9-8] 



ANGLE TRACKING LOOP POSITION ERRORS 



491 



LOS 3(0.13) 9(0.0246) 



esp" = (JTP^ - (ec^ + cnp') = (0.105)2 - [(0.086) ^ + (0.0397) 2] = 0.002053 

 esp = 0.0453° 

 ""See footnote to Fie. 9-5. 



included to illustrate how the higher-order terms become less important 

 in the series for the particular conditions used. Again the bias error is 

 considerably less than that allowed. However, as before, the input did not 

 include the sudden changes that often occur in some attack courses, and 

 under these circumstances, the bias error could be much larger. For 

 example, if the 1.05° rate input had been applied suddenly, the peak error 

 would be about 0.16° for a short time.^^ 



From the preceding discussions, it appears that the track loop transfer 

 function shown in Fig. 9-8 would meet the tracking loop error requirements. 

 It should be noted that the loop phase margin is greater than 50°. This is 

 necessary to provide adequate damping during the tracking operation. 



LO 



'(ife+') 



s(ss«)(l+>) 



Fig. 9-8 Tracking Loop Transfer Function. 

 i^See Chapter 8 where transient errors due to ramp inputs are discussed. 



