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

Abstract

A sliding mode heading control system is developed for overactuated, hover‐capable autonomous underwater vehicles (AUVs) operating over a range of forward speeds. A simplified switching function is introduced, and simulation studies are proposed accordingly. The results with this novel switching function show a significant improvement in the chattering problem when compared to other conventional switching function candidates. Studies on sensitivities to a range of hydrodynamic parameter uncertainties are presented, and the parameters that have major influences on the sliding mode control performance are highlighted. The proposed control system is also proven in the field trials to enhance vehicle response, yielding consistent, and robust performance over the entire range of vehicle's speeds, even when subjected to external disturbance. It also shows superior heading tracking performance when compared to a proportional‐derivative (PD) based approach implemented on the same vehicle. However, this improved performance requires intense control actions as a trade‐off, causing the AUV to expend more energy than with the P‐D approach. Path following trials, where the AUV is demanded to follow a set of GPS coordinates at the water surface, are presented. These demonstrate the applicability of the proposed heading control system in a practical operation. The presented SMC scheme can be applied to any vehicle straightforwardly, but the control allocation part may need to be modified regarding the actuator configuration of that vehicle.

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 ).…”

“…When trying to get within an altitude region close to terrain, the vehicle operator can influence the quality of the results by modifying Table 1), whilst keeping the vehicle submerged throughout the path. (Tanakitkorn et al, 2016) and heading control at the surface (Tanakitkorn, Wilson, Turnock, & Phillips, 2017). 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 14).…”

Model Predictive Super-Twisting Sliding Mode Control for an Autonomous Surface Vehicle

“…Substituting the equation (12) in (11), the cost function can be expressed based on sliding function and its first derivative as follows:…”

“…A control law for path tracking of marine vessel was adopted in [9], where a singular perturbation method was used to decompose the system into two Lyapunov theory based control subsystems. Some research projects concerning adopting the higher order sliding mode algorithms such as super-twisting for control of the maritime autonomous robots, were carried out in [10,11]. In [12] there were presented two control algorithms for the trajectory tracking of an autonomous marine platform, in which the input constraints and disturbances induced by constant ocean currents were regarded.…”

Model analysis, design and experiment of a fan-wing underwater vehicle

“…Generally, each UUV should have at least 3 moving parts to achieve no less than 5 degrees of freedom (DOFs) movement in a space. Some kinds of UUVs even have 10 moving parts for unique requirements, such as hover-capable (Tanakitkorn et al, 2017). The spindle-shaped UUVs usually have 6 moving parts, including a buoyancy regulation system, a forward main thruster and 4 rudders, which can achieve only 5 DOFs movement in a space.…”