垂直面欠驱动自治水下机器人定深问题的自适应输出反馈控制

针对垂直面欠驱动自治水下机器人(AUV)定深控制问题,本文仅使用可测量的深度和纵摇角信息,基于反步法设计自适应输出反馈控制器.为此首先设计观测器,实现不可测纵摇角速度反馈;再利用径向基神经网络对不确定水动力系数和纵荡、垂荡及纵摇角速度耦合产生的非线性结构进行补偿;采用自适应策略对纵荡和垂荡速度形成的有界干扰进行抑制.本文采用AUV一阶非完整模型,不以线性化为目的,放宽了纵摇角只能在小范围内变化的限制.最后通过理论证明和仿真实验表明该方法能够实现AUV深度和姿态控制,对未建模非线性动态和有界扰动具有很强的自适应性和鲁棒性.     

舵鳍联合控制参数优化及仿真

船舶上装置的舵和减摇鳍系统分别完成航向和横摇减摇控制,但是两者之间存在着耦合,因此提出了舵鳍联合控制,实现多翼面的协调控制.建立船舶运动系统横荡、艏摇和横摇的三自由度运动、舵和减摇鳍的驱动控制、海浪干扰等数学模型,构建仿真环境.利用线性二次型最优控制理论设计舵和减摇鳍的联合控制器,并采用多目标优化手段确定舵速和鳍速参数,仿真表明,在不同的海况,以及船体不同航行状态下,都取得了显著的减摇效率,效果较减摇鳍单独减摇效果更佳,且能够保证良好的航向控制精度,说明舵鳍联合减摇有效地协调舵和鳍控制水翼的控制力和控制力矩.     

船舶舵减摇控制研究综述

船舶海上航行,受波浪影响会发生横摇、纵摇、艏摇、横荡、纵荡和垂荡等状况。这些船体运动会使船员生活的舒适度降低、船舶操纵困难、海上作业危险甚者发生船舶倾覆。减摇舵是一种新型的主动式减摇装置,所占的空间小,成本较低。因此,船舶舵减摇控制成为运动控制中一个重要的领域。本研究重点阐述了国内外关于船舶舵减摇控制的发展过程和研究现状,对各类技术的优劣进行分析讨论,并对接下来的研究方向做了展望。     

基于CFD的船舶斜浪三自由度运动仿真研究

针对船舶在斜浪中的多自由度耦合运动问题, 建立了三维粘性流耐波性数值波浪水池, 采用边界条件造波法生成高精度的斜向规则波, 通过同时求解RANS方程和刚体运动学方程, 结合网格整体移动方法和滑移网格方法, 实现了船舶斜浪航行的垂荡、纵摇及横摇三自由度耦合运动数值模拟。给出了DTMB5512船模斜浪中的垂荡、纵摇及横摇的频率响应函数, 与线性切片理论计算结果进行比较, 吻合良好。该方法可为船舶斜浪航行的耐波性预报提供一种有效的途径。     

航母运动对舰载飞机弹射起飞特性影响研究

舰载飞机的弹射起飞安全受运动影响显著,本文针对舰载飞机的弹射起飞过程,进行了六自由度的仿真建模,通过弹射起飞仿真计算,分析了航母纵摇、垂荡运动对其弹射起飞特性的影响。结果表明由于舰首距离航母纵摇中心距离较大,航母纵摇运动相位变化对舰载飞机的弹射起飞影响较大,而选择在舰首抬升阶段离舰,有利于起飞安全。     

利用MATLAB进行船舶舵鳍联合减摇智能控制系统设计与仿真

该文针对象船舶舵鳍联合减摇系统这样的复杂模型的仿真以及智能控制系统设计中需训练控制器、仿真中的变参数控制等特点,介绍了一种用SIMULINK对变参数顺系统进行仿真的方法,给出了利用MATLAB环境设计如神经网络控制器等智能控制器的方案,最后给出了所述设计方案和仿真方法的具有实例：利用遗传算法训练模糊神经网络控制器对船舶舵鳍联合减摇系统进行控制。     

潜艇近水面低航速减摇的自适应神经元变结构控制

潜艇在近水面低航速航行时,为了有效克服波浪干扰力矩的作用,依据仿生翼减摇原理和变结构控制理论,在潜艇非线性模型基础上提出横摇控制器和纵摇控制器的设计方法.该方法以横摇角和纵摇角各自的偏差及其导数建立变结构控制切换面,选取相应的指数趋近律,计算了横摇和纵摇的变结构控制律.针对抖振现象,利用自适应神经元对趋近率进行在线修正.仿真结果表明,改进后的变结构控制提高了潜艇近水面低航速航行时的减摇控制性能.     

SWATH船纵向运动模糊自适应控制

针对SWATH船载重不同和航行过程中由升沉运动引起的水线变化对船舶运动参数的影响提出了一种模糊自适应控制策略。为保证S W A T H船纵向运动稳定性,根据李雅普诺夫稳定性定理,对纵摇控制器提出了最优控制器设计,通过选用合适的权函数,保证S W A T H船的航行性能。仿真结果表明,模糊化自适应控制系统对于不同频率下的正弦波响应和不同海况下的耐波性响应都能具有良好的控制性能,解决了船舶在不同载重、不同水线下参数变化对控制器影响的问题。     

高海情下全浸式水翼艇姿态控制的研究

本文根据随机最优跟踪控制理论,对高海情下全浸式水翼艇翼航姿态的控制问题进行了研究。讨论了跟踪信号为海浪这样的随机输入信号的跟踪控制问题,研究了水翼艇的爬浪控制,提出了具有积极意义的准爬浪控制规律。最后,对PCH水翼艇在五级海情下的翼航姿态进行了数学仿真,结果表明:本文的研究结果是正确的,采用本文的准爬浪控制规律,全浸式水翼艇在高海情下的翼航姿态控制可获得令人满意的效果。     

潜艇垂直面滑模控制仿真研究

针对潜艇垂直面运动强非线性、耦合性和参数不确定的特点,分别基于垂直面非线性和线性模型,考虑舵的动态响应,用艏舵控制深度,艉舵控制纵倾角,采用改进型趋近律设计滑模控制器并进行了仿真研究。仿真结果表明,两类滑模控制器均具有良好的控制性能和较强的鲁棒性,且无明显抖振。     

Robust nonlinear motion control of a helicopter

We consider the problem of controlling the vertical motion of a nonlinear model of a helicopter, while stabilizing the lateral and horizontal position and maintaining a constant attitude. The reference to be tracked is given by a sum of a constant and a fixed number of sinusoidal signals, and it is assumed not to be available to the controller. This represents a possible situation in which the controller is required to synchronize the vehicle motion with that of an oscillating platform, such as the deck of a ship in high seas. We design a nonlinear controller which combines recent results on nonlinear adaptive output regulations and robust stabilization of systems in feedforward form by means of saturated controls. Simulation results show the effectiveness of the method and its ability to cope with uncertainties on the plant and actuator model.     

运动控制中的鲁棒自适应死区补偿

在高精度PD控制器中,死区可能会产生极限环,而且,死区参数往往未知.本文针对有非对称死区的直流伺服系统,设计了一种鲁棒自适应预补偿控制器,这种控制器不仅对死区的不确定性具有鲁棒性,而且对惯性及粘性摩擦等参数的不确定性,及外部扰动都有较强的鲁棒性.采用Lyapunov理论证明了这种控制器能够保证跟踪误差一致最终有界.并且调整调节控制器的参数可以改变跟踪误差.仿真结果表明了这种方法的有效性.     

考虑剩余浮力影响的欠驱动水下机器人深度控制

为了实现水下机器人带有剩余浮力影响的欠驱动深度控制, 将垂直面控制划分为定速航行控制和深度控制. 采用成熟的S 面速度控制器保证速度控制稳定, 着重解决深度控制问题. 引入虚拟控制量, 使剩余浮力影响下的深度偏差映射为目标纵倾角, 通过设计俯仰控制器实现对目标纵倾角的跟踪. 稳定性分析表明, 所研究的欠驱动深度控制是稳定的, 且对于参数估计的偏差不敏感. 仿真实验结果表明, 所提出的方法能够抵抗剩余浮力的影响, 深度控制准确, 并具有良好的鲁棒性.

     

Iterative method based on CFD data for the assessment of seakeeping control effects,considering amplitude and rate saturation

An iterative procedure for the frequency domain evaluation of control effects in nonlinear loops is introduced. The article focuses on ship seakeeping control, to attenuate ship motions. There is no model of the ship, only CFD tabulated data. The proposed procedure could be used for design or empirical tuning of a controller. The actuators have angle and rate limits. In the case of a ship, the actuators are submerged moving wings: flaps, fins and T‐foil. The control evaluation procedure uses a describing function approach. The paper considers amplitude and rate saturation in series. The results are validated with experiments using a scaled ship in a towing tank facility. Copyright © 2010 John Wiley & Sons, Ltd.     

Feasibility Study on Stability of Gait Patterns with Changeable Body Stiffness Using Pneumatic Actuators in a Quadruped Robot

An oscillator-type gait controller for a quadruped robot with antagonistic pairs of pneumatic actuators is proposed. By using the controller, a feasibility study on the stability of gait patterns with changeable body stiffness is reported. The periodic motions of the legs are generated and controlled by an oscillator network with state resetting. This type of controller has robustness in its gaits against variation in walking conditions or changes of environment. However, it sometimes loses robustness under conditions of actuation delay, decrease of actuator accuracy, etc. We investigated whether an oscillator-type controller with phase resetting is also effective under such conditions. The stability of locomotion also strongly depends on the mechanical properties of the body mechanism, especially the joint stiffness. In this report, the muscle tone of the robot on the pitching motion at the trunk is changeable by using the changeable elasticity of the pneumatic actuators. The stability of quadruped locomotion in walk and trot patterns with changeable body stiffness was evaluated with numerical simulations and hardware experiments.     

Optimization of the motion of a flapping airfoil using sensitivity functions

The motion of a flapping NACA0012 airfoil is optimized by means of numerical simulations for a Reynolds number equal to 1100. The control parameters are the amplitudes and the phase angles of the flapping motion in addition to the mean angle of attack. Sensitivity functions are used to compute the gradient of a cost functional related to the propulsive efficiency of the airfoil and a quasi-Newton method is adopted to drive the control parameters towards their optimal values. The ability of a flapping airfoil to produce sufficient lift and thrust forces for appropriate kinematics is demonstrated. Furthermore, a linear dependence between heaving and pitching amplitudes is found for optimal configurations leading to a constant value of the maximum effective angle of attack roughly equal to 11°. This value corresponds to the angle yielding the maximal lift-to-drag ratio for this Reynolds number when the NACA0012 airfoil does not flap. Previous results such as the high propulsive efficiency when a 90° phase angle exists between heaving and pitching, or the reversal of the von Karman street for a Strouhal number close to 0.2, are confirmed here with a new methodology. Finally, optimal kinematics for various types of missions are given and the corresponding flows are described.     

Control of Shape Memory Alloy Actuators with a Neuro-fuzzy Feedforward Model Element

This paper describes development of a motion controller for Shape Memory Alloy (SMA) actuators using a dynamic model generated by a neuro-fuzzy inference system. Using SMA actuators, it would be possible to design miniature mechanisms for a variety of applications including miniature robots for micro manufacturing. Today SMA is used for valves, latches, and locks, which are automatically activated by heat. However it has not been used as a motion control device due to difficulty in the treatment of its highly nonlinear strain-stress hysteresis characteristic. In this paper, a dynamic model of a SMA actuator is developed using ANFIS, a neuro-fuzzy inference system provided in MATLAB environment. Using neuro-fuzzy logic, the system identification of the dynamic system is performed by observing the change of state variables (displacement and velocity) responding to a known input (input voltage to the current amplifier for the SMA actuator). Then, using the dynamic model, the estimated input voltage required to follow a desired trajectory is calculated in an open-loop manner. The actual input voltage supplied to the current amplifier is the sum of this open-loop input voltage and an input voltage calculated from an ordinary PD control scheme. This neuro-fuzzy logic-based control scheme is a very generalized scheme that can be used for a variety of SMA actuators. Experimental results are provided to demonstrate the potential for this type of controller to control the motion of the SMA actuator.     

Fuzzy control of the vertical acceleration of fast ferries

This paper shows the design and implementation of a fuzzy control system used to reduce the vertical motion of a TF-120 fast ferry. The system increases the comfort of the passengers and crew by reducing the main cause of seasickness. The aim of this controller—which is based on a fuzzy model of the ship behaviour—is to decrease the pitch acceleration by controlling the position of some actuators and varying their working angles. Experiments have been carried out on a ship scaled-down replica. The motion sickness incidence has been evaluated and results have proved to be highly satisfactory.     

Ship motions using single-phase level set with dynamic overset grids

The problem of surface ships free to pitch and heave in regular head waves is analyzed numerically with an unsteady Reynolds averaged Navier Stokes (URANS) approach. The unsteady single-phase level set method previously developed by the authors was extended to include six degrees of freedom (6DOF) motions. The method uses rigid overset grids that move with relative motion during the computation, and the interpolation coefficients between the grids are recomputed dynamically every time the grids move. The motions in each time step are integrated implicitly using a predictor-corrector approach. An earth-based reference system is used for the solution of the fluid flow, while a ship-based reference system is used to compute the rigid-body equations of motion. Predicted results for sinkage and trim and resistance at two Froude numbers (medium, Fr = 0.28 and large, Fr = 0.41) were compared against experimental data, showing good agreement. Pitch and heave motions were computed for near-resonant cases at Fr = 0.28 and 0.41, with regular linear head waves with slope ak = 0.025 and wavelength λ = 1.5L, with L the ship length. The predicted motions compare favorably with existing experimental data. A solution for a large amplitude head wave case (ak = 0.075) was also obtained, in which the transom wave breaks and extreme motions are observed. The medium Froude number case was subject to a verification and validation analysis. A problem with two ships pitching and heaving one behind the other is demonstrated.     

压电驱动器的免疫PID控制技术研究

针对压电驱动器的伺服控制问题,提出了一种基于生物免疫反馈调节规律的PID控制算法;对于具有非线性滞环特性的压电驱动器,采用线性PID控制器难以达到理想的控制效果;如果借助于生物免疫反馈调节规律来自动整定PID控制器的参数,就有可能使压电驱动器的阶跃响应无振荡现象发生并具有较好的鲁棒性;试验结果表明,与传统的压电驱动器PID控制系统比较,应用免疫PID控制算法可以使伺服系统获得更好的动态特性。