Critical Design Review

1. Critical Design Review 12/7/04 Team Uno Bunker Curnes Shawn Houlahan Stephanie Rohrs Steve Schwall Chuck Smith

2. Objective Design and build an intelligent device that provides continuous shade for a defined volume.

3. Key Requirements • Must shade a 2’ x 3.5’ x 5’ rectangular prism1 that is 1.5’ above the ground while the sun is above 30° from the horizon • 50lbs max weight2 • Function in winds up to 25mph3 • Must provide 12hrs of shade 1 National Center for Health Statistics 2 National Institute for occupational safety and health 3 Australian Government Bureau of Meteorology

4. Key Requirements • Material selected for fabrication must be water, rust, and corrosion resistant • Must have a manual turn on/off option • Maximum repositioning time must be under a minute • Noise volume of the device must be under 60 decibels4 • All electronics and power sources must be enclosed in waterproof casings 4 League for hard of hearing

5. Result – The SmartShade • Two degrees of motion • Tilt joint and rotational joint • Triangulated sensor array • Mechanically functional prototype • Functional control logic • Attempts to orients umbrella towards sun • Motor control issues

6. Tilt Joint Requirements • Required Motor Torque • T=(F*dm/2)((1+pi*f*dm)/(pi*dm – f*l)) • F = force transmitted to screw by four-bar linkage • Torque on Pin • F = (Cd) *(.5p*V^2*A) • Cd = 1.2

7. Tilt Joint Design • The motor drives the • threaded rod. • The threaded rod causes the collar and connecting rod to rise or lower depending on the motor direction. • As the connecting rod moves it causes the triangle and upper pole to tilt.

8. Tilt Joint Demo

9. Tilt Joint Demo

10. Tilt Joint Demo

11. Tilt Joint Demo

12. Power Screw • Held in position by two Delrin disks • Load supported by two thrust bearings • Connected to motor shaft by coupling • Length of threaded region on threaded rod equal to amount of thread needed for stroke

13. Rotation Joint Requirements • Torque on Pole • F = (Cd) *(.5p*V^2*A) • Cd = .6 • Required Motor Torque • Maximum torque requirement when umbrella tilted 60°

14. Rotational Joint Design • Chain Driven • 3.89:1 Mechanical Advantage • Pole Supported by 3 Delrin Bearings

15. Rotational Joint Demo

16. Motor Selection and Power • For rotational motion, a speed of 1/3 rpm and a torque rating of 16 ft lb was needed • Purchased motor: • 4 rpm • 4.16 ft lb torque • For the tilting motion, a speed of 84 rpm and a torque rating of 1.3 ft lb was desired • Purchased motor: • 47 rpm • 2.33 ft lb torque • Since both motors were 24 V DC, two 12 V DC batteries were used in series

17. Control Logic - Overview • In order to shade our specified area continuously, the umbrella must always be oriented towards the brightest light source. • To accomplish this, three sensors are placed in a triangular pattern around the canopy. • When all three sensors are equal, the umbrella is pointed towards the sun.

18. Sensors • Three photo-diode sensors are used in an isosceles triangle pattern • Output .6 V in direct sunlight • As light goes down, output varies linearly to zero • Op-Amps and resistors provide a gain of 9 to microcontroller

19. Control Logic Light Sensors Microcontroller Motors Input Output Changes in motor positions change input from light sensors • Microcontroller receives input from light sensors one and two and moves the rotational motor until the two sensors are equal. • Once sensors are equal, the microcontroller receives input from sensor three and moves tilt motor until all three sensors equal. • When all sensors are equal, system sleeps for 15 minutes. 3 1 2

20. Enhancing Control Logic • For the sensor and op-amp assembly, a resolution of +/- 1% is possible. The difference of 1% in output voltages is .04 V. • If overshoot occurs, the program can be designed to automatically account for this and reverse direction until the sensors are within their specified range. • Once the sensors return a value less than 3V (dusk), the system repositions itself to vertical.

21. Capabilities • Prototype • Tilts 60 degrees from vertical • Rotates 360 degrees • Moves from initial position to desired position in 90 seconds or less • Easy to open and close • Final Product • Can reposition itself to continuously shade a defined volume • Motor control • Control logic • Conserves power by sleeping when dark • Able to function for 30 days before batteries must be recharged

22. Features • Simple user interface • Does not interfere with sitting users • Low maintenance • Portable • Rechargeable batteries • Can be disassembled for storage • Safe adjusting speed

23. Budget Total Budget Allowance: $500 Total Amount Spent: $499

24. Future Design Considerations • Integration motor into pole • Weatherproof casings • Wind vents in umbrella • Operating Noise

25. Future Design Considerations • Aesthetics • Tilt joint • Base • Materials • Safety issues • Exposed wires • Pinch points • Additional Features • Radio, beverage cooler, cup holders, built-in chairs

26. Questions?