Group D

1. Group D Ray Price Matt Vaughn Cyrus Griffin David Epting John Abbott ECE 496: Gyrobot Project

2. Introduction • The Gyrobot is an underactuated pendulum, consisting of a single link with a flywheel driven by a dc motor mounted at the free end.

3. Topics • Group Structure / Schedule • Project Specifications • Mechanical • Design • Fabrication • Status • Problems • Software • Design • Status • Problems • Webpage • Future Plans

4. Group D Structure Ray Price – Group Leader Matt Vaughn – Software Design Cyrus Griffin – Software Design John Abbott – Mechanical Design David Epting – Mechanical Design

5. Group D Structure Gant Chart

6. Project Specifications • The Gyrobot had to fit the following criteria: • Must comply to the mechanical specification of thesis by Adrian Jenkyn Lee out of the University of Illinois at Urbana-Champaign. • Must utilize motor/flywheel inertia to invert pendulum and then balance. • Utilizes Simulink RTW controller.

7. Mechanical • The Gyrobot shaft: • Design • Dimensions: 18” • Material: Aluminum • Mounting: threaded shaft utilizing 3/8” nuts and a lock washer • Fabrication • Milliken • Status • The arm is in place with motor attached • Problems • None

8. Mechanical • The Gyrobot arm: • Design • Shape: Dumbbell shape • Dimensions: • 17 ½’’ long • ¼’’ thick • ½’’ wide along shaft • ¾’’ radius at circular ends and center • Material: Aluminum • Mounting: held onto threaded shaft with 2 3/8” nuts and a lock washer • Fabrication • Milliken • Status • The arm is in place with motor attached • Problems • None

9. Mechanical • The flywheel • Design • Dimensions • 3 ½’’ total radius • 2 ½’’ radius to lip • ½’’ thick at lip • ¼’’ thick inside lip • Material: Brass • Mounting: Pressed onto motor • Fabrication • Milliken • Status • The flywheel is currently attached to the motor • Problems • A bit of wobble, but hopefully not detrimental.

10. Mechanical • Position Encoder: • Product: • Arm position/speed Encoder: US Digital E3 • Stats: 1024 CPR • Mounted utilizing USD mounting plate and metal bracket. • Current Status • The Encoder is attached to the Gyrobot shaft and operational • Problems • Encoder was a tight fit onto shaft

11. Mechanical • The Motor: • Pittman 9237S011 • No Load Speed: 5,331 rpm • Continuous Torque: 11.5 oz-in • Peak Torque: 77 oz-in • Weight: 19 oz • Motor is mounted to base by 4 6-32 screws • Encoder: • 3 Channels with 500 CPR • Problems • Arrival Time • Bad Encoder • Current Status • New Motor should be here Thursday

12. Mechanical • Base • Large piece of channel iron • Used because of weight and cost • Unistrut is utilized to secure bearings and position encoder base • Position encoder is attached to a piece of 1/32” sheet steel bent at a 90 degree angle with slot cut in middle for shaft connection • Position encoder base is attached to a perpendicular piece of unistrut mounted with 4-40 screws which is mig welded to the base. • Fabrication was done by Milliken • Problems • Did not sit stable on the table • Current Status • Base was attached to the table using 2 C clamps and rubber matting was placed underneath to help stabilize • Gyrobot base is stable and robust

13. Mechanical • Bearings • ½” Pillow block bearings manufactured by NKB • Brass sleeves were used to reduce the size down to the 3/8” shaft size • Bearings are mounted to base via a perpendicular piece of unistrut which is mig welded to the base • Bearings were pressed onto unistrut • Problems • Brass sleeves were difficult to install • Bearings were tight after sleeves were installed • Current Status • Bearings were reeled and aligned which created a good fit • Arm swings freely with little resistance

14. Software • Collocated Swing Up • Non-Collocated Swing Up • Sinusoidal Swing Up

15. Software • Swing Up Control • Status • Decided to go with the Sinusoidal Swing Up • Smoother • Faster due to the harmonics • Less bouncing in controls compared to other two. • Problems • Deciding to use radians or degrees for the angle

17. Software • Switch from Swing up to balance • Design • Position • Speed factor • Problems • Determining the negative and positive angle and how the computer will be able to distinguish quickly. • Determining where the cut off angle is going to be for swing-up and balancing.

19. Software • Balance Control - The Model

20. Balance Control • Important Variables: • Arm position (theta 1) • Arm velocity (theta dot) • Flywheel velocity (theta2dot)

21. Balance Control • Arm Position • Must add enough energy to move mass of assembly to the highest position. • Fighting gravity • Gain based on center of gravity and mass of the mobile assembly (motor, flywheel, arm, shaft). • Considering trying using cosine function to expand functional range (making it a non-linearized system).

22. Balance Control • Arm Velocity • First goal is to have the arm slow as it approaches vertical. • Second goal is to have arm fight acceleration if it falls away from vertical. • Gain based on rotational inertia of the whole mobile system.

23. Balance Control • Flywheel Velocity • Goal is to stop the flywheel when the arm is balancing. • Gain made to be small, in effect creating an underdamped system, so slowing the flywheel doesn’t seriously affect the balance. • Gain is negative to bring the speed of the flywheel to zero (instead of slowly ramping up).

24. Encoder Processing • Getting Velocity from Position • Obvious way is by taking derivative of position, but there are limitations in simulink. • So, better solution, and solution used in the thesis, was to estimate the derivative through a frequency-domain formula. • This yields far more smooth, continuous results than the built-in derivative functional block.

25. Webpage

26. Future Plans • Replace Motor • Ensure action of Windows/Simulink environment • Finish balancing routine • Finish swing up / switching routine