A Comparative Study on Motion Characteristics of Three Two-Degree-of-Freedom Pointing Mechanisms

2016 ◽  
Vol 8 (2) ◽  
Author(s):  
Jingjun Yu ◽  
Kang Wu ◽  
Guanghua Zong ◽  
Xianwen Kong
Keyword(s):  
Parallel Manipulators ◽  
Degree Of Freedom ◽  
Pure Rolling ◽  
Motion Characteristics ◽  
And Control ◽  
Self Motion ◽  
Tracking Devices ◽  
Two Degree Of Freedom ◽  
Typical Difference ◽  
Composition Theorem

Two-degree-of-freedom (2DOF) pointing mechanisms have been widely used in areas such as stabilized platforms, tracking devices, etc. Besides the commonly used serial gimbal structures, another two types of parallel pointing mechanisms, i.e., spherical parallel manipulators (SPMs) and equal-diameter spherical pure rolling (ESPR) parallel manipulators, are increasingly concerned. Although all these pointing mechanisms have two rotational DOFs, they exhibit very different motion characteristics. A typical difference existing in these three pointing mechanisms can be found from their characteristics of self-motion, also called spinning motion by the authors. In this paper, the spinning motions of three pointing mechanisms are modeled and compared via the graphical approach combined with the vector composition theorem. According to our study, the spinning motion is essentially one component of the moving platform's real rotation. Furthermore, image distortions caused by three spinning motions are identified and distinguished when the pointing mechanisms are used as tracking devices. Conclusions would facilitate the design and control of the pointing devices and potentially improve the measuring accuracy for targets pointing and tracking.

Comparison Study on Motion Characteristics of Three 2-DOF Pointing Devices

2014 ◽  
Author(s):  
Kang Wu ◽  
Jingjun Yu ◽  
Guanghua Zong ◽  
Xianwen Kong
Keyword(s):  
Optical Sensors ◽  
Parallel Manipulators ◽  
The Self ◽  
Pointing Device ◽  
Basic Image ◽  
Motion Characteristics ◽  
Self Motion ◽  
Human Eyes ◽  
Realistic Images ◽  
Two Degree Of Freedom

Two degree-of-freedom (DOF) manipulators have been widely applied in pointing devices. Besides the commonly used gimbal platforms, two different kinds of parallel platforms base on parallel manipulators are presented as real applications in this paper. In a situation, a pointing device acquires and tracks a remote target via optical sensors amounted on the device. As the authors’ recent research, there are image distortions caused by deflected camera axis while the pointing device changing its attitudes. The paper refers the phenomena to the self-motion characteristics as the 2-DOF platforms rotate around the fixed platform axis. Basic image distortion principles of the three platforms are illustrated and discussed. Relationship between the self-motion and revolution are analyzed via the graphic approach and simulated on the software. Results indicate that these different phenomena are due to the different inherent characters of the platform’s freedom lines and freedom disks. Conclusions revealed in this paper would help the engineers with the type selections and applications, especially for the remote virtual reality devices which can provide realistic images for the human eyes. This work will facilitate the image processing and improve the measuring accuracy for the pointing devices.

Two-Degree-of-Freedom Helicopter Closed-Loop Identification through a Cascade Controller

2011 ◽  
Vol 403-408 ◽  
pp. 4649-4658 ◽  
Author(s):  
Pouya Ghalei ◽  
Alireza Fatehi ◽  
Mohamadreza Arvan
Keyword(s):  
Closed Loop ◽  
Flight Simulation ◽  
Degree Of Freedom ◽  
Input Output ◽  
Closed Loop Identification ◽  
Practical Algorithm ◽  
Nonlinear Autoregressive Model ◽  
And Control ◽  
Nonlinear Autoregressive ◽  
Two Degree Of Freedom

Input-Output data modeling using multi layer perceptron networks (MLP) for a laboratory helicopter is presented in this paper. The behavior of the two degree-of-freedom platform exemplifies a high order unstable, nonlinear system with significant cross-coupling between pitch and yaw directional motions. This paper develops a practical algorithm for identifying nonlinear autoregressive model with exogenous inputs (NARX) and nonlinear output error model (NOE) through closed loop identification. In order to collect input-output identifier pairs, a cascade state feedback (CSF) controller is introduced to stabilize the helicopter and after that the procedure of system identification is proposed. The estimated models can be utilized for nonlinear flight simulation and control and fault detection studies.

Workspace optimization of a class of zero-torsion parallel wrists

Robotica ◽  
2018 ◽  
Vol 37 (7) ◽  
pp. 1174-1189 ◽  
Author(s):  
Yuanqing Wu ◽  
Marco Carricato
Keyword(s):  
Tilt Angle ◽  
General Class ◽  
Parallel Manipulators ◽  
Degree Of Freedom ◽  
Geometric Properties ◽  
Large Rotation ◽  
Workspace Optimization ◽  
Two Degree Of Freedom

SUMMARYWe present singularity-free workspace optimization of a class of two-degree-of-freedom (2-DoF) parallel wrists with large rotation range capability. The wrists in consideration are kinematically equivalent to two families of 2-DoF homokinetic couplings. The first family comprises fully parallel wrists with N (N ≥ 3) double-universal ($\mathcal{UU}$) legs. The second family comprises spherical N-$\mathcal{UU}$ parallel wrists with interconnecting revolute ($\mathcal{R}$) joints. Both families belong to the more general class of zero-torsion parallel manipulators, and are, therefore, collectively referred to as zero-torsion wrists (ZTWs). We carry out a unified singularity-free workspace optimization by utilizing geometric properties of zero-torsion motion manifolds. Our work may serve as a conceptual guide to the design of ZTWs for large tilt-angle applications.

Motion Performance Analysis of Double-Cylinder Parallel Manipulators

2009 ◽  
Author(s):  
Hong Zhou ◽  
Shehu T. Alimi ◽  
Aravind Ravindranath ◽  
Hareesh Vepuri
Keyword(s):  
Performance Analysis ◽  
Parallel Manipulator ◽  
Critical Role ◽  
Parallel Manipulators ◽  
Degree Of Freedom ◽  
Serial Manipulators ◽  
Operation Speed ◽  
Transmission Angle ◽  
Motion Performance ◽  
Two Degree Of Freedom

Double-cylinder parallel manipulators are closed-loop two-degree-of-freedom linkages. They are preferred to use because of their simplicity plus the common advantages of parallel manipulators such as high stiffness, load-bearing, operation speed and precision positioning. Like other parallel manipulators, the output motion of double-cylinder parallel manipulators is not as flexible as two-degree-of-freedom serial manipulators. The motion performance analysis plays a critical role for this type of parallel manipulator to be applied successfully. In this paper, the linkage feasibility conditions are established based on the transmission angle. When feasibility conditions are satisfied, there is no dead position during operation. The workspace is generated by using curve-enveloping theory. The singularity characteristics are analyzed within the workspace. The motion performance index contours within the workspace are produced using the condition number of the manipulator Jacobian matrix. The results of this paper provide guidelines to apply this type of parallel manipulator.

DYNAMICS AND CONTROL OF A TWO-DEGREE-OF-FREEDOM VIBRATION-DRIVEN SYSTEM

2007 ◽  
Vol 40 (14) ◽  
pp. 109-114
Author(s):  
Nikolai N. Bolotnik ◽  
Mikhail Pivovarov ◽  
Igor Zeidis ◽  
Klaus Zimmermann
Keyword(s):  
Degree Of Freedom ◽  
Driven System ◽  
Dynamics And Control ◽  
And Control ◽  
Two Degree Of Freedom

Analysis of the Spinning Motion and the Orientation Description Methods for 2-DOF RMs

2018 ◽  
Author(s):  
Liu Kai ◽  
Yu Jingjun ◽  
Kong Xianwen
Keyword(s):  
Virtual Prototype ◽  
Degree Of Freedom ◽  
Graphical Approach ◽  
Motion Models ◽  
Motion Characteristic ◽  
Motion Characteristics ◽  
Two Degree Of Freedom ◽  
Rotational Freedom

In this work, two degree-of-freedom rotational mechanisms (2-DOF RMs) also called 2-DOF pointing mechanisms are discussed systematically about their motion characteristic and orientation description methods. Based on the graphical approach, 2-DOF RMs are divided into three types in term of the features of their instantaneous rotational freedom lines, and the models of the spinning motions for all the three types of 2-DOF RMs are built respectively by constraint conditions. According to the spinning motion models, the orientation description methods suitable for the three types of 2-DOF RMs are introduced in detail severally to simplify the kinematic equations in succedent work. Then the correctness of the spinning motion models is verified via the virtual prototype simulation with several examples. Finally, the methods suitable for describing the orientation of these mechanisms are proposed. Conclusions would facilitate the analysis of kinematics of 2-DOF RMs and exhibit the motion characteristics of 2-DOF RMs expressly.

Type Synthesis of 2-DOF Rotational Parallel Manipulators With an Equal-Diameter Spherical Pure Rolling Motion

2013 ◽  
Author(s):  
Kang Wu ◽  
Jingjun Yu ◽  
Guanghua Zong ◽  
Xianwen Kong
Keyword(s):  
Theoretical Model ◽  
Parallel Manipulators ◽  
Rolling Motion ◽  
Geometrical Parameters ◽  
Graphic Method ◽  
Type Synthesis ◽  
Pure Rolling ◽  
Lower Mobility ◽  
Two Degree Of Freedom ◽  
Conventional Type

Two-degree-of-freedom (2-DOF) rotational parallel manipulators (RPMs) have been widely used in pointing devices and robot wrists. This paper focuses on a class of 2-DOF RPMs achieving an equal-diameter spherical pure rolling motion (ESPRM) around the base. At first, a theoretical model of spherical pure rolling motion is analyzed and the characteristic of the associated constraint space is derived. Taking the Omni-Wrist III as a typical 2-DOF RPMs with an equal-diameter spherical pure rolling motion, mappings between the geometry and the motion are established and eight useful constraint conditions are derived which will be instructive for the type synthesis. Then, with focus on symmetrical structures, nine classes of 2-DOF RPMs with equal-diameter spherical pure rolling motion are synthesized based on the graphic method. Most of these RPMs have already been used in practice. Unlike the conventional type synthesis of lower-mobility parallel manipulators in literatures, some geometrical parameters of links, in addition to the distributions of joints and limbs, are taken into consideration in the type synthesis in this paper. This proposed research may help produce novel architectures.

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