Modeling and Validation of a Passive Truss-Link Mechanism for Deployable Structures Considering Friction Compensation with Response Surface Methods

In this study, a passive truss-link mechanism applicable to large-scale deployable structures was designed to achieve successful deployment in space. First, we simplified the selected truss-link mechanisms to the two-dimensional geometry and calculated the degrees of freedom (DOF) to determine whether a kinematic over-constraint occurs. The dimensions of the truss-link structure were determined through a deployment kinematic analysis. Second, a deployment simulation with the truss-link was conducted using multibody dynamics (MBD) software. Finally, a deployment test was performed considering gravity compensation, and the results were compared with those of MBD simulation. The results of the deployment simulations were confirmed to be slightly faster than those of the deployment test due to friction effects existing in the joints and gravity compensation devices. To address this issue, inverse identification of the equivalent frictional torque (EFT) at the revolute joints in the deployment test was conducted through response surface methods (RSM) combined with the central composite design technique. As a result, we confirmed that the deployment angle history of the deployment simulation was similar to that of the deployment test.

Magnetically Deployable Robots Using Layered Lamina Emergent Mechanism

The steady rise of deployable structures and mechanisms based on kirigami and origami principles has brought about design innovations that yield flexible and lightweight robots. These robots are designed based on desirable locomotion mechanisms and often incorporate additional materials to support their flexible structure to enable load-bearing applications and considerable efficient movement. One tetherless way to actuate these robots is via the use of magnets. This paper incorporates magnetic actuation and kirigami structures based on the lamina emergent mechanism (LEM). Three designs of magnetic-actuated LEMs (triangular prism, single LEM (SLEM), alternating mirror dual LEM (AMDLEM)) are proposed, and small permanent magnets are attached to the structures’ flaps or legs that rotate in response to an Actuating Permanent Magnet (APM) to yield stick-slip locomotion, enabling the robots to waddle and crawl on a frictional surface. For preliminary characterization, we actuate the three designs at a frequency of 0.6 Hz. We observed the triangular prism, SLEM, and AMDLEM prototypes to achieve horizontal speeds of 4.3 mm/s, 10.7 mm/s, and 12.5 mm/s on flat surfaces, respectively. We further explore how changing different parameters (actuation frequency, friction, leg length, stiffness, compressibility) affects the locomotion of the different mechanisms.

Active Control of Stiffness of Tensegrity Plate-like Structures Built with Simplex Modules

The aim of this study is to prove that it is possible to control the static behavior of tensegrity plate-like structures. This possibility is very important, particularly in the case of deployable structures. Here, we analyze the impact the support conditions of the structure have on the existence of specific characteristics, such as self-stress states and infinitesimal mechanisms, and, consequently, on the active control. Plates built with Simplex modules are considered. Firstly, the presence of the specific characteristics is examined, and a classification is carried out. Next, the influence of the level of self-stress state on the behavior of structures is analyzed. A geometrically non-linear model, implemented in an original program, written in the Mathematica environment, is used. The results confirm the feasibility of the active control of stiffness of tensegrity plate-like structures characterized by the presence of infinitesimal mechanisms. In the case when mechanisms do not exist, structures are insensitive to the initial prestress level. It is possible to control the occurrence of mechanisms by changing the support conditions of the structure. Based on the obtained results, tensegrity is very promising structural concept, applicable in many areas, when conventional solutions are insufficient.

Investigation of tape flexures for space borne deployable structures

Space exploration arises the demand for launching large size structures to satisfy the need of high bandwidth telecommunication, earth observation and deep space interplanetary missions. Launching of these monolithic structures of sizes 3 m or more are not feasible due to limited launch fairing space of state-of-the-art launch vehicles. Therefore, the development of innovative deployment mechanisms is need of the hour. Deployment process of space borne deployable systems is the process of transition from mechanism to structure which is one of the unreliable stage due to existence of many conventional rotary joints which causes loss of energy due to backlash, friction and misalignment. An investigation study is presented in this paper for churning out a solution of flexible hinges using tape springs in state-of-the-art space deployable configurations which eliminates the factors causing loss of energy. Analytical and experimental methods are evaluated for investigating the bending behaviour of tape flexures. Tape flexures demonstrate to be a suitable candidate for compliant deployable configuration. The proposed configuration with combination of two tape flexures mounted in such a way that concave curve of each tape faces each other are structurally analysed for desired rotation angle. A comparison study is carried out for various material options of single and double layered tape flexures proposed for a flexure hinge. Practical feasibility of the proposed configuration is also demonstrated successfully on space borne deployable structures.

The influence of joint eccentricity on the foldability of four deployable structure systems

The study of deployable structures has been carried out traditionally by simplifying their constituent elements—joints and rods—to ideal entities. However, in this paper the dimensional thickness of these elements is taken into account, in order to evaluate their incidence on the foldability of four deployable structure systems. We have examined the eccentricity that occurs specifically at the joints themselves. Our study ultimately characterizes the incidence of this factor by defining noteworthy parameters common to both tube bundle and scissor systems, enabling us to establish a comparison and draw relevant conclusions.

Kinematic Design of Deployable Structures With Low Actuation Requirements Based on Pop-Up Folding

This paper presents the kinematic modeling and design of deployable structures inspired by pop-up books. These pop-up structures can exhibit large changes in area and volume through deployment motion that resembles opening the pages of a book. The pop-up structures have a modular topology and are formed by multiple parallelepiped units, here termed as pop-up units. The analysis of the kinematics of single pop-up units and assemblies of these that form larger structures is presented. An algorithm that integrates multiple pop-up units to form structures that approximate two-dimensional and three-dimensional target shapes when deployed is subsequently devised. The algorithm ensures that the structures formed by the assemblies of multiple pop-up units retain the single degree of freedom of a pop-up unit. The stored strain energy of these structures, which can provide the means to deploy them in practice, is also analyzed. Finally, various examples showing the applicability of the design algorithm in the synthesis of pop-up structures that approximate a diverse set of two-dimensional and three-dimensional target shapes are provided. The pop-up structures can be applied to a large spectrum of applications that need extensive deployment from small volumes while requiring a low number of degrees of freedom. These applications may include aerospace structures and MEMS.