8,121 research outputs found
Observer techniques for estimating the state-of-charge and state-of-health of VRLABs for hybrid electric vehicles
The paper describes the application of observer-based state-estimation techniques for the real-time prediction of state-of-charge (SoC) and state-of-health (SoH) of lead-acid cells. Specifically, an approach based on the well-known Kalman filter, is employed, to estimate SoC, and the subsequent use of the EKF to accommodate model non-linearities to predict battery SoH. The underlying dynamic behaviour of each cell is based on a generic Randles' equivalent circuit comprising of two-capacitors (bulk and surface) and three resistors, (terminal, transfer and self-discharging). The presented techniques are shown to correct for offset, drift and long-term state divergence-an unfortunate feature of employing stand-alone models and more traditional coulomb-counting techniques. Measurements using real-time road data are used to compare the performance of conventional integration-based methods for estimating SoC, with those predicted from the presented state estimation schemes. Results show that the proposed methodologies are superior with SoC being estimated to be within 1% of measured. Moreover, by accounting for the nonlinearities present within the dynamic cell model, the application of an EKF is shown to provide verifiable indications of SoH of the cell pack
On the Localized superluminal Solutions to the Maxwell Equations
In the first part of this article the various experimental sectors of physics
in which Superluminal motions seem to appear are briefly mentioned, after a
sketchy theoretical introduction. In particular, a panoramic view is presented
of the experiments with evanescent waves (and/or tunneling photons), and with
the "Localized superluminal Solutions" (SLS) to the wave equation, like the
so-called X-shaped waves. In the second part of this paper we present a series
of new SLSs to the Maxwell equations, suitable for arbitrary frequencies and
arbitrary bandwidths: some of them being endowed with finite total energy.
Among the others, we set forth an infinite family of generalizations of the
classic X-shaped wave; and show how to deal with the case of a dispersive
medium. Results of this kind may find application in other fields in which an
essential role is played by a wave-equation (like acoustics, seismology,
geophysics, gravitation, elementary particle physics, etc.). This e-print, in
large part a review, was prepared for the special issue on "Nontraditional
Forms of Light" of the IEEE JSTQE (2003); and a preliminary version of it
appeared as Report NSF-ITP-02-93 (KITP, UCSB; 2002). Further material can be
found in the recent e-prints arXiv:0708.1655v2 [physics.gen-ph] and
arXiv:0708.1209v1 [physics.gen-ph]. The case of the very interesting (and more
orthodox, in a sense) subluminal Localized Waves, solutions to the wave
equations, will be dealt with in a coming paper. [Keywords: Wave equation; Wave
propagation; Localized solutions to Maxwell equations; Superluminal waves;
Bessel beams; Limited-dispersion beams; Electromagnetic wavelets; X-shaped
waves; Finite-energy beams; Optics; Electromagnetism; Microwaves; Special
relativity]Comment: LaTeX paper of 37 pages, with 20 Figures in jpg [to be processed by
PDFlatex
Combined battery SOC/SOH estimation using a nonlinear adaptive observer
International audience— This work presents a modeling and estimation techniques for State of Charge and State of Health estimation for Li-ion batteries. The analysis is done using an adaptive estimation approach for joint state and parameter estimation and by simplifying an existing nonlinear model previously obtained from experiments tests. A switching mechanism between two observers, one for the charging phase and one for the discharging phase, is done to avoid transients due to the discontinuity of model's parameters. Simulations on experimental data show that the approach is feasible and enhance the interest of the proposed estimation technique
Sensor failure detection system
Advanced concepts for detecting, isolating, and accommodating sensor failures were studied to determine their applicability to the gas turbine control problem. Five concepts were formulated based upon such techniques as Kalman filters and a screening process led to the selection of one advanced concept for further evaluation. The selected advanced concept uses a Kalman filter to generate residuals, a weighted sum square residuals technique to detect soft failures, likelihood ratio testing of a bank of Kalman filters for isolation, and reconfiguring of the normal mode Kalman filter by eliminating the failed input to accommodate the failure. The advanced concept was compared to a baseline parameter synthesis technique. The advanced concept was shown to be a viable concept for detecting, isolating, and accommodating sensor failures for the gas turbine applications
The predictive functional control and the management of constraints in GUANAY II autonomous underwater vehicle actuators
Autonomous underwater vehicle control has been a topic of research in the last decades. The challenges addressed vary depending on each research group's interests. In this paper, we focus on the predictive functional control (PFC), which is a control strategy that is easy to understand, install, tune, and optimize. PFC is being developed and applied in industrial applications, such as distillation, reactors, and furnaces. This paper presents the rst application of the PFC in autonomous underwater vehicles, as well as the simulation results of PFC, fuzzy, and gain scheduling controllers. Through simulations and navigation tests at sea, which successfully validate the performance of PFC strategy in motion control of autonomous underwater vehicles, PFC performance is compared with other control techniques such as fuzzy and gain scheduling control. The experimental tests presented here offer effective results concerning control objectives in high and intermediate levels of control. In high-level point, stabilization and path following scenarios are proven. In the intermediate levels, the results show that position and speed behaviors are improved using the PFC controller, which offers the smoothest behavior. The simulation depicting predictive functional control was the most effective regarding constraints management and control rate change in the Guanay II underwater vehicle actuator. The industry has not embraced the development of control theories for industrial systems because of the high investment in experts required to implement each technique successfully. However, this paper on the functional predictive control strategy evidences its easy implementation in several applications, making it a viable option for the industry given the short time needed to learn, implement, and operate, decreasing impact on the business and increasing immediacy.Peer ReviewedPostprint (author's final draft
Design and application of advanced disturbance rejection control for small fixed-wing UAVs
Small Unmanned Aerial Vehicles (UAVs) have seen continual growth in both research and
commercial applications. Attractive features such as their small size, light weight and
low cost are a strong driver of this growth. However, these factors also bring about some
drawbacks. The light weight and small size means that small UAVs are far more susceptible
to performance degradation from factors such as wind gusts. Due to the generally low
cost, available sensors are somewhat limited in both quality and available measurements.
For example, it is very unlikely that angle of attack is sensed by a small UAV. These
aircraft are usually constructed by the end user, so a tangible amount of variation will
exist between different aircraft of the same type. Depending on application, additional
variation between flights from factors such as battery placement or additional sensors may
exist. This makes the application of optimal model based control methods difficult.
Research literature on the topic of small UAV control is very rich in regard to high
level control, such as path planning in wind. A common assumption in such literature
is the existence of a low level control method which is able to track demanded aircraft
attitudes to complete a task. Design of such controllers in the presence of significant wind
or modelling errors (factors collectively addressed as lumped disturbances herein) is rarely
considered.
Disturbance Observer Based Control (DOBC) is a means of improving the robustness
of a baseline feedback control scheme in the presence of lumped disturbances. The method
allows for the rejection of the influence of unmeasurable disturbances much more quickly
than traditional integral control, while also enabling recovery of nominal feedback con-
trol performance. The separation principle of DOBC allows for the design of a nominal
feedback controller, which does not need to be robust against disturbances. A DOBC
augmentation can then be applied to ensure this nominal performance is maintained even
in the presence of disturbances. This method offers highly attractive properties for control
design, and has seen a large rise in popularity in recent years.
Current literature on this subject is very often conducted purely in simulation. Ad-
ditionally, very advanced versions of DOBC control are now being researched. To make
the method attractive to small UAV operators, it would be beneficial if a simple DOBC
design could be used to realise the benefits of this method, as it would be more accessible
and applicable by many.
This thesis investigates the application of a linear state space disturbance observer to
low level flight control of a small UAV, along with developments of the method needed
to achieve good performance in flight testing. Had this work been conducted purely in
simulation, it is likely many of the difficulties encountered would not have been addressed
or discovered.
This thesis presents four main contributions. An anti-windup method has been devel-
oped which is able to alleviate the effect of control saturation on the disturbance observer
dynamics. An observer is designed which explicitly considers actuator dynamics. This
development was shown to enable faster observer estimation dynamics, yielding better
disturbance rejection performance. During initial flight testing, a significant aeroelastic
oscillation mode was discovered. This issue was studied in detail theoretically, with a pro-
posed solution developed and applied. The solution was able to fully alleviate the effect in
flight. Finally, design and development of an over-actuated DOBC method is presented.
A method for design of DOBC for over actuated systems was developed and studied. The
majority of results in this thesis are demonstrated with flight test data
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