1,720,969 research outputs found
Dynamic/control interactions between flexible orbiting space-robot during grasping, docking and post-docking maneuvers
No full textRobotic systems are expected to play an increasingly important role in future space activities, such as repairing, upgrading, refuelling, and re-orbiting spacecraft. These technologies could potentially extend the life of satellites, enhance the capability of space systems, reduce the operation costs, and clean up the increasing space debris. Recent proposals for missions involving the use of space manipulators and/or automated transfer vehicles are presented as a solution for a lot of problems which now affect the procedures and the performance of the in-orbit space systems. Other projects involving space manipulators have been developed by DARPA aiming to demonstrate several satellite servicing operations and technologies including rendez-vous, proximity operations and station-keeping, capture, docking, fluid transfer (specifically, “hydrazine”), and ORU (Orbit Replaceable Unit) transfer. Of course the dynamic coupling between the manipulator and its base mounting flexible solar arrays is very difficult to model. Furthermore the motion planning of a space robots is usually much more complicated than the motion planning of fixed-base manipulators. In this paper first of all the authors present a mixed NE/EL formulation suitable for synthesizing optimal control strategies during the deploying manoeuvres of robotic arms mounted on flexible orbiting platform (i.e. the chaser). Then two new control strategies able compensate the flexibility excitations of the chaser satellite solar panels during the capturing of a flexible target spacecraft with the use of two robotic arms are presented and applied to a grasping manoeuver
Dynamic/control interactions between flexible orbiting space-robot during grasping, docking and post-docking manoeuvres
No full textRobotic systems are expected to play an increasingly important role in future space activities, such as repairing, upgrading, refuelling, and re-orbiting spacecraft. These technologies could potentially extend the life of satellites, enhance the capability of space systems, reduce the operation costs, and clean up the increasing space debris. Recent proposals for missions involving the use of space manipulators and/or automated transfer vehicles are presented as a solution for a lot of problems which now affect the procedures and the performance of the in-orbit space systems. Other projects involving space manipulators have been developed by DARPA aiming to demonstrate several satellite servicing operations and technologies including rendez-vous, proximity operations and station-keeping, capture, docking, fluid transfer (specifically, “hydrazine”), and ORU (Orbit Replaceable Unit) transfer. Of course the dynamic coupling between the manipulator and its base mounting flexible solar arrays is very difficult to model. Furthermore the motion planning of a space robots is usually much more complicated than the motion planning of fixed-base manipulators. In this paper first of all the authors present a mixed NE/EL formulation suitable for synthesizing optimal control strategies during the deploying manoeuvres of robotic arms mounted on flexible orbiting platform (i.e. the chaser). Then two new control strategies able compensate the flexibility excitations of the chaser satellite solar panels during the capturing of a flexible target spacecraft with the use of two robotic arms are presented and applied to a grasping manoeuver. The mission is here divided into three main phases: the approaching, the docking and the post-grasping phase. Several numerical examples will complete the work.Robotic systems are expected to play an increasingly important role in future space
activities, such as repairing, upgrading, refuelling, and re-orbiting spacecraft. These
technologies could potentially extend the life of satellites, enhance the capability of space
systems, reduce the operation costs, and clean up the increasing space debris. Recent
proposals for missions involving the use of space manipulators and/or automated transfer
vehicles are presented as a solution for a lot of problems, which now affect the procedures
and the performance of the in-orbit space systems. Other projects involving space
manipulators have been developed by DARPA aiming to demonstrate several satellite
servicing operations and technologies including rendez-vous, proximity operations and
station-keeping, capture, docking, fluid transfer (specifically,
“
hydrazine
”
), and Orbit
Replaceable Unit (ORU) transfer. Of course the dynamic coupling between the manipulator
and its base mounting flexible solar arrays is very difficult to model. Furthermore, the
motion planning of space robots is usually much more complicated than the motion
planning of fixed-base manipulators. In this paper first of all the authors present a mixed
NE/EL formulation suitable for synthesizing optimal control strategies during the deploy-
ing manoeuvres of robotic arms mounted on flexible orbiting platform (i.e. the chaser).
Then two new control strategies able to compensate the flexibility excitations of the
chaser satellite solar panels during the capturing of a flexible target spacecraft with the
use of two robotic arms are presented and applied to a grasping manoeuvre. The mission
is here divided into three main phases: the approaching, the docking and the post-
grasping phase. Several numerical examples will complete the wor
Dynamic modelling and control of a flexible spacecraft with fuel slosh
No full textModern spacecraft often contain large quantities of liquid fuel to execute station keeping and attitude maneuvers for
space missions.
In recent works a hybrid control method based on input shaping technique and feedback linearization
for liquid-filled spacecraft maneuvers has been proposed to guarantee that the attitude maneuver does not excite the
liquid-fuel slosh. In general the combined liquidstructure system is very difficult to model, and the
analyses are based on some assumed simplification. A realistic representation of the liquid dynamics inside closed containers can
be approximated by an equivalent mechanical system. The technique of equivalent mechanical models can be
considered a very useful mathematical tool for solving the complete dynamics problem of a system containing liquid Thus
they are particularly useful when designing a control system or to study the stability margins of the coupled dynamics
The commonly used equivalent mechanical models are the mass–spring models and the pendulum models
An Integrated Multi-Body/FEM Approach for Space Applications
No full textDynamics and control of space mechanisms will be a profitable field of research in the near future, due to the worldwide development of complex space missions including large platforms, huge deployable appendages, robotic arms. These mechanisms will be challenging due to a specific and hard space environment, to the complex dynamics described by non-linear equations, by the limited power – mechanical, electric, computational – available on board. On account of the different features of the requirements, generated by all subsystems, the optimization of the mechanisms’ design should be searched in a multidisciplinary approach. Additional issues come from the design and production management side. Due to the complexity of the space programs, it is likely that several engineering firms from different sites should work together. It means that, since initial steps, a kind of unique design (and delays and coordination problems expected) or a parallel design should be. This way each group, once agreed on common interfaces, will work at its best in their field. Modern design integration processes and tools are needed to address these challenges and implement multidisciplinary optimization in an effective manner. In recent years, the aero/space industry has been moving towards the integrated analysis of multidisciplinary systems at every stage of the design and manufacturing process. The availability of commercial multibody analysis software is pushing this approach. Codes such as ADAMS, MECANO, Sympack, DCAP (developed by TAS-I and the European Space Agency) allow the dynamic and kinematic numerical modeling of complex aerospace systems, offering a powerful tool to understand the working principles of these components in a complex environment. Moreover multibody systems are intended as a collection of bodies that hold their degrees of freedom by means of kinematic or flexible constraints. Modern multibody codes are able to handle not only kinematic interfaces, but also they can profitably take multiphysics characteristics into account, so that the complex interactive design becomes possible
3D minimum reaction control for space manipulators
No full textThis paper presents a novel controller for a generic 3D multibody space system. The control is designed to minimize the dynamic coupling between one of the bodies and the rest of the system, e.g. a spacecraft endowed with a robotic manipulator. Standard control techniques suffer of some limitations. For instance, the Jacobian Transposed (JT) control does not explicitly address the reduction of the reaction forces over the main body. Or else, the so-called “Reaction Null” (RN) technique has a limited workspace due to the strictness of the constraint of zero reactions over the spacecraft. A new closed-loop controller, called Minimum Reaction (MR) control, is designed by combining the RN and JT approaches, so that the dynamic coupling between base platform and manipulator is reduced, while achieving the desired end effector position with great precision. In fact, the reactions on the base are minimized but not constrained to be null as in RN, so that the workspace of the manipulator is extended at its maximum. To this end, the non-linear 3D dynamics of a multibody system is derived in matrix form. Then, a minimum reaction control problem is formulated and solved analytically using a quadratic cost function. The presented solution is applied to a typical mission scenario involving a robotic arm deployment, both in the case of a rigid multibody system and in the case in which a flexible appendage (such as a solar panel) is included. Results are compared with a Jacobian Transposed controller and a Reaction Null controller and discussed
A Minimum State Multibody/FEM Approach for Modelling Flexible Orbiting Space Systems
No full textIn the past the deployment of space structures has widely been analysed by using multibody formulations. The two leading approaches are usually based on the Newton-Euler (NE) formulation and Euler-Lagrange (EL) formulation. Both of them present advantages and drawbacks. The ideal approach for describing multi-body systems should be represented by a combination between the NE and EL formulations. This can be obtained by taking the NE formulation for assembling the equation of motion into account and then by defining the ODE governing equations by using a minimum set of variables. In this paper the authors present a mixed NE/EL formulation suitable for synthesizing optimal control strategies during the deploying maneuvers of robotic arms or solar arrays. The proposed method has two main characteristics: (i) the reference frame, which all the bodies motions are referred to, is a floating reference frame attached to the orbiting base platform body; (ii) it leads to a more organic formulation which makes a shifting from the NE to the EL formulations possible, through the use of a Jacobian matrix. In the present work this mixed formulation is derived to describe a fully elastic multi-body spacecraft. Furthermore the presented formulation, complemented with gravity, gravity gradient and generalized gravitational modal forces, will be used to study the dynamic behaviour of an orbiting manipulator with flexible appendages. Finally a Reaction Null/Jacobian Transpose control strategy will be applied to control and deploy the robotic arms to grasp an orbiting flexible spacecraf
A reaction-null/Jacobian transpose control strategy with gravity gradient compensation for on-orbit space manipulators
No full textThe dynamics and the control of space manipulators floating in 3D space is analyzed in this paper. A minimum state variable approach for describing the dynamics of a free-floating space manipulator under gravity and gravity gradient forces is presented. A new control strategy involving a combination of Reaction Null and Jacobian Transpose controllers, including also the gravity gradient compensation, is suggested and compared with the Jacobian Transpose control and the conventional Proportional Derivative control. Several numerical examples will be presented and discussed, considering platforms with single and double manipulators, showing the advantages and drawbacks related to these control strategies. © 2014 Elsevier Masson SAS.The dynamics and the control of space manipulators floating in 3D space is analyzed in this paper. A minimum state variable approach for describing the dynamics of a free-floating space manipulator under gravity and gravity gradient forces is presented. A new control strategy involving a combination of Reaction Null and Jacobian Transpose controllers, including also the gravity gradient compensation, is suggested and compared with the Jacobian Transpose control and the conventional Proportional Derivative control. Several numerical examples will be presented and discussed, considering platforms with single and double manipulators, showing the advantages and drawbacks related to these control strategies
Design of robotic manipulators for orbit removal of spent launchers’ stages
No full textThis paper deals with the main drivers for the design of a space manipulator aimed to the removal of the final stages which remain in Low Earth Orbit after releasing their payloads. At the scope, the different phases of a debris removal mission are considered, starting from the parking orbit where the servicing spacecraft equipped with the manipulator (chaser) waits for the call on duty, encompassing the approach to the target and its grasping and finally dealing with the dismissal of the captured object. The characteristics and requirements of each phase, in terms of torques to be applied to the joints of the manipulator(s) and to the forces to be generated via thrusters at the system level, are analysed. The number of robotic arms, the number of joints of each arm, and the torque level that each joint motor should supply are mainly defined by the grasping phase and the de-orbit phase. During the grasping, the tumbling target must be tracked with a large degree of robustness, and, to this aim, a redundant manipulator must be designed, so that its workspace can be as large as possible. On the other hand, increasing the degrees of freedom of a robotic arm means higher complexity and manufacturing costs. The number of arms depends also on the final de-orbit phase, in which the powerful apogee motor of the chaser satellite is ignited to change the composite system (chaser+target) orbit. The thrust, applied on the chaser, is transferred to the target by means of the manipulator(s): it is shown that a single robotic arm could not be sufficient to withstand the high stress acting during this phase. The torques at the joints required to maintain the arms in the desired configuration end up to be very high too, and the motors – as well as in general the structural elements of the arms – should be sized according to this phase of the mission
A hybrid formulation for modelling multibody spacecraft
No full textIn order to simulate the behavior of a space multibody system, the paper shows the possibility of shifting from a Newton Euler (NE) multibody approach to Lagrange Euler (LE) like formulation of equations of motion. The NE is convenient to understand and to write down the mechanics equations of the system, but the EL based equations of motion show a minimal mathematical complexity and a minimum number of equations in a minimum number of variables. The proposed procedure also allows to swiftly turn back to the NE formulation to calculate the reaction forces and torques among the bodies. The overall revised hybrid formulation, built by mixing both NE and EL approaches, is applied for simulating the deploying phase of spacecraft solar panels
Deployment analysis and control strategies of flexible space manipulators
No full textThe dynamics and the control of articulated structures for an in-orbit manipulation is a profitable field of research due to worldwide development. The dynamics and the control of such systems is a challenging task, since the equations that govern their motion are highly nonlinear and the control strategies need to take the limited resources carried on board of the common space systems into account. They refer for instance to limited energy power, limited computational power and limited control power of the actuators; furthermore the base platforms of these robotic systems are generally floating in space or subjected to gravity gradient and other environmental torques and forces. For these reasons an investigation on the deploying strategies for orbiting space manipulators is necessary in order to find the best solutions. In this paper three different control strategies are analyzed: the Reaction Null control, the Jacobian Transpose control and the conventional Proportional Derivative control that are compared in terms of power consumption and of the relevant control efforts. The analysis involves both single and double space manipulator systems. The effects of the elasticity of the motor shafts on the behaviour of the deploying manoeuver are also analysed. Numerical simulations, obtained by a space optimized multibody code, are used for demonstrating the suitability and the proficiency of this kind of control strategies
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