outputs of the potentiometer control signal and the two telemetered buoy signals of pitch 

 and stabilizer angle. 



As in Mode 2, the stabilizer angle will remain fixed (servo motor stopped) if the sum 

 of the three inputs to the servo amplifier equals zero (referenced to ground). For example, 

 if the buoy pitch is steady, the stabilizer angle will remain essentially constant. If the buoy 

 pitch tends to nose down, the telemetered buoy-pitch signal will change and the summed 

 input signals will change from zero. The servo amplifier will energize the servo motor which 

 will cause the stabilizer incidence angle to change to a leading-edge-down position. The new 

 stabilizer incidence angle will cause the buoy pitch to change to a nose-up position. The 

 stabilizer will continue to rotate until the buoy pitch equals the desired pitch at which time 

 the servo motor will stop and the stabilizer will be reset to a new incidence angle to maintain 

 the proper pitch. The buoy pitch angle can be arbitrarily changed or reset by manipulation 

 of the Control Potentiometer. 



The fourth mode of operation, the BIAS buoy automatic depth-keeping mode, was 

 basically designed for two ranges of depth: (1) a nominal 20-feet below the surface, and 

 (2) a nominal 4-feet below the surface. The 4-foot depth will be referred to as the surface- 

 following depth since the buoy is required to track the seaway surface contour of swells and 

 waves. The surface-following depth requires a dynamically responsive servo system, whereas 

 the 20-foot depth keeping requires steady-state servo response. 



In regard to the 20-foot depth-keeping mode, the Automatic Manual Selector Switch is 

 placed in the AUTOMATIC position. The Pitch Control Switch is set to position 1 and the 

 gain settings at the input of the servo amplifier are adjusted. The servo amplifier inputs con- 

 sist of the d-c bias signal from the control potentiometer, the two telemetered buoy signals of 

 stabilizer angle and shallow depth, and a buoy pitch-rate signal from a network in the BIAS 

 data control unit. The pitch-rate signal may be considered negligible under steady towing 

 conditions at the 20-foot depth. 



As in Mode 2, the stabilizer will remain at a fixed angle if the sum of the four inputs 

 to the servo amplifier equals zero. If the towing speed is lowered, the buoy will tend to rise 

 to the surface; the telemetered depth signal will change as will the summed input signals. As 

 a result, the stabilizer incidence angle will change to a leading-edge-up position and cause the 

 buoy to pitch down and seek the 20-foot depth level. 



The buoy depth can be controlled anywhere in the range of 4 to 40 feet by adjustment 

 of the Depth-Set Control. If the Depth-Set Control is adjusted to make the buoy follow 

 4-feet below the surface, the pitch-rate signal will become a significant input signal to the 

 servo amplifier, particularly in a rough sea. The pitch-rate signal is phased so that any change 

 in buoy pitch will cause the stabilizer to rotate in a direction to oppose the pitch change. For 

 example, if the buoy is being towed 4-feet below the surface and encounters a 2-foot high 



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