Graphical transmission angle control in planar linkage synthesisControle graphique de l'angle de transmission dans la synthese de liaisons planes

Graphical techniques are presented which permit control of the maximum transmission angles (the transmission angle is here taken as the angle between the coupler and the normal to the driven crank) in the design positions for precision position linkage synthesis. This method does not directly control the maximum transmission angle magnitude throughout a motion cycle. It does permit elimination of all solutions whose transmission angle magnitude exceed nominated limits in the design positions. The constructions involve only circles and lines. They would seem well suited to implementation in interactive computer graphic synthesis programs.     

Synthesis of position,path and function generating 4-bar mechanisms with completely rotatable driving linksSynthese de la position,de la trajectoire et de la generation de fonctions d'un mecanisme a quatre barres articulees

A unified treatment of the synthesis of position, path and function generating mechanisms with completely rotatable input links is presented in this paper. Algebraic-geometrical techniques are used to obtain all proper crank-rocker and drag-link linkage solutions with transmission angles in the range 45° ≤ μ ≤ 135°.     

Synthesis of optimum slider-crank mechanismsCИ

For the spatial slider-crank mechanism formulas are obtained to allow the user determine the link sizes and slider offset for a predetermined stroke with an acceptable pressure angle at the extremes of slider travel as well as by a given angle between the crosshead guide of the slider and a plane in which the crank revolves. Formulas for determining the sizes of links of the plane slider-crank mechanism as a special case of the spatial mechanism are also presented. The particular cases of mechanisms havingequal angles of pressure as well as at extreme values of an angle between crosshead guide and the revolution plane of the crank are discussed. It is shown, that the plane mechanism case provides maximum slider travel when other things are equal.     

Synthesis of double-rocker mechanism with optimum transmission characteristicsSynthese du double mecanisme oscillant a bielle avec caracteristiques optima de transmission

A simple analytical procedure is presented for the synthesis of the planar 4-bar double-rocker mechanism for coordinating the prescribed extreme positions. For optimum transmission characteristics, the design criterion used is the equal deviation of the transmission angles from 90° at the two dead-centre positions. Numerical examples are provided to illustrate the method.     

Graphical synthesis of a 4-bar mechanismLa synthese graphique d'un mecanisme avec quatre barres

For a mechanism operating at steady state, the synthesis technique for specified coupler point location, velocity and acceleration is developed from the geometric nature of the acceleration pole. Two examples are presented. One example is based on a known site for the acceleration pole and the other depends on locating the pole from a specified acceleration.     

Nomogramme für die Wattsche GeradführungNomograms for Watt's straight-line linkages

Two nomograms for a quick synthesis of Watt's straight-line linkages are presented. They are based upon optimization formulas which were derived, by means of Chebyshev's principle, in a foregoing paper [1]. After having chosen the arm length LA = MB = a and the coupler AB = 2b of a double-rocker mechanism LABM, the nomogramsgive immediately the position coordinates of the pivots L(?e,f), M(e,?f) and the maximal deviation ±h for an approximate straight-line motion over a normed length 1 = 100.     

Four-square sprocket test machineMachine d'essai en boucle ferme pour les roues a chaines

A 4-square sprocket test machine was built to obtain load vs cycle life data for various chain and sprocket geometry and material combinations. Sprockets were evaluated at various rotational speeds and chain loads that provided accelerated failures. Instrumentation on the machine recorded total sprocket cycles and a sensing switch automatically shut-off the machine when a failure occurred in the sprocket-chain system. Failure was defined as the point at which the chain-sprocket system ceased to function normally. In this paper, the 4-square sprocket test machine is described, preliminary load-cycle life results are given, and an SEM study of failed sprockets is presented.     

Three position precessing mechanism synthesisLa synthese d'un mecanisme a preceder en trois positions

This paper presents a complex number development of a three position geared five-bar precessing mechanism synthesis.The methodology which is presented in this study is based on an extension of Burmester cycloidal circlepoint-centerpoint theory[2]. This paper presents the mathematical formulation of the synthesis process.A structured FORTRAN computer program was developed on a VAX 11/780 computer in order to implement the synthesis process. The synthesis program is capable of presenting the synthesis results on a graphical display. Typical results are shown.     

MICRAS,Microcomputer interactive codes for robot analysis and simulationMICRAS: Logiciel interactif sur micro-ordinateur pour l'analyse et la simulation des robots

With the growth and acceptance of interactive computer graphics, contemporary robotic research trends are focusing on the development of robot simulation packages. This paper describes a new microcomputer interactive package for the analysis and simulation of industrial robots. The package represents an extension of the state-of-the-art developments in the technology of industrial robots. The novel features are derived from the use of the microcomputer for analysis and simulation. The package includes all aspects of the kinematic analysis of the six general geometric structures of industrial robots.MICRAS is a package of microcomputer interactive codes for robot analysis and simulation. The program WORKSPACE is used for obtaining the value and plot of the workspace of two- and three-link revolute-jointed arms. DIRKIN is a program that generates the forward solution for any robot with up to six degrees of freedom. The data input section provides the robot geometric parameters and joint angles interactively. The program REVKIN is constructed to give the inverse solution of the six major kinematic structures of robots and display all possible configurations for each robot. COJOINT is a program that implements coordinated joint motion of a robot with defined range of motion of each joint. The modules with prefix CAT constitute the program for the simulation of robot movements for a specified cartesian path of the end effector. Finally, DIRDIF is a program for the differential kinematic analysis of robots.     

The six-legged walking robot capable of terrain adaptationLe robot a six pieds marchant capable de l'adaptation au terrain

This paper presents some results of the development of the control system for a six-legged walking robot. New results on visual-and force-feedback are presented. Now the robot features the active compliance and can move over a terrain with a complex relief.     

On the optimal design of multi-speed gear trainsConception optimale des trains d'engrenages aux vitesses multiples

An efficient method for analyzing multi-speed gear trains is presented and used in this paper. This new technique obtains equations for the diameters of all the gears used in the transmission based on information contained in the speed diagram. The form of the equations is such that they can be generated by the computer automatically. Further, the equations are applicable to the general arrangement, the single composite arrangements, and the double composite arrangements. As a result, all of the promising kinematic arrangements possible for a given number of speeds can be easily studied. By promoting different constraints and objective functions, trace-offs between different parameters can easily be examined. The technique is illustrated using a case study of a 9 speed gear train. A multi-parameter optimization technique is used to solve 19 different arrangements for a weighted objective function minimizing volume and maximizing stiffness.     

Application of whitworth quick return mechanism for high velocity impacting pressL'application du mecanisme a retour rapide de whitworth pour une presse d'impact a grande vitesse

The Whitworth quick return mechanism has been modified and used for constructing high-velocity impacting press. The impacting press drive comprises a Whitworth quick return mechanism consisting of a crank and a drive arm together with a variable speed d.c. motor, a flywheel, bearings, etc. The end of the drive arm is attached by a connecting rod to a cycloidal cam. In single cycle operation, the cam is made to engage with an upper platen (or ram) which impacts the workpiece. The upper platen and cam are both mounted on multirod supports with linear ball bushings. A brake is provided on the flywheel for emergency purposes. The high-speed impacting presses are subject to severe dynamic forces when operating at speeds of 200 rpm and greater. Although the mechanism has been designed to withstand operation at higher frequencies, the loads transmitted to the building foundations cause unwanted vibrations and noise. This paper also examines the causes of the unbalanced forces and means to reduce the loads transmitted to the foundations of the high velocity impacting press. An analysis is presented which yields an approximate expression for the angular displacement, velocity and acceleration of the quick return mechanism. Rapid changes in acceleration and high-peak values contribute to the severity of the problem. The bearing reaction forces are determined. Different approaches of this problem have been discussed and analyzed.     

Unbalance response of rotor disks supported by fluid film bearings with a negative cross coupled stiffness using influence coefficient methodReponse de desequilibre d'un rotor multidisque sur paliers lisses par a methode des coefficients d'influence

The dynamic response of a multidisk rotor system supported by fluid-film bearing using the method of influence coefficient is presented. The stiffness and the damping coefficients have been considered as speed dependent. The two bearings, which support the rotor shaft, are dissimilar. The dynamic response is calculated by varying parameters such as spacing between the disks, the viscosity ratio of the oil of the bearings, the bearing clearance ratio and the relative mass of the rotor disks. The effect of damping on the rotor response and the critical speed is also presented.     

Closed-form analytic synthesis of a five-link spatial motion generatorLa synthese analytique non-iterative d'un generateur de mouvement spatial avec cinq barres

In the synthesis of motion generating mechanisms we seek to determine the key dimensions of a preconceived type of single-degree-of-freedom mechanism which will guide one of its links through a sequence of finitely or infinitesimally separated arbitrarily prescribed positions. In space, each such finitely separated precision position can be specified by the radius vector of the origin and the Euler angles of orientation of a coordinate system, embedded in the guided link, with respect to a fixed coordinate system of reference.The motion generator mechanim considered here consists of two grounded S-S links, ⁵ one grounded C-S link, a ternary S-S-S coupler and the R-R-C fixed frame. Motion of the coupler is to prescribed. Each equation of synthesis is written by expressing the closure of the vector polygon covering the starting and one displaced position of one dyad formed by a grounded link and the coupler. The resulting system can be solved for unknown vectors defining the dyad in its starting position, in closed form for up to three precision positions.     

Optimum synthesis of an angular function generating mechanism with prescribed time ratio and rocker angular swing amplitudeSynthese optimisee d'un generateur de fonction angulaire avec rapport des temps et l'amplitude angulaire prescrites

Two important parameters related to the motion of a crank rocker angular function generating mechanism are the amplitude of rocker angular swing, and the ratio of two crank angular rotations required to move the rocker between its limit positions. In instances where the crank rotates at a constant rate, the latter is called the time ratio. A synthesis procedure is presented where the above two user prescribed parameters are satisfied, and a user defined objective function is optimized.     

Triangular nomograms for symmetrical coupler curvesHoмoгpaммa тpeyгoльнoй фopмы длы cиммeтpичныч мaтyнныч кpaивычNomogrammes triangulaires pour les courbes symmetriques

Triangular nomograms have been constructed as a simple means of finding symmetrical coupler curves of the crank-rocker linkage. A nomogram of this kind has been presented by the author of this article during a Conference of the Institution of Mechanical Engineers at London in 1972. Twenty-seven versions have now been developed and fully worked out.They are dimensionless and have then three angles as parameters to determine the type of curve with all its properties.The curve types are concerned with those characteristics which the crank-rocker linkage yields for symmetrical coupler curves such as: curves with one or two points of reversal; with internal contact; 8-shaped curves; curves with 2 equal radii of curvature; curves with one or two undulation points on the axis of symmetry; curves with two undulation points oriented symmetrically in relation to each other and a top angle; curves with Burmester points, where the second derivative of the radius of curvature is zero; and curves with one or two tangents which touch the curve at three different points each.The 27 triangular nomograms refer to the symmetrical coupler curves of the 4-bar linkage and are used for selection of the type of curve and corresponding data for the linkage.This article will deal with three of them which relate to coupler curves with the property that a tangent touches the curve at three separate points, while two more examples of the various verions of the nomogram will be presented.A example of the application of the nomogram is given by the design of a transfer mechanism, where use has been made of a curve with two cusps and further modification to a 6-bar linkage.     

Design synthesis of a gyrogrinder using direct search optimizationConception synthetique d'une meule gyroscopique par optimisation a recherche directe

A novel grinding mechanism operating on the principle of gyroscopic tracking of arbitrary contours is presented. The mathematical model describing the mechanism of gyrogrinding and the conditions under which the grinding wheel remains in contact with the periphery of template are established. The design parameters that greatly influence the performance of gyrogrinding are identified as the radius of the grinding wheel, the length of the spin axis, rotational speed of grinding wheel, and the mass polar moment of inertia of rotor and inner gimbal. In this paper, the design synthesis of a gyrogrinder is formulated as an optimization problem so that the optimal values of the design variables are calculated using a direct search multiparameter optimization method for continuous grinding with no dynamic shattering of grinding wheel. Three typical templates: elliptical, Limacon of Pascal and Four Leaved Rose, which represent possible shapes in cam production were considered and the optimal values of design parameters for each cam configurations were found using the optimization strategy. Results show that optimal design parameters lie within a small range for the three cam configurations. The mean optimal values of the design parameters were calculated and used in the dimensioning of the rotor and inner gimbal. A prototype was then built based on this investigation and when tested functioned effectively grinding the template. This paper illustrates the use of computer-aided optimization in the design synthesis of a gyrogrinder.     

Conditions for backward synchronous whirl of a flexible rotor in hydrodynamic bearingsConditions pour une precession synchrone retrograde d'un rotor flexible dans les paliers hydrodynamiques

This paper deals with the dynamic unbalance response of a single mass Jeffcott rotor in hydrodynamic bearings. The cross-coupled spring coefficients are considered in the analysis and damping has been neglected. It has been shown that there could be either two distinct critical speeds of the rotor with a backward synchronous whirl between them, or that there is no possible conventional critical speed of the rotor. Two case studies are presented.     

The effect of link parameter on the working space of general 3R robot armsL'effet d'un parametre d'un accouplement sur l'espace de travail des bras du robot 3R general

This paper will consider a robot into two parts: “regional structure” and “orientational structure”. The regional structure contributes the gross motion of the robot hand, and the orientational structure contributes the orientation of the robot hand. By studying the effects of kinematic parameters on the general 3R robots, the optimum regional structure and the optimum orientational structure are arrived in this paper.     

Mechanics and adaptation systems in robotsLa mecanique et les systemes d'adaptation dans les robots

Modern requirements for industrial robots as a main means of the automatization of technological and transport operations are accuracy, efficiency, universality and the possibility of readjusting easily to manufacturing. Above mentioned robots' performances are determined by the characteristics of their motor system, mechanics, drive and system of adaptation. Some ways of developing the mechanics and adaptation of industrial robots based on the modern level of technical ideas and satisfying the increased demands are discussed in this paper.