Overview of Status of Analysis, Design, Fabrication, Tests, etc.
The final design features two primary systems: the mobility system features an outer frame and 4 wheels: 2 front swivel wheels on angled struts, and 2 fixed back wheels. The sit-stand system features an isolated inner frame that supports the comfort components (harness, saddle), and hinges to lower the rear end while an unlatching system releases the front harness.
The preliminary hardware prototype of the final design was completed, without the electrical components (actuators, switch). Hardware testing was performed on Sunday (2/10) to evaluate the wheelchair's hardware design and Bodie's performance in it. Key findings confirmed the 4-wheel design as more comfortable, stable, and easy to load than 2-wheel design. Lifting/lowering by hand was performed to imitate the actuator motion to test for potential problems.
Parts in progress are the final design of the sit-stand cam lock, whose purpose is to release Bodie's front half when his rear is lowered to enable him to lay down or sit up at his own will. Goals for this week focus on the electrical components, including testing of the actuator-switch system and actuator mounting.
Accomplishments from Previous Week
Fabricated preliminary prototype of final design (4 wheels, isolated sit-stand system)
Machined parts and mounted hinging mini-frame
Fabricated and mounted angled front struts
Hardware testing performed
Performed second round of force analysis for actuator requirements to validate required specs (stroke length, force)
FoS: min 1.67
Goals for Next Week (list names after each item). Use specific and measurable objectives.
Make refinements to current prototype hardware (Team)
Adjusting gap between inner frame and outer frame
How comfort components can be ideally attached and placed
Make front of frame more comfortable so it doesn't hit Bodie
Design method for unlatching/re-latching harness (Elias)
Order parts (Sherman):
(1) DPDT switch
(2) actuators (4" stroke, 200lbs)
Electrical testing of switch-actuator circuit (Ming Ming)
Does the switch work as expected? Is the interface simple and easy to train/operate?
Is the speed of the actuators appropriate for Bodie's needs?
Do the power supplies provide enough power to both the switch and actuators?
Configure and mount actuators mechanically (Aryan)
Are the actuators operating as expected - particularly w.r.t. angle change, range of motion, avoiding interference?
Sponsor Comments from Last Meeting and Actions Taken to Address these Comments (indicate date of comments and if via email or in person)
Hardware Testing (Prototype with Isolated Sit-Stand System, No Actuators) - Results & Feedback
Over the shoulder latching harness is preferred and easier to mount (in person, 2/10)
Front harness may not be necessary, as long as Bodie can pull the cart as he moves
Different harness designs will be explored in conjunction with cam lock design feature, as the two must interface
Location/angle of the saddle in down position prevents Bodie from laying down (in person, 2/10)
Alternate saddle locations/mounting will be explored for comfort/lifting systems
More clearance needed between outer frame and mini frame (in person, 2/10)
Fabrication of next mini-frame prototype will account for clearance
Front/back wheel struts can be repositioned for better balance (in person, 2/10)
Front/back wheel struts were moved further apart
Instructor Comments from Last Meeting and Actions Taken to Address these Comments (indicate date of comments and if via email or in person)
Start working on button mechanism for Bodie, Professor foresees interference and mounting issues (in person, 2/5)
Look into force-assist if needed to get off the ground (springs?) (in person, 2/5)
Comments from Other Students in the Class (indicate date of comments and if via email or in person)
Look into having his rear raised much higher than rest of body, since Bodie has most vigor while in sling, which involves lifting rear completely clear off the floor (in person, 2/5)
Consider spring to assist up/down motion (in person, 2/5)
Perform FEA (email, 2/5)
Risks and Areas of Concern
Incompatible electrical components - mounting, actuator force supplied, power draw
Resources or Information Required but not Available
Schedule
Describe upcoming milestone:
Order and test new actuators (mechanically & electrically)
Design and develop harness latching mechanism - either cam lock or other
Update Gantt chart
Budget (list amount spent and amount remaining)
(4) 8020 extrusion bars--$41.39
Loop Clamps--$12.00
Corner brackets--$29.05
Home Depot trip for screws--$4.94
Linear actuators & peripheral components (power supply, mounts): $310
Gate latch--$4.49
4'' actuators:
Amount Remaining: $2210.62 (out of $2600)
Upcoming purchases: perforated tubing and components for front 2 swivel wheels (wheels, fasteners, rods . . .)
Progress on Report and Webpage
report is 50% done as expected by the week 5 deadline
webpage has content on front page, most of our working files are still on separate drive