Multibody Analysis and Design of a Reconfigurable Parallel Kinematics Manipulator

2015 ◽  
Author(s):  
Matteo Palpacelli ◽  
Massimo Callegari ◽  
Luca Carbonari ◽  
Giacomo Palmieri
Keyword(s):  
Control Strategy ◽  
Degrees Of Freedom ◽  
Parallel Kinematics ◽  
Analysis And Design ◽  
Pure Rotation ◽  
Analytic Expressions ◽  
Robot Leg ◽  
Moving Platform ◽  
Actuation Systems ◽  
Three Degrees Of Freedom

This paper presents the design of a reconfigurable parallel kinematics machine endowed with three degrees of freedom of pure translation, or alternately of pure rotation. Such reconfigurability results from the use of lockable spherical joints, which realize the connection between each robot leg and the moving platform. Three actuated legs are used to drive the platform motion. The change of configuration occurs only at a specific pose, called home configuration. A control strategy allows to manage the shift phase and activate the two mobilities one at a time. Multibody simulations allowed to analyze the dynamic behavior of the manipulator and to verify the choices made with regard to the robot mechanics and the size of actuation systems. Position and differential kinematics of the manipulator are briefly introduced in order to demonstrate the simplicity of the analytic expressions and the mechanical feasibility of the manipulator.

Potential of the 3-UPU Translational Parallel Manipulator

2010 ◽  
Author(s):  
Ahmed Hachem Chebbi ◽  
Vincenzo Parenti-Castelli
Keyword(s):  
Parallel Manipulator ◽  
Degrees Of Freedom ◽  
Joint Clearance ◽  
General Frame ◽  
Pure Rotation ◽  
Work Done ◽  
Relevant Work ◽  
Three Degrees Of Freedom

The 3-UPU three degrees of freedom fully parallel manipulator, where U and P are for universal and prismatic pair respectively, is a very well known manipulator that can provide the platform with three degrees of freedom of pure translation, pure rotation or mixed translation and rotation according to the relative directions of the revolute axes. Many studies have been reported in the literature on singularities, workspace and joint clearance influence on the platform accuracy of this manipulator. However, much work has still to be done to reveal all the features this topology can offer to the designer. This paper collects the previous most relevant work done on the 3-UPU parallel manipulator and shows the main results in a coherent general frame. The paper proposes new architectures of the 3-UPU manipulator which offer interesting features to the designer. Finally, based on a number of indexes, a procedure is proposed that allows the designer to select the best architecture of the 3-UPU manipulator for a given task.

Analysis and simulation of a new Cartesian cable-suspended robot

2009 ◽  
Vol 224 (8) ◽  
pp. 1717-1726 ◽  
Author(s):  
G Castelli ◽  
E Ottaviano ◽  
A González
Keyword(s):  
Numerical Simulation ◽  
Degrees Of Freedom ◽  
Robot Arm ◽  
Fixed Frame ◽  
Cartesian Space ◽  
Compliant Assembly ◽  
Moving Platform ◽  
Geometry Analysis ◽  
Three Degrees Of Freedom

In this article, a manipulator is presented belonging to the class of cable-suspended robots, for which the cable length variations are related by suitable functions in order to achieve specific kinematic characteristics. In particular, in this article, a Cartesian cable-suspended robot is proposed that has eight cables to have three degrees of freedom (DOF) in Cartesian space. The eight cables of the robot are arranged in parallel by pairs with identical length, with the aim of constraining the moving platform to keep a constant orientation with respect to the fixed frame. The robot can be used for selective compliant assembly robot arm (SCARA) motions (when an additional revolute actuated joint is placed on the moving platform) for a variety of applications in which a large workspace is required. In this article, a geometry analysis of the robot is presented together with a numerical simulation of the kinetostatics and dynamics to investigate the robot's performances in several operative conditions. Furthermore, a characterization of the position workspace regions is reported for this cable-suspended robot.

Study on Scanner for Large-Diameter Tubular Joint Welds Based on Ultrasonic Phased Array

2006 ◽  
Vol 532-533 ◽  
pp. 265-268
Author(s):  
Zong Quan Deng ◽  
Guang Ping Hao ◽  
De Wei Tang ◽  
Bao Hua Shan
Keyword(s):  
Control Strategy ◽  
Degrees Of Freedom ◽  
Phased Array ◽  
Large Diameter ◽  
Ultrasonic Inspection ◽  
The Other ◽  
Tubular Joints ◽  
Ultrasonic Phased Array ◽  
Tubular Joint ◽  
Three Degrees Of Freedom

For the complexity of weld, the automatic inspecting for the tubular joints which are in working is difficult. Therefore the scanner which has three degrees of freedom for inspecting of large-diameter tubular joints was studied and manufactured based on the scanning principle of ultrasonic phased array. The following of probe to weld is realized by the simultaneous motion of two degrees of freedom and the pose between probe and weld is adjusted by the other degree of freedom. The control strategy of the scanner was provided. Experiments were made with scanner on reference blocks, the results indicate that the automatic ultrasonic phased array inspection is more excellent than the conventional ultrasonic inspection in reliability and repetition.

The Nonexistence of Three Degrees of Freedom Rotational Fully Decoupled Parallel Mechanism

2013 ◽  
Vol 284-287 ◽  
pp. 1951-1955 ◽  
Author(s):  
Yu Lei Hou ◽  
Da Xing Zeng ◽  
Yan Bin Duan ◽  
Yong Sheng Zhao
Keyword(s):  
Control System ◽  
Parallel Mechanism ◽  
Degrees Of Freedom ◽  
Screw Theory ◽  
Structure Design ◽  
Theoretical Significance ◽  
Moving Platform ◽  
Configuration Synthesis ◽  
Three Degrees Of Freedom ◽  
Serial Mechanism

The existence of coupling makes the parallel mechanism possess some special advantages over the serial mechanism, while it is just the coupling that brings about the parallel mechanism some difficulties in kinematics and dynamic analysis, the development of control system, and the trajectory planning. Therefore the research on the decoupled parallel mechanism becomes one of the hot of the mechanism fields. While whether the parallel mechanism can realize decouple is the premise for synthesis and analysis of the parallel mechanism. Based on screw theory, the existence of the three degrees of freedom (3-DoF) rotational fully-decoupled parallel mechanism is distinguished. Then taking the 6-PUS/UPU parallel mechanism as example, the rotation angles of the moving platform are measured, which is verified the impossibility of the 3-DoF rotation decoupling. The contents of this paper should possess theoretical significance for the innovative configuration synthesis and structure design of rotational decoupled parallel mechanism.

Full-Mobility Three-CCC Parallel-Kinematics Machines: Kinematics and Isotropic Design

2017 ◽  
Vol 10 (1) ◽  
Author(s):  
Wei Li ◽  
Jorge Angeles
Keyword(s):  
Kinematic Analysis ◽  
Degrees Of Freedom ◽  
Large Region ◽  
Parallel Kinematics ◽  
Six Degrees Of Freedom ◽  
Parallel Kinematics Machines ◽  
The Subject ◽  
Moving Platform

The subject of this paper is twofold: the kinematics and the isotropic design of six degrees-of-freedom (DOF), three-CCC parallel-kinematics machines (PKMs). Upon proper embodiment and dimensioning, the PKMs discussed here, with all actuators mounted on the base, exhibit interesting features, not found elsewhere. One is the existence of an isotropy locus, as opposed to isolated isotropy points in the workspace, thereby guaranteeing the accuracy and the homogeneity of the motion of the moving platform (MP) along different directions within a significantly large region of their workspace. The conditions leading to such a locus are discussed in depth; several typical isotropic designs are brought to the limelight. Moreover, the kinematic analysis shows that rotation and translation of the MP are decoupled, which greatly simplifies not only the kinetostatic analysis but also, most importantly, their control. Moreover, it is shown that the singularity loci of this class of mechanism are determined only by the orientation of their MP, which also simplifies locus evaluation and eases its representation.

scholarly journals A Tabular Format for Computing Inverse Kinematic Equations for a 3DOF Robot Leg

10.5772/7234 ◽  
2009 ◽  
Vol 6 (3) ◽  
pp. 26 ◽  
Author(s):  
F. Nickols
Keyword(s):  
Power Series ◽  
High Speed ◽  
Degrees Of Freedom ◽  
Inverse Kinematic ◽  
Coordinate Space ◽  
Power Series Method ◽  
Cylindrical Coordinate ◽  
Field Programmable ◽  
Robot Leg ◽  
Three Degrees Of Freedom

A method is presented for accurately computing the three servomechanism angles that place the leg tip of a 3DOF robot leg in cylindrical coordinate space, R, θ, Z. The method is characterized by (i) a multivariable integer power series for each degree of freedom that can be used to replace traditional trigonometrical functions, and, (ii) only integer numbers are used. A technique is shown that derives the coefficients, Ci j k, of each of the terms in the series that represents a servomechanism angle, S. This power series method has the advantage of; (i) satisfying accuracy requirements, (ii) producing a unique solution, (iii) high speed realtime computation, (iv) low memory requirement and (v) implementation into a generic algorithm or hardware such as a field programmable gate array. The series can represent many continuous kinematic systems just by changing the values of the coefficients. The coefficients are rapidly computed via a spreadsheet. The method can be extended to more than three degrees of freedom and also mapped into other coordinate frames such as a Cartesian or spherical.

Miniature Tripod with Parallel Kinematics for Use in Clean Room Medical Laboratory Applications

2015 ◽  
Vol 220-221 ◽  
pp. 116-125
Author(s):  
Andrzej Zbrowski
Keyword(s):  
Degrees Of Freedom ◽  
Kinematic Chain ◽  
Medical Laboratory ◽  
Modular Construction ◽  
Parallel Kinematics ◽  
Medical Test ◽  
End Effector ◽  
Freedom Movement ◽  
Scanning Systems ◽  
Three Degrees Of Freedom

The paper presents the structure of a precise parallel tri-axle manipulator with the functionality of progressing-tilting table. The end effector of the device is a platform, for which three coordinates of position are defined. The manipulator has three degrees of freedom: movement perpendicular to the base and rotation in two mutually perpendicular axes contained in the surface parallel to the base.The concept of the positioning mechanism is based on parallel tripod kinematics where the end effector – the platform – is seated on three active limbs – actuators. The use of parallel kinematics allowed modular construction of the positioning mechanism. The developed modular functional mechanism with minimal number of elements in kinematic chain ensures high positioning resolution. The concept of application of eccentric mechanism for platform positioning is an original idea in this solution. The compact construction allows applying the manipulator in medical devices that require meeting of the hygienic conditions in the medical test and research laboratories. The possibility of the utilisation of the precise manipulator covers wide areas of science and technology where precise positioning of the object is required, e.g. sample positioning for microscopes, scanning systems.

scholarly journals Robust Control Design of Active Front-Wheel Steering on Low-Adhesion Road Surfaces

2021 ◽  
Vol 12 (3) ◽  
pp. 153
Author(s):  
Chuanwei Zhang ◽  
Bo Chang ◽  
Jianlong Wang ◽  
Shuaitian Li ◽  
Rongbo Zhang ◽  
...  
Keyword(s):  
Robust Control ◽  
Control Strategy ◽  
Degrees Of Freedom ◽  
Reference Model ◽  
Front Wheel ◽  
Good Path ◽  
Road Surfaces ◽  
Robust Control Design ◽  
The Stability ◽  
Three Degrees Of Freedom

In order to improve the stability of vehicle steering on low-adhesion road surfaces, this paper designed a hybrid robust control strategy, H2/H∞, for active front-wheel steering (AFS) based on robust control theory. Firstly, we analyzed the influence of the sidewall stiffness and road adhesion coefficient of the tires on vehicle stability, through which we can study the wheel deflection characteristics of low-adhesion roads. Secondly, the reference yaw velocity of the vehicle was calculated using the three-degrees-of-freedom model as the reference model, through which, taking the norm H∞ as the objective function and the norm H2 as the limit to control the output, the hybrid robust control strategy H2/H∞ of the AFS system on a low-adhesion road surface was developed. Finally, the simulation experiment was carried out by the Simulink/CarSim co-simulation platform and a hardware-in-the-loop (HIL) experiment. In this paper, the results show that the AFS control strategy can improve the vehicle handling stability on low-adhesion road surfaces, and the controller has good path tracking performance and robustness.

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