Close encounter of the haptic type

June 30, 2014 //By Julien Happich
Close encounter of the haptic type
An interesting branch of haptics deals with so-called encountered-type interfaces, whereby the user can not only touch but grasp the interface (often a joystick, a pen, a plate or a ball) mounted on a retro-active feedback mechanism.

The retro-active force allows the system to “resist” the user's input based on what the user ought to feel when interacting with the objects shown on a screen. The force feedback can be calculated based on simulated material properties (for example when interacting with virtual objects), or it can be derived from real sensor data, for example when the user is operating a robot remotely.

Two industrial sponsors of this year’s EuroHaptics, Force Dimension and Haption are well established players in this market, offering joystick-like interfaces with resistive forces and torques felt across multiple degrees of freedom.

The perception you get is bluffing as you manipulate virtual objects in 3D, with hard and soft boundaries, weights and elastic behaviour. When operating robots, the scaling of movement and forces can be tuned arbitrarily in software. In the case of robotic surgery, appropriate software can filter out tremors and breathing movements for added precision.

In academia, new shapes and implementations crop up, such as the adaptive interface presented by researchers of the Kyung Hee University (Korea). By controlling the size of a movable silicone balloon (inflated through a pneumatic actuator in accordance with the size of a virtual object being touched) and with finger video tracking, the researchers recreate the sensation of a real interaction with soft round-shaped objects.

(a) The concept of this pneumatic haptic interface, (b-d) the size of the balloon adjusted to fit the contact area, and (e-g) the user can grasp the interface and move the hand to feel the variations in size.

The balloon is mounted on a position-controlled robotic arm so as to adapt its position to follows the user’s hand and get in contact only when the both the hand and the object are making contact in the virtual world. This system could be used to interact with a human avatar, or to palpate virtual organs, say for medical training purposes.

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