Beyond Anthropometrics: Prehensile Control Analysis for Capability Assessment

How can we design objects that are better suited to people with disabilities? Finite Element Analysis is a useful technique for engineering physical objects, but optimal design must be informed by how the human interacts with objects. Our group is attempting to model the control of hand movements in order to create CAD packages that allow object design to be informed by an individual’s sensorimotor control strategies (Prehensile Control Analysis). Prehension, the ability to reach-grasp-and-manipulate objects, is one of the most important human capabilities. Numerous activities of daily living (dressing, feeding, cleaning etc.) rely on dexterity, so it is perhaps unsurprising that impairment of prehension (through illness, injury or ageing decline) is often associated with disability. The kinematics of reach-to-grasp movements show high levels of stereotypicality in neurologically intact adults whilst impairment produces predictable kinematic changes in behaviour. Moreover, kinematics change lawfully as a function of the task and the properties of the object. These facts open up the exciting possibility of modelling prehensile kinematics so that a designer can determine the optimal object properties for an individual with a given impairment. This chapter presents a simple model for characterising an individual’s quality of movement in a given reach-to-grasp movement. Our model is able to capture typical and atypical prehension and is the first step in the development of CAD for handheld objects: a tool that allows design around people.