基于构造矩阵零空间的动力定位系统推力分配方法

在动力定位系统中,推力分配方法是联系运动控制算法和执行机构的纽带,具有十分重要的意义。回顾目前用于海洋工程船舶动力定位系统的主要推力分配算法,针对动力定位系统中常见的过驱动推力分配问题提出了一种基于船舶推进器构造矩阵零空间的分配算法。该方法将构造矩阵分解为基空间和零空间,目标推力可以由基空间保证;零空间向量并不影响总的目标推力,但影响单台推进器的推力,目标函数可以在零空间上优化。并将这一算法应用于某一工程船的动力定位仿真模拟,对该算法进行了验证。     

快速转向推进器推力优化分配研究

随着船舶推进技术的不断发展,动力定位船舶将更多地使用快速转向推进器以提高其定位性能。快速转向推进器的使用将引入大角度变化率,这会造成优化分配求解域明显的非凸性,给优化问题的求解带来了挑战。针对装备快速转向推进器的动力定位船舶,运用区域外切近似法对其推力分配的非凸性问题进行了凸化,采用增广拉格朗日乘子法对控制力进行了优化分配。仿真结果表明:推荐的凸化处理方法能有效地解决推力分配的非凸问题,分配算法可以充分利用快速转向推进器的机械性能优势,寻找更优的可行解,从而显著地减少动力定位船舶的能耗,提高其定位性能。     

单体喷水推进船舶动力定位控制方法研究

面向一型喷水推进器为动力定位执行机构的单体喷水推进船舶,开展了船舶仿真模型建立、推力分配及进一步动力定位相关控制算法设计与仿真模拟。针对传统的定步长Kalman滤波提出了改进方案,同时考虑到单体喷水推进船舶的特殊性,对推力分配算法进行了优化,并基于荷载前馈的PD控制算法开展了不同工况下的仿真试验。试验结果表明,所提出的喷水推进推力分配算法能够有效控制一型单体喷水推进船舶实现定点、定艏向、移位、转艏等动力定位典型功能,并具备一定抗外部干扰能力。     

基于人工神经网络的半潜平台动力定位系统推力分配策略研究

针对带有禁止角的半潜平台动力定位系统推力分配算法功率较大的问题,提出了一种基于人工神经网络拟合桨—桨干扰推力损失函数的序列二次规划推力分配算法。该方法考虑了半潜平台桨—桨干扰造成的推力损失,引入推力系数来表达推力损失。利用人工神经网络拟合推力系数,将推力损失加入到推力分配的数学模型中,取消了禁止角。采用序列二次规划求解推力分配数学模型。最后以某半潜式钻井平台为例,选取三种浪向角工况进行推力分配仿真模拟,结果显示该算法在高效分配定位所需推力的同时有效减小了功率消耗,应用前景广泛。     

半潜式平台动力定位系统控制力动态约束分配法

半潜式平台动力定位推力分配系统通过计算每个推力器的推力和推力角,将控制力分配到推力系统的各推力器上。基于系统耗能最小模式,根据推力器之间的损失模型,通过动态设置推力可行域,将推力分配问题转化为求解二次型优化模型。考虑推力器的物理性能,以推力变化率和转角变化速率为控制参数,利用序列二次规划法得到数值计算结果。该方法充分考虑推力器的物理性能,降低推力器的机械磨损,且可以避免处理可行域为非凸集问题,有效地提高推力器的推力效率。     

自治水下机器人机械手系统协调运动研究

简单描述了自治水下机器人搭载的三功能水下电动机械手的设计,鉴于自治水下机器人-机械手系统运动学冗余、内部可能干涉以及载体圆筒式外形等特点,将惩罚调节因子引入系统运动学伪逆矩阵,保证了关节在允许范围内运动,避免载体大幅度姿态变化及载体与机械手之间的干涉,同时采用梯度投影法优化海流作用下的系统推力。仿真表明,该算法在解决系统冗余度的同时,有效地协调多任务下的系统动作。     

基于多源定位数据的实时船舶监控系统设计

船舶监控涉及多类异构数据源,互联难度大。本文提出了一种采用多源定位数据的实时船舶监控系统(Vessel Monitoring System,VMS)设计方案,解决了多源异构数据的互联问题。该方案通过可扩展接口采集各类船舶终端的定位数据,采用多源定位数据融合算法,实现了实时显示船舶位置及快速回放船舶航行轨迹,并能与不同类型的船舶终端交互信息。经实际验证,该系统有效可行,对于促进中国船舶监控物联网发展具有重要作用。     

半潜式平台动力定位系统推进器失效时域模拟

针对某最新的深水半潜平台,应用PID控制策略和卡尔曼滤波技术相结合的方法对其动力定位能力进行了研究,重点关注在两台推进器于不同时刻分别失效后的平台运动和推进器功率消耗信息。在平台的运动时域分析中,通过采用数值模拟与实验验证相结合的方法来获得平台的水动力数据;而在推力分配过程中,以最小功率消耗为优化目标,并考虑了推进器的机械物理特性及水动力干扰造成的推力损失对推进器的推力进行了分配。结果表明编制的模拟软件具有理想的模拟效果,该平台在指定海况下动力定位能力良好。     

码头-缆绳-动力定位船舶耦合系统的时频特性分析

为研究系泊状态下动力定位船舶与码头及缆绳间的耦合作用,采取凝集质量法计算系泊缆索有效张力,设置弹簧阻尼单元用以计算码头碰垫间的非线性反力,应用比例-积分-微分控制系统(PID)进行推力控制。在系泊状态下,以动力定位船舶和无动力定位船舶为研究对象,分析了耦合系统中侧推器对消除因一阶波浪载荷而引起的船舶运动影响的作用;针对动力定位船舶,讨论了码头-缆绳及目标位置两个因素对动力定位船舶的定位能力及侧推器性能的影响。结果表明,在选取合理目标位置的情况下,耦合系统中的侧推器性能及动力定位船舶的定位能力均得到了有效提高。     

Bancroft算法应用于GPS/BDS/GLONASS三系统伪距单点定位

为了提高多系统组合单点定位的运算效率,将Bancroft算法推广应用于GPS/BDS/GLONASS三系统伪距单点定位,并推导了该方法的详细计算流程,比较了Bancroft算法、最小二乘算法和组合两种算法的精度、迭代次数以及运算时间。利用实测数据进行实验,结果表明,3种算法精度相当,Bancroft算法比最小二乘算法迭代次数少,运算效率提高了38%,利用Bancroft为最小二乘算法提供初值,收敛速度加快,运算效率提高了36%。最终得出结论,Bancroft算法应用于GPS/BDS/GLONASS三系统伪距单点定位满足精度要求,且Bancroft算法对于减少迭代次数,提高运算效率有重要意义。     

Cognitive radio resource allocation based on coupled chaotic genetic algorithm

A coupled chaotic genetic algorithm for cognitive radio resource allocation which is based on genetic algorithm and coupled Logistic map is proposed. A fitness function for cognitive radio resource allocation is provided. Simulations are conducted for cognitive radio resource allocation by using the coupled chaotic genetic algorithm, simple genetic algorithm and dynamic allocation algorithm respectively. The simulation results show that, compared with simple genetic and dynamic allocation algorithm, coupled chaotic genetic algorithm reduces the total transmission power and bit error rate in cognitive radio system, and has faster convergence speed.     

动力定位采矿船高海情下的运动响应分析

本文对具有动力定位深海采矿船高海情下的运动响应及运动特性开展研究。针对具有6个推进器构成的动力定位系统,考虑高海情及空载和满载两种典型工况,基于推力最小和运动最小条件,应用卡尔曼滤波器结合线性二次型最优控制理论的控制算法优化推力,进行动力定位系统的参数整定,实时优化调整推力的方向和大小,计算采矿船高海情下的运动和推力的时间历程响应和分析运动特性。经计算,得到了深海采矿船空载和满载工况在高海情下实施海上定位的浪向及需要的推力大小,确定了采矿船动力定位系统在高海情下的适应性,评估了高海情下深海采矿船的定位能力。     

Coupled dynamic analysis of deep-sea mining support vessel with dynamic positioning

Deep-sea mining (DSM) is an advanced concept. A simulation method of coupled vessel/riser/body system in DSM combined with dynamic positioning (DP) is proposed. Based on the three-dimensional potential flow theory, lumped mass method, and Morison’s equations the dynamic models of the production support vessel, riser and slurry pump are established. A proportion integration differentiation (PID) controller with a nonlinear observer and a thrust allocation unit are used to simulate the DP system. Coupled time domain simulation is implemented with the vessel operated in two DP modes. Results of the vessel and pump motions, riser tension, and thruster forces are obtained. It shows that the pump will be lifted by the riser when the vessel is chasing the next set point. Riser tension is influenced by the wave frequency motions of the vessel in positioning mode and low-frequency motions in tracking mode. The proposed simulation scheme is practical to study the DSM operation.     

A universal algorithm to generate pseudo-random numbers based on uniform mapping as homeomorphism

A specific uniform map is constructed as a homeomorphism mapping chaotic time series into [0,1] to obtain sequences of standard uniform distribution. With the uniform map, a chaotic orbit and a sequence orbit obtained are topologically equivalent to each other so the map can preserve the most dynamic properties of chaotic systems such as permutation entropy. Based on the uniform map, a universal algorithm to generate pseudo random numbers is proposed and the pseudo random series is tested to follow the standard 0-1 random distribution both theoretically and experimentally. The algorithm is not complex, which does not impose high requirement on computer hard ware and thus computation speed is fast. The method not only extends the parameter spaces but also avoids the drawback of small function space caused by constraints on chaotic maps used to generate pseudo random numbers. The algorithm can be applied to any chaotic system and can produce pseudo random sequence of high quality, thus can be a good universal pseudo random number generator.     

A chattering-free sliding-mode controller for underwater vehicles with fault-tolerant infinity-norm thrust allocation

There are two objectives to this paper. First, a chattering-free sliding-mode controller is proposed for the trajectory control of remotely operated vehicles (ROVs). Second, a new approach for thrust allocation is proposed that is based on minimizing the largest individual component of the thrust manifold. With regards to the former, a new adaptive term is developed that eliminates the high-frequency control action inherent in a conventional sliding-mode controller. As opposed to the common adaptive approach, the new adaptive term does not require the linearity condition on the dynamic parameters and the creation of a regressor matrix. In addition, it removes the need for a priori knowledge of upper bounds on uncertainties in the dynamic parameters of the ROV. With regards to the latter, it is demonstrated that minimizing the l_∞ norm (infinity-norm) of the thrust manifold ensures low individual thruster forces. The new control and thrust allocation concepts are implemented in numerical simulations of a work class ROV, and the chattering-free nature of the controller is demonstrated during typical ROV manoeuvres. In the simulation studies, the l_∞ norm-based thrust allocation problem is cast as a linear programming problem that allows direct incorporation of the thruster saturation limits and a fault-tolerant property. To achieve real-time solution rates for the l_∞ norm-based thrust allocation problem, a recurrent neural network is designed. In the simulation studies, the l_∞ norm-based thrust allocation provides smaller maximum absolute value of the largest component of the thrust manifold than that of a conventional l₂ norm (2-norm) minimization, satisfies the saturation limits of each thruster, and accommodates faults that are introduced arbitrarily during the manoeuvre.