active vibration control system

Top PDF active vibration control system:

An Offset Hub Active Vibration Control System for Mitigating Helicopter Vibrations during Power Loss: Simulation and Experimental Demonstration

An Offset Hub Active Vibration Control System for Mitigating Helicopter Vibrations during Power Loss: Simulation and Experimental Demonstration

The initial condition response of Eqn. (12) with optimal damping coefficients for each imbalance mass and each test was simulated. A comparison of simulated and experimental data is plotted in Figure 21 and 22 for a time interval of 20 seconds after power is disconnected from the motors. The time at which the motor power was disconnected is defined as t=0, and the time at which the simulation is within π of the mass’s final angle is marked by a dashed vertical line. All the imbalances settle out to a consistent predetermined angle after approximately 30 revolutions: via simulation in 8 seconds and experimental result in under 5 seconds. The empirical linear damping model does show error since in reality the system is non-linear, but this approximation is sufficient for an accurate system model which predicts the number of revolutions and the time before the imbalance masses achieve a statically balanced condition. Additional practical design features such as electronic motor braking can be applied to the OHAVCS causing the imbalances to be slowed to near zero velocity in seconds, further mitigating the 1/Rev vibration.
Show more

40 Read more

Numerical Investigation on Toggled Actuator Forces in Active Vibration Control System

Numerical Investigation on Toggled Actuator Forces in Active Vibration Control System

The state vector [𝑍(𝑡)], can be solved easily using LSIM function in M ATLAB ® software package. In this procedure, it is assumed that the control force [𝑢(𝑡)] is known. In an optimal closed-loop control system, optimal control force [𝑢(𝑡)] is adjusted based only on the feedback of [𝑍(𝑡)], i.e. the state vector comprising the displacements and velocities. Therefore, to attain the state vector, the relevant response in the building structure must be measured at time instant 𝑡 by installing the displacement and velocity sensors at the proper locations on each floor. Since the specifications of the two systems, i.e. toggle and tendon systems, have been considered identical, the derived structural displacement responses for both systems would be the same. These structural responses due to the applied earthquake excitations can be calculated using the function LSIM in M ATLAB ® software as follows:
Show more

20 Read more

Characterisation of Magnetorheological Fluids and Its Application in Semi-active Vibration Control System in Automobiles

Characterisation of Magnetorheological Fluids and Its Application in Semi-active Vibration Control System in Automobiles

A typical MR damper includes an MR fluid, a pair of wires, housing, a piston, a magnetic coil, and an accumulator. The MR fluid is filled within the cylinder and flows through a small orifice. The magnetic coil is built in the piston or in the housing of the piston-cylinder arrangement. The MRF particles are aligned and the fluid changes from the initial liquid state to the final semi-solid state within milliseconds, when a current is supplied to the coil. Consequently, a controllable damping force is produced. The force procedured by a MR damper depends on magnetic field induced by the current in the damper coil and the piston velocity . It is capable of generating a force with magnitude sufficient for rapid response in large scale applications [16,2], while requiring only a battery for power [20]. Additionally, their performance is unresponsive to temperature changes or impurities in the fluid and these devices offer highly reliable operations [4,6]. As a result, there has been active research and development of MR fluid dampers and their applications [1,12,18-23].
Show more

5 Read more

Active Vibration Control for a CNC Milling Machine

Active Vibration Control for a CNC Milling Machine

There is a requirement for improved three-dimensional surface characterisation and reduced tool wear when modern computer numerical control (CNC) machine tools are operating at high cutting velocities, spindle speeds and feed rates. For large depths of cut and large material removal rates, there is a tendency for machines to chatter caused by self- excited vibration in the machine tools leading to precision errors, poor surface finish quality, tool wear and possible machine damage. This study illustrates a method for improving machine tool performance by understanding and adap- tively controlling the machine structural vibration. The first step taken is to measure and interpret machine tool vibration and produce a structural model. As a consequence, appropriate sensors need to be selected and/or designed and then integrated to measure all self-excited vibrations. The vibrations of the machine under investigation need to be clearly understood by analysis of sensor signals and surface finish measurement. The active vibration control system has been implemented on a CNC machine tool and validated under controlled conditions by compensating for machine tool vibrations on time-varying multi-point cutting operations for a vertical milling machine. The design of the adaptive control system using modelling, filtering, active vibration platform and sensor feedback techniques has been demonstrated to be successful.
Show more

17 Read more

II.M ETHODOLOGY A. Vibration Detection

II.M ETHODOLOGY A. Vibration Detection

Fig. 5 shows a schematic of the hardware setup developed for verification of the proposed methodology. The plant is a cantilever beam of plain carbon steel (dimensions: 550 mm x 25 mm x 4.5 mm). Two electromagnetic shakers are used to provide primary disturbance force (shaker 1) and control force (shaker 2) to the beam. These shakers are located at 150 mm and 380 mm from the clamped end, at each side of the beam respectively. To minimize the effect of the shakers on the structure, they are attached to the beam through stingers. These serve to isolate the shakers from the structure, reduce the added mass, and cause the force to be transmitted axially along the stingers. The control shaker is attached to the beam firmly; but the primary shaker simply pushes up against the beam. The resulting preload is used to maintain contact between the control shaker and the beam. The objective of the active vibration control system is to minimize the
Show more

6 Read more

Non contact Active Vibration control of Cantilever Beam Using Neural Networking

Non contact Active Vibration control of Cantilever Beam Using Neural Networking

In the case of chirp signal the amplitude of signal is kept at a constant value of 2N. The frequency of the chirp signal is varied keeping the natural frequency of the beam within the lower and upper values of the chirp signal frequencies. It is observed that in case of the uncontrolled vibration of the beam there is a distinct resonance which is controlled using this active vibration control system. It has been observed in fig.6 that the actuator can easily reduce the vibration using neural network controller.

8 Read more

Study on Unbalanced Magnetic Pulling Analysis and Its Control Method for Primary Helium Circulator of High-Temperature Gas-Cooled Reactor

Study on Unbalanced Magnetic Pulling Analysis and Its Control Method for Primary Helium Circulator of High-Temperature Gas-Cooled Reactor

So far, the active magnetic bearing system (AMBs) used in PHC has been verified and will be put into commercial operation [4]. The PHC rotor is completed in accordance with strict standards in material selection, manufacturing and processing, etc., so the rotor mass imbalance is not serious. However, due to imprecise installation, the geometric centers between the rotor and the stator are out of alignment in PHC engineering prototype (PHC-EP), which eventually leads to multi-frequency vibrations. Moreover, the most serious is double-frequency vibration, which leaves the potential safety hazard to HTR-EP safety operation.
Show more

17 Read more

Semi active damping control for vibration isolation of base disturbances

Semi active damping control for vibration isolation of base disturbances

passive devices are used [4, 9]. It has been established that isolation systems with parameters that can be adapted to changing excitation and response characteristics can provide better isolation performance than passive systems with fixed parameters [13, 14]. Active control systems can be used when greater performance is required and passive techniques alone cannot perform adequately (or when accomplishing a task not even possible with passive devices). Active control uses actuators to both add and dissipate energy from the system based on signals obtained from various sensors. Active control systems have demonstrated superior performance than that of the best possible passive systems. But it is also known that the active systems in general are more costly, more complex and less reliable than passive systems. The primary limitation in the application of an active system for vibration isolation is the need for external power. Thus the implementation of active vibration systems has been limited to cases in which the performance gains outweigh the disadvantages of increased cost, complexity, and weight. By recognising both the performance benefits as well as the limitations of active systems the concept of semi-active vibration control has been developed [15].
Show more

194 Read more

ACTIVE VIBRATION CONTROL OF A FLEXIBLE MANIPULATOR USING MODEL PREDICTIVE CONTROL AND KALMAN OPTIMAL FILTERING

ACTIVE VIBRATION CONTROL OF A FLEXIBLE MANIPULATOR USING MODEL PREDICTIVE CONTROL AND KALMAN OPTIMAL FILTERING

The active damping of flexible manipulators is subject to a large number of research papers due to its high potential for industrial applications. For small amplitude vibration on very flexible structures, active approaches lead to lightweight and high performance control systems [1]. Used as sensors or actuators, piezoelectric materials have been well-studied [1], with [2] the first to suggest this idea. Bailey and Hubbard [3] used distributed-parameter control theory and a piezoceramic actuator to actively control vibration on a cantilever beam actively. Other researchers [4,5] studied the effect of the actuators on the host structures for vibration control through modal shape analysis. A variable structure adaptive controller developed by [6] to control contact forces on a cantilever beam used only the output force as feedback, resulting in undesirable chattering. Artificial neural networks (ANN) for identification and state feedback control of flexible structures have been implemented with good preliminary results [7]. Robust control focuses on the ability to have good control performance and stability in the presence of uncertainty in the system model as well as its exogenous inputs, including disturbances and noise.
Show more

13 Read more

Active vibration control in linear time-invariant and nonlinear systems

Active vibration control in linear time-invariant and nonlinear systems

All systems in nature are nonlinear. A good understanding of the effects of nonlinearity improves the active vibration control design in nonlinear systems. A comprehensive study of the effects of softening structural nonlinearity in aeroelastic systems is presented in Chapter 5 [131], which sheds new light on to topic that is not completely understood. Complex dynamic behaviour is demonstrated using the illustration of a nonlinear binary flutter model with a cubic stiffness in the pitch degree of freedom. The identification and stability analysis of limit cycles in the frequency domain using describing functions and the receptances of the underlying linear system are carried out. Numerical integration of the governing differential equations in the time domain confirms the frequency domain results and also reveals new behaviour, including asymmetric LCO and chaos. Also, aeroelastic stability in the presence of softening structural nonlinearity is found to be strongly dependent upon initial conditions. LCO and chaos may be destabilised when the amplitude of oscillation approaches the static divergence boundary and predicted stable LCO are prohibited. Bifurcation analysis using numerical continuation methods are undertaken to demonstrate that the aeroelastic systems with softening nonlinearity are characterised by Hopf, fold, pitchfork and period doubling bifurcations. Complete bifurcation analysis and two-dimensional sections of the basin of attraction allow the nature of stability occurring over the whole speed range to be explained. In some circumstances, the basins of attractions are not singly connected regions, so that the boundaries between different dynamic regimes are not simple. Dependent upon the wing parameters, regions may appear where the predicted stable LCO are free from the destabilising effect of softening nonlinearity.
Show more

208 Read more

Design and realization of a one-dimensional vibration isolation setup for floor vibrations

Design and realization of a one-dimensional vibration isolation setup for floor vibrations

We introduced three active vibration control strategies: the adaptive feedforward control using the MFxLMS algorithm, classic fixed gain feedback control using a +PI+ controller, and induced mode feedback control. Simulation results showed that the adaptive feedfor- ward control provides broadband noise reduction, while the other two feedback solutions installed artificial damping at the expected resonances. The feedback +PI+ control scheme is actually a velocity feedback strategy based on the acceleration measurements, while the induced mode control makes the controlled system to mimic the vibration attenuation per- formance of an ideal passively isolated system. These two feedback solutions gave similar simulation results, but the induced mode control scheme has the advantage of gaining con- trol action and saving energy for the piezo-actuator in the low frequency range.
Show more

78 Read more

Hard Disk Drive Mechanism Vibration Damping Using Disturbance Observer

Hard Disk Drive Mechanism Vibration Damping Using Disturbance Observer

Abstract Variety of the usage in Hard Disk Drives relies on the high speed, positioning system precision and reliability of their control mechanisms. Vibration is one of the most important concerns in the control mechanisms due to rotational movement of the HDD drivers and the data head speed so as to keep the performance under control, the movement disturbances should be accurately monitored. Disturbance Observers (DOBs) increase the control system robustness whilst improving the dynamic performance of the systems without employing sophisticated calculations and prerequisite; the plant inverse model calculation is eliminated in this method which empowers the usage and simplifies its implementation. This paper focuses on the suppression of vibration using Disturbance Observer and compares it with PID controller and Intelligent Active Force Controller to figure out the advantages of DOB.
Show more

6 Read more

Dynamic Modeling and Active Vibration Control of a Flexible Beam: A Review

Dynamic Modeling and Active Vibration Control of a Flexible Beam: A Review

Vibration is mechanical phenomenon which oscillations occur about an equilibrium point and it also happen when mechanical mechanism is moved intentionally and unintentionally. The unwanted vibration may cause damage to the structures or degradation to system‟s performance [1]. The aircraft structures are always tend to be impacted by winds, forces and vibration during travelling in space. The high vibration impact will affect the stability of the aircraft and accuracy during travelling. The long term of vibration exposure will cause damage to the structure and will be risky to human‟s health in space operation [2]. In order to reduce or eliminate the vibrational effects in the mechanical structure, several approaches have been developed such as passive vibration and active vibration techniques. Passive vibration control usually has added weight such as a damper to reduce vibration. It works well in high frequencies or in a narrow frequency range but has added weight to mechanical structure [3]. Active vibration control (AVC) is a concept in which vibration of a structure is controlled by applying counter force to the structure which out of phase but equal in amplitude to the original force. So, the two opposite forces will cancel each other and the vibration will be stopped [4]. It has become useful approach in the recent years, due to improvement of vibration susceptibility of light weight structure with the least possible increase in mass [5].
Show more

6 Read more

Active Vibration Control of a Fixed Beam using PZT Patches

Active Vibration Control of a Fixed Beam using PZT Patches

In the paper of Yavuz Yaman et al. [5] the smart plate consists of a rectangular aluminum plate modeled in cantilever configuration with surface bonded piezoelectric patches. The patches were symmetrically bonded on top and bottom surfaces. ANSYS (v.5.6) software was used to derive the finite element model of the smart plate. The study first gave the influences of the actuator placement and size on the response of the smart plate and determined the maximum admissible piezoelectric actuation voltage. The optimal sensor locations are found and actual smart plate is produced. These experimental results of the smart plate are then used to determine a single input single output system model. Melin Sahin et al. [6] presented the theoretical and experimental studies conducted in Aerospace Engineering Department of Middle East Technical University on smart structures. They gave particular attention to the structural modeling characteristics and active suppression of in-vacuo vibrations. The smart structures considered in these analyses are flat aluminium cantilever beam-like and plate-like structures with surface bonded PZT patches. Finite element models of smart beam and smart fin are obtained. The experimental readings are taken to study regarding open loop behavior of the structures performed by using strain gauges and laser displacement sensor to determine the system models.
Show more

7 Read more

Analysis of Vibration Characteristics of PD Control Active Magnetic Bearing and Cracked Rotor System (RESEARCH NOTE)

Analysis of Vibration Characteristics of PD Control Active Magnetic Bearing and Cracked Rotor System (RESEARCH NOTE)

Active magnetic bearings are becoming the preferred method for the bearing of high speed and ultra-high speed rotary machines. Compared with medium and low-speed rotors, high speed and ultra-high speed rotors may generate cracks more easily due to high rate cyclic stress. If crack is not detected on time, which would lead to rotor failure or even an accident.

6 Read more

Experimental Investigation of Damping characteristics for various Damping Materials

Experimental Investigation of Damping characteristics for various Damping Materials

system can have dual purpose of comfort and safety. Xu shows[3] how vibration of parts can effect the mechanism. Ebrahimi, Khamesee and Golnaraghi [4] demonstrate passive damping can be achieved by addition of viscous fluid to the active damper, which guaranties a failsafe damper in case of power failure. The electromagnetic dampers have lesser reliability because of dependence on external power source and higher weight. Lee, Park, Min and Chung[5] shows how to control seismic response of building structures using tuned liquid damper. Yau and Chen[6] shown vibration suppressing system using electric- hydraulic actuator design using squeeze film damper. Lee and Jee[7] the vibration of a flexible cantilever beam using active piezoelectric type servo damper to suppress both small and large amplitude vibrations. Martins et al[8]proposed a new hybrid damper design for vehicle suspension application. Linear actuator was the active unit and the hydraulic passive damping effect as a passive part. Lin and Roschke and Loh [9]proposed a hybrid base isolation with MR dampers, and showed that a combination of high damping rubber bearing isolators and MR damper can provide robust control of vibration for large civil engineering structures from a wide range of seismic events.
Show more

6 Read more

Active vibration control

Active vibration control

These considerations led to the proposal of a semi-active eddy current damping system. In this system, a magnet is moved in opposition to conductors attached to the vibrating structure such that the conductors cut the perpendicular components of the permanent magnetic field. The magnets motion is provided by an electromagnetic shaker which is driven by the controller’s output signal. This allows the generation and subsequent dissipation of eddy currents in the conductor, resulting in a viscous damping effect. The major advantages of this system are firstly, its simplicity and the requirement of readily obtainable equipment such as permanent magnets and copper plates. Secondly, bounded input, bounded output stability is guaranteed as no mechanical energy is added to the system. Finally, the use of eddy currents in vibration suppression is a new and relatively unexplored concept. The following diagrams show the basic setup of the eddy current damper.
Show more

107 Read more

An active control method to reduce friction induced vibration caused by negative damping

An active control method to reduce friction induced vibration caused by negative damping

Normally there are three major methods to study and reduce brake squeal, namely through mathematical modelling, experimental and finite element (FE) methods. A recent study that proposed a method for reducing brake noise using FE can be found in reference [7], where the authors created a dynamic FE model of the brake system. In their analysis, they showed that pad design changes can be used in the FE model to determine the potential improvements in the dynamic stability of the system and also in noise reduction. Wagner et al. presented a new mathematical rotor based model of a brake system that is suitable for noise analysis [8]. In their work, a brief description of the previous mathematical models that have been developed by other researchers was also given. Besides, there is also an active control method known as dither control which makes use of high frequency disturbance signal for the suppression of the automotive disc brake squeal [9]. Through this scheme, the dither signal stabilizes friction induced self-oscillations in the disc brake using a harmonic vibration, with a frequency higher than the squeal frequency generated from a stack of piezoelectric elements placed in the caliper piston of the brake system. The results seem to be fine in reducing the noise, how ever other operating factors such as wear, temperature, friction and speed are required to be considered for evaluating the effectiveness of the system.
Show more

16 Read more

Active power flow control of wind pv hybrid system using ai technique

Active power flow control of wind pv hybrid system using ai technique

The solar generated electricity is called Photovoltaic (PV). These are solar cells that convert sunlight to DC electricity. Solar cells in PV module are made from semiconductor materials. When light energy strikes the cell, electrons are emitted. The electrical conductor attached to the positive and negative scales of the material allow the electrons to be captured in the form of a DC current. The generated electricity can be used to power a load or can be stored in a battery. Photovoltaic system is classified into two major types: the off- grid (standalone) systems and inter-tied system. The off-grid system are mostly used where there is no utility grid service. It is very economical in providing electricity at remote locations especially rural banking, hospital and ICT in rural environments. PV systems generally can be much cheaper than installing power lines and step-down transformers especially to remote areas. Solar modules produce electricity devoid of pollution, without odour, combustion, noise and vibration. Hence unwanted nuisance is completely eliminated. The major components include PV modules, battery and inverter. The most efficient way to determine the capacities of these components is to estimate the load to be supplied. The size of the battery bank required will depend on the storage required, the maximum discharge rate, and the minimum temperature at which the batteries will be used. When designing a solar power system, all these factors are to be taken into considerations when battery size is to be chosen. Lead-acid batteries are the most common in PV systems because their initial cost is lower and also they are readily available nearly everywhere in the world. Deep cycle batteries are designed to be repeatedly discharged as much as 80 percent of their capacity and so they are a good choice for power systems.
Show more

5 Read more

Download
			
			
				Download PDF

Download Download PDF

In this way, the introduction of active control improves the robustness of the system in situations that require to refine/improve the vibration control. On the other hand, the passive control considerably reduces the displacements, so that the control system works well in situations of loss of electric power and, consequently, impossibility of actuation of the active system. However, when the structure is subjected to a detuned excitation in relation to the prevailing vibration frequency of the tower, the active control actuators begin to correct or improve/refine the behavior of the purely passive control, since the active control also works well for a frequency of excitation not tuned at any of the modal frequencies of the uncontrolled tower structure. Such performance of hybrid and active systems may become, in certain cases of practical application, indispensable for the proper functioning and safety of the tower structure and its users.
Show more

21 Read more

Show all 10000 documents...