Research Papers

Static Joint Torque Determination of a Human Model for Standing and Seating Tasks Considering Balance

[+] Author and Article Information
Jingzhou (James) Yang2

Department of Mechanical Engineering, Texas Tech University, Lubbock, TX 79409james.yang@ttu.edu

Joo H. Kim

Department of Mechanical and Aerospace Engineering, Polytechnic Institute of NYU, Brooklyn, NY 11201


Corresponding author.

J. Mechanisms Robotics 2(3), 031005 (Jul 14, 2010) (9 pages) doi:10.1115/1.4001782 History: Received October 23, 2009; Revised May 03, 2010; Published July 14, 2010; Online July 14, 2010

Estimation of the risk of injury to human different joints during occupational tasks plays an important role to reduce injuries before the operators carry out the tasks. This paper presents a methodology for determining the static joint torques of a human model considering balance for both standing and seating tasks such as weight lifting, material handling, and seated operating tasks in the assembly line. A high fidelity human model has been developed, and recursive dynamics has been used to formulate the static equation of motion. An alternative and efficient formulation of the zero-moment point for static balance and the approximated (ground/seat) support reaction forces/moments are derived from the resultant reaction loads, which includes the gravity and externally applied loads. The proposed method can be used for both standing and seating tasks for assessing the stability/balance of the posture. The proposed formulation can be beneficial to physics-based simulation of humanoids and human models. Also, the calculated joint torques can be considered as an indicator to assess the risks of injuries when human models perform various tasks. The computational time for each case is close to 0.015 s.

Copyright © 2010 by American Society of Mechanical Engineers
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Figure 1

A kinematic chain of joints

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Figure 2

Whole-body human mechanism and global DOFs: (a) global DOFs; (b) human model

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Figure 5

Free-body diagram of the human-like mechanism and the resultant reaction loads without SRFs

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Figure 6

Global orientations in terms of the Euler angles

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Figure 8

The feet support region for standing tasks

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Figure 9

The top view of the seat support region

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Figure 10

Illustration of the proposed algorithm for SRFs

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Figure 11

The reaction forces are distributed to two points on the body-seat contact surface

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Figure 12

Standing posture

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Figure 14

Seated posture: (a) pushing button (Posture 1) and (b) pulling toolbox (Posture 2)

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Figure 15

ZMP plot for postures (circle—0.1 N; square—50 N)

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Figure 16

Numerical algorithm flow chart



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