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