156B Week 8

Overview of Status of Analysis, Design, Fabrication, Tests, etc.

• • Still waiting on the Stepper motors to come in (should be any minute)

  • Mechanical Advantage idea/concept almost finalized

  • Final stage design for 2X model has been CAD

Accomplishments from Previous Week

• • Steeper motors ordered

  • Mechanical Advantage idea being completed

  • CAD of theta stage for 2X model is done

  • Met with Jerry last week to nail out some details (see instructor comments)

Goals for Next Week (list names after each item). Use specific and measurable objectives.

• • Finish Mechanical Advantage concept (James)

  • Print out theta stage of 2X model (Sean)

  • Implement stepper motors in the 2X model (Razi/Julie/Dylan)

  • Finish the 2nd draft of the project (ALL)

Sponsor Comments from Last Meeting and Actions Taken to Address these Comments (indicate date of comments and if via email or in person)

Meeting with Delta Design 5/14

• • Try to catch Jerry on campus to find out more on the mechanical advantage aspect of the project

  • Easy drivers for stepper motors

  • board for bipolar stepper - quad stepping motor driver

  • use a spring for stepper backlash (0.001 in)

  • Hall effect sensor from last time

    • Check sensors in the bag for the part number

  • Mill test for encoders

    • 40 microns of drift

    • If the angle was fixed, 10 microns of drift

    • Test with twisting (1 degree) - Do you see changes in in the encoder? What happens to the counts?

    • Test if the drift is linear or not. (If the drift is consistent, we can factor it out)

  • We want to see closed loop. -Stick with the hall effect analog input

  • Lever - there is not enough wall space

  • Finite state machine

    • Arduino code

Instructor Comments from Last Meeting and Actions Taken to Address these Comments  (indicate date of comments and if via email or in person)

Meeting with Dr. Delson (5/14)

• • Assemble the 105 mm stage so that it has more of a gap between stages

  • Mechanical advantage

    • Scissor jack (variable design)

      • Equations for virtual work

      • torsional springs at pivots

      • modified geometry

    • Cantilever - If both beams flex, we will lose a percent of travel

  • Hall effect sensor (Check to see if this is really called an encoder.)

  • Stepper motor shields - Radio Shack or Amazon

  • Look into ratchet from flea - advantage is more travel

Meeting with Dr. Tustaniwskyj (5/15)

• • Mechanical Advantage

    • 10mm throw and maximum of 10 times mechanical advantage

    • There are risks in the current muscle wire approach

    • Our design will not be used until a couple of years down the line when the balls in BGA become denser

    • Delta Design wants us to investigate the pros and cons

    • The needed force is very low

    • Lever - 5:1 mechanical advantage is not the end of the world

    • Encoders - some inaccuracy in data is fine

    • Stepper - home position as soon as it is powered up and then open loop

    • We can use hall effect sensors

    • i2c - We don't need this for our proof of concept

    • 3 motors and 3 encoders with Mega (without i2c)

    • Lever is simple, and simple is better

Comments from Other Students in the Class (indicate date of comments and if via email or in person)

Comments from Proof of Concept Presentation (5/7)

• • Some compliments:

    • Good prototypes

    • Good job with the problem definition

    • Nice CAD, video, and pictures

    • Good progress and way to get a moving part

  • Some suggestions:

    • Have another video at a different angle or with better lighting.  Maybe point to the parts that are moving since our project is so small

    • Explain company's intention for having a 2X model.  Will be be downsized in the future?

    • Good luck on programming with I2C.  Talk to Steve Roberts on I2C programming

    • Pico-motors as a possible alternative to squiggle motors

    • Make sure that since you are splitting up the work to still communicate with each other

    • Utilize 3D printing.  What are you going to do for mechanical advantage?

Risks and Areas of Concern

• • Mounting the magnets and encoders/sensors

  • Programming for closed loop control once we implement the stepper motors

Resources or Information Required but not Available

• • N/A

Schedule

• • Milestones:

    • Implementing the stepper motors in the final design

    • Controlling motors

    • Completing mechanical advantage concept

    • Finishing the 2nd draft of the report

Budget (list amount spent and amount remaining)

• • For a detailed account of the project budget please see the "budget" section of the website.

Progress on Report and Webpage

• • The website is being constantly updated

  • The progress reports are being constantly updated