闭环控制微波理疗机的设计

介绍了一种基于PIC16F877高性能单片机控制的微波理疗机的设计及系统工作原理,提出了闭环反馈功率控制方案,并较为详细的阐述了系统数据采集、D/A转换、功率调节等硬件电路设计,同时还指出了软件实现的特点。该理疗机输出功率范围为30~150W,并具有数字显示,报警提示等功能。     

PID控制回路的工程应用

从实际工程应用角度,对常规PID控制回路的组态内容进行了比较深刻的分析,具有实际意义。     

Cautious stochastic computer control applied to concrete mixing

An application of direct digital control of a concrete mixing process is presented. The process which is irreversible is modelled as a linear stochastic system. The control problem is formulated as a final value control problem. A general final value prediction problem is formilated and solved. The regulator becomes an adaptive stochastic regulator. Its control actions are based on the uncertainty in the control-error which is calculated as the difference between the setpoint and the predicted final value. The resulting algorithm is implemented on a small minicomputer based control system and is used in every day production since more than a year ago.     

Subspace identification of closed loop systems by the orthogonal decomposition method

In this paper, we consider a problem of identifying the deterministic part of a closed loop system by applying the stochastic realization technique of (Signal Process. 52 (2) (1996) 145) in the framework of the joint input-output approach. Using a preliminary orthogonal decomposition, the problem is reduced to that of identifying the plant and controller based on the deterministic component of the joint input-output process. We discuss the role of input signals in closed loop identification and the realization method based on a finite data, and then sketch a subspace method for identifying state space models of the plant and controller. Since the obtained models are of higher order, a model reduction procedure should be applied for deriving lower order models. Some numerical results are included to show the applicability of the present technique.     

Identification of processes in closed loop—identifiability and accuracy aspects

It is often necessary in practice to perform identification experiments on systems operating in closed loop. There has been some confusion about the possibilities of successful identification in such cases, evidently due to the fact that certain common methods then fail. A rapidly increasing literature on the problem is briefly surveyed in this paper, and an overview of a particular approach is given. It is shown that prediction error identification methods, applied in a direct fashion will given correct estimates in a number of feedback cases. Furthermore, the accuracy is not necessarily worse in the presence of feedback; in fact optimal inputs may very well require feedback terms. Some practical applications are also described.     

纯滞后环对数字电源环路影响的研究

研究了滞后环对数字电源的影响和滞后环的等效简化模型,给出了基于Matlab数字电源补偿器的设计步骤。仿真和实验表明,通过该方法设计的数字电源环路稳定性得到了有效保证。     

Computer control in the polymerization industry

Experiences in control of continuous and discontinuous polymerization processes did prove that process computers can successfully replace conventional control systems, yielding a better performance. It has also been shown that marked process improvements are possible by application of advanced control concepts such as multivariable control, adaptive control and dynamic optimization. Because of the complexity and size of new batch systems, computer control is widely accepted. Its ability to enforce on-off sequencing and continuous control on the batch process and its adaptation flexibility to all process needs ensures high production levels by minimizing labor cost and lost production on idle equipment.     

石英挠性加速度计数字再平衡回路设计

针对传统石英挠性加速度计模拟再平衡回路的不足,研究设计了一种加速度计数字再平衡回路.通过系统参数辨识的方法,获得加速度计表头的数学模型;采用增量式PID控制算法,设计加速度计闭环系统;在硬件结构上选用浮点型DSP作为控制单元,采用外扩式AD/DA模块,提高转换精度.实验结果表明:加速度计系统带宽为190 Hz,响应时间为1.6ms,稳态误差为0.所设计的数字再平衡回路有效改善了系统动静态特性,提高了输出精度.     

A closed loop supply chain under retail price and product quality dependent demand

The importance of remanufacturing of used products, maintaining the same quality as new ones has been widely recognized in practice. In this paper, we address a closed loop supply chain where the manufacturer manufactures a product with a decent quality acceptable to customers, and sells it through a retailer in the market. A third party collects the used products from consumers and sends to the manufacturer. The manufacturer re-manufactures the used product and the quality of remanufactured product is the same as that of the manufactured one. For such a closed loop supply chain, we construct five different scenarios – centralized, decentralized or Nash game and three different Stackelberg games, led by the manufacturer, retailer and third party respectively. We compare the optimal results to find out the best decentralized scenario out of the four mentioned. A numerical example is taken to study the impacts of product quality on demand as well as optimal decisions and investigate sensitivity of some key model-parameters.     

Multiloop,feedforward, modal and optimal control of an evaporator

The goodness of the ‘classical’ multiloop, dynamic feedforward, modal and optimal control methods, as approaches to multivariable regulatory control, are evaluated on the basis of the experience obtained by designing and experimentally implementing control systems on a double effect pilot plant evaporator. A fifth order state space model is used in the theoretical designs. The criteria used in evaluating the goodness of a control method are the soundness of its principles, its synthesis power and the demands for sophistication in actual implementation.     

Modeling and analysis of closed loop manufacturing systems using parameter coupling

Closed loop manufacturing systems (CLMSs) with recirculating material handling devices are extensively used in various industrial environments. The performance of such systems is impacted by many factors such as the total capacity of pallets, the actual number of pallets in the system, the machine reliability and processing time, the pallet index speed, and the positions of loading/unloading points. These factors make the accurate analysis and optimization of complex CLMSs very difficult and challenging. This paper presents a new parameter coupling technique to model and analyze a wide range of CLMSs. It is an enhancement based on the existing open production line analysis with unreliable assembly machines and finite buffers. Virtual assembly machines are introduced to represent the specific phenomena of CLMSs such as the recirculation of empty pallets and the sharing of conveyor space. Two types of parameter coupling patterns, the machine parameter coupling, and the buffer capacity coupling, are introduced to reflect the characteristics of the CLMSs. The parameter coupling technique is simple and effective for analyzing a broad range of CLMSs. Comparisons between this analytic method and simulation experiments demonstrate that the proposed parameter coupling technique is fast, accurate and robust.     

Fuzzy control of the activated sludge wastewater treatment process

The activated sludge process is a commonly used method for treating sewage and waste waters. It is characterised by a lack of relevant instrumentation, control goals that are not always clearly stated, the use of qualitative information in decision making and poorly understood basic biological behaviour mechanisms. In this brief paper we examine the behaviour of an experimental fuzzy control algorithm constructed to reflect actual operational practice. We conclude that this algorithm does rather well and that a fuzzy controller would be a useful and practical way of regulating the activated sludge process.     

The design of distributed control computer systems

The top-down approach in the design of Distributed Control Computer Systems, DCCS, is presented. The starting point of the study is three statements: (i) the design approach should be production process control oriented; (ii) for real time process control applications, computer networks require an efficient communication subsystem, the most important features of which are high reliability and short message transmission times and (iii) recent research has shown that the tools and methodologies used in both computing and control should be complementary to each other in order to solve some of the distributed control computer system/distributed computer control system design problems. The paper contains the design problems of distributed control computer systems, the presentation of the methods and tools for the study and design of the DCCS, the top-down approach in the design of the DCCS, and examples of two design stages.     

A novel closed loop identification method and its application of multivariable system

Motivated by the fact that many classical identification methods cannot be directly used for closed loop control system for the excitation signal without the strict requirement, a novel identification method is proposed to simultaneously estimate model parameter and the structure. To improve the optimizing efficiency of the particle swarm, the global best particles are further optimized via a nonlinear stochastic search during the certain iteration of PSO and the novel method is denoted NPSO. On the basis, the frequency response estimation is introduced to provide a rough initial for the presented algorithm to improve the validity and accuracy. We simplify the complexity of the closed loop identification via the equivalent input and output. Simulation examples of SISO systems and MIMO systems are given to demonstrate the effectiveness and accuracy of the proposed algorithm.     

一种新型PID控制的全数字锁相环的设计与实现

一种采用积分分离的PID控制作为环路滤波器的全数字锁相环。该滤波器对序列滤波器输出的加减脉冲个数在反馈信号的上升沿进行综合,然后通过PID控制算法将综合值作为压控振荡器的分频值来实现相位的调整,最终达到相位锁定。PID控制算法响应时间短并可控制超调量,相比PI算法具有更快的上升时间,且不增加超调量。另外,该环路具有结构简单、易于集成等特点,可以作为一个子系统或功能块构成片上系统(SoC),用以提高控制系统的可靠性,简化系统硬件结构。     

Improvement of robust digital control by identification in the closed loop. Application to a 360° flexible arm

This paper presents a procedure for the improvement of identification results from open-loop experiments by identification in a closed loop without modification of the identification protocol. Several available identification algorithms are considered, and two methods for the validation of the model identified in a closed loop are introduced. As a consequence, an improved robust controller is obtained. Results are presented from experiments on a very flexible 360° arm.     

数字DC/DC开关电源环路补偿器设计

建立了数字控制DC/DC开关电源闭环系统的s域小信号模型,采用数字重设计法针对给定的系统参数设计了数字补偿器。应用SISO Design Tool仿真平台,在伯德图分析和根轨迹法的基础上设计了连续域的模拟补偿器,并进行了离散化处理。在建立系统s域模型时引入了模数转换器和数字脉宽调制发生器产生的延迟效应,使补偿器的设计考虑了采样速率对系统的影响,改善了传统离散设计的误差。基于数字重设计法构建的数字补偿器实现了对脉宽调制信号的可编程精确控制,保证了变换器闭环工作良好的动态特性。仿真实验结果验证了所设计的数字补偿器的性能。     

Distributed observer-based cooperative control of multiple nonholonomic mobile agents

In this article, cooperative output feedback control of a group of nonholonomic mobile agents is considered. Distributed observer-based cooperative control laws are proposed with the aid of Lyapunov techniques and results from graph theory. Robustness of the stability of the closed-loop systems with the proposed control laws is considered. The effectiveness of the proposed controllers is verified by simulation results.     

Closed loop parameter identifiability and adaptive control of a linear stochastic system

We show that if the parameters of a linear stochastic control system are identifiable using a persistently existing input then the same systems remains parameter identifiable if the system operates under closed loop in a certain way. We assume that the controller itself depends on the test value of the system parameters, and as usual the control signal is dithered. The estimation problem is formulated as the problem of minimizing an appropriate asymptotic cost function. It is shown that a suitable modification of the gradient of the cost function converts our problem into another problem for which Ljung's scheme can be applied. Thus the theorem provides a general method for the solution of the local adaptive control problem.