Haptic Interfaces
Haptic interfaces are devices that provide force and tactile feedback to the user as they interact with objects in a computer-generated virtual world. Our research effort is focused on development of portable haptic devices. With the help of such devices and by wearing a head-mounted display and position sensors, we can step inside a computer-generated virtual world to interact with virtual objects. For example, we can "hold" two CAD models in our hands. We can try to assemble these parts and feel the interaction forces through the haptic interface. Such a system would allow evaluation of designs thoroughly before a physical prototype is manufactured leading to reduced time to market and cost. Other uses for haptics have been realized in areas of training; such as a medical students practicing virtual surgery or a soldier performing a simulated military operation.
In this section you will find brief information about three haptic interface research projects:
MR-Glove
Recently, we developed a force feedback glove (MR-Glove) that uses compact MR- brakes placed on the back of each finger. The glove is interfaced to a virtual reality simulation to provide the sensation of holding an object in the virtual world. When the digital hand model in the VR world grasps an object, the glove activates its brakes to stop the user’s fingers to providing the sensation of holding the object.
The MR-brakes were designed to be compact to fit on the back of the hand. The brakes use magneto-rheological (MR) fluid. An electromagnet inside the brake creates a magnetic field in the brake which causes the MR-fluid to change its viscosity. Normally, the MR fluid is a free-flowing liquid similar to motor oil. However, when activated by a magnetic field, its consistency changes to that of peanut butter. When activated, the fluid causes considerable friction between the moving parts of teh brake creating a braking torque.
Experiments indicate that the users wearing the MR-Glove could grasp a virtual object in one-third the time it took too grasp the same object without any haptic feedback.
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Air-Glove
Our research goal was to explore use of air jets in the design of a haptic interface to create thrust forces on the user’s hand. We mainly focused on reflecting gravitational forces to the user so that sensation of weight of a virtual object can be created in a virtual environment.
The Air-Glove uses six air nozzles mounted in a Cartesian coordinate frame setting to apply a force to the user's wrist. At any given time, only three nozzles exhaust air jets. The magnitude and direction of the applied force are controlled by changing the flow rate of the air jets and by activating different nozzles, as the user's hand position and orientation are changing.
Precise control of the magnitude of each air jet was achieved by implementing a digital controller and servo valves. Experiments indicated that user could distinguish as little as 50-100 grams (~2-3 oz.) of weight difference between two virtual objects using the Air-Glove.
Funded by a grant from the Society of Manufacturing Engineers Education Foundation
Nanomanipulator with Haptic interface
In order to manipulate materials at the nanometer scale, we developed a force-feedback interface for an atomic-force-microscope (AFM). With the aid of this interface, direct positioning of the AFM probe is possible. In addition, the interface enables the user to feel tip-to-sample force interactions in real-time.
Using the AFM as a nanomanipulation tool involves a scan-manipulate-scan cycle. First, a surface scan is obtained to get an image of the sample surface. Then, the AFM is used as a nanomanipulator to interact with the sample. However, this interaction is done blindly since the image cannot be dynamically updated during the interaction. Finally, a new scan is obtained to see the results of the nanomanipulation.
Preliminary experiments with the system indicated that the haptic device provided the necessary sensory feedback during the blind manipulation stage. Using this system, polystyrene microspheres with 465 nanometer diameter could successfully be repositioned. The AFM images below show a string of such particles being split by the user with the help of the interface.
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Selected publications
- "AirGlove: A force feedback device for virtual reality," Proceedings of Telemanipulation and Telepresence Technologies VIII, SPIE Conference, Proc. SPIE vol. 4570, pp. 69-77, Boston, MA, October 2001.
- "Design of a haptic device for weight sensation in virtual environments," Proceedings of DETC'02: ASME 2002 Design Engineering Technical Conferences and Computers and Information in Engineering Conference, October 2, 2002, Montreal, Canada.
- "Weight sensation in virtual environments using a haptic device with air jets," ASME Transactions, Journal of Computing and Information Science in Engineering, vol. 3, no. 2, June 2003.
- "Magnetorheological fluid brake for a force feedback glove for virtual environments," Proceedings of IDETC/CIE 2005: ASME 2005 Design Engineering Technical Conferences and Computers and Information in Engineering Conference, September 2005, Long Beach, California.
- "AFM-based nanomanipulator with haptic interface," Proceedings of EuroHaptics 2006, July 2006, Paris, France.