光电编码器与棱体轴线平行度对转角误差的影响

光电轴角编码器轴线与棱体轴线不平行会降低转角误差测试结果的置信度，为了减小光电轴角编码器转角测试误差，将由光电轴角编码器轴线与棱体轴线不平行引入的转角测试误差控制在光电轴角编码器转角误差的1/3~1/5以内，建立了由光电轴角编码器轴线和棱体轴线平行度引入的转角测试误差数学模型及Y向偏置数学模型。由仿真结果可知，光电轴角编码器转角测试误差和Y向偏置随转角的增大呈现周期性变化，周期分别为和2，棱体轴线倾斜方向相同时，两轴线夹角越大，转角测试误差峰值和Y向偏置峰值越大，两轴线夹角相同时，棱体轴线倾斜方向大小只会改变转角测试误差曲线和Y向偏置曲线相位，不会改变曲线形状。根据多面棱体-自准直仪法对建立的数学模型进行了实验验证。实验结果表明:测试结果与数学模型具很好的自洽性。在实际测试中，对转角误差进行预先测试，绘制偏置曲线并对曲线进行最小二乘法拟合，求取平行度与倾斜方向，根据倾斜方向调整两轴线平行度大小，直到误差峰值满足测试要求。

Influence of parallelism between photoelectric shaft encoder axis and polyhedron one on the rotation angle error

The confidence level of rotation angle error test result was reduced by nonparallelism between photoelectric shaft encoder axis and polyhedron one. In order to decrease rotation angle test error, the rotation angle test error caused by nonparallelism between photoelectric shaft encoder axis and polyhedron one was controlled within 1/3-1/5 of photoelectric shaft encoder angle error. The mathematical models of rotation angle test error and Y bias introduced by nonparallelism between photoelectric shaft encoder axis and polyhedron one were established. The simulation results showed that rotation angle test error and Y bias had periodic change with the angle increase, the cycle were and 2 respectively. When the tilt direction of polyhedron axis was fixed, the bigger angle between encoder axis and polyhedron one, the bigger peak values of angle test error and Y bias, when the angle between photoelectric shaft encoder axis and polyhedron one was fixed, the tilt direction of polyhedron axis only changed the phases of rotation angle test error curve and Y bias one and not changed the shapes of the curves. According to the polyhedron-autocollimator method, the established mathematical models were verified by experiments. Experimental results indicate that the test results and the mathematical models are in good conformity. In the actual test, the rotation angle test error is pretested, the curve is drawn and fitted by the least squares method, the parallelism and tilt direction are obtained, the parallelism is adjusted according to tilt direction until error peak satisfies test requirement.