4.3 Heading Alignment Controller

4.3.1 Testing Procedure

 The first step necessary to test the heading alignment controller was to calibrate the

PNI Corporation TCM2-20 digital compass. A serial connection was established

between the digital compass and a Dell Inspiron 8100 laptop computer and the digital

compass was placed into polling mode. Then, the compass was given the command to

start its calibration cycle and the Andros was slowly rotated in a circle for approximately

four minutes. Once this was completed, a series of "Set Behavior 1" commands were

sent from the OCU to the Andros JAUS controller, along with the desired heading. The

JAUS controller was coded such that the "Set Behavior 1" command initiated the heading

alignment code. The first series of tests were administered to determine the minimum

allowable tolerance value that the system could accept without the system becoming

unstable. In this situation, the system would be unstable if the controller continually

reversed the rotation of the Andros in an attempt to move the Andros to the desired

heading. From these initial tests, the allowable tolerance for the system was found to be

+/- 4 degrees. After this was completed, another set of "Set Behavior 1" commands were

sent from the OCU and the commanded heading, compass heading, and final Andros

heading were recorded. The compass heading is the value that the digital compass last

reported to the controller to illicit a stop rotation command. The final Andros heading is

the compass measure of the heading of the Andros when the rotation actually stops.

4.3.2 Results

 Figure 4-7 depicts a plot of the controller commanded halt heading and the vehicle

halt heading versus the desired heading sent from the OCU. The controller commanded

halt heading is the heading returned to the controller at the instant that the controller