Automated Controls Flashcards
Define control systems
Set of mechanical or electronic devices that regulate other devices or systems by way of control loops
Define open loop
Controlled only by set point commands, without feedback measurement signals. Uses one control like on/off or a timer
Define closed loop
Uses feedback signals from the system to provide automatic control and maintain specific settings. Uses two or more controls.
Define negative feedback
reduce the change or output. Dampen or buffer changes.
Which feedback provides system stability/equilibrium?
Negative feedback
Define positive feedback
increases the change or output. Enhances or amplifies changes. Moves system away from equilibrium.
What is another term for negative feedback?
Self-regulated
What are some examples of a negative feedback system?
House temp closed loop control system, flyball governor, water level control, cruise control
What is an example of positive feedback?
Schmitt Trigger
Define direct action (non-inverting)
Controller output signal will respond to any controller input signal change in the same direction
Define reverse acting (inverting)
Controller output signal will respond to any controller input signal change in the opposite direction
What is the key function/component of an open loop system?
Timers
What is the fundamental process for a flyball governor?
Centripetal force
What is the purpose of a solvent tank?
Provide a constant level of solvent regardless of various load behaviours.
proportional control in proportion to demand
What type of loop and feedback system is a solvent tank?
Proportional closed loop negative feedback system
What are the four steps in a control system/control block?
Process, measurement, controller/error detector, final control
Define a transfer function?
Represents the relationship between output signal of a control system and the input signal
Each transfer function can be described using what two terms?
Transfer gain K (static) and speed of response D (dynamic)
Digital signal is what type of control mode?
Discontinuous - On/Off
Analog signal is what type of control?
Continuous - proportional, integral, derivative
What is the first block of the block diagram?
Process - what needs to be controlled
Ex) water level
What is the second block of the block diagram?
Measurement Sensor - senses the controlled variable and produces a corresponding signal which is sent to the controller.
Can be called controlled variable (CV), measured variable (MV), or process variable (PV)
What is the third block in the block diagram?
Controller/Error Detector. Block receives measured variable from sensor, controller decides on what size and direction of output signal to send.
What is the fourth block in the block diagram?
Final Control - received output signal from controller, adjusts energy or material flow to or from a process.
Also called manipulated variable (MV).