基于NURBS曲面拟合的特大型齿轮齿廓偏差评定

Profile error evaluation of large gears based on NURBS surface fitting

在中等尺寸齿轮测量中,通常以轴线作为测量的基准,但对特大型齿轮来说,要精确获取其轴线存在较大困难。为了特大型齿轮特征线测量问题,本文提出并采用了三维测量与评定的方法。首先利用激光跟踪仪进行被测齿轮的粗定位,获取被测齿轮与三维平台的相对位置关系;然后利用所设计的三维平台在被测齿面获取大量的数据点,对这些数据点进行NURBS曲面拟合,建立真实齿面的三维参数化模型;最后将所建立的参数化模型与理论模型相比较得到齿廓等偏差。实验结果表明,该方法在解决特大型齿轮特征线测量方面具有较好的可行性。

In middle size gear measurement,the center axis of the gear is often used as the measurement reference. However,for large gears,it is difficult to get their center axis. In order to overcome this difficulty and solve the profile measurement problem of super large gears,a three dimensional measurement and evaluation method is proposed in this paper. Firstly,a laser tracker is used to perform the rough positioning of the gear under test,and obtain the relative position relationship between the gear under test and the 3D measurement platform. Secondly,plenty of data points are acquired on the tooth surface of the gear under test using the designed 3D measurement platform,and NURBS surface fitting is conducted on these data points. Thus,the parametric model for the real gear surface is built. Finally,the built parametric model is compared with the theoretical model to obtain the gear profile error. Experiment results indicate that this method has good feasibility in large gear profile measurement.