Synchronized Switch Damping Research Articles

A novel approach for synchronized switch damping control based on voltage sources in parallel

This paper presents a novel hybrid model, termed Synchronized Switch Damping with Voltage Sources in Parallel (SSDVP), for enhancing the performance of synchronized switch damping (SSD) control by addressing the flipping voltage and voltage drop issues in piezoelectric elements. The effectiveness of SSD control is closely related to the voltage applied to the piezoelectric element. However, at high voltages, such as the maximum capacity of 1.5 kV for piezoelectric materials, charge leakage becomes significant and cannot be ignored. This results in substantial voltage drop during switching intervals, particularly in low-frequency applications. The proposed SSDVP method combines the advantages of SSDI and Bang-bang control to generate a stable high voltage across the piezoelectric element with minimal power consumption. The working principle and mathematical model of the SSDVP method are described, including the expression of the voltage across the piezo patch and the energy consumption of the control circuit. Simulation and experimental comparisons are conducted among the traditional SSDV model, Bang-bang control, and the proposed SSDVP model to demonstrate the advantages of the novel approach.

Mechanism of interconnected synchronized switch damping for vibration control of blades

The Synchronized Switch Damping (SSD) is regarded as a promising alternative to mitigate the vibration of thin-walled structures in aero-engines, especially for blades or bladed disks. The common manner is to shunt the switch circuit independently to a single piezoelectric structure. This paper is aimed at exploring a novel way of using the SSD, i.e., the SSD is interconnected between two piezoelectric structures or substructures. The damping mechanism, performance, and effective range of the interconnected SSD are studied numerically and experimentally. First, based on a dual cantilever beam finite element model, the time domain and frequency domain modeling and solving methods of the interconnected SSD are deduced and validated. Then, the influence of the amplitude and phase relationship on the damping effect of the interconnected SSD is numerically studied and compared with the shunted SSD. A self-sensing SSD control board is developed, and experimental studies are carried out. The results show that the interconnected SSD establishes an additional energy channel between the corresponding piezoelectric structures. When the amplitudes of the two cantilever beams are different, the interconnected SSD balances the vibration level of each beam. When the amplitudes of the two cantilever beams are the same, if the appropriate interconnection manner is selected according to the phase, the resonance peak can be reduced by more than 30%. When the vibration is in-phase/out-of-phase, the damping generated by the interconnected SSD in a cross/parallel manner is even more significant than the shunted SSD. Furthermore, this novel connection scheme reduces the number of SSD circuits in half. Finally, for engineering applications, we implement the proposed damping technology to the finite element model of a typical dummy bladed disk. A piezoelectric damping ratio of 13.7% is achieved when the amount of piezo material is only 10% of blade mass. Compared with traditional friction dampers, the major advancements of the interconnected SSD are: (A) it can reduce the vibration level of blades without friction interface; (B) the space constraint is overcome, i.e., the vibration energy is not necessarily dissipated independently in one sector or through physically adjacent blades, and instead, the dissipation and transfer of vibrational energy can be realized between any blade pair. If a specific gating circuit is adopted to adjust the interconnection manner of the SSD, vibration mitigation under variable working conditions with different engine orders will be expected; (C) designers do not need to worry about the annoying nonlinearities related to working conditions anymore.

Self-sensing synchronized switch damping based on zero-crossing detection with voltage decay compensation

Synchronized switch damping (SSD) techniques have been developed for structural vibration suppression in recent years. In SSD control, a self-sensing approach can invert the voltage on piezoelectric materials at displacement extrema without sensors or real-time controllers. However, tracing extrema from the voltage on piezoelectric materials has become challenging since the voltage generated by the vibration of controlled mode is minor compared with noises as the increase of damping performance. Furthermore, the voltage decay caused by the current leakage is dominant when the host structure vibrates at a low frequency. This paper proposes a self-sensing approach based on the zero-crossing detection technique with voltage decay compensation. The switching delay and voltage decay are considered in the electromechanical model of the SSD system. Accordingly, a band-limited proportional-differential circuit is implemented to offset the voltage decay and generate zero-crossings at displacement extrema simultaneously. Experiments show that the proposed method is still effective when the voltage decay in the SSD control is dominant.

Design and analysis of unsymmetrical SSD based negative capacitance technique for vibration suppression

Synchronized switch damping on negative capacitance (SSDNC), as one of the nonlinear synchronized switch damping (SSD) techniques, has been received much attention in recent years. The damping effect depends on the effective voltage on the piezoelectric actuator in SSDNC control. The applicable bipolar voltage of a piezoelectric element is unsymmetrical. However, the voltage on the piezoelectric actuator is applied symmetrically in SSDNC, which greatly wastes the driving capability. An unsymmetrical SSDNC (un-SSDNC) is proposed in this paper to further boost the voltage on the PZT actuator and make full use of the driving ability to improve the control performance. A bypass capacitor, two diodes and switches are attached to the SSDNC circuit to realize unsymmetrical bipolar voltage. The control logic of the switches is introduced and the switched voltage is derived as well as the control performance. Experiments and simulations were carried out to verify the designed circuit and the theoretical results of the switched voltage. The influence of the bypass capacitor on the switched voltage and the stability of the un-SSDNC system were investigated. The voltage ratio and control performance increase with increasing bypass capacitor, but too large of bypass capacitor will cause the problem of system stability.

On the network of synchronized switch damping for blisks

This paper presents a new semi-active piezoelectric damping strategy for the vibration suppression of integrally bladed disk (blisk). The main novelty is the networking of the synchronized switch damping (SSD). Different from the independently shunted SSD broadly studied in the literature, in our approach the piezoelectric materials distributed to different blade sectors are first connected in few electric networks. The blades in the same network share a single SSD circuit. In this way, additional electrical energy channels are established, and the vibration energy can be thereby dissipated and redistributed globally. In addition, the overall number of the SSD circuits will be drastically reduced, decreasing the complexity of the system. To illustrate and demonstrate such an idea, numerical and experimental studies are conducted. First, We presents the governing equations of a general discrete blisk model with the SSD network and derive a linearization method to solve the steady-state solutions. Next, the optimal topologies of the SSD network for different vibrational modes are summarized through numerical simulation. The proposed network exhibits better performance than other candidates for the mistuned case. Then, through the Mont–Carlo simulation, statistical results prove that the network is also effective for the suppression of the amplitude magnification due to mistuning. Eventually, these findings are validated experimentally through a dummy blisk.

Semi-active vibration control of the motorized spindle using a self-powered SSDV technique: simulation and experimental study

SSD (synchronized switch damping) is used for vibration control of the motorized spindle based on piezoelectric stack. Moreover, inspired by self-powered SSDI, a self-powered SSDV circuit was designed to overcome the disadvantages of requiring readjusting control parameters and sensor re-positioning of SSDI (synchronized switch damping on inductor) and SSDV (synchronized switch damping on voltage source). A simulation and an experimental were built, and the results show vibration control performance of self-powered SSDV is better than self-powered SSDI and is more flexible and effective than self-powered SSDI by adjusting the DC voltage to adapt to different speeds of the motorized spindle.

Semi-active piezoelectric structural damping adjustment and enhancement by synchronized switching on energy injection technique

Synchronized switch damping (SSD) principle and derived techniques are a classical semi-active vibration control method based on piezoelectric elements. This paper presents a novel energy injection based SSD technique which has better effect of vibration reduction but with simpler implementation of electronic circuitry. The proposed circuit is composed of a flyback transformer, an ordinary low voltage source and two kinds of synchronized switches. Through controlling the synchronized switches, the electrical energy is extracted from the voltage source to the transformer, and then injected to the piezoelectric elements, increasing the piezoelectric voltage as needed. Moreover, this injection energy can be easily adjusted by changing the duty cycle of the corresponding switch control signal. The operation principle of this technique is introduced, the analytical expression of vibration attenuations is also derived for a typical electromechanical model. Finally, theoretical predictions confirmed by experimental results show that the proposed SSD technique provides an adaptive structural damping and enhances the effect of vibration attenuation.

Bandgap coupling effects between hybrid nonlinear synchronized switch damping and linear two-order resonant bandgaps in piezoelectric meta-structures

To study the bandgap coupling mechanism between nonlinear synchronized switch damping and multi-order linear resonant bandgaps, this research investigates the bandgap coupling effects between nonlinear synchronized switch damping and two-order linear resonant bandgaps in a piezoelectric meta-structure. Specifically, a piezoelectric meta-structure with hybrid nonlinear synchronized switch damping and linear two-order linear resonant electrical networks is proposed. Based on the theoretical modeling of the proposed structure, band structure and vibration transmittance performance are investigated in detail. Results showed that bandgap coupling can produce a trade-off with the advantages of both nonlinear and two-order linear resonant bandgaps. The new bandgap can not only realize broadband wave attenuation performance but also greatly enhance the attenuation in selected frequency bands, which provides a new method to manipulate elastic waves in a diversified way.

A new design of unsymmetrical shunt circuit with negative capacitance for enhanced vibration control

Piezoelectric elements are widely used in structural vibration suppression. The applicable bipolar voltage of a piezoelectric element is unsymmetrical, but in most control systems, the voltage on the piezoelectric actuator is applied symmetrically, which greatly wastes the driving capability. In synchronized switching damping (SSD) approaches for structural vibration control, the damping effect depends on the effective voltage range on the piezoelectric actuator. A novel method of realizing unsymmetrical bipolar voltage with SSD method based on negative capacitance shunt circuit for vibration control is proposed for improvement of the control performance in this study. A resistance and a diode that added into constructed negative capacitance circuit are used to realize unsymmetrical bipolar voltage. The general expression of the switched voltage on the piezoelectric actuator is derived. The stability of negative capacitance shunt circuit is addressed. The added offset resistance in the negative capacitance circuit plays an important role in system stability. The simulation analysis results agree very well with the theoretical results, both of which reveal that the unsymmetrical voltage ratio depends on the resistance in the negative capacitance circuit. Finally, experiments are carried out to verify the designed circuit and the excellent damping performance.

Design and Analysis of Piezoelectric Energy Harvesting Systems

This Paper presents a new technique of electrical energy generation using mechanically excited piezoelectric materials and a nonlinear process. This technique, called double synchronized switch harvesting (DSSH), is derived from the synchronized switch damping (SSD), which is a nonlinear technique previously developed to address the problem of vibration damping on mechanical structures. This technique results in a significant increase of the electromechanical conversion capability of piezoelectric materials. An optimized method of harvesting vibrational energy with a piezoelectric element using a dc–dc converter is presented. In this configuration, the converter regulates the power flow from the piezoelectric element to the desired electronic load. Analysis of the converter in discontinuous current conduction mode results in an expression for the duty cycle-power relationship. Using parameters of the mechanical system, the piezoelectric element, and the converter; the “optimal” duty cycle can be determined where the harvested power is maximized for the level of mechanical excitation. A circuit is proposed which implements this relationship, and experimental results show that the converter increases the harvested power by approximately 365% as compared to when the dc–dc converter is not used.

A Linearised Analysis for Structures With Synchronized Switch Damping

Synchronized Switch Damping (SSD) is a semi-active damping technology based on piezoelectric materials. It has advantages such as broadband and no need to tune. Despite the nonlinear governing equations, structures with SSD exhibit quasi-linear behaviour such as the resonant frequencies hardly vary with respect to energy level of excitation. Inspired by these phenomena, in this paper we propose a linearisation method for SSD, where the nonlinear force is equivalent to frequency-dependent viscous damping and linear stiffness coefficients. Closed-form expressions of these linearised parameters are given, making the method applicable both for lumped parameter models and finite element (FE) models. In the derivation a general force equation is used, so the linearised method is applicable for several typical variants of SSD, such as SSDS (S for 'on short-circuited'), SSDI (I for `on inductance'), SSDV (V for `on voltage') and SSDNC (NC for `on negative capacitance'). The method is first validated against nonlinear simulations with harmonic and random vibration respectively, then further compared with experimental data in a published paper. Good agreements are found. We show that the proposed method can dramatically accelerate the computational efficiency, which is especially suitable for predicting the dynamic performance of complex structures with SSD. Eventually, a dummy integrally bladed disk with SSD is analysed to illustrate a potential application direction. There are more than 120k DOFs in the FE model, making full nonlinear simulation very time-consuming. However the simulation is finished within seconds by the proposed method and the typical damping characteristics of SSD are well captured.

A Modified Nonlinear Modal Synthesis Scheme for Mistuned Blisks with Synchronized Switch Damping

In the authors’ previous work (MSSP 2017), we show that the synchronized switch damping based on negative capacitor (SSDNC) is a good candidate for vibration suppression of tuned blisks. In this paper, we consider the mistuned case and propose an efficient numerical approach to accelerate the required statistical analysis. Although SSDNC is a type of nonlinear piezoelectric damping, through an in-depth nonlinear modal analysis, we show that the modal information of the system remains unchanged with respect to the nonlinear modal amplitude. Based on this, an accelerated nonlinear component modal synthesis (NCMS) method is proposed to predict and further analyse the dynamic characteristics of the nonlinear system. The precision and efficiency of the proposed method is compared with that of the multiharmonic balance method. The stochastic characteristics of the blisk are studied with two sources of mistuning. The first one is random stiffness mistuning and the second one is capacitance mistuning. The investigation is carried out with different mistuning levels and under different engine-order excitations. The results show that the NCMS method can accurately predict the forced response of the mistuned blisk with SSDNC, and the calculation cost can be considerably reduced. Two advantages of the SSDNC technique applied to the mistuned blisk have been revealed in the statistical view. The first one is that the SSDNC can suppress the amplified vibration induced by the mistuning of the blisk significantly. The second one is that the vibration-suppression performance of SSDNC is insensitive to the mistuning of the blisk and that of the electrical circuits.

Superharmonic vibration and its reduction in SSD control by increase of voltage inversion time

The semi-active synchronized switch damping (SSD) approach has been widely used in vibration suppression owing to its many advantages compared with the active and passive approaches. The SSD method is realized by switching the voltage on the piezoelectric patch embedded in the structure, synchronically with the vibration of the mode to be controlled. Although good control performance can be obtained in the targeted mode, vibrations of high-order harmonic frequencies are usually excited due to the rectangular waveform of the switched actuator voltage because of infinitesimal inversion time, as observed in the previous experiments. This drawback of the SSD method has greatly hindered its application in practical engineering structures. In order to overcome this drawback, the authors propose a new method in this study to suppress the high-order harmonic components in the switched voltage by increasing the inversion time of the voltage. The theoretical expressions of the switched voltage and the dynamic response of the structure were formulated for the cases with finite voltage inversion time. The theoretical results show that increasing the inversion time may weaken the vibration control effect of the targeted mode, but it can significantly reduce the excitation force of the high-order harmonic components. When the inversion time is half of the period of the targeted mode, all the high-order harmonic components in the actuator voltage are completely erased and the control force of the targeted mode decreases by 21%. An experimental setup of a flexible beam was used to verify the theoretical results of the switched voltage and control performance under different inversion time.

The Use of Damping Based Semi-Active Control Algorithms in the Mechanical Smart-Spring System

In recent decades, semi-active control strategies have been investigated for vibration reduction. In general, these techniques provide enhanced control performance when compared to traditional passive techniques and lower energy consumption if compared to active control techniques. In semi-active concepts, vibration attenuation is achieved by modulating inertial, stiffness, or damping properties of a dynamic system. The smart spring is a mechanical device originally employed for the effective modulation of its stiffness through the use of semi-active control strategies. This device has been successfully tested to damp aeroelastic oscillations of fixed and rotary wings. In this paper, the modeling of the smart spring mechanism is presented and two semi-active control algorithms are employed to promote vibration reduction through enhanced damping effects. The first control technique is the smart-spring resetting (SSR), which resembles resetting control techniques developed for vibration reduction of civil structures as well as the piezoelectric synchronized switch damping on short (SSDS) technique. The second control algorithm is referred to as the smart-spring inversion (SSI), which presents some similarities with the synchronized switch damping (SSD) on inductor technique previously presented in the literature of electromechanically coupled systems. The effects of the SSR and SSI control algorithms on the free and forced responses of the smart-spring are investigated in time and frequency domains. An energy flow analysis is also presented in order to explain the enhanced damping behavior when the SSI control algorithm is employed.

An Efficient Inductorless Dynamically Configured Interface Circuit for Piezoelectric Vibration Energy Harvesting

Vibration energy harvesting based on piezoelectric materials is of interest in several applications such as in powering remote distributed wireless sensor nodes for structural health monitoring. Synchronized switch harvesting on inductor and synchronous electric charge extraction circuits show good power efficiency among reported power management circuits; however, limitations exist due to inductors employed, adaption of response to varying excitation levels, and the synchronized switch damping (SSD) effect. In this paper, an inductorless dynamically configured interface circuit is proposed, which is able to configure the connection of two piezoelectric materials in parallel or in series by periodically evaluating the ambient excitation level. The proposed circuit is designed and fabricated in a 0.35 μHV CMOS process.The fabricated circuit is cointegrated with a piezoelectric bimorph energy harvester and the performance is experimentally validated. With a low power consumption (0.5 μW), the measured results show that the proposed rectifier can provide a 4.5 × boost in harvested energy compared to the conventional full-bridge rectifier without employing an inductor. It also shows a high power efficiency over a wide range of excitation levels and is less susceptible to SSD.

Adaptive synchronized switch damping on an inductor: a self-tuning switching law

Synchronized switch damping (SSD) techniques exploit low-power switching between passive circuits connected to piezoelectric material to reduce structural vibration. In the classical implementation of SSD, the piezoelectric material remains in an open circuit for the majority of the vibration cycle and switches briefly to a shunt circuit at every displacement extremum. Recent research indicates that this switch timing is only optimal for excitation exactly at resonance and points to more general optimal switch criteria based on the phase of the displacement and the system parameters. This work proposes a self-tuning approach that implements the more general optimal switch timing for synchronized switch damping on an inductor (SSDI) without needing any knowledge of the system parameters. The law involves a gradient-based search optimization that is robust to noise and uncertainties in the system. Testing of a physical implementation confirms this law successfully adapts to the frequency and parameters of the system. Overall, the adaptive SSDI controller provides better off-resonance steady-state vibration reduction than classical SSDI while matching performance at resonance.

Enhanced vibration damping and modal energy transfer in a smart structure

The next challenge in the field of embedded structures is the development of an efficient, energetically autonomous vibration control technique. The proposed new approach consists in transferring energy between modes of the same structure: energy is harvested in a uncontrolled mode to increase attenuation in a targeted mode. This approach may even permit a ‘stand-alone’ design by generating constant voltages by using the structural motion with an energy harvesting technique. The proposed electrical architecture – called synchronized switch damping and harvesting (SSDH) – is composed of a harvesting circuit (synchronized switch harvesting on inductor [SSHI]), a DC-DC converter (buck-boost topology), and a modal circuit to control vibration (similar to combining the synchronized switch damping on voltage [SSDV] and modal synchronized switch damping on inductor [SSDI] methods). The theoretical analysis and numerical simulation of this architecture addressed the transfer of modal energy through a smart structure based on an academic case: a cantilever beam. The study aimed to increase damping in a selected mode by using the energy of other modes in configurations with realistic energy distributions. The circuit and energy transfer were analyzed to determine the minimum modal contributions necessary to achieve this aim and to ensure long-term stability (steady state). Compared with traditional SSDI, the bi-harmonic excitation used with this new technique increased attenuation damping by 13 dB. The proposed general approach can be extended to the majority of complex or composite industrial structures subjected to vibration.

Multimodal vibration damping using energy transfer

The vibration control using the piezoelectric elements is an area interesting for many industrial sectors. Within this framework, we propose an improved control technique based in synchronized switch damping by energy transfer. It realizes the energy transfer using storage capacitances and switches synchronized with the structure modal coordinates or piezo-voltages. These switches produce either a voltage inversion on the piezoelements for damping or energy extraction purposes, or oscillating discharges between the piezoelements and the storage capacitances for energy transfer. This new method has an improvement in the modal damping technology SSDI-Max. Their performance is simulated with a model representative of a clamped plate with four piezoelectric elements coupled with the structural modes while taking into account realistic transfer losses. The damping effect is simulated in multi-modal with pulse or multi-sine excitation.

Semi-active vibration control based on unsymmetrical synchronized switch damping: Analysis and experimental validation of control performance

In semi-active synchronized switch damping (SSD) approaches for structural vibration control, the damping effect is achieved by properly switching the voltage on the piezoelectric actuators. Unsymmetrical SSD switch circuit has been designed in the previous paper to increase the effective voltage range on the PZT actuator for improvement of the control performance. In this study, analysis and experimental validation of control performance of a synchronized switch damping system based on the unsymmetrical switch circuit are carried out. First the model of an unsymmetrical SSD system is presented and the working principle is introduced. The general expression of the switched voltage on the piezoelectric actuator is derived. Based on its periodicity in steady-state control, the harmonic components of the actuator voltage are derived using Fourier series expansion. Next, the displacement response of the system is derived under combined actions of the excitation and switched voltage. Finally, a setup of a flexible beam with unsymmetrical switch circuit is used to demonstrate the control performance under different voltage sources and to verify the theoretical results. The results show that the control performance mainly depends on the voltage range on the PZT. A higher effective voltage range can be generated in unsymmetrical SSDV than in symmetrical SSDV and better control performance can be achieved at the same negative actuator voltage. The unsymmetrical SSDV makes better utilization of the actuator capability.

Self-powered synchronized switch damping on negative capacitance for broadband vibration suppression of flexible structures

Synchronized switch damping (SSD)techniques using piezoelectric materials have been used by different researchers for many years for the structure vibration control. In these techniques, a piezoelectric patch is bonded on or embedded into the vibrating structure and connected to or disconnected from a network of electrical components through an electronic switch, which is controlled by a digital signal processor (DSP), in synchronous with the structure motion. Recently, Self-powered SSD techniques have emerged in which the DSP is replaced by a low pass filter, thus making the whole system self-powered. The control performance of the previously used Self-powered SSD techniques heavily relied on the electrical quality factor of the shunt circuit, thus limiting their control performance as the electrical quality factor could not be increased beyond certain limit. However, in order to bypass the influence of the electrical quality factor on the control performance, a new Self-powered SSD technique has been proposed in this paper in which the inductance in the previous Self-powered SSD techniques has been replaced with a negative capacitance thus making the whole circuit capacitive without resonance. However, it is found that the voltage on the piezoelectric patch can still be inverted. In order to access the control performance of the proposed technique in comparison with the previous Self-powered SSD techniques, experiments are performed on a cantilever beam subjected to both single mode and multimode excitations. Keeping the value of negative capacitance slightly greater than the inherent capacitance of the piezoelectric patch gave the optimum damping performance. Experiments results confirmed the effectiveness of the proposed technique as compared to the previous SSD techniques.