156B Week 1
Overview of Status of Analysis, Design, Fabrication, Tests, etc.
We are now waiting for input from Dr. Jones on which pedal layout he prefers and whether he has any changes he wants to make. After his input, we will finalize a list of products that may fit our needs for the controlling of speed and direction of motor. For the horizontal motion of the syringe, we are finalizing a list of linear actuators and close to prototyping the mount for the linear actuators and a holder for the plunger. With the pressure readout, we are researching which op-amp would fit our needs and will be hopefully purchased by sometime next week.
Accomplishments from Previous Week
Completed Risk Reduction presentation. Areas covered: Pedal-human interface design, Circuit for reading pressure transducer signals, Mechanism and analysis of squeezing syringe, Clasp to hold onto syringe.
Goals for Next Week (list names after each item). Use specific and measurable objectives.
Individual Component Analysis (Everyone)
Work on Website (Everyone)
LaserCAMM a prototype of the linear actuator for future testing (Kevin and Ethan)
Discuss and finalize foot pedal interface and design with sponsor (Oscar)
Obtain circuit components (op amp, Cord splitter, and resistors) and assemble prototype for the pressure reading circuit (Shawn)
3d print clasp design for syringe (Tom)
Sponsor Comments from Last Meeting and Actions Taken to Address these Comments (indicate date of comments and if via email or in person)
(email 4/4/2012) Hey guys,
All I can say is "WOW"!! I'm very impressed with the presentation. I like it a lot. A couple of thoughts - if this thing doesn't get into full scale commercial production the thing that will make it interesting as a research tool would be the pressure sensing capabliity, therefore if possible, I think this should be moved to a high priority item (again, if possible).
Secondly, I really like the thought that has gone into the footpedal design. It's a bit difficult to assess them all without being able to lay hands . . . or feet . . . on each of them which wouldn't be practical. Just going by the schematics, I think the original design, the tilt design, and the strap design would all do the job nicely. The original design would entail a lot of foot movements but probably is the safest. The tilt design would require little foot movement but I could envision my foot not being squarely on one side or the other and accidentally injecting in the wrong direction. The strap design would also require little foot movement and seems very intuitive. I'm pretty dextrous with my feet and toes but operating a joystick might pose quite a challenge! We can talk more at our meeting.
Lastly, like I told you at our first meeting and as you mentioned in the presentation, controlling the speed of the injector is crucial. It will need to be able to inject very slowly all the way up to the quickest injection time of 3 sec for a whole syringe (as you state in the powerpoint) with sufficient footpedal control over the speed of injection.
Nice job thus far. I can't wait to see a prototype.
Carter
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 on Presentation)
Overview slide should use bullet points and include figures of operation
Safety should be a functional requirement
Explain why the syringe must be able to move forward and backwards
Explain how the pressure transducer is required
Pulley driven slide will require a spring
Factor is safety is usually multiplied in pressure analysis section
Pedal Design 3 (Tilt) is a good design
Good range of concepts
Add DFMEA to milestones
Comments from Other Students in the Class (indicate date of comments and if via email or in person)
Digital display to avoid error
Possibly separate syringe A and B with different pedals
Have an enclosed mechanism to avoid possible fluid spills
Design a fail-safe to stop motor when there is an error
Design (3): Have a vertical orientation rather than a horizontal for forward and reverse controls
Have constant applied pressure to the fluid. Use the pedal to open valve to deliver fluid at a rate based on what the doctor wants.
Combine one pedal for slection of fluid. Have an interface that lights up depending on which fluid was selected; either fluid A or Fluid B or both.
Entire pad can use rubber mat attached below to resist movement.
Don’t strap foot to pedal, possible tripping hazard and uncomfortable
Good presentation
Good to use a spring but spring forces change as displacement changes.
How about constant force spring?
How will you refill the syringe with your system?
Can you incorporate a refiller mechanism?
Make it simple: 1. on/off 2. How fast 3.Type of syringe
Pedal design will be difficult to differentiate how hard to push….
I say design III is best
For the switching syringe, program it so that if you press right for > 5seconds, it will be syringe A or left for >5 seconds, it will switch to B.
Have it ‘speak’ to tell you which syringe is chosen and how much is left.
Use a switch for the pedal to simply turn it on and off might help with safety.
Create a display with LED’s that would let user know which syringe is selected.
Risks and Areas of Concern
Areas of concern are currently with the pedal layout that Dr. Jones would prefer as well as the placement and mobility needed for the pedals. Speed control of the linear actuator is also an area of concern. Current ideas include the use of a potentiometer to control the speed of the motor, and two switches to control selection of syringe and either forward or reverse direction of plunger. Precision of the pressure readout is also of concern. We don’t want the arduino shutting down the linear actuators if the pressure is misread. In terms of the linear actuators, we simply need to meet the power requirements needed to inject the dosage in three seconds.
Resources or Information Required but not Available
We need to know the feel of the pedal
Performance of syringe when injecting into flesh
Op amps and resistors (can we get these supplies from Steve)
Schedule
Upcoming Milestones
Determine best possible way to extract pressure transducer data during meeting with Steve.
Fabricate a prototype syringe holder by the end of next week.
Update Gantt chart.
Budget (list amount spent and amount remaining)
$0 spent
$2000 available
Progress on Report and Webpage
Report requirements are being reviewed
A new gantt chart program is being implemented and utilized for Project Management.