e-NABLE Hand Test Rig

e-NABLE Hand Test RigP16061David Schwartz, Tia Parks, Shannon Barry, Samantha Mason, Charles Rumfola

Agenda● Recap

○ Customer Requirements○ Engineering Requirements ○ Effective Access Technology Conference

● Subsystems○ Subsystems from Last Phase○ Subsystems from This Phase

■ Motor■ Load Cell Amplifier Shield ■ Display / Data Analysis

● Prototyping○ Clamp Mounting Prototyping○ Strain Gauge Prototyping

● Design Drawings● Bill of Materials● Risk Assessment ● Block diagram● Test Plans ● Plans for Next Phase ● Preliminary Plans for MSD II

Customer Requirements

● Inexpensive, $200 should be the maximum for construction● Portable● Repeatable● Adaptable to other prosthetic models● Easy to use● Continuous Data Acquisition● Does not alter prosthetics or remove any pieces● Test the full hand strength, an overall grip strength test

versus the angle of the wrist flexion

Engineering Requirements

Requirement # Importance Metric Unit Target Value Subsystem

S1 9 Cost $ 200 Entire ApparatusS2 6 Weight of tester lbs 50 Entire ApparatusS3 5 Duration of test min 5 MotorS4 9 Max Force of Sensor lbs 50 Load CellS5 8 Torque oz/in 250 Motor

S6 8Force Measurement Accuracy oz +/- 1 Load Cell

S7 8Angle Measurement Accuracy ° +/- 2 Motor

S8 7Repeatability using gauge R&R

%10% due to

measurement error

Entire Apparatus

Effective Access Technology Conference

● MAGIC ACT e-NABLE Lab’s booth● November 10th, 2015

Subsystem Chosen

Clamp 6" Medium Trigger Clamp

Strain Gauge 50kg Single Point Load Cell

Controller / Processor Arduino Uno

Motor Shield Adafruit Motor/Stepper/Servo Shield

Subsystems from Last Phase

Subsystem Chosen

Motor Stepper Motor- NEMA-23

Load Cell Amplifier Shield RobotShop - Load Cell Amplifier Shield

Display / Data Analysis PLX-DAQ

Subsystems from This Phase

Motor- Torque Requirements● Torque requirements determined through

measuring e-NABLE gauntlet length and max force exerted

● Due to the small sample size and uncertainty of the data, the highest value calculated was multiplied by a factor of 3 to yield our basis for holding torque

● _max = 11.79 lb*in (189 oz*in)

NameMax

ForceGauntlet Length

Calculated Torque (F*L/2)

Torque Value

Raptor (Green) 1 lb 2 oz 4 in 2.25 lb*in 36 oz*in

Raptor (Blue) 1 lb 1 oz 3.4 in 1.81 lb*in 28.96 oz*in

Raptor (Black and White w/ Whippletree)

1 lb 13 oz

4.33 in 3.93 lb*in62.88 oz*in

Motor Pugh Chart● Stepper Online Nema 23

○ $24.42○ Requirements - 24-48V, 2.83A○ Holding Torque - 283 oz*in○ Step Angle - 1.8°

● Pololu 1477○ $49.95○ Requirements - 8.6V, 1.0A○ Holding Torque - 190 oz*in○ Step Angle - 1.8°

● Robotshop Nema 17○ $48.00○ Requirements - 12V, 1.7A○ Holding Torque - 667 oz*in○ Step Angle - 0.018°

● MPJA Nema 23○ $23.95○ Requirements - 5.7V, 2.3A○ Holding Torque - 222 oz*in○ Step Angle - 1.8°

Criteria Stepper Online

Nema 23

Pololu 1477

Robotshop Nema 17

MPJA Nema 23

Cost

Datum

- - +

Required Voltage + + +

Required Current + + +

Holding Torque - + -

Step Angle S + S

+

Datum

2 4 3

S 1 0 1

- 2 1 1

Total 0 3 2

Even though Nema 17 scores higher, the torque is way over what is needed, and the cost is high

Motor Pugh Chart Cont.Criteria Stepper Online

Nema 23 Pololu Robotshop MPJA Nema 23

Cost + -

Datum

+

Required Voltage - + S

Required Current - + -

Holding Torque - - -

Step Angle - - -

+ 1 2

Datum

1

S 0 0 1

- 4 3 3

Total -3 -2 -2

MPJA Nema 23 scored higher in the first assessment.

Load Cell Amplifier ShieldThis load cell shield was chosen this phase. Rather than using an instrumentation OpAmp

Reasons behind the switch:-We won't have to make our own PCB. -Easier for end user/maker to obtain.-Commonly used with the Strain Gauge that we have chosen.-It is compatible with Arduino

Display / Data Analysis

PLX-DAQ was chosen.

● “GoBetwino” is a computer program, not just an Arduino function. This makes both options having equivalent ease of use.

● PLX-DAQ was design to interface between Arduino and Microsoft Excel.

● Previous experience with PLX-DAQ.

Clamp Prototyping● The clamp was mounted to a pair

of screws after drilling holes through it

● On the final prototype, these screws will be much longer rods that can be adjusted based on the hand

● The hard, plastic surface of the clamp was supplemented with adhesive foam to improve grip strength

Strain Gauge Prototyping

● With provided code, strain gauge prototyping was a success.○ Outputs were meaningless because it

was not calibrated.● Interfacing with PLX-DAQ was

unsuccessful.○ Planning a consult with someone

more familiar with PLX-DAQ.

Design Drawing

Design Drawing Continued

New method of clamp mounting due to prototyping

Bill of MaterialsID Part Name Quantity Vendor Price/Unit Total Price Make/Buy1 Arduino Uno 1 Mouser $24.95 $24.95 Buy2 Stepper Motor 1 MPJA $23.95 $23.95 Buy

3 Wood Base 3 - - Acquire

4 Wooden Wheel 1 Home Depot $5.85 $5.85 Buy/Make

5 Clamp 1 Home Depot $10.97 $10.97 Buy

6 Sensors 5 $8.95 $44.75 Buy7 Load Cell 3 RobotShop $7.00 $21.00 Buy8 Motor Shield 1 Mouser $19.95 $19.95 Buy

9 Wooden Dowel 1 $6.94 $6.94 Buy

10 Screws 4 - - Acquire11 Op Amp 2 Mouser $4.74 $9.48 Buy12 Power Supply 1 Mouser $11.34 $11.34 Buy13 Load Cell Amp Shield 1 RobotShop $19.95 $19.95 Buy

Total - - - $199.13 -

Order Totals with Shipping Price StatusOrdered from Mouser $73.27 DeliveredOrdered from MPJA $38.03 On OrderOrdered from RobotShop $49.95 DeliveredTotal $161.25 -

Risk Assessment

Risk Assessment cont.

● Risk Improvements: ○ Sensor force range ○ Budget○ Material arrival○ Clamp risks (breaking hand, doesn’t mount well)

● New Risks: ○ Additional padding on clamp not secure○ Components not compatible○ Missing components

● Biggest Risks: ○ Lack of knowledge with programming & Electrical ○ Clamp does not secure hand well enough

Electrical Schematic

Apparatus Test

Motor Testing

Duration Testing: Measure how long it takes the fingers of the prosthetic hand to reach 45 degrees from starting position

Motor Testing ContinuedTorque Testing:

Motor Testing Continued

Angle Measurement Accuracy Testing:

Strain Gage Testing

Plans for Next Phase

Preliminary MSD II Plans● Finalize Prototype

○ Assemble Components for Base○ Assemble Strain Gauge○ Assemble Subsystems together○ Code Arduino

● Test Prototype○ Verify Engineering Requirements are met○ Repeat tests with different hands○ Test with customer

● Acquire customer feedback● Order more parts if needed● Revise Prototype

○ Make adjustments to design as necessary● Finalize Apparatus Design

○ Test Apparatus