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Introduction
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Introduction to Haptic Display: Teleoperation
by Blake Hannaford, University of Washington
Teleoperation is the remote control of robot manipulators. Although
commands can be sent from user to remote robot at different levels of
abstraction, this section describes a kind of low-level teleoperation
in which the human directly controls the motions and contact forces of
the remote manipulator in real time. Perhaps the most common
application of this technique is in construction equipment such as
excavators in which the operator controls the velocity of the joints
of the "robot" to accomplish the task. However construction equipment
does not provide force feedback directly to the hand. When the user
is located farther from the remote robot, considerable engineering
effort must be applied to reproduce the sensory feedback information
which allows accurate and efficient control.
Both teleoperation and virtual environments require this rich and
self-consistent sensory feedback. Haptic feedback devices were
pioneered in teleoperation systems as far back as the 1940's. In both
teleoperation and virtual environment applications of haptics, a loop
is closed between the human operator's motion "inputs" and forces
applied by the haptic device. In teleoperation this loop is closed
via a communication link, robot manipulator, and the environment. In
virtual environments, the loop is closed via a computer simulation.
Key issues for the advancement of teleoperation technology include:
- Performance Evaluation:
What quantitative measures can be developed with which to quantify the
quality of a teleoperation system (including haptic displays)?
- Control:
How can stable, high performance, control be obtained in spite of
highly variable human operator and environment dynamics, time delays
in communication channel, and kinematic effects such as singularities?
- Scaling:
What are the requirements for effective user interfaces when there is
a large difference in scale (either up or down) between the master
(human operator) and slave (remote robot)?
- Mechanization:
High quality teleoperation and haptic interaction depends critically
on advanced mechanism designs for both master and slave sides. Key
issues are light stiff structures and linkages, actuators with high
torque/mass ratios and high linearity, compact, high resolution
sensors for position velocity and force/torque.
- Kinematics of Teleoperation:
How can effective use be made of redundant degrees of freedom in
teleoperation systems (i.e. when the number of slave DOF > number of
master DOF)?
