-28] 



STATIC AND DYNAMIC CONTROL LOOP ERRORS 



445 



Fig. 8-32 shows the nature of the error transient that occurs if the 

 direction of the horizontal sweep changes instantaneously. An important 



Fig. 8-32 Dynamic Transients, (a) Approximate position error transient for 

 linear search sweep, r = horizontal search sweep velocity; 002 and coc are defined 

 in design equations, (b) Open-loop transfer function. Design equations (approxi- 

 mations usually accurate enough for engineering design purposes): (1) Gain: 



(2) Phase: 



180° + (/);„ 



C02\C0i/ 

 TT /tT CoA /tT 0)2 \ CO^/ A 



2/3„ 



57.3 



(3) Minimum Phase atcj^: t~^ = 



2cOm 



NOTE: Substitute ( — ^ )in Equation 2 when solving for coi or a;2- 

 (c) The search loop (azimuth channel). 



point is that the peak error of the transient, frequently neglected, can be 

 much larger than the steady-state error, and a relatively large time may be 

 required for it to settle if aj2 in Fig. 8-32 is small. Actually, there are several 

 ways in which the dynamic error can be specified. For example, the time 



