Efficiency characteristics of piezostack pump for linear actuators

A piezostack pump for linear actuators is presented and studied in terms of mechanical energy efficiency (MEE), energy conversion efficiency (ECE) and design method. MEE is defined as the ratio of the output mechanical energy to that converted from input electrical energy, and ECE is the ratio of output mechanical energy to input electrical energy. The analysis results show that both MEE and ECE decrease with the increase of stiffness of the chamber diaphragm (k _s), which is a function of the radius ratio (rigid disk radius to chamber radius). There is respective optimal external load (F _c) for them to achieve peak value for a given piezostack with blocked force (F _b) and stiffness (k _a). The optimal force ratio (F _c/F _b) is a constant of 0.5 for maximum MEE, and between 0.57 and 0.5 for maximum ECE. Considering the deflection of the pump chamber and dynamic response of the piezostack, the stiffness ratio (k _s/k _a) should be limited between 0.3 and 1, and the relative radius ratio is between 0.7 and 0.8. With the increase of the radius ratio in the range, the maximal MEE decreases from 0.38 to 0.25, and the peak ECE decreases from 0.20 to 0.14.     

压电叠堆泵驱动的新型直线马达

提出一种利用压电叠堆泵驱动的新型直线马达(简称压电液压马达),介绍了其系统构成及工作原理,并进行了理论及试验研究.理论分析结果表明,压电液压马达的性能是由压电振子/泵腔/截止阀/液压缸的结构尺寸、负载及工作频率等多种要素共同决定的,只有当相关要素合理配置时才能实现压电液压马达的预期功能.在其他参数确定的情况下,当负载为其最大驱动力的二分之一时输出功率和能量最大.利用尺寸为4 mm×4 mm×80 mm的压电叠堆制作了腔体直径为30 mm的压电泵,并对其直接输送流体及驱动液压缸时的流量、压力及功率等性能进行了测试与对比分析.结果表明,采用直径为15 mm的液压缸时,压电液压马达的最大速度、推力及功率分别为12.5 mm/s、32 N和93 mW.     

燃料电池汽车机电制动力分配策略

文章对燃料电池汽车机电制动分配控制方法进行研究,以ECE法规和理想制动力分配曲线为依据,提出常规气压制动与电机制动协调控制的方法,建立相应的机电制动力分配模型,并采用MATLAB/Simulink软件进行仿真分析。结果表明,该控制策略与理想制动力分配策略和最大化能量回收策略相比,既能充分利用电机制动力,提高制动能量回收效率,又能保证整车制动的安全性和舒适性。     

电比例斜盘式恒压柱塞泵的联合仿真与特性研究

为了研究电比例斜盘式恒压柱塞泵的动静态特性，在分析其工作原理、运动特性和流量特性的基础上，利用SimulationX软件搭建恒压泵的机械、液压联合仿真模型进行研究，分析了变量缸大小腔直径比、变量缸弹簧刚度和主控压力阀的阀芯直径对恒压泵动态特性的影响。研究结果表明：电比例斜盘式恒压柱塞泵泵具有良好的动静态特性；主控压力阀阀芯直径越大，压力稳态值越接近设定压力值；弹簧刚度的增大和变量缸大小腔直径比值的减小都会提高恒压泵的动态响应速度，但超调量也会随之增大。     

压电单晶梁发电机的能量效率

压电发电装置的能量转换效率主要取决于其结构形式、几何参数及材料性能等.为提高压电发电机的机电能量转换效率及其发电能力,利用欧拉一伯努利方法建立了发电装置的能量转换模型,研究了结构及参数等对压电发电机能量转换效率及发电能力的影响规律.结果表明,存在最佳厚度比(基板/总厚)可使发电机获得最大的能量转换效率和发电量;随杨氏模量比(基板/陶瓷)的增加,最佳厚度比降低,但效率提高.钼、铝基板发电机的最佳厚度比和效率分别为(O.4,2.74%)和(O.7,2.25%).此外,压电发电机的发电能力还与激励方式有关,恒力激励时存在的最佳杨氏模量比使产生的电量最多,恒位移激励时产生的电量随杨氏模量比的增加而增加.因此,设计时应根据激励方式确定基板的材料及合理的厚度比.     

一种新型单腔双振子压电泵的结构设计和性能试验

为优化单腔双振子压电泵的结构,提高输出性能,设计了一种新型结构的单腔双振子压电泵。将新设计结构同前期设计结构进行了比较,并对两种结构的试验样机进行了输出流量测试。试验显示,新结构的输出流量是前期结构输出流量的2倍,最大流量可达800mL/min。将新结构加工了不同腔体初始容积样机,得到了压缩比对泵输出性能的影响。试验发现,当腔体高度为1.2mm,工作时的压缩比为1/46,此时单腔双振子压电泵整体输出效果最好。分析了单腔双振子压电输送液体和气体时工作特点,得到泵输送液体介质时最佳工作频率点远远低于输送气体介质。     

不同容积比的双腔串联压电泵测试分析

为提高双腔串联压电泵的输出性能,对泵的进口腔与出口腔的容积比进行了优化设计。分别设计了容积比为1.9、1.5、1.3三种串联压电泵样机,并对样机进行了试验测试。试验结果显示,采用增加容积比的方式可以提高双腔串联压电泵的输出流量,但不能提高其输出压力;对每个不同腔体容积比的双腔串联压电泵在异步驱动和同步驱动下进行了输出性能测试,测试结果显示,当输送气体时,两种驱动方式均有很好的流量输出,且输出结果比较接近,但仅有异相驱动时才能输出液体。分析结果为提高双腔串联压电泵的输出性能提供了很好的依据。     

Performance analysis of piezoelectric bimorph generator

In this paper, the theoretical model and simulation of the performance of a piezoelectric (PZT) bimorph generator is introduced. The generator consists of two piezoelectric plates bonded on a substrate metal plate. For an effective electromechanical coupling coefficient (EECC) and the generated energy, the analytical formulae are established with the thickness ratio and the Young’s modulus ratio as variables. After giving correlative material parameters, the EECC and generated energy can be computed. The results show that there is a optimal thickness ratio for a piezoelectric bimorph generator to achieve the maximum EECC and electrical energy. The EECC and generated energy decrease with an increase of the Young’s modulus ratio. In addition, the influence of mechanical source on electrical energy generation and power output is also considered.     

Performance analysis of piezoelectric bimorph generator

In this paper, the theoretical model and simulation of the performance of a piezoelectric (PZT) bimorph generator is introduced. The generator consists of two piezoelectric plates bonded on a substrate metal plate. For an effective electromechanical coupling coefficient (EECC) and the generated energy, the analytical formulae are established with the thickness ratio and the Young’s modulus ratio as variables. After giving correlative material parameters, the EECC and generated energy can be computed. The results show that there is a optimal thickness ratio for a piezoelectric bimorph generator to achieve the maximum EECC and electrical energy. The EECC and generated energy decrease with an increase of the Young’s modulus ratio. In addition, the influence of mechanical source on electrical energy generation and power output is also considered.     

微型摆式内燃发电机的循环能量分析及效率计算

微型摆式内燃发电机(M ICSPG)是微型摆式内燃机和发电机的有机集成体。在左、右燃烧室的交替驱动下,M ICSPG通过自由活塞组件(SFPA)的往复摆动,实现燃料的化学能和电能的直接转换。本文从M ICSPG的一个工作循环着手,按照能量的输入、流动、耗散及输出的传递过程,剖析了M ICSPG中能量的转换规律;并以此为基础,估算了M ICSPG的效率、平均输出功率、SFPA的最大瞬时速度等特性参数。研究结果对M ICSPG中各能量组件依存关系的理解、控制系统的设计、工作特性及效率的提高提供了有益的参考。     

容积伺服一体化系统泵控单元传递效率特性

电液伺服泵控单元是容积伺服一体化电液系统的重要组成部分,由伺服电机与双向闭式泵集成于一体。电液伺服泵控单元作为整个系统的动力输入与控制单元,其自身的传递效率直接影响了系统的输出效率,所以电液伺服泵控单元的能量传递效率已经成为了衡量该系统性能的一个重要指标。通过建立容积伺服一体化电液系统数学模型,重点分析影响伺服电机与双向闭式泵传递效率的各种能量损耗,得到电液伺服泵控单元效率模型,并对电液伺服泵控单元在不同负载工况下进行了效率特性测试,将为容积伺服一体化电液系统的工程推广应用奠定基础。     

新型高效脱硫泵的研制

基于固液两相流泵设计方法,采用叶片进口超长延伸及叶片极大扭曲的方法来设计叶轮,压水室设计为螺旋形双流道;结构上创新地设计了压水室耐磨板间隙自动补偿装置和叶轮轴向位移调节装置,机械密封采用集装式结构,轴承箱设计为可放气式结构,进而设计了一种新型高效的脱硫泵。采用自行研制的M26-23V合金钢,用熔模铸造工艺进行加工,并对脱硫泵的性能进行了检测。结果表明,泵的各项指标都满足设计要求,泵的额定点效率达到85.28%,该泵设计合理,效率高,性能曲线平坦,高效率区宽,有无过载特性,且耐磨性能好,使用寿命比同类产品提高了25%以上。该泵的研制成功,对于促进我国脱硫泵的国产化、电力行业的节能减排以及行业的经济效益和社会效益的提高具有重要的现实意义。     

A valveless piezoelectric pump with novel flow path design of function of rectification to improve energy efficiency

Existing valveless piezoelectric pumps are mostly based on the flow resistance mechanism to generate unidirectional fluid pumping, resulting in inefficient energy conversion because the majority of mechanical energy is consumed in terms of parasitic loss. In this paper, a novel tube structure composed of a Y-shaped tube and a ȹ-shaped tube was proposed considering theory of jet inertia and vortex dissipation for the first time to improve energy efficiency. After verifying its feasibility through the flow field simulation, the proposed tubes were integrated into a piezo-driven chamber, and a novel valveless piezoelectric pump with the function of rectification (NVPPFR) was reported. Unlike previous pumps, the reported pump directed the reflux fluid to another flow channel different from the pumping fluid, thus improving pumping efficiency. Then, mathematical modeling was established, including the kinetic analysis of vibrator, flow loss analysis of fluid, and pumping efficiency. Eventually, experiments were designed, and results showed that NVPPFR had the function of rectification and net pumping effect. The maximum flow rate reached 6.89 mL/min, and the pumping efficiency was up to 27%. The development of NVPPFR compensated for the inefficiency of traditional valveless piezoelectric pumps, broadening the application prospect in biomedicine and biology fields.     

基于圆弧限位的压电发电装置

提出一种基于圆弧限位压电发电装置来提高发电能力及可靠性。介绍了该装置的结构及工作原理,建立了其机电能量转换模型。通过模拟仿真分析获得了压电振子厚度比（基板与总厚度比）对最小限位圆弧半径及能量、及压电振子厚度和限位圆弧半径对电压及能量的影响规律。结果表明,最小限位圆弧半径随厚度比的增加而线性减小,且存在共同的最佳厚度比（0.35）使不同厚度压电振子的输出电压和能量最大;在最佳厚度比时,输出电压和能量随压电振子厚度增加或限位圆弧半径降低而增加。制作了一组限位圆弧半径不等的发电装置,并进行了相关试验测试。结果表明,压电振子的最大输出电压（变形量）仅与限位圆弧半径有关,故采用最小限位圆弧半径可同时获得最大的发电能力和较高的可靠性。     

利用体块PZT制备膜片式压电微泵

利用锆钛酸铅(PZT)的逆压电效应,设计并制备了膜片式压电微泵。通过将电能转换为机械能,实现了液体的微流体控制。微泵由微驱动器与单向微阀两部分组成;微驱动器主要为液体流动提供驱动力,单向微阀则用于精确控制液体的流动方向。通过对PZT-Si膜片的位移量、位移形状的仿真分析,确定了微驱动器的设计尺寸,并估算其液体驱动性能。利用共晶键合工艺、研磨减薄工艺、硅深反应离子刻蚀工艺和准分子激光加工工艺等制备出了微驱动器和单向微阀。最后,设计了驱动测试实验,检测了微泵的液体驱动性能。测试结果表明:所制备的膜片式压电微泵驱动的谐振频率约为70kHz,能驱动微米量级的液体位移或运动。当微泵驱动电压为30Vp-p、频率为600Hz时,液体的驱动流速约为65μL/min。该微泵具有体积小,线性度好等特点。     

Optimal Motion Planning for Differentially Flat Underactuated Mechanical Systems

Underactuated mechanical system has less independent inputs than the degrees of freedom(DOF) of the mechanism. The energy efficiency of this class of mechanical systems is an essential problem in practice. On the basis of the sufficient and necessary condition that concludes a single input nonlinear system is differentially flat, it is shown that the flat output of the single input tmderactuated mechanical system can be obtained by finding a smooth output function such that the relative degree of the system equals to the dimension of the state space. If the fiat output of the underactuated system can be solved explicitly, and by constructing a smooth curve with satisfying given boundary conditions in flat output space, an energy efficiency optimization method is proposed for the motion planning of the differentially fiat underactuated mechanical systems. The inertia wheel pendulum is used to verify the proposed optimization method, and some numerical simulations show that the presented optimal motion planning method can efficaciously reduce the energy cost for given control tasks.     

泵阀并联进出口独立系统特性

为结合阀控系统响应快和泵控系统能效高的优点,并减少传统四边联动阀带来的节流损失,提出一种泵阀并联进出口独立控制系统方案,应用于某6 t液压挖掘机动臂及斗杆系统。建立多学科联合仿真模型,设计泵阀协同驱动控制策略,研究了阀控单元与泵控单元输出功率比对系统特性的影响,并应用泵控单元消除了多执行器载荷差异带来的节流损失,对比分析传统进出口独立控制系统与所提系统的运行特性和能耗特性。仿真结果表明,增大阀控单元输出功率占比,可提高系统动态响应;增大泵控单元输出功率占比,可有效减少系统能耗。与传统进出口独立控制系统相比,该系统可减小节流损失90%,降低系统能耗41%,并改善重载执行器响应滞后现象。     

Vane tip detachment in a positive displacement vane pump

This paper reports on the theoretical study of the transient chamber, pressure and vane motion in a positive displacement vane pump which widely used in the automotive power steering systems. For analyzing the vane detachment, dynamic equation of vane motion and flow continuity equations are derived and then solved simultaneously using the numerical integration. Vane detachment is shown to be a function of the chamber pressure, rotational speed, and the design geometry of pump. Vane detachment occurs due to excess compression of chamber volume, and it can be reduced by adjustment of design parameters. Specially, silencing V-groove in side plate and radius reduction ratio of compression zone in the cam ring are important design factors for reducing the vane detachment.     

Vibration control efficiency of piezoelectric shunt damping system

The piezoelectric shunt damping technique based on the direct piezoelectric effect has been known as a simple, low-lost, lightweight, and easy to implement method for passive damping control of structural vibration. In this technique, a piezoelectric material is used to transform mechanical energy to electrical energy. When applying the piezoelectric shunt damping technique to passively control structural vibration, the piezoelectric materials must be bonded on or embedded in host structure where large strain is induced during vibration, thus to ensure vibrational mechanical energy to be transformed into electrical energy as much as possible. In this paper, the concept of vibration control efficiency of a piezoelectric shunt damping system is proposed and studied theoretically and experimentally. In the study, PZT patches are used as energy converter, and the vibration control efficiency is expressed by the vibration reduction rate per area of the PZT patches. Emphasis is laid on the effect of the generalized electromechanical coupling coefficient K₃₁ on the vibration control efficiency. Four PZT patches with different sizes are bonded on the geometrical central area of four similar clamped aluminum plates, respectively, and vibration control experiments are conducted for these plates using the R-L shunt circuit. The results indicate that the bigger the coupling coefficient K₃₁, the larger the rate of vibration reduction, and hence, the higher the vibration control efficiency. It also shows that the vibration responses of the first mode of the plates bonded with different PZT patches can be reduced by about 30.5%，48.58%，85.47%, and 89.91%, respectively. It comes to a conclusion that the vibration control efficiency of the piezoelectric shunt damping system decreases with the increase of the area of the PZT patch, whereas the vibration reduction of the plate increases with the area of the PZT patch. Therefore, it is necessary to make topology optimization for the PZT patch in the vibration control utilizing the piezoelectric shunt damping technique.     

差分吸收NO_2激光雷达波长漂移和能量波动对浓度反演的影响

为评估差分吸收二氧化氮激光雷达中激光器的稳定性对反演浓度的影响,以NO_2的吸收谱和激光雷达方程为基础,分析了波长漂移和能量波动对距离分辨差分吸收激光雷达浓度反演带来的相对误差。采用两台Nd:YAG激光器的354.7nm波长分别泵浦两台染料激光器的方式,产生差分吸收探测所需的两个波长λon(448.10nm)和λoff(446.80nm),搭建探测大气NO_2实验系统,并就波长漂移和能量波动对NO_2浓度反演影响进行了实验验证。实验结果表明:在没有稳频条件下,当λon和λoff波长漂移≤0.005nm时,引起的浓度相对误差为≤3%;能量波动对反演浓度没有影响,但能量降低减小探测距离,当能量下降≤5%时,探测距离≤100m,实验结果与理论计算基本一致。最后,开展了大气NO_2浓度实验观测,获得实验期间水平及垂直高度0.5~3km内NO_2浓度的分布廓线,系统稳定可靠。本方法为实用化NO_2差分吸收激光雷达的设计及应用提供了理论依据及技术支持。