R. I. T Multidisciplinary Senior Design Phase-Appropriate Feasibility Analysis Rochester Institute of Technology Mechanical Engineering Department Rochester, NY USA

R. I. T Multidisciplinary Senior Design Session Objectives Motivation: Risk Analysis, Metrics & Specs Assignment Examples EE CE ISE/ID ME

R. I. T Multidisciplinary Senior Design Engineering Requirement Requirement = Metric + Specification Metrics = what measurement you are going to make to determine whether your design is successful Specification = the target (or minimally acceptable or ideal) value to achieve for that measurement Use preliminary feasibility here!

R. I. T Multidisciplinary Senior Design Project Risks Schedule risks Things take longer than expected to design, order, receive, build, test Personnel risks Staffing is insufficient, team member is unable to complete his or her work, team dynamics become an issue Resource risks Project is over budget, lack space, equipment missing, can’t get into machine shop, etc. Use preliminary feasibility here!

R. I. T Multidisciplinary Senior Design Technical Risks Risks associated with your design. Design is not feasible Specs are not feasible Components don’t perform to spec Components can’t be manufactured as designed Technology is not as developed as anticipated Expertise of team is overestimated Use preliminary feasibility here!

R. I. T Multidisciplinary Senior Design Session Objectives Motivation: Risk Analysis, Metrics & Specs Assignment Examples EE CE ISE/ID ME

R. I. T Multidisciplinary Senior Design Prepare for class: List one question about your design that can be answered by phase-appropriate feasibility analysis Discuss this as a team ahead of time – do not duplicate effort between team members! Determine whether the question is best answered with analysis, benchmarking, or prototyping List assumptions, governing equations, materials, competitors, etc. as appropriate Use simple tools to solve the problem in your logbook. You will present this to your peers during the next class!

R. I. T Multidisciplinary Senior Design Session Objectives Motivation: Risk Analysis, Metrics & Specs Assignment Examples Disclaimer: taken mostly as-is from team documents! EE CE ISE/ID ME

R. I. T Multidisciplinary Senior Design EE Example from MSD - Analysis From P12015/6 Navigation Aid for Blind Person Preliminary feasibility question #1: how much power will our device consumer? Assumptions: Use some good candidate off-the-shelf components and an off- the-shelf battery. It takes 20 minutes at most for the user to move from one location to another, and this happens at most 10 times per day.

R. I. T Multidisciplinary Senior Design P12015: Power Calculations RFID Reader1.5796W*hr Motors W*hr MCU W*hr Magnetometer0.0913W*hr Keypad W*hr *Sum W*hr *For (10) 20 minute intervals of navigation

R. I. T Multidisciplinary Senior Design Hold on a minute! Significant figures… ????? Use datasheets and maintain significant figures That give us…

R. I. T Multidisciplinary Senior Design P12015: Better Power Calculations RFID Reader1.58W*hr Motors0.02W*hr MCU0.047W*hr Magnetometer0.09W*hr Keypad0.08W*hr *Sum W*hr Math skills involved: Reading datasheets, multiplying voltage and current, maintaining significant figures. Value to team: High! *For (10) 20 minute intervals of navigation

R. I. T Multidisciplinary Senior Design ME/EE Example from MSD – Analysis & Benchmarking From P13002 Active Ankle Foot Orthotic Preliminary feasibility question: How fast of a walking speed can our sensor reliably measure? Assumptions: Gait data follows a 4 th order Fourier series (i.e., signal content 4x fundamental gait frequency) Using IR sensors to quantify gait patterns

R. I. T Multidisciplinary Senior Design Benchmarking: representative IR sensor Don’t use first 53 ms of data! Could take as long as 48 ms to acquire each additional sample.

R. I. T Multidisciplinary Senior Design Analysis 48 ms per sample  ~20 samples/sec Looking for frequency content 4x fundamental gait frequency, Nyquist criterion says to sample at 2x that  take 8 samples per step Max quantifiable gait speed is: (20 samples/sec) / (8 samples/step) = 2.25 steps/sec Use this information to bound system specs!

R. I. T Multidisciplinary Senior Design CE Example from MSD – Analysis & Benchmarking From P12015/6 Navigation Aid for Blind Person Preliminary feasibility question #2: How much onboard storage do we need for a building map? Assumptions: Building map will be stored onboard and will be the biggest memory hog.

R. I. T Multidisciplinary Senior Design Map representation Major considerations include the size of the map file (limited memory space on the board), the ASCII character set requirement spec, and the 1000 maximum tags spec Maps consist of: o tags, each with an ID (12 bytes) and X and Y coordinates in inches or centimeters (range: 0~4000); o map vertices (e.g., rooms, water fountains, bathrooms, hall intersections), each with X and Y coordinates; o walking paths between vertices, which include the start and end vertices o assumption that the device is currently only being used to navigate one floor of one building

R. I. T Multidisciplinary Senior Design Map representation (continued) Possible solution: use base64 notation (ASCII-safe but still small) o Tags, with their large ID fields, will likely comprise the largest part of the file o With base64 notation, tag IDs require 16 'digits' and the coordinates will use 2+2 'digits' = total of 20 bytes per tag o The MCU memory must be able to accommodate up to 1000 tags = 20KB minimum per map (restricts MCU choice!) Store the graph underlying the map of destinations and paths densely (low connectedness)

R. I. T Multidisciplinary Senior Design ISE & ID Example from MSD - Prototyping P14042 – Una-Crutch Preliminary Feasibility Question: What type of design is going to be most appealing to users? Can we find out before spending lots of time doing detailed analysis and manufacturing planning? Approach: foam + PVC pipe models (non-load bearing) and user survey

R. I. T Multidisciplinary Senior Design Axilla Pads and Handles Prototypes Created

R. I. T Multidisciplinary Senior Design C B Frames and Connective Mechanisms Prototypes B, C, and G G

R. I. T Multidisciplinary Senior Design ME Example from MSD - Analysis P12007 – Equilibrate Balance Assessment System Preliminary Feasibility Question: Can we reduce system weight without compromising stability/deflection? Approach: ANSYS Before using finite element software, conduct parametric analysis using Strength of Materials models (save ANSYS for detailed design phase)

R. I. T Multidisciplinary Senior Design Full system: team targets footplates for weight reduction System weight: 44 lb Footplates: 8.7 lb! Customer: “Reduce weight, reduce cost, increase functionality”

R. I. T Multidisciplinary Senior Design Systems-Level Design Simple spreadsheet analysis of representative loading scenario allows the team to evaluate different materials and thicknesses. Generous on assumptions, but lets us compare options in an educated manner. Once a decision is made, detailed design can focus on a single material configuration

R. I. T Multidisciplinary Senior Design Summary Decide what questions you need to answer Decide the best means of answering them (analysis, benchmarking, prototyping) Use phase-specific tools Hand calculations Logic Benchmarking Basic physics Simple prototypes