Parameter identification of inertially stabilized platforms using current command design

Accurate parameter identification is essential when designing controllers for inertially stabilized platforms (ISPs). But traditional identification methods suffer from observation measurement noise and operating restrictions of ISPs. To address this issue, a novel identification method based on current command design and multilevel coordinate search (MCS) algorithm without any higher order measurement differentiations was proposed. The designed current commands were adopted to obtain parameter decoupled models with the platform operating under allowable conditions. MCS algorithm was employed to estimate the parameters based on parameter decoupled models. A comparison experiment between the proposed method and non-linear least square method was carried out and most of the relative errors of identified parameters obtained by the proposed method were below 10%. Simulation and experiment based on identified parameters were conducted. A velocity control structure was also developed with disturbance observer (DOB) for application in disturbance compensation control system of an ISP. Experimental results show that the control scheme based on the identified parameters with DOB has the best disturbance rejection performance. It reduces the peak to peak value (PPV) of velocity error integral to 0.8 mrad which is much smaller than the value (10 mrad) obtained by the single velocity controller without DOB. Compared with the control scheme based on sweep model with DOB compensation, the proposed control scheme improves the PPV of velocity error integral by 1.625 times.

Reduced-order design of Robust H_∞ Controller for an Inertial Stabilized Aerial Platform

The uncertainty disturbance is one of the main disturbances that seriously influences the stabilization precision of an aerial inertially stabilized platform(ISP)system.In this paper,to improve the stabilization precision of the ISP under disturbance uncertainty,a robust H∞controller is designed in this paper.Then,the reduction order is carried out for high-order controllers generated by the robust H∞loop shaping control method.The application of the minimum implementation and balanced truncation algorithm in controller reduction is discussed.First,the principle of reduced order of minimum implementation and balanced truncation are analyzed.Then,the method is used to reduce the order of the high-order robust H∞loop shaping controller.Finally,the method is analyzed and verified by the simulations and experiments.The results show that by the reduced-order method of minimum implementation and balanced truncation,the stabilization precision of the robust H∞loop shaping controller is increased by about 10%.

应用于运动平台光电跟瞄系统的惯性参考单元研究综述

目标的变化和任务的拓展对光电跟瞄系统提出了快速机动的要求,从地基平台到车载、船载、机载、星载等运动平台是光电跟瞄系统的重要发展趋势。基于惯性参考单元(Inertial Reference Unit,IRU)的视轴稳定方式是克服运动平台高频扰动,实现光电跟瞄系统微弧度甚至亚微弧度级跟瞄的主要技术手段。针对运动平台光电跟瞄系统精确指向对载体基座扰动抑制的需求,分析和对比了IRU的各种技术方案,特别介绍了利用低噪声、宽频带惯性传感器敏感角扰动,并通过反馈控制实现视轴惯性稳定的系统方案。从此类IRU系统的工作原理出发,阐述了系统的两种工作模式及功能特点,建立了系统数学模型。然后,介绍了IRU的国内外研究进展及发展方向,指出惯性传感、支承结构和控制系统是决定IRU稳定能力的关键因素,梳理了三项关键技术的研究动态。最后,总结了IRU的空间应用情况,并结合目前的应用需求对其未来应用领域进行了探讨。

Improved Angular Velocity Estimation Using MEMS Sensors with Applications in Miniature Inertially Stabilized Platforms

The performance of any inertially stabilized platform （ISP） is strongly related to the bandwidth and accuracy of the angular velocity signals. This paper discusses the development of an optimal state estimator for sensing inertial velocity using low-cost micro-electro-mechanical systems （MEMS） sensors. A low-bandwidth gyroscope is used alone with two low-performance accelerometers to obtain the estimation. The gyroscope has its own limited dynamics and mainly contributes to the low-frequency components of the estimation. The accelerometers have inherent biases and mainly contribute to the high-frequency components of the estimation. Extensive experimental results show that the state estimator can achieve high-performance signals over a wide range of velocities without drifts in both the t- and s-domains. Furthermore, with applications in miniature inertially stabilized platforms, the control characteristic presents a significantly improvement over the existing methods. The method can be also applied to robotics, attitude estimation, and friction compensation.

Application in prestiction friction compensation for angular velocity loop of inertially stabilized platforms

Abstract To overcome the influence of the nonlinear friction on the gimbaled servo-system of an inertial stabilized platforms （ISPs） with DC motor direct-drive, the methods of modeling and compensation of the nonlinear friction are proposed. Firstly, the inapplicability of LuGre model when trying to interpret the backward angular displacement in the prestiction regime is observed experimentally and the reason is deduced theoretically. Then, based on the dynamic model of direct-drive ISPs, a modified LuGre model is proposed to describe the characteristic of the friction in the prestiction regime. Furthermore, the state switch condition of the three friction regimes including presliding, gross sliding and prestiction is presented. Finally, a composite compensation controller including a nonlinear friction observer and a feedforward compensator based on the novel LuGre model is designed to restrain the nonlinear friction and to improve the control precision. Experimental results indicate that compared with those of the conventional proportion-integrationdifferentiation （PID） control method and the PID plus LuGre model-based friction compensation method, the dwell-time has decreased from 0.2 s to almost 0 s, the position error decreased to 86.7% and the peak-to-peak value of position error decreased to 80% after the novel compensation controller is added. It concludes that the composite compensation controller can greatly improve the control precision of the dynamic sealed ISPs.

High-precision gyro-stabilized control of a gear-driven platform with a floating gear tension device

This study presents an improved compound control algorithm that substantially enhances the antidisturbance performance of a gear-drive gyro-stabilized platform with a floating gear tension device.The tension device can provide a self-adjustable preload to eliminate the gap in the meshing process.However,the weaker gear support stiffness and more complex meshing friction are also induced by the tension device,which deteriorates the control accuracy and the ability to keep the aim point of the optical sensors isolated from the platform motion.The modeling and compensation of the induced complex nonlinearities are technically challenging,especially when base motion exists.The aim of this research is to cope with the unmeasured disturbances as well as the uncertainties caused by the base lateral motion.First,the structural properties of the gear transmission and the friction-generating mechanism are analyzed,which classify the disturbances into two categories:Time-invariant and time-varying parts.Then,a proportional-integral controller is designed to eliminate the steady-state error caused by the time-invariant disturbance.A proportional multiple-integral-based state augmented Kalman filter is proposed to estimate and compensate for the time-varying disturbance that can be approximated as a polynomial function.The effectiveness of the proposed compound algorithm is demonstrated by comparative experiments on a gear-drive pointing system with a floating gear tension device,which shows a maximum 76%improvement in stabilization precision.

Generation of Accelerated Stability Experiment Profile of Inertial Platform Based on Finite Element

The residual stress generated in the manufacturing process of inertial platform causes the drift of inertial platform parameters in long-term storage condition.However,the existing temperature cycling experiment could not meet the increased repeatability technical requirements of inertial platform parameters.In order to solve this problem,in this paper,firstly the Unigraphics（UG） software and the interface compatibility of ANSYS software are used to establish the inertial platform finite element model.Secondly,the residual stress is loaded into finite element model by ANSYS function editor in the form of surface loads to analyze the efficiency.And then,the generation based on ANSYS simulation inertial platform to accelerate the stability of experiment profile is achieved by the application of the analysis method of orthogonal experimental design and ANSYS thermal-structural coupling.The optimum accelerated stability experiment profile is determined finally,which realizes the rapid,effective release of inertial platform residual stress.The research methodology and conclusion of this paper have great theoretical and practical significance to the production technology of inertial platform.

惯性平台稳定回路的自抗扰控制

讨论了惯性平台稳定回路自抗扰控制的设计问题。平台稳定系统要求响应速度快,抗干扰能力强,稳态精度高等优良特性。但这些性能指标之间是有矛盾的。采用经典的控制方法综合设计校正时,往往取折中的方案,很难兼顾所有的性能。仿真结果表明,用自抗扰控制方法设计控制规律,其稳定回路跟踪能力和抗干扰能力得到了较大的改善,提高了惯性稳定平台的可靠性和精度。

车载惯性平台稳定位置解算算法

根据船摇位置自稳定的思想,提出了基于坐标转换的惯性平台位置稳定解算算法。该算法通过坐标变换实时解算出惯性平台相对载体的位置值并将其作为位置稳定控制的位置环输入,从而有效隔离载体对平台位置的干扰,实现平台的稳定。实验结果表明:平台的外框架稳定精度为0.1 mrad,内框架稳定精度为0.3 mrad,满足了指标1 mrad的要求。该算法有效地解决了车载惯性平台的稳定性问题,提高了整个稳定系统的性价比。

惯性稳定平台自适应前馈控制

结合反馈控制提出了一种自适应前馈控制方法来提高惯性稳定平台稳定控制的指令跟踪性能。应用子空间辨识算法,由输入输出数据辨识稳定平台动态模型的状态空间描述;采用频域回路成型方法设计反馈回路控制器,用于抑制外部扰动。应用递推最小二乘(RLS)自适应滤波器构建反馈控制回路逆模型,构造指令信号的全通特性,提高指令跟踪能力。针对不同的指令信号进行跟踪实验,验证了自适应前馈控制方法的有效性。实验结果表明:提出的自适应前馈方法对阶跃指令响应快,超调量可由反馈控制的30%降低至4.5%,对30 Hz正弦信号的响应幅值无衰减,相位滞后由反馈控制的90°降低至54°。得到的结果显著提高了系统的暂态性能,控制性能优于单独的反馈控制回路。

航空重力与重力梯度测量对惯性稳定平台的需求分析

从航空重力与重力梯度测量原理出发,先后导出航空重力与重力梯度测量的观测方程和测量误差方程,然后依据地球重力场特征和功率谱的相关理论,结合航空重力与重力梯度测量中的GPS定位、惯性稳定平台的指向和稳定性、加速度计和梯度仪的误差模型,分析了航空重力与重力梯度测量对稳定平台的需求,在此基础上以航空重力测量中国外常用的双水獭(Twin-Otter)固定翼飞机的实际飞行参数为例,通过数值计算给出了航空重力测量分辨率达到1 mGal时,对惯性稳定平台的角度指向精度、稳定性和随机漂移的要求分别为0.0005°、0.006°/h/Hz和0.0003°/h;航空重力梯度测量分辨率1 E时,对稳定平台对应的指标要求分别降低为0.5°、0.01°/hr/Hz和0.01°/hr。

航空遥感用三轴惯性稳定平台不平衡力矩前馈补偿方法

航空遥感用三轴惯性稳定平台用于稳定成像载荷,获取高分辨的遥感数据。但是由于稳定平台承载大且存在质量偏心,在载机加速度的作用下平台产生幅值较大的不平衡力矩,导致平台的稳定精度下降和相机成像质量退化。为了有效抑制不平衡力矩产生的影响,提高平台的稳定精度,提出了一种基于不平衡力矩观测器的惯性稳定平台不平衡力矩前馈补偿方法。首先设计一种不平衡力矩观测器,实时估计出平台的不平衡力矩;然后通过前馈补偿的方法抑制不平衡力矩的作用,从而达到提高平台的稳定精度的目的。仿真结果显示,平台的稳定精度得到大幅度提高,基于不平衡力矩观测器的惯性稳定平台不平衡力矩前馈补偿方法有显著补偿效果。

高精度伺服稳定跟踪平台数字控制器研制

以陀螺伺服稳定跟踪平台为背景 ,介绍了以DSP为处理核心的平台数字伺服运动控制器的研制 .指出惯性速率环和电机速度环的本质不同 ;提出增加电机转矩 (电流 )环用于提高电机输出转矩线性度的方法 ,从而达到提高惯性速率稳定环的控制效果 ;介绍了以CCD图像或增量式码盘测角组成系统位置闭环 ,以光纤速率陀螺作为惯性速率反馈传感器组成系统速率闭环 ,附带电流反馈组成电机转矩 (电流 )环和速度、加速度前馈装置的前馈反馈复合控制系统 .组成伺服跟踪平台系统联调后测试结果表明 ,系统具有良好的动、静态性能指标和很好的控制效果 .

航空遥感用三轴惯性稳定平台动力学建模与仿真

航空遥感用三轴惯性稳定平台由于其机械结构特点,飞机姿态的扰动会耦合到安装在平台的相机上,影响相机的成像质量。为了对复杂耦合关系进行分析,从分析力学的角度出发,采用拉格朗日第二类方程,考虑轴承摩擦,建立了航空遥感用三轴惯性稳定平台动力学模型。在此基础上,对基座振动对相机相对于惯性系的扰动进行了数值仿真。仿真结果表明:基座振动同框架间的耦合力矩相比,基座振动对相机相对于惯性系的扰动占主导作用。当轴承间为动摩擦时,基座振动频率越高,对相机相对惯性系的扰动越小,并从理论上证明了此结论的正确性。研究结果为深入研究航空遥感用三轴惯性稳定平台的振动主动控制提供了理论依据。

航空遥感惯性稳定平台内框架拓扑优化设计

为了提高航空遥感惯性稳定平台动态性能,减小振动环境对光电载荷成像质量的影响,基于变密度法的拓扑优化理论,采用NX/TOSCA软件,以结构加权柔度最小化为目标函数,以节点的变形量和体积比约束为设计响应限制,对航空遥感惯性稳定平台内框架进行了拓扑优化设计。依据优化结果,对内框架具体结构形式进行了详细设计。采用NX/Nastran软件对优化后的内框架结构进行了仿真分析。静态分析结果显示,内框架最大变形量为3.5μm,满足指向精度误差分配的要求;模态分析结果显示,内框架结构一阶频率由260 Hz提高到334 Hz,其刚度满足伺服带宽的要求。拓扑优化设计使得内框架的质量由3.6 kg减小到1.8 kg,有利于平台轻量化的实现。最后,通过对指向精度和稳定精度的检测数据以及外场的飞行试验,验证了仿真分析的正确性,表明对内框架拓扑优化设计是成功的。

车载动平台位置干扰的传递解算

在研究平台稳定原理的基础上,结合工程结构配置特点,提出了平台稳定位置干扰值的传递解算算法。该算法首先在稳定平台上安装一个中间惯导,然后建立中间惯导与稳定平台的一致性关系;接着根据实测数据建立车载惯导和中间惯导的关系转换矩阵,通过转换矩阵和车载惯导即可求出中间惯导的值。最后由此构建一个"虚拟惯导"代替中间惯导,该"虚拟惯导"的值就是稳定平台的位置干扰值。实验结果表明:该算法具有较高的解算精度,误差最大值为0.056 1°。该算法在不调整车载惯导状态的基础上,利用现成的车载惯导实现了平台的稳定性,既提高了工作效率,又提高了性价比。目前,该算法已成功应用于车载动平台的稳定中。

航空遥感用惯性稳定平台动力学耦合分析

航空遥感用惯性稳定平台承载重量较大的成像载荷,系统相对复杂,耦合明显。根据航空遥感用三轴惯性稳定平台的结构特点,应用矢量叠加原理推导了平台环架运动学方程,建立了欧拉动力学模型,并分析了基座运动情况下各环架间的动力学耦合误差。仿真结果表明,基座对平台环架耦合较大,环架交叉耦合相对较小,且在外界干扰下基座及环架间的耦合加强。研究结果为稳定平台控制系统设计提供了依据。

基于AVR单片机的机载惯性稳定云台设计

针对多旋翼无人机在航拍时,画面会随着巡航时俯仰、横滚等飞行动作而变得不稳定的问题,设计了一种基于AVR单片机和MEMS陀螺仪的机载惯性稳定云台。该云台利用经卡尔曼滤波(Kalman Filtering)的陀螺仪输出数据对飞机在三个轴向上的角速度变化进行监测和判断,驱动步进电机对云台姿态进行实时反向补偿,实现这一系统使摄影机拍摄的画面能够时刻保持稳定。实验结果表明,系统稳定、可靠、性能良好。

光纤陀螺惯性平台数字稳定回路设计

为了延长某型导弹训练惯性平台的使用寿命,提出了组建光纤陀螺惯性平台稳定系统的设计方案。该新型惯性平台系统在原有平台机械结构的基础上,采用干涉式光纤陀螺代替原有的气浮单自由度陀螺仪作为惯性平台的敏感元件。重新建立了平台系统稳定回路的数学模型,并运用经典博德图方法设计了系统的校正网络,给出了基于DSP的数字校正网络的实现方法。Simulink仿真结果表明,该数字稳定回路具有较好的动态性能和稳态性能,能够满足系统的设计要求。经初步实验验证,该光纤陀螺惯性平台系统已实现功能要求。目前该方案已应用于某型导弹的平台改造研制中。