Effects of 2 Ergonomic Aids on the Usability

7/27/2019 Effects of 2 Ergonomic Aids on the Usability

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Effects of 2 ergonomicaids on the usability of

an in-line screw driver

Ajay Vasanth.X [M.Tech]

PR11ME1003


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Abstract

2 ergonomic aids on in-line screw driver (pneumatic).Aids are hand support & sleeve softening the handle.

Experiment are done in 15 subject (10 men & 5

women).

Drove screws into horizontal plywood.

4 four arm muscles activities are measured (EMG).Force acting on the screw are measured.

Subjective rated the properties with respect to

physical exertion, ease of holding the tool, comfort of

grip, surface texture.


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Introduction:

Used in assembly process.

Vertical direction. Tool handled seeing the work piece only.

Physical exertion depends on:

No. of repetitions.

Torque.

Thrust force along the shaft.

Design of the screw driver.

No. GOLDEN STANDARD for assessing the usability of tool.

As comfort cant be measured.

Work depended, some freedom


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Measured Variables:

Usability assumed to be affected by:

Physical exertion (exertion). Ease of taking hold of tool (catching).

Comfort of the grip (comfort).

Surface texture (surface).

Independent variables:

Controlled: Eg :task are kept constant.

Non-controlled:

Eg : fatigue were minimized as far as possible.


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Subjects:

15 healthy volunteers (10 men & 5 women).

Age range 24-60 year. All are right handed person.

Grip sixe was measured in standard manner.

Measure of the radius of circle formed by index finger &

fleshy muscle of the base of the thumb when gripping by

standard Herig cone.


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Tools:

Four different combinations of screw drivers & ergonomic aids:


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A old fashioned model without ergonomic aids.

B old fashioned model with hand support.

Cold fashioned model with sleeve.D model ergonomic model.

Task:

Screws drove into predrilled to 3.5 mm holes in plywood plates.

Each plates contain 24 screws positioned at equal distance. Torque acting is the screw are noted.

Procedure:

Height of work table adjusted so that fore arm is horizontal.

All the ABCD are performed in random. Before the task, subjects were allowed to practice.


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Measurements:

ECU (Extensor Carpi Ulnaris).

ECR (Extensor Carpi Radialis). FDS (Flexor Digitorum Superficialis).

FDP (Flexor Digitorum Profundus).

Measured by usingbipolar surface

electrodes

Electrodes were applicated on shin of forearm in same posture of

driving screws.

Signals are amplified, processed and sampled (100 samples) . Signals are stored in a microcomputer disc at 2000 Hz. By Mega

electronics.

Before the first and after the last time, subjects perform 2 maximal

isometric gripping contractions using dynamometers.

For measuring the gripping force that is used for normalizing the

activities recorded. Thrust force along the shaft of screwdriver is measured with Kyowa

Lt200 kg gauge.


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Subjective properties of usability were inquired:

Concerning the tool individually.

Comparing the tool with the previous one. Comparing the tool individually.

A scale was used for getting the values (1 to 7)

Scale Individually Comparing

with

previous

Overall

comparison

1 Very bad Much worse Worst

4 Neutral Neutral

7 Very good Much better Best


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Statistical analysis

Measured force (objective data), answers to quires (subjective

data) are interpreted as sets of relations of form ABCD. Meaning tool A is better than B, B is better than C, & C than D.

Pre-processing makes result invariant for selection of system

of measurement between variables & subjects.

This is done individually for each forearm muscles.

Then the mean value is found out for each category.Results & Discussion:

The most popular was BDCA for Physical exertion.

The most popular was DCBA for Catching.

The most popular was DCBA for Comfort.

The most popular was CDBA for Surface.


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The results clearly shows that the model D is the most

compromising of all in all the cases.

Suggestions & Alterations Although the statistical approach is used in many areas of

finding the optimal solutions, it has a backdrop.

Instead GA can be used because if its advantages.

Search space is not altered in any cases at all.

Certain uncertainty area always present in all cases that isencountered by using mutation process.


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Effects of 2 Ergonomic Aids on the Usability