为了对环境中的低频声能量进行高效回收,提出了一种基于Helmholtz共鸣器、压电单晶片以及接口电路的压电式微型俘能器.通过理论分析了俘能器的最佳工作频率,通过实验对理论分析结果进行了验证,并且研究了声源在不同距离下,俘能器的输出特性.实验结果表明:当俘能器在共振频率下工作时,在距离声源0.1 m,声压级为110 dB,负载值为48 kΩ时,最大输出功率高达24 mW;当距离从1 m增加至4 m时,输出功率从1.17 mW降低至0.38 mW,俘能器在距离较远的情况下仍能够提供足够的功率为微电子器件进行远距离独立供能.

针对工业外场环境下,传统电池供能方式存在污染环境及不易更换的问题,通过压电陶瓷将微型风能转换成电能后,直接为无线传感节点等微型电子设备供电,可以缓解这一问题.针对经典电路回收微型风能功率较低的问题,提出了一种无源自供能接口电路,可以更高效地采集微型风能.对电路进行了理论分析和Multisim软件仿真,仿真结果表明:设计的电路回收微型风能是经典电路的4倍左右.

由于体积大、污染环境、需要定期更换,传统电池供能方式已不能适应当前外场工作的需求.涡激振动的微型风能采集装置将风能转换成电能,能够对无线传感节点等微型电子设备直接供电.基于经典Buck-Boost电路,提出了一种适用于涡激振动微型风能采集的能量接口电路.通过理论与仿真分析,所设计的能量接口电路存在最优占空比,及其对应的最大功率点.基于LabVIEW平台设计了控制程序,实验结果表明,所设计的电路与程序能够对占空比进行自动寻优,保持微型风能采集装置以最大功率输出.

针对传统桨叶风力发电系统体积庞大、不适用于微小型电子系统的问题,利用压电材料、钝体、接口电路,设计了一种微型风力发电系统.基于涡激振动原理改进了发电装置的能量回收电路,既可对风能进行有效回收,又能输出较高电压,解决了微电子器件的供能需求.分析了装置的固有频率,对两种接口电路进行了仿真分析,通过实验研究了装置使用VD接口电路后,在不同风速下的输出电压特性,以及在不同负载、不同风速的条件下的输出电压与输出功率特性.实验结果表明:输出电压、功率随风速增加而增加,在风速22 m/s时,最大开路电压有效值为36.2 V,存在最优负载使得输出功率最高,实测为560 kΩ,最高输出功率为375.5μW,相比标准(Standard)电路提升了7.07％,可独立对微电子器件供能.

为了高效回收环境中的声能,基于阵列式压电换能器、直管谐振腔以及能量回收电路提出了一种声能量回收系统.当声波进入直管谐振腔,管中产生谐振驻波作用于压电换能器,将声能转换为电能.本文设计了能量回收电路并且进行理论、仿真分析实验研究了压电振子数量、声波频率、声压级对输出电压的影响,分析了负载电阻对输出电压及功率的影响.实验结果表明,该装置可回收不同频率的声能量,在声波频率为96Hz时发电效果最优.当入射声压级为110dB时,不使用能量回收电路,输出交流电压有效值最高达12.9V,输出交流功率最高达到799μW;使用设计的能量回收电路,最高输出直流电压为64.2V,最高输出直流功率为473μW.该声能量回收系统不仅可以作为声能量采集器,还能对无线传感节点等独立工作的微型电子系统供能.

为了降低压电陶瓷驱动器的迟滞非线性,提出了改进型的Maxwell-slip模型并引入自适应控制,使压电驱动器在宽频带下有良好的迟滞补偿效果.在经典Maxwell-slip模型中,输出力与输入位移的关系会出现迟滞现象,表现为平行四边形,与压电陶瓷驱动器的迟滞特性接近.由于每一单元滑块的最大静摩擦力与弹簧弹性系数成比例关系,若弹簧系数取定值时,每一个单元的最大静摩擦力在系统实时控制中是不变的,因此可以采用自适应控制算法对输出信号权值进行更新,从而更精确地补偿压电陶瓷驱动器.为了验证该模型,搭建了悬臂梁结构压电实验平台,运用该迟滞模型进行迟滞补偿控制,实验结果表明,对于Maxwell-slip模型自适应控制,在0.1～20 Hz宽频带下的均方根误差(RMSE)和绝对平均误差(MAE)均有减小.其中,在0.1 Hz下无前馈补偿控制的RMSE为0.037 5 μm,而通过自适应控制可以将压电微定位平台的RMSE降低到0.012 4μm以内.与经典模型相比,所提出的Maxwell-slip模型自适应控制具有在宽频带内进行精密定位的优点.

碳纤维复合芯(ACCC)导线的结构不同于钢芯铝绞线(ACSR),传统的导线检测方法难以在ACCC导线上得到有效应用.为了保证电力系统运行的稳定性与可靠性,有必要对ACCC导线的结构健康进行快速、全面的检测.根据ACCC导线的结构与弹性波的传播特性,分析了弹性波的相速度、群速度及频散特性,采用虚拟仪器技术,提出了一种基于弹性波检测技术的ACCC导线结构健康监测系统.基于小波变换理论,分析了峰值到达时间的计算方法,研究了激励信号的波形、频率、幅值及波峰数的选择策略.根据弹性波的信号特征,进行了幅值衰减特性实验,研究了信号幅值随距离变化的规律与不同中心频率下的幅值变化特征,结果表明,激励信号的幅值在传播过程中随距离呈指数衰减.以ACCC/TW导线为实验对象,搭建实验平台,进行了损伤定位与损伤辨识,实验中定位的最大误差不超过4.28 cm.通过比较损伤的实际位置与结构健康监测系统的输出结果,表明所研究的系统能够有效地对ACCC导线损伤进行定位并具有良好的精度.基于功率谱密度的分析方法,实验研究了不同频率和不同损伤条件下的信号特征.结果表明,通过分析功率谱密度曲线的特征,实现了对ACCC导线不同损伤状态的辨识.

针对一台电动汽车用4极4 kW低速异步电动机,采用损耗分离法,研究计算了定子槽各尺寸对电机损耗与温度的相关程度.结合有限元法,对该电机进行电磁-热联合仿真分析.分析结果表明,在保证电机运行性能基本不变的情况下,可以通过调整槽半径、槽宽、槽口宽度、槽肩角、槽高等参数实现对电机的优化,从而有效降低电机的运行温度,提高电机的整体效率.

In order to analyze the structure stress and the current density distribution on the pulsed reactor in the course of working,the test on the stress was designed.The hoop stress on both the edge and the center of copper belt was obtained by the resistance transducer.The stress result was validated by calculating the thick wall cylinder model with the inflation pressure.To calibrate the stress value,the copper belt coil with a ballonet inside was designed.The half-bridge circuit,electrical grounding of the bridge cases and shielding wires were designed and put in practice to reduce the pulsed electromagnetic interference.The disturbance generated by the parasitic resistance and the stray capacitance was reduced by electrical grounding of the bridge cases.The experiment results show that the hoop strain is larger than the axial strain,the strain on the edge is larger than the strain in the center.Reinforcement should be applied on the edge of the copper belt.And it can be speculated that the current density on the edge is about 1.2 times near the center.

To compensate the hysteresis nonlinearity of a piezoelectric biomorph actuator,a new model with hyperbola functions was proposed to describe the Preisach type hysteresis nonlinearity,and an inverse controller was designed with the proposed model.Two hyperbola functions were used to fit the curves of hysteresis major loop and then the first-order ascending and descending branches were described by the coordinate conversion.Based on the wiping-out and congruency property of Preisach model,the minor loops were modeled by the corresponding first-order curves.As the parameters of the proposed model are much less than those of classic hysteresis models,such as Preisach model,the proposed model is suitable for the smart material systems including piezoelectric actuators.Experimental results show that the inverse controller designed with the proposed model can compensate the hysteresis of piezoelectric biomorph actuator,and the maximum control error with inverse controller has reduced by 44.26%.

To improve the accuracy of piezoelectrically driven two-dimensional micro-positioning stage,a compound control system incorporating feedforward,decoupling and feedback controllers was designed to compensate for the hysteresis of piezoelectric actuator and attenuate the coupling effect between different actuating directions.With modified Prandtl-Ishlinskii hysteresis model,two feedforward controllers were designed to compensate for the hysteresis in the x and y directions,respectively.To attenuate the coupling effect,the decoupling controller was used to estimated the coupling shift and then manipulate the voltage to counteract this shift.The compound control system incorporating feedforward,decoupling and PID feedback controllers to reduce the tracking error.Experimental result shows that the maximum absolute values of tracking error were 4.16 μm in the x direction and 4.18 μm in the y direction without control,while they were reduced to 0.06 μm and 0.07 μm,respectively,with the compound control system.It indicates that the compound control system can well compensate for hysteresis and attenuate coupling effect without modifying the structure.