1,721,104 research outputs found
Simulation of stochastic systems via polynomial chaos expansions and convex optimization
No full textNonlinear stochastic model predictive control via regularized polynomial chaos expansions
No full text
Automatic crosswind flight of tethered wings for airborne wind energy: Modeling, control design, and experimental results
Full text linkCalcium homeostasis: A feedback control point of view
Full text linkMathematical tools are not very common in the analysis of biological systems. This is due to the fact that biology had long been considered to be a highly qualitative science. Considering the impact that feedback control theory had on technological and physical sciences and the fact that feedback mechanisms abound in biological systems, it might be highly fruitful to place those systems in the same framework. This point is demonstrated by examining the calcium homeostatic mechanism. For animals and humans, maintaining a constant concentration of calcium is crucial for proper nerve and muscle function. Normally, maintaining such concentrations is accomplished by an effective feedback control mechanism. At parturition, however, the sudden increase in demand for calcium and the associated hypocalcemia can stress the calcium homeostatic system tremendously. The large deviations in the calcium concentration that develop cannot be properly understood without understanding the dynamics of the underlying feedback mechanism. In this thesis, it will be shown that such an understanding can also be used in explaining the cause of parturient paresis, a common disease associated with calving and lactation in dairy cows
Robust controller design for rigid body manipulator
Full text linkAlthough PID controllers are easily implementable, the performance requirements of the robot with these controllers may not be totally satisfied if we do not have the exact knowledge of parameters of the robot. In order to improve the performance and stability range of operation of the manipulator, more sophisticated control methods should be considered. One such method is robust control. Broadly speaking, robust control is concerned with the design of a controller for the system without exact knowledge of the parameters of the system. In this thesis, we will consider robust control of rigid body manipulators under some unknown perturbations. All signals considered here belong to L(subscript)∞ signal space
Synthesis of a robust control system in the L₁ framework
Full text linkThis thesis addresses the ℓ₁ control problem. The objective of the ℓ₁ control problem is to design a stabilizing controller that minimizes the peak error signals due to unknown bounded disturbances and unmodeled dynamics in the system. In mathematical words, we want to design a linear time invariant controller that minimizes the induced ℓ∞ norm of the transfer function relating unknown bounded disturbances and unmodeled dynamics in the system, and the regulated output signals of interest. Since the induced ℓ∞ norm of the transfer function is equal to the 1-norm of the impulse response of the transfer function, a 1-norm optimization problem is to be solved.
In this thesis, an ℓ₁ control problem with multi dimension perturbations is presented. The ℓ₁ robust performance problem is shaped as a robust stability problem. To satisfy design constraints, the ℓ₁ control problem is converted into an unconstrained nonlinear programming problem. Thus we want to solve an unconstrained nonlinear optimization problem as a function of some optimization parameters for an optimal. Several deterministic unconstrained nonlinear programming methods were utilized to optimize the problem. They range from one dimensional to multidimensional optimization algorithms. Post-optimal analysis of the optimal solution is performed to check whether the closed loop system has met the robust performance and robust stability conditions. As a result, decision can be made regarding the existence of a linear time invariant controller that meets the robustness and stability constraints. If the controller exists, then the Youla parameterization method is used to retrieve the parameters of the desired controller from the post optimal solution data
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Robustness analysis for thyristor controlled series compensators in power systems and its performance comparison against static var compensators
Full text linkTransferring more electric power from one point in the transmission grid to another has been a topic of research for a long time. In doing so, stability problems have arisen in the system. Thyristor Controlled Series Compensator (TCSC) has been known to) be able to successfully improve damping performance and stability limits. The current industry practice for the analysis and gain tuning of TCSC uses conventional linear analysis tools. This method does not guarantee robustness over a range of operating points. This thesis provides the framework for robust stability analysis and gain tuning of TCSC in power systems. It involves the application of the structured singular value (SSV or [Mu]) analysis to tune the gain of TCSC and to perform the robust stability analysis on power system with TCSC over a given range of operating points. This thesis also presents the performance comparison of TCSC and Static Var Compensator (SVC) with and without a Supplementary Damping Controller (SDC). The technique was applied to two test systems: the IEEE 4-machine system and the IEEE 50-machine system. The results showed that TCSC tuned with the [Mu]-based TCSC gain tuning technique improved the stability limit and damping performance
- …
