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Akhil Shankar, Chinonso Ezekwesili, Daniel Villarreal, Victoria McGuire
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Blog #1
The issue of limited mobility is a growing concern as the global population ages. According to the World Health Organization (WHO), between 2015 and 2050, the proportion of the world's population over 60 years old will nearly double from 12% to 22%. Elderly individuals often face challenges in vehicle entry and exit due to weakened muscles and decreased agility. A solution that improves these handles could significantly increase accessibility and independence for elderly and mobility-impaired individuals, reducing injury risks and enhancing their quality of life.
Our team is addressing the problem of limited functionality in portable automotive support handles, particularly for elderly and mobility-impaired drivers and passengers. Current handles have no way to adjust their orientation thus limiting their usability. The new handle would be compatible with vehicles with U-shaped door striker pins, this would make it compatible with many of the common vehicles found on the road. The key physical constraints include designing a handle that can withstand user forces up to 500 pounds, as current designs typically have weight limits in the 250-500 pound range. The shaft of the handle must have a solid core for tensile strength, and its grip should be adjustable either parallel or perpendicular to the door striker pin to cater to different user needs. By focusing on this limited fuctionality scope, we aim to create a more accessible and durable product that better serves its intended users. Our goals will be informed by user testing and technical simulations.
One of our biggest challenges will be designing a handle that’s both strong and lightweight. It needs to be portable, but it also has to be able to support up to 500 pounds of weight. Another obstacle will be creating a locking system that allows users to adjust the handle’s angle while keeping it secure and durable. We’ll also need to do extensive testing—both through computer simulations and physical prototypes—to make sure the design is safe and effective for a wide range of users.
Figure 1: Current popular commerical design
Figure 2: Example of current design in use
Blog #2
The fitted sheet inserter will accommodate several constraints to ensure usability and effectiveness. It must be able to lift the mattress at least 5 centimeters to correspond with existing mattress lifting solutions using less than 40 Newtons and tuck in the fitted sheet 5 centimeters using no more than 30 Newtons. These 4 constraints are the central constraints that will guarantee that the device will be able to function properly. On the ergonomics side, the device has to weigh less than 3 pounds to be lightweight, have a grip diameter between 3 and 5 centimeters, and have a high coefficient of static friction; these constraints ensure that a user with physical limitations will be able to handle the tool using one hand.
These constraints pose certain challenges: the device must be strong enough to lift a mattress while remaining lightweight enough to be operable with one hand and using less than 40 Newtons of force. These 3 constraints define the task of lifting the mattress successfully. Maintaining structural integrity and minimizing the weight of the device together will require thoughtful design optimization and preliminary physical calculations demonstrating the material properties of mattresses and the gravitation force they exert onto the device.
Another essential constraint is the sheet tucking distance of 5 centimeters; a large part of the design problem will be developing mechanical solutions that could satisfy this constraint whilst meeting the other constraints. The limited force inputs also restrict the potential solutions for tucking the fitted sheet because the device must tuck it in while requiring less than 30 Newtons from the user. The weight and handle constraints pose a less drastic design challenge on their own, focusing more on the ergonomic aspects of the design, which are important, but do not demand complex mechanical designs.
The technical analysis plan:
1) Create concept sketches based on constraints, goals, background.
2) Research materials that can withstand maximum mattress weight and lift weight while staying within constraints and budget
3) Perform static and dynamic mechanics calculations based on the desired clamping, lifting, static and sliding friction coefficients.
4) Perform stress calculations on loading points
1. User Experience and Comfort
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Challenge: The design might meet technical requirements but may still be uncomfortable or unintuitive for users, especially for individuals with disabilities, the elderly, or left-handed people (depending on the context).
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How to Address: Your team will need to focus on ergonomics, user interaction, and feedback during the design phase. This might involve working with potential users to understand their needs better or conducting usability testing with different demographics.
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Measuring Success: Conduct usability tests using time-motion studies to quantify task completion times. Establish a benchmark for user effort in Newtons and set a target for reducing cognitive load using standardized scales like NASA-TLX.
2. Accessibility and Inclusivity
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Challenge: The solution may unintentionally exclude certain users, such as those with specific disabilities, limited technical knowledge, or cultural differences in how a product is used.
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How to Address: Incorporate inclusive design principles to ensure the product is accessible to a wide range of users. Involving experts in accessibility and universal design might help in identifying areas of improvement.
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Measuring Success: Conduct compliance testing against ADA guidelines. Measure the range of forces or hand dexterities required, ensuring the device operates within defined limits. Use accessibility-focused user testing with diverse groups, recording success rates in task completion.
3. Adaptability and Customization
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Challenge: The design may not be flexible or adaptable enough to suit different users' preferences or unique situations.
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How to Address: Consider integrating customization features or modular design elements that allow users to adjust the product to their needs (e.g., adjustable sizes, interchangeable parts, etc.).
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Measuring Success: Test the device’s adjustability over a range of settings (e.g., heights, forces) with multiple users. Record and analyze the ease of customization via time-to-adjust metrics and mechanical robustness over cycles. Target fewer than 3 user-reported adjustments needed for optimal performance.
4. Cost and Affordability
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Challenge: The design may be too costly to produce, resulting in a product that is financially out of reach for the intended users.
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How to Address: Consider the balance between performance and cost by evaluating materials, manufacturing processes, and potential design simplifications. Think about how to offer a range of product tiers (basic, premium) to suit different budgets.
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Measuring Success: Success can be measured by ensuring the cost is within the target market's price range, while still maintaining the core functionality and value of the product. Perform cost analysis using design-for-manufacturing (DFM) methods.
5. Ease of Setup and Storage
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Challenge: The device may solve the functional problem but could be difficult to set up, store, or keep within reach, creating frustration or taking up too much space in the home.
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How to Address: Focus on making the device compact, lightweight, and easy to assemble or store. Design it to fit into a bedroom environment without being a nuisance or requiring frequent assembly.
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Measuring Success: Perform setup time tests, recording the time required for first-time and repeat setups. Use spatial analysis to measure the required storage footprint, ensuring it fits within a defined volumetric constraint (e.g., less than 0.05 cubic meters). Target setup times under 2 minutes.
6. Device Safety and Stability
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Challenge: The device may pose safety risks if it is not stable or secure when in use, potentially leading to accidents, particularly with elderly users who are prone to injury from falls.
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How to Address: Prioritize safety features like slip-resistant materials, automatic locking mechanisms, or safety stops that prevent the device from slipping during use. Consider fail-safe designs that minimize risks in case of misuse or malfunction.
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Measuring Success: Conduct failure mode and effects analysis (FMEA) to identify critical points of instability. Perform drop tests, stability tests, and friction coefficient measurements under various conditions. Ensure safety factor thresholds (e.g., >1.5) for load-bearing components and stability metrics like tip-over thresholds.
Constraints | Value | Reasons |
|---|---|---|
Handle coefficient of friction | ≥1.6 | Minimum coefficient for non-slip grip material |
Device weight limit | ≥ 3 pounds | Maximum allowable weight for one-handed lightweight tool according to CCOHS |
Radius of gripping surface | ≥ 3 centimeters
≤ 5 centimeters
| Guidelines set by DIR-CA & CCOHS |
Fitted sheet tucking distance | ≤ 5 centimeters
| Minimum tuck distance to ensure a snug fit |
Force required to tuck fitted sheet in | ≤ 30 Newtons
| Above average maximum elastic force from fitted sheet and below maximum repetitive input force |
User horizontal input force for elevating mattress | ≤ 40 Newtons | Recommended repetitive input force from CCOHS |
Mattress Lift Height | ≤ 5 centimeters | Lift height of existing lifting solutions |
Maximum mattress weight to accomodate | 800 Newtons | Maximum weight of king-sized mattress |
Table 1: Constraints
Fig. 1: Actual Image of Mattress Lifter
Fig. 2: Base Drawings of Mattress Lifter
Fig. 3: Detailed Drawings of Mattress Lifter
7. Learning Curve and Cognitive Accessibility
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Challenge: Some users, especially older individuals or those with cognitive impairments, might find it difficult to learn how to operate the device or remember how to use it over time.
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How to Address: Focus on simplifying the design to make it as intuitive as possible. Reduce the number of steps required to use the device and avoid overly complicated instructions. Consider visual or tactile feedback to guide users.
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Measuring Success: Success can be measured by tracking how quickly new users can learn to operate the device and by monitoring whether users can consistently use it over time without additional assistance
8. Durability and Maintenance
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Challenge: If the device breaks down frequently or requires ongoing maintenance, it may discourage users from relying on it or cause frustration.
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How to Address: Ensure the device is made of durable, high-quality materials and design it to be low-maintenance. Parts that are prone to wear and tear should be easily replaceable, and the device should require minimal upkeep.
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Measuring Success: Success can be measured by assessing the device’s performance over an extended period of use and by user feedback on the frequency of repairs or maintenance required. Conduct accelerated life testing (ALT) and wear analysis to measure product durability.
References:
[1] “Accelerated Life Testing.” 2024. COMSOL. 2024. https://www.comsol.com/model/accelerated-life-testing-17361.
[2] Government of Canada, Canadian Centre for Occupational Health and Safety. 2015. “(None).” Ccohs.ca. 2015. https://www.ccohs.ca/oshanswers/ergonomics/handtools/tooldesign.html.
[3] “Hand Tool Ergonomics - Select the Tool.” n.d. Www.dir.ca.gov. https://www.dir.ca.gov/dosh/dosh_publications/handtools5.html.
[4] ILO Content Manager. 2011. “Tools.” Iloencyclopaedia.org. Your Joomla! Site hosted with CloudAccess.net. March 14, 2011. https://iloencyclopaedia.org/part-iv-66769/ergonomics-52353/work-systems-design/item/634-tools.
[5] “US8191191B2 - Apparatus and Method for Lifting a Mattress - Google Patents.” 2009. Google.com. October 14, 2009. https://patents.google.com/patent/US8191191B2/en.
Blog #3
In the past two weeks, Team 23 dove into the design phase with our finalized “Eel Mouth” concept, chosen for its approach to simplifying sheet tucking for users with limited mobility. The concept offers a clamping mechanism designed to grip fitted sheets securely with minimal effort. We’ve started bringing this idea to life by sketching out the main parts on SolidWorks. Figure 1 shows a hand-drawn, isometric sketch that helped us visualize the Eel Mouth’s form and functionality before moving into the CAD work. Now, in Figure 2, you can see our CAD model with critical components like the upper and bottom lips, the handle, and a spring-loaded “tongue” that will slide through a tunnel to connect the handle to the clamping mechanism. The tunnel and spring interface are central to the design, allowing the device to securely grip sheets without requiring much strength from the user.
Looking ahead, we’ll focus on completing the tongue component and running motion studies to make sure the clamping mechanism functions smoothly. These studies will help us confirm that the design exerts enough force to keep the sheet in place without slipping. We’ll also conduct a stress analysis to ensure the device can handle regular use without risk of failure. Getting these tests right will be a big milestone, moving us one step closer to prototyping and ensuring our device holds up in real-life scenarios.
As we work on these moving parts, we do expect some challenges in modeling the clamping and release mechanisms. The complexity of these components means our 3D model will need to be pretty precise, which can be tricky in CAD. To manage this, we’ll simplify the mechanism if needed and focus on building sub-assemblies to isolate and refine specific movements. These strategies should keep us on track and help us tackle the complex moving parts without getting bogged down.
Figure 1: Eel Mouth Concept (hand-drawn)
Figure 2: Lips & Handle (CAD Drawing Render)
Current Status:
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The team has completed the first iteration of 3D CAD assembly
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More iterations and refinement will be completed for the Design Review Report
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Will serve as basis for 3D printing file
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FEA and Load Analysis still needs to be performed in COMSOL
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During the analysis, the geometry and dimensions of the design will be adjusted to avoid failure from stress concentrations, but there will be no major revisions to the overall geometry & shape
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Potential Failures:
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3D printing can result in user errors that can cause time delays
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3D printing courses will be taken over winter break to minimize the risk & prevent wasted time in the spring semester during fabrication
Final Design Description:
The device utilizes a lever-actuated mechanism that opens and closes the "tongue" for controlled clamping of a fitted sheet. The lever mechanism provides users with precise control over the clamping force, making it easier to secure the sheet in place. The upper lip portion of the device is designed similarly to existing market solutions, maintaining the tuck and lifting capabilities commonly used in bed-making. A seamless top end prevents the device from getting caught during the tucking process, ensuring smooth operation. The spring-loaded "tongue" provides the necessary clamping force to hold the sheet securely. The spring assembly consists of four metal coil springs arranged in a 2x2 array on the lower surface of the upper housing. These springs are housed in four pockets located on both the "tongue" and upper housing, ensuring proper alignment and stability. To secure the springs in place, epoxy adhesive is used for strong plastic-to-metal bonding, ensuring durability and reliable performance over time. This design effectively simplifies the bed-making process, especially for individuals with physical limitations.
Key Analyses
Stress Analysis For Material Selection:
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The maximum load capacity of the device is 100 N
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The area of the top section of the upper lip is 76.2mm x 20mm
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The tensile strength of eSUN PLA+ is 63 MPa
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Thus, the maximum expected stress on the top section is 65 kPa, well below the tensile strength and not at risk of breakage
To be at risk of failure, the cross-sectional area of a part must decrease to 1.6 mm². The design will ensure all cross-sectional areas are larger than 3.2 mm² and achieve a factor of safety of 2.
Spring Description Analyses
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The selected spring from “The Spring Store” has a diameter of 30 mm → allows 2 springs to be placed side by side along the 76 mm width, with a spring constant of 3.24 N/mm
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The desired clamp force is 70 N
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Each individual spring should exert 17.5 N of force onto the tongue → while the device is at its resting position, each spring will be compressed 5.40 mm
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The maximum allowable clamping force is 127 N, so the springs will be compressed another 4.39 mm when the lever is fully pulled back by the user
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This will lead to the tongue and bottom lip separating by 17.57 mm (~2/3 inches)
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Blog #4
Remaining Semester Work Overview
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The final weeks of the semester will be used to gather data from the Load and Stress simulations
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Adjustment of the device’s dimensions and handle geometry accordingly to ensure product reliability.
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Design revisions will also consider the fabrication process, i.e. the method for installing the compression springs into their housing
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Ensuring that the device can undergo a more intuitive assembly process during the fabrication process
During the Break :
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The 3D print filaments and spring components will be gathered, and the designated 3D print resource for the Spring semester will be selected
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The Harris County Public Library offers in-person orientation courses, which will be leveraged to make prototype fabrication less prone to user error.
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Additionally, SolidWorks offers a free, online course for “Additive Manufacturing”
Winter Break will be utilized to ease the transition from any addition design refinement to fabrication work, and educating the team on the 3D printing process
Blog #5
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From the work period of January 13 – February 1, we have finalized our 3D CAD along with the remaining technical analysis. The technical analysis includes our finished FEA of the pinhole in our device, showing that our material’s flexural strength will withstand the maximum stress load anticipated. We have also updated our milestones accordingly to account for up to 3 iterations of our prototype within the given time we have left for the semester. In addition, we added another milestone to help us optimize our prototype each iteration in which we will conduct preliminary testing on each prototype iteration to assess critical points mainly and to revise our 3D CAD with each iteration.
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For the work period of February 1 – February 15, the team will proceed with our prototype fabrication milestone and prepare to fabricate the first prototype. We will schedule allotted time with the Houston Public Library to 3D print our first prototype and conduct preliminary testing on it after assembly. This will allow us enough time to revise our 3D CAD so that we can schedule ahead of time to reprint our next iteration of our prototype.
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The biggest obstacle that the team will face over the next two weeks is determining how much time will it take to print just one iteration of the prototype and complete the preliminary testing for it. However, the plan to print each iteration in separate teams of 2 with each trip will exponentially speed up the process of 3D printing since it will divide the prototype into equal components for each team to print, thus reducing time overall printing just one iteration.
Blog #6
During this period, our team successfully 3D-printed all the necessary components for the first prototype of our fitted sheet inserter. Due to printer size constraints, we scaled the prototype to 80% of the original CAD model. This version allows us to test the assembly process with additional components, including springs, a pin rod, and securing nuts. The primary objective now is to evaluate the structural stability of the assembled prototype and assess whether any modifications are needed.
In the coming weeks, our focus will be on refining the design based on initial testing. The next major milestone is printing a downsized version of the device with an improved layout for ease of use and compactness. Additionally, we will begin functional testing to ensure that the mechanism properly grips and releases a fitted sheet as intended. If necessary, minor design adjustments will be made in CAD before producing the next iteration.
One potential challenge is ensuring the prototype remains stable when assembled with the pin rod and springs. If alignment issues arise, we may need to adjust tolerances in the CAD model. Additionally, the current material strength of the 3D-printed parts will be assessed; if weaknesses are found, we will explore alternative print settings or materials to enhance durability.
Blog #7
As we progress through our capstone project, the past two weeks have been pivotal in refining our design and preparing for upcoming demo testing and validation phases. During this work period, our team completed several key tasks and made significant progress toward achieving our project goals.
Over this period, we finalized CAD adjustments for our second iteration, focusing on redesigning the handle and lever to improve comfort and reduce printing time. Two prototype versions were printed—one at 100% scale for demonstration purposes and another at 50% scale as a backup. Additionally, with the transition to less stiff springs, we are revisiting our spring analysis from Capstone 1 to ensure optimal performance. Since adjustments were made to the tongue geometry, we also updated our Finite Element Analysis (FEA) model to reflect these changes accurately.
Over this period, we finalized CAD adjustments for our second iteration, focusing on redesigning the handle and lever to improve comfort and reduce printing time. Two prototype versions were printed—one at 100% scale for demonstration purposes and another at 50% scale as a backup. This second iteration printing phase was significantly faster due to our use of the UH MECE department printers, along with the addition of a second, much faster and higher-quality printer at the HPL location we previously used. Additionally, with the transition to less stiff springs, we are revisiting our spring analysis from Capstone 1 to ensure optimal performance. Since adjustments were made to the tongue geometry, we also updated our COMSOL model to reflect these changes accurately.
One potential issue we foresee is the need to replace the springs, which may prove challenging as our device is currently super-glued together, making component swaps difficult. To address this, we are exploring alternative jointing and cut-out methods that would allow for easier disassembly and adjustments while maintaining structural integrity.
Figure 1: Second Interation (50% scale) - Tongue & Lower Housing
Figure 1: Second Interation (50% scale) - Complete Device
Blog #8
2 full-scale prototypes have been created thus far, and a major problem that has continued to beset their success is the stress concentration near the fulcrum of the tongue and lever overwhelming the device and causing the lever to snap off the tongue after repeated use. This major problem has prevented the group from gathering desired validation data.
From March 22nd to April 12th, the focus of the group has been to iterate upon the design to prevent the device from failing after repeated use. The following steps have been taken to mend the issue:
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The initial prototypes tended to use a smaller infill density of 20%. For the third iteration, 60% infill density will be used to create the tongue and lever. We expect this will allow the internal structure of the part to distribute stress much more evenly thus reducing the potential of stress concentration failure.
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In prior designs, the lever emerged mostly behind the fulcrum, leading to a lot of stress along the edge of the lever facing the tongue when the device was activated. For the third iteration, the lever has been translated to be in front of the fulcrum to avoid the tension stress developing. This will result in stress concentrating along the back edge of the lever.
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Superglue will be pre-emptively applied to this high-stress edge as a preventative.
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The design of the lever has also been slightly revised, adding a thicker base nearer to the fulcrum to reduce stress by increasing the potential area for stress concentration.
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During the fabrication process of the 2nd prototype, a small 50% scale prototype was created to experiment with to gather ideas and concepts for improvement. The lever broke off the tongue for the prototype as well, and afterwards a small hole was drilled into the lever and tongue, a small metal rod lubricated in super glue was inserted into the lever and tongue, effectively bonding the two separated parts together. After drying, this rod was able to firmly bond the lever and tongue together after breaking. For the third prototype, a metal rod will be similarly inserted preemptively as rebar-style reinforcement.
Further revisions were made to improve the ergonomics of the device such as smoothing the edges of the device to prevent possible sheet tearing or poking and redesigning the handle to be more comfortable.
Current validation results are inadequate. As previously mentioned, the existing iterations have been subject to failure before proper validation can be conducted. However, prior to the 2nd prototype breaking, the device was able to successfully perform a fitted sheet tucking operation
The 2nd prototype was also capable of lifting a mattress beyond the desired goal without any visible structural deformation; the mattress lifting portion of the device has presented no issues.
The group is not satisfied with the achievements thus far, mostly due to the lack of validation, but that the 2nd prototype was able to perform a sheet tucking maneuver prior to failure inspires confidence that after that major problem is overcome, we will be able to gather the desired data.
The group is currently in the process of fabricating the third prototype. The last remaining weeks of the project will be dedicated to performing our validation plan to measure the success of our project. Once the 3rd iteration is completely fabricated, the validation plan described in the table below will be executed and recorded.
Team 23 Poster
