Trade-off Between Time Delays and Control Effort

2000 ◽  
Vol 33 (31) ◽  
pp. 287-291
Author(s):  
Pedro Albertos ◽  
Manuel Olivares ◽  
Mario E. Salgado
Keyword(s):  
Time Delays ◽  
Control Effort ◽  
Trade Off ◽  
And Control

An LQ Approach to Active Control of Vibrations in Helicopters

1996 ◽  
Vol 118 (3) ◽  
pp. 482-488 ◽  
Author(s):  
Sergio Bittanti ◽  
Fabrizio Lorito ◽  
Silvia Strada
Keyword(s):  
Optimal Control ◽  
Active Control ◽  
Linear Quadratic ◽  
Control Effort ◽  
Vibration Effect ◽  
Suitable Definition ◽  
Lq Optimal Control ◽  
The One ◽  
Definition Of ◽  
And Control

In this paper, Linear Quadratic (LQ) optimal control concepts are applied for the active control of vibrations in helicopters. The study is based on an identified dynamic model of the rotor. The vibration effect is captured by suitably augmenting the state vector of the rotor model. Then, Kalman filtering concepts can be used to obtain a real-time estimate of the vibration, which is then fed back to form a suitable compensation signal. This design rationale is derived here starting from a rigorous problem position in an optimal control context. Among other things, this calls for a suitable definition of the performance index, of nonstandard type. The application of these ideas to a test helicopter, by means of computer simulations, shows good performances both in terms of disturbance rejection effectiveness and control effort limitation. The performance of the obtained controller is compared with the one achievable by the so called Higher Harmonic Control (HHC) approach, well known within the helicopter community.

scholarly journals Reading input flooding versus listening input flooding: Can they boost speaking skill?

2017 ◽  
Vol 5 (1) ◽  
pp. 39-58
Author(s):  
Mojgan Rashtchi ◽  
Leila Mohammad Yousefi
Keyword(s):  
Control Group ◽  
Coding System ◽  
Trade Off ◽  
Efl Learners ◽  
Speaking Skill ◽  
Listening Group ◽  
And Control

Abstract The present study compared the effects of reading input flooding and listening input flooding techniques on the accuracy and complexity of Iranian EFL learners’ speaking skill. Participants were 66 homogeneous intermediate EFL learners who were randomly divided into three groups of 22: Reading input flooding group, listening input flooding group, and control group. The reading flooded input group was exposed to the numerous examples of the target structures through reading. In the same phase, the listening group was given relatively the same task, through listening. The participants’ monologues in the posttest were separately recorded, and later transcribed and coded in terms of accuracy and complexity through Bygate’s (2001) standard coding system. The results of ANCOVA indicated the outperformance of reading input flooding group. The study also supported the trade-off effects (Skehan, 1998, 2009) between accuracy and complexity.

scholarly journals Escherichia coli O157 infection on Scottish cattle farms: dynamics and control

2010 ◽  
Vol 8 (60) ◽  
pp. 1051-1058 ◽  
Author(s):  
Xu-Sheng Zhang ◽  
Mark E. J. Woolhouse
Keyword(s):  
Escherichia Coli ◽  
Herd Size ◽  
Parameter Estimates ◽  
Control Effort ◽  
Considerable Uncertainty ◽  
Targeted Interventions ◽  
Dynamics And Control ◽  
And Control ◽  
Parameter Values ◽  
Cattle Farms

In this study, we parametrize a stochastic individual-based model of the transmission dynamics of Escherichia coli O157 infection among Scottish cattle farms and use the model to predict the impacts of both targeted and non-targeted interventions. We first generate distributions of model parameter estimates using Markov chain Monte Carlo methods. Despite considerable uncertainty in parameter values, each set of parameter values within the 95th percentile range implies a fairly similar impact of interventions. Interventions that reduce the transmission coefficient and/or increase the recovery rate of infected farms (e.g. via vaccination and biosecurity) are much more effective in reducing the level of infection than reducing cattle movement rates, which improves effectiveness only when the overall control effort is small. Targeted interventions based on farm-level risk factors are more efficient than non-targeted interventions. Herd size is a major determinant of risk of infection, and our simulations confirmed that targeting interventions at farms with the largest herds is almost as effective as targeting based on overall risk. However, because of the striking characteristic that the infection force depends weakly on the number of infected farms, no interventions that are less than 100 per cent effective can eradicate E. coli O157 infection from Scottish cattle farms, implying that eliminating the disease is impractical.

Optimal Control Design of a Bimorph Optical Beam Deflector

2001 ◽  
Author(s):  
Chang-Po Chao ◽  
Jeng-Sheng Huang ◽  
Ching-Lung Ou Yung ◽  
Rong-Fong Fung
Keyword(s):  
Optimal Control ◽  
Position Control ◽  
Angular Position ◽  
Control Design ◽  
Element Model ◽  
Optical Beam ◽  
Optimal Feedback Control ◽  
Central Position ◽  
Control Effort ◽  
And Control

Abstract The optical beam deflector is composed of two piezoelectric layers, one sandwiched brass layer in the middle with both ends clamped and a mirror attached to the upper surface of the top piezoelectric layer in the central position. This structure is designed to deflect the mirror to a certain angular position by applying external voltage supply to piezo-layers. This study proposes an optimal angular position control scheme of the attached mirror. The governing partial differential equations are first derived for the ensuing analysis and control design, which is followed by the establishment of finite element model in ten nodes specified at some longitudinal points of the optical beam deflector. In order to achieve a faster convergent rate for the deflector to reach the desired angular position, the optimal control of LQ regulator with final states fixed is employed to explore the possibility of shorter transient response and less cost of control effort and states. The optimal feedback control is obtained based on solving a dynamic Riccati equation backward in time. The numerical simulation results are finally provided to validate the theoretical control design.

scholarly journals A Theory of Experimenters: Robustness, Randomization, and Balance

2020 ◽  
Vol 110 (4) ◽  
pp. 1206-1230 ◽  
Author(s):  
Abhijit V. Banerjee ◽  
Sylvain Chassang ◽  
Sergio Montero ◽  
Erik Snowberg
Keyword(s):  
Decision Maker ◽  
Real World ◽  
Robust Performance ◽  
Control Groups ◽  
Trade Off ◽  
Performance Guarantees ◽  
Important Concern ◽  
Expected Performance ◽  
And Control ◽  
Shed Light

This paper studies the problem of experiment design by an ambiguity-averse decision-maker who trades off subjective expected performance against robust performance guarantees. This framework accounts for real-world experimenters’ preference for randomization. It also clarifies the circumstances in which randomization is optimal: when the available sample size is large and robustness is an important concern. We apply our model to shed light on the practice of rerandomization, used to improve balance across treatment and control groups. We show that rerandomization creates a trade-off between subjective performance and robust performance guarantees. However, robust performance guarantees diminish very slowly with the number of rerandomizations. This suggests that moderate levels of rerandomization usefully expand the set of acceptable compromises between subjective performance and robustness. Targeting a fixed quantile of balance is safer than targeting an absolute balance objective. (JEL C90, D81)

Comprehensive Assessment of Semi-Active Vibration Suppression Including Energy Analysis

2006 ◽  
Vol 129 (1) ◽  
pp. 84-93 ◽  
Author(s):  
Kanjuro Makihara ◽  
Junjiro Onoda ◽  
Kenji Minesugi
Keyword(s):  
Time Delays ◽  
Energy Exchange ◽  
Vibration Suppression ◽  
Electrical Energy ◽  
Model Errors ◽  
Active Vibration Suppression ◽  
Suppression Mechanism ◽  
Active Vibration ◽  
Switching Method ◽  
And Control

This paper presents an extensive investigation on the LR-switching method (also called the energy-recycling semi-active method). Compared with the energy-dissipative R-switching method, the LR-switching method has been shown to have significantly better vibration suppression performance. However, certain essential issues affecting a system employing the LR-switching method remained to be dealt with. In particular, we had to clarify its vibration suppression mechanism from the viewpoint of mechanical and electrical energy exchange. Second, the robustness of the method against model errors and control time delays had to be verified. The experiments and numerical simulations that we conducted on a 10-bay truss structure demonstrate that the LR-switching method outperforms other suppression methods under sinusoidal and random excitations, which are more common in real systems and more difficult to deal with than transient vibrations. This paper provides fundamental insights on the LR-switching method and gives the method a guarantee for actual applications.

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