A simplified schematic of the automatic depth-keeping system is shown in Figure 5 and 

 a detailed schematic is provided in DTNSRDC Drawing C-398-4. A servo motor, mounted in 

 the buoy center vertical fin, is capable of producing 3-foot-pounds of torque to drive or posi- 

 tion the horizontal stabilizer attack angle. The servo motor is remotely controlled from the 

 data center via two leads in the toWcable. The servo motor, and hence the stabilizer, can be 

 remotely controlled in four operational modes: three modes utilize a servo amplifier and one 

 mode uses a double-pole, triple-throw switch directly coupled to a power supply. 



The various modes of horizontal stabilizer control were provided to maximize operational 

 flexibility during evaluation experiments of the BIAS buoy system. The principles of opera- 

 tion of each mode are discussed in order that the final depth-keeping mode of operation 

 might be more easily perceived. 



The first mode allows for manual positioning of the stabilizer to any angle within the 

 allowable plus or minus 15-degree range. The Automatic Manual Selector Switch is set to 

 the MANUAL position. The Manual Control Direction Switch is a three position spring- 

 return-to-center switch; the center position is OFF (no power to the servo motor). When 

 this switch is held to one side, the stabilizer rotates in one direction; if the switch is held to 

 the other side of center, the stabilizer rotates in the opposite direction. The position of the 

 stabilizer is determined from observing the recorded angle on the strip-chart recorder of the 

 measurement system. 



The second mode, using the servo amplifier, allows for potentiometer control of the 

 stabilizer position wherein the angle of the stabilizer is preset to any desired angle by discrete 

 positioning of the Control Potentiometer. The Automatic Manual Selector Switch is placed 

 in the AUTOMATIC position and the gain adjustments of the servo amplifier are adjusted to 

 zero except for the stabilizer position input which is adjusted for proper gain. The telem- 

 etered horizontal stabilizer-angle signal from the discriminator is summed with the d-c output 

 or bias signal of a control potentiometer energized from a fixed voltage supply of plus and 

 minus 15-volts (see Figure 5). When the sum of the stabilizer-angle signal and the Control 

 Potentiometer signal are zero (referenced to ground), the servo motor is stopped. If the 

 Control Potentiometer position is manually changed, the summing voltage will change pro- 

 portionately from ground level; the servo amplifier will generate an output signal to rotate 

 the servo motor and change the stabilizer angle. The stabilizer will rotate until the stabilizer 

 position sensor output nulls the Control Potentiometer output and the servo motor will stop, 

 thus accomplishing the desired new stabilizer-angle setting. 



A third mode allows for automatic control of buoy pitch where the stabilizer angle 

 automatically changes to hold a predetermined buoy pitch. The Pitch Control switch is 

 placed in position 2 and the gain adjustment of the pitch/pitch-rate channel of the servo 

 amplifier input is adjusted for proper gain. The servo amplifier now receives the summed 



10 



