Active vibration isolator for flexible bodies Patent

Vibration control of flexible bodies in steady accelerating environmen

Design and implementation of robust decentralized control laws for the ACES structure at Marshall Space Flight Center

Many large space system concepts will require active vibration control to satisfy critical performance requirements such as line-of-sight accuracy. In order for these concepts to become operational it is imperative that the benefits of active vibration control be practically demonstrated in ground based experiments. The results of the experiment successfully demonstrate active vibration control for a flexible structure. The testbed is the Active Control Technique Evaluation for Spacecraft (ACES) structure at NASA Marshall Space Flight Center. The ACES structure is dynamically traceable to future space systems and especially allows the study of line-of-sight control issues

Magnetic bearings for vibration control

A survey is presented on the research of the Institute of Mechanics of the ETH in the field of vibration control with magnetic bearings. It shows a method for modelling an elastic rotor so that it can be represented by a low order model amenable to control techniques. It deals with the control law and spill-over effects, and it also discusses experimental results for an active resonance damper

Active Vibration Control of Structures using an Impedance Matching Control Technique

Active vibration control of structures has gained a lot of interest in recent years. This paper presents an active vibration control methodology of a structure using piezoelectric actuators. The proposed methodology is useful in practical applications where the system to be controlled is difficult to model due to the presence of complex boundary conditions. The impedance matching control technique uses a power flow approach wherein the controller is designed such that the power flow into the structure is minimized. The system transfer function is obtained from the experimental collocated actuator/sensor pair data using Eigen Realisation Algorithm (ERA). The controller is designed for the system transfer function according to impedance matching theory. The above approach is targeted towards the vibration control of wind tunnel stings, which suffer from flow-induced vibration. A wind tunnel sting model is designed and fabricated for this study. The real time implementation of the impedance matching controller has been carried out using dSPACE® Digital Signal Processor (DSP) card. The results are encouraging and demonstrate the feasibility of applying this technique in the wind tunne

Intelligent Learning Algorithms for Active Vibration Control

YesThis correspondence presents an investigation into the comparative performance of an active vibration control (AVC) system using a number of intelligent learning algorithms. Recursive least square (RLS), evolutionary genetic algorithms (GAs), general regression neural network (GRNN), and adaptive neuro-fuzzy inference system (ANFIS) algorithms are proposed to develop the mechanisms of an AVC system. The controller is designed on the basis of optimal vibration suppression using a plant model. A simulation platform of a flexible beam system in transverse vibration using a finite difference method is considered to demonstrate the capabilities of the AVC system using RLS, GAs, GRNN, and ANFIS. The simulation model of the AVC system is implemented, tested, and its performance is assessed for the system identification models using the proposed algorithms. Finally, a comparative performance of the algorithms in implementing the model of the AVC system is presented and discussed through a set of experiments

Vibration control strategies for proof-mass actuators

Proof-mass actuators have been considered for a broad range of structural vibration control problems, from seismic protection for tall buildings to the improvement of metal machining productivity by stabilizing the self-excited vibrations known as chatter. This broad range of potential applications means that a variety of controllers have been proposed, without drawing direct comparisons with other controller designs that have been considered for different applications. This article takes three controllers that are potentially suitable for the machining chatter problem: Direct velocity feedback, tuned-mass-damper control (or vibration absorber control), and active-tuned-mass-damper control (or active vibration absorber control). These control strategies are restated within the more general framework of Virtual Passive Control. Their performance is first compared using root locus techniques, with a model based on experimental data, including the low frequency dynamics of the proof-mass. The frequency response of the test structure is then illustrated under open and closed-loop conditions. The application of the control strategies to avoid machine-tool chatter vibrations is then discussed, without going into detail on the underlying physical mechanisms of chatter. It is concluded that virtual passive absorber control is more straightforward to implement than virtual skyhook damping, and may be better suited to the problem of machining chatter

Active vibration control in microgravity environment

The low gravity environment of the space station is suitable for experiments or manufacturing processes which require near zero gravity. An experiment was fabricated to test the validity of the active control process and to verify the flow and control parameters identified in a theoretical model. Zero gravity is approximated in the horizontal plane using a low friction air bearing table. An analog control system was designed to activate calibrated air jets when displacement of the test mass is sensed. The experiment demonstrates that an air jet control system introduces an effective damping factor to control oscillatory response. The amount of damping as well as the flow parameters, such as pressure drop across the valve and flow rate of air, are verified by the analytical model

Maneuvering and vibration control of flexible spacecraft

Equations of motion, control strategy, perturbation, rigid-body maneuvers, quasi-modal equations, and vibration control are discussed for flexible spacecraft