Gyro Motion Boundedness under Uncertain Vehicle Spin and Acceleration

An analysis is presented of the motion of a single axis rate gyroscope mounted in a space vehicle, which is simultaneously accelerating and spinning about the output and spin axis, respectively, of the gyro. The time-varying acceleration and deceleration ?x(t) and the spin rate ?z(t) of the vehicle are unknown but bounded functions of time t. It is shown that the motion of the gyro remains bounded if the bound ?*2 on the uncertainty in ?z(t) does not exceed some threshold ?*2 and that this threshold depends on the various parameters of the gyro. Furthermore, by a proper selection of the gyro parameters, its motion can be forced to remain in a small neighborhood (called region of ultimate boundedness) of the origin in ?-? plane after a certain finite interval of time for any bounded uncertain ?x(t) and ?z(t). Analytical relations are derived for the selection of gyro parameters to keep the error caused in the measurement of the input rate due to ?x and ?z within any given limit.     

Stability of Gyro with Harmonic Nonlinearity in Spinning Vehicle

A stability analysis of a single-axis rate gyroscope mounted in a space vehicle which is spinning with uncertain angular velocity ?z about the spin axis of the gyro is presented. The complete nonlinear equation of motion, which includes the fundamental and second harmonic nonlinear terms, arising due to ?z, is considered. For time-varying ?z(t), using the circle criterion, it is shown that the gimbal motion is globally asymptotically stable if the Nyquist plot of the linear transfer function of the gyro lies in the interior of a certain disk. For the case of uncertain constant ?z, using the Lyapunov approach, conditions for global asymptotic stability (GAS) and asymptotic stability are derived. Stable regions in parameter space of the gyro and state space are obtained. Analytical relations for the selection of gyro parameters are derived.     

Asymptotically Stable Motions of a Gyro in a Spinning Vehicle

An analysis of the motion of a single-axis rate gyroscope mounted in a space vehicle which is spinning with uncertain constant angular velocity xz about the spin axis of the gyro is presented. The nonlinearity in the equation of motion of the gimbal is retained. Using the Lyapunov approach, regions are obtained in the k-xz plane where k is the torsional spring constant, for asymptotic stability and for global asymptotic stability, and an estimate of the region of stability in state space is presented. Analytical relations for the selection of the gyro parameters are derived.     

Stability of Gyro in a Vehicle Spinning with Uncertain Angular Velocity

The analysis of a single-axis rate gyroscope mounted in a vehicle which is spinning with uncertain angular velocity about the spin axis of the gyro is presented. The nonlinearity in the equation of motion of the gimbal is retained. Using circle criterion, it is shown that the gimbal motion is globally asymptotically stable if Nyquist plot of the linear transfer function of the gyro lies in the interior of a certain disk. A simple analytical relation for the selection of gyro parameters for stability is derived.     

Error estimation of INS ground alignment through observabilityanalysis

A systematic analysis of the observability of an inertial navigation system (INS) in ground alignment with Bar-Itzhack and Berman's error model is presented. It is shown that the unobservable states are separately contained in two decoupled subspaces. The constraints on the selection of unobservable states are discussed. An estimation algorithm which is derived fully from the horizontal velocity outputs for computing the misalignment angles is provided. It reveals that the azimuth error can be entirely estimated from the estimates of leveling error and leveling error rate, without using gyro output signals explicitly     

某型方位旋转平台惯导系统转速模型分析与验证

某型平台惯导系统采用方位旋转调制技术,通过对台体匀速转动的控制调制陀螺的漂移。台体的转速不是固定值,是随惯导系统所在地区而改变的,且台体转速异常必伴随方位陀螺故障。为了正确判断台体转速的理论是否正常,文章推导了转速的理论计算公式,不同地区惯导系统的实测数据表明实测值与理论计算值一致,验证了转速计算公式的正确性,为监控方位陀螺状态提供了技术途径。     

陀螺动力学系统计算机仿真

推导出了适于计算机仿真的陀螺完整运动方程式并给出了仿真曲线,可看出在外力矩作用下陀螺仪从起动到稳定这一段时间内的转动角速度和转角的变化规律。通过降低陀螺转速并减小外力矩,使无锁紧机构的陀螺仪消除起动时的剧烈抖动而达到平稳起动的目的。     

Inertial System Platform Rotation

Differential error equations are derived for the navigation errors of a local level undamped pure inertial platform that continuously rotates in azimuth. From these, the time response equations for the vector position error produced by a constant level gyro drift error, as a function of platform rotation rate, are computed and evaluated. It is shown that platform rotation attenuates the system position error due to level gyro bias and that this attenuation is a nonlinear function of rotation rate.     

Transient Performance of Gyro in Spinning Spacecraft

Transient performance of a single-axis rate gyroscope mounted in a spacecraft which is spinning about the spin axis of the gyro is presented. Analytical expressions for various time-domain and frequency-domain specifications as functions of the spin rate of the vehicle are obtained. Numerical results are presented which are useful in selecting the gyro parameters if it is to be used for the measurements of the angular velocity in spinning space vehicles.     

Tracking Accuracies with Position and Rate Measurements

Tracking accuracies for the radial component of motion are computed for a track-while-scan radar system which obtains position and rate data during the dwell time on a target These results will be of interest to persons developing trackers for pulse Doppler surveillance radars. The normalized accuracies, computed for a two state Kalman tracking filter with white noise maneuver capability, are shown to depend upon two parameters, r = 4?0/?aT2 and s = ?dT/?0. The symbols ?0 and ?d are the position and rate measurement accuracies, respectively, ?a is the standard deviation of the white noise maneuver process and T is the antenna scan time. The scalar tracking filter equations are derived and numerical results are presented. Lower steady state tracking errors plus the earlier attainment of steady state accuracies are the direct consequence of incorporating the rate measurements into the tracking filter.     

一类含动态扰动的随机非线性系统的FNN控制

针对一类非仿射且带有动态扰动的纯反馈随机非线性不确定系统,在随机Lyapunov稳定性理论框架下,利用自适应Backstepping方法并结合模糊神经网络( FNN),设计出保证闭环系统所有信号概率意义下有界的自适应控制器。在控制器设计中,对系统动态扰动进行参数化处理,并对系统不确定性进行FNN逼近,以四层神经网络为基础构架,引入模糊逻辑对网络进行推理,其输出权值可自适应调整,设计方法有效地减少了可调参数的数量,数值仿真结果也表明设计方法的有效性。     

一类非线性系统的神经网络自适应控制

针对一类单输入单输出不确定非仿射型非线性系统,基于多层神经网络提出了一种直接自适应控制方法。该设计方法首先应用多层神经网络自适应模拟逼近逆解中的未知部分,然后应用逆设计和自适应反演设计出虚拟控制量,最后应用反馈线性化设计方法和神经网络设计了直接自适应控制律。并利用Lyapunov稳定性定理推导了神经网络的参数调节律,保证了闭环系统的所有信号均最终一致有界。     

Linearization errorʼs measure and its influence on the accuracy of MEKF based attitude determination method

Multiplicative Extended Kalman Filter (MEKF) is one of the most widely used satellite attitude estimation methods. However, the linearization error?s influence is an inherent limitation of this method. In this paper, we aim to analyze this linearization error in the typical satellite attitude determination system with star sensors and gyros. The formulation of linearization error is first derived and the curvature metric is then employed to measure the linearization error. Additionally, we show the reason why linearization error has influence on the performance of MEKF. Based on these analyses, we point out that star sensors? sampling frequency, initial estimated error and accuracy of gyro?s measurement model are the factors that could enlarge the system model?s linearization error. They all affect the linearization error and attitude determination accuracy by decreasing the predicted accuracy. More concretely, the influence of star sensor?s sampling frequency is large, while initial estimated error and gyro?s measurement error within a certain range have little influence on MEKF. Finally, combined with plenty of experiments, validity of the above analyses is verified.     

带有不确定因素的最优拦截制导律

本文从微分对策观点出发,利用极小极大原理讨论了带有不确定因素的最优拦截制导律。在选择特定的过渡时间时,最优拦截制导律具有综合形式。仍由二部分组成:一部分是变系数比例导航,另一部分是与导弹加速度有关的修正项。     

Dynamics of a Solenoidal-Torqued Gyro-Stabilized Seeker Assembly for Guidance and Tracking

Several low-cost gyro-stabilized, bang-bang seeker assemblies for missile guidance and tracking applications have used similar physical structures. A magnetic dipole is an integral part of the gyro rotor assembly. The nominal spin axis of the gyro is colinear with the axis of a cylinder about which is wound a helix of wire. By properly modulating the current that is passed through that helix, the precession torque acting upon the gyroscope is controlled. One rather generalized model of such a seeker assembly is modeled, the equations of motion are derived, and the dominant error sources are identified and parametrically evaluated. Because this is such a commonly encountered structure, yet no such analysis has been published, to the author's knowledge, it is hoped that this is a useful contribution to the literature.     

陀螺稳定平台视轴稳定系统自适应模糊PID控制

 在运动载体上的光电跟踪系统中，需要采用建立在陀螺稳定平台上的视轴稳定控制。分析了平台结构和惯性稳定隔离原理。针对系统机械谐振、力矩耦合及电气参数波动等非线性不确定因素的影响，设计了复合自适应模糊PID控制器。引入自适应调整因子进行控制规则和参数的在线修正，采用复合控制克服模糊控制固有的盲区，实现无差调节。在光电跟踪转台上的实验结果显示该方法能够有效地隔离载体扰动，减小扰动造成的误差，保证视轴对目标的准确瞄准，具有快速的动态响应和较强的抗干扰性。     

Spectral Analysis of Optimal and Suboptimal Gyro Monitoring Filters

Gyro monitoring filters are used to estimate and correct gyro drift rates of local-level inertial navigation systems. Conventional gyro monitoring filters are usually designed based on a simplified model of gyro drift rate. Furthermore, the effectiveness of these filters-and of many filters of the "Kalman" type-is often measured in terms of the root mean square (rms) criterion in contrast to the spectral content criterion typical of classical Wiener filtering theory. This paper has two objectives: to propose a gyro monitoring filter which is based on a more detailed model of gyro drift rate; and to propose a method of filter performance evaluation which uses as criterion a measure of the spectral content of the error process. The proposed gyro monitoring filter is shown to have improved spectral contents resulting in superior navigation performance for the gyro error models used in the calculations (comparable to commercial-grade aircraft gyros).     

光纤陀螺惯导稳定平台与旋转调制方法

光纤陀螺仪在随机误差方面表现出极佳的性能优势,但受限于其标度因数不理想的现实。针对航海用长航时、高精度光纤陀螺惯导系统的使用需求,设计了基于光纤陀螺数字信号实现载体三维角运动隔离的同时完成惯性测量装置的旋转调制功能,可有效减小光纤陀螺标度因数误差与载体运动角速度的耦合误差,同时充分发挥光纤陀螺随机游走小的精度优势。理论仿真验证了光纤惯导稳定平台加旋转调制方法的优越性和可行性,为光纤陀螺惯导系统在高精度导航领域中的应用提供了技术基础。     

Adaptive Sliding Control of Six-DOF Flight Simulator Motion Platform

本文使用Newton-Euler法推导了六自由度飞行模拟器运动平台完整的线性化形式的动力学方程,并以此为基础,提出了一种在任务空间中的非线性自适应滑模控制方法。这种控制方法将系统中的不确定性分为定常不确定参数和时变不确定参数,利用非线性自适应控制对定常不确定参数进行辨识,同时结合滑模控制对时变不确定参数和外部扰动进行补偿。通过数值仿真分析表明,该控制策略能准确识别运动平台的载荷、惯量、重心等参数,同时又能有效地提高系统的鲁棒性能。     

面向过失速机动的风洞动态试验相似准则探讨

为进行更加准确的风洞试验,讨论了针对过失速机动的风洞动态试验的相似准则问题。从六自由度运动方程推导出了进行动态风洞试验需要满足的运动相似参数;从N—S方程中得到满足流动相似的相似参数。针对不同类型的风洞动态试验,提出了具体对应的相似参数作为主要的模拟量。得到的结论可以为风洞动态试验参数选择提供参考。