Smart Cane – P14043Sub Systems Design Review

Lauren Bell, Jessica Davila, Jake Luckman, William McIntyre, Aaron Vogel

Agenda• Project Scope• Concept Selection• Engineering Requirements• Component Breakdown• Engineering Analysis• Test Plan• Risk Analysis• Project Plan• Audience Feedback Please

Project ScopeProject Deliverables - Handle that provides directional signals to the user

Objects to left or right of user Battery Life for 4-5 hours

Comfortable Handle Reasonable Cost

- Simulation testing device

Concept Selection• Final Concept Ideas• Finger Scroll• Palm Roller• Palm Roller and Finger Scroll

• Final Concept Selection• Palm Roller without Finger Scroll

Engineering Requirements

Estimated Power Consumption

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

* 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, 19-22 Aug. 201

Required Motor Torque• Worst Case – Excessive grip stalls motor

• Maximum moment caused by design pressure• 50.1 oz-in

Motor Type Selection• Design Factors to meet Engineering Requirements• Rotational speeds of 30 to 60 RPM• Commonly available at 50 oz-in

DC Motor Stepper Motor Servomotor

Smooth rotation Yes No Yes

Won’t stall at slow shaft speed

No Yes Yes

Generally maintains speed under varying grips

No Yes Yes

Dimensions < 2” No (Gears needed) No Yes

Cost < $30 Yes Yes Yes

Totals 2 Yes 3 Yes 5 Yes

Engineering Analysis:Bump Rotation Characteristics• Effective haptic zone – lower

palm• Effective Bump Height • Bump Frequency

Component Breakdown

Roller Analysis• Bumps per rotation• Servo to Roller Spacing• Effectiveness of our

model – Audience?

Roller Force/Stress Analysis

Force/Stress Cont’d

Roller Assembly Support

Handle Material Selection• Desirable Qualities• Moisture wicking• Higher Coefficient of Friction

• Possible Options • Softex• Neoprene• Tennis Racquet Handle Cover

• Top Choice• Synthetic Cloth - Nylon• Tennis Racquet Handle Cover

Handle Weight Estimate

Component Quantity Weight (grams) Weight (lbs)

SpringRC SM-S4303R Servo Motor 1 41 0.09

WhataGrip Handle Cover 1 2.8 0.006

AA Batteries 4 92 0.203

Cross-Bar/Plate for Servo 2 136.1 0.3

5/16" Ball Bearings 4 8.24 0.02

MSP430 Microcontroller 1 2.8 0.006

Total 282.94 0.625

Cost EstimateComponent Quantity Price per Item (US Dollars) Total Cost (US Dollars)

SpringRC SM-S4303R Servo Motor 2 12.95 25.90

Handle Cover 2 2.97 5.94

Set of Batteries 1 8.00 8.00

Cross-Bar/Plate for Servo (Cost of Aluminum)2"x2"x1' Block 1 23.95 23.95

5/16" Ball Bearings 4 1 1.00

MSP430 Microcontroller 2 5.00 10.00

Rocker Switches 3 5.00 15.00

Ultrasonic Sensors 3 30.00 90.00

Handle Material*

White Aluminum Cane 1 27.00 27.00

Shipping Costs 15.00

Total 221.79

*Handle Material has not yet been decided

Test Plan

Simulation and Detection System

Micro Family Selection

Risk Assessment ID Risk Item Likelihood Severity Importance

1 Burning out micro controller 3 2 6

2 Software is ineffective 2 3 6

3 Haptic handle and testing systems integration issues 2 3 6

4 Not meeting customer expectations 2 3 6

5 Not obtaining parts on time 2 2 4

6 Battery malfunction 2 2 4

7 Over budget 2 2 4

8 5 volunteers for user test are not established in time 2 2 4

9 Cane does not stay together, durability failure 1 3 3

10 Not completing software component 1 3 3

11 Haptic forces not being strong enough 1 3 3

12 Hardware and software integration 1 3 3

13 Detection is ineffective 1 3 3

14 Team Member leaves team 1 3 3

15 Cane gets dropped repeatedly on the ground 1 3 3

16 Excessive tapping 1 3 3

17 Handle material is not effective (Tears with consistent wear) 1 3 3

18 Uncoordinated team schedules 1 2 2

19 Selected power and components produce excessive heat 1 2 2

20 Necessary facilities and personnel are not available when needed 1 2 2

21 System is too heavy for desired cane weight 1 1 1

Project Plan

Network Diagram