八连杆压力机传动机构的优化设计

Optimization design on transmission mechanism for eight-bar linkage press

在ADAMS中建立传动机构的铰接点,连接各点建立八连杆机构的虚拟样机模型。参数化各铰接点的横纵坐标作为设计变量,比较各设计变量对工作行程内滑块速度标准差的影响,选择敏感度较大的设计变量作为优化变量。基于曲柄存在条件建立约束关系,以工作行程内滑块速度标准差的最小值作为优化目标。采用广义简约梯度法,引入松弛变量将不等式约束转化成等式约束,用非基变量表示基变量,将目标函数改写成关于非基变量的表达式,进行迭代计算得到优化结果。适当调整优化后设计变量的值,得到最终的结果。与优化前机构对比,工作行程内,最大速度由590 mm·s^(-1)降至425 mm·s^(-1),速度标准偏差由175 mm·s^(-1)降至120 mm·s^(-1)。

In ADAMS,the hinge point of the transmission mechanism was established,and the virtual prototyping model of the eight-bar linkage mechanism was established. The vertical and horizontal coordinates of each hinge point were parameterized as the design variables,and the more sensitive design variables were chosen as optimization variables by comparing the influence of each design variable on the standard deviation of the slider speed within the work stroke. Then,the minimum value of the standard deviation of the slider speed in the working stroke was regarded as the optimization target based on the existence of crank to establish restrictions. Furthermore,inequality constraints were turned to equality constraints by generalized reduced gradient and introducing the slack variable,and the objective function was changed into the expression with non-base variables by taking the non-base variables expressing the base variables. Finally,the optimal results were obtained by adjusting appropriately design variables. Compared with the pre-optimization mechanism,the maximum speed is decreased from 590 mm · s^（-1） to 425 mm · s^（-1）,and the standard deviation of the speed is decreased from 175 mm·s^（-1） to 120 mm·s^（-1） within the work stroke.