变杆长对曲柄滑块机构位移可靠性的影响分析

为分析杆长变化对滑块位移可靠性的影响,建立了包含杆长尺寸误差和运动副间隙因素下偏置曲柄滑块机构滑块位移可靠性的计算模型。对所建立的滑块位移可靠性计算模型的计算精度进行了仿真验证,结果表明其计算精度可满足工程设计要求。基于MATLAB软件的仿真得出滑块位移可靠性随着曲柄长度减小、连杆长度增加、偏距长度减小而提高。在运动副间隙为连续接触模型时,杆长变化对可靠性的提高比非连续接触模型时更显著。此研究结果对平面机构位移可靠性的提高具有一定的参考价值。     

空间曲柄滑块机构的运动分析

应用矢量回转法对空间曲柄滑块机构—RSSP机构进行了运动学分析,计算出滑块位移、速度、加速度函数。并基于Pro/E软件平台,对该RSSP机构进行了三维建模、运动仿真,得到滑块的位移、速度、加速度曲线,与理论计算进行对比,结果表明,两种方法所得结果完全一致。所得结论可为该机构在机床设计中的应用奠定理论基础。     

含橡胶连杆的曲柄滑块机构非线性动力学研究

针对橡胶材料构件对机构动力学影响问题,利用有限元方法构建了含橡胶连杆的刚柔耦合曲柄滑块机构动力学模型。对曲柄滑块机构中橡胶材料构件的柔性、曲柄转速、曲柄和橡胶连杆轴承外径尺寸等方面进行了研究,对不同条件下曲柄滑块机构中滑块的位移、速度和加速度等变化规律进行了归纳,通过相图观察法、计算最大Lyapunov指数法和功率谱法讨论了刚柔耦合系统的运动稳定性。研究结果表明:曲柄滑块机构中,橡胶材料柔性和曲柄转速变化对滑块的位移、速度影响较小,对滑块的加速度影响较大;在连杆有效长度不变的条件下,曲柄和橡胶连杆轴承外径尺寸变化对滑块的位移、速度影响较小,对滑块的加速度影响较大;考虑橡胶材料构件柔性时滑块运动是混沌的,曲柄转速和橡胶连杆轴承外径尺寸变化对系统运动的稳定性会产生一定的影响。     

由串联四杆机构组成的多连杆压力机下死点精度的研究

针对压力机的工作特点,分析了滑块下死点精度对于工件精度和模具寿命的重要性。利用系统动力学软件ADAMS建立了串联四杆机构的多体动力学模型并作了运动仿真。研究了曲柄长度、曲柄转速、滑块质量和滑块偏心距的变化对滑块下死点位移曲线的影响。仿真结果表明:随着曲柄长度、曲柄转速或者滑块质量的增加,滑块的下死点会向下偏移,且滑块在下死点附近的位移曲线波动会增大;而滑块偏心距的增加对滑块下死点位移的影响具有相反的作用。文中研究结果可对多连杆压力机的开发提供参考。     

Excel下曲柄滑块机构的可视化、运动分析与动态仿真

建立了通用曲柄滑块机构的运动学计算模型,在Excel环境下对模型进行了可视化、运动分析和机构运动仿真,实现了对曲柄滑块机构位移、速度和加速度变化的动态模拟,为曲柄滑块机构的运动和动力特性分析和优化提供了一种简捷而实用的方法.     

磁流变阻尼器的分数阶Bingham模型研究

为解决磁流变阻尼器的Bingham模型在拟合阻尼力-位移关系时"具有较高精度,但是无法准确描述阻尼力-速度的滞后"的问题,基于传统Bingham模型进行了改进,应用分数阶微分形式的Bingham模型,更加准确地拟合了速度-阻尼力的滞回特性。在改进的模型中以分数阶导数代替了传统模型中位移的一阶导数,既能够描述磁流变液屈服后的粘性剪切流动,又包含磁流变液体在低剪切速率下未屈服时的弹性变形。对一种磁流变阻尼器进行了实验,比较传统Bingham模型和改进分数阶模型阻尼力-位移和阻尼力-速度拟合的精度,分析分数阶微分项阶数与控制电流及阻尼力-速度滞后特性的关系。实验结果表明,分数阶微分形式的Bingham模型拟合磁流变阻尼器力-位移和力-速度关系,其精度均较传统Bingham模型有明显提高。     

考虑间隙的发动机曲柄滑块系统动态特性仿真研究

发动机是汽车的核心部件,曲柄滑块机构是发动机中的重要的传递力和位移的机构。建立曲柄滑块系统的多刚体模型,并通过对系统的运动学机型分析,得到曲柄滑块系统的速度方程与加速度方程。分析转动副间的间隙,并通过建立系统的尺寸链,利用极限法计算得到考虑转动副间隙影响时滑块运动到上止点时的位置。分析发动机的压缩比,建立发动机压缩比计算公式,找到发动机压缩比与滑块上止点的位置、转动副间隙之间的关系。利用MATLAB/Simulink对曲柄滑块系统进行运动仿真,分别得到曲柄作匀速、匀加速运动时,滑块位移与输入的关系。根据仿真得到的滑块运动位移结果,分别计算考虑和忽略转动副间隙时发动机的压缩比。通过结果对比可以看出,由于转动副间隙的存在,减小了发动机压缩比,降低了发动机性能,不利于发动机燃油经济性。     

基于正运动学分析的混合驱动压力机优化设计

考虑冲压过程中压力加工工艺对滑块位移和速度特性的要求，将混合驱动机构用于驱动压力机，并对该机构进行了正运动学分析，建立了优化数学模型；通过两步优化使滑块的实际位移曲线尽量逼近理想的位移曲线，优化得出了各构件的尺寸和实现不同运动规律的伺服电机的运动规律，从而可使滑块的输出运动能实现一组较理想的轨迹，分析了混合驱动压力机的优点。     

对心椭圆曲柄滑块机构运动特性分析

椭圆曲柄是能够生成椭圆曲线的行星机构,用椭圆曲柄作为曲柄滑块机构的驱动曲柄,相当于一个具有变化的长度和速度沿着椭圆曲线运动的曲柄,从而改变了滑块的运动特性。文中研究了对心椭圆曲柄滑块机构的运动特性,给出了机构的曲柄存在条件、最小传动角、滑块极限位置、行程速度变化系数等性能参数的计算方法。提出了按位移特性对椭圆曲柄滑块机构进行类型划分的分型方法,给出了各类型机构的存在条件。     

多连杆压力机优化设计

针对某一新型的多连杆高速压力机,进行了运动学分析建模。根据给定的性能指标,基于Matlab编程软件,利用步长搜索法对各杆件的结构尺寸进行优化设计。在优化参数基础上,获得压力机主滑块的位移、速度和加速度曲线,并与传统曲柄滑块机构运动曲线进行了比较,结果表明此多连杆压力机具有下死点附近位移曲线相对平缓,进程和回程速度快等特点,对于工件成型精度和提高加工效率有一定的意义。     

A real-time NURBS motion interpolator for position control of a slide equilateral triangle parallel manipulator

This study presents a real-time non-uniform rational B-spline (NURBS) motion interpolator command generation for position control of a new design to achieve a six-degree-of-freedom (6dof) slide equilateral triangle parallel manipulator (SETPM). The existing method utilizes the approximate method to obtain the characteristics of curves of the velocity and acceleration for the feed-forward compensation in the joint space. However, the NURBS motion interpolator command generation is related to the geometric characteristics of curves including position, tangent, and curvature to the motion dynamics of the SETPM including position, velocity and acceleration for applied directly the feed-forward compensation in the global space. The inverse dynamics controller (IDC) is the power of control law. However, implementing the inverse dynamics control laws requires accurately knowing the system dynamic model parameters and computing the complete equations of motion in real time. To reduce the time for calculating the inverse dynamic, this study proposes a feed-forward compensation with feedback proportional derivate (PD) control to take the place of inverse dynamics control for reducing both the inverse dynamic calculation time and the tracking error. The proposed real-time NURBS motion interpolator command generation and feed-forward compensation with feedback PD control are also successfully applied to a slide equilateral triangle parallel manipulator on a PC-based system to achieve high motion precision.     

Whitworth急回机构运动特性分析及仿真研究

文章先用解析法建立Whitworth急回机构运动特性的数学模型,举例求出曲柄在不用位置时,滑块的运动变化情况。然后基于UG的运动仿真,将滑块的运动结果以图表和电子表格的形式输出。最后将解析法计算值与仿真运算结果进行比较,以验证解析法数学模型的正确性,并用电子表格找出滑块的速度和加速度的极值,为机构的动力分析和优化设计提供参考依据。     

搬运机械臂的初始加速度和速度连续运动规划研究

工业机械臂在执行搬运任务时可能会出现初始关节加速度和速度跳变的情况,这会影响机械臂电机的使用寿命,并使搬运的物品受到较大的冲击力,从而造成物品的损坏.针对该情况,设计了一种基于伪逆的机械臂初始加速度和速度连续运动规划方案.首先,根据机械臂关节角状态和末端执行器运动状态,对机械臂在加速度层以及速度层上建立伪逆算法求解模型...     

Electronic cam motion generation with special reference to constrained velocity, acceleration, and jerk

Electronic cam motion involves velocity tracking control of the master motor and trajectory generation of the slave motor. Special concerns such as the limits of the velocity, acceleration, and jerk are beyond the considerations in the conventional electronic cam motion control. This study proposes the curve-fitting of a Lagrange polynomial to the cam profile, based on trajectory optimization by cubic B-spline interpolation. The proposed algorithms may yield a higher tracking precision than the conventional master-slaves control method does, providing an optimization problem is concerned. The optimization problem contains three dynamic constraints including velocity, acceleration, and jerk of the motor system.     

基于精度控制的刀具轨迹自适应拟合算法

为解决传统数控系统在进行曲线曲面离散连续微小线段刀具轨迹加工中频繁加减速、加工速度缓慢、加工质量不高等问题,提出了一种基于精度控制的刀具轨迹自适应NURBS曲线拟合算法,该算法通过提取连续微小线段刀具轨迹的主要特征点,进行基于精度控制的自适应添加特征点的迭代拟合。仿真测试结果表明,该算法可以在保证拟合精度的条件下有效提高计算效率,压缩数据量。     

High Resolution Clinometers for Measurement of Roll Error Motion of a Precision Linear Slide

This paper proposes a new method for measurement of the roll error motion of a slide table in a precision linear slide. The proposed method utilizes a pair of clinometers in the production process of a precision linear slide, where the roll error motion measurement will be carried out repeatedly to confirm whether the surface form errors of slide guideways in the linear slide are su ciently corrected by hand scraping process. In the proposed method, one of the clinometers is mounted on the slide table, while the other is placed on a vibration isolation table, on which the precision linear slide is mounted, so that influences of external disturbances can be cancelled. An experimental setup is built on a vibration isolation table, and some experiments are carried out to verify the feasibility of the proposed method.     

High Resolution Clinometers for Measurement of Roll Error Motion of a Precision Linear Slide

This paper proposes a new method for measurement of the roll error motion of a slide table in a precision linear slide. The proposed method utilizes a pair of clinometers in the production process of a precision linear slide, where the roll error motion measurement will be carried out repeatedly to confirm whether the surface form errors of slide guideways in the linear slide are sufficiently corrected by hand scraping process. In the proposed method, one of the clinometers is mounted on the slide table, while the other is placed on a vibration isolation table, on which the precision linear slide is mounted, so that influences of external disturbances can be cancelled. An experimental setup is built on a vibration isolation table, and some experiments are carried out to verify the feasibility of the proposed method.     

Drawing motion profile planning and optimizing for heavy servo press

An efficient drawing mode for heavy servo press was proposed with four sections which are defined on the whole slide motion stroke. Four key control points, which represent the requirements of drawing process, were employed to realize the eccentric drawing motion profile planning. To reduce the power requirement of the servo motor, a flexible acceleration and deceleration control algorithm was proposed, and the eccentric motion profile of the servo press was constructed based on the algorithm. Then, the optimization model of the drawing eccentric motion profile was established to maximize the production rate, taking into account all boundary conditions including the maximum velocity and acceleration of slide, the space and time limit of feeder, the torque and thermal limit of servo motor. This optimization model was solved by the combination of the penalty function and the complex method, which need the least time. The program of the drawing motion profile optimization was developed and applied on a 2,500 t servo press. Finally, the experimental validation of the body side panel drawing was carried out. The results show that the proposed efficient drawing mode and the optimization method could obtain the optimal motion profile and the maximum production rate. This research provides the theoretical foundation and optimization method for the drawing motion profile optimization design for heavy servo press.     

A control strategy with motion smoothness and machining precision for multi-axis coordinated motion CNC machine tools

The advanced manufacture technology requires that multi-axis coordinated motion computer numerical control (CNC) machine tools have the capability of high smoothness and high precision. At present, the study of the motion smoothness mainly concentrates on the acceleration and deceleration control method and the look-ahead process of velocity planning in the interpolation stage. The control strategy of the contouring error mainly focuses on tracking error control, cross-coupling control, and optimal control. In order to improve the motion smoothness and contouring precision for multi-axis high-speed CNC machine tools, a multi-axis modified generalized predictive control approach was presented in this paper. In the control strategy, the estimation models of tracking error, contouring error, velocity error, and acceleration error were structured separately. A new improved quadratic performance index was proposed to guarantee the minimum of these errors. Generalize predictive control was also introduced, a multi-axis generalized predictive control model was deduced for motion smoothness and machining precision for multi-axis coordinated motion CNC system, and an approved multi-axis generalized predictive controller based on the model was designed in this paper. The proposed predicted control approach was evaluated by simulation and experiment of circular, noncircular, and space line trajectories, respectively. These simulative and experimental results demonstrated that the proposed control strategy can significantly improve the motion smoothness and contouring precision. Therefore, the new position control method can be used for the servo control system of multi-axis coordinated motion CNC system, which increases motion smoothness and machining precision of CNC machine tools.     

时变位姿下行星齿轮传动系统动应力计算模型及其参数影响研究

考虑行星轮系内部非惯性和机体时变位姿外部非惯性的综合影响,推导了任意时变位姿下带有机匣的行星轮系构件运动方程,计入时变啮合刚度、啮合误差、侧隙和啮入冲击,建立了时变位姿下行星齿轮传动系统级动力学模型,并采用精细积分时程法（Precision integration method,PIM）求解得到了动态啮合力序列。根据齿间载荷分配关系进一步得到单齿啮合力序列。最后结合修正Heywood公式与Hertz公式构建了时变位姿下行星齿轮传动系统齿根弯曲动应力和接触动应力计算模型,并研究了机体平飞、滚转和筋斗位姿参数对接触动应力、弯曲动应力的影响规律。结果表明：不同时变位姿参数对弯曲、接触动应力影响显著,且对不同齿轮副影响不同,即加剧了齿轮副间承载不均;筋斗运动角速度对动应力影响比平飞加速度、滚转角速度以及筋斗回转半径对其影响复杂;机匣对动应力影响随加速度增大而增加。研究成果为时变位姿下行星齿轮传动动应力计算与高可靠性设计提供了理论依据。