Question

Prosthetic hand
Component
Description
Title Page
Project engineers names (make sure to use the words project engineer)
Name of build
Dates
Table of Contents
Title of each page and page #
Header
Title page info on each page
Footer
Page numbers
Problem Statement page
Problem Statement
Criteria
Constraints
Supplies
Brainstorm
3 or more unique sketches
Pugh Chart
Table created to show which is the best choice.
Minimum of 4 criteria and 4 build sketches
Written description that clearly defines why this model was the best choice for this project. Use all the criteria in your reasoning. Also think about contrasting your decision making with the reasons why the other models were not chosen.

Answer 1

Title Page (Page 1)
- Project name: Adaptive Assist Hand — Prototype Build
- Project Engineers:
- Project Engineer: Alice Johnson
- Project Engineer: Miguel Santos
- Project Start Date: 2025-09-01
- Report Date: 2025-12-11

Header (appears on every page)
- Adaptive Assist Hand — Project Engineers: Alice Johnson, Miguel Santos

Footer (appears on every page)
- Page number (bottom center)

Table of Contents (Page 2)
1. Title Page — Page 1
2. Table of Contents — Page 2
3. Problem Statement & Requirements — Page 3
4. Supplies & Constraints — Page 3
5. Brainstorm — Sketches & Descriptions — Pages 4–7
- Sketch 1 — Page 4
- Sketch 2 — Page 5
- Sketch 3 — Page 6
- Sketch 4 — Page 7
6. Pugh Chart — Comparative Evaluation — Page 8
7. Decision and Rationale — Page 8

Problem Statement & Requirements (Page 3)
Problem Statement
- Many upper-limb amputees or people with limited hand function need an affordable, reliable prosthetic hand that restores basic grasping and holding functions for activities of daily living (ADLs). The project goal is to design and build a prototype prosthetic hand that is low-cost, durable, easy to manufacture/repair, and provides functional grasping (cylindrical, pinch, and power grips).

Design Criteria (prioritized)
1. Dexterity / Functionality — ability to perform common grasps (weight: 4)
2. Cost — total parts and manufacturing cost (weight: 3)
3. Reliability / Durability — expected lifetime under normal use (weight: 3)
4. Ease of Build / Maintainability — skills, tools required, repairability (weight: 2)
5. Weight / Comfort — mass and wearability (weight: 2)

Constraints
- Budget limit: target < $300 in parts for prototype (excluding tools)
- Tools/materials available: 3D printer, hand tools, basic electronics bench, sewing kit
- Time: prototype build and testing within 12 weeks
- Safety: no sharp exposed parts; pinch forces limited to safe levels for user training
- Regulatory: non-clinical prototype (for testing/education only) — not for clinical prescription without further certification

Supplies (example parts & materials)
- 3D printing filament (PLA or PETG) and access to printer
- Nylon fishing line or braided cable (for tendon/cable actuation)
- Small DC motor + planetary gearbox or servo motor (if powered)
- Springs / elastic bands for return
- Aluminum or PLA palm plate / structural pieces
- Finger joints (printed flex joints or pin-and-bushing)
- Fasteners, screws, velcro straps for mounting
- Foam/silicone for cosmetic glove or padding
- Microcontroller (optional; e.g., Arduino Nano) and battery if powered
- Myoelectric sensors (optional and more expensive if doing EMG control)
- Hand tools, soldering iron, adhesives

Brainstorm — Sketches & Descriptions (Pages 4–7)
Note: below are four distinct build concepts. For each: title, short description, materials, pros/cons, and a simple drawing instruction (use these to make quick sketches).

Sketch 1 — Cable-driven multi-joint 3D-printed hand (Baseline)
- Description: Each finger has multiple joints printed with pin/bushing or flex-joint. Tendons routed through finger channels attach to wrist-mounted cable anchors. A single wrist-mounted pull (or single actuating lever) tensions multiple cables to close fingers; return springs or elastic reopen them.
- Materials: 3D printed parts, fishing line, springs, screws, wrist anchor plate.
- Pros: Low cost; straightforward to print; scalable; lightweight.
- Cons: Limited independent finger control; may be less adaptive to irregular objects; manual or single actuator limits dexterity.
- Sketching directions (simple): draw palm plate, four fingers with 3 segments, lines representing tendons going into wrist anchor. Label springs at finger bases.

ASCII mini-diagram:
Palm [====] — fingers: |—|—| |—|—| |—|—| |—|—|
Cables -> wrist anchor [O]

Sketch 2 — Body-powered split-thumb (lever or harness actuation)
- Description: Mechanical harness channels user shoulder/elbow motion (via cable) to actuate fingers and rotate a split-thumb for opposition; no motors or electronics. Thumb movement is mechanical and adjustable for different grip types.
- Materials: Cables, harness straps, pulleys, lightweight linkages, 3D-printed finger segments.
- Pros: Very low power requirements (no battery), intuitive control, robust in field, lower cost.
- Cons: Requires wear on body/harness; limited fine control; can be fatiguing to user; may be less acceptable cosmetically.
- Sketching directions: draw harness on shoulder, a cable to wrist anchor, mechanical linkage to thumb and finger cables.

Sketch 3 — Myoelectric motorized hand (multi-DoF)
- Description: Multiple small motors (or smart servos) drive each finger joint or finger group; control via EMG sensors detecting residual muscle signals. Provides independent finger motion and better dexterity.
- Materials: Micro servos/motors, motor drivers, myoelectric sensors, microcontroller, battery, printed structural parts.
- Pros: High dexterity, better for complex tasks, more natural control potential.
- Cons: High cost, complexity in control and electronics, heavier, requires calibration and maintenance.
- Sketching directions: draw palm with motors at the palm, wires to fingers, EMG electrodes on forearm, battery and controller mounted proximally.

Sketch 4 — Underactuated adaptive hand — single motor, compliant fingers (Selected candidate)
- Description: A single motor (or hand-crank) drives a differential/tendon routing system so fingers adapt to object shape (underactuation). Fingers have compliant joints or elastic elements so contact forces are distributed automatically, enabling robust grasps with fewer actuators.
- Materials: 3D-printed palm and finger phalanges, 1 motor or manual actuator, tendon routing, passive springs/compliance, simple linkage/differential mechanism.
- Pros: Good balance of dexterity and cost; adaptive grip for irregular objects; fewer motors → lower weight and maintenance; robust.
- Cons: Less independent control per finger than full myoelectric solution; mechanism design more complex than simple cable hand.
- Sketching directions: draw single motor at base, a differential box or pulley distributing cable to fingers, fingers with flexible joints.

ASCII mini-diagram:
Motor -> differential pulley [@] -> 4 tendons -> fingers
Fingers: [|—|—|] [|—|—|] [|—|—|] [|—|—|]

Pugh Chart — Comparative Evaluation (Page 8)
- Method: Use Design A (Cable-driven multi-joint 3D-printed hand) as the baseline (score = 0). For each other design, evaluate relative performance against baseline on each criterion: + (better), 0 (same), - (worse). Use weighted scoring: +1 = weight, 0 = 0, -1 = -weight. Sum scores to get comparative ranking.

Criteria and weights:
- Dexterity (weight 4)
- Cost (weight 3)
- Durability/Reliability (weight 3)
- Ease of Build/Maintainability (weight 2)
- Weight/Comfort (weight 2)
Total possible per design depends on signs.

Designs:
A — Baseline: Cable-driven multi-joint 3D-printed hand (score = 0 by definition)
B — Body-powered split-thumb
C — Myoelectric motorized hand
D — Underactuated adaptive hand (single motor)

Pugh scoring table (relative to A):

Criteria (wt) | B (Body-powered) | C (Myoelectric) | D (Underactuated)
Dexterity (4) | - ( -4 ) | + ( +4 ) | + ( +4 )
Cost (3) | + ( +3 ) | - ( -3 ) | + ( +3 )
Durability (3)| + ( +3 ) | - ( -3 ) | + ( +3 )
Ease of Build (2)| + ( +2 ) | - ( -2 ) | 0 ( 0 )
Weight (2) | + ( +2 ) | - ( -2 ) | + ( +2 )
---------------------------------------------------------------
Sum | (-4+3+3+2+2)=+6 | (4-3-3-2-2)=-6 | (4+3+3+0+2)=+12

Interpretation:
- Design D (Underactuated adaptive hand) scores highest (+12).
- Design B (Body-powered) is a decent alternative (+6); strongest on cost and durability but lower dexterity.
- Design C (Myoelectric) scores lowest (-6) because although high on dexterity, the cost, weight, complexity and maintenance penalties outweigh benefits for this project’s constraints.
- Baseline A is moderate; D improves dexterity while keeping cost and durability favorable.

Decision and Rationale (Page 8)
Selected model: Design D — Underactuated adaptive hand (single motor with compliant fingers)

Why this model is the best choice (use all criteria)
- Dexterity (weight 4): Underactuated designs give significant functional gains because finger tendons and compliance allow the hand to conform to a wide variety of object shapes, enabling effective cylindrical and pinch grasps with a single actuator. This yields better practical dexterity than the baseline cable-driven design (which lacks adaptive force distribution) and is close to multi-motor myoelectric hands in everyday tasks.
- Cost (weight 3): Using a single motor and mostly 3D-printed structural parts keeps parts costs low compared with multi-motor myoelectric hands. It’s slightly more expensive than purely body-powered systems but provides much better functionality for a modest increase in cost.
- Durability/Reliability (weight 3): Fewer moving motors and simpler electronics reduce failure modes. Mechanical differentials and tendon routing are robust and easier to maintain than multiple small servos. Compared with myoelectric options, D is less likely to fail in field conditions.
- Ease of Build/Maintainability (weight 2): The underactuated solution requires more careful mechanism design than a basic cable-hand, but it avoids complex electronics and sensor calibration demanded by myoelectric wrists. Repairs typically involve tendons, springs, or a single motor replacement, simplifying maintenance compared with multi-actuator systems.
- Weight/Comfort (weight 2): One motor and compact transmission keeps the distal mass lower than multi-motor hands, improving comfort versus design C and comparable to A and B.

Contrast with other models
- Versus Design A (Baseline cable-driven multi-joint): D retains many low-cost, printable advantages but adds adaptive behavior so it achieves more reliable, conforming grasps. It trades a small increase in mechanical complexity for a large gain in functional performance.
- Versus Design B (Body-powered): B is low-cost, durable, and simple, but requires a harness and user exertion, which can be fatiguing and less socially acceptable. D delivers improved ease of use (motorized closure or simple mechanical actuator) and better grasp adaptation while keeping cost and reliability good.
- Versus Design C (Myoelectric): C offers the highest theoretical dexterity, but at the expense of cost, weight, electronics complexity, calibration needs, and maintenance. For the project constraints (budget, simple manufacture, short timeline), the myoelectric approach is not practical for a first prototype.

Implementation notes (next steps)
- Detailed CAD of palm/differential pulley box and finger geometry (optimize finger length ratios and flex compliance).
- Prototype one finger module and test tendon routing, joint compliance, and return-spring forces.
- Select motor with appropriate torque and gearbox (aim for safe pinch force and reasonable speed).
- Fabricate full prototype, implement simple control (on/off motor control or proportional PWM) and test common ADLs (grasp a cup, pick up a key, hold a bottle).
- Iterate based on user feedback: adjust tendon paths, finger stiffness, and mount ergonomics.

Appendix (optional)
- Suggested parts list for Design D (example):
- 3D filament: 500 g PLA/PETG
- Single DC motor with gearbox (e.g., 12V, 10–20 kg·cm after gearbox)
- Motor driver and small battery pack (if powered)
- 4x lengths of braided fishing line (tendons)
- Compression springs for finger return or elastic bands
- Fasteners, velcro strap for forearm mounting
- Foam glove or silicone coating for fingertip friction

Notes for document formatting
- Put the header text at the top of each page exactly as: "Adaptive Assist Hand — Project Engineers: Alice Johnson, Miguel Santos"
- Put the page number centered in the footer.
- Place the Title Page information (as listed) on every page header per requirement.
- Replace the sample Project Engineer names, dates, or build name as desired.

If you want, I can:
- Produce printable sketches (SVG/PDF) from the sketch descriptions.
- Create a CAD-ready parts list or BOM with estimated costs.
- Draft the assembly instructions for the selected Design D with step-by-step fabrication guidance. Which would you like next?