Postscript Version

A NEW 6-DOF HAPTIC INTERFACE USING LORENTZ LEVITATION

Ralph L. Hollis (P.I.) and David Baraff (co-P.I.)

The Robotics Institute
Carnegie Mellon University

CONTACT INFORMATION

Ralph Hollis
The Robotics Institute
Carnegie Mellon University
5000 Forbes Avenue
Pittsburgh, PA 15213
Phone: (412) 268-8264
Fax : (412) 268-5570
E-mail: rhollis@cs.cmu.edu

WWW PAGE

Magnetic Levitation Haptic Interfaces

PROGRAM AREA

KEYWORDS

Haptics, magnetic levitation, virtual environments

PROJECT SUMMARY

Abstract

This project investigates how computer users can be given a sense of convincingly real haptic (touch) interaction with computers. Whereas there has been progress in this area, chiefly through the use of back-driven robotic-like manipulators, this is a substantially new approach which promises a qualitative leap in improvement of such capabilities: a user interacts with the computer by grasping a levitated rigid tool whose behavioral description is computed, employing this tool to interact with computed environments which are semantically meaningful in terms of the application. The computed environment exerts realistic forces and torques on the tool's handle which are felt by the user. The vision is one of providing the computer user immediate, high-fidelity, convincingly real interaction with computed environments. The new haptic interface approach is based on a recently developed magnetic levitation technology, and on recent advances in the art of physically-based simulation. The magnetic levitation technology uses Lorentz forces to stably levitate and control a rigid body (which includes the handle through which the user interacts) in six degrees of freedom, giving a new and heretofore unexplored physical basis for haptic interaction. The new simulation methods are based on special-purpose techniques that promise to be simpler, faster, and more robust than their generic counterparts. Robust realistic physical simulation, coupled with high bandwidth six-degree-of-freedom force reflection, has the potential to greatly improve the state of the art in the feel, performance, and capabilities of virtual environment systems for use in a wide range of human activities.

Status

Progress to date has taken place in two main areas: (1) the magnetic levitation haptic device, and (2) the environment for haptic interaction:

Magnetic Levitation Haptic Device.

During the first year, we successfully operated a prototype magnetic levitation haptic device [1]. During the latter part of the first year, and the first part of the second year, we completed the design of a new, higher performance, more ergonomic device using solid modeling and 3D magnetic finite element analysis tools [2]. In addition to the design activity, all of the many consituent parts, some requiring aluminum casting and spinning techniques, have been fabricated, either in house or by vendors, and the assembly is completed. All of the electronics have now been assembled as well. We are currently performing calibration of the internal optical sensors and expect to have our new device operational this summer. The next step is to integrate our new device with our 3D physically based modelling environment, followed by studies of user interaction efficacy.

Environment for Haptic Interaction.

Over the past year, the simulation toolkit, now in complete 3D form, has begun to see increasing use within the CMU Robotics and Computer Science community in a variety of control, design, and medical projects. The simulation toolkit has also attracted industrial attention, and is currently licensed to Silicon Graphics, Inc. The simulator is, we believe, currently the world's fastest 3D simulation system supporting general geometric linkages, collision, contact, and friction for multi-body systems. Some experiments with using the simulation system in a haptic environment were performed. Combining the simulation system with a PHANToM haptics interface (manufactured by Sensible Devices, Inc.), we were able allow the user to experience first-hand forces arising from dynamics manipulation of 2D and 3D objects. The user could feel impact, smooth compliant contact, and friction. (Because the PHANToM device limits us to point contact, the user is restricted to pushing on objects at one point. However, since we simulate friction, one point contact actually gives sufficient control to move objects around in a plane, merely by pressing down on them and exerting both downward and lateral forces.) Although the PHANToM's capabilities are limited, they clearly demonstrate that the combination of good haptics with realistic, fast simulation will allow for novel and powerful input interactions.

PROJECT REFERENCES

AREA BACKGROUND

Haptic interaction with computers is an emerging new field. There is presently no real consensus on how this can best be achieved. Widespread availability of such systems could have a profound effect on many fields of human activity. It is often said that one does not understand something really well until a ``hands on'' approach is taken. Successful approaches could lead to several promising applications: Medical procedures could be practiced and refined on virtual patients using virtual scalpels and other instruments with anatomic viscoelastic properties of tissues modeled and felt by the surgeon. Effort-reflected flight or other vehicle control could be accurately simulated with reaction forces and vibration fed back to the operator. In CAD, the designer of a complex assembly could rapidly manipulate the parts of his or her design, feeling how the parts will come together. In other fields, complex multi-dimensional data could be more rapidly explored and comprehended.

AREA REFERENCES

RELATED PROGRAM AREAS

  • 1. Virtual Environments
  • 6. Intelligent Interactive Systems for Persons with Disabilities

    POTENTIAL RELATED PROJECTS

    Whereas the current project is focussed on high-bandwidth high-resolution 6-DOF interaction with virtual environments, we seek to extend the technique to remote telemanipulation taks in the real world.