-22] 



THE ANGLE MEASUREMENT STABILIZATION PROBLEM 



431 



desired space volume. The antenna is commanded to move in a direction 

 opposite to that of the aircraft. The general means for solving the stabiliza- 

 tion problem in this phase are shown in Fig. 8-24. The antenna is driven by 



An.c 



Antenna Command 



TIME-^ SPACE REF 



Fig. 8-24 Basic Search Stabilization System: Single Axis. 



a generated command function y^TL.c as shown. A feedback signal Aa 

 provides stabilization by subtracting the aircraft orientation angle from 

 the command angle. Thus, we may write 



^TL = Ga{/iTL,c — ^ a) + ^'i A 



(8-23) 



AtL = GaATL,c + (1 - Ga)/lA- 



If Ga is essentially unity over the frequency range o^ Atl,c and A a 



Aa = Atl,c (8-24) 



which is the desired result. 



The critical elements of such a system are seen to be: 



1. The accuracy of the angular reference which provides the feedback 

 signal. 



2. The closed-loop gain and frequency response of the antenna drive 

 which must be sufficient to follow the input commands Atl,c and the 

 stabilization feedback signals. Generally, the dynamic response require- 

 ments imposed by the command function are the most severe. 



Additional complications are introduced by the more practical problem 

 of stabilization in two or three axes. While the basic principles remain the 

 same, the problem geometry will involve somewhat complex angular 



