平面四杆机构急回运动特性的分析

急回特性是平面四杆机构的重要特性,极位夹角的大小决定着急回特性的程度.针对现有极位夹角定义存在的缺陷,对平面四杆机构极位夹角的定义做了较确切的表述,并且对行程速比系数的可能取值范围进行了分析.     

关于曲柄摇杆机构极位夹角的若干命题及其应用

针对具有急回特性的Ⅰ、Ⅱ型曲柄摇杆机构,通过深入分析极位夹角与构件尺寸之间的内在关系,获得了Ⅰ型曲柄摇杆机构极位夹角分别小于、等于或大于90?的几何条件以及Ⅱ型曲柄摇杆机构极位夹角一定小于90?的结论,揭示了曲柄摇杆机构设计时作为已知条件的极位夹角和摇杆摆角之间应满足的要求。首次将研究结果综合形成为5个定理,并通过实例说明了这些定理的应用。     

平面低副四杆机构极位夹角及行程速比系数分析

通过对平面低副四杆机构极位夹角传统定义的分析,根据机构中各杆长的变化,对极位夹角的定义进行了扩展,在此基础上对行程速比系数的取值范围进行了合理的选择。     

曲柄摇杆机构极位夹角的定义及图解设计新思路

曲柄摇杆机构的急回特性与其极位夹角θ密切相关.通过对曲柄摇杆机构急回特性运动分析,提出更符合工程应用实际,具有通用性的新的极位夹角θ定义和反映行程速比系数k与极位夹角θ的关系式,并提出一种图解法设计的新思路.     

平面四杆机构的极位夹角及行程速比系数分析

通过对平面四杆机构急回特性的分析,重新对极位夹角进行了定义,克服了现行众多教科书中的行程速比系数K与极位夹角θ的关系式在应用上的局限性,分析了行程速比系数的变化范围,并从工程实际出发,总结了平面四杆机构行程速比系数的合理取值。     

关于平面连杆机构极位夹角的定义

在平面连杆机构设计中，极位夹角的大小决定着机构急回运动的程度。针对现有的极位夹角的定义所存在的缺陷，提出了补充修改意见，给出了对各种连杆机构都适用的意义。     

三解圆定理的全面表述与证明--再谈曲柄摇杆机构的辅助圆图解设计法

根据文献[1]对极位夹角定义的完善,曲柄摇杆机构极位夹角θ的定义范围由0<θ<90°扩大为0<θ<180°,相应对三解圆定理[2]的表述作了较大的调整,并进行补充证明。新的三解圆定理是对传统图解设计法的更大改进,简明易行,不仅适用于极位夹角为锐角的情况,而且适用于极位夹角为钝角或直角的情况。     

平面低副四杆机构极位夹角的研究

对平面低副四杆机构极位夹角的定义进行了探究.提出了一种可以解决实际问题的全新概念,扩展了平面低副四杆机构极位夹角的取值范围,更符合工程实际,具有较强的实用性,为设计出急回程度更大的机械提供了依据.     

平面连杆机构极位夹角定义的探讨

急回平面连杆机构实现了机构工作行程的慢速进给和空间行程的快速退回，从而提高了生产率，而平面连杆机构的急回特性与其极位夹角θ密切相关，现行的众多教科书中对极位夹角的定义和锐角的取值范围，限制了书中所确定的行程速比系数k与极位夹角θ的关系式的通用性，本文对极位夹角θ的新定义解决了这个问题，并通过实例说明了其正确性和可行性。     

曲柄摇杆机构中极位夹角定义及图解法研究

针对教材中的曲柄摇杆机构极位夹角定义，提出了新的定义，并对极位夹角的范围给出了新的取值范围，使其更符合工程实际。针对新的定义提出新的图解法，使其更全面。     

曲柄摇杆机构极位夹角新定义及按K值图解设计方法的探讨

就曲柄摇杆机构急回运动分析中所涉及到的几个问题 ,如曲柄摇杆机构极位夹角 θ的定义问题、行程速比系数 K的表达式以及根据 K值图解设计四杆机构的方法提出了自己的一些新的见解     

A comprehensive genetic algorithm for design optimization of Z-bar loader working mechanism

The operation mechanism is generally considered as a key component of a wheel loader. Its working performance has great influence on the service life, stability, efficiency and economy of the loader. This paper establishes a mathematical model of Z-bar loader mechanism in polar coordinate with four-bar linkage and six-bar Watt linkage synthesis, investigates the working performance, such as mechanism transmission ratio, carry stability, parallelism, dumping in any position, bucket flat setting, maximum dig depth, extreme transmission angle and so on. Then we explore new design methods of joint-position of Z-bar loader linkage between tilt cylinder and loader frame to perfect some of the performance. A new method, comprehensive genetic algorithm, is presented to optimize non-linear equation with multi-constraints, and the results improve the multidisciplinary performance. Furthermore, a virtual prototype of the working mechanism is modeled to simulate and verify the optimization results.     

按最大压力角确定直动杆凸轮机构的基本尺寸

本文基于平面凸轮机构与平面四杆机构运动和动力特性相似原理,直动从动件盘形凸轮机构最大压力角作用位置与瞬时替代的曲柄滑块机构最大压力角位置相同,导出凸轮机构最大压力角,及其作用位置与从动件运动规律的关系式,得出最大压力角作用位置仅与运动规律有关,与基本尺寸无关。由关系式计算最佳凸轮机构的基本尺寸。     

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.     

Comprehensive optimum and adaptable design methodology for the working mechanism of a wheel loader

The working mechanism is an important part of a wheel loader. It is used to accomplish the shoveling, loading, lifting, and dumping tasks. Usually, the working mechanism is a Z-bar linkage and the dimensional design of the linkage directly affects the loader’s service performance, such as dumping clearance and dumping height. As there are many other performance indexes and various field requirements for the loader, comprehensive optimum, and adaptable design methodology with full-parameterized kinematic model attracts engineers’ research interests. Focusing on the multi-objective and multi-variable problems, this paper firstly establishes an accurate and simplified kinematic model of the Z-bar linkage with deduced expression of the basic parameters, and then investigates the performance indexes including mechanism transmission ratio, lifting stationary, dumping angle in any position, bucket flat setting, and extreme transmission angle, etc. With the full-parameterized kinematic model and the optimum algorithm, modified complex method, a comprehensive and adaptable design platform is built to solve the multi-objective and multi-variable problems of the Z-bar linkage. A case study with two optimization schemes as “full variables design” and “partial variable design” is conducted. The simulation results show that both schemes are better than the original one. The methodology and platform in this paper are of importance in generating user requirement oriented linkage design schemes with enough consideration and optimization of multiple performance indexes.     

Development of a novel variable rake angle mechanism for noncircular turning and its control

A prototype tool stage with a variable rake angle mechanism has been developed and controlled. The objective of the variable rake angle mechanism is to provide two-degrees-of-freedom to the conventional noncircular turning process, so that the rotational tool mechanism can compensate for the rake angle change caused by the noncircular cam profile itself while the translational tool motion generates the cam profile. Inverse kinematics, kinematic sensitivity and stiffness, and design of the variable rake angle mechanism are discussed. Robust repetitive controllers are designed for two actuators in the variable rake angle mechanism. Two actuators operate together to change the tool position as well as the tool angle. Experimental results on the variable rake angle mechanism support the design concept and control approach.