Department of Mechanical Engineering
Northwestern University
2145 Sheridan Rd.
Evanston, IL 60208
Phone: (847) 491-4264
Fax : (847) 491-3915
Email: colgate@nwu.edu
http://lims.mech.nwu.edu/haptic
Other Communication Modalities
Haptic, simulation, stability, passivity
This project addresses the implementation of multibody simulationsfor haptic display. Of particular concern are the ability to providestability guarantees and to ensure a real-time realization. We haveintroduced the concept of a virtual coupling between the multibodysimulation and haptic display hardware. This coupling separates thesimulation design process from the sampled-data stability issues thatarise during its implementation with a haptic display. Our primaryanalytical tool has been passivity, which has permitted a rigoroussampled-data analysis of the haptic display. Implications fornumerical integration and collision response algorithms have beenstudied. We have explored the use of an impulse-based simulation asa general purpose multibody simulator for haptic display. The"impact state" has been identified as a critical feature of thecontact model, and we have outlined the various ways it can bechosen. Finally, we have implemented a general planar multibodysimulator on one and two-axis haptic displays, and are currentlyporting it to a 4-axis device.
``Passive implementation of multibody simulations for haptic display", J. Michael Brown and J. Edward Colgate, Proceedings of the 1997 ASME International Mechanical Engineering Congress and Exhibition, Dallas,TX, accepted.
``Real-timeimpulse-based simulation of rigid body systems for haptic display", Beeling Chang and J. Edward Colgate, Proceedings of the1997 ASME International Mechanical Engineering Congress andExhibition, Dallas, TX, accepted.
``Issues in the haptic display of tool use'', J. Edward Colgate, Michael C. Stanley and J. Michael Brown, 1995 IEEE/RSJ International Conferenceon Intelligent Robots and Systems, Pittsburgh, PA, pp. 140-145.
A haptic display (or force reflecting interface) is a device which lets the user touch, feel and manipulate a computer-generated virtualenvironment, rather than just see it. Haptic display systems come inmany different sizes, from room-sized flight simulators to desktopdevices that interact with just the fingertip. They can evoke avariety of haptic sensations, from whole-body orientation in the caseof the flight simulators to kinesthetic, tactile, and thermalsensations in smaller devices. They have been either used or proposedfor use in a wide variety of applications, including moleculardocking, medical simulations, micro-gravity astronaut training,virtual prototyping, and video games. The guiding principle behindall of these devices and applications is to allow the user tophysically interact with a real-time computer simulation.
A haptic display consists of a real-time simulation of a virtualenvironment and a robot which serves as the interface between thehuman operator and the simulation. The operator grasps the robotthrough some mechanical interface (i.e. a handle) and movesthroughout the workspace. Based on information from various sensors,the simulation calculates reactions to output with the robot'sactuators. These reactions are felt by the operator through thehandle, making it seem to the operator as if he/she is actuallyinteracting with the virtual environment. The major areas of researchinclude hardware design, control and stability issues, simulationdesign, and psychophysics. The difficulty of implementing a hapticdisplay in any real-world application is that all four of thesecategories are important and interdependent.
Burdea, G. Force and Touch Feedback for Virtual Reality,John Wiley and Sons, New York, 1996.
The Haptics Community Web Page: http://haptic.mech.nwu.edu.
Virtual environments.
Virtual environments -- haptic feedback is increasingly being incorporated into virtual environment systems for surgical simulation, CAD, and rapid prototyping. Our work on stability may help lead to more robust and powerful implementations. Additionally, the stability and performance problems encountered in such projects may inform and refine our work.
Usability and User-Centered Design -- one of the most exciting uses of haptic interface is in improving the usability of computer interfaces. We are quite interested in projects that would address the appropriate application of haptic interface.