散布式磁致伸缩平板扬声器研制

为了改善现有单个超磁致伸缩驱动器平板扬声器输出功率及音色方面的不足,提出了基于超磁致伸缩驱动器(GMA)的散布式多点配置平板扬声器设计.研究了用于新型散布式多点配置平板扬声器的音频驱动器的设计,分析了超磁致伸缩平板扬声器多点配置原理,并讨论了音板材料的选择,最后利用专业测试软件对研制的散布式多点配置磁致伸缩扬声器进行了性能测试.结果显示,与单点驱动扬声器相比较,该扬声器音显而易见提高,音质得到了进一步的改善.     

Active vibration control of trim panel using a hybrid controller to regulate sound transmission

This paper presents a method for actively controlling the sound transmission through an aircraft trim panel using a hybrid feedforward/feedback control technique. The method involves measuring the frequency transfer function of the trim panel system and then creating an autoregressive moving average model using frequency domain curve fitting. The control technique is designed to minimize the vibration of a panel that has a limited piston-like motion. The hybrid controller consists of an adaptive feedforward controller that operates in conjunction with a linear quadratic Gaussian feedback controller. The feedback controller increases the damping capacity of the secondary plant to augment the convergence rate of the adaptive feedforward controller. Experimental results indicate that the hybrid controller effectively reduces the vibration of active trim panels and therefore also reduces the sound transmission of the panel.     

主动噪声控制技术及其在车内噪声控制中的应用

主动噪声控制是集声学、自适应控制及数字信号处理等技术为一体的高新技术,已成为国内外噪声控制界的研究热点。基于主动噪声控制的Swinbanks多极子系统理论,证明了主动噪声控制技术适合于低频．1k的理论依据。阐述了决定主动噪声控制效果的决定因素及在车内噪声控制中应用的发展过程,并指出当前研究中需解决的问题和今后的研究方向。     

基于EMD与响度的有源噪声控制系统

为了提高有源噪声控制系统的降噪效果,提出了基于经验模态分解( empirical mode decomposition,EMD)和响度的控制系统.该系统首先采用EMD方法对噪声源进行自适应分解,并对分解后的各个固有模态函数(intrinsic mode function,IMF)分量的响度进行计算,然后根据各个分量的响度大小进行残差滤波器的设计.与基于A计权曲线设计的残差滤波器相比,该方法所设计滤波器能更好地抑制响度较小的信号频率成分.对有源噪声控制系统的降噪效果进行了仿真,结果表明,所提出的控制系统比传统滤波-X LMS(filtered-X least mean square)方法和采用基于A计权残差滤波器的系统降噪效果更好.     

Clad height control in laser solid freeform fabrication using a feedforward PID controller

In this paper, a feedforward proportional-integral-derivative (PID) controller is developed to effectively control the clad height in laser solid freeform fabrication (LSFF). The scanning velocity is selected as the input control variable and the clad height is chosen as the output. A novel knowledge-based Hammerstein model, including a linear dynamic and a nonlinear memoryless block, is developed, and its parameters are identified offline using experimental data. The architecture of the controller consists of a PID and a feedforward module, which is the inverse of the identified model. The advantage of adding a feedforward path to the PID controller is evaluated experimentally, in which the results show a lower overshoot and faster response times. Also, the performance of the controller is verified in the presence of geometrical disturbances, as well as in the fabrication of a nonplanar part.     

A sliding mode control proposal for open-loop unstable processes

This papers presents a sliding mode controller based on a first-order-plus-dead-time model of the process for controlling open-loop unstable systems. The proposed controller has a simple and fixed structure with a set of tuning equations as a function of the desired performance. Both linear and nonlinear models were used to study the controller performance by computer simulations.     

Active vibration suppression of a flexible structure using sliding mode control

In this paper, sliding mode control (SMC) is designed and applied to an elastic structure to suppress some of its vibration modes. The system is an elastic beam clamped on one end and the designed controller uses only the deflection measurement of the free end. The infinite dimensional mathematical model of the beam is reduced to an ordinary differential equation set to represent the behavior of required modes. Since the states of the finite dimensional model are not physically measurable quantities, an observer is designed to estimate these states by measuring the tip deflection of the beam. The performance of the observer is important because the observed states are used in the SMC design. In this study, by using the output information, an observer is designed and tested to estimate the states of the finite dimensional model of the beam. Then the designed SMC is applied to the experimental beam system which gives satisfactory suppressed vibrations.     

A local active noise control system based on a virtual-microphone technique for railway sleeping vehicle applications

Low-frequency broadband noise generated on a railway vehicle by the wheel–rail interaction could be a big annoyance for passengers in sleeping cars. Low-frequency acoustic radiation is extremely difficult to attenuate by using passive devices. In this article, an active noise control (ANC) technique has been proposed for this purpose. A three-dimensional cabin was built in the laboratory to carry out the experiments. The proposed scheme is based on a Filtered-X Least Mean Square (FXLMS) control algorithm, particularised for a virtual-microphone technique. Control algorithms were designed with the Matlab-Simulink tool, and the Real Time Windows Target toolbox of Matlab was used to run in real time the ANC system. Referring to the results, different simulations and experimental performances were analysed to enlarge the silence zone around the passenger's ear zone and along the bed headboard. Attenuations of up to 20 and 15 dB(A) (re:20 μPa) were achieved at the passenger's ear in simulations and in experimental results, respectively.     

Synchronization of chaotic systems with known and unknown parameters using a modified active sliding mode control

This paper defines a new surface in an active sliding mode to synchronize two chaotic systems with parametric uncertainty. To verify the capability of the proposed scheme, signals are also contaminated by measurement noise. The integral acting surface produces a dynamics for error, where the appropriate eigenvalues are easily assigned. Using this surface, calculation of parameters of the controller becomes simpler than the classical alternative. A sufficient condition, as a guideline of the designated procedure, is dedicated to provide a robust stability of the error dynamics. Finally, a simulation study is performed to verify the robustness and effectiveness of the proposed control strategy.     

键盘接口技术在某显控设备中的应用

提出了一种利用键盘接口采集按键、开关输入的方案.该方案介绍了键盘的工作原理及与工控机通信的方法,给出了某显控设备中显控键盘的构成原理框图以及软硬件实现方法.     

Modified-filtered-u LMS algorithm for active noise control and its application to a short acoustic duct

This paper presents a new adaptive algorithm for active noise control (ANC) that can be effectively applicable to a short acoustic duct, such as the intake system of an automobile engine, where the stability and fast convergence of the ANC system is particularly important. The new algorithm, called the modified-filtered-u LMS algorithm (MFU-LMS), is developed based on the recursive filtered-u LMS algorithm (FU-LMS) incorporating the simple hyper-stable adaptive recursive filter (SHARF) to ensure the control stability and the variable step size to enhance the convergence rate. The MFU-LMS algorithm is implemented by purely experimental ways, and is applied to active control of noise in a short acoustic duct, and is validated using two experimental cases of which the primary noise sources are a sinusoidal signal embedded in white noise and a chirp signal. The experimental results demonstrate that the proposed MFU-LMS algorithm gives a considerably better performance than other conventional algorithms, such as the filtered-x LMS (FX-LMS) and the FU-LMS algorithms.     

Combined MIMO adaptive and decentralized controllers for broadband active noise and vibration control

Model errors in multiple-input multiple-output adaptive controllers for reduction of broadband noise and vibrations may lead to unstable systems or increased error signals. In this paper, a combination of high-authority control (HAC) and low-authority control (LAC) is considered for improved performance in case of such model errors. A digital implementation of a control system is presented in which the HAC (adaptive MIMO control) is implemented on a CPU and in which the LAC (decentralized control) is implemented on a high-speed Field Programmable Gate Array. Experimental results are given which demonstrate that the HAC/LAC combination leads to performance advantages in terms of stabilization under parametric uncertainties and reduction of the error signal.     

平板式熨平压花机液压系统的性能改进和噪声控制

介绍了皮革加工专用的平板式熨平压花机工作原理.同时列举了改进其工作性能,特别是控制噪声所采取的一系列方法.这些方法对其他类似液压设备的降噪有借鉴意义.     

一种触摸屏监控的分布式控制系统的实现

介绍了一种触摸屏监控的PLC网络系统,阐述了系统的组成及原理。     

Modal space vibration control of a beam by using the feedforward and feedback control loops

This paper introduces a vibration control method for a flexible beam subjected to arbitrary, unmeasurable disturbance forces. The concept of independent modal space control is adopted. Here, we choose the modal filters as the state estimator to obtain the modal coordinates and modal velocities for the modal space control. Because of the existence of the disturbance forces, applying only the state feedback to suppress the vibration usually cannot achieve the desired control performance. The modal space feedforward control is then introduced to cancel out the disturbance forces. In this paper, the feedforward and feedback control method is implemented to reduce the beam vibration. The disturbance force observer is established to observe the disturbance modal forces for the feedforward control. The control gains are derived from the extended optimal control algorithm, where the disturbance modal forces are treated as exogenous state variables. By combining the feedback, feedforward control laws and the disturbance force observer together, the vibration control performances are discussed.     

A distributed model predictive control based load frequency control scheme for multi-area interconnected power system using discrete-time Laguerre functions

This paper proposes a distributed model predictive control based load frequency control (MPC-LFC) scheme to improve control performances in the frequency regulation of power system. In order to reduce the computational burden in the rolling optimization with a sufficiently large prediction horizon, the orthonormal Laguerre functions are utilized to approximate the predicted control trajectory. The closed-loop stability of the proposed MPC scheme is achieved by adding a terminal equality constraint to the online quadratic optimization and taking the cost function as the Lyapunov function. Furthermore, the treatments of some typical constraints in load frequency control have been studied based on the specific Laguerre-based formulations. Simulations have been conducted in two different interconnected power systems to validate the effectiveness of the proposed distributed MPC-LFC as well as its superiority over the comparative methods.     

On the control of distributed parameter systems using a multidimensional systems setting

The unique characteristic of a repetitive process is a series of sweeps, termed passes, through a set of dynamics defined over a finite duration with resetting before the start of the each new one. On each pass an output, termed the pass profile is produced which acts as a forcing function on, and hence contributes to, the dynamics of the next pass profile. This leads to the possibility that the output, i.e. the sequence of pass profiles, will contain oscillations which increase in amplitude in the pass-to-pass direction. Such behavior cannot be controlled by standard linear systems approach and instead they must be treated as a multidimensional system, i.e. information propagation in more than one independent direction. Physical examples of such processes include long-wall coal cutting and metal rolling. In this paper, stability analysis and control systems design algorithms are developed for a model where a plane, or rectangle, of information is propagated in the pass-to-pass direction. The possible use of these in the control of distributed parameter systems is then described using a fourth-order wavefront equation.     

Developing a CASE tool for distributed control applications

The function block (FB) concept has been adopted by recent International Electrotechnical Commission (IEC) standards to define a methodology for the development of modular, re-usable, open, and vendor-independent distributed control applications. Control engineers are already familiar with the FB construct, and field devices and fieldbuses are expected to be compliant with this approach in the near future. New generation FB-oriented CASE tools are required to support the whole development process. This paper presents an approach to the design and development of an IEC-compliant CASE tool (ICT). The proposed approach is based on a four-layer architecture that successfully unifies the FB concept with the Unified Modelling Language. During the development of our prototype ICT, this architecture proved to be very significant for the identification of the key abstractions that the ICT must provide as building blocks of its various diagrams used during the modelling process of control systems.     

Robust control design for a wheel loader using and feedback linearization based methods

The heavy equipment industry is building more and more equipment with electro-hydraulic control systems. The existing industry practices for the design of control systems in construction machines primarily rely on classical designs coupled with ad-hoc synthesis procedures. Such practices produce desirable results, but lack a systematic procedure to account for invariably present plant uncertainties in the design process as well as coupled dynamics of the multi-input multi-output (MIMO) configuration. In this paper, two H_∞ based robust control designs are presented for an automatic bucket leveling mechanism of a wheel loader. In one case, the controller is designed for the base plant model. In another case, the controller is designed for the plant with a feedback linearization control law applied yielding improved stability robustness. A MIMO nonlinear model for an electro-hydraulically actuated wheel loader linkage is considered. The robustness of the controller designs are validated by using analysis and by simulation using a complete nonlinear model of the wheel loader linkage and hydraulic system.