Computer-aided design of suboptimal feedback controllers using optimal low-order models

The fully automated design of optimal or near-optimal feedback controllers is considered for least-pth and minimax cost functions. Solutions are obtained by approximating to the desired optimal output by a rational function. Optimal results for a 2nd-order model and suboptimal responses for the corresponding 7th-order linear system are used to illustrate the method.     

On the design of the feedforward compensator in two-degree-of-freedom controllers

This paper presents an innovative methodology to design the feedforward path of two-degree-of-freedom (2-d.o.f.) regulators for ‘optimal’ set point tracking. The proposed methodology is totally independent of the structure of the feedback controller, of the way it is designed, and of the characteristics of the set point signal. By using a nonparametric model of the control loop, that can be easily identified on-line, various tracking problems can be cast into a unified, and easily interpreted optimisation framework. Simulated and physical examples demonstrate the simplicity and efficacy of the proposal.     

Short seeking by multirate digital controllers for computation saving with initial value adjustment

Multirate control has been proposed to reduce the real-time computation in hard disk drive (HDD) servo systems. It has been showed that computation can be saved greatly without performance degradation by using a multirate controller for track following. This paper proposes a novel method for short seeking control based on multirate track following control and initial value adjustment. This method, which uses the same multirate controller and the same servo structure as track following, adjusts the initial values of the track following controller for short seeking. Real-time computation is greatly saved in two aspects: 1) computation is saved by multirate scheme, and 2) initial value adjustment of the feedback controller makes the use of the feed-forward controller and reference trajectory unnecessary. Simulation and experimental results verify the effectiveness of the proposed method.     

Singular perturbation methods in the design of observers and stabilising feedback controllers for multivariable linear systems

Singular perturbation methods are used to reduce the design of stabilising feedback controllers for a class of (n+m)th-order systems with inaccessible states to the design of nth-order observers and associated feedback controllers for nth-order reduced systems obtained by ignoring `parasitic? elements that correspond to the presence of a small parameter in the state equations of the (n+m)th-order systems.     

Lyapunov-function-based design of fuzzy logic controllers and itsapplication on combining controllers

This paper presents the design of fuzzy logic controllers (FLCs) for nonlinear systems with guaranteed closed-loop stability and its application on combining controllers. The design is based on heuristic fuzzy rules. Although each rule in the FLC refers to a stable closed-loop subsystem, the overall system stability cannot be guaranteed when all these rules are applied together. In this paper, it is proved that if each subsystem is stable in the sense of Lyapunov (ISL) under a common Lyapunov function, the overall system is also stable ISL. Since no fuzzy plant model is involved, the number of subsystems generated is relatively small, and the common Lyapunov function can be found more easily. To probe further, an application of this design approach to an inverted pendulum system that combines a sliding-mode controller (SMC) and a state feedback controller (SFC) is reported. Each rule in this FLC has an SMC or an SFC in the consequent part. The role of the FLC is to schedule the final control under different antecedents. The stability of the whole system is guaranteed by the proposed design approach. More importantly, the controller thus designed can keep the advantages and remove the disadvantages of the two conventional controllers     

如何用无桥图腾柱功率因数校正控制器实现出色的AC-DC功率转换效率

电网提供的电能是交流电,但我们使用的大多数设备都需要直流电,这意味着进行这种转换的交流/直流电源是能源网上最常见的负载之一.随着世界关注能效以保护环境并管理运营成本,这些电源的高效运行变得越来越重要.     

A practical approach to the design of robust speed controllers formachine drives

This paper presents a practical approach to the robust speed control of electrical drives. The approach is based on sliding mode control (SMC), but it is shown how sampling time, system noise, actuation limit, and antiwindup integrator reduce the control to an online maximum-gain selection constrained by system noise. The paper proposes a trajectory-reference compensator and fuzzy gain interpolator to fully exploit the system actuation while avoiding chattering and remaining within specified noise limits, only the SMC switching line needs to be selected; the remaining control design is systematic and, thus, should be of interest to drive engineers in industry. Experimental results on a vector-controlled AC motor drive rig with variable-inertia loads are presented to verify the approach     

Mechatronic design of open-structure multi-robot controllers

The paper proposes a structure for open, hierarchical, multi-device controllers. The proposed structure takes into account that the system may contain several robots of different types, a certain number of cooperating devices, diverse sensors and also the fact that the task, the system has to execute, and the number and type of its components may vary considerably over time. The concept has been verified by designing a controller for a prototype Robot of a New Type (RNT) robot. The flexibility of the system is due to the software, so the programming aspect is treated comprehensively in the paper.     

Bounds on the throughput of congestion controllers in the presence of feedback delay

We consider decentralized congestion control algorithms for low-loss operation of the Internet using the ECN bit. There has been much analysis of such algorithms, but with a few exceptions, these typically ignore the effect of feedback delays in the network on stability. We study a single node with many flows passing through it, with each flow (possibly) having a different round-trip delay. Using a fluid model for the flows, we show that even with delays, the total data rate at the router is bounded; and this bound shows that the (peak) total rate grows linearly with increase in system size, i.e., the fraction of overprovisioning required is constant with respect to N, the number of flows in the system. Further, for typical user data rates and delays seen in the Internet today, the bound is very close to the data rate at the router without delays. Earlier results by Johari and Tan have given conditions for a linearized model of the network to be (locally) stable. We show that even when the linearized model is not stable, the nonlinear model is upper bounded, i.e., the total rate at the bottleneck link is upper bounded, and the upper bound is close to the equilibrium rate for TCP.     

Synthesis of linear multivariable feedback systems with prescribed stochastic-response characteristics

The letter presents a simple method of synthetising a class of linear multivariable feedback systems with prescribed steady-state stochastic-response characteristics.     

Transfer-function matrix of multivariable systems with cascade and feedback controllers

Simple expressions relating the closed-loop transfer function matrix to the cascade and feedback controller matrices are derived for a multivariable system. An important result is deduced which can simplify some of the design procedures of linear multivariable systems.     

Adaptive filtering with bandwidth constraints in the feedback path

This paper introduces a new, adaptive-filter-based controller that shows advantageous properties from the viewpoint of its communication requirement. The algorithm is called signed-error filtered-x LMS (SE-FxLMS). Its novelty is characterized by the fact that it makes possible data compression in the feedback path of adaptive-filter-based control loops in a very simple way. This feature is especially useful in such closed-loop systems where the feedback signals are transmitted over a low-bandwidth communication channel. This is a typical case in so-called networked control systems (NCS), where the communication is carried out over a shared communication channel, e.g., using a wireless sensor network. The paper introduces an analysis of the algorithm as well.     

On Chebyshev design of linear-phase FIR filters with frequency inequality constraints

The alternation theorem is the basis of the Remez algorithm for unconstrained Chebyshev design of finite-impulse response (FIR) filters. In this paper, we extend the alternation theorem to the inequality-constrained case and present an improved Remez algorithm for the design of minimax FIR filters with inequality constraints in frequency domain. Compared with existing algorithms, the presented algorithm has faster convergence rate and guaranteed optimal solutions.     

On the design of signals for sequential and nonsequential detection systems with feedback

The design of signals for binary communication systems employing feedback has previously been considered by Turin. A delayless, infinite-bandwidth forward channel disturbed by additive, white, Gaussian noise is assumed. At each instant of time, the log likelihood ratio of the two possible signals is fed back to the transmitter via a noiseless and delayless feedback channel. The forward-channel signals are said to be optimally designed when the feedback information is so utilized that the average (for sequential detection) or fixed (for nonsequential detection) transmission time is minimized, subject to a specified probability of error. Average and peak power constraints are also placed on the signals. Turin has solved the signal design problem for extreme values (i.e., very large or equal to one) of the peak-to-average power constraint ratio. These results are extended in this paper to arbitrary values of the power constraint ratio, for both sequential and nonsequential detection.     

Adding feedforward blade pitch control to standard feedback controllers for load mitigation in wind turbines

Combined feedback/feedforward blade pitch control is compared to industry standard feedback control when simulated in realistic turbulent winds. The feedforward controllers are designed to reduce fatigue loads, increasing turbine lifetime and therefore reducing the cost of energy. Two feedforward designs are studied: collective-pitch model-inverse feedforward using a non-causal series expansion and individual-pitch gain-scheduled shaped compensator. The input to the feedforward controller is a measurement of incoming wind speed, which could potentially be provided by LIDAR. Three of the designs reduce structural loading compared to standard feedback control, without reducing power production.     

Partially adaptive beamformer design subject to worst-caseperformance constraints

Proposes two methods for designing partially adaptive beamformers that satisfy a performance specification over a set of likely interference scenarios. Both methods choose the adaptation space in a sequential fashion; the dimension is increased one by one until the performance specification is attained. In the multilevel point design method, each dimension of the adaptation space is chosen to give optimum performance at a single interference scenario. The constrained minimization design method chooses each dimension of the adaptation space to exactly satisfy the performance specification at a single interference scenario while approximately minimizing the average interference output power over neighboring scenarios. Simulations indicate that both methods result in better performance than existing methods while using fewer degrees of freedom     

An evaluation of the key design criteria to achieve high updaterates in packet classifiers

The increased capacity of networks and nodes might enable us to keep pace with the growing traffic load, but the change of paradigm in IP networks towards a QoS-aware and multimedia-friendly infrastructure creates new bottlenecks in the communication path. An example of such a bottleneck is dynamic packet classification, which is fundamental to supporting any sort of QoS and value-added services. Typically, high update rates in packet classification designs have been sacrificed to achieve better search times or to reduce storage capacity requirements. By carefully analyzing current proposals, we unveil three previously neglected key design criteria for general classifiers to successfully achieve high update rates at wire speed: filter localization, nonstructural dependencies, and dynamic precomputation. We also analyze their impact in current algorithms     

A two-dimensional numerical approach to achieve a silicon BCCD celloptimal design

The single charge stored in a silicon buried-channel charge-coupled device (BCCD) is studied under different technological specification. The approach is to seek an accurate determination of this parameter by using a 2-D numerical device analysis program. The calculated data are compared to experimentally measured BCCD characteristics. These investigations have led to some trends for design optimization for designers whose main motivation is the scaling down of BCCDs     

基于FPGA实现简易数字频率计的设计

简易数字频率计的设计,采用FPGA实现对模数转换芯片A/Dtlc549的控制,对外来信号采样,实现信号从模拟到数字的转换,在单位时间内通过计数器的累加实现对频率的计数。该设计实现的频率精度为1Hz,测量范围为0～100MHz,经实际电路测试,仿真结果表明,该频率计具有较高的实用性和可靠性。