5,542 research outputs found
A comparative study of several control techniques applied to a boost converter
In this paper a comparison among three control strategies is presented, with application to a boost DC-DC converter. The control strategies are developed on the switched boost circuit model and validated on the nonlinear model by use of simulations. The classical PID, a 2dof-IMC (two degree of freedom internal model controller) and an alternative controller - MAC (uprocessor advanced control) are applied, tested and compared on the nonlinear system. Additional tests show the robustness of the controllers on the highly nonlinear circuit
Nonlinear Dual-Mode Control of Variable-Speed Wind Turbines with Doubly Fed Induction Generators
This paper presents a feedback/feedforward nonlinear controller for
variable-speed wind turbines with doubly fed induction generators. By
appropriately adjusting the rotor voltages and the blade pitch angle, the
controller simultaneously enables: (a) control of the active power in both the
maximum power tracking and power regulation modes, (b) seamless switching
between the two modes, and (c) control of the reactive power so that a
desirable power factor is maintained. Unlike many existing designs, the
controller is developed based on original, nonlinear,
electromechanically-coupled models of wind turbines, without attempting
approximate linearization. Its development consists of three steps: (i) employ
feedback linearization to exactly cancel some of the nonlinearities and perform
arbitrary pole placement, (ii) design a speed controller that makes the rotor
angular velocity track a desired reference whenever possible, and (iii)
introduce a Lyapunov-like function and present a gradient-based approach for
minimizing this function. The effectiveness of the controller is demonstrated
through simulation of a wind turbine operating under several scenarios.Comment: 14 pages, 9 figures, accepted for publication in IEEE Transactions on
Control Systems Technolog
Walking dynamics are symmetric (enough)
Many biological phenomena such as locomotion, circadian cycles, and breathing
are rhythmic in nature and can be modeled as rhythmic dynamical systems.
Dynamical systems modeling often involves neglecting certain characteristics of
a physical system as a modeling convenience. For example, human locomotion is
frequently treated as symmetric about the sagittal plane. In this work, we test
this assumption by examining human walking dynamics around the steady-state
(limit-cycle). Here we adapt statistical cross validation in order to examine
whether there are statistically significant asymmetries, and even if so, test
the consequences of assuming bilateral symmetry anyway. Indeed, we identify
significant asymmetries in the dynamics of human walking, but nevertheless show
that ignoring these asymmetries results in a more consistent and predictive
model. In general, neglecting evident characteristics of a system can be more
than a modeling convenience---it can produce a better model.Comment: Draft submitted to Journal of the Royal Society Interfac
Cogging torque reduction in brushless motors by a nonlinear control technique
This work addresses the problem of mitigating the effects of the cogging torque in permanent magnet synchronous motors, particularly brushless motors, which is a main issue in precision electric drive applications. In this work, a method for mitigating the effects of the cogging torque is proposed, based on the use of a nonlinear automatic control technique known as feedback linearization that is ideal for underactuated dynamic systems. The aim of this work is to present an alternative to classic solutions based on the physical modification of the electrical machine to try to suppress the natural interaction between the permanent magnets and the teeth of the stator slots. Such modifications of electric machines are often expensive because they require customized procedures, while the proposed method does not require any modification of the electric drive. With respect to other algorithmic-based solutions for cogging torque reduction, the proposed control technique is scalable to different motor parameters, deterministic, and robust, and hence easy to use and verify for safety-critical applications. As an application case example, the work reports the reduction of the oscillations for the angular position control of a permanent magnet synchronous motor vs. classic PI (proportional-integrative) cascaded control. Moreover, the proposed algorithm is suitable to be implemented in low-cost embedded control units
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