Space Deployable Mechanism Research Articles

Dynamic Analysis Strategy of Generalized Deployable Units via NCF-IGA with Force Constraint

Space deployable mechanisms typically employ modular designs, where each unit that can be independently deployed is defined as a generalized deployable unit (GDU), typically consisting of rigid components, flexible components and generalized kinematic pairs. Given the high-performance demands of spatial transmission mechanisms, generalized kinematic pairs frequently integrate flexible factors like torsion springs and flexible hinges, which control the motion according to the attitude and position of the component. In this investigation, a new modeling and solution strategy for rigid-flexible coupled dynamics is established by combining NCF and IGA. It can not only accurately describe the large deformation and large rotation of flexible components, but also consider the influence of flexible factors in the kinematic pairs. The rigid components are modeled by the Natural Coordinate Formula (NCF), and the flexible components are discretized in the inertial coordinate system using spline curves in Isogeometric Analysis (IGA). The intermediate reference coordinates were integrated into the NCF-IGA framework, overcoming the boundary constraints between B-spline and NCF elements, and the geometric constraint equation of the kinematic pair was established. Subsequently, this paper proposes the concept of force constraint in controllable deployable mechanisms. Based on the force constraint equation, the mechanical model of flexible joints is established. The dynamic equations of GDUs are derived considering both geometric and force constraints, and generalized-[Formula: see text] method is introduced to solve the equations. Finally, three numerical examples are provided to illustrate the applicability and superiority of the proposed method.

Design, kinematics and dynamic analysis of a novel double – scissors link deployable mechanism for space antenna truss

A novel truss deployable mechanism composed of scissors links is proposed in this paper. First, the geometry analysis of the general single modular unit of truss deployable antenna and the construction of the planar double scissors link mechanism module is conducted. The entire antenna is prepared by connecting the single module in a circular configuration. Using the Gruebler's method, the mobility of the double scissors link truss deployable module is proved equals to 1. Furthermore, based on the Newtonian approach, kinematic characteristics of the double scissors link truss deployable mechanism are examined. The velocities and accelerations of the antenna components obtained analytically are validated through simulations in MATLAB, SolidWorks and ADAMS. In addition to this, the forces, torques and bearing stresses involved in various struts and joints are calculated to ensure that the operation is within the yield limits. The dynamic characteristics of the antenna i.e., acceptable natural frequency is calculated by developing a 10 DoF vibration model. The analytical equations are solved using MATLAB, and the results are validated through simulations in ANSYS Workbench. The novel antenna assembly gives the natural frequency response of 0.0652 Hz with a 1.6 % error. The proposed double scissors link truss deployable mechanism shows storage ratio of 1 and 10.2 along vertical and radial directions respectively. The dynamic response and storage ratio of novel assembly is validated with results in literature. The research lays the foundation for the kinematics and dynamics analysis of other space deployable mechanisms.

Kinematic accuracy reliability evaluation method of space deployable mechanism based on dynamic model

Space deployable mechanisms are widely used in aerospace missions. The uncertainties in the geometric or physical parameters seriously affect the kinematic accuracy of the mechanism during the deployment process. In this paper, a kinematic accuracy reliability evaluation method of the space deployable mechanism based on dynamic model and adaptive hybrid surrogate models is presented. Firstly, the dynamic model of the space deployable mechanism is established based on the Lagrange method, and the motion error function considering the factors such as the mass, dimension and load is established. In order to improve the efficiency, an adaptive hybrid surrogate model reliability evaluation method based on improved weight measurement method is further proposed. The weight measurement method considers the global errors and local errors of the models. Finally, the Monte Carlo method is used to verify the accuracy of the hybrid surrogate model method. The relative error of the failure probability calculated by the proposed method is within 2.5 %, indicating that the proposed method has high calculation accuracy and efficiency.

Design and dynamic analysis of supporting mechanism for large scale space deployable membrane sunshield

AbstractStray light from the sun is one of the most significant factors affecting image quality for the optical system of a spacecraft. This paper proposes a method to design a deployable supporting mechanism for the sunshield based on origami. Firstly, a new type of space mechanism with single-closed loop was proposed according to thick-panel origami, and its mobility was analysed by using the screw theory. In order to design a deployable structure with high controllability, the tetrahedral constraint was introduced to reduce the degree of freedom (DOF), and a corresponding deployable unit named tetrahedral deployable unit (TDU) was obtained. Secondly, the process to constructing a large space deployable mechanism with infinite number of units was explained based on the characteristics of motion and planar mosaic array, and kinematics analysis and folding ratio of supporting mechanism were conducted. A physical prototype was constructed to demonstrate the mobility and deployment of the supporting mechanism. Finally, based on the Lagrange method, a dynamic model of supporting mechanism was established, and the influence of the torsion spring parameters on the deployment process was analysed.

Kinematic Characteristics Analysis and Assembly Application of the Rectangular Pyramid Deployable Mechanism

Deployable mechanisms have the characteristics of complex loops and strong coupling. As a result, the solution to the degrees of freedom (DOFs) and kinematic characteristics of the basic mechanism unit are often complicated, and the solution for combined mechanisms is rarely reported in the relevant literature. In this paper, the kinematic characteristics of the rectangular pyramid deployable mechanism (RPDM) are analyzed, and the DOFs of the RPDM are calculated based on the screw theory. In addition, the DOF number and properties of its moving components are analyzed. Based on the condition that the nonhomogeneous linear equations have a unique solution, the singularity analysis of the mechanism is complete, which indicates that the mechanism can be continuously deployed and folded. Based on the geometric characteristics of the mechanism, its folded ratio is calculated. Finally, a ring, a planar, and a parabolic truss deployable antenna mechanism are assembled based on the RPDM, and the DOF variation for the different assembly modes is obtained via the screw constraint matrix. This study provides a good reference for the design and analysis of such multi-closed-loop deployable mechanisms, and the large-scale space-deployable mechanisms constructed in this paper have good application prospects in the aerospace field.

Assembly Error Modeling and Tolerance Dynamic Allocation of Large-Scale Space Deployable Mechanism toward Service Performance

As a satellite’s critical load-bearing structure, the large-scale space deployable mechanism (LSDM) is currently assembled using ground precision constraints, which ignores the difference between the ground and space environments. This has resulted in considerable service performance uncertainties in space. To improve satellite service performance, an assembly error model considering the space environment and a tolerance dynamic allocation method based on as-built data are proposed in this paper. Firstly, the factors influencing the service performance during ground assembly were analyzed. Secondly, an assembly error model was constructed, which considers the influence factors of the ground and space environment. Thirdly, on the basis of the assembly error model, the tolerance dynamic allocation method based on as-built data was proposed, which can effectively reduce the assembly difficulty and cost on the premise of ensuring service performance. Finally, the proposed method was validated in an assembly site, and the results show that the pointing accuracy, which is the core indicator of the satellite service performance, was improved from 0.068° to 0.045° and that the assembly cost was reduced by about 13.5%.

Design and dynamic analysis of a scissors hoop-rib truss deployable antenna mechanism

As the support mechanism of space-borne antennas, space deployable antenna mechanism belongs to complex multi-closed-loop coupling mechanism, configuration design and dynamic analysis are more difficult than general parallel mechanism. In this paper, an unequal-length scissors mechanism (ULSM) is proposed by changing the position of the internal rotational joint through a basic scissors mechanism. A scissors hoop-rib truss deployable antenna mechanism (SHRTDAM) is constructed by replacing the parabolic rib with the ULSM. Kinematic analysis of SHRTDAM is conducted, and the degree of freedom (DOF) of the whole antenna mechanism is analyzed based on screw theory, the result showed that it has only one DOF. Velocity and acceleration characteristics of SHRTDAM are obtained by the screw derivative and rotation transformation. Based on Lagrange equation, dynamic model of this mechanism is established, the torque required to drive the mechanism is simulated and verified by Adams and MATLAB software. In addition, a ground experiment prototype of 1.5-m diameter was fabricated and a deployment test is conducted, which demonstrated the mobility and deployment performance of the whole mechanism. The mechanism proposed in this paper can provide a good reference for the design and analysis of large aperture space deployable antennas.

Dynamic analysis and wear calculation of space deployable mechanism considering spherical joints with clearance and coating

In the space deployable mechanism considering spherical joints with clearance, the kinematic stability and working life of will be seriously affected. To address this problem, this paper proposes a nonlinear stiffness coefficient expression and an improved viscous damping coefficient expression considering the wear reduction properties of coatings, so as to obtain a conformal contact force model based on the analysis and comparison of the existing common normal contact force models. The new contact force model is qualitatively analyzed from three aspects, namely clearance size, recovery coefficient, and material properties, so as to demonstrate the correctness and applicability of the model. In the prefabricated space deployable mechanism (RSSP) with spherical joint clearance, the acceleration variation of the actuator is analyzed and compared by using the new contact force model, and the wear quantity of the spherical joints with clearance and coating is predicted. The dynamic results show that spherical joints with clearance have a significant effect on the acceleration of the actuator, and the long working time will inevitably lead to increased vibration and reduce the motion accuracy and life of the mechanism. By comparing with the calculation results of wear, it is found that the wear of spherical joint clearance with coating decreases significantly in all vector directions, and the wear area of the Euler Angle increases slightly compared with that without coating because of the increase of contact collision frequency. Therefore, the wear calculation method and coating strategy proposed in our work can provide a theoretical basis for improving the kinematic accuracy and working life of space deployable mechanism system considering spherical joints with clearance.

Analysis of the influence of clearance on bending stiffness of space deployable mechanism in the locked state

The future space station, which can simulate the gravity environment by rotation, has attracted the attention of scholars in recent years. It is considered a feasible scheme to fold the mechanism on the ground and assemble it into an artificial gravity ring after entering orbit. The deployable mechanism used to attach the space station is required to be large-scale and sufficiently high stiffness after deployment to ensure the safety and accuracy of the payload. However, the clearance will significantly reduce the stiffness of the mechanism, which is in the locked state. In this paper, the deployable mechanism with enhanced bending and torsion resistance configuration will be taken as the research object. First, based on the classical hinge stiffness model, the hinge equivalent model and the sliding joint equivalent model are proposed. Then, the finite element model based on equivalent stiffness is analyzed, and the effectiveness of the finite element model is verified by comparing the experimental results. Finally, the finite element model was used to analyze the influence of the clearance of the pin hole, the clearance of the sliding fit, and the position of the clearance on the bending stiffness of the deployable mechanism. The results show that the clearance greatly reduces the stiffness of the mechanism under small loads and weakens the bearing performance of components. At the same time, the position of the clearance should be taken seriously in the mechanism design.

Assembly state detection technology based on virtual reality for key components of large space deployable mechanism

Aiming at the highly reliable assembly demand of large space deployable mechanisms with complex interface relationships of components such as bars and hinges, the intelligent assembly state detection of components based on Mixed Reality technology was studied. We designed and built the assembly condition detection system of key components of large space deployable mechanisms, realized the installation position detection of key parts with the Histogram of Oriented Gradients and Support Vector Machine as the recognition algorithm of truss joint base and image processing of screws with truss joint. The detection system is applied to the assembly of the large space truss mechanism. The results show that the accuracy of part recognition is 100%. The system can reduce problems of missing or the wrong assembly and improve the automatic level of large space deployable mechanism assembly detection.

Human-centric collaborative assembly system for large-scale space deployable mechanism driven by Digital Twins and wearable AR devices

The mass personalization of spacecraft challenges the experience and skill of assembly operators, which is caused by the poor collaboration between the elements in assembly. A large number of research works show that the role of human is irreplaceable in the process of assembly, but few publications focus on improving the collaboration to reduce the strict requirement for operators. To address those challenges, this paper proposes a human-centric collaborative assembly system (HCAS) for Large-scale Space Deployable Mechanism (LSDM) that is the core supporting structure of satellite, to solve the problem of poor collaboration between human and the resources in assembly site. Three Digital Twins (DTs), i.e., assembly process DT, assembly operator DT, and assembly quality DT are developed to achieve the collaboration among the elements of human-cyber-physical in HCAS. The breakthroughs brought by the three DTs are 1) adaptive assembly process sensing based on real-virtual scenes fusion with the help of assembly process DT and wearable AR device enhances the synergy between physical system and cyber system; 2) Based on the assembly operator DT and the Knowledge Graph, the adaptive assembly tasks assignment with operator-centric is realized; 3) Dynamic tolerance allocation of LSDM assembly considering space service environment based on assembly quality DT guides the operator to adjust the process parameters in real time. In addition, in view of the special requirement of gravity compensation of LSDM assembly, the method of using Co-robot to simulate microgravity and AR to plan robot path online is included to improve the human-machine collaboration. Finally, a prototype system is developed and applied in assembly site. Application results show that the developed method and system reduce the dependence on human experience and debases the frequency of rework, which achieve the purpose of improving assembly efficiency and quality.

Research on the influence mechanism of assembly stress on reliability of space deployable mechanism

The on-orbit performance of spaceborne SAR satellite mainly depends on the unwrapping precision of antenna panel, which is determined by its supporting pole system. The assembly stress of the pole system affects the antenna deployable precision in the assembly process of SAR antenna deployable mechanism. Aiming at this problem, this work presents a efficient method that the three-dimensional model of the deployment mechanism of SAR antenna is established, and the method of finite element simulation analysis is adopted. Prestress is applied to the pole system to simulate its assembly stress, and then we study the deformation law of the antenna panel under different assembly stress combinations of the mast system, and the mapping relationship is determined between the mast system and the flatness of the antenna panel. The most sensitive pole affected by the antenna panel deformation is obtained. The results show that the flatness of the antenna panel is related to the dimensional tolerance and position of the pole system, especially Large dimensional tolerance results in large deformation of antenna panel. In addition, the deformation area of antenna panel is determined by the assembly stress of different pole combinations. According to this research, it is concluded that the poles which should be controlled are obtained in the assembly process of the antenna deployable mechanism, which lays a theoretical foundation for the high precision assembly of the truss space deployable mechanism.

Review of Deployable Mechanism Test Technologies Oriented Towards Deep Space Exploration

Space deployable mechanisms refer to the mechanisms that can be folded into a compact configuration and be deployed into a large predetermined shape. With the development of deep-space exploration, deployable mechanisms become one of the best choices for the deep- space probes. Large-scale, large folding ratio, high stiffness and lightweight have become the development trend of deployable mechanisms, leading to the high demands for validation of the field test. During the design and production stage, many special tests for the mission goals and the space environment need to be carried out besides the traditional spacecraft tests. In this paper, some typical tests of deployable mechanism for deep space exploration are analysed, the scheme and the performance of the special test program are summarized, such as the low gravity simulation and the vibration test. In addition, some suggestion is also made for future test methods and technology development.

Novel Surface Design of Deployable Reflector Antenna Based on Polar Scissor Structures

Space-deployable mechanisms can be used as supporting structures for large-diameter antennas in space engineering. This study proposes a novel method for constructing the surface design of space reflector antennas based on polar scissor units. The concurrency and deployability equations of the space scissor unit with definite surface constraints are derived using the rod and vector methods. Constraint equations of the spatial transformation for space n-edge polar scissor units are summarized. A new closed-loop deployable structure, called the polar scissor deployable antenna (PSDA), is designed by combining planar polar scissor units with spatial polar scissor units. The over-constrained problem is solved by releasing the curve constraint that locates at the end-point of the planar scissor mechanism. Kinematics simulation and error analysis are performed. The results show that the PSDA can effectively fit the paraboloid of revolution. Finally, deployment experiments verify the validity and feasibility of the proposed design method, which provides a new idea for the construction of large space-reflector antennas.

Design and analysis of truss deployable antenna mechanism based on a novel symmetric hexagonal profile division method

As the deployment, supporting, and stability mechanisms of satellite antennas, space-deployable mechanisms play a key role in the field of aerospace. In order to design truss deployable antenna supporting mechanisms with large folding rate, high accuracy, easy deployment and strong stability, aiming at the geometric division of the parabolic reflector, a novel method based on symmetric hexagonal division and its corresponding modular truss deployable antenna mechanism is proposed, and the original method based on asymmetric triangular division and its corresponding mechanisms are presented for comparative analysis. Then, the screw theory is employed to analyze the mobility of different mechanisms. Furthermore, the improved three-dimensional mesh method is used to divide the reflector surface of a large parabolic antenna designed by the two different methods, and the profile accuracy and the type of links are taken as the evaluation indexes to quantitatively analyze the division results. Finally, a three-dimensional model of the modular deployable mechanism based on the symmetric hexagonal design is developed, and the deployable mechanisms with different configurations based on the two design methods are compared and analyzed from the mechanical perspective. The research results provide a good theoretical reference for the design of deployable truss antenna mechanisms and their application in the aerospace field.

Data-driven and AR assisted intelligent collaborative assembly system for large-scale complex products

With the continuous improvement of function diversity, quality and reliability, the complexity and scale of significant products such as aerospace equipment are increasing. This trend poses severe challenges to the assembly process. The large scale of products requires the fixed-position assembly with multiple roles of workers in parallel, and it increases the difficulty of multi-person assembly. The high complexity of products makes the assembly process tedious. It is time-consuming and laborious for workers to understand the 2D documents, and it easily leads to mis-operation. The assembly process of complex products can produce huge amounts of data, which have the potential for improving efficiency and quality but remain underutilized. The high reliability of products puts forward high requirements for real-time detection of the assembly process. With the development of information technology, data driven approach and Augmented Reality (AR) provide an efficient way to change the above situation. Therefore, this paper proposes an intelligent collaboration assembly system (ICAS) combining real-time data driven method with AR technology. In the ICAS, real-time data driven method is used to realize the human-to-human and human-to-machine collaboration under the fixed-position assembly, and AR is introduced to the system to assist the assembly of large-scale complex products. The intelligent detection method in the ICAS combines 3D reconstruction with sensors measurement data, and the detection result is displayed in an intuitive way by AR. The proposed system is verified in the assembly process of a large-scale space deployable mechanism, and it paves the way for the further development of intelligent assembly in the future.

Design and analysis of a scissors double-ring truss deployable mechanism for space antennas

Space deployable mechanism plays an important role in the orbital deployment and stable support of the antenna reflection surface, which is an important component for the spacecraft radar antenna. In order to improve the structural stiffness of the ring truss deployable antenna mechanism when it has a large diameter, a scissors double-ring truss deployable mechanism is proposed in this paper. First, structure analysis of general ring truss deployable antenna and construction of the scissors double-ring truss deployable mechanism are conducted, and the whole mechanism is decomposed to a plurality of mechanism units. Then, degree of freedom (DOF) of the scissors double-ring truss deployable mechanism is analyzed based on screw theory, the result showed that it has only one DOF. Furthermore, based on screw theory, kinematic characteristics of the scissors double-ring truss deployable mechanism are examined, velocities and accelerations of the components in the mechanism are obtained, as well as the Jacobian matrixes. Finally, based on Newton-Euler equation and the principle of virtual work, a dynamic model of the whole mechanism is established, numerical calculation and simulation verification are carried out, and the results verified the correctness of the theoretical analysis. The scissors double-ring truss deployable mechanism proposed in this paper can be well applied in the field of space antennas, and the theoretical analysis method based on screw theory used in this paper can provide insights into other spatial deployable mechanisms.

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With the continuous improvement of function diversity, quality and reliability, the complexity and scale of significant products such as aerospace equipment are increasing. This trend poses severe challenges to the assembly process. The large scale of products requires the fixed-position assembly with multiple roles of workers in parallel, and it increases the difficulty of multi-person assembly. The high complexity of products makes the assembly process tedious. It is time-consuming and laborious for workers to understand the 2D documents, and it easily leads to mis-operation. The assembly process of complex products can produce huge amounts of data, which have the potential for improving efficiency and quality but remain underutilized. The high reliability of products puts forward high requirements for real-time detection of the assembly process. With the development of information technology, data driven approach and Augmented Reality (AR) provide an efficient way to change the above situation. Therefore, this paper proposes an intelligent collaboration assembly system (ICAS) combining real-time data driven method with AR technology. In the ICAS, real-time data driven method is used to realize the human-to-human and human-to-machine collaboration under the fixed-position assembly, and AR is introduced to the system to assist the assembly of large-scale complex products. The intelligent detection method in the ICAS combines 3D reconstruction with sensors measurement data, and the detection result is displayed in an intuitive way by AR. The proposed system is verified in the assembly process of a large-scale space deployable mechanism, and it paves the way for the further development of intelligent assembly in the future.

Design and Experiment of Triangular Prism Mast with Tape-Spring Hyperelastic Hinges

Because of the limited space of the launch rockets, deployable mechanisms are always used to solve the phenomenon. One dimensional deployable mast can deploy and support antenna, solar sail and space optical camera. Tape-spring hyperelastic hinges can be folded and extended into a rod like configuration. It utilizes the strain energy to realize self-deploying and drive the other structures. One kind of triangular prism mast with tape-spring hyperelastic hinges is proposed and developed. Stretching and compression stiffness theoretical model are established with considering the tape-spring hyperelastic hinges based on static theory. The finite element model of ten-module triangular prism mast is set up by ABAQUS with the tape-spring hyperelastic hinge and parameter study is performed to investigate the influence of thickness, section angle and radius. Two-module TPM is processed and tested the compression stiffness by the laser displacement sensor, deploying repeat accuracy by the high speed camera, modal shape and fundamental frequency at cantilever position by LMS multi-channel vibration test and analysis system, which are used to verify precision of the theoretical and finite element models of ten-module triangular prism mast with the tape-spring hyperelastic hinges. This research proposes an innovative one dimensional triangular prism with tape-spring hyperelastic hinge which has great application value to the space deployable mechanisms.

Kinematic accuracy and dynamic performance of a simple planar space deployable mechanism with joint clearance considering parameter uncertainty

Joint clearance and the uncertainty of geometric and physical parameters significantly influence the kinematic accuracy and dynamic response of space deployable mechanisms. Such mechanisms have been widely employed in astronautic missions to improve the capabilities of launchers. This paper proposes a methodology to investigate the kinematic accuracy and dynamic performance of space deployable mechanism with joint clearance while considering parameter uncertainty. The model of space deployable mechanism with a planar revolute joint is provided. With consideration of several uncertain parameters, the solving procedure of the dynamic equations is presented based on the Monte Carlo method. A case study is conducted to reveal the effect of parameter uncertainty on its kinematic accuracy and dynamic performance. The results indicate that parameter uncertainty should be considered to accurately evaluate the performance of long-term operating space deployable mechanisms, especially for such systems with clearance joints. According to the results, brief suggestions for design and evaluation of the mechanisms are provided.