Brent Gillespie
Publication Abstracts
Journal Publications
Kinematic Creep in a Continuously Variable Transmission
:
Traction Drive Mechanics for Cobots
B. Gillespie, C. Moore, M. Peshkin and J.E. Colgate
ASME Journal of Mechanical Design (to appear)
Two continuously variable transmissions are examined, one
that relates a pair of linear speeds and another that relates a pair of
angular speeds. These devices are elemental in the design of cobots, a new
class of robot that creates virtual guiding surfaces to aid a human operator
in assembly tasks. Both of these transmissions are traction drive mechanisms
that rely on the support of either lateral or longitudinal forces across
rolling contacts with spin. When a rolling contact between elastic bodies
or even between rigid bodies in spin is called upon to transmit a tractive
force, kinematic creep develops, expressing a departure from the intended
rolling constraint. Creep in turn gives rise to non-ideal properties in
a cobot's virtual guiding surfaces. This paper develops simple models of
these two transmissions by expressing the relative velocity field in the
contact patch between rolling bodies in terms of creep and spin. Coulomb
friction laws are applied in a quasi-static analysis to produce complete
force-motion models. These models may be used to evaluate a cobot's ability
to support forces against its virtual guiding surfaces.
Please e-mail me for a pre-print at : brentg@umich.edu
A General Framework for Cobot Control
B. Gillespie, J.E. Colgate, M. Peshkin, and W. Wannasuphoprasit
IEEE Journal on Robotics and Automation, Vol.
17, No. 4, pp. 391-401, August
2001.
A general framework is presented for the design and analysis
of cobot controllers. Cobots are inherently passive robots intended for direct
collaborative work with a human operator. While a human applies forces and
movements, the contoller guides motion by tuning the cobot's set of continuously
variable transmissions. In this paper, a path following controller is developed
that steers the cobot so as to asymptotically approach and follow a pre-planned
path. The controller is based on feedback linearization. Generality across
cobot architectures is assured by designing the controller in task space and
developing transformations between each of four spaces : task space, joint
space, a set of coupling spaces, and steering space.
Cobot Architecture
M. Peshkin, J.E. Colgate, W. Wannasuphoprasit, C. Moore and
B. Gillespie
IEEE Journal on Robotics and Automation, Vol. 17, No. 4, pp.
377-390, August 2001.
We describe a new robot architecture: the collaborative robot, or cobot.
Cobots are intended for direct physical interaction with a human operator.
The cobot can create smooth, strong virtual surfaces and other haptic effects
within a shared human/cobot workspace. The kinematics of cobots differs markedly
from that of robots. Most significantly cobots have only one mechanical degree
of freedom, regardless of their taskspace dimensionality. The instantaneous
direction of motion associated with this single degree of freedom is actively
servo-controlled, or steered, within the higher dimensional taskspace. This
paper explains the kinematics of cobots, and the continuously variable transmissions
(CVTs) which are essential to them. Powered cobots are introduced, made possible
by a parallel interconnection of the CVTs. We discuss the relation of cobots
to conventionally actuated robots and to nonholonomic robots. Several cobots
in design, prototype, or industrial testbed settings illustrate the concepts
discussed.
Conference Publications
Extremal
Distance Maintenance for Parametric Curves and Surfaces
V.
Patoglu and
B. Gillespie
IEEE
Conference on Robotics and Automation, Washington D.C., May 11-15,
2002.
A new extremal distance tracking algorithm is presented for parametric curves and surfaces undergoing rigid body motion. The
essentially geometric extremization problem is transformed into a dynamical control problem by differentiating with respect to time. Extremization is then solved with the design of a stabilizing controller. We use a feedback linearizing controller. The controller simultaneously accounts for the
surface shape and motion while asymptotically achieving (and maintaining) the extremal pair. Thus collision detection takes place in a
framework fully analogous to the framework used for the simulation of dynamical response.
(8 Pages PDF)
Haptic
Feedback and Human Performance in a Dynamic Task
F.
Huang, B.
Gillespie, and A. Kuo.
IEEE
Virtual Reality Conference, Orlando, FL, March 24-28, 2002.
This
study explores the effects of haptic feedback on performance and learning by
human subjects executing a dynamic task.
We present the results of experiments involving the control of a ball and
beam.
Human subjects perform position targeting of the ball through hand
operation of the beam angle.
In our dynamic analysis we discuss how this prototype task may be used to
test the efficacy of various haptic feedback conditions.
We obtain results for two conditions of haptic feedback, produced using
two ball sizes, and apply various metrics to analyze performance.
We also examine ordering effects that occur in the presentation of these
haptic conditions.
Our analysis and experimental findings indicate that the performance of a
dynamic task is governed by the complexity of system dynamics and the magnitude
of haptic feedback. Our results provide modest support to recommend exposure to
a more complex, higher force-feedback task prior to the execution of a simpler
lower feedback task.
(8 Pages PDF)
Shared
Control Between Human and Machine
M. Steele and B. Gillespie
Human Factors and Ergonomics Society 45th
Annual Meeting, Minneapolis, MN, October 2001.
When humans interface with machines, the control
interface is usually passive and its response contains little information
pertinent to the state of the environment.
Usually, information flows through the interface from human to machine
but not so often in the reverse direction.
This work proposes a control architecture in which bi-directional
information transfer occurs across the control interface, allowing the human to
use the interface to simultaneously exert control and extract information.
In this alternative control architecture, which we call shared control,
the human utilizes the haptic sensory modality to share control of the machine
interface with an automatic controller. We
present a fixed-base driving simulator experiment in which subjects take
advantage of a haptic steering wheel, which aids them in a path following task.
Results indicate that the haptic steering wheel allows a significant
reduction in visual demand while improving path following performance.
(8 Pages PDF)
Cancellation of Feedthrough
Dynamics Using a Force Reflecting Joystick
B. Gillespie, P. Tang, and C. Hasser
Presented at: ASME IMECE, Nashville, TX.
November, 1999.
This paper reports on a set of theoretical and experimental
investigations into the use of force reflection to enhance the
dynamic behavior of human piloted vehicles, especially
joystick-controlled vehicles such as fly-by-wire jets, bulldozers,
and powered wheelchairs. Briefly, force reflection is used in the
manual controls to cancel the effects of feedthrough dynamics.
Feedthrough dynamics refers to generation of inadvertent steering or
speed command inputs due to the action of inertia forces between the
pilot's hand and manual controls. These inertia forces arise in the
pilot's body in response to vehicle accelerations. To eliminate
feedthrough dynamics, a canceling force is produced on the
force-reflecting joystick using a model of the pilot dynamics and the
known vehicle accelerations. A custom motion platform and a
commercial force-reflecting joystick are used in a set of experiments
to test the idea. Parameter values for an assumed model are
estimated by observing the response of the pilot's body to known
platform accelerations. Cancellation of feedthrough dynamics is
demonstrated for a human subject.
(8 Pages PDF)
The Virtual Teacher
B. Gillespie, S. O'Modhrain, P. Tang, C. Pham, and D.
Zaretsky
Proceedings of the ASME IMECE, DSC-Vol. 64, Anaheim, CA
Nov 15-20, 1998. pp. 171-178.
This paper introduces the virtual teacher, a device or agent that
supplements an environment in order to facilitate acquisition by a
human user of a manual skill. Like the virtual fixture, a virtual
teacher generally acts as an aide or facilitator to task execution,
but unlike the virtual fixture, the virtual teacher is present only
during training periods. During eventual task performance the teacher
is absent. The virtual teacher's objective, implicitly understood by
the user, is to promote independent mastery over the task. We review
and organize common paradigms for the teaching of manual skills in
real-world settings and use these as inspiration for the design of
virtual teachers. In particular, we are interested in the ways in
which a teacher, real or virtual, can demonstrate a strategy or
impart a `feel' for a task by guiding movement of the pupil's hand.
A pilot study involving 24 participants was used to test the virtual
teacher concept with a simulated crane moving task. The present
virtual teacher implementation did not significantly improve learning
curves. However, further performance interpretations indicate that
the lack of positive effect can be remedied with modifications to the
virtual teacher that address component skills and ensure suitability
to various initial skill levels.
(8 Pages PDF)
A Survey of Multibody Dynamics for
Virtual Environments
B. Gillespie and J. E. Colgate
Proceedings of the ASME IMECE, DSC-Vol. 61, Dallas, TX.
Nov 15-20, 1997. pp. 45-54.
The field of computational dynamics is surveyed, focusing on
issues relevant to the construction of a general purpose simulator
with haptic display. The various formalisms available for
generating dynamical models will be examined with regard to the form
of the equations of motion which they produce. To render
the effects of intermittent contact and other transient phenomena as
driven by a human haptic explorer, a model is needed which is
computationally efficient yet can handle changing kinematic
constraints neatly. Models in dependent and independent
coordinates produced with the Newton-Euler, Lagrange and Kane
formalisms will each be examined in order to provide a vantage point
from which an informed selection may be made from among the many
tools now available in computational dynamics.
(10 pages PDF)
Stable User-Specific Rendering of the
Virtual Wall
B. Gillespie and M. Cutkosky
Proceedings of the ASME IMECE, DSC-Vol. 58, Atlanta, GA, Nov
17-22, 1996. pp. 397-406.
Efficient control algorithms are developed to implement stiff
virtual walls without chatter. An analysis of the complete
coupled system comprising controller, interface device, and user's
finger underlies the design of a wall algorithm, thus each
virtual wall is tailored to a specific user impedance. The
finger is modeled as a static second order impedance with
justification drawn from empirical studies of limb dynamics
available in the literature and from observations of the disparity
in time scales between contact instability and volitional
control. Compensation is incorporated for the destabilizing
effects of the zero order hold using either model based prediction
or design in the digital domain. The destabilizing effects
of asynchronous wall on/off switching times and sampling
times are tracked by a special watchdog while deadbeat control is
used to periodically eliminate these effects. Extensions are
discussed, including on-the-fly system identification of the user
impedance.
(10 pages PDF)
The Moose: A Haptic User Interface
for Blind Persons
S. O’Modhrain and B. Gillespie
Proceedings of the Third WWW6 Conference, Santa Clara, CA,
April 1997.
- This paper presents our work to date on a haptic interface
whose immediate aim is to provide access for blind computer users
to graphical user interfaces. In this presentation, we
describe the hardware and supporting software which together
reinterprets a Microsoft Windows screen for the haptic
senses. Screen objects such as windows, buttons, sliders,
and pull-down menus are mapped to the workspace of a two-axis
haptic interface called the Moose where they emerge as patches and
lines of varying resistance. The Moose operates much like a
mouse except that it is able to move under its own power and
thereby make apparent touchable virtual objects. Thus
presented to the hand, interface objects may be located,
identified, and even manipulated or activated. Using
Microsoft Windows as a test bench, we have proven the feasibility
and usefulness of the haptic interface approach for non-visual
computer access. Extensions to haptic browsing of the Web
are discussed.
Examining the Influence of Audio
and Visual Stimuli on a Haptic Display
N. Miner, B. Gillespie, and T. Caudell
Proceedings of the 1996 IMAGE Conference, Phoenix, AZ, June
23-25, 1996.
- This paper presents the results of a cross-modal study that
examines the perceptual influence of visual and auditory stimuli
on a virtual object presented through a haptic interface device.
The experiment yields a characterization of the effectiveness of
visual and auditory stimuli at reinforcing a haptic percept.
Results also indicate that the visual stimuli, and the combination
of the visual and auditory stimuli, influenced a subject's haptic
perception. The auditory stimuli alone did not significantly
influence the haptic perception. This finding may be due to the
specific auditory stimuli used, thus highlighting the importance
of carefully selecting and characterizing the perceptual qualities
of sensory stimuli. These results provide an impetus for further
investigation into cross-modal interfaces, especially as a means
for creating more convincing virtual objects for the haptic
senses.
(http
document)
The Virtual Piano Action: Design and
Implementation
B. Gillespie
Proceedings of the International Computer Music Conference,
Aahus, Denmark, Sept 12-17, 1994. pp. 167-170.
The design of a virtual piano action composed of a keyboard of
motorized keys and a real-time mechanical system simulation is
presented. Using this simulator, we have re-created
certain aspects of the feel of the grand piano by numerically
integrating the equations of motion of a simplified piano action
in real time in a human-in-the-loop simulation scheme. In
this paper, the simulation of the release and catch of the
hammer is used to introduce the simulator
architecture. The structure of a software module which
manages the simulation of models with changing kinematic
constraints is discussed, including a finite state machine driver
which allows for the simulation of rigid-body systems which may
take on various constraint conditions in a sequence dependent on
run-time interaction.
(4 pages PDF)
The Moose: A Haptic User Interface for Blind
Persons with Application to the Digital Sound Studio
B. Gillespie and S. O’Modhrain
Stanford University Department of Music Technical Report
STAN-M-95, October, 1995.
This project involves the development of a new computer
interface based on haptics. Information will be transferred
from computer to user mechanically (by touch) instead of visually
or aurally. The immediate aim is to provide access for blind
sound engineers to the graphics-based computer interfaces
currently found in digital sound studios.
Access for blind persons to computer applications with
graphical user interfaces is virtually nonexistent at
present. A mouse is of no use without the user's visual
tracking of the cursor on the screen. With a haptic
interface, screen objects such as buttons, sliders and pull-down
menus will be presented mechanically to the user's haptic senses
(kinesthetic and tactile), where they can be felt, located,
identified, and, through the use of the same device for input,
activated. We have built a prototype two-axis device which
operates much like a mouse, except that it is also able to move
under its own power. By producing forces on the user's hand
which are a function of both the user's motions and the buttons or
windows under the cursor, touchable representations of the screen
objects are created. Using this prototype device we
have already proven the feasibility and usefulness of the haptic
interface approach for non-visual computer
access. We expect that haptic interface devices
will become standard computer interface tools, supplementing the
visual resentation with haptic presentation for all
users. Less attention to visual tracking would be
needed. A more complete
and holistic presentation of information will be made by the
computer. This approach is, we believe, particularly
valuable in the design of application interfaces for digital audio
editing.
(8 pages PDF)
Design of High-fidelity Haptic Display for
One-dimensional Force Reflection Applications
B. Gillespie and L. Rosenberg
Telemanipulator and Telepresence Technology, Proceedings
of the International Society of Optical Engineers (SPIE) East
Coast Conference, Boston, MA, Oct 31-Nov 1, 1994, pp. 44-54.
This paper discusses the development of a virtual reality
platform for the simulation of medical procedures which involve
needle insertion into human tissue. The paper's focus will
be the hardware and software requirements for haptic display of a
particular medical procedure known as Epidural Analgesia. To
perform this delicate manual procedure, an anesthesiologist must
carefully guide a needle through various layers of tissue using
only haptic cues for guidance. A simplifying aspect for the
simulator design, all motions and forces involved in the task
occur along a fixed line once insertion begins.
To create a haptic representation of this procedure, we have
explored both physical modeling and perceptual modeling
techniques. A preliminary physical model was built based on
CT-scan data of the operative site. A preliminary perceptual
model was built based on current training techniques for the
procedure provided by a skilled instructor. We compare and
contrast these two modeling methods and discuss the implications
of each. We select and defend the perceptual model as a
superior approach for the epidural analgesia simulator.
(11 pages PDF)
Interactive Dynamics with Haptic
Display
B. Gillespie and M. Cutkosky.
Proceedings of the ASME Winter Annual Meeting, New Orleans,
LA, Nov 28-Dec 3, 1993. DSC-Vol. 49 pp. 65-72.
The simulation of virtual environments which are
multi-degree-of-freedom presents unique challenges to the designer
of control software for haptic display devices. Once the
successfully rendered stiffness, damping, and mass elements are
interconnected to form multibody systems, a host of controller
implementation choices arise. For one, the control law must
manifest the dynamics of the simulated multibody system.
Further extensions are required if the interconnection topology is
allowed to change, as in the case of changing kinematic
constraints. The control law must be able to undergo
transformations in order to reflect these. We want to include such
capabilities in our simulator repertoire, as these are among the
most interesting to explore haptically. This paper describes a
combined simulation and experimental apparatus for exploring
issues in the haptic display of dynamical models. In particular,
we address problems in the simulation of changing kinematic
constraints with numerical integration methods which have been
specialized for real-time mechanical system simulation. Issues in
the software design of a haptic display are addressed. A
simplified model of the piano action is used as an illustrative
example.
(8 pages PDF)
The Touchback Keyboard
B. Gillespie
Proceedings of the International Computer Music Conference,
San Jose, CA, Oct 14-18, 1992. pp. 447-448.
- A digital control system capable of simulating multi
degree-of-freedom dynamical systems in real time with visual,
audio, and haptic displays is presented. A set of software
and hardware tools form a testbed in which a dynamical system can
be modeled, reduced to equations of motion, and simulated.
The user interacts with a powered key to influence the behavior of
the dynamical system and feel the computed interaction forces
being fed back in real-time. Of primary interest for
simulation with haptic display are the grand piano action and
other keyboard instrument controllers. Various keyboard
actions are demonstrated.
(2 pages PDF)
Dynamical Modeling of the Grand Piano
Action
B. Gillespie and M. Cutkosky.
Proceedings of the International Computer Music Conference,
San Jose, CA Oct 14-18, 1992, pp. 77-80.
The grand piano action is modeled as a set of four rigid bodies
using Kane's method. Computerized symbol manipulation is
utilized to streamline the formulation of the equations of motion
so that several models can be considered, each of increasing
detail. Various methods for checking the dynamical model
thus derived are explored. A computer animation driven by
simulation of the equations of motion is compared to a high-speed
video recording of the piano action moving under a known force at
the key. For quantitative evaluation, the velocities and
angular velocities of each of the bodies are extracted from the
video recording by means of digitization techniques. The
aspects of the model of particular interest for emulation by a
controlled system, namely, the mechanical impedance at the key and
the velocity with which the hammer strikes the string, can be
studied in the equations of motion and compared to empirical
data.
(4 pages PDF)
Brent Gillespie, brentg@umich.edu
4 July, 2002