中文摘要：

提出了一种用双圆弧对二次均匀B样条曲线的分段逼近方法。首先，对一条具有n＋1个控制顶点的二次均匀B样条曲线按照相邻两节点界定的区间分成n-1段只有三个控制顶点的二次均匀B样条曲线段；然后对每一曲线段构造一条双圆弧进行逼近。所构造的双圆弧满足端点及端点切向量条件，即双圆弧的两个端点分别是所逼近的曲线段的端点，而且双圆弧在两个端点处的切向量是所逼近的曲线段在端点处的单位切向量。同时，双圆弧的连接点是双圆弧连接点轨迹圆与其所逼近的曲线段的交点。这些新构造出来的双圆弧连接在一起构成了一条圆弧样条曲线，即二次均匀B样条曲线的逼近曲线。另外给出了逼近误差分析和实例说明。

英文摘要：

A biarc method for piecewise approximating quadratic uniform B-spline curve was presented. First, a quadratic uniform B-spline curve with n ＋ 1 control points was divided into n - 1 segments controlled by only three control points in a knot interval. Then, one biarc was constructed to approximate each segment. The biarc has the same end points and the same unit tangent vectors with those of the approximated segment. In the meantime, the joint point of the biarc was the intersection point between the segment and the locus of the joint points of the biarc, which was a circle. In this way, an arc spline, which consisted of the built biarcs, was obtained, which approximated the given quadratic uniform B-spline curve. Some error analysis on the approximation error and some examples were provided as well.