9-9] 



ANGLE TRACKING LOOP MECHANIZATION 



Typical Servo 



495 



1 -^ I I I I I I I I I 



(3=60 



(3=20° Ca 



Fig. 9-11 Two-Dimensional Responses to Step Input. 



amount of coupling between the channels from each gyro is proportional 

 to J jH, where 7 is the moment of inertia of the gyro gimbal about its output 

 axis and H is the angular momentum of the gyro wheel. Therefore it is 

 important to select and orient the gyros so that the 7/// ratio is a minimum. 

 If the J jH ratio becomes too great, the cross coupling will become large 

 enough to cause instability in the two loops. This is particularly true if the 

 stabilization loop bandwidth is greater than 15 cps, because the J IH 

 coupling becomes more pronounced at higher frequencies and it is the 

 normal attenuation of the higher frequencies by the stabilization loops 

 that prevents instability in most cases. ^^ 



i^A complete discussion of this problem is given in a paper "Analysis of Gyro Orientation," 

 by Arthur Mayer in the IRE Transactions on Automatic Control, PGAC-6, December 1958, 

 p. 93. 



