Search

Summary: This paper describes a new robust model predictive control (MPC) scheme to control the discrete‐time linear parameter‐varying input‐output models subject to input and output constraints. Closed‐loop asymptotic stability is guaranteed by including a quadratic terminal cost and an ellipsoidal terminal set, which are solved offline, for the underlying online MPC optimization problem. The main attractive feature of the proposed scheme in comparison with previously published results is that all offline computations are now based on the convex optimization problem, which significantly reduces conservatism and computational complexity. Moreover, the proposed scheme can handle a wider class of linear parameter‐varying input‐output models than those considered by previous schemes without increasing the complexity. For an illustration, the predictive control of a continuously stirred tank reactor is provided with the proposed method. [ABSTRACT FROM AUTHOR]

In this paper, the delayed state fractional order derivative (DSFOD) is introduced into the existing traditional consensus protocol aiming to improve the robustness of fractional-order multi-agent systems against communication time delay. Both of communication channels with time-delay and without time-delay cases are considered. Based on the frequency-domain analysis and algebraic graph theory, it is shown that properly choosing the intensity of DSFOD can improve the robustness of fractional-order multi-agent systems against communication delay. Finally, a simulated example with simulations is presented to confirm the correctness and effectiveness of the theoretical results. [ABSTRACT FROM AUTHOR]

This paper extends the existing proximate time-optimal servomechanism control methodology to the more typical second-order servo systems with a damping element. A parameterized design of expanded proximate time-optimal servomechanism control law with a speed-dependent linear region is presented for rapid and smooth set-point tracking using a bounded input signal. The control scheme uses the time-optimal bangbang control law to accomplish maximum acceleration or braking whenever appropriate and then smoothly switches into a linear control law to achieve a bumpless settling. The closed-loop stability is analyzed, and then the control scheme is applied to the position--velocity control loop in a permanent magnet synchronous motor servo system for set-point position regulation. Numerical simulation has been conducted, followed by experimental verification based on a TMS320F2812 digital signal controller board. The results confirm that the servo system can track a wide range of target references with superior transient performance and steady-state accuracy. [ABSTRACT FROM AUTHOR]

To function well in an unpredictable environment using unreliable components, a system must have a high degree of robustness. Robustness is fundamental to biological systems and is an objective in the design of engineered systems such as airplane engines and buildings. Cognitive systems, like biological and engineered systems, exist within variable environments. This raises the question, how do cognitive systems achieve similarly high degrees of robustness? The aim of this study was to identify a set of mechanisms that enhance robustness in cognitive systems. We identify three mechanisms that enhance robustness in biological and engineered systems: system control, redundancy, and adaptability. After surveying the psychological literature for evidence of these mechanisms, we provide simulations illustrating how each contributes to robust cognition in a different psychological domain: psychomotor vigilance, semantic memory, and strategy selection. These simulations highlight features of a mathematical approach for quantifying robustness, and they provide concrete examples of mechanisms for robust cognition. [ABSTRACT FROM AUTHOR]

ABSTRACT A compact dual-frequency rectenna has been developed. The receiving antenna is based on a planar inverted F antenna for dual frequency operation. A voltage doubler is proposed to improve the output voltage and the robustness of the rectenna. The simulation and measurement results validate the performance of the rectenna. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:319-322, 2015 [ABSTRACT FROM AUTHOR]

We discuss robust M-estimation of INARCH models for count time series. These models assume the observation at each point in time to follow a Poisson distribution conditionally on the past, with the conditional mean being a linear function of previous observations. This simple linear structure allows us to transfer M-estimators for autoregressive models to this situation, with some simplifications being possible because the conditional variance given the past equals the conditional mean. We investigate the performance of the resulting generalized M-estimators using simulations. The usefulness of the proposed methods is illustrated by real data examples. [ABSTRACT FROM AUTHOR]

Simultaneous localization and mapping ( SLAM) is an important and challenging task for the operation of autonomous mobile robots in which both the pose of the robot and features of the environment need to be estimated at the same time. In particular, it is desirable to achieve robustness and efficiency in the SLAM implementation. Robots in unknown environment are likely to be subject to modeling errors which cannot be easily characterized in terms of statistical properties. To mitigate the effect of uncertainties and disturbances, robust filters such as the H∞ filter can be employed. However, robust filters are complex to implement, demanding a significant amount of computational resources. This study proposes a compressed H∞ filter to solve the robust SLAM problem in which robot dynamics are subject to uncertainties and measurements are subject to bounded-but-unknown disturbances. To achieve an efficient implementation, the state is partitioned into active and inactive states where the latter refers to state variables which are invariant and independent of the measurement at the epoch. With such a partitioning, the active state represents the robot pose and locations of landmarks inside a certain area surrounding the robot. The computational load is reduced since only active state needs to be estimated within a time segment. An update scheme is proposed to refine the whole state at the end of the time segment. Moreover, the relative landmark representation which results in a small cross-correlation between active state and inactive state is employed to reduce the errors. As a result, both efficiency and robustness can be achieved. Simulations reveal that the results obtained from the proposed compressed H∞ filter, which has lower computational complexity, are very close to those from the full order H∞ filter. Further, the compressed H∞ filter is more robust than EKFs and FastSLAM. [ABSTRACT FROM AUTHOR]

Abstract: Mutual inhibitory positive feedback (MIPF), or double-negative feedback, is a key regulatory motif of cellular memory with the capability of maintaining switched states for transient stimuli. Such MIPFs are found in various biological systems where they are interlinked in many cases despite a single MIPF can still realize such a memory effect. An intriguing question then arises about the advantage of interlinking MIPFs instead of exploiting an isolated single MIPF to realize the memory effect. We have investigated the advantages of interlinked MIPF systems through mathematical modeling and computer simulations. Our results revealed that interlinking MIPFs expands the parameter range of achieving the memory effect, or the memory region, thereby making the system more robust to parameter perturbations. Moreover, the minimal duration and amplitude of an external stimulus required for off-to-on state transition are increased and, as a result, external noises can more effectively be filtered out. Hence, interlinked MIPF systems can realize more robust cellular memories with respect to both parameter perturbations and external noises. Our study suggests that interlinked MIPF systems might be an evolutionary consequence acquired for a more reliable memory effect by enhancing robustness against noisy cellular environments. [Copyright &y& Elsevier]