Search

In recent years, an innovative underactuated robot was developed, named as underactuated cable-driven truss-like manipulator (UCTM), to be suitable in aerospace applications. However, there has been strong consensus that the stabilization of planar underactuated manipulators without gravity is a great challenge since the system includes a second order nonholonomic constraint and most classical control methods are not suitable for this kind of system. Furthermore, the complexity of the truss-like structure results in tremendous difficulty of computational complicacy and high nonlinearity during dynamic modelling in addition to controller design. It is paramount to solve these difficulties for UCTM’s future applications. To solve the above difficulties, this paper presents a dynamic modelling method for UCTM and a trajectory tracking control method based on partial feedback linearization (PFL) that fulfills the control goal of moving UCTM from its original position to a desired position by tracking a given trajectory of the joint angles. To achieve this, a model equivalent method is proposed to make UCTM equivalent with a three-link manipulator in the sense of dynamic behavior. Then the Lagrangian equation combined with complex vector method is proposed in the dynamic modelling process of UCTM, which simplifies the derivation procedure. Based on the established dynamic model, a coordinate transformation method is proposed to transform the control force matrix into the conventional form of an underactuated system, so that the control force can be separated from the unactuated term. The PFL method in combination with the LQR control method is then proposed to realize the targets that the joint angles can track given desired trajectory. Simulation experiments are conducted to verify the correctness and effectiveness of the proposed methods.

Aiming at the problem that the membrane structure is prone to creases in the process of folding and compaction, a proxy model is used to replace the creases to introduce initial defects for the folded membrane to realize the research of the deployment simulation of the membrane. Based on the finite-element method, the Z-folding and deploying process of the membrane is simulated and the elastic-plastic behavior of the crease is parameterized. The ABAQUS connector is used to replace the crease area of the membrane to simulate the characteristics of the crease and its effectiveness is verified. The deployment of Miura-ori membrane is simulated to explore the influence of force driving and constant-speed driving on the deploying process and deployment results of the membrane. In view of the self-contact phenomenon in the membrane deploying process when driven at a constant-speed, referring to the motion trajectory of the membrane loading corner of the force drive, a step-speed driving method is proposed. The research results show that using a step-speed to drive the deployment of folded membrane can reduce the curvature of the membrane surface, solve the problem of membrane self-contact, and eliminate the phenomenon of stress concentration of membrane surface. In addition, compared with other driving methods, the step-speed driving method has a significant advantage in improving the stability of the deploying process of a membrane.

Space deployable mast, which is a supporting mechanism, especially for a space telescope, requires high repeatability. In this study, a deployed space tri-prism mast was taken as the research object, and the change of a tensional cable’s tension force was equivalent to an external load. Based on the accurate stiffness model of the mast, the repeatability of the tri-prism mast was calculated by using the Monte Carlo method. Then, the influences of the number of units, the change in the tension force, the thickness of the linkage, and the radius of the tensional cable on the repeatability of the tri-prism mast were studied. Moreover, the correctness of the analytical model was verified by the repeatability experiments. Results demonstrated that the proposed method could be used to analyze the repeatability of tri-prism mast. This study provided references and suggestions for the design of high-precision space deployable mast.

Motion strategy analysis at the pre-bending stage is a fundamental component of underactuated finger grasp research. This study presents the pre-bending motion strategy and corresponding analysis of cable driving forces a 3-DOF underactuated finger comprising cable truss units. The structure and four motion strategies at the pre-bending stage are illustrated. The equivalent joint-driven and quasi-static motion models are established in the case where one or two cable driving forces drive the finger. Quasi-static motion model is established, and four typical quasi-static coupled motion space and distributions of corresponding cable driving forces are analysed. In accordance with the kinetic energy theorem and Lagrange’s dynamical method, a sampled and general dynamic model is established. Through matrix transformation, a hypothetical “PPA” type dynamic model is obtained. On the basis of the “PPA” dynamic model, three grasping control strategies at pre-bending stage are carried out. Valid simulations and experiments are conducted to verify the accuracy of the coupled bend inwards motion and control strategy.

In this study, a new type of cable-strut tensioned antenna mechanism is proposed and subjected to multi-objective optimization. First, a series of new cable-strut tension element configurations is proposed, and the optimal configurations are optimized on the basis of six topological characteristics of stable spatial cable-strut tensioned structures. Second, the mathematical surrogate models between configuration parameters, structural parameters, and fundamental frequencies of antenna mechanisms are established with the response surface method. Third, the optimization of the antenna mechanism synthesis is established, and the antenna configuration with optimal stiffness and mass synthesis is obtained with a genetic algorithm. Finally, the correctness and rationality of the proposed structural configuration is verified by developing a 2 m caliber prototype and conducting a dynamic characteristic test. The results should serve as a useful reference for the design of large caliber satellite antennas in aerospace engineering.

This article proposes a novel soft pneumatic actuator inspired by the segmented structure of earthworms. The actuator adopts a new structure of free bottom to eliminate the constraint of the bottom and enlarge the bending capacity of the actuator. Through simulation, it is found that the new actuator improves the bending angle by 20% and output force by 40% compared with traditional actuator. Moreover, key parameters of the actuator are analyzed to acquire their effect on bending angle and bending linearity. A guideline for the design and optimization of the actuator is proposed. To validate the simulation results, we build up a test platform to test bending angle and output force of the actuators, the results shows that errors between the simulation and the test remained in the limit of about 10%. Finally, a three-jaw soft gripper is fabricated and its grasping strategy is studied. The quantitative analysis shows its excellent adaptability and load capacity.

A C-cross section thin-walled composite deployable boom (C boom) can be flattened and coiled elastically. Furthermore, C boom can be deployed by releasing stored strain energy. Finite element (FE) models of C booms are constructed based on a nonlinear explicit dynamics analysis. The full simulation is divided into six consecutive steps: flattening, end-compacting, releasing, coiling, holding, and deploying around a hub. An optimal design method for the coiling and deploying of the C boom is presented based on the response surface method (RSM). Twenty-seven sample points are obtained by using a full-factorial design of experiment method. Surrogate models of the maximum moment and stress during the fully simulated process, including the mass of the C boom, are created by the RSM. The maximum moment and mass are set as objectives, and the maximum stress is set as a constraint to increase deploying statue stiffness and enhance use times. A multi-objective optimization design of the C boom is performed by sequential quadratic programming algorithm. Lastly, FE models for the optimal design are built to validate the accuracy of the optimization and the response surface results.

Aiming at a series of characteristics of the membrane structure in the folded configuration during the deploying process, the initial defect of the membrane crease is introduced by proxy model, and to realize the study of the deploying process of the membrane. Based on the finite element method, the deploying process of the multi-element Miura membrane is simulated. And the stretch ratio, maximum mises stress, deployment rate, wrinkle deformation, etc. of membrane structure are discussed. The existence of creases can cause damage to the membrane surface, so the total length of the creases should be within an appropriate size range. By changing the number of elements and the longitudinal crease angle of the same size membrane respectively, the influence of the above two factors on the total crease length, storage volume and deploying process of the folded membrane is studied. The results show that when the longitudinal crease angle is 15°, the transverse and longitudinal displacements of the Miura folded membrane with different element numbers are not synchronized during the deploying process. By keeping the number of elements constant and increasing the angle of the longitudinal creases from 15° to 45°, the synchronization of the transverse and longitudinal displacements during the membrane deploying process is gradually enhanced. In addition, the experiment on the membrane deploying process verifies the reliability of the finite element simulation results.

This paper presents a combination of biological and screw theories for analyzing mechanisms, namely, cytology of mechanism (CM). In CM, kinematic pairs are considered as cells and they are the most important part of mechanisms. CM comprises four concepts, namely, cell division, cell division–differentiation, cell combination, and cell combination–variation. Consequently, mathematical models based on screw theory are employed to describe those concepts. A cell division method (CDM) is also proposed for mobility analysis of multi-loop mechanisms based on cell division. The basic principle of this method is to transform mobility analysis into constraint analysis between kinematic pairs and mobility analysis of parallel sub-mechanisms. Finally, CDM is used for analyzing the mobility of three typical multi-loop mechanisms to verify its correctness and practicality.

Capturing non-cooperative targets in space is a cutting-edge technology in the aerospace field. In this study, a novel n(3RRlS) metamorphic serial-parallel manipulator (MSPM) with multiple working conditions is proposed, which can serve as the fingers of a large-scale reconfigurable space multifingered hand (LSRSMFH). First, a limb combination coding method is proposed to describe the topological graph and determine the isomorphism of the n(3RRlS) MSPM. Subsequently, the topological graphs and the limb combination codes (LCCs) of the 1(3RRlS) MSPM, 2(3RRlS) MSPM and 3(3RRlS) MSPM are further analyzed, and the isomorphism of all the actuation distribution configurations (ADCs) and metamorphic configuration states (MCSs) is determined. Second, a two-actuator method is applied for the n(3RRlS) MSPM, and the workspaces of all MCSs of all ADCs of the 1(3RRlS) MSPM, 2(3RRlS) MSPM and 3(3RRlS) MSPM are analyzed using a transformation method. The results show that the n(3RRlS) MSPM can realize their respective functions of the LSRSMFH under three working conditions with the minimum number of actuators, which can reduce the number of actuators and the weight of the LSRSMFH and can gain benefits in multitask adaptability, simplified control, precision and rigidity improvement, energy saving and risk reduction.

Compared with non-overconstrained deployable units, overconstrained deployable units are widely used in space missions for their higher stiffness characteristics. Besides the performance of a three-step topological structural analysis and design of the rectangular pyramid deployable truss unit (PDTU), conducting a structural synthesis of an overconstrained deployable unit requires the determination of the relative position and direction of each kinematic axis. The structural synthesis of an overconstrained deployable unit is investigated based on screw theory and its topological structure. The possible overconstrained cases of the rectangular PDTUs are analyzed, and corresponding screw expressions are obtained. Thus, the rectangular PDTUs, which can be folded into a plane, are synthesized systemically, and a series of overconstrained rectangular PDTUs is obtained. Furthermore, the feasibility of the folded and deployed motions under one degree of freedom for those deployable units is verified in dynamical simulation by using ADAMS 2010. Keywords: Assembly SAR antenna, Common overconstraint, Deployable truss structure, Screw theory, Structural synthesis

This research proposes a single degree of freedom (DOF) cable-truss hybrid double-layer deployable mechanical network (DLDMN) consisting of equilateral Bennett linkages and planar symmetric four-bar linkages. The kinematics of the equilateral Bennett linkage is investigated. Then a single-loop four-bar hybrid linkage is constructed using the equilateral Bennett linkage and planar symmetric four-bar linkage. The original form of the Bennett linkage in the hybrid linkage is replaced by its alternative form and a synchronous mechanism is introduced to obtain a hybrid linkage interlayer vertical pillar with an adjustable height. The interlayer vertical pillar is employed to a single-layer mechanical network consisting of Bennett linkages. Connecting these pillars with cables, a cable-truss hybrid DLDMN that could fit various surfaces is assembled. An offset paraboloid antenna is set up using the DLDMN. A prototype is manufactured to verify the feasibility of the design. The proposed single DOF DLDMN has the advantages of high deployment ratio of spatial single-loop linkages and normative motion of planar linkages. The proposed network can be used to construct a large-scale spaceborne deployable antenna with high stiffness.

Self-adaptation is a typical and widespread characteristic in underactuated finger grasp. This paper presents the self-adaptive grasp process and equilibrium configuration of a 3-DOF underactuated finger comprising cable-truss units, which uses a tendon-pulley transmission and parallel four-linkage mechanism to realise grasps. The structure and the self-adaptation at the grasp closing stage are illustrated. On the basis of a situation where one or two phalanges are in contact with the object, fixed-point grasp models and the joint workspaces are discussed, respectively. The corresponding workspace that is formed when the distal phalange contacts the object at a fixed point is assessed through numerical analysis. The expression of general static contact force is established by using the virtual work principle, and expressions reveal that the phalanges’ static statuses are obtained. According to the middle phalange contacting or not contacting with the object, the distributions of every phalange condition are assessed, and the self-adaptive grasp process in complex distribution regions and four equilibrium grasp configurations are analysed from two grasp situations. Valid and adequate self-adaptive grasp experiments are conducted to verify the accuracy of the self-adaptive grasping analysis.

Composite ultra-thin boom can be folded elastically. Moreover, such booms are able to self-deploy by releasing stored strain energy, which can be applied in deployable antenna, solar sail, and optical telescopes. Surrogate models for imperfection-sensitive quantities of interest and multi-objective optimization are developed for the design of a new N-shape cross-section composite ultra-thin deployable boom. The proposed optimal design method integrates four general steps: (1) design of experiments, wherein the sampling designs of the N boom are created on the basis of the two-factor five-level full factorial design of experiments method; (2) efficient computational analyses of each design sample, wherein the post-buckling behavior of the N boom are analyzed under three different axial directions using nonlinear finite element ABAQUS/Explicit solver; (3) establishing the surrogate models of bending stiffness around the x-and yaxes and torsional stiffness around the z-axis by response surface method (RSM); (4) performing the multi-objective optimization design using modified non-dominated sorting genetic algorithm to realize the optimal design. The bending stiffness around the x-and yaxes and the torsional stiffness around the z-axis are set as the objectives, mass is set as the constraint, and the bonded web height and the central angle of the middle tape spring of the N boom are set as the variables. The typical surrogate modeling method can be applied to different problems in structural and material design.

To meet the requirement of large aperture development trend of space deployable antenna, a space deployable antenna with high folding ratio and light weight is researched. A folding rib deployable antenna mechanism configuration is proposed and the structure analysis of deployable antenna mechanism is carried out based on modular design idea. Based on the basic theory of robotics, the forward kinematics model of the mechanism is established, and the inverse kinematics analysis is carried out from two aspects: identification of deployment state and research on driving law. The mechanism principle, forward kinematics model and inverse kinematics analysis are verified by numerical simulation software. The numerical simulation results show that the folded rib deployable antenna mechanism can realize the movement change from fully stowed to fully deployed without singularity. The movement law of key points at the end of mechanism is closely related to the development law of each corner in mechanism. The configuration scheme of folding rib deployable antenna mechanism proposed in this paper is reasonable and feasible. The established forward/reverse kinematic model can provide reference and help for kinematic characteristics analysis of mechanism and driving law research of mechanism.

With the in-depth study of the construction of space bases, the demand for super-large deployable manned cabins in space is becoming increasingly urgent. In this study, a brand-new large space modular expandable cabin mechanism is proposed, and equivalent mechanical modeling research is conducted based on its modular characteristics. First, the overall configuration and the deployment driving scheme of the cabin section with the best comprehensive performance are optimized. In addition, a detailed structural design of the cabin section mechanism is carried out. Second, the mechanical equivalent continuous model of the cabin mechanism is established. The static and dynamic characteristics of the cabin mechanism are studied based on finite element simulation and equivalent model calculation, respectively. The correctness of the equivalent mechanical model established in this study is verified through comparative analysis. Finally, a scaled prototype is developed to verify the feasibility of the configuration and the new drive proposed in this study.

With the increase of defunct satellites, the orbit resource of the Earth is becoming more and more shortage. As one of the key technologies, the capture of non-cooperative targets has become a research hotspot. Due to its obvious characteristics, easy identification, high strength and high stiffness, the Launch Adapter Ring (LAR) has become a capture object on the defective and tumbling satellite. In this paper, a novel LAR capture tool is developed, and the LAR capture tool is designed, manufactured and tested. In order to improve the probability of grasp, the direct drive was adopted. The main research contents are as follows: overall design of the capture tool, design of electromagnetic brake, analysis of kinematics, and test the prototype.

In order to meet the development requirements of the large-scale space deployable antenna, the analysis and research on the topological characteristics of truss structure for modular deployable truss antenna are carried out, and the space equal envelope circle method is proposed. According to the general requirements of the working surface configuration of the deployable antenna, the structural composition and characteristics of the module are analyzed, and the geometric relationship between the number of envelope circles and the number of module layers and the total number of modules is established. Based on the basic theories of differential geometry and robotics, the geometric models of the central layer envelope circle, the second layer envelope circle and the third layer envelope circle are established respectively. The space geometry model of deployable antenna structure is constructed to meet the three-layer topology requirements. Finally, a numerical example is used to verify the geometric model, and the correctness of the model is proved. The topological method of deployable antenna structure proposed in this paper provides reference for the research of basic theory of deployable antenna and large-scale engineering application.

This paper proposes an approach to designing rigid origami flashers that can be deployed onto curved-surface configurations. The method of designing planar origami flashers that can be wrapped around regular polygonal central hubs is presented. Based on the principle of parallel projection, planar origami flashers are projected onto target spherical surfaces to obtain the vertices on the boundary creases between sections of adjacent origami flashers. The geometric relationships of thin-panel curved origami flashers are established in terms of foldability, and other vertices in each section are calculated using numerical methods. Flexible and elastic hinges modify the thin-panel curved origami flashers into thick-panel rigid flashers. The thick rigid panels maintain the shape of flashers, and the flexible creases treated using thickness-accommodating methodologies are used to maintain the foldability of the thick panels. Additionally, we analysed the parameters that affect the accuracy of the surface fitting. The feasibility of the proposed approach is verified using numerical simulations and physical prototypes. The novel designing of deployable curved-surface rigid origami flashers facilitates their potential applicability in solid surface antennas, surface reflectors, and other space engineering applications.

A method involving conceptual configuration synthesis and topology structure analysis is developed based on graph theory to obtain a series of double-layer hoop deployable antenna units (DHDAUs) that can be folded into straight lines. First, a procedure for synthesizing the conceptual configurations of DHDAUs is obtained by combining graph properties, weighted adjacency matrixes, and several principles. Second, a fundamental topological graph is presented to describe joint connections in a DHDAU on the basis of the adjacency matrix. The fundamental topological graph is reduced to a two-color topological graph by applying various simplified rules and topology properties. Third, a procedure for the identification of kinematic joints is established to fold DHDAUs into lines. Finally, three types of DHDAUs are obtained through this synthesis approach. The models, which were produced via 3D printing, can be deployed flexibly, thus proving the correctness of the theoretical analysis. These methods can provide guidance for the design of large aerospace deployable mechanisms.

The large deployable antenna has continuously received research interest in space technology. The design of such large structure has certain inherent challenges, such as limited mass and volume because of the inadequate capabilities of launchers. This constraint affects different aspects, including shapes, dimensions, and stiffness requirements. This study explores a new large cable–rib deployable antenna structure with radial ribs and tensioned cables. This structure has the advantages of high stiffness/mass ratio, which is suitable for constructing large-scale deployable antennas. A structural optimization method with a dynamic constraint for the maximum stiffness/mass ratio is proposed; this method is based on structural design formulas and the dynamic model of the deployable antenna structure. A genetic algorithm is introduced for parameter optimization with frequency constraint. Numerical examples are conducted to demonstrate the effectiveness of the proposed optimization method. By using these analysis methods, a 1.8 m prototype is fabricated and tested. Afterward, the feasibility and dynamic characteristics of the proposed cable–rib tension deployable structure are validated.

The variable-span and cambered span morphing wing for unmanned aerial vehicle (UAV) can greatly improve its flight efficiency. In this work, a new extendable and bendable morphing wing with double driving is designed. The morphing skeleton of wing is composed of the basic unit module which is seven-bar mechanism in series. The rubber-filled corrugated sandwich corrugated skin is designed according to the requirement of morphing skeleton. The kinematics model of morphing skeleton that is composed of three modules in series is established, then the kinematics analysis of morphing skeleton is carried out, at last the expressions of the deformed position and driving angle are obtained. In the case of the same wing span, the influence of different rod length ratio on the maximum extension length of the morphing wing is analyzed, and the influence of different driving speed on the maximum bending angle under the same rod length ratio is compared and analyzed.

This paper presents the self-adaptive grasp of a novel cable-driven finger, which is an underactuated finger comprising cable-truss units. The underactuated cable-truss finger uses tendon-pulley transmission and parallel four-linkage mechanism to realize grasps. The working principle of the underactuated cable-truss finger and the self-adaptation at the grasp-closing stage are introduced. A self-adaptive grasping model is constructed to analyze the self-adaptation, and a new analysis method that considers the position and posture of grasping point in distal phalange is proposed. A new generalized coordinate, which directly shows the contacting position and the relative angular displacement in the distal phalange, is established. The expression of general static grasping force is established by using the virtual work principle, which reveals the relationship among the driving force, the equivalent torques on joints and the grasping forces. The workspace of the underactuated cable-truss finger and distributions of grasping force in new generalized coordinate are assessed through numerical analysis. The balance conditions of the self-adaptive grasp and the corresponding statuses are theoretically illustrated. Valid and adequate self-adaptive grasping experiments are conducted to verify the accuracy of self-adaptive grasping analysis.

This study proposes a conceptual configuration synthesis method based on graph theory to obtain a series of quadrangular prismatic deployable units (QPDUs) which can be folded into a straight line. Firstly, according to graph theory, graphs of statically determinate QPDUs are synthesized. Secondly, in order to establish the conceptual configuration of QPDUs, weighted graph, weighted adjacency matrix and some rules are analyzed. Combined with graph properties, a procedure for synthesizing conceptual configuration of QPDUs is obtained. Finally, all 78 kinds of QPDUs are discovered by using synthesis approach mentioned above. These QPDUs are then used to build large deployable space mechanisms, such as mast, planar and hoop mechanisms, in different construction methods. This study expands the deployable unit configuration library, and the method can provide experience for the theoretical research in aerospace deployable mechanisms.

In this study, the mobility of the threefold-symmetric Bricard linkage and its network are analyzed using screw theory. First, the screw motion equation of the linkage is derived. By applying the modified Grübler–Kutzbach criterion, we deduce that the degree of freedom (DOF) of the linkage is equal to 1. Then, we analyze the mechanical network constructed of threefold-symmetric Bricard linkages and provide its topological constraint graph. Using graph theory and screw theory, the constraint matrix of the mechanical network is obtained. Then, we solve the matrix rank via linear column transformation. Results show that the DOF of the mechanical network is equal to 1. The mobility analysis method of the mechanical network proposed in this study facilitates the solution of the constraint matrix rank and can be used as a reference for other mechanical networks constructed of single-loop linkages.

Space manipulation has great prospects in aerospace applications. In this work, a multiloop robot, namely 3-R(SRS)RP multiloop mechanism, is presented. Its design, kinematics, singularity, and workspace are studied. The novel design is mainly reflected in the robot’s structure, variable section, and novel compound hinge. Given these features, the forward-displacement undertaken with a closed-loop method leads to a complex mapping diagram. Only numerical solutions are obtained in this model due to the variable section parameter λ. This variable affects kinematic performances such as bending and folding properties. Moreover, the node differential kinematics and the Jacobian matrix are solved to analyze singular configurations of the mechanism. The workspace is then evaluated via a numerical method with varying λ. The bending and folding properties and the continuous workspace of the given robot vary while changing λ. Hence, the robot has great potentials of good performances in various applications. With this robot, a multimodule manipulator with a wide range of operations, increased mobility and rigidity, variable geometry, and adaptable shape based on mission requirements can be constructed.

In order to accurately research the dynamic characteristics of truss structure for modular space deployable truss antenna, dynamic experiments are carried out. Based on the basic theory of dynamics and the characteristics of antenna structure, a set of dynamic experimental system is designed, and the modal experiments under free boundary conditions are carried out by means of single-point input and multi-point output. The experimental results show that the autocorrelation coefficients of all the modes of the antenna structure are 100%, and the correlation functions between the modes are small, the maximum value is only 15.45%, which shows that the experimental results are correct. The maximum relative error of natural frequency is only 10.59%. In addition, the experimental mode shapes with the frequency of 32.781 Hz and 58.003 Hz are all in good agreement with the first and the third mode shapes of finite element analysis. The experimental method proposed in this paper can provide reference for modal analysis of other large space deployable truss structures.

In order to meet the requirement of spacecraft instrument’s repeated deployment, this paper presents a novel cable-driven space telescopic boom (STB) which can be orderly deployable/retractable. First, a novel metamorphic mechanism cell (MMC) which can realize locking, unlocking and interlocking with other cells is proposed, and the metamorphic principle, degree of freedom and motion condition of this type of cells are analyzed. Second, the novel 9-tube cable-driven STB is proposed based on MMCs. Modal analysis of the STB is performed using ANSYS WROKBENCH to verify that the STB has good rigidity. And the kinematics simulation of the STB is conducted using ADAMS software to verify that the deploying and locking functions.

Origami-inspired design is becoming an innovative approach to create functional mechanisms with a variety of attractive features including scalability, programmability and simplicity. This paper presents the design of a webbed-foot-inspired gripper by employing a novel origami webbing structure, which is generated by strategically integrating several elementary Miura-ori and waterbomb-ori modules. The grasping behaviour of the proposed webbed gripper can be accustomed through rearranging the 2D crease pattern of the origami webbing by taking advantage of shape and kinematic programmability for each elementary module. And based on the rigid panels and joints, a comprehensive quantitative approach to achieve specific grasping performance is performed in terms of closed extendable configuration and enclose input angle. The origami webbing can be fabricated from a single flat paper sheet and deploy along a straight path symmetrically together with supporting skeletons. A sample webbed gripper activated with cables is designed to exhibit potential applications, and primary experimental work focusing on object grasping capability is carried out. The results demonstrate the feasibility and practicability of the origami-inspired webbed gripper design, and numerous novel origami webbing structures can be developed based on this construction strategy.

According to a description of the topology structure of deployable antennas, this work proposes the configuration synthesis method of over-constrained deployable units on the basis of screw theory and conducts example analyses on the basis of an analysis method and certain design steps. First, the basics of screw theory are introduced in detail, and an over-constrained deployable unit is represented by a screw. Second, through over-constraint analysis, the kinematic pair configurations of the mechanism under over-constraint have been established. Third, according to the general process of the deployable unit with common over-constraints proposed in this paper, the example is analyzed in detail. Finally, the model is verified according to the obtained configuration synthesis results. The cubic deployable unit mechanism is obtained through 3D printing, and the folding function is tested to verify the correctness of the theoretical analysis, which can provide theoretical reference for the mechanism design of large deployable units.

Under the prospective aerospace applications of deployable tensegrity, this work aims to research on the ultralight annular deployable tensegrity antenna to satisfy the space requirements. To begin with, the deployment principle of this antenna is illuminated and the parametric modeling is carried out. After node matrix and connectivity matrix is established, the matrices of both bars and strings are obtained. Configuration parameters are planted into the computing system through node matrix. On this base, the configuration parameters is able to be calculated out through geometric analysis and interior force analysis for the antenna. Then, the algorithm of deploying process is established with MATLAB. With initial set of constant bar length and changing range of structure radius, design parameters are put into the spotlight in order to construct an efficient deployable antenna. The geometric trait of this annular tensegrity confines the solution domain of design parameters to a narrow area. Since then, in the solution domain, the optimization on the synthetical standard of various configuration parameters is performed and a combination of design parameters is selected eventually. With determined design parameters, configuration parameters can be calculated out in any state of the deploying process. Additionally, simulation for deploying process can be executed with concrete numerical values, and the results provide guides for the prototype hardware design. The prototype is manufactured and assembled, and it turns out to deploy effectively. Comparing the theoretical values and practical ones, the analysis and simulation matches the experiment to some degree.

Capturing noncooperative targets in space has great prospects for aerospace application. In this work, the knuckle unit of a large-scale reconfigurable space multifingered hand (LSRSMFH) for multitask requirements is studied. A plurality of knuckle units is connected in series to form a finger of the LSRSMFH. First, the lockable spherical (lS) joint, a new metamorphic joint that can function as a Hooke (lS1) or spherical (lS2) joint and is driven by shape memory alloy (SMA) material, is proposed. Based on the lS joint, this paper presents a new metamorphic parallel mechanism (MPM) (i.e., 3RRlS MPM), which has four configurations, namely, 3RRlS1, 3RRlS2, 2RRlS1-RRlS2, and 2RRlS2-RRlS1 configuration. The degree-of-freedom (DOF), overconstraint, and parasitic motion of the 3RRlS MPM are analyzed using screw theory, of which the DOF can be changed from 1 to 3. The 3RRlS1 configuration has a virtual constraint, and the 3RRlS2 configuration has parasitic motions. The results indicate that the mechanism motion screws can qualitatively represent the mechanism parasitic motions, and it is verified by deriving the kinematic equation of the 3RRlS MPM based on its spatial geometric conditions, the workspace of the 3RRlS MPM is further solved. The kinematic analysis indicates that the 3RRlS MPM can realize the folding, capturing, and reconfiguring conditions of the LSRSMFH.

Capture is a key component for on-orbit service and space debris clean. The current research of capture on-orbit focuses on using special capture devices or full-actuated space arms to capture cooperative targets. However, the structures of current capture devices are complex, and both space debris and abandoned spacecraft are non-cooperative targets. To capture non-cooperative targets in space, a lightweight, less driven under-actuated robotic hand is proposed in this paper, which composed by tendon-pulley transmission and double-stage mechanisms, and always driven by only one motor in process of closing finger. Because of the expandability, general grasping model is constructed. The equivalent joint driving forces and general grasping force are analyzed based on the model and the principle of virtual work. Which reveal the relationship among tendon driving force, joint driving forces and grasping force. In order to configure the number of knuckles of finger, a new analysis method which takes the maximum grasping space into account, is proposed. Supposing the maximum grasped object is an envelope circle with diameter of 2.5 m. In the condition, a finger grasping maximum envelope circle with different knuckles is modeled. And the finger lengths with corresponding knuckles are calculated out. The finger length which consists of three knuckles is the shortest among under-actuated fingers consists of not more than five knuckles. Finally, the principle prototype and prototype robotic hand which consists of two dingers are designed and assembled. Experiments indicate that the under-actuated robotic hand can satisfy the grasp requirements.

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.

This paper presents a novel six-DOF positioning and active vibration isolation platform based on magnetic levitation principle, which is intended to be used in space or laboratory environment to obtain an ability of payload precision positioning and vibration attenuation so that a favorable environment for science experiment, precision measurement and material processing can be obtained. A maglev actuator scheme is proposed which enable the ability of six-axis motion. The transformation and dynamics model of whole system is derived. An adaptive robust sliding mode controller and a vibration filter controller combined with acceleration compensation is designed and implemented for different circumstances. Extensive simulation and experiments validate the performance of motion range and vibration isolation. Further improvements of modeling method and control algorithm are discussed as well.

While many researchers have investigated the dynamics analysis of underactuated mechanisms in recent years, little work has been published on that with underactuated cable-truss mechanism. Dynamics analysis has important significance in the research of trajectory planning, driven project designing and the optimization design of the mechanisms. The mechanism dynamics equations were established based on Lagrange equation and the dynamics equations corresponding to the capture scheme that has been chosen were separately listed. To prove the correctness of the dynamics analysis, the simulation of the capture scheme was presented. Some capture experiments were done in order to verify the adaptive capture function of the underactuated cable-truss mechanism.

Cable net structures are important in the construction of large deployable space antennas. The shape and tension of a cable net must be properly designed for the operating requirements of a reflector in orbit. The application demand for large-scale space antennas highlights the problem of the flexible deformation of deployable structures. Thus, such deformation, which has a significant effect on surface accuracy, should be considered in the form finding design of cable nets. In this study, an approach considers the flexible deformation of deployable structures for identifying the desired shape for a cable net is proposed. First, the dimension of the triangles used for dividing the cable net of a cable–rib tension antenna is designed for the required accuracy, and the shape of the cable net is determined by introducing the sag effect in the design of boundary cables. Then, an approach that is based on force density and nonlinear finite element methods and ensures the appropriate node position and uniform tension of the cable net is proposed for the form finding problem. A feature of the developed method involves an optimization model that calculates the deformation of the deployable structure and iteratively modifies the node position to form the cable net. The genetic algorithm is employed for the acquisition of a set of optimal tensions with constraints. Finally, numerical examples and experimental test results are presented to validate the veracity and effectiveness of the proposed approach.

Sarrus mechanism and its modified configurations are widely used in space missions as one-dimensional deployable mechanisms. The degree of freedom (DOF) of the classic Sarrus mechanism is analyzed using the modified Kutzbach-Grubler criterion, which is based on screw theory. Inspired by the modified configurations, which has three branches used in high stiffness extendible and retractable mast and four branches used in fold articulated square truss mast, the general form of Sarrus mechanism is obtained. Two novel Sarrus mechanisms are synthesized based on the general form, which expands the configurations of one-dimensional deployable mechanism.

The function of the elevator is to help lunar rover arrive lunar surface from the top of Lander after landing. Rocker-arm elevator makes Lander overturn easily because its arm is too long. Different compress extent of the Lander leg, complicated condition of landing location, micro-gravity and unloading acceleration have great influence to the stability of Lander. The paper set the ZMP coordinate equation and the coordinate of support polygon by D-H coordinate law, and builds the rule of the stability. Example simulation result shows that the equation and the rule meet the requirement of Lander stability analysis on all different conditions.

To meet space science experiments in micro-gravity environment, micro-spacecraft vibration isolation technology was developed in recent years. A new kind of 2-degree-of-freedom electromagnetic actuator based on Lorentz principle was developed in this article. The composition and working principle of the actuator were introduced, the parametric model for electromagnetic actuator was established, the structural optimization was carried out with the help of genetic algorithm in the MATLAB toolbox, and the final optimal structural parameters were obtained. For achieving the magnetic induction intensity in radial and axial directions, theoretical model for electromagnetic characteristics of the 2-degree-of-freedom actuator was established, and the expression for electromagnetic force was obtained. A static electric–magnetic coupling simulation of the whole actuator and also the experiments for measuring magnetic induction and magnetic force were carried out, and the correctness of theoretical model was verified.

This paper presents an novel approach for stand-by mode sensorless speed estimation scheme for flywheel energy storage system (FESS). The proposed scheme eliminates the sensors required for flywheel speed monitoring, and estimates rotor speed in very short duration without affecting FESS in standby mode. This proposed algorithm only needs minimal change to the existing sensorless-based field orientation control(FOC) scheme of the flywheel. The algorithm is evaluated by simulation and experiment with short duration of excitation to the flywheel. The results also shows this method can estimate the speed without affecting the energy stored in the flywheel.

The microvibration has a serious impact on science experiments on the space station and on image quality of high resolution satellites. As an important component of the active vibration isolation platform, the maglev actuator has a large stroke and exhibits excellent isolating performance benefiting from its noncontact characteristic. A maglev actuator with good linearity was designed in this paper. Fundamental features of the maglev actuator were obtained by finite element simulation. In order to minimize the coil weight and the heat dissipation of the maglev actuator, parametric design was carried out and multiobjective optimization based on the genetic algorithm was adopted. The optimized actuator has better mechanical properties than the initial one. Active vibration isolation platforms for different-scale payload were designed by changing the arrangement of the maglev actuators. The prototype to isolate vibration for small-scale payload was manufactured and the experiments for verifying the characteristics of the actuators were set up. The linearity of the actuator and the mechanical dynamic response of the vibration isolation platform were obtained. The experimental results highlight the effectiveness of the proposed design.

Based on modular idea, deployable truss antenna use for satellites has become a new type of deployable antenna, which can meet the space science missions. According to the structural characteristics of deployable truss antenna, design requirements of basic frame are proposed. On this basis, six schemes of basic frame are developed. Using fuzzy comprehensive evaluation method, six schemes are evaluated. The comprehensive evaluation models are built, which are composed of factor set, the evaluation set, the weighing set and evaluation matrix. The fuzzy composite operator is determined. Finally, an optimal configuration is obtained according to maximum membership degree law. Using the optimal configuration, an deployable truss antenna is designed.