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Volume 8, Issue 3 (Iranian Journal of Ergonomics 2020)                   Iran J Ergon 2020, 8(3): 36-47 | Back to browse issues page

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Karimi Avargani S, Maleki A, Besharati S, Ebrahimi R. Muscle Moment and Angle of Hip, Knee and Ankle Joints in a Seven- Link Model of Backpack Sprayer Operator. Iran J Ergon 2020; 8 (3) :36-47
URL: http://journal.iehfs.ir/article-1-694-en.html
Muscle Moment and Angle of Hip, Knee and Ankle Joints in a Seven- Link Model of Backpack Sprayer Operator
Sedigheh Karimi Avargani1 , Ali Maleki *2 , Shahin Besharati3 , Reza Ebrahimi4
1- MSc Student, Department of Mechanical Engineering of Biosystems, Faculty of Agriculture, Shahrekord University, Shahrekord, Iran
2- Associate Professor, Department of Mechanical Engineering of Biosystems, Faculty of Agriculture, Shahrekord University, Shahrekord, Iran , maleki@sku.ac.ir
3- Lecture, Department of Mechanical Engineering of Biosystems, Faculty of Agriculture, Shahrekord University, Shahrekord, Iran
4- Assistant Professor, Department of Mechanical Engineering, Faculty of Engineering, Yasouj University, Yasouj, Iran
Keywords: Muscle moment, Body model. Seven-link model, Backpack sprayer
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Introduction

Carrying of backpack sprayers is an inevitable part of agricultural operations that increases the risk of injury along with undesirable changes in walking mechanics. When carrying a load, a lot of force is applied to different joints of the body, and if this force is prolonged, it can cause serious damage to various organs. Carrying backpack sprays can also cause damage to various parts of the body, including the spine, and the joints of the knees and ankles, which can even cause some agricultural workers to become homeless. Therefore, the necessity of modeling the operator's body to investigate and reduce the forces applied to different organs is necessary. The purpose of this study is to formulate the muscle moment changes in the hip, knee and ankle for the backpack sprayer operator body.
To date, no study has been performed on the dynamic model of a person to investigate the forces applied to the joints during spraying operations with motor rear sprayers. Therefore, the difference between this study and previous studies was in presenting a seven-link model of the operator's body with a motorized backpack sprayer. This dynamic model can be used to simulate the effect of various working factors during spraying operations (including the position of the sprayer with respect to the body and the speed of the sprayer motor and the mass of the sprayer) on the amount of force applied to the joints and, consequently lead to efforts to minimize the damage.

 

Materials and Methods

 In this study, a seven-link sprayer operator model is designed and the moment changes in the hip, knee and ankle joints are evaluated. Data are obtained using Plot-digitizer software. Excel software is used to fit the third degree curve on the data.

Figure 1. Dynamic model presented for a person in the buoyancy stage during spraying operations
Figure 1. Dynamic model presented for a person in the buoyancy stage during spraying operations
 

Table 1. The values of the parameters of the dynamic model presented to the person in the buoyancy stage during the spraying operation
Row Symbol Parameter Amount
1 l Foot length 0.7  m
2 ls Leg length  0.31 m
3 lt Thigh length 0.38 m
4 mb Upper body mass 26.62  kg
5 mf Plantar mass 2.66 kg
6 mh Pelvic mass 19.97 kg
7 ml Foot mass 11.53 kg
8 ms Leg mass 3.45 kg
9 msp Sprayer mass 10.5 kg
10 mt Thigh mass 8.047kg
11 g Gravity acceleration 9.81 m/s2
12 xsp Horizontal coordinates of the mass center of the sprayer with respect to the center of mass of the upper half 0.175 m
13 ysp Vertical coordinates of the mass center of the sprayer with respect to the center of mass of the upper half 0.038 m


Figure 2. Changes in muscle moment with respect to the angle of rotation of the joints during actual human gait. (A) thigh, (B) knee, and (C) ankle in standing position [16]
Figure 2. Changes in muscle moment with respect to the angle of rotation of the joints during actual human gait. (A) thigh, (B) knee, and (C) ankle in standing position [16] 


Figure 3. Changes in muscle moment with respect to the angle of rotation of the joints in the proposed model. (A) thigh in the floating stage and (B) knee in the floating stage and (C) ankle in the standing stage
Figure 3. Changes in muscle moment with respect to the angle of rotation of the joints in the proposed model. (A) thigh in the floating stage and (B) knee in the floating stage and (C) ankle in the standing stage

Figure 4. Changes in the angle of the joints with respect to time. (A) changes in the angle of the joints with respect to time as a human walks [16] and (B) changes in the angle of the joints with respect to time for the proposed model
Figure 4. Changes in the angle of the joints with respect to time. (A) changes in the angle of the joints with respect to time as a human walks [16] and (B) changes in the angle of the joints with respect to time for the proposed model

Table 2. Equations obtained from changes in muscle moment and changes in the angle of the hip, knee and ankle joints
Table 2. Equations obtained from changes in muscle moment and changes in the angle of the hip, knee and ankle joints


 

Results

In the hip joint, the moment is reduced by changing the angle from zero to 15°. At the end of the swing phase, the moment applied to the hip joint increases with increasing the angle up to 30°. In the beginning of the swing phase, the knee joint starts to open at -55°. At the end of the swing phase, the knee joint releases up to -5° and the moment applied to the knee joint increases slowly. The moment applied to the ankle joint increases by changing the ankle angle from -7.5° to 7.5°.
 

 
Discussion

Studying and simulating the effect of different working parameters (such as sprayer mass and sprayer motor speed and sprayer position with respect to the body) on the forces on the sprayer operator's joints in order to minimize muscle fatigue and injuries caused by these forces, requires a dynamic model of the body with the sprayer. The first step in presenting a dynamic model of the body is to find the equations of muscle moment. Experiments performed to estimate the muscle moment applied to the joints showed that the joint moment depends only on changes in the angle of the joints. This dependence is due to neurological factors and physiological properties of muscles [16, 21].
In recent years, several studies have been performed on the muscle moment applied to the joints, and in some of them, optimization methods have been used to minimize muscle forces [22]. Although research has been done in the field of cargo transportation in agriculture, the researchers in this article did not find a study that provided a dynamic model of a person during spraying operations. In the results of the present study, moment equations were obtained in the hip, knee and ankle joints, which were consistent with the laboratory results of the study of Frigo et al. and Sinkjaer et al. Using the results of this study, the extraction of equations governing the whole dynamic model of the body of the sprayer operator is proposed in future research to simulate the force applied to the joints considering different working parameters and the minimum values of these forces to reduce joint injuries when walking and carrying back engine sprayer.


 

Conclusion

According to the results of this study, amount of moment changes of hip, knee and ankle joint affect the force applied to the backpack sprayer operator body. With the knowledge of the moment changes of joints, practical solutions can be provided to reduce amount of damage to these joints.
 

Acknowledgements

The authors thank all the financial, laboratory and service support of Shahrekord University for conducting this research.

 

Conflicts of Interest

The authors declared no conflict of interest.

 

Type of Study: Research | Subject: Other Cases
Received: 2020/02/13 | Accepted: 2020/05/29 | ePublished: 2020/09/5
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