Description of and Applications for a Motion Analysis Method for Upper Limbs

Description of and Applications for a Motion Analysis Method for Upper Limbs

Hiromi Nishiguchi (Tokai University, Japan)
DOI: 10.4018/978-1-4666-2196-1.ch001
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Abstract

In daily life, we often perform activities with the upper limbs. Various motions of the upper limbs are required when performing activities of daily living (ADL), such as eating, dressing, grooming, or operating a home appliance. When problems first occur with human upper limb motions, a detailed analysis should be performed to determine where the difficulty with motion exists and to identify conditions under which we can perform these activities more easily and efficiently. Next, adjustments should be made to the activity or to the interface design of appliances to reduce the difficulty posed by the problematic motion. In this chapter, the methods of motion analysis for human upper limbs are explained and the effective method of utilization is shown. A case study is also provided to demonstrate the analysis of the pointer operation for cerebral palsy patients using a laptop PC which operates by a graphical user interface operating system (GUI OS) to provide a barrier-free approach. Additionally, an applied case study of the motion analysis methods for human upper limbs is shown, and the countermeasure to develop an effective pointer operation for cerebral palsy patients is discussed.
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Characteristics Of The Upper Limb Motions

In this paragraph, some technical terms are explained to clarify the process by which the characteristics of human upper limb motions were analyzed.

Fitts's Law

The difficulty of upper limb work is usually evaluated using the index of difficulty (ID), which was developed by Fitts. Fitts's law states that the difficulty index is influenced by both the distance of the upper limb movement and the target size, and it is calculated by formula (1), where A is the movement distance and W is target size.

ID = log2(2A/W) (1)

In addition, motion time (MT) is calculated using formula (2), where a worker’s work performance is given as the index of performance (IP).

IP = ID/MT (2)

The ID was originally derived from the result of an experiment analyzing upper limb movement, in which the measurement was based on the placement of a stylus pen point on a target plate. There are several studies reporting that ID calculation can be applied to pointer operation on a GUI screen (Card, S. K. et al., 1978, Epps, B.W. et al., 1986).

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