CSSE 120 -- Intro. to Software Development

Homework 5

Complete the assigned reading for the next session, Zelle sections 5.1- 5.7, 5.9 (skim 5.8 as reference).
(26 pts) Complete the Angel quiz over this reading. You'll find this on the course Angel page, under Lessons → Homework → Homework 5 → Graphics and Objects
(30 pts) File output and string formatting: Storing information in files is a very important exercise for engineers running experiments that generate a large quantity of useful data. The stored data can later be analyzed, categorized, and manipulated to allow engineers to draw useful conclusions.

Often, the generated data is formatted so that another program can automate the process of analyzing, categorizing, and manipulating the data. In this problem you are to write a program, funcDump.py, that implements the following design:
- Prompt the user for a file name
- Open a file with the given name
- Write 720 lines to the file. Each line should have the data:
  n 200 + 200cos(nπ/180)
  
  where n ranges from 0 to 719. Make sure the file is neatly formatted so numbers and decimal points line up. Below is a sample of the expected output. Your program's output should match this format exactly.
```
 98   172.165
 99   168.713
100   165.270
101   161.838
102   158.418
103   155.010
104   151.616
105   148.236
106   144.873
107   141.526
108   138.197
109   134.886
110   131.596
111   128.326
112   125.079
113   121.854
114   118.653
115   115.476
116   112.326
117   109.202
118   106.106
119   103.038
120   100.000
121    96.992
122    94.016
```
- Close the file
Submit your Python source file and the generated output to the funcDump Drop Box in the Homework 5 folder on ANGEL.
If you didn't do this for bonus points last session, you need to do it now (for no bonus)... In the next session, we will begin using a new development environment called PyDev that runs inside Eclipse. Freshman laptops have some of these steps done, as noted below:
1. Install Eclipse by following these instructions. (Upperclassmen need to update to Eclipse 3.4; freshmen can skip this.)
2. Install and configure PyDev for Eclipse by following these instructions. (Upperclassmen need to do all of this; freshmen can skip the beginning and start at step 3 of Install the PyDev plug-in for Eclipse.)
3. Install and configure Subclipse for Eclipse by following these instructions. (Everyone needs to do this.)
4. You must show us in class next session (if you haven't already):
  1. Launch Eclipse and show us your Hello World Python program running.
  2. In Eclipse, show us your modified "spam.py" file that you checked out using Subclipse. If you didn't get this working, instead choose Window > Open Perspective > Other..., and show us that "SVN Repository Exploring" appears in the list.
(20 pts) RobotPathViaPoints. (Due Session7) You will write a module, via.py, that will drive the robot through an environment using moves to via points stored in a file. The program will:
1. Prompt the user for the port to which they are connected.
2. Prompt the user for the file name and open the file with that name.
3. Read each line of the file. Each line will contain 4 values (turnAngleInDeg, turnVelocity, fwdDistanceInCm, fwdVelocity)
4. For each line, turn the robot based upon the turn angle and speed, then drive the robot forward based upon the forward distance and velocity. For example (this is box.txt):
Hints:
1. You will likely use the go(), sleep(), and stop() functions to move the robot, as you did last time. This is easiest, since it sends a command, waits the right amount of time (which you'll have to calculate), then sends the next command, etc.
2. Don't forget to close both the file and the connection to the robot (using robot.shutdown()) at the end of your code!
3. Another option to sleeping, that some may wish to try, is to use feedback from the encoders to drive a certain distance. (An encoder is a mechanical device attached the robot's wheels to measure how far it has traveled). In this paradigm, your program sends all the commands at once, and the robot does them in the order it receives them. The advantage is that you don't need to calculate how long to sleep, the waitAngle() and waitDistance() methods do that for you. Caution: once you send the robot the shutdown() command, it will stop immediately; the workaround is to insert a long sleep before the shutdown command. See the pycreate documentation for details.
4. What you notice is that the more the robot moves the less accurate it will become in moving the prescribed distance or returning to the same point. This robot drifting is called odometry error. Odometery error means that the longer the robot travels, the sensor used to calculate the distance traveled (the encoder) begins to accumulate error. This error is based upon wheel slippage, friction, uneven surfaces, wobbling wheels or sensor inaccuracy. In other words, the robot may “think” it is at a different place in the world than it actually is. This is a common problem in robotics research and it is necessary to add hardware or write control algorithms to combat this. For your homework, it is important to recognize the problem but you will not modify your program to compensate for it.
Test your program using simple.txt, negatives.txt, smallBox.txt, box.txt, and asterisk.txt (right-click on the link and choose "save link as..." to download the whole files). Note, you must place these files in the same folder as via.py in order to read them. Submit your Python source file only (not the test files) to the ViaPoint Drop Box in ANGEL.
Challenge Problem: This problem is not required, but is an interesting extension that you might like to try.
1. Create a version of funcDump.pyabove that prompts the user to enter the function for column 2 instead of hard-coding the function.
Web links, bacon, eggs, and spam: One of today's in-class examples was a reference to the Penguin sketch. We hope you enjoy this four minute cultural experience!