Static and dynamic characterization of the 6-Dofs parallel robot 3CRS (original) (raw)
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Stiffness Analysis of Parallel Manipulator Using Matrix Structural Analysis
Proceedings of EUCOMES 08
The paper generalizes existing contributions to the stiffness modeling of robotic manipulators using Matrix Structural Analysis. It presents a unified and systematic approach that is suitable for serial, parallel and hybrid architectures containing closed-loops, flexible links, and rigid connections, passive and elastic joints, flexible and rigid platforms, taking into account external loadings and preloadings. The proposed approach can be applied to both under-constrained, fully-constrained and over-constrained manipulators in generic and singular configurations, it is able to produce either non-singular or rank-deficient Cartesian stiffness matrices in a semi-analytical manner. It is based on a unified mathematical formulation that presents the manipulator stiffness model as a set of two groups of matrix equations describing elasticity of separate links and connections between the links in the form of constraints. Its principal advantage is the simplicity of the model generation that includes straightforward aggregation of link/joint equations without conventional merging of rows and columns in the global stiffness matrix. The advantages of this method and its application are illustrated by an example that deals with the stiffness analysis of NaVaRo parallel manipulator.
Kinematic and Dexterity Analysis of a 3-DOF Parallel Manipulator
A new three Degree Of Freedom (3-DOF) parallel manipulator has been proposed in this study. Because the parallel manipulator has three Degree Of Freedom (DOF), one translation degree of freedom and two rotational degrees of freedom, it has received considerable attention from both researchers and manufacturers over the past years. The inverse kinematic and Jacobain matrix were derived. The dexterity of the parallel manipulator is presented. The key issue of how the kinematic performance in term of dexterity varies with differences in the structural parameters of the parallel manipulator is investigated. The simulation results, using MATLAB, testify the validity of the analytic model and illustrate the structural parameters have direct effect upon dexterity characteristic of the 3-DOF parallel manipulator.
Performance based design optimization of an intrinsically compliant 6-dof parallel robot
Mechanics Based Design of Structures and Machines, 2020
Parallel robots are preferred over serial robots owing to their enhanced accuracy and rigidity which comes from their higher stiffness. However, there are applications both in industry and in healthcare where higher accuracy is required alongside high compliance (reduced stiffness). Accuracy and compliance being conflicting to each other are difficult to achieve simultaneously. To address this issue, an intrinsically compliant 6dof parallel robot is proposed in this work. Kinematic and analytical modeling is performed for its conceptual design to obtain the Jacobian matrix and thereby map the joint and Cartesian spaces. Robot's structure design is analyzed, and the wrench analysis is also carried out to estimate the link forces and stiffness. It is shown that by small changes in the proposed robot design; its compliance can be altered making it suitable for a range of applications. It is also shown mathematically that the robot design can be optimized to maintain higher accuracy together with higher compliance. To carry out design optimization, three important performance criteria, namely; global condition number (for higher accuracies), norm of link forces (to reduce actuator power requirement) and robot compliance (for response to an external wrench) are mathematically formulated. Later, a multi-criteria optimization is performed using an evolutionary algorithm to simultaneously optimize these performance criteria. From the final robot design selected, it is evident that a higher robot compliance with optimal condition number and link forces can be achieved.
Latin American Journal of Solids and Structures, 2016
The effects of distinctive parameters such as revolute joint angle or spherical joint location of mobile platform in a 6-DOF 6-RUS parallel manipulators on workspace, kinematic, and dynamic indices are investigated in this study to select proper structure commensurate with performance. Intelligent multi-objective optimization method is used to design the manipulator. Considering distinctive parameters, relevant relations for developing inverse kinematic and Jacobin matrix are obtained. In order to study dynamic properties, mass matrix is obtained from calculating the total kinetic energy of the manipulator. After modifying multi-objective Bees algorithm, it used to optimize the manipulator structure considering all geometrical parameters with proper constraints. In addition of comparison of three well known 6-RUS manipulators' types, variation diagram of workspace, local and global dynamics and kinematics performance indices have been drawn with respect to structural parameters variation and limitation of these parameters with proper value are determined. Moreover, considering all dimensional parameters, Pareto front line of multi objective optimization of structure is presented based on dynamic and kinematic performance in predetermined workspace. Based on the results, a fairly comparison among various types of 6-RUS manipulators can be conducted and the most appropriate set of dimensional parameters are selected based on specific demand.
Dynamic modelling of a parallel robot with six degrees of freedom
2010
Parallel robots seem to be the most suitable spots requiring high performance such as speed and accuracy. Such performances sought now are that the dynamics of parallel structures is no longer negligible. This work represents a contribution in this latter context; it deals in the whole dynamic study of a parallel robot with six degrees of freedom constituting the so-called Gough Stewart platform. In determining the direct and inverse geometric model, we use a setup based on Khalil and Kleinfinger ratings [7] for structures with closed loops. The kinematical modeling, using the calculation of the Jacobian matrix and its inverse, were deduced from the joint velocities of the six cylinders in order to follow a desired trajectory for the platform. The Newton Euler formalism is used to model the dynamics of the robot and the first to consider each kinematics chain (legs) as a serial structure, and then by considerations of balance and closed chain, we determine the dynamics of the platform.
The Kinematics and the Full Minimal Dynamic Model of a 6DOF Parallel Robot Manipulator
Nonlinear Dynamics, 1999
In this paper we present a particular architecture of parallel robots which has six-degrees-of-freedom (6-DOF) with only three limbs. The particular properties of the geometric and kinematic models with respect to that of a classical parallel robot are presented. We show that inverse problems have an analytical solution. However, to solve the direct problems, an efficient numerical procedure which needs
Assessment of Parallel Robot Dynamic Characteristics, 2022
The high accuracy of industrial robots is the main aim of designers and manufacturers, one of the effective factors to get the goal is the stability of the robot structure, the determination of the structural dynamic characteristics is the main step to evaluate the performance also unlock the knowledge of amendment and improvement of the structure to get the optimum design. In this paper, two methods were applied to evaluate the dynamic structural performance of three degrees of freedom parallel robot, firstly, experimental modal analysis was applied to a multi-model with different platform dimensions using a data acquisition system, the natural frequencies, and damping ratios for all models were obtained to be evaluated and correlated with the second method. The measured models were modeled using Solidworks software and exported to Ansys finite element (FE) software, the modeled systems were used to obtain natural frequencies, damping ratios, and mode shapes from frequency response curve (FRF) and modal analysis, the results of experimental and FEM work were correlated to evaluate the system performance and verify the accuracy of the two methods. The results give a clear view to operators about the range of frequencies that must be avoided during the selection of machining operation, provide the scope of errors between the used methods, and supply a valuable guide to evaluate the quality of the structural integrity of the parallel robot.
Characterisation of parallel kinematic machines based on structural workspaces
Mechanics & Industry, 2013
In this paper, we present the static and dynamic structural characterisation of a low-mobility parallel kinematic manipulator, involving analysis of its stiffness and vibrational dynamic behaviour. The study starts by building numerical models of the behaviour of the manipulator to be compared to experimental measurements from a prototype. For the case study, we consider a four-degree-of-freedom (x, y, z, θz) manipulator with prismatic actuators designed by the COMPMECH research group at the University of the Basque Country. The characterisation allows the behaviour of the static and dynamic stiffness, as well as the natural frequencies of the manipulator, to be mapped in the manipulator workspace. These maps together with kinematic, static and dynamic constraints lead to the definition of operational, static, dynamic and structural workspaces, respectively. Further, we analyse the modes of the manipulator to determine dynamic displacements, these being key in the performance in the machining tasks for which the robot was designed.
Kinematic design of a family of 6-DOF partially decoupled parallel manipulators
2009
Parallel manipulators (PMs) with 6-DOF decoupled motion can simplify the manipulator kinematics and thus facilitate its motion planning and control. This paper studies the kinematic design of a family of partially decoupled parallel manipulators (DPMs) with 3-limb symmetrical structure, in which 3-DOF spatial motion composed of a vertical translation and two horizontal rotations can be independently controlled. The concept of group decoupling (GD) is introduced for classification and synthesis of decoupled motion PMs. Type synthesis of this manipulator family is carried out systematically based on GD and wrench system analysis. As a result, six DPM architectures, five of which are new, are obtained from this exercise. Instantaneous kinematics shows that the order of the Jacobian matrices of the newly found manipulator architectures can be reduced from six to three. The reduction of Jacobian order for the decoupled motion PMs facilitates analysis of manipulator singularity, displacement and statics. Hence, the approach can be utilized for decoupled PMs in other decoupled motion groups.
Kinematic and Dynamic Analysis of a 3-PRUS Spatial Parallel Manipulator
Chinese Journal of Mechanical Engineering, 2020
Parallel Kinematic Machines (PKMs) are being widely used for precise applications to achieve complex motions and variable poses for the end effector tool. PKMs are found in medical, assembly and manufacturing industries where accuracy is necessary. It is often desired to have a compact and simple architecture for the robotic mechanism. In this paper, the kinematic and dynamic analysis of a novel 3-PRUS (P: prismatic joint, R: revolute joint, U: universal joint, S: spherical joint) parallel manipulator with a mobile platform having 6 Degree of Freedom (DoF) is explained. The kinematic equations for the proposed spatial parallel mechanism are formulated using the Modified Denavit-Hartenberg (DH) technique considering both active and passive joints. The kinematic equations are used to derive the Jacobian matrix of the mechanism to identify the singular points within the workspace. A Jacobian based stiffness analysis is done to understand the variations in stiffness for different poses ...