Team Vision for Detailed Design Phase
The Purpose of this Phase
- Refine the prototype for the hanging frame design
- Experiment with different rear harnesses to determine optimal design
- Test different iterations of the hanging frame design with Trey
- Quantitatively determine the viability of each design change in context of the client’s tolerances
- Use rapid prototyping techniques to develop the prototypes in the necessary time scale
Key Questions to Answer During this Phase
- Does the hanging frame prototype provide the correct posture support?
- What is the best number of joints for the most ergonomic fit?
- What sort of clearances should be allowed for the most ergonomic fit?
- What is the most comfortable harness setup for Trey?
- What wheel size will allow for the most mobility?
Progress ReportAn update on progress toward the detailed design review was sent out on November 21st, 2016. The content was as follows:
What does the team plan to accomplish by the Detailed Design Review?
- Two new prototypes will be available to be tested before the review, one for Trey and another for Delilah.
- An improved harness will be made and integrated into the cart frame for best fit.
- A new bill of materials is in progress for both new cart designs.
What tasks have been accomplished so far?
- A first iteration bottom-support frame is currently being designed for Trey in SolidWorks.
- A third iteration hanging frame is in the works Delilah.
- Improved harness designs are being finalized.
What tasks remain, and who is the owner of each?
- Jeff is working on Trey's cart design.
- Matthieu is improving upon Delilah's cart design.
- Colin and Sarah are working the harness design.
What decisions have been made so far?
- Delilah has responded well to the hanging cart design, so it will be optimized for her.
- Trey will most likely benefit from a bottom-support design, so that route has been explored.
- The Do-It-Yourself aspect of the designs are still up in the air, due to the complexity of the carts.
Drawings and Sketches
Below are a collection of sketches that detail the beginning thoughts and ideas that led to the designs of the top frame rev.3 and bottom frame rev.1 cart designs.
Prototyping, Engineering Analysis, Simulation
Top Frame Cart rev.2 DesignThis is the second revision of the top frame cart design. The goal of this prototype was to determine the effectiveness of this frame design on both Trey and Delilah.
The primary modification to this frame from the initial design was the increased height of the frame from the bottom of the wheel, essentially the 'leg' length of the cart. This was done because the original prototype was too small in size for the subjects and resulted in discomfort.
Top Frame Cart rev.3 DesignThis is the third revision of the top frame cart design. The goal of this prototype was to further refine the cart fit on Delilah and determine any additional design additions or modifications that need to be completed to better suit her. This prototype was not tested on Trey because it was determined to not properly suit her needs and a different cart would be designed to better fit her.
The primary revision to this design was the addition of two supporting frames to each side of the cart. This was done with the intention of improving the overall stability of the cart. The previous revisions only provided support via a spinal aligned rod, which created a torque when the cart was moved. It is believed this causes discomfort for the cat and inhibit fine motor control.
Bottom-Frame Cart rev.1 (Under Construction)This is the first revision of the bottom frame cart design. This prototype is still still under construction, but its main goal is to specifically cater to Trey's mobility needs. This is primarily done through the addition of a third wheel that allows the cart to self-balance, allowing Trey to focus on movement and not balancing the cart while she walks.
Bill of Material (BOM)The bill of materials is shown for each prototype as if each part had to be purchased for each prototype. In reality, many of the materials are re-used between each revision of the cart design so the actual project budget is lower than the sum of all of the bill of materials.
Test Plans(#) Denotes areas of priority
Top Frame rev.2 Testing Notes and Observations
- (#) Cart balance is off, Trey cannot stand straight while wearing it
- Spinal support tube too long for Trey
- Frame height is too tall
- (#) Harness is far too loose
- Diaper harness has too much freedom of movement
- Frame width is too wide
- Front harness causes discomfort
- Front harness not secured
- (#) Harness is too loose for Delilah
- Frame height is too short
- (#) Not balanced for Delilah
- Extreme harness discomfort
- Front harness not secured
- Frame causes curvature of the spine
- Create custom front harness to maximize tightness and reduce discomfort
- Create an adjustable means of attaching harness
- Create adjustable frame to match cat size
- Balance the cart more effectively
Top Frame rev.3 Testing Notes and ObservationsThis cart is only intended to be tested on Delilah, there is a Bottom Frame cart currently under development for Trey to use.
- (#) Delilah was very aggravated, was only willing to be in the cart for under a minute
- The frame was still too wide despite modifications
- (#) Couldn't tightly attach Delilah's front harness to the frame
- The frame wasn't long enough for the front harness attachment points to reach her shoulders
- The wheels were angled in, making it more likely for her to tip over
- The harness was still very loose
- Delilah was raising her hind legs instead of pushing down on the ground
- (#) Delilah was unwilling or unable to balance the cart with her hind legs
- Angle in the side bars to give a better front harness mounting point
- Lengthen the side bars
- Fix the wheel angle
- Actively design the harness in an integrated method with the cart
- Narrow the cart in general
Future testing will include completing a testing metrics form to better quantify improvements and flaws in current design. Included below is a link to the current revision of the document used.
Below are some links to testing videos that document the fit and performance of the rev.2 prototype
Plans for the Next Phase
With the close of MSD I there has been a lot of excellent progress in the development of cart prototypes. During the testing of the third cart revision it was evident that refinement of the harness and better balancing of the cart is necessary for greater successes in testing to be achieved in future revisions.
To facilitate this success, the key goals of MSD II are as follows:
- Finish the design and construction of the Trey rev.3 cart prototype
- Develop and more secure and robust harness for both Trey and Delilah
- Review the shortcomings of the Delilah rev.3 prototype and implement the appropriate improvements into the rev.4 design
- Determine if Delilah’s cart balancing issues stem from a problem with the cart design or a lack of training on the part of Delilah in how to use the cart
- Perform a week-long test with both Trey and Delilah once a suitably developed cart prototype has been made
It is expected that multiple cart revisions for both Trey and Delilah will be needed before the design that offers the greatest combination of comfort and usability is experimentally determined.
Imagine RIT Shared Vision
Best Case Scenario:In a best-case scenario, both cats will be acclimated to the carts enough for easy attachment. Trey and Delilah will move around an enclosure, utilizing the carts in a way that demonstrates their comfort and improved quality of life. People will be able to interact and play with the cats to an extent, due to both cats being social with the large number of spectators. The robust carts will not succumb to any sort of wear-and-tear and become damaged during Imagine RIT. Pet owners will ask a plethora of questions regarding the origins of the designs and how the team plans to “advertise” the open-source carts. People who work for other shelters and/or owners of cats with rear limb paralysis will ask about how to build a cart best-suited for felines in need of improved mobility.
Moderate Case Scenario:A likely scenario is that Trey will be willingly put in her cart, while Delilah will put up a fight. Due to a lack of complete comfort as a result of minimal time spent in the carts, the cats will take time to warm up and begin to move around. The carts will provide the necessary amount of support and movement to both cats for a time, until the cats either become fed-up for the day or Imagine RIT comes to a close. Parts will not fail, though the cats may tip over or get wheels stuck in some way while moving throughout the enclosure. People will be intrigued by the project and ask questions because animals typically draw a crowd. If the cats decide enough is enough, a video will be played which shows the carts being attached to the cats, and the cats moving and maneuvering freely.
Worst Case Scenario:In a worst-case scenario, demonstrations will be halted by both Trey and Delilah refusing to be in their respective carts. Neither cat will move and instead flip over or attempt to get out of the harnesses. Printed parts will fail, and/or harnesses will tear as the cats mess around. Trey and Delilah’s obvious discomfort will be evident to on-lookers, as their mid-sections sag due to poor spinal support and their legs/fur become caught in various cart components. Too many people around the cats makes them uncomfortable and even defensive, and Karla will take them home, leaving any demonstrating to a pre-recorded, looping video. The carts will be deemed a failure, the team’s efforts will have been for nothing, and over-priced carts will still be the only option for owners of paralyzed cats and kittens.
Elevator SpeechOur team’s senior design project challenged us to create a cart which would allow cats with little to no use of their back legs the opportunity to move around normally. Two designs have been created for two different felines with different types of paralysis. Trey is a cat born without any use of her rear legs, so her cart is designed such that she is supported the entire length of her torso by a free-standing chassis. Delilah has limited rear-leg use due to a neuro-muscular issue, so her cart supports the rear portion of her body in a way which encourages the use and development of her rear legs, similar to the function of training wheels on a bicycle. Both designs have their merits and are meant to be open-source, low-cost, do-it-yourself designs which accommodate a large spectrum of cat sizes.
DDR Presentation Action ItemsAll of these action items are intended to be completed before the week 5 review of MSD II.
- Create an Imagine RIT section in Edge that envisions what the event would be
- Create a standardized cat pictures that demonstrates different cat sizes
- A render of what the different cart sizes will look like
- A description of what the DIY (do it yourself) finished product will be and include
- A document describing, as an outside person building the DIY cart, why you would choose one cart over another and why you would choose one size over another
- Write a rubric for the test metrics used on the test evaluation form
- Need to perform another evaluation of Trey and Delilah within the first 5 weeks of MSD II
Gate Review DocumentationBelow you will find links to all of the relevant material for the MSD I Gate Review.
MSD II Plan
5 Week Shared Vision
DDR Action Items
Imagine RIT Shared Vision
MSD I Post Mortem