加速度差分有限状态机计步算法

在用户行为无法预知的实际计步应用中,如何保持计步算法的准确性和稳定性是一个极具挑战的问题。传统的计步算法利用阈值设定和峰值检测,并不能解决计步算法的普适性和稳定性。针对上述问题,提出了基于加速度差分作为特征的有限状态机(acceleration differential based on finite state machine,AD-FSM)计步算法。该算法将原始加速度取平方和,并通过卡尔曼滤波去除噪声干扰,最后使用加速度差分有限状态机实现计步检测。实验结果表明,该算法在正常和干扰情况下能够提供精确的计步结果,误差分别为1.12%、4.00%,验证了该计步算法在降低状态机复杂度的同时具有较强的稳定性和鲁棒性,更能适应复杂的应用场景。

基于速度差分的车窗纹波防夹算法研究

汽车行业快速发展对汽车安全性要求越来越高,为解决车窗夹伤造成的伤害以及降低车窗防夹成本,采用纹波防夹技术实现车窗防夹,根据车窗系统结构及纹波防夹工作原理搭建车窗防夹算法模型,提出一种基于速度差分的车窗纹波防夹判定方法,通过设计防夹算法软件、标定车窗防夹电压影响因子和扭矩影响因子参数来搭建实验室台防夹架测试工装,实施不同电压、不同温度、不同防夹测试位置的正交试验。试验结果表明:在电机电压处于9~16V区间,环境温度从-35℃到85℃,测得车窗防夹力为50~80N之间,误防夹率为0%,满足法规防夹力小于100N的要求。因此基于速度差分的车窗纹波防夹算法可以很好自适应不同电压、温度工况下的车窗防夹判定。

基于差分信息的加速度快速校正算法

在利用惯性传感器求解姿态时,常通过陀螺仪融合加速度计以卡尔曼滤波体系计算姿态,此方法依赖历史状态,尤其在加速度存在干扰的情况下会产生误差积累,导致融合算法在长时间的误差积累下很难获取准确的姿态信息。此外,在资源受限的空间环境中,对于加速度的校正成本与速度也有较高的要求。针对以上问题,提出一种无误差积累的加速度快速校正算法。利用融合角速度可以得到较准确的加速度差分信息的特点,使用传感器的少量测量数据列出加速度与其差分关系的方程组,并在重力方程的约束下解算方程组,进而解算加速度。实验表明算法能获得较准确的加速度,且解算速度较卡尔曼滤波体系提高10倍。

一种大厚度的三轴差分电容式硅微加速度计

介绍了一种新型三轴全差分电容式加速度计的设计和制备。设计的加速度计采用了三个共用同一玻璃衬底的大厚度差分电容式微结构 ,分别用于检测三个垂直方向的加速度。同时 ,对所设计的微结构从理论和数值上进行了详细的分析。用有限元分析工具 ANSYS对器件进行了模拟 ,模拟结果显示出器件设计的合理性。最后 。

等效原理检验卫星的超精密加速度测量方法

为在更高精度上检验等效原理,采用基于卫星平台利用空间超静环境检测等效原理的方法,结合美国斯坦福大学正在研制的STEP卫星,将理论上对等效原理失效的检验转化为工程上可实现的物理量测量,分析了利用卫星检验等效原理必须突破的Drag-free卫星和超高精度加速度计的关键技术,研究了针对STEP任务设计的Drag-free控制系统和超高精度加速度计的方案与分析,作为实现在10-18精度上等效原理检验的技术支撑.

重力探测新技术:卫星重力梯度测量

从经典力学的基本理论出发，系统论述了卫星重力梯度测量的基本原理，并讨论了其主要误差源及相应减弱措施。与传统的重力探测技术比较，对这一新技术的特点作出了若干评述。

基于不同空间尺度测站网的BDS-3 GEO卫星轨道机动实时监测

地球静止轨道(GEO)卫星为保持地球同步特性,需要频繁进行轨道机动,及时准确的对卫星轨道机动的状态进行动态监测,有助于对卫星真实轨道进行修复,使其在机动过程中仍能提供基本可用的轨道参数.利用基于历元差分测速原理的卫星轨道监测模型,对北斗三号卫星导航系统(BDS-3)的2颗GEO卫星各12次历史机动进行了分析.结果表明:所选不同空间尺度测站网均可以对C59卫星的机动时间与轨道动态变化进行实时监测,且监测结果基本一致.另外,本文所选的不同空间尺度测站网均可对C60卫星机动时间进行精准探测,但在对其轨道状态进行实时监测时,空间尺度较大的测站网监测结果更优.

基于谱元法考虑层间接触状态的Rayleigh波频散特征正演计算

为了提升Rayleigh波应用于成层土基勘探的精细化水平,本文基于谱元法原理,通过Goodman模型和Matsui层间滑移系数建立了可考虑层间不同接触状态的Rayleigh波理论频散方程。针对典型土基成层结构,运用谱元法和快速矢量传递解析法对比计算了层间完全连续状态下土基的Rayleigh波多阶模态频散曲线,结果显示谱元法计算结果与解析法相应结果之间的平均相对误差在0.3%以下,具有较高的计算精度。在此基础上,通过改变层间接触状态和敏感性分析,揭示了层间接触状态对Rayleigh波基阶频散特征的影响。最后,结合速度-应力有限差分数值计算,验证了谱元法计算层间不同接触状态下R波频散特征的可靠性。

Adaptation of feed rate for 3-axis CNC high-speed machining

To improve the efficiency of CNC machining, assumptive transit circular arc is used to contour two adjacent moves together on the comer to make smooth paths. The radios of transit circular arc can be adjusted with contour accuracy, and the feed rate on the corner can be controlled through limiting the maximum feed rate of transit circular arc segment. A look-ahead algorithm for a series of moves is proposed for speed adjustment in advance, which avoids the occurrence of overload of cutting tool on the comer and reduces the servo track error of parts on the corner or of circular arc move. Equivalent trapezoidal velocity profile is used to analyze the speed of S-curve velocity profile and work out its accurate interpolation, which overcomes the disadvantage of looking up table to calculate feed rate approximately, hence high accuracy and fine surface quality can be obtained while the machining speed is high. The proposed methods can meet the requirements of real-time analysis of high-speed machining. The presented algorithm is effective and has been adopted by CNC system of newly developed high-speed milling machine.

低温超导位移传感中的磁场干扰研究

低温超导位移传感技术是分辨率最高的位移探测技术之一,在重力梯度测量和引力波探测中有重要应用。在基于低温超导位移传感技术的引力测量实验中,各种磁场干扰是提高实验精度的严重制约因素。文章在液氦温度研究了各种磁场对加速度测量的影响及其作用机制;测量了引力源通过磁场与探测器耦合的刚度系数;测量了超导体检验质量剩磁并分析了其特性;测量了超导磁屏蔽层对外界磁场的屏蔽效率;分析了磁场引起残余差分加速度扰动的机制;为实验改进提出了合理建议。

One-dimensional consolidation of double-layered soil with non-Darcian flow described by exponent and threshold gradient

Based on non-Darcian flow law described by exponent and threshold gradient within a double-layered soil, the classic theory of one-dimensional consolidation of double-layered soil was modified to consider the change of vertical total stress with depth and time together. Because of the complexity of governing equations, the numerical solutions were obtained in detail by finite difference method. Then, the numerical solutions were compared with the analytical solutions in condition that non-Darcian flow law was degenerated to Dary's law, and the comparison results show that numerical solutions are reliable. Finally, consolidation behavior of double-layered soil with different parameters was analyzed, and the results show that the consolidation rate of double-layered soil decreases with increasing the value of exponent and threshold of non-Darcian flow, and the exponent and threshold gradient of the first soil layer greatly influence the consolidation rate of double-layered soil. The larger the ratio of the equivalent water head of external load to the total thickness of double-layered soil, the larger the rate of the consolidation, and the similitude relationship in classical consolidation theory of double-layered soil is not satisfied. The other consolidation behavior of double-layered soil with non-Darcian flow is the same as that with Darcy's law.

Highly Efficient Lattice Boltzmann Model for Compressible Fluids:Two-Dimensional Case

We present a highly efficient lattice Boltzmann model for simulating compressible flows. This model is based on the combination of an appropriate finite difference scheme, a 16-discrete-velocity model [Kataoka and Tsutahara, Phys. Rev. E 69 （2004） 035701（R）] and reasonable dispersion and dissipation terms. The dispersion term effectively reduces the oscillation at the discontinuity and enhances numerical precision. The dissipation term makes the new model more easily meet with the yon Neumann stability condition. This model works for both high-speed and low-speed flows with arbitrary specific-heat-ratio. With the new model simulation results for the well-known benchmark problems get a high accuracy compared with the analytic or experimental ones. The used benchmark tests include （i） Shock tubes such as the Sod, Lax, Sjogreen, Colella explosion wave, and collision of two strong shocks, （ii） Regular and Mach shock reflections, and （iii） Shock wave reaction on cylindrical bubble problems. With a more realistic equation of state or free-energy functional, the new model has the potential tostudy the complex procedure of shock wave reaction on porous materials.

Stride length-velocity relationship during running with body weight support

Background： Lower body positive pressure （LBPP） treadmills can be used in rehabilitation programs and/or to supplement tun mileage in healthy runners by reducing the effective body weight and impact associated with running. The purpose of this study is to determine if body weight support influences the stride length （SL）-velocity as well as leg impact acceleration relationship during running. Methods： Subjects （n = 10, 21.4 ± 2.0 years, 72.4 ± 10.3 kg, 1.76 ± 0.09 m） completed 16 run conditions consisting of specific body weight support and velocity combinations. Velocities tested were 100%, 110%, 120%, and 130% of the preferred velocity （2.75± 0.36 m/s）. Body weight support conditions consisted of 0, 60%,5, 70%, and 80% body weight support. SL and leg impact accelerations were determined using a light-weight accelerometer mounted on the surface of the anterior-distal aspect of the tibia. A 4 × 4 （velocity x body weight support） repeated measures ANOVA was used for each dependent variable （a = 0.05）. Results： Neither SL nor leg impact acceleration were influenced by the interaction of body weight support and velocity （p 〉 0.05）. SL was least during no body weight support （p 〈 0.05） but not different between 60%, 70%, and 80% support （p 〉 0.05）. Leg impact acceleration was greatest during no body weight support （p 〈 0.05） but not different between 60%, 70%, and 80% support （p 〉 0.05）. SL and leg impact accelerations increased with velocity regardless of support （p 〈 0.05）. Conclusion： The relationships between SL and leg impact accelerations with velocity were not influenced by body weight support.

Influence of feature size of micro-scale channel on ink flow characteristics

Under the micro-scale condition,feature size of the channel is one of the main factors influencing the fluid flow characteristics. In printing process,ink thickness in the extrusion zone formed by two ink rollers may reach micron scale. Compared with macroscopic fluid,the velocity field and the pressure field of fluid may change when the feature size of fluid channel reaches micron scale. In order to control printing quality,it is necessary to research the influence of feature size on ink flow characteristics in micro scale. This paper analyzes it in theory,and then numerical simulation of an ink flow model with different feature sizes is carried out in no slip condition. The influence of the feature size on the ink flow characteristics and the wall shear force are obtained. Besides,the ink flow model with different feature sizes is simulated numerically in slip condition,and the influence of feature size on ink flow characteristics is obtained. Finally,by comparing and analyzing the above results,it can be concluded that both the ink velocity and pressure at the inlet of the extrusion zone are inversely proportional to the feature sizes whether in slip condition or not. And the ink velocity in slip condition is larger than that without slip,the pressure at the inlet of the extrusion zone is less than that in no slip condition. Within the micro-scale range,the ink velocity difference between the two conditions cannot be ignored. Therefore,it is necessary to consider slip when analyzing the influence of feature size of micro-scale channel on ink flow characteristics.

Simulation on Driving System Used for Differential Steering of Electric Scooter

To investigate the feasibility and effectiveness of the designed control system used for driving and steering of an electric scooter, a model of differential steering was developed. The function of electronic differential steering was realized by controlling the speed of right or left wheel and the corresponding speed difference. The control system was simulated with MATLAB/SIMUL1NK and ADAMS. It is found that the motor load torque is proportional to the tire vertical force, so the adhesive capacity is met. The electric scooter can operate stably on the slope road at a speed of more than 1.5 m/s and turn stably at yawing velocities of 10° and 90°per second.

Analysis of unsteady supercavitating flow around a wedge

Supercavitating flow around a slender symmetric wedge moving at variable velocity in static fluid has been studied. Singular integral equation for the flow has been founded through distributing the sources and sinks on the symmetrical axis. The supereavity length at each moment is determined by solving the singular integral equation with finite difference method. The supercavity shape at each moment is obtained by solving the partial differential equation with variable coefficient. For the case that the wedge takes the impulse and uniformly variable motion, numerical results of time history of the supercavity length and shape are presented. The calculated results indicate that the shape and the length of the supercavity vary in a similar way to the case that the wedge takes variable motion, and there is a time lag in unsteady supercavitating flow induced by the variation of wedge velocity.

Failure mechanism of large-diameter shield tunnels and its effects on ground surface settlements

A new technique for the analysis of the three-dimensional collapse failure mechanism and the ground surface settlements for the large-diameter shield tunnels were presented.The technique is based on a velocity field model using more different truncated solid conical blocks to clarify the multiblock failure mechanism.Furthermore,the shape of blocks between the failure surface and the tunnel face was considered as an entire circle,and the supporting pressure was assumed as non-uniform distribution on the tunnel face and increased with the tunnel embedded depth.The ground surface settlements and failure mechanism above large-diameter shield tunnels were also investigated under different supporting pressures by the finite difference method.

Comprehensive modeling approach of axial ultrasonic vibration grinding force

The theoretical model of axial ultrasonic vibration grinding force is built on the basis of a mathematical model of cutting deforming force deduced from the assumptions of thickness of the undeformed debris under Rayleigh distribution and a mathematical model of friction based on the theoretical analysis of relative sliding velocity of abrasive and workpiece. Then, the coefficients of the ultrasonic vibration grinding force model are calculated through analysis of nonlinear regression of the theoretical model by using MATLAB, and the law of influence of grinding depth, workpiece speed, frequency and amplitude of the mill on the grinding force is summarized after applying the model to analyze the ultrasonic grinding force. The result of the above-mentioned law shows that the grinding force decreases as frequency and amplitude increase, while increases as grinding depth and workpiece speed increase; the maximum relative error of prediction and experimental values of the normal grinding force is 11.47% and its average relative error is 5.41%; the maximum relative error of the tangential grinding force is 10.14% and its average relative error is 4.29%. The result of employing regression equation to predict ultrasonic grinding force approximates to the experimental data, therefore the accuracy and reliability of the model is verified.

Output Speed and Torque of Differential Double-Stator Swing Hydraulic Multimotors

A new type of differential double-stator swing hydraulic motor, based on double stator structure, was introduced. Compared with the traditional swing hydraulic motors, it could provide various kinds of rotational speeds and torques under the same conditions of input flow rate and pressure. The operating prindple and graphic symbols were described. The output speed and torque characters in multifarious connection modes were analyzed through single-acting differential double-stator swing hydraulic multi-motors. Then the differential connection modes and differential principles of differential double-stator swing hydraulic multi-motors were stated. Furthermore, the output speed and torque characters of double- acting and triple-acting ones in multifarious connection modes were gotten. The interaction between output torque and the displacement ratio was studied. Finally, the internal leakage that influenced the volumetric efficiency was researched. The theoretical and experimental researches show that the differential double-stutor swing hydraulic multi-motors can provide various kinds of rotational speeds and torques. Predictably, this new kind of swing hydraulic multi-motors has broad application prospects in machine tool equipments, engineering machineries, and simulation turntables.

Application of linear active disturbance rejection control for photoelectric tracking system

Dynamic characteristics and tracking precision are studied in the photoelectric tracking system and a linear active disturbance rejection control( LADRC) scheme is proposed for position loop. A current and speed controller is designed by a transfer function model,which is obtained by adaptive differential evolution. Model error,friction and nonlinear factor existing in position loop are treated as ‘disturbance',which is estimated and compensated by generalized proportional integral( GPI)observer. Comparative results are provided to demonstrate the remarkable performance of the proposed method. It turns out that the proposed scheme is successful and has superior features,such as quick dynamic response,low overshoot and high tracking precision. Furthermore,with the proposed method,friction is suppressed effectively.