence angle is studied as well as methodologies to include dynamic motion in the pointing of the sensor beam. The methods examined include fixed angle with respect to the aircraft, dynamics driven by a simple gain, and dynamics directed to gather the terrain information a fixed time interval ahead of the aircraft. Incidence angles of 25, 50, 75, and 90 are examined. The terrain obstacles include a single parabolic hill, a step change is terrain, and a double parabolic hill. Compensator design was accomplished using MATLAB (Trademark) software using Linear Quadratic Gaussian Techniques. State space system realization of the closed loop dynamics were used by a FORTRAN program to run the simulations. Performance was judged by qualitative assessment of flight path, quantitative score of summed distances away from commanded 300 ft AGL altitude, and amount of control power required. The best performance was achieved by the 50 degree incidence angle. Dynamic motion of the sensor beam improved performance but required more control deflection. The best dynamic pointing method was the constant time interval technique.