Author
Hoon Lee
Other affiliations: Ohio State University, General Motors
Bio: Hoon Lee is an academic researcher from Caterpillar Inc.. The author has contributed to research in topics: Sliding mode control & Control theory. The author has an hindex of 8, co-authored 15 publications receiving 813 citations. Previous affiliations of Hoon Lee include Ohio State University & General Motors.
Papers
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TL;DR: Analysis of chattering in such systems with unmodeled based on the Lyapunov theory and the describing function method and various approaches to reduce chattering are described including methods based on relay control gain adaptation.
535 citations
TL;DR: The chattering can be caused by fast dynamics which were neglected in the ideal model, and these `unmodeled' dynamics with small time constants are usually disregarded in models of servomechanisms, sensors and data processors.
167 citations
05 Jun 2006
TL;DR: In this article, the authors considered the problem of sliding mode control with small time constants of real differentiators, which can lead to oscillations in the vicinity of discontinuity surfaces in the system state space.
Abstract: In practical applications of sliding mode control, engineers may experience undesirable phenomenon of oscillations having finite frequency and amplitude, which is known as `chattering'. At the first stage of sliding mode control theory development the chattering was the main obstacle for its implementation. The major attention was paid to the systems with motion equations in canonical space - space of a system output and its high order derivatives. Small time constants of real differentiators could not be disregarded, if control actions were discontinuous state functions, and they led to oscillations in the vicinity of discontinuity surfaces in the system state space. Chattering is a harmful phenomenon because it leads to low control accuracy, high wear of moving mechanical parts, and high heat losses in power circuits. There are two reasons which can lead to chattering. Similarly to the systems in canonical space, the chattering can be caused by fast dynamics which were neglected in the ideal model. These `unmodeled' dynamics with small time constants are usually disregarded in models of servomechanisms, sensors and data processors. The second reason of chattering is utilization of digital controllers with finite sampling rate, which causes so called `discretization chatter'. Theoretically the ideal sliding mode implies infinite switching frequency. Since the control is constant within a sampling interval, switching frequency can not exceed that of sampling, which lead to chattering as well
90 citations
TL;DR: A design principle of sliding mode control for a multiphase controller is proposed and provides desired phase shifts between phases with the help of adaptive width for the hysteresis loops in switching elements.
Abstract: For the system with sliding mode controllers operated by on/off switches, ‘chattering’ appears in the output of the system when its switching frequency is restricted. In power systems, the switching frequency is commonly limited to prevent power losses, and chattering or ‘ripple’ appears especially in the system current. Common methods to decrease such ripple are based on ‘harmonic cancellation’ using the multiple number of phase channels having the desired phase shift that brings cancellation in the sum of outputs from the individual channels. In this article, a design principle of sliding mode control for a multiphase controller is proposed. The methodology is originated from the concept of multidimensional sliding mode and provides desired phase shifts between phases with the help of adaptive width for the hysteresis loops in switching elements. The chattering suppression effect is demonstrated by simulations for the DC–DC converter systems in various situations.
88 citations
01 Aug 2006
TL;DR: To reduce the chattering, new sliding mode control design is proposed using the methods of changing switching gain along the system states or the magnitude of equivalent control.
Abstract: This paper presents analysis of the chattering and a new approach of the chattering suppression. The chattering caused by the unmodeled dynamics is discussed and analyzed by the Lyapunov method and the describing function approach. It is shown that the amplitude of chattering depends on the magnitude of discontinuous control. To reduce the chattering, new sliding mode control design is proposed using the methods of changing switching gain along the system states or the magnitude of equivalent control. To support the methods, simulation results are provided.
48 citations
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TL;DR: The goal is to obtain a robust sliding mode adaptive-gain control law with respect to uncertainties and perturbations without the knowledge of uncertainties/perturbations bound (only the boundness feature is known).
Abstract: This article proposes new methodologies for the design of adaptive sliding mode control. The goal is to obtain a robust sliding mode adaptive-gain control law with respect to uncertainties and perturbations without the knowledge of uncertainties/perturbations bound (only the boundness feature is known). The proposed approaches consist in having a dynamical adaptive control gain that establishes a sliding mode in finite time. Gain dynamics also ensures that there is no overestimation of the gain with respect to the real a priori unknown value of uncertainties. The efficacy of both proposed algorithms is confirmed on a tutorial example and while controlling an electropneumatic actuator.
676 citations
TL;DR: Analysis of chattering in such systems with unmodeled based on the Lyapunov theory and the describing function method and various approaches to reduce chattering are described including methods based on relay control gain adaptation.
535 citations
TL;DR: In this paper an adaptation methodology is developed for searching the minimum possible value of control based on evaluations of the, so-called, equivalent control by a low-pass filter based on direct measurements of the first-order low- pass filter.
436 citations
TL;DR: Methods applicable to stationary obstacles, moving obstacles and multiple vehicles scenarios are reviewed, and particular attention is given to reactive methods based on local sensory data, with a special focus on recently proposed navigation laws based on model predictive and sliding mode control.
Abstract: We review a range of techniques related to navigation of unmanned vehicles through unknown environments with obstacles, especially those that rigorously ensure collision avoidance (given certain assumptions about the system). This topic continues to be an active area of research, and we highlight some directions in which available approaches may be improved. The paper discusses models of the sensors and vehicle kinematics, assumptions about the environment, and performance criteria. Methods applicable to stationary obstacles, moving obstacles and multiple vehicles scenarios are all reviewed. In preference to global approaches based on full knowledge of the environment, particular attention is given to reactive methods based on local sensory data, with a special focus on recently proposed navigation laws based on model predictive and sliding mode control.
390 citations