Lecture 3, Process Flashcards
What is a process?
it is defined as the chnaging or refining of raw materiales that pass through or remain in different states to create end products
what is a single-variable processes?
one vriable is be controlled
what is a multi-variable processes?
which many vriables perhaps interrelated, may require regulation
What is process control?
it refers to the methods that are used to control process variables when manufacturing a prodcut
What are the main reasons for process control?
to reduce product variability
increase efficiency
Ensure process safety
what are the three tasks of control loops?
Measurement, comparison and Adjustment
what is a process variable?
it is a condition of the processed material that can change the manufacturing process in some way
What is a setpoint?
is a value for process variables that is desired to be maintained, no fluctuation value needed
Draw a control loop
Do you know how to do it?
how do we control vriables in a process?
by measuring the variable
what is a measurement?
it refers to the conversion of the variable into some corresponding analogue signal of the vairale (electrical voltage)
what is a sensor?
a device that perofrms the initial measurement (energy conversion into a electrical information)
what is a transducer?
a device that converts any signal from one form to another
ae al sensors transducers?
yes, but not all transducers are sensors
what is an Error?
it is the difference between the measured variable and the setpoint.
what is the objective of any control scheme?
it is to minimized or eliminate error
what are the three major components of an error?
Error magnitude
Duration of error
Rate of change of error
Error magnitude is?
the deviation between the values of the setpoint and the porcess variable
Duration of error is?
the length of time that an error condition has existed
Rate of change of error
the error magnitude at any point in time compared to the previous error. This procides the basis for determining the change in error
what is an Error detector?
a device that determines if the process variable is above or below the desired setpoint
what happedn if the PV is above or brrlow the setpoint?
an error singal proportional to the error is generated
what is an error signal used for?
it is used by the controller to generate a control action
what is often a part of the controller device?
error detector
what is a controller?
a device that acts on the error signal generated to determine what control action should be taken
what is an evaluation of the process
it consists of determining action required to bring the controlled variable to the setpoint value
What are control element?
a device that provides the required chnages in the controlled variable to bring it to the setpoint
what does it accept?
an input from the controller, which is then transformed into some proportional operation performed on the process
What are Manipulated vairable?
this are varaible which can be manipulated in order to have control over the process vairable, also call control variable
draw the relationship between the setpoint, measured vairable and controller?
do you know it?
what are the componten of a process control loop?
error detector, controller and final control element
what is an open loop?
no feedback from the process
what is the main difference between an open and a feedback loop?
in an open loop, the control action does not depend on changes in the process variable. Rather the control action is based on changes in the input to the porcess
how does the signal flow?
its form a complete circuit from the process through measurement, error dector, controller and final control element
why do we called the process control loop also a feedback loop?
because one determine an error and feed back a correction to the porcess
draw an open, feed forward and feed backward loop
hope you know it
What is the most important ccontroller?
Proportional-integral-derivative controller (PID)
how does a PId works?
it continuously caculates an error value as difference between the setpoint and a measured process variable. its then apply a correction based on proportional, integral and derivative terms
what does proportional in the PID controller means?
the magnitude of the deviation, how far is the current value far from the actual value (SP-PV), describing the current value
what does integration in the PID controller means?
is the duration over time, it decrease if the error is eliminated (SP-PV), past values
what does derivative in the PID controller means?
slop, rate of change, estimation of the future trend (SP-PV)
What is a process capability?
the ability of a process to meet the design specification
what is the eqaution for the c(P)
USL-LSL/6sigma
when is c(P) valid?
if real mean is equal to the nominal value
when is the process capable?
when c(P) is greater than 1
when can c(P) be used?
by measuring of variation only
what is the better value to describe the process capability?
process capability index
What is the process capability index equation?
c(PK)= min(USL-mean/3 sigma); )mean-LSL/3sigma)
when can c(Pk) is a?
measnue of location and variation
