Development of Posture Analysis Software for Continuous Farm
- Slides: 8
Development of Posture Analysis Software for Continuous Farm Work Masafumi Mitarai 1, Hironori Matsuoka 1, Julius Caesar Sicat 2, Tomohiro Mino 1, Sayaka Hosoyamada 1 1 Faculty of Agriculture, Miyazaki University, Miyazaki City, Japan 2 Department 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 VM 12 -512.
Mac Enaduo (VM 12 -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. 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. Figure 1. The angle sensors Table 1. Specification of work posture monitor
The posture analysis software assumes farm work to be twodimensional. Also, the study focuses on the L 5/S 1 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. L 5/S 1 (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
Shearing force at L 5/S 1 disc : Fs Force at erector spinal : Fm Compression force at L 5/S 1 disc : Fc Abdominal pressure : Fa L 5/S 1 Figure 3. Biomechanical model of lumbar loads
Angle between L 5/S 1 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 L 5/S 1 and the shoulder joint - thigh joint line： θa=sin^-1{(L 30*sinθb)/L 31} ･･･(4) Inclination angle of lower body trunk：θp=θ 3 -θb ･･･(5) Inclination angle of upper body trunk：θq=θ 3+θa ･･･(6) Force at erector spinal：Fm = (pmp * 9. 807 - Fa * D) / e ･･･(7) Compression force at L 5/S 1 disc：Fc = Twp* 9. 807 * Cos(Ra) + Lw * 9. 807 * Cos(Ra) - Fa + Fm ･･･(8) Shearing force at L 5/S 1 disc：Fs = Twp * 9. 807 * Sin(Ra) + Lw * 9. 807 * Sin(Ra) ･･･(9) where、 pmp：Bending moment at L 5/S 1 D： Lever arm of L 5/S 1 (abdominal pressure) Twp：Weight above L 5/S 1 Lw：Weight of hand load Fa：Abdominal pressure e：Lever arm of the force at erector spinal Ra：Inclination angle of L 5/S 1 joint surface
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.
