This paper presents the results of a heading estimation method for a remotely operated vehicle (ROV). The output rate of commercially available underwater compasses is typically in the order of a few Hz. Heading frequencies of at least 1 KHz are desirable for navigation and control purposes.
The estimation was performed by fusioning the signals of three inertial sensors: the ROV’s own underwater compass (which operates roughly at 10 Hz or less), the ROV’s embedded gyro and an additional angular rate sensor that provides readings from 1 to 3 KHz. The output signal of the additional angular rate sensor is not part of the proposed Kalman filter. Nonetheless a five-point Newton-Cotes closed integration of such signal is fed into the Kalman filter implementation that performs the required heading estimation at 1 KHz or more.
The proposed Kalman filter implementation is a suitable approach to estimate heading position even though the original compass signal rate is significantly slower than the signal required for both assisted and autonomous control.
The estimated heading yield good results in both simulation and experimental environments.
The method was embedded in a dedicated 16-bit DSP that handles both the acquisition of the three signals and the heading estimation, hence resulting in a very low-cost solution. The embedded solution was tested in the developed submarine and the obtained high-rate heading parameter is now used by the control system of the ROV.
The authors acknowledge the staff of the Center for Engineering and Industrial Development, who kindly helped during the ROV design and the experimental setup. This work was supported by the Mexican National Council for Scientific and Technological Development, grants CB-2005-01-49106 and TAMU-CONACYT-2007.
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