Multiple and conflicting objectives Flashcards
Lecture 20
What are performance indices?
- Identify material attributes that are fixed
- Decide performance criterion to be maximised/minimised
- Substitute for free variables using constraints
- Read off combination of properties to optimise
What are possible methods to consider performance indices?
min-max method
penalty functions
What is the min-max method?
As both have the same objective of minimising mass, we calculate the mass
Step 1:
- Choose the largest (maximum) mass m between M1 and M2 for each material (what is the worst case mass for each material based on two objectives?)
Step 2:
- Select the material with the lowest (minimum) worst case mass m (from step 1)
What are the often main objectives m material selection for compoments?
- Minimising mass
- Minimising volume
- Minimising cost
- Minimising environmental impact
What is a penalty function?
Combine the conflicting objects to form a single objective function -> the minimum of this function should define the most preferable solution
What is the equation for “yield before break?”
What is the equation for “yield before break?”
What is the equation for “leak before break”?
What is the equation for “minimise thickness”?
Yield before break performance index?
Leak before break performance index?
Minimising thickness performance index?
Identifying the search region with “yield before break”, “Leak before break” and “minimising thickness”?
Conflicting inficies example - minimising the mass of a tie
What is the equation used to work out a locally linear penalty function (Z)?
What is the equation for the exchange constants?
What is the equation for costs?
How do we find the best choice with parameters of cost and mass?
