Active Modal Control Research Articles

Precise Configuring of Actuators/Sensors for Active Control of Sound Quality in Cabs with Modal Vibration Energy and LA-PSO

Active control of structural modal vibration is an effective strategy to enhance the sound quality of cabs in commercial vehicles. However, accurate determination of the positioning and quantity of modal active control sensors and actuators is crucial for cabs with intricate structures, owing to the presence of multiorder modes and their coupling. The study presented herein focuses on the cab of a commercial vehicle and contemplates the features of the irregular large-space structure of the cab. By capitalizing on the modal frequency and mode shape of the cab, utilizing the piezoelectric control principle and modal vibration energy as the assessment index, an advanced multimode composite control criterion is postulated to ascertain the configuration of primary sensors and actuators. The particle swarm optimization (PSO) objective function is constructed to accomplish the optimal position matching of the actuator/sensor, using the multimodal surface velocity vector of the vibration sensor as the core parameter. Furthermore, an improved linear adaptive particle swarm optimization (LA-PSO) technique is advanced to satisfy the requirements of optimal convergence performance and accuracy of the complex cab structure. The optimization culminates in a 9 × 9 multichannel active control scheme for determining the optimal position of the actuators/sensors. This investigation provides a technical foundation for the active control of sound quality in automotive cabs and presents an innovative method for implementing effective noise control systems in large-scale machinery and equipment.

Chatter suppression for milling of thin-walled workpieces based on active modal control

Owing to the low stiffness of workpiece, chatter easily occurs in milling of thin-walled structures, which may cause poor surface quality and uncontrolled machining accuracy. For suppressing milling chatter of thin-walled workpieces, this paper presents an active control method with a piezoelectric patch actuator. As a flexible body, thin-walled workpieces have more than one modals participating in milling vibration, and its dynamic characteristics vary with tool position. This paper establishes dynamic model of the thin-walled workpiece with a semi-analytical method. Considering three order modals of workpiece, actuator position is optimized and active controller is designed. The varying dynamic characteristics of workpiece are overcome by designing controller with the parameters on the maximum vibration position to stabilize the whole process. Experiments verify the necessity of considering more than one modals of workpiece in active control through various chatter characteristics dominant by different modals. With the designed control method, the stable cutting depth improves from 0.2 mm to 1 mm.

Active Vibration Control on a Smart Composite Structure Using Modal-Shaped Sliding Mode Control

Abstract This article proposes an active modal vibration control method based on a modal sliding mode controller applied to a smart material composite structure with integrated piezoelectric transducers as actuators and sensors. First, the electromechanical coupled system is identified using a modal reduced-order model. The sliding surface is based on the modal-filtered states and designed using a general formulation allowing the control of multiple vibration modes with multiple piezoelectric sensors and actuators. The performance and stability of the nonlinear controller are addressed and confirmed with the experimental results on a composite smart spoiler-shaped structure. The nonlinear switching control signal based on the modal-shaped sliding surface improves performances of the linear part of the control while maintaining not only stability but also robustness. The attenuation level achieved on the target modes on all piezoelectric sensors starts from −14 dB up to −22 dB, illustrating the strong potential of nonlinear switching control methods in active vibration control.

Research on Vibration Suppression of the Long Flexible Arm Based on Three Tilt Sensors

In this research, a new method based on the equivalence of modal characteristics, differential flatness (DF), and active disturbance rejection control (ADRC) is proposed for the stabilization control of the long flexible arm (LFA). There are two major problems in the system of the LFA. The first problem is that the LFA is very prone to the multiple-mode coupling, while the control systems need as few sensors as possible. Another problem is that the structure of the LFA in practice is often complex and subject to various disturbances. Therefore, in this paper, the equivalent multirigid body dynamic model of a LFA is derived from the modal information of the equivalent rigid body model of the prototype. Then, the output values of the three tilt sensors are synthesized into an output based on the DF method. Finally, the effectiveness of the proposed method is verified through physical experiments. Compared with PID, the proposed method has shorter settling time. The LFA can be restored within 7 seconds under the ADRC, while it needs 90 seconds or more to calm down without the control.

Active structural modal control for sound reduction in an enclosure: Experimental verification

Sound radiation from a vibrating enclosure into an enclosed space can be actively reduced using sensors and actuators attached to the enclosure. However, the sound cannot be effectively reduced by merely minimizing the structural vibration, as the levels of the vibration and the radiated sound are not proportional to each other. Moreover, reducing the sound using the actuators can lead to increased vibration. In an earlier work by the authors, a control system was theoretically developed to achieve two goals simultaneously. The primary objective was to effectively reduce the sound in the enclosure, and the secondary objective was to prevent the vibration of the enclosure from increasing. In this study, an experiment is conducted to verify this theory. The control system design begins with identifying the most acoustically contributive structural modes, by theoretically calculating the structural modal acoustic potential energies. Once the most acoustically contributive structural modes are identified, sensors and actuators are configured to preferentially measure and control these structural modes. The control strategy is based on the idea that the most acoustically contributive structural modes should be suppressed by the actuators, whereas the other structural modes should not be affected by the actuators. The experimental results indicate that sound in the enclosure can be effectively reduced and the vibration of the enclosure can be prevented from increasing.

Optimization of parameters of a modal active control in a beam of composite material

The present work proposes the active vibration control in a beam of composite material, using electromagnetic actuators, in order to obtain a reduction in the response of the displacement of the system associated to a reduction in energy consumption. The control theory used was the linear quadratic regulator solved by linear matrix inequalities. The electromagnetic actuator was then linearized using a methodology similar to that used in magnetic bearings. The work also proposes to study the optimization of parameters applied in this active control, by means of the heuristic optimization methods. From numerical simulations, the system´s response was obtained in the time domain that demonstrated the efficiency of the proposed technique in the active control of vibrations.

Modal active control of Chinese gongs.

Instruments that belong to the gong family exhibit nonlinear dynamics at large amplitudes of vibration. In the specific case of the xiaoluo gong, this nonlinear behavior results in a pitch glide of several modes of the instrument in addition to harmonic distortion and internal resonances. This study applies a linear modal active control to a xiaoluo gong in an attempt to change its sound properties. First, a modal damping control of the fundamental mode based on a linear identification and a state space controller is applied in the small amplitude regime (no pitch glide). Results indicate that modal control influences not only the controlled mode but also the frequency components involved in distortion or internal resonance phenomena. Second, a modal damping control is performed in the large amplitude regime (in the presence of pitch glide). Results show that modal control does not affect the pitch glide. However, the controller becomes effective at a time trigger which is related to the instantaneous frequency.

Modal active control: A tool to finely adjust the sound of string instruments

Controlling the vibratory properties of musical instruments is an important challenge for musical acousticians, musicians, and instrument makers. The latter try to control these properties modifying mechanical parameters of instruments like their shape or their materials to obtain some expected sound attributes. Musicians also modify the vibratory properties of their instruments to change their sound using mutes, for example. Musical acousticians try to modify these properties because it is an intuitive way to investigate the relationship between the instrument mechanisms and their sound attributes. Inspired by industrial techniques, active control was revealed as a convenient way to answer to the latter goal. Moreover, modal active control is a preferred method for the application to musical instruments since their modal parameters are believed to be good descriptors of their vibratory properties. This study aims at applying modal active control on string instruments. First, the possibilities offered by ...

Active Modal Control of Rain-Wind Induced Vibration of Stay Cables

Rain-wind induced vibrations have been observed on numerous cable-stayed bridges around the world, which has resulted in an urgent need to gain further understanding of the phenomenon and to develop efficient means of mitigating the large-amplitude vibrations. It is believed that this aeroelastic instability problem is due to the formation and oscillation of a water rivulet on the upper cable surface, which changes the cable aerodynamics and absorbs energy into the system. In this paper, an analytical study of the phenomenon is conducted by formulating a finite element model for the cable and the upper rivulet with non-linear coupling effect. Linearization of the equations of motion of the cable-rivulet system is next carried out, based on which active vibration controller can be designed. Pole allocation control method has been employed for mitigating RWIV in the present study, which is able to add sufficient damping to several excited modes. The active controller is designed such that the closed-loop poles are allocated on the left half of the complex plane of eigenvalues. The controller gains obtained from the equivalent linear system are then applied to the original non-linear cable-rivulet system. Simulation results show that the proposed active modal controller performs much better in suppressing RWIV than an optimally tuned linear viscous damper.

Modal proportional and derivative state active control applied to a simplified string instrument

This study proposes an application of modal active control to musical string instruments. Its aim is to control the modal parameters of the soundboard in order to modify the sound of the instrument. Using both state and derivative state modal control, a method is given, from the modeling of the active structure through to the design of the control system. Issues such as the identification of the structure’s characteristics or the stability of the control system are dealt with for this original control method. Then, this technique is applied to a model of a simplified string instrument soundboard. Time simulations are conducted to study its effect on the instrument vibration. They show that, thanks to soundboard modal active control, it is possible to modify the amplitude of the sound harmonics to change the timbre as well as the sound level of the instrument.

Active control and sound synthesis--two different ways to investigate the influence of the modal parameters of a guitar on its sound.

The vibrational behavior of musical instruments is usually studied using physical modeling and simulations. Recently, active control has proven its efficiency to experimentally modify the dynamical behavior of musical instruments. This approach could also be used as an experimental tool to systematically study fine physical phenomena. This paper proposes to use modal active control as an alternative to sound simulation to study the complex case of the coupling between classical guitar strings and soundboard. A comparison between modal active control and sound simulation investigates the advantages, the drawbacks, and the limits of these two approaches.

Experimental Demonstration of the Modification of the Resonances of a Simplified Self-Sustained Wind Instrument Through Modal Active Control

This paper reports the experimental results of modifying the resonances of wind instruments using modal active control. Resonances of a simplified bass clarinet without holes (a cylindrical tube coupled to a bass clarinet mouthpiece including a reed) are adjusted either in frequency or in damping in order to modify its playing properties (pitch, strength of the harmonics of the sound, transient behaviour). This is achieved using a control setup consisting of a co-located loudspeaker and microphone linked to a computer with data acquisition capabilities. Software on the computer implements an observer (which contains a model of the system) and a controller. Measuring and adjusting the transfer function between the speaker and microphone of the control setup enables modifications of the input impedance and the radiated sound of the instrument.

Simulations of Modal Active Control Applied to the Self-Sustained Oscillations of the Clarinet

This paper reports a new approach to modifying the sound produced by a wind instrument. The approach is based on modal active control, which enables adjustment of the damping and the frequencies of the different resonances of a system. A self-sustained oscillating wind instrument can be modeled as an excitation source coupled to a resonator via a non-linear coupling. The aim of this study is to present simulations of modal active control applied to a modeled self-sustained oscillating wind instrument in order to modify its playing properties. The modeled instrument comprises a cylindrical tube coupled to a reed and incorporates a collocated loudspeaker and microphone; it can thus be considered to approximate a simplified clarinet. Modifications of the pitch, the strength of the harmonics of the sound produced by the instrument, and of the oscillation threshold are obtained while controlling the first two resonances of the modeled instrument.

Adjusting the soundboard’s modal parameters without mechanical change: A modal active control approach

How do modes of soundboards affect the playability and the sound of string instruments? This talk will investigate this question experimentally, using modal active control. After identifying modal parameters of a structure, modal active control allows the adjustments of modal frequency and damping thanks to a feedback loop, without any mechanical changes. The potential of this approach for musical acoustics research will be presented for three different instruments: a simplified piano, a guitar, and a cello. The effects of modal active control of soundboards will be illustrated on attack, amplitude of sound partials, sound duration, playability, and “wolf tone” production.

Active modal damping control of a smart truss structure using a self-organizing fuzzy controller

This paper presents design, implementation and experimental results of active vibration control of a truss structure using a pair of piezoelectric ceramic stack actuators. To reduce the vibrations caused by an impulse force, two active strut members are installed along a vertical of the base bay of the truss. The active strut element consists of a piezoelectric ceramic actuator stack, a force transducer and mechanical interfaces. A self-organizing fuzzy controller (SOFC) is designed to suppress vibration of the truss. The SOFC, which uses the input and output history in its fuzzy rules, is designed to maximize modal damping of a constructed truss structure. Experimental results illustrate that the active piezoceramic strut actuators and the SOFC can effectively reduce vibration of the truss.

Numerical and Experimental Modal Control of Flexible Rotor Using Electromagnetic Actuator

The present work is dedicated to active modal control applied to flexible rotors. The effectiveness of the corresponding techniques for controlling a flexible rotor is tested numerically and experimentally. Two different approaches are used to determine the appropriate controllers. The first uses the linear quadratic regulator and the second approach is the fuzzy modal control. This paper is focused on the electromagnetic actuator, which in this case is part of a hybrid bearing. Due to numerical reasons it was necessary to reduce the size of the model of the rotating system so that the design of the controllers and estimator could be performed. The role of the Kalman estimator in the present contribution is to estimate the modal states of the system and to determine the displacement of the rotor at the position of the hybrid bearing. Finally, numerical and experimental results demonstrate the success of the methodology conveyed.

Design of piezoelectric transducer arrays for passive and active modal control of thin plates

To suppress vibration and noise of mechanical structures piezoelectric ceramics play an increasing role as effective, simple and light-weighted damping devices as they are suitable for sensing and actuating. Out of the various piezoelectric damping methods this paper compares mode based active control strategies to passive shunt damping for thin plates. Therefore, a new approach for the optimal placement of the piezoelectric sensors/actuators, or more general transducers, is proposed after intense theoretical investigations based on the Kirchhoff kinematical hypotheses of plates; in particular, modal and nilpotent transducers are discussed in detail. Based on the proposed distribution a discrete design for modal transducers is implemented, tested and verified on an experimental setup. For active control the modal sensors clearly identify the eigenmodes, whereas the modal actuators impose distributed eigenstrains in order to reduce the transverse plate vibrations. In contrast to the modal control, passive shunt damping works without requiring additional actuators or auxiliary power and can therefore act as an autonomous system, but it is less effective compensating the flexible vibrations. Exemplarily, an acryl glass plate disturbed by an arbitrary force initialized by a loudspeaker is investigated. Comparing the different methods their specific advantages are highlighted and a significant broadband reduction of the vibrations of up to -20dB is obtained.

Experimental identification of smart material coupling effects in composite structures

Smart composite structures have an enormous potential for industrial applications, in terms of mass reduction, high material resistance and flexibility. The correct characterization of these complex structures is essential for active vibration control or structural health monitoring applications. The identification process generally calls for the determination of a generalized electromechanical coupling coefficient. As this process can in practice be difficult to implement, an original approach, presented in this paper, has been developed for the identification of the coupling effects of a smart material used in a composite curved beam. The accuracy of the proposed identification technique is tested by applying active modal control to the beam, using a reduced model based on this identification. The studied structure was as close to reality as possible, and made use of integrated transducers, low-cost sensors, clamped boundary conditions and substantial, complex excitation sources. PVDF (polyvinylidene fluoride) and MFC (macrofiber composite) transducers were integrated into the composite structure, to ensure their protection from environmental damage. The experimental identification described here was based on a curve fitting approach combined with the reduced model. It allowed a reliable, powerful modal control system to be built, controlling two modes of the structure. A linear quadratic Gaussian algorithm was used to determine the modal controller–observer gains. The selected modes were found to have an attenuation as strong as −13 dB in experiments, revealing the effectiveness of this method. In this study a generalized approach is proposed, which can be extended to most complex or composite industrial structures when they are subjected to vibration.

Active control applied to simplified wind musical instrument

Musicians have always been interested in the evolution of their instruments. This evolution might be done either to adapt an instrument’s quality to musicians’ and composers’ needs, or to enable it to produce new sounds. In this study, we want to control the sound quality and playability of wind instruments, using active control. The active control makes it possible to modify the input impedance (frequency, gain, and damping) of these instruments and to modify the instrument’s quality. Simulations and first experiments on a simplified reed instrument are presented. We simulate a control of the modes (frequency, damping) of a cylinder using two different approaches: classic feedback and modal active control. Then, we apply these control methods on a simplified reed instrument with embedded microphone and speaker. Finally, the effects on sound and playability of the instrument is studied.

Active modal control simulation of vibro-acoustic response of a fluid-loaded plate

Active modal control simulation of vibro-acoustic response of a fluid-loaded plate is presented. The active modal control of the vibro-acoustic response is implemented using piezoelectric actuators/sensors. The active modal damping is added to the coupled system via negative velocity feedback. The feedback gain between the piezoelectric actuators/sensors for the modal control is obtained using the in-vacuo modal matrix and the incompressible fluid-loaded modal matrix. The modal control performance of structural vibration and acoustic radiation of a baffled plate is numerically studied. It is shown that the proposed method increases the modal damping ratio and achieves reduction in the mean square velocity and the sound power for given modes of the fluid-loaded plate.