Synthesis Of Spatial Mechanisms Research Articles

СИНТЕЗ ПРОСТРАНСТВЕННЫХ ПЯТИ- И ШЕСТИЗВЕН-НЫХ МЕХАНИЗМОВ С ВРАЩАТЕЛЬНЫМИ ПАРАМИ ПО ДВИЖЕНИЮ ВЫХОДНОГО ЗВЕНА

The research was carried out in order to identify the optimal structural schemes of three-dimensional five- and six-link mechanisms with rotational pairs, which reproduce with the required accuracy a linear function during oscillatory and rotational motion of the output link. Spatial mechanisms, which are used as transmission and base mechanisms, make it possible to recreate the movement of the output or any working link with a given accuracy and provide the necessary rigidity, reliability and compactness of the structure. The synthesis of spatial mechanisms was carried out according to the given law of the output link. To implement oscillatory motion with working sections on the forward and reverse stroke, you can use crank-rocker five-links, in which the angles of crossing of the geometric axes of the hinges of adjacent links 4 and 5 are equal to . In a similar way, the synthesis of a spatial five-link was carried out, in which the angles of crossing the axes of the hinges of the output link α_4 and the rack α_5 are related by the dependence α_4= , by reproducing the oscillatory motion of the output balancer with the working stroke in a straight section. Optimal structural schemes of three-dimensional five- and six-link mechanisms are revealed, which reproduce with the required accuracy a linear function during the oscillatory and rotational motion of the output link. The resulting dependencies will be used to automate the optimization synthesis for the objective function of the six-link mechanism (or its five-link modification), which reproduces a linear function on a certain part of the turn of the output link with its full cranking

Synthesis of the Four-Bar Double-Constraint Mechanisms by the Application of the Grubler's Method

The paper provides investigations on the structural synthesis of kinematic schemes of a spatial double-constraint mechanisms with one DOF. The investigations have been carried out with the use of the Grubler's method. The Grubler's condition for planar closed kinematic chains was developed for spatial chains including two general imposed constraints with consideration of relative movements and kinematic pairs. By means of introduction of two rotative joints, one screw pair and one cylindrical joint two different variations of spatial four-bar closed kinematic chains have been designed in the current investigation. Six kinematic schemes of non-isomorphic one DOF mechanisms have been designed from these two chains by fixing one link. The approach offered in this paper can be applied for the structural synthesis of spatial mechanisms from other families in accordance with the used kinematic pairs and numbers of imposed constraints.

Kinematic analysis of a spatial mechanism for estimating shaking effects

Spatial mechanisms are the most general category of kinematic devices. They offer the greatest capability to accomplish any desired kinematic task. A mechanism exerts forces and moments on its supporting frame, which result in vibration. Besides of its effect on efficiency, reducing vibration has become inevitable in the current industrial environment where stern standards on noise and vibration prevail. Balancing of shaking forces and shaking moments in mechanisms is important in order to improve their dynamic performance and fatigue life by reducing vibration, noise and wear. The analysis and synthesis of spatial mechanisms which involves extensive vector mathematics and linear algebra is to be simplified to be taught to engineers in undergraduate education. In the present paper the kinematic analysis of a spatial four-link RSCR mechanism is done to get the velocities and accelerations of its various links which is necessary for the estimation of inertia forces in a mechanism.

New Approach for Spatial Mechanism Synthesis with the C-S Binary Crank by Adaptive Saddle-Fitting

The new approach for approximately synthetically spatial C-S Binary with adapt saddle-fitting is presented, given the definition of adapt saddle-fitting cylinder surface and approximate cylinder surface point, constructed unified mathematical model of adapt saddle-fitting cylinder surface fitting of spatial curve and unified error standard . It is solved by saddle-point programming. The example shows optimization methods are effective and global convergent.

Type synthesis of spatial mechanisms for forging manipulators

In this study, a systematic method is proposed to synthesize the parallel and hybrid serial–parallel mechanisms for the forging manipulators based on the screw theory. First, several typical configurations of five-degrees-of-freedom parallel mechanism for the forging manipulators are synthesized, and they are all non-overconstrained mechanisms. Then, two kinds of hybrid serial–parallel mechanisms for the forging manipulators with the advantages of motion decoupling are constructed, which are also not overconstrained. The configurations obtained in this study would provide more type selection for the heavy-duty forging manipulators in engineering.

Analysis and optimal synthesis of single loop spatialmechanisms

In this work, a systematic approach is presented to obtain the input-output equations of a single loop 4-bar spatial mechanisms. The dialytic method along with Denavit-Hartenberg parameters can be used to obtain these equations efficiently. A genetic algorithm (GA) has been used to solve the problem of spatial mechanisms synthesis. Two types of mechanisms, e.g., RSCR and RSPC (R: revolute; S: spherical; C: cylindrical; P: prismatic), have illustrated the application of the GA to solve the problem of function generation and path generation. In some cases, the GA method becomes trapped in a local minimum. A combined GA-fuzzy logic (GA-FL) method is then used to improve the final result. The results show that GAs, combined with an adequate description of the mechanism, are well suited for spatial mechanism synthesis problems and have neither difficulties inherent to the choice of the initial feasible guess, nor a problem of convergence, as it is the case for deterministic methods.

A New Approach to Dimension Synthesis of Spatial Four-Bar Linkage Through Numerical Atlas Method

This paper presents a new method for the synthesis of spatial mechanism. Using harmonic analysis, the coupler curve and output angle function of spatial mechanism can be described as a series of harmonic characteristic component. For the path generation problem of the spatial mechanism, a technique of normalization processing eliminates the effects of scale, translation, and rotation; in other words, the harmonic characteristic component of the coupler curve is just determined by the basic dimensional type of spatial mechanism but not by the real dimension and the installing position. The numerical atlas database of coupler curve or output angle function of spatial mechanism can be created by the harmonic characteristic components and associated basic dimensional type of spatial mechanism. The best suitable basic dimensional type of spatial mechanism for prescribed function can be decided by using fuzzy identification method and numerical atlas database. On the basis of the basic dimensional type and formulas, which compute the coupler point, true size, and installing dimensions of the spatial mechanism, the dimension synthesis of the spatial mechanism is made possible. This paper takes the RSSR mechanism and RRSS mechanism as an example to illustrate the analysis process and application of this method.

Formulation for actuators' number enumeration for main planar structures in robotics

Mechanisms and Machines Theory (MMT) contributed greatly to planar and spatial mechanism synthesis with different degrees of freedom. Some of the current industrial robots with planar chains have a main structure created by the kinematic graphs of MMT. This paper deals with a formulation allowing computing the number of possibilities for actuators' attachment for planar pin-jointed main driving mechanisms in robotics. It is based on the sub-chains symmetries of structures taking into account the position of the actuator of the robot. Pairs of groups of mutually symmetrical mechanisms are detected. Thus, eliminating the symmetrical ones confines the number of possible configurations. Different cases of symmetries have been studied. Expressions for calculation of the number of actuator position of a mechanism are presented. They enable the reduction of the number of structures by avoiding those that are isomorphic. Following this, examples for applications for various planar pin-jointed kinematic structures are presented, enabling the field of research to be restricted to the possible solutions. La Théorie des Mécanismes et des Machines (TMM) a largement contribué dans la synthèse des mécanismes plans et spatiaux à différents degrés de mobilité. Certains robots industriels actuels ont des structures principales issues des graphes cinématiques fournis par la TMM. Ce papier concerne une formulation permettant un calcul restreint de mécanismes moteurs plans à liaisons pivots en robotique. Il est basé sur la notion de symétrie des structures concernant la position de l'actionneur du robot. Différents cas de combinaisons de couples de mécanismes symétriques sont détectés. Ainsi le nombre de configurations possibles est restreint par élimination de ceux qui sont symétriques. Différents cas de combinaisons de symétries sont étudiés. Des formulations pour calculer le nombre de possibilités d'ancrer un actionneur sont présentées. Elles permettent de réduire le nombre de structures tout en évitant celles qui sont isomorphes. Par la suite différents exemples d'application sont présentés permettant de restreindre le champ de recherche parmi les solutions possibles.

Dimensional Synthesis of Spatial Mechanisms and the Problem of Non-Assembly

In this paper a general method for dimensional synthesis of both planar and spatial mechanisms is presented. The method addresses the problem of non-assembly. A gradient based optimization algorithm is employed and the sensitivities are calculated analytically using the method of direct differentiation. A well established and general method of computational kinematics is employed, in a slightly modified variant, to avoid the problem of non-assembly. The modification consists of a minimization of the residuals of the kinematic constraint equations, rather than equating them to zero. The point-coordinate formulation is applied. Several examples are provided.

CONSTRUCTION OF SCREW GEOMETRY VIA 3-D CAD SYSTEM FOR THE ANALYSIS AND SYNTHESIS OF SPATIAL MECHANISMS

This paper investigates the application of computer-aided design and drawing (CAD) software to the kinematic analysis and synthesis of spatial mechanisms based upon screw geometry. The advantages of the graphic method for the synthesis and analysis of mechanisms are straightforward, comprehensive, clearly represented, and easy to correlate to a real mechanism. Using conventional 3-D CAD software, the screw axes and joint axes are constructed as virtual parts. The relationships of joint axes that are constrained by screw geometry are the assembly conditions for the virtual parts in the CAD system. This paper shows that, similar to the synthesis of a planar linkage, the synthesis of a spatial C-C dyad by the graphical method in a CAD system is an efficient process.

709 運動成分拘束を考慮した空間機構の総合(G.S. 機素潤滑設計II)

709 運動成分拘束を考慮した空間機構の総合(G.S. 機素潤滑設計II)

Kinematic differential geometry of a rigid body in spatial motion—III. Distribution of characteristic lines in the moving body in spatial motion

Based on the results of Parts I and II, the kinematic conditions for the moving body to be connected with a binary link by a kinematic pair are discussed and described by the geometrical properties of the line trajectory and the constraint ruled surface. And then, there are 11 kinds of the characteristic lines corresponding to 11 kinds of the combinations of the kinematic pairs, respectively, whose constraint equations are derived by the contact theory of two ruled surfaces and the above kinematic conditions. The solutions are analysed, and the distributions or the numbers of each characteristic line in the moving body are examined. All of these are believed to be presented for the first time and to provide a solid theoretical basis for path analysis and synthesis of spatial mechanisms.

A simple and general method for kinematic synthesis of spatial mechanisms

In this paper a simple and efficient method for optimum kinematic synthesis of multibody systems is presented. The proposed formulation is based on the use of a set of fully Cartesian coordinates. Using the coordinates, the system is described by a set of geometric constraints and the design requirements are introduced by a set of functional constraints. An objective function is defined and minimized to obtain the values for design parameters. Finally, some planar and three-dimensional examples are presented that illustrate the application of the method.

Type Synthesis of Spatial Mechanisms with Consideration of General Constraint.

In the design of non-uniform motion mechanisms with pairs of multiple degrees of freedom, the influence of components of motion upon the allocation of degree of freedom of pairs is one of the important problems which must be solved for improvement of the output precision of mechanisms. In this paper, similarly to spatial mechanisms which are constructed with multiple closed circuits, a systematic synthesis of spatial mechanisms is carried out with consideration of general constraints of mechanisms. Namely, constraint conditions required to construct the pair in mechnisms with multiple closed circuits are formulated. Moreover, Structures of mechanisms with multiple closed circuits are represented accurately with incidence matrices whose components are the degrees of freedom of each pair, to obtain optimum allocation of degree of freedom of pairs. Based on the above analytical results, a systematic system for the spatial mechanism is proposed which determines the optimum allocation of degree of freedom of pairs. Finally, the spatial six-link mechanism which satisfies requirements of the above-mentioned conditions is synthesized to verity the method.

Synthesis of Spatial Mechanisms with Consideration of Interference of Structural Elements.

In the present paper, regarding spatial mechanisms with prismatic and sphere-groove pairs on the coupler, an arrangement system of structural elements for the mechanism with consideration of mutual interferences among links is investigated. In order to determine optimum profiles of links which avoid mutual interferences among the structural elements, such as pairing shafts, pairs and links in the mechanisms, a rotary plane which is arbitrarily fixed on one of the moving links in the mechanism is introduced, and relative loci of pairing points and relative positions of each link with this plane are analyzed. Furthermore, conditions to determine arrangements of links and pairs avoiding mutual interferences of moving links are formulated. Based on the above analytical results, an element-arrangement system is constructed which obtains the optimum profiles and arrangements of links and pairs of spatial mechanisms. Applying the system, a spatial 4-bar mechanism with a prismatic and sphere-groove pairs on the coupler is synthesized as a practical example.

Synthesis of Spatial Mechanism with Consideration of Degree of Freedom of Mechanism

In this paper, a systematic synthesis of the optimum arrangements of links and pairs in spatial mechanisms with multiple moving closed circuits is studied with consideration of the degrees of freedom of the mechanisms. Namely, the conditions required to construct the mechanisms with multiple moving closed circuits are formulated. Moreover, mechanisms with multiple moving closed circuits are constructed with some basic links and open chains, obtaining the optimum arrangement of links and pairs. Based on the above analytical results, a synthesis system is proposed which determines the optimum arrangements of links and pairs. Finally, the types of spatial seven-link mechanisms which satisfy requirements of the above-mentioned basic links and open chains are synthesized to illustrate the method.

A Type Synthesis of Spatial Mechanism with Consideration of Degrees of Freedom of Mechanism.

In this paper, a systematic synthesis of the optimum arrangements of links and pairs in spatial mechanisms with multiple moving closed circuits is studied with consideration of the degrees of freedom of the mechanisms. Namely, the conditions required to construct the mechanisms with multiple moving closed circuits are formulated. Moreover, mechanisms with multiple moving closed circuits are constructed with some basic links and open chains, obtaining the optimum arrangement of links and pairs. Based on the above analytical results, a type synthesis system is proposed which determines the optimum arrangements of links and pairs. Finally, the types of spatial seven-link mechanisms which satisfy requirements of the above-mentioned basic links and open chains are synthesized to illustrate the method.

Type synthesis of spatial mechanisms.

In this paper, a type synthesis system for production of prototype spatial multilink mechanisms constructed with multiple closed loops is investigated. This study was carried out to obtain optimum arrangements of links in the mechanisms. Consideration was given to the restrictive conditions of the mechanisms to be produced; i.e., closed loops in the mechanisms were constructed with some open chains, which are called open-chain elements in the present paper. Moreover, optimum conditions to satisfy the types of spatial mechanisms required were formulated using characteristics of the above-mentioned open chains, and a type synthesis system which determines the types of spatial multilink mechanisms was obtained. Applying the system, we synthesized a type of spatial six-link mechanism as a practical example.

Type synthesis of spatial mechanisms.

In this paper, a type synthesis system for production of prototype spatial multilink mechanisms constructed with multiple closed loops is investigated. This study was carried out to obtain optimum arrangements of links in the mechanisms. Consideration was given to the restrictive conditions of the mechanisms to be produced; i.e., closed loops in the mechanisms were constructed with some open chains, which are called open-chain elements in the present paper. Moreover, optimum conditions to satisfy the types of spatial mechanisms required were formulated using characteristics of the above-mentioned open chains, and a type synthesis system which determines the types of spatial multilink mechanisms was obtained. Applying the system, we synthesized a type of spatial six-link mechanism as a practical example.

A PHIGS-based graphics input interface for spatial-mechanism design

A graphics preprocessor that interactively assists in the definition of spatial-mechanism problems is described. Methods of depth cueing and six-degree-of-freedom data entry are presented. To achieve graphics device independence, the proposed graphics standard PHIGS (Programmer's Hierarchical Interactive Graphics System) has been used. Examples of applications include generation of input commands for the Integrated Mechanisms Program (IMP) and generation of input for spatial-mechanism synthesis routines.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>