Development of Posture Analysis Software for

Continuous Farm Work

Masafumi Mitarai1, Hironori Matsuoka1, Julius Caesar Sicat2,Tomohiro Mino1, Sayaka Hosoyamada1

1Faculty of Agriculture,Miyazaki University,Miyazaki City,Japan2Department of Science and Technology Regional Office No.3, Pampanga, Philippines

Manual farm work is often accompanied by intense work load. Aging farmers doing agriculture in present-day Japan are gradually increasing in number. As a result, problems of accumulated physical stress and weariness increase as well. Therefore, to solve these problems, it is necessary to improve farm working postures as related to the amount of work loads.

To date, various ways of evaluating working postures were developed. Examples are OWAS, RULA, NIOSH and Bless Pro. However, evaluation of work processes and working moments using these softwares is a bit complicated. Also, they are not able to measure the forces and bending moments associated with continuous farm work operations.

A software which analyzes work posture and determines the optimum working posture was developed to solve the problems mentioned above. It can evaluate continuously the forces and bending moments acting on critical body parts of the worker. The body angle data were continuously measured using a work posture monitor VM12-512.

Mac Enaduo (VM12-512) made by VINE company was used as work posture monitor. It was developed to measure the posture of the worker moving continuously. It can measure the inclination angle of each part of the body (body trunk, upper arm, forearm, thigh and portion below the thigh) by angle sensors.

　 The angle sensors detect the angular change of measured part relative to the vertical line.

Figure 1. The angle sensors 　 Table 1. Specification of work posture monitor

Incidentally, the posture analysis software is limited to the capacity of the work posture monitor, but it can analyze continues work of 27 minutes at intervals of 0.5 seconds.

L5/S1

　 The posture analysis software assumes farm work to be two-dimensional. Also, the study focuses on the L5/S1 joint where waist ailment called lumbago frequently occurs. The software analyzes a load that divides the body into two: the upper part of the body trunk and the lower part of the body trunk.

(1) 　 The work posture display

(2) 　 Joint bending moment analysis

(3) 　 Estimation of forces on lumbar vertebrae

Figure 2. The　human　body　model　for　calculating　the　various　forces　and　moments　on　the　different　joints

L5/S1

Shearing　force　at　

L5/S1　disc :Fs

Compression　force　at　L5/S1　disc　:Fc　

Force　at　erector　spinal :Fm

Abdominal　pressure :Fa

Figure 3. Biomechanical model of lumbar loads

Angle between L5/S1 and the thigh joint - shoulder joint line：

　　　　　　 θb=59.255-0.33339*H-0.002562*H^2-0.00072369*K^2+0.003309*H*K 　 ･･･ (3)

Angle between L5/S1 and the shoulder joint - thigh joint line：

θa=sin^-1{(L30*sinθb)/L31} ･･･ (4)

Inclination　angle　of　lower　body　trunk： θp=θ3-θb ･･･ (5)

Inclination　angle　of　upper　body　trunk： θq=θ3+θa ･･･ (6)

Force　at　erector　spinal： Fm　=　(pmp　*　9.807　-　Fa　*　D)　/　e ･･･ (7)

Compression　force　at　L5/S1　disc： Fc　=　Twp*　9.807　*　Cos(Ra)　+　Lw　*　9.807　*　Cos(Ra)　-　Fa　+　Fm ･･･ (8)

Shearing　force　at　L5/S1　disc： Fs　=　Twp　*　9.807　*　Sin(Ra)　+　Lw　*　9.807　*　Sin(Ra) ･･･ (9)

　where、

　　　　　　　　　　pmp： Bending　moment　at　L5/S1　　　　　　　 Fa： Abdominal　pressure　　

　　 D ： Lever　arm　of　L5/S1　(abdominal　pressure)　　　 　　e： Lever　arm　of　the　force　at　erector　spinal

　　 Twp：Weight　above　L5/S1　　　　　　 Ra： Inclination　angle　of　L5/S1　joint　surface　　

　　　 Lw：Weight　of　hand　load

START…?

Figure 4. the　menu　screen　of　the　posture　analysis　software

The work posture analysis software was found effective in the following conditions:

(1) Continuous analysis and evaluation when the work positions of legs and hands are different and loads on both hands are different as well.

(2) Evaluation and improvement of work posture which bends forward and down and momentary overloaded postures such as in manual farm work.

(3) Evaluation and improvement of difficult farm work such as carrying and lifting heavy load.

(4) Analysis and improvement of unstable farm work in inclined places.