Turn Table


                    



The AutoCAD reference files for optimization are located at the bottom of the page.  Motor Arms should be cut from 1/8'' thick acrylic.  Drive Wheels should be cut from 1/4'' thick acrylic, and press fit to your motor.  Should you decide to change the drive wheel, see the TA's about taking the drive wheel off the motor.

Objective

Operate the turntable in the fastest times for the following:
  • Open-loop test for 270°. Starting from rest rotate the turntable as fast as possible to 270°.
  • Closed-loop test for 180°. Starting from rest rotate the turntable 180° and come to a stop with an accuracy of ± 2°.
  • The turntable must demonstrate the ability to reach the final target position from an arbitrary starting position from 90° to 270° as chosen by a TA.

What is Not Allowed

  • Removing material from the rotating turntable component. It is ok to make small modifications, as long as less than 10% of the turntable mass is removed.
  • Modifying the motor or using a power supply other than what is provided.

What is Allowed

  • Modifying or adding acrylic components such as a drive wheel on the motor.
  • Using Delrin and rubber tape (6 inch strips are available from TAs).
  • Modifying or recutting the motor mounts. Ask TAs for acrylic if necessary.
  • Adding rubber bands or use of lubricants. Students can provide their own to augment those provided in the Design Studio.

Deliverables in Lab (demo to TA on day of lab)

  • Week 1. 
    • During section: Electronics workshop.
    • Lab assignment due by beginning of section week 2. Complete packet, install Arduino software, and fabricate turntable before week 2 lab.
      • Check that turntable is operational by connecting motor to power supply in lab.
      • Solder 3 wires to your pot, so you can hook it up in section.
  • Week 2. 
  • Week 3. First Optimization of Turntable including:
    • Use open-loop control at maximum voltage  (i.e. turn on the motor at full speed at record pot position and time). Turn in plot of turntable position (in degrees) vs time (in seconds).  Indicate at what time the turntable reaches 270°.
  • Week 4. Final Optimization of Turntable. Optimized closed-loop turntable performance including:
    • Demonstrate the best open-loop and closed-loop performance. TAs will inspect code for proper output of setting  time. This time will be the final turntable performance used for grading the hardware performance.
    • Closed-loop demo to 180° and arbitrary position.


Timing Criterion

For all teams to have consistent methods for measuring completion times, each team should:
  • Store the overall start time at the beginning of your loop and at the end of the completion of the rotation. Use the "millis" command.
    • unsigned int StartTime, ElapsedTime;
    • StartTime = millis();
    • (do your loop here and test for reaching endpoint)
    • ElapsedTime = millis() - StartTime;  //Print this out
  • The position error must be within ± 5 counts for the loop to end, and the turntable must visually be stopped and at the 180° position.
  • Show your code to the TA after the demo.

Optimization Log

Throughout the turntable project each pair should keep a log of the turntable performance. Download the templates below and record every-time you change your design:
  • Date results
  • Description of configuration and changes made from prior tests
  • Time to reach open loop and closed loop positions in degrees
  • Comments
This log will be used in your final report to justify the design decisions made throughout the project.

Areas of Optimization

This is an optimization assignment, with areas of optimization including:
  • Friction reduction
  • Gear Ratio based on drive wheel selection added to motor shaft. See Example of Optimization of Machine Dynamics.
  • Friction drive optimization
  • Control optimization (gain selection and other methods)
  • Other?


Turn Table Grade


50% of the Turntable grade will be based on turntable performance, and 50% based upon a report.
  • Open-loop test  75% of performance grade
  • Closed-loop test  25% of performance grade

Turn Table Report Components

  • The main portion of the report should be ten (10) pages or less in length, neatly organized, typed, and formatted.
  • Additional graphs can be placed in an appendix. The optimization log should also be in the appendix.
  • Grading of the reports will emphasize clarity, correct analysis, and interpretation of results.
  • One report is required for each two-person turntable team.

Cover sheet: (not counted in page total) should clearly show author names.

Summary of Optimization Effort (20 pts): Summarize final performance and then give a 3-5 sentence description of the optimization effort and impact in the following areas. Reference the optimization log where appropriate.
  • Friction Reduction
  • Gear ratio
  • Friction Drive Improvements
  • PID gain selection
  • Other
Theoretical Model (30 pts): Create a theoretical model of the open-loop performance of the turntable. Include:
  • Assumptions
  • Dynamic Equations used (HW solutions can be used).
  • Include documented computer code in the appendix.
  • Parameter estimations of the following variables. For each variable show how the values were calculated AND how the values were verified. For each parameter value, provide a +/- amount that you believe your estimate is within and explain. The parameters are:
  • System Inertias
  • Motor Torque used in open-loop test
  • System friction
Comparison of Theory to Experimental Results (20 pts):

  • A single plot showing the theoretical and experimental curves of position verses time for an open loop test. Use units of degrees vs. milliseconds.
  • A single plot showing the theoretical and experimental curves of velocity verses time for an open loop test. Show both filtered and unfiltered experimental velocities. Use units of degrees/second vs. milliseconds.
  • Discuss the difference between the experiment and theory.

Detail Discussion of Specific Optimization Efforts (30 pts)

Choose two areas of optimization and discuss them in more depth. Discussion can include Free Body Diagrams, block diagrams, closed-loop simulations, choosing PID gains, or an expansion of any of the topics covered in section 1. Grading will be based on proper understanding of experimental data and insightful use of theory for optimization.




Student Turntable Times


Ĉ
James Strawson,
Jan 14, 2013, 4:33 PM
ċ
Nathan Leahy,
Jan 10, 2013, 12:04 PM
Ċ
Nathan Leahy,
Jan 9, 2013, 3:51 PM
ċ
Nathan Leahy,
Jan 10, 2013, 12:04 PM
Ĉ
James Strawson,
Jan 14, 2013, 4:33 PM
ĉ
James Strawson,
Jan 18, 2013, 10:11 AM
Ċ
James Strawson,
Jan 17, 2013, 12:09 AM
ĉ
James Strawson,
Jan 18, 2013, 10:11 AM
Ċ
James Strawson,
Jan 15, 2013, 4:50 PM
ċ
TT CAD 2013.zip
(6940k)
James Strawson,
Feb 11, 2013, 8:50 PM
ĉ
James Strawson,
Jan 18, 2013, 10:18 AM
Ċ
James Strawson,
Jan 18, 2013, 10:18 AM
ċ
step_response_code.ino
(7k)
James Strawson,
Jan 14, 2013, 4:33 PM
Comments