1 EG 10111: Introduction to Engineering Module 1, Homework 3 Due in Learning Center, Week of September 19, 2011 Reading: Brockman, Sections 2.2.1-2.2.3 Your homework assignments should typically be typed using Microsoft Word or another software package to make it easy for your student assistant to grade your assignment. But in some instances the assignment may ask for something that is time consuming to generate electronically (formulas or a sketch). Unless the assignment specifically indicates that a question must be electronic, you can just leave a blank space in the document for that question where you could NEATLY write your response. 1. Communicating the Results of an Experiment In last week’s learning center, each group programmed a vehicle to travel one meter in a straight line by counting the revolutions of the driving wheel. Although each robot was programmed the same way, the results that we obtained for actual driving distance varied. The average driving distances from everyone’s sets of three trials are available on Concourse under this week’s homework assignment, in a file called DrivingDistances.csv . This is just a set of distances (in meters) listed on separate lines, which can be opened with any text editor/Microsoft Office. (a) Construct a bar chart (in this case, also called a histogram) to visually display the results of all of our trials. To do this, you should count the number of trials that fall into the ranges below, then plot the ranges on the X-axis and the count (frequency) on the Y-axis. You may choose to either plot this neatly by hand (using a ruler and/or graph paper) or electronically (using a program like Excel or MATLAB). Less than 0.814 m 0.814 m to less than 0.876 m 0.876 m to less than 0.938 m 0.938 m to less than 0.999 m 0.999 m to less than 1.060 m 1.060 m to less than 1.122 m 1.122 m to less than 1.183 m At least 1.183 m (b) The average value of our data is .0999 meters. Determine the percentage of trials that lie within 0.072 meters of this value; that is, the percentage of trials whose distances are between 0.938 and 1.060 m. (c) Determine the percentage of trials whose distances are between 0.876 and 1.122 m. (d) Explain one way in which our program/experiment could be modified in order to get more trial distances closer to exactly 1.00 meters.
2 Solution: (a) (b) There were 86 values between 0.938 and 1.060 out of the 98 data values. 86/98*100%=87.8% (c) There were 93 values between 0.876 and 1.122 out of the 98 data values. 93/98*100%=94.9% (c) One method to improve our vehicle would be to use a control scheme to “force” the vehicle to drive straight, instead of preprogramming a specific motor power for each wheel. This would require reading the value of the rotation sensor for both driven wheels, and whenever one value is larger than the other, slowing the corresponding motor automatically. We’ll talk a bit about control systems in a later lecture.
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