A Control-Theoretic Model for Human Time-Motion Evaluation in Pick-and-Place Operations

This paper deals with physical modeling of human hand–eye coordinated movement for applications in time-motion study of pick-and-place operations. Time-motion studies typically use experimentations to closely examine each segment of a worker's pick-and-place movements in order to design a more optimized operation. This paper presents two different methods that can replace the need for experimentation or estimation in the time motion process with control-theoretic models. The first method is a control-theoretic physical model of the human hand–eye coordinated movement in performing a pick-and-place operation. It is based on an extension of control theoretic models of airplane pilots. The second method combines two existing techniques developed in the literature for different purposes. It is shown in this paper that the combination of these two existing methods provides for an alternative approach that can be used for time-motion studies related to the human pick-and-place operation. Using simple experimentation, it is shown that both methods provide reasonable model-based representation of time motion studies for pick-and-place tasks. In developing the physical model, a method based on the use of the quantitative feedback theory (QFT) is also developed for tuning the physical model that can be utilized in making the model specific to different applications involving human hand–eye coordinated movements. Furthermore, the physical model is applied in a predictive fashion and it is shown that it can successfully estimate the movement time for manual pick-and-place tasks found in some industrial applications.