An robust tracking control architecture is proposed for a class of continuous-time nonlinear dynamic systems actuated by piezoelectric actuators. Generally, hysteresis nonlinearity exists in the piezoelectric actuator...
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An robust tracking control architecture is proposed for a class of continuous-time nonlinear dynamic systems actuated by piezoelectric actuators. Generally, hysteresis nonlinearity exists in the piezoelectric actuator, which may cause undesirable inaccuracy. Based on solutions of a general hysteresis model, an approximation function is introduced to compensate for effects of the hysteresis nonlinearities. This approximation function is implemented by fuzzy logic method, which is expressed as a series expansion of basis functions. Combining this approximation function with adaptive control techniques, a robust control algorithm is developed. As a result, global asymptotic stability of the system is established in the Lyapunov sense.
This paper presents the theoretical development and experimental results of an active control system used to create a variable impedance termination on a Timoshenko beam that allows for the arbitrary setting of the re...
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This paper presents the theoretical development and experimental results of an active control system used to create a variable impedance termination on a Timoshenko beam that allows for the arbitrary setting of the reflection and/or transmition coefficients at the active boundary of the beam. A realizable feedforward control configuration with one input and two outputs is derived where a cost function constructed by filtering the response from four closely spaced sensors is minimized. The effectiveness of the system was evaluated experimentally on an aluminum beam with four patches of PVDF piezofilm used as sensors and two pairs of PZT piezoceramic patches used as bending moment actuators.
The optimal motion control of an asymmetric rotor-magnetic bearing system based on the linear quadratic regulator theory (LQR) is addressed in this paper. To this end, and as a basic prerequisite, a rigorous modeling ...
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The optimal motion control of an asymmetric rotor-magnetic bearing system based on the linear quadratic regulator theory (LQR) is addressed in this paper. To this end, and as a basic prerequisite, a rigorous modeling of the rotor-magnetic bearing system that includes also the unbalance effect is considered. The derivation of the equations of motion is based upon the application of the Hamilton's variational principle. New schemes related to the selection of the state weighting matrix Q and the control weighting matrix R involved in the quadratic functional to be mimized are proposed. The obtained results are compared with those reported in the available literature and the benefices of the selected weighting matrices are revealed.
An experimental testbed is described that is used to study the feasibility of control of a class of flows that have low Reynolds numbers. The experimental testbed is comprised of a thin airfoil with a backward facing ...
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An experimental testbed is described that is used to study the feasibility of control of a class of flows that have low Reynolds numbers. The experimental testbed is comprised of a thin airfoil with a backward facing step machined into the upper surface. A thin PZT composite flap is mounted at the edge of the backward facing step to enable modification of the flow. Output measurement sensors consist of MEMs-based shear stress sensors, and conventional pressure taps, located on the surface of the airfoil. This paper derives a control framework for the synthesis of control methodologies for the testbed. A reduced order control model is obtained by employing reduced basis approximations of the two dimensional Navier-Stokes equations. Preliminary open loop experimental results are reported that illustrate the existence of convected large scale structures in the flow.
A theory for localized vibration control that is based on a partitioned Linear Quadratic Regulator (LQR) synthesis is presented. The present localized control consists of two components: a localized LQR controller tha...
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A theory for localized vibration control that is based on a partitioned Linear Quadratic Regulator (LQR) synthesis is presented. The present localized control consists of two components: a localized LQR controller that minimizes the control effort to attenuate the disturbances directly applied to each partitioned substructural system, and a controller that mitigates the interface transmission forces. The present theory is applicable both for quasistatic structural shape control and for the attenuation of structural vibrations. The localized controllers can be implemented in terms of strain actuation, proof-mass actuators, and strain rate-type active dampers. The basic features of the present theory are illustrated via numerical experiments as applied to the control of vibrations of a beam.
This paper is concerned with the real-time automatic tuning of the multi-input multi-output positive position feedback controllers for smartstructures by the genetic algorithms. The genetic algorithms have proven its...
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This paper is concerned with the real-time automatic tuning of the multi-input multi-output positive position feedback controllers for smartstructures by the genetic algorithms. The genetic algorithms have proven its effectiveness in searching optimal design parameters without falling into local minimums thus rendering globally optimal solutions. The previous real-time algorithm that tunes a single control parameter is extended to tune more parameters of the MIMO PPF controller. We employ the MIMO PPF controller since it can enhance the damping value of a target mode without affecting other modes if tuned properly. Hence, the traditional positive position feedback controller can be used in adaptive fashion in real time. The final form of the MIMO PPF controller results in the centralized control, thus it involves many parameters. The bounds of the control parameters are estimated from the theoretical model to guarantee the stability. As in the previous research, the digital MIMO PPF control law is downloaded to the DSP chip and a main program, which runs genetic algorithms in real time, updates the parameters of the controller in real time. The experimental frequency response results show that the MIMO PPF controller tuned by GA gives better performance than the theoretically designed PPF. The time response also shows that the GA tuned MIMO PPF controller can suppress vibrations very well.
A neural network-based control system is developed for self-adapting vibration control of laminated plates with piezoelectric sensors and actuators. The conventional vibration control approaches are limited by the req...
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A neural network-based control system is developed for self-adapting vibration control of laminated plates with piezoelectric sensors and actuators. The conventional vibration control approaches are limited by the requirement of an explicit and often accurate identification of the system dynamics and subsequent 'offline' design of an optimal controller. The present study utilizes the powerful learning capabilities of neural networks to capture the structural dynamics and to evolve optimal control dynamics. A hybrid control system developed in this paper is comprised of a feed-forward neural network identifier and a dynamic diagonal recurrent neural network (DRNN) controller. Sensing and actuation are achieved using piezoelectric sensors and actuators. The performance of hybrid control system is tested by numerical simulation of composite plate with embedded piezoelectric actuators and sensors. Finite element equations of motion are developed based on shear deformation theory and implemented for a plate element. The dynamic effects of the mass and stiffness of the piezoelectric patches are considered in the model. Numerical results are presented for a flat plate. A robustness study including the effects of structural parameter variation and partial loss of sensor and actuator is performed. The hybrid control system is shown to perform effectively in all these cases.
In this paper, the concept of variable structure system (VSS) with sliding mode was used to develop a fuzzy controller for a class of nonlinear system. The proposed sliding mode fuzzy controller (SMFC) preserves the f...
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In this paper, the concept of variable structure system (VSS) with sliding mode was used to develop a fuzzy controller for a class of nonlinear system. The proposed sliding mode fuzzy controller (SMFC) preserves the fundamental property of sliding mode control that is stability and robustness in the presence of disturbances and model uncertainties. To reduce the number of design parameters in SMFC, we adopted the concept of parameterization or input-output mapping factor and devised a systematic tool for analyzing and enhancing the performance of SMFC. For demonstration, we applied the SMFC to the inverted pendulum problem. Simulation results indicates that the fuzzy sliding mode control perform well in the presence of disturbances and is insensitive to the parameter variation of the system.
Coupling adjacent buildings with supplemental damping devices is a developing method of mitigating structural responses due to wind and seismic excitations. The concept is to allow structures, vibrating at different f...
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Coupling adjacent buildings with supplemental damping devices is a developing method of mitigating structural responses due to wind and seismic excitations. The concept is to allow structures, vibrating at different frequencies, to exert control forces upon one another to reduce the overall responses of the system. Previous studies have identified optimal coupled building configurations and have introduced passive, active and 'smart' damping control strategies. This paper will focus on the application of 'smart' dampers as coupling link devices to produce control forces between three tall buildings. smart dampers are semi-active dampers capable of changing their dynamic characteristics in real-time to allow for a variety of control forces to be produced without requiring significant energy. A clipped optimal control strategy is employed for the smart dampers that can provide increased performance, over a comparable passive control strategy, during moderately severe seismic events.
A systematic method is introduced for optimal integration of smart (active) materials based actuators into the structure of cooperating robots and robot manipulators with parallel kinematics chain for the purpose of e...
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A systematic method is introduced for optimal integration of smart (active) materials based actuators into the structure of cooperating robots and robot manipulators with parallel kinematics chain for the purpose of eliminating the high harmonic components of their actuated joint motions. As a result, the potential excitation of the natural modes of vibration of such systems and their related control problems are greatly reduced. The resulting robotic systems are capable of operating at higher speeds with increased precision.
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