测力台在体育测试中的应用研究

在生物力学研究中,利用测力台对三维力进行动态测量,是一个很重要的手段。测力台可以直接输出三维力,采样频率高,测试精度准确,用于动作技术的地面反作用力的测试,下肢运动损伤,预防损伤,稳定能力,平衡能力的测试,运动装备,尤其是运动鞋的运动性能测试,运动场地材质的缓冲性能测试等。对三维力动态测量理论,以及用于三维力动态测量的测力台进行了相关的研究,得出了测力台应用于体育测试的具体方法,将测力台应用于体育测试、训练必将显著提高体育竞技成绩,有着广阔的前景。     

基于多维测力台的有限元分析研究

设计了一种用于人体静态平衡研究的多维力传感器的测力台。多维力传感器采用了均匀壁厚的薄壁圆筒形的弹性体,实现多维力的测量。并对多维测力台进行了有限元分析,计算出弹性体的应力分布,进而精确定位弹性体上应变片的粘贴位置。采用4个多维力传感器联合组桥的方式消除维间耦合并提高测量灵敏度。     

Virtual reality in posturography.

Balance dysfunctions are common, especially among elderly people. Present methods for the diagnosis and evaluation of severity of dysfuntion have limited value. We present a system that makes it easy to implement different visual and mechanical perturbations for clinical investigations of balance and visual-vestibular interaction. The system combines virtual reality visual stimulation with force platform posturography on a moving platform. We evaluate our contruction's utility in a classification task between 33 healthy controls and 77 patients with Ménière's disease, using a series of tests with different visual and mechanical stimuli. Responses of patients and controls differ significantly in parameters computed from stabilograms. We also show that the series of tests achieves a classification accuracy slightly over 80% between controls and patients.     

Macro-scale atomic force microscope: An experimental platform for teaching precision mechatronics

A macro-scale atomic force microscope (macro-AFM) has been designed and used for teaching precision mechatronics. The macro-AFM uses a novel electromagnetic self-sensing self-actuating probe. It operates in frequency-modulation AFM (FM-AFM) mode with intermittent contact. The AFM has an imaging volume of 250 mm × 40 mm × 1 mm with a resolution of about 1 μm at 1 Hz measurement bandwidth. The macro-AFM is simple and relatively inexpensive to build. It is scaled to make motion visible to the eye and is robust for a lab environment, all of which make it an affordable and effective educational tool. The macro-AFM is used in Mechatronics (2.737), a graduate level course at MIT, where in a series of 11 laboratory exercises, the students assembled and programmed the AFM system. This article provides the design and theory used for making and controlling the macro-AFM, as well as experimental results.     

A mobile service platform using proxy technology

This paper proposes iMobile, a proxy‐based platform for developing mobile services for various mobile devices and wireless access technologies. iMobile acts as a message gateway that allows mobile devices to relay messages to each other through various protocols on different access networks. It allows mobile devices to access internet services, corporate databases and to control various network devices. iMobile implements three key abstractions: dev‐let, info‐let and app‐let. An info‐let provides abstract view of information space. An app‐let implements service or application logic by processing information from various info‐lets. A dev‐let receives and sends messages through any particular protocols for mobile devices. The let engine supports user and device profiles for personalization and transcoding, and invokes proper app‐lets and info‐lets to answer requests from a dev‐let. The iMobile modular architecture allows developers to write device drivers, information access methods and application logic independently from each other. Copyright © 2005 John Wiley & Sons, Ltd.     

A statistical model for interpreting computerized dynamic posturography data

Computerized dynamic posturography (CDP) is widely used for assessment of altered balance control. CDP trials are quantified using the equilibrium score (ES), which ranges from zero to 100, as a decreasing function of peak sway angle. The problem of how best to model and analyze ESs from a controlled study is considered. The ES often exhibits a skewed distribution in repeated trials, which can lead to incorrect inference when applying standard regression or analysis of variance models. Furthermore, CDP trials are terminated when a patient loses balance. In these situations, the ES is not observable, but is assigned the lowest possible score--zero. As a result, the response variable has a mixed discrete-continuous distribution, further compromising inference obtained by standard statistical methods. Here, we develop alternative methodology for analyzing ESs under a stochastic model extending the ES to a continuous latent random variable that always exists, but is unobserved in the event of a fall. Loss of balance occurs conditionally, with probability depending on the realized latent ES. After fitting the model by a form of quasi-maximum-likelihood, one may perform statistical inference to assess the effects of explanatory variables. An example is provided, using data from the NIH/NIA Baltimore Longitudinal Study on Aging.     

Seat support surface optimization using force feedback

The development, implementation and evaluation of an algorithm designed to find optimal seat support surfaces are presented. The algorithm has been developed and implemented on an active contour measurement device. The device consists of an array of positioning elements equipped with force sensors for feedback. With a patient seated on the array, the algorithm is designed to find a seat contour that optimally satisfies given performance criteria. The performance criteria are based on measured stiffness of the soft tissues. A theoretical development of the algorithm is presented along with the modifications made to the algorithm during implementation. The results from several tests using man-made test bodies and a prototype contour gauge are presented to verify the algorithm's performance     

Precise, fault-tolerant pointing using a Stewart platform

Presents a precision pointing strategy. The principal contribution is the development of a fault-tolerant control which allows active pointing to continue despite multiple failures. A six-axes active platform is utilized to reject disturbances from a vibrating base to a precision payload. A decentralized controller is proposed which converts desired rotations into corresponding strut lengths via a decoupling transformation. The decoupling approach allows for simple single-input-single-output compensator design and for the incorporation of fault-tolerant strategies. The proposed strategy was evaluating on the microprecision interferometer testbed (a full-scale model of a future spaceborne optical interferometer) at the Jet Propulsion Laboratory, Pasadena, CA. Experimental pointing results demonstrate 50 dB of disturbance rejection at low frequency. In the laboratory ambient disturbance environment, this corresponds to a 1-μrad rms pointing error     

Picosecond electrical sampling using a scanning force microscope

A scanning force microscope probe for measuring ultrafast voltage signals is demonstrated. The new technique is based on mixing due to the square-law force interaction present between the microscope tip and sample. Correlation of 100 ps pulses and mixing up to 20 GHz have been achieved.<>     

海藻酸薄膜表面超微结构的原子力显微镜研究

本文采用原子力显微镜（ＡＦＭ）对海藻酸生物薄膜表面的超微结构进行了实验研究,选择出最佳观察方法。结果发现薄膜上分布不规则的微孔,其长短孔径之比大约为３：２,微孔的中心距为孔径的２倍。     

Sampling electrostatic force probing using pulse positionmodulation technique

A sampling electrostatic force microscopy method utilising a pulse position modulation technique is demonstrated. High frequency arbitrary waveforms within integrated circuits are measured by down converting the high frequency spectrum of the circuit waveform to within the active frequency band of the mechanical frequency response of the probe     

舰载雷达稳定转台系统受力计算和有限元分析

对舰载雷达稳定转台系统进行了详细的受力计算,并运用I-DEAS软件对部分结构件进行有限元分析和研究,给出了其固有频率和应力应变等。研究结果能对稳定转台系统生产、质检提供理论支撑和技术支持。     

An outdoor navigation system using GPS and inertial platform

The use of global positioning system (GPS) in outdoor localization is quite a common solution in large environments where no other reference is available and there are not so demanding positioning requirements. Of course, fine motion without the use of an expensive differential device is not an easy task, even now that available precision has been greatly improved as the military encoding has been removed. In this paper we present a localization algorithm based on Kalman filtering that tries to fuse information coming from an inexpensive single GPS with inertial data and map-based data. The algorithm is able to produce an estimated configuration for the robot that can be successfully fed back in a navigation system. Some experiments show difficulties and possible solutions of this sensor fusion problem     

利用ArcGIS API构造健身步道平台系统

该系统为市民提供科学的步道健身指导和步道交友平台,使市民合理健身,为实现步道建设的现代化管理和健康步行的科学指导提供有力支撑.该系统使用各种先进的技术,通过构建"步道健身项目工程一张图"、实现步道的实时查询、分布等服务,充分利用互联网技术手段,通过用户移动的距离(也就是根据用户在地图上经纬度的变化来计算用户移动的距离)来对数据进行实时接收,然后在健身步道信息管理平台系统上展示每个健身者的步道数据.正确引导市民适度健身,扩大健身的影响力.该平台的设计充分运用云计算、物联网、GIS等最新IT技术,是市民步道健身规划的最新发展需求.     

Aluminium-based packaging platform for led using selectively anodising method

An aluminium-based packaging platform with microreflector and electrical via for an interconnection electrode is first proposed for a package component of a light-emitting diode (LED). The electrode-guided interconnection with 180 mum thickness has been successfully fabricated by using the selectively anodising process, and not by either the plating or the solder paste technique. The reflector was formed during the isotropic etching process. By mainly a two-step chemical process, the LED packaging platform integrated microreflector and electrical via in one body was developed in a low-cost process.     

Evaluating particle scattering effects by using turbulence scattering theories

The possibility of an alternative approach for particle scattering is presented. In this approach, a correlation function is derived that describes the permittivity fluctuations due to sharp gradients at the boundary of a particle and the particle distributions to the level of pair correlation. Once such a correlation function is available, some conceptions of turbulence scattering become eligible for application. Analytic results in the cases when the permittivity contrast is weak or the particle size is small are shown to be in good agreement with the corresponding ones that are obtained by using the conventional approach. This new approach is expected to be useful in solving some difficult problems in particle scattering systems such as computing the higher moments and temporal behavior, at least in the extreme cases mentioned above.     

A precision linear actuator using piezoelectrically driven friction force

A friction drive-type precision actuator which is capable of high positioning accuracy was developed by using piezoelectric elements. To anticipate dynamic behavior, system modeling was performed by using stick-slip friction models such as classical, Karnopp, and reset integrator. Dynamic characteristics over various types of driving input signals and driving conditions were investigated by simulation and experiment. By varying phase angle difference and amplitude of driving inputs, it was found that it is possible to control the moving direction and distance of the slider. From simulation and experimental results, it was observed that the dynamic behavior of the simulation predictions agreed well with that of experimental results. This indicates that the model developed in this study is applicable to many other precision mechanisms in which driving friction force is generated by ellipsoidal motion.     

State-dependent friction force compensation using periodic adaptive learning control

This paper uses the periodic adaptive learning control (PALC) for the compensation of a state-dependent non-Lipschitz external disturbance of electromechanical systems. Theoretically, we are interested in designing a non-Lipschitz friction force compensator, where the friction force is considered position-dependent external disturbance. The key idea of the proposed scheme is to make use of state-periodicity of an external disturbance on the iterative state domain. The state-periodical adaptive compensator designed based on Lyapunov stability analysis guarantees an asymptotical stability of the system after the first iterative trajectory and onwards. The designed-adaptive compensator is verified through an actual DC motor control test.     

Slip detection and control using tactile and force sensors

In this paper, some results concerning the detection and control of the relative motion (slippage) of two bodies in contact are presented. The main motivation of this research can be found in advanced manipulation with robotic systems, in which, depending on the particular task to be executed, it might be desirable either to avoid or to exploit the slippage of the manipulated object. The main contribution of this paper is that, besides the linear Coulomb friction effect, the rotational case is also addressed and, therefore, both translational and rotational motions are taken into account. This result is achieved by using an integrated sensor constituted by a force/torque and a tactile sensor. Experimental results are presented considering both the detection of the slippage and its subsequent control     

Interaction force measurement of parallel robots based on structure-integrated force sensors using interpretable linear neural networks

The parallel robot in this research is mainly designed for the human-machine collaboration, which has two working modes: follow-up mode and pressing mode. In order to better realize these two functions, the measurement of the interaction force is mainly concerned. In the arrangement of the hardware, different from the six-dimensional force sensor method and current estimation method commonly used in industry, the structure-integrated force sensors (SIFS) measurement method is used. In the calculation method, a back propagation neural networks (BPNN) method is introduced to calculate the interaction force. Then, based on the prior knowledge of physics, a new interpretable linear neural networks (ILNN) method is proposed. The details of the ILNN algorithm and its differences from the classic neural network methods are given. Finally, the experimental results of the direct Newton–Euler method, the least square method, the BPNN method, and the ILNN method are compared. Experimental results show that the inference accuracy of the ILNN method is slightly better than the direct Newton–Euler method and the least square method, and its generalization ability is much better than the BPNN method. The use of the ILNN method based on the FIFS arrangement makes the measurement of the interaction force more accurate and reliable.