Overview of Status of Analysis, Design, Fabrication, Tests, etc
The final design the wheelchair has been completed and fabricated. Most systems (the inner frame hinging motion, the actuator mount design, the 4-wheel mobility) have undergone individual component testing, and have been validated in performing as expected. Next steps are assembling the full wheelchair and conducting performance testing with Bodie.
3D printed locking components have been made and are going through iterative improvement (lock-teeth interface, lengths-distances-angles, relations to mini frame)
all components for 1 lock spool are on hand, including steel pin to hook the spring onto, uprights for mounting the spool, and spacers for ensuring components line up.
adjustments to be made include interacting of the teeth of the lock and the spool, as well as making sure both sides of the spool have teeth lined up.
machined inner frame with perforated square steel tubing, aluminum corner brackets and gussets.
some interfacing and interference issues with mounts; will be recreating them
performance testing of actuators with Bodie's load was conducted and validated at most recent meeting
appropriate speed
able to lay down
sufficient force supplied
planning & design on Bodie button interface is behind schedule. team has ideated but has not designed/manufactured yet
Accomplishments from Previous Week
3D printed locking mechanism was successfully procured, and simply requires testing, redesigning and reprinting iteratively until an optimum performance is reached.
tests on lifting the mini frame with a load using the actuators were performed both on standard weights as well as on Bodie, which served to prove that the idea works.
25-lb load testing
test bed: box of 25 lb load applied into saddle at very rear of the inner frame
stalled when lifting from down position
not necessarily due to insufficient force, but slipping of screw at inner frame hinging point
Bodie testing
the actuators provide enough force to lift Bodie even when only supplied with 1A
even the arbitrary mounting angle of the actuators was enough to lift Bodie's rear. further optimization of mounting location will help increase FoS
inner frame and connector components were manufactured and procured for fully functional frame.
Goals for Next Week (list names after each item). Use specific and measurable objectives.
*design options for trigger button such that we can use the next couple meetings testing them with Bodie (Aryan)
purchase battery, DPDT button, wire casing (Ming Ming)
assemble and mount brake locks. perform component testing (Elias, Sherman)
re-manufacture
back wheel struts such that they are not angled (or at least are less angled), since the cart is too wide with those angled struts
components to fasten together inner frame (gussets & corner brackets)
back bar for outer frame (still using back bar from last year's cart)
Sponsor Comments from Last Meeting and Actions Taken to Address these Comments (indicate date of comments and if via email or in person)
if Bodie's lying position in the saddle is too strenuous on him, consider a hinging saddle mount, such that the saddle can always stay in the optimal orientation around his waist. (2/24, in-person)
This design would be similar to a seesaw or the seat on a swing, which is simple to accomplish and is lower priority than objects like procuring and testing a battery, the button trigger issue, and having 3D printed components interface properly. Therefore we will pursue this idea if we have time after the top priority objectives.
Our conception for mounting the actuators were previously to either mount at the top of the wheel struts or to design upright mounts. Dr. Yu posed the idea of a cross bar hanging across the front and back wheel struts that the top hole of the actuator could be mounted to, as this would distribute the load on the outer frame across both the front and back of the cart.(2/24, in-person)
Regarding our button trigger designs, we should move forward with multiple designs in parallel, such that if one fails we don't have to return to ideating in the final weeks of the project (2/24, in-person)
the two main streams of ideas involve interaction with his front paw (having him step on a button or a pedal, or interaction with his face (he may swing his head and hit a pressure plate to trigger the actuators, or he may bite a pressure sensor disguised as a chew toy to trigger the actuators)
use spiral wire wraps to enclose wires for final design, such that there are no dangling wires that can get caught or disconnected.
Bodie's behavior during actuation was for him to try and take off before the process completed, we must investigate if this will pose a problem in operation or not.
Instructor Comments from Last Meeting and Actions Taken to Address these Comments (indicate date of comments and if via email or in person)
explore batteries and test if power supplied is enough (gel pack vs lithium ion). test 1 vs 2 batteries, test life span (Ahrs) (2/19, in-person)
ensure center of mass of cart is stable when heavy components are mounted (actuators, batteries) (2/19, in-person)
larger caster wheels (2/19, in-person)
spool locking mechanism should work without much difficulty, it requires precision but it is a proven locking method. (2/19, in-person)
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
Some challenges with locking mechanism due to required level of precision.
Button interface design.
Resources or Information Required but not Available
N/A
Schedule
Describe upcoming milestone
Update Gantt chart.
Budget (list amount spent and amount remaining)
Progress on Report and Webpage