Control Based on the Modification of the Relation between the Reaction Force and the Human Force and its Effects on the Weight Perception

With the evolution of the family structure and the increasing longevity, our society is relying more and more on power assist devices. Since these devices are meant to work in cooperation with the user, considering only the characteristics of the device is not enough, the human response must also be taken into account. However, the weight perception is commonly affected by illusions, like the Charpentier effect. When no power assistance is supplied, the relation between the reaction force and the human force is linear. The objective of the experiment reported on this paper was to determine how the modification of such linearity affected the perceived weight when lifting an object with a 1DOF power assist device. For this, in the control, 7 modifying symmetric pairs of equations and 1 equation without modification were tested. The symmetry of the equations was relative to the characteristic curve between the reaction force and the human force. Besides the perceived weights, the position, acceleration, reaction and human force were recorded. The results showed that, albeit the detaching phase is brief, modifying the linearity between the reaction and the human force affects proportionally the weight perception.