伺服加速度计在抗振动干扰攻角测量中的应用与设计

提出采用双伺服加速度同轴和垂直系统的两种方法,能够解决风洞模型攻角传感测量中的抗振动干扰问题,通过对两种系统的分析与比较,给出了较为合理的设计方案。     

Accelerometer spiking under cryogenic conditions

Spurious transient outputs of a piezoelectric accelerometer have been observed when the accelerometer is attached to a surface undergoing rapid cool-down to a cryogenic temperature. Such conditions occur in cryogenic propellant rockets on assemblies such as feedlines and turbopumps. Under exposure to liquid oxygen, surface temperatures can drop to near −300°F in a matter of minutes. The occurrence of spurious output depends on the internal construction of the accelerometer and on the effectiveness of thermal isolation provided by the mounting for a susceptible accelerometer. Specifically, an Endevco Model 2271AM20 charge-mode, compression-type accelerometer (CTA) has been observed to produce intermittent spurious output spikes during flight of a launch vehicle, during ground test firing of a rocket engine and in laboratory experiments. It is suggested that this spiking, also known as the pyroelectric effect, can be attributed to charge buildup due to thermal effects in the piezo-electric crystal stack. In the case studies, sporadic jumping of this charge across a gap at the outer edge of the plating on the crystal stack face is believed to cause momentary saturation of the charge amplifier. A replacement Endevco Model 7722 shear-type accelerometer (STA) using a different type of crystal arrangement as well as a different crystal material proved to eliminate these spurious charge jumps in a series of laboratory tests. This paper presents the results of experiments conducted to evaluate both the CTA and the STA. The effectiveness of different mounting configurations, used to provide thermal isolation sufficient to eliminate the spikes from the CTA, was evaluated. It is also suggested that observations of a particular type of nonzero mean signal in the time domain and broad, elevated, low-frequency content in the frequency spectrum can be useful in detecting the presence of pyroelectric-induced transients, even if the spikes are visually buried within high-amplitude vibration data.     

Wind identification along a flight trajectory,part 2: 2D-kinematic approach

This paper deals with the identification of the wind profile along a flight trajectory by means of a two-dimensional kinematic approach. In this approach, the wind velocity components are computed as the difference between the inertial velocity components and the airspeed components. The airspeed profile is obtained from flight measurements. The inertial velocity profile is obtained by integration of the measured inertial acceleration. The accelerometer biases and the impact values of the inertial velocity components are determined by matching the computed flight trajectory with the measured flight trajectory, available from the digital flight data recorder and air traffic control radar. This leads to a least-square problem, which is solved analytically for both the continuous formulation and the discrete formulation. Key to the precision of the identification process is the proper selection of the integration time. Because the measured data are noise-corrupted, unstable identification occurs if the integration time is too short. On the other hand, if the integration time is too long, the hypothesis of two-dimensional motion (flight trajectory nearly contained in a vertical plane) breaks down. Application of the 2D-kinematic approach to the case of Flight Delta 191 shows that stable identification takes place for integration times in the range τ = 120 to 180 sec before impact. The results of the 2D-kinematic approach are close to those of the 3D-kinematic approach (Ref. 1), particularly in terms of the inertial velocity components at impact (within 1 fps) and the maximum wind velocity differences (within 2 fps). The 2D-kinematic approach is applicable to the analysis of wind-shear accidents in take-off or landing, especially for the case of older-generation, shorter-range aircraft which do not carry the extensive instrumentation of newer-generation, longer-range aircraft.     

两位置法快速测定近钻头惯性测量模块的温漂模型

近钻头惯性测量模块(Near-bit Inertial Measurement,NIM)用于石油钻井中实时测量导向外套的姿态角,是导向钻进闭环控制中的重要组成部分。它采用三轴加速度计组合测量重力加速度实现姿态角测量。为了提高加速度计在工作温度范围内的测量精度,需对其进行温漂模型标定。针对三轴加速度计组合的传统12位置翻滚温度模型测定方法存在耗时长、操作效率低的局限性,提出一种新的加速度计三轴组合温度模型标定方法——两位置法,并通过实验验证了温度补偿的效果。在10℃~150℃的温度范围内,补偿后加速度的测量精度达5×10~(-4)g,完全满足NIM测量姿态角的要求。     

高g值加速度计的设计与冲击特性分析

针对特殊场合的测试需求,设计了四端全固支的高过载梁岛结构加速度计;利用Hopkinson杆冲击校准装置对该加速度计的动态特性进行了测试。测试结果表明,传感器的灵敏度为1.2V/g,线性度5%左右;结构受到2105g冲击后完好且输出信号正常,能有效满足高冲击、强烈振动场合的特殊测试要求,可以应用于侵彻系统。 更多还原     

一种新的舰船航姿测量方法

提出了一种采用加速度计、磁强计和GPS芯片为主要传感器构成的舰船航姿测量模型,开发了由运动生成模块和姿态解算模块两部分组成的仿真程序,对舰船航姿测量模型进行了仿真实验分析验证。实验结果表明,该模型可以实时解算舰船航姿。在GPS速度测量误差为0.05 m/s,加速度计分辨率为10-5g,磁强计测量精度为0.5μT的情况下,舰船航向测量精度优于0.68°,姿态测量精度优于0.35°。     

基于比力差分测量的加速度计温度误差补偿方法

针对温度变化引起的惯导系统中石英挠性加速度计测量误差,提出了一种基于比力差分测量的加速度计温度误差补偿方法。首先,建立包含温变速率影响的温度误差模型,利用标定惯导系统加速度计参数时的温度作为标定参数温度基准。其次,借助不带转台的温箱对惯导系统进行全温测试,通过同一方位前后时间段加速度计输出的差分消除未知的比力真值,只保留由于温度改变引起的标度因数与零偏变化,通过多位置观测对这两项参数进行最小二乘拟合估计,获得对应温度系数。该方法不需要温箱具备高精度定位基准,能够实现全温范围与快速变温工作条件下温度误差的精确建模。试验结果表明,应用该补偿方法可使加速度计测量精度在全温范围内保持在10μg量级。     

一种新型的单陀螺多加速度计捷联惯导系统

在无陀螺捷联方案的基础上，提出了单陀螺多加速度计的捷联方案。中详细推导了角速度和加速度的解算方法，并以智能炮弹为背景，进行了仿真，得到了误差曲线，并指出了应注意的问题。     

大量程石英加速度计二元调宽再平衡回路的设计与应用

二元调宽再平衡回路具有施矩功率恒定，转换精度高，易于同计算机通讯等一系列优点，因而在惯性元件伺服回路中得到广泛应用。中介绍了二元调宽再平衡回路在大量程石英加速度计线路上的应用，通过理论设计和试验，选择合理电参数，并取得了满意的结果。     

一种弹性盘光纤加速度传感器的探讨

本文介绍了一种采用Ｍａｃｈ－Ｚｅｎｄｅｒ干涉仪结构的中心固支弹性盘光纤加速度传感器。该传感器利用弹性盘的变形引起光纤长度的变化，进而引起位相的变化，通过干涉仪感测出。文中分析了两种结构，并加以实现与对比。