A Screw Theory Approach to Computing the Instantaneous Rotation Centers of Indeterminate Planar Linkages

This paper presents a screw theory approach for the computation of the instantaneous rotation centers of indeterminate planar linkages. Since the end of the 19th century, the determination of the instantaneous rotation, or velocity centers of planar mechanisms has been an important topic in kinematics that has led to the well-known Aronhold–Kennedy theorem. At the beginning of the 20th century, it was found that there were planar mechanisms for which the application of the Aronhold–Kennedy theorem was unable to find all the instantaneous rotation centers (IRCs). These mechanisms were denominated complex or indeterminate. The beginning of this century saw a renewed interest in complex or indeterminate planar mechanisms. In this contribution, a new and simpler screw theory approach for the determination of indeterminate rotation centers of planar linkages is presented. The new approach provides a simpler method for setting up the equations. Furthermore, the algebraic equations to be solved are simpler than the ones published to date. The method is based on the systematic application of screw theory, isomorphic to the Lie algebra, se(3), of the Euclidean group, SE(3), and the invariant symmetric bilinear forms defined on se(3).

Design of deployable mechanisms based on Wren parallel mechanism units

This paper presents a series of deployable mechanisms based on n-UU (universal joint) Wren parallel mechanism (PM) units, which undergo one degree-of-freedom (DOF) Borel-Bricard motion. First, the PM unit is developed into ortho-planar mechanisms by adopting an R-R joint. The link parameters of the mechanism are optimized to maximize the folding ratio while avoiding interference. Then, the optimized PM units are piled up to construct a novel 1-DOF multi-layer mechanism which has the largest folding ratio among similar structures in the literature. Moreover, polyhedral deployable mechanisms are obtained by connecting the PM unit using U joint or U-U joint. Apart from saving space, the polyhedral mechanisms can transform among different shapes of polyhedrons. Finally, variations of the n-UU PM are investigated with different shapes of platforms, and each mechanism has its unique movement characteristics.

Kinematic and dynamic analysis and distribution of stress for seven-item mechanism by means of the SolidWorks program

This paper presents a kinematic and dynamic analysis and distribution of the stress for seven-item planar mechanism by means of the SolidWorks software. The authors of the introduced paper deal with the kinematic analysis of planar mechanisms as well as with the implementation of the vector method into the SolidWorks software program in order to determine the kinematic variables (quantities) of the individual bodies in the whole complex system. The dynamic analysis is performed on the basis of the kinematic analysis. Dynamic analysis allows us to design a system of bodies correctly and it is with the respect to the dynamic loading. For the interpretation of the introduced analysis, the seven-item planar mechanism was selected. Graphic dependence of kinematic and dynamic magnitudes of some points is given in dependence on the angle of rotation of the driving item and in dependence on time. In relation to the kinematic and dynamic analysis and subsequent simulation of the planar as well as spatial mechanisms, it is perfect solution to use SolidWorks software program. The considerable advantage of this mentioned program is based on its simplicity from the aspect of modeling and moreover, it is important to point out that utilisation of the mentioned program leads to results which are precise and accurate in the case of the numerical solution of the equations in the whole magnitude referring to motion of mechanism while the given results are obtained in the graphic form.

Kinematic and dynamic analysis and distribution of stress for six-item mechanism by means of the SolidWorks program

This paper presents a kinematic and dynamic analysis and distribution of the stress for six-item planar mechanism by means of the SolidWorks software. The main purpose of the investigation is connected with the kinematic analysis of planar mechanisms as well as with the implementation of the vector method into the SolidWorks software program in order to determine the kinematic variables of the individual bodies in the whole investigated system. The process of the dynamic analysis is based on the kinematic analysis. The dynamic analysis makes possible to design a system of bodies correctly and it is with the respect to the dynamic loading. For the interpretation of the introduced analysis, the six-item planar mechanism was used as example (representative). Graphic dependence of kinematic and dynamic magnitudes of some points is given in dependence on the angle of rotation of the driving item and in dependence on time. In relation to the kinematic and dynamic analysis and subsequent simulation of the planar as well as spatial mechanisms, it is great solution to use SolidWorks software program. The considerable advantage of this mentioned program is based on its simplicity from the aspect of modeling and moreover, it is important to point out that utilisation of the mentioned program leads to results which are precise and accurate in the case of the numerical solution of the equations in the whole magnitude referring to motion of mechanism while the given results are obtained in the graphic form.

Assessment of computer vision methods for motion tracking of planar mechanisms

One of the main challenges on the use of planar mechanisms is to verify and monitor that the trajectories described by the mechanism correspond to those originally required. However, very few research studies have focused on tracking and monitoring the motion of target points located on the mechanisms during operation conditions. In this paper, a comparative study to evaluate the performance of several computer vision methods (CVMs) when used in motion tracking of planar mechanisms is presented. The aim is to compare and identify the best CVM, in terms of precision, speed, low cost, and computational performance, to track the movement of planar mechanisms. For this purpose, a case study corresponding to a planar four-bar mechanism is selected and analysed. The results show that the vision methods based on the homogeneous and non-homogeneous solution of the camera calibration matrix are a technological alternative for monitoring motion trajectories of planar mechanisms.

Optimum design of two-material bending plate compliant devices

PurposeThe purpose of this study is to explore the optimum design of bending plate compliant mechanisms subjected to pure mechanical excitations using topological-derivative-based topology optimization. The main objective is to design the reinforcement in a plate of base material.Design/methodology/approachThe optimum design is performed by means of a level-set representation method guided by topological derivatives. Kirchhoff and Reissner–Mindlin models are used to solve the linear bending plate problem. A qualitative comparison has been carried out between the optimal obtained topologies for each model.FindingsThe proposed methodology was able to design reinforcement in a plate of the base material. The obtained reinforcements notably improve the device’s behavior. The shape and topology of the reinforcements vary depending on the mechanical plate model considered. In fact, in the Reissner–Mindlin solutions, very thin flexo-torsional hinges connecting big zones of the reinforcement material are designed.Originality/valueUp to date, the synthesis of ortho-planar mechanisms by means of continuum topology optimization was only boarded within a multi-physics context. In this work, the optimal design of pure ortho-planar compliance actuators is addressed. The best performance is found by analyzing the results for two classical mechanical plate models.