Lab Curve Fitting

ENGR1121 – Computing in Mechanical Engineering Lab Curve fitting Lab due: end of lab Total points: 20 Labs are to be individual work. You may use MATLAB Marina, MATLAB’s help, and your notes. Lab work will be graded during lab time and working results must be shown to the lab instructor by the end of the scheduled lab time. All MATLAB programs and functions must be completed and submitted in accordance with the Computing Assignment Format and the MATLAB Coding Style. Submit an electronic copy of your lab work to the appropriate Dropbox Folder in GSU’s Folio by the end of lab. No hard copy needed unless specifically requested by the instructor. Grading Each problem will be graded according to: program design (identifying inputs/givens, process, and outputs; algorithm) and program style (program comments, variable names, proper formatted input and output including units) 25%, and program correctness 75%. Lab Work The data for the following problems are given in the Excel file: engr1121data using appropriate worksheets. Use the MATLAB command xlsread to read the appropriate data for each problem. 1. (10 points) Measurements of the fuel efficiency of a car FE at various speeds v are shown in the table in the Excel file, worksheet autofuel. a) Curve-fit the data with a 2nd order polynomial. b) Use the polynomial to estimate the fuel efficiency at 60 mi/h. c) Make a plot of the points and the polynomial. d) Curve-fit the data with a 3rd order polynomial. e) Use the polynomial to estimate the fuel efficiency at 60 mi/h. f) Make a plot of the points and the polynomial. Display outputs with appropriate descriptive texts. 2. (10 points) Using the measured position of an automobile, estimate the initial velocity and the acceleration of the automobile. The measured position and corresponding elapsed time were saved in the worksheet autoposition. You may assume that the automobile acceleration was constant over the trial. To determine estimates: a) Plot the measured data using discrete markers (position versus time) to get an idea of the general form of the data. b) The formula for position given the initial position, initial velocity and acceleration is s =s0 + vo t + 12 a0t 2 . Fit a polynomial function to the measured data. You do not need to plot this polynomial. c) From the polynomial coefficients of the fit function, determine estimates of initial velocity vo and acceleration a0 . d) Display your estimates including appropriate descriptive text and units. Display the estimated velocity both in m/s and in km/hr. Make sure the estimated initial velocity and acceleration are reasonable for an automobile. 1 Instructor: Dr. Priya Goeser