Highly responsive heading control of underactuated modified BlueROV using sliding-mode controller

Abstract

The control of Autonomous Underwater Vehicle (AUV) presents some challenging tasks such as dealing with the nonlinearity of AUV dynamics, coupling effects, and taking into consideration the hydrodynamics uncertainties and disturbances such as current. One of the more robust control method for controlling a nonlinear system is Sliding-Mode Control (SMC). In literature, SMC had been used to control the depth and yaw of an underactuated AUV. However, the switching term of the SMC had to be tuned to get a proper balance between performance and robustness and it has low responsiveness to track desired reference signal. This paper introduces the usage of smoothing filter to make the SMC more responsive to track desired heading motion. The methodology starts with deriving heading model of an AUV, then estimating the parameters in the AUV model, followed by designing the heading controller based on SMC, and finally optimizing the controller parameters. The design model is based on underactuated modified BlueROV. Results shown that when the reference heading signal is smoothed, the SMC is able to achieve 95.55% responsiveness compared to only just 78.05% responsiveness without smoothing. The thrusts produced by the AUV is also less strained when the smoothing filter is applied. Therefore, to get a highly responsive SMC and to preserve the longevity of the thrusters of an AUV, a smoothing filter had to be considered in controller design of an underactuated AUV.