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为了提高直线电机驱动的双直接进给轴的运动精度,对该类进给轴的热误差进行了建模并研究了误差补偿方法。分析了双直接进给轴进给过程中热误差产生的原因及其补偿的复杂性,给出一种基于潜变量回归的双直接进给轴热误差在线补偿方法。该方法应用激光干涉仪测量进给轴的热变形量,使用热电偶和红外测温仪测量进给轴关键点的温度变化;通过时间匹配变形和温度数据得到统计样本并建立基于潜变量回归的热误差识别模型。以模型的在线计算确定误差补偿量,给出了与数控系统兼容的补偿控制输出策略及补偿系统构建方案。在自构建的龙门双直线电机驱动进给轴平台上进行了在线补偿实验。结果表明:应用潜变量回归方法对双直接进给轴进行热误差补偿可使双直接进给轴的热误差减小75%。 相似文献
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《机械工程学报》2017,(9)
为了提高双直线电动机驱动的同步直接进给轴的运动精度,对该类直接进给轴的全行程热误差在线补偿方法进行了研究。分析了双直接进给轴全行程热误差的影响因素,提出一种基于核偏最小二乘法(Kernel partial least squares,KPLS)和模糊逻辑相结合的双直接进给轴全行程热误差的在线补偿方法。应用激光干涉仪测量其热变形量,使用热电偶和红外测温仪测量进给机构关键点的温度,以时间匹配温度和变形量数据建立统计样本,在均匀离散点位置建立热误差KPLS识别模型,通过在线计算得到离散点热误差补偿量,再根据任意位置与离散点的模糊关联程度,综合计算全行程任意位置处热误差补偿量。以此理论为基础,建立补偿决策函数和补偿系统,依据补偿决策函数智能推断补偿值,通过向数控系统发送补偿码实现在线补偿。在自构建的龙门双直线电动机驱动的直接进给轴平台上,进行全行程热误差在线补偿试验研究,结果表明:混合KPLS与模糊逻辑可以有效的对双直接进给轴全行程热误差在线补偿,经过随机测试验证,补偿后的进给精度提高了50%。 相似文献
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为了提高龙门2x/y直线进给轴联动的圆轮廓精度,对进给轴联动圆轮廓误差的测量、评价和补偿方法进行研究。分析直线电动机驱动的进给轴联动过程存在圆轮廓偏差的原因及其补偿的复杂性,给出一种基于学习的联动轴圆轮廓误差在线精密补偿方法,此方法通过双光束激光干涉仪动态精密测量x/y联动轴的实时坐标值,应用最小二乘圆方法评价确定理想圆,接着通过与理想圆轴坐标位置的比较,计算得到轴向偏差学习样本,建立基于最小二乘支持矢量回归机(Least square support vector regression,LS-SVR)方法的轴向偏差离线识别模型,通过模型的在线回归计算确定联动进给过程的偏差补偿量,给出补偿量控制输出策略与补偿系统构建方案,在自构建的直线进给轴平台上进行在线补偿试验。结果表明应用该方法对2x/y直线进给轴联动的轴向偏差进行在线补偿,可使圆轮廓精度提高68.7%。 相似文献
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为了探索直线电机驱动的高速直线进给轴热扭曲变形的影响因素,在试验的基础上,给出应用向前变量智能自筛选的偏最小二乘线性回归模型(Partial least squares regression,PLSR)分析影响进给轴热扭曲行为关联因素的分析方法。通过在自构建的进给轴试验平台,建立进给轴扭曲变形的测试系统,给出直线进给轴在发热过程和强冷却作用过程的热扭曲变形采样与进给轴温度动态采集方案。应用周期大变异的遗传算法为偏最小二乘回归参数的自检验方法,给出分析方法的具体实现步骤。通过实验和回归识别计算,分析了进给轴的温度分布及其对热扭曲行为的影响规律。结果表明,给出的变量自筛选偏最小二乘线性回归分析方法,可有效的筛选复相关的温度测点变量,并保持较高的回归识别精度,给出的方法与全变量PLSR和向后变量筛选的Bootstrap方法进行了比较,进一步表明了给出的回归分析方法的优越性。 相似文献
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针对进给轴热误差建模中忽略电控数据和时间序列影响的问题,提出一种考虑温度变化与电控数据的长短期记忆(Long-Short Term Memory,LSTM)神经网络热误差预测模型.以三轴立式加工中心为试验对象,首先对进给轴进行热变形分析,再以温度变化、电控数据为输入样本,建立了LSTM神经网络热误差预测模型,随后通过与仅考虑温度变化的LSTM神经网络,以及同时考虑温度变化与电控数据的BP神经网络进行对比分析,试验论证表明,对数控机床进给轴进行热误差建模时,在考虑温度变化的基础上,进一步考虑电控数据可以提高模型的预测精度和鲁棒性,且在同样输入条件下,LSTM神经网络热误差预测模型相较于BP神经网络有更好的预测精度和鲁棒性. 相似文献
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针对进给轴热误差建模中忽略电控数据和时间序列影响的问题,提出一种考虑温度变化与电控数据的长短期记忆(Long-Short Term Memory,LSTM)神经网络热误差预测模型.以三轴立式加工中心为试验对象,首先对进给轴进行热变形分析,再以温度变化、电控数据为输入样本,建立了LSTM神经网络热误差预测模型,随后通过与仅考虑温度变化的LSTM神经网络,以及同时考虑温度变化与电控数据的BP神经网络进行对比分析,试验论证表明,对数控机床进给轴进行热误差建模时,在考虑温度变化的基础上,进一步考虑电控数据可以提高模型的预测精度和鲁棒性,且在同样输入条件下,LSTM神经网络热误差预测模型相较于BP神经网络有更好的预测精度和鲁棒性. 相似文献
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热变形引起的误差是影响数控机床精度的主要因素之一。为了减小热误差对数控机床精度的影响,提出一种基于CNN-GRU组合神经网络的热误差预测方法。通过热误差实验,采集螺旋曲面专用数控机床直线进给系统的温升数据和热误差数据;利用模糊C均值聚类和灰色关联度分析筛选进给系统温度敏感点;以温度敏感点的温升数据和进给系统热误差为数据样本,建立CNN-GRU热误差预测模型。为验证模型的准确性和实用性,与基于CNN-LSTM和基于LSTM的传统热误差预测模型进行预测对比分析,结果表明CNN-GRU模型预测结果的平均绝对误差、均方根误差和决定系数均优于CNN-LSTM模型和LSTM模型,具有较高的预测精度和鲁棒性。提供的热误差模型可为后续误差补偿奠定基础,为数控机床的热误差预测提供思路。 相似文献
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Qianjian Guo Jianguo Yang Hao Wu 《The International Journal of Advanced Manufacturing Technology》2010,50(5-8):667-675
Thermal errors are the major contributor to the dimensional errors of a workpiece in precision machining. Error compensation technique is a cost-effective way to reduce thermal errors. Accurate modeling of errors is a prerequisite of error compensation. In this paper, four key temperature points of a NC machine tool were obtained based on clustering method. A thermal error model based on the four key temperature points was proposed by using ant colony algorithm-based back propagation neural network (ACO-BPN). The ACO-BPN method improves the prediction accuracy of thermal deformation in the NC machine tool. A thermal error compensation system was developed based on the proposed model, and which has been applied to the NC machine tool in daily production. The results show that the thermal drift in workpiece diameter has been reduced from 33 to 8 μm from its center of tolerance. 相似文献
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Application of synthetic grey correlation theory on thermal point optimization for machine tool thermal error compensation 总被引:6,自引:6,他引:0
J. Y. Yan J. G. Yang 《The International Journal of Advanced Manufacturing Technology》2009,43(11-12):1124-1132
This paper presents two new methods to optimize the selection of minimum number of thermal sensors for machine tool thermal error compensation. The two methods, namely, direct criterion method and indirect grouping method, are based on the synthetic grey correlation theory. They are applied to analyze the data of an air cutting experiment on a CNC turning center. After optimization, the number of thermal points reduced from 16 to four. Thus, for machine tool thermal error modeling, the number of temperature variables is greatly reduced while coupling problems among temperature variables can be avoided. A real cutting experiment is then conducted to verify the efficiency of the presented optimization methods under practical manufacturing conditions. The comparison of the results between the model with all 16 thermal sensors and the model with four optimized thermal sensors indicates that, after optimization, the model accuracy is greatly improved. 相似文献
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无温度传感器的数控机床进给轴热误差补偿 总被引:1,自引:0,他引:1
分析了目前常见的进给轴热误差补偿方法的缺点,如需要多个温度传感器、模型的鲁棒性较差等。提出一种基于无温度传感器的、强鲁棒性的机床进给轴热误差补偿方法,在恒温环境下实现对运动生热导致的热误差的补偿。给出了热误差模型的推导过程以及应用ISIGHT平台进行参数优化的过程。热误差模型基于摩擦生热、热传导和散热机理实时预测滚珠丝杠的温度场,以实现预测并补偿丝杠热误差的目的。在一台立式加工中心VMC850上对x、y、z轴进行了热误差测试并给出了模型的仿真效果。在另一台立式加工中心VMC850上采用激光干涉仪进行了热误差补偿前后的对比试验和加工对比试验。试验结果表明,该热补偿方法具有很高的精度稳定性和强鲁棒性。 相似文献
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为研究数控机床热变形规律,实现数控机床误差在机实时补偿,进行数控机床主轴热变形理论及试验分析,结果表明,数控机床主轴热变形与主轴温变在距热源约1/3位置存在近似线性关系,即主轴热变形存在伪滞后现象,这一结果为数控机床测温点优化布置及热误差鲁棒建模提供理论依据。为验证机床热变形伪滞后现象,对VM850加工中心主轴热漂移误差在机实时检测并建模,通过自主研发数控机床误差在线实时补偿系统对主轴热漂移误差进行实时补偿,经补偿,机床主轴热漂移误差减少90%以上,有效提高了数控机床主轴精度。 相似文献
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Compensation of machine tool thermal deformation in spindle axis direction based on decomposition method 总被引:2,自引:0,他引:2
Jiri Vyroubal 《Precision Engineering》2012,36(1):121-127
One of the fundamental areas in high precision cutting is represented by the machine's thermal state monitoring. Understanding of this state gives significant information about the overall machine condition such as proper performance of cooling system as well as software compensation of machine's thermal deformation during manufacturing. This paper presents a method focused on compensation of machine's thermal deformation in spindle axis direction based on decomposition analysis. The machine decomposition is performed with the help of specially developed measuring frame, which is able to measure deformation of machine column, headstock, spindle and tool simultaneously. Compensation is than calculated as a sum of multinomial regression equations using temperature measurement. New placements of temperature measurement like spindle cooling liquid or workspace are used to improve the accuracy of this calculation. Decomposition process allows describing each machine part's thermal dynamic more precisely than the usual deformation curve usually used one deformation curve for the complete machine. The residual thermal deformation of the machine is considerably reduced with this cheap and effective strategy. The advantage is also in the simplicity of presented method which is clear and can be used also on older machines with slower control systems without strong computing power. 相似文献
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Modified Elman network for thermal deformation compensation modeling in machine tools 总被引:7,自引:7,他引:0
Zhiyong Yang Minglu Sun Weiqian Li Wenyong Liang 《The International Journal of Advanced Manufacturing Technology》2011,54(5-8):669-676
Thermal deformation is one of the most significant causes of machining errors in machine tools. One effective method is to build a compensation system to offset the thermal errors. Therefore, an accurate model is the key part of the compensation system. This study proposed a modified Elman network (EN) to improve the prediction accuracy of the compensation model in machine tools. And the improved EN can be regarded as a feed-forward neural network with feedback from hidden layer and output layer as an additional set of inputs. The structure of this network determines its dynamic characteristic with memory function. On the other hand, thermal deformation of the spindle contributes the largest part of total thermal errors in precision machining. Then a precise finite element model of machine tool spindle was established. And a new method for calculating the heat transfer convection coefficient on the surface of the spindle was proposed in this paper. The improved EN was used to map the nonlinear relationship between temperature field and thermal errors of the spindle. At last, a verification experiment was implemented on a CNC center and some satisfying results were achieved. 相似文献
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基于实时反馈的机床热误差在线补偿模型 总被引:1,自引:0,他引:1
为建立一种能够适应机床不同工况且具有准确预测能力的热误差补偿模型,提出一种基于限定记忆递推最小二乘法辨识热误差模型参数的机床热误差预测建模方法。该方法随着机床工作状况的改变,根据实时反馈的温度和热误差数据,采用递推方法对模型参数进行即时修正,使热误差模型能够及时跟踪机床系统的热特性变化,实现以较高的预测精度对机床热误差进行补偿。通过数控车床主轴轴向热误差辨识建模及补偿实验可以看出,限定记忆递推最小二乘法比一步最小二乘法辨识精度有较大提高,最大残差值减小了52.3%,标准差减小了67%。实验结果表明,利用该方法进行机床热误差模型参数辨识具有较高的预测精度和鲁棒性,有效可行。
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