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Lecture 9

# ENG 06: Engineering Problem Solving with MATLAB – Lecture 9 notes

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Department
Engineering
Course
ENG 6
Professor
Professor Rajeevan Amirtharajah
Semester
Spring

Description
ENG 06 – Lecture 9; 2/5/2013 Project 1:  Read over tonight, have questions to ask this week (don’t wait) Custom Functions  Inline and Anonymous Functions o If you want to write a function that you’ll need for a few minutes o Not a good idea to use these regularly; not for big projects  Inline Function o Explicit definition of arguments  Inline(expr,arg1,arg2,…) constructs an inline function  Arguments specificed by strings  Anonymous Functions o Fhandle = @(arglist) expression  @ sign constructs function handle  arglist is comma separated list of input arguments  ex. log8 = @(x) log(x)/log(8)  Feval and Function handles o Use feval to call and evaluate other functions by their function handle o First input is function handle, calls function indirectly  Example of why Function Handles are Useful o function [] = funplot(fun, a, b, xlab, ylab)  o % Makes a plot of function fun between the limits a and b and insert x label and y label as provided in xlab and ylab o x=linspace(a,b,100);  o y=feval(fun,x);  o plot(x,y);  o xlabel(xlab); o ylabel(ylab);  o end  funplots(@sin,0,pi,’xx’,’yy’) returns the answer  funplots(sin,0,pi,’xx’,’yy’) returns an error  Auto-code generation feature of MATLAB o >>x=linspace(1,10,30); o y1=sin(x) o y2=cos(x) o plot(x,y1,x,y2)  create graph  interactively modify graphs  auto generate code  Summary for functions o Functions defined in a file of the same name using key word function to distinguish from scripts o Parameters are copied in sequence into the function and given names of formal parameters o Results are returned to caller by assigning values to return variables o Variables within function have scope only in functions code block (unless they are declared global) o Helper functions are accessible only to functions within the same file may be added behind main function and obey the same rules as the main function Engineering Design  Relationship between Science, Engineering, and Technology o Science needs to understand natural world, often needs new tools o Engineers use scientific discovery to design products and process that meet society’s needs  Generic Engineering Design Cycle o Ask o Imagine o Plan o Create o Improve  NASA Case Study:Develop a Lunar plant growth chamber o Launched 10 million cinnamon basil seeds o Almost all seeds were returned to earth for students to grow in growth chambers they designed o 16 seeds were left, grown on the ship, to demonstrate growing plants in a microgravity environment  Detailed Engineering Design: o Identify the problem o Identify criteria and constraints o Brainstorm possible solutions o Generate ideas o Explore possibilities o Select an approach o Build a model or prototype o Refine the design  Design example: develop a lunar plant growth chamberd o Identify the problem: restate in your own words o ID: criteria and constraints: growth chamber must have surface of 10 square feet  Constraints: must be accessible to astronauts without leaving the spacecraft o Brainstorm possible solutions: sketch ideas, quick and brief o Generate ideas: develop 2 or 3 ideas more thoroughly, create new drawings o Explore possibilities: pros and cons of ideas o Select and approach: identify the design that appears to solve the proble
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