Search

AbstractA motion generation method for a planar four-bar mechanism without prescribed timing is proposed in this article. A characteristic of coupler points is found: for the coupler points of a four-bar mechanism in a standard installation position rotated by the corresponding input angle clockwise around the origin of the Cartesian coordinate system xOy, the generated points lie on the feature coupler circles. Next, based on this, the design process is divided into three steps. In the first step, the relative input angles, the relative coupler angles and five geometric parameters of the desired four-bar mechanism are optimized. In the second step, the basic dimensional types and initial input angle are determined, and then, the input angles are obtained. In the third step, the real size of the desired linkage mechanism is calculated. Because the dimension of the design variables in each step is exceptionally small, the motion synthesis method can yield design solutions with high precision in a short time. Six comparison examples are presented to demonstrate the efficacy of the proposed method. In addition, the method is used to design a robot for lower limb rehabilitation for application to the human foot. [ABSTRACT FROM AUTHOR]

This paper presents two types of new deployable mechanisms based on the motion characteristics of the four-bar slider–crank mechanism (FBSCM): the prism mechanism with constant cross-section and the round deployable mechanism. A new basic planar deployable unit based on the path-generating characteristics of the FBSCM is proposed. The method of building a deployable mast unit with one DOF from the new planar deployable mechanism is given. The prism mechanism with constant cross-section of one DOF is constructed, and the magnification ratio is analyzed. Moreover, the deployable unit with a negative Poisson's ratio for building the round deployable mechanism based on the properties of functional output of the FBSCM is proposed. The structure of the round deployable mechanism is described, and the parameter model with multilevel deployment is calculated and validated with cases given; the DOF of the round deployable mechanism is one. Last, the static analysis of the round deployable mechanism is studied by simulation; by locking 6 guide rails, the structure is found to have a balanced bearing capacity, and the bearing performance is improved compared with locking only one guide rail. [ABSTRACT FROM AUTHOR]

Based on the simplified mapping model of the geometric characteristics of a cobweb structure, a new umbrella-type deployable mechanism with a planar four-bar crank slider mechanism as the deployable unit is proposed. First, the model is statically analyzed and optimized using the Ansys Workbench software, and the optimal ratio of the spiral thread spacing in the model is determined. Additionally, the stiffness matrix of the cobweb rigid frame model is established, and the optimal angle between the spiral threads is determined using the matrix displacement method. Then, according to the optimized model angle and ratio, a new umbrella-type deployable mechanism is proposed, and its static performance is simulated and analyzed. The results show that the strength of the umbrella-type developable mechanism is improved, and the movement process is simulated to verify the effectiveness of the model deployment and folding process. [ABSTRACT FROM AUTHOR]

A method for the path synthesis of a planar five-bar mechanism based on wavelet analysis theory is proposed in this paper. Wavelet transform analysis is used to extract wavelet characteristic parameters(WCPs) from the basic dimensional types(BDTs) database. Combined the numerical atlas method with multidimensional search tree, a four dimensions search tree with a depth of five is obtained, in which numbers of leaf nodes are 4,096, and each node stores 59,787 groups of BDTs database numbers. Meanwhile, an index keyword database is established. By comparing the WCPs of a prescribed curve with index keywords, the leaf node where the desired mechanism is located is found. The WCPs of the BDTs in the leaf node are extracted, and a dynamic self-adaptive atlas database is established. Based on the design requirements, the desired mechanism can be obtained by fuzzy identification. Then, a mathematical model is established for calculating the actual sizes of the desired mechanism. The arbitrary design interval path synthesis of a five-bar mechanism is realized. Two examples are presented to demonstrate the veracity and practicality of the method proposed. [ABSTRACT FROM AUTHOR]

This paper introduces a method for the synthesis of the multiple tasks of a planar six-bar mechanism by wavelet series. Based on the theory of wavelet series, a mathematical model for assessing the output of multiple tasks of planar linkage mechanisms was generated. The multiple tasks that combine a function generation and a rigid body guidance will be presented throughout this paper. For function generation, a numerical atlas database, including 31,775 groups of basic dimensional types of a planar slider-crank mechanism was created based on the relationships of the wavelet feature parameters. For rigid body guidance synthesis, an output feature parameters database of a planar four-bar motion generation, including 178,810 groups of the basic dimensional types was created by analysing the relationships of the wavelet coefficients between the rigid body rotation angle and the coupler rotation angle of its corresponding basic dimensional types. The actual sizes and installation position parameters of the planar six-bar mechanism were calculated using the fuzzy identification method and theoretical formulas. Finally, an application is presented to illustrate the validity and practicality of the proposed theory. [ABSTRACT FROM AUTHOR]

In this study, a synthesis method for a non-integer periodic function generator of a four-bar mechanism using a Haar wavelet is presented. Using wavelet theory, the mathematical model for the output of a four-bar mechanism is established. Next, the characteristics of the four-bar mechanism output variable are described by the wavelet feature parameters; the relationship of the wavelet feature parameters between the output and its translation or dilation is also investigated. Based on this finding, three numerical atlas databases comprising of 203,500 groups of basic dimensional types of planar four-bar mechanisms, 148,995 groups of basic dimensional types of spherical four-bar mechanism and 11,175 groups of basic dimensional types of planar slider–crank mechanism are compiled. According to the internal relationship between the wavelet feature parameters, the sizes of the objective mechanism can be obtained using fuzzy recognition. Based on a genetic algorithm, optimization of the link parameters can be realized. Three examples are presented to demonstrate the efficacy and practicality of the proposed theory. [ABSTRACT FROM AUTHOR]