Piezoelectric Positioning System Research Articles

An explainable neural network integrating Jiles-Atherton and nonlinear auto-regressive exogenous models for modeling universal hysteresis

The inherent nonlinear and memory-dependent input-output characteristics of piezoelectric actuators pose challenges to the precision of piezoelectric positioning systems. In order to solve this problem, this paper firstly transforms the Jiles-Atherton (JA) model into a neural network structure, designs the Jiles-Atherton neural network (JANN), and combines JANN with nonlinear autoregressive exogenous input (NARX) neural network. A hybrid JA-NARX neural network model is proposed for the first time. This model has the advantages of simple structure, high modeling accuracy, and good interpretability. The effectiveness of the proposed JA-NARX neural network model is validated through a series of experiments, specifically assessing its capacity to accurately capture rate-dependent and asymmetric hysteresis characteristics. The results show that although the proposed neural network model has fewer layers and relatively simple structure, it can realize the high-precision modeling of piezoelectric hysteresis dynamics at a lower computational cost. The experimental data shows that, under the excitation of 60 Hz input signal, the model's PV error only accounts for 0.82% of the full scale range, and the modeling performance is far superior to other models.

Nonlinear resonance suppression method of 3D contact probe based on dynamic TSVD inversion

High-precision measurement of 3D probe is usually inseparable from the quasi-static measurement model. However, insufficient dynamic characteristics and uncertainty of the measured characteristics make the measurement results inevitably affected by the resonance nonlinear factors in dynamic measurement. This paper proposes a nonlinear suppression method of dynamic resonance based on truncated singular value decomposition (TSVD) inversion. The dynamic time-domain response function based on the transfer function of the probe system is constructed, and the basic characteristics of nonlinear resonance response and the causes of error are revealed. Then, a piezoelectric positioning system is used to generate a wide-band dynamic excitation signal, and dynamic broadband response signals with linear and nonlinear comprehensive characteristics is inversed with high accuracy through the dynamic measurement experiment. By comparing with typical measurement methods, the advantages of the proposed method in improving dynamic measurement accuracy and suppressing resonance nonlinearity are quantitatively verified.

Synchronous Electrical Conductance‐ and Electron Tunnelling‐Scanning Electrochemical Microscopy Measurements

AbstractThe requirement to separate topographical effects from surface electrochemistry information is a major limitation of scanning electrochemical microscopy (SECM). With many applications of SECM involving the study of (semi)conducting electrode surfaces, the hybridisation of SECM with scanning tunnelling microscopy (STM) or a surface conductance probe would provide the ultimate topographical imaging capability to SECM, but previous attempts are limited. Here, the conversion of a general scanning electrochemical probe microscopy (SEPM) platform to facilitate contact electrical conductance (C)‐ and electron tunnelling (T)‐SECM measurements is considered. Measurements in air under ambient conditions with a Pt/Ir wire tip are used to assess the performance of the piezoelectric positioning system. A hopping‐mode imaging protocol is implemented, whereby the tip approaches the surface at each pixel until a desired current magnitude is exceeded, and the corresponding z position (surface height) is recorded at a set of predefined xy coordinates in the plane of the surface. At slow tip approach rates, the current shows an exponential dependence on tip‐substrate distance, as expected for electron tunnelling. For measurements in electrochemical environments, in order to overcome well‐known problems with leakage currents at coated‐wire tips used for electrochemical STM, Pt‐sensitised carbon nanoelectrodes are used as tips. The hydrogen evolution reaction on 2D Au nanocrystals serves as an exemplar system for the successful simultaneous mapping of topography and electrochemical activity.

Parameter identification of hysteresis nonlinear dynamic model for piezoelectric positioning system based on the improved particle swarm optimization method

An improved particle swarm optimization method that has better equilibrium characteristic between global search and local search is proposed for parameter identification of hysteresis nonlinear dynamic model for piezoelectric positioning system. In this article, a general electromechanical-based piezoelectric positioning systems’ hysteresis nonlinear dynamic model suitable for engineering optimization is introduced, and a parameter identification technique based on improved particle swarm optimization for this dynamic model is presented. For increasing the speed and precision of identification process, the hysteresis effect is described by the generalized Prandtl–Ishlinskii model, and the symmetric solutions of the system are applied to solve the hysteresis nonlinear dynamics equations and then the working process of the improved particle swarm optimization method is given. In order to verify the effectiveness of the proposed method, comparisons between experimental data and simulation data are carried ou...

Temperature compensation in integrated CMOS-MEMS scanning probe microscopes

The authors report on the operation of complementary metal-oxide semiconductor microelectromechanical system (MEMS) scanning probe microscope (SPM) with integrated three-dimensional electrothermal actuation and three-axis position sensing. Conventional SPM makes use of piezoelectric positioning systems which are bulky (leading to thermal drift and poor vibration immunity) and suffer from inherent creep (leading to image distortion). The scanner design is intended to leverage the myriad physical benefits of dimensional scaling to improve the performance and to reduce the barrier to entry for SPM ownership when compared to the state-of-the-art. However, the integration of multiple electrothermal actuators on chip introduces several complications owing to coupling between electrical, thermal and mechanical domains. The focus of this Letter is to discuss the origins of these effects, and the strategies that are implemented to mitigate them. Specifically, the authors discuss the open-loop and closed-loop control methods that are used to drive the lateral and vertical actuators and propose and verify a method to compensate for the parasitic effects observed in the piezoresistive force sensors. To the best of the authors' knowledge, this is the first integrated MEMS-SPM with multiple imaging modes that can image a sample without the need for off-chip scanners or laser-based position sensing.

Dynamics, load balancing, and modal control of piezoelectric tube actuators

In piezoelectric positioning systems the achievable bandwidth is often limited by weakly damped resonant modes. System performance may be improved by avoiding the excitation of these modes. If sufficient mechanical damping is present this can be done by shifting resonant modes towards anti-resonant modes through manipulation of the mechanical boundary conditions. In a second approach the anti-resonances may be shifted towards the resonances by the application of modal actuation. Using this method the excitation of the second and higher order modes can be avoided by adjusting the distribution of actuation forces. This paper investigates and compares the application of modal control techniques in systems that are based on piezoelectric tube actuators such as atomic force microscopes.

Adaptive Compensation of Hysteretic and Creep Non-linearities in Solid-state Actuators

Solid-state actuators based on active materials allow high operating frequencies with nearly unlimited displacement resolution. Their hysteretic characteristics cause a non-linear and ambivalent relationship between the electrical control quantity and the mechanical output quantity during large-signal operation. This behavior can highly restrict the usability of solid-state actuators and is therefore not wanted. In the following, a novel method based on the so-called Prandtl—Ishlinskii approach is presented, which allows extensive compensation of the hysteretic and creep non-linearities during actuator operation. With continuously measured control and output quantities it is possible to compensate not only the non-linearities but also the influence of slowly changing external disturbances such as temperature, mechanical pre-stress, aging, and fatigue of the material. The fast variations due to the force response of the surrounded mechanical structure cannot be considered here. This influence has to be directly introduced into the transducer model. Finally, the capability of this adaptive compensation method is shown in an example involving a two-axis piezoelectric positioning system.

Dynamics and Modal Control of Piezoelectric Tube Actuators

In piezoelectric positioning systems the achievable bandwidth is often limited by weakly damped resonant modes. System performance may be improved by avoiding the excitation of these modes. If sufficient mechanical damping is present this can be done by shifting resonant modes towards anti-resonant modes through manipulation of the mechanical boundary conditions. In a second approach the anti-resonances may be shifted towards the resonances by the application of modal actuation. Using this method the excitation of the second and higher order modes is avoided by changing the distribution of actuation forces. This paper investigates and compares the application of modal control techniques in systems based on piezoelectric tube actuators such as atomic force microscopes using finite element analysis and experimental verification.

A micromachined nanoindentation force sensor

A capacitive force sensor for in situ nanoindentation experiments in TEM has been designed, manufactured and evaluated. The confined space of the TEM specimen holder restricts the size of the fabricated sensor to 2 mm × 1.5 mm × 2 mm to allow mounting. A unique feature of the sensor is an integrated fixture for interchangeable tips, e.g. diamond tips. The sensor is fabricated in silicon anodically bonded to glass and the device is formed by DRIE. To improve the control of spring thickness and circumvent problems during fabrication a SOI wafer and slightly altered design was used in conjunction to an improved process, which resulted in a yield near 100%. The sensor is characterized by a force application using a piezoelectric positioning system, an electrostatic evaluation and a resonance frequency test using a scanning laser doppler vibrometer. The capacitance is measured with an off-chip read-out circuit. The resonance frequency test yielded a spring constant of 750 N/m, which results in a sensitivity of 0.27 pF/0.1 μN for small deflections. The evaluation shows that the force sensor is suitable for in situ nanoindentation for measurements in the range of 0–100 μN.

Electron field emission from thin fine-grained CVD diamond films

The field emission properties of thin, fine-grained diamond films were investigated by measuring emission currents versus electric field curves. The measurements were performed with a spherical electrode attached to a piezoelectric positioning system. The lateral distribution was analyzed by accelerating emitted electrons onto a fluorescent screen. In addition the transient behavior of the emission current was investigated. These characterization techniques were applied to a large number of CVD diamond films deposited by microwave plasma-assisted CVD. The samples were prepared with various methane concentrations (0.5–7%) and deposition temperatures (700–900°C). Undoped as well as boron- and nitrogen-doped samples were studied. Under optimized conditions threshold field strengths as low as 2 V/μm were realized, yielding current densities in the range of several mA/cm2 at 5 V/μm. The density of emission sites is on the order of 104 sites/cm2.