Team Vision for System-Level Design Phase
During the systems level design phase our team sought out to understand the shortcomings of the current prototype and develop a list of solutions that would allow the system to function in a manner that would satisfy the customer's requirements. Our team planned to identify and map the functions of our design and develop design components that would satisfy each. From this, the team aimed to develop design concepts that combined these components. 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. The team spent one day at the prototype measuring and testing the functions of the design. 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 meet the customer's needs.
This analysis in combination with the customer requirements allowed us to complete functional analysis and a functional decomposition tree for the new product. 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. These developed ranges allowed us to understand what metrics we would be able to test to, and helped the team develop a detailed feasibility analysis document for the next project phase.
These findings helped our team to design concepts to satisfy each function of the new design in a thoughtful manner. After all team members developed design concepts, duplicates were removed and a morph chart was created of all possible design concepts to consider. The team decided to meet with a licensed plumber to discuss each concept and some of the benefits and concerns with each. This meeting also helped our team understand some of the plumbing considerations and standards we would need to take into account in our final design.
These concepts were then combined to create 27 design options, which were narrowed by team members after much discussion and a voting session. Each team member voted on their top design choices which led us to 5 designs for consideration. Using selection criteria these designs we were able to develop one design concept we will be moving forward with in the next phase
Using the Customer and Engineering requirements the team was able to identify a list of key functions that the final design of the articulating toilet much include.
First it was determined that the overall function of the toilet is to assist handicapped users in going to the rest room.
In order to meet this function the system must do 3 things:
- The seat position must adjust for ease of transfer
- The product must provide the user support
- The product must provide clearance for the user to take care of personal hygiene needs.
These functions were then further broken down to help determine what components would be needed in the final design. This document will be updated as needed throughout the life cycle of this project.
About the DocumentThe functional decomposition document is owned by the teams lead engineer - Daniil Sushko
The document will be reviewed throughout the life cycle of the project, and if it is determined that a function has been missed, the document will be updated accordingly.
The functional decomposition live document can be found here.
PurposeBenchmarking was completed to offer the team a view of the products on the market that serve a similar functionality to the prototype created. During the benchmarking phase the team was able to identify 12 products (including the prototype created last year) to collect data from.
These products were used to help the team develop ideal ranges in which we would like our new product to function. Many of the products currently on the market served some - but not all of the desired functions that the customer would like to see, and almost all were designed for an in-home restroom rather than the desired public restroom facility we are designing for.
This analysis allowed our team to develop idea ranges for a series of our key design parameters including:
- Weight Capacity: 450-550 Lbs
- Degree of Tilt: No more than 45 degrees
- Vertical Travel Distance: 8-13 Inches
- Total Unit Weight: 20-40 Lbs
- Price to Consumer: No more than $2,000
The benchmarking live document can be found here.
The benchmarking document is controlled by Marlon Naveda and will only be updated if it is determined that there is has been a shortcoming in the range the team has determined appropriate.
As of current, it was determined that the prototype created by the P190011 was the design that most closely meets the needs of the customer, but through analysis it was determined that there are many components of this design that need reworking. Using the benchmarked products in combination with the customer requirements, engineering requirements, and shortcomings of the current system our team was able to develop a series of concepts to meet each of the required system functions.
Tools used to Develop Concetps
- Function Decomposition: As mentioned before under our "Functional Decomposition" section, the team was able to develop a list of functions that we want our product to accomplish. Those functions were then broken down into separate sub-functions, which gave birth to our functional decomposition function tree, which can once again be viewed here.
- Results of Benchmarking: Our initial benchmarking analysis involved each team member conducting research on various products whose functions are comparable to our prototype. The next step had the team think of a set of desired ranges for each benchmarking parameter. These results can be viewed here.
- Analysis and Prototyping: The team visited the current prototype to identify shortcomings, strengths, and dimensions.
Current Prototype Shortcomings
On Tuesday, September 24th, 2019 the team decided to go directly to the livability lab during class time. The purpose of this visit was to gain as much information on the current state of the prototype. How many issues exist with this most recent design? What are these issues and how can they be resolved? By making observations and conducting some light testing, the team was able to obtain a good idea of which functions/sub-functions and components might require re-design or any modification. The list of shortcoming that exist with the prototype can be seen below:
- The hydraulic cylinders stick and are unable to move whenever they are fully compressed and at the lowest height.
- The lever that adjusts the occupant's height is extremely loose and detaches itself with minimal required force.
- The bar that is attached to the rear side of the prototype becomes loose when the frame is raised.
- There is not enough clearance between the rear side of the prototype and the rear side of the toilet.
- The current arm supports are short, bulky, and can only be adjusted to one single orientation/position.
- The hydraulic cylinders sometimes tend to raise and lower at uneven paces, which leads to the prototype unintentionally tilting to one side.
- The prototype base width is currently really narrow, which might make this design incompatible with certain toilets/bathrooms.
- This current design does not provide the occupant with any torso support whatsoever.
- One of our customer requirements states that the prototype should be able to tilt forward/backward when desired. The current prototype does not include any tilting options or features.
A full document detailing how the team plans to go about fixing these limitations can be viewed here.
Concepts DevelopedThrough analysis our team was able to develop design concepts for the following components:
1. System Mount:
Figure 2.6: (Left to Right) Motor w/ Rack & Pinion, Hydraulic Pistons, Lever Operated Hydraulic Jack, Motor w/ Chain & Sprocket, Wheel w/ Rack & Pinion
Figure 2.7: (Left to Right) Two Lifting Mechanisms, Axis Platform, Adjustable Back Bar, Adjustable Front Bar, Elevating Pole
Figure 2.8: (Left to Right) Swinging Arms, Hinge Up Arms, Telescoping Arms, Rest Above Tank, Auditorium Desk w/ Arm Rest, Button Adjustable Arms, Fold Up Arms
Figure 2.10: (Left to Right) Adjustable Strap, Hinge & Snap to Front, Lowered Swinging Bar, Snap On Bar, Telescoping and Lock w/ Pegs
Feasibility: Prototyping, Analysis, Simulation
PurposeSince this project has been completed several times in the past and there are multiple similar products that we found throughout our benchmarking, we can be confident in the feasibility of a good portion of the project. For this reason, the feasibility analysis was narrowed down to focus on the aspects of our project that are more unique. In particular, a key difference between the P20011 project and P19011 project is the addition of a tilting functionality powered by hydraulics. The team also agreed that it was critical to determine the hydraulic piston sizing early on, in order to ensure that the product fits around a standard toilet.
AnalysisFirst, here is an analysis of the lift piston sizing. This is determined based on the case that the device is installed in a bathroom with very low supplied water pressure and is used by an individual at the maximum load capacity of the device.
We can also compare this calculation with the requirements defined by the ADA related to toilet placement in accessible stalls to ensure that there will be sufficient space for the hydraulic pistons between the toilet bowl and any walls.
Based on this information and prior benchmarking, we can determine that there is at least 8” of space between the toilet bowl and the wall, so there should be plenty of room for the hydraulic pistons.
Next, we looked at the tilting functionality of the product. From the initial benchmarking analysis, four of the comparable products included tilting functionality. Of those four, the average tilt angle is 30 degrees, so that angle will be used for the feasibility analysis.
From here, the team determined the physical parameters of the tilt piston. The piston diameter was determined based on the maximum load capacity and minimum water pressure once again. The calculation was done for a single piston and double piston design. The team also calculated the distance that the piston would have to move to achieve the desired 30 degree tilt.
A hydraulic system layout was also developed that includes independent tilting and lifting control.
Morphological Chart and Concept Selection
In order to design a variety of concepts for each function of the device, each team member was given a designated sub-function and asked to sketch at least five designs. The morphological chart is a diagram to organize all of these designs in one place with their respective sub-functions. This is the final morphological chart for team P20011:
The morphological chart live document can be found here.
Full Concept Creation
From the sub-function concepts in the morphological chart, the team came up with 27 unique designs for the whole system. In order to narrow down the number of system concepts from 27 to 5 each team member got 5 votes to cast for the design concepts that the thought would work the best. Here is the matrix with all 27 designs and the votes as cast by the members of the team:
These designed were then reviewed and each team member was given the opportunity to vote to select the designs they deemed most viable. From this vote, the top 5 design concepts were selected and input to the PUGH chart for further analysis.
In the Pugh chart the team compiled the 5 final system designs and compared them using selection criteria. The selection criteria chosen by the team were cost, design complexity, ergonomic compatibility, manufacturability, size, ease-to-sanitize, serviceability, compatibility with other design components, ease of install, aesthetics, durability, and level of innovation. These points of comparison were chosen based on factors such as the customer and engineering requirements as well as the discretion of the team. A live link to the Pugh chart can be found here.
The morph chart and Pugh chart are owned and maintained by Christina Eker.
After analyzing the selection criteria and the results of the Pugh chart our team determined that none of the presented designs offered the best combination of solutions. From here it was decided that a new design would be created that combined the best aspects of all design concepts and delivers a highly customizable, stable, and functional articulating toilet.
The chosen concept consists of a device that will be mounted to the floor. It will lift vertically using three sets of hydraulic pistons. One set will be installed on the back end of the prototype and the other two will be installed on the front end. These sets of pistons will also enable the device to tilt either forward or backward depending on the occupant's preference. Arm support will be achieved through adjustable arm rests with locking levers and the back support will click into the base and torso support will consist of a click in adjustable bar that will have the ability to swing back and forth. To view the live document that consists all of the chosen concepts, click here.
Concept Improvement: When selecting our final concept, the team utilized the scoring matrix and the PUGH chart shown in Figure 2.18 and in Figure 2.19, respectively. For the scoring matrix, each team member was asked to use the different functional concepts that we developed to come up with at least five different system concept combinations. These different combinations were added to the scoring matrix and each team member voted for their five favorites. After all of the vote totals were collected, we narrowed our choices down to five final options (six if including the current built prototype design). This eventually gave birth to the PUGH chart. Each of the six remaining concepts were then compared against one another until one final concept remained. Once the concept with the highest score was chosen, the team noticed a pattern in the concept selection process. The concepts that had the highest scores (the concepts that the team liked the most) involved the use of click-in components. This includes click-in arms, back, and torso support. Therefore, we decided to combine some of these final concepts to create one concept that contained all of our preferred functional components. This led to the team choosing the final system design described above in Figure 2.21.
A link to the document can be found here.
Designs and Flowcharts
Figure 2.22 shows a visual representation of the team's chosen system design. Not only does it show the different functions and components that are present, but it also shows how these components interact and work with each other. The live document for this flow chart can be seen here.
The risks document is owned and controlled by Marlon Naveda. He is responsible for making sure that the list stays updated throughout the duration of MSD.
Since the last design review took place, the team has successfully made updates to the risk analysis that was previously conducted. To view the live risk management spreadsheet, click here.
It should be noted that the spreadsheet shown here is known as revision 2. Revision 1 corresponds to the risks that were created during the Problem Definition stage (risks #1 through #15). Revision 2 merely consists of updates made to revision 1, in addition to the previously made risks.
Design Review MaterialsHere are links for documents referenced during the Systems Level Design Review:
Plans for next phase
Team Level Goal
In the next design phase the team is expected to focus in on the technical details behind each design component. This includes conducting research on the standards identified in the previous design phase, as well as understanding the range of limb sizes in the expected user population. Once research has been collected, the design team will work to draft design options with dimensions that support the research collected. From this point the team will work to develop CAD models for each design component that will assemble to create a finished system.The focus of the team this design phase is to develop a functional hydraulics system that addresses the shortcomings of the previous design. A stretch goal of the team is to complete CAD designs for all systems components as well as their corresponding Bills of materials and manufacturing plans.
At the end of this design phase the team will be able to deliver a project plan that will be carried out throughout the remainder of the projects life-cycle, as well as detailed descriptions of each of the systems components and how they interface with one another. The team also hopes to complete a donation request to be submitted by the end of this phase for design materials to use in the prototyping of the design components drafted.
Next Phase Design Priorities
The team will place priority on the following system components during this phase but will aim to complete modeled designs for all intended systems components by the phase review.
- Hydraulics for tilt and vertical lift
- Redesign of Seat
- Redesign of System Base
- Telescoping Torso Support
- Arm Support
- Back Brace
Figure 2.25 (below) is a pyramid ranking the risks for the next page based on level of complexity of the task and risk that the task will not be completed. Moving forward the team has decided to prioritize the risks with the highest rank.
The Teams Individual Three Week Plans are as Follows: