Robust automatic aircraft lateral beam guidance control using gain-phase margin tester method

For the very high frequency omni-range (VOR) coupled automatic lateral guid ance system, the variation of the distance, from the airplane to the transm itting station it is approaching, nearly always generates a stability probl em. One method for eliminating such instability is to adequately switch the adjustable gain constants as the airplane proceeds. In this paper, the gai n-phase margin tester method is exploited to obtain sufficient information that enables some adjustable system parameters to be altered to compensate for the increasing instability of the beam guidance system as it approaches the VOR transmitter. Some performance specifications of the controlled sys tem can also be satisfied. A practical model of an airplane in flight is st udied to help understand the resulting performance of the system. It is pro ved that one can have acceptable closed-loop stability with the pre-specifi ed safety margins by using the proposed gain-phase margin tester method, (C ) 2001 The Franklin Institute. Published by Elsevier Science Ltd. All right s reserved.