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HAPTIC INTERFACES
The feeling of touch or force is transferred from the virtual world and sensed by the user using special devices designed for haptics. There exists a variety of haptic interfaces, with variations in degrees of freedom, workspace area and force capabilities being some of the characteristics that help distinguish the devices. The interface chosen depends on the type of application. Let's look at a few commercially available haptic devices.
The Novint Falcon
The Falcon is a haptic interface aimed primarily at the gaming community. Priced substantially lower than other haptic devices, it is a 3 Degrees Of Freedom (DOF) device that can move in the x,y and z directions. Though the Falcon doesn't possess the high precision of other more expensive devices, it is capable of rendering a higher range of forces. However, the workspace area is limited. We have found the Falcon to be quite sturdy and that makes it great when testing out new applications.
The Quanser 5-DOF Haptic Wand
The Quanser Haptic Wand is a 5-DOF haptic interface that may be used for high precision applications such as medical/surgical simulations and for commercial research. It allows for three translations and two rotations (roll and pitch).This is achieved by using a dual-pantograph arrangement driven by DC motors. This arrangement also allows it to render feedback in the form of torques. The workspace of the wand is large which makes it ideal for research in our lab dealing with kinesthetic haptic interaction.
The Phantom Omni
The Phantom Omni is a 6 Degrees of Freedom device that has a pen-like interface. Though it can sense the movement of the stylus in the x,y and z directions, and rotations - pitch, roll and yaw, it does not render any output torques. The range of forces it renders is smaller than the Falcon, but it has better force resolution capabilities. The Phantom Omni is medium priced and is good for applications requiring the higher freedom and larger workspace it provides, for example, in 3D sculpting and other applications involving the manipulation of virtual objects.
The Butterfly Maglev Magnetic Levitation Haptic Interface
Unlike most commercially available haptic interfaces that use robot-arms or other mechanical elements with motors to render forces, the Maglev uses magnetic fields. This allows for complete 6-DOF freedom. The Maglev can sense the position and orientation of the handle and in turn, output forces and torques. By using magnetic fields, the Maglev provides a very high resolution and high position and force bandwidths. The high performance comes at the expense of a small workspace, and scaling and other techniques may be required for many applications.