Fuzzy sliding mode with region tracking control for autonomous underwater vehicle

This paper presents fuzzy sliding mode control with region tracking control for a single autonomous underwater vehicle. The vehicle is needed to track a certain moving region whilst under the influence of wave current. The fuzzy logic is used to tune the gain and to reduce the effect of chattering effect, the signum function is replaced by saturation function. Simulation result is presented to demonstrate the performance of the proposed tracking control of the AUV

A robust dynamic region-based control scheme for an autonomous underwater vehicle

Intelligent control of an autonomous underwater vehicle (AUV) requires a control scheme which is robust to external perturbations. These perturbations are highly uncertain and can prevent the AUV from accomplishing its mission. A well-known robust control called sliding mode control (SMC) and its development have been introduced. However, it produces a chattering effect which requires more energy. To overcome this problem, this paper presents a novel robust dynamic region-based control scheme. An AUV needs to be able not only to track a moving target as a region but also to position itself inside the region. The proposed controller is developed based on an adaptive sliding mode scheme. An adaptive element is useful for the AUV to attenuate the effect of external disturbances and also the chattering effect. Additionally, the application of the dynamic-region concept can reduce the energy demand. Simulations are performed to illustrate the effectiveness of the proposed controller. Furthermore, a Lyapunov-like function is presented for stability analysis. It is demonstrated that the proposed controller works better then an adaptive sliding mode without the region boundary scheme and a fuzzy sliding mode controller

Review of sliding mode control application in autonomous underwater vehicles

973-984This paper presents a review of sliding mode control for autonomous underwater vehicles (AUVs). The AUVs are used under water operating in the presence of uncertainties (due to hydrodynamics coefficients) and external disturbances (due to water currents, waves, etc.). Sliding mode controller is one of the nonlinear robust controllers which is robust towards uncertainties, parameter variations and external disturbances. The evolution of sliding mode control in motion control studies of autonomous underwater vehicles is summarized throughout for the last three decades. The performance of the controller is examined based on the chattering reduction, accuracy (steady state error reduction), and robustness against perturbation. The review on sliding mode control for AUVs provides insights for readers to design new techniques and algorithms, to enhance the existing family of sliding mode control strategies into a new one or to merge and re-supervise the control techniques with other control strategies, in which, the aim is to obtain good controller design for AUVs in terms of great performance, stability and robustness

Continuous adaptive sliding-mode control scheme for an autonomous underwater vehicle with region-based approach

Set point method has been typically used for trajectory tracking of Autonomous Underwater Vehicle (AUV). However, this method has several limitations. In this regard, region based method has been applied in trajectory tracking of AUV in order to solve the limitations of set point method. The main idea behind the region-based method is the tracking target of an AUV set as a region, so that the AUV will maintain its position under weak ocean current. This method uses lower energy compared to set point method because the AUV will not turn on its thrusters as long as it maintains its position within the region. Realistically, there is also strong current that can drift vehicle away from the required region. The purpose of the thesis is to develop a robust controller with region-based method. Robust control enables an AUV to reject the disturbance and re-enter the region even under the influence of external disturbance. Based on the literature review, adaptive sliding mode control was chosen as the proposed controller in this study. Sliding mode control is known for its insensitivity towards uncertainty and external disturbance. Adaptive component was introduced to replace switching component. This substitute enables AUV to reject external disturbance better compared to conventional sliding mode control. The stability of the proposed controller was analyzed using Lyapunov function. The energy consumption of region based method was compared with the set point tracking method. It has been shown from this study that the energy consumption for region-based method is indeed lower than set point method. The effectiveness of the proposed controller was compared with adaptive controller using simulation under the influence of ocean current. Underwater vehicle model used in the simulation was Omni Directional Intelligent Navigator (ODIN). It has been proven that the proposed controller performed better compared to adaptive controller. The proposed controller had managed to handle ocean current and re-enter the region

Development of Robust Control Strategies for Autonomous Underwater Vehicles

The resources of the energy and chemical balance in the ocean sustain mankind in many ways. Therefore, ocean exploration is an essential task that is accomplished by deploying Underwater Vehicles. An Underwater Vehicle with autonomy feature for its navigation and control is called Autonomous Underwater Vehicle (AUV). Among the task handled by an AUV, accurately positioning itself at a desired position with respect to the reference objects is called set-point control. Similarly, tracking of the reference trajectory is also another important task. Battery recharging of AUV, positioning with respect to underwater structure, cable, seabed, tracking of reference trajectory with desired accuracy and speed to avoid collision with the guiding vehicle in the last phase of docking are some significant applications where an AUV needs to perform the above tasks. Parametric uncertainties in AUV dynamics and actuator torque limitation necessitate to design robust control algorithms to achieve motion control objectives in the face of uncertainties. Sliding Mode Controller (SMC), H / μ synthesis, model based PID group controllers are some of the robust controllers which have been applied to AUV. But SMC suffers from less efficient tuning of its switching gains due to model parameters and noisy estimated acceleration states appearing in its control law. In addition, demand of high control effort due to high frequency chattering is another drawback of SMC. Furthermore, real-time implementation of H / μ synthesis controller based on its stability study is restricted due to use of linearly approximated dynamic model of an AUV, which hinders achieving robustness. Moreover, model based PID group controllers suffer from implementation complexities and exhibit poor transient and steady-state performances under parametric uncertainties. On the other hand model free Linear PID (LPID) has inherent problem of narrow convergence region, i.e.it can not ensure convergence of large initial error to zero. Additionally, it suffers from integrator-wind-up and subsequent saturation of actuator during the occurrence of large initial error. But LPID controller has inherent capability to cope up with the uncertainties. In view of addressing the above said problem, this work proposes wind-up free Nonlinear PID with Bounded Integral (BI) and Bounded Derivative (BD) for set-point control and combination of continuous SMC with Nonlinear PID with BI and BD namely SM-N-PID with BI and BD for trajectory tracking. Nonlinear functions are used for all P,I and D controllers (for both of set-point and tracking control) in addition to use of nonlinear tan hyperbolic function in SMC(for tracking only) such that torque demand from the controller can be kept within a limit. A direct Lyapunov analysis is pursued to prove stable motion of AUV. The efficacies of the proposed controllers are compared with other two controllers namely PD and N-PID without BI and BD for set-point control and PD plus Feedforward Compensation (FC) and SM-NPID without BI and BD for tracking control. Multiple AUVs cooperatively performing a mission offers several advantages over a single AUV in a non-cooperative manner; such as reliability and increased work efficiency, etc. Bandwidth limitation in acoustic medium possess challenges in designing cooperative motion control algorithm for multiple AUVs owing to the necessity of communication of sensors and actuator signals among AUVs. In literature, undirected graph based approach is used for control design under communication constraints and thus it is not suitable for large number of AUVs participating in a cooperative motion plan. Formation control is a popular cooperative motion control paradigm. This thesis models the formation as a minimally persistent directed graph and proposes control schemes for maintaining the distance constraints during the course of motion of entire formation. For formation control each AUV uses Sliding Mode Nonlinear PID controller with Bounded Integrator and Bounded Derivative. Direct Lyapunov stability analysis in the framework of input-to-state stability ensures the stable motion of formation while maintaining the desired distance constraints among the AUVs

Fuzzy sliding mode with region tracking control for autonomous underwater vehicle

This paper presents fuzzy sliding mode control with region tracking control for a single autonomous underwater vehicle. The vehicle is needed to track a certain moving region whilst under the influence of wave current. The fuzzy logic is used to tune the gain and to reduce the effect of chattering effect, the signum function is replaced by saturation function. Simulation result is presented to demonstrate the performance of the proposed tracking control of the AUV

Comparison of two type of fuzzy sliding mode with region tracking control for autonomous underwater vehicle

This paper presented two type of fuzzy sliding mode control with region tracking control for a single autonomous underwater vehicle. The vehicle is needed to track a certain moving region whilst under the influence of wave current. The first fuzzy logic proposed is used to tune the gain and to reduce the chattering effect; the signum function is replaced by saturation function. In second fuzzy type sliding mode controller, the switching term or reaching law is modeled using fuzzy logic. Simulation result is presented to demonstrate the performance of the two proposed tracking control of the AUV and the performance is compared

Comparison of two type of fuzzy sliding mode with region tracking control for autonomous underwater vehicle

This paper presented two type of fuzzy sliding mode control with region tracking control for a single autonomous underwater vehicle. The vehicle is needed to track a certain moving region whilst under the influence of wave current. The first fuzzy logic proposed is used to tune the gain and to reduce the chattering effectthe signum function is replaced by saturation function. In second fuzzy type sliding mode controller, the switching term or reaching law is modeled using fuzzy logic. Simulation result is presented to demonstrate the performance of the two proposed tracking control of the AUV and the performance is compared