Assembly Missions Research Articles

A guide to global access to HPV vaccination to all women in low- and middle-income countries; a minireview of innovation and equity.

Cervical cancer is caused by the human papillomavirus (HV), and accounts for more than 311,000 preventable deaths annually, with 85% occurring in low-and middle-income countries. Despite being preventable through screening and screening, significant barriers to implementing HPV vaccination persist in developing nations. This review study aims to identify these barriers and propose innovative, evidence-based solutions to improve vaccination rates and reduce cervical cancer mortality. A systematic review search was conducted using PubMed, Embase, and Cochrane Database of Systemic Reviews. Keywords related to HPV vaccination barriers and implementation strategies in developing countries were used. Relevant demonstration projects, pilot studies, and evidence-based research articles were reviewed. Identifiable barriers to a successful vaccine implementation program in a developing country include vaccine costs, societal, cultural resistance, misinformation, logistical challenges in vaccine delivery, and inadequate human resources. Solutions to these barriers include a subsidized vaccine pricing, community sensitization, education and well-trained media professionals to dispel misinformation, and partnerships with both public and private sector for efficient vaccine distribution. These findings highlight critical barriers that impede HPV vaccination efforts in developing countries and offers practical solutions to overcome these challenges. This aggregate of data can help inform future developing countries' implementation programs to further the World Health Assembly mission to vaccinate 90% of eligible girls globally by 2030.

Robotic technologies for in-orbit assembly of a large aperture space telescope: A review

Space telescopes have been instrumental in enlightening our understanding of the universe, from the iconic Hubble Space Telescope to specialized instruments like Chandra and Kepler. Pushing the frontiers of cosmic exploration, the future of space exploration hinges on modular Large Aperture Space Telescopes (LAST), much larger than the recently launched 6.5 m James Webb Space Telescope, necessitating robotic assembly in orbit. This paper introduces a paradigm shift in astronomical observation by featuring robotic in-orbit assembly of a large aperture space telescope. This review paper starts by tracing the evolution of telescopes and presents a comprehensive overview of the state-of-the-art space telescopes. This paper then reinforces the need for LAST to address the constant clamour for higher-resolution astronomy. While current semi-autonomous robotic manipulators operate from the International Space Station, their limited walking capabilities constrain their workspace, making them unsuitable for the LAST mission. This paper presents a detailed trade-off analysis of the challenges associated with the in-orbit assembly of LAST using candidate robots to understand the technological gaps. Further, the evolution of space robotic manipulators is presented, highlighting design features, advantages, and drawbacks for in-orbit spacecraft servicing and assembly missions. To tackle design and modelling challenges for robotic systems in space, amidst the various perturbations in the extreme space environment, linear and non-linear control systems necessary for achieving ultra-high precision performance are also discussed. This paper advances the walking space manipulator technology by introducing the next generation of walking space manipulators – the End-Over-End Walking Robot (E-Walker). The dexterous and modular design of the E-Walker makes it an ideal candidate for missions involving assembly, manufacturing, servicing, and maintenance.

Autonomous assembly of multiple spacecraft by tether-aided rendezvous and docking: From theory to experiment

Utilizing the tether-aided rendezvous and docking to realize an on-orbit autonomous assembly of multiple spacecraft is a novel and prospective space mission. The paper presents the dynamics and control of this assembly mission mode in a spinning scenario numerically and experimentally. The system equations in general form are first established. Based on several feasible assumptions, the coupling effects among the chaser spacecraft are eliminated, a set of simplified governing equations described by the tether length and the libration angle are then obtained. By employing the trapezoidal tether retrieval law, an assembly strategy composed of the tangential and normal thrust controllers is proposed. The operation constraints of the tether tension and the libration angle are explicitly considered. Numerical simulation results verify the feasibility and effectiveness of the designed control strategy. In addition, the corresponding tether-aided assembly process is further validated by the air-bearing experiment based on the upgraded system SOOHLS.

Integrated Dynamics of Space Rigid-Flex Combination System with Time-Varying Configuration

Dual numbers were applied to the dynamics of a rigid-flexible combination system (RFCS) with time-varying configuration in this paper. The six-dimensional spinor form of the motion of flexible modules, including the dual vector, dual momentum, dual inertia operator, dual coupling coefficient operator, and dual-modal coordinates, was derived using the dual numbers that could represent spiral motion in a compact form. On this basis, the integrated dynamic model of a rigid-flexible combination system with a time-varying configuration was proposed. And then, the relative dynamics equations between two rigid-flexible combination systems which both have time-varying configuration were provided. An on-orbit assembly mission of flexible modules transported and operated by free-flying space robots (FFSRs) is presented as an exemplary application of relative dynamics. Simulation results illustrate the complex coupling effects on the relative motion between two rigid-flex combination systems with time-varying configuration.

Experimental study on autonomous assembly of multiple spacecraft simulators in a spinning scenario

Utilizing the autonomous rendezvous and docking among multiple spacecraft to construct a large space structure is a prospective on-orbit autonomous assembly mission. This paper presents a planar air-bearing experiment on the autonomous assembly of two chaser spacecraft simulators and one spinning target spacecraft simulator. The mission process includes four distinct phases. While the first two phases use the real-time assembly and collision avoidance controllers proposed, the assembly control laws with analytical expressions play its role in the remaining phases. Both neighboring spacecraft simulators and external object serve as the obstacles during the design process. The hardware-in-the-loop experimental system consists of three spacecraft simulators with electromagnetic docking mechanism installed, a granite testbed, a motion tracking system and a wireless transmission system. The experimental results show that the proposed multistage control strategy can successfully realize the autonomous collision-free assembly of three spacecraft simulators in the spinning scenario.

Analytical method for computing assembly errors in modular antenna during on-orbit assembly

AbstractTo meet the increasing communication demands, the satellites need to be equipped with the high-accuracy and large-aperture antennas. One of the effective methods to construct the modular antennas with ultra-high accuracy and ultra-large aperture is on-orbit assembly technology. During the on-orbit assembly missions, the assembly error is a key factor to affect the surface accuracy of the modular antennas. This paper studies the node design of each module and the assembly error analysis of the modular antennas. A design method of the module nodes is presented with consideration of the assembly gap between two modules. Meanwhile, a soft connection mechanism is designed to ensure the mobility among the assembly modules. To investigate the transmission law of the assembly errors, an analytical model of assembly error is derived based on the exponential product method. In order to establish the deformation surface with rotation and displacement assembly errors, an error ball concept is proposed by the analytical model. To decrease the assembly errors, the actuators are installed among some modules. Moreover, an adjustment method is proposed to obtain the adjustment amounts of actuators. Finally, the correctness of analytical model and the effectiveness of the adjustment method are demonstrated by the numerical simulations.

Model Predictive Framework for Guidance and Control of a Multi-Satellite Assembly in Elliptic Orbit

In this paper, a guidance and control system for multi-satellite assembly missions in proximity operations is proposed. Utilizing the Tschauner-Hempel relative motion equations, the system is developed within the framework of model predictive control. Linear inequality constraints are employed to handle control input saturation of thrusters and to ensure collision avoidance between satellites. Additionally, a new line-of-sight constraint method is introduced to facilitate smooth docking while simplifying the optimization problem. The proposed algorithm aims to minimize a predefined cost function, which is a weighted sum of state errors and control efforts. At each sampling time, an online quadratic optimization problem is solved to determine the optimal control action that satisfies all mission constraints. Nonlinear numerical simulations in MATLAB are used to demonstrate that the proposed guidance and control system achieves the desired performance. The algorithm is tested for various multi-satellite assembly configurations (cubic and hexagonal) in elliptic orbits of arbitrary eccentricity. A comparative study is conducted between the proposed algorithm and a linear model predictive control algorithm based on the Clohessy-Wiltshire linear model. The results show that the proposed algorithm achieves superior performance in terms of constraint satisfaction and control efforts.

Hierarchical multi-agent planning for flexible assembly of large-scale lunar facilities

Several national space agencies and commercial aerospace companies plan to set up lunar bases with large-scale facilities that rely on multiple lunar robots’ assembly. Mission planning is necessary to achieve efficient multi-robot cooperation. This paper aims at autonomous multi-robot planning for the flexible assembly of the large-scale lunar facility, considering the harsh lunar environment, mission time optimization, and joint actions. The lunar robots and modules are scattered around the mission area without fixed assembly lines. Thus, the traditional assembly planning methods ignoring the optimal selection of modules are unable to handle this problem. We propose a hierarchical multi-agent planning method based on two-stage two-sided matching (HMAP-TTM) to solve this critical problem. First, the distributed planning framework with multi-replica public agents is introduced, ensuring robot plan knowledge consistency through public agents’ communication. Second, the hierarchical task graph (HTG) divides the mission into task layers based on task dependency knowledge. Third, we develop a novel two-stage two-sided matching algorithm. Time-optimal plans emerge from the matching games among public and private agents in each layer of HTG. Agents make decisions in the game based on action knowledge updated during planning. Finally, an assembly mission is presented to prove the method’s effectiveness. The simulation results show that the HMAP-TTM can generate plans with shorter mission time and require smaller communication costs than the baseline methods.

Cross-coupling relative dynamics for on-orbit assembly in rotating frame of reference

Dual numbers are applied in this paper to relative dynamics between rigid-flex combination systems. In space cooperative missions, the relative dynamic equations with engineering applicability require description in rotating frame of reference. Taking advantages of dual numbers which can represent spiral movement in a compact form with respect to the rotating frame, the dual vector, dual momentum, dual inertia operator, dual coupling coefficient operator and dual modal coordinates of flexible modules are derived. The algebra of dual numbers for rigid-flex combination system is further developed. On this basis, relative equations of motion between two rigid-flex combination systems in rotating frame of reference are proposed. The behaviors of relative dynamics present complex cross-coupling effects between attitude-orbit coupling and rigid-flex coupling. An on-orbit assembly mission of flexible modules via free flying robots is presented as an exemplary application of the cross-coupling relative dynamics. Ground testing results illustrate the cross-coupling effects on the six degree-of-freedom motion of rigid-flex combination system. Simulation results prove the engineering significance of the cross-coupling relative dynamic model.

Design engineering a walking robotic manipulator for in-space assembly missions.

In-Space Services aim to introduce sustainable futuristic technology to support the current and growing orbital ecosystem. As the scale of space missions grows, there is a need for more extensive infrastructures in orbit. In-Space Assembly missions would hold one of the key responsibilities in meeting the increasing demand. In the forthcoming decades, newer infrastructures in the Earth’s orbits, which are much more advanced than the International Space Station are needed for in-situ manufacturing, servicing, and astronomical and observational stations. The prospect of in-orbit commissioning a Large Aperture Space Telescope (LAST) has fuelled scientific and commercial interests in deep-space astronomy and Earth Observation. However, the in-situ assembly of such large-scale, high-value assets in extreme environments, like space, is highly challenging and requires advanced robotic solutions. This paper introduces an innovative dexterous walking robotic system for in-orbit assembly missions and considers the Large Aperture Space Telescope system with an aperture of 25 m as the use case. The top-level assembly requirements are identified with a deep insight into the critical functionalities and challenges to overcome while assembling the modular LAST. The design and sizing of an End-over-end Walking Robot (E-Walker) are discussed based on the design of the LAST and the specifications of the spacecraft platform. The E-Walker’s detailed design engineering includes the structural finite element analysis results for space and earth-analogue design and the corresponding actuator selection methods. Results of the modal analysis demonstrate the deflections in the E-Walker links and end-effector in the open-loop due to the extremities present in the space environment. The design and structural analysis of E-Walker’s scaled-down prototype is also presented to showcase its feasibility in supporting both in-orbit and terrestrial activities requiring robotic capabilities over an enhanced workspace. Further, the mission concept of operations is presented based on two E-Walkers that carry out the assembly of the mirror modules. The mission discussed was shortlisted after conducting an extensive trade-off study in the literature. Simulated results prove the dual E-Walker robotic system’s efficacy for accomplishing complex in-situ assembly operations through task-sharing.

Post-capture detumble trajectory stabilization for robotic active debris removal

Recent increase in space debris combined with the increase in the number of satellites launched has created an increased risk of collisions. The effects of the increased risk can be seen in the form of an increased number of near misses in recent years. The use of robotic manipulators has been suggested for Active Debris Removal (ADR) to reduce the risk of potential future collisions that generate more debris in the orbits around Earth. Compared to other ADR methods, robotic manipulators provide increased versatility as they can be reused for On-Orbit Servicing as well as On-Orbit Assembly missions. A robotic ADR operation consists of three phases: Approach, Capture, and Detumble. This paper provides a method for performing feedback-based stabilization of post-capture detumble trajectories of the chaser-debris system. The approach presented here uses Time-Varying Linear Quadratic Regulator (TVLQR) for stabilization along the detumble trajectory. The contributions of this paper are as follows: A quaternion-based linearization method for multibody systems with a free-floating base, TVLQR for stabilizing the optimal detumble trajectory, and a probabilistic Region of Attraction analysis of the resulting closed-loop system. The estimated Region of Attraction could serve as the goal for the capture controller thus allowing for controller composition through ADR phases while guaranteeing stability and successful detumble.

Cooperative Game Method for On-Orbit Substructure Transportation Using Modular Robots

This article studies the problem of cooperative substructure transportation using multiple modular robots in an on-orbit assembly mission. Two kinds of modular robots, termed as force and torque robots, are used to provide control forces and torque for the substructure, respectively. Using the framework of cooperative games, a set of Pareto optimal control problems are formulated to solve for the optimal control forces and torque of modular robots, such that they can cooperatively bring the substructure to dock with the main body of a large space structure. Additionally, an event-triggered coordinated compensatory control mechanism using the model predictive control principles is designed for modular robots, which guarantees that the substructure can follow the desired optimal trajectories with the computation and communication burden of modular robots being reduced. Numerical simulations demonstrate the effectiveness of the proposed method.

Modeling a Controlled-Floating Space Robot for In-Space Services: A Beginner's Tutorial.

Ground-based applications of robotics and autonomous systems (RASs) are fast advancing, and there is a growing appetite for developing cost-effective RAS solutions for in situ servicing, debris removal, manufacturing, and assembly missions. An orbital space robot, that is, a spacecraft mounted with one or more robotic manipulators, is an inevitable system for a range of future in-orbit services. However, various practical challenges make controlling a space robot extremely difficult compared with its terrestrial counterpart. The state of the art of modeling the kinematics and dynamics of a space robot, operating in the free-flying and free-floating modes, has been well studied by researchers. However, these two modes of operation have various shortcomings, which can be overcome by operating the space robot in the controlled-floating mode. This tutorial article aims to address the knowledge gap in modeling complex space robots operating in the controlled-floating mode and under perturbed conditions. The novel research contribution of this article is the refined dynamic model of a chaser space robot, derived with respect to the moving target while accounting for the internal perturbations due to constantly changing the center of mass, the inertial matrix, Coriolis, and centrifugal terms of the coupled system; it also accounts for the external environmental disturbances. The nonlinear model presented accurately represents the multibody coupled dynamics of a space robot, which is pivotal for precise pose control. Simulation results presented demonstrate the accuracy of the model for closed-loop control. In addition to the theoretical contributions in mathematical modeling, this article also offers a commercially viable solution for a wide range of in-orbit missions.

Grappling Spacecraft

This article provides a survey overview of the techniques, mechanisms, algorithms, and test and validation strategies required for the design of robotic grappling vehicles intended to approach and grapple free-flying client satellites. We concentrate on using a robotic arm to grapple a free-floating spacecraft, as distinct from spacecraft docking and berthing, where two spacecraft directly mate with each other. Robotic grappling of client spacecraft is a deceptively complex problem: It entails designing a robotic system that functions robustly in the visually stark, thermally extreme orbital environment, operating near massive and extremely expensive yet fragile client hardware, using relatively slow flight computers with limited and laggy communications. Spaceflight robotic systems are challenging to test and validate prior to deployment and extremely expensive to launch, which significantly limits opportunities to experiment with new techniques. These factors make the design and operation of orbital robotic systems significantly different from those of their terrestrial counterparts, and as a result, only a relative handful of systems have been demonstrated on orbit. Nevertheless, there is increasing interest in on-orbit robotic servicing and assembly missions, and grappling is the core requirement for these systems. Although existing systems such as the Space Station Remote Manipulator System have demonstrated extremely reliable operation, upcoming missions will attempt to expand the types of spacecraft that can be safely and dependably grappled and berthed.

Research and application on an embedded cabin non-contact detection and precision docking technology

In the assembly missions of spacecraft, the cabins docking are the final part of the product assembly to form the probe into a whole, which is one of the most critical parts of the assembly task. The spacecraft of Insertion and Containment in cabin docking faces difficulties such as eccentricity of mass, small safety spacing, and non-visibility. In this paper, interference detection method based on reverse engineering non-contact virtual assembly and precision docking process method with tiny spacing of cabin eccentricity were proposed, and a large eccentric inline cabin docking device was developed to solve the problem of inline cabin precision docking. The above-mentioned method was applied to achieve nearly 100 successful dockings during the AIT process, which ensured the success of the spacecraft mission.

Collision-free optimal trajectory generation for a space robot using genetic algorithm

Future on-orbit servicing and assembly missions will require space robots capable of manoeuvring safely around their target. Several challenges arise when modelling, controlling and planning the motion of such systems, therefore, new methodologies are required. A safe approach towards the grasping point implies that the space robot must be able to use the additional degrees of freedom offered by the spacecraft base to aid the arm attain the target and avoid collisions and singularities. The controlled-floating space robot possesses this particularity of motion and will be utilised in this paper to design an optimal path generator. The path generator, based on a Genetic Algorithm, takes advantage of the dynamic coupling effect and the controlled motion of the spacecraft base to safely attain the target. It aims to minimise several objectives whilst satisfying multiple constraints. The key feature of this new path generator is that it requires only the Cartesian position of the point to grasp as an input, without prior knowledge a desired path. The results presented originate from the trajectory tracking using a nonlinear adaptive H∞ controller for the motion of the arm and its base simultaneously.

In-space structural assembly using predefined performance based method

PurposeThe purpose of this paper is to propose a pre-defined performance robust control method for pre-assembly configuration establishment of in-space assembly missions, and collision avoidance is considered during the configuration establishment process.Design/methodology/approachFirst, six-degrees-of-freedom error kinematic and dynamic models of relative translational and rotational motion between transportation systems are developed. Second, the prescribed transient-state performance bounds of tracking errors are designed. In addition, based on the backstepping, combining the pre-defined performance control method with a robust control method, a pre-defined performance robust controller is designed.FindingsBy designing prescribed transient-state performance bounds of tracking errors to guarantee that there is no overshoot, collision-avoidance can be achieved. Combining the pre-defined performance control method with a robust control method, robustness to disturbance is guaranteed.Originality/valueThis paper proposed a pre-defined performance robust control method. Simulation results demonstrate that the proposed controller can achieve a pre-assembly configuration establishment with collision avoidance in the existence of external disturbances.

ACTIVE-CONTROL-ORIENTED DYNAMIC MODELLING FOR ON-ORBIT ASSEMBLY SPACE STRUCTURE

Subject to carrying capacity of a launch vehicle, on-orbit assembly technology has become one of the most promising solutions for building ultra-large space structures in the future. The size of the space structure is gradually increasing, and the dynamic characteristics are changing during the assembly process, which brings new challenge to the dynamic modelling and structural active control. Aiming at this issue, an active-control-oriented dynamic modelling method for the on-orbit assembly space structure is proposed in this paper. As the on-orbit assembly mission possess high regularity and repeatability, the basic model database is firstly established for different modules to improve the modelling efficiency, including the module type, the assembly interface, etc. In order to describe the varying on-orbit assembly space structure, the adjacent matrices of modules are defined. The form of intelligent component (IC) oriented to distributed control are then designed, taking the characteristics of the assembly task into consideration. Based upon the finite element modelling method, the 'node freedom degree loading' method is proposed to develop the dynamic models of the IC and the whole space structure, which are adaptively updated along with assembly. Finally, the numerical simulation are carried out on the truss structure under the assembly impact, including the dynamics analysis and the distributed vibration control. The simulation results show that the dynamic characteristics of truss structure experience obvious changes during the process, and the active vibration control is necessary; the modelling method proposed in this paper, with the established basic model database and the 'node freedom degree loading', applies to various on-orbit assembly space structure; According to the adjacency relation matrix, the active-control-oriented dynamic models of the IC can be updated in a limited range during the assembly process, which reduces the complexity of control system and is suitable for distributed active control of on-orbit assembly structure.

Dynamics and control for in-space assembly robots with large translational and rotational maneuvers

There are two major characteristics of in-space structure assembly missions. First, in order to improve the transport efficiency of assembly robot and reduce the number of structural modules, the size of each structural module is usually designed as large as possible. Second, it is necessary for autonomous assembly robot to quickly transport such large-sized flexible structural modules to the desired locations for integration. However, the coupling effect between the deformation of structural module and large-scale maneuver of robot is inevitably involved during transportation. In this paper, a dynamics modeling method for in-space assembly (ISA) robot with large translational and rotational maneuvers was proposed. The descriptions of dual quaternions were expanded, and a general expression for the dynamics model of rigid-flex system was derived to describe motion of the assembly robot. Innovation of this method is that it considered the complex coupling effect among deformation of structural modules, translational and rotational maneuvers of the assembly robot during transportation in ISA missions. On this basis, the proportional-derivative (PD) controllers were adopted as the in-space structural module assembly method. Finally, taking the ISA of antenna as an example, successful application of the proposed dynamics model and controller to the assembly mission was verified.

A Communication-Free Human-Robot-Collaboration Approach for Aircraft Riveting Process Using AI Probabilistic Planning

<div class="section abstract"><div class="htmlview paragraph">In large scale industries attempts are continuously being made to automate assembly processes to not only increase productivity but also alleviate non-ergonomic tasks. However this is not always technologically possible due to specific joining challenges and the high number of special-purpose parts. For the riveting process, for example, semi-automated approaches represent an alternative to optimizing aircraft assembly and to reduce the exposure of workers to non-ergonomic conditions entailed by performing repetitive tasks.</div><div class="htmlview paragraph">In [<span class="xref">1</span>], a semi-automated solution is proposed for the riveting process of assembling the section barrel of the aft section to its pressure bulkhead. The method introduced a dynamic task sharing strategy between human and robot that implements interaction possibilities to establish a communication between a human and a robot in Human-Robot-collaboration fashion. Although intuitive, interacting with the robot constantly is still not natural for the worker as in the manual process no explicit communication between both workers is needed.</div><div class="htmlview paragraph">In this work a communication-free Human-Robot-collaboration solution is presented. The method developed not only enables sharing assembly missions by dividing tasks based on skills, but also offers the possibility of decision making to the robot. In this context, off-the-shelf Artificial Intelligence planning tools are used to model the work-flow of the human as well as the task of the robot handling alongside possible uncertainties yielding while perceiving the environment or the activity of the human.</div></div>