1. Introduction to Systems Engineering

- Objectives:

To analyze the dynamic operation of a process
To investigate and implement changes in system
in order to improve performance

- Incentives for automatic process control

To minimize the effect of disturbance
To ensure that operation remains within constraints
To optimize performance

- Modeling Questions:

Which way? (does increasing flow rate in decrease temperature?,etc.)
How fast? (how much time does it take to reduce pressure by 50% ?)
Can targets be reached? (is it stable?) How ? (Does it oscillate?)

- One effective way to model dynamic behavior: differential equations
dx/dt = f ( x, u, d )
• Classification of variables
• x - process variables (or state variables or states)
• Types:

a)  Measured:
i) controlled
ii) uncontrolled
b)  Unmeasured
• u - manipulated variable
• d - disturbance variable
• Types:

a)  Measured
b)  Unmeasured


- Modeling guidelines:
 

1. Determine system boundaries: distinguish process variables from external variables
2. Understand the objectives of the models
• which variables will be monitored or controlled ?
• what level of complexity is needed ?
• what simplifying assumptions are appropriate ?
3. Determine performance requirements
• safety/stability
• product quality
• speed of response
4. Investigate contributions of parameters (for retrofit) and control design