Linear Ultrasonic Motor Research Articles

Adaptive Trajectory Tracking Control of Linear Ultrasonic Motor Based on Fuzzy Recurrent Neural Network

In view of the strong non-linear and time-varying characteristics of linear ultrasonic motors, a fuzzy recurrent neural network controller is put forward. In order to improve the control of the convergence speed and robustness of the proposed controller, the differential evolution algorithm is used for the rapid preliminary off-line optimization of the weights and parameters of network，and then combines the adaptive law and BP algorithm and gradient descent optimization mechanism for learning and accurate optimization. The results show that the fuzzy recurrent neural network controller is better than PID and self-structuring neural network controller, and has a good anti-interference capability.

Mechanical Characteristics on Asynchronous Parallel Connection of Linear Ultrasonic Motors

In order to meet the demand for high power linear ultrasonic motors (LUSMs) for many applications, the concept, asynchronous parallel connection (APC) of LUSMs, has been proposed. The basic principle is that multiple stators (vibrators) alternately drive a slider (rotor) in a vibration cycle, the actual driving frequency then increases by the order of the quantity of stators, and better output performance can be obtained. Analysis shows, in the APC, increasing the contact frequency between stator and slider can enhance the output force, speed of LUSM, while at the same time, the mutual interference of different stators in synchronous parallel connection (SPC) can be avoided. Experimental results of double-driving-tips LUSMs demonstrate that, in APC, over 30% more loading force is obtained than in SPC, and over 25% more is obtained than the sum of loading forces from single LUSM driven respectively. In APC, the no-load linear velocity of LUSM is increased more than 10% from that of individual LUSM driving.

Contact analysis and modeling of standing wave linear ultrasonic motor

A contact model for describing the contact mechanics between the stator and slider of the standing wave linear ultrasonic motor was presented. The proposed model starts from the assumption that the vibration characteristics of the stator is not affected by the contact process. A modified friction models was used to analyze the contact problems. Firstly, the dynamic normal contact force, interface friction force, and steady-state characteristics were analyzed. Secondly, the influences of the contact layer material, the dynamic characteristics of the stator, and the pre-load on motor performance were simulated. Finally, to validate the contact model, a linear ultrasonic motor based on in-plane modes was used as an example. The corresponding results show that a set of simulation of motor performances based on the proposed contact mechanism is in good agreement with experimental results. This model is helpful to understanding the operation principle of the standing wave linear motor and thus contributes to the design of these types of motor.

Adaptive Sliding-Mode Control with Self-Tuning Fuzzy Compensation for a Piezoelectric-Actuated X-Y-Z Table

This paper aims to develop and implement intelligent control for a X-Y-Z three-dimensional table using linear ultrasonic motors as the actuators. Functional approximation technique (FAT) is integrated with the sliding-mode control design to capture the unknown system dynamics and release the requirement of mathematical modeling. In order to deal with the approximation error and the uncertainties of the system, an adaptive fuzzy sliding-mode controller (AFSMC) is used as a compensation of the FAT-based sliding-mode control. Lyapunov stability theory is applied to assure the closed-loop stability and design the updating laws for weighting coefficients of Fourier series and fuzzy tuning parameters. Experimental results indicate that FAT-based sliding-mode control augmented with AFSMC compensation (FA+AFSMC) performs better than the solely FAT-based sliding-mode control.

A New Standing-Wave Linear Moving Ultrasonic Motor Based on Two Bending Modes

Linear ultrasonic motors have been of significant research interests for its excellent characteristics, but it’s hindered by complicated structure. The purpose of this paper is to design and manufacture a prototype by utilizing ANSYS software based on the analysis of mechanism. The vibrator of linear motor is composed of a three teeth rectangular medal block, two group of PZT elements which is adhered on the surface of metal block and slider. It is found that the result of FEA analysis is consistent with experiment result.

Improvements in Controllability of Ultrasonic Linear Motors by Longitudinal-Bending Multilayered Transducers with Independent Electrodes

Ultrasonic motors are nonlinear in input–output characteristics, which causes problems for precise control. To obtain good controllability and realize low-cost fabrication, we proposed an ultrasonic linear motor using a multilayered transducer with independent electrode sets for the first longitudinal mode and the second bending mode. We can change the shape of the vibration locus at the friction head arbitrarily by independently controlling the amplitude and phase of each vibration component. Controllability in the proposed motor was investigated by changing the shape of the vibration locus. In the proposed motor, the nonlinear part of the input–output characteristics is suppressed to 1/20 of that in conventional ultrasonic motors. As a result, a good positioning resolution of 20 nm and a low-speed drive of 0.1 mm/s were obtained with a simple closed-loop control system.

Improvements in Controllability of Ultrasonic Linear Motors by Longitudinal-Bending Multilayered Transducers with Independent Electrodes

Improvements in Controllability of Ultrasonic Linear Motors by Longitudinal-Bending Multilayered Transducers with Independent Electrodes

Two-Axis MEMS Lens Alignment System for Free-Space Optical Interconnect

We present a two-axis microelectromechanical systems (MEMS) lens aligner with a 260 μm × 220 μm translation range that positions a 6.35 mm lens with focal length f = 12.1 mm for alignment compensation of free-space optical interconnects (FSOIs) between computer servers separated by 50 mm spacing. Efficient ultrasonic linear piezoelectric motors (PMs) provide actuation with zero power required to hold the lens alignment. A four-channel FSOI is demonstrated with 1 × 4 vertical cavity surface-emitting laser (VCSEL) and photodiode (PD) arrays capable of 10 Gb/s transmission bandwidth. Demonstrated minimum step size of 1.68 μm is sufficient for aligning the 20 μm VCSEL spots onto the 40 μ m PD receivers. Force transmission between PMs and a silicon MEMS flexure stage is accomplished using a 1-mm steel ball bearing in a magnetic groove, providing compliance in the nondriven axis. The ball-coupling design has 15 μm backlash and induces a maximum of 8 μm of cross-axis motion.

A New Type Butterfly-Shaped Transducer Linear Ultrasonic Motor

This article presents a new type butterfly-shaped transducer linear ultrasonic motor, which utilizes symmetrical modal and anti-symmetric modal of a composite piezoelectric transducer. First, the drive principle of the motor and the formation of the elliptical trajectory of particles on the surface of the driving feet are analyzed. The use of the symmetric modal and anti-symmetric modal of the transducer (stator) realizes the function of driving the slider pressed on the driving feet twice in one cycle. Second, two key problems combined with the design processes of the motor are discussed: frequency consistency adjustment and mounting of the stator to ensure both the high stiffness in the driving direction and elasticity in the direction along which the slider is pressed against the stator. Finally, experimental investigation of the characteristics of the motor is presented. The maximum no-load speed is 870 mm/s, the maximum thrust is 24 N, and the maximum efficiency is 44%.

Analysis of a Linear Ultrasonic Motor Using L-B Hybrid Transducer

In this study, a linear ultrasonic motor using longitudinal and bending hybrid transducer is proposed, which contains two exponential shape horns located on two ends, and the end tips of the horns are used as the driving feet. Two groups of bending PZT ceramics are set in the middle of the transducer, and two groups of longitudinal PZT are set between the bending PZT and two horns, respectively. In this new design, longitudinal and bending vibrations of the transducer are composing and formed elliptical trajectory vibrations on the two end tips of the horns. The runners are in contact with the end tips of the horns, and the driving forces are the frictional forces between the runners and the driving tips. By using FEM method, the longitudinal and bending vibration modes are gained, and the corresponding resonant frequencies are tuned to realize the modal degeneration. At last, transient analysis is developed to gain the vibration trajectories of the driving tips, and elliptical motion trajectories are observed to be formed, which verify the feasibility of the proposed design.

Study on V-Shaped Linear Ultrasonic Motor and its Experiments

A V-shaped linear ultrasonic motor with a stator and a slider has been developed. The stator consists of two orthogonal Langevin actuators which is joined together in their ends. The Langevin actuators are symmetrical and have same first order longitudinal mode. A linear motion of the slider is generated by friction between the stator and the slider when the two first order longitudinal modes are combined. In this paper, structural dynamic design on the stator is completed with Finite Element Method(FEM). The prototype motor is manufactured based on the design results. The operation modes of the stator and the output performances of the motor are tested. The diameter and length of the Langevin actuator are 20mm and 58mm, respectively. The mass of the stator is 290g. The first order longitudinal frequency of the Langevin actuator is 27.47 kHz (FEM simulating result) and 27.36 kHz (expermental result), respectively. The maximum driving force of the motor approaches 40N. The maximum velocity of the motor is about 100 mm/s. So the stator’s operation modes are consistent with the design results, and the motor output properties have characteristics of slower velocity and stronger force.

A New Type Multi-Mode Linear Ultrasonic Motor

A prototype for multi-mode linear ultrasonic motor has been proposed and designed. It is designed using a combination of the first longitudinal and the first bending mode. The piezoelectric ceramics convert energy using the longitudinal d33 effect which allows an improved reliability, large vibration amplitudes and excellent piezoelectric coupling. The normal direction motion of the driving element is excited by the first longitudinal mode. The tangential direction motion of the driving element is excited by the first bending mode. The resulting displacement of the driving element is transmitted by the frictional force between the vibrator and the rail in a linear motion. The analysis on the modals of the composite vibrator by using the ANSYS finite element software has been presented in this paper. Finally, the vibrator structure of the motor and the motor's own structures are designed. The basic design is discussed and simulations are compared with the experimental results, the results show that the motor characteristics can be optimized for a particular task by choosing the appropriate operating parameters such as exciting voltage, exciting frequency and normal force.

Research of a Ring-Type Linear Ultrasonic Motor

A new ring-type linear ultrasonic motor is proposed in this study. In this new design, bending vibration traveling wave is generated in a long ring by two groups of PZT ceramics bonded on the inner sides of the linear beams. Elliptical trajectory motions can be formed at particles on the teeth, which can realize the linear driving by frictional force. The working principle of the proposed design is introduced. Two bending vibration modes that have a phase difference of 90deg on space are analyzed. The elliptical motion trajectory of node on the tooth gained by the transient analysis verifies the excitation of bending traveling wave. A prototype motor is fabricated and measured, and a maximum speed of 15mm/s is reached.

用于精密定位平台的直线超声电机的异步并联

A concept of Asynchronous Bundle of Linear Ultrasonic Motor(ABLUSM) was proposed to improve the resolution,thrust and the speed of driving unit for a precision positioning stage.It points out that a numbers of stators(vibrators) alternately drive a mover(rotor) in a vibration cycle,the actual driving frequency is increased doubly,and better output performance can be expected.An analysis shows that increasing the contact frequency between stator and mover is able to improve the output force,speed and transient response characteristics of a Linear Ultrasonic Motor(LUSM).Meanwhile,it can avoid the mutual interference of different stators in Synchronous Bundling of LUSM(SBLUSM).Experimental results of two types of motors show that the maximum load force of the ABLUSM is 30% upon that of the SBLUSM or 25% over that of the sum of two motors when they drive the slider respectively.Results of minimum resolution test show that the minimum displacement resolution of the ABLUSM is 32.6 nm,which is 62.8% that of a single LUSM or 38.5% that of the SBLUSM.The mechanical characteristic experiments of the LUSM with one driving tip also prove that the no-load speed of ABLUSM has increased by 10% as compared with that both of the single stator and the SBLUSM.Moreover,the maximum efficiency has by 50% over that of the SBLUSM.Transient response time is shorter than SBLUSM,which is about 50% of a single stator.

Influence of a high vacuum on the precise positioning using an ultrasonic linear motor

This paper presents an investigation of the ultrasonic linear motor stage for use in a high vacuum environment. The slider table is driven by the hybrid bolt-clamped Langevin-type ultrasonic linear motor, which is excited with its different modes of natural frequencies in both lateral and longitudinal directions. In general, the friction behavior in a vacuum environment becomes different from that in an environment of atmospheric pressure and this difference significantly affects the performance of the ultrasonic linear motor. In this paper, to consistently provide stable and high power of output in a high vacuum, frequency matching was conducted. Moreover, to achieve the fine control performance in the vacuum environment, a modified nominal characteristic trajectory following control method was adopted. Finally, the stage was operated under high vacuum condition, and the operating performances were investigated compared with that of a conventional PI compensator. As a result, robustness of positioning was accomplished in a high vacuum condition with nanometer-level accuracy.

Electrode design of multilayered piezoelectric transducers for longitudinal-bending ultrasonic actuators

To improve the controllability of ultrasonic linear motors in the longitudinal-bending mode, we have developed a multilayered transducer with independent electrode sets for the first longitudinal mode and the second bending mode. Since the vibration components are controlled independently by the transducer, it is possible to change only the driving vibration component with the component for friction control kept constant. The optimal shape and area of the electrodes in terms of efficiency were investigated analytically and experimentally. It was confirmed that an electrode shape in accordance with the mode strain contour gave a large output and that an optimum electrode area existed. The transducer with an optimal electrode pattern exhibited an efficiency improvement of approximately 10% and a 30% reduction of the temperature rise during motor operation.

Holding and Preloading Mechanism Using a Buckling Parallel Leaf Spring for Ultrasonic Linear Motor

To increase the applicability of ultrasonic linear motors, we have developed a holding mechanism for the transducer using parallel leaf springs. The present mechanism is compact since the parallel leaf spring structure has functions for both holding and preloading at the same time. Also, a special design for the spring characteristics provides a non-linear load-displacement region with buckling phenomena. These results in a constant preload for some range of the displacement, then the motor performance does not alter even after abrasion of contact surfaces. In this report, the relationship between the dimension of the leaf spring and the force-displacement curves was investigated in order to obtain the design appropriate for constant preloading. Moreover, the effect of the vibration reduction by the holding mechanism was investigated theoretically and experimentally. The vibration reduction was as small as less than 10 % since the stiffness in terms of the vibration direction was relatively small. Finally, the dynamic responses of the motor with the holding mechanism were measured for a sinusoidal control signal. No prominent peak was observed in the motor's responses, however, the motor velocity change was distorted near the natural frequency of the holding mechanism.

Robust intelligent backstepping control system using RCMAC for tracking periodic trajectories

Since the backstepping control technique is a systematic and recursive design methodology for nonlinear systems, a robust intelligent backstepping control (RIBC) system is proposed in this study to control a linear ultrasonic motor (LUSM) for the tracking of periodic reference trajectories. In the proposed control system, an adaptive recurrent cerebellar model articulation controller (RCMAC) is used to mimic an ideal backstepping control and a robust controller is designed to attenuate the effects caused by unmodeled dynamics, disturbances and approximate errors. The proposed adaptive RCMAC has superior capability to the conventional cerebellar model articulation controller (CMAC) in efficient learning mechanism and dynamic response. Moreover, the Taylor linearization technique is employed to derive the linearized model of the RCMAC. The online adaptation laws of the RIBC system are derived in the sense of the Lyapunov function, the Taylor linearization technique and the H ∞ control approach, so that the stability of the system and robust tracking performance can be guaranteed. Finally, the effectiveness of the proposed control system is indicated in comparison with an integral–proportional (IP) position control system. Experimental results show that high-precision tracking performance can be achieved by using the proposed RIBC system.

Optimal design of V-type ultrasonic motor

V-type ultrasonic linear motor fabricated using a simple punching technique was proposed to utilize as an actuator of small precision machine. The stator of the motor is composed of a thin elastic body and four ceramics attached to the upper and bottom areas of the body. The ceramics have each direction of polarization. When two harmonic voltages with a 90° phase difference are applied to the ceramics, symmetric and anti-symmetric displacements will generate at the tip to produce an elliptical motion. A finite element analysis (ATILA) was conducted to simulate the motion pattern for the contact tip of the stator. To develop a model that generates the maximum displacement at contact tip, the FEM program was used for various lengths. In addition, an optimal model was chosen by considering the magnitude and shape of the displacement according to changes in frequency. The maximum elliptical displacement is shown by W2L11 model, which has a ratio of ceramic width to length of 1:5.5. However, the displacement of the contact tip is reduced by the bucking phenomenon if the ratio is larger than 1:6.

A new standing-wave-type linear ultrasonic motor based on in-plane modes

This paper presents a new standing-wave-type linear ultrasonic motor using combination of the first longitudinal and the second bending modes. Two piezoelectric plates in combination with a metal thin plate are used to construct the stator. The superior point of the stator is its isosceles triangular structure part of the stator, which can amplify the displacement in horizontal direction of the stator in perpendicular direction when the stator is operated in the first longitudinal mode. The influence of the base angle θ of the triangular structure part on the amplitude of the driving foot has been analyzed by numerical analysis. Four prototype stators with different angles θ have been fabricated and the experimental investigation of these stators has validated the numerical simulation. The overall dimensions of the prototype stators are no more than 40 mm (length) × 20 mm (width) × 5 mm (thickness). Driven by an AC signal with the driving frequency of 53.3 kHz, the no-load speed and the maximal thrust of the prototype motor using the stator with base angle 20° were 98 mm/s and 3.2 N, respectively. The effective elliptical motion trajectory of the contact point of the stator can be achieved by the isosceles triangular structure part using only two PZTs, and thus it makes the motor low cost in fabrication, simple in structure and easy to realize miniaturization.