Large Deployable Mechanisms Research Articles

Design and analysis of modular deployable antenna mechanism based on a class of self-limiting position units

With the rapid development of space technology, deployable mechanisms have attracted much attention because of their potential applications. In this paper, novel deployable mechanism units with self-limiting position function are proposed. Then, the ring truss deployable mechanisms are constructed according to two schemes of shared-nodes and shared-edges. The ring truss deployable mechanism constructed using the shared-edges scheme has higher stability, to further expand the application potential of this scheme, a procedural method is proposed to obtain the ring topology with larger aperture. Next the degree of freedom(DOF) of deployable units are analyzed using screw theory, and according to the synchronization between the units, it is proved that the constructed ring truss deployable mechanisms have only one DOF. The dynamic model of the deployable mechanism unit with the passive actuation is established and verified by simulation. Compared with others, the deployable mechanism units proposed in this paper have the advantages of strong scalability and high stability, and they have good application prospect in constructing large deployable mechanisms.

Construction Method of Loop-Watt Mechanism Based on Watt Six-bars Units

In this paper, three Watt six-bar units are proposed to construct a loop connection mechanism (Loop-Watt mechanism) with a single degree of freedom (DOF) through the loop connection of rotating joints, and the constructed mechanism can complete the turnover motion. First of all, by analyzing the characteristics of the Watt six-bars unit and the theme idea of loop connection, the concrete method of loop connection is proposed, and the construction method of the Loop-Watt mechanism (LW-M) is obtained. Secondly, the DOF, motion forms, and motion characteristics of the Loop-Watt mechanism are analyzed, and its motion modes are obtained. Finally, the correctness of the analysis results is verified by establishing a 3D model in SolidWorks software. The Loop-Watt mechanism constructed in this paper is expected to have important application prospects in sealing mechanisms and large deployable mechanisms.

Equivalent Dynamic Model for Large Parabolic Cylindrical Deployable Mechanism

With the development of the space industry and the demand of future complex space missions, large space deployable antennas require high deployable ratio, high precision, and lightweight. A large parabolic cylindrical deployable (PCD) mechanism with a multilayer tape-spring (MLTS) hinge was proposed. The energy method was adopted to establish the equivalent dynamic model of the large PCD mechanism with MLTS hinges. The new problems encountered in the dynamic analysis of the new mechanism are solved. First, the nonlinear effects of the tape-spring hinges and cable in the PCD mechanism were considered. The relationship equations of strain and kinetic energy were derived. Then, the stiffness and mass matrices of the PCD mechanism were obtained. Based on Timoshenko beam theory, the modal analysis of the PCD mechanism in cantilever state was conducted. The finite element method was used to verify the correctness of the equivalent continuum model of the large PCD mechanism with MLTS hinges. The equivalent dynamic analytical method can be applied to the spatial large deployable mechanism.

Design of Hybrid Magnetic Stage for a Magnetic–Pneumatic Levitation System

This article presents a magnetic–pneumatic levitation system for gravity offload system of large deployable mechanisms, which combines the attractive force of magnetic stage and thrust force of air-bearing and is characterized by inner stability. The article focuses on the design of the hybrid magnetic stage. The equivalent magnetic circuit network method is used to analyze the electromagnetic (EM)-permanent hybrid magnetic field, the distribution of magnetic flux density of the air gap is solved, and then the magnetic force is obtained. To improve the design efficiency, the two-step design is adopted. First, the air gap is determined by sweeping the reluctance ratio to reduce the influence of parameter deviation of cast iron on the magnetic force. Then, the other parameters of the hybrid magnetic stage are optimized based on the multi-objective particle swarm optimization (MOPSO) algorithm. Through the comparison between the results of finite-element simulation and prototype experiments, the accuracy of the model is verified, and the expected design goal is achieved.

Design and Kinematic Analysis of a Large Deployable Mechanism of the Parabolic Cylindrical Antenna with Multi Tape-spring Hinges

Design and Kinematic Analysis of a Large Deployable Mechanism of the Parabolic Cylindrical Antenna with Multi Tape-spring Hinges

Design and analysis of a cable-winding device driving large deployable mechanisms in astrophysics missions

Cables are widely used because of their light weight and wide range of arrangement. To guarantee successful deployment and retraction of cable-driven mechanisms, this paper proposes a novel cable-winding device to fulfil particular requirements of a space mission, such as a large driving force output, large cable displacement, and high reliability. The device consists of three parts: the transmission assembly, cable arrangement assembly, and redundancy motor assembly. The transmission assembly transforms the torque of a motor into a large driving force. Cables can be wound layer-by-layer on a winch with the cable arrangement assembly. The redundancy motor assembly ensures normal movement of the mechanism if one motor fails, and can offer greater torque than a single motor. A prototype of the proposed cable-winding device is fabricated, and experiments are conducted to verify the performance of the device. The device has also been used in a large telescopic boom, which further validates its feasibility for actuating deployable mechanisms.

Design of Large Single-Mobility Surface-Deployable Mechanism Using Irregularly Shaped Triangular Prismoid Modules

This paper presents the design methodology for a single-mobility, large surface-deployable mechanism using irregularly shaped triangular prismoid units. First, we demonstrate that the spherical shell, as the deployed profile of the large deployable mechanism, cannot be filled with identical regular-shaped triangular prismoids (truncated pyramid) without gaps, which makes the design challenging because a large set of nonidentical modules should be moved synchronously. Second, we discuss the design of a novel deployable mechanism that can be deployed onto irregularly shaped triangular prismoids, which will be used as the basic module to fill the spherical shell. Owing to high stiffness and ease of actuation, a planar scissor-shape deployable mechanism is applied. Third, we study the mobile assemblies of irregularly shaped modules in large surface-deployable mechanisms. We discover that hyper kinematic redundant constraints exist in a multiloop mechanism, making the design even more difficult. In order to address this issue, a methodology for reducing these redundant constraints is also discussed. Finally, a physical prototype is fabricated to demonstrate the feasibility of the proposed design methodology.

Design and Mobility Analysis of Large Deployable Mechanisms Based on Plane-Symmetric Bricard Linkage

In this paper, a class of large deployable mechanisms constructed by plane-symmetric Bricard linkages is presented. The plane-symmetric Bricard linkage is a closed-loop overconstrained spatial mechanism composed of six hinge-jointed bars, which has one plane of symmetry during its deployment process. The kinematic analysis of the linkage is presented from the perspectives of geometric conditions, closure equations, and degree-of-freedom. The results illustrate that the linkage has one degree-of-freedom and can be deployed from the folded configuration to one rectangle plane. Therefore, the plane-symmetric Bricard linkage can be used as a basic deployable unit to construct larger deployable mechanisms. Four plane-symmetric Bricard linkages can be assembled into a quadrangular module by sharing the vertical bars of the adjacent units. The module is a multiloop deployable mechanism and has one degree-of-freedom. The singularity analysis of the module is developed, and two methods to avoid singularity are presented. A large deployable mast, deployable plane truss, and deployable ring are built with several plane-symmetric Bricard linkages. The deployment properties of the large deployable mechanisms are analyzed, and computer-aided design models for typical examples are built to illustrate their feasibility and validate the analysis and design methods.

Flexible attitude control design and on-orbit performance of the ZDPS-2 satellite

ZDPS-2, the 2nd generation nano-satellites designed and manufactured by Microsat Research Center of Zhejiang University, were successfully launched by the new generation rocket CZ-6 on Sep 20th, 2015. They are two 20kg identical nano-satellites (ZDPS-2-A and ZDPS-2-B) with a large deployable mechanism with a truss structure. The main mission of these two satellites is on-orbit demonstration of several new technologies, including large lightweight and flexible deployable mechanisms, a custom-designed panoramic wide field of view micro camera Sun sensor and infrared Earth sensor, and a micro-propulsion system as well as dual-satellite formation flying technology. The satellite is a 25cm cube with a deployable mechanism, whose fundamental frequency is only approximately 0.13Hz. This brings several challenges to attitude control. Flexible structure dynamics and its influence on attitude stabilization must be taken into consideration. A robust control scheme is developed by fully utilizing environmental torques with limited control actuator capability. On-orbit performance verified this design. ZDPS-2 satellites have successfully achieved rate damping, sun-pointing control and 3-axis stabilized Earth-pointing control, with a control accuracy of 5° (3σ) and stability superior to 0.1°/s (3σ). This paper demonstrates the flexible attitude dynamics modeling, illustrates the attitude control system design of ZDPS-2 and presents the on-orbit performance as well.

Design of a type of deployable/retractable mechanism using friction self-locking joint units

To develop a new type of deployable/retractable mechanism, the joint friction effect is considered in this paper. Several types of mechanisms with self-lock and unlock functions are presented as design units. These units can be constructed in parallel, in series, or in both ways to form a type of large deployable mechanisms. The self-locking and unlocking conditions of the designed units are analysed, and a new type of deployable mechanism, which can be extended and retracted along a straight line, is designed with the proposed unit constructing method. The relationship between the unit constraint matrices at various configurations is presented. During the moving process, the topology structure of the deployable mechanism is variable, including changes of the joint direction and the joint number. A cable driving prototype with only one motor is built, and relevant simulations are conducted to verify the design method. The results demonstrate that the joint units perform perfectly and that a larger dimension deployable mechanism can be established.

Design and optimization of large deployable mechanism constructed by Myard linkages

Large deployable mechanisms (LDMs), which consist of a set of basic deployable units, are widely used in aerospace industries, such as deployable masts, antennas, solar panels, etc. The Myard linkage with one degree of freedom can deploy to a planar configuration and fold to a compact bundle, can be used as the basic unit to build the LDM. In this paper, two mobile assembly methods of multi-units are proposed, and the mobility analysis of the novel deployable mechanism is developed. Parametric optimization for the deployable mechanism in an integrated design environment of iSIGHT is developed. The proposed deployable mechanism is optimized toward the goal of maximizing the fundamental frequency and minimizing the structural weight to enhance its stiffness. The prototype is constructed with limited deployable units and the deployable and foldable characteristics are initially verified.

Mobile Assemblies of Large Deployable Mechanisms

The large deployable mechanisms can be constructed by a set of basic deployable mechanical modules via mobile connection between the modules, i.e., the necessary mobility of each module is retained after connecting to other modules. In the large deployable mechanical networks, however, the mobility is always overconstrained due to the multiple close-loop structures in the mechanisms. This fact makes the mechanisms easily become rigid structures that are not movable even if small dimensional error happens to the mechanisms. Thus, eliminating redundant constraints so that the mechanisms still movable under the possible geometric dimensional errors, is very important for this kind of mechanisms. In this paper, efficient methods for the mobile connection between deployable single loop mechanisms (DSLMs) are first synthesized systematically; using some of these methods, lots of deployable units can be repeatedly used to build large deployable mechanical networks. A theoretic approach for eliminating the redundant constraints in the large deployable networks is proposed to make the deployable networks not so sensitive to dimensional errors. Finally, physical prototypes are fabricated to illustrate the feasibility of the proposed approach.