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-switchSet from 65o (max performance)

to 50o (min performance) from

vertical

•Relay point

–Switch from swing-up to balancing

–Set at 8o 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

CostPart Cost Flywheel Donated Motor (with S&H) $139.10 Link Donated US Digital Encoder $50.00 Shaft and ball bearings Found Dinner for donations $15.00 Misc. Hardware $17.84 Total $221.94 Winning Priceless

Suggestions

• Wrong– Obtain equipment early– Use fan

• Right– Heavy flywheel– Low friction ball-ball bearings– Thin shaft– Good voltage monitoring