Static Balancing of Translational Parallel Mechanisms

2011 ◽  
Author(s):  
Teunis van Dam ◽  
Patrice Lambert ◽  
Just L. Herder
Keyword(s):  
Range Of Motion ◽  
Parallel Manipulators ◽  
Static Equilibrium ◽  
Static Balance ◽  
Parallel Mechanisms ◽  
Static Balancing ◽  
Delta Robot ◽  
Balancing Conditions

Static balancing is a technique to create static equilibrium throughout a certain range of motion. Static balancing for spatially moving parallel manipulators tends to result in considerable added complexity which hampers application. This paper presents a simple static balancing technique for the subclass of translational parallel manipulators such as the Delta robot. Mathematically perfect static balance is achieved without addition of links. Only springs need to be added. The concept and the balancing conditions will be presented. A prototype is being manufactured at the time of writing which demonstrates the feasibility of the concept.

Static Balancing of Spatial and Planar Parallel Manipulators With Prismatic Actuators

1998 ◽  
Author(s):  
Marc Leblond ◽  
Clément M. Gosselin
Keyword(s):  
Parallel Manipulators ◽  
Geometric Interpretation ◽  
Degree Of Freedom ◽  
Parallel Mechanisms ◽  
Static Balancing ◽  
Inertial Parameters ◽  
Dimensional Parameters ◽  
Balancing Conditions ◽  
Static Conditions ◽  
Planar Parallel Manipulators

Abstract In this paper, the static balancing of existing spatial and planar parallel manipulators by the addition of balancing elements is addressed. Static balancing is defined here as the set of conditions on manipulator dimensional and inertial parameters which, when satisfied, ensure that the weight of the links does not produce any force (or torque) at the actuators for any configuration of the manipulator, under static conditions. These conditions are derived here for spatial six-degree-of-freedom parallel manipulators and it is shown that planar three-degree-of-freedom parallel manipulators can be treated as a particular case of the spatial 6-dof mechanisms. The static balancing conditions associated with planar mechanisms can therefore easily be found, but are not given here because of space limitations. A brief geometric interpretation of the balancing conditions which are associated with statically balanced spatial mechanisms is then carried out. It is shown that balancing is generally possible even when the dimensional parameters are imposed, which is a useful property since dimensional parameters are usually obtained from kinematic design or optimization. Finally, examples of balanced planar and spatial parallel manipulators are given. Static balancing leads to considerable reduction in the actuator forces (or torques), which in turn leads to less powerful actuators and more efficient designs. Moreover, the possibility of balancing existing systems by introducing additional elements, as demonstrated here, is of interest for retrofitting existing parallel mechanisms.

scholarly journals Introduction to the special issue: parallel manipulators.

Robotica ◽  
1997 ◽  
Vol 15 (4) ◽  
pp. 353-353
Author(s):  
François Pierrot
Keyword(s):  
North America ◽  
Parallel Manipulators ◽  
Parallel Robots ◽  
Parallel Mechanisms ◽  
Special Issue ◽  
Industrial Areas

It has been a pleasure for me to arrange this Special Issue of Robotica on Parallel Robots which provides 9 papers from authors from Asia, Oceania, North America and Europe; worldwide research on this topic is proof of the growing interest of both the scientific and the industrial areas of parallel mechanisms. I truly believe that the main reason for this enthusiasm is that parallel mechanisms research extends from theoretical mathematics and kinematics to applied robotics, and even beyond, creating new technological challenges.

A Statically Balanced Gough/Stewart-Type Platform: Conception, Design, and Simulation

2009 ◽  
Vol 1 (3) ◽  
Author(s):  
Marco Carricato ◽  
Clément Gosselin
Keyword(s):  
Sufficient Conditions ◽  
Parallel Manipulators ◽  
Point Of View ◽  
Theoretical Point ◽  
Constant Force ◽  
Parallel Mechanisms ◽  
End Effector ◽  
Neutral Equilibrium ◽  
The Difference ◽  
Elastic Elements

Gravity compensation of spatial parallel manipulators is a relatively recent topic of investigation. Perfect balancing has been accomplished, so far, only for parallel mechanisms in which the weight of the moving platform is sustained by legs comprising purely rotational joints. Indeed, balancing of parallel mechanisms with translational actuators, which are among the most common ones, has been traditionally thought possible only by resorting to additional legs containing no prismatic joints between the base and the end-effector. This paper presents the conceptual and mechanical designs of a balanced Gough/Stewart-type manipulator, in which the weight of the platform is entirely sustained by the legs comprising the extensible jacks. By the integrated action of both elastic elements and counterweights, each leg is statically balanced and it generates, at its tip, a constant force contributing to maintaining the end-effector in equilibrium in any admissible configuration. If no elastic elements are used, the resulting manipulator is balanced with respect to the shaking force too. The performance of a study prototype is simulated via a model in both static and dynamic conditions, in order to prove the feasibility of the proposed design. The effects of imperfect balancing, due to the difference between the payload inertial characteristics and the theoretical/nominal ones, are investigated. Under a theoretical point of view, formal and novel derivations are provided of the necessary and sufficient conditions allowing (i) a body arbitrarily rotating in space to rest in neutral equilibrium under the action of general constant-force generators, (ii) a body pivoting about a universal joint and acted upon by a number of zero-free-length springs to exhibit constant potential energy, and (iii) a leg of a Gough/Stewart-type manipulator to operate as a constant-force generator.

A Comparison of Architectures of Parallel Mechanisms for Workspace and Kinematic Properties

1995 ◽  
Author(s):  
Clement M. Gosselin ◽  
Rémi Ricard ◽  
Meyer A. Nahon
Keyword(s):  
Parallel Manipulators ◽  
Parallel Architectures ◽  
Parallel Mechanisms ◽  
Design And Optimization ◽  
Stiffness Properties ◽  
Structural Differences ◽  
Six Degree Of Freedom ◽  
Kinematic Properties ◽  
Better Than ◽  
Normalization Factors

Abstract This paper presents a study of the workspace and kinematic properties of four different architectures of six-degree-of-freedom parallel mechanisms. For each architecture, the volume of the Cartesian workspace is computed at different orientations of the moving platform. The distribution of the workspace is also found by computing the 2D sections of the 3D workspace. The rotational workspace is then determined at the reference position of the platform. Finally, the stiffness properties of the architectures are obtained. Normalization factors are then defined to account for the structural differences between the architectures of mechanisms. The comparison of the different architectures of parallel mechanisms has been performed using SIMPA, a specialized CAD tool developed for the kinematic analysis and optimization of parallel manipulators. The results thus obtained illustrate the range of performance which can be expected from different parallel architectures. Although none of the architectures proves to be better than all the others in all respects, particular architectures do excel in particular performance measures. The approach proposed would therefore be useful in further studies relating to the design and optimization of parallel manipulators and mechanisms.

A Method for Compliance Modeling of Five Degree-of-Freedom Overconstrained Parallel Robotic Mechanisms With 3T2R Output Motion

2016 ◽  
Vol 9 (1) ◽  
Author(s):  
Wen-ao Cao ◽  
Huafeng Ding ◽  
Donghao Yang
Keyword(s):  
Screw Theory ◽  
Parallel Manipulators ◽  
Static Equilibrium ◽  
Equilibrium Equations ◽  
Element Analysis ◽  
Compliance Matrix ◽  
Fea Model ◽  
Stiffness Model ◽  
Compliance Modeling ◽  
The One

This paper presents an approach to compliance modeling of three-translation and two-rotation (3T2R) overconstrained parallel manipulators, especially for those with multilink and multijoint limbs. The expressions of applied wrenches (forces/torques) exerted on joints are solved with few static equilibrium equations based on screw theory. A systematic method is proposed for deriving the stiffness model of a limb with considering the couplings between the stiffness along the constrained wrench and the one along the actuated wrench based on strain energy analysis. The compliance model of a 3T2R overconstrained parallel mechanism is established based on stiffness models of limbs and the static equilibrium equation of the moving platform. Comparisons show that the compliance matrix obtained from the method is close to the one obtained from a finite-element analysis (FEA) model. The proposed method has the characteristics of involving low computational efforts and considering stiffness couplings of each limb.

scholarly journals Rethinking the neurological examination I: static balance assessment

2011 ◽  
Vol 69 (6) ◽  
pp. 954-958 ◽  
Author(s):  
Péricles A. Maranhão-Filho ◽  
Eliana Teixeira Maranhão ◽  
Marcos Martins da Silva ◽  
Marco Antônio Lima
Keyword(s):  
Elderly Patients ◽  
Neurological Examination ◽  
Sensory Integration ◽  
Static Equilibrium ◽  
Static Balance ◽  
Clinical Test ◽  
Balance Assessment ◽  
Risk Of Falling ◽  
Functional Reach ◽  
Functional Reach Test

The authors advocate a modernization of the neurologic exam with regard to the evaluation of static equilibrium through the application of some easily performed and interpreted bedside maneuvers like the Clinical Test of Sensory Integration and Balance - modified and the Functional Reach Test. The authors also believe that these and other assessments, such as that of the risk of falling for elderly patients, should be incorporated into the routine neurological examination.

A Novel Method on Singularity Analysis in Parallel Manipulators

2006 ◽  
Author(s):  
Hodjat Pendar ◽  
Maryam Mahnama ◽  
Hassan Zohoor
Keyword(s):  
Closed Loop ◽  
Parallel Manipulators ◽  
Singularity Analysis ◽  
Parallel Mechanisms ◽  
Kinematic Chains ◽  
Working Space ◽  
Novel Approach ◽  
Main Technique ◽  
Novel Method ◽  
Constraint Plane

A parallel manipulator is a closed loop mechanism in which a moving platform is connected to the base by at least two serial kinematic chains. The main problem engaged in these mechanisms, is their restricted working space as a result of singularities. In order to tackle these problems, many methods have been introduced by scholars. However, most of the mentioned methods are too much time consuming and need a great amount of computations. They also in most cases do not provide a good insight to the existence of singularity for the designer. In this paper a novel approach is introduced and utilized to identify singularities in parallel manipulators. By applying the new method, one could get a better understanding of geometrical interpretation of singularities in parallel mechanisms. Here we have introduced the Constraint Plane Method (CPM) and some of its applications in parallel mechanisms. The main technique used here, is based on Ceva Theorem.

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