1. Smart Cane – P14043 Sub-Systems Design Review
Lauren Bell, Jessica Davila, Jake Luckman, William McIntyre, Aaron Vogel

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

3. 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
Additional Haptic Feedback
Left or Right
Better than previous design
Tie in customer/engineering requirements

4. Concept Selection Final Concept Ideas Final Concept Selection
Finger Scroll
Palm Roller
Palm Roller and Finger Scroll
Final Concept Selection
Palm Roller without Finger Scroll
Lauren
Probably good to mention both scroll and palm rubber. And concepts within, only mention best of the original concepts?

5. Engineering Requirements
Jake

6. Estimated Power Consumption
Item
Power (W)
Quanity
Total (W)
Ultra Sonic Sensor
0.011 3
0.033
MSP 430 1
Continous Servo
1.2
Total Estimated Power (W)= BJ
If we use 4 AA Akali Batteries
Battery
System
10.8Wh
W*xH
x=8.7 Hours

7. 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

8. 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

9. 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
Won’t stall at slow shaft speed
Generally maintains speed under varying grips
Dimensions < 2”
No (Gears needed)
Cost < $30
Totals
2 Yes
3 Yes
5 Yes
Jake

10. Engineering Analysis: Bump Rotation Characteristics
Effective haptic zone – lower palm
Effective Bump Height
Bump Frequency
After narrowing our concepts to the palm roller, we determined that we needed to determine the effective area where the user would feel the greatest haptic feedback. After doing some research, we found that the ulnar and median nerves of the hand would both be used in interpreting haptic information. Also, we picked the area of the palm where there is the highest nerve density, to maximize the probability of sensing haptic feedback.
We then created a mock up to determine an acceptable bump height for our customer and found that 0.325’’ height was satisfactory. However, we only had 1 bump on our mock up, and it didn’t work in the exact same manner as our projected initial design. The mock up being passed around now has multiple and resembles the current design we are looking into. We decided on multiple bumps around the handle a better idea for the sake of increasing the frequency of bumps, at a speed where a faster user response can be obtained with more nerve contact by multiple bumps. We still need to additional testing to determine what is effective, and we would like to pass the mock up around now with a piece of paper. With the person next to you, have them spin the cane while you lightly hold the cane with the cloth wrapped around your hand. If you can determine what direction the pipe is spinning at 0.5 to 1 Hz with your eyes closed, please mark so on the piece of paper. Vice versa for cannot tell.

11. Component Breakdown
Jake

12. 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?

13. 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.

14. 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.

15. Roller Assembly Support

16. Handle Material Selection
Desirable Qualities
Moisture wicking
Higher Coefficient of Friction
Possible Options
Softex
Neoprene
Tennis Racquet Handle Cover
Top Choice
Synthetic Cloth - Nylon
Lauren

17. Handle Weight Estimate
Component
Quantity
Weight (grams)
Weight (lbs)
SpringRC SM-S4303R Servo Motor 1 41
0.09
WhataGrip Handle Cover
2.8
0.006
AA Batteries 4 92
0.203
Cross-Bar/Plate for Servo 2
136.1
0.3
5/16" Ball Bearings
8.24
0.02
MSP430 Microcontroller
Total
282.94
0.625
Lauren

18. Cost Estimate Component Quantity Price per Item (US Dollars)
Total Cost (US Dollars)
SpringRC SM-S4303R Servo Motor 2
12.95
25.90
Handle Cover
2.97
5.94
Set of Batteries 1
8.00
Cross-Bar/Plate for Servo (Cost of Aluminum) 2"x2"x1' Block
23.95
5/16" Ball Bearings 4
1.00
MSP430 Microcontroller
5.00
10.00
Rocker Switches 3
15.00
Ultrasonic Sensors
30.00
90.00
Handle Material*
White Aluminum Cane
27.00
Shipping Costs
Total
221.79
*Handle Material has not yet been decided
Lauren

19. Test Plan
Who Dat?

20. Signal Flow Diagram

21. Test Plan Detection System SimulatorBJ

22. Micro Family Selection
Arduino
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
Power
.825mW
.5mW BJ

23. Action to Minimize Risk
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
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
Create a good software building plan, test plan and look into different algorithms and methods
Will
Haptic handle and detection systems integration issues
Poor design, miscalculation
Poor/no communication between systems resulting in improper/no haptic guidance
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.
Keep in contact with customer. Follow and continually reevaluate project plan and risk assessment. Focus on the most important specs.
Jake 5
Not able to meet with customers this week (10/7 – 10/11)
Schedule conflicts, don’t respond to s
Not able to make concept selection, can’t finalize requirements (detection system)
Follow-up daily ( , phone, office hours)
Lauren
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
Stay ahead of schedule, identify the critical path
Aaron  7
Battery malfunction
Too much current being pulled, heat generated is not being removed affectively, batteries themselves
Loss of power supply, damage components
Functioning power management, removal of heat, sealed off from dirt 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
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 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
Communicate with customer and ABVI 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
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
Start early, ask for help if needed, learn program ahead of time
These are the risks that we have compiled. The importance number on the column all the way to the right is the product of the likelihood and the severity of the risk. The first 4 listed are the ones with the highest importance and they’re the tasks that are associated with the critical path. For our risk response control we have made plans to either mitigate or avoid the risk all together.

24. Action to Minimize Risk
Risk Assessment ID
Risk Item
Cause
Effect
Likelihood
Severity
Importance
Action to Minimize Risk
Owner 12
Haptic forces not being strong enough
Miscalculations, poor design
Misguided user, don’t meet customer requirements 1 3
Add adjustability to feedback, adequate components, overdesign with adjustability
Jess 13
Hardware and software integration
Poor hardware/software choice
User won’t receive haptic feedback
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
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.
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
Keep components in protective housing, keep cane in a locker when not being used 17
Excessive tapping
User cane technique, learning curve with our cane,
Make sure components are secure within their housings. 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
Consensus, reflect back to team values, consider compromises 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
Appropriate analysis of material, Acquiring material early in process for testing purposes 20
Select power and components produce excessive heat
Insufficient selection and analysis of handle components
Handle will be uncomfortable for user 2
Analysis on heat produced by components 21
Necessary facilities and personnel are not available when needed
Requesting facilities too late, contacting personnel too late
Behind schedule on necessary building/ testing
Establish early on what facilities are needed and what personnel are necessary to speak to 22
Uncoordinated team schedules
Busy workload for other classes
Deliverables not reviewed with team when needed, late deliverables
Coordiate appropiately with team's scheudles 23
System is too heavy for desired cane weight
Not properly calculating weight
Do not meet customer requirements
Make sure that everything is the desired weight

25. Risk Growth Curve
This is our risk growth curve. This graph represents the total importance of all the risks over time. We started with none and then add to the list. We plan to reduce this number to ____ by the end of MSDI.

26. Project Plan
This is our project plan leading up to the DDR. We have arranged the tasks under the different categories that they fall under. For any unforeseen delays or setbacks in the project schedule we’ve created a time buffer of one week. Those tasks that are highlighted are part of our critical path as mentioned in the risk slide.

27. Network Diagram
This diagram represents the tasks that you saw on the previous page just in more of a flow chart view so that it is easier to show the sequence of activities

28. 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]
The plan consisted of everything that we need to do for the next review, but our immediate steps are outlined here with their completion date within the next week.