System Level Design

Team Vision for System-Level Design Phase 

Our goal for the system level design phase was to start breaking down the overall system design into various subsections. We also planned to look at previous years progress and determine the functionality, shortcoming, or failures with the current design of the device and see where improvements can be made or what needs to be redone. We hoped to identify selection criteria that would help us narrow down these design concepts for a final deliverable of 1-2 concepts we hoped to move forward with in the preliminary detailed design phase.

During this phase of the project, our team was able to understand the shortcomings of the current prototype as well as some of the design limitations that may exist. This helped us to understand how the components in the system interact with one another, as well as which ones would need to be improved upon. When compared to the customer requirements, the team determined that the best course of action would be to redesign the prototype entirely to improve comfort and stability along with aesthetics.

Next, our team was able to complete a functional analysis and functional decomposition tree for our new product given the customer requirements and a complete analysis of the current prototype. We used this in combination with the original bench marking document created in phase 1 to identify a range of ideal operating conditions that the new design would be able to satisfy. Given this information, we were able to understand the metrics we would be able to test to. This also helped us develop a detailed feasibility analysis document for the Preliminary Detailed design phase.  

After we fully understood the functional analysis, and current shortcomings, we each came up with possible design concepts to satisfy each function of the new design. After each member developed their own detailed list, the duplicates were removed, and a morph chart was created of all possible design concepts to consider. As a team, we went through the morph chart and determined two possible designs to consider. Using the selection criteria and the PUGH chart, we came up with one design concept we will be moving forward with in the preliminary detailed design phase.

Figure 2.1: P21011 Phase 2 Project Plan

Functional Decomposition

Figure 2.2: P21011 Functional Decomposition

A functional decomposition was created based off the customer and engineering requirements and is included above. The goal of a functional decomposition is to compile a list of main functions a final design needs to include. We decided that the overarching function of our project, CHAD for Toilets, is to assist wheelchair users to go to the restroom. In order to do that, the design needs to do the following things:

1. Adjust the toilet seat height to user
2. Provide comfort and support for the user
3. Aid sanitation and fit to current toilet system

From there, we broke them down to specific ways in which the design should meet these functions. These were then used to influence the individual components selected later on down the road.

This document can be found here and is owned by Gina Wilson.

Benchmarking

Purpose

Benchmarking was complete to determine what is currently on the market that is similar to the prototype created. The team was able to find 10+ different products on the market that would perform similar functions. (WAR is included from last years) These products helped the team develop ideal ranges in which we would like our product to function.

Many of the current functions on the market serve their purpose and can only do some of the functions not all. Almost all of these designs were also made for in home use instead of a public restroom setting.

Figure 2.3: P21011 Benchmarking Comparison

This analysis helped our team develop desired ranges for our key parameters:

Weight Capacity: 350-400 lbs

Weight Capacity arm rests: 200-250 lbs

Degree of Tilt: None

Vertical Travel Distance: 13" - 28"

Total unit weight: 20-40 lbs

Price to customer: No more than 1,000$

Must have aesthetic arm rests!

The Live benchmarking document can be found here

Concept Development 

Purpose

After studying the previous year's team design, P20011, as the team we determined that in order to better meet the needs of the user, the design needs to be reworked in order to be more visually appealing to the user as well and offer more features that allow for easier transfer on and off the device and facilitates a more efficient and more sanitary process for using the restroom, whether in a public or private setting. To begin brainstorming new concepts, each of the essential functions were taken from the Functional Decomposition, and several new concepts for each function were generated. The concepts were generated from taking ideas from the benchmarked products, the customer requirements, as well as new team generated solutions determined from out of the box brainstorming. 

Initial Concept Generation

Each team member had a role in this initial concept generation process, the idea was to generate as much as ideas as possible and not every idea has to be high quality. Some ideas came from similar ideas from benchmarking or others were "out-of-the-box" ideas, that we may not directly use but may inspire other ideas for new concepts. A few of the ideas for each of the essential functions of the device are pulled out below. 

Concepts Developed for Adjusting Seat Height to User:

Figure 2.4: Concepts Developed from Left to Right: Hydraulic Lift System, Pulley System, Inflatable Lifting Toilet Seat, Compressed Air Life, and a Slider Crank Mechanism.

There are pros and cons with all the different portions of the concepts listed above, the hydraulic lift system may be a useful concept since we would just need to tap into the existing water line, the pulley system would allow more open floor space around the toilet but may be unstable. Similarly, the inflatable toilet seat may provide open floor space around the toilet but may be unstable or material issues with sanitation may be an issue, the compressed air lift may be a good alternative, but the crank mechanism may take up too much space to be utilized. 

Concept Development for Aiding Self-Cleaning

Figure 2.5: Concepts Developed from Left to Right: Bidet, Large Access Space from Behind and to the Side, Side Guide Rails/Armrests for Leaning

The bidet could be an ideal option for the user since, it would reduce the amount of time the user will be needing to complete self-cleaning procedures after using the restroom and is a feature that some of the benchmark products have, the large access space may be useful if the user does not need as much support when going through the process, however it is more likely more support is needed for majority of users. The armrest, are an important feature that could be used, since it enable to user to be stable and lean to the side during the cleaning process and could lead to a more efficient process. 

Concepts Developed for Providing Support to User

Figure 2.6: Concepts Developed From Left to Right: Hinged Torso Support, Pull Bar from Ceiling, Amusement Park Ride Style Harness, Fixed Armrests, Hinged Armrest. 

Having the hinged armrest could allow for the user to slide up the armrest to allow to slide onto the seat easier during transfer but still allow for support during cleaning, as with the hinged torso bar. Additionally, the bar from the ceiling could allow for support if needed but is not the most practical design. Neither is the ride harness since this could limit access during cleaning. The fixed armrest are a good concept that just allow for stable support throughout the process. 

Concept Development for Providing Comfort

Figure 2.7: Concepts Developed From Left to Right: Padded Toilet Seat, Padded Armrests, Padded Torso Support, Padded Back Support. 

Having a Padded Toilet Seat could provide comfort for a user in a private setting but in a public setting it may be too unsanitary to utilize depending on the material. The padded armrests would be a necessary feature if the user will need to lean on the structure for self-cleaning and the same goes for the padded torso bar. The padded back support is an idea, but may not be as necessary as some of the other concepts generated based on the current customer requirements. 

Above lists and shows some of the examples of the different concepts generated for each of the functions of the device. As we move through the semester, some new concepts will continued to developed as the project moves forward, based on testing of prototypes, concept analysis, and changing customer requirements. 

Feasibility: Prototyping, Analysis, Simulation 

Purpose

CHAD for wheelchair users is an ongoing project currently on its 4th generation. Through benchmarking it is shown that there are multiple similar products currently on the market, but none that meet the exact specifications we are working to meet with our prototype. We are confident in the feasibility of our current project concepts. For this reason, the feasibility analysis is narrowed down to focus on the aspects of our project that are more unique from other assistive restroom devices available for consumers now. In particular, a key difference between the P21011 project and P20011 project is the change of a tilting functionality to a vertical lifting function powered by hydraulics. The team also has chosen to focus on incorporating comfort and sanitation into the design of the prototype. Each idea of comfort or sanitation seem feasible to include in the final concept selection. 

Analysis

The customer requirements include finding a solution to better the ease of cleaning and self sanitation. The team decided the best way to do so is by designing a bidet attachment into the seat of the device.  

For both support and ease of cleaning, a team has decided on using hinged arm support bars and a torso support system. 

They will need to meet all engineering requirements set for the project. S1 under Ease of Use/Comfort requires the arm rests hold a weight capacity of 200lbs - 250lbs. The armrests must also be placed apart at an inside distance of at least 23in - 27in according to engineering requirement S7, based off of the average distance between the arms of a wheelchair. The torso bar must also support a weight capacity of up to 200-250lbs and must be easily moveable for ease of access, S6. The bar should be able to be lifted out of the was for ease of access to the seat. 

As mentioned before, last year’s team focused on adding a tilt function to the hydraulic lift design. After reviewing their work and speaking with the client, the possible risks involved with a tilt in the lift were mentioned. The team was concerned that while feasible engineering wise, the tilting aspect would increase the fall risk for those using the device with little to no lower body mobility. We have decided to instead have the device lift the seat vertically up and down following the set of engineering requirements shown below: 

Based off of the customer and engineering requirements, the team was able to put together a morphological chart to help us complete the final concept selection. Overall, the current devices on the market and previous project concepts are a starting point to meet the the final goal set for the device. There is not a device currently for sale that includes every factor that we have decided to incorporate into our design, and we have decided to change course from the previous teams design to better meet all of the requirements we have set for the project. 

Morphological Chart and Concept Selection

A morphological chart was created with the most viable options created during our initial concept development. From here, we went through and selected the ideas we liked the best and felt as though would combine well to create a feasible and reasonable design. The figure below shows our morphological chart, with blue highlights denoting our first choice of design, with purple denoting a backup design.

Figure 2.8: P21011 Morphological Chart

Our main design (blue) refers to a design with the following elements. We intend to mount the device to the wall and use a hydraulic system to raise and lower the seat. This design will incorporate at least one arm rest that can fold up to get out of the way to allow for clean transfer from the side while utilizing an existing toilet seat. This design also includes a movable torso bar which would allow the user to lean forward for support, without falling off. It would also include some sort of padding on said torso bar to make it more comfortable. In addition, this design may include a bidet to allow for easier self cleaning.

Our secondary design (purple) refers to a design with the following elements. We intend to mount the device to the floor and use a motorized system to raise and lower the seat. This design would use fixed arm rests in order to provide the most sturdy of support while replacing an existing toilet seat with one attached to the device. It would include a strap or belt to keep a user from falling off without the use of a torso bar. Self cleaning would also be aided simply by the use of arm rests to hold or lean onto. Since this design has no torso bar and relies on the arm rests for a decent amount of support, the arm rests would be padded in an attempt to make the whole experience more comfortable.

This file is owned by Gina Wilson can be found here.

Concept Selection 

The team chose each of the 4 concepts analyzed in the Pugh chart after conducting benchmarking and feasibility and building the morphological analysis. Both of the concepts from the morphological chart and two of the benchmarking on the market devices  closest to our final concept goal were compared against last years Articulating Toilet MSD team P20011. The Pugh chart is a tool used for evaluating multiple options against each other. Rather than basic consideration of the pros and cons of each funding option, the Pugh chart gives a holistic overview of the needs, goals and other important criteria for the team versus the available alternatives.

Figure 2.9: P21011 Pugh Chart

* The hydraulic system is the closest to last years design, while incorporating the ideas from this years current team to better address customer and engineering requirements. With a net score of 1, it has been ranked #1 showing the most possible improvement to the current prototype and filling any gaps that currently exists in on the market devices. 

*The motorized system is closer to what is currently on the market, and is the most feasible to prototype after the hydraulic system.  Due to the electrical components the ease of cleaning and simplicity of design and maintenance were disrupted, ranking it the lowest out of the 4 concepts compared. It is farther away from the customer and engineering requirements but is more technologically feasible for the team, so we decided to include the concept over some of the other possibilities from the morphological chart. 

*The Disabled Wheelchair Seat Chair is a great currently on the market example of a seat that has both comfort and function. The padding around the device and the level of support it provides is important to our final design, but it is stationary and is lacking the lift component necessary for our prototype 

*The Mountway Solo Toilet Lift has the lift functionality we are looking to include in our device and is the most aesthetically pleasing out of all of the benchmarking devices. The seat does not provide any sort of support for wheelchair users, and the lift function tilts instead of rising vertically. It was chosen because the devices design is welcoming to the user. The cost of the system is something the team was concerned about, as our goal is to keep the prototype cost at or below $500, and this system is over double that. 

Our final concept selection is a hydraulic lift seat with a removable torso bar that has the level of comfort and support of the wheelchair seat, and the welcoming design of the Mountway lift. Our prototype following this concept selected should meet all customer and engineering requirements. Pricing and materials will be evaluated further as the team progresses with the chosen concept. 

Systems Architecture

Figure 2.10: P21011 Systems Architecture Diagram

Starting from our functional decomposition, and Concept Selection, the overall system was broken down into subsystems that perform those functions. The device structure will provide the overall stability, the wall attachment will help stabilize the system against against horizontal forces, and the toilet attachment will stabilize against vertical forces. The user support system is broken down into three subsystems: Arm support, Torso support, and the toilet seat attachment. The arm and torso support are intended to support the upper body of the user, while the toilet seat attachment will support the weight of the user. The user cleaning system is composed of the bidet and the water supply to the bidet, which will aid in the user's cleaning process. The lifting system encapsulates the actuation mechanism, the power source for the mechanism to function, and the user input to control the vertical motion. In the case of a hydraulic system, water will flow into the mechanism to provide power to lift the user upward, and will exit through a return path into the toilet. This system will function as the vertical support between the device structure and the user support system 

Mass flow: waterline → Hydraulic mechanism and bidet→ toilet

Force interactions  user → seat → lift mechanism → structure

Designs and Flowcharts 

Purpose

The purpose of this section is to give a high-level overview of the elements that are going into the system (our device) and how they interact with the different subsystems of our device and how the different sub-components within our system interact with each other. The chart shows the subsystem interfaces and the projected system operation. The potential failure modes of the device are also discussed. 

Document owner: Hannah Husarek

Flowchart:

Figure 2.11: This flowchart shows the different elements coming into the system, and the different interaction between the different components. 

The development of this document began during the system level design phase but the development of this chart will continue during the subsequent phases, the link to the live document will be found here.

Some potential Failure modes of the device include the hydraulic lift system, not responding to the lift controller commands, which would prevent the user from user from using the device as intended. Another is the lack of pressure from the water line, which would prevent the seat from rising.

Risk Assessment 

The only new risk we found was the possibility that the hydraulic system is not rated for the water pressure, causing it to rupture. We will need to take this into consideration when designing the lifting subsystem.

Design Review Materials 

Include links to:

• Pre-read
• Presentation and/or handouts
• Notes from review
• Action Items

Plans for Next Phase

Team Level Goal:

The team level goal for the next phase is to determine how the different subsystems are going to interact with each other and how the team is going to deal with the different interfaces between each subsystem. During the next phase, we plan to complete a sketch of the completed system with approximated dimensions, which we will then use to design an almost complete, to a complete CREO model of the device. Additionally, from the model we will determine if changes are needed to be made in terms of component design, if determined unfeasible. Material research will be conducted to greater extent in order to determine the best materials that provide strength as well as ease of sanitation. Towards the end of phase, at the completion of material research, materials may be purchased to test quality and cleanliness standards.  Moreover, the old hydraulics system will be analyzed and tested to see if functional, otherwise a new hydraulic system will begin to be redesigned or reworked. Additionally, bidets will be researched to see how the product can be integrated into the toilet fixture. 

Individual Three Week Plans:

• Hannah Husarek
• Jared Moore
• Gina Wilson
• Kaylie McEntire
• Chad Wake