Collision prevention of eccentric proof mass applied for micro-gyroscope

An innovative 3-phase AC (Alternative Current) drive circuit for the seismic disc in micro-gyroscopes is designed and verified by computer simulations and experiments. The in-plane dynamic model of the seismic disc with mass eccentricity and air gap against the centre bearing and the mathematic expression of two sinusoidal magnetic fields are developed respectively. In order to prevent the seismic disc from collision with the centre bearing and the EM (Electromagnetic) poles, an anti-collision controller is established by employing two Look-up tables which define the intensity of the applied current to the EM poles. Self-sensing technique is included to measure the real-time offset and angular position deviation (i.e., precession) of the disc by two orthogonal pairs of EM poles, without any additional sensors. The drive circuit under SPWM (Sinusoidal Pulse Width Modulation) operation and the anti-collision strategy are verified by intensive computer simulations via commercial software, OrCAD 9, and experiments.     

整体双层盘式永磁涡流联轴器及其转矩特性分析

基于对传统单层盘式永磁体涡流联轴器的磁路分析,设计了一种整体双层盘式永磁体涡流联轴器。该联轴器将两个单层盘式永磁涡流联轴器的永磁体以N-S对应的方式安装到一块背铁的正反面上,减小了背铁磁阻在磁路中带来的损耗,提高了永磁体的磁能利用率,增大了转矩。通过等效磁路法建立该结构的数学模型,并与有限元法仿真模型相结合,综合分析了其转矩特性。搭建了该永磁涡流联轴器的样机,通过实验验证了上述分析的可靠性。结果表明：所建数学模型准确,并且该联轴器的转矩相对于传统永磁涡流联轴器转矩有较大提高。     

电动轮式小车控制系统设计与可靠性分析

针对电动轮式小车驱动控制及可靠性问题,建立了动力、转向驱动控制系统。设计了一种电动轮式小车的动力及转向系统,并对其可靠性进行了分析和实验验证。动力部分由STM32作为主控制器,通过基于全桥驱动芯片IR2136的驱动电路对4个无刷直流电机进行驱动控制,转向部分由基于半桥驱动芯片IR2103的驱动电路驱动2个有刷直流电机进行转向控制,控制系统采用速度环、电流环双闭环,算法上采用模糊自适应比例-积分-微分(proportion integration differentiation,简称PID)算法。对系统可靠性进行实验并分析的结果表明,能够很好地跟随负载以及降低启动电流,使小车可靠运行。此驱动控制系统负载能力良好,启动电流小,安全稳定,转向精确,满足设施农业作业需求。     

圆形可倾瓦与扇形瓦推力轴承性能的比较

应用有限元程序分别对圆形瓦和扇形瓦推力轴承在中心支承条件下的性能进行了计算。并根据计算结果对两种瓦形的轴承性能作了比较。其结果和实验结论比较一致。最后得出圆形瓦轴承比扇形瓦轴承在某些方面有一定的优越性。     

内外侧铰点耙爪的特性分析

利用计算机模拟方法，得到了铰点设在转盘中心内、外例耙装机构的运动轨迹、速度和加速度，以及受力变化情况，并比较分析了两种布置方式耙装机构的特征，为评价和研究不同布置方式下耙装机构的性能提供了方法和依据。     

大功率IGBT在广州地铁三号线列车牵引系统的应用

通过对广州地铁三号线列车牵引系统中IGBT(绝缘栅双极晶体管)控制电路、驱动电路的介绍,展现了其控制电路简单、高耐压及承受电流大的特性,及其集成驱动电路的高性能、高可靠性及体积小的优点。     

高能球磨机变频调速电路设计

针对高能球磨机的运转控制特性,设计了一种交流变频调速电路。主电路采用IGBT功率器件构成的三相桥式SPWM逆变器,控制电路采用16位单片机87C196MC作为控制核心,IR2130作为驱动电路;用该变频调速电路控制Y801—2三相异步电动机,当频率在0.5-50Hz变化时,可实现Y801—2三相异步电动机在28．5-2850r／min转速范围内的无极调速。系统工作稳定,较好地满足了高能球磨机的变频调速需求。     

Effect of Disk Flexibility on Rocking Mode Frequencies of a Disk Drive Spindle Motor System

The lowest natural frequency of a hard disk drive related to a spindle motor is the so-called “rocking mode,” the frequency at which the rotor of the motor is whirling conically. A traditional rotordynamics theory with thick/rigid disks is not able to predict the rocking mode frequencies correctly. In this paper, the rocking mode frequencies of a single-disk rigid-rotor motor were solved analytically, including the effects of disk flexibility and ball bearing contact angle. In addition, the disk flexibility model was integrated to a finite element-based (FEM) flexible-shaft rotordynamics computer program. The closed-form solution of the analytical model provides design engineers a tool to identify critical design parameters. It was found that the rocking mode frequency, which is mainly affected by the clamped condition at the inner radius of the disk, is the flexible disk one-nodal-diameter mode frequency reduced by the compliance of ball bearings. The results obtained from both the analytical model and the FEM computer program matched the experimental results with an error less than two percent. Neglecting the effect of ball bearing contact angle increases the error three times. The effects of design parameters were also investigated.     

恒高拖靶舵机系统的设计

为了实现某型掠海恒高拖靶系统的高度控制功能,设计了舵机执行机构和舵回路控制电路。舵机执行机构由组合式螺杆驱动系统、滑动块、支撑架、摇臂及翼角反馈电位器等组成。舵回路控制电路由电流环和位置环组成的双闭环控制结构。针对具体性能指标要求,采用了螺旋滑动丝杠传动机构,确定了牙形角、公称直径和导程等参数,并计算了螺母和螺纹的长度,验证了机构自锁条件;通过对减速比的计算,选择了合适的减速箱型号;通过对电机功率及速度常数的计算,参照电机样本数据表资料,完成了电机的正确选型,并进行了指标验算;设计了以1292功放模块为直流电机驱动器的舵回路控制电路,并对位置反馈和电流反馈作了简要说明。实际使用结果表明,该设计合理、可靠,各项性能能够满足使用要求。     

基于FPGA的光栅莫尔信号正弦性误差补偿电路研制

针对光栅莫尔信号正弦性误差对细分结果造成影响问题,对基于粒子群算法(PSO)的光栅莫尔信号正弦性误差补偿方法展开研究。在量化分析信号正弦性误差引入的细分误差的基础上,对基于PSO算法的正弦性误差补偿方法进行阐述。设计基于FPGA的补偿算法实现电路,对实现过程中的关键问题进行分析并提出解决方案。最终在FPGA电路板上对实际信号进行算法电路有效性验证,结果表明,应用该电路能有效地补偿信号正弦性误差,将信号的细分误差峰峰值由0.7″降低到0.14″。     

Anti-windup embedded magnetic actuator applied for near-high-speed milling

A fuzzy anti-windup (AW) compensator is proposed and applied to the embedded cylindrical-array magnetic actuator (ECAMA) to ensure the superior performance of spindle position regulation for milling machines under actuator saturation. Since ECAMA is a type of active magnetic bearing (AMB), the supplied coil current and the induced magnetic force are both limited by the maximum current and power output of the AMB and the associated amplifier. Once the magnetic actuator is saturated, the required control input cannot be realized by ECAMA and may lead to drastic tremble of spindle position. In this work, an AW compensator, based on fuzzy logic algorithm, is therefore proposed to rectify the control input to ECAMA. By employing commercial software MATLAB/Simulink and signal processing interface, Module DS1104 by dSPACE, the efficacy of the fuzzy AW compensation is practically verified by intensive experiments.     

Mode-selective ultrasonic wave sensor and its characteristics

A magnetostrictive sensor is proposed that can selectively measure the specified mode among two kinds of elastic waves transmitted through a ferromagnetic shaft, and its various characteristics are examined by experiments. The magnetic circuit of the proposed sensor is configured by using permanent magnets and its mode selection is accomplished by only reversing the poles of the permanent magnets. By means of finite element analysis, the validity of the proposed sensor is verified. Prototype sensors are made and their sensitivity and linearity are investigated as basic characteristics. The results show the proposed sensors are able to measure the target mode waves with good sensitivity and linearity. By exciting undesirable modes of waves intentionally, it is verified that the sensor can measure the target modes and reject the undesirable wave modes considerably.     

一种基于小型空压机的直驱系统

针对气动系统能量效率低这一主要问题,提出一种气动系统节能的新方法。其思想是通过使用小型气泵直接驱动执行机构,形成闭式回路,循环利用执行机构腔内已经产生的高压气体,消除传统回路的排气阶段。首先设计了小型空压机直接驱动的气动回路,搭建了相应的闭式回路实验台;其次,开展不同工况下气缸往复运动实验研究,验证原理上的可行性;然后,针对直驱系统的问题进行回路改进以满足系统所需的空气量及响应要求;最后,通过实验验证了直驱系统的节能特性。结果表明,所提出的直驱系统相比传统回路运行简单且能提高气动系统的能量效率。     

瞬变载荷作用下滑动轴承轴心轨迹计算仿真

为了研究动压滑动轴承在瞬变载荷作用下的润滑状况,在考虑轴颈惯性力和非线性油膜力的基础上,建立了滑动轴承轴心轨迹的运动方程,提出了采用欧拉法求解有限长滑动轴承瞬时轴心轨迹的数值方法。分别计算了在阶跃、矩形脉冲和正弦脉冲瞬变载荷作用下轴心轨迹、最大油膜压力及最小油膜厚度的变化规律。分析结果表明,在瞬变载荷作用时,轴心轨迹、最大油膜压力及最小油膜厚度都有较大的变化并呈现出一定的振荡过程。由于脉冲载荷的作用时间有限,随着其消失,轴心乃收敛于原平衡位置,而阶跃载荷则使轴心收敛于新的平衡位置。     

介电型电活性聚合物圆柱形驱动器的驱动效率

研究了介电型电活性聚合物(DEAP)驱动器的机电能量转换机理、能量损耗和驱动效率。建立了驱动器机电能量转换模型,并通过试验测算了驱动器等效电路的模型参数,分析了电极材料等因素对DEAP相对介电常数的影响。深入研究了驱动器漏电流损耗,试验验证了漏电流对驱动器性能的影响。最后,设计了驱动器驱动试验台,完成了不同行程的准静态驱动试验,数值计算了驱动器的驱动效率。结果表明:由于等效电路电容未参与能量转换,驱动器机电转换效率分别为17.6%和25.6%。低电压、小行程驱动时,试验误差与理论分析误差不超过15%;而高电压、大行程驱动时,DEAP膜的漏电流等非线性因素使其驱动效率变化明显。该结果可为DEAP圆柱形驱动器的优化设计及合理使用提供指导。     

基于电流传送器的正弦波振荡电路

提出了一种基于电流传送器的RC正弦波振荡电路。该电路只采用一个第二代电流传送器、两个电容和三个电阻，电路结构简单。本文详细分析了振荡器起振条件和振荡频率。理论分析与仿真结果表明，电路振荡频率可调且频率稳定。     

Statistical description of the sine-wave frequency estimator provided by the interpolated DFT method

This paper describes the effect of the spectral interference and wideband noise on the accuracy of the sine-wave frequency estimator provided by the Interpolated Discrete Fourier Transform (IpDFT) method based on some commonly used cosine windows. It is shown that the spectral interference contribution from the image component has a sinusoidal behaviour with respect to the sine-wave phase and the expression for its amplitude is derived. Also, a simple expression for the variance of noise contribution is derived. Based on the achieved results, the Probability Density Function (PDF) of the sine-wave frequency estimator is obtained. The accuracy of each expression derived in the paper is verified by means of computer simulations. Furthermore, the accuracy of the PDF of the sine-wave frequency estimator is verified by means of experimental results.     

STOCHASTIC PROGNOSTICS FOR ROLLING ELEMENT BEARINGS

The capability to accurately predict the remaining life of a rolling element bearing is prerequisite to the optimal maintenance of rotating machinery performance in terms of cost and productivity. Due to the probabilistic nature of bearing integrity and operation condition, reliable estimation of a bearing's remaining life presents a challenging aspect in the area of maintenance optimisation and catastrophic failure avoidance. Previous study has developed an adaptive prognostic methodology to estimate the rate of bearing defect growth based on a deterministic defect-propagation model. However, deterministic models are inadequate in addressing the stochastic nature of defect-propagation. In this paper, a stochastic defect-propagation model is established by instituting a lognormal random variable in a deterministic defect-propagation rate model. The resulting stochastic model is calibrated on-line by a recursive least-squares (RLS) approach without the requirement of a priori knowledge on bearing characteristics. An augmented stochastic differential equation vector is developed with the consideration of model uncertainties, parameter estimation errors, and diagnostic model inaccuracies. It involves two ordinary differential equations for the first and second moments of its random variables. Solving the two equations gives the mean path of defect propagation and its dispersion at any instance. This approach is suitable for on-line monitoring, remaining life prediction, and decision making for optimal maintenance scheduling. The methodology has been verified by numerical simulations and the experimental testing of bearing fatigue life.     

Investigation of the physical mechanisms in rolling bearings during the passage of electric current

With the increasing use of frequency converters as control units for electric motors, bearing failures caused by the passage of electric current through the bearings are more common. This paper discusses the most relevant parasitic current loops in frequency converter‐driven motors that can lead to damage of bearing raceways or deterioration of lubricants. Electrical stray capacitances, which are inevitably present in any electric motor, in combination with the high‐frequency components of the drive voltages, have been identified as the source of electric discharge machining (EDM) currents. Based on an EDM equivalent electric circuit, the passage of electric current through the rolling contact of a bearing is simulated. A set‐up is introduced to initiate EDM processes in bearings under well‐controlled electrical and mechanical conditions. The effect of EDM currents on bearing elements in the presence of different lubricants is studied. Initial results are presented.     

电磁轴承-刚性转子系统轴承传递力主动控制

针对电磁轴承支承的刚性转子系统轴承传递力的主动控制,分析了轴承传递力的组成,基于一种变步长三角形迭代搜寻算法辨识出转子位移中同频分量的方法构建了零电流控制及零传递力控制策略,分别在恒定转速和匀加速运动过程中对两种控制策略的有效性进行了仿真分析,最后在某磁悬浮高速飞轮储能系统上进行了试验验证。理论与试验结果表明,零电流控制策略能对绝大部分轴承传递力进行抑制,零传递力控制策略能对轴承传递力进行完全消除。