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S5-Q120.) What principle is the basis for mechanical governor operation?

a.) *Centrifugal force
Correct. Rotation of a flywheel causes force to be applied to the throttle.
b.) Suction
Suction would be a vacuum device not mechanical.
c.) Mechanical operation
There are rotational forces on an engine readily available. Creating a mechanical force would not be
cost effective.
d.) Closed loop servo gain
This would be an electronic governor.

S5-Q121.) Electronic governors are what type of system?

a.) *Closed loop gain
Correct. The loop is closed by the sensor monitoring speed, the controller deciding
what to do in response to that input, and the actuator providing the appropriate force to
complete that action.
b.) Open loop gain
Control could not take place without a closed loop.
c.) Feed-forward control only
Feed-forward is predictive and the controller cannot be certain that the actions were carried out
without feedback (closed loop).
d.) Dynamic static control
There is no such thing. A system is dynamic or static, not both.

S5-Q122.) What device is necessary for Electronic Speed Control systems compare a speed reference signal to
the actual speed?

a.) Integrator
Not necessary for comparison, but may be used for control if reset is part of the control equation.
b.) *Summing junction
Correct. All feedback (closed loop) systems must compare the input signal to what t the output
sensor is reading. This is done in a summing junction.
c.) Differential amplifier
There must be an error or differential to amplify. That error is determined by the summing junction.
d.) Common Mode Rejection Ratio
This is a phenomenon common to Operational Amplifiers, not control systems.

S5-Q123.) Other then directly monitoring the speed of the engine, how can an Electronic Speed Controller
determine the actual speed of the engine?

a.) *Monitor the frequency of the generator
Correct. Frequency is directly dependent on engine RPM. By monitoring the frequency, engine
adjustments can be implemented.
b.) Monitor the voltage of the generator
Voltage is a function of flux which engine speed has no affect over.
c.) Monitor the current of the generator
Current is a function of load. The engine has no control over the load.
d.) Monitor the exhaust gas pressure
While this would give some indication of engine dynamics, it would be very difficult to devise a
control scheme from.

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