Controls Flashcards
Define a control system (broad)
Any interconnection of components to provide a desired function
The portion of the system that is to be controlled.
The Plant (or Process)
A device used to produce a desired behavior of the plant.
Controller
What does a controller do (broad)?
Generates plant input signals desired to produce desired outputs
Define an open loop control system:
- the control inputs are not influenced by the plant outputs; No feedback around the plant.
Define a closed loop (feedback) system:
- a path (or loop) is provided from the output back to the controller.
- some or all of the system outputs are measured and used by the controller.
- a controller may then compare a desired plant output with the actual output and act to reduce the difference between the two.
What are some of the advantages of feedback control? (4)
- Increased accuracy.
- Reduced sensitivity to changes in components.
- Reduced effects of disturbances.
- Increased speed of response and bandwidth.
If a system’s impulse response decays asymptotically to zero with time. What can be said about the system.
The system is input-output stable.
- a system is stable iff all of its characteristic roots are to the left of the imaginary axis on the complex plane.
In a block diagram. What is a summer?
An element used to show additions and subtract ions of signals.
- a summer can have any number of input signals but only one output signal.
In a block diagram. What is a junction (pickoff point)?
A junction indicates that the same signal will go several places.
List 5 components of a control loop
- Sensor (with or without transmitter)
- Controller
- Analog/digital output device
- Actuator
- Mechanical or electrical equipment to change the control media
List 6 components of a controller
- Power Supply
- Input points (dig/ana)
- Output points (dig/ana)
- Totalizer input
- Software point
- Program (control loop, EMS, custom logic)
What does a panel typically contain? (4)
- Controllers
- Relays
- Switches
- Time Clocks
What does a PID controller do?
A PID controller continuously calculates an error value e(t) as the difference between a desired setpoint and a measured process variable and applies a correction based on proportional, integral, and derivative terms.
PID - Proportional, derivative, integral control ~ PID is an algorithm that is used to accurately and quickly reach an output based on a desired setpoint.
What is the output of a PID controlled device?
it is an output function generated from the sum of errors provided by the proportional, integral, and derivative control.
