Overview of Status of Analysis, Design, Fabrication, Tests, etc.
Linear Slider Design: Designed
Drive System: Designed
Motor torque analysis conducted, motor ordered
LabView + Arduino: Ready to program
Limit Switches: Risk Reduction needs to be conducted
Bearings: Bearing analysis being conducted, IGUS for plastic bearings
Fiber Optics: Receiver/Transmitter circuitry still needs to be finalized
Accomplishments from Previous Week
Ordered Motor and Motor Driver
Received 40-4080-LITE T-Profile from Machine Shop
Borrowed plastic limit switches from Chris Cassidy to use for risk reduction test for limit switches
Goals for Next Week (list names after each item). Use specific and measurable objectives.
Order bearings and begin fabricating carriage and wheels
Conduct Plastic Limit Switch Risk Reduction
Begin writing LabView/Arduino Program + GUI
Finalize Fiber Optics, Belt and Pulley sizes, and order
Sponsor Comments from Last Meeting and Actions Taken to Address these Comments (indicate date of comments and if via email or in person)
Need to design to avoid needing cleaning because of animal urine, hair, etc...
seal away as much access as possible
Will check with IT to get LabView on Physio Computer
Sponsor prefers LabView control with Arduino
Wants a parts list (with part numbers) and maybe an instruction manual
Include a manual method to move the system
include anti-crash technology
use motor current to turn off system
guide rail which guarantees alignment
Instructor Comments from Last Meeting and Actions Taken to Address these Comments (indicate date of comments and if via email or in person)
Design Suggestions (Delson)
before purchasing, verify that motor can handle both torque and speed requirements
calculate power needed = force x velocy = torque + angular velocity (rad/sec)
use this to choose motor, then choose gearbox
stepper motors have numerous spec torques (holding torque, etc...)
please review manufacturers' spec sheet, show that you understand
Holding Torque = 400 oz.-in
Found the Torque vs. Speed curve
You can use the indexing signal as a pseudo absolute encoder, but using index to zero
If using acrylic for main plate, consider purchasing higher precision (cast) acrylic to reduce warpage
Presentation Comments (Delson)
Give background
research MRI
types of experiments
Describe challenges of designing around MRIs
explain material constraints
avoid using magnetic metals, minimize non-magnetic metals
indicate time of travel
travel to from home to isocenter in 10 seconds
take pictures of test setup
give dollar value for comparisons
explain what a floating bearing is in more detail
Design Suggestions (Pedro)
is stepper motor operating at full step?
it can operate at full or half steps
fiber optic cables and LED emitters/detectors - easy to adapt to arduino?
after talking to Steve Roberts, it seems fairly easy
Presentation Comments (Pedro)
Background?
"Finding a gearbox that can give us high enough resolution" - is that the right word?
"small enough step size" would probably be a better term
Comments from Other Students in the Class (indicate date of comments and if via email or in person)
How much precision necessary to align wheels in single beam slider?
less than using parallel linear guide rails
Use a rat funnel to keep rat parts in tube
generic guide rail/tube design is in the works
Use optical sensor for safety features?
planning to use mostly plastic limit switches for now, risk reduction test will be conducted soon
Check out movie camera tracks?
carriage requires wheels at 45 degree angle, but also doesn't look to provide cantilever support
Beagle Bone Black micro controller?
we will look into it, but Arduino might be better because we have more experience with it
Provide an overall picture showing complete design solution with a list of all the parts
3D printed lead screws
less feasible for the length we need
Will the circuitry in the room be affected by the magnetic field?
it did not have any noticeable effect during the motor risk reduction tests, but we will need to test for that. Worse case, we will add a Faraday Cage.
Arduino Fiber Optics Shield?
could not find any
How accurate does alignment need to be within the bore?
Depending on the size of the animal/sample, it will vary
Be careful of resolution and delay between DAQ and system
How can you use motor current to avoid damage to body parts and avoid system shut down due to excess friction/misalignment?
We are thinking of a different solution to avoid damage to animals
Shouldn't need encoders with stepper motors
while stepper motors should be very accurate as long as there is enough torque to avoid losing steps, an encoder is an added level of confidence
Risks and Areas of Concern
Magnetic field strength at the end of the table
Encoder operates < 40 Gauss
Resources or Information Required but not Available
Purpose of mounting base in relation to size
Which LabVIEW version is being used at cfMRI
make sure that program is backwards compatible just in case (Arduino toolkit works with NI LabView 2009+)
Schedule
Order parts and build prototype
Update Gantt chart.
Budget (list amount spent and amount remaining)
Spent: $218.95 of $1500
Remaining: $1281.05
Progress on Report and Webpage
Chapters 1-3 have been assigned
Home page is still under construction