航空重力梯度仪研究现状

本文给出了重力梯度的具体涵义,重点介绍了目前正在使用和处于研发阶段的4种航空重力梯度仪的原理及存在的问题.并总结指出在航空重力梯度仪的研发过程中的一些关键技术及后续研究中需要注意的一些问题.     

基于矩形棱柱结构的单轴重力梯度仪设计

为了实现在共振的模式下进行重力梯度测量,提出一种基于矩形棱柱结构的单轴重力梯度仪.该重力梯度仪基于扭矩式测量原理,质量块采用矩形棱柱形,可减小随机噪声,提高空间分辨率.此设计结构实现了在被测方向上重力梯度值的准确测量,减少了其他方向重力场对测量的影响.给出了矩形棱柱结构重力梯度仪的系统数学模型,设计了一种单轴重力梯度仪的结构并进行了结构仿真.通过测试结果表明:该重力梯度仪实现了系统在共振的模式下进行重力梯度测量,具有结构设计简单,灵敏度高等特点.     

一种高精度的加速度计寻北仪系统研究

随着导航技术的不断发展,寻北仪在航空航天事业、武器精准制导、汽车导航、石油勘探等领域变得更加重要.本文首先介绍了寻北仪系统应用发展情况,通过对加速度计寻北仪系统的工作原理的研究,并对其结果进行误差分析与计算,选择使用铅垂轴系转台的寻北方案,使得寻北时间大幅度减少,精度更高.     

对日定向卫星所受重力梯度力矩对轮控系统的影响分析

本文以空间太阳望远镜为参考对象，对其在轨运行时所受到的重力梯度力矩进行了详细分析和定量计算，给出全年不同时期的重力梯度力矩和单轨道周期内重力梯度力矩冲量的数值分布曲线模型。最后针对所得到的模型分析其对姿态指向精度和稳定度造成的影响，并给出其对姿态控制执行机构所需动量轮和卸载所需磁力矩器的容量要求。     

基于加速度计的数字式倾角仪的设计

所设计的数字式倾角仪是一种基于MEMS热电偶加速度计的智能测量仪,可用于测量0°~360°倾角,同时,针对环境温度变化时对加速度计的影响,通过软件进行了补偿,测试表明:该倾角仪的测量精度达±0. 1°,并具有良好的工作稳定性和较高的性价比。     

基于加速度计的数字倾角仪误差建模与分析

基于加速度计的数字倾角仪在实际应用过程中,其精度在很大程度上受加速度计测量误差的影响。为了提高倾角仪的测量精度,需要对传感器本身引入的误差进行建模和分析,根据加速度计倾角仪的测量原理,得出其误差源为加速度计传感器测量误差。在对传感器的测量误差建立数学模型的基础上,通过仿真分析及实验进行验证。该误差模型不仅给出了倾角仪测量的俯仰角及滚转角的最小误差范围,还可以为传感器选型及后续的误差分析和补偿提供理论参考,具有一定的实用价值。     

MEMS数字倾角仪的标定补偿方法研究

在介绍MEMS数字倾角仪组成结构的基础上,根据数字倾角仪内部MEMS加速度计的输出特性,对MEMS加速度计的敏感单元建立数学标定模型,提出并推导了一种适用于MEMS数字倾角仪的标定方法;该方法可以得到双轴MEMS数字倾角仪中加速度计的零位电压、标度因数矩阵、安装误差系数等敏感项参数;通过重力场静态翻转实验对实验室研制的数字倾角仪进行标定;最后使用MATLAB拟合计算得到所求标定参数,并对测试结果进行了误差分析和补偿对比;实验结果表明,该方法能使MEMS数字倾角仪的测量精度提高到±0.05°,可以满足高精度的角度测量需求。     

一种数字倾角仪自标定系统的研制

介绍一种利用高精度的步进电机对数字倾角仪进行标定的自标定系统。该标定系统利用固定于步进电机转轴上的数字倾角仪随步进电机旋转，一方面通过步进电机旋转的步数得到具体的旋转角度，另一方面通过单片机记录微加速度计的信号输出而达到标定数字倾角仪的目的。经过实践证明，该自标定系统具有标定速度快，效率高和精度好等优点。     

一种适用于单轴MEMS倾角仪的快速标定方法及实现

针对单轴倾角仪核心元件MEMS加速度计零点电压和标度因数在反复上电后会发生改变,且在外场环境下,不能通过转台对其进行修正的问题,本文根据MEMS加速度计的安装误差、输出模型推导了单轴倾角仪的标定模型,提出了一种适用于单轴倾角仪的快速标定方法,并利用实验室研制的MEMS单轴倾角仪及LABVIEW软件编写的上位机对该方法进行了试验验证.实验表明,该快速标定方法可快速、准确地修正MEMS加速度计零点和标度因数的漂移,从而保证倾角仪的测量精度,具有良好的工程实践意义.     

高温超导磁梯度仪测控系统的设计与实现

针对高温超导磁梯度仪手动调节控制器操作繁琐,工作效率低的问题,设计并实现了一种高温超导磁梯度仪的自动测量控制系统;通过实时采集和分析超导量子干涉器输出的调制三角波信号,自动调整其工作点参数,实现高温超导磁梯度仪的自动调试功能。通过微处理器控制前置放大器内的锁相环路的闭合,实现高温超导磁梯度仪信号输出;设置大容量Flash存储器实现仪器工作点参数和测量数据的存储;采用光电隔离技术,降低了测量控制系统对仪器前端工作电路的噪声干扰;实验结果表明,设计的测量控制系统在野外可稳定可靠工作,效率高,方便了高温超导磁梯度仪在地球物理磁法勘探中的应用。     

Applications of tensor theory to object recognition and orientation determination

A method is developed by which images resulting from orthogonal projection of rigid planar-patch objects arbitrarily oriented in three-dimensional (3-D) space may be used to form systems of linear equations which are solved for the affine transform relating the images. The technique is applicable to complete images and to unlabeled feature sets derived from images, and with small modification may be used to transform images of unknown objects such that they represent images of those objects from a known orientation, for use in object identification. No knowledge of point correspondence between images is required. Theoretical development of the method and experimental results are presented. The method is shown to be computationally efficient, requiring O(N) multiplications and additions where, depending on the computation algorithm, N may equal the number of object or edge picture elements.     

The influence of heated or cooled seats on the acceptable ambient temperature range

In 11 climate chamber experiments at air temperatures ranging from 15 to 45°C, a total of 24 subjects, dressed in appropriate clothing for entering a vehicle at these temperatures, were each exposed to four different seat temperatures, ranging from cool to warm. In one simulated summer series, subjects were preconditioned to be too hot, while in other series they were preconditioned to be thermally neutral. They reported their thermal sensations, overall thermal acceptability and comfort on visual analogue scales at regular intervals. Instantaneous heat flow to the seat was measured continuously. At each ambient room temperature, the percentage dissatisfied was found to be a second-order polynomial function of local heat flow. Zero heat flow was preferred at an air temperature of 22°C and the heat flow that minimized the percentage dissatisfied was found to be a single linear function of air temperature in all conditions. The analysis indicates that providing optimal seat temperature would extend the conventional 80% acceptable range of air temperature for drivers and passengers in vehicle cabins by 9.3°C downwards and by 6.4°C upwards.     

The influence of heated or cooled seats on the acceptable ambient temperature range

In 11 climate chamber experiments at air temperatures ranging from 15 to 45 degrees C, a total of 24 subjects, dressed in appropriate clothing for entering a vehicle at these temperatures, were each exposed to four different seat temperatures, ranging from cool to warm. In one simulated summer series, subjects were preconditioned to be too hot, while in other series they were preconditioned to be thermally neutral. They reported their thermal sensations, overall thermal acceptability and comfort on visual analogue scales at regular intervals. Instantaneous heat flow to the seat was measured continuously. At each ambient room temperature, the percentage dissatisfied was found to be a second-order polynomial function of local heat flow. Zero heat flow was preferred at an air temperature of 22 degrees C and the heat flow that minimized the percentage dissatisfied was found to be a single linear function of air temperature in all conditions. The analysis indicates that providing optimal seat temperature would extend the conventional 80% acceptable range of air temperature for drivers and passengers in vehicle cabins by 9.3 degrees C downwards and by 6.4 degrees C upwards.     

Identifying the task variables that influence perceived object assembly complexity

There is a general lack of understanding as to what issues affect assembly task performance when using diagrammatic instructions because few of the task variables contributing to assembly complexity have been identified. Using a task analysis of a range of self-assembly products, seven task variables hypothesized to predict assembly complexity were identified and studied in the instruction comprehension phase of assembly. Experiment 1 took nine real world assembly instructions and described each in terms of the seven task variables. Seventy-two participants gave a subjective rating of assembly difficulty for each assembly, showing a clear relationship between the task variables and perceived assembly difficulty. As real world assemblies provide little control a second experiment used an orthogonal design to systematically vary the values of each of the assembly task variables in 16 abstract assemblies. Forty-two participants compared the 16 assembly instructions to a final assembly. There was a clear relationship between the task variables and the time taken to view the instructions. Further, it was found that it is possible to predict the complexity of assembly tasks based upon the levels of the task variables identified. The task variables identified are a significant step towards identifying the factors that influence assembly complexity, together with providing progress towards a tool for predicting assembly complexity.     

From an image sequence to a recognized polyhedral object

The paper describes the combination of several novel algorithms into a system that obtains visual motion from a sequence of images and uses it to recover the three-dimensional (3D) geometry and 3D motion of polyhedral objects relative to the sensor. The system goes on to use the recovered geometry to recognize the object from a database, a stage which also resolves the depth/speed scaling ambiguity, resulting in absolute depth and motion recovery. The performance of the system is demonstrated on imagery from a well carpentered constructive solid geometry (CSG) model and on real imagery from a simple wooden model.     

Grasping an augmented object to analyse manipulative force control

Augmented reality allows changes to be made to the visual perception of object size even while the tangible components remain completely unaltered. It was, therefore, utilized in a study whose results are being reported here to provide the proper environment required to thoroughly observe the exact effect that visual change to object size had on programming fingertip forces when objects were lifted with a precision grip. Twenty-one participants performed repeated lifts of an identical grip apparatus to a height of 20 mm, maintained each lift for 8 seconds, and then replaced the grip apparatus on the table. While all other factors of the grip apparatus remained unchanged, visual appearance was altered graphically in a 3-D augmented environment. The grip apparatus measured grip and load forces independently. Grip and load forces demonstrated significant rates of increase as well as peak forces as the size of graphical images increased; an aspect that occurred in spite of the fact that extraneous haptic information remained constant throughout the trials. By indicating a human tendency to rely - even unconsciously - on visual input to program the forces in the initial lifting phase, this finding provides further confirmation of previous research findings obtained in the physical environment; including the possibility of extraneous haptic effects (Gordon et al. 1991a, Mon-Williams and Murray 2000, Kawai et al. 2000). The present results also suggest that existing knowledge concerning human manipulation tasks in the physical world may be applied to an augmented environment where the physical objects are enhanced by computer generated visual components.     

Identifying the task variables that influence perceived object assembly complexity

There is a general lack of understanding as to what issues affect assembly task performance when using diagrammatic instructions because few of the task variables contributing to assembly complexity have been identified. Using a task analysis of a range of self-assembly products, seven task variables hypothesized to predict assembly complexity were identified and studied in the instruction comprehension phase of assembly. Experiment 1 took nine real world assembly instructions and described each in terms of the seven task variables. Seventy-two participants gave a subjective rating of assembly difficulty for each assembly, showing a clear relationship between the task variables and perceived assembly difficulty. As real world assemblies provide little control a second experiment used an orthogonal design to systematically vary the values of each of the assembly task variables in 16 abstract assemblies. Forty-two participants compared the 16 assembly instructions to a final assembly. There was a clear relationship between the task variables and the time taken to view the instructions. Further, it was found that it is possible to predict the complexity of assembly tasks based upon the levels of the task variables identified. The task variables identified are a significant step towards identifying the factors that influence assembly complexity, together with providing progress towards a tool for predicting assembly complexity.