Topological Characteristics Analysis for a Family of Novel SCARA Parallel Mechanisms

Abstract Direct kinematics with analytic solutions is critical to the real-time control of parallel mechanisms. Therefore, the type synthesis of a mechanism having explicit form of forward kinematics has become a topic of interest. Based on this purpose, this paper deals with the type synthesis of 1T2R parallel mechanisms by investigating the topological structure coupling-reducing of the 3UPS&UP parallel mechanism. With the aid of the theory of mechanism topology, the analysis of the topological characteristics of the 3UPS&UP parallel mechanism is presented, which shows that there are highly coupled motions and constraints amongst the limbs of the mechanism. Three methods for structure coupling-reducing of the 3UPS&UP parallel mechanism are proposed, resulting in eight new types of 1T2R parallel mechanisms with one or zero coupling degree. One obtained parallel mechanism is taken as an example to demonstrate that a mechanism with zero coupling degree has an explicit form for forward kinematics. The process of type synthesis is in the order of permutation and combination; therefore, there are no omissions. This method is also applicable to other configurations, and novel topological structures having simple forward kinematics can be obtained from an original mechanism via this method.

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Towards the design of monolithic decoupled XYZ compliant parallel mechanisms for multi-function applications

Mechanical Sciences ◽

10.5194/ms-4-291-2013 ◽

2013 ◽

Vol 4 (2) ◽

pp. 291-302 ◽

Cited By ~ 24

Author(s):

G. Hao

Keyword(s):

Natural Frequency ◽

Dynamic Modelling ◽

Performance Characteristics ◽

Geometrical Parameters ◽

Parallel Mechanisms ◽

Redundant Design ◽

Acceleration Sensors ◽

Characteristics Analysis ◽

Motion Range ◽

Energy Harvesting Devices

Abstract. This paper deals with the monolithic decoupled XYZ compliant parallel mechanisms (CPMs) for multi-function applications, which can be fabricated monolithically without assembly and has the capability of kinetostatic decoupling. At first, the conceptual design of monolithic decoupled XYZ CPMs is presented using identical spatial compliant multi-beam modules based on a decoupled 3-PPPR parallel kinematic mechanism. Three types of applications: motion/positioning stages, force/acceleration sensors and energy harvesting devices are described in principle. The kinetostatic and dynamic modelling is then conducted to capture the displacements of any stage under loads acting at any stage and the natural frequency with the comparisons with FEA results. Finally, performance characteristics analysis for motion stage applications is detailed investigated to show how the change of the geometrical parameters can affect the performance characteristics, which provides initial optimal estimations. Results show that the smaller thickness of beams and larger dimension of cubic stages can improve the performance characteristics excluding natural frequency under allowable conditions. In order to improve the natural frequency characteristic, a monolithic decoupled configuration that is achieved through employing more beams in the spatial modules or reducing the mass of each cubic stage mass can be adopted. In addition, an isotropic variation with different motion range along each axis and same payload in each leg is proposed. The redundant design for monolithic fabrication is introduced in this paper, which can overcome the drawback of monolithic fabrication that the failed compliant beam is difficult to replace, and extend the CPM's life.

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Dynamic Response and Chaotic Characteristics Analysis of Spatial Parallel Mechanisms with Multiple Spherical Clearance Joints

Journal of Vibration Engineering & Technologies ◽

10.1007/s42417-021-00387-7 ◽

2021 ◽

Author(s):

Xiulong Chen ◽

Ruiguang Wu ◽

Yonghao Jia

Keyword(s):

Dynamic Response ◽

Parallel Mechanisms ◽

Clearance Joints ◽

Characteristics Analysis

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Kinematic design of a translational parallel mechanism based on sub-kinematic chain determined workspace superposition

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1177/09544062211004653 ◽

2021 ◽

pp. 095440622110046

Author(s):

Huiping Shen ◽

Yinan Zhao ◽

Guanglei Wu ◽

Ju Li ◽

Damien Chablat

Keyword(s):

Parallel Mechanism ◽

Kinematic Chain ◽

Inverse Kinematic ◽

Parallel Mechanisms ◽

Kinematic Modeling ◽

Symbolic Model ◽

Kinematic Design ◽

Decoupled Motion ◽

Topological Characteristics ◽

Kinematic Solution

This paper presents the kinematic design of a translational parallel mechanism (PM) named Vari-Orthoglide by means of the workspace superposition, according to the sub-kinematic chain (SKC) based PM composition principle. The main topological characteristics of the manipulator with two SKCs under study, such as the position and orientation (POC) characteristics, degree of freedom (DOF) and coupling degree are analyzed, which turns out that the coupling degree equals to 1, implying the partially decoupled motion. With the topological characteristics based kinematic modeling principle, a symbolic model of the kinematics is established to derive its symbolic direct and inverse kinematic solutions. Based upon the direct kinematic solution, the workspaces for the two SKCs can be efficiently found. Moreover, the singularity loci are identified for finding the singularity-free workspace, where a regular workspace is fitted as the task workspace as expected. The presented work shows an approach to design translational parallel mechanisms considering motion decoupling and regular workspace, applicable to other types of parallel mechanisms.

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