Sea floor geometry approximation and altitude control of ROVs

• A method to approximate the sea floor geometry based on DVL measurements is proposed.
• An expression of the altitude rate of change is derived.
• A guidance law that produces the desired depth for altitude control is proposed.
• The feed forward term in the guidance law assures correct vertical velocity.
• The proposed methods are tested on a ROV and experimental results are presented.

This paper presents a method for sea floor geometry approximation in a local region beneath a remotely operated vehicle (ROV) for use in altitude control. The method is based on Doppler velocity log (DVL) altitude measurements and ROV state estimates. The ROV altitude and sea floor gradient, which are obtained from the sea floor approximation, are used in a guidance law for altitude control. The altitude observer and guidance law have been implemented in the control system of NTNU׳s ROV Minerva. Results from simulations and sea trials demonstrating the performance of the proposed altitude estimation and guidance system are presented in the paper.