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
Sum
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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]