ECE 496- Project: Gyrobot Group C- “The Swingers” April 23, 2001

TOC Intro Background (rules) Design strategy Physical system- link, flywheel, shaft Electrical system- BB, encoders, amp Software –Swing-up –Balance Results Cost Suggestions

Introduction ECE 496 is a course required for all Electrical Engineers that is intended to highlight the transition from academic analysis to industrial goal-oriented engineering practice. This course unites electrical engineering students with different

Introduction cont’d areas of interest to work together “thinking outside of the box” on a project in a design competition. For Spring 2001, our project was the Gyroscopic Pendulum, which is an under actuated pendulum or the Gyrobot.

Background Rules 1.A schematic drawing which details the Gyrobot specifications is given in a PDF file found on the ECE 496 Web Page. 2. The Gyrobot must behave as an inverted pendulum as determined by the course instructor.

Background Rules cont’d 3.The specifications for the size of the Gyrobot is given in a PDF file found on the ECE 496 Web Page. 4.Check with the course instructors to see if any of your innovative concepts are acceptable as solutions to this problem.

Background Rules cont’d 5. Only sensors may be connected to the Gyrobot bars. That is, no motors can be used to move the bottom Gyrobot link. 6. Once your Gyrobot is in the "starting position", it can receive no outside assistance.

Background Rules cont’d 7. No magnets can be used for levitation. The team can not use a purchased motor control system. 9. The team can use a motor that already has a sensor mounted to it.

Background Rules cont’d 10.Only one actuator or motor can be used in the project. 11. The faculty makes all rules and determines whether a rule is satisfied or violated. If any rule is unclear, check with instructor.

Hardware Design Strategy Low Friction – used ball bearings Low Force on Link – used longer shaft CHEAP!!! Otherwise, built to specifications given

Support Mount was supported on 2x4 Use skateboard ball bearings to support shaft Use conduit brackets to hold bearings in place.

Wheel and Link Acquired aluminum and steel from Matthews Welding Acquired bronze from Morrow Enterprises, Inc. Josh Whitmire and Jeff Parker of Morrow Enterprises, Inc. donated time to complete machine work

Motor and Encoder Tried Mabuchi RS-540SH (remote controlled car motor) Ordered Pittman with Encoder

Electrical System Encoders –Output a signal showing the number of counts –Software converts to position and velocity Link position- theta1 –US Digital –8000 counts per revolution Motor shaft position- theta2 –Pre-mounted on Pittman motor –2000 counts per revolution

Electrical System Breakout Board –Servo-to-Go –Connects encoders to computer –Connects to linear amplifier –Max output: 8V Linear Amp –Reads voltage from breakout board –Powers motor –Max output: 22.4V

Software: Swing-up Sinusoidal Swing-up –Torque constant increased to -3 kick harder Rapid response Decreasing performance of motor –Due to temperature –Seen in max theta2 velocity –Corrected in external off-switch

Swing-up Schematic

Software: Swing-up Off-switch Set from 65 o (max performance) to 50 o (min performance) from vertical Relay point –Switch from swing-up to balancing –Set at 8 o from vertical

System Schematic A/D Converter

Software (balance) Originally used: Feedback Linearization Finally used: modified PD balancing [Fig 1. Schematic of balancing] negative K- theta2dot Integration [bonus day pic?]

Results Time was in 2.8 seconds Measured time was in 3.4 seconds Velocity of flywheel would decrease as temperature increased Could only repeat if motor was cool Could repeat if slower time was used

Cost PartCost FlywheelDonated Motor (with S&H) $ Link Donated US Digital Encoder $50.00 Shaft and ball bearings Found Dinner for donations $15.00 Misc. Hardware $17.84 Total $ WinningPriceless

Suggestions Wrong –Obtain equipment early –Use fan Right –Heavy flywheel –Low friction ball-ball bearings –Thin shaft –Good voltage monitoring