A review of recent studies on non-resonant piezoelectric actuators

Recent trends in piezoelectric actuators for precision motion and their applications: a review

A piezoelectric platform driven by a bionic quadruped piezoelectric actuator is developed. It uses the operating principle of combining bionic walking and swinging actuation modes to achieve nanopositioning in a large travel range. The mechanical structure is introduced, the operation principle is illustrated, and the dynamic model and control method are developed. The open-loop performances are first tested to verify the effectiveness of the operating principle and the dynamic model, and the simulation results agree well with the experimental results. Then, the closed-loop experiments in bionic walking and swinging actuation modes are carried out, respectively, and the controllers are designed based on the dynamic model. In the point-to-point positioning control experiments, the steady-state errors for the target position of ±1000  μ m in axes X and Y are within ±1  μ m in bionic walking actuation mode, and they are within ±20 nm for the target position of ±2  μ m in bionic swinging actuation mode. The closed-loop experiments under the combination of the bionic walking actuation mode and swinging actuation mode are performed, and a switched controller is developed to obtain the switching of the two modes automatically; the steady-state errors are within ±20 nm. The experimental results confirm that the method combining bionic walking and swinging actuation modes and switched control is valid in enhancing the positioning precision and travel range for the nanopositioning platform.

Development of a Nanopositioning Platform With Large Travel Range Based on Bionic Quadruped Piezoelectric Actuator

The ability to do dexterous automated and semi-automated tasks at the micro- and nano-meter scales inside a Scanning Electron Microscope (SEM) is a critical issue for nanotechnologies. SEM-integrated nano-robotic systems with several Degrees Of Freedom (DOF) and one or several end-effectors have therefore widely emerged in research laboratories and industry. The Piezoelectric Stick-Slip (PSS) is one of the best actuation principle for SEM-integrated nano-robotic systems as it has two operating modes, namely a coarse positioning mode with long travel range, and a fine positioning mode with a resolution of the order of the nanometer. The main contribution of this paper is the design of a switch control strategy to deal efficiently and in a transparent way from the user's point of view, with the transition between the coarse and the fine operating modes of PSS actuators. The aim is to be able to perform positioning tasks with a millimeter displacement range and a nanometer resolution without worrying about the mode of operation of the actuator. The coarse mode and the fine mode are respectively controlled with a frequency/voltage proportional control and a H∞ control. The switch control is based on an internal model of the actuator. Experimental results show the effectiveness of the new mixed coarse/fine mode control strategy to satisfy closed-loop stability and bumpless specifications at the switching time. For the best knowledge of the authors, this result is the first demonstration of such a control capability for PSS actuators.

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Mixed stepping/scanning mode control of stick-slip SEM-integrated nano-robotic systems

During the raster scanning of atomic force microscopes (AFMs), the coupling effect from the fast-axis to the slow-axis is extraordinarily pernicious, especially when the scanning rate is set high. Whilst great efforts have been made in the field of piezo-actuated stages, less attention is paid on control design to mitigate this coupling effect. In this paper, we propose a modified repetitive control based cross-coupling compensation (MRC-CCC) approach for high-speed and high-precision scanning motion control of a piezoelectric tube scanner in AFMs. Based on the experimental observations, we first describe this coupling effect as the periodic disturbance to the output of the slow-axis when the fast-axis is designed to track triangular trajectories. Then, the MRC-CCC controller is developed to remedy the periodic disturbances, which generates the compensation signals targeting the coupling effect. Therefore, the complicated modeling of the cross-coupling effect is avoided, which significantly reduces the complexity of usage. To ensure the high-precision tracking performance for the slow-axis in scanning, we further design a tracking controller that combines with the offline trained MRC-CCC controller. Finally, comparative experiments are conducted on an AFM piezoelectric tube scanner. Experimental results show that the developed MRC-CCC approach significantly compensates for the coupling effect, in which the root-mean-square tracking error is substantially reduced from 172.1 to $3.3\text{ nm}$ at the scanning rate of 40 Hz. We also perform high-speed scanning tests for AFM imaging to verify the effectiveness of the development.

Modified Repetitive Control Based Cross-Coupling Compensation Approach for the Piezoelectric Tube Scanner of Atomic Force Microscopes

Positive acceleration, velocity and position feedback based damping control approach for piezo-actuated nanopositioning stages

Hysteresis modeling is interesting yet challenging for piezoelectric actuated systems, which are often used in micro/nano scale measurement and manufacturing equipments. However, due to its complexity, few efforts have been devoted to characterizing cross-coupling hysteresis effect of multiaxis piezoelectric micropositioning stages. To this end, a distributed Hammerstein model, composed of a cascaded connection of a static nonlinearity and a dynamic linearity, is proposed in this paper to approximate the nonlinear spatial/temporal cross-coupling effect. This model outperforms conventional piezo models, such as the Preisach model. Meanwhile, theoretical analysis is provided to guarantee the convergence of the proposed Hammerstein model. Finally, extensive experiments are conducted to verify the superiority of the proposed modeling method.

Distributed Hammerstein Modeling for Cross-Coupling Effect of Multiaxis Piezoelectric Micropositioning Stages

The invention provides a motion-decoupled rope-driven non-individual body mechanical arm and a robot. The mechanical arm comprises mechanical arm sleeves, traction rope sets and knuckles, wherein the number of the mechanical arm sleeves, the number of the traction rope sets and the number of the knuckles are more than one. The mechanical arm sleeves are sequentially arranged, and the adjacent mechanical arm sleeves are hinged to form a mechanical arm body through the knuckles. The front end of the mechanical arm body is used for being connected with a rope-driven base. The traction rope sets are used for driving the corresponding knuckles. The traction rope sets and the knuckles are in one-to-one correspondence. One end of each traction rope set is connected with the corresponding knuckle, and the other end of each traction rope set is used for being connected with the rope-driven base after sequentially penetrating through through-holes in multiple knuckle rope guiding discs arranged on the front side of the corresponding knuckle. The mechanical arm has multiple degrees of freedom, is thin and long in body type and suitable for survey and operation in narrow spaces, and has large application potential.

Motion-decoupled rope-driven non-individual body mechanical arm and robot

The scanning speed of atomic force microscopes (AFMs) is typically limited by the frequency of the triangular trajectory used in generating the raster scan. This is because the higher harmonics of the triangular trajectory have a tendency to excite the mechanical resonances of the nanopositioners incorporated in the AFM; thereby, introducing significant positioning errors. To address this issue, this article proposes a novel scanning trajectory smoothing method to enable high-speed raster scanning. The proposed method utilizes the acceleration-continuous B-spline to replace the backward path of the triangular trajectory for the fast axis. As a result, the advantage of uniform sampling along the forward path is preserved. The trajectory generation process is described in detail. A hysteresis compensation method is employed to improve the tracking performance of the scanner. Experiments conducted on a commercial piezoelectric tube scanner are presented to demonstrate the performance improvement delivered by the proposed method when compared with the traditional raster scanning method. It is shown that the proposed method enables a five-fold improvement in achievable scanning rate, from 10 to 50 Hz.

Linlin Li

Papers

Positive acceleration, velocity and position feedback based damping control approach for piezo-actuated nanopositioning stages

Modified Repetitive Control Based Cross-Coupling Compensation Approach for the Piezoelectric Tube Scanner of Atomic Force Microscopes

Distributed Hammerstein Modeling for Cross-Coupling Effect of Multiaxis Piezoelectric Micropositioning Stages

Motion-decoupled rope-driven non-individual body mechanical arm and robot

Erratum to “A Smoothed Raster Scanning Trajectory Based on Acceleration-Continuous B-Spline Transition for High-Speed Atomic Force Microscopy”