中文摘要：

提出了一种基于浮力的三维实体测量新方法。其基本原理是采用精密运动平台来控制物体等步长浸泡于液体中，实现对被测物体的虚拟分层；提出变臂长测量方法，通过测量浮力变化来获取虚拟断层的横截面面积和重心坐标信息；对如何建立测量数据转换的数学模型、优化算法及将结果转换成体素单元的空间坐标信息等进行了研究；而且根据测量原理研制出了测量装置样机。通过原理验证，表明该方法可以不破坏被测物体而实现内外部轮廓测量，是一种全新且很有发展前景的三维实体测量技术。

英文摘要：

A new method of 3 D entity measurement based on buoyancy is presented which is especially suitable for entities of equable density. The measured entity is divided into many virtual layers when they are immerged in a liquid with equal step under the control of ultra precision stage. A non-fixed-arm measure scheme is proposed and applied to studying how to obtain each virtual tomography＇s cross-sectional area and barycentric coordinate from the buoyancy change. We explained in detail about： （1） how to build up the mathematical model of metrical datum transition ; （2） the optimization algorithm of the mathematical model ; （3） how to convert calculational datum to voxel units＇ spatial coordinates. In addition, a set of measure prototype device has been designed and assembled successfully on the basis of the new method. Experimental result demonstrates that the proposed method can be applied successfully to measuring the interior and exterior cotour of 3D entity without destructing it, and it is a brannew and advanced technology for 3D entity measurement.