Multiple Piezoelectric Actuators Research Articles

Coupled hysteresis and resonance control of three-degree-of-freedom tip-tilt-piston piezoelectric stage

In order to solve the coupled hysteresis and resonance problems in three-degree-of-freedom tip-tilt-piston piezoelectric stage, a coupled hysteresis model and a coupled integral resonance compensation model are designed. The inverse coupled hysteresis feedforward control combined multi-axis coupled resonance control and high-gain integral tracking controller are used to improve the tracking speed and positioning accuracy of the stage. Firstly, a kinematic model of the stage is built to translate the three-degree-of-freedom motion of the end-effector into the outputs of three piezoelectric actuators. Then, a coupled hysteresis model based on the rate-dependent Prandtl–Ishlinskii model is established and parameterized to simultaneously compensate for the hysteresis of a single piezoelectric actuator and the coupled hysteresis between multiple piezoelectric actuators. The effectiveness of the model is verified by open-loop and closed-loop inverse model feedforward control experiments. Afterwards, a coupled integral resonance compensation model is also established and parameterized to suppresses the resonance and expand the system bandwidth. Finally, the proposed controller is used to conduct tracking experiments on a composite signal, and the results show that the accuracy and speed of trajectory tracking are further improved, and the mechanical coupling between axes are significantly reduced.

Experimental Evaluation of Wearable Piezo Ring for Bolted Connection Monitoring Using the Active Sensing Approach

As a safe and reliable connection, bolted connection is widely used in various structural systems. Monitoring the bolted connection is beneficial to ensure the safety of the whole structure. In this study, a wearable piezoelectric ring based on piezoelectric material is designed and it can be easily integrated into the bolt connection as a washer. To verify the feasibility of wearable piezoelectric ring, single-bolt looseness experiment based on wearable piezoelectric ring was carried out. Firstly, the wearable piezoelectric ring was installed on the bolted joint, acting as a piezoelectric sensor, and multiple piezoelectric actuators were installed in different location of the plate surface. Then, different torque level was applied to the bolt and the stress wave signals were obtained by piezoelectric active sensing technique. Finally, the recursive analysis method was introduced to extract nonlinear recursive features of the stress wave signals. The experimental results showed that the change of the bolt looseness could be qualitatively characterized by the phase space trajectory and the recurrence plots. Moreover, the recursive entropy could quantitatively characterize the bolt looseness, showing a bright prospect in monitoring the bolt looseness using the wearable piezoelectric ring.

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.

Haptic Soft-Keyboard for Tablet-Sized Touchscreens

Most users are not satisfied with the typing vibration feedback from linear motors of mobile phones since it feels like buzzing rather than physical key pressing feedback. For larger touchscreens, such as 10.1 inch tablets, there is no commercial tactile soft keyboard developed yet. Therefore, there is the need to develop a haptic soft keyboard technology imitating the physical keyboard for the tablet-sized touchscreen. In the present study, we present a new approach introducing an optimal design of a multilayered piezoelectric actuator that meets the need for a haptic soft keyboard for 10.1 inch tablets, implementing stronger tactile feedback that utilizes human sensitivity to time differences obtained by a psychophysical experiment and equalizes the force distribution of the touchscreen when using multiple piezoelectric actuators. The developed system was evaluated by a user study measuring typing performance.

A Charge Controller for Synchronous Linear Operation of Multiple Piezoelectric Actuators

The charge controller can greatly improve the hysteresis of the piezoceramic without the sensor. It is widely used in open-loop controlled nano-positioning systems. However, conventional charge controllers are not suitable for synchronous high linear operation of multiple piezoelectric actuators. This paper proposes a novel charge control scheme which can be used for synchronous high linear operation of multiple piezoelectric actuators. The control scheme combines similar control and traditional charge control. We verify the feasibility of this control scheme through experiments. The trajectory deviation between the two piezoelectric actuators reaches 0.79% of the travel range, while their respective trajectory errors do not exceed 1.2%. Because the controller in this paper has a simpler grounding configuration, it can also replace the traditional charge controllers for high linearity operation. The experimental results show that the charge controller achieves 0.65% positioning error of the piezoelectric actuator with grounding configuration. In addition, a T-type resistor network has also been introduced into the charge controller, which enables low-frequency linear operation of piezoelectric actuators with small capacitance.

Interacting Automultiscopic 3D With Haptic Paint Brush in Immersive Room

In this paper, we propose an interactive artwork system with automultiscopic 3D and haptic paint brush in an immersive room. Our system consists of a 81-view automultiscopic display, a handheld haptic paint brush, and a large-scale color palette station in a CAVE-like cubic room filled with the visual scene of the artwork. The 81-view rendering and multiplexing technology is applied by setting up the virtual cameras in the off-axis layout. The haptic paint brush is designed and implemented using a 2D array of multiple piezoelectric actuators. It provides the tactile feedback of spatial distance information between a virtual brush and a distal 3D object displayed on the automultiscopic display for the precise control of the brush when it is interacting with automultiscopic 3D. We demonstrate a proof-of-concept system that integrates a classic artwork into an innovative interactive system using novel multimedia and interactive technologies and evaluate our system using the handheld haptic brush for its performance and usability to enhance the user experiences.

Modeling and Inverse Compensation for Coupled Hysteresis in Piezo-Actuated Fabry–Perot Spectrometer

An imaging Fabry–Perot spectrometer (FPS) utilizes multiple piezoelectric actuators (PEAs) to tune the gap spacing between two optical lenses at nanometer level in order to scan the desired optical band. Due to the nonlinear hysteresis in PEAs and the mechanical coupling, the output responses of the PEAs are quite different, which cause unparallel movement of the FPS positioning stage. For precise positioning control, a model for describing the coupled hysteresis effect is proposed in this paper and a decoupling hysteresis feedforward compensator is constructed based on this model. Experimental results show that the proposed model predicts the coupled hysteresis effect very well and the compensator mitigates the coupled hysteresis efficiently.

Shared inductor hybrid topology for weight constrained piezoelectric actuators

This paper presents a new circuit topology designed to minimise the weight of the control circuit required to actuate multiple piezoelectric actuators. It can independently set the phase and bias voltage on each piezoelectric actuator through the use of a single inductor. This is highly desirable in weight constrained applications such as unmanned aerial vehicles as the ferroelectric material required for the inductor is heavy. Furthermore, the circuit topology can also use the same inductor to generate the high bias voltage required to drive the actuators. The full system has been verified in PSpice and a pair of piezoelectric actuators have been successfully driven using off the shelf components.

Active Structural Acoustic Control of a Softcore Sandwich Panel Using Multiple Piezoelectric Actuators and Reddy's Higher Order Theory

The purpose of the present work is to theoretically investigate the active control of radiated sound power from a simply supported soft-core sandwich panel with a line moment excitation. Since noise transmission in the low frequency region through a soft-core sandwich panel mainly occurs due to flexural and dilatational modes, therefore, the focus of this study is to control these modes and achieve sound attenuation in a large frequency band. Two control methods, volume velocity and weighted sum of spatial gradients (WSSG) are used to drive three piezoelectric actuators (PZTs) attached on the exterior side of the bottom face plate. The governing equation of the sandwich panel with the PZTs is derived using the Hamilton's principle considering Reddy's third order shear deformation theory. Numerical studies indicate that while the line moment is at the mid vertical line, WSSG is able to attenuate the radiated sound power irrespective of core loss factor whereas volume velocity could not. However, both the control metrics are able to attenuate most of the structural modes, when the line moment is off the midline, and therefore, attenuate significant amount of radiated sound power in a broad frequency range. And the maximum increase in sound power is small in WSSG as compared to volume velocity. These results show that WSSG can be used as an effective control metric to mitigate low frequency sound.

Typing performance evaluation with multimodal soft keyboard completely integrated in commercial mobile devices

Recently touch screens are widely used for mobile devices to provide intuitive and natural interactions with hands and fingers. However, the lack of tactile responses makes it difficult for users to get key-click confirmations during text entry with soft keyboards. This paper examines the effect of tactile feedback on typing performance with the soft QWERTY keyboard, the most commonly-used, multi-finger text entry and thumb typing methods in mobile devices. In order to investigate the typing performance, we implemented tactile feedback functions by embedding multiple piezoelectric actuators that was attached under the touchscreen to simulate the key-click effect in commercial mobile platforms, MS Surface Pro (tablet) and Nokia Lumia520 (phone). We conducted an experiment of transcription tasks to measure typing performance and user preference. The experiments involved transcribing given phrases with three feedback conditions: visual only, visual with audio, and visual with tactile. The results showed that the typing performance (KSPC, WPM, UER, CER) has been significantly improved by adding tactile feedback to the existing visual display on a commercial tablet and phone. A further quantitative analysis by questionnaire also showed that all of the participants preferred tactile or aural feedback to visual feedback only. This study thus provides researchers and designers with practical guidelines regarding tactile feedback on commercial mobile devices.

Influence of Matrix Circuit Switching Device Junction Capacitance on Piezoelectric Actuator Drive Performance

Piezoelectric actuators are widely used as fine-motion actuators for positioning devices. Current pulse driving reduces displacement hysteresis, and the drive circuit provides current pulses considered constant charge pulses to the piezoelectric actuator. The circuit for devices with multiple degrees of freedom using multiple piezoelectric actuators should be simple. Matrix circuits are used to drive liquid crystal displays to reduce the number of drive-circuit control signals and components. A group of 2 × 2 piezoelectric actuators was driven alternately using a 4-switch matrix circuit, and two field effect transistors were used as a fast matrix circuit switch. Piezoelectric actuator drive performance was studied in the case of using the current pulse circuit and the matrix circuit. When the matrix circuit drove actuators performing as capacitive loads, switching device junction capacitors adversely affected drive performance.

Placement of Multiple Piezo Patch Sensors and Actuators for a Cantilever Beam to Maximize Frequencies and Frequency Gaps

Active vibration control is implemented using multiple piezoelectric actuators and sensors bonded to the top and bottom surfaces of a cantilever beam. The control is exercised using closed-loop displacement feedback. The objective of the study is to determine the optimal locations of patch actuators and sensors such that the fundamental frequency or the frequency gap between higher frequencies of the beam is maximized. Maximizing the fundamental frequency is useful to avoid resonance when the excitation frequency is less than the fundamental frequency. Alternatively, the excitation frequency can also be placed in between two higher order frequencies and the difference between the two higher order frequencies can be maximized. In the present study the fundamental frequency and the frequency gaps between the higher order frequencies are investigated with respect to actuator and sensor locations with a view towards determining their optimal locations for largest frequency gaps. The locations of the piezo patches to maximize first, second and third frequencies are also given. The differential equation governing the vibrations of a feedback controlled beam/piezo patch system is solved using an integral equation approach. The numerical results are given for various patch combinations and the optimal locations of the actuators and the sensors are determined. It is observed that the optimal locations of the piezo patches depend on the specific frequency gap as well as the patch configurations.

Adaptive input shaping and control for simultaneous precision positioning and vibrationsuppression of smart composite plates

This paper focuses on simultaneous precision positioning and vibration suppression ofsmart composite plates with multiple piezoelectric patch actuators. Following the analysis,measurement, and estimation of a smart composite plate dynamics is the development of amulti-reference and multi-channel adaptive algorithm and an adaptive controlstrategy. The introduced adaptive control strategy consists of an adaptive inputshaping unit and an adaptive positioning/vibration control unit, and both units aredesigned by applying the adaptive algorithm. The adaptive input shaping unit isused to suppress free vibration due to the smart composite plate motion and toexpedite the convergence of the adaptation of the adaptive positioning/vibrationcontroller. The adaptive positioning/vibration controller then provides precisionpositioning control and reduces the vibration due to the motion of the plate and/orexternal disturbances. In addition, an internal model configuration is employedto provide the reference needed in the adaptive control strategy and the effectof the discrepancy between the estimated dynamic model and the plate on theperformance of the controller is also explored. The experiments demonstrate that theadaptive control strategy has excellent capabilities of positioning and vibrationcontrols for various positioning and vibration conditions of the smart compositeplate.

Compliant Mechanical Amplifier Design using Multiple Optimally Placed Actuators

This article discusses a methodology for designing compliant mechanisms with piezoelectric actuation to obtain maximum deflection and force at the output point. The focus is on design of compliant mechanisms with multiple piezoelectric actuators. The number, size, and position of the actuators within the compliant mechanism are optimized for the maximum output deflection. Predicted results demonstrate that compliant mechanisms with multiple, optimally placed actuators outperform those with a single actuator placed at a predetermined location.

Novel Approach to Self-Sensing Actuation for Semi-Active Vibration Suppression

A novel self-sensing method using piezoelectric actuators for semi-active vibration suppression is proposed and investigated. By using extended system equations, this self-sensing method can be implemented with a Kalman filter instead of the conventional bridge circuit technique. The method separates electrical status into two cases concerning electrical current, and characterizes each of these to establish the self-sensing system. This method is applicable to multiple-degree-of-freedom structures with multiple piezoelectric actuators. A numerical vibration suppression simulation demonstrated that the self-sensing method works well on a truss structure and has significant robustness against parameter variations. Experimental results also demonstrated that the self-sensing method suppresses not only single-mode vibration but also multiple-mode vibration.

Optimized electric networks for vibration damping of piezoactuated beams

This paper studies the multimodal vibration damping of an elastic beam equipped with multiple piezoelectric actuators connected to an electric network. Two analytical models of the electromechanical coupled structure are considered: a homogenized one, accurate when a large number of actuators is employed, is used to derive simple design criteria for the electric network; and a discrete one, able to face real situations when few actuators are employed, is adopted to test the network performance, defined as the exponential time-decay rate of the free vibrations of the controlled structure. Some electric networks are presented and compared in simulation to networks previously proposed in the literature, in order to evaluate their performances in broadband vibration control.

An impedance approach for vibration response synthesis using multiple PZT actuators

For a structure bonded with multiple piezoelectric (PZT) patches, a method of formulating the couplings between the PZT patch and the host structure, and among the PZT themselves has been proposed using the impedance method. An approach to synthesizing a designated response of a thin plate using multiple PZT patches is presented to show that the impedance technique has a great potential in solving the inverse vibration problem analytically. Moreover, a modified structural impedance model of the host structure is proposed to include the inertia effect caused by the PZT patch on the vibration response of the host structure, which proves to be important for a typical intelligent structure usually bonded with multiple PZT patches. With this proposed modified structural impedance, the force prediction for each PZT patch in producing a designated vibration response is more accurate.

An impedance approach for vibration response synthesis using multiple PZT actuators

For a structure bonded with multiple piezoelectric (PZT) patches, a method of formulating the couplings between the PZT patch and the host structure, and among the PZT themselves has been proposed using the impedance method. An approach to synthesizing a designated response of a thin plate using multiple PZT patches is presented to show that the impedance technique has a great potential in solving the inverse vibration problem analytically. Moreover, a modified structural impedance model of the host structure is proposed to include the inertia effect caused by the PZT patch on the vibration response of the host structure, which proves to be important for a typical intelligent structure usually bonded with multiple PZT patches. With this proposed modified structural impedance, the force prediction for each PZT patch in producing a designated vibration response is more accurate.

Simultaneous Design of Piezoelectric Shape and Control System for Smart Structures (Shape Optimization of Multiple Piezoelectric Actuators)

A smart structure is composed of the piezoelectric film sensor and actuator in order to reduce the structural vibration. H2 controller is designed with the reduced order model of the smart structure which is obtained by finite element and modal analyses. The control force is applied by the piezoelectric film actuator and the feedback signals are detected by the piezoelectric film sensor and the accelerometer in the system. The vibration response is suppressed by the modal control and the displacement control in which the modal coordinate displacement and the spatial displacement are taken as the controlled variable. The shapes of the multiple piezoelectric actuators and the H2 control system are simultaneously optimized to achieve an enhanced vibration control performance. Efficient optimization algorithm based on a two-step procedure is employed in the simultaneous optimization. It is verified that an enhanced performance on vibration suppression can be achieved by the presented optimal design.

Wave Propagation Induced by Multiple Piezoelectric Actuators in Electromechanical Structures

This paper provides a theoretical analysis of the elastic wave propagation in an elastic medium induced by embedded piezoceramic actuators under dynamic electric loads. A new actuator model involving the deformation in both the transverse and longitudinal directions of the actuators is used to study the wave propagation induced by multiple actuators. The resulting waveform is determined using a pseudo-incident wave technique and solving the resulting integral equations in terms of the interfacial shear stress and transverse displacement of the actuators. Numerical simulation is conducted to evaluate the effects of the geometry, the loading frequency, and the interaction between actuators upon the resulting wave propagation.