Design of Novel S-plane Controller of Autonomous Underwater Vehicle Established on Sliding Mode Control

Based on the deep analysis of the mathematical model of an autonomous underwater vehicle( AUV),comprehensive considerations are given to the coupling effect of AUV's longitudinal velocity on the other degrees of freedom. In the meantime,discussions are made on the influence of residual buoyancy and restoring moment.A novel S-plane controller established on sliding mode control( SMC) is hereby proposed in this study. The strengths of traditional S-plane controller including simple structure and easily adjustable parameters are maintained in the improved design while the weakness of unsatisfactory control effect at the time of high-speed operation is also overcome. Lyapunov function is introduced to make the stability analysis of the controller before it is successfully applied to the basic motion control of AUV-X. Then the comparative experiment test is carried out between the traditional S-plane controller and the novel S-plane controller. The effectiveness and feasibility of the novel S-plane controller established on sliding mode control in the AUV basic motion control is verified by the comparative analysis of experiment results.

Adaptive Backstepping Terminal Sliding Mode Control Method Based on Recurrent Neural Networks for Autonomous Underwater Vehicle

The trajectory tracking control problem is addressed for autonomous underwater vehicle(AUV) in marine environ?ment, with presence of the influence of the uncertain factors including ocean current disturbance, dynamic modeling uncertainty, and thrust model errors. To improve the trajectory tracking accuracy of AUV, an adaptive backstepping terminal sliding mode control based on recurrent neural networks(RNN) is proposed. Firstly, considering the inaccu?rate of thrust model of thruster, a Taylor’s polynomial is used to obtain the thrust model errors. And then, the dynamic modeling uncertainty and thrust model errors are combined into the system model uncertainty(SMU) of AUV; through the RNN, the SMU and ocean current disturbance are classified, approximated online. Finally, the weights of RNN and other control parameters are adjusted online based on the backstepping terminal sliding mode controller. In addition, a chattering?reduction method is proposed based on sigmoid function. In chattering?reduction method, the sigmoid function is used to realize the continuity of the sliding mode switching function, and the sliding mode switching gain is adjusted online based on the exponential form of the sliding mode function. Based on the Lyapu?nov theory and Barbalat’s lemma, it is theoretically proved that the AUV trajectory tracking error can quickly converge to zero in the finite time. This research proposes a trajectory tracking control method of AUV, which can e ectively achieve high?precision trajectory tracking control of AUV under the influence of the uncertain factors. The feasibility and e ectiveness of the proposed method is demonstrated with trajectory tracking simulations and pool?experi?ments of AUV.

State Feedback Sliding Mode Control without Chattering by Constructing Hurwitz Matrix for AUV Movement

This paper presents a new method to eliminate the chattering of state feedback sliding mode control （SMC） law for the mobile control of an autonomous underwater vehicle （AUV） which is nonlinear and suffers from unknown disturbances system. SMC is a well-known nonlinear system control algorithm for its anti-disturbances capability, while the chattering on switch surface is one stiff question. To dissipate the well-known chattering of SMC, the switching manifold is proposed by presetting a Hurwitz matrix which is deducted from the state feedback matrix. Meanwhile, the best switching surface is achieved by use of eigenvalues of the Hurwitz matrix. The state feedback control parameters are not only applied to control the states of AUV but also connected with coefficients of switching surface. The convergence of the proposed control law is verified by Lyapunov function and the robust character is validated by the Matlab platform of one AUV model.

Improved Nonsingular Fast Terminal Sliding Mode Control of Unmanned Underwater Hovering Vehicle

An improved nonsingular fast terminal sliding mode manifold based on scaled state error is proposed in this paper.It can significantly accelerate the convergence rate of the state error which is initially far from the origin and achieve the fixed-time convergence.In addition,conventional double power term based reaching law is improved to ensure the convergence of sliding state in the presence of disturbances.The proposed approach is applied to the hovering control of an unmanned underwater vehicle.The controller exhibits both fast convergence and strong robustness to model uncertainty and external disturbances.

Fixed-time Sliding Mode Formation Control of AUVs Based on a Disturbance Observer

In this paper,we investigate formation tracking control of autonomous underwater vehicles(AUVs)with model parameter uncertainties and external disturbances.The external disturbances due to the wind,waves,and ocean currents are combined with the model parameter uncertainties as a compound disturbance.Then a disturbance observer(DO)is introduced to estimate the compound disturbance,which can be achieved within a finite time independent of the initial estimation error.Based on a DO,a novel fixed-time sliding control scheme is developed,by which the follower vehicle can track the leader vehicle with all the states globally stabilized within a given settling time.The effectiveness and performance of the method are demonstrated by numerical simulations.

Adaptive Controller Design for Dynamic Maneuvers of High Speed Underwater Vehicles

The control synthesis of the high-speed underwater vehicle faces many technical challenges due to its inherent structure and surrounding operational environment.In this paper,the dynamical behavior is firstly described through a bifurcation analysis to give some insights for robust control synthesis.Then a novel adaptive fractional-order sliding mode controller(AFOSMC)is realized to effectively manipulate the supercavitating vehicle against payload changes,nonlinear planing force,and external disturbances.The fractional order(FO)calculus can offer more flexibility and more freedom for tuning active control synthesis than the integer-order counterpart.In addition,the adaptation law has been presented to directly handle the payload change effects.The stability of the controlled vehicle system is proven via Lyapunov stability theory.Next,the dynamic performance of the proposed controller is verified through extensive simulation results,which demonstrate the control accuracy with faster responses compared with existing integer-order controllers.Finally,the proposed fractional order controllers can provide higher performance than their integer order counterparts with control algorithms.

Robust Modeling, Sliding-Mode Controller, and Simulation of an Underactuated ROV Under Parametric Uncertainties and Disturbances

A dynamic model of a remotely operated vehicle(ROV)is developed.The hydrodynamic damping coefficients are estimated using a semi-predictive approach and computational fluid dynamic software ANSYS-CFX?and WAMIT?.A sliding-mode controller(SMC)is then designed for the ROV model.The controller is subsequently robustified against modeling uncertainties,disturbances,and measurement errors.It is shown that when the system is subjected to bounded uncertainties,the SMC will preserve stability and tracking response.The paper ends with simulation results for a variety of conditions such as disturbances and parametric uncertainties.

Nonlinear trajectory tracking control of a new autonomous underwater vehicle in complex sea conditions

Autonomous underwater vehicles (AUVs) navigating in complex sea conditions usually require a strong control system to keep the fastness and stability. The nonlinear trajectory tracking control system of a new AUV in complex sea conditions was presented. According to the theory of submarines,the six-DOF kinematic and dynamic models were decomposed into two mutually non-coupled vertical and horizontal plane subsystems. Then,different sliding mode control algorithms were used to study the trajectory tracking control. Because the yaw angle and yaw angle rate rather than the displacement of the new AUV can be measured directly on the horizontal plane,the sliding mode control algorithm combining cross track error method and line of sight method was used to fulfill its high-precision trajectory tracking control in the complex sea conditions. As the vertical displacement of the new AUV can be measured,in order to achieve the tracking of time-varying depth signal,a stable sliding mode controller was designed based on the single-input multi-state system,which took into account the characteristic of the hydroplane and the amplitude and rate constraints of the hydroplane angle. Moreover,the application of dynamic boundary layer can improve the robustness and control accuracy of the system. The computational results show that the designed sliding mode control systems of the horizontal and vertical planes can ensure the trajectory tracking performance and accuracy of the new AUV in complex sea conditions. The impacts of currents and waves on the sliding mode controller of the new AUV were analyzed qualitatively and quantitatively by comparing the trajectory tracking performance of the new AUV in different sea conditions,which provides an effective theoretical guidance and technical support for the control system design of the new AUV in real complex environment.

Virtual Reality Simulation of Fuzzy-logic Control during Underwater Dynamic Positioning

In this paper, graphical-user-interface （GUI） software for simulation and fuzzy-logic control of a remotely operated vehicle （ROV） using MATLABTM GUI Designing Environment is proposed. The proposed ROV＇s GUI platform allows the controller such as fuzzy-logic control systems design to be compared with other controllers such as proportional-integral-derivative （PID） and sliding-mode controller （SMC） systematically and interactively. External disturbance such as sea current can he added to improve the modelling in actual underwater environment. The simulated results showed the position responses of the fuzzy-logic control exhibit reasonable performance under the sea current disturbance.

Development of A Three-Dimensional Guidance System for Long-Range Maneuvering of A Miniature Autonomous Underwater Vehicle

The present paper introduces a three-dimensional guidance system developed for a miniature Autonomous Underwater Vehicle（AUV）. The guidance system determines the best trajectory for the vehicle based on target behavior and vehicle capabilities. The dynamic model of this novel AUV is derived based on its special characteristics such as the horizontal posture and the independent diving mechanism. To design the guidance strategy, the main idea is to select the desired depth, presumed proportional to the horizontal distance of the AUV and the target. By connecting the two with a straight line, this strategy helps the AUV move in a trajectory sufficiently close to this line. The adjacency of the trajectory to the line leads to reasonably short travelling distances and avoids unsafe areas. Autopilots are designed using sliding mode controller. Two different engagement geometries are considered to evaluate the strategy＇s performance： stationary target and moving target. The simulation results show that the strategy can provide sufficiently fast and smooth trajectories in both target situations.

High Speed On/Off Valve Control Hydraulic Propeller

The work-class remotely-operated-underwater-vehicles（ROVs） are mainly driven by hydraulic propulsion system,and the effeciency of hydraulic propulsion system is an important performance index of ROVs.However,the efficiency of traditional hydraulic propulsion system controlled by throttle valves is too low.Therefore,in this paper,for small and medium ROVs,a novel propulsion system with higher efficiency based on high speed on/off valve control hydraulic propeller is proposed.To solve the conflict between large flow rate and high frequency response performance,a two-stage high speed on/off valve-motor unit with large flow rate and high response speed simultaneously is developed.Through theoretical analysis,an effective fluctuation control method and a novel pulse-width-pulse-frequency-modulation（PWPFM） are introduced to solve the conflict among inherently fluctuation,valve dynamic performance and system efficiency.A simulation model is established to evaluate the system performance.To prove the advantage of system in energy saving,and test the dynamic control performance of high speed on/off valve control propeller,a test setup is developed and a series of comparative experiments is completed.The smimulation and experiment results show that the two-stage high speed on/off valve has an excellent dynamic response performance,and can be used to realize high accuracy speed control.The experiment results prove that the new propulsion system has much more advantages than the traditional throttle speed regulation system in energy saving.The lowest efficiency is more than 40%.The application results on a ROV indicate that the high speed on/off valve control propeller system has good dynamic and steady-state control performances.Its transient time is only about 1 s-1.5 s,and steady-state error is less than 5%.Meanwhile,the speed fluctuation is small,and the smooth propeller speed control effect is obtained.On the premise of good propeller speed control performance,the proposed high speed on/off valve control propeller can improve the effeciency of ROV propulsion system significantly,and provides another attractive ROV propulsion system choice for engineers.

面向海流扰动和通信时延的欠驱动AUV编队跟踪控制

由欠驱动自主水下航行器(Autonomous Underwater Vehicle,AUV)编队组成的水下探测阵列具有响应快、机动性好、智能化程度高的特点。针对无速度信息传输的多AUV在海流和时延复合扰动下的编队控制问题,提出一种虚拟轨迹、轨迹预测、自适应反演滑模控制技术相结合的编队控制方法。使用领航者的位置信息和期望队形得到跟随者的参考轨迹,并引入虚拟轨迹使其与跟随者参考轨迹有限时间重合,从而得到跟随者的期望位置和速度。在此基础上,使用最小二乘法拟合轨迹曲线进行时延补偿,并通过自适应反演滑模控制技术完成海流干扰下的编队轨迹跟踪。理论分析和仿真结果表明,新方法具有可行性和有效性。

故障检测与重构下基于AFTSMO的ROV三维航迹跟踪控制

针对传统的滑模观测器在缆控水下机器人(ROV)系统状态估计与故障重构过程中存在渐近收敛、无法及时准确重构故障信号的问题,提出一种基于自适应快速终端滑模观测器(adaptive fast terminal sliding mode observer)的故障检测和控制优化方法。建立带有推进器故障、未知外界干扰和模型参数不确定性等复合干扰的ROV系统故障模型;设计具有自适应特性的快速终端滑模控制器,保证所有的状态估计误差在有限时间内收敛;通过等效输出误差注入法对推进器引起的故障进行估计重构。采用Lyapunov稳定性理论验证控制系统的稳定性,仿真结果表明,所设计的故障检测方法能够快速检测和重构故障,保证ROV系统较高的跟踪精度,并通过实验验证了所提算法的有效性。

基于RBF神经网络补偿的ROV运动控制算法

针对作业型遥控水下航行器(ROV)在模型参数不确定和外部环境干扰下的运动控制问题,提出了一种基于径向基函数(RBF)神经网络的自适应双环滑模控制策略。首先,对于ROV外环位置控制采用改进趋近律的积分滑模控制方法,对于ROV内环速度控制采用指数趋近律的积分滑模控制方法;其次,为进一步改善滑模控制的抖振问题,引入双曲正切函数作为滑模切换项;然后,利用RBF神经网络控制技术对ROV模型的不确定参数和外部扰动进行估计与补偿;最后,利用李雅普诺夫稳定性理论证明了整个闭环系统的稳定性,并对作业型ROV的运动控制进行了数值仿真。仿真结果验证了所设计的控制器可以实现ROV航行的精确控制,并能够有效抑制模型不确定参数和外部扰动对ROV运动的影响。

基于模型预测的AUV轨迹跟踪滑模控制方法

针对自主水下航行器(AUV)在模型参数不确定和外界海流干扰情况下轨迹跟踪误差大的问题,提出一种基于模型预测的滑模控制方法。首先,基于李雅普诺夫稳定性理论,设计一种滑模控制器;其次,为高效利用计算资源,提高AUV的轨迹跟踪性能,设计一种滑模控制器与模型预测控制相结合的控制框架;考虑到执行器饱和问题,利用滑模跟踪控制律,在该控制框架上构造收缩约束,确保闭环系统的稳定性;最后,采用仿真实验验证,实验结果表明所提方法与滑模控制器比较,在模型参数确定且无干扰情况下均方跟踪误差减小了60%以上,在模型恢复力参数不确定和海流扰动情况下均方跟踪误差减小了80%以上,能够克服时变恢复力对系统的影响,并对外界海流干扰有较好的抑制作用,保证了系统的鲁棒性。

基于固定时间积分滑模观测器的双闭环UUV轨迹跟踪控制

针对水下无人航行器(UUV)轨迹跟踪控制问题,设计一种基于固定时间积分滑模观测器(FTISO)的双闭环运动控制策略。建立UUV运动数学模型,对运动学外环设计积分滑模控制器,使用非线性微分器获得外环虚拟控制律的导数,以保证航行器位置能够精确收敛。考虑动力学内环存在的模型不确定性和外部干扰难以测量等问题,采用FTISO实现对集总干扰快速估计,同时引入李雅普诺夫函数分析系统的稳定性。在仿真环境下对比基于FTISO的双闭环积分滑模控制与积分滑模控制、RBF网络自适应滑模控制的控制效果。仿真结果表明:基于FTISO的双闭环滑模控制对集总干扰有良好的补偿能力,可提高控制系统的性能及精度,可保证UUV在不同环境下均能实现轨迹跟踪。

基于IGWO-MPC和NDO-ISMC级联算法的UUV轨迹跟踪控制器设计

为了解决水下机器人(UUV)在受海流等复杂干扰力影响时的轨迹跟踪问题,设计了一种基于改进灰狼算法的模型预测控制(IGWO-MPC)和基于非线性干扰观测器的积分滑模控制(NDO-ISMC)级联的轨迹跟踪控制器。基于MPC方法设计了运动学控制器,提出利用在GWO算法中引入非线性收敛因子,基于个体经验和权重更新灰狼位置,以及反向学习策略所设计出的IGWO算法,来优化MPC的滚动优化求解过程,使机器人以期望的最优速度对给定位姿进行跟踪。基于IGWO-MPC运动学控制器得到的期望速度指令,设计了NDO-ISMC动力学控制器,该控制器利用NDO对干扰力进行估计,并对ISMC动力学输出控制律进行补偿以抑制扰动对跟踪精度的影响,同时输出扰动条件下机器人能够稳定跟踪上期望速度的控制推力。最后,利用MATLAB进行三维空间环境仿真,验证文章提出的将IGWO-MPC与NDO-ISMC算法级联的轨迹跟踪控制器能够使UUV在复杂水下环境下实现精确且稳定的轨迹跟踪。

输入受限下自主水下航行器路径跟踪控制

针对欠驱动式自主水下航行器AUV的三维路径跟踪控制问题,设计了一种按设定误差性能指标函数收敛的反演滑模控制器。首先基于航行器的运动学和动力学模型将路径跟踪问题转化为非线性系统的镇定问题;然后,利用反演法和李雅普诺夫稳定性理论逐步修正虚拟控制律,从而使控制器能够保证系统的稳定性和鲁棒性。为解决舵执行器的速率受限的问题,通过调整跟踪误差的收敛过程速度的方法设计了控制器。仿真结果表明,上述控制器能够实现对三维直线路径的精确跟踪,而且明显降低了控制系统执行器的速率要求。

基于干扰观测器的AUV三维路径滑模跟踪控制

为了确保欠驱动自主式水下机器人(AUV)在受到外界干扰情况下仍然可以实现对三维路径的跟踪控制,设计基于干扰观测器的反步滑模控制器。针对欠驱动AUV 5自由度状态方程,考虑外界干扰对AUV运动的影响,设计干扰观测器实时估计干扰;通过欠驱动AUV的状态方程与三维路径跟踪误差模型得到系统的镇定模型;利用得到的干扰估计值,设计反步滑模复合控制器来控制AUV实现三维路径跟踪,并通过Lyapunov稳定性理论证明闭环系统渐近稳定。仿真结果表明:该控制器对欠驱动AUV实现三维路径的精确跟踪有良好的控制效果和抗干扰能力。

混合驱动水下机器人浮游与爬行双模式轨迹跟踪控制

针对混合驱动水下机器人在进行水下浮游和爬行双模式作业时的轨迹跟踪控制问题,结合混合驱动水下机器人在浮游模式和爬行模式下的不同运动学特性,分别设计了一种基于改进灰狼优化模型预测控制算法的控制器,以实现机器人在浮游模式下的轨迹跟踪,以及一种基于模糊滑模控制算法的控制器,以实现机器人在爬行模式下的轨迹跟踪。仿真结果表明:所设计的改进灰狼优化模型预测控制器通过引入改进灰狼优化算法求解模型预测控制器滚动优化阶段中的目标函数,使得浮游模式的水下机器人能够快速、精确和稳定地跟踪预设轨迹;所设计的模糊滑模控制器采用模糊控制对滑模控制器中趋近律参数进行在线调整,使得爬行模式下的水下机器人能够实现有限时间收敛的同时并抑制抖振问题。