数控速度规划中的过象限摩擦误差约束

High-speed feed-rate planning with friction error constraints

数控高速加工复杂轨迹时,过象限摩擦误差是轮廓误差的重要来源。将过象限摩擦误差约束加入速度规划模型,能有效弥补伺服系统中的摩擦力反馈补偿缺乏全局信息的缺陷,在保证加工精度的同时实现最优加工效率。首先建立了考虑摩擦影响的机床进给伺服系统动力学模型,结合数学推导与参数正交实验方法,针对光滑复杂轨迹研究了过象限摩擦误差产生机理,提出了系统换向时由摩擦产生的最大跟随误差的预测数学模型,并将其作为约束加入数控速度时间最优规划模型。实验结果表明:该模型可以较为精确地预测过象限摩擦误差。对比轨迹跟踪结果证明了包含过象限摩擦误差约束的速度规划能有效控制最终轨迹轮廓精度。

Feed-rate planning models must be accurate to improve contouring performance and efficiency.Quadrant protrusion errors caused by friction forces are an important source of contour error in high-speed contouring of complex curves.A theoretical analysis is given here to describe the relationships among the curvature,feed rate and quadrant protrusion error.Then,experiments with a wide range of parameters are used to develop a friction error model for feed-rate planning with the friction error as a constraint.Tests show that the model can accurately estimate the friction error and guarantee the contour accuracy requirements.