Active control of a piezo-composite rotating beam using coupled plant dynamics

Optimal control of a thin-walled rotating beam is considered using a higher-order shear deformation theory (HSDT). The beam is pretwisted, doubly tapered, and carries a tip rotor. it comprises an orthotropic host with surface-embedded transversely isotropic piezoelectric sensor-actuator pairs. Spanwise and thicknesswise variation of the electric field applied to actuators is considered. This yields a coupled electro-mechanical system, wherein all displacement variables are coupled via the electric field. Hence, coupling between bending-transverse shear and extension-twist occurs even when the ply angle configuration has circumferentially uniform stiffness. Optimal LQR control with state feedback is used to obtain the control input. i.e., charge density (hence voltage) applied to actuators. Parametric studies involving ply-angle, rotation speeds of beam and rotor, pretwist, taper, rotor mass, and saturation constraint on actuator voltage, are performed. The HSDT yields lowest coupled natural frequencies (as compared to unshearable and first-order shear models) thus providing conservative data, useful for passive and active control designs. The present plant model, with spanwise varying electric field, yields an order-of-magnitude reduction in settling time and control voltage, and lower response, vis-a-vis the decoupled approach

Lateral-Torsional Response Control of MR Damper Connected Buildings

Lateral-torsional seismic response control of two single-storey asymmetric plan buildings, interconnected using multiple magnetorheological (MR) dampers, is studied. LQR control is used to obtain desired control forces. The desired damper force, for the two damper case studied herein, is obtained using least square minimization. Command voltages for the dampers are predicted using either a Recurrent Neural Network (RNN) or Clipped Voltage Law (CVL). Effective controllers are obtained based on performance criteria, by varying damper configurations and using ElCentro excitation. Response for harmonic excitation is obtained using the effective controllers. LQR-CVL and LQR-RNN prove considerably more effective than Passive-off control for response reduction of flexible building B1 but not so for rigid building B2. They yield a re-distribution of base shear and torque between the buildings. When compared to Passive-on control their performance ranges from superior to comparable, except for torsional acceleration of B2 for which it is inferior. They yield considerable reduction in peak base shear/torque, and require much less power, compared to Passive-on control where saturation voltage is applied. LQR-RNN is somewhat more effective than LQR-CVL in response attenuation. Hence, lateral-torsional response of adjacent asymmetric buildings can be attenuated using MR damper coupling driven by a LQR-RNN controller

Semi-active control using magnetorhelogical dampers with output feedback and distributed sensing

Control of seismic response of a building fitted with magnetorheological dampers is considered using Optimal Static Output Feedback (OSOF) for desired damper forces. The Modified Bouc-Wen damper model is used and two control voltage laws based on the MR constraint filter, i.e., Semi-inverse Quadratic Voltage Law and Semi-inverse On-Off Voltage Law, are proposed. These appear to perform at least as well as an existing Clipped Voltage Law. Comparisons with available results from a robust reliability-based controller show OSOF control to be quite effective. Controlled response using OSOF is compared with Linear Quadratic Guassian (LQG) and passive-on controllers. Moderate to substantial reduction in maximum peak/RMS responses is mostly obtained with base configuration of sensors when using OSOF control, and controller CPU time reduces by two orders of magnitude. Parametric studies regarding sensor configuration and state/control weighting matrices are performed in order to obtain effective control. Effective OSOF control requires drift feedback with drift sensor preferably collocated with damper

LQG and OSOF Control of Tall Building Using Variable Stiffness Tuned Mass Damper

The Linear Quadratic Gaussian (LQG) and Optimal Static Output Feedback controls (OSOF) are used to control wind excited benchmark building by using semiactive variable stiffness-tuned mass damper (SAVS-TMD/ST) at its top. The control force is realized by varying the device stiffness around nominal stiffness which corresponds to the structure's fundamental frequency, by changing device configuration within its specified linear range and by using a simple control law. The time invariance of the system is maintained. The control is applied to nominal structure and structure with +/- 15% variation in stiffness, by using output feedback as one acceleration in STLQG (ST with LQG) control and three drifts and one velocity in STOSOF (ST with OSOF) control. Results show that, in response reduction the present STLQG controller is equally effective as ALC (active TMD with LQG) controller and mostly better than STSC (ST with Short Time Fourier Transform) controller, and STLC (ST with LQR) controller. The STOSOF also perform well as ALC and is mostly better than STSC in response reduction, for the 0% and -15% stiffness variation cases. For the +15% stiffness variation case, although STOSOF is not as good as ALC in all responses and as STSC in peak responses, it is still comparable with STLC in all responses and with STSC in RMS responses. With substantially less power and control force as compared to ALC, and with limited sensors, both controllers perform well in controlling the structural response

Bridge Deck Flutter Control Using Winglets and Static Output Feedback

Control of wind-induced flutter of a bridge deck is studied using static output feedback. Servomotor-actuated winglets provide the control forces. Deck and winglets are modeled as flat plates and their aerodynamic interaction is neglected. Self-excited wind forces acting on deck and winglets are modeled using the Scanlan-Tomko model, with flat plate flutter derivatives (FDs) obtained from Theodorsen functions. Rogers rational function approximation (RFA) is used for time domain representation of wind forces in order to simplify the stability and control analyses. Control input to servomotors is based on direct feedback of vertical and torsional displacements of deck. Feedback gains that are constant, or varying with wind speed, are considered. Winglet rotations being restricted, flutter and divergence behavior is studied using system eigenvalues as well as responses. Results show that variable gain output feedback (VGOF) control using servomotor driven winglets is very effective. It provides the maximum increase in critical speed and maximum attenuation of response, followed by control with gain scheduling, with the former requiring less input power. Control with constant gain is least effective. Control of deck rotation generally appears to improve with wind speed

LQR Control of Wind Excited Benchmark Building Using Variable Stiffness Tuned Mass Damper

LQR control of wind induced motion of a benchmark building is considered. The building is fitted with a semiactive variable stiffness tuned mass damper adapted from the literature. The nominal stiffness of the device corresponds to the fundamental frequency of the building and is included in the system matrix. This results in a linear time-invariant system, for which the desired control force is computed using LQR control. The control force thus computed is then realized by varying the device stiffness around its nominal value by using a simple control law. A nonlinear static analysis is performed in order to establish the range of linearity, in terms of the device (configuration) angle, for which the control law is valid. Results are obtained for the cases of zero and nonzero structural stiffness variation. The performance criteria evaluated show that the present method provides displacement control that is comparable with that of two existing controllers. The acceleration control, while not as good as that obtained with the existing active controller, is comparable or better than that obtained with the existing semiactive controller. By using substantially less power as well as control force, the present control yields comparable displacement control and reasonable acceleration control