基于模态预测及敏度分析的机床动特性设计方法

Improving Machine Tool Dynamic Performance Using Modal Prediction and Sensitivity Analysis Method

为了提高机床的动态性能,以机床整机固有频率和频响函数振幅为目标,提出基于机床测试数据、进行试验模态分析及灵敏度计算的机床动态特性设计方法。方法首先提取机床测试数据建立机床结构原型模型,逐步计算机床大件结构和整机的固有频率对刚度、质量的灵敏度,确定结构薄弱环节;继而,对薄弱结构,采用模态预测和灵敏度分析方法设计计算,获取更合理的质量和刚度;之后,将设计分析结果输入LMS_Test.lab软件,借助软件完成对原型结构的模态修改,对修改后结构的动力学特性进行模态预测;最后,进行预测结果模态置信验证,确认模态预测的正确性,完整机床动态特性设计方法体系。将该方法应用于实际机床设计中,对比整机优化前后的频响函数曲线和仿真分析验证均证明,基于模态预测及灵敏度分析的机床动态特性设计方法完成的机床优化设计使得机床固有频率得到提高的同时振幅下降,机床的大件结构及整机的动态性能均有提升。

Based on machine test data, test mode analysis and sensitivity calculation, a design method is proposed to improve the dynamic performance of the machine tool, in which the natural frequencies of the machine tool and the amplitude of frequency response function are taken as the research objects. Firstly, the stiffness and mass sensitivity with respect to natural frequency are calculated to find weaknesses position of the structures, for the main components and the whole machine tool, respectively. Secondly, the more reasonable stiffness and mass are deduced based on the proposed method for the weaken structures. Thirdly, the improved scheme is modified by the LMS Test.lab software and the reliability of the results is ensured by the modal analysis criterion (MAC). The method is applied to the machine tool design, and the simulation results show that the new machine tool dynamic performances are improved with the increased natural frequencies and the decreased amplitudes.