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.