GRASP REDESIGN STANFORD

Pinching Unit Redesign – VA Rehabilitation Research & Development Center

Redesign of Free Force Sensor Pinching Unit : GRASPVA Rehabilitation Research & Development Center, Palo Alto

July-August 2005


Project Team

IIT Kanpur VA Rehabilitation Research & Development Center

Aakash Kumar

Ruchin Chaudhary

Niels Smaby

Mary Elise Johanson

Wendy Marie Murray

Eric Topp

Deborah Ellen Kenney

Stanford University

Maurice Leblanc


Project Team


Aakash Kumar

Ruchin Chaudhary

Niels Smaby

Mary Elise Johanson

Wendy Marie Murray

Eric Topp


Stanford University

Maurice Leblanc


Project Team


Aakash Kumar

Ruchin Chaudhary

Niels Smaby

Mary Elise Johanson

Wendy Marie Murray

Eric Topp


Stanford University

Maurice Leblanc


Project BriefSystem ObjectivesSystem SchematicsSystem AnalysisNeed StatementSpecifications & ConstraintsPrimary Product RequirementErgonomic AnalysisAnalysis of Existing DesignReferences and LiteratureConcept GenerationDiscussions/InteractionsPhysical mock-ups, PrototypesPreliminary User Testing & AnalysisDetailing and validationFinal PrototypeFinal Prototype AnalysisDiscussionFuture Scope*

Project Methodology: Schedule

22nd June

29th June

1st July

4th-20th July20th July

26th July27th July- 11th

August

16th August


• Tetraplegics have restricted limb movements • The tendon transfer surgery for hand can be helpful,it assist them to apply forces through thumb and index finger*• Reconstructive hand surgery enables the “key-pinch” in the subjects• Research is oriented towards these pinch force measurements

*Journal of Rehabilitation Research and Development,Mar-Apr 2004 , Niels Smaby, MS; Mary Elise Johanson, MS, PT; Brian Baker, BA; Deborah Ellen Kenney, MS, OTR;Wendy Marie Murray, MS, PhD; Vincent Rod Hentz, MD

System Objectives- Medical Application

Schematics for surgery and functioning


• Tetraplegics have restricted limb movements• The tendon transfer surgery for hand can be helpful,it assist them to apply forces through thumb and index finger*• Reconstructive hand surgery enables the “key-pinch” in the subjects• Research is oriented towards these pinch force measurements















The product is an assistive device to a study that aims to establish target pinch forces for completing selected tasks that represent a range of useful functional activities in daily life*.

• Opening and closing two types of zippers • Inserting and removing a plug• Inserting and removing a key• Inserting and removing an ATM card• Stabbing “food” with a fork• Using a remote control button


System Objectives- Bio-Medical Research






Activities of daily living (ADLs)



• Opening and closing two types of zippers• Inserting and removing a plug• Inserting and removing a key• Inserting and removing an ATM card• Stabbing “food” with a fork• Using a remote control button



































“The pinching unit or the GRASP is the clinical testing simulator of ADLs(activities of daily livings) tasks with variable openings and lateral adjustments for different individuals”

System Objectives- Product Application


System Schematics : Lateral pinch testing


“To re-design a comfortable* physical interface for a lateral pinch testing medical equipment”

* Comfortable to both, the Subject and to the Clinician

Re-Design Need Statement


Quantitative

1) Must be adjustable vertically from 14mm to 40mm2) Should weigh less than 100gms3) Must accommodate FF Sensor -Dimension Ø 40mm, Ht: 12.25mm/ Dimension Ø 17mm, Ht: 14.50mm

Qualitative

4) Must maintain a comfortable lateral pinch posture 5) Should be secured properly to the hand6) Must have quick lateral adjustment 7) Must accommodate a thumb lateral angular calibration8) Should interface with the micro scribe

Specifications and Constraints


a) Vertical adjustment: 14-40mm

b) Lateral pinch posture with hand securement

c) Quick lateral adjustment (proximal-distal adjustment)

d) Thumb orientation Calibration

e) Space orientation measurement

Keeping the comfort of the users (Subjects as well as Clinicians) into account

Primary requirements









X


































• 5%ile and 95%ile fingers and thumb data (male/female)

• Reach of the thumb and fingers (5-95-M-F)

• Comfortable grips and postures*

• Restricted and unrestricted thumb-finger movements

*Strength Data for Design Safety, Product Safety and Testing Group, Institute for Occupational Ergonomics and Division of Manufacturing Engineering and Operations Management,University of Nottingham, University Park, Nottingham NG7 2RD

Ergonomics Analysis

Hand Anthropometrics


a) Vertical adjustment

• Minimum 3mm required distance is not achievable (sensor limitation)

• Additional caps for height adjustment –Time consuming and complex(Management of additional elements required)

• Cap’s vertical wall obstruct the thumb for reaching the Sensor

Existing Design: Analysis w.r.t. primary requirements















• Strap forcefully affects the pinching direction

• Obstructs with the sensor as well as the hand at different positions

• Grip??? Is it required?

• Grip angle and girth might not cater to the entire population

























• The current distance adjustment is 11mm, required is 20mm(5-95%ile data)

• Current adjustment requires screws and dismantling entire pinching assembly- takes time

• Is it really required or can ergonomics can take care of it?


Proximal-Distal adjustment in existing design







Proximal-Distal adjustment in existing design & assembly system







Proximal-Distal adjustment in existing design & hand’s natural calibration


d) Thumb orientation measurement

• Transparent protractor printed on OHP sheet.

• Redesign needs to accommodate the calibration within the product


• Design must mate with existing micro scribe for calibration

















Concept 1 Modified Existing-1

• With Ergonomic Grip design

• Micro scribe attachment in grip

• To be strapped to the fingers

• With caps

• Existing modified-mates with the current handle

• Handle can be rotated for better fit


Concept 2 Modified Existing-2

• With Ergonomic Grip design



• With caps


• Thumb contours for maximum reach


Concept 3 Telescopic tube grip less

• Without Grip design

• Micro scribe attachment in front tube


• With telescopic shaft

• Close to the ADLs situation


Concept 4 Grip less strap design


• Micro scribe attachment in platform


• With caps


• Natural calibration


Concept 5 Grip less snap design


• Micro scribe attachment in platform sides

• To be tight-snapped to the fingers

• With caps




Concept 6 Grip less ring design


• Micro scribe attachment in platform-front

• To be worn on the fingers

• With caps




Concept 7 Thumb Grip design


• Micro scribe attachment in platform-front

• To be strapped to the wrist

• With caps



• Additional stability around thumb


With grip and without grip issue

Already a lot of patients have been tested “with grip” pre-operatively, thus achange in the entire system would not be desirable right now. So the primarydesign would focus on the ‘with grip design’. And the team can possibly explorethe other concepts for future scope.

Necessary improvements in the discussed concepts:

1) Fillets for avoiding thumb hitting the edges2) Hand Grip adjustment3) Tactile improvements for the grip surface4) Strap section to act like a grip in itself(preferable)5) Attach straps to the grip less and test it for functionality

Chosen Concepts for further detailing: 2, 4, 7

1st Discussions/Iterations/Clinician’s Interaction - 7/20/2005


Concept 2

• With Grip design



• Thumb profile contours at top

• With caps


Prototyping/Physical Mock-ups


Concept 4

• Grip-less design

• Micro scribe attachment

• Finger guide


• With Caps/Without caps



Concept 7

• Grip-less design

• Micro scribe attachment in front

• To be strapped to the wrist

• Cushioning at the hand interaction with device

• With caps



• Number of subjects-2 (1male,1female)

• Extreme cases-one close to maximum and other minimum

• Mixed reactions to the prototypes

• Contour ergonomics felt comfortable to the subjects in all the cases better than the existing

• Strapping needs to be stabilize and to be in soft Velcro (clinician’s suggestion)

Preliminary User testing and analysis 07/26/2005-SCI Lab. VAPAHCS

User testing at SCI Lab



Concept 4 Concept 7 Concept 2

Vertical adjustment 14-40mm (closest to ADLs)

14-40mm (close to ADLs)

14-40mm (with grip)

Lateral pinch posture with hand securement

Unstable. Movement with straps. Secured to forefingers

Stable. Slight movement with strap. Secured at wrist and thumb

Stable. No movement. Secured to forefingers and palm

Quick lateral adjustment (proximal-distal adjustment)

Not required Not required. Can be incorporated

Required

Thumb orientation measurement

On the platform chassis On the platform chassis On the platform chassis

Space orientation measurement

Mate with micro-scribe (in front)

Mate with micro-scribe (in front)

Mate with micro-scribe (in grip)

User’s Opinion (subjects)

Fair Good Good

User’s Opinion (Clinicians)

Good Fair Good

Detailing and Validation- Selection Criteria


The final prototype selected from the above comparative analysis for further detailing is concept 2

Detailing and Validation- Selection Criteria

Evolution of concept-2 throughout the project


• Sketches to dimensioned drawings

• Drawings to AutoCAD data files for slices

• AutoCAD dxf files to Laser cutter

• SolidWorks model from AutoCAD data

• STL/IGES data exchange for CNC milling (possible CAM application)

• Laser cutter slices assembly and finishing

• Velcro assembly and fittings /Alternate details

Detailing and Validation- CAD/CAM


Final Prototype

Images showing the comfortable strapping and grip posture

Adjustability for lateral movement through caps


Final Prototype – Working Drawings/ Platform

`

Platforms with High Visibility Thumb calibration


Final Prototype – Working Drawings/ Caps

Different sized caps


Final Prototype – Cost Specifications

• Raw material (wood-Balsa, Bass) ___ U.S.$ 12.50• Glues/Adhesives ___ U.S.$ 2.75• Laser cutter running cost ($2.5/Hr) ___ U.S.$ 7.50• Velcro Straps ___ U.S.$ 3.00

Total Prototype Cost ___ U.S.$ 25.75(INR 1,112)


Final Prototype: Comparative Analysis with Existing Design

• Eliminated the rings-only caps required

• Two angles for lateral pinch posture

• Compact proximal-distal adjustment

• Mates with the current micro-scribe

• Integrated Thumb calibration provided

• Comfortable profile for the subject (fillets)

• Better securement to the hand

• Close to the correct position of Key-Pinch

• Less interchangeable parts for Clinicians

• Quick and easy adjustment of straps
























































• Comfortable profile for the thumb (fillets)


































































• Better finish prototype with CNC milling or rapid prototyping (assembly drawings ready)

• Minimum 3mm distance can be achieved by cantilever and 2nd lever application (Conceptual sketches already discussed)

• Concept-7 can be developed further with CNC machined elastomeric material for comfort fit (assembly drawings ready)

• Caps can be eliminated through telescopic assembly in the shaft, which would provide quicker and compact assembly(Conceptual sketches already discussed/optional)

• Robotic arm sensor can be calibrated with Gyro and Micro scribe to be used as pinching unit

• Pinch pulling through friction can be tested for very small gapopenings

Future Scope








Future Scope





• Caps can be eliminated through telescopic assembly in the shaft,which would provide quicker and compact assembly(Conceptual sketches already discussed/optional)



Future Scope








Future Scope






• Robotic arm sensor can be calibrated with Gimbals and Micro scribe to be used as pinching unit


Future Scope








Future Scope


2nd Discussions/Iterations/Clinician’s Interaction - 8/16/2005

• Satisfied with the development of the final prototype

• Likes the idea, that improved design is in coherence with current system

• Soon the prototype would be developed in the final product (Manufacturing)

• Would like to observe the subject’s interaction with the final design, and would notify Design team of results and necessary changes, if required


Thank you !

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