John Y. Hung

Bio: John Y. Hung is an academic researcher from Auburn University. The author has contributed to research in topics: Control theory & Control system. The author has an hindex of 30, co-authored 149 publications receiving 6958 citations. Previous affiliations of John Y. Hung include University of Illinois at Urbana–Champaign & University of Alabama.

Variable structure control: a survey

Abstract: A tutorial account of variable structure control with sliding mode is presented. The purpose is to introduce in a concise manner the fundamental theory, main results, and practical applications of this powerful control system design approach. This approach is particularly attractive for the control of nonlinear systems. Prominent characteristics such as invariance, robustness, order reduction, and control chattering are discussed in detail. Methods for coping with chattering are presented. Both linear and nonlinear systems are considered. Future research areas are suggested and an extensive list of references is included. >

Future Energy Systems: Integrating Renewable Energy Sources into the Smart Power Grid Through Industrial Electronics

Abstract: This paper discusses about integrating renewable energy sources into the smart power grid through industrial electronics. This paper discusses photovoltaic power, wind energy conversion, hybrid energy systems, and tidal energy conversion.

Evaluation of DSP-Based PID and Fuzzy Controllers for DC–DC Converters

Abstract: In this paper, digital proportional-integral-derivative (PID)-type and fuzzy-type controllers are compared for application to the buck and boost dc-dc converters. Comparison between the two controllers is made with regard to design methodology, implementation issues, and experimentally measured performance. Design of fuzzy controllers is based on heuristic knowledge of converter behavior, and tuning requires some expertise to minimize unproductive trial and error. The design of PID control is based on the frequency response of the dc-dc converter. Implementation of linear controllers on a digital signal processor is straightforward, but realization of fuzzy controllers increases computational burden and memory requirements. For the boost converter, the performance of the fuzzy controller was superior in some respects to that of the PID controllers. The fuzzy controller was able to achieve faster transient response in most tests, had a more stable steady-state response, and was more robust under some operating conditions. In the case of the buck converter, the fuzzy controller and PID controller yielded comparable performances.

Implementation of a fuzzy controller for DC-DC converters using an inexpensive 8-b microcontroller

Abstract: This paper presents an implementation of a fuzzy controller for DC-DC power converters using an inexpensive 8-bit microcontroller. An "on-chip" analog-to-digital (A/D) converter and PWM generator eliminate the external components needed to perform these functions. Implementation issues include limited on-chip program memory of 2 kB, unsigned integer arithmetic and computational delay. The duty cycle for the DC-DC power converter can only be updated every eight switching cycles because of the time required for the A/D conversion and the control calculations. However, it is demonstrated here that stable responses can be obtained for both buck and boost power converters under these conditions. Another important result is that the same microcontroller code, without any modifications, can control both power converters because their behavior can be described by the same set of linguistic rules. The contribution shows that a nonlinear controller such as fuzzy logic can be inexpensively implemented with microcontroller technology.

Denial of service attacks on network-based control systems: impact and mitigation

Abstract: Replacing specialized industrial networks with the Internet is a growing trend in industrial informatics, where packets are used to transmit feedback and control signals between a plant and a controller. Today, denial of service (DoS) attacks cause significant disruptions to the Internet, which will threaten the operation of network-based control systems (NBCS). In this paper, we propose two queueing models to simulate the stochastic process of packet delay jitter and loss under DoS attacks. The motivation is to quantitatively investigate how these attacks degrade the performance of NBCS. The example control system consists of a proportional integral controller, a second-order plant, and two one-way delay vectors induced by attacks. The simulation results indicate that Model I attack (local network DoS attack) impairs the performance because a large number of NBCS packets are lost. Model II attack (nonlocal network DoS attack) deteriorates the performance or even destabilizes the system. In this case, the traffic for NBCS exhibits strong autocorrelation of delay jitter and packet loss. Mitigating measures based on packet filtering are discussed and shown to be capable of ameliorating the performance degradation.

A control engineer's guide to sliding mode control

Abstract: Presents a guide to sliding mode control for practicing control engineers. It offers an accurate assessment of the so-called chattering phenomenon, catalogs implementable sliding mode control design solutions, and provides a frame of reference for future sliding mode control research.

Proportional-resonant controllers and filters for grid-connected voltage-source converters

Abstract: The recently introduced proportional-resonant (PR) controllers and filters, and their suitability for current/voltage control of grid-connected converters, are described. Using the PR controllers, the converter reference tracking performance can be enhanced and previously known shortcomings associated with conventional PI controllers can be alleviated. These shortcomings include steady-state errors in single-phase systems and the need for synchronous d-q transformation in three-phase systems. Based on similar control theory, PR filters can also be used for generating the harmonic command reference precisely in an active power filter, especially for single-phase systems, where d-q transformation theory is not directly applicable. Another advantage associated with the PR controllers and filters is the possibility of implementing selective harmonic compensation without requiring excessive computational resources. Given these advantages and the belief that PR control will find wide-ranging applications in grid-interfaced converters, PR control theory is revised in detail with a number of practical cases that have been implemented previously, described clearly to give a comprehensive reference on PR control and filtering.

Discrete-time variable structure control systems

Abstract: This paper presents a treatment of discrete variable structure control systems. The purpose is to lay a foundation upon which design of such type of systems can be made properly. Phenomena of switching, reaching, and quasi-sliding mode are investigated thoroughly. Terms pertaining to discrete variable structure control are defined. A method of quasi-sliding mode design is given. The inherently existing quasi-sliding mode band is analyzed. A recently introduced "reaching law approach" is conveniently used to develop the control law for robust control. Comments are given regarding chattering. The design technique is illustrated by a simulated system. >

Neural Network Control of Robot Manipulators and Nonlinear Systems

Abstract: From the Publisher: This graduate text provides an authoritative account of neural network (NN) controllers for robotics and nonlinear systems and gives the first textbook treatment of a general and streamlined design procedure for NN controllers. Stability proofs and performance guarantees are provided which illustrate the superior efficiency of the NN controllers over other design techniques when the system is unknown. New NN properties, such as robustness and passivity are introduced, and new weight tuning algorithms are presented. Neural Network Control of Robot Manipulators and Nonlinear Systems provides a welcome introduction to graduate students, and an invaluable reference to professional engineers and researchers in control systems.