Dualities in the Analysis of Mechanisms With Multiple Loops and Parallel Mechanisms With Loops in Their Connecting Chains

2004 ◽  
Author(s):  
Koichi Sugimoto
Keyword(s):  
Dynamic Analysis ◽  
Parallel Mechanism ◽  
Jacobian Matrix ◽  
Parallel Mechanisms ◽  
Body System ◽  
Multi Body ◽  
The Relationship

There exists a duality relationship between a twist and a wrench in the dynamics of a mechanism or a multi-body system. Using this relationship, the coordinate-free expressions for the dynamic analysis of multi-loop mechanisms is derived. In the analysis, a Jacobian matrix expressing the relationship among loops is defined, and it is clarified, by using this matrix, that both twists and wrenches can be easily analyzed based on the duality relationship among them. A parallel mechanism having connecting chains with loops is also analyzed, and it is shown that the same procedure can be applied to a parallel mechanism with connecting chains, each loop of which has a motion space that is different from that of the mechanism.

Design of a Four Legged Parallel Mechanism to Improve the Dexterity of Walking Robot

2009 ◽  
Author(s):  
ChiHyo Kim ◽  
KunWoo Park ◽  
TaeSung Kim ◽  
MinKi Lee
Keyword(s):  
Parallel Mechanism ◽  
Degrees Of Freedom ◽  
Jacobian Matrix ◽  
Topology Design ◽  
Condition Numbers ◽  
Walking Robots ◽  
Rough Terrain ◽  
Parallel Mechanisms ◽  
Walking Robot ◽  
Intermediate Mechanism

This paper designs a four legged parallel mechanism to improve the dexterity of three layered parallel walking robot. Topology design is conducted for a leg mechanism composed of four legs, base and ground, which constitute a redundant parallel mechanism. This mechanism is subdivided into four sub-mechanism composed of three legs. A motor vector is adopted to determine the 6×8 Jacobian of the redundant parallel mechanism and the 6×6 Jacobian of the sub-mechanisms, respectively. The condition number of the Jacobian matrix is used as an index to measure a dexterity. We analyze the condition numbers of the Jacobian over the positional and orientational walking space. The analytical results show that a sub-mechanism has lots of singularities within workspace but they are removed by a redundant parallel mechanism improving the dexterity. This paper presents a parallel typed walking robot to enlarge walking space and stability region. Seven types of three layered walking robots are designed by inserting an intermediate mechanism between the upper and the lower legged parallel mechanisms. They provide various types of gaits to walk rough terrain and climb over a wall with small degrees of freedom.

A Quasi-Static Model for Planar Compliant Parallel Mechanisms

2009 ◽  
Vol 1 (2) ◽  
Author(s):  
Cyril Quennouelle ◽  
Clément Gosselin
Keyword(s):  
Parallel Mechanism ◽  
Applied Load ◽  
Jacobian Matrix ◽  
Static Model ◽  
Parallel Mechanisms ◽  
Compliance Matrix ◽  
End Effector ◽  
Kinematic Constraints ◽  
Compliant Parallel Mechanism ◽  
External Loads

In this paper, the mobility, the kinematic constraints, the pose of the end-effector, and the static constraints that lead to the kinematostatic model of a compliant parallel mechanism are introduced. A formulation is then provided for its instantaneous variation—the quasi-static model. This new model allows the calculation of the variation in the pose as a linear function of the motion of the actuators and the variation in the external loads through two new matrices: the compliant Jacobian matrix and the Cartesian compliance matrix that give a simple and meaningful formulation of the model of the mechanism. Finally, a simple application to a planar four-bar mechanism is presented to illustrate the use of this model and the new possibilities that it opens, notably the study of the kinematics for any range of applied load.

scholarly journals Type synthesis and kinematics analysis of a family of three translational and one rotational pick-and-place parallel mechanisms with high rotational capability

2019 ◽  
Vol 11 (6) ◽  
pp. 168781401985307
Author(s):  
Xing Zhang ◽  
Dejun Mu ◽  
Yuze Liu ◽  
Jie Bi ◽  
Hongrui Wang
Keyword(s):  
Parallel Mechanism ◽  
Jacobian Matrix ◽  
Hessian Matrix ◽  
Parallel Mechanisms ◽  
Kinematics Analysis ◽  
Type Synthesis ◽  
Lie Group Theory ◽  
Revolute Joints ◽  
Pick And Place ◽  
Pick And Place Operation

This article proposes a family of spatial three translational and one rotational parallel mechanisms (PMs) for pick-and-place operation. Their features are one independent rotation of the mechanism with four identical limbs, which are provided by the four revolute joints on the moving platform. The rotational capability of the PMs has a range of at least 180°. This article focuses on the synthesis of the PMs and kinematics analysis of the 4- P(2-SS)R parallel mechanism. First, based on the Lie group theory, three parallelograms are used in designing the PMs. The limbs are listed and two types of three translational and one rotational PMs are synthesized. Then, a typical 4- P(2-SS)R PM is selected, the 6 × 6 Jacobian matrix and the 6 × 6 × 6 Hessian matrix of the mechanism are derived for solving the displacement, velocity, and acceleration of the mechanism. Finally, singularity configurations are disclosed from the 6 × 6 Jacobian matrix, and the workspace of the mechanism is provided to illustrate the high rotational capability.

Investigations on the principle of full decoupling and type synthesis of 2R1T and 2R parallel mechanisms

2019 ◽  
Vol 43 (2) ◽  
pp. 263-271 ◽  
Author(s):  
Yundou Xu ◽  
Bei Wang ◽  
Zhifeng Wang ◽  
Yun Zhao ◽  
Wenlan Liu ◽  
...  
Keyword(s):  
Parallel Mechanism ◽  
Degrees Of Freedom ◽  
Parallel Mechanisms ◽  
Type Synthesis ◽  
Rotational Degrees Of Freedom ◽  
The Relationship

Based on the relationship between constraint wrenches and rotational axes, the principle of full decoupling of two rotational degrees of freedom (DOFs) for a two-rotation and one-translation (2R1T) parallel mechanism and two-rotation (2R) parallel mechanism with three supporting branches is systematically analyzed. Two conditions for full decoupling of two rotational DOFs of such mechanisms are obtained. The relationship between the two rotational axes of the parallel mechanisms is classified into two cases: intersecting and different. Next, based on the two conditions, type synthesis of the 2R1T and 2R parallel mechanisms with fully decoupled two rotational DOFs is carried out. A series of novel 2R1T and 2R parallel mechanisms with fully decoupled two rotational DOFs are obtained, such as RPU–UPR–RPR. Several of these mechanisms contain only eight single-DOF passive joints, one fewer than in existing mechanisms of this type, and thus have broad applications.

The Multi-Body Dynamics Analysis and Experiment of Long Distance Steel Belt Transmission

2014 ◽  
Vol 971-973 ◽  
pp. 816-822
Author(s):  
Zhi Ping Chen ◽  
En Dao Xu ◽  
Zhen Jie Zhang ◽  
Shuai Mou ◽  
Shi Feng Yue ◽  
...  
Keyword(s):  
Stress And Strain ◽  
Body System ◽  
Long Distance ◽  
Sliding Motion ◽  
Body Dynamics ◽  
Coupling Dynamics ◽  
Belt Transmission ◽  
Multi Body ◽  
The Relationship ◽  
Element Theory

This paper establishes the dynamic model of the long distance steel belt friction transmission with multi-body system rigid-flexible coupling dynamics theory, employs the boundary element theory to research the setting of the boundary conditions, and then improve the reliability of the simulation and calculation. This paper simulates and analyzes the relationship between pre-load and load,as well as that between stress and strain,so that gets the better transmission accuracy. Starting with experiment, this paper researches on the tension characteristics, running deviation and transmission accuracy of the long distance steel belt. by comparing the result of the simulation, this paper obtains the fitting function of the pre-load of the long distance steel belt and proves it have high transmission accuracy under certain condition which has proper pre-load and load.The experiment shows that the home-made precision friction transmission testbed has the ability of precision transmission. Taking advantage of the friction transmission features of steel belt, it can solve the low transmission accuracy of conventional belt transmission which results from small Elastic modulus and big elasticity sliding motion, and fulfills the long distance friction transmission on the engineering, the deviation can be smaller than 0.5%.

The Maximal Singularity-Free Workspace of the Gough–Stewart Platform for a Given Orientation

2008 ◽  
Vol 130 (11) ◽  
Author(s):  
Qimi Jiang ◽  
Clément M. Gosselin
Keyword(s):  
Case Studies ◽  
Parallel Mechanism ◽  
Stewart Platform ◽  
Parallel Robots ◽  
Analytic Method ◽  
Robot Design ◽  
Parallel Mechanisms ◽  
Leg Length ◽  
Maximal Singularity ◽  
The Relationship

The maximal singularity-free workspace of parallel mechanisms is a desirable criterion in robot design. However, for a 6DOF parallel mechanism, it is very difficult to find an analytic method to determine the maximal singularity-free workspace around a prescribed point for a given orientation. Hence, a numerical algorithm is presented in this paper to compute the maximal singularity-free workspace as well as the corresponding leg length ranges of the Gough–Stewart platform. This algorithm is based on the relationship between the maximal singularity-free workspace and the singularity surface. Case studies with different orientations are performed to demonstrate the presented algorithm. The obtained results can be applied to the geometric design or parameter (leg length) setup of this type of parallel robots.

Optimum Design of Local Cam Profile of a Valve Train

2010 ◽  
Vol 224 (11) ◽  
pp. 2487-2492 ◽  
Author(s):  
W J Qin ◽  
J Q He
Keyword(s):  
System Dynamics ◽  
Valve Train ◽  
Dynamic Responses ◽  
Dynamics Simulation ◽  
Body System ◽  
Dynamics Model ◽  
Adams Software ◽  
Cam Profile ◽  
Multi Body ◽  
The Relationship

In this paper, optimization of the local cam profile of a valve train modelled by a parameterized Bezier curve is described. Dynamic responses of the valve train are simulated through its multi-body system dynamics model built using ADAMS software. The kriging method is used to build the surrogate model, which presents the relationship between dynamic responses resulting from the multi-body system dynamics simulation and the parameters of the local Bezier profile. The local cam profile is optimized through a generic algorithm, such that the acceleration peak at the valve open phase is reduced significantly.

scholarly journals Kinematic analysis of a novel 3-CRU translational parallel mechanism

2015 ◽  
Vol 6 (1) ◽  
pp. 57-64 ◽  
Author(s):  
B. Li ◽  
Y. M. Li ◽  
X. H. Zhao ◽  
W. M. Ge
Keyword(s):  
Parallel Mechanism ◽  
Degrees Of Freedom ◽  
Jacobian Matrix ◽  
Screw Theory ◽  
Structural Characteristics ◽  
Parallel Mechanisms ◽  
Reachable Workspace ◽  
Potential Applications ◽  
Moving Platform ◽  
And Performance

Abstract. In this paper, a modified 3-DOF (degrees of freedom) translational parallel mechanism (TPM) three-CRU (C, R, and U represent the cylindrical, revolute, and universal joints, respectively) structure is proposed. The architecture of the TPM is comprised of a moving platform attached to a base through three CRU jointed serial linkages. The prismatic motions of the cylindrical joints are considered to be actively actuated. Kinematics and performance of the TPM are studied systematically. Firstly, the structural characteristics of the mechanism are described, and then some comparisons are made with the existing 3-CRU parallel mechanisms. Although these two 3-CRU parallel mechanisms are both composed of the same CRU limbs, the types of freedoms are completely different due to the different arrangements of limbs. The DOFs of this TPM are analyzed by means of screw theory. Secondly, both the inverse and forward displacements are derived in closed form, and then these two problems are calculated directly in explicit form. Thereafter, the Jacobian matrix of the mechanism is derived, the performances of the mechanism are evaluated based on the conditioning index, and the performance of a 3-CRU TPM changing with the actuator layout angle is investigated. Thirdly, the workspace of the mechanism is obtained based on the forward position analysis, and the reachable workspace volume is derived when the actuator layout angle is changed. Finally, some conclusions are given and the potential applications of the mechanism are pointed out.

Coupling Degree of Mechanism and Its Application

2006 ◽  
Author(s):  
Jing Xiong ◽  
Ting-Li Yang ◽  
Xiangdong Yang ◽  
Dongchao Yang ◽  
Ken Chen
Keyword(s):  
Dynamic Analysis ◽  
Topological Structure ◽  
Parallel Mechanism ◽  
Kinematics And Dynamics ◽  
Parallel Mechanisms ◽  
Kinematic Chains ◽  
Unified Modeling

The kinematic and dynamic analysis of an spatial multi-loop mechanism especially parallel mechanism is significant but always complex. Based on the topological structure of mechanisms, this paper proposes the concept of coupling degree of mechanism systematically, and applies it to the criterion of basic kinematic chains(BKCs) and other problems. The relation between topology, kinematics and dynamics of parallel mechanisms is established, and then it is achieved to quantitatively describe the analysis complexity of a parallel mechanism and to obtain its simplest solving path, according to its topological structure. The preliminary method for unified modeling of the topology, kinematics and dynamics of parallel mechanisms is proposed, using BKC as the basic analysis unit. Some suggestions for optimization and selective preference of parallel mechanisms are also presented.

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