Height Control Scheme without Using Pitch Angle for Fixed Wing UAVs

Classical height control loop usually uses a pitch angle measurement in an inner loop to properly damp the short period and phugoid modes for a fixed wing UAV. The pitch angle measurements from low cost sensors can have significant biases under large maneuvers. This paper presents an alternate linear height control scheme based on the vertical acceleration measurement. An added advantage of this ‘g-control’ scheme is that load factor can be controlled precisely during pull-up or pull-down maneuvers. Secondly high performance can be achieved using low cost sensor measurements. The controller parameters are tuned in a nonlinear optimization setup that satisfies various controller design requirements. The presented height control scheme is tested in a high fidelity nonlinear simulation of the King Saud University testbed UAV with satisfactory results.