log scale

I G(jo) I

 K,


-1 slope


o rad/sec


-2 slope


Figure 8.23. Generalized open-loop Bode diagram of a lag-lead compensated velocity control
 system.


process was completed by increasing the lag factor allowing the gain, K, and the bandwidth of

the compensator to be increased. Thus, the low-frequency gain of the system was increased for

minimized steady-state error and the bandwidth was increased for maximum response speed

and lowered overshoot values.

 The worst case for controlling the velocity system for joint 0 occurred when the actuator

was fully retracted and moving in the upward direction (Kv = 0.039 (deg/sec)/(D/A word), ) =

21.4 rad/sec, and 8 = 0.21). This case was considered worst because the resonant peak elevated

higher above the unity magnitude than any of the other trials. Therefore, this case would

limit the maximum value for the controller's gain and establish a conservative lag factor.

Initial choices of the controller's parameters placed the lag factor at 1 rad/sec (zi = 1.0 sec) to

lower the resonant peak. The lead factor was set at 100 rad/sec (td = 0.01 sec) effectively

eliminating its effect on the system. A very conservative controller gain, Kc, of 3.0 (D/A

word)/(deg/sec) was chosen to decrease the steady-state error without causing instability.