光电跟踪器船摇自稳定建模及仿真

为弥补只针对横摇和纵摇建模的不足,提出了包含艏摇的完整的三自由度视轴稳定模型。采用位置坐标变换把大地坐标系的位置引导数据转换到甲板坐标系,引导光电跟踪器在甲板坐标系捕获目标,以解决船摇位置扰动。通过速度坐标变换建立视轴速度干扰模型,应用前馈控制技术补偿船摇速度扰动,从而提高原Ⅰ型位置伺服系统海况跟踪测量的精度和平稳性。应用所建模型进行仿真,结果表明,光电跟踪器的视轴指向与船摇扰动的隔离度超过40dB,可以保证光电跟踪器在五级海况下实现自稳定功能。     

三体船在迎浪不规则波中的运动和载荷试验研究

通过三体船自航模型试验,对三体船迎浪不规则波下的运动和载荷状态进行对比和分析。统计不规则波下运动特征值,分析船体纵摇、升沉以及主船体加速度随浪级和航速的变化规律;在船体模型上合理的布置传感器,对不规则波下船体剖面载荷纵向分布进行研究,并分析浪级和航速变化对于载荷的影响;统计船艏上浪的次数和船体表面压力的极值,研究压力极值随船长、型深以及片体内外侧的分布规律,给出不规则波下浪级和航速对波浪砰击载荷的影响。经一系列的模型试验,为三体船的设计以及后续的结构强度评估提供支持。     

考虑艏摇的半潜式平台涡激运动试验研究

为研究半潜式平台的涡激运动特征,进行了水槽模型试验研究。测试了流向角为0°、15°、30°及45°时,在不同来流速度下半潜式平台的横荡、纵荡及艏摇运动响应;并以艏摇运动为重点,从响应幅值、运动频率等角度出发,探讨其涡激运动的关键特征。结果表明:在不同来流方向情况下,半潜式平台均未发生明显的频率锁定现象。当流向角为0°和15°时,平台三自由度响应随约化速度的增加近似呈线性增大的趋势;当流向角为30°和45°时,在约化速度4～10附近平台响应出现了明显的共振现象,并在此现象结束后响应大幅减小,之后,随着约化速度的增加再次大幅增大。除个别工况外,艏摇与横荡均高度耦合,其响应频率主峰值基本保持1∶1关系;艏摇固有周期对平台三自由度运动频率及幅值影响均不明显。流向角为45°时,平台的艏摇运动最为剧烈,在各个约化速度下响应幅值均数倍于其他流向角。另外,在0°流向角时观察到了"驰振"现象;15°流向角的多个约化速度下观察到了"自激"现象。     

船舶横甩吸引域的数值研究

建立在某型船的船体水动力和螺旋浆推力和自动舵作用下考虑波浪激励力和二阶定常漂移力时的非线性艏摇运动微分方程模型，以船速，船波偏角和自动舵参数为变参数，运用数值积分和胞映射分析结合的方法，研究了随浪中船舶的横甩吸引域。     

船载炮射击时的角度修正

分析了船在航行中的几种摇荡对火炮射击精度的影响 ,主要介绍了用于消除船体纵摇角和横摇角影响的数学平台的建立方法 ,以及射击角的修正。     

横摇和纵摇非线性耦合下船舶运动的全局动力学

针对横摇和纵摇非线性耦合下船舶的混沌运动,首次应用能量相位法研究了船舶动力系统在1∶2内共振,第2阶主共振情形下系统的全局分叉及多脉冲混沌动力学行为,揭示了船舶运动存在模态作用、能量转移和多脉冲混沌运动的机理,并给出了船舶系统发生多脉冲混沌运动的参数区间。数值模拟验证了横摇和纵摇非线性耦合下船舶运动系统存在多脉冲混沌运动。     

深水半潜式平台Mathieu不稳定问题研究

半潜式平台的垂荡运动相对较大, 当平台的纵摇固有有周期和垂荡固有周期处于一定的倍数关系时, 平台的纵摇/横摇运动可能落入Mathieu不稳定区。该文对半潜式平台Mathieu 方程进行了推导, 获得了各参数的计算公式;根据Mathieu不稳定图谱或数值计算方法, 可判断纵摇/横摇运动的稳定性。选取了一个生存状态下的半潜式平台为算例, 分析了平台发生Mathieu 不稳定问题的条件, 并通过调整关键参数抑制不稳定问题的发生, 从而获得了避免Mathieu不稳定问题的工程措施, 为今后半潜式平台设计提供参考。     

海上浮式集装箱起重机的小车位置跟踪和吊重消摆控制研究

浮式集装箱起重机(OCC)是新型的海上吊运系统,能够对锚泊在深海的大型集装箱运输船进行装卸作业,来解决港口拥堵和大型船舶因港口水浅无法靠岸过驳等问题;但是由于受海上风浪干扰影响,所吊运的载荷会产生复杂的非线性动力学响应,严重影响作业效率,甚至引发安全事故。针对此问题,推导船体横摇和升沉运动下OCC系统负载吊运过程的摆振动力学模型,并设计吊运轨迹跟踪的非线性控制器,同时实现海浪干扰和起重小车运动耦合下OCC系统的位置跟踪和负载的消摆控制;采用Lyapunov方法严格证明了控制器的稳定性;最后,比较仿真和实验结果验证所提方法的有效性。通过此方法能抑制海浪激励对集装箱吊运轨迹的影响,确保OCC系统安全高效运行。     

风浪不共线对浮式风机基础动态特性影响研究

旨在研究风载方向和波浪方向不共线对浮式风机基础动态特性影响。以5 MW浮式风机为研究对象,采用等效载荷法模拟空气动力载荷,建立浮式风机系统耦合动力学模型,研究风浪呈0°、30°、60°和90°夹角工况时,浮式风机基础动态特性变化。结果表明:风浪不共线对浮式平台纵荡和横荡运动平衡位置影响很大,对垂荡运动响应影响很小。随着风浪夹角增大,横摇和艏摇运动振荡范围增大,纵摇运动振荡范围减小。风浪不共线使得系泊系统张力响应变化明显,张力变化趋势与平台运动及系泊布置有关。     

微小型平面机器人

微小型平面机器人可在显微镜下等狭小的空间内实现精密定位.压电元件与柔性铰链机构结合能实现精密定位,并使定位系统小型化,它可用于设计微小型平面机器人.为使平面机器人的结构更加紧凑,提出了单驱动三自由度运动机构.柔性铰链机构采用对称设计,以实现导向功能.应用蠕动式的运动原理可合成机构上的三自由度运动,并实现大行程运动.装配后的微小型平面机器人尺寸仅为20mm×20mm×12mm.研制了图像处理位移检测系统以检测微小型平面机器人的三自由度位移.     

声学多普勒测速仪标校技术研究

为了提高声学多普勒测速仪输出速度的准确度,安装过程中测速基阵与载体之间的偏差角不可忽略,安装偏差角包括航向偏角,横摇角及纵摇角三类。介绍了一种三维空间上的多普勒标定技术,通过高精度的GPS导航仪以及多普勒测速仪对海底测速,利用速度比值差校准航偏角。通过纵向剖面的几何关系,从航偏角出发进而获得纵摇角和横摇角的大小,完成了三维方向上多普勒测速仪的校准,使多普勒测速仪坐标系与载体坐标系能够进行精确转换,从而提高了声学多普勒测速仪输出速度的准确度。外场试验较好地证明了该方法的有效性,分析结论看出在二维平面上,造成误差的原因主要在于安装偏角的航向偏角,而在三维空间上,尤其垂向速度,误差主要由纵摇角和横摇角产生。该方法可以快速地对三维安装偏角进行校准,运算量小,并且在对海水测速后续研究中可以形成一套体系。     

脱靶量累加前馈补偿电视跟踪器的跟踪误差

电视跟踪系统通常采用速度、位置双闭环控制。前馈控制可以提高跟踪精度但无法实现;速度、加速度滞后补偿,跟踪精度提高有限。动态高型方法是在负反馈控制系统中增加若干积分环节以提高跟踪精度。随着目标速度的提高和光电跟踪设备自动化程度的提高,对电视跟踪器伺服系统的跟踪精度提出了越来越高的要求。本文创新性引出一种斜坡累加补偿方法,通过理论证明和仿真,指出它与动态高型技术高度相似,从而从新的角度解释了动态高型提高跟踪精度的机理,并为动态高型方法在工程上实现电视跟踪伺服系统的跟踪精度的提高提供了坚实的理论依据。     

Vision-based flight control in the hawkmoth Hyles lineata

Vision is a key sensory modality for flying insects, playing an important role in guidance, navigation and control. Here, we use a virtual-reality flight simulator to measure the optomotor responses of the hawkmoth Hyles lineata, and use a published linear-time invariant model of the flight dynamics to interpret the function of the measured responses in flight stabilization and control. We recorded the forces and moments produced during oscillation of the visual field in roll, pitch and yaw, varying the temporal frequency, amplitude or spatial frequency of the stimulus. The moths’ responses were strongly dependent upon contrast frequency, as expected if the optomotor system uses correlation-type motion detectors to sense self-motion. The flight dynamics model predicts that roll angle feedback is needed to stabilize the lateral dynamics, and that a combination of pitch angle and pitch rate feedback is most effective in stabilizing the longitudinal dynamics. The moths’ responses to roll and pitch stimuli coincided qualitatively with these functional predictions. The moths produced coupled roll and yaw moments in response to yaw stimuli, which could help to reduce the energetic cost of correcting heading. Our results emphasize the close relationship between physics and physiology in the stabilization of insect flight.     

Angular sensitivities of volume gratings for substrate-mode optical interconnects

The angular sensitivities of slanted volume gratings (VGs) illuminated by three-dimensional (3-D) converging-diverging spherical Gaussian beams for substrate-mode optical interconnects in microelectronics are analyzed by application of 3-D finite-beam rigorous coupled-wave analysis. Angular misalignments about the z, y, and x axes that correspond to yaw, pitch, and roll misalignments resulting from manufacturing tolerances of chips are investigated. Two cases of linear polarization of the central beam of the Gaussian are considered: E perpendicular K and H perpendicular K, where K is the grating vector. From worst-case manufacturing tolerances, the ranges of yaw, pitch, and roll misalignment angles are alpha = +/-1.17 degrees, beta= +/-3.04 degrees, and gamma = +/-3.04 degrees, respectively. Based on these ranges of misalignment angles, the decreases of diffraction efficiencies for slanted VGs that are due to both the yaw and the roll misalignments are relatively small. However, the efficiency of substrate-mode optical interconnects achieved by slanted VGs could be reduced by 61.04% for E perpendicular K polarization and by 58.63% for H perpendicular K polarization because of the pitch misalignment. Thus the performance of a VG optical interconnect is most sensitive to pitch misalignment.     

Determination of model airplane attitudes using dynamic holographic interferometry

We demonstrate how real-time holographic interferometry yielding two-dimensional fringes can be recorded and used to determine changes in three-dimensional attitude of a model airplane through digital image processing. A simple bench-top experiment with a model airplane as a test object is conducted to demonstrate interference fringes superposed on the image due to changes in attitudes (pitch, yaw, and roll) as well as distortion. A novel second-generation thermoplastic camera suitable for dynamic multiple reversible registration of thin-phase holograms using thermoplastic and semiconductor film on glass substrate is used for in situ recording and readout during real-time holographic interferometry. Thin-phase holograms also offer the advantage of exact image reconstruction from forward-phase conjugation.     

卫星姿态抖动对LASIS成像质量的影响

由于卫星姿态抖动(俯仰、侧滚和偏航)使得LASIS(大孔径静态干涉成像光谱仪)干涉图产 生了非正常的像素偏移量,相邻干涉图之间的非正常偏移量在0.1像素量级或更小,但累积偏移量最多可达上百个像素,必须对干涉图进行校正处理。研究结论为设计正确有效的LASIS图像校正算法提供了参考依据,同时也为卫星平台设计提供了参考。     

Mathematical modeling of sway, roll and yaw motions: order-wise analysis to determine coupled characteristics and numerical simulation for restoring moment’s sensitivity analysis

This paper investigates sway, roll and yaw motions of a floating body with the aim to determine coupled motion characteristics based on the order-wise analysis of hydrodynamic coefficients. To compute the hydrodynamic coefficients and wave force exerted on the floating body, we employ speed-dependent strip theory. The governing equations are solved analytically for linear restoring moment. For nonlinear restoring moment which is expressed as an odd-order polynomial of fifth degree in roll angle, we apply the Runge–Kutta–Gill method to solve the coupled equations. To investigate the effect of initial disturbances on sway, roll, yaw and speed of the body, numerical experiments have been carried out for a Panamax Container ship under the action of a sinusoidal wave of periodicity 11.2 s with varying wave height and speed. For the linear restoring moment, we first derive associated motion equations for various cases based on the relative magnitude of the hydrodynamic coefficients. The order-wise analysis leads to the classification of coupled characteristics exhibiting the nature of coupling. For the nonlinear restoring moment, we notice that the initial disturbance plays an important role in the ship’s stability. The effects of forward speed and variation in wave heights are illustrated through typical numerical experiments.     

Kevlar织物软壁包容环抗冲击数值仿真分析研究

针对机匣包容性问题,提出Kevlar平纹织物本构模型的拟合方法,分别采用单层壳、多层壳、层合壳三种有限元建模方式对Kevlar织物软壁包容环弹道冲击过程进行模拟,发展了机匣包容性仿真分析模型。结果表明,多层壳模型和层合壳模型的计算结果更准确,并且可以通过调节摩擦因子使仿真结果与试验结果更接近。在此基础上研究了撞击点位置和弹体入射姿态对弹体剩余速度的影响。结果表明:在较小偏移距离内,撞击点的位置对剩余速度的影响可以忽略不计;滚转角和俯仰角对剩余速度影响较小,而对于偏航角,当角度大于30°时,剩余速度会随着角度的增大明显呈下降趋势,且弹体出射姿态也会发生明显变化。     

An experimental stationary quadrotor with variable DOF

Unmanned air vehicles (UAV) and especially quadrotors have drawn great attention in recent years because of their maneuverability, ease of design and control. Most of the works concentrate mostly on control; yet, design and communication are also some sub-topics. In this research, a stationary, four rotor air vehicle with limited/controlled degree of freedom is constructed so that various control algorithms and their changing effects with varying vehicle dynamics can be studied on the ground for safety purposes. Ascending/descending, pitch/yaw/roll motions can be limited/controlled by setting the vehicle’s degree of freedom mechanically, resulting better net observability of the control algorithms on the vehicle’s dynamic performance. Design, in terms of mechanics, mechatronics and software is presented and the usability of the system is shown. Parallel self tuning fuzzy PD + PD control is applied to the system for preliminary studies and results are discussed. Inspite of the sensor noise, satisfactory pitch/roll/yaw control is achieved.