Accurate and computationally efficient approach for simultaneous feedrate optimization and servo error pre-compensation of long toolpaths—with application to a 3D printer
Accurate and computationally efficient approach for simultaneous feedrate optimization and servo error pre-compensation of long toolpaths—with application to a 3D printer
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DOI：
10.1007/s00170-021-07200-5
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发表时间：
2021-05
期刊：
影响因子：
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通讯作者：
Heejin Kim;C. Okwudire
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文献类型：
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作者：
Heejin Kim;C. Okwudire
为了提高计算机控制制造机械的精度和速度，通常分别进行进给速度优化和伺服误差预补偿。然而，这种独立的方法会导致速度和准确性之间的过度权衡。为了解决这个问题，作者提出了一个同时FO和SEP（或FOSEP）的新概念，其中SEP集成到FO中，在不牺牲相对于独立FO和SEP的定位精度的情况下大幅减少运动时间。然而，在他们之前的工作中，作者使用线性规划来实现FOSEP导致以下问题：(i)执行非线性约束的不准确性和（ii）长刀具路径的计算效率差。为了解决这两个问题，本文提出了一种基于有窗序列线性规划的FOSEP算法。SLP的使用提高了FOSEP在施加非线性约束方面的精度；然而，它降低了FOSEP的计算效率。窗口通过将SLP应用于小批量重叠的FOSEP，解决了计算效率低的问题。窗口SLP的缺点是它可能导致优化的不可行性。在逼近不可行性的情况下，通过在窗口SLP得到的最优解和备用保守解之间平滑切换，解决了这一问题。仿真结果表明，该方法在保证可行性的同时，显著提高了FOSEP的精度和计算效率。在3D打印机上的实验证明了所提出的FOSEP方法的实际优势，与传统的独立FO和SEP方法相比，它在不牺牲打印质量的情况下减少了25%的周期时间，这两种方法都适用于长刀具路径。
Feedrate optimization (FO) and servo error pre-compensation (SEP) are often performed independently to improve the accuracy and speed, respectively, of computer-controlled manufacturing machines. However, this independent approach leads to excessive tradeoff between speed and accuracy. To address this issue, the authors have proposed a new concept of simultaneous FO and SEP (or FOSEP) where SEP is integrated into FO, yielding large reductions in motion time without sacrificing positioning accuracy relative to independent FO and SEP. However, in their prior work, the authors used linear programming to achieve FOSEP resulting in the following: (i) inaccuracy in enforcing nonlinear constraints and (ii) poor computational efficiency for long toolpaths. To address these two problems, this paper proposes a new approach for FOSEP using windowed sequential linear programming (SLP). The use of SLP improves the accuracy of FOSEP in enforcing nonlinear constraints; however, it lowers the computational efficiency of FOSEP. Windowing addresses the problem of low computational efficiency by applying SLP to FOSEP in small overlapping batches. A downside of windowed SLP is that it may lead to infeasibility in the optimization. This problem is resolved by smoothly switching between the optimal solution obtained using windowed SLP and a backup conservative solution in case of impending infeasibility. The proposed windowed SLP with smooth switching approach for FOSEP is validated in simulations where it significantly improves the accuracy and computational efficiency of FOSEP while guaranteeing feasibility. The practical benefits of the proposed approach for FOSEP is demonstrated in experiments on a 3D printer where it achieves up to 25% reduction in cycle time without sacrificing printing quality relative to the conventional approach of independent FO then SEP, both applied to a long toolpath.