压电三向测力单元的精度提高方法研究

随着动态力测试量程的不断增加以及对测试精度要求的提高,压电测试技术的关键性作用日益凸显,并被广泛应用于重载设备以及航空航天的矢量力测量中。针对压电三向测力单元装配及施加预紧力过程中出现的上下压块偏转、不同轴等问题,基于力的分载原理对误差进行了量化,建立了测力单元的自预紧误差理论模型,并设计了新型的装配夹具,进行了两种夹具装配下的测力单元角度偏转测试实验以及静态标定实验。实验结果表明,使用新夹具装配的测力单元测试精度明显得到很大提高,相间干扰最大值由6.06%减少为2.97%,为后续测力单元的精度提升途径以及相应的结构研制提供了理论支撑。

大尺寸压电测力仪输出性能研究

为满足大型丁业生产设备工作过程中的三向载荷测试需求、提升力测试装置的测试精度,对大尺寸多点布局式压电测力仪的输出性能进行了研究。针对4点布局式压电测力仪侧向干扰输出大、载荷作用位置求解精度低的问题,采用变形分析方法建立了测力仪等效理论模型,并基于原结构提出了测力单元8点布局式改进方案。标定结果显示:改进后各测力单元在主向加载时的侧向干扰输出减小了47.44%,测力仪主向、侧向非线性及重复性误差小于0.5%,各向相间干扰均小于2%,对载荷作用位置的求解误差小于4 mm,有效解决了4点布局式测力仪现存的问题。该研究大幅改善了压电测力仪的测试性能,为大尺寸、弱刚度背景下力测试装置精度低的问题提供了解决方案,对多维力测试装置的结构改良具有借鉴意义。

旋锁载荷称重系统研究

为解决岸边集装箱起重机传统测量方法响应慢、精度差、可靠性低、易损坏的问题,提出一种基于旋锁称重的集装箱起重机载荷监测系统。旋锁载荷称重系统由测力单元、数据处理器及系统内通信总线、司机室报警显示单元、系统对外通信总线和数据存储单元组成,用于监测集装箱起重机吊具的起吊质量,将测力单元的传感器集成在集装箱起重机的旋锁内。该系统具有响应快、精度高、可靠性高、不易损坏等优点,同时可以实时监测、显示吊具每个旋锁上的载荷,并将质量数据存储起来。在监测到旋锁载荷异常时,系统可以迅速进行声光报警,或直接锁定吊具驱动电机,阻止非正常起吊,预防事故发生,提升集装箱起重机的安全性。此外,采用旋锁载荷称重系统可以保障提升机构的钢丝绳不会因过重而出现变形和损坏,进一步提升岸边集装箱起重机的安全性。

搅拌摩擦焊焊接过程多维力测试研究

搅拌摩擦焊(FSW)是一种应用广泛的固相连接技术,其焊接工艺参数可通过获取焊接过程作用力的方式来进行研究。针对焊接过程中作用力跨尺度、多维的特点,利用ABAQUS动态仿真获得了跨尺度顶锻力、进给力和侧向力值,为测力仪量程的确定提供依据。采用四点支撑式测量方法,通过仿真分析得出单个测力单元的最优量程。根据量程和石英晶片性能,完成了压电测力单元设计。对设计的测力单元进行静态标定,得出非线性、重复性和向间干扰等静态指标。结果表明,该测力单元具有向间干扰小(1.5%)、量程大(50000 N)、固有频率高(8 kHz)等优点。

Sensor fusion for heading angle estimation based on random forest algorithm

To improve the accuracy of the calculation of a heading angle under magnetic interference,magnetometers and inertial measurement units(IMUs)were fused.The observation value of the heading angle was deduced on the basis of the modeling of the magnetometer error and the analysis of the relation of the magnetometer triaxial output and the distribution characteristics of the magnetic field at two adjacent time periods.Meanwhile,the gyro state and angular velocity increment were used as the basis of the IMU to calculate the prediction value of the heading angle.With the changes in the heading angle and environmental interference,a random forest(RF)algorithm was used to iteratively calculate the weights to fuse the observation value of the heading angle based on the magnetometer and the prediction value of the heading angle based on the IMU.The results show that relative to the common sensor fusion method,the proposed sensor fusion method based on the RF algorithm achieved an approximate 60%improvement in heading angle accuracy.Hence,the proposed method can effectively improve the accuracy of the heading angle under magnetic interference by using an RF algorithm to calculate the output weights of the magnetometer and IMU.

Sensor monitoring of a newly designed foundation pit supporting structure

A new type of pit supporting structure, which was tested and verified using the sensor monitoring technology, was presented. The new supporting structure is assembled by prefabricated steel structural units. The adjacent steel structural units are jointed with fasteners, and each steel structural unit has a certain radian and is welded by two steel tubes and one piece of steel disc. In order to test and verify the reliability of the new supporting structure, the field tests are designed. The main monitoring programs include the hoop stress of supporting structure, lateral earth pressure, and soil deformation. The monitoring data of the field tests show that the new supporting structure is convenient, reliable and safe.

Research on Construction Process of Steel Box Girder Bridge and Its Stress Analysis

The paper introduce the construction method of large segment hosting and its difficulty, and drawing up corresponding liner and stress monitoring plan. The paper gives the calculation method of shear area for such a big cantilever thin-walled steel box girder section, namely the shear coefficient computation theory of Professor Hu Haichang, and the use of this shear area perfect beam element model, structure model and the experiment prove that the shell model is more consistent, given a certain reference for similar section project.

Development of a Stabilized Pan/Tilt Platform and the State of the Art

In the context of this paper, a small scale, medium precision, stabilized pan/tilt platform is developed as a prototype, which is used to compare various stabilization algorithms experimentally. The overall performance of the system depends on rigid body dynamics, structural dynamics, servo control loops, stabilization control algorithm, sensor fusion algorithm and sensory feedback such as from the IMU （inertial measurement unit）. In the case that the response bandwidth of the overall system is high enough, the same hardware can also achieve active vibration isolation. All of these design aspects are investigated in the paper via numerical models and with their experimental verification.

Channel flow of the lower crust and its relation to large-scale tectonic geomorphology of the eastern Tibetan Plateau

The Tibetan Plateau is a large-scale tectonic geomorphologic unit formed by the interactions of plates.It has been commonly believed that convective removal of the thickened Tibetan lithosphere,or lateral flow of the lower crust beneath the Tibetan plateau plays a crucial role in the formation of the large-scale tectonic geomorphologic features.Recent geological and geo-physical observations have provided important evidence in support of the lower crustal channel flow model.However,it re-mains unclear as how the geometry of lower crustal channel and the lateral variation of crustal rheology within the lower crust channel may have affected spatio-temporal evolution of the tectonic geomorphologic unit of the Tibetan Plateau.Here,we use numerical methods to explore the mechanical relations between the lower crustal channel flow and the tectonic geomorpho-logic formation around the eastern Tibetan plateau,by deriving a series of governing equations from fluid mechanics theory.From numerous tests,our results show that the viscosity of the channeled lower crust is about(1-5)×1018 to(1-4)×1020 Pa s(Pa.s) beneath the margin of the eastern Tibetan Plateau,and increases to about 1022 Pa s beneath the Sichuan Basin and the southern region of Yunnan Province.Numerical tests also indicate that if channel flows of the lower crust exist,the horizontal propagation and the vertical uplifting rate of the eastern Tibetan Plateau margin could be accelerated with the time.Thus,the present results could be useful to constrain the rheological structure of the crust beneath the eastern Tibetan plateau,and to understand the possible mechanics of rapid uplift of the eastern Tibetan Plateau margin,especially since its occurrence at 8Ma as revealed by numerous geological observations.