Overview of Status of Analysis, Design, Fabrication, Tests, etc.
The final design of the second wheelchair prototype has been completed and hardware testing #2 performed. New design changes include adding 2 front swivel wheels and a new back frame bracket to alleviate the issues of poor weight distribution and loose corner brackets observed from prototype testing #1. A new frame was also fabricated out of perforated aluminum tubing to avoid the loosening/sliding bolts and to allow for adjustments at discrete intervals. The 2 fixed wheels were kept for the back, and the 2 swivel casters (3" diam.) were selected after quick hardware testing on grass. Each team member performed another round of sit-stand component analysis. Design solutions were discussed and pitched to the sponsor to reach a consensus on the optimal sit-stand mechanism. The system will feature two linear actuators mounted to the back struts that lift/lower the horizontal frame, while the two struts hinge and sprawl forward as the frame is lowered. Parts will be ordered after final analysis and review.
Accomplishments from Previous Week
Completed second prototype. Includes aluminum perforated tubing frame, mounted back bracket, 2 fixed back wheels, 2 front swivel wheels.
Purchased: steel telescoping rail frame, 2 swivel casters, lock nuts, #10-32 screws for mounting and fastening.
Fabricated: perforated aluminum frame (steel was too heavy), 4 wheel struts
Hardware testing for Prototype #2
Swivel casters testing: bigger wheels move better across uneven terrain (3" dia. wheels > 2" dia. wheels)
Optimal height for rear end (feet elevated, neutral posture): 31.75 mm (12.5") from pelvic floor to ground
Sit-stand component analysis
Finalized method of sit-stand: linear actuator-powered lowering of the back wheel struts, with collapsible front wheel struts
Goals for Next Week (list names after each item). Use specific and measurable objectives.
Fine-tune the fitting, dimensions (height), and positioning of comfort components on the wheelchair.
Modify and reinforce 80/20 prototype frame for position finding (Aryan, Sherman)
Closer research, analysis, and review to finalize the sit-stand mechanism. Force calculations, failure/FoS analysis, and code for actuators. (Elias)
Locking system for front wheels (Sherman)
Rail/linear actuator system for back wheels (Ming Ming)
Order parts for sit-stand mechanism: (Ming Ming)
Ex. Linear actuators (2), locking pins, back-bar/frame material
Sponsor Comments from Last Meeting and Actions Taken to Address these Comments (indicate date of comments and if via email or in person)
Concern over potential hazard to Bodie in sit-stand ideas involving pulleys and rope (1/27, in person)
Moving forward with motorized design without pulleys
Wants Bodie to have freedom in his front half when being lowered into sitting/lying down positions (1/27, in person)
Proposed design features collapsible front wheel struts to allow Bodie freedom of motion in his front half
Suggests allowing time for training Bodie to work with new assist device (1/27, in person)
Ending our ideating phase this week to allow as much time as possible to build, test, iterate, and train
Would like to see more analysis-backed justification against motorized assist for sit-stand mechanism, otherwise insistent on using motor. (1/20, in person)
Ming Ming explored a motorized design solution using linear actuators for the sit-stand mechanism.
Instructor Comments from Last Meeting and Actions Taken to Address these Comments (indicate date of comments and if via email or in person)
Clarify with sponsor his needs and goals for this project, in particular regarding the sit-stand mechanism. (1/22, in person)
At sponsor meeting (1/27): main goals are comfort, extended use, and independence from owner.
Button - Bodie is to be independent, so any button/switch must be designed with consideration for a dog to initiate
Terrain - "extended use" was stressed by our sponsor, meaning the ability to sit, stand, lie down, and move around different surfaces ranging from carpet to tile to pavement, and even grass
Recommended to build off of previous design (folding sit-stand) by examining their analyses, possibly adding motorized or mechanical assist. (1/22, in person)
Each team member pitched a CAD-modeled or sketched design solution for the sit-stand mechanism.
Feedback on report (1/22, in person)
Add pictures to Background Information. Done
Use index numbers for pictures. Done
Comments from Other Students in the Class (indicate date of comments and if via email or in person)
N/A
Risks and Areas of Concern
We are to finalize analysis for our general idea for our design, and must make sure the math checks out (geometry & stroke size of actuators are feasible in this application, we have the required power in the correct orientation to enable a sit to stand transition, . . .)
Work with linear actuators once they arrive to make sure they can do what the specs say they can do, and if they will work in this application. If not, we need to either go towards a different type of linear actuators, or in worse case scenario shift gears again to another mechanism
Test the mechanical geometry of whatever sit-stand transition we want to pursue to make sure it can adhere to Bodie's required range of motion.
Resources or Information Required but not Available
N/A
Schedule
Finalize sit-stand concept.
Modify 80/20 prototype for position finding.
Build prototype with sit-stand mechanism for testing.
Update Gantt chart.
Budget (list amount spent and amount remaining)
4x 8020 extrusion bars--$41.39
Loop Clamps--$12.00
Corner brackets--$29.05
Home Depot trip for screws--$4.94
Upcoming purchases: perforated tubing and components for front 2 swivel wheels (wheels, fasteners, rods . . .)
Amount Remaining: $2512.62 (out of $2600)
Progress on Report and Webpage
On track for required report sections, will work on first report full draft due later this week.
Not much work has been done on our website, most files have been on a personal drive, we can work on organizing the website and copying those files onto the website