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The work deals with design and application of robust controllers for a shell-and-tube heat exchanger. The heat exchanger is used for pre-heating of petroleum by hot water. The control objective is to keep the outlet temperature at a reference value. Two robust control techniques are used. In the first approach the robust PI controller design is based on plotting the stability boundary locus in the...
Proportional-resonant (PR) compensator and LCL filter becomes a better choice in grid-connected inverter system with high performance and low costs. However, the resonance phenomenon caused by LCL filter affect the system stability significantly. In this paper, the stability problem of three typical current feedback control schemes in LCL grid-connected system are analyzed and compared systematically...
This paper presents an improved phase lead repetitive compensator (RC) for a linear actuator (LA) system. The linear phase lead compensation provided by the proposed compensator structure compensates the phase lag of the feedback system caused by payload variations and nonlinear friction present in the LA system. Unlike conventional phase lead RC structures which use a pure linear phase advance compensator...
A novel approach to robust controller design with input hard constraints is presented. The proposed design procedure contains robust stability condition based on the M-delta structure and it is used for system with additive uncertainty. The obtained results, illustrated on example, show the applicability of the designed robust controller and its ability to cope with model uncertainties.
Phase-looked Loop (PLL) is a critical component for the control and grid synchronization of grid-connected power converters. This paper presents a benchmarking study on the small-signal dynamics of three commonly used PLLs for single-phase converters, including enhanced PLL, second-order generalized integrator based PLL, and the inverse-PLL. First, a unified small-signal model of those PLLs is established...
The negative imaginary (NI) property occurs in many important applications. For instance, flexible structure systems with collocated force actuators and position sensors can be modeled as negative imaginary systems. In this paper, we present a controller synthesis methodology for negative imaginary systems based on data driven controller. In this approach, a measured frequency response data of the...
This paper develops a single-phase voltage source inverter mainly containing a high frequency flyback bidirectional DC-DC converter — as a previous stage, and a full-bridge module. The flyback bidirectional converter generates a rectified sinusoidal voltage waveform across the output capacitor. The full bridge transistors switch two times in one AC period in order to transform the output capacitor...
This paper proposes a controller design method for the Hammerstein models which are linear models with static input nonlinearities and are a kind of nonlinear systems. The method requires only closed-loop step response data for controller design. The information in time domain of the data is used to estimate the plant model, and that in frequency domain is used to confirm the validity of the linear...
Many ideas have been proposed to reduce traffic congestion. Driving a platoon of vehicles with constant spacing seems to be a promising idea as it increases traffic density. But keeping constant inter-vehicle spacing requires very reliable communication. Another control policy is to drive the platoon with a time headway between vehicles. It is a robust and well known policy but large inter-vehicle...
It is shown that for the case of minimum phase stable plants there exists, among the set of stabilizers controllers, a solution, simultaneously decoupling the outputs and at-tenuating the perturbations of the system. At the same time, the dynamics is assigned to stable positions. The at-tenuation is given by an approximation of the controllers rejecting the perturbations, which are singulars. These...
In this paper a PI decentralized constant-volume controller for open-channels is designed by minimizing the H2 norm of a suitable transfer function matrix. Since the fundamental property which must be retained for all possible perturbations of the plant is stability of the feedback system, we have studied whether the proposed feedback design is robust in the face of output-multiplicative perturbations...
This paper discusses the question of saturating actuators in a multi-input multi-output (MIMO) control system design. It is shown that direct application of standard anti-windup schemes can lead to loss of closed-loop stability, as well as, the degradation of the directional properties of the system. Consequently, a novel anti-windup scheme is proposed, where the intended procedure ensures stability,...
The paper presents a synthesis of some author's activity. A speed control system for dc drives, based upon a PI fuzzy controller with integration at the output, with a simple rule base with only 9 rules is developed, analyzed and simulated. The sum-prod inference method is used with the center of gravity defuzzification. The performance criteria of the fuzzy control system are compared with the performance...
The importance of anti-windup compensation in control systems with saturations has been widely recognized in applications. However, only recently the stability and performance of such compensators has been discussed from a rigorous mathematical viewpoint. In this paper, a simple performance criterion is derived in terms of a frequency domain inequality for the anti-windup compensator filter. In particular,...
For any two n-th order polynomials a(s) and b(s), the Hurwitz stability of their convex combination is necessary and sufficient for the existence of a polynomial c(s) such that c(s)/a(s) and c(s)/b(s) are both strictly positive real.
A relay feedback linear system with the transfer function of the pole excess equal to two can have a sliding mode in the set of co-dimension two and chattering mode around it. The chattering can be a part of a limit cycle in the relay feedback system and this limit cycle can be unique and globally stable. It was shown before that a limit cycle exists for a special class of systems with stable denominator...
The anti-windup problem is formulated in discrete-time using a configuration which effectively decouples the nominal linear and nonlinear parts of a closed loop system with constrained plant inputs. Conditions are derived which ensure an upper bound on the induced l2 norm of a certain mapping which is central to the anti-windup problem. Results are given for the full-order case, where a solution always...
This paper proposes a new method for the measurement of the infinity norm of the sensitivity functions of linear systems. A nonlinear feedback structure is derived from existing relay experiments. The proposed scheme may produce a limit cycle at a frequency where the sensitivity function of a given system achieves a selected magnitude. Necessary and sufficient conditions for the occurrence of the...
A stability and controllability analysis of a production control scheme based on the demand forecast, on finished product inventory level and work in progress feedback signal is presented. The controllability analysis helps to identify the causes of the production control inefficiency in recovering inventory offsets when an unpredictable event changes the work in progress or the completion rate values...
In this paper, we study H∞ performance of interval systems. We show that, for an interval system, the maximal H∞ norm of its sensitivity function is achieved at twelve (out of sixteen) Kharitonov vertices. Furthermore, we study robustness of multivariable systems with parametric uncertainties, and establish a multivariable version of Edge Theorem. An illustrative example is presented.
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