Homework 4
UCR CS122B Embedded Systems Design, T. Givargis and F. Vahid, Winter 2001
Due 2/20/01


1. Experiment with the oven controller simulator at 
   http://newton.ex.ac.uk/teaching/CDHW/Feedback/  (see the Oven Simulator).
   (a) Create a P-only controller by setting the D and I values to 0. 
       Examine P values ranging from 1 to 100,000. 
       Describe the controller's behavior for different ranges of P.
       Provide a printout for the "best" P, including your definition of best. 
   (b) Create a PD controller, using P = 1000. 
       Describe the controller's behavior for different ranges of D. 
       Provide a printout for the "best" D, including your definition of best.
   (c) Create a PI controller, using P = 1000. 
       Describe the controller's behavior for different ranges of I.
       Provide a printout for the "best" I, including your definition of best.
   (d) Create a PID controller. Try to use the approach described in the 
       article handed out in class to obtain values for P, I and D.
       Did the approach in class work?  Can you improve those values?
       Provide a printout for the "best" PID controller you can obtain, and 
       compare with your earlier versions of P, PD, and PI controllers.
   (e) Run an ON/OFF controller simulation, and compare the results
       with the PID controller. Explain what an on/off controller is.
   (General suggestion: I suggest you click on the table-of-contents link
    of the URL and read the overview -- it's an excellent summary of
    control!)
       
2. Search the web for a similar site that allows PID control simulation.
   Try to find one that can be implemented locally (e.g., a Java applet
   with source code). Provide the URL, a printout of what it looks like,
   explain how you found the site, and compare it's capabilities with
   the above site.  Be sure to do this indepedently from other students!   

3. Using Excel, create a simulation of the cruise-control system from
   ESD Chapter 9, this time for a PI controller only. Show simulations (graphs
   data tables) for the following P and I values. Remember to include
   throttle saturation in your equations. You can ignore disturbance.
   (a) P=3.3, I=0  
   (b) P=4.0, I=0   (How do the results differ from part a? Explain!)
   (c) P=3.3, I=X   
   (d) P=3.3, I=Y   
   You choose X and Y to achieve a meaningful tradeoff -- explain that
   tradeoff.
   
4. (a) Discuss the concepts of reliability and safety, and how they are
       related.  
   (b) Define fault and failure.
   (c) Describe the two main approaches to achieving reliability.
   (d) Describe the key to fault tolerance, and define and contrast the 
       two main approaches to achieving fault tolerance.