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encapsulation in a plastic coating material. This reduction in size of the sensor module
and the improved routing of the wires allows the original covers to be reinstalled. Figure
5-2 compares the previous sensor system of the IPRV to the current sensor system on the
PML.
Magnets
Hall
Sensor
IPRV Original Configuration [2]
PML Modified Configuration
Figure 5-2: Modification to the Hall sensor module
The robot'
s operating system (ROS) works by constantly repeating a basic cycle
composed of several computational tasks. Some tasks are repeated every cycle, while
others occur less frequently. Early experiments indicated that the ROS cycle rate would
slow down when doing the more complicated computational tasks. When performing
the simplest tasks, the ROS would operate at its fastest cycle rate and complete a cycle in
approximately 3 ms. When the program was required to perform the more difficult
tasks, the cycle time would increase to as much as 5 ms. The ROS is structured so that it
will read both position sensors only once during each cycle. Therefore, the position
count frequency is directly dependent upon the ROS cycle rate.