Papers by Keyword: Parallel Mechanism

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Authors: Tian Yu Li, Ding Xuan Zhao, Fang Yuan Han, Zhong Ke Shi, Meng Wang, Guo Ping Huang
Abstract: Parasitic motion of 3-PRS (prismatic-revolute–spherical) parallel mechanism is discussed, inverse kinematics model of this mechanism is established. Based on the structure feature of 3-PRS parallel mechanism, a new forward kinematics algorithm for this mechanism is presented. The algorithm consists of approximate calculation and iterative calculation. The mathematical model of the proposed algorithm is clear simple, no derivative operation or Jacobi matrix inverse operation is needed, so computation is less. The experiment shows that in the same computing environment, the calculation speed of the proposed algorithm is about 2 times of the existing algorithms to achieve the same accuracy, so it can be applied to real-time control. Complexity and workload of programming is less than half of before. The algorithm is based on 3-PRS parallel mechanism, but it is also applicable for other parallel mechanism.
Authors: Xin Zhao, Xing Long Zhu, Nan Yin, Shang Gao
Abstract: Owing to the deficiency of pinhole imaging model, a method to measure the depth information of the object based on lens imaging principle is proposed in this paper. By drawing on the two states of the measured object before and after changing position, this method manages to adjust the position of lens until the image become clearest, record the related information of position variation in order to obtain the depth information of the object. Meanwhile, whether the lens central plane is parallel to the CCD plane or not is also discussed, which is the reason why the image is fuzzy. A new kind of two degrees of freedom parallel adjusting mechanism was designed to solve the two problems above, which can achieve two degrees of freedom including independent moving and independent rotating. The clearest image can be obtained by adjusting the object distance and the image distance without changing the focal length of the camera. Besides, the mechanism can also be used to detect whether the installation position of lens central plane matches the CCD plane or not.
Authors: Dong Lai Xu, Shuai Zhang, Jun Tao Si, Wei Yu
Abstract: By applying quaternion and Sylvester resultant elimination method, and with the help of Mathematica 8.0 software, the 3-Dof 3-PC(RR)N spherical parallel mechanism location is analyzed. In solving inverse solution, there are 512-group input angle solutions, and 64-group real solutions. In the example of this paper, there are a total of 8-group real solutions by removing the extraneous roots.
Authors: Ping Zou, H.R. Qiu, Shan Min Gao, Ming Hu
Abstract: This paper presents a new type of drill grinder based on a special universal joint. The special universal joint is composed of a parallel mechanism with three legs as the inputs. One can rotate as a spindle; other two legs can drive a moving platform and make a drill point get an accurate position in workspace. Due to the simple mechanical structure comparing the grinder with the existing conventional CNC cutting tool grinders, it should be easy for the grinder to manufacture at a low cost. In addition, inverse kinematic equations of the special type of universal joint are derived.
Authors: Xing Qiang Tan, Zhi Jiang Xie, Guo Yun Li
Abstract: A new kind of parallel mechanism used for faster response and higher maneuverability test of wind tunnel is introduced. Based on static equilibrium analysis and screw theory, the static equilibrium equation of motion platform is established, and then kinematic Jaccobian matrix is achieved by use of force Jaccobian matrix. By means of kinematic Jaccobian matrix the singularity of 6_PUS parallel mechanism is analyzed and three kinds of singularity and their conditions are identified.
Authors: Guo Qin Gao, Hai Bin Zheng, Xue Mei Niu
Abstract: This paper addresses the motion control of the parallel mechanism of virtual axis machine tool, which has a complex system model, the nonlinear and strong coupling characteristics and has strong external disturbances in high-speed machining. To further enhance its motion control performances, a novel adaptive dynamic sliding mode control method is proposed. The designed control system stability is proved theoretically. By building a new switching function, the second-order dynamic sliding mode control algorithm is designed to reduce the chattering of the conventional sliding mode control effectively and overcome the adverse effects of the fast changing dynamics of the actuators. By introducing the adaptive control, unknown external disturbances can be estimated online, which can improve the ability of resisting strong disturbances and the control precision of virtual axis machine tool. The simulation results for the virtual axis machine tool show that the designed control system has the good performances in tracking and resisting strong disturbances and can achieve the high precision motion control of the parallel mechanism of virtual axis machine tool.
Authors: Yu Lei Hou, Da Xing Zeng, Zhan Ye Zhang, Chang Mei Wang, Xin Zhe Hu
Abstract: In the field of spatial orientation, the rotational parallel mechanism is widely used. While the existence of coupling brings about the parallel mechanism some difficulties in kinematics and dynamic analysis, the development of control system, and so on. This condition restricts the application fields and effects of the rotational parallel mechanism. Therefore, this paper proposes a novel 2-DOF (two degrees of freedom) rotational DPM (decoupled parallel mechanism). The feature of the mechanism is described and their movement form is analyzed with screw theory. The proposition of the novel rotational DPM will enrich the configurations of the parallel mechanism, and the contents of this paper should be useful for the further research and application of the rotational parallel mechanism.
Authors: Florentin Buium, Dumitru Leohchi, Ioan Doroftei
Abstract: The paper deals with a workspace problem of the 3 RRR planar parallel mechanism, used as parallel robot structure. Depending on the dimensional parameters and constructive characteristics, the authors search to depict the shape and particularities of the mechanism workspace of a 3 RRR planar parallel mechanism. This characterization of the mechanism workspace depending on the dimensional parameters can be usefull in mechanism designing accorded to some functional particularities and also can help in avoiding singular configurations.
Authors: Badreddine Aboulissane, Dikra El Haiek, Larbi El Bakkali
Abstract: The objective of kinematic synthesis is to determine the mechanism dimensions such as link lengths, positions or joint coordinates, in order to approximate its output parameters such as link positions, trajectory points, and displacement angles. Kinematic synthesis is classified into three categories: function generation, path generation, and motion generation. This paper is dedicated only to path generation. As the number of trajectory points increases, analytical methods are limited to obtain precisely mechanism solutions. In that case, numerical methods are more efficient to solve such problems. Our study proposes an improved heuristic algorithm applied to four-bar mechanism path-generation. The objective of this work is to find optimum dimensions of the mechanism and minimize the error between the generated trajectory and the desired one, taking into consideration constraints such as: Grashof condition, transmission angle, and design variables constraints. Finally, our results are compared with those found by other evolutionary algorithms in the literature.
Authors: Zi Yun Xue
Abstract: With the dual relationship between parallel mechanism and serial mechanism on the structure and performance characteristics, the emergence of parallel mechanism, expand the areas of application of the robot. In this paper, a survey on the origin, main characteristics, field of application, and theoretical research of parallel manipulators are reviewed. Finally, some important problems of the parallel manipulator are mentioned to be solved.
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