P17011: Wheelchair-Accessible Restroom

Systems Design

Table of Contents

Team Vision for System-Level Design Phase

Plans For This Phase

During this project phase, we set out to expand the stakeholders interviewed using their input to refine our understanding of the problem. We were able to take this additional input to reiterate through many of the deliverables for the previous phase. Simultaneously we began to develop key functions, product concepts and a systems level design.

What We Accomplished This Phase

We conducted interviews with several more users, caretakers, architects, and facility managers. From these we reiterated through the steps of problem definition. Using this information we developed key functions, product concepts and a systems level design.

Functional Decomposition

The process needed to meet the customer and engineering requirements was broken down into its smallest pieces, displayed below in the functional decomposition.

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During this phase, we chose to narrow our scope and remove some of our functions. This will allow us to better meet our client's needs (notice that our customer and engineering requirements are mostly unchanged) without spreading the project too thin for other potential stakeholders.


To continue our benchmarking process, we looked at our client's bathroom, which is the best available solution for him on the market. However, it still doesn't fully meet his needs. Comparing this to our solution will be very helpful in the coming weeks.

Concept Development

Each function received a series of potential implementations, which were then sorted (we used sticky notes and a whiteboard to get everything organized). Some sample photos are below, and the full file can be found here.

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Feasibility: Prototyping, Analysis, Simulation

The section of the system that needed feasibility research was the seat mounting subsystem (i.e. the lifting mechanism and the joint connecting it with the seat).

For the lifting mechanism, we did research on hydraulics, mechanical lifters, and linear actuators. All three methods were able to provide the lift required, but mechanical systems were limited by bulk, and linear actuators are significantly more expensive. Because of these limitations, future testing will be done with a hydraulic bottle jack.

A rough analysis of the moments and forces acting on the location of the joint ended up requiring FEA, which will be done once we have CAD models done.

A small comparison chart of the specifications of our options can be found here.

Morphological Chart and Concept Selection

Individual concepts from the functional decomposition were addressed and put into a morphological chart:

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These concepts were then built into system-level concepts and compared using a preliminary Pugh chart.

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After the first round, six "semifinalists" were chosen and put into a second Pugh chart. They turned out to all be relatively similar, which helped with producing the system architecture and choosing directions for feasibility research.

Systems Architecture

With all functions in mind, we developed a systems architecture.

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Designs and Flowcharts

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Risk Assessment

Risk assessment has been expanded to account for design changes and growth. The primary additions revolved around the more clearly defined system and its new components.

With a more clearly defined set of risks, assignments have been made to individual group members or to subgroups.

The updated FMEA can be found here.

Design Review Materials

It might be helpful for you to see our "semifinalists" from the concept selection phase. You can see all of the similarities and get a general idea of what kinds of features the implementation would have.

The review presentation might be useful as well.

Plans for next phase

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