Formulation of Model to Execute the Comfortability Factor for Office Workstation

Formulation of Model to Execute the Comfortability Factor for Office Workstation

Mangesh Phate1, Sunil Dambhare1, Kiran Jathar3, Nitin Kendre4, Meghna Nehete 5, J. Patil6

1,2 Faculty, Department of Mechanical Engg,TSSMS,PVPIT,Bavdhan, Pune University, Pune,MH,India

3-5 Student, Department of Mechanical Engg,TSSMS,PVPIT,Bavdhan, Pune University, Pune ,MH,India

Abstract :Nowadays use of computer workstations are increasing as computer technology advances, as a result occupational health and safety problems are continuously increasing.The objective of research is to study and identify ergonomic deficiencies in the office chair design in the typical educational offices. Physical measurement and questionnaires were used to study 100 workstations. Major ergonomic deficiencies were in physical design and layout of workstations, postures, work practices and training. The consequences in terms of user health and other problems were significant.

INTRODUCTION

Ergonomics is the science and technology of fitting the activities and environment to the abilities, dimensions, and needs of people to improve while enhancing comfort, health and safety. Companies have realized the importance of ergonomics because ergonomically designed products have a competitive advantage in the marketplace. A product may be simple or complex; however, its development process involves a series of events of identifying the users needs, defining design concepts, making a prototype, testing usability, and releasing a product to the market. Iterative application of the most relevant knowledge and experience throughout this process will yield an ergonomically sound product. Ergonomists aim to provide working conditions which were well above the minimum required to ensure health and safety of the workforce. Thus, in achieving a comfortable, productive and satisfying office environment, any musculoskeletal complaints would also be minimized. To design such an environment, it was necessary to consider not only furniture and equipment, but also the job designs, lighting, noise, air quality, office landscaping and personal space. This work concentrates on furniture and equipment which both had a strong influence on postures.

HISTORY: As early as 18th century doctors noted that workers who required to maintain body positions for long periods of time developed musculoskeletal problems. Within last 20 years research has clearly established connections between certain job tasks and RSI or MSD.ergonomy caused various types of problems like Thoracic Outlet Syndrome.

Experimentation:

PARAMETERS UNDER INVESTIGATION

Anthropometric parameters:

1. Eye height 2.Eye height sitting 3. Sitting height

4. Shoulder breadth 5.Chest depth 6. Heap breadth

7. Heap breadth sitting 8. Acrimony height sitting 9. Shoulder elbow length

10. Elbow Hand length 11.Maximum horizontal reach 12. Elbow rest height

13. Buttock knee length 14.Buttock popliteal length 15. Direct thigh length

16. Knee height 17. Popliteal height 18. Elbow center to hand length

19. Elbow elbow breadth 20. Thigh clearance height 21.Knee knee breadth

22. Leg length

Chair Design Parameter:

a .Seat height b. Seat depth c. Seat width d. Backrest height

e. Backrest width f. Backrest lumbar g. Arm rest height h. Arm rest length

1. Distance between arm rests Workstation Parameters:

   1. Horizontal eye-to-moniter distance 2. Eye to monitercentre distance

3. Angle of elbow 4. Angle of knees

5. Shoulder to mouse distance 6. Workstation height

7. Leg minimum height clearance 8. Chair seat height

1. Seat depth

   1. Backrests	2.Visibility	3.Neck	4. Shoulders	5. Eye height
   6. Numbness	7. Hands	8. Lower back	9. Upper back	10. Legs

   Output parameters: Comfortable level(Survey Base):

   Observation Table:-

   Parameters

   Staff 1

   Staff2

   Staff3

   –

   –

   –

   –

   –

   Staff100

   Age

   24

   25

   26

   –

   –

   –

   –

   –

   36

   Experience

   1

   6months

   2

   –

   –

   –

   –

   –

   10

   Weight

   68

   64

   70

   –

   –

   –

   –

   –

   79

   Eye height

   157

   150

   155

   –

   –

   –

   –

   –

   134

   Eye height sitting.

   115

   106

   113

   –

   –

   –

   –

   –

   114

   Sitting Height.

   126

   125

   128

   –

   –

   –

   –

   –

   119

   Shoulder Breadth.

   46

   45

   47

   –

   –

   –

   –

   –

   45

   Chest depth.

   35

   35

   35

   –

   –

   –

   –

   –

   35

   Hip breadth.

   38

   40

   42

   –

   –

   –

   –

   –

   34

   Hip breadth sitting.

   43

   45

   45

   –

   –

   –

   –

   –

   37

   Acrimony height sitting.

   43

   45

   45

   –

   –

   –

   –

   –

   37

   Shoulder elbow length.

   30

   32

   30

   –

   –

   –

   –

   –

   35

   Elbow hand length.

   29

   28

   28

   –

   –

   –

   –

   –

   31

   Maximum horizontal reach.

   76

   75

   75

   –

   –

   –

   –

   –

   75

   Elbow rest height.

   60

   59

   60

   –

   –

   –

   –

   –

   71

   Buttock knee length.

   54

   57

   55

   –

   –

   –

   –

   48

   Buttock popliteal length.

   43

   45

   43

   –

   –

   –

   –

   –

   39

   Leg length.

   86

   89

   89

   –

   –

   –

   –

   95

   Direct thigh length.

   48

   50

   46

   –

   –

   –

   –

   –

   44

   Knee height.

   55

   53

   53

   –

   –

   –

   –

   –

   54

   Popliteal height.

   46

   48

   48

   –

   –

   –

   –

   –

   53

   Elbow centre to hand length.

   50

   49

   48

   –

   –

   –

   –

   –

   43

   Elbow elbow breadth

   43

   43

   45

   –

   –

   –

   –

   –

   53

   Thigh clearance height.

   3

   4

   3

   –

   –

   –

   –

   –

   4

   Knee to knee bre-adth

   46

   48

   46

   –

   –

   –

   –

   –

   42

   Chair datasheet

   Parameters

   chair 1

   Chair2

   Chair3

   –

   –

   –

   –

   –

   Chair100

   Seat height ( Popliteal height + Shoe Allowance )

   46

   45

   47

   –

   –

   –

   –

   –

   50

   Seat depth ( Buttock Popliteal length clearance allowance)

   40

   43

   43

   –

   –

   –

   –

   –

   49

   Seat width ( Hip Breadth , sitting + Clothing allowance)

   50

   51

   46

   –

   –

   –

   –

   –

   46

   Back rest height ( none )

   41

   40

   45

   –

   –

   –

   –

   –

   49

   Backrest breadth )

   width

   (

   Waist

   50

   55

   39

   –

   –

   –

   –

   –

   31

   Backrest Lumbar ( none)

   55

   72

   75

   –

   –

   –

   –

   –

   85

   Armrest height ( Elbow rest height)

   50

   43

   43

   –

   –

   –

   –

   –

   64

   Armrest length ( none )

   69

   65

   63

   –

   –

   –

   –

   –

   68

   Distance between armrest ( Hip breadth ,sitting + Clothing allowance )

   49

   49

   51

   –

   –

   –

   –

   –

   47

   Workstation datasheet

   Parameters	Workstation 1	Workstation 2	Workstation 3	–	–	–	–	Workstation 100
   Horizontal eye-tomonitor distance.	55	72	75	–	–	–	–	78
   Eye-to-monitor center distance.	52	70	72	–	–	–	–	75
   Angle of Elbow	60	75	75	–	–	–	–	79
   Angle of knees	120	115	118	–	–	–	–	120
   Shoulder to mouse distance	80	118	95	–	–	–	–	80
   Workstation height.	56	85	70	–	–	–	–	56
   Leg minimum height clearance.	76	60	76	–	–	–	–	76
   Chair seat height	30	28	29	–	–	–	–	30
   Seat depth	33	28	43	–	–	–	–	39

   Procedure-

   Firstly we selected the model for our project. We selected the project related to our project and then we tried to gather information on our related topic. We gathered information from various research papers searched and also from the books related to the topic.

   Then we analyzed all the parameters which affect the ergonomic comfort of humans. We divided them into anthropometric parameters, chair parameters and workstation parameters. We considered them and divide them into various positions. We defined various parameters of anthropometric parameters, chair parameters and workstation parameters.

   We defined workstation in our college institution. Then took the readings of various parameters with 100 different workstations. We also divided comfort zone in various parameters between rating 1 to 5, where 1 is worst condition and 5 is best condition. Then analyzed the data by plotting graph. We came on conclusion that there is vast difference in readings depending upon gender, age and size. So we needed to develop mathematical model to come on specific conclusion .Response curve was plotted depending upon the readings. Then we gave various parameters to the specific readings. By Mapping Buckinghams pi theorem to regression situation. We prepared the equation so that we can find out the paramerters.Final result was drawn from the mathematical model.

   FLOWCHART (PROCSS FOLLOWED IN COMPLETING PROJECT

   START

   SELECT TOPIC

   RESEARCH ON TOPIC

   GATHER RESEARCH PAPER RELATED TO PROJECT

   SELECTION OF VARIOUS PARAMETERS WHICH AFFECT ERGONOMY AND DIVIDE THEM INTO VARIOUS PARAMETERS.

   DEFINE ANTHROPOMETRIC PARMETERS, WORKSTATION PARAMETERS AND CHAIR PARAMETERS.

   A

   A

   ANALYSE GRAPH AND DRAW RESPONSE CURVE.

   SUBSTITUTE VALUES GATHERED BEFORE IN MATHEMATICAL MODEL.

   FINAL RESULT

   DISCUSSION AND CONCLUSION

   FUTURE SCOPE RELATED TO PROJECT

   END

   Model Formulation: Following symbols are used:

   IP1: Input dimensionless pi term for human personal data IP2: Input dimensionless pi term for Anthropometric data IP3: Input dimensionless pi term for chair design parameters IP4: Input dimensionless pi term for Workstation parameters Op1: Output dimensionless pi term for chair seat

   Op2: Output dimensionless pi term for chair Visibility parameters Op3: Output dimensionless pi term for discomfort in the body

   The possible relation may be linear, log linear, polynomial with n degrees. Linear with products of independent pi terms. In this manner any complicated relationship can be evaluated and further investigated for error. Mapping Buckinghams pi theorem to regression situation.

   Op1 = K0 x IP1 K1 x IP2 K2 x IP3K3 x IP4 K4 (Eqn. 1)

   This dimensionless statement is easily transformed into linear relationship using log operation.

   Log(OP1)=Log( K0) +K1 Log( IP1) +K2 Log(IP2 ) +K3Log( IP3)+ K4Log( IP4) (Eqn 2)

   In this case we have six independent entities, ruling out the possibility of polynomial relationship i.e.

   Y= a0 + a1 x + a2 x2 + a3 x3 +———+ an xn (Eqn. 3) The general form of Buck hams pi theorem can be stated as

   Op1 = K0 x IP1 K1 x IP2 K2 x IP33K3 x IP4 K4 (Eqn.4)

   Old K0 is not referred hereinafter for any purpose. Wherever necessary value of constant can be computed by e new K0 hence equation is modified as

   OP1 = eK0 x IP1 K1 x IP2 K2 x IP33K3 x IP4 K4 (Eqn. 5)

   Obtaining the log on both sides we get

   Log (OP1) =K0 +K1 Log (IP1) +K2 Log (IP2) +K3Log (IP3) + K4Log (IP4) (Eqn. 6)

   This linear relationship now can be viewed as the hyper plane in five dimensional spaces. To simplify further let us replace the log terms by linear terms implies

   Z1= K0 + K1 (A) + K2 (B) +K3 (C) + K4 (D) (Eqn. 7) Where Z= Log(OP1), A= Log( IP1), B= Log(IP2 ), C= Log( IP3) , D=Log( IP4),

   This is true linear relationship between IP1—— IP4 to reveal OP1.

   Applying the theories of regression analysis, the aim is to minimize the error.SayYc is the computed value of OP1 using regression equation and Ya is the value of same term obtained from experimental data with exactly same values of IP1—-

   — IP4 then

   Error (E) = Ya-Yc. (Eqn. 8)

   An attempt to minimize error (E) is normally translated to minimization of E2 conventionally in regression, using differential algebra the point of minimum can be easily obtained by stating.

   E 2

   x 0

   It will ensure the extreme position of error with parameter x which may mean either maximization or minimization.

   The second differentiation of E2 awards the confidence whether it is maximum value or minimum value. This entire process can be reduced to finding the values of K0, K1, K2, K3, K4, K5 and K6. Once these values are known the relation between independent and dependent variables can be is completely established. Since the aim is to obtain values like K0, K1, K2, K3, K4, K5 and K6 it is obvious that square of error should be differentiated with respect to the constant of equation.

   E= Yc- Ya = (K0 + K1 A + K2 B +K3 C + K4 D Ye) Implies

   E2 = (K0 + K1 A + K2 B +K3 C + K4 D Ye) 2 Differentiating with respect to K0

   E 2 =2 (K0 + K1 A + K2 B +K3 C + K4 D Ye) =0

   Ko

   E 2

   K1

   =2 (K0 + K1 A + K2 B +K3 C + K4 D Ye) A =0

   =2 (K0A + K1 A2 + K2 AB +K3 AC + K4 AD AYe) =0

   E 2

   K 2

   E 2

   K3

   E 2

   K4

   =2 (K0B + K1 AB + K2 B2 +K3 BC + K4 BD BYe) =0

   =2 (K0C + K1 AC + K2 BC +K3 C2 + K4 CD CYe) =0

   =2 (K0 D+ K1 AD + K2 BD +K3 CD + K4 D2 DYe) =0

   All equations are equated to zero and hence the constant term 2 can be dropped. In matrix form it can be written as

   1 A

   1. A 2

   2. AB

   3. AC

   4. AD

B C D KO

AB AC AD K1

B 2 BC BD K 2

–

CB C 2 CD K 3

BD CD D 2 K 4

Ye 0

AY e 0

BY e 0

=

C Y e 0

DY e 0

Replacing symbol Ye by Z and shifting it to right AND Applying summation over all experimental findings we get,

N A B C D K0 Z

A A2 AB AC AD K1 AZ

B AB B2 BC BD

K2 BZ

C AC BC C2 CD X K3 = CZ

D AD BD DC D2 K4 DZ

Using array names viz P, K and Z we get, [ P] x [ K] = [Z] [ K] = [Z] x [ P]-1

After obtaining all the summation indicated in array P and array Z the statement of the problem can be computed. After inverting array P and post multiplying with array Z we get all the required values i.e. values of K0, K1, K2, ——-K4 are known after this process. The value of associated error now can be found out. Once the values of all k are known the computed value Yc can be generated.

Calculations:-

Chart On Calculations

Grade Rank

(Table:Chart on Comfortability Calculation )

60

50

40

30

20

10

0

Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9 Q10 Q11 Q12

Assessment Criterion

GRADE1 GRADE2 GRADE3 GRADE4

GRADE5

Where

• Grade 1: Very Uncomfortable

• Grade 2: Unconformable

• Grade 3 : Just Right

• Q1 : Comfortable with the chair

• Q2 : Backrest Adjustment range

• Q3: Vertical Adjustment range

• Grade 4 : Comfortable

• Grade 5 : Very Comfortable

• Q4 : visibility from the chair

• Q5: feel about buttock after working with chair

li>

Q6 : Feel about hands

• Q7 : Feel about Legs

• Q8 : Feel about Upper Backs

• Q9 : Feel about Upper Backs

  • Q10: Feel about Shoulders

  • Q11: Feel about Eye Sights

  • Q12: Feel about Numbness in Body Parts

RESULTS AND DISCUSSION:

Feel about

Comfortable

Backrest

Numbness in the

Discomfort rating in %

with the

Adjustment

Body Parts 16%

Feel about

Eye Sights 6%

Feel about Feel about

chair 5%

range 9%

Vertical Adjustment range

7%

Upper Backs 15%

Feel about Legs

Shoulders 0%

Feel about Upper Backs

Feel about buttock after working

Feel about hands with chair

Visibility from the chair 14%

9% 6%

8% 5%

Pie-chart diagram of discomfort rating in percentage

Discomfort rating in %

16

14

12

10

8

6

4

2

0

CONCLUSION:

From the ergonomics assessment of chairs used in different office, it could be concluded that the presents chairs were not designed as per the ergonomic standards. It was observed that the ergonomic assessment of chair was very discomfort in the that legs, upper backs, visibility and numbness.

The chair had to design by considering the following six questions

1. Is the chair comfortable to sit in for the way that you work?

2. Can you adjust the important features of the chairs?

3. Is the chair stable when you sit on it?

4. Does the chair have comfortable armrests?

5. Is the back rest high enough to provide support to the thoracic area.

6. Does the seat depth fulfilling the objectives like safety, comforts, ease of use, productivity and performance?

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