Human reach posture prediction based on psychophysical discomfort

A man model is a useful design tool for the evaluation of man-machine systems and products with less time delay and cost, specifically at the early stage of design. For a man model to be truly useful, it must be integrated with a proper posture prediction model, especially, an arm reach prediction model. In this study, a regression model to Predict the perceived discomfort with respect to the joint movement was developed using a central composite design based on the response surface method. Joint angles of the upper body with seven degrees of freedom and the weight of a load were treated as independent variables while the perceived discomfort measured using a magnitude estimation technique was used for the response variable. The perceived discomfort in the category scale and the normalized EMG of six muscles were also collected. A three-dimensional reach posture prediction model using an inverse kinematics technique was then developed, based on the prediction of perceived discomfort. The model predicts the posture by selecting the minimum discomfort configuration among feasible body postures to reach a target point. The reach posture prediction model developed in this study was found to simulate human arm reach posture accurately and the discomfort prediction model will help understand the human arm reach movement. Relevance to industry. Accurate reach posture prediction will be a useful function for any ergonomic evaluation. The model effectively assists the process of design and evaluation of man-machine systems and products with less time delay and cost.