156B Week 7

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

• • Analysis: Recalculated using actual specifications

  • Design: Completed

  • Fabrication: Mostly completed, waiting on belt end-clamp and motor shaft coupling to arrive

  • Tests: Waiting on brass screws to make carriage completely non-magnetic, test entire system for noise during MRI scan

  • GUI: Most functionality is implemented, working on visual interface and last couple of functions

  • Fiber Optics + PCB: LEDs and photodetectors ordered; finalizing PCB layout, will send in order soon

Accomplishments from Previous Week

• • GUI: completed majority of functions needed

  • PCB: finalized majority of layout, need to add current sensor circuit

  • Assembly: Finished except belt end-clamp and motor shaft coupling

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

• • Order PCB (5/19, Alex, Sally)

  • Complete GUI (5/19 Brian, Sally, Ola)

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

• • GUI

    • current position

    • home button

    • indicator for moving and stationary

    • entry box for inputting position (denote direction of the carriage in and out of the bore)

    • status of stepper motor: holding vs. disabled

    • easy for end-user but include debugging options

  • Test all parts of system for image distortion

  • Electromechanical details are more important than mechanical details

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

• • Presentation Comments (Delson, 5/8)

    • good project progress but presentation was hard to follow

      • lacked figures early on

    • problem definition: explain why one needs to move in and out

    • show CAD/some figure of the complete project

    • fiber optics: show figure or block diagram showing rooms and connections between them

    • force analysis: figure not clear; include labels to clarify sample, tooling, etc

    • bearing comparisons: list dollar amounts

    • motor analysis

      • show equation for total inertia; show percentage of rotor and percentage of mass

      • continuity in figures regarding position of mass

      • speed-torque curve: coincidence to be on edge? show placement using actual values

    • carriage test: measure time and compare to prediction

  • Report Comments (Delson, 5/13)

    • abstract

      • include brief explanation for constraints imposed by magnetic fields and sensitive radio frequency equipment

      • good abstract in general but need to make it shorter (a little)

    • project description

      • separate requirements and deliverables

    • description of final design solution

      • rewrite and improve; better explanation of control interface is needed

      • improve on description of mechanical design/integration

    • design of key components

      • move analysis to appendix and reference it

      • expand on what the results tell us

      • images next to different options

      • writing needs to be more formal

  • Website Comments (Delson, 5/13)

    • too many words; need to condense to a paragraph at most

    • summarize objective, requirements, and deliverables as bullets/items

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

Presentation Comments (via in person, 5/8)

• • NEMA 23 slide has too much data

  • include slide #'s

  • annotate figures

  • draw out physical design to help describe functions

  • include assumptions for FBD's

  • consider optical switch with 0V/5V digital outputs connected to gate of bipolar junction transistor

  • make a CAD animation of the design to clarify how it moves with an MRI

  • ask Steve Roberts about PCB; he recommended silk screening and solder masking when we asked

  • order the PCB early; it's taking awhile to get order confirmation through JV

  • consider making a UI in labVIEW and make it as an .exe

  • are the RF noise tests yielding the same RMS stability values for repeated tests?

    • haven't done repeated tests for the same configurations but sponsor believes that the values are consistent considering the small range

  • is there a specific reason the carriage is made of metal? can you make it from glass or other nonmagnetic material so that it can enter the MRI and you can remove the cantilever?

    • does not need to enter the MRI bore, carriage is made of aluminum because we were concerned about plastic threads stripping

    • cantilever is part of sponsor's system; rails could not be placed inside the bore

  • consider nylon screws

  • how much maintenance would it take to maintain the system and fix it if something goes wrong?

    • design has minimal custom fabricated parts, we are planning to cover up as many holes to minimize cleaning

  • have you looked into using nonmagnetic metals i.e. titanium that they use in medical implants?

    • aluminum would be good enough

Presentation Comments (via email, 5/13)

• • what kind of shielding material will you be using? they have to be low resistance right?

    • currently shielding is not necessary due to the low noise interference; potentially creating a simple copper box

  • what are the pros and cons of using optical sensors?

    • pros: nonmagnetic

    • cons: needs more circuitry

Risks and Areas of Concern

• • PCB

  • Current Sensor sensitivity

Resources or Information Required but not Available

• • None

Schedule

• • Complete assembly, complete GUI, Connect fiber optics

  • Update Gantt chart.

Budget (list amount spent and amount remaining)

• • Total budget: $1500

  • $515.23 spent, $984.77 remaining

Progress on Report and Webpage

• • minor updates to report and webpage