Depth control for an over-actuated, hover-capable autonomous underwater vehicle with experimental verification

Abstract

A PI-D based control system is developed for over-actuated, hover-capable AUVs which enables a smooth transition from hover-style to flight-style operation. A system stability and convergence is proven using a Lyapunov-based approach. The performance of the controller is demonstrated by simulation but crucially is proven to provide satisfactory performance experimentally. The approach is able to operate over a range of vehicle ballasting configurations, and to imposed external disturbances. The proposed system is computationally inexpensive and does not require a detailed hydrodynamic model to implement. By monitoring the energy consumption on board, the cost of maintaining depth at a range of forward speeds with different buoyancy conditions can be quantified and their impact on cost of transport is highlighted for future optimisation of energy consumption.

Experimental analysis of low‐altitude terrain following for hover‐capable flight‐style autonomous underwater vehicles

“…The experiment paths were crossed at 0.3, 0.6 and 1.0 m/s surge velocity. They represent low, medium and high speeds for Delphin2 and are well understood from previous experiments on diving control (Tanakitkorn et al, ) and heading control at the surface (Tanakitkorn, Wilson, Turnock, & Phillips, ). During the horizon tracking experiments, the control allocation at 1 m/s speed was varied, to increase the use of thrusters from the default thruster weight of 0 to a factor of 0.5 (“half”) and 1.0 (“full”; see Figure ).…”

“…Compared with COT of depth tracking at different speeds in Tanakitkorn et al (), the COT for altitude tracking increases around 10% for flight‐style actuation, 20% for hover‐capable actuation and 20% for flight‐style actuation with thruster use. For hover‐capable control, the thrusters are both used for generating a pitching moment and vertical translation.…”

“…It is below 3 m for 0.3 m/s hover‐capable control and increases to over 7 m for flight‐style control. Using flight‐style actuation only, at 1 m/s speed a significant portion of the experiments shows an oscillation in the pitch angle (see Figures and ) that is not observed when tracking a depth with the same controller (see Tanakitkorn et al, ). Due to the dynamics of the AUV acting as a low pass filter this oscillation is barely noticeable in the altitude and depth measurements.…”

Sliding mode heading control of an overactuated, hover‐capable autonomous underwater vehicle with experimental verification

“…Since the Delphin2 AUV is almost symmetric about the longitudinal axis, the dynamics model parameters on this horizontal plane subsystem may be adapted from the vertical plane subsystem previously presented by Tanakitkorn and colleagues . The corresponding coefficients on the two subsystems are assumed to have the same magnitude, but they may feature different signs as to comply with the sign convention of the b‐frame .…”

“…Since this AUV can be considered to have a redundant set of actuators for controlling a given degree of freedom, it is referred to as overactuated AUV. More details on the Delphin2 AUV development are given by …”