Transmission optimization of spatial 4-link mechanisms

The design of plane crank-and-rocker linkages with given rocker swing angle, corresponding crank rotation and optimum force transmission are well known problems in kinematic synthesis. This investigation is concerned with the transmission optimization of the skew crank-and-rocker linkage and the skew slider-crank mechanism. The algebraic loci of the moving joints are used to express the lengths of the moving links as a function of a single parameter, the optimum value of which is obtainable as a constrained minimization problem involving 1-parameter scanning. The results are presented in tables as well as in design charts.     

轴间距可变的等角速平面铰链机构综合

从最简单的等角速平面铰链机构出发，综合得到轴间距可变的等角速平面铰链机构。给出了这些机构一般Ｓｃｈｍｉｄｔ圆盘联轴器的双曲柄条件，论证了这些机构的传动等角速性。     

Skew control of a quay container crane

In this paper, the skew control of the load (container) in the quay crane used in the dockside of a container terminal is investigated. The mathematical model of the 3-dimensional (3D) motions of the load is first derived. The container hooked to a spreader is suspended by four ropes in air. When the container is accelerated by the trolley or is disturbed by winds, it will make a rotational motion (trim, list, and skew) as well as a sway motion in the vertical plane. In such a case, the position of the container becomes difficult to control accurately due to the rotational motion even with the sway motion under control. This paper proposes an input shaping technique for the skew control based on the 3D dynamics of the container. The adopted skew control system uses four electric motors to vary the length of the four ropes individually. Simulation results show the effectiveness of the proposed system in controlling the skew motion.     

基于旋转法的歪斜零件加工中角度计算不同方法比较

在刀具、卡具、模具的设计与加工中,经常遇到歪斜结构,其倾斜的轴线或平面需经过2次旋转,才能转化为垂直或平行面。从解决工程实际中存在的具体问题出发,在工程图学的理论基础上,对上述结构的空间角度问题给出了解析计算与图解2种不同方法,并对其作了科学地比较。     

Ultrasonic beam propagation in highly anisotropic materials simulated by multi-Gaussian beams

The necessity of nondestructively inspecting fiber-reinforced composites, austenitic steels, and other inherently anisotropic materials has stimulated considerable interest in developing beam models for anisotropic media. The properties of slowness surface play a key role in the beam models based on the paraxial approximation. In this paper, we apply a modular muiti-Gaussian beam (MMGB) model to study the effects of material anisotropy on ultrasonic beam profile. It is shown that the anisotropic effects of beam skew and excess beam divergence enter into the MMGB model through parameters defining the slope and curvature of the slowness surface. The overall beam profile is found when the quasilongitudinal (qL) beam propagates in the symmetry plane of a transversely isotropic gr/ep composite. Simulation results are presented to illustrate the effects of these parameters on ultrasonic beam diffraction and beam skew. The MMGB calculations are also checked by comparing the anisotropy factor and beam skew angle with other analytical solutions.     

Mechano mathematical models for mechatronic systems for vibration jaw crushing processes

The aim of this paper is creation, investigation of mono frequency and poly frequency plane and spatial vibrations of two mass vibration systems with a suitable adjustment of the mechanical system. The physical object is a vibrating jaw crusher. The mechanical and mathematical modeling is created on the basis of a two mass dynamic model with six degrees of freedom in plane case—three for each mass and 12 degrees of freedom in spatial model—six for each mass. The influence of the elastic linkages between the two masses and also the energy mutual linkages between the coordinates of the two bodies are investigated.

Natural frequencies and amplitudes of movement are obtained by means of computer experiment in plane and spatial aspect. The obtained results can be used for optimization of the constructive parameters of the vibrating jaw crusher and also for improving harmful resonance effects     

Über verzweigungslagen bei sphärischen viergelenkgetriebenOn the change-points of the spherical four-bar linkage

In discussing the laws of motion of a specific linkage with variable parameters, the limiting or exceptional cases where a change-point position becomes possible is frequently of interest. In this paper it is explained how to obtain the ratios of velocities for spherical four-bar linkages with change-point positions. The positions of the relative pole axes 31 and 20 (i.e. motion of the input link with respect to the output link or motion of the coupler with respect to the fixed link) are of special interest. Passing to the limit leads to the corresponding plane four-bar linkages. Two examples, one linkage from the plane and one from spherical kinematics, conclude the paper.     

Spring equilibrator theory for static balancing of planar pantograph linkages

Static spring balancing theory for planar pantograph linkages is developed using a potential energy approach. Application of this theory achieves static balancing of pantograph linkages in a gravitational field throughout the full range of motion by guaranteeing perfect energy transfer between system gravitational and elastic potential energies. The general planar pantograph linkage is addressed by means of four pantograph types where each type represents a different revolute/prismatic joint arrangement. Equilibrator design for two of these pantograph types represents a first introduction of equilibrium theory to include linkages having prismatic pairs. Applications for walking machine leg design and for vertical plane selective compliance assembly robot design are discussed.     

平面连杆机构轨迹发生器的高阶综合

以运动约束原理为基础，讨论平面连杆机构轨迹发生器高阶综合的一种新方法，并给出全铰链三支座Ｓｔｅｐｈｅｎｓｏｎ型六杆机构的综合实例．     

A numerical study on flow and heat transfer characteristics of film cooling with a compound angle hole

A numerical simulation has been performed for the investigation of flow and heat transfer characteristics of a film cooling system injected through a hole with compound angle orientation. The finite volume method is employed to discretize the governing equations based on the non-orthogonal coordinate with non-staggered variable arrangement. In order to analyze flow and heat transfer characteristics, velocity, temperature, aerodynamic loss coefficient, skin friction and vorticity are calculated with the variation of the skew angle. The maximum longitudinal vorticity and aerodynamics loss depend strongly on the skew angle. For the symmetric case of β=0 deg, a pair of counter-rotating vortices are formed and the maximum value of the film cooling effectiveness has appeared in the center plane where the skin friction is the minimum. For the skew angle of β=30 deg and above, only one strong counter-clockwise vortex remains in the downstream region and the maximum value of the film cooling effectiveness are obtained on the right side of the vortex. The predicted results for the film cooling effectiveness show good agreements with previous experimental data except the near-hole region.     

制造误差对过约束机构性能影响的研究

针对平面闭链机构为超静定的过约束结构和制造误差的非平面性，将结构力学中处理超静定结构的力分析法与平面连杆机构的动力分析相结合，以构件的扭转变形和弯曲变形为变形协调条件，建立了考虑非运动平面过约束的平面加杆机构动力学分析模型，仿真结果揭示了制造误差对过约束机构性能的影响。     

Synthesis of position generating crank-rocker or drag-link mechanismsSynthese de generateurs de position par des mecanismes a manivelle oscillante ou a manivelle double

A method is presented to synthesize crack-rocker or drag-link mechanisms which exactly generate a given set of finitely separated positions of a moving plane with a complete solution to the problem of transmission angle control. This paper is an extension of the recent works [1–3] where partial solutions of input-link rotatability and transmission angle control were considered. It is shown how to eliminate the branch defect from the designed linkages.     

Approximation formulae for natural frequencies of simply supported skew plates

By using the reduction method proposed previously by the author and the exact relation between natural frequencies of an isotropic simply supported skew plate and a skew membrane with the same boundary shape, a few approximation formulae for estimating the natural frequency of simply supported isotropic and orthotropic skew plates are derived from the natural frequency of skew membranes without solving the partial differential equation governing the free vibration of the orthotropic skew plate.     

桥式起重机运行机构啃轨原因分析及处理方法

桥式起重机车轮发生啃轨现象会造成诸多不良后果,分析了啃轨产生的原因,并提出啃轨的修复方法和防止啃轨发生的措施。对促进桥式起重机安全高效工作具有一定的实际应用价值。     

An overconstrained 5-bar with a plane of quasi-symmetry

By means of algebraic screw system theory, Waldron was able to demonstrate full-cycle mobility for classes of line-symmetric and plane-symmetric linkages. They included some classical loops as special cases. In this paper it is shown that one of Waldron's classes, the general plane-symmetric 5-bar is itself a special case of another 5-bar group, possessing a plane of quasi-symmetry, but basically defined by having two pairs of adjacent screw axes parallel.     

Solution region synthesis method of planar one-dof six-bar linkages for specifying 4-positions of a 3R open chain

This paper addresses the synthesis problem of one-dof six-bar linkage motion generation for four precision points. A novel and convenient synthesis approach is introduced. With our method, a 3R chain that guides the movement of its end-effector through a set of four specified task positions is given. We then attach two RR links to this 3R chain to obtain a six-bar linkage. Motion generation can produce an infinite number of solutions for four desired positions. It is difficult for designers to synthesize defect-free linkages and synthesize the best linkage through rapidly and precisely selecting curve points that satisfy every design condition. To solve this problem, a solution region method is given in this paper. With this method an infinite number of mechanism solutions can be expressed on a coordinate plane. In addition, the paper still puts forward a distinguishing method for testing circuit and branch defects for Watt-I six-bar linkages. The feasible mechanism solution regions without any defects are obtained by using the solution region method.     

Prediction of Roller Skewing in Tapered Roller Bearings

The paper proposes a comprehensive model to predict the skew movement of a roller in tapered roller bearings. Numerical solutions are given on a LM48548/LM48510 bearing. The effect of the shaft speed, ring misalignment, and lubricant temperature on the roller skew angle is presented and compared to the experimental data available in the literature. The results indicate that the skew angle depends first on the misalignment angle between the cup and the cone. The roller skew is also greatly influenced by the traction at the roller-flange contact, the skew angle increasing with the traction at this contact, and by the geometry of the roller end.     

Nine-link plane mechanisms for two-variable function generation—II. SynthesisNeunglieddrige ebene funktions getriebe für zwie unabhängige veränderliche: Tiel 2 - Synthese

Methods of synthesizing nine-link plane mechanisms for two-variable function generation are presented. These are simplified procedures which employ identical relative positions and identical absolute positions of links. These techniques split the problem into syntheses of two single-freedom linkages when proper mechanisms are chosen, out of the available nine-link mechanisms. Up to 16 precision points (specified) can be directly satisfied, depending on the mechanism chosen. Numerical examples demonstrate that nine-link mechanisms as two-variable function generators are a practical proposition, especially with the synthesis techniques presented.     

Rolling Element Skew in Tapered Roller Bearings

This paper reports on the roller skew in tapered roller bearings monitored by contact potential difference probes. The effect of the load, rotational speed, and viscosity of lubricant on roller skew angle, along with the variation of bearing torque with the running conditions, were measured on a LM501300 bearing. Two greases (SHC15 and SHC460) were used to lubricate the bearing. The skew angles were found to vary from 0.15° to 0.6°. The results indicate that the skew angle depends on the friction force at the roller-rib interface. An empirical equation is derived which relates the skew angle to the bearing operational parameters.     

Proposals for a finite 5-dimensional atlas of crank-rocker coupler curvesVorschlagen für ein endlich funfdimensional Kurbelschwingen Koppelkurvenatlas

The coupler curves traced by planar 4-bar crank-rocker linkages are examined with the objective of providing guidelines for a new awareness survey. It is found that the coupler points chosen by Hrones and Nelson[1] in the best known atlas of this kind leads to some avoidable duplication and omissions. It is concluded that coupler points should be confined to a circle on the coupler plane having centre on the coupler-rocker bearing and radius equal to the distance between coupler bearings. Five non-dimensional variables are proposed, three of which are discussed in more detail in earlier work[6].