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.
Label each function of PID based on their error type:
Proportional - Steady State Error
Integral - Sum of instantaneous error over time
Derivative - slope (rate of change) of error over time
