A Dual Space Approach for Force/Motion Transmissibility Analysis of Lower Mobility Parallel Manipulators

2015 ◽  
Vol 7 (3) ◽  
Author(s):  
Haitao Liu ◽  
Manxin Wang ◽  
Tian Huang ◽  
Derek G. Chetwynd ◽  
Andrés Kecskeméthy
Keyword(s):  
Systematic Approach ◽  
Local Maximum ◽  
Parallel Manipulators ◽  
Joint Space ◽  
Unified Framework ◽  
Different Types ◽  
Indeterminate Form ◽  
Lower Mobility ◽  
Space Approach ◽  
Dimensional Optimization

By drawing on the duality of twist space and wrench space, this paper presents a general and systematic approach for force/motion transmissibility analysis of lower mobility nonredundant and nonoverconstrained parallel manipulators. This leads to the formulation of a complete and justifiable model that enables the force/motion transmissibility analysis to be integrated into a unified framework under the umbrella of a homogenous and decoupled linear transformation that maps the coordinates of the platform wrench/twist in the joint space to its natural coordinates in the operation space. Utilizing the penalty method to avoid the indeterminate form “0/0” when the local maximum of a virtual coefficient approaches zero, a set of dimensionally homogeneous transmission indices is proposed which can be employed for precisely representing the closeness to different types of singularities defined in twist space as well as for dimensional optimization. An example is given to illustrate the effectiveness of this approach.

A General Approach for Geometric Error Modeling of Lower Mobility Parallel Manipulators

2011 ◽  
Vol 3 (2) ◽  
Author(s):  
Haitao Liu ◽  
Tian Huang ◽  
Derek G. Chetwynd
Keyword(s):  
Systematic Approach ◽  
Parallel Manipulators ◽  
Geometric Error ◽  
Error Modeling ◽  
Kinematic Calibration ◽  
Accuracy Improvement ◽  
Linear Map ◽  
Homogeneous Transformation Matrix ◽  
Lower Mobility ◽  
Source Errors

This paper presents a general and systematic approach for geometric error modeling of lower mobility manipulators. The approach can be implemented in three steps: (1) development of a linear map between the pose error twist and source errors within an individual limb using the homogeneous transformation matrix method; (2) formulation of a linear map between the pose error twist and the joint error intensities of a lower mobility parallel manipulator; and (3) combination of these two models. The merit of this approach lies in that it enables the source errors affecting the compensatable and uncompensatable pose accuracy of the platform to be explicitly separated, thereby providing designers and/or field engineers with an informative guideline for the accuracy improvement achievable by suitable measures, i.e., component tolerancing in design, manufacturing and assembly processes, and kinematic calibration. Three typical and well-known parallel manipulators are taken as examples to illustrate the generality and effectiveness of this approach.

An Approach for Acceleration Analysis of Lower Mobility Parallel Manipulators

2011 ◽  
Vol 3 (1) ◽  
Author(s):  
Haitao Liu ◽  
Tian Huang ◽  
Derek G. Chetwynd
Keyword(s):  
Hessian Matrix ◽  
Parallel Manipulators ◽  
Unified Framework ◽  
Generalized Jacobian ◽  
New Approach ◽  
Kinematic Chains ◽  
Lower Mobility ◽  
Acceleration Analysis ◽  
Definition Of ◽  
Closure Constraints

This paper presents a new approach to the velocity and acceleration analyses of lower mobility parallel manipulators. Building on the definition of the “acceleration motor,” the forward and inverse velocity and acceleration equations are formulated such that the relevant analyses can be integrated under a unified framework that is based on the generalized Jacobian. A new Hessian matrix of serial kinematic chains (or limbs) is developed in an explicit and compact form using Lie brackets. This idea is then extended to cover parallel manipulators by considering the loop closure constraints. A 3-PRS parallel manipulator with coupled translational and rotational motion capabilities is analyzed to illustrate the generality and effectiveness of this approach.

Structure Synthesis of a Class of Parallel Manipulators with Fully Decoupled Projective Motion

2021 ◽  
pp. 1-17
Author(s):  
Chin-Hsing Kuo ◽  
Jian S. Dai
Keyword(s):  
Special Class ◽  
Degrees Of Freedom ◽  
Systematic Approach ◽  
Parallel Manipulators ◽  
Joint Space ◽  
End Effector ◽  
Geometrical Reasoning ◽  
Structure Synthesis ◽  
Decoupled Motion ◽  
One To One

Abstract This paper describes the structure synthesis of a special class of parallel manipulators with fully decoupled motion, that is, a one-to-one correspondence between the instantaneous motion space of the end-effector and the joint space of the manipulator. A notable finding of this study is that a fully decoupled design can be achieved for parallel manipulators with any number of degrees of freedom (DOFs) when the rotational DOF of the end-effector is expressed in the form of a projective angle representation. On the basis of the geometrical reasoning of the projective motion interpreted by screw algebra, a systematic approach is developed for synthesizing the structures of f-DOF (f ≤ 6) parallel manipulators with fully decoupled projective motion. Several 2-, 3-, 4-, 5-, and 6-DOF parallel manipulators with fully decoupled projective motion were designed for illustrating the developed method.

An Approach for Acceleration Analysis of Lower Mobility Parallel Manipulator

2010 ◽  
Author(s):  
Haitao Liu ◽  
Tian Huang ◽  
Derek G. Chetwynd
Keyword(s):  
Parallel Manipulator ◽  
Hessian Matrix ◽  
Parallel Manipulators ◽  
Unified Framework ◽  
Generalized Jacobian ◽  
Kinematic Chains ◽  
Lie Bracket ◽  
Lower Mobility ◽  
Acceleration Analysis ◽  
Definition Of

This paper presents an approach for velocity and acceleration analyses of lower mobility parallel manipulators. Based on the definition of the acceleration motor, the forward/inverse velocity and acceleration equations are formulated with the goal to integrate the relevant analyses under a unified framework based on the generalized Jacobian. A new Hessian matrix of serial kinematic chains (or limb) is developed in an explicit and compact form using Lie bracket. This idea is then extended to cover parallel manipulators by considering the loop closure constraints. A 3-PRS parallel manipulator with coupled translational and rotational moving capabilities is taken as example to illustrate the generality and effectiveness of this approach.

scholarly journals Multiple objects tracking in the UAV system based on hierarchical deep high-resolution network

2021 ◽  
Author(s):  
Wei Huang ◽  
Xiaoshu Zhou ◽  
Mingchao Dong ◽  
Huaiyu Xu
Keyword(s):  
High Resolution ◽  
Object Tracking ◽  
High Performance ◽  
State Of The Art ◽  
Class Imbalance ◽  
Unified Framework ◽  
Multiple Objects ◽  
Tracking Process ◽  
Objects Tracking ◽  
Different Types

AbstractRobust and high-performance visual multi-object tracking is a big challenge in computer vision, especially in a drone scenario. In this paper, an online Multi-Object Tracking (MOT) approach in the UAV system is proposed to handle small target detections and class imbalance challenges, which integrates the merits of deep high-resolution representation network and data association method in a unified framework. Specifically, while applying tracking-by-detection architecture to our tracking framework, a Hierarchical Deep High-resolution network (HDHNet) is proposed, which encourages the model to handle different types and scales of targets, and extract more effective and comprehensive features during online learning. After that, the extracted features are fed into different prediction networks for interesting targets recognition. Besides, an adjustable fusion loss function is proposed by combining focal loss and GIoU loss to solve the problems of class imbalance and hard samples. During the tracking process, these detection results are applied to an improved DeepSORT MOT algorithm in each frame, which is available to make full use of the target appearance features to match one by one on a practical basis. The experimental results on the VisDrone2019 MOT benchmark show that the proposed UAV MOT system achieves the highest accuracy and the best robustness compared with state-of-the-art methods.

scholarly journals Dimensional Synthesis of a Novel 3-URU Translational Manipulator Implemented through a Novel Method

Robotics ◽  
2022 ◽  
Vol 11 (1) ◽  
pp. 10
Author(s):  
Raffaele Di Gregorio
Keyword(s):  
Parallel Manipulators ◽  
Geometric Parameters ◽  
Dimensional Synthesis ◽  
Positioning Precision ◽  
Platform Motion ◽  
Operational Space ◽  
Lower Mobility ◽  
Novel Method ◽  
Block Diagonal

A dimensional synthesis of parallel manipulators (PMs) consists of determining the values of the geometric parameters that affect the platform motion so that a useful workspace with assigned sizes can be suitably located in a free-from-singularity region of its operational space. The main goal of this preliminary dimensioning is to keep the PM far enough from singularities to avoid high internal loads in the links and guarantee a good positioning precision (i.e., for getting good kinematic performances). This paper presents a novel method for the dimensional synthesis of translational PMs (TPMs) and applies it to a TPM previously proposed by the author. The proposed method, which is based on Jacobians’ properties, exploits the fact that TPM parallel Jacobians are block diagonal matrices to overcome typical drawbacks of indices based on Jacobian properties. The proposed method can be also applied to all the lower-mobility PMs with block diagonal Jacobians that separate platform rotations from platform translations (e.g., parallel wrists).

scholarly journals Regions of Feasible Point-to-Point Trajectories in the Cartesian Workspace of Fully-Parallel Manipulators

1999 ◽  
Author(s):  
Damien Chablat ◽  
Philippe Wenger
Keyword(s):  
Parallel Manipulator ◽  
Cartesian Product ◽  
Parallel Manipulators ◽  
Joint Space ◽  
Inverse Kinematic ◽  
Connected Components ◽  
Feasible Point ◽  
Cartesian Space ◽  
Point Trajectories ◽  
Point To Point

Abstract The goal of this paper is to define the n-connected regions in the Cartesian workspace of fully-parallel manipulators, i.e. the maximal regions where it is possible to execute point-to-point motions. The manipulators considered in this study may have multiple direct and inverse kinematic solutions. The N-connected regions are characterized by projection, onto the Cartesian workspace, of the connected components of the reachable configuration space defined in the Cartesian product of the Cartesian space by the joint space. Generalized octree models are used for the construction of all spaces. This study is illustrated with a simple planar fully-parallel manipulator.

A new class of isotropic generators for developing 6-DOF isotropic manipulators

Robotica ◽  
2008 ◽  
Vol 26 (5) ◽  
pp. 619-625 ◽  
Author(s):  
K. Y. Tsai ◽  
T. K. Lee ◽  
Y. S. Jang
Keyword(s):  
Reference Point ◽  
Parallel Manipulators ◽  
Geometric Constraint ◽  
Kinematic Chains ◽  
New Class ◽  
New Methods ◽  
Center Point ◽  
Different Types ◽  
Different Shapes ◽  
Straight Lines

SUMMARYDeveloping 6-DOF isotropic manipulators using isotropic generators is simple and efficient, and isotropic generators can be employed to develop serial, redundant, or parallel isotropic manipulators. An isotropic generator consists of a reference point and six straight lines. The existing generators, however, have one common geometric constraint: the reference point is equidistant from the six straight lines. Some practical isotropic designs might not be obtained due to this constraint. This paper proposes methods for developing new isotropic generators. The generators thus developed are not subject to the constraint, and the new methods allow us to specify the location of the tool center point, the size of the platform or the base, or the shape of isotropic parallel manipulators. Many new generators are presented to develop 6-DOF parallel manipulators with different shapes or different types of kinematic chains.

Wrench capabilities of planar parallel manipulators. Part I: Wrench polytopes and performance indices

Robotica ◽  
2008 ◽  
Vol 26 (6) ◽  
pp. 791-802 ◽  
Author(s):  
Flavio Firmani ◽  
Alp Zibil ◽  
Scott B. Nokleby ◽  
Ron P. Podhorodeski
Keyword(s):  
Parallel Manipulators ◽  
Joint Space ◽  
Linear Mapping ◽  
Redundant Manipulators ◽  
Task Space ◽  
Performance Indices ◽  
Study Case ◽  
And Performance ◽  
Planar Parallel Manipulators

SUMMARYThis paper is organized in two parts. In Part I, the wrench polytope concept is presented and wrench performance indices are introduced for planar parallel manipulators (PPMs). In Part II, the concept of wrench capabilities is extended to redundant manipulators and the wrench workspace of different PPMs is analyzed. The end-effector of a PPM is subject to the interaction of forces and moments. Wrench capabilities represent the maximum forces and moments that can be applied or sustained by the manipulator. The wrench capabilities of PPMs are determined by a linear mapping of the actuator output capabilities from the joint space to the task space. The analysis is based upon properly adjusting the actuator outputs to their extreme capabilities. The linear mapping results in a wrench polytope. It is shown that for non-redundant PPMs, one actuator output capability constrains the maximum wrench that can be applied (or sustained) with a plane in the wrench space yielding a facet of the polytope. Herein, the determination of wrench performance indices is presented without the expensive task of generating polytopes. Six study cases are presented and performance indices are derived for each study case.

Dynamic Modelling of Lower Mobility Parallel Manipulators

2019 ◽  
pp. 292-298
Author(s):  
Haitao Liu ◽  
Weifeng Chen ◽  
Tian Huang ◽  
Huafeng Ding ◽  
Andres Kecskemethy
Keyword(s):  
Dynamic Modelling ◽  
Parallel Manipulators ◽  
Lower Mobility
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