Performance characteristics of anthropomorphic prosthetic hands

IEEE International Conference On Rehabilitation Robotics Rehab Week Zurich, ETH Zurich Science City, Switzerland

By

JOSEPH T. BELTER AND AARON M. DOLLAR

Presented byA.C.K. Priyankara100414A

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ANTHROPOMORPHIC PROSTHESES

“suggesting human characteristics for animals or inanimate things”

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SPECIFICATIONS OF CURRENT HANDS

• PHYSICAL PROPERTIES

• HAND WEIGHT

• HAND SIZE

• DURABILITY/ CYCLE OF USE

• ACTUATION PROPERTIES

• ACTUATION TYPES

• GRIP FORCE

• GRASP SPEED

• KINEMATIC PROPERTIES

• ACHIEVABLE GRASP

• JOINT COUPLING METHOD

• THUMB DESIGN

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HAND WEIGHT

• AVERAGE HUMAN HAND WEIGHT AROUND 400G

• 79% OF USERS CONSIDERED THEIR DEVICE IS TOO HEAVY

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• RANGE OF 113-615 GRAMS IS SEEN IN CURRENT COMMERCIAL PROSTHETICS

• 350 TO 2200 GRAMS IN RESEARCH BASED HANDS

HAND SIZE

• LENGTH BETWEEN 180-198 MM

• WIDTH OF 75-90 MM

• COSMETIC APPEARANCE

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Type Overall Size Weight

Hosmer hand 124mm long 113-312g

SensorHand - 350-500g

Becker Hand 143mm long 382-467g

i-Limb 180-182mm/80-75mm/35-41mm

450-615g

Bebionic 198mm/90mm 495-539g

DURABILITY/ CYCLE OF USE

• REQUIRED ACTIVE TIME IS HIGHER THAN 8 HOURS A DAY

• 2500-3000 GRASPING MOTIONS OF THE NATURAL DOMINANT HAND

• TYPICAL PROSTHETIC HAND WILL UNDERGO 1200 CYCLES PER DAY

• LIFETIME OF PROSTHETIC HAND 300, 000 CYCLES

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• DC MOTORS

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ACTUATION TYPES

GRIP FORCE

• GRASP FORCES DEPENDING ON THE SIZE OF

THE OBJECT

• HUMAN HAND CAN EXERT AN AVERAGE OF

95.6 N OF FORCE IN PRECISION GRASP

• THE FORCES CAN REACH UP TO 400 N IN

POWER GRASP

• MINIMUM GRIP FORCE OF 45 N FOR

PROSTHETIC HANDS FOR PRACTICAL USE

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GRASP SPEED

• 100% OF FEMALES, 76% OF MALES, AND 50% OF CHILDREN STATED RESPONSE

TIME IS TOO LOW

• MAXIMUM FLEXION SPEED OF HUMAN HAND IS 2290 DEGREES/SEC

• AVERAGE HUMAN HAND SPEED IS 172 TO 200 DEGREES/SEC

• ONE SECOND CLOSING TIME IS ADEQUATE FOR PROSTHETIC ARM

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ACHIEVABLE GRASP

• TYPICAL DAILY ACTIVITIES FOR AN AMPUTEE CAN BE ACCOMPLISHED USING A FINITE

SET OF PREDEFINED GRASPS

• 35% OF POWER

• 30% OF PRECISION

• 20% OF LATERAL

• 15% OF OTHER (HOOK, TRIPOD, FINGERPOINT, AND GESTURING)

• MOVEMENT OF THE THUMB CIRCUMDUCTION AXIS TO ACCOMPLISH FIVE OF THE

SEVEN COMMON GRASP PATTERNS

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JOINT COUPLING METHOD

• NUMEROUS JOINTS WILL BE COUPLED TO ACT AS A SINGLE COMPOUND MOTION

• UNDER ACTUATION

• ADAPTIVE FINGER DESIGNS

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THUMB DESIGN

• THE THUMB ACCOUNTS FOR UP TO 40% OF THE ENTIRE FUNCTIONALITY OF THE

HUMAN HAND

• THE THUMB IS ACTUATED IN FLEXION/EXTENSION AND ALONG THE

CIRCUMDUCTION AXIS

• AVERAGE CIRCUMDUCTION MOTION IS 90.2 DEGREES

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THANK YOU

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