Quantitative shape measurement of an inflatable rubber dam using inertial sensors

Shape measurement is of great importance for the effective control and safe operation of inflatable rubber dams. This paper presents for the first time a method to measure the cross-sectional shape of a rubber dam by placing an array of inertial measurement units (IMUs) on the peripheral of the rubber dam. The IMU array measures tangent angles of the dam peripheral by fusing accelerometer and gyroscope measurements. A continuous tangent angle function is derived by interpolating the tangent angles at discrete locations using a cubic spline. Finally, the shape is reconstructed by integrating the tangent angle function along the peripheral of the rubber dam. The performance of the measurement system is validated against a camera on a purpose-built test rig. Experimental results show that the measured and reference shapes are very similar, with a maximum similarity index of 8.5% under typical conditions. In addition, it is demonstrated that the system is robust against node failure by excluding readings of faulty nodes from shape reconstruction.