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 Scope

Project 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

Item Power (W) Quanity Total (W)

Ultra Sonic Sensor 0.011 3 0.033

MSP 430 0.000506 1 0.000506

Continous Servo 1.2 1 1.2

Total Estimated Power (W)= 1.233506

If we use 4 AA Akali Batteries

Battery System

10.8Wh 1.233506W*xH

x=8.7 Hours

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• 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

Motor Type Selection• Design Factors to meet Engineering Requirements• Rotational speeds of 50 to 70 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

Bump Rotation/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

Signal Flow Diagram

Test Plan Detection System Simulator

Micro Family SelectionArduino MSP430

Price $20-100 $3-15

Architecture 8 Bit RISC 16 Bit RISC

Clock Speed 8-16 MHz 8-25 MHz

Stand Alone Capability No Yes

Maskable Interrupt Lines 2 2

Power .825mW .5mW

Risk Assessment ID Risk Item Cause Effect Likelihood Severity Importance Action to Minimize Risk Owner

1 Burning out micro controller

Power mismanagement, stalled motors, shorted wires Device will not be operational 3 2 6 Sockets, good wiring

2 Software is ineffective Poor software planning and algorithm development, bad software design

Detection system does not identify objects, detection system does not interface to the haptic feedback, the haptic feedback dose not respond properly, poor response time

2 3 6Create a good software building plan, test plan and look into different algorithms and methods

Will

3Haptic handle and detection systems integration issues

Poor design, miscalculation Poor/no communication between systems resulting in improper/no haptic guidance 2 3 6

Check and double check all calculations and perform more than sufficient research on analog and digital communication circuitry

Aaron

4 Not meeting customer expectations

Not enough communication with customer. Too many specs. Ineffective project planning

Customer is not able to use prototype for future projects. Impacts MSD evaluation grade. 2 3 6

Keep in contact with customer. Follow and continually reevaluate project plan and risk assessment. Focus on the most important specs.

Jake

5Not able to meet with customers this week (10/7 – 10/11)

Schedule conflicts, don’t respond to emails Not able to make concept selection, can’t finalize requirements (detection system) 2 3 6 Follow-up daily (email, phone,

office hours) Lauren

6 Not obtaining parts on time Lack of planning, shipping issues, supplier complications

Behind on building, order different parts or rush order, over budget, prevent from testing other parts

2 2 4 Stay ahead of schedule, identify the critical path Aaron

7 Battery malfunctionToo much current being pulled, heat generated is not being removed affectively, batteries themselves

Loss of power supply, damage components 2 2 4Functioning power management, removal of heat, sealed off from dirt

Will

8 Over budget

Not enough budgeted to begin with, overspending in procurement of materials in determination of concept selection, poor budget of materials, poor initial design lacking all components, misuse and breaking of parts during assembly and fabrication

Displeased Customer and Guide 2 2 4

Make a very detailed budget of materials, design the product without missing a single component, ask for more money from the customer when the draft bill of materials is made and considerably under-budget, limit spending on concept selection, use existing safe fabrication techniques and consult experienced professionals prior to manufacturing and assembly

Aaron

9 5 volunteers for user test are not established in time Communication issues, volunteer backs out Contact and relationship not built with

volunteers for test 2 2 4 Communicate with customer and ABVI Lauren

10 Cane does not stay together, durability failure

Parts are not secured onto cane, user misuse, shock absorbent

Parts could disconnect from the cane, structure of cane can break, loose wiring will break apart 1 3 3 Housing for components Jake

11 Not completing software component

Poor time management, problems with software

Electrical components won’t work, user won’t receive feedback 1 3 3 Start early, ask for help if needed,

learn program ahead of time Lauren

Risk AssessmentID Risk Item Cause Effect Likelihood Severity Importanc

e Action to Minimize Risk Owner

12 Haptic forces not being strong enough Miscalculations, poor design Misguided user, don’t meet customer

requirements 1 3 3Add adjustability to feedback, adequate components, overdesign with adjustability

Jess

13 Hardware and software integration Poor hardware/software choice User won’t receive haptic feedback 1 3 3

Stay on or try to keep ahead of critical path, make sure programming is done correctly

Lauren

14 Detection is ineffective Poor design, sensors do not detect certain mediums, sensors were not calibrated,

Not fast enough, does not detect the correct things 1 3 3

Make sure the sensors used can detect all objects, research multiple algorithm development methods, and develop a feature to calibrate sensors.

Will

15 Team Member leaves team

Expulsion/financial issues/choice/family emergency

Risk of losing expertise the team member may have. Heavier workload on team members. 1 3 3

Communicate with team. Share and decentralize expertise. Document all work and systems. Allow for buffer time in project plan to accommodate possible higher workloads.

Jake

16 Cane gets dropped repeatedly on the ground Accidental/Falls Damage or loss of parts, cane no longer works 1 3 3

Keep components in protective housing, keep cane in a locker when not being used

Lauren

17 Excessive tapping User cane technique, learning curve with our cane, Damage or loss of parts, cane no longer works 1 3 3 Make sure components are secure

within their housings. Will

18 Group can’t agree on concept Stubborn, set on the person’s own concept Behind on critical path, won’t meet

deliverables for DDR, conflicts in group 1 3 3 Consensus, reflect back to team values, consider compromises Jess

19 Handle material is ineffective

Insufficient selection and analysis of handle material

Material tears with consistent wear, does not absorb excess moisture, produces unnecessary friction on hand

1 3 3Appropriate analysis of material, Acquiring material early in process for testing purposes

Lauren

20Select power and components produce excessive heat

Insufficient selection and analysis of handle components Handle will be uncomfortable for user 1 2 2 Analysis on heat produced by

components Jake

21Necessary facilities and personnel are not available when needed

Requesting facilities too late, contacting personnel too late

Behind schedule on necessary building/ testing 1 2 2

Establish early on what facilities are needed and what personnel are necessary to speak to

Jess

22 Uncoordinated team schedules Busy workload for other classes Deliverables not reviewed with team when

needed, late deliverables 2 1 2 Coordiate appropiately with team's scheudles Jess

23 System is too heavy for desired cane weight Not properly calculating weight Do not meet customer requirements 1 1 1 Make sure that everything is the

desired weight Lauren

Risk Growth Curve

14-Aug 3-Sep 23-Sep 13-Oct 2-Nov 22-Nov 12-Dec0

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MSD I

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Project Plan

Network Diagram

Immediate Next Steps• Engineering Analysis [ 10/28] • Power Requirement • Moment of Inertia• Research “standard” haptic sensitivity

• Electrical Subsystem [10/31 ] • Engineering standards electrical design must meet• Design power supply• Layout sensor, micro and power supply location• Estimate weight distribution• Pseudo code

• Mechanical Subsystem [ 10/31]• CAD drawings• Assembly drawings• Select shelf parts

• Test Plan [ 10/28]• Establish and draft test plans

• Risk Growth Curve [Weekly]