PD control with gain-scheduling depending on the distance for a 3-dof network based haptic system

This paper presents a Proportional Derivative (PD) controller with gain-scheduling depending on the distance for haptic interfaces and virtual environments subject to communication delays. It is well known that the presence of delays deteriorates the overall system performance. More precisely, depending on the proposed architecture as, for example, bilateral position-position coupling, time-delays introduce a feeling of viscosity in free motion and reduce the sense of stiffness in the case of hard contacts. Even in the presence of time-delays, the controller gains can be tuned in order to guarantee the desired behavior and performances for one case (free or restricted motion) with the price of the completely loss of the other case performances and behavior. To overcome this drawback, a gain-scheduling controller is designed, able to guarantee the desired behavior and performances for free and restricted motion. The experimental results obtained on a three-degree of freedom real-time experimental platform enforce the theoretical developments.