多变量龙门铣床振动主动控制方法的研究

Research on Active Vibration Control Method for Multivariable Gantry Milling Machine

针对龙门铣床垂直滑枕容易发生颤振,导致加工产品精度下降的问题,对多变量龙门铣床振动主动控制的方法进行研究。对垂直滑枕的模态进行分析,观察其结构的模态形状,以研究其动态特性。采用多输入多输出系统中的自动功率谱及交叉功率谱求取其传递函数,并得到多变量传递函数的频域公式。利用多变量传递函数的奇异值信息,获取多变量系统的数学模型。通过H∞回路成形方法求取开环系统的补偿函数,在扰动系统鲁棒裕度值的基础上,求取稳定控制器模型,对龙门铣床垂直滑枕进行振动主动控制。采用所提方法及PID方法对不同激励信号下垂直滑枕产生的振动进行控制,结果表明:在方波及正弦波激励信号下,利用所提方法控制的最大振动幅度较PID方法控制的最大振动幅度分别减小了39.88%和37.21%。该方法对垂直滑枕的振动控制效果较好,能够提高龙门铣床工作时的稳定性。

Aimed at the problem that vertical ram of a gantry milling machine is prone to flutter,which leads to the decrease of machining precision,an active vibration control method for multivariable gantry milling machine was studied.The modal of the vertical ram was analyzed,and the modal shapes of its structure were observed to study its dynamic characteristics.The transfer function was obtained by using the automatic power spectrum and the cross power spectrum in the MIMO system,and the frequency domain formula of the multivariable transfer function was obtained.The singular value information of the multivariable transfer function was used to obtain the mathematical model of the multivariable transfer system.The compensation function of the open-loop system was obtained by using H∞loop shaping method.On the basis of robust margin of disturbance system,the stability controller model was obtained to actively control vibration of the vertical ram of the gantry milling machine.The proposed method and PID method were used to control vibration of the vertical ram under different excitation signals.The results show that the maximum vibration amplitude of the vertical ram controlled by the proposed method is reduced by 39.88%and 37.21%respectively compared with that of PID method under square wave and sine wave excitation signals.The method has good effect on vibration control of vertical ram and can improve the stability of the gantry milling machine.