P17011: Wheelchair-Accessible Restroom
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Preliminary Detailed Design

Table of Contents

Team Vision for Preliminary Detailed Design Phase

What we planned to accomplish:

During this phase, we intended to solidify our concept selection, flesh out our subsystems, and begin planning for testing.

What we accomplished:

We made progress solidifying our concepts, but don't have it fully defined yet. There are still some unknowns in the lifting mechanism and the overall balancing of the device (we need to account for the cantilever). The other subsystems are more defined, and test planning is underway.

Feasibility: Prototyping, Analysis, Simulation

Mounting Options

The first goal for narrowing down our concept was to decide between a floor-mounted setup and a toilet-mounted setup. We had a feeling that the floor-mounted setup would be more stable, but it needed proving. To do this, we looked at the stresses in the toilet with normal loading and compared them to those with the cantilevered loading. The stresses with the cantilever were twelve times higher, so it can be assumed that this loading is beyond the limit of the toilet's design. This allowed us to rule out the toilet-mounted seat.
Our model of a normal toilet

Our model of a normal toilet

The stress on the toilet with normal loading

The stress on the toilet with normal loading

Our model with the basic loading setup of the cantilever's worst case

Our model with the basic loading setup of the cantilever's worst case

The stress on the toilet with the cantilever

The stress on the toilet with the cantilever

Seat Lifting Mechanism

Both of these setups require the rack-and-pinion lifting mechanism we've chosen to bear the weight of the user. We needed to find our rack's dimensions to keep it from buckling.

Rack buckling calculations

Rack buckling calculations

The major unknown with this system is the actual lifter, which we've pulled from the seat of an old VW.

The lifting mechanism

The lifting mechanism

We don't know the lifting capabilities of this mechanism. We're going to make the assumption that it can hold as much weight as we need it to, but we'll be doing testing to make sure it's safe to use before we let humans use it.

Portable Hand Clamps

We also investigated the portable clamp idea, and it seems like there isn't a good way to implement it without impeding transfers or risking the safety of the user or toilet. The idea is sidelined for now while we look at the possibility of using our armrests to address the need of hygiene.

The portable handle concepts

The portable handle concepts

Armrests and Backrest

Finally, there were some calculations to check that the armrests and backrest can bear the necessary load. Because the forms aren't final yet, we didn't put too much time into it, but the backrest will need to be thicker than we had originally planned.

The armrest limitations

The armrest limitations

The backrest changes

The backrest changes

Drawings, Schematics, Flow Charts, Simulations

Drawings and schematics will be available when our parts are fully designed.

Bill of Material (BOM)

Because our system is not fully defined, we don't have a complete list of necessary materials. The BOM will not be filled out until we have our systems ready.

Test Plans

ID Testing Criteria and Method

Engineering Preliminary Testing Plan

Design and Flowcharts

Our systems architecture has had a few changes in this time period, primarily the removal of the portable clamps and the possibility of a telescoping mechanism on the armrests.
The systems architecture

The systems architecture

Risk Assessment

As our systems change, we are continually updating our FMEA.

Design Review Materials

Our presentation for the Preliminary Detailed Design Review can be found here. The final two slides of this file contian the comments and action items from the presentation.

Plans for next phase

Our plan for the detailed design phase can be found here.

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