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Control System Principles
Simplified Positioning
System Design
5.
In order to execute positioning by the semiclosed-loop method with ac-
celeration and deceleration, target positions are set consecutively in the
error counter for processing, thus enabling smooth acceleration and de-
celeration.
Desired
position
(pulses)
Error
counter
count
(pulses)
Speed
voltage
6.
The target position becomes the count for the error counter and controls
the motor by conversion to a speed voltage for the servomotor driver.
Thus, the position equals the total count of target positions (shaded area
in the figure), and the speed will depend on the desired position per unit
time.
Consider the following positioning system where millimeter is selected as the
unit:
N
Servomotor
Rotary encoder
Where:
N = rotary encoder resolution (pulse/rev)
M = reduction ratio
V = speed of moving object (mm/s)
P = feed-screw pitch (mm/rev)
L = distance moved (mm)
V
L
M
Moving object
Reduction gear
Section 1-6
Time
Time
Time
P
Feed-screw pitch
9
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