Verification of a six-degree of freedom simulation model for the REMUS autonomous underwater vehicle

Abstract

Improving the performance of modular, low-cost autonomous underwater vehicles (AUVs) in such applications as long-range oceanographic survey, autonomous docking, and shallow-water mine countermeasures requires improving the vehicles' maneuvering precision and battery life. These goals can be achieved through the improvement of the vehicle control system. A vehicle dynamics model based on a combination of theory and empirical data would provide an effcient platform for vehicle control system development, and an alternative to the typical trial-and-error method of vehicle control system field tuning. As there exists no standard procedure for vehicle modeling in industry, the simulation of each vehicle system represents a new challenge.Developed by von Alt and associates at the Woods Hole Oceanographic Institute, the REMUS AUV is a small, low-cost platform serving in a range of oceanographic applications. This thesis describes the development and verification of a six degree of freedom, non-linear simulation model for the REMUS vehicle, the first such model for this platform. In this model, the external forces and moments resulting from hydrostatics, hydrodynamic lift and drag, added mass, and the control inputs of the vehicle propeller and fins are all defined in terms of vehicle coeffcients. This thesis describes the derivation of these coeffcients in detaiL. The equations determining the coeffcients, as well as those describing the vehicle rigid-body dynamics, are left in non-linear form. to better simulate the inherently non-linear behavior of the vehicle. Simulation of the vehicle motion is achieved through numeric integration of the equations of. motion. The simulator output is then checked against vehicle dynamics data collected in experiments performed at sea. The simulator is shown to accurately model the motion of the vehicle.

Simulation as a designed tool for material flow analysis by means of Witness Horizon

“…The main rules for creating simulation are right set conditions, which influence the whole simulation. By way of example may be mentioned simulation of torpedo with name REMUS, where has been verified this model of six-degrees of freedom [1].…”

Line-of-sight iceberg edge-following using an AUV equipped with multibeam sonar

“…The targeted AUV during the simulator development is the RE-MUS 100 AUV (Norgren and Skjetne, 2014). The model parameters have been taken from a previous REMUS 100 model by Prestero (1994).…”

“…Both the stern planes and the rudder planes are moving together; that is, the two horizontal fins cannot be controlled individually, and neither can the vertical fins. Prestero (1994) derived the following expressions for the forces and moments from the rudder and pitch fins…”

“…The remaining variables of (22)- (25) are the linear and angular velocities of the AUV, ν = [u v w p q r] , and δ s and δ r are the stern and rudder angles relative to the body x-axis, respectively. The coefficients are found in (Prestero, 1994). …”

“…The propeller model of Prestero (1994) was designed for small deviations from a given forward speed. Since the control system of the REMUS vehicle outputs a desired propeller shaft speed, we chose to alter the propeller shaft model by adopting the model of Carlton (2012):…”