Implicit Accuracy Constraints in Two-Fingered Grasps of Virtual Objects with Haptic Feedback

Using virtual objects that provided haptic feedback we studied two-fingered movements of reaching to grasp and lift an object. These reach-grasp-lift movements were directed to objects of identical physical size but with the different physical properties of mass, and coefficient of friction between the floor and object. For each condition, the resulting forces and kinematic properties of movements were recorded after a brief amount of practice with reaching to grasp and lift the object. It was found that for conditions where the object was more stable to perturbation, such as large mass or high friction, the contact force with the object was greater. This suggests that the stability of the object, is quickly and easily learned and subsequently influences the accuracy of the movement. The possibility is discussed that such programming of contact force is incorporated into the planning of grasps and how this would interact with the execution of grasps to virtual objects with and without haptic feedback