Block 1 - lecture 1 Flashcards
What’s control?
altering the performance of a system
What are the possible aims of control?
- regulate output
- tracking a varying value
- time/event driven sequencing
Benefits of process control?
- predictable
- stable
- constant
Purpose of sensor?
to measure output
Purpose of actuator?
to adjust input
Purpose of controller?
coordinates sensors and actuators
Setpoint?
a value to be maintained
Discrete-state control systems?
sequence of on/off events
Open loop control?
input isn’t controlled by the output (input on = output on)
Closed-loop control?
input is influenced by the output (eg. thermostat)
Question to ask before choosing closed-loop control?
- really needed?
- input measureable?
- save energy?
- easy to set up/maintain?
- safe?
What are the objectives of control systems?
- stable
- steady state regulation
- transient regulation
What desired quality of a control system can reduce stability?
faster responses
Steady state error?
difference between output and input at steady state
Transient response?
how the system reacts to change
What’s tuning?
adjusting a process-control loop
2 ways to measure transient response?
- response to change of setpoint
- response to transient disturbance
types of response?
- damped
- cyclic
features of a cyclic response?
- overshoot (step input change/first overshoot)
- decay rate (second overshoot/first)
- rise time (time for step change)
- settling time
Cyclic response with quarter amplitude?
decay rate of 1/4
Aims of cyclic tuning?
- reduce area either side of setpoint after rise time
- reduce decay rate
- time rise
Analog vs digital processing?
- analog is smooth
- digital has steps
ADC?
Analog to digital convertor
DAC?
Digital to analog convertor
Bi-directional on/off control system?
max on, no effort, max off
Analog control system?
continuously variating input/output
Supervisory control?
still analog, computer monitors the output
Direct digital control?
computer is fed the output and generates the input
Can give error detection
LAN?
Local Area Networks
PLCs?
Programmable logic controllers (self contained microcomputer)
