PARTE I – FUNDAMENTOS PARA ANÁLISE DA DEMOCRACIA,
1. A DEMOCRACIA QUESTIONADA
1.2 Evolução histórica: avanços e retrocessos
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4.5.7 MOUNTAIN MAZE
The mountain maze was constructed from plywood, chicken wire, expandable foam, plaster cloth and Bondo. A rough sketch of the desired maze path was first constructed. Care was taken to insure the pass was wide enough to accommodate the robot. The maze platform was constructed from 3/8 inch plywood on 2 by 4 inch framing material. Maze walls were also constructed from the plywood and supported with steel L brackets.
With the basic structure complete, the maze walls were covered with chicken wire. The chicken wire was secured to the plywood with staples. The chicken wire was then covered with plaster cloth (Creative Mark Artist Products #15006). To provide additional stability, expandable foam was sprayed under the chicken wire (Guardian Energy Technologies, Inc. Foam It Green 12).
The mountain scene was then covered with a layer of Bondo for additional structural stability. Bondo is a two–part putty that hardens into a strong resin. Mountain pass construction steps are illustrated in4.14. The robot is shown in the maze in Figure4.15
4.5. MOUNTAIN MAZE NAVIGATING ROBOT 151
Figure 4.14: Mountain maze.
Figure 4.15: Robot in maze (photo courtesy of J. Barrett, Closer to the Sun International).
4.5.8 PROJECT EXTENSIONS
• Modify the turning commands such that the PWM duty cycle and the length of time the motors are on are sent in as variables to the function.
• Develop a function for reversing the robot.
• Equip the motor with another IR sensor that looks down toward the maze floor for “land mines.” A land mine consists of a paper strip placed in the maze floor that obstructs a portion of the maze. If a land mine is detected, the robot must deactivate the maze by moving slowly back and forth for three seconds and flashing a large LED.
• The current design is a two wheel, front wheel drive system. Modify the design for a two wheel, rear wheel drive system.
• The current design is a two wheel, front wheel drive system. Modify the design for a four wheel drive system.
4.6. SUMMARY 153
• Develop a four wheel drive system which includes a tilt sensor. The robot should increase motor RPM (duty cycle) for positive inclines and reduce motor RPM (duty cycle) for negatives inclines.
• Equip the robot with an analog inertial measurement unit (IMU) to measure vehicle tilt. Use the information provided by the IMU to optimize robot speed going up and down steep grades.
4.6 SUMMARY
In this chapter, we discussed the design process, related tools, and applied the process to a real world design. As previously mentioned, this design example will be periodically revisited throughout the text. It is essential to follow a systematic, disciplined approach to embedded systems design to successfully develop a prototype that meets established requirements.
4.7 REFERENCES
• Anderson, M. “Help Wanted: Embedded Engineers Why the United States is losing its edge in embedded systems.” IEEE–USA Today’s Engineer, Feb 2008.
• Barrett, Steven and Daniel Pack. Embedded Systems Design and Applications with the 68HC12 and HCS12. Upper Saddle River, NJ: Pearson Prentice Hall, 2005. Print.
• Seaperch,www.seaperch.com
• Barrett, Steven and Daniel Pack. Processors Fundamentals for Engineers and Scientists. Morgan and Claypool Publishers, 2006.www.morganclaypool.com
• Barrett, Steven and Daniel Pack. Atmel AVR Processor Primer Programming and Interfacing.
Morgan and Claypool Publishers, 2008.www.morganclaypool.com
• Fowler, M. with K. Scott. UML Distilled A Brief Guide to the Standard Object Modeling Language.
2nd edition. Boston, MA:Addison–Wesley, 2000.
• Dale, N. and S.C. Lilly. Pascal Plus Data Structures. 4th edition. Englewood Cliffs, NJ: Jones and Bartlett, 1995.
4.8 CHAPTER EXERCISES
1. What is an embedded system?
2. What aspects must be considered in the design of an embedded system?
3. What is the purpose of the structure chart, UML activity diagram, and circuit diagram?
4. Why is a system design only as good as the test plan that supports it?
5. During the testing process, when an error is found and corrected, what should now be accom-plished?
6. Discuss the top–down design, bottom–up implementation concept.
7. Describe the value of accurate documentation.
8. What is required to fully document an embedded systems design?
9. For the Blinky 602 robot, modify the PWM turning commands such that the PWM duty cycle and the length of time the motors are on are sent in as variables to the function.
10. For the Blinky 602 robot, equip the motor with another IR sensor that looks down for “land mines.” A land mine consists of a paper strip placed in the maze floor that obstructs a portion of the maze. If a land mine is detected, the robot must deactivate it by rotating about its center axis three times and flashing a large LED while rotating.
11. For the Blinky 602 robot, develop a function for reversing the robot.
12. Provide a powered dive and surface thruster for the SeaPerch ROV. To provide for a powered dive and surface capability, the ROV must be equipped with a vertical thruster equipped with an H–bridge to allow for motor forward and reversal. This modification is given as an assignment at the end of the chapter.
13. Provide a left and right thruster reverse for the SeaPerch ROV. Currently the left and right thrusters may only be powered in one direction. To provide additional maneuverability, the left and right thrusters could be equipped with an H–bridge to allow bi–directional motor control. This modification is given as an assignment at the end of the chapter.
14. Provide proportional speed control with bi–directional motor control for the SeaPerch ROV.
Both of these advanced features may be provided by driving the H–bridge circuit with PWM signals. This modification is given as an assignment at the end of the chapter.
15. For the 4WD robot, modify the PWM turning commands such that the PWM duty cycle and the length of time the motors are on are sent in as variables to the function.
16. For the 4WD robot, equip the motor with another IR sensor that looks down for “land mines.”
A land mine consists of a paper strip placed in the maze floor that obstructs a portion of the maze. If a land mine is detected, the robot must deactivate it by rotating about its center axis three times and flashing a large LED while rotating.
17. For the 4WD robot, develop a function for reversing the robot.
18. For the 4WD robot, the current design is a two wheel, front wheel drive system. Modify the design for a two wheel, rear wheel drive system.
4.8. CHAPTER EXERCISES 155 19. For the 4WD robot, the current design is a two wheel, front wheel drive system. Modify the
design for a four wheel drive system.
20. For the 4WD robot, develop a four wheel drive system which includes a tilt sensor. The robot should increase motor RPM (duty cycle) for positive inclines and reduce motor RPM (duty cycle) for negatives inclines.
21. Equip the robot with an inertial measurement unit (IMU) to measure vehicle tilt. Use the information provided by the IMU to optimize robot speed going up and down steep grades.
22. Develop an embedded system controlled dirigible/blimp (www.microflight.com,www.
rctoys.com).
23. Develop a trip odometer for your bicycle (Hint: use a Hall Effect sensor to detect tire rotation).
24. Develop a timing system for a four lane Pinewood Derby track.
25. Develop a playing board and control system for your favorite game (Yahtzee, Connect Four, Battleship, etc.).
26. You have a very enthusiastic dog that loves to chase balls. Develop a system to launch balls for the dog.
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