1,721,145 research outputs found
Position analysis of the tripod joint: An alternative approach
No full textThe position analysis, which is the most challenging phase of the kinematic analysis of a mechanism, was solved for the tripod joint, in exhaustive form, a few decades ago. The method proposed at the time was supposed to be able to find all possible assembly configurations of the joint. Regrettably, it becomes useless when the angle that parametrizes the position of one of the connected shafts reaches some specific values, which happens several times for each turn of the shaft; moreover, an error in the expression of a coefficient of a pivotal equation hampers adoption of the method. This paper presents a new procedure whose steepest step is finding the roots of a fourth order algebraic equation. It is shown that eight assembly configurations do exist for the adopted kinematic model of tripod joint, in the complex domain. The proposed procedure has a more direct approach than the previous one and is not affected by its singularities. Moreover, because no arbitrarily-selected movable reference frame is introduced, it leads to equations whose coefficients reveal the periodicity of the dependence of some parameters of the joint configuration on the angular position of one of the connected shafts. This means that some aspects of the tripod joint behavior can be hinted even without solving the equations. A numerical example shows application of the new procedure to a case study
Development of a new geneva mechanism with improved kinematic characteristics: Two station Geneva mechanisms
No full textPosition and velocity analyses of the tripod joint with aspherical rollers
No full textThe paper addresses the kinematics of a type of tripod joint that has seen application over the past two decades in the automotive industry, due to its anti-shudder features. The joint encompasses three rollers externally delimited by axisymmetric non-spherical surfaces. The rollers run on tracks machined on one of the connected shafts. Each roller has a cylindrical inner surface that is in contact, theoretically along a circle, with the spherical ending of a trunnion extending from the other shaft. The paper solves for the first time in polynomial form the position analysis of this type of joint. Then, after pointing out that a tripod joint does not have an instantaneous transmission ratio, the paper addresses the first-order kinematics of the joint. As a further original result, the paper demonstrates that the analyzed tripod joint, when connected in series to a ball non-plunging constant velocity joint, gives rise to a three-shaft driveline which is strictly homokinetic if the axes of the terminal shafts are parallel. Numerical examples show application to case studies of the procedures proposed to solve the position and velocity analyses
Forward kinematics in polynomial form of the general stewart platform
No full textThe paper presents a new algorithm to solve, in polynomial form, the forward kinematics of the generalgeometry 6-6 fully-parallel manipulator. The forty solutions that the problem at hand admits in the complex domain are found by determining the roots of a 40th-order univariate polynomial equation. Unlike the existing algorithm, the proposed one is suitable for implementation in a standard floating-point computation environment. A numerical example shows application of the new algorithm to a case study
Position analysis in analytical form of the 7-link assur kinematic chain featuring one ternary link connected to ternary links only
No full textThe paper presents the analytical-form position analysis of one of the three existing 7-link Assur kinematic chains, precisely the one featuring three binary links and four ternary links, one of the ternary links being joined to the other three. The analysis results in a 14th order polynomial equation in one unknown whose 14 roots correspond, in the complex domain, to as many assembly configurations. The contribution widens the set of planar linkages whose kinematic analysis can be thoroughly and exhaustively solved. A case study is finally provided. © 1997 Elsevier Science Ltd. All rights reserved
Polynomial solution to the position analysis of the 7-link assur kinematic chain with one quaternary link
No full textFollowing a couple of previous papers devoted to the position analysis of two different 7-link Assur kinematic chains, this paper presents the algebraic-form position analysis of the remaining 7-link Assur kinematic chain, which can be distinguished from the others because it alone features one quaternary link. The position analysis, devoted at determining all possible assembly configurations of the considered Assur kinematic chain, is performed by first devising a system of two algebraic equations in two unknowns. After dialytic elimination, a final polynomial equation of eighteenth order is found whose solutions provide, in the complex field, 18 assembly configurations for the examined Assur kinematic chain. As a corollary, it can also be stated that two coupler point curves drawn by two distinct four-bar linkages intersect each other at 18 real points at most. Finally, a numerical example shows application of the new theoretical results. © 1995
Closed-form determination of the location of a rigid body by seven in-parallel linear transducers
No full textThe paper presents an original analytic procedure for unambiguously determining the relative position and orientation (location) of two rigid bodies based on the readings from seven linear transducers. Each transducer connects two points arbitrarily chosen on the two bodies. The sought-for rigid-body location simply results by solving linear equations. The proposed procedure is suitable for implementation in control of fully-parallel manipulators with general geometry. A numerical example shows application of the reported results to a case study. © 1998 by ASME
Kinematic clearance sensitivity analysis of spatial structures with revolute joints
No full textThe paper presents a new method to assess the influence of joint clearances in spatial structures that are composed of links connected by revolute joints. The method allows assessment of the amount by which joint clearances affect the rigid-body position of a generic link of the structure when an external load is exerted on the link. Unlike other procedures, the proposed method relies on the clearance-free idealization of the structure under investigation. An example shows application of the proposed method to the analysis of the structure derived from a multi-loop manipulator by freezing its actuators
A framework for efficiency evaluation of multi-degree-of- freedom gear trains
No full textThe paper proposes a new approach to the efficiency evaluation of any one- or multi-degree-of-freedom gear trains. The suggested approach generalizes the known procedures developed for two-degree-of-freedom gear trains. It is based on the determination of a vector whose components are the torques delivered to the shafts of the gear train. Furthermore the paper shows that, for a notable category of gear trains, such a vector can have only a finite number of directions, which implies that a limited number of experimental data suffices for estimating the efficiency at any operational condition. Examples of application of the proposed methodology are provided. © 1996 by ASME
Analytical-form position analysis of the 7-link assur kinematic chain with four serially-connected ternary links
No full textThe paper addresses the position analysis of the 7-link Assur kinematic chain that features three binary links and four serially-connected ternary links. The analysis, aimed at finding all possible assembly configurations of the Assur kinematic chain, is carried out by first devising a set of three constraint equations in a corresponding number of unknowns. Then, by an original elimination procedure, two out of the three unknowns are simultaneously dropped out. As a result, a final algebraic equation of degree sixteen with only one unknown and free from extraneous roots is obtained. The sixteen solutions of this equation provide as many assembly configurations for the Assur kinematic chain in the complex field. Finally, a case study is reported. © 1994 by ASME
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