75 research outputs found
Motion Planning for the On-orbit Grasping of a Non-cooperative Target Satellite with Collision Avoidance
A method for grasping a tumbling noncooperative
target is presented, which is based on
nonlinear optimization and collision avoidance. Motion
constraints on the robot joints as well as on the
end-effector forces are considered. Cost functions of
interest address the robustness of the planned solutions
during the tracking phase as well as actuation
energy. The method is applied in simulation to different
operational scenarios
On Grasping a Tumbling Debris Object with a Free-Flying Robot
The grasping and stabilization of a tumbling, non-cooperative target satellite by means of a free-flying robot is a challenging control problem, which has been addressed in increasing degree of complexity since 20 years. A novel method for computing robot trajectories for grasping a tumbling target is presented. The problem is solved as a motion planning problem with nonlinear optimization. The resulting solution includes a first maneuver of the Servicer satellite which carries the robot arm, taking account of typical satellite control inputs. An analysis of the characteristics of the motion of a grasping point on a tumbling body is used to motivate this grasping method, which is argued to be useful for grasping targets of larger size
Robot Excitation Trajectories for Dynamic Parameter Estimation using Optimized B-Splines
In this paper we adressed the problem of finding
exciting trajectories for the identification of manipulator link
inertia parameters. This can be formulated as a constraint
nonlinear optimization problem. The new approach in the
presented method is the parameterization of the trajectories
with optimized B-splines. Experiments are carried out on a
7 joint Light-Weight robot with torque sensoring in each
joint. Thus, unmodeled joint friction and noisy motor current
measurements must not be taken into account. The estimated
dynamic model is verified on a different validation trajectory.
The results show a clear improvement of the estimated dynamic
model compared to a CAD-valued model
Control Strategy of Hardware-in-the-Loop Simulator EPOS 2.0 for Autonomous Docking Verification
This paper briefly describes the hybrid simulator system called European Proximity Operation Simulator (EPOS 2.0) and the
development of the hardware-in-the-loop (HIL) docking simulation concept. A critical requirement for the docking simulation
of this HIL simulator is that the 6-DOF robots in the loop have to exactly mimic the dynamic response of the two satellites
during a contact operation. The main challenges to meet this requirement are in the stiffness of the robots, which is unlike
that of the satellites, as well as the time delay in the HIL simulator. The paper mainly presents the impedance parameter
identification concept for matching the impedance between the satellites impact model and the EPOS robots. In addition
it presents the contact dynamics model used, and the control strategies to meet the requirements of the docking simulator.
Finally it presents the preliminary results and future work
Dynamics Modeling of Structure-Varying Kinematic Chains for Free-Flying Robots
2008 IEEE International Conference on Robotics and Automation Pasadena, CA, USA, May 19-23, 200
Generalization of Optimal Motion Trajectories for Bipedal Walking
Abstractā Control of robot locomotion profits from the use of pre-planned trajectories. This paper presents a way to generalize globally optimal and
dynamically consistent trajectories for cyclic bipedal walking. A small task-space consisting of stride-length and step time is mapped to spline parameters which fully define the optimal joint space motion. The paper presents the impact of different machine learning algorithms for velocity and torque optimal trajectories with respect to optimality and feasibility. To demonstrate the usefulness of the trajectories, a control approach is presented that allows general walking including transitions between points in the task-space
Autonomous Spacecraft Rendezvous using Tube-based Model Predictive Control: Design and Application
As the concentration of large space debris increases, how rendezvous maneuvers involving these typically non-cooperative, freely-tumbling bodies are planned and executed is evolving. The rendezvous must be carefully planned, employing up-to-date in situ data to identify the inertial and motion parameters of the target body, and executed in a manner which accounts for
the remaining uncertainty in these parameters. This paper presents an extension of the TRACE pipeline used in the ROAM/TumbleDock Astrobee experiment campaign, which sequences the target state estimation, motion planning, controller design, and maneuver execution tasks while additionally providing logical loop-back avenues to previous tasks, increasing the chances of a successful maneuver. The pipelineās performance is analyzed in simulation, utilizing: target state estimates generated in a previous
activity on a dedicated on-ground testbed; online motion planning, based on non-linear programming and warm-started using a trajectory library generated offline with a novel GPU-based method; and Tube-based Model Predictive Control to robustly track the planned trajectory. Tube-based Model Predictive Control is an actively evolving subject, distributed over multiple publications and various research interests. The necessary theory and considerations for practical implementation of the method are consolidated; its use, features, and limitations in the proposed task are demonstrated
Singularity Maps of Space Robots and their Application to Gradient-based Trajectory Planning
We present a numerical method to compute singularity sets in the configuration space of free-floating robots, comparing two different criteria based on formal methods. By exploiting specific properties of free-floating systems and an alternative formulation of the generalized Jacobian, the search space and computational complexity of the algorithm is reduced. It is shown that the resulting singularity maps can be applied in the context of trajectory planning to guarantee feasibility with respect to singularity avoidance. The proposed approach is validated on a space robot composed of a six degrees-of-freedom (DOF) arm mounted on a body with six DOF
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
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