基于随机森林算法和摩擦起电传感器的人体运动识别研究

人体运动传感器是可穿戴设备、物联网等领域的关键传感器，低成本的聚合物多功能运动传感器有广阔的应用前景。基于摩擦起电原理，聚合物传感器可实现多种运动的感知。通过对传感器结构和电荷转移规律的分析，表明其可有效感知三维直线运动。将传感器固定在测试人员脚踝处，测得跑步和走路等不同运动状态下的输出电压。选择部分电极输出电压的极差和标准差作为特征量，采用随机森林算法对特征量进行分析，研究结果表明该方法对走路和跑步的识别准确率可达98.3%,为该型传感器在可穿戴设备上的应用奠定了基础。     

同步电感提取技术在压电风能采集装置中的应用

虽然同步电感能量提取技术(SSHI)能够显著提高压电能量采集装置的采集效率,但需要额外的位移传感器对压电片的动作状态进行检测,在压电片发生复杂形变时此方法不适用。为了提升俘能电路在非线性激励下的工作效率,本文基于小旗式压电风能采集装置,设计了一种新型自供电、自感知式同步电感能量采集接口电路,该电路可以根据压电片输出的电压判断压电片的形变量,实现同步电感开关的自动控制。同时,利用Multisim电路仿真软件,对标准接口电路及新型接口电路进行仿真分析。仿真结果表明,新型接口电路能够有效提高俘能电路在非线性激励下的能量俘获效率,与传统俘能电路相比,新型俘能电路可以使输出功率提升30%。该研究为非线性俘能电路的设计提供了理论依据。     

基于振荡共振原理的人体触觉传感装置设计

针对老年人对外部刺激的触觉感知灵敏度下降的问题,本文设计了一套人体触觉振荡共振传感装置。该系统选用STM32F103ZET6为中央处理器,利用加速度传感器MPU6050采集人体姿态特征信息,通过串口模块CP2012将采集到的信息发送到上位机实时显示和存储,依据姿态信息驱动微电机产生高频振荡作用于触觉感知部位,以提高人体的触觉感知功能。通过对微电机振动产生的振荡进行数字化录音,对其频谱分析观测到不同输入电压下对应电机振动输出频率的变化情况。仿真结果表明,该装置能够产生不同振动强度的高频刺激,为利用振荡共振理论在人体医学功能的应用提供了实验依据。该研究在人体触觉感知领域奠定了实验基础,具有一定的实际应用价值。     

高效电磁式振动能量收集装置的设计

为了提高能量收集效率,降低装置复杂度,便于工业制造,提出一种新型方形振子电磁振动能 量收集装置．该装置形成了闭合磁路能量转化效率高;同时使用方轴固定振子振动路径和磁轭对称 放置的方法消除振子运动中的定位力;装置中永磁体、线圈位置固定,提高了装置的使用寿命．通过 Ａｎｓｏｆｔ　Ｍａｘｗｅｌｌ静态仿真,分析了气隙宽度、导磁材料相对磁导率和振子齿的厚度对铁芯中磁感 应强度的影响,得出参数的最优值．利用动态仿真,得出优化后的装置单个线圈可产生１．２Ｖ的感 应电动势,空载时最大功率为４７４．１ｍＷ,带负载时最大有效输出功率为１１８．５ｍＷ,可以为多数低 功耗无线传感网络节点供电．     

压电振动能量采集器的性能分析与功率优化

为了预测压电振动能量采集器的输出特性,优化输出功率,以压电双晶片串联型振动能量采集器为研究对象,综合考虑结构与电路耦合因素,利用有限元法和ANSYS软件建立压电振动能量采集器的有限元机电耦合动力学模型和网格实体模型.分析在外力激振条件下负载电阻对压电振动能量采集器的振动特性和电输出特性的影响,得到不同负载电阻下压电能量采集器的振动特性和电输出特性曲线.通过调节负载电阻使之与能量采集器的阻抗匹配,实现了对能量采集器输出功率的优化,得到了优化的负载电阻和输出功率.研究结果表明,采用压电能量采集器能够输出大的开路电压、大的短路电流,优化后的开路和短路谐振时的最大输出功率分别达到57.81和55.12 W.     

磁悬浮技术轨道机车振动在线监测

为实现轨道平整度测量,设计了轨道机车磁悬浮振动测试系统,计算了光电位移传感器的灵敏度,推导了振子动力学方程,等效方程为常系数线性微分方程。根据振动测试理论,设计的磁悬浮振动测试系统可实现绝对式振动测量。在轨道机车匀速运动时实测了有、无振动和减速运动情况下的波形以及机车进入站台时产生的振动,并且进行了功率谱和相轨迹分析。磁悬浮轨道振动测量是由振子处于悬浮状态进行的测量,因此具有测量灵敏度高、测试范围宽等优点。进一步研究还可对轨道机车运行中对周围环境的振动进行测量。     

以振动能量转化为供电策略的无线矿山粉尘监测系统

提出一种以收集振动能量为供电策略的矿山粉尘无线监测系统.供电系统由压电振动能量收集结构和以LTC3588为核心的能量收集电路构成.低功耗MCU(STM8s)对DSM501A灰尘传感器输出的PWM信号进行采集和处理,输出粉尘浓度信息.由高性能嵌入式MCU(STM32)和YL-800T组合成的主机每隔一定时间依次采集各子节点所监测的浓度信息,上位机对主机的信息进行采集并处理,以实时曲线和地图报警模式显示.报警发生时,上位机传输控制信息给下位机,在警报的子节点位置进行一些降尘措施.应用结果表明:该系统具有实用性好、可靠度高和绿色环保等优点,实现了粉尘浓度的持续检测.     

两自由度压电式轨道振动能量采集器

提出一种轨道板垂向振动能量采集方法,设计3种不同方案的两自由度压电式轨道振动能量采集器,并建立其运动方程和机电耦合方程.通过运用谐波平衡法,在简谐激励下分析得到压电式轨道振动能量采集器的输出电压和输出功率的幅频响应,通过直接的数值模拟验证了分析结果的正确性,得到两自由度轨道压电式振动能量采集器的最优方案.该方案采集器的能量采集效果远高于其他两种方案.通过调节刚度参数,可以有目的地增强两个共振峰中的任意一个,从而达到与轨道振动激励谐振的目的.     

低功耗自供电机械设备状态监测系统设计

为解决机械设备安全运行监测设备的续航能力差、需要频繁更换电池的问题,设计了一种低功耗自供电机械设备状态监测系统.该系统由磁悬浮电磁能量采集器、能量管理电路、低功耗无线传感电路以及监测上位机组成,通过收集机械设备运行状态下溢散的振动能量为监测节点供电,同时将机械设备运行状态下的温度和振动信息通过蓝牙传输方式发送到接收器,并在监测上位机显示和存储.设计了低功耗传感监测电路并优化了供电逻辑.对监测系统性能进行了实验测试,结果表明该系统可以实现机械设备的无线自供电监测.     

分块式永磁振动发电机的结构及输出电压

设计了分块式永磁振动发电机,分析了永磁振动发电机的结构及不同条件下的输出电压,运用有限元方法计算了发电机的磁场与输出电压,提出了设计分块式永磁振动发电机的条件.制作了分块式径向充磁的永磁振动发电机,对永磁振动发电机进行了实验研究,理论和实验表明,振动发电装置在振幅为50 mm振动周期为2 s的正弦振动时,输出开路电压峰值为3.6 V;有效值为2.24 V.研究对于研制分块式永磁振动发电机具有重要指导作用.     

车载传感器压电和电磁混合式自供电技术

研究了一种用于车载传感器自供电的压电和电磁复合式能量收集技术,给出了系统的数学模型,分析了系统共振频率与系统结构参数的关系,设计了一套压电和电磁复合式能量收集装置.实验结果表明,数学模型基本反映了系统的输出特性,在共振频率为18 Hz,加速度为0.5 g时,复合式能量收集装置的最大负载功率为3.75 mW,相比于采用单一电磁技术时的最大负载功率3.2 mW增加了17%.     

Electromechanical coupling properties of a self-powered vibration sensing device for near-surface observation tower monitoring

The wind-induced vibration of a remote sensing tower is the key factor affecting the stability of image sensing and structural reliability. Monitoring the vibration of a long-time unattended tower is critical to its proper operation. Currently, most monitoring devices are supplied with wired power or battery, significantly limiting their practical applications in remote areas. In this paper, a self-powered vibration sensing device based on hybrid electromechanical conversion mechanisms is proposed. The device depends on a cylindrical magnetic levitation structure sensitive to ambient vibration for transferring mechanical energy and takes as a dual-functional heterogeneous integrated system comprising electromagnetic, piezoelectric, and triboelectric generators. When the device vibrates under environmental force driving, the suspension magnet reciprocates vertically and generates induced electromagnetic energy, which is used to power the device. Moreover, the triboelectric and piezoelectric voltages, respectively originating from magnet impact on two separation friction materials and magnetic field repulsion-induced strain deformation of a piezoelectric sheet, are used as the synergistic sensing signals. To improve the output energy, a set of dual-segmented annular coils is designed in an electromagnetic generator, which greatly avoids the obstructive effect of the suspended magnet on the magnetic flux change at its end. Compared with a whole isochoric coil, it increases the output voltage by 78.3%. For the triboelectric sensing module, a silicone film with a large specific surface area is fabricated via 3D modification, which improves the output voltage by 29.4%. Furthermore, a pair of piezoelectric sensing modules is set to improve the accuracy of comparative sensing data. The experimental measurement shows that the device maintains a high sensitivity of 6.711 V (m s^?2)^?1 and excellent linearity of 0.991 in the range of 0–14 m s^?2. This work provides a practical strategy for the vibration monitoring of remote sensing tower and exhibits attractive potential in early warning and data analysis.

     

大跨空间结构减震控制装置设计与试验研究

基于大跨空间结构振动主动控制方法,以超磁致伸缩材料为核心元件,充分利用其输出力大、响应速度快、可靠性高、驱动电压低等优良磁控特性设计出一种将电磁能转化为机械能的减震控制装置—超磁致伸缩作动器,分析了其工作原理和设计方法,然后对其进行力和位移输出性能测试.结果表明,该作动器磁路结构良好,磁机转换效率较高,在驱动电流作用下可输出较大的力和位移,其与驱动电流基本呈线性关系且对电流的变化非常敏感,为这种作动器在大跨空间结构中的应用打下了良好的基础.     

Low frequency wide bandwidth MEMS energy harvester based on spiral-shaped PVDF cantilever

In this paper,a piezoelectric energy harvester based on spiral-shaped polyvinylidene fluoride(PVDF)cantilever is designed and fabricated for harvesting low frequency vibration energy in the environment.In this design,the spiral-shaped PVDF cantilever is major for lowering the resonant frequency by increasing the length of the cantilever;Copper and silicon proof masses on both sides are working on further decreasing the resonant frequency and widen its bandwidth.Due to the high flexibility of the PVDF cantilever,this device is extremely sensitive to vibration and can harvest weak vibration energy.Both simulation and experimental results have approved that this device can operate at very low frequency which is about 20 Hz and can effectively harvest energy from 15–50 Hz.The peak of the output voltage can reach 1.8 V with the acceleration of 0.2 g.This is a promising harvester for powering the wireless sensors in the future.     

A triboelectric/electromagnetic hybrid generator for efficient wind energy collection and power supply for electronic devices

Harvesting energy from ambient environment has been considered as a promising strategy for driving portable electronic devices in a sustainable way. A wind driven triboelectric-electromagnetic hybrid nanogenerator has been fabricated to convert wind energy into electricity. It is composed of an electromagnetic generator(EMG) and a triboelectric nanogenerator(TENG) with the output power of 35 and 0.32 mW, respectively when the wind speed is 5 m/s. Generally, TENG shows a low current output with a high voltage output characteristic, on the contrary the EMG shows a high current output and a low voltage output. This hybrid nanogenerator overcomes these problems and exhibits comprehensive and efficient performance on scavenging energy.Moreover, in view of the output performance and charging ability of the hybrid nanogenerator, it shows high stability, making it suitable for charging capacitors or batteries and driving portable electronics sustainably. A new structure of integrated TENG and EMG was designed to harvest wind energy, which shows potential applications in portable and small device power supply system, especially in the areas of remote mountains, deserts, islands, etc., as emergency power supply.     

超声波电动机定子振动能量回收转换特性

为了向密封、恶劣等极端环境中工作的微型机器人提供驱动力矩和电能,根据行波型超声波电机定子孤极频率反馈跟踪原理,研制能量回馈型超声波电机.与传统超声波电机相比,该电机不仅具有驱动功能,还具有将定子振动能量回收并转换成电能的功能.根据能量回馈型超声波电机驱动原理改进了超声波电动机压电陶瓷的极化分区模式,将超声波电机定子压电陶瓷极化分成3个区,即：激振区、能量采集区和传感区（孤极）.利用定子能量采集区压电陶瓷的正压电效应采集回收超声波电动机定子的机械振动能量.根据铁摩辛柯梁理论和压电本构方程建立超声波电动机定子振动能量采集回收的理论分析模型,研究能量采集区压电陶瓷负载阻抗的匹配问题.利用该模型仿真分析了电机激励频率、激振电压、外接负载电阻等对能量采集区压电陶瓷输出电压、输出电流和输出功率的影响规律,通过实验验证了仿真结果的正确性.     

A cubic triboelectric generator as a self-powered orientation sensor

Recently, triboelectric generator(TEG) has attracted a lot of attention due to its high output voltage and low-cost fabrication process. Here, a novel cubic TEG box is designed, which has separated electrodes on different surfaces. Thanks to the specially designed structure, it can scavenge vibration energy from all directions. Firstly the device is investigated through finite element method(FEM) simulation. Then the device is evaluated by experiments. The measuremental results show that this device can generate an amount of 25 n C charge during once shake by charging a 10 n F capacitor. Besides, an output voltage about 100 V is obtained, which is able to directly light up several light-emitting diodes(LEDs) simultaneously. At last, the device is utilized as a self-powered orientation sensor, which shows explicit directivity. This work extends the applications of TEG for ambient vibration energy harvesting techniques and the self-powered orientation sensor.     

Research on a tensegrity parallel mechanism for wave energy harvesting

To solve the problem that the conventional floating wave power device can not transform the rotational kinetic energy into electric energy, a novel wave energy harvesting device based on tensegrity parallel mechanisms is proposed. The dynamic model of the novel device is developed on the basis of Airy's linear wave theory and Lagrange's equation. Then, the kinematic and dynamic analyses of the float are made. Afterwards, the efficiency of the novel wave energy harvesting device and conventional floating wave power device is computed and compared. The results indicate that the efficiency of energy harvesting of the proposed device is higher than that of the conventional floating wave power device. Moreover, the ability of the proposed device to resist destructive water waves is better than that of the conventional floating wave power device.     

Optimization of cantilevered piezoelectric energy harvester with a fixed resonance frequency

Piezoelectric energy harvesting is widely used to scavenge vibration energy in the environment.For some vibration sources with fixed frequency,cantilevered harvester can generate the energy effectively,so the optimization theory for cantilevered harvester in such an application is needed.In this article,we present the theoretical and experimental studies of the cantilevered piezoelectric energy harvester with a fixed resonance frequency.An analytical model based on energy method is used to estimate the open-circuit voltage and generated energy.Considering that the harvester may be subjected to the static force or steady-state sinusoidal vibration excitation,static and dynamic analysis is performed for device structure to achieve efficient energy.In the analysis,the effects of geometrical dimension on the energy harvesting performance are discussed comprehensively.Eventually,a prototype is designed and fabricated using(1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3(PMN-PT)single crystal with ultrahigh piezoelectric properties and coupling factor.Performances of the cantilever with different clamped length are evaluated under sinusoidal vibration excitation,proving the good consistency between experimental results and theoretical prediction.The established analysis can provide useful guidelines for the structure design of cantilevered piezoelectric energy harvester with a fixed resonance frequency.     

Ferroelectric materials for vibrational energy harvesting

Energy harvesting is an appealing technology that makes use of the ambient energy which is otherwise wasted. Piezoelectric materials directly convert the elastic energy to the electric energy, and thus have a great advantage in scavenging vibrational energy for simplicity in device structure with relatively high power density. This paper provides an overview on the research of piezoelectric materials in energy harvesting in recent decades, from basics of piezoelectricity and working principle of energy harvesting with piezoelectric materials, to the progress of development of high-performance piezoelectrics including ceramics, single crystals and polymers, then to experimental attempts on the device fabrication and optimization, finally to perspective applications of piezoelectric energy harvesting (PEH). The criteria for selection of materials for PEH applications are introduced. Not only the figure of merit but also maximum allowable stress of materials are taken into account in the evaluation of their potential in achieving high energy density and output power density. The influence of the device configuration on the performance is also acknowledged and discussed. The magnitude and distribution of induced stress in the piezoelectric unit upon excitation by the vibration source play an important role in determining the output power density and can be tuned via proper design of device configuration without changing its resonant frequency. Approaches to address the issue of frequency match accompanying with the resonant mode are illustrated with literature examples. Usage of PEH devices can be extended to a variety of vibration sources in everyday life as well as in nature. Some appealing applications of PEH, such as in implantable and wearable devices, are reviewed.