Estimation of applied force by using human body dynamics model

Recently, many developed countries have begun to experience the problems associated with an aging society. One problem in particular is the growing number of older adults in the labor force who suffer from various physical restrictions. Aiming to develop technology to assist these individuals, our laboratory has proposed a wire suspension-type power assist system that amplifies the force applied by the user. This system can be used even by older adults with insufficient strength for controlling the position and the configuration of heavy objects. The power assist system currently being developed in our laboratory uses a load cell to detect simultaneously both the force applied to the object by the user and the weight of the object. Therefore, the weight of the object is limited due to the signal-to-noise ratio (i.e., the ratio of the applied force to the weight of the object). Thus, we propose a new system that estimates the force applied to the object on the basis of the ground reaction force. This paper presents a model of the force applied by a human hand which is based on the ground reaction force. Then, the validity of the model is verified through simulation and experiment. As a result, it is confirmed that the force applied by a user can be estimated from the ground reaction force.