自适应加加速度NURBS曲线前瞻插补算法研究

针对现有NURBS曲线直接插补算法在曲率变化较大的拐角处容易出现弓高误差超限现象,导致加工精度降低等问题。提出一种自适应加加速度NURBS曲线前瞻插补算法。该算法首先用弓高误差和法向加速度作为约束条件限制曲线各插补点的进给速度,并在曲率极大值处进行分段处理;然后,基于前瞻控制与非对称S型曲线加减速控制对分段点进给速度优化处理,并自适应修正加速与减速运动阶段的加加速度;最后,以调整后的参数进行加减速控制并进行插补输出。实验测试结果表明,该算法即使在曲率较大区域的弓高误差、加速度和加加速度也不会超出CNC系统的限制,并实现平滑运动和高精度的加工。

永磁直线同步电动机伺服系统的自适应加加速度控制

针对永磁直线同步电动机(PMLSM)伺服系统中易受不确定性因素影响的问题,该文提出一种自适应加加速度控制(AJC)方法。首先建立含有不确定性的PMLSM伺服系统动态方程。然后,通过模型前馈控制补偿系统的参数不确定性所产生的模型误差,提高系统的响应速度。最后,采用AJC抑制系统中外部扰动、非线性摩擦力等不确定性因素,自适应律使鲁棒增益收敛于有界范围内,提高系统的鲁棒性;AJC的输出信号积分后形成了反馈控制律,削弱了控制律中开关函数激励未建模动态引起的高频谐振,保证了控制信号的稳定性和连续性。系统实验结果表明,该控制方法能够产生平稳的控制信号,明显地提高系统的控制性能,减小跟踪误差,避免高频振荡,进而改善PMLSM伺服系统的控制精度。

NURBS CURVE INTERPOLATOR WITH ADAPTIVE ACCELERATION-DECELERATION CONTROL

The feedrate profile of non-uniform rational B-spline （NURBS） interpolation due to the contour errors is analyzed. A NURBS curve interpolator with adaptive acceleration-deceleration control is presented. In interpo- lation preprocessing, the sensitive zones of feedrate variations are processed with acceleration-deceleration control. By using the proposed algorithm, the machining accuracy is guaranteed and the feedrate is adaptively adjusted to he smoothed. The mechanical shock imposed in the servo system is avoided by the first and the second time derivatives of feedrates. A simulation of NURBS interpolation is given to demonstrate the validity and the effectiveness of the algorithm. The proposed interpolator can also be applied to the trajectory planning of the other parametric curves.

一种双轴直驱平台新型同步渐近跟踪控制设计

针对双轴直驱平台伺服系统中存在同步进给的问题,提出一种交叉耦合迭代学习控制器与自适应加加速度控制器相结合的新型同步控制方法。首先,构建同步误差,利用交叉耦合控制器解决双轴的耦合问题;设计自适应PD型学习律减小同步误差,实现双轴协调同步。采用模型前馈控制补偿系统的参数不确定性,提高系统的响应速度。自适应加加速度控制器抑制系统中外部扰动、摩擦力等不确定性因素,实现系统的渐近跟踪控制。加加速度积分后形成反馈控制律,保证了控制信号的稳定性和连续性。设计自适应更新律,使鲁棒增益实现指数收敛并削弱测量噪声对系统的影响,增强系统的鲁棒性。系统实验结果表明,该方法能够明显地提高系统的同步性能,改善双轴直驱平台伺服系统的控制精度。

High speed interpolation for micro-line trajectory and adaptive real-time look-ahead scheme in CNC machining

CNC machining plays an important role in mechanical manufacturing.A key issue is to improve the machining feedrate while keeping the machining precision and satisfying the acceleration constraints of the CNC machine.For the consecutive micro-line segments interpolation,the velocities at the junction of two segments are the bottlenecks for the machining efficiency.This paper proposes a multi-period turning method to improve the feedrate at the junctions using the linear acceleration and deceleration mode,which utilizes the maximal acceleration capabilities of the NC machine while satisfying the machining precision.A new and more efficient look-ahead method and a feedrate override method are also proposed to boast the global machining speed.The proposed algorithm has been implemented on Blue Sky NC System,and experimented in real material manufacturing.Compared with several existing algorithms,the current algorithm can improve the manufacturing time ranging from 50% to 180%,depending on the machining parameters,and also results in better machining quality.In addition,the algorithm also satisfies the need of real-time interpolation.