LCS EC EXAM QUESTIONS AND
ANSWERS
1.1 What are the main components of a feedback control
system? - Answer-Plant, Actuator, sensor, controller, input reference, output, possible disturbances,
error signal
1.2 What is the purpose of the sensor? - Answer-To provide a feedback signal so the system can adjust
to the actual plant output
1.3 Give three important properties of a good sensor. - Answer-Must be fast, accurate, precise, linear
Low Noise, large range, large bandwidth, cheap, unbiased, easy to calibrate
1.4 What is the purpose of the actuator? - Answer-It acts on the plant in some fashion to achieve a
certain output based on some input reference
Converts some input (often electrical) into some output force, signal, torque, ect
1.5 Give three important properties of a good actuator. - Answer-Fast, accurate, precise, large range of
control
, 1.6 What is the purpose of the controller? Give the input(s) and output(s) of the controller. - Answer-A
controller has the job on translating some error signal based on feedback, into some input the actuator
needs, that will get the desired output
1.7 What physical variable is measured by a tachometer? - Answer-Tachometers measure angular
velocity
1.8 Describe three different techniques for measuring temperature. - Answer-Bimetalic strip
Thermocouple
Thermistors
Blackbody radiation
1.9 Why do most sensors have an electrical output, regardless of the physical nature of the variable
being measured? - Answer-Because electricity is a fast signal that is used by countless electronic
controllers that may be able to be reprogrammed
Easily Manipulated
2.1 What is a "free-body diagram"? - Answer-A representation of all the forces (or torques) acting on
some body, often represented as a point mass
2.2 What are the two forms of Newton's law? - Answer-The sum of all forces equals the mass times
acceleration
Sum of all Torques is the moment of inertia times angular accell.
2.3 For a structural process to be controlled, such as a robot arm, what is the meaning of "collocated
control"? - Answer-Actuator and sensor are on the same rigid body
"Noncollocated control"?
Sensor is on a different rigid body than the actuator
ANSWERS
1.1 What are the main components of a feedback control
system? - Answer-Plant, Actuator, sensor, controller, input reference, output, possible disturbances,
error signal
1.2 What is the purpose of the sensor? - Answer-To provide a feedback signal so the system can adjust
to the actual plant output
1.3 Give three important properties of a good sensor. - Answer-Must be fast, accurate, precise, linear
Low Noise, large range, large bandwidth, cheap, unbiased, easy to calibrate
1.4 What is the purpose of the actuator? - Answer-It acts on the plant in some fashion to achieve a
certain output based on some input reference
Converts some input (often electrical) into some output force, signal, torque, ect
1.5 Give three important properties of a good actuator. - Answer-Fast, accurate, precise, large range of
control
, 1.6 What is the purpose of the controller? Give the input(s) and output(s) of the controller. - Answer-A
controller has the job on translating some error signal based on feedback, into some input the actuator
needs, that will get the desired output
1.7 What physical variable is measured by a tachometer? - Answer-Tachometers measure angular
velocity
1.8 Describe three different techniques for measuring temperature. - Answer-Bimetalic strip
Thermocouple
Thermistors
Blackbody radiation
1.9 Why do most sensors have an electrical output, regardless of the physical nature of the variable
being measured? - Answer-Because electricity is a fast signal that is used by countless electronic
controllers that may be able to be reprogrammed
Easily Manipulated
2.1 What is a "free-body diagram"? - Answer-A representation of all the forces (or torques) acting on
some body, often represented as a point mass
2.2 What are the two forms of Newton's law? - Answer-The sum of all forces equals the mass times
acceleration
Sum of all Torques is the moment of inertia times angular accell.
2.3 For a structural process to be controlled, such as a robot arm, what is the meaning of "collocated
control"? - Answer-Actuator and sensor are on the same rigid body
"Noncollocated control"?
Sensor is on a different rigid body than the actuator
