Space Manipulator Systems (SMS) are key enablers for future on-orbit servicing, debris removal, and large-structure assembly missions. However, their control remains challenging due to strong dynamic coupling and vibration effects induced by lightweight and flexible appendages. This paper presents an Adaptive Nonlinear Dynamic Inversion (ANDI) control framework for a rotation-free-floating SMS operating in the presence of structural flexibility. The proposed approach combines Nonlinear Dynamic Inversion (NDI) with a Model Reference Adaptive Control (MRAC) scheme to achieve dynamic decoupling and robustness without requiring precise knowledge of the flexible dynamics. A scalable, channel-wise MRAC adaptation law is introduced, and the control gains are synthesized through a Linear Matrix Inequality (LMI)-based optimization grounded in Lyapunov stability theory. This ensures closed-loop stability of the manipulator throughout its workspace while effectively attenuating vibration effects. The proposed controller is validated through high-fidelity, real-time simulations of an SMS with flexible appendages. The results demonstrate improved dynamic decoupling, superior vibration suppression, and robustness to modeling uncertainties.

Space Manipulator Systems (SMS) are becoming pivotal in space exploitation and exploration, offering a versatile range of solutions from space debris capture to structure assembly. However, recent missions involving manipulators aboard satellites and space structures must contend with lightweight and large elements that exhibit flexible behaviors. Despite the challenges posed by flexible elements in their surroundings, enhancing the autonomy of SMS remains crucial to ensure their viability as solutions. For the pre-design of the SMS, path-planning applications, or controller design, there is a necessity for methods to assess the couplings between the manipulator, the SMS platform, and any flexible elements moved by a manipulator or attached to the platform. Moreover, recently proposed control strategies have demonstrated a keen interest in developing model-based controllers, which advantageously provide an efficient utilization of actuators and mitigation of internal disturbances within the system. This paper initially presents, for control purposes, the derivation of the kinematics and dynamics of a free-floating Space Manipulator System (SMS) with a flexible body at the end of a kinematic chain, employing a Lagrangian formalism. Subsequently, a robust joint-space control law is designed for the On-Orbit Servicing (OOS) of a satellite with flexible appendages. The control structure consists of Nonlinear Dynamic Inversion (NDI) for system linearization and decoupling. A structured H infinity controller synthesis is developed to provide robustness against flexible disturbances, model uncertainties, and sensor noise. To evaluate the effectiveness of this control strategy, it is implemented on a real-time simulation platform that ensures tight and high-fidelity space robot dynamics and flexible structures. This platform incorporates visual environment models and virtual sensors to provide an accurate representation of real-world conditions. The considered use-case involves the servicing of a satellite equipped with a flexible solar array using a free-floating dual-arm SMS with flexible appendages. (c) 2025 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

The growing need for space debris mitigation and satellite life extension has intensified interest in Space Manipulator Systems (SMS) for Active Debris Removal (ADR) and On-Orbit Servicing (OOS). Among the most critical challenges is the capture of uncooperative, tumbling targets. This work builds on a robust control architecture based on Nonlinear Dynamic Inversion (NDI) and Nonlinear Disturbance Observation (NDO), previously applied in On-Orbit Assembly, and adapts it to the unique dynamics of target capture. We focus on two key challenges: managing uncertainties due to incomplete target knowledge and handling the momentum transfer during postcapture stabilization. To ensure robustness throughout both pre- and post-capture phases, we propose a joint synthesis of control and observer gains using Linear Matrix Inequalities (LMI). The proposed framework is validated in high-fidelity simulations across a range of target inertias and uncertainty sources, demonstrating its effectiveness and feasibility for future ADR and OOS missions.

Space robotics require high-precision autonomous control technologies to meet the demands of On-Orbit Servicing (OOS) applications. In such scenarios, robotic manipulators must address the challenge of managing flexible vibrations in large and lightweight structures, which significantly impact control performance. Given the high level of difficulty associated with experimental testing and validating control approaches, this paper introduces recent advancements in a real-time simulation platform. This platform is designed to facilitate rapid conception, prototyping, and testing of model-based control solutions at a low time-scale. The software/hardware architecture of the platform ensures tight and high-fidelity space robot dynamics and flexible structures, incorporating visual environment models for state observation, computer vision processing, virtual sensor data fusion, and full robot control. To showcase the utility of the platform, a robust joint-space control framework is introduced, implemented, and contrasted with a separated base/manipulators control approach for an OOS scenario. The control structure consists of a Nonlinear Dynamic Inversion (NDI) for system linearization and decoupling, together with a structured H-infinity controller to provide robustness against flexible disturbances, model uncertainties, and sensor noise.

This work presents a novel approach for the online supervision of robotic systems assembled from multiple complex components with skillset-based architectures, using Petri nets (PN). Predictive runtime verification is performed, which warns the system user about actions that would lead to the violation of safety specifications, using online model-checking tools on the system PNs.

Space manipulators allow to respond to a variety of problems in future space exploitation and exploration such as on-orbit deployment, active debris removal or servicing operations. However, a difficulty to autonomously control space manipulator systems arise with large and light structures presenting flexible behavior. Flexible dynamics remain a challenging study focus as its modeling may present a first difficulty while the different coupling with the manipulator may deteriorate the control quality. This paper addresses design and control problems related to autonomous space manipulator equipped with kinetic moment exchange devices for spacecraft rotation control when dealing with system internal disturbances, model uncertainties and measurement errors. One advantage of modeling the rigid–flexible dynamics of a multi-body system is the possibility of including the non-measurable states in the system decoupling and linearization. In this work, in addition to the development of an extended state observer (ESO) that estimate the flexible dynamics, a nonlinear disturbance observer (NDO) is also introduced and included in a nonlinear dynamic inversion (NDI) framework where both modeling uncertainties and measurement errors are considered. Inter-dependencies between observers and control dynamics motivate a simultaneous computation of their gains to improve system stability and control performances. This is achieved by the resolution of linear matrix inequalities (LMI). In order to highlight the interest of the proposed scheme and validate our approach in a realistic environment, extensive tests of an on-orbit space telescope assembly use-case are performed on a high-fidelity simulator.

This paper presents the development of an Extended Kalman Filter for the navigation system of a spacecraft in a parabolic flight. The algorithm blends the measurements coming from two Inertia Measurement Units, one mounted on the spacecraft and one on the baseplate of the aircraft; and a camera system connected to the baseplate as well. During the zero-g phases the attitude and position of the spacecraft in the experimental area are recovered thanks to a series of Alvar markers attached on the spacecraft casing and detected by the camera system. Results from parabolic test campaign of October 2019 are finally presented.

On-orbit operations are facing a growing need for autonomous robotic systems. Debris removal, on-orbit servicing and in-space deployment/assembly are examples of applications considering the use of robot manipulators. This paper addresses design and control problems related to autonomous space manipulator systems when using kinetic moment exchange devices in presence of flexible appendages. The paper introduces a method to develop a common control of the spacecraft base and manipulator. An extended state observer is used in the Nonlinear Dynamic Inversion (NDI) in order to improve performances and reduce vibration disturbance impacts on the base attitude. A simultaneous synthesis of a control law and an observer gain is proposed with Linear Matrix Inequalities (LMI) resolutions which allow system variation considerations. Simulations are run on an actual assembly scenario to illustrate the proposed method.

The PULSAR (Prototype for an Ultra Large Structure Assembly Robot) project, aims at developing and demonstrating core technologies enabling the in-orbit assembly of the 8m-diameter primary mirror of a space telescope with an autonomous robotic system. This paper presents the demonstrator of In-Space Assembly in Simulation, which is designed as an integrated simulation tool for the prototyping and development of these autonomous assembly technologies.

Advances in our understanding of the universe have been enabled by ground and particularly by space-based telescopes (e..g. the Hubble), free of interferences from Earth’s atmosphere. However, current astronomical challenges in areas such as exoplanets, interstellar medium and structure of the universe, require larger telescope apertures. Using deployable structures and a segmented primary mirror, such as in the James Webb telescope, allows an increase of the aperture, but the maximum size of the telescope is anyways limited mainly by the fairing size of the launch vehicle. Further increasing the size of the telescope requires a technological change, to move toward space-based assembly using autonomous robotic systems. This paper provides a survey of existing concepts for in-space assembly of telescopes, and introduces PULSAR (Prototype of an Ultra Large Structure Assembly Robot), the latest European effort toward proving feasibility of the technologies required for autonomous robotic assembly of a telescope or a large spaceborne structure.

This paper addresses control allocation for redundant systems with the Extended Kalman Filter formalism. This method is compatible with the low computational power available in space environment, and presents a flexible framework to include constraints such as singularity avoidance. The convergence domain of the allocator is derived from the contraction theory framework, depending on specific parameters of the system. A general formulation is proposed to maximize the convergence domain with regard to these parameters. The method is applied to design a steering law of Control Moment Gyroscopes. Experimental tests show that the control allocation allows the actuators to work efficiently along nominal trajectories while avoiding singularities when necessary.

This paper addresses the issue of controlling a spacecraft with a redundant pyramidal Control Moment Gyro (CMG) cluster. A rapid analysis of the mathematical problem to steer the attitude control system is carried out with a focus on how to use the redundancy to start the attitude maneuvers in optimal conditions. A set of initial positions that ensures no singularity is encountered during an unidirectional maneuver is defined thanks to the study of the topology of the cluster and simulations. The desired initial position is derived onboard the spacecraft from the direction of the maneuver. After reaching this position without creating torque errors thanks to the null-motion trajectories, the Moore-Penrose steering law is used. The cases of a pyramidal six-CMG cluster without CMG failures and with two failures are studied. Finally, simulations show the characteristics of the designed steering laws.

Autonomous assembly of large structures in space is a key challenge to implement future missions that will necessitate structures to be self-deployed as a single piece. This paper presents a mission analysis of existing concepts for in-space assembly of telescopes, provides a survey of relevant robotics technologies and introduces the expected contribution of the PULSAR (Prototype of an Ultra Large Structure Assembly Robot) project to this challenge.

There is a growing need for space and in-orbit operations that would require use of advance robotic systems. The robotics systems could be used in debris removal from orbits, as well as, in on-orbit servicing activities. This paper is addressing design and control problems related to autonomous spacecraft-manipulator system for space operation. The dynamics equations for rotation floating manipulator were introduced using Lagrange approach with additional states representing the kinetic moment exchange actuators. In this paper, a serial-link manipulator with multi degree of freedoms mounted on the satellite platform was used. For detailed analysis of base motion and manipulability of the end effector, the special indices were introduced. Simulation examples to illustrate kinematic indices were shown with physical parameters for a microsatellite from Myriade series equipped with a robotic arm.

The attitude control of a satellite equipped with a six-Control Moment Gyro (CMG) cluster is studied, taking into account CMG failure cases and constraints like actuator saturation and real-time aspects. The design of the steering law that allocates the required torques among the actuators is made complex by singularities (gimbal angles of the CMGs where no torque can be created along an axis). This paper describes the problem of a constrained allocation applied to the CMG system, and explains the selected solution. An experimental setup with six CMGs has been designed. It calculates in real-time the attitude guidance laws and control loop. Agile manoeuvres simulating nanosatellite attitude reorientations have been successfully carried out during a European Space Agency (ESA) parabolic flight campaign. The results show that the steering law performs as expected even in case of CMG failures.

The context of this paper is a research project on a Cable-Driven Parallel Manipulator uses to reproduce the free flight condition of aircraft models in wind tunnels (SACSO Project). The force control of the CDPM enables to simulate the thrust of the aircraft engine, and to modify the scale model mass and inertia. A very important point for an efficient force control is an accurate estimation of the cables tension. In this paper, an original Cable Driving Unit with an integrated 3D force sensor is developped to improve the cable tension observability. An associated Extended Kalman Filter implementation is then proposed to estimate the cables tension.

This paper presents a design process based on an advanced flexible robots modeling tool associated with realistic actuators models and pre-defined control architecture. This process implements dedicated feasibility and performance indicators, which are used to evaluate a design and its sensitivity on the considered parameters. The proposed approach is illustrated with theoretical and experimental results obtained with the YAKA robot.

Input shaping techniques for vibration control of flexible structures received many interest due to its simplicity and efficiency proven in various practical cases. This paper proposes an adaptation of those techniques by addressing two main specificities of robot manipulators. As a first contribution, the design of input shapers for multiple-input and multiple-modes complex robot is studied. Design indicators based on elastic-dynamic model are proposed in order to choose one input shaper design among thousands of possible combinations. As a second contribution, the vibration mode frequency evolution of robot manipulators over their workspace is compensated by an adaptive control scheme. It is proposed to interpolate the modal variations over the workspace and tune the input shaper parameters dynamically. This contribution is implemented on a large scale flexible robot and shows promising results.