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P14043-Smart Cane Senior Design Final Presentation
Jess
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Introductions Lauren Bell – Mechanical Engineer
All -if we dive into it, explain a bit of what your main contributions were BJ electrical Aaron manufacturing Jess Lauren Jake Lauren Bell – Mechanical Engineer Jessica Davila – Industrial Engineer Jake Luckman – Mechanical Engineer William McIntyre – Electrical Engineer Aaron Vogel – Mechanical Engineer
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Agenda Problem Description Design Challenge
System Design and Operation Testing and Traceability Project Process Conclusion Recommendations Lessons Learned Acknowledgements Jess Describe briefly to the audience our project from inception to closure through MSD1 and 2
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Problem Description Safe and easy navigation in the world is difficult for the blind and deaf/blind Project Goal Inexpensive Intuitive Expensive Training Required Limited Situation Feedback COMMON SOLUTIONS Excellent Situation Feedback Lauren Cane advantages – inexpensive and available , little or no training, users can feel their environment Disadvantages – slow navigation – cane is only means of judging the environment Guide dogs advantages – take commands , understand tricky obstacles , guide the user Disadvantages – expensive , can get sick/hurt, requires a lot of training . Waiting lists for animals are long – not allowed in some areas, user don’t feel their environment Common solutions Traditional White Canes Guide Dogs Drawbacks and limitations Need more information about surrounding environment
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Design Challenge… …To design, fabricate, assemble and validate a ‘haptic handle’ To be attached to a traditional cane Provide directional feedback to blind and deaf/blind users BJ Just a handle, not a detection system, just ability to connect with Less expensive Little training Can feel the environment and provides haptic feedback Longer range beyond the tip of the cane
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MSD Process Overview MSD I MSD II Concept Selection
Many ideas to one Design Considerations Defining the engineering requirements & constraints Generation of Design Drawings, Documentation Fabrication and Assembly Testing of Prototype Proof that prototype meets eng. requirements MSD I BJ MSD II
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Design Considerations
Customer desires needed to be transformed into technical requirements… Customer Desire Technical Requirement Light weight < 1 lbs. Small Grip Diameter < 1.5 inches Quick Signal to User < 500 milliseconds User Can Detect Direction *Will Elaborate Later Battery Life > 4 hours Jake Learned – Fully understand the customer needs ASAP …otherwise time will be wasted
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Learned – Prototyping accelerates the concept selection process
Potential Concepts Brainstorming and benchmarking yielded the following likely candidates… Track Ball Piston Push Feedback Torque ‘Jerk’ Magnetic Force Feedback Scroll Navigation Aaron Over the course of the first few weeks, we had a lot of trouble choosing a rough concept because we had so many. However, after using tools we learned from MSD like morph charts brainstorming, and benchmarking, we were able to narrow our selection to a scroll navigation concept, which transmits a signal to the user and works in the opposite manner as a computer mouse. With the scroll navigation concept, we hit the ground running on the details. After making some prototype mock ups, doing some simple testing, and interacting in a constructive manner with our customers, we were able to get the right feedback in order to move onto a more detailed design. Learned – Prototyping accelerates the concept selection process
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Optimizing Roller Design
Roller Speed Roller Shape Bump Height Jake Learned – Quick and simple tests/prototypes will quickly narrow the design. Don’t overanalyze!
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Electrical Design BJ Electrical design driven by mechanical design and Engineering requirements
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Design provides effective directional feedback
Mechanical Design ‘Bump’ Roller Sub-assembly DC gear motor Roller arms Dowel pins Press fit ball bearings Cold Dawg The roller sub assembly is the heart or crux of tactile communication to users of the smart cane. There were many key considerations in the design of the bump assembly, including bump characteristics, shaft speed and shape, power consumption, stress analysis, deflection analysis, tolerance stack ups, etc. We used a lot of the mechanical engineering theory that we have been taught to ensure that our design would work. Design provides effective directional feedback
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Documentation of everything is crucial for future project iterations
Final Design Aaron So, here’s some photos of our cane as designed and fabricated if you can’t see it from the back. This is what we will be handing off to our customer. Ultimately, the final design specifications were stitched together with analysis, optimization, CAD, and documentation of everything, so that we can pass this project to future groups of MSD. Documentation of everything is crucial for future project iterations
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Fabrication and Assembly
~25 manufactured parts Material Changes Part Modifications Time management Learned – Fabrication and assembly will expose necessary changes in the design Cold Dawg Through the course of the manufacturing and assembly process, we made many changes to our design and have the documentation with revision control to prove it. In fact, more than 30% of our parts had changes. Some things were minor, and some were major. We changed the handle shell from fiberglass to ABS for improved strength and machinability. We made some slots bigger because supplier parts didn’t meet specifications. We made some screws shorter after puncturing a lithium ion battery housed inside the shell, which luckily only destroyed our h-bridge on our pcb. You should have seen the cane glow. We learned that prototypes are always redesigned, and that you can’t really see how things come together without the tools and screws in hand. There will always be a loop back to design changes in the manufacturing and assembly process.
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Final tests were within predicted values
Testing and Traceability Jake Final tests were within predicted values
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Prototype meets all non-technical requirements
Testing and Traceability Jake Prototype meets all non-technical requirements
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Problem Tracking System
1. Identifying & Selecting Problem 2. Analyzing Problem 3. Generating Potential Solutions 4. Selecting and Planning Solution 5. Implementing Solution 6. Evaluating Solution Jess We implemented a problem tracking system in MSD II. Seen here are the 6 steps that were used. We saw that once problems started to arise, this system significantly helped us manage the problems. Learned – Once problems started to arise and stack up, Problem Tracking significantly helped us manage the problems
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Useful tool to track actual status against planned
Risk Curve Reduction of risks due to analysis (heat, stress, weight) RISKS: Machining issues with thin ABS covers, ABS back cover breaks during testing phase, PCB not arriving on time PCB working, assembly between handle & cane holds together, wires fit into handle design Jess This was our risk curve for the entire process of MSD. It tracked the importance of each risk (importance is the likelihood x the severity). We used this to make sure that we were on track with where we planned to be. As you can see there were some points were we significantly dropped our risks or increased them, and they can be explained in the text boxes. Useful tool to track actual status against planned
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Project Plan and Efficiency
Final Deliverables Task Planned Duration Actual Duration Difference Efficiency Order Electrical Parts 14 21 7 67% Fabrication of Parts 18 34 16 53% Order PCB 5 30 25 17% Testing 13 28% Assembly of Handle 15 10 33% Technical Paper 27 52% Total MSDII Tasks 83 108 77% Jess Final Screenshot of project plan
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Imagine RIT 200+ “Users” ~100% Positive Feedback
University News Interview Lauren Pictures Once people were shown how to hold the cane, they we able to feel positive feedback Add in pictures Users at Imagine RIT demonstrated our project met its objectives and was a success.
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Lessons Learned Project Management Customer Interaction
Creating a good team dynamic “What’s the best thing I can be doing right now?” Lauren
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Recommendations Complete cane with integration to sensors
Improve handle to provide feedback on changes in elevation and proximity of obstacles. Redesign handle with fewer parts and simple assembly Attempt to redesign with smaller batteries Strengthen the outer structure of handle Water/weather proof BJ
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Recommendations for MSD
Shorter presentations in MSD I Teach project management skills in other courses Evenly distribute the team resources Use guides from industry
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Acknowledgements Guides Customers Professor Mark Indovina
Gary Werth Gerry Garavuso Customers Dr. Patricia Iglesias Gary Behm Tom Oh Professor Mark Indovina Jeff Lonneville
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Motor Analysis Torque/speed Power consumption
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Design Grip Pressure Spec
Ensure handle functions under excessive grip Measure pressure of displaced air for rough idea Median pressure ~3 psi Compare to Grip Pressure Study* FSR sensors on glove “Crush grip” measured on 50mm diameter handle 5 male and 5 female adults Maximum pressure ~3.1 psi Our measurements matched the study, therefore: Marginal Grip Pressure: 3 psi Maximum (Design) Pressure: 5 psi “Crush grip” stronger than pinch and support/carrying * Tao Guo qiang; Li Jun yuan; Jiang Xian feng, "Research on virtual testing of hand pressure distribution for handle grasp," Mechatronic Science, Electric Engineering and Computer (MEC), 2011 International Conference on, pp.1610,1613, Aug. 201
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Required Motor Torque Maximum moment could happen when:
Grip reaches design pressure Pressure force is perpendicular to contact point Palm contact area is maximum on roller Two rollers are contacted Maximum moment caused by design pressure 50.1 oz-in Motor selection will not be heavily constrained Variety of motors that meet torque, size and rotation requirements Jake
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Bump Rotation/Roller Analysis
Bumps per rotation Servo to Roller Spacing Effectiveness of our model – Audience? After determining an effective bump height for the mock up, through another mock up, we decided that 4 bumps - 90° apart was effective in conveying directional feedback in a faster manner than say 1 or two bumps, concluding that contact with many nerve regions simultaneously gives better feedback. Being 90 degrees apart, users can clearly feel the displacement of the diameter changing. With 8 bumps and 45 degrees, the effective change in diameter is too small. We have not tried 3 bumps yet, `120 degrees apart, and that is what has just been passed around. Taking a look at the diagram here, you can see the components we are going to use. For bumps, we will be using metal spheres. Spheres will be held by pins, allowing rotation and contact simultaneously. Note the band that extends around the rollers. This band will be fixed to the cane in front of and behind the target area of contact. The balls will rotate about the servo, as well as spin on the pins, minimizing the kinetic friction on the band. Taking a look at the maximum diameter, you will see we are at the limit of our maximum handle grip diameter of 1.5”. Also, the calculation of effective bump height is shown. I have determined that this displacement in diameter should be effective in communicating direction. Any suggestions from the audience?
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Roller Force/Stress Analysis
This is a slide that shows a little bit of force analysis on the draft design to make sure that the design is reasonable. Using the maximum grip force, force distributions were determined and shear and bending moment diagrams were drawn up. In our analysis, the pin was of most concern by intuition, being the smallest part in the force transmission.
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Force/Stress Cont’d We determined the maximum stress on the pin, and found that with aluminum components, the design will not break. Maximum stress is 6ksi, where aluminums strength is 24ksi. Also, stress analysis was done on the x-arm to show that we have little worry in that area.
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