悬浮式球转子压电作动器的设计及实验研究

针对机械转子式陀螺仪对支承和高转速的特定要求,设计出一种兰杰文振子和压电圆盘复合驱动的定子,从而在定子振动输出面获得足够振幅的行波运动,实现对球转子的超声近场非接触支承和高速驱动。对圆盘定子进行了结构动力学设计,使其工作频率与兰杰文振子频率基本一致。样机模态实验表明复合定子频率一致性较好。通过悬浮高度和转速测试发现,转子悬浮稳定,转速与驱动频率有关,在200 V激励电压下的共振频率附近可获得最大转速3 880  r/min。     

非接触式弱电实验供电平台的设计

非接触式弱电实验供电平台是一种新型非接触式电能供应系统,通过电磁感应耦合,实现非接触式能量传输,为负载提供电能。整个系统主要由电能转换、耦合变压器和能量调节三部分组成。电能转换主要完成能量逆变;耦合变压器将逆变后的能量耦合到用户端;能量调节主要为提高耦合到用户端能量的传输能力。该平台克服了传统导线多点接触式电能传输方式的不可靠和不可迁移等缺点,为移动电气设备、易燃易爆环境和水下设备的能量供给提供便捷、安全的解决方案。     

Cable Identification Method for Power Plants

Before cables can be replaced in power plants, they must be properly identified. We have developed a new cable identification method that does not need contact with the conductor of the cable before replacement. The method uses two techniques. The first is based on inductive coupling by a high-frequency search signal that is injected into the cable. The second is based on the change in the cable signal propagation characteristic, which occurs by applying or by removing a magnetic core on the cable. We carried out an experiment in an environment like that of actual cable laying conditions to confirm the effectiveness of our developed method and found that the cables could be identified accurately.     

Prediction of Behavior of Low‐Power Noncontact Charger

This paper proposes a method to predict the charging current, the output power, and the power transfer efficiency of a low‐power, noncontact charger with reasonable accuracy. The low‐power, noncontact charger model considered in this paper consists of a sinusoidal voltage source, a sending and receiving coil, a full wave rectifier circuit, and an AA nickel metal‐hydride battery. The capacitor that is connected in series in the sending coils of the low‐power noncontact charger model to improve the power factor was also examined. The self‐inductance, the mutual inductance, and the resistances of the coils were calculated using axisymmetric finite element analysis, and were substituted into the circuit equations. The circuit equations were solved by using the Runge‐Kutta method. The calculated charging current, output power, and power transfer efficiency were in good agreement with the experimental results.     

露天煤垛内部高温非接触式红外测量方法

目前常采用人工手持测温杆逐个煤垛不定点测量的方法进行露天煤垛温度监测,人工测温法存在重复性差、测量位置有限和工作量大等问题。为实现大范围、全天候、多煤垛在线自动测温,提出了一种非接触式煤垛内部温度红外测量的方法和内部温度分层式计算模型,并设计实现了相应的露天煤垛内部高温红外监测系统。该方法将煤垛分为表层与内层两部分,两层的交界定义为边界面,表层受外界环境的影响,内层则不随外界环境变化。先由红外热像仪采集煤垛的表面温度,结合小型气象站采集得到的天候参数,通过温度校正算法去除天候环境对表面温度的影响,获得煤垛表面的真实温度。然后采用表面热平衡方程由校正后的表面真实温度计算得到边界面温度,再由内层温度与距离的指数关系即可计算得到内部温度值。通过现场实验证实,该方法对内热源温度的计算误差约为10.36%,能够满足工程实际要求,能非接触式直接测量露天煤垛内部温度。     

A Noncontact Ultrasound Approach for Mechanical Property Determination of Cheeses

ABSTRACT: Noncontact ultrasound parameters, such as velocity and attenuation coefficient, were directly measured using air instability compensation transducers and correlated with Young's modulus, hardness, and toughness of different types of cheeses. Ultrasound velocity was highly correlated with the mechanical properties of cheeses whereas no significant relationship between the ultrasound energy attenuation coefficient and the mechanical properties were shown. The noncontact ultrasound technique demonstrated excellent performance for thickness measurement of cheeses with an accuracy of 99.98% (standard error = 0.089 mm). Results indicated that noncontact air instability compensation ultrasound technique has a good potential for nondestructive and accurate measurement of ultrasound parameters, thickness, and mechanical properties of food materials.     

Noncontact Damage Detection of a Rotating Shaft Using the Magnetostrictive Effect

The objective of this investigation is to develop a cost-effective noncontact diagnostic method for rotating shafts in operation. Unlike most existing diagnostic methods developed for rotating shafts, longitudinal stress waves are used and processed for damage assessment. For the non-contact measurement of stress waves in rotating shafts, we propose to use magnetostrictive effect. Shaft rotations inevitably accompany lateral vibrations; thus the effects of the vibrations on the measurement accuracy of the sensor are studied to verify the validity of the magnetostrictive effect application to rotating shafts. For damage location estimation, we use the continuous wavelet transform of the measured wave signals. In particular, we propose to adopt the real-valued Gaussian wavelets as the mother wavelet in order to pinpoint accurately the arrival time of the reflected wave from a crack. Several case studies are considered to show the effectiveness of the present diagnostic method.     

Chinese‐Noodle‐Inspired Muscle Myofiber Fabrication

Much effort has been made to engineer artificial fiber‐shaped cellular constructs that can be potentially used as muscle fibers or blood vessels. However, existing microfiber‐based approaches for culturing cells are still limited to 2D systems, compatible with a restricted number of polymers (e.g., alginate) and always lacking in situ mechanical stimulation. Here, a simple, facile, and high‐throughput technique is reported to fabricate 3D cell‐laden hydrogel microfibers (named hydrogel noodles), inspired by the fabrication approach for Chinese Hele noodle. A magnetically actuated and noncontact method to apply tensile stretch on hydrogel noodles has also been developed. With this method, it is found that cellular strain‐threshold and saturation behaviors in hydrogel noodles differ substantially from their 2D analogs, including proliferation, spreading, and alignment. Moreover, it is shown that these cell‐laden microfibers can induce muscle myofiber formation by tensile stretching alone. This easily adaptable platform holds great potential for the creation of functional tissue constructs and probing mechanobiology in three dimensions.     

Study of Capacitive Tilt Sensor with Metallic Ball

In this paper, a new, simple capacitive tilt sensor with a metallic ball is proposed. The proposed tilt sensor has only two electrodes and a metallic ball, and this design assists in managing the inherent contact problem in measuring tilt angles. Capacitive sensing, compared with other types of tilt sensor, has many advantages such as simplicity, noncontact measurement, long‐throw linear displacement, and sub‐micron plate spacing. Its design and fabrication process are significantly simpler than previous types of tilt sensors. The dimensions of the prototype tilt sensor are , and the diameter of the polystyrene tube is 5 mm with a tube thickness of 0.15 mm. An analytical study of the prototype capacitive tilt sensor was undertaken, and the experimental results demonstrate the relationship between the tilt angles and measured capacitances compared with the analytical study.