1. ECE 100: Intro to Engineering Design, Presentation No. 11 Daniel E. Rivera Department of Chemical and Materials Engineering Arizona State University ECE 100: Introduction to Engineering Design Understanding Engineering Control Strategies

2. ECE 100: Intro to Engineering Design, Presentation No. 11 Motivating Philosophy “…it is a redeeming feature of life that we are able to use many things without understanding every detail of them.” L. Ljung, 1987

3. ECE 100: Intro to Engineering Design, Presentation No. 11 Control Engineering You have been applying engineering control principles throughout your life, even if you have not been fully aware of it. Control engineering is a broadly-applicable field that spans all areas of engineering: –Chemical –Electrical –Mechanical and Aerospace –Civil / Construction –Industrial –Biomedical –Computer Science and Engineering

4. ECE 100: Intro to Engineering Design, Presentation No. 11 Control Engineering (Cont.) Considers how to manipulate system variables in order to transform dynamic behavior to desirable from undesirable Open-loop: refers to system behavior without a control policy Closed-loop: refers to system behavior once a controller/decision policy is implemented.

5. ECE 100: Intro to Engineering Design, Presentation No. 11 Control Engineering (Cont.) Many examples of control applications in society: –Cruise control and climate control in automobiles –The “sensor reheat” feature in your microwave oven –Home heating and cooling –The insulin pump for Type-I diabetics –“Fly-by-wire” systems for high-performance jet aircraft –Many, many, more… The development of improved sensors and actuators, coupled with increasing embedded computing capabilities, will continue to facilitate the application of control engineering in many diverse application settings.

6. ECE 100: Intro to Engineering Design, Presentation No. 11 An Industrial Control Problem QuickTime™ and a BMP decompressor are needed to see this picture. Objective: Use fuel gas flow to keep outlet temperature under control, in spite of occasional yet significant changes in the feed flowrate.

7. ECE 100: Intro to Engineering Design, Presentation No. 11 The “Shower” Control Problem The presence of delay or “transportation lag” makes this a difficult control problem

8. ECE 100: Intro to Engineering Design, Presentation No. 11 Definitions Controlled Variable (y): system variable that we wish to keep at a reference value or setpoint (r). Control Error (e=r-y): the difference between the controlled variable and the setpoint; we wish to take this to zero. Manipulated Variable (u): system variable whose adjustment influences the response of the controlled variable; its value is determined by the controller/decision policy. Disturbance Variable (d): system variable that influences the controlled variable response, but cannot be manipulated by the controller; disturbance changes occur external to the system (hence sometimes referred to as exogeneous variables)

9. ECE 100: Intro to Engineering Design, Presentation No. 11 The “Shower” Control Problem Think about what may constitute controlled, manipulated and disturbance variables in this system Controlled: Temperature, Total Water Flow Manipulated: Hot and Cold Water Handle Positions Disturbances: Inlet Water Flows, Temperatures

10. ECE 100: Intro to Engineering Design, Presentation No. 11 Feedback and Feedforward Control Strategies In feedback control strategies, a controlled variable (y) is examined and compared to a reference value or setpoint (r). The controller issues actions (decisions on the values of a manipulated variable (u)) on the basis of the discrepancy between y and r. In feedforward control, changes in a disturbance variable (d) are monitored and the manipulated variable (u) is chosen to counteract anticipated changes in y as a result of d.

11. ECE 100: Intro to Engineering Design, Presentation No. 11 Closed-Loop Feedback Control “Block Diagram” C = Controller P = Process “Transfer Function” Pd = Disturbance “Transfer Function” Controlled: Measured Temperature, Total Water Flow Manipulated: Hot and Cold Water Handle Positions Disturbances: Inlet Water Flows, Temperatures Reference: Desired Temperature, Total Water Flow

12. ECE 100: Intro to Engineering Design, Presentation No. 11 Shell Westhollow Research Center’s Pumper (a.k.a. Fire Truck)

13. ECE 100: Intro to Engineering Design, Presentation No. 11 The Front Line Crew

14. ECE 100: Intro to Engineering Design, Presentation No. 11 “Catching The Plug”

15. ECE 100: Intro to Engineering Design, Presentation No. 11 For Discussion As a team, review the problem description presented by Dr. Rivera and determine the following: –What are the controlled, manipulated, and disturbance variables in the problem? –What control strategy is best suited to this problem (feedback or feedforward)?

16. ECE 100: Intro to Engineering Design, Presentation No. 11 Supply Chain “Level” Control Problem LT ORDER DECISIONS Demand Meet demand (with forecast possibly given  f days beforehand) for a node with  day production (or order fulfillment) time and  d delivery time. Do so with the lowest possible cost. CTL

17. ECE 100: Intro to Engineering Design, Presentation No. 11 Inventory Management Problem Controlled Variable: Candidates include –On-Hand Inventory –Net Stock –Inventory Position –Costs Manipulated Variable: Orders Disturbance Variable: Demand

18. ECE 100: Intro to Engineering Design, Presentation No. 11 Feedback-Only Control Problem LT CTL Demand In the feedback-only control problem, ordering decisions are calculated based only on perceived changes to “level” (e.g., inventory position or equivalent variable).

19. ECE 100: Intro to Engineering Design, Presentation No. 11 Closed-Loop Feedback Control “Block Diagram” C = Feedback Controller P = Process “Transfer Function” Pd = Disturbance “Transfer Function” (Demand) (Measured Net Stock Or Inventory Position) (Desired Net Stock Or Inventory Position) (Orders)

20. ECE 100: Intro to Engineering Design, Presentation No. 11 Combined Feedback/Feedforward Control LT CTL Demand Meet demand (with forecast given  f days beforehand) for a node with  day production (or order fulfillment) time and  d delivery time. Demand Forecast (known  f days beforehand)  order fulfillment time)  d delivery time)

21. ECE 100: Intro to Engineering Design, Presentation No. 11 Combined Feedback/Feedforward Block Diagram (Orders) (Desired Net Stock Or Inventory Position) (Measured Net Stock Or Inventory Position) (Forecasted Demand) (Unforecasted Demand)

22. ECE 100: Intro to Engineering Design, Presentation No. 11 In-Class Read and discuss with your team the “Retailer Inventory Dynamics Simulation” handout. Break up into sub-teams and work with a partner to attempt Scenarios 1 – 4. Keep track of the results of your runs and record your observations, as described in the handout. If you have time (or if you do not find Scenarios 1 – 4 challenging enough) give Scenarios 5 – 8 a try. Stay until we have completed an in-class discussion of the results of the exercise (and be willing to perform the “challenge” in front of the rest of the class). Responses to the questions posed in the exercise will be part of Modeling Assignment 3 and Project 1.

23. ECE 100: Intro to Engineering Design, Presentation No. 11 Modeling Assignment No. 3 Add an engineering-based Proportional-Integral- Derivative (PID) decision policy to your previousl Excel-based simulation that compares the four EOQ strategies. Use your simulation to determine which choice of controlled variable (net stock or inventory position) is “best” suited for this application. Evaluate each policy for a 60-day time period. More details will be provided on Tuesday.

24. ECE 100: Intro to Engineering Design, Presentation No. 11 Coming Up Tuesday, March 4: Modeling Assignment No. 2 is due; we will begin working on Modeling Assignment No. 3. Thursday, March 6: Continued work on Modeling Assignment No. 3. Class may meet again in ECG 224 – this will be confirmed via email.