ROKVISS - Automation & Robotics - Esa

ROKVISS
Verification of Advanced Tele-Presence Concepts
for Future Space Missions
ASTRA 2002
Klaus Landzettel, Bernhard Brunner, Alexander Beyer, Erich Krämer,
Carsten Preusche, Bernhard-Michael Steinmetz, Gerd Hirzinger
DLR Oberpfaffenhofen
Insitute of Robotics and Mechatronics
D-82234 Wessling
Email: Klaus.Landzettel@dlr.de

"The goal of ROKVISS is to test and verify the long-term
reliability of a new generation of lightweight robotics
components in free space operation.
"The intelligent robotic joints were developed at DLR‘s
Institute of Robotics and Mechatronics in
Oberpfaffenhofen.
"The new light weight robot is able to handle loads equal
to its own mass, while conventional robots only achieve
a ratio of roughly 1:10 to 1:15.

DLR‘s new generation of light weight robots

Kinematics Example

Control architecture
4-th order joint state feedback: qm, dqm, τ, dτ Joint level
Position k➔maxImpedance
k➔0 Torque
control control
3kHz
control
stiff robot
dynamics
inverse
kinematics
serial bus
1kHz
Impedance
control
adaptive gain
adjustment
Force
control
motor position
joint torque
link position
cartesian
level
Force-torque
sensor

Modifications Towards Free Space Application
"Joint arrangement modified from an
inline arrangement to an offset
arrangement.
"For ROKVISS PCBs are mounted into
separate circular aluminum housings
and shedded afterwards.
"Input current observing to prevent destruction due to single
event latch-ups.

ROKVISS Components
"ROKVISS will be installed at the Russian Service
Module (SM).
"It consists of a small 2-joints robot, mounted on a
Universal Workplate (UWP), a controller, a stereo
camera, an illumination system, a power supply, and a
mechanical contour device to verify the robot's functions
and performance.

ROKVISS Robotic System
Joint 1
Joint 2
Stylus
Stereo camera & illumination
Experiment contour

Operational Modes
"ROKVISS will be operated in the tele-presence mode
while the ISS is in direct (S-band) radio contact with the
German tracking station in Weilheim.
"Robot tasks are executed in autonomous mode to verify
and identify joint parameters during non contact phases.
The joint parameters are stored on-board and downlinked
on demand during the next possible radio contact
phase.
"All experiments will be repeated several times during the
entire mission to yield comparable sets of data.

Tele-Presence Mode for ROKVISS
" For the most space robotics applications in the field of servicing and
maintenance, the direct inclusion of an human operator into the
control loop is inevitable, because such missions couldn’t be
prepared in detail off-line on-ground.
" It opens up a much broader range of applications for telerobotic
systems, because the operator can apply his skills on the remote
site, almost as if he would be currently present there.
" ROKVISS provides a good means to evaluate and demonstrate the
capability of the tele-presence mode in a realistic space mission
scenario.

Tele-Presence Mode for ROKVISS
"Tele-presence demands a low signal round trip time,
high sampling frequency and a neglectable jitter.
– Round trip < 500 ms
• Ground LEO ~ 2 ms
• Ground GEO ~ 240 ms
• Ground LEO via relay in GEO ~ 480 ms
– Sampling rate 2 ms min
– Jitter < 50% of sampling rate

ROKVISS Experiments
" Tele-Presence Mode Experiments
" Peg-in-hole
" Contour-following
" Virtual-spring
" Real-spring
" Experiments with simulated increased round trip time
" Automatic Mode Experiments
" Experiments for the identification of the joint dynamics
parameters for controller design
" Experiments for impedance control
" Contact Dynamics Experiment (CSA)
" Public Outreach Experiments
" It is planned to take photos of the ISS, incoming and outgoing
spacecraft, and the extravehicular activities of the astronauts.