Overview of Status of Analysis, Design, Fabrication, Tests, etc.
Modified 80/20 frame last week such that harness ring can slide over frame and enable more accurate positioning of components
Frame was used in meeting on Thursday (1/31) to relocate component's positions and relations.
Tests revealed more accurate positions & heights for frame & components for the next prototype
Linear actuators were selected for use in sit-stand system. Parts were ordered and received and tested for strength and stroke.
Design assumptions were reviewed, we found front and rear comfort components (saddle & harness) need to be able to vertically translate independently of each other.
Under the assumption that our actuators will provide however much power we need for sit-stand, must finalize mechanical contraptions that can achieve the 3 separate states of stand, sit and lie down.
Potential redesign under consideration. Instead of last week's proposal of vertically lowering the entire main frame, the team discussed an isolated "mini-frame" laid inline the main frame that will hinge to lower the back harness. Clever design may allow the usage of smaller, lighter actuators and more effectively leveraging all the force they supply.
Accomplishments from Previous Week
Modify 80/20 frame such that harness ring can slide over frame and enable more accurate positioning of components
this was used in a meeting on Thursday (1/31) to relocate component's positions and relations.
Prototype testing:
Size adjustment needs
Shoulder harness rear wheel distance found - for comfortable harness resting
Vertical height from ground to frame found - for good neutral posture (spine parallel to ground)
Components ordered for sit-stand mechanism:
(2) Rod linear actuators: 12' stroke
(2) Power supplies (12VDC, 1A), mounts
Gate latch mechanism to see if it can work as a lock for our front wheel design
Goals for Next Week (list names after each item). Use specific and measurable objectives.
Review design ideas and project schedule (Ming Ming)
In Saturday team meeting (2/2), defined functional requirement for front and rear comfort components to independently achieve different vertical heights
Due to the sitting posture: saddle at ground level while harness is at the chest level
Place order through Roxanne (Ming Ming)
Do force analysis for linear actuator requirements contingent upon geometry of component placement (Aryan)
Analyze & plan CAD for CAM lock mechanism (Elias)
Analyze cable lengths for potential pulley system alongside linear actuators (Sherman)
Sponsor Comments from Last Meeting and Actions Taken to Address these Comments (indicate date of comments and if via email or in person)
Sponsor wanted to see adjustments to 80/20 model to find optimal positioning of parts (1/24, in person)
Trimmed extrusion to allow easy positioning of front saddle
Added gussets to frame to reinforce corners
Hardware testing:
4-wheel design helps Dr. Yu load easier by himself, pursue 4-wheel design (1/31, in person)
Solid saddle is easier to work with when loading Bodie, loose saddle may enable more swing leeway for Bodie (if saddle is rigid, Bodie's swing may make cart swing) (1/31, in person)
Sponsor prefer's solid saddle for loading, see if loose saddle offer's any advantages, and pick tautness of saddle to move forward with
Saddle tautness also affects Bodie's vertical position in relation to the cart, so picking a tautness may require offsetting some components vertically to make up for it
When implementing actuator's into sit-stand mechanism, potentially use aluminum extrusion bars in extrusion frame solely for finding precise actuator positioning (1/31, in person)
Instructor Comments from Last Meeting and Actions Taken to Address these Comments (indicate date of comments and if via email or in person)
Explore battery options for size, weight and electrical output (1/29, in person)
1 larger 5A battery vs 2 smaller 1A batteries - ordered for testing
Explore actuator options for weight, strength & distribution (1/29, in person)
1 large strong actuator vs 2 smaller weaker actuators - ordered for testing
Explore specifically where actuators are mounted (rear crossbar, side frame bars, alogn leg struts themselves . . .)
Bodie being in middle of the cart provides space constraint for connecting actuators & other components with cables (if do cables, need to route them along the frame) (1/29, in person)
Explore how to guarantee the front struts go all the way up at the top of their range (spring-loaded, strings/linkages?) (1/29, in person)
also involves the question of how the front & back struts are connected in range of motion
if using Bodie-operated button near his front, potentially have the button on a gooseneck to prevent crashing button into stuff (1/29, in person)
Actuator-button interaction & potential need for peripheral code components (1/29, in person)
will button be tap & go or will it need to be held down
if want tap & go, may need controller or internal chip
may want to use limit switch to cut power to circuit once end of range is reached
Industry call was made: simple wiring with DPDT switch + actuator's internal limit switches automatically open the circuit once fully extended/retracted (2/1)
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
General risks of potential redesign. Actuators work as powered components for our purposes, but still need to refine sit-stand system design.
As stated earlier, we defined a potential need to have front and rear comfort components translate vertically independently. Our most recent model assumes that the frame is parallel to ground during whole transition, but based on hardware testing and more market research, may reassess that decision and redesign model to work around the 3 dog states of stand, sit, and lie down.
Uncertain if actuators can supply enough force. One of out models involves a hinging frame that is controlled by an extension linear actuator placed midway. This will enable us to use a shorter stroke but will also require a greater force.
More actuator research needed to see if we actuator can provide enough greater forces.
Lead time of parts ordered.
Resources or Information Required but not Available
N/A
Schedule
Describe upcoming milestone
Finalize sit-stand contraption and check for compatibility with chosen actuators in terms of actuator size & strength
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
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
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