S~2 BHCA-Multiple AUVs cooperation oriented control architecture

Oceanographic survey, or other similar applications should be the applications of multiple AUVs. In this paper, the skill & simulation based hybrid control architecture (S2BHCA) as the controller's design reference was proposed. It is a multi-robot cooperation oriented intelligent control architecture based on hybrid ideas. The S BHCA attempts to incorporate the virtues of the reactive controller and of the deliberative controller by introducing the concept of the "skill". The additional online task simulation ability for cooperation is supported, too. As an application, a multiple AUV control system was developed with three "skills" for the MCM mission including two different cooperative tasks. The simulation and the sea trials show that simple task expression, fast reaction and better cooperation support can be achieved by realizing the AUV controller based on the S2BHCA.     

Market based framework for multiple AUVs cooperation

A“Market” based framework for multiple AUVs team is introduced in this paper. It is a distributed meta-level task allocation framwork. The formulation and the basic concepts of the “Market” such as “goods” and “price” are discussed first, then the basic algorithm of the “auction”. The loosely coupled v-MDTSP tasks are considered as an example of the task allocation mission. A multiple AUV team controller and a detailed algorithm are developed for such applications. The simulation results show that the controller has the advantages such as robustness and low complexity and it can achieve better optimization results than the classical central controller （ such as GA） in some tasks. And the comparison of two different local solvers also implies that we should get the reasonable task allocation even not using the high quality algorithm, which can considerably decrease the cooperation computation.     

Design and evaluation of a hierarchical control architecture for an autonomous underwater vehicle

This paper researches on a kind of control architecture for autonomous undelwater vehicle （AUV）. After describing the hybrid property of the AUV control system, we present the hierarchical AUV control architecture. The architecture is organized in three layers： mission layer, task layer and execution layer. State supervisor and task coordinator are two key modules handling discrete events, so we describe these two modules in detail. Finally, we carried out a series of tests to verify this architecture The test results show that the AUV can perform autonomous missions effectively and safely. We can conclude the control architecture is valid and practical.     

Expert S-surface control for autonomous underwater vehicles

S-surface control has proven to be an effective means for motion control of underwater autonomous vehicles （AUV）. However there are still problems maintaining steady precision of course due to the constant need to adjust parameters, especially where there are disturbing currents. Thus an intelligent integral was introduced to improve precision. An expert S-surface control was developed to tune the parameters on-line, based on the expert system, it provides S-surface control according to practical experience and control knowledge. To prevent control output over-compensation, a fuzzy neural network was included to adjust the production rules to the knowledge base. Experiments were conducted on an AUV simulation platform, and the results show that the expert S-surface controller performs better than an S-surface controller in environments with currents, producing good steady precision of course in a robust way.     

带吊舱水下机器人运动建模与仿真(英文)

To provide a simulation system platform for designing and debugging a small autonomous underwater vehicle’s (AUV) motion controller, a six-degree of freedom (6-DOF) dynamic model for AUV controlled by thruster and fins with appendages is examined. Based on the dynamic model, a simulation system for the AUV’s motion is established. The different kinds of typical motions are simulated to analyze the motion performance and the maneuverability of the AUV. In order to evaluate the influences of appendages on the motion performance of the AUV, simulations of the AUV with and without appendages are performed and compared. The results demonstrate the AUV has good maneuverability with and without appendages.     

Research on framework for formation control of multiple underwater robots in a dynamic environment

In this paper a practical framework is proposed to keep formation control of multiple underwater robots in a dynamic environment. The approach is a viable solution to solve formation problem. The approach allows online planning of the formation paths using a Dijkstra‘s search algorithm based on the current sensor data. The formation is allowed to be dynamically changed in order to avoid obstacles in the environment. A controller is designed to keep the robots in their planned trajectories. It is shown that the approach is effective and feasible by the simulation of computer.     

水下无人潜航器航向H_∞鲁棒容错控制器设计(英文)

In order to improve the security and reliability for autonomous underwater vehicle (AUV) navigation, an H∞ robust fault-tolerant controller was designed after analyzing variations in state-feedback gain. Operating conditions and the design method were then analyzed so that the control problem could be expressed as a mathematical optimization problem. This permitted the use of linear matrix inequalities (LMI) to solve for the H∞ controller for the system. When considering different actuator failures, these conditions were then also mathematically expressed, allowing the H∞ robust controller to solve for these events and thus be fault-tolerant. Finally, simulation results showed that the H∞ robust fault-tolerant controller could provide precise AUV navigation control with strong robustness.     

带不确定动态的欠驱动水面船舶鲁棒自适应路径跟踪控制(英文)

A robust adaptive control strategy was developed to force an underactuated surface vessel to follow a reference path,despite the presence of uncertain parameters and unstructured uncertainties including exogenous disturbances and measurement noise.The reference path can be a curve or a straight line.The proposed controller was designed by using Lyapunov’s direct method and sliding mode control and backstepping techniques.Because the sway axis of the vessel was not directly actuated,two sliding surfaces were introduced,the first one in terms of the surge motion tracking errors and the second one for the yaw motion tracking errors.The adaptive control law guaranteed the uniform ultimate boundedness of the tracking errors.Numerical simulation results were provided to validate the effectiveness of the proposed controller for path following of underactuated surface vessels.     

Fuzzy sliding mode control method for vertical motion of autonomous underwater gliders北大核心CSCD

［Objective］This paper proposes a fuzzy sliding mode controller based on T-S fuzzy logic for the vertical plane motion control of an autonomous underwater glider (AUG) with limited actuator capability. ［Methods］In the fuzzy sliding mode controller, the fuzzy switching rate is used to replace the switching rate in the fixed time controller to effectively suppress buffeting. The fuzzy switching rate is obtained by fitting the switching rate of the fixed time controller with T-S fuzzy rules. Based on the limited capabilities of AUG actuators, a saturation auxiliary system is designed to improve the actuator saturation effect. Finally, the performance of the system is verified by Lyapunov stability analysis and numerical simulation. ［Results］The results show that the AUG under the fuzzy sliding mode controller and the saturation auxiliary system can converge in finite time. The effectiveness of the fuzzy sliding mode controller and the saturation auxiliary system are verified by numerical simulation. ［Conclusions］By making comparisons with the fixed-time controller, it is verified that the two controllers have similar control performance, and the buffeting of the fuzzy sliding mode controller is lesser. © 2022 Journal of Clinical Hepatology. All rights reserved.     

护卫舰横摇稳定舵的H∞/H2控制器的设计和比较（英文）

The roll motions of ships advancing in heavy seas have severe impacts on the safety of crews, vessels, and cargoes; thus, it must be damped. This study presents the design of a rudder roll damping autopilot by utilizing the dual extended Kalman filter(DEKF)–trained radial basis function neural networks(RBFNN) for the surface vessels. The autopilot system constitutes the roll reduction controller and the yaw motion controller implemented in parallel. After analyzing the advantages of the DEKFtrained RBFNN control method theoretically, the ship's nonlinear model with environmental disturbances was employed to verify the performance of the proposed stabilization system. Different sailing scenarios were conducted to investigate the motion responses of the ship in waves. The results demonstrate that the DEKF RBFNN–based control system is efficient and practical in reducing roll motions and following the path for the ship sailing in waves only through rudder actions.     

Application of H∞ control in rudder/flap vector robust control of a ship＇s course

Given the uncertainty of parameters and the random nature of disturbances that effect a ships course, a robust course controller should be designed on the basis of rudder/flap vector control. This paper analyzes system uncertainty, and the choice of weighting functions is also discussed. When sea waves operate on a ship, the energy-concentrating frequency varies with the angle of encounter. For different angles of encounter, different weighting functions are designed. For the pole of a nominal model existing in an imaginary axis, the bilinear-transform method is used. The ＂2-Riccati＂ equation is adopted to solve the H∞ controller. A system simulation is given, and the results show that, compared with a PID controller, this system has higher course precision and more robust performance. This research has significant engineering value.     

智能水下机器人的建模和控制策略研究(英文)

To provide a suitable model for AUV simulation and control purposes, a general nonlinear dynamic model including a novel thruster hydrodynamics model was derived. Based on the modeling method, the “AUV-XX” simulation platform was established to carry out fundamental tests on its motion characteristics, stability, and controllability. A motion control strategy consisting of both position and speed control in a horizontal plane was designed for different task assignments of underwater vehicles. Combined control of heave and pitch was adopted to compensate for the reduction of vertical tunnel thrusters when the vehicle is moving at a high speed. An improved S-surface controller based on the capacitor plate model was developed with flexible gain selections made possible by different forms of restricting the error and changing the rate of the error. Simulation results show that the derived general mathematical model together with simulation platform can provide a test bed for fundamental tests of motion control. Additionally, the capacitor plate model S-surface control shows a good performance in guiding the vehicle to achieve the desired position and speed with sufficient accuracy.     

H∞ Robust Fault-Tolerant Controller Design for an Autonomous Underwater Vehicle＇s Navigation Control System

In order to improve the security and reliability for autonomous underwater vehicle (AUV) navigation, an H_∞ robust fault-tolerant controller was designed after analyzing variations in state-feedback gain. Operating conditions and the design method were then analyzed so that the control problem could be expressed as a mathematical optimization problem. This permitted the use of linear matrix inequalities (LMI) to solve for the H_∞ controller for the system. When considering different actuator failures, these conditions were then also mathematically expressed, allowing the H_∞ robust controller to solve for these events and thus be fault-tolerant. Finally, simulation results showed that the H_∞ robust fault-tolerant controller could provide precise AUV navigation control with strong robustness.     

基于强化学习的自主式水下潜器障碍规避技术（英文）

Obstacle avoidance becomes a very challenging task for an autonomous underwater vehicle(AUV) in an unknown underwater environment during exploration process. Successful control in such case may be achieved using the model-based classical control techniques like PID and MPC but it required an accurate mathematical model of AUV and may fail due to parametric uncertainties, disturbance, or plant model mismatch. On the other hand, model-free reinforcement learning(RL) algorithm can be designed using actual behavior of AUV plant in an unknown environment and the learned control may not get affected by model uncertainties like a classical control approach. Unlike model-based control model-free RL based controller does not require to manually tune controller with the changing environment. A standard RL based one-step Q-learning based control can be utilized for obstacle avoidance but it has tendency to explore all possible actions at given state which may increase number of collision.Hence a modified Q-learning based control approach is proposed to deal with these problems in unknown environment.Furthermore, function approximation is utilized using neural network(NN) to overcome the continuous states and large statespace problems which arise in RL-based controller design. The proposed modified Q-learning algorithm is validated using MATLAB simulations by comparing it with standard Q-learning algorithm for single obstacle avoidance. Also, the same algorithm is utilized to deal with multiple obstacle avoidance problems.     

水下潜器改进S面控制及控制系统仿真(英文)

S surface controllers have been proven to provide effective motion control for an autonomous underwater vehicle (AUV). However, it is difficult to adjust their control parameters manually. Choosing the optimum parameters for the controller of a particular AUV is a significant challenge. To automate the process, a modified particle swarm optimization (MPSO) algorithm was proposed. It was based on immune theory, and used a nonlinear regression strategy for inertia weight to optimize AUV control parameters. A semi-physical simulation system for the AUV was developed as a platform to verify the proposed control method, and its structure was considered. The simulation results indicated that the semi-physical simulation platform was helpful, the optimization algorithm has good local and global searching abilities, and the method can be reliably used for an AUV.     

AUV控制系统试验平台

随着AUV(自主式潜器)技术的不断发展,对其自主性能的要求越来越高.AUV控制系统试验平台可以实现各种自主控制、动态控制算法及软件的系统集成.文章以能够自主完成地形勘察使命的AUV为研究对象,设计了AUV控制系统试验平台,对AUV控制系统硬件系统和基于行为仲裁的分层递阶软件系统做了较全面的介绍,利用QNX操作系统的多线程和消息传递技术实现了任务协调算法.在半实物试验平台上进行的地形勘察使命仿真结果验证了控制系统试验平台硬件结构合理,算法及软件集成可实现.     

Numerical simulations of fatigue crack initiation and propagation based on re-tensile plastic zone generating load criterion for in-plane gusset welded joints

Many accidents are caused by fatigue in welded built-up steel structures, and so it is important to estimate the fatigue lives of such structures quantitatively for safety reasons. By assuming that fatigue cracks cannot grow without an accumulation of alternating tensile/compressional plastic strain, one of the authors identified an improved effective stress intensity factor range ΔK _RPG based on the re-tensile plastic zone generating (RPG) load, which represents the driving force for fatigue cracks, and suggested that ΔK _RPG should be used as the parameter to describe fatigue crack growth behavior. The “FLARP” numerical simulation code in which ΔK _RPG is implemented as the fatigue crack growth parameter, was developed in order to predict fatigue crack initiation and propagation behavior. In this paper, it is demonstrated that FLARP gives accurate estimates for fatigue life by comparing the estimated fatigue crack growth curves and S–N curves with the experimental results for in-plane gusset welded joints, which are used in many welded steel structures. Moreover, the effect of induced bending moment due to the linear misalignment in the out of plane direction on the fatigue strength of in-plane gusset welded joints is investigated through numerical simulations.