共查询到19条相似文献,搜索用时 171 毫秒
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本文运用活动标架法和曲线与直纹面相伴理论 ,证明了连杆空间运动时 ,在任意瞬时 ,其动定瞬轴面于瞬轴上相切地接触 ,并有相同的 Frenet标架。得出了瞬轴面诱导结构参数的运动学意义 ,即 α* 仅与连杆的瞬时移动有关 ,β*仅与连杆的瞬时转动有关。并计算出了连杆上的加速度瞬心 ,变向点和拐点 相似文献
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与自由曲面相比,直纹面是一参数直线集,由直线L在空间沿轨迹曲线Γ运动得到,其加工方法技术较复杂,成本高。利用空间连杆机构结构简单、控制容易、运动连续等特点,主动曲柄的连续转动驱动机构运动,同时改变机构杆长、副长或扭角,可使起始点于连杆端点的刀具沿连杆运动曲线作主运动,并沿该连杆本身作直线进给运动,完成直纹面的切削加工。该方法技术原理简单成本低,并能实现高效率,高精度的曲面零件连续线接触精加工。 相似文献
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以四连杆假肢膝关节机构为研究对象,建立了该机构的运动学模型,并利用三心定理导出了连杆瞬心轨迹.围绕假肢膝关节运动必须接近人体自然运动的要求,提出了在满足假肢膝关节机构仿生学约束、双摇杆机构尺寸、连杆实际瞬心与理想瞬心轨迹相似等约束的前提下,充分考虑了瞬心变化的敏感性,使运动过程中连杆实际瞬心与理想瞬心最大偏差最小化的假肢膝关节机构优化设计方法. 相似文献
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平面连杆曲线的分布规律及其曲线绘制的一种简捷方法 总被引:1,自引:0,他引:1
基于平面四杆机构的连杆对机架作平面运动的一对瞬心线,研究了连杆平面的运动及连杆曲线的形成情况,从而给出了平面四杆机构的连杆曲线形状变化及其类型分布的规律,并提出一种绘制连杆曲线的简捷方法。 相似文献
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通过对斯蒂芬森六连杆机构滑块产生低速运动机理的分析,指出机械压力机滑块能否产生低速运动主要是由连杆曲线是否具有低速运动段所决定的。生成具有低速运动段的连杆曲线的条件是铰链四杆机构的连杆的长度应该比较短,摇杆的长度应该和机架长度接近或相等,生成连杆曲线的P点应该在距离瞬心C点很近的位置。滑块产生低速运动的关键参数是连杆的长度和P点到瞬心C点的距离。以公称压力为2 MN的JH23-200型机械压力机的技术参数为依据,设计出了斯蒂芬森六连杆机械压力机。该机械压力机与同规格的原机械压力机相比较, 其低速锻冲特性有了明显的提高。 相似文献
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在五轴联动数控系统中,相邻刀位点间的运动通过直线、圆弧或样条曲线进行插补运动,其中直线插补方法最具典型性。以圆柱刀侧铣加工直纹面时因线性插补引起的非线性误差为研究对象,首先,在被加工曲面上采用最佳一致逼近法规划圆柱刀侧铣直纹面的刀具位置;然后,利用包络原理建立刀具线性插补时所形成的包络面解析表达式;以理想曲面为基准面,利用牛顿迭代法求取点到曲面的最小距离,从而建立刀具包络面与理论曲面的误差模型,以此得到刀具线性插补时产生的非线性误差;最后,利用MATLAB软件通过数值算例对影响非线性误差的规律、大小以及其影响因素进行了分析。 相似文献
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本文对挠性件连杆组合机构的运动特性进行了研究,介绍了分析这种机构的瞬心图解法,利用计算机缓制了间歇、逆转与角加速度峰值变化曲线,最后讨论了运动学参数对运动性能与动力性能的影响。 相似文献
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The position synthesis of planar linkages is to locate the center point of the moving joint on a rigid link, whose trajectory is a circle or a straight line. Utilizing the min-max optimization scheme, ... 相似文献
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Josef Hoschek 《Mechanism and Machine Theory》1982,17(3):197-206
Fully intermeshed, co-rotating multiple-screw machines constitute an important class of equipment in the chemical processing and plastics industries. Such machines have rotors, which are customary congruent. D. G. TAYNAN [1] has constructed rotor-profiles, these profiles consist of segments of circles and have tips. From the kinematical point of view the congruent profiles are twin envelopes. In the present paper we determine smooth twin envelopes in the plane, the method is further extended to spherical and spatial motions. As a special case we obtain in the plane and on the sphere twin noncircular centrodes and in the space twin noncircular axodes, since the velocity ratio isn't assumed to be constant. By this way we find the relations due to FREUDENSTEIN and PRIMOSE. 相似文献
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Plücker's and Klein's equations provide an upper bound on the number of real inflections on the coupler curve of a hinged planar four-bar mechanism. Generally, for any configuration of the four-bar, the coupler points whose trajectories exhibit inflections lie on a circle. The coupler plane is partitioned by the envelope of the inflection circles into connected regions within which every coupler point has the same number of inflections on its trajectory. This enables us to locate coupler curves exhibiting the maximum possible number of inflections. 相似文献
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含有C-C二副杆的空间机构自适应运动综合方法 总被引:1,自引:1,他引:0
提出了用球面像曲线和空间腰曲线来描述空间直纹面的几何性质,进而将含有C-C二副杆的空间机构近似运动综合转化为球面像曲线和空间腰曲线的自适应拟合问题,给出了近似球面像圆点、近似圆柱面腰点等定义,构造了球面像曲线的自适应圆锥拟合和空间腰曲线的自适应圆柱面拟合的统一数学模型,建立了含有C-C二副杆的空间机构近似运动综合的自适应方法,并给出了通用的鞍点规划求解方法,算例表明该优化方法是收敛的、有效的。 相似文献
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Adaptive tool-path generation on point-sampled surfaces 总被引:1,自引:0,他引:1
In this paper, we present a new approach to generate tool paths for machining point sampled surfaces using a direct projection algorithm, which is based on generating tool paths along planar intersection curves. In our implementation, a guide surface, with simple geometry like planes or cylinder surfaces, is first created according to the bound volume of the point cloud and initial tool paths are planned on it in terms of the motion pattern of the cutters. For each point of the initial tool paths, then, the corresponding cutter contact point (CC) of the point set surface is located by projecting the point onto the point cloud using the direct projection algorithm. In order to obtain adaptive cutter location points (CL), a least squares-based curve fitting method is applied to approximate the CC points using piecewise cubic Bezier, and a numerical method derived to estimate the length of the curve is used to adjust the position of the points along the curve, and make them evenly spaced on the curve with equal arc lengths. In addition, considering that offset curves or surfaces are necessary for locating CL points in many applications, such as machining using ball end milling cutter, torus ended milling cutters, an offset strategy for cubic Bezier curves is also studied. By testing the proposed method on several point clouds, it has been demonstrated to be promising. 相似文献
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逆向工程软件的曲面反求中,曲率较大的地方往往难以得到较好的曲面反求效果,针对该问题提出了一种基于曲率变化的分块曲面构建拼接方法。该方法根据曲率显示的点的颜色特征进行点云数据的分割,分别获得单片光滑曲面,然后将单片曲面拼接起来以实现完整的自由曲面造型。在曲面拼接过程中,调整两片曲面相邻两列控制点,使其三点共线,以达到拼接处一阶连续。最后通过一个典型的实例证明该方法构造的曲面与原始点云的最大误差为由点阵直接拟合生成的曲面误差的1/3,为由点一线一面构造的整块曲面误差的1/5。 相似文献
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M. H. Korayem A. Heidari A. Nikoobin 《The International Journal of Advanced Manufacturing Technology》2008,36(5-6):606-617
In this paper a general formula for finding the maximum allowable dynamic load (MADL) of flexible link mobile manipulators
is presented. The main constraints used for the proposed algorithm are the actuator torque capacity and the limited error
bound for the end-effector during motion on a given trajectory. The accuracy constraint is taken into account with two boundary
lines which are equally offset due to the given end-effector trajectory, while a speed-torque characteristics curve of a typical
DC motor, is used for applying the actuator torque constraint. Finite element method (FEM), which is able to consider the
full nonlinear dynamic of mobile manipulator is applied to derive the kinematic and dynamic equations. In order to verify
the effectiveness of the presented algorithm, two simulation studies considering a flexible two-link planar manipulator mounted
on a mobile base are presented and the results are discussed. 相似文献
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M. H. Korayem A. Heidari A. Nikoobin 《The International Journal of Advanced Manufacturing Technology》2008,36(9-10):1010-1021
In this paper a general formulation for finding the maximum allowable dynamic load (MADL) of flexible link mobile manipulators is presented. The main constraints used for the proposed algorithm are the actuator torque capacity and the limited error bound for the end-effector during motion on a given trajectory. The accuracy constraint is taken into account with two boundary lines which are equally offset due to the given end-effector trajectory, while a speed-torque characteristics curve of a typical DC motor is used for applying the actuator torque constraint. The finite element method (FEM), which is able to consider the full nonlinear dynamics of mobile manipulators, is applied to derive the kinematic and dynamic equations. In order to verify the effectiveness of the presented algorithm, two simulation studies considering a flexible two-link planar manipulator mounted on a mobile base are presented and the results are discussed. 相似文献