National Instruments 370753C-01 Manual De Usuario
Chapter 1
Introduction
© National Instruments Corporation
1-9
Close the loop using the single-input syntax of
feedback( )
, which
implements direct unity-gain negative feedback, and obtain the system’s
step response using
step response using
step( )
:
Kc = 2; cl_syscomp1 = feedback(Kc*K1s*K2s*Gs);
v = step(cl_syscomp1, 0:.2:25);
plot(v,{xlab="Time",
ylab="Horizontal Velocity"})
The resulting plot is shown in Figure 1-3. This result is not desirable. You
want the output (the helicopter velocity) to track the step input provided as
the rotor tilt angle, not zero out its effects over time (which would be an
appropriate response if the input corresponded to a disturbance). This
results from the compensator zero at s = 0 in the forward path of the
feedback loop.
want the output (the helicopter velocity) to track the step input provided as
the rotor tilt angle, not zero out its effects over time (which would be an
appropriate response if the input corresponded to a disturbance). This
results from the compensator zero at s = 0 in the forward path of the
feedback loop.
Figure 1-3. Helicopter Velocity Response to a Step Input at the Rotor
Instead, you now place K
1
(s) in the forward path and K
2
(s) in the feedback
path, so that the closed-loop system now has the configuration shown in
Figure 1-4.
Figure 1-4.