As the basic functions of an AUV test-bed, the depth control and waypoint tracking control functions were tested. A sliding mode controller was designed and tested for ISiMI's depth control. The experimental results are plotted with the simulation results of the linear and non-linear models in Fig. 14. The initial depth was 0.4 m, and the reference depth was 1 m. Both the experimental and simulated results showed good convergence with the reference depth. The settling time of the experiment results was longer, however, than that of the simulation results, and the amplitude of the pitch rate response in the simulation was larger than that in the experiment results. It is supposed that the discrepancies in the responses are due to the errors of the numerical and real model in pitch motion. A more exact numerical model will be estimated based on the experimental data using the system identification method in future works.
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