Vast majority of haptic applications are focused on single contact point interaction between the user and the virtual scenario. One contact point is suitable for haptic applications such as palpation or object exploration. However, two or more contact points are required for more complex tasks such as grasping or object manipulation. Traditionally, when single-point haptic devices are applied in a complex task, a key or a switch is used for grasping objects. Using multiple contact points for this kind of complex manipulation tasks significantly increases the realism of haptic interactions. Moreover, virtual scenarios with multiple contact points also allow developing multi-user cooperative virtual manipulation since several users simultaneously interact over the same scenario and perceive the actions being performed by others. It represents a step forward in the current haptic applications that are usually based on one single user.
Recreating these scenarios in a stable and realistic way is a very challenging goal due to the complexity of the computational models that requires integrating all interactions of multiple haptic devices and calculations of the corresponding actions over the virtual object scenarios. It also requires solving mathematical equations in real time that properly represent the behavior of virtual objects. Delays in these calculations can lead to instabilities that may produce vibrations in the haptic devices and reduce the realism of the simulations. In order to offset these problems, different kinds of solutions have been considered, such as (i) models based on simplified calculations of forces and torques that are involved in object interactions, (ii) models based on virtual coupling between objects in order to ensure stability of the simulation.
Experiments shown in this work have been performed by using a multifinger haptic device called MasterFinger-2(MF-2). Is has been applied in different kinds of multiple contact point applications.