2,826 research outputs found
A Nonlinear Observer for Free-Floating Target Motion using only Pose Measurements
In this paper, we design a nonlinear observer to estimate the inertial pose
and the velocity of a free-floating non-cooperative satellite (Target) using
only relative pose measurements. In the context of control design for orbital
robotic capture of such a non-cooperative Target, due to lack of navigational
aids, only a relative pose estimate may be obtained from slow-sampled and noisy
exteroceptive sensors. The velocity, however, cannot be measured directly. To
address this problem, we develop a model-based observer which acts as an
internal model for Target kinematics/dynamics and therefore, may act as a
predictor during periods of no measurement. To this end, firstly, we formalize
the estimation problem on the SE(3) Lie group with different state and
measurement spaces. Secondly, we develop the kinematics and dynamics observer
such that the overall observer error dynamics possesses a stability property.
Finally, the proposed observer is validated through robust Monte-Carlo
simulations and experiments on a robotic facility.Comment: 8 pages, 6 figure
Automated Rendezvous & Docking Using 3D Vision
The robustness and accuracy of a vision system for motion estimation of a
tumbling target satellite are enhanced by an adaptive Kalman filter. This
allows a vision-guided robot to complete the grasping of the target even if
occlusion occurs during the operation. A complete dynamics model, including
aspects of orbital mechanics, is incorporated for accurate estimation. Based on
the model, an adaptive Kalman filter is developed that estimates not only the
system states but also all the model parameters such as the inertia ratio,
center-of-mass, and the rotation of the principal axes of the target satellite.
An experiment is conducted by using a robotic arm to move a satellite mockup
according to orbital mechanics while the satellite pose is measured by a laser
camera system. The measurements are sent to the Kalman filter, which, in turn,
drives another robotic arm to grasp the target. The results demonstrate
successful grasping even if the vision system is blocked for several seconds
Trajectory Optimization and Following for a Three Degrees of Freedom Overactuated Floating Platform
Space robotics applications, such as Active Space Debris Removal (ASDR),
require representative testing before launch. A commonly used approach to
emulate the microgravity environment in space is air-bearing based platforms on
flat-floors, such as the European Space Agency's Orbital Robotics and GNC Lab
(ORGL). This work proposes a control architecture for a floating platform at
the ORGL, equipped with eight solenoid-valve-based thrusters and one reaction
wheel. The control architecture consists of two main components: a trajectory
planner that finds optimal trajectories connecting two states and a trajectory
follower that follows any physically feasible trajectory. The controller is
first evaluated within an introduced simulation, achieving a 100 % success rate
at finding and following trajectories to the origin within a Monte-Carlo test.
Individual trajectories are also successfully followed by the physical system.
In this work, we showcase the ability of the controller to reject disturbances
and follow a straight-line trajectory within tens of centimeters.Comment: Accepted to IROS2022, code at
https://gitlab.com/anton.bredenbeck/ff-trajectorie
Finding and Following Optimal Trajectories for an Overactuated Floating Robotic Platform
The recent increase in yearly spacecraft launches and the high number of
planned launches have raised questions about maintaining accessibility to space
for all interested parties. A key to sustaining the future of space-flight is
the ability to service malfunctioning - and actively remove dysfunctional
spacecraft from orbit. Robotic platforms that autonomously perform these tasks
are a topic of ongoing research and thus must undergo thorough testing before
launch. For representative system-level testing, the European Space Agency
(ESA) uses, among other things, the Orbital Robotics and GNC Lab (ORGL), a
flat-floor facility where air-bearing based platforms exhibit free-floating
behavior in three Degrees of Freedom (DoF). This work introduces a
representative simulation of a free-floating platform in the testing
environment and a software framework for controller development. Finally, this
work proposes a controller within that framework for finding and following
optimal trajectories between arbitrary states, which is evaluated in simulation
and reality.Comment: 16th Symposium on Advanced Space Technologies in Robotics and
Automation 202
Aerial Manipulation: A Literature Review
Aerial manipulation aims at combining the versatil- ity and the agility of some aerial platforms with the manipulation capabilities of robotic arms. This letter tries to collect the results reached by the research community so far within the field of aerial manipulation, especially from the technological and control point of view. A brief literature review of general aerial robotics and space manipulation is carried out as well
Robotic Manipulation and Capture in Space: A Survey
Space exploration and exploitation depend on the development of on-orbit robotic capabilities for tasks such as servicing of satellites, removing of orbital debris, or construction and maintenance of orbital assets. Manipulation and capture of objects on-orbit are key enablers for these capabilities. This survey addresses fundamental aspects of manipulation and capture, such as the dynamics of space manipulator systems (SMS), i.e., satellites equipped with manipulators, the contact dynamics between manipulator grippers/payloads and targets, and the methods for identifying
properties of SMSs and their targets. Also, it presents recent work of sensing pose and system states, of motion planning for capturing a target, and of feedback control methods for SMS during motion or interaction tasks. Finally, the paper reviews major ground testing testbeds for capture operations, and several notable missions and technologies developed for capture of targets on-orbit
Robot Manipulators
Robot manipulators are developing more in the direction of industrial robots than of human workers. Recently, the applications of robot manipulators are spreading their focus, for example Da Vinci as a medical robot, ASIMO as a humanoid robot and so on. There are many research topics within the field of robot manipulators, e.g. motion planning, cooperation with a human, and fusion with external sensors like vision, haptic and force, etc. Moreover, these include both technical problems in the industry and theoretical problems in the academic fields. This book is a collection of papers presenting the latest research issues from around the world
Robust control of rotation-floating space robots with flexible appendages for on-orbit servicing
On-orbit operations are facing a growing need for autonomous robotic systems to achieve
risky and repetitive tasks. Debris removal, on-orbit servicing and in-space
deployment/assembly are examples of applications considering the use of robot
manipulators. The presence of large and light appendages in future spacecrafts, such as
solar arrays, antennas and sun shields yields to flexible disturbances inside the structure
making the control of the manipulator challenging. This paper addresses design and contro
Performing heavy transfers for offshore wind maintenance
As offshore wind farms become larger and further from the shore, there are strong economic and climate incentives to perform transfers required for operations and maintenance from floating vessels, rather than employing expensive and slow jack up rigs. However, successful transfers of heavy and sensitive equipment from a floating vessel (in all but benign sea/wind conditions) are heavily dependent on multiple degrees of freedom, high performance control. This project aims to bring a novel modelling and simulation methodology in Simulink that could be used to assess offshore wind installation and maintenance procedures. More specifically, the
goal is to demonstrate that a crane prototype assumed to be located on a floating ship can transfer loads of hundreds of tons onto a fixed platform. Furthermore, this process should be completed with good precision and minimal impact force during equipment loading onto the stand. This problem has not yet been answered in research, with the only relevant patent in the field being the Ampelmann platform, a motionless bridge allowing technicians to access the offshore turbine. The first main contribution to knowledge of this thesis was the design of a 90 m crane that could handle a 660 tons load. This thesis presents a procedure, based on both mechanical/hydraulics design as well as empirical findings, which could be re-used for scaling the crane model to a more realistic dimension. It is worth noting that the goal here was to assess whether a realistically weighing piece of equipment could be stably handled, while the actual size of the crane was deemed unimportant. Another missing gap in literature this project wanted to fill was achieving active motion
compensation for a larger scale system such as the current one. This refers to balancing out the base motions on multiple axes, so the payload can be moved on a given trajectory unaffected by them. Currently, research in the field mainly consists of crane mechanisms that feature active heave compensation, which only refers to the vertical axis. Hence, two control design methods were employed to assess the viability of heavy payload positioning from floating vessels through the development of a simulation approach using Simulink. The crane prototype was designed and modelled to operate under simulated vessel motions given by sea states with a significant wave height of 5 m and maximum wave frequency of 1 rad/s. Then, traditional control (feedback and feedforward) was designed to achieve active motion compensation with steady-state position errors under 20 cm. A second controller architecture was then designed/implemented as a comparison basis for the first one, with the aim being to find the most robust solution of the two. The nonlinear generalised minimum variance (NGMV) control algorithm was chosen for control design in this application. Due to its ability to compensate for significant system nonlinearities and the ease of implementation, NGMV was a good candidate for the task at hand. Tuning controller parameters to stabilize the system could also be based on the previously determined traditional control solutions. An investigation of controllers’ robustness against model mismatch was carried out by introducing various levels of uncertainty which influence actuators’ natural frequency to assess system sensitivity. The outcome of the investigation determined that traditional and NGMV controllers provided comparable regulating performance in terms of reference tracking and disturbance
rejection, for the nominal case. This confirmed the assertion that the PID-based NGMV weightings selection is a useful starting point for controller tuning. Increasing the mismatch between the nominal system based on which the controllers’ were designed and the actual plant showed that the traditional control was marginally more robust in this application. The final contribution to knowledge this thesis aimed to bring was minimising the impact force during load placement on a fixed and rigid platform. To that end, the contact forces between the payload and a platform were first successfully modelled and measured. A switching algorithm between position and force control was then developed based on a methodology found in literature but on a microscopic scale project. To execute smooth load placement, an automated hybrid
force/position control scheme was implemented. The proposed algorithm enabled position control on x and y axes, while minimising impact forces on the z-axis. Unfortunately, preliminary findings showed that there is still work to be done to claim any success in this regard. However, the author hopes this offers a good starting point for future work.As offshore wind farms become larger and further from the shore, there are strong economic and climate incentives to perform transfers required for operations and maintenance from floating vessels, rather than employing expensive and slow jack up rigs. However, successful transfers of heavy and sensitive equipment from a floating vessel (in all but benign sea/wind conditions) are heavily dependent on multiple degrees of freedom, high performance control. This project aims to bring a novel modelling and simulation methodology in Simulink that could be used to assess offshore wind installation and maintenance procedures. More specifically, the
goal is to demonstrate that a crane prototype assumed to be located on a floating ship can transfer loads of hundreds of tons onto a fixed platform. Furthermore, this process should be completed with good precision and minimal impact force during equipment loading onto the stand. This problem has not yet been answered in research, with the only relevant patent in the field being the Ampelmann platform, a motionless bridge allowing technicians to access the offshore turbine. The first main contribution to knowledge of this thesis was the design of a 90 m crane that could handle a 660 tons load. This thesis presents a procedure, based on both mechanical/hydraulics design as well as empirical findings, which could be re-used for scaling the crane model to a more realistic dimension. It is worth noting that the goal here was to assess whether a realistically weighing piece of equipment could be stably handled, while the actual size of the crane was deemed unimportant. Another missing gap in literature this project wanted to fill was achieving active motion
compensation for a larger scale system such as the current one. This refers to balancing out the base motions on multiple axes, so the payload can be moved on a given trajectory unaffected by them. Currently, research in the field mainly consists of crane mechanisms that feature active heave compensation, which only refers to the vertical axis. Hence, two control design methods were employed to assess the viability of heavy payload positioning from floating vessels through the development of a simulation approach using Simulink. The crane prototype was designed and modelled to operate under simulated vessel motions given by sea states with a significant wave height of 5 m and maximum wave frequency of 1 rad/s. Then, traditional control (feedback and feedforward) was designed to achieve active motion compensation with steady-state position errors under 20 cm. A second controller architecture was then designed/implemented as a comparison basis for the first one, with the aim being to find the most robust solution of the two. The nonlinear generalised minimum variance (NGMV) control algorithm was chosen for control design in this application. Due to its ability to compensate for significant system nonlinearities and the ease of implementation, NGMV was a good candidate for the task at hand. Tuning controller parameters to stabilize the system could also be based on the previously determined traditional control solutions. An investigation of controllers’ robustness against model mismatch was carried out by introducing various levels of uncertainty which influence actuators’ natural frequency to assess system sensitivity. The outcome of the investigation determined that traditional and NGMV controllers provided comparable regulating performance in terms of reference tracking and disturbance
rejection, for the nominal case. This confirmed the assertion that the PID-based NGMV weightings selection is a useful starting point for controller tuning. Increasing the mismatch between the nominal system based on which the controllers’ were designed and the actual plant showed that the traditional control was marginally more robust in this application. The final contribution to knowledge this thesis aimed to bring was minimising the impact force during load placement on a fixed and rigid platform. To that end, the contact forces between the payload and a platform were first successfully modelled and measured. A switching algorithm between position and force control was then developed based on a methodology found in literature but on a microscopic scale project. To execute smooth load placement, an automated hybrid
force/position control scheme was implemented. The proposed algorithm enabled position control on x and y axes, while minimising impact forces on the z-axis. Unfortunately, preliminary findings showed that there is still work to be done to claim any success in this regard. However, the author hopes this offers a good starting point for future work
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