Sanmin Wang

Mobility analysis of the deployable structure of SLE based on screw theory

Scissor-like element has a number of applications in deployable structures such as planar deployable structure (PDS) and ring deployable structure(RDS). However, the mobility analysis of the multi-loop deployable structures is made more difficulty by the traditional mobility formula, because the deployable structure is a very complex structure with multi-loop. Therefore, On the basis of screw theory, the calculation method of mobility of deployable structures of SLE is thoroughly discussed. In order to investigate the mobility, decomposing and composing structures(DCS) are developed, and the basic units are able to be obtained. On the basis of the deployable structures’ geometrical characteristics, there exists a closed-loop quadrilateral structure and some non-closed-loop quadrilateral structures in PDS. Also, a six legs parallel structure is present in RDS. The basic units’ mobility can be solved by both the methods of screw theory and topology constraint graphs. Then, composing the related basic units, the formula of planar deployable structures’ mobility can be built and solves the mobility of ring deployable structure. The analysis method solves the mobility analysis of the multi-loop deployable structures which is difficulty by the traditional method, and plays an important role in further research about the mobility of other complex deployable structures.

Dynamic characteristics of planar linear array deployable structure based on scissor-like element with joint clearance using a new mixed contact force model

This paper aims at investigating precisely the dynamic performance of deployable structure constituted by scissor unit mechanisms with clearance joint. Based on the motion law in real joints, the contact model is established using an improved Gonthier nonlinear continuous contact force model, and the friction effect is considered using LuGre model. Moreover, the resulting contact force is suitable to be included into the generalized force of the equations of motion of a multibody system and contributes to replace motion constraints. In the sequel of this process, the effect of joint clearance is successfully introduced into the dynamical model of scissor deployable structure and the dynamic characteristics of deployable structure with joint clearance are obtained using a direct default correction method, which can directly modify the coordinates and speed of the system to avoid the numerical results divergence. Also, the new hybrid contact force model of revolute joint clearance is verified through comparing with the original model. The numerical simulation results show that the improved contact model proposed here has the great merit that predicts the dynamic behavior of scissor deployable structure with joint clearance.

Kinematics and dynamics of deployable structures with scissor-like-elements based on screw theory

Because the deployable structures are complex multi-loop structures and methods of derivation which lead to simpler kinematic and dynamic equations of motion are the subject of research effort, the kinematics and dynamics of deployable structures with scissor-like-elements are presented based on screw theory and the principle of virtual work respectively. According to the geometric characteristic of the deployable structure examined, the basic structural unit is the common scissor-like-element(SLE). First, a spatial deployable structure, comprised of three SLEs, is defined, and the constraint topology graph is obtained. The equations of motion are then derived based on screw theory and the geometric nature of scissor elements. Second, to develop the dynamics of the whole deployable structure, the local coordinates of the SLEs and the Jacobian matrices of the center of mass of the deployable structure are derived. Then, the equivalent forces are assembled and added in the equations of motion based on the principle of virtual work. Finally, dynamic behavior and unfolded process of the deployable structure are simulated. Its figures of velocity, acceleration and input torque are obtained based on the simulate results. Screw theory not only provides an efficient solution formulation and theory guidance for complex multi-closed loop deployable structures, but also extends the method to solve dynamics of deployable structures. As an efficient mathematical tool, the simper equations of motion are derived based on screw theory.

Dynamic characteristics of planar linear array deployable structure based on scissor-like element with differently located revolute clearance joints:

This paper comprehensively investigates the parametric effects of differently located revolute clearance joints on the dynamic behavior of planar deployable structure based on scissor-like element. Considering the real physical mechanical joints, the normal and the tangential forces in the revolute clearance joints are respectively modeled using Flores contact-force model and LuGre friction model. The resulting forces and moments are embedded in the equations of motion of the scissor deployable structure for accurately describing the effect of joint clearance and governing the dynamic response of this structure. The effects of the main parameters such as the location of the clearance joint, the clearance size and the number of clearance joints on the dynamic characteristics of a multibody mechanical system have been numerically evaluated, and the results indicate that joints at different locations in a mechanical system have different sensitivities to the clearance size, and the more sensitive joint should be controlled to reduce the nonlinear behavior of this structure. Also, it can be concluded that the motion in one revolute clearance joint will affect the motion in the other clearance joints and the dynamic interaction of clearance joints is the important source of structural behavior change. Therefore, in order to accurately predict the dynamic responses of the mechanical system, the clearance effect of each joint on the multibody system should be investigated and understood.

Dynamics Analysis of Deployable Structures considering a Two-Dimensional Coupled Thermo-Structural Effect

The deployment accuracy of deployable structures is affected by temperature and flexibility. To obtain the higher accuracy, various measures such as the optimization design and the control process are employed, and they are all based on deployment dynamics characteristics of deployable structures. So a precise coupled thermo-structural deployment dynamics analysis is important and necessary. However, until now, only a one-dimensional thermal effect is considered in the literatures because of simplicity, which reduces the accuracy of the model. Therefore, in this paper, a new model coupling mechanical field with a temperature field is presented to analyze the deployment dynamics of a deployable structure with scissor-like elements (SLEs). The model is based on the absolute nodal coordinate formulation (ANCF) and is established via a new locking-free beam element whose formulation is extended to account for the two-dimensional thermally induced stresses due to the heat expansion for the first time. Namely, in the formulation, the thermal influences are along two-dimensional directions, the axial direction and the transverse direction, rather than along a one-dimensional direction. The validity and precision of the proposed model are verified using a flexible pendulum example. Finally, the dynamics of a linear deployable structure with three SLEs modeled by the element is simulated under a temperature effect.

Configuration Design and Kinematics Research of Scissor Unit Deployable Mechanism

Scissor unit deployable mechanism is widely used in aerospace and architecture, and the configuration design and kinematics analysis are two important problems that need to be solved in the application process. The first order and second order influence coefficient matrices are derived by coordinate transform. Kinematics analysis model and its calculating examples are presented, and the displacement, velocity and acceleration of all the hinged points are calculated. Moreover, the numerical example is used to verify the effectiveness of analysis method which also presented in this paper.

The Design and Simulation of a New Time-Controlled Spring Driven Hinge for Deployable Structures

Driving hinge, the core part of deployable structure, is commonly used in aerospace nowadays. This paper describes the design process of a new type of time controlled spring driven hinge. In this process, on the one hand, we derive a new transmission ratio distribution method in the transmission system, with which we could get the minimum center distance by optimizing the design. Given all other conditions are fixed, the hinge get smaller size due to the design under the optimal transmission ratio we derived. On the other hand, inspired by clock timing device, we design a new time-controlled system and research the relationship between timekeeping time and transmission ratio to improve the preciseness and controllability of deploying time. At last, we create 3D model and timing function with simulation method to prove the fact that time-controlled system is precise enough to control deploying time.

The Configuration Design and Kinematic Analysis of the Deployable Mechanism Based on Bennett Linkage

Bennett linkage can be applied to build kinds of spatial deployable mechanism, and they have been used in the aviation fields, shelters fields and so on. The paper derives the transformation formula of the adjacent Bennett linkage units and puts forward a deployable mechanism configuration design method based on Bennett linkage. The coordinate transformation theory is applied to build the kinematic analysis model of this deployable mechanism, and an example is provided to verify the kinematic analysis model. The effects of the parameters of Bennett linkage on the kinematics of the deployable mechanism and its scale are researched.

Dynamics Analysis of Linear Array Deployable Structure Based on Symmetrical Scissor-Like Element

Based on the Cartesian frame, the dynamic model of the linear array deployable structures was established, the motion constraint equations were completed by the constraint conditions of the scissor-like element (SLE). The numerical calculation was carried out using multi-step Runge–Kutta method, the law of velocity and acceleration during the motion process were obtained, and the constraint default stabilization method was also utilized to avoid the divergence of the results. The results show that the velocity, acceleration, and reaction force of the scissor mechanism along y-axis presents better symmetry properties because the horizontal constant force is in x direction. Meanwhile, at the side of the mechanism withstanding the external force, the dynamic properties of each node along x direction change more obviously; however, the changing amplitude of the velocity, acceleration, and other physical quantities are very small along x-axis on the non-force side.

A Novel Analytical Solution Method for Constraint Forces of the Kinematic Pair and Its Applications

Constraint forces of the kinematic pair are the basis of the kinematics and dynamics analysis of mechanisms. Exploring the solution method for constraint forces is a hot issue in the mechanism theory fields. Based on the observation method and the theory of reciprocal screw system, the solution method of reciprocal screw system is improved and its solution procedures become easier. This method is also applied to the solution procedure of the constraint force. The specific expressions of the constraint force are represented by the reciprocal screw system of twist. The transformation formula of twist under different coordinates is given and it make the expression of the twist of kinematic pair more facility. A slider-crank mechanism and a single loop spatial RUSR mechanism are taken as examples. It confirms that this method can be used to solve the constraint force of the planar and spatial mechanism.