Optimization of Redundant-Limb Layout in Cable-Driven Parallel Manipulators

2008 ◽  
Author(s):  
Mahir Hassan ◽  
Amir Khajepour
Keyword(s):  
Parallel Manipulators ◽  
Degree Of Freedom ◽  
Mobile Platform ◽  
Optimization Approach ◽  
Cable Tension ◽  
Tensile Forces

Cable-driven mechanisms can be used as fast pickup-and-place manipulators due to the low inertia of the cables. Maintaining cable tension can be achieved by cylinders applying forces on the mobile platform to generate tensile forces in the cables to prevent cable slack during the operation. This paper presents an optimization approach to determine the optimum layout of the cylinders in the manipulator, i.e., the optimum positions of the cylinders connection points on the mobile platform and the base. The goal of this optimization is to achieve the desired distribution of the generated tension across the cables. An example 6-degree-of-freedom spatial manipulator is presented where this approach is applied to optimize the layout of one, two and three cylinders.

Analysis of Hybrid Cable-Actuated Parallel Manipulators With a Constraining Leg for Lower-Degree-of-Freedom Operation

2009 ◽  
Author(s):  
Mahir Hassan ◽  
Amir Khajepour
Keyword(s):  
Parallel Manipulators ◽  
Degree Of Freedom ◽  
Lower Degree ◽  
Redundant Actuation ◽  
Task Space ◽  
Cable Tension ◽  
Task Constraints ◽  
Rigid Link ◽  
Moving Platform

This paper presents a kinetostatic analysis of a class of hybrid cable-driven parallel manipulators consisting of cables and a rigid-link serial leg for lower-degree-of-freedom tasks. The serial leg provides the task constraints and the cables provide the required actuation to move the platform in the task space. Having a rigid-link serial leg providing the required constraints for the moving platform in lower-degree-of-freedom applications reduces the number of cables required to support the moving platform in the task space. As a result, the manipulator can be designed with fewer cables and actuators. In order for the manipulator to balance arbitrary applied wrenches, redundant actuation is required. This redundant actuation can be obtained from a redundant actuator mounted on one (or more) serial-leg joint(s). Conditions for analyzing the capability of the redundant actuation to generate cable tension are explained in the paper. A discussion is also given on the optimization of the cable layout and the redundant actuator forces to minimize the tension generated in the cables.

Determination of the Workspace of 6-DOF Parallel Manipulators

1989 ◽  
Author(s):  
C. Gosselin
Keyword(s):  
Parallel Manipulator ◽  
Graphical Representation ◽  
Three Dimensional ◽  
Parallel Manipulators ◽  
Degree Of Freedom ◽  
Geometrical Properties ◽  
Cartesian Space ◽  
Six Degree Of Freedom

Abstract This paper presents an algorithm for the determination of the workspace of parallel manipulators. The method described here, which is based on geometrical properties of the workspace, leads to a simple graphical representation of the regions of the three-dimensional Cartesian space that are attainable by the manipulator with a given orientation of the platform. Moreover, the volume of the workspace can be easily computed by performing an integration on its boundary, which is obtained from the algorithm. Examples are included to illustrate the application of the method to a six-degree-of-freedom fully-parallel manipulator.

Determination of the Singularity Loci of Spherical Three-Degree-of-Freedom Parallel Manipularors

1992 ◽  
Author(s):  
Clément M. Gosselin ◽  
Jaouad Sefrioui
Keyword(s):  
Graphical Representation ◽  
Jacobian Matrix ◽  
Parallel Manipulators ◽  
Degree Of Freedom ◽  
End Effector ◽  
Cartesian Space ◽  
Singularity Locus ◽  
Three Degree Of Freedom ◽  
Analytical Expressions

Abstract In this paper, an algorithm for the determination of the singularity loci of spherical three-degree-of-freedom parallel manipulators with prismatic atuators is presented. These singularity loci, which are obtained as curves or surfaces in the Cartesian space, are of great interest in the context of kinematic design. Indeed, it has been shown elsewhere that parallel manipulators lead to a special type of singularity which is located inside the Cartesian workspace and for which the end-effector becomes uncontrollable. It is therfore important to be able to identify the configurations associated with theses singularities. The algorithm presented is based on analytical expressions of the determinant of a Jacobian matrix, a quantity that is known to vanish in the singular configurations. A general spherical three-degree-of-freedom parallel manipulator with prismatic actuators is first studied. Then, several particular designs are investigated. For each case, an analytical expression of the singularity locus is derived. A graphical representation in the Cartesian space is then obtained.

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.

The Ray Optimization Method for the Determination of Workspaces of Planar Parallel Manipulators of General Design

2000 ◽  
Author(s):  
A. M. Hay ◽  
J. A. Snyman
Keyword(s):  
Computer Code ◽  
Parallel Manipulators ◽  
Optimization Method ◽  
Optimization Approach ◽  
Arbitrary Geometry ◽  
Planar Manipulators ◽  
Planar Parallel Manipulator ◽  
Point Interior ◽  
General Method

Abstract An extension to a novel optimization approach for the determination of workspaces of planar manipulators is presented. This approach provides a general method for the determination of manipulator workspaces and has the advantage that it may easily be automated. The method consists of finding a suitable initial radiating point interior to the accessible output set of the manipulator, and then determining the points of intersection of a representative pencil of rays, emanating from this point, with the boundary of the accessible set. The points of intersection are determined by means of an optimization approach in which a dynamic constrained optimization algorithm is used. If any section of the workspace boundary cannot be determined due to non-convexity, then the missing section is mapped using a suitably chosen new radiating point. The method is illustrated by its application to a generally constrained planar parallel manipulator. The method has been implemented in a practical, interactive computer code that has been used to determine convex and non-convex workspaces of different parallel manipulators of arbitrary geometry.

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.

Sensitivity of Muscle Force Estimations to Changes in Muscle Input Parameters Using Nonlinear Optimization Approaches

1992 ◽  
Vol 114 (2) ◽  
pp. 267-268 ◽  
Author(s):  
Walter Herzog
Keyword(s):  
Nonlinear Optimization ◽  
Muscle Force ◽  
Anatomical Variations ◽  
Degree Of Freedom ◽  
Optimization Approach ◽  
Force Sharing ◽  
Input Parameters ◽  
Synergistic Muscles

The purpose of this study was to analyze the sensitivity of muscle force calculations to changes in muscle input parameters. Force sharing between two synergistic muscles was derived analytically for a one-degree-of-freedom system using three nonlinear optimization approaches. Changes in input parameters that are within normal anatomical variations often caused changes in muscular forces exceeding 100 percent. These results indicate that errors in muscle force calculations may depend as much on inadequate muscle input parameters as they may on the choice of the objective and constraint functions of the optimization approach.

A Novel Five-Degree-of-Freedom Parallel Manipulator and Its Kinematic Optimization

2014 ◽  
Vol 6 (4) ◽  
Author(s):  
Yimin Song ◽  
Binbin Lian ◽  
Tao Sun ◽  
Gang Dong ◽  
Yang Qi ◽  
...  
Keyword(s):  
Design Method ◽  
Dynamic Performance ◽  
Parallel Manipulators ◽  
Flow Path ◽  
Degree Of Freedom ◽  
Numerical Control ◽  
Dimensional Synthesis ◽  
Nsga Ii ◽  
Executive Mechanism ◽  
Five Axis

Driven by requirements of five-axis numerical control (NC) machine for its executive mechanism, this paper creatively proposes a flow path to synthesize a novel class of n-degree-of-freedom (n-DoF, 4 ≤ n ≤ 6) parallel manipulators (PMs) resorting to four steps, and takes a patented 5-DoF PM, named T5, for example to demonstrate the flow path in depth. Comparing with existing five-axis executive mechanisms, this novel class of the PMs has some advantages of light end-effector, good static, dynamic performance, and so on. Upon the underlying architecture of T5, the kinematic analysis and optimal design are carried out for the first time, in which two essential procedures are involved, one is the kinematic performance index by means of the reciprocal product associated with the wrench screw and twist screw with specific physical meaning, the other is the design method adopted to perform the multi-objective dimensional synthesis using an artificial intelligence approach, that is nondominated sorting genetic algorithm II (NSGA-II). This paper is aimed at laying a solid theoretical and technical foundation for the prototype design and manufacture of T5 PM.

Kinematics of a partially decoupled 3R2T symmetrical parallel manipulator 3-RCRR

2008 ◽  
Vol 222 (2) ◽  
pp. 277-285 ◽  
Author(s):  
S-J Zhu ◽  
Z Huang ◽  
M Y Zhao
Keyword(s):  
Control System ◽  
Cervical Spine ◽  
Parallel Manipulator ◽  
Parallel Manipulators ◽  
Degree Of Freedom ◽  
Short History ◽  
Translational Degree ◽  
And Performance

The 3R2T (three rotational and two independent translational degree of freedom (DoF)) symmetrical parallel manipulator may be adopted in bionics, for example, simulating the motion of a cervical spine based on their mobility property and performance close to isotropic limit. However, up to now, characteristics of this class of manipulators have not been well studied because of its short history. Hence, to study the feasibility of this class of manipulator for bionics, kinematics for 3-RCRR is analysed including position, singularity, velocity, and acceleration. Different from other 3R2T 5-DoF symmetrical parallel manipulators, the mobility of 3-RCRR is partially decoupled, which makes the realization of control system easier than in others.

An Optimization Approach to Vibration Isolation of Rigid Bodies

1997 ◽  
Vol 25 (3) ◽  
pp. 165-175
Author(s):  
P. S. Heyns
Keyword(s):  
Design Problem ◽  
Vibration Isolation ◽  
Rigid Bodies ◽  
Degree Of Freedom ◽  
Optimization Approach ◽  
Local Minima ◽  
Single Degree Of Freedom ◽  
Single Degree

The conventional single-degree-of-freedom approach to isolator design dealt with in most undergraduate curricula, is not always adequate for the design of practical isolator systems. In this article, an optimization approach to the design problem is presented and the viability of the approach demonstrated. It is, however, also shown that multiple local minima may exist and that due care should be exercised in the application of the method.

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