Closed-loop magnetic control of a spin-stabilized satellite

Autonomous closed-loop magnetic control is achievable for a spinning satellite in a near magnetically polar orbit for maintaining a programmed spin rate and a spin pointing-axis normal to the orbit plane. The system requires a spin-pointing coil to generate magnetic moments parallel to the spin axis, a spin rate coil with an axis normal to the spin vector, an earth sensor, a magnetometer measuring the earth field components normal to the spin, and electronic logic and circuitry to perform timing measurements between the earth sensor pulses and detect errors in spin rate and pointing elevation angles between the spin axis and the horizontal (roll). Programmed altitude corrections to these timing measurements are required for non-circular orbits. In addition, the electronics make sequenced samples of the magnetometer signals, perform the control law logic, and command the electrical connections to energize the magnetic coils. The spin control generates magnetic torque when the field is detected in the appropriate direction to provide spin torque in the direction to correct spin rate.     

Decentralized control of the Tennessee Eastman Challenge Process

A decentralized control system is developed for the Tennessee Eastman Challenge Process (TE problem). The design procedure begins with the selection of the method for production-rate control, to which inventory controls and other functions are then coordinated. Results show that production rate can be maximized at any of the three standard product compositions, even when the feed of reactant A is lost. All specifications of the challenge problem are satisfied despite large disturbances in feed composition and reaction kinetics. Variability in product rate and quality is less than that seen in previous studies. The process can operate on-spec for long periods without feedback from composition measurements. Setpoints for certain variables (such as reactor temperature and concentrations of A and C in the reactor feed) must be chosen a priori, and the effect on operating cost is estimated. The performance of the proposed decentralized control is compared to that of a nonlinear model predictive control (NMPC) developed previously. There appears to be little, if any, advantage to the use of NMPC in this application. In particular, the decentralized strategy does a better job of handling constraints - an area in which NMPC is reputed to excel. Reasons for this are discussed.     

Implementation and application of microprocessor-based self-tuners

The implementation of a class of self-tuning controllers using a portable microcomputer system is described. The self-tuning control theory is shown to provide a variety of control objectives such as model-reference, optimal Smith prediction and the minimization of a general k-step-ahead cost-function. Hardware and software details of the portable computer, SESAME, are presented with particular reference to the use of a new high-level language, Control Basic. Studies of the application of self-tuning to the control of room-temperature, acid neutralization, and batch chemical reactors in industry are outlined.     

Adaptive configuration control of multiple UAVs

Several missions including surveillance, exploration, search-and-track, and lifting of heavy loads are best accomplished by multiple unmanned aerial vehicles (UAVs). Another important advantage to utilizing multiple vehicles is a reduction in the risk to successful completion of a mission due to the loss of a single vehicle. This increased robustness can lead to a commensurate decrease in vehicle specifications and cost, further improving the argument for swarm operations. This paper describes the development of an adaptive configuration controller for multiple vehicles executing a cooperative task in the presence of parametric uncertainty. A novel adaptive outer-loop controller that uses both local and global information is presented.     

A New Control Scheme of Single-link Flexible Manipulators Robust to Payload Changes

A new scheme is presented in this paper to control single-link flexiblemanipulators. The objective is to control the tip position of the flexiblearm in the presence of joint friction and payload changes. The controlscheme is based on two nested loops: an inner feedback loop to control themotor position which is robust to joint friction, and an outer loop tocontrol the tip position which is robust to payload changes. This outer loopis composed of a feedforward term and a feedback term. This results in asimple control law that needs minimal computing effort and, thus, can beused for real time control of flexible arms. The proposed method is generalin the sense that it can be applied to very different arm structures anddiverse sensor systems configurations. Results corresponding to twodifferent arm setups are presented.     

Networked Control Systems: A Survey of Trends and Techniques

Networked control systems are spatially distributed systems in which the communication between sensors, actuators,and controllers occurs through a shared band-limited digital communication network. Several advantages of the network architectures include reduced system wiring, plug and play devices,increased system agility, and ease of system diagnosis and maintenance. Consequently, networked control is the current trend for industrial automation and has ever-increasing applications in a wide range of areas, such as smart grids, manufacturing systems,process control, automobiles, automated highway systems, and unmanned aerial vehicles. The modelling, analysis, and control of networked control systems have received considerable attention in the last two decades. The ‘control over networks’ is one of the key research directions for networked control systems. This paper aims at presenting a survey of trends and techniques in networked control systems from the perspective of ‘control over networks’, providing a snapshot of five control issues: sampled-data control, quantization control, networked control, event-triggered control, and security control. Some challenging issues are suggested to direct the future research.     

Stabilization of robot motion and contact force interaction for third-order motor dynamics

An approach to the synthesis of control laws stabilizing motion and force in contact tasks, based on the exponential stability of the closed-loop control system, is described. When using the synthesized control laws, simultaneous stabilization of both motion and force is achieved with a preset quality of the transient responses. The task is solved in a most general form, taking into account the constraints on robot control, its position and the force of interaction of the robot and the environment, and the external perturbations and inaccuracies of the measuring sensors, when the environment dynamics is being described by nonlinear second-order differential equation, and the robot dynamics includes the third-order equations of the robot actuators dynamics.     

The preview control of a class of linear systems and its application in the fault-tolerant control theory

In the fault-tolerant control theory based on model following control, the desired signal of the control system is the output of a reference system. This paper is concerned with the design of the preview controller for a class of fault systems. A composite vector is introduced by including error vector, fault system state vector and reference system state vector. Then, we derived an augmented system from the known system equation, in which the reference input has equal status with the desired signal in the traditional preview control theory. Therefore, we can use the known theory to design the preview controller for the augmented system, then the preview controller of the original fault system can be obtained by the integration method. This paper strictly discusses the connection between stabilisation and detectability of the augmented system and the corresponding characteristics of the original system. Finally, by applying this theory to a real steam generator water level control system, it is found that the actions of the reference input preview and the fault signal preview can effectively eliminate the effect of the fault signal on the water level of the steam generator. The simulation shows the effectiveness of the controller designed.     

一类非线性系统的间接自适应模糊滑模控制

基于启发式知识的模糊控制是一种解决非线性系统控制问题的有效方法。然而其设计缺乏系统性,并且系统的稳定性和鲁棒性难以保证。本文利用滑模控制的概念和Lyapunov综合方法提出一种针对一类非线性系统的间接自适应模糊滑模控制（IAFSMC）方法。仿真研究表明即使在缺少系统先验知识和不确定性干扰的情况下,系统性能也十分理想。     

一种具有非线性观测器的分散式自适应鲁棒机器人控制新方案

本文提出一种新型的分散式自适应鲁棒机器人控制方案。它主要解决以下诸方面的问题:1)减少在线计算量;2)通过设置一个非线性观测器来及时修正模型信息,以适应负载及其他因素变化的需要,进而有效地减少所需控制值(尤其当系统处于平稳工作状态时,效果更加明显),相应地,也就减少了系统工作时的动能损耗。这一点对[1]中提出的机器人分散式变结构控制算法有较大改进;3)对系统的不确定性和扰动作用具有鲁棒性。     

模糊PID控制在葡萄酒发酵过程中的应用

针对某葡萄酒厂的发酵过程进行研究,由于其特性随时间变化,需要适时地对PID控制器的参数进行整定.常规的PID控制器没有自适应能力,只能依靠人工重新整定参数,这很难适应参数连续变化的发酵过程.因此需要一种有自适应能力的控制器,经对发酵过程的常规PID控制和模糊PID控制进行仿真和对比,最终选用最优控制方案.     

预估模糊控制在循环水加药控制中的应用

针对Smith预估控制对模型误差较敏感,适应对象参数变化较差的缺点,提出了一种Smith预估模糊控制方法,利用模糊逻辑实现被控对象模糊化,利用Smith预估控制对被控对象滞后环节进行补偿。以火电厂循环水加药控制为例,对该控制方法进行仿真和实际应用研究,结果表明该系统能有效地避免纯滞后环节在控制系统中带来的振荡现象,工程应用取得了理想的控制效果,为纯滞后、大惯性、模型不确定系统的控制提供了很好的解决方法。     

Optimization of boiler control to improve the load-following capability of power-plant units

The capability to perform fast load changes has been an important issue in the power market, and will become increasingly more so due to the increasing commercialization of the European power market. An optimizing control system for improving the loadfollowing capability of power-plant units has therefore been developed. The system is implemented as a complement, producing control signals to be added to those of the existing boiler control system, a concept which has various practical advantages in terms of implementation and commissioning. The optimizing control system takes account of the multivariable and load-dependent nonlinear characteristics of the boiler process, as a scheduled LQG controller with feedforward action is utilized. The LQG controller improves the control of critical process variables, making it possible to increase the load-following capability of a specific plant. Field tests on a 265 MW coal-fired power-plant unit reveals that the maximum allowable load gradient that can be imposed on the plant, can be increased from 4 to 8 MW/min.     

一种新型非线性PID控制器

将非线性函数与简单的PID控制器相级联，构成一种新型的非线性PID控制器，以提高现有PID控制器的性能，新型PID控制器的设计过程十分简单，只要适当构造非线性函数，并与原PID控制器级联起来便可实现，数值仿真结果表明，所提出的PID控制器比简单的PID控制器具有更好的动静态性能。     

鲁棒变结构模型参考自适应控制器的分析与设计(Ⅱ)

对含未建模动态且建模部分相对阶大于 1(n >1) 的SISO定常线性系统提出了一种控制增益可切换的变结构模型参考自适应控制方案 .主要结果是 :得到了系统跟踪误差与辅助误差间关系的明确表达式 ,进而证明 ,对各辅助子系统 (均为相对阶为 1的子系统 ) ,只要按相对阶为 1时所提出的变结构律进行设计 ,使它们满足预先给定的性能指标 ,就可保证系统跟踪误差在预先给定的过渡过程时间内收敛到一个残集内 ;研究结果还表明 ,当n >1时 ,平均值滤波器对系统的影响相当于一个未建模动态对系统的影响     

水泥窑外分解窑的自动控制

本文针对水泥窑外分解窑控制的多变量强耦合,非线性和时变的特点,提出了一种基于知识的智能控制方法,其基本思想是采用专家判别方法辨识工况,对系统参数进行失效诊断,进而自动选择不同的控制策略——随机多变量最优控制或基于模糊控制语言的自学习模糊控制,该方法已经实际应用于窑外分解窑的自动控制。     

Practical-optimal control of a drum boiler power plant

Multivariable control of power plants has been studied by many researchers and also a number of practical applications have been presented in the last few years with the aim of improving the load following capabilities of thermal units. This paper summarizes the main results of an experimental application of optimal control to a drum boiler power plant at the Italian national electricity board. Referring to a previous work for the process model building, first a model reduction is performed with the main purpose of getting a simplified control structure. Then, an optimal regulator including feedforward and integral control is synthesized and some practical drawbacks of the synthesis are discussed with referrence to traditional control schemes leading to a reformulation of the optimal regulator which, while conserving optimality, exhibits a number of practical advantages and improved robustness against typical plant parameter variations. Since the motivation of the control structure reformulation is mostly derived from experimental results, field trials are reported where the performances of a well tuned coordinated control, of the classical optimal regulator and of the reformulated optimal control structure are compared. Perspectives of future industrial applications are briefly discussed in the conclusions.     

On the worst-case disturbance of minimax optimal control

We consider a minimax optimal control problem for uncertain stochastic systems. The uncertainty in the underlying stochastic system is formulated in terms of probability measure perturbations satisfying a relative entropy constraint. By characterizing the worst-case measure for a related stochastic minimax game, it is shown that the worst-case uncertain system can be represented in the form of a parametric perturbation of the nominal system. A numerical example is presented to illustrate theoretical results developed in this paper.     

Decoupler and PID controller design of TITO systems

This paper treats controller design and tuning for systems with two input signals and two output signals in the process industry. Two design methods that can be combined to form a core in an algorithm for automatic design and tuning for the considered systems are presented. The proposed controller consists of a decoupler and a diagonal PID controller. The decoupler has the property that as little dynamics as possible is introduced in the decoupler. The PID design method is based on exhaustive search. The methods are combined and tested in an industrial environment in a paper mill.