Image Processing Reference
In-Depth Information
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(a)
Pitch number
(b)
Pitch number
FIGURE 9.8 (a) Convergence plot of Vl h with respect to pitch number. (b) Plot of actuator
V g (U g ) with respect to pitch number.
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(a)
Pitch number
(b)
Pitch number
FIGURE 9.9 (a) Convergence plot of Vl l with respect to pitch number. (b) Plot of actuator
X(U l ) with respect to pitch number.
electrostatic control system when the desired unexposed and exposed voltages on
the photoconductor are given by x d ΒΌ
100] T volts.
[
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S OLUTION
Figures 9.8 and 9.9 show the convergence of the unexposed and exposed
voltages as the actuators (grid voltage and laser intensity) are changed every
photoconductor pitch. Clearly, except for a small overshoot in Vl, l , the transient
performance is similar to the performance expected by a system with closed-loop
poles at 0.2 and 0.3.
The length of the time that the charge is retained on a photoconductor is
determined by the decay rate in the dark. Charge and exposure do not take
place instantaneously. Sometimes the period between charge and exposure can
lead to signi
cant loss of charge. Automatic control systems, if designed to be
stable, that is, with closed-loop eigenvalues within the unit circle, can maintain
the exposure level to the desired value inspite of the dark decay as seen in the next
example.
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