Download - Group D ECE 496: Gyrobot Project Ray Price Matt Vaughn Cyrus Griffin David Epting John Abbott
Group D
ECE 496: Gyrobot Project
Ray PriceMatt VaughnCyrus GriffinDavid EptingJohn Abbott
IntroductionThe Gyrobot is an underactuated pendulum, consisting of a single link with a flywheel driven by a dc motor mounted at the free end.
TopicsGroup Structure / ScheduleProject SpecificationsMechanical Design Fabrication Status Problems
Software Design Status Problems
WebpageFuture Plans
Group D Structure
Ray Price – Group Leader
Matt Vaughn – Software Design
Cyrus Griffin – Software Design
John Abbott – Mechanical Design
David Epting – Mechanical Design
Group D StructureGant Chart
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.
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
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
MechanicalThe 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.
MechanicalPosition 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
MechanicalThe 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
MechanicalBase 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
MechanicalBearings 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
Software
Collocated Swing Up
Non-Collocated Swing Up
• Sinusoidal Swing Up
Software
Swing Up ControlStatus 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
Software
Switch from Swing up to balanceDesign 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.
Software
Balance Control - The Model
Balance ControlImportant Variables:Arm position (theta 1)Arm velocity (theta dot)Flywheel velocity (theta2dot)
Balance Control
Arm PositionMust 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).
Balance Control
Arm VelocityFirst 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.
Balance Control
Flywheel VelocityGoal 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).
Encoder Processing
Getting Velocity from PositionObvious 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.
Webpage
Future Plans
Replace Motor
Ensure action of Windows/Simulink environment
Finish balancing routine
Finish swing up / switching routine