The seismic response of a single-story steel building frame with a smart base isolation system is evaluated. The isolation system consists of sliding bearings combined with an adaptive fluid damper. The damping capaci...
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The seismic response of a single-story steel building frame with a smart base isolation system is evaluated. The isolation system consists of sliding bearings combined with an adaptive fluid damper. The damping capacity of the fluid damper can be modulated in real-time based on feedback from the measured ground motion and superstructure response. The adaptive capabilities of the fluid damper enable the isolation system displacement to be controlled while simultaneously limiting the interstory drift response of the superstructure. This paper concentrates on the development of analytical models and control algorithms for the isolation system components and the superstructure. In general, the results from numerical simulations demonstrate that, for disparate earthquake ground motions, the smart isolation system is capable of simultaneously limiting both the response of the bearings and the superstructure.
This paper presents a semi-active control of a scaled two-span bridge structure. Magneto-rheological fluid (MRF) dampers are utilized as the semi-active devices and a bridge vibration control system is developed. Both...
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This paper presents a semi-active control of a scaled two-span bridge structure. Magneto-rheological fluid (MRF) dampers are utilized as the semi-active devices and a bridge vibration control system is developed. Both open and closed-loop control systems are used to suppress the bridge deck motion under simple harmonic and simulated earthquake excitation. Effectiveness of each system is discussed. It is demonstrated that the closed-loop control systems can reduce the relative deck displacement of the bridge, while simultaneously limiting the peak damper forces.
On-blade smart structure actuators are capable of actively altering the earodynamic loads on rotor blades. With a suitable feedback control law, such actuators could potentially be used to counter the vibrations induc...
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On-blade smart structure actuators are capable of actively altering the earodynamic loads on rotor blades. With a suitable feedback control law, such actuators could potentially be used to counter the vibrations induced by periodic aerodynamic loading on the blades with lower weight penalties than the previous actuation methods and without the bandwidth constraints. This paper covers the development and testing of a new, robust individual blade control (IBC) methodology for rotor vibration suppression using piezo actuated trailing edge flaps and active twist tip rotors. The controller uses a neural network to learn to actuate the trailing edge flap thus adaptively suppressing the blade or hub vibrations. In this application, no offline training is performed. Instead, a neural network is used in real time to adaptively command the actuator deflections thus reducing vibrations. Closed loop experimental tests with piezo actuated scale rotor systems were conducted on the University of Maryland hover test stand. The results include two different Mach scale smart rotor systems (trailing edge flaps and active tip twist) that were controlled by the same adaptive neurocontrol algorithm. These tests demonstrate the controller's robust ability to successfully learn to control the rotor vibrations with no a priori information about the blade/actuator structure or the aerodynamic loading.
The dynamics of a flexural beam actuated by induced strain surface bonded (piezoelectric) actuators is considered. The bending moment produced by the single actuator is evaluated by means of the pin-force model. A mod...
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The dynamics of a flexural beam actuated by induced strain surface bonded (piezoelectric) actuators is considered. The bending moment produced by the single actuator is evaluated by means of the pin-force model. A modal approach is then used to build special dynamic influence functions which explicitly account for the size and the position of the actuator. Simple optimal geometrical conditions are then obtained and illustrated fur several cases with different boundary conditions.
An Modal filter based Independent Modal Space control (IMSC) method is proposed for active damping enhancement of a flexible space intelligent truss structure. Modal Filter (MF) is used to extract modal states from re...
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An Modal filter based Independent Modal Space control (IMSC) method is proposed for active damping enhancement of a flexible space intelligent truss structure. Modal Filter (MF) is used to extract modal states from response measurement. The MF is developed for the structures with closely spaced modes, or even repeated frequencies. Modal acceleration can then be extracted form physical acceleration measurements via MF. A modified Leunberger observer is adopted to estimate modal displacement and modal velocity from modal acceleration. The MF-based IMSC method is employed to enhance damping of the space intelligent truss structure with active members. A real-time computer control system is developed to implement the MF-based IMSC strategy. Experimental results demonstrate that the intelligent structure design is successful and the active control method is effective.
An integrated structures/controls optimization is developed for vibration suppression of a composite box beam with surface bonded piezoelectric actuators. The penalty approach is used to perform the multi-objective hy...
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An integrated structures/controls optimization is developed for vibration suppression of a composite box beam with surface bonded piezoelectric actuators. The penalty approach is used to perform the multi-objective hybrid optimization to enhance damping of the first lag, flap, and torsion modes while minimizing control input. The objective functions and constraints include damping ratios, and natural frequencies. The design variables include ply orientations of the box beam walls, and the location and size of the actuators. Two box beam configurations are investigated and the results are compared. In the first, piezoelectric actuators are bonded to the top and bottom surfaces and in the second, actuators are bonded to all four walls for additional in-plane actuation. Optimization results show that significant reductions in control input and tip displacement can be achieved in both cases, however, improved response trends are obtained with in-plane actuation.
Much research in this decade has concentrated on the application of modal space control to simplify control design and system monitoring. This investigation will address the fidelity limitations of the modal filter ba...
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Much research in this decade has concentrated on the application of modal space control to simplify control design and system monitoring. This investigation will address the fidelity limitations of the modal filter based classical control strategies. Specifically, when the eigen-parameters shift, in concert with semi-global changes in the systems structural properties resulting in similar mode shape but dramatic shift in frequency. Expressly, this examination will concentrate on two spatially similar five bay box trusses of exactly the same geometry (connections and element lengths) and different materials (steel and plastic) and some shift in cross-sectional dimension. The limitation of these parameter shifts should present a practical bound for future application. The investigation incorporated both analytic and experimentally based models of the structural frequency response and residue matrices to analytically model the control problem. The control is investigated for the lower frequency modes due to experimental model limitations. Investigation includes single and multimode control.
Robot manipulators with parallel kinematics chains and two or more robots manipulating an object form closed kinematics chains. When revolute joints are used in the construction of such robotic manipulation systems, t...
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ISBN:
(纸本)0819436038
Robot manipulators with parallel kinematics chains and two or more robots manipulating an object form closed kinematics chains. When revolute joints are used in the construction of such robotic manipulation systems, the presence of closed chains and their associated kinematics nonlinearity demands high harmonic motions in at least a number of the actuated joints. This is the case even if all the links are relatively rigid and attempt is made to synthesise the joint motions with minimal harmonic content. The presence of high harmonic components in the actuated joint motions is undesirable since as the operating speed is increased, their frequencies would rapidly increase and move beyond the dynamic response limitations of the actuating drives, thereby causing vibration and control problems. The performance of the system in terms of cycle time, tracking precision and the like would therefore suffer. This is particularly the case since the dynamics of such systems is also highly nonlinear and require higher harmonic components in the actuating torques (forces). In this paper, a systematic method is presented 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 the result, the potential excitation of the natural modes of vibration of such systems and their related control problems can be greatly reduced. The resulting robotic systems should therefore be capable of operating at higher speeds with increased precision.
In the scanning electron microscope (SEM), specially designed microrobots can act as a flexible assembly facility for hybrid microsystems, as probing devices for in-situ tests on IC structures or just as a helpful tel...
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In the scanning electron microscope (SEM), specially designed microrobots can act as a flexible assembly facility for hybrid microsystems, as probing devices for in-situ tests on IC structures or just as a helpful teleoperated tool for the SEM operator when examining samples. Several flexible microrobots of this kind have been developed and tested. Driven by piezoactuators, these few cubic centimeters small mobile robots perform manipulations with a precision of up to 10 nm and transport the gripped objects at speeds of up to 3 cm/s. In accuracy, flexibility and price they are superior to conventional precision robots. A new SEM-suited microrobot prototype is described in this paper. The SEM's vacuum chamber has been equipped with various elements like flanges and CCD cameras to enable the robot to operate. In order to use the SEM image for the automatic real-time control of the robots, the SEM's electron beam is actively controlled by a PC. The latter submits the images to the robots' control computer system. For obtaining three-dimensional information in real time, especially for the closed-loop control of a robot endeffector, e.g. microgripper, a triangulation method with the luminescent spot of the SEM's electron beam is being investigated.
This paper presents a time domain study of control actuator scheduling for active structural-acoustic control systems. It is a follow-up study of a previous work on control signal scheduling for reducing the adaptive ...
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This paper presents a time domain study of control actuator scheduling for active structural-acoustic control systems. It is a follow-up study of a previous work on control signal scheduling for reducing the adaptive controller dimensionality in the frequency domain. For a system whose response to acoustic disturbance is well characterized by a small set of measurable state variables, it may be possible to avoid the computational expense associated with the real-time adaptation of a large multichannel controller. Instead, the optimal solution of the controller may be identified off-line as a function of the state variables. The scheduler would identify the best solution given the measured system state, leaving only a small set of magnitudes and phases to be updated by a real-time adaptive algorithm. This work demonstrates how to implement a neural network based actuator scheduling procedure in the time domain. Numerical simulations show good performance of the proposed control strategy. Further experimental studies are needed to validate the theoretical development in real time.
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