进给系统振动特性研究及新型加减速控制策略

不平滑的运动指令导致数控机床进给过程中产生振动。本研究基于滚珠丝杠进给系统集中质量动力学模型,建立了伺服电机扭矩激励与进给系统响应的理论模型,分析了运动指令加速度曲线功率谱与进给系统振动响应的相关关系。针对加减速策略中存在的加加速曲线开始点和结束点不连续而引入振动激励的问题,提出一种类余弦加加速加减速控制策略,实现了加加速全过程的平滑过渡。以某滚珠丝杠进给实验台架为例,建立并实验验证了该台架的集中质量动力学模型,在此基础上建立了加减速控制策略激励特性分析的仿真模型,对加减速控制策略的激励特性进行了对比分析。仿真结果表明,类余弦加加速策略的激励特性最小,其工作台响应的功率密度是有限加加速策略的万分之一,是正弦加加速策略的1%。

Excitation Response Characteristics of Ball Screw Feed Drive System and Cosine-Like Jerk Motion Profiles

The motion commands to feed drives constitute a major source for excitation of the machine tool feed drive vibrations. Firstly, based on the lumped mass model of ball screw feed drive system, a theoretical model between servo motor torque excitation and system response is established. The co-relation between acceleration profile of motion command and the excitation response characteristics of feed drive system is analyzed. The discontinuous curve at the start point and the end point of jerk profiles in the existing motion profiles leads to frequency contents, which may cause the feed drive into vibration. Secondly, a Cosine-like Jerk motion profile is proposed, which eliminate the discontinuous jerk curve and reduce the excitation on the feed drive system. Finally, taking a ball screw feed drive test bench as the research object, the lumped mass model is established and experimentally verified. On this basis, a simulation model to study the excitation characteristics of motion profiles is established, and then the excitation characteristics of motion profiles are compared and analyzed. Simulation result shows that, Cosine-like Jerk motion profiles has the smallest excitation characteristics, the power density of the second order nature frequency of the work table response is only about 1/10000 of the Jerk-limited motion profiles and about 1/100 of the sine Jerk profiles.