P17012: Torque Assisting Knee Brace Team Members: Benjamin Boseck, David Gooden, Linzey Miller, Farrukh Mohiuddin, Emily Sanseverino, Andrew Tock
Overview Background Review Project Changes Hinge Subsystem Hardware/Software Test Plan Test Rig Risk Analysis Feasibility Next Steps
Background Goal: inexpensive knee brace that assists with Torque Current common knee braces only stabilize the knee Spring Loaded Technology, Expensive Multiple fittings by an Orthotist $100 Wear for extended periods of time Flexible in terms of wearing over or under clothing Data Acquisition
Project Changes Shock Absorption Torque Assist Product Benchmarking (Levitation) Talked to our Customer
Use Case Scenario
Functional Decomposition
Concept Development
Selected Concept Function Concept Secure Knee / Secure to Leg Elastic/Velcro Measure Knee Angle Rotary Encoder Measure Force on Knee Rotary Encoder Measure Motion Rotary Encoder Display Data PC / Android Absorb Shock Spring Mechanism Supply Power to Microcontroller Battery Transmit Data Bluetooth Charge Device No solution Provide Comfort Use existing knee compression sleeve
Hinge Subsystem: Extended
Hinge Subsystem: Flexed
Hinge Feasibility: Springs and Cord
Draft Assembly Drawing
Hinge Feasibility: Cord Concept
Electronic Hardware Microcontroller Bluetooth Module Potentiometric Sensor Battery Voltage Regulation
Electronic Software PC data collection application Android mobile application API (Application Programming Interface) Instantaneous Position Force Dissipated (Spring force equations) Derived Steps Taken
Electronic BOM - Prototype Prototype Design Subsystem Electronic Component Model(s) Potentiometer COM-09288 COM-09939 Bluetooth Module Microcontroller Unit Cost Quantity Total Cost Source Adjusted Cost $0.95 1 CE Lab $0.95 Manager $0 RN42 $18.95 1 $18.95 Customer $0 NetDuino +2 $59.95 1 $59.95 Customer $0 $79.85 $0 Subsystem Cost:
Electronic BOM - Manufacturing Scale 30,000 scale manufacturing Design Subsystem Electronic Component Model(s) Potentiometer COM-09288 COM-09939 Bluetooth Module RN42 Microcontroller Unit Cost Quantity Total Cost $0.49950 1 $0.49950 $13.14000 1 $13.14000 MSP430 $1.10000 1 $1.10000 PCB N/A $0.11000 1 $0.11000 Battery CR2032 $0.50000 1 $0.50000 Voltage Regulator LD1117V33 $0.12700 1 $0.12700 Capacitors Various $0.00168 2 $0.00336 Resistors Various $0.00121 2 $0.00242 Electronic Unit Cost: 1 $15.48 Electronic Cost: 30000 $464,468.40
Electronics Feasibility Issues: Low Low Low Low Power - 1.2837 mw (worst case) ~ 600 hour life Cost - $16 / unit at scale, Pain Point: Bluetooth Profile - ½ inch x ½ inch PCB Mechanical Risk - Prototyping Required Function Concept Secure Knee / Secure to Leg Elastic/Velcro Measure Knee Angle Rotary Encoder Measure Force on Knee Rotary Encoder Measure Motion Rotary Encoder Display Data PC / Android Absorb Shock Spring Mechanism Supply Power to Microcontroller Battery Transmit Data Bluetooth Charge Device No solution Provide Comfort Use existing knee compression sleeve
Test Plan - Human Subjects Test Plan Criteria Initial Comfort Walking Test Climbing Test Final Comfort Variations Loaded Different module set ups (1 vs 2 modules)
Test Rig Material Motor 2x4 wood PVC pipe (larger) PVC Pipe (smaller) plywood (wheel) metal rod (0.5in dia) Amount 1 38in Rod locks 13 24in 24in 1 ft Dia 36in
Risk Analysis
IP Standards
Waterproofing Electronic Potting Used for resisting (electric) shock & exclusion of moisture Thermo-setting plastics or silicone rubber
Waterproofing Parylene Coating Thin, vacuum deposited layer of a parylene dimer, in the form of a transparent polymer film Deposition in gas form to allow for deep penetration
Waterproofing - Feasibility Electronic Potting Pros Cons Parylene Coating Pros Cons Largest & most powerful barrier Obscures the look of the device No residue & no difference in appearance of the device Almost impossible to remove 2-step process faster & cheaper: ~$30 Difficult to modify components of the device Process is involved, but results in an extremely thin and protective layer Only professionally done; expensive: ~$250 per lb. Can be personally done Impossible to remove Biocompatible Water resistant; not waterproof
Plans for Next Phase
Questions?