电磁激励谐振式MEMS压力传感器闭环控制研究

在谐振器动力学分析的基础上,系统地比较了谐振式压力传感器检测速度谐振频率和检测位移谐振频率的优缺点.设计出一种零相移的电磁激励谐振式MEMS压力传感器闭环控制系统,该系统利用检测速度谐振频率提高传感器的信号检测稳定性,并且控制电路无需移相环节即可保证传感器在工作频率范围内实现稳定可靠的闭环自激.实验结果表明,采用该闭环控制系统的传感器具有较高的稳定性,传感器长时漂移低于0.025%F.S.,在10 hPa～1 050 hPa范围内非线性度为0.06%.     

新型模糊滑模控制器在交流位置伺服系统中的应用研究*

为解决交流位置伺服系统速度不可控的问题,利用滑动模态的控制思想,设计出一种新型速度位置一体化控制器作为位置伺服系统外环控制器。通过对速度曲线的规划,实现理想的速度控制和精确的定位。在此基础上,采用模糊控制补偿负载变化和外界扰动对系统的影响,同时柔化控制信号,减弱了滑模控制系统中固有的抖振现象。仿真结果证明了所设计控制器的正确性及控制策略的有效性。     

A MEMS-based tracking milli-mirror for high-density optical disk drives

We present a new MEMS-based milli-mirror for precise tracking in high-density optical disk drives (ODDs). The device consists of a torsionally suspended mirror plate, one pair of torsion springs, which support the mirror plate and offer a restoring torque, and two pairs of electrodes attached to the mirror plate and glass substrate. The dimensions of mirror plate and torsion springs were determined so that a 5 V dc bias ±4.5 V ac drive voltage would provide the mirror with ±0.02° rotation to transmit laser beam spot on spinning disk. The MEMS-based milli-mirror was successfully fabricated using MEMS technology. Displacement–voltage linearization scheme was implemented by differential voltage driving. The static and dynamic performances of mirror prototype, such as capacitance versus driving voltage, rotation angle versus driving voltage, and resonant frequency were characterized and compared well with the simulation solutions. The mechanical resonant frequency of the mirror is expected to be high enough to satisfy the requirement of the servo bandwidth of precise tracking-control in high-density blue-laser optical disk drive.     

On the mechatronic servo bandwidth of a stewart platform for active vibration isolating in a super antenna

As being independent of the magnitude of reference input signal, the conventional concept of servo bandwidth stemming from electronics fails to reflect the ability of the multiple degree-of-freedom (DOF) mechatronic system to perform vibration control. Considering the magnitude and frequency of reference input signal, a novel definition of mechatronic servo bandwidth of the Stewart platform-based active vibration isolator for a super antenna is proposed firstly. Then its mechatronic servo bandwidth is theoretically evaluated according to electrical and mechanical performances by using an optimization method. Experiments were conducted on the Stewart platform prototype, and the results validate the definition of and solution to the mechatronic servo bandwidth. From the application point of view, the mechatronic servo bandwidth can be employed to measure the manipulating rapidity of a multiple DOF mechatronic system and the range of vibrations that an isolator is able to overcome.     

Dynamics simulation of MEMS device embedded hard disk drive systems

Currently, hard disk drives (HDD) use rotating disks to store digital data and magnetic recording heads are flying on the disk to read/write data. The recording heads are mounted on a slider–suspension assembly, which makes heads move from one track to another on the disk. The heads movement is controlled by close-loop feedback servo systems. It is well known that dynamic behaviors of head–slider–suspension-assembly (HSA) systems are of great influence on the track per inch capacity of HDD [1, 2]. As the problem is structurally complex, it is usually investigated using experimental methods or finite element simulation models [3]. Furthermore, the dual-stage servo system has been commonly considered as one promising solution to increase the servo bandwidth of the recording positioning system for high TPI HDDS. In particular, MEMS device embedded systems are superior to others in batch-fabrication. However, this dual-stage system has also resulted in more difficulties in predicting HDD dynamic performance. This paper presents the study of the problem using the macromodeling simulation approach. It applies efficient FEM based sub-structuring syntheses (SSS) [4] and fast boundary element method (BEM) approaches incorporated with system dynamics technology to investigate the dynamic characteristics of MEMS actuator embedded HSA systems for HDD.This research is funded by the Agency for Science, Technology and Research of Singapore, Strategic Research Program. Also, the authors would like to thanks Miss Jia Wenhui, who is a Research Student with ECE Department at National University of Singapore, Mr. Lim Boon Buan, the former research engineer with Data Storage Institute, for the MEMS actuator modeling and analytical work.     

Tunable magnetic metamaterial based multi-split-ring resonator (MSRR) using MEMS switch components

The split-ring resonator (SRR) arrays are commonly used to form a negative refractive index metamaterial that exhibits an effective negative permeability. However, the region of negative permeability obtained by SRR unit cell is generally limited to a narrow bandwidth at a fixed frequency. In this paper, we present a tunable metamaterial based on multi-split-ring resonators (MSRR) with MEMS switch components to realize controllable magnetic resonant frequency. Numerical simulations are performed to validate the proposed theory and tunability. The simulated results show that the MSRR structure metamaterial can realize digital tuning mode and continuous tuning mode by controlling state and height of MEMS switch components, respectively. Moreover, the simulated results are consistent with the theoretical results, which verify that the proposed theory is effective in prediction and analysis of magnetic resonant frequency. Therefore, such a tunable metamaterial can be reconfigured into a variety of states for use in different applications.     

高精度伺服系统的ZPETC控制仿真研究

为满足数控伺服系统高精度和快速响应的性能要求,设计了一种新型零相位误差跟踪控制器,实现对象的零相位和单位幅值跟踪控制.分析了零相位误差跟踪控制算法的工作原理,证明了其控制效果的无差性.结合数控伺服系统的特性,介绍了控制系统的设计方法和控制过程.MATLAB仿真结果表明,系统具有更宽的输入频率带宽,更低的输入输出幅度和相位误差,输出信号可十分精确地跟踪正弦和随机输入信号.对于数控伺服系统及其它具有快速响应和高精度性能要求的系统,ZPETC具有很好的控制效果和广泛的应用前景.     

基于单片FGPA的谐振式光纤陀螺数字系统设计与实现

谐振式光纤陀螺（Resonator Fiber Optic Gyro,RFOG）是基于Sagnac效应产生的谐振频率差来测量旋转角速度的一种新型光学传感器,在小型化和集成化方面具有明显优势。相比于传统的模拟检测技术,数字检测技术具有稳定性好、抗干扰能力强、处理速度快和体积小、易于集成等优势。论文建立了基于单片可编程逻辑器件（Field Programmable Gate Array,FPGA）的数字RFOG系统,在单片FPGA上实现了基于比例积分控制技术的谐振频率伺服回路、用于自动反馈补偿相位调制器由于环境温度等发生变化时引起的2π复位电压漂移问题,以及体现Sagnac频差信号的第二闭环反馈控制回路。最后将研制的基于单片FPGA的闭环数字检测电路应用于实际RFOG系统,顺利验证了上述功能,并实际观测了陀螺转动信号。     

面向精密调整的6-HTRT并联机器人

为实现光学精密调整,研制出了由交流伺服电机驱动的6-HTRT并联机器人,它具有6个自由度,其结构特点决定了该机器人可以完成高精度定位调整。分析了机器人的位置逆解,并对不同位姿下的工作空间进行了仿真。控制系统采用基于ISA总线的闭环控制方式,测试结果显示:该并联机器人工作空间较大、分辨率高、重复定位精度高,说明机器人结构和控制系统设计的合理性。最后应用此并联机器人成功完成了光学精密装配试验。     

A resonant microstructure tunability analysis for an out-of-plane capacitive detection MEMS magnetometer

In this paper, the method of tuning the resonant frequency of a micro-resonant clamped–clamped beam has been successfully applied to a MEMS capacitive magnetometer. The resonant structure frequency, which presents the vital component of the sensor, was tuned by applying a bias voltage between the interdigitated capacitive comb-fingers in order to control its spring constant. It has been proved that an applied DC voltage increases the structure stiffness and as a result the resonance frequency to higher values, especially for low motion magnitude. The shifting causes were described through an accurate analytic analysis using the generated electrostatic force between movable and fixed combs, and thereafter have been proved by characterization. The measured resonance frequency of the clamped–clamped beam structure was changed by up to 38 % from the original value (around 18.2 kHz) when a bias voltage of 52 V was applied. Tuning the resonant frequency of the resonating structure has many advantages for the magnetometer since it can serve as a feedback mechanism for error compensation.

     

基于RBF神经网络补偿的直线伺服系统滑模鲁棒跟踪控制

永磁直线伺服系统具有高速、高响应和直接驱动等优点,但负载扰动、端部效应、非线性摩擦及系统参数变化会降低系统的伺服性能.为了在保证系统的跟踪性能的基础上.消除上述不确定性因素的影响,本文提出一种将变结构控制(VSC)和径向基函数神经网络(RBFNN)相结合的鲁棒跟踪控制策略.变结构控制具有快速响应,对不确定因素的不变性的优点.但是其“抖振”现象将影响直线伺服系统的平稳性和定位精度.采用径向基函数神经网络来模拟端部效应、参数变化、摩擦和外部负载等不确定因素,引入带死区的目标函数以缩短学习过程.通过RBFNN的补偿控制来减弱“抖振”输入的程度,进一步提高系统的稳态精度.仿真结果表明,该方案对直线伺服系统不确定性有很强的鲁棒性,同时,系统具有较好的跟踪性能,大大提高了直接驱动直线伺服系统的鲁棒跟踪精度.     

Improved disturbance rejection with online adaptive pole-zero compensation on a Φ-shaped PZT active suspension

In feedback control systems, the anti-resonant zeros cannot be arbitrarily placed, hence degrading tracking performance as well as input disturbance and noise rejection capabilities due to reduced gain at the frequencies of the zeros. In this paper, an online adaptive inverse control with saturation (OAICS) algorithm is proposed for compensating the minimum phase resonant poles and anti-resonant zeros of a PZT active suspension using measured position error signal. Experimental results on a Φ-shaped PZT active suspension using laser Doppler vibrometer (LDV) shows the proposed OAICS is effective in cancelling the first two dominant minimum phase pole-zero pairs to achieve high servo bandwidth and low sensitivity servo system with small overshoot during set-point tracking.     

An Active Disturbance Rejection Based Approach to Vibration Suppression in Two‐Inertia Systems

This study concerns the resonance problems found in motion control, typically described in a two‐inertia system model as compliance between the motor and the load. We reformulate the problem in the framework of active disturbance rejection control (ADRC), where the resonance is assumed to be unknown and treated as disturbance, estimated and mitigated. This allows the closed‐loop bandwidth to go well beyond the resonant frequency, which is quite difficult using existing methods. In addition, such level of performance is achieved with minimum complexity in the controller design and tuning: no parameter estimation or adaptive algorithm is needed, and the controller is tuned by adjusting one parameter, namely, the bandwidth of the control loop. It is also shown that the proposed solution applies to both the velocity and position control problems, and the fact that ADRC offers an effective and practical motion control solution, in the presence of unknown resonant frequency within the bandwidth of the control system. Finally, frequency response analysis is performed where stability margin is obtained before the simulation results are verified in the hardware experiments.     

基于遗传算法的直流伺服系统参数辨识及摩擦补偿控制

针对静态摩擦力对数控机床直流伺服系统的干扰问题,提出了一种先利用遗传算法对静态摩擦模型中的参数进行辨识,然后采用基于摩擦模型补偿的伺服控制方法。该方法首先根据直流伺服系统的摩擦特性建立摩擦模型,再将摩擦补偿引入到直流伺服系统的反馈控制结构中,获取伺服电机的位置误差。采用遗传算法对摩擦补偿模型进行参数辨识,使摩擦补偿量在数值上不断逼近实际的摩擦干扰,并利用摩擦补偿量来抵消摩擦给伺服系统带来的影响。为了验证参数辨识的效果,将普通PD控制与基于摩擦补偿的PD控制进行了仿真比较,实验结果表明,后者能够消除由于静摩擦的存在而造成的位置跟踪中出现的平顶现象,能够达到理想的跟踪效果。因此,本文所提出的方法具有较强的摩擦干扰补偿能力,能够实现对直流伺服系统的精确控制。     

基于视觉伺服的LED芯片形状匹配算法研究

LED芯片的定位是LED芯片检测、分选等后封装过程的关键步骤,其定位速度和精度直接决定了LED芯片检测设备的生产效率。为了提高芯片定位的精度,提出了基于视觉伺服的反馈补偿技术,有效补偿了芯片定位误差;为了提高芯片定位的速度,在视觉伺服系统的基础上,针对LED芯片的特点,提出形状匹配优化算法,通过减小匹配过程中匹配的面积和搜索的角度,有效弥补了因视觉运动补偿所消耗的时间。通过以上两方面提高了LED芯片定位精度和速度,满足LED芯片高精和高速的定位需求。     

基于重掺杂的谐振式传感器频率温度系数补偿研究

MEMS谐振式传感器具有精度高、准数字输出、抗干扰能力强等特点,高精度压力传感器、应力传感器等多采用谐振式工作原理.频率温度系数补偿是实现高精度谐振式传感器的关键技术.通过实验研究了利用重掺杂改善硅频率温度系数的技术.实验表明:P型掺杂浓度达到7 × 1019/cm3 时,〈110〉晶向频率温度系数降低到-11. 68 ×10-6/K;N型掺杂浓度达到6 ×1019/cm3 时,〈100〉晶向谐振频率是温度的二次函数,在80℃左右频率温度系数有过零点.首次实验演示了利用低功耗加热控制结合N型重掺杂,当环境温度由30℃变化到40℃时,谐振频率温度漂移仅为1. 13 ×10-7/℃.利用该技术可实现超高温度稳定性的谐振式传感器.     

基于APT控制技术的Ku/Ka双频机载动中通系统设计

随着航空用户对上网需求的逐步增加,结合航天制造、卫星通信及惯性稳定平台技术,设计了一种基于APT控制技术的Ku/Ka双频机载动中通系统。该系统具有较高的高动态响应及精准卫星捕获、跟踪能力；APT控制技术融合陀螺稳定、漂移补偿、多数据融合及精准伺服控制关键技术,系统采用程序跟踪、动态跟踪控制策略,可根据ModMan控制指令在不同载体扰动情况下迅速完成Ku、Ka天线切换及对星,保障链路通信正常,以最佳带宽服务理念为航空用户提供多层次通信服务保障。目前已完成样机研制和地面跑车模拟、摇摆台试验,技术指标符合总体设计要求具有良好的应用前景。     

伺服系统时域特性与频域带宽的算法研究

为了通过伺服系统时域特性计算频域带宽,并提高带宽测算的精确度,针对实际的高阶非线性伺服系统,借助典型二阶线性控制系统时域与频域指标间的明确关系式,研究了两种由时域性能指标计算频域带宽的算法,并通过对两种算法的误差分析,利用"夹逼"原理,推导了带宽最终计算公式,经在多种军用雷达上的测试试验证明,具有较高的计算精度和实用性.     

A reinforced learning control using iterative error compensation for uncertain dynamical systems

This paper investigates a learning control using iterative error compensation for uncertain systems to enhance the precision of a high speed, computer-controlled machining process. It is specially useful in mass-produced parts produced by a high-speed machine tool system. This method uses an iterative learning technique which adopts machine commands and cutting errors experienced from previous manoeuvres as references for compensation actions in the current manoeuvre. Non-repetitive disturbances and nonlinear dynamics of the cutting processes and servo systems of the machine which greatly affect the convergence of the learning control systems were studied in this research. State feedback and output feedback methods were used for controller design. Stability and performance of learning control systems designed via the proposed method were verified by simulations on a single degree of freedom servo positioning system.     

Fourier-Neural-Network-Based Learning Control for a Class of Nonlinear Systems With Flexible Components

This paper considers an output feedback learning control for a class of uncertain nonlinear systems with flexible components. The distinct time delay caused by system flexibility leads to the phase lag phenomenon and low system bandwidth. Therefore, the tracking problem of such systems is very difficult and challenging. To improve the tracking performance of such systems, an iterative learning control scheme using the Fourier neural network (FNN) is presented in this paper. This scheme uses only local output information for feedback. FNN employs orthogonal complex Fourier exponentials as its activation functions and the physical meaning of its hidden-layer neurons is clear. The FNN-based learning controller introduced here relies on the frequency-domain method, which converts the tracking problem in the time domain into a number of regulation problems in the frequency domain. A novel phase compensation method is introduced to deal with the phase lag phenomenon, so that the bandwidth of the closed-loop system is increased. Experiments on a belt-driven positioning table are conducted to show the effectiveness of the proposed controller.