The development of a flexible operation test-bed, based around a commercially available ASEA industrial robot is described. The test-bed was designed to investigate fundamental human factors issues concerned with the unique problems of robotic manipulation in the hostile environment of Space

Davies, Barry F.

English

NASA Technical Reports Server

N90-29012
DEVELOPMENT OF A FLEXIBLE TEST-BED FOR ROBOTICS,
TELEMANIPULATION AND SERVICING RESEARCH
Barry F. Davies
British Aerospace PLC, Sowerby Research Centre
P.O. Box 5, Filton, Bristol BSI2 7QW
United Kingdom
Abstract
This paper describes the development of a flexible operation test-bed,
based around a commercially available ASEA industrial robot. The test-bed was
designed to investigate fundamental human factors issues concerned with the
unique problems of robotic manipulation in the hostile environment of Space.
I. Introduction
The work to be described here forms part of a contract placed on British
Aerospace Space and Communications Division at Stevenage by the European Space
Agency, entitled "Teleoperation and Contro]." The study to be performed will
be carried out by a team under the technical lead of the British Aerospace
Sowerby Research Centre Human Factors Department, Filton. The remainder of the
study team comprises of the United Kingdom Atomic Energy Authority Laboratories
at Culham and Harwell.
The overall objective of this study is the development and delivery to the
European Space Agency of a flexible (modular) teleoperatlon test-bed, based
around a commercially available ASEA industrial robot, which will permit the
experimental investigation of a variety of approaches to the control and
supervision of robotic manipulation in Space. Experiments were designed to
allow a comparative study of the control and display concepts in order to
optimise and evaluate the use of sensor supplied feedback information to a
human operator.
The experiments were designed with two mission models as a baseline:
Mission Model i. The human operator is located on the ground whilst
controlling a manipulator whJcb is located on a free-f]ying servicing vehic]e.
Mission Model 2. A human operator is located en the aft deck of the
shuttle, controlling a manipul_tor servicing a payload in the cargo area.
In addition to providing information about the above scenarios, the
project will address five ov,_1! objectives:
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- To analyse specific MMl/humanfactors issues concerned with the
unique prob]ems of teleoperation.
- To provide data which will permit the optimisation of the man-machine
interface before delivery of the experimental workstation to ESA.
- To provide results which maybe used to formulate future research
programmes,to determine the HumanComputer Interaction requirements
which can be satisfied in the short and long term and to determine
possible roles for telepresence strategies.
- To provide results which maybe applied in identifying options forthe design of future workstations.
- To establish a test-bed facility and research programmewhich
demonstrate a sound European capability in teleoperation workstation
design and in research into remote handling and inspection in Low
Earth Orbit (LEO).
2. Overall Test-Bed Concept
The development and use of an experimental test-bed stems from the need to
establish a programme of experimentation and research into teleoperation in
Space. It is important that in achieving this aim the test-bed should remain
as flexible as possible. This allows the test-bed to be used both for future
research programmes and for the development and implementation of new systems.
The programme of test-bed development has been driven by past theoretical
research (e.g. Milgram et al, 1983; Sheppard et al, 1986) and by developments
in the fields of the ESA crew workstation (CWS) and EUROSIM projects.
To obtain and maintain the maximum degree of flexibility, the test-bed was
developed along modular lines. The modules were defined as follows:
- Subject control and display station
- Experimenter's control and display station
- Video system
- Robot system (ASEA IRb6)
- End-effector and sensors
- Task box and work area. (See Figure I)
The requirements for the test-bed, workstation and video system were
dictated by the nature of the experiments and pilot studies to be carried out
using them. The pilot studies and experiments were concerned with the
following issues:
- Time delay selection (Pilot Study I)
- Control law optimisation (Pilot Study 2)
- Controller selection (Experiment I)
- Feedback optimisation (Pilot Study 3)
- Comparison of feedback options (Experiment 2)
130
Since the test-bed is an evaluative and experimental tool its design and
requirements for its construction were preceded by detailed assessments of the
evaluative studies to be performed upon it.
3. Definition of Research and Experimentation
The main objective of the teleoperatlon and control study is to perform an
experimental and comparative evaluation of a variety of concepts regarding the
human operator's efficient use of control and feedback options. Previous
research studies have been predominantly theoretical in their approaches to key
human factors aspects of teleoperation in Space. Therefore, it is appropriate
to address these issues from a practical perspective. Both quantitative and
qualitative data will be collected in order to provide as complete an
evaluation and analysis as possible.
Experimental Designs
The specific designs of the experiments have determined the hardware and
software requirements for these investigations. However, the need for
flexibility and modularity was not overlooked in this process so as to allow
easy implementation of future developments and additions. It is important that
there is a logical progression from one experiment to the next. For this
reason, a number of pilot or optimisation studies will be undertaken. These
will help the experimenters select or optimise the characteristics of the
independent variables which will be used in the main experimental designs.
This series of investigations places emphasis on both sensory and motor
variables. The series of designs does not deal with these two key areas in
isolation, but instead the emphasis of the designs will change from one area to
the other as the experiments progress.
At the end of this series of investigations, the main sensory and motor
factors which influence remote teleoperation will have been considered. The
results of these studies will be fed directly into the development of the
flexible teleoperation facility for ESA.
The experimental designs are outlined below:
Pilot Study i. To identify from existing literature and preliminary
experimentation, three time delays for use in Experiments 1 and 2.
One of the major areas of concern in the field of Space teleoperation is
the performance penalties which are incurred by the human operator controlling
systems in the presence of a transmission time delay. Some research has been
performed, but this relates specifically to tracking tasks in the presence of a
time delay. In the present investigation, consideration will be given to both
tracking and pick-and-place tasks.
Three time delays will be considered for use in the main experiments:
(a) Human perceptual threshold. Identified as 60 milliseccnds in
Sheppard et al (1986).
131
(b) Humancontrol disruption (i.e. a time delay which produces 'stop andgo' motions).
(c) Time delay for LEO:maximumdelay likely to be experienced in a Space
teleoperation system.
This pilot study will attempt to establish a representative time delay
which will produce a humancontrol disruption. Therefore, the result of this
pilot study will be the specification of a control time delay which would
interfere with all operators' ability to perform the tasks.
The third time delay which will be used in Experiments i and 2 will be
representative of the time delay which would be experienced when controlling a
task in LEO from the ground. This time delay will be identified from
literature concerned with satellite/ground station communication links.
Pilot Study 2. To specify and compare control laws for a variety of
control devices with the overall aim of selecting the most suitable control law
for each device and to optimise the law more finely on the basis of this
selection.
Three different Joysticks and configurations have been selected for this
pilot study. These joysticks will be used in the joystick comparison and
evaluation study (Experiment I), but the control law for each individual device
must be optimised before the main study can be undertaken. The joysticks for
which the control laws are to be optimised are as follows:
(a) 2x3 axis joysticks. Translational movements of the robot
end-effector will be controlled by a three-axis horizontally mounted,
whole-hand joystick. Rotational movements of the end-effector (hence
changing the orientation of the end-effector at the same point in
Space) will be controlled using a three-axis, vertically mounted,
whole-hand joystick.
(b) Single multifunction joystick. This joystick will be used to control
both translational and rotational movements. Selection of either
translational or rotational modes will be made via a switch mounted
on the joystick itself. The joystick chosen for this evaluation is
the same as the rotational controller used in the previous
configuration (a).
(c) DFVLR hand controller. This device is a ball controller capable of
controlling six independent degrees of freedom. The controller is a
force-torque device with only a perceptibly small degree of motion in
each axis.
With these two pilot studies completed, Experiment 1 can commence.
Experiment I. To evaluate and compare a variety of control devices for
the task of remote handling in the presence of time delays and to provide data
for subsequent designs.
132
In addition to the three joystick configurations discussed in the previous
pilot study, a 'replica' controller, kinematically similar to the ASEArobot,
will also be considered. All the devices will be comparedusing the control
laws established in Pilot Study I (position control for the replica and
optimised fixed or proportional rates for the other devices) and the
independent variable of time delay (as in Pilot Study i). (See Figure 2)
Performance measures of whole and part-task time along with whole and
part-task accuracy will be taken. In addition to this quantitative data,
certain qualitative data such as general operator strategies and workstation
interaction difficulties will also be recorded.
The outcome of this experiment will be the specification of a controller
Which produces the most efficient performance of benchmark operations in the
presence of time delays. In the event of interaction effects between
controllers and time delays, then the controller deemed, in general, to be the
most satisfactory will be selected for use in later experimentation.
Pilot Study 3. The optimisation of remote cameras, display configurations
and remote lighting.
The aim of this pilot study is to optimise the various chosen methods of
sensory feedback, feedback being the presentation of both visual and auditory
information, moreover, to optimise the presentation of this information.
Issues to be addressed include the levels of ambient lighting in the
experimental environment and the positioning of artificial lighting to meet
human visual requirements and task requirements as outlined in Stone et al
(1985).
This pilot study, in conjunction with the lighting, will also consider the
positioning of the remote cameras. This will also be carried out to meet both
human visual requirements and the requirements demanded by the task.
This pilot study, in contrast to the previous pilot studies, will be of a
predominantly qualitative nature, where subjects' comments will be used to
determine the optimal location of both lighting and camera configurations.
Experiment 2. The evaluation and comparison of a number of sensory
feedback options in terms of their effect on operator performance.
This experiment will incorporate all the results of the previous pilot
experiment studies. At this stage the controller or controllers will have been
selected and the sensory information will have been optimised. Therefore, the
experiment will encompass all that has been learnt from previous research and
experimentation and will involve a fully configured task box and test-bed.
The options to be examined in the experiment will be:
(a) Visual feedback only. Only the remote cameras and lighting will be
used.
133
(b) Visual feedback with force-torque display. In addition to the remote
cameras, the subject will be provided with a graphics display of the
forces and torques being exerted at the end-effector.
(c) Visual feedback with a proximity display. In this condition the
subject will be provided with remote camera views plus the view from
a proximity camera mounted on the wrist of the robot. (See Figure 3)
These conditions will be carried out under the three time-delay conditions
mentioned earlier and a further condition of obscured/unobscured view of the
task box. The obscured view will be achieved by degrading the image of one or
more of the remote cameras, thereby forcing the subject to use one camera view
more than another.
As in the previous experiment, performance measures of whole and part-task
timings and accuracy will be taken.
4. Overview of Requirements for the Flexible Teleoperation Facility
From the outset of the study, it was a major priority that the design of
the flexible teleoperation facility should be driven by the design of the
experimental investigations to be carried out on it. Secondly, the design of
the facility should be flexible such that future extensions and developments
could be effectively carried out by ESTEC. This flexibility should permit
development of the test-bed to such a level that it can be used ultimately as a
development or training simulator, and possibly even as a back-up system to an
operational ground-based Robotics Telemanipulation and Servicing (RTS)
workstation.
Test-bed Requirements for Human Factors Experimentation
Once the experiments were designed and the general requirements for the
modular components of the test-bed were broadly defined, it was appropriate to
define these more rigidly:
- The robot system chosen for the test-bed is the ASEA IRb6. This
choice was made for the sake of convenience as the test-bed will
ultimately be based at ESTEC where it will be used with an ASEA IRb60
already situated there. More importantly, the robot should be
available with six degrees of freedom. This requirement was made to
ensure that operators would develop strategies that would be
representative of strategies used by operators using a fully dextrous
six degrees of freedom manipulator in LEO. Control of the degrees of
freedom must be available in both control of individual degrees of
freedom and of control of all six degrees simultaneously.
- The subject's control and display station was designed following
ergonomic principles and to allow quick and efficient interfacing of
the various joystick configurations. The displays and controls for
the remote camera systems were also mounted on this workstation,
again following ergonomic principles.
134
- With regard to the video system, this was designed to provide both
worksite/task feedback and subject surveillance. With regard to the
former, the following criteria were adhered to in order to ensure the
satisfaction of human factors issues raised in Sheppard et al (1986).
The system shall:
(a) Provide detailed and close-up views of the end-effector/task box
interface for inspection and fine control.
(b) Provide global worksite and manipulator views to enhance the
operator's notion of the orientation of the remote equipment
relative to the workslte.
(c) Permit the efficient change of the remote views by the operator,
both in terms of display quality and content.
(d) Permit symbolic or graphical representations of remote sensory
data to be optimally displayed to the human operator, in a way
which does not conflict with his perception of the video
imagery.
5. Summary
This paper has described the development of a flexible (modular)
teleoperation testbed, based around a commercially available ASEA industrial
robot. The intention of the study to be carried out on the test-bed is to
investigate fundamental human factors issues concerned with the control and
sensory feedback problems of a remotely operated robot.
This paper discussed the experiments and investigations to be carried out
on the test-bed and the philosophy behind the development of the test-bed using
the design of the experiments as the principal driver. The components of the
test-bed are described in detail along with the need for modularisation in
order to maintain the degree of flexibility required of the test-bed to ensure
efficient and trouble-free development in the future.
Acknowledgements
I wish to thank Mr. Laird Evans of Sowerby Research Centre, British
Aerospace, for his invaluable help and support in the preparation of this paper.
References
Milgram, P. et al. "ESA Contract 5594/83: Control Loops with Human
Operators in Space Operations, Parts I-V." National Aerospace Laboratory NLR
(NLR TR 84 16L) (1983).
Sheppard, J. et al. "Teleoperatlon and Control Study: Final Report."
Space and Communications Division, Stevena_e, Report TP8268 (May 1986).
BAe
Stone, R. et al. "AERE Contract H2C 547430 ES: Human Factors Evaluation
of the MA-23M Servomanlpulator." BAe Report No. JSI0561 (March 1986).
135
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136
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137
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TELEROBOT ARCHITECTURES
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Development of a flexible test-bed for robotics, telemanipulation and servicing research

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