Path-Following Control With Obstacle Avoidance of Autonomous Surface Vehicles Subject to Actuator Faults

This paper investigates the path-following control problem with obstacle avoidance of autonomous surface vehicles in the presence of actuator faults,uncertainty and external disturbances.Autonomous surface vehicles inevitably suffer from actuator faults in complex sea environments,which may cause existing obstacle avoidance strategies to fail.To reduce the influence of actuator faults,an improved artificial potential function is constructed by introducing the lower bound of actuator efficiency factors.The nonlinear state observer,which only depends on measurable position information of the autonomous surface vehicle,is used to address uncertainties and external disturbances.By using a backstepping technique and adaptive mechanism,a path-following control strategy with obstacle avoidance and fault tolerance is designed which can ensure that the tracking errors converge to a small neighborhood of zero.Compared with existing results,the proposed control strategy has the capability of obstacle avoidance and fault tolerance simultaneously.Finally,the comparison results through simulations are given to verify the effectiveness of the proposed method.

Reinforcement Learning Based Obstacle Avoidance for Autonomous Underwater Vehicle

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.

Dynamic A^*path finding algorithm and 3D lidar based obstacle avoidance strategy for autonomous vehicles

This paper presents a novel dynamic A^*path finding algorithm and 3D lidar based local obstacle avoidance strategy for an autonomous vehicle.3D point cloud data is collected and analyzed in real time.Local obstacles are detected online and a 2D local obstacle grid map is constructed at 10 Hz/s.The A^*path finding algorithm is employed to generate a local path in this local obstacle grid map by considering both the target position and obstacles.The vehicle avoids obstacles under the guidance of the generated local path.Experiment results have shown the effectiveness of the obstacle avoidance navigation algorithm proposed.

A Novel Obstacle Avoidance Consensus Control for Multi-AUV Formation System

In this paper, the fixed-time event-triggered obstacle avoidance consensus control for a multi-AUV time-varying formation system in a 3D environment is presented by using an improved artificial potential field and leader-follower strategy(IAPF-LF). Firstly, the proposed fixed-time control can achieve the desired multi-AUV formation within a fixed settling time in any initial system state. Secondly, an event-triggered communication strategy is developed to govern the communication among AUVs, and the communication energy consumption can be decremented. The time-varying formation obstacle avoidance control algorithm based on IAPF-LF is designed to avoid static and dynamic obstacles, the desired formation is maintained in the presence of external disturbances, and there is no Zeno behavior under the fixed-time event-triggered consensus control strategy.The stability of the system is proved by the Lyapunov function and inequality scaling. Finally, simulation examples and water pool experiments are reported to verify the performance of the proposed theoretical algorithms.

Real-Time Fuzzy Obstacle Avoidance Using Directional Visual Perception

This paper presents a novel vision-based obstacle avoidance approach for the Autonomous Mobile Robot (AMR) with a Pan-Tilt-Zoom (PTZ) camera as its only sensing modality. The approach combines the morphological closing operation based on Sobel Edge Detection Operation and the (μ-kσ) thresholding technique to detect obstacles to soften the various lighting and ground floor effects. Both the morphology method and thresholding technique are computationally simple. The processing speed of the algorithm is fast enough to avoid some active obstacles. In addition, this approach takes into account the history obstacle effects on the current state. Fuzzy logic is used to control the behaviors of AMR as it navigates in the environment. All behaviors run concurrently and generate motor response solely based on vision perception. A priority based on subsumption coordinator selects the most appropriate response to direct the AMR away from obstacles. Validation of the proposed approach is done on a Pioneer 1 mobile robot.

Application of A* Algorithm for Real-time Path Re-planning of an Unmanned Surface Vehicle Avoiding Underwater Obstacles

This paper describes path re-planning techniques and underwater obstacle avoidance for unmanned surface vehicle(USV) based on multi-beam forward looking sonar(FLS). Near-optimal paths in static and dynamic environments with underwater obstacles are computed using a numerical solution procedure based on an A* algorithm. The USV is modeled with a circular shape in 2 degrees of freedom(surge and yaw). In this paper, two-dimensional(2-D) underwater obstacle avoidance and the robust real-time path re-planning technique for actual USV using multi-beam FLS are developed. Our real-time path re-planning algorithm has been tested to regenerate the optimal path for several updated frames in the field of view of the sonar with a proper update frequency of the FLS. The performance of the proposed method was verified through simulations, and sea experiments. For simulations, the USV model can avoid both a single stationary obstacle, multiple stationary obstacles and moving obstacles with the near-optimal trajectory that are performed both in the vehicle and the world reference frame. For sea experiments, the proposed method for an underwater obstacle avoidance system is implemented with a USV test platform. The actual USV is automatically controlled and succeeded in its real-time avoidance against the stationary undersea obstacle in the field of view of the FLS together with the Global Positioning System(GPS) of the USV.

A Generalized Real-Time Obstacle Avoidance Method Without the Cspace Calculation

An important concept proposed in the early stage of robot path planning field is the shrinking of a robot to a point and meanwhile the expanding of obstacles in the workspace as a set of new obstacles. The resulting grown obstacles are called the Configuration Space （Cspace） obstacles. The find-path problem is then transformed into that of finding a collision-free path for a point robot among the Cspace obstacles. However, the research experiences have shown that the Cspace transformation is very hard when the following situations occur： 1） both the robot and obstacles are not polygons, and 2） the robot is allowed to rotate. This situation gets even worse when the robot and obstacles are three dimensional （3D） objects with various shapes. For this reason, direct path planning approaches without the Cspace transformation is quite useful and expected. Motivated by the practical requirements of robot path planning, a generalized constrained optimization problem （GCOP） with not only logic AND but also logic OR relationships was proposed and a mathematical solution developed previously. This paper inherits the fundamental ideas of inequality and optimization techniques from the previous work, converts the obstacle avoidance problem into a semi-infinite constrained optimization problem with the help of the mathematical transformation, and proposes a direct path planning approach without Cspace calculation, which is quite different from traditional methods. To show its merits, simulation results in 3D space have been presented.

基于ESP32的智能履带式移动机器人的设计

随着计算机和机器人技术的不断发展,移动机器人呈现出广泛的应用前景.作为移动机器人的一种,履带式移动机器人可以在危险恶劣的环境中开展工作.研究了一种基于ESP32开发板的智能避障系统,该系统集成了多个传感器和执行器,能够实现自主避障、智能显示障碍物位置信息以及播放音乐等功能.通过详细的硬件设计、软件开发和控制系统分析,对履带式移动机器人进行了系统性的研究.实验结果表明,该机器人具有较高的稳定性和可靠性,能够实现履带式移动机器人的设定功能.研究结果对履带式移动机器人的系统设计提供了新的思路和方法,为进一步拓展移动机器人在救援及其他相关领域的应用奠定了基础.

利用激光点云的智能网联汽车自主换道横向避障

通过智能网联汽车自主换道横向避障设计,提高车辆自主驾驶安全性能,提出基于激光点云的智能网联汽车自主换道横向避障方法,构建基于全激光雷达的无人驾驶系统的汽车行驶环境激光点云数据采集模型,通过激光雷达激光点云图像检测方法实现对智能网汽车行驶环境感知。结合障碍物检测、车道线检测、可行驶区域检测的方法,分析智能网联下汽车换道障碍物和车道的相关性特征量,通过激光点云的自主寻优方法寻找边界点直到搜索路径达到阈值,再结合直线道路模型和车道线连续性原则实现对汽车自主换道横向避障规划设计。仿真结果表明,采用该方法进行汽车自主环控避障,在5 s时达到收敛状态,障碍物坐标识别误差距离低于0.7,并且该方法的识别精度达到了0.970以上,提高了车道信息的感知能力,准确高效地估计可行驶区域,提高车辆避障能力。

煤矿履带式定向钻机路径规划算法

煤矿履带式定向钻机路径规划过程中存在机身体积约束和实际场景下的行驶效率需求,而常用的A^(*)算法搜索速度慢、冗余节点多,且规划路径贴近障碍物、平滑性较差。提出一种以改进A^(*)算法规划全局路径、融合动态窗口法(DWA)规划局部路径的煤矿履带式定向钻机路径规划算法。考虑定向钻机尺寸影响,在传统A^(*)算法中引入安全扩展策略,即在定向钻机和巷道壁、障碍物之间加入安全距离约束,以提高规划路径的安全性;对传统A^(*)算法的启发函数进行自适应权重优化,同时将父节点的影响加入到启发函数中,以提高全局路径搜索效率;利用障碍物检测原理对经上述改进后的A^(*)算法规划路径剔除冗余节点,并使用分段三次Hermite插值进行二次平滑处理,得到全局最优路径。将改进A^(*)算法与DWA融合,进行煤矿井下定向钻机路径规划。利用Matlab对不同工况环境下定向钻机路径规划算法进行仿真对比分析,结果表明:与Dijkstra算法和传统A^(*)算法相比,改进A^(*)算法在保证安全距离的前提下,加快了搜索速度,搜索时间分别平均减少88.5%和63.2%,且在一定程度上缩短了规划路径的长度,路径更加平滑;改进A^(*)算法与DWA融合算法可有效躲避改进A^(*)算法规划路径上的未知障碍物,路径长度较PRM算法和RRT^(*)算法规划的路径分别平均减小5.5%和2.9%。

复杂环境下DWA与RRT算法融合的AUV局部路径规划

针对复杂水下环境下的自主水下航行器(autonomous underwater vehicle,AUV)局部路径规划问题,传统动态窗口法(dynamic window approach,DWA)存在复杂障碍物中陷入局部停滞,动态避障性能不佳等问题,本文提出了一种基于DWA与快速随机搜索树(rapid-exploration random tree,RRT)算法融合的路径规划算法。改进的DWA算法速度空间根据整个动态窗口的周期生成,重设了评价函数并结合AUV任务环境引入洋流能耗评价函数;改进的RRT算法在局部已知空间内规划导引点,帮助DWA脱离局部停滞状态并实现更安全的动态避障。将2种算法融合,实现了AUV在复杂水下环境中的局部路径规划。仿真表明,该融合算法能够降低AUV在洋流中的能耗代价,解决了DWA在复杂障碍物中陷入局部停滞的问题,能够安全有效地躲避动态避障物。

室内环境下改进的混合路径规划算法

为了解决室内非结构化复杂环境下的机器人在路径规划时常常出现目标点不可达、规划过程产生折角偏移、规划过程无法及时规避动态障碍物等问题,提出一种改进的混合室内路径规划算法。该算法将改进的全局路径规划与改进的局部路径规划算法相融合。首先,优化传统A-Star算法的启发因子,减少搜索范围和节点,再通过角平分线切点法对传统A-Star算法进行平滑处理。其次,综合路径与环境信息,采用改进的人工势场算法进行局部路径规划,通过修正斥力场参数来解决目标点不可达问题,同时构造了动态的势力场函数,使其具备决解决动态障碍物的能力。最后,对混合算法进行实际环境的路径规划实验,比起传统的混合算法文中提出的混合算法在路径规划长度上减少11.4%,运行时间减少11.1%,少经过34个冗余节点,结果表明该融合算法可以有效解决室内非结构化复杂的路径规划问题。

多车环境下智能货车的紧急转向决策及轨迹规划

决策与规划是实现自动驾驶的关键技术,针对自动驾驶货车在紧急转向避障时需要考虑换道时目标车道的安全性和规划出最优避障轨迹的问题,采用将换道时左右车道上的车辆与自车的相对距离和换道的最小安全距离的差值分别建立模糊关系的方法,通过比较模糊规则推理设计的安全值,选择更安全的车道进行转向避障,为了迅速规划出最优避障轨迹,采用三阶贝塞尔曲线,通过设计4个控制点坐标形成避障曲线,为了防止转向时横向加速度过大导致货车发生侧翻和速度过快与前车发生碰撞,设计车辆的稳定性边界和碰撞边界对控制点进行约束,使用MATLAB中的函数求解出不同车速下的最优换道轨迹,最后使用仿真软件进行仿真验证,结果表明设计出的避障决策和轨迹规划可以安全、有效地避开障碍。

改进蚁群算法的AGV自主避障

针对传统蚁群算法在AGV任务调度效率的不足和避障问题,提出了一种改进的蚁群算法。首先,通过引入路径忙碌值,改进蚁群算法中的路径信息素浓度,提高路径规划解的质量;其次,对启发式的信息素浓度添加随机影响因子,进而提高算法的搜索效率。然后,在改进的蚁群算法基础上,引入路径多次规划参数和工作运行影响参数,并对AGV制定基本调度规则和任务优先级,提出一种综合的避障策略来解决冲突问题。仿真实验结果表明改进的蚁群算法可以评估路径使用率,进而规划最优的路径。在多任务调度效率上有明显优势,并能有效实现自主避障,解决碰撞问题。

基于改进机器学习的图书馆机器人自主避障控制研究

为控制图书馆机器人在行进过程中自动躲避障碍,达到理想工作效果,提出基于改进机器学习的图书馆机器人自主避障控制方法;采集图书馆机器人与目标障碍物距离信息,感知环境特征向量,当成卷积神经网络输入,经卷积、池化等操作,输出图书馆机器人对当前环境感知结果,该结果经输入输出变量模糊化、模糊推理以及输出变量解模糊等操作后,实现图书馆机器人自主避障无冲突运行;实验结果表明:该方法自主避障控制效果较好,避障行驶距离短,高速运行时反应更快,能够避开多个障碍物,识别分类结果与实际感知环境类型一致。

Obstacle-avoiding path planning for multiple autonomousunderwater vehicles with simultaneous arrival

This paper focuses on planning the obstacle-avoiding paths of multiple autonomous underwater vehicles(AUVs) in complex ocean environment, with the time coordination of simultaneous arrival. By imitating the nature phenomenon that river water avoids rocks and reaches the destination, the interfered fluid dynamical system(IFDS) is first presented to obtain the single-AUV path for obstacle avoidance, where the modulation matrix is calculated to quantify the influence of obstacles especially. Then the two-layer comprehensive adjustment to path length and voyage speed is utilized, aiming to achieve the simultaneous arrival at destination between multi-AUVs. By adjusting reactive parameters of IFDS, the former is to roughly ensure the intersection of AUVs' potential arrival time range to be non-null. On this basis, the latter adjusts each AUV's voyage speed finely using the consensus method with state predictor, which has faster convergence speed. If the multi-AUVs communication network is connected, the whole system will quickly converge to the consensus state, i.e., the estimated time of arrival(ETA) of each AUV tends to be equal. Finally, the simulation results verify the advantages of our proposed method.

基于模型预测的海缆铺设用水下航行器最优避障控制

[目的]自主水下航行器(AUV)在海底复杂地形环境下执行独立铺缆作业时,需要兼顾铺缆质量和自身安全,即在避障的同时还需要保持船体与海底平面的相对高度。为此,设计一种基于模型预测的海缆铺设AUV最优避障控制方法。[方法]首先,基于模型预测控制(MPC)建立AUV的路径跟踪模型,将海底不规则障碍物分类为凸起和凹陷地形,并分别建立障碍物的工程简化数学模型;然后,根据不同地形和海缆铺设要求来设计多个目标优化函数;最后,根据地形特征点迭代计算与海底平面保持稳定高度且路径最短的最优避障路径。[结果]仿真结果表明,该方法响应性能好、可靠性高,能够使AUV选择最短路径并避开意外障碍物。[结论]在复杂的海底环境下,该方法既保障了AUV作业过程中的自身安全,又极大提高了海缆的铺设质量。

5G通信技术在船舶电气控制系统中的应用

文章探讨了5G通信技术在船舶电气控制系统中的应用。5G通信技术凭借其高带宽、低时延以及高可靠性,显著提升了船舶电气系统的实时监控、远程控制以及智能电网管理能力。同时,5G通信技术在自主航行与避障系统、船岸一体化通信中发挥着关键作用。通过优化能耗管理,提升系统的灵活性和适应性,5G通信技术为船舶电气系统的智能化发展提供了重要支持。

基于多传感器融合的无人机自主避障方法

针对无人机利用单一传感器进行避障时存在准确度低、信息缺失等问题,提出了一种基于多传感器融合的无人机自主避障方法。通过改进的贝叶斯融合算法将二维激光雷达与深度相机获取的点云信息进行融合,以弥补二维激光雷达无法检测的区域。同时,利用融合点云生成八叉树地图,并根据不断更新的地图信息对无人机进行实时航迹重规划,实现无人机在未知环境中的自主避障。实验结果表明,所研究方法不仅提高了无人机感知周围环境的准确度,融合点云的均方根误差小于0.06 m,还具有良好的避障效果,无人机与障碍物的距离均大于0.5 m,保证了其在未知环境中的安全飞行。

基于秃鹰搜索算法优化的三维多无人机低空突防

三维空间环境复杂,多无人机的低空突防航迹规划计算量大,现有多目标秃鹰搜索算法存在求解易趋于中心点及精度低的缺陷,为此提出基于改进多目标秃鹰搜索算法(IMBES)的三维多无人机低空突防方法.构建三维环境模型、威胁源模型、无人机物理约束模型、多无人机协同约束模型以及路径平滑度约束模型,确定多目标代价函数.设计耦合混沌映射初始化,有效提高初始化种群质量;设计基于“侦察鹰”的自适应高斯游走策略,平衡开发与搜索能力;引入快速非支配排序,进一步提高算法效率.利用秃鹰位置与无人机速度、转弯角度、爬升角度的对应关系,采用IMBES高效搜索无人机构型空间,找到最优的帕累托前沿.实验结果表明,IMBES的成功率为70.5%.与现有路径规划方法相比,所提方法的优化能力强、能耗低,适用于多无人机协同低空突防.