基于状态空间模型的机床加工精度分析

伺服进给系统的机电耦合特性直接影响数控机床的加工精度,单独针对伺服系统或机械系统建立的模型不足以准确分析系统参数对机床整机加工精度的影响。因此,综合考虑机床伺服系统与机械结构之间的耦合关系,建立伺服进给系统机电耦合动力学模型具有重要意义。首先,为保证伺服进给系统建模精度,利用状态空间法建立了机床机电耦合状态空间方程。其次,建立了伺服进给系统机电耦合Simulink模型,在此基础上采用复合控制提高系统的响应速度和加工精度。随后,利用多体动力学软件建立机床进给系统的刚柔耦合动力学模型,添加摩擦、阻尼等非线性因素,并导入Simulink与伺服系统建立耦合关系。最终,建立了卧式加工中心伺服进给系统的刚柔-机电耦合仿真加工平台,通过模拟机床加工轨迹以验证机电耦合状态空间模型的可靠性。结果表明:该状态空间模型能准确描述系统内部参数和系统输入输出的耦合关系;采用复合控制结构能有效提高系统的响应速度和加工精度。研究结果为数控机床的仿真建模和提高加工精度提供理论依据,为机床机电系统的设计提供有效指导。

Machining accuracy analysis of machine tool based on state space model

The machining accuracy of the CNC (computer numerical control) machine tool is directly affected by the electromechanical coupling characteristics of the servo feed system, which means a model established for servo system or mechanical system alone is not sufficient to study the influence of system parameters on the machining accuracy exactly. Therefore, it is important to synthetically consider the coupling relationship between servo system and mechanical structure of machine tool and establish the electromechanical coupling dynamics model of the servo system. Firstly, in order to ensure the accuracy of servo feed system modeling, the mechanical and electromechanical coupling state space equations of machine tools were established by the state space method. Secondly, the electromechanical coupling Simulink model of servo feed system was established, and on this basis, the composite control was adopted to improve the responding speed and tracking accuracy of the system further. Subsequently, the rigid-flexible coupling dynamics model of machine tool feed system was established by using multi-body dynamics software, and the dynamics model was imported into Simulink and coupled with the servo control system after added the nonlinear factors such as friction and damping. Finally, the rigid-flex and electromechanical coupling simulation platform of the horizontal machining center servo feed system was established and the reliability of the state space model was verified by simulating the machining path on the platform. The results showed that the coupling relationship between the internal parameters and the input and output parameters of the system was described more accurately by the state space model, and the performance of the system was improved greatly by the compound control structure. The research results can provide theoretical basis for theoretical modeling and improvement of machining accuracy of CNC machine tools， and provide effective guidance for the electromechanical system design of CNC machine tools.