ratio of Resistor F, to the output impedance of the 7,—F, reference circuit. In this condition 
the tachometer output is compared to the preset reference voltage, and the motor drive is auto- 
matically adjusted to maintain the preselected velocity. Changes in servo loading affect the 
tachometer output, and appropriate compensation is performed by the feedback loop. When the 
servo is within 1 degree of the command position, the polarized relay returns to its central 
position. The velocity-reference signal is removed and the proportional control signal restored. 
A damping signal of appropriate amplitude is applied through &,. With proper adjustment of the 
damping signal, the servo will run-in to a preselected position with negligible undershoot or 
overshoot. The speed-load curve for several velocity settings is shown in Figure 7. Velocity 
control setting versus speed is shown in Figure 8. 
3.2 PROPULSION-CONTROL CHANNELS 
The radio-control system contains two separate propulsion-control channels. Either 
channel may be used separately, or both may be used simultaneously. Propulsion power and 
direction of motor rotation are remotely controlled by levers on the console. Propulsion-motor 
voltage is approximately linearly proportional to lever position. Power for the propulsion 
motors is obtained from motor generators driven by a storage battery as described in the follow- 
ing section on Power and Power-Control Equipment. Motor-generator output voltage is con- 
trolled and regulated by an error regulator which amplifies a low-level error signal to a level 
capable of driving the field of the generator. The propulsion system is designed for use with 
series-wound d-c motors requiring 3 kilowatts or less. Propulsion motors are reversed by 
reversing connections to the motor armature. One or more propulsion motors may be used on 
each motor-generator as long as the maximum current output of 10 amperes is not exceeded. 
Propulsion-motor speed and direction are remotely controlled by subcarrier and tone 
channels. The propulsion levers control tapped potentiometers and microswitches. The 
potentiometers control the frequency of subcarrier oscillators and are arranged so that the 
full dynamic range of the subcarrier circuit is used for either the forward or reverse condition. 
The microswitches control relays which turn tones on or off depending upon the direction of 
motor rotation desired. Four tone frequencies handle all possible conditions of propulsion- 
motor control in addition to the fail-safe circuitry described in the following section. When 
tone ‘‘A’’ is on, both propulsion motors are connected for forward operation. If tone ‘‘B’’ is 
on, only the port motor is reversed, or if tone ‘‘C’’ is on, only the starboard motor is reversed. 
Tone ‘‘D’’ reverses both motors. These propulsion-control signals are combined with the other 
control signals and transmitted over thé common radio-control link. The propulsion discrim- 
inator (s) and tone detectors in the model separate the propulsion-channel data from the 
composite-control signal. The output of each discriminator is applied to an error regulator . 
which controls and regulates motor-generator output voltage. 
