Preliminary Detailed Design
Team Vision for Preliminary Detailed Design Phase
Our goals for the first half of the detailed design phase centered around finalizing system and subsystem design concepts, generating 3D renderings of those concepts, translating engineering requirements into future test plans, performing feasibility analysis on our concepts, and beginning to consider material selection for our subsystems.
Finalized Objective Statement
Our objective is to design a product that enables disabled individuals to enjoy trapping / kicking a ball.
Updated Systems Architecture
The working systems architecture depicts the mass, information, and energy flows of the system. The diagram displayed below represents the current design the team is working on however in the link you will find a different artchitecture representing an alternate design the team came up with.
A link to the working Systems Architecture flow diagram as well as additional description and design alternative architectures can be found here.
Feasibility: Prototyping, Analysis, Simulation
- The goal in terms of the frame is to design it such that it could incorporated and attached securely to a large variety of mobility aids including both power and manual wheelchairs. It has yet to be decided on what exact type of material to use construct the frame, however given its properties (easy to weld, lightweight, color coating, not too expensive, durable, and malleable) at the moment we are thinking of using 4130 Chromium Steel. The following images are renderings from solid works of the new proposed frame in a side and isometric view:
- In order to maintain the focus and goal of the frame it must be able to adjust in various ways. It can be adjustable in the z-axis to accommodate for various user waist sizes. It can be adjustable in the y-axis to accommodate for different user heights. The frame idea was based off the previous design by the customer.
- In addition, to implement the previous semester’s design of a striker this frame could potentially work for both devices that involve the upper extremity and lower extremity as shown below:
- For this frame to attach to a large variety of mobility aids the attachments are required to be interchangeable. To allow for that the bat can be removed and the different attachments can be placed. The cut out of the attaching mechanism for manual wheelchair involved a concave shape to accommodate for various diameters of bars that it will connect to. Given that concave shape it could be universal for any given bar diameter. On the other hand in regards to the attaching mechanics of a power wheel chair the attachments will clamp on the side of the chair producing an inwards force, whereas on the manual wheel chair the attachments produce an outwards force. An exploded view of how the attachments and locking mechanism are matted together is shown below:
- The locking mechanism requires the following formula below where there is an origin, a y value, x-value and some constant. To mimic the locking behavior the y-value must be greater than the x. Therefore to enable it to lock y must equal the sum of x and some allowable deformation. This deformation depends on the type of material this locking mechanism is made out of. Given that it must be slightly deformed at the moment thermoplastics are what we are thinking of using. In addition, a drawing shows how the attachments will lock in place to the different wheelchairs shown (power and manual wheelchairs).
- Below is a diagram that compares the previous frame the customer had designed to the new proposed frame:
Inputs and Source
- Engineering Requirements
- Concept Selection
- Results of preliminary prototyping, analysis, and simulation
Outputs and Destination
- A list of Design Parameters, Quantified Targets, and acceptable tolerances
- Sensitivity analysis
- Refined concept Selection
- Drawings, Schematics, Flow Charts, etc.
Drawings, Schematics, Flow Charts, Simulations,Feasibility
User Interface Modeling
The user interface was CAD modeling in SolidWorks 2017. The primary plan is to make modifications to a road bicycle shifting mechanism because of its compact indexing nature to close the arms and preload the launching mechanism.
The following is a contingency plan and the SolidWorks model of the user interface if the usage of the bike shifting mechanism becomes unfeasible. The system works similar to a bicycle shifter, utilizing an indexing ratcheting gear with a quick release mechanism. In addition to the model shown, small modifications will be made to attach a cable to the ratcheting wheel, and ergonomic levers to the device for preload and launch.
The cable will then be split using a cable tripler to attach to the arms and launcher assembly shown in the following section. Shown below is an example of a cable doubler which will be modified to accommodate splitting into three cables instead of two.
Catch and Launch Modeling
The Catch and Launch system was CAD modeled in SolidWorks 2017. The system contains many parts included a base, arms, pins, launcher, and a spacer.
The base, arm, and launcher in the un-launched position, respectively.
The whole system assembled in the open and ready to catch position can be seen below:
The whole system in the closed position, with a ball caught and ready to launch can be seen below:
The whole system in the process of launch was mocked up in SolidWorks and can be seen below.
Each element is at a different height to avoid accidental collisions. This allows the arms to overlap in catching and the launcher to travel over the arms. This height distribution can be seen below:
The working SolidWorks 2017 files can be downloaded here.
As part of the development of these models we ran calculations to determine rough values we would need to have for the catch and launch system. Below is a quick graph of our input values, developed from our engineering requirements and design development and the corresponding values that we got out of those inputs.
To better understand the functionality of the device, a functional system timing diagram was developed based on the key subsystems of the design. The diagram incorporates rough approximations of time taken to accomplish the high level functions required of the device. The diagram is investigating the timing taken by the cantilever arm design specifically.
A link to the working Timing Diagram can be found here.
Bill of Material (BOM)A preliminary BOM was constructed in order to begin accounting for expenses and determine whether we will be able to deliver our product within our allowed budget. This activity caused us to rethink some of the choice of parts and materials that we had previously picked.
Our live preliminary BOM can be viewed in Google Sheets. A preview is shown below. Exact quantities and costs have not been finalized thus far in the design phase.
Input and Source
- Design Files.
Output and Destination
PurposeOur test plans are at a preliminary stage at this point, and will continue to be updated as the design is finalized. The image below is a snapshot of our current User Testing plans. These were designed based on our use cases and engineering requirements, focusing on the aspects of the device that are most important to the end user. In the future, we will add test plans for specific subsystems, which will be populated to the Detailed Design page.
A link to the live-updated version of our test plans can be found here.
Inputs and Source
Outputs and Destination
- IRB Submission, if applicable (allow at least 30 days for this to be reviewed - more time is idea, since the IRB outcome may be a request for you to modify your proposed test protocol)
The risk analysis was updated from last cycle and a link to the working risk assessment document can be found here. The risks are categorized and ranked based on a product of their probability of occurence and severity if they were to occur. The scaling is a 1-3-9 system where 9 is most important and 1 is least important.
Design Review Materials
Our PDDR Slides were created on Google Slides and presented on Thursday, November 16th at 12:30 in GLE-4425.
Plans for next phaseAt the end of phase 3, our team reflected on our work so far for the current phase. We went back to our Individual Plans for Cycle 3 and compared our predictions to what we actually worked on during phase 3. We also reflected on some of the things we learned during the Preliminary Detailed Design phase.
Then, to be better prepared for the next phase, our team took a look at the upcoming deliverables due for the next phase. We came up with task lists for the individual work that we would complete to contribute to our Phase 4 Design Review. The Individual Plans for Cycle 4 were created as a Google doc and will be updated after the completion of Phase 4 with what we actually did and learned during Phase 4.
In terms of overall project planning, the next phase will primarily be focused on improving and adding final details to our design so far. In addition conducting more complex prototyping, we will make final decisions about materials and components, and begin to identify suppliers to order from. These changes will be updated to our Bill of Materials (BOM). We will also finish test plans, to be used in MSD II while we build the prototype. As always, we will continuously update risk management.
Our team is continuing to use Trello to track and assign individual task information. Our Trello board can be viewed here.