No abstract

This paper presents the design of a haptic interface called the Haptic Lever, to show four force-related phenomena for haptic augmentation towards Smart Learning Environments. The Haptic Lever is a mechanism with a sensorless torque control developed by means of a Disturbance Observer (DOB) to render forces that allow users to feel virtual phenomena. The control response converges in the torque reference as a result of a gain calibration and the DOB response. The Haptic Lever was evaluated experimentally with four dynamic models for constant (membrane), linear (Hook's law and viscous damping), and exponential (Coulomb's law) haptic augmentation. In the first experiment, the user can feel a constant force when passing between two reference points and feel resistance while moving through a virtual membrane. In the second and third experiment, the user can feel and interact with the linear dynamic models of Hook's law and viscous damping, in the form of a compression or tension spring by pushing or pulling them, respectively. Finally, in the fourth experiment, the user can feel an attraction or repulsion force between two virtual point charges that follows the exponential dynamic model of Coulomb's law. The results obtained from the experiments showed that the Haptic Lever successfully rendered the equivalent forces to each virtual phenomenon. The haptic sensation is estimated in terms of the torque response under a profile determined by the dynamic models. From the experimental results, it can be observed that the torque in Nm corresponded to each represented phenomenon.