Page 314 - Robots Androids and Animatrons : 12 Incredible Projects You Can Build

Once home, we can start and replay a script, knowing that the drift
occurring during one run of the script is probably so minimal that
the robotic arm will hit all its marks. Once the script is finished,
the arm is reset to its home position and the script file is replayed.
Sometimes a home position does not give enough feedback to per-
form certain operations, for instance, picking up an egg without
crushing the shell. For these applications, more sophisticated
methods of feedback need to be employed. Signals from trans-
ducers are processed using analog-to-digital (A/D) converters. The
processed signals are used to determine factors such as position,
pressure, speed, and torque. A simple example will illustrate.
Imagine mounting a small linear potentiometer on the gripper sec-
tion. The potentiometer is mounted so that when the gripper
opens or closes, the slider on the potentiometer slides back and
forth. So as the gripper opens and closes, the resistance of the
potentiometer varies. Once calibrated, the resistance could accu-
rately tell how far the gripper closed (or opened).
Feedback systems add another layer of complexity and cost to the
system. One can always use the manual control system to override
and reposition the robotic arm as a script is running.
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Connecting manual control to interface

After the interface is running properly, connect manual control to
the interface using the eight-pin header. Orient the manual con-
trol’s Molex connector to the eight-pin interface header as shown in
Fig. 15.10. Press the connector firmly onto the header to seat. The

15.10 Connecting the manual control
Team LRN
Robotic arm and IBM PC interface and speech control