Piezoelectric Ultrasonic Motor Research Articles

Enhanced dielectric, ferroelectric and piezoelectric properties of lead-free (Ba,Ca)(Sn,Ti)O3 ceramics by optimisation of sintering temperature

Lead-zirconate-titanate [Pb(Zr,Ti)O3 PZT] crystals possess superior ferroelectric, dielectric and piezoelectric properties. However, due to the toxicity of lead there is a demand for lead-free alternatives. In the present work, we focus on the production of the lead-free (Ba,Ca)(Sn,Ti)O3 (BCST) ceramics via solid-state synthesis method. BCST ceramics calcined at 1050°C, 1100°C, 1150°C, 1200°C and 1250°C were characterized using XRD analysis which showed that at temperatures above 1150°C the structure was free from impurities. Rietveld refinements confirmed a tetragonal structure with P4mm space group for the material calcined at 1150°C. Scanning electron microscopy image analysis of samples sintered at 1200°C, 1250°C and 1300°C showed an increase in grain size and density with temperature. The material sintered at 1300°C had a higher dielectric constant compared to other ceramics. A larger grain size facilitated high ferroelectric polarisation (3.38 μC/cm2), dielectric constant (6100) and d33 piezoelectric coefficient (236 pC/N) for the ceramics. This study demonstrates the potential for using lead-free BCST ceramics for device applications, such as piezoelectric actuators, transducers and ultrasonic motors.

Design and analysis of impedance matching for a radial standing wave piezoelectric ultrasonic motor.

Impedance matching circuits are capable of tuning and wave filtering, which is beneficial to performance improvement of piezoelectric ultrasonic motors. At present, impedance matching for piezoelectric ultrasonic motors is usually realized through a series inductance, which has the problem of poor wave filtering effect. Different from the previous series inductance matching method for ultrasonic motors, a series inductance and capacitance matching method is proposed for a radial standing wave piezoelectric ultrasonic motor. The series capacitance is added to adjust the quality factor of the resonance tank so that a desired wave filtering effect can be obtained. The values of the series inductance and capacitance are derived based on the Butterworth-Van Dyke model of the piezoelectric ultrasonic motor. Simulations are conducted to verify the feasibility of the proposed matching method. Finally, the waveforms of voltages and currents as well as torque-speed curves of the motor are measured. The results validate the proposed matching method. In addition, the previous series inductance matching method is compared. The results show that the proposed series inductance and capacitance matching method not only achieves tuning function but also obtains a significantly improved wave filtering effect. Moreover, the torque-speed characteristics of the motor are also improved with the proposed matching method.

A Symmetric-Actuating Linear Piezoceramic Ultrasonic Motor Capable of Producing a Scissoring Effect.

Conventionally, to produce a linear motion, one motor's stator is employed to drive one runner moving forward or backward. So far, there is almost no report of one electromechanical motor or piezoelectric ultrasonic motor that can directly generate two symmetrical linear motions, while this function is desired for precise scissoring and grasping in the minimally invasive surgery field. Herein, we report a brand-new symmetric-actuating linear piezoceramic ultrasonic motor capable of generating symmetrical linear motions of two outputs directly without additional mechanical transmission mechanisms. The key component of the motor is an (2 × 3) arrayed piezoceramic bar stator operating in the coupled resonant mode of the first longitudinal (L1) and third bending (B3) modes, leading to symmetric elliptical vibration trajectories at its two ends. A pair of microsurgical scissors is used as the end-effector, demonstrating a very promising future for high-precision microsurgical operations. The sliders of the prototype show the following features: (a) symmetrical, fast relative moving velocity (~1 m/s) outward or inward simultaneously; (b) high step resolution (40 nm); and (c) high power density (405.4 mW/cm3) and high efficiency (22.1%) that are double those of typical piezoceramic ultrasonic motors, indicating the full capacity of symmetric-actuating linear piezoceramic ultrasonic motor working in symmetric operation principle. This work also has enlightening significance for future symmetric-actuating device designs.

Traveling wave ultrasonic piezoelectric motor modelling for the control design of an Automatic Headlight Levelling System

This work deals with some major aspects of ultrasonic traveling-wave piezoelectric motor modelling in the context of an automotive application. The aim here is to establish a proper model of this type of actuator, reflecting its behaviour. This work is a part of a larger study on the headlight automatic position control on vehicles conducted in the framework of the OpenLab “Electronics and Systems for Automotive” combining IMS laboratory and Stellantis company. The main complexity of this work is to create a proper simulator of this type of actuator, and discussing and simulating some of its behaviours, beyond what is commonly discussed in the literature, such as the direction inversion, and holding torque. Analyses are conducted on various inputs to prepare the control design.

Transient measurement of mechatronic multi-parameters and kinetics performances for linear piezoelectric motors

Due to the time-dependent correlations, the measurement and characterization of electronic and mechanical parameters are critical for linear piezoelectric ultrasonic motors (USMs) during the running process. This study constructed a homemade system to measure the electromechanical multi-parameters and kinetics performances agilely, transiently, and synchronously. The principles and structures of the test system were demonstrated based on virtual instrument technology. A signal conditioning circuit is designed and used for physical signal processing, A/D conversion, and transmission. The difference in resonant frequencies was discovered for the synchronization acquisition of mechatronic parameters, and the instantaneous characteristics of electromechanical parameters for SWUM (e.g., driving voltage, input current, thrust force, and speed during the start-up and power-off process) were established based on the experimental data. This study is significant for the measurement/evaluation of the dynamic and transient performances of linear piezoelectric motors and actuators.

Wear evaluation model of a linear piezoelectric ultrasonic motor considering temperature effect

Ultrasonic motor relies on interface friction to drive the slider movement. During continuous operation, the contact surfaces between the stator and slider are worn, which will affect the performance and service life of the motor. A novel wear evaluation model considering temperature effect is established to estimate the remaining life and performance for a linear piezoelectric ultrasonic motor. The interactions of temperature with resonance frequency and material parameters are considered. The relationship between wear volume and preload as well as the variations of surface roughness parameters are taken into account. An experimental platform is built to identify the critical parameters and verify the accuracy of this model. The results show that the developed model can not only predict the temperature and service life, but also evaluate the performance of the motor, which can provide valuable guidance for motor design and optimization.

Radiation tolerance testing of piezoelectric motors for ITER (first results)

As a part of ITER diagnostics design and development, ultrasonic and stick-slip piezoelectric motors and several types of piezoelectric ceramics were tested under severe neutron and gamma ray irradiation (∼ 1019 per cm2 at E > 0.1 MeV) in a pool-type fission reactor. The fission neutron and gamma ray spectra were corrected to comply with conditions expected under ITER divertor cassettes. Taking into account possible neutron-induced amorphization of crystal structure, four types of piezoelectric ceramics were pre-selected. To restore the electronic structure of piezoelectric ceramic damaged by gamma rays, recovery polarization (i.e. heating while applying reverse bias) was suggested. The motors and piezoceramic samples were assessed for performance before and after irradiation as well as after recovery polarization. Recovery polarization was performed at 330 °C as it is expected close to the divertor cassettes during baking. Two most promising types of piezoelectric ceramics survived multiple cycles of depolarization/polarization at both 330 °C and 200 °C as appropriate for baking ITER divertor and vacuum vessel, respectively. All the experiments and procedures are described in detail.

Lift Generation by a Miniature Piezoelectric Ultrasonic Motor-Driven Rotary-Wing for Pico Air Vehicles

Actuators are key components for further miniaturization of insect-scale microrobots. It is challenging to create a new miniature actuator suited for rotary-wing pico aerial vehicles (PAVs), which have a wing span of a few centimeters and a mass of a few grams. In this paper, we propose a miniature piezoelectric ultrasonic motor that permits high-speed rotation at a sufficient torque to achieve the flight of the simplest device comprising the proposed motor and rotor blades. The prototype motor, which employs a bending vibration mode as a principle, measures 1.6 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times1.6$ </tex-math></inline-formula> mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times2$ </tex-math></inline-formula> mm and weighs 25 mg. The experimental results show that the miniature motor rotates rotor blades having a length of 20 mm with an angular velocity of over 1800 rad/s. The thrust force generated from this system exceeds its total mass of 110 mg and successfully lifts the system. Although the flight is tethered, the set of the proposed motor and rotor blades demonstrates a takeoff that represents the possibility of rotary-wing PAVs.

Engineered hard piezoelectric materials of MnO2 doped PZT-PSN ceramics for sensors applications

ABSTRACT In this study, MnO2-doped 0.96Pb(Zr0.515,Ti0.485)O3-0.04Pb(Sb0.5,Nb0.5)O3 (0.96PZT-0.04PSN) hard piezoelectric ceramics were fabricated by employing a conventional mixed-oxide process. Hard piezoelectric materials are suitable for mechanical device applications such as transducers or piezoelectric ultrasonic motors owing to their high mechanical quality factor. To improve the hard piezoelectric properties, MnO2 was selected and doped into 0.96PZT-0.04PSN ceramics in this study. When MnO2 was introduced into piezoelectric lead zirconate titanate (PZT) ceramics, the resistivity and dielectric permittivity decreased, leading to an increase in the mechanical quality factor. MnO2-doped 0.96PZT-0.04PSN ceramics have a lower piezoelectric charge coefficient and dielectric permittivity compared to those of 0.96PZT-0.04PSN ceramics. However, an enhanced mechanical quality factor of 1600 was obtained for the 0.96PZT-0.04PSN ceramics doped with 0.5 wt% of MnO2. In contrast to other hard piezoelectric materials, MnO2 doped 0.96Pb(Zr0.515,Ti0.485)O3-0.04Pb(Sb0.5,Nb0.5)O3 ceramics have a high Qm value while having an appropriate piezoelectric charge coefficient d33 and electromechanical coupling coefficient kp.

Design and characterization of a thin linear ultrasonic motor for miniature focus systems

We present a miniature linear piezoelectric ultrasonic motor with a thin and hollow design, which can serve as an essential component of autofocusing features in next-generation camera modules. It consists of a thin square stator with a hole and an elastic cylindrical slider with a slit. The motor design, in which the slider inserted into the stator hole expands outward, enables a hollow structure for centering a lens and an optimal preload for enhancing the motor thrust force. In this study, we model the relationship between the dimensions and the preload statically to quantify the preload value and clarify the design methodology of the motor. After optimizing the preload empirically, we evaluate the fundamental characteristics experimentally. The stator with a side length of 4.5 mm and a thickness of less than 1 mm provides a thrust force of 12.9 mN that leads to a quick response, which is a requirement of autofocusing. Finally, the motor drive system with visual feedback control is used to demonstrate the positioning of an actual lens group in front of an image sensor to obtain clearer images.

PID-type sliding mode-based adaptive motion control of a 2-DOF piezoelectric ultrasonic motor driven stage

This paper presents a new scheme of adaptive sliding mode control (ASMC) for a piezoelectric ultrasonic motor driven X–Y stage to meet the demand of precision motion tracking while addressing the problems of unknown nonlinear friction and model uncertainties. The system model with Coulomb friction and unilateral coupling effect is first investigated. Then the controller is designed with adaptive laws synthesized to obtain the unknown model parameters for handling parametric uncertainties and offsetting friction force. The robust control term acts as a high gain feedback control to make the output track the desired trajectory fast for guaranteed robust performance. Based on a PID-type sliding mode, the control scheme has a simple structure to be implemented and the control parameters can be easily tuned. Theoretical stability analysis of the proposed novel ASMC is accomplished using a Lyapunov framework. Furthermore, the proposed control scheme is applied to an X–Y stage and the results prove that the proposed control method is effective in achieving excellent tracking performance.

A Disc-Type High Speed Rotary Ultrasonic Motor with Internal Contact Teeth

This paper presents a disc-type ultrasonic piezoelectric motor, which is designed for micro flying vehicles. It provides a high output rotation speed under low operating voltage, compared with common piezoelectric devices, by employing a “contact teeth” wave transmission structure. The ultrasonic motor (USM) consists of a trimorph disc stator, with triple internal contact teeth, a shaft and two hemispheric hard-wearing rotors. The operating principle of the USM is based on the superposition of the in-plane B03 vibration mode of the trimorph disc, and the first longitudinal vibration of the contact teeth. An optimization method of the stator structure parameters was proposed and validated by numerical modeling. The diameter and thickness of the stator are 20 mm and 1 mm, respectively. A prototype with the weight of 2 g was made for this experimental test. The optimal frequency of the excitation signal and the preload force are 98.5 kHz and 0.5 N, respectively. The minimum operating voltage was tested under 7.5 V and reached the speed of 225 rpm, and the maximum unloaded rotational speed of the USM reached 5172 rpm when 30 V driving voltage was applied. The maximum lifting force generated by this USM was measured as 46.1 mN, which is 2.35 times bigger than its weight.

Simulation study of T-shaped piezoelectric linear ultrasonic motor based on PZT piezoelectric ceramics

In this paper, the T-shaped structure of linear ultrasonic motor was studied by means of establishing a THREE-DIMENSIONAL model of mechanical structure through SolidWorks and completing relevant simulation analysis through ANSYS Workbench. The finite element simulation analysis consists of four part: i. modal analysis, it determines the working mode and ensures that the frequency difference between the two working modes is as small as possible; ii. Harmonic response analysis furtherly verifies that the resonant response occurs at the operating mode frequency; iii. transient dynamic analysis demonstrates that the motion trajectory of the motor stator driving foot meets the theoretical requirements of ellipse shape. iv. drive signal and prototype are tested to verify the simulation analysis.

Enhanced Bipolar Strain and Electrocaloric Response in Gadolinium/Tantalum Co-Substituted Sodium Bismuth Titanate Lead-Free Ceramics

High performance piezoelectric materials with an ABO3 perovskite structure have received growing attention in recent research due to their technological applications in sophisticated research, medical and defence devices like piezoelectric sensors, transducers, ultrasonic motors, nano-positioners, actuators and imaging devices, etc. The technical utility of these materials stems from the various possibilities they offer for cation substitution in the A (or) B sites, which provide valuable opportunities for the optimization and tailoring of desired properties. To date, lead based perovskites, such as lead zirconate titanate (PZT), PZN-PT, and PMN-PT materials, have been extensively investigated in the literature. Although lead based materials exhibit highest piezoelectric coefficients, their wide-scale application has often been hampered by considering the toxicity of lead and its effect on environment and health. This triggered the search for alternative materials that could replace the lead-based ceramics and results in less-hazardous production methods, use and recycling. This has led to a continuous search of potentially attractive alternative lead-free ceramic materials to their counterpart lead based materials for specific applications. Among various kinds of lead-free piezoelectric materials, Na0.5Bi0.5TiO3 (NBT)-based materials are considered to be promising candidates for replacing the lead-based materials. They have been extensively investigated by the condensed materials physics community because of their complicate phase transitions and superior piezo-response. Compared to various chemical substitutions, tantalum (Ta) substitution provides superior electro-strain for the NBT- based ferroelectrics, while the effect of tantalum oxide additive was rarely reported. Gd3+ and Ta5+ co-substituted (Na0.5Bi0.497Gd0.003)Ti1-xTaxO3 (NBGT-Tax) lead-free piezoelectric ceramics are synthesized by using hydrothermal technique. The influence of Ta5+ substitution on the sintering, microstructure, phase transition, and various electrical properties of NBGT ceramics was investigated. Tantalum substitution has no remarkable effect on the microstructure and densification within the studied doping composition. The X-ray diffraction studies revealed that both NBGT-Tax (x=0.000) and NBGT-Tax (x=0.003) ceramics exhibited single phases monoclinic crystal structure with Cc phase. However, with substitution of tantalum the antiferroelectric phase zone gets broader. Simultaneously, the temperature for a ferroelectric to antiferroelectric phase transition is reduced along with an increase in temperature for a transition from antiferroelectric phases to paraelectric phases. This results indicate that tantalum occupies B site of the perovskite structure behaving as a donor, producing A-site cation vacancies. The undoped NBGT ceramics shows good ferroelectric and piezoelectric properties (remnant polarization Pr = 34.2 μC/cm2). The value of remnant polarization was found to increase with Ta substitution along with an increase in coercive field as shown in the figure attached. This is because of the ferroelectric properties being influenced by composition and its homogeneity, defects, external field and orientation of domains, which eventually contributed to the materials response. Meanwhile, the addition of Ta leads to an increase in the electro-strain, together with a higher normalized strain. Moreover, the materials with temperature dependent polarization can be used for solid state cooling applications. The NBGT-Tax compositions shows decrement in the remnant polarization with the increasing temperature which causes increment in the change in entropy. Consequently, the material exhibits the conventional electrocaloric effect (ECE). This simultaneous presence of large field-induced bipolar strain and ECE response along with isothermal change in entropy opens window for great potential applications in the field of electronic devices. Figure 1

Characterization of bulk piezoelectric element-based ultrasonic motors

We propose miniature ultrasonic motors using stators made of a single bulk piezoelectric element. The bulk piezoelectric stator has the potential to increase output by reducing the dissipation that occurs in the adhesion layer between the PZTs and a metallic component in the stator. In this paper, we build two kinds of bulk piezoelectric stators: a cubic bulk stator with a side length of 4.2 mm and a hole of 3 mm in diameter, and a cylindrical bulk stator with an outer diameter of 4.2 mm and the same hole diameter. We evaluate their electrical and mechanical characteristics, such as impedance and vibration velocity. The experiments clarify the advantages of the bulk piezoelectric stators, such as low dissipation. The cubic bulk stator, which shows higher performance than the cylindrical one, is compared with a similar-shaped stator using a bronze cube and thin piezoelectric plates. The performance measures of the cubic bulk ultrasonic motor are optimized by the preload between the stator and rotor.

Design of Unimorph Type 3DOF Ultrasonic Motor

A new design of 3 degrees of freedom (DOF) piezoelectric ultrasonic motor (USM) is introduced in this paper. The concept of this design is to incorporate a spherical rotor between two piezoelectric transducers. Each transducer is coupled with a flange, and it operates like a unimorph structure. Such a design of the transducer allows to increase the amplitude of the vibrations and to generate the higher torque and driving force used to achieve 3DOF rotary motion of the spherical rotor. The proposed USM may be used for humanoid robots, optomechanical systems, or small satellites. This USM consists of several components, is lightweight and reliable. Numerical analysis and experimental studies were performed to validate the feasibility of this drive, to find out proper resonant frequencies for the unimorph, and optimize the shape of the flange. Experimental studies were accomplished to validate the results of the numerical analysis and to validate the operating principles of the piezoelectric motor.

A Method to Realize Low Velocity Movability and Eliminate Friction Induced Noise in Piezoelectric Ultrasonic Motors

In a piezoelectric ultrasonic motor (USM) or resonance drive type piezoelectric motor (RPM), movement is generated between a vibrator (stator) and a slider (rotor). Since the microscopic vibrations on a stator are transferred to a slider through friction interaction, the movement of a slider has a nonlinear characteristic due to the nature of the friction force. This nonlinear behavior causes large position errors due to the occurrence of discontinuous stick-slip movements and unpleasant audible noise, especially at a low velocity drive. This friction induced acoustic sound is magnified at low velocities as the natural frequency of the mechanical system of a piezoelectric motor with mass and the holding and prestress spring forces are dependent on the closed loop motion controller. This article addresses the abovementioned issues. First, a mechanical model, which considers the nature of movements in a resonance drive type piezoelectric motor, was established. The model could suitably define the friction induced forced vibration and noise source. Second, a new driving method for resonance drive type piezoelectric motors was proposed, in which the piezoelectric vibrator was excited using two driving sources at two different frequencies. The difference between the two excitation frequencies was synchronized to the servo sampling frequency of the digital control unit. Finally, the performance of the proposed driving method was compared with those of the conventional driving methods. It was noted that in addition to the realization of silent and smooth low velocity movements, the positioning error for the linear movements between the desired and actual positions decreased to less than 10 nm for velocities ranging from 1 to 0.001 mm/s.

Integral terminal sliding-mode-based adaptive integral backstepping control for precision motion of a piezoelectric ultrasonic motor

The versatile and effective piezoelectric ultrasonic motor (PUM) has been widely used in many significant industrial and scientific applications, including precision positioning systems and surgical devices. However, the inherent friction, hysteresis nonlinearity, model uncertainties as well as various invariably presented external disturbances bring great challenges on the precision motion of PUM. In this development, a novel integral terminal sliding-mode-based adaptive integral backstepping control (ITSMAIBC) is formulated to accommodate theses adverse impacts and retain high tracking precision. In particular, the second-order auxiliary differential equations based on the integral terminal sliding-mode surface are constructed to obtain the property of finite-time convergence and desired steady-state performance. Through employing integral backstepping methodology with the auxiliary equations, the asymptotic stability is guaranteed and a high-order sliding-mode control (SMC)-like performance is also achieved to relieve the chattering phenomenon. An adaptive law is further incorporated into the proposed controller to estimate the upper bound of the total disturbance. The robust stability is proven by the Lyapunov theory. Moreover, the implementation of ITSMAIBC is simple without any high-order derivative or observer. The actual experiments on a PUM verify the effectiveness of the controller through tracking continuous sinusoidal waves and discontinuous triangular waves with different frequencies and amplitudes, and the proposed scheme achieves the best tracking performance in comparison with three benchmark controllers. A surgical operation on a mock membrane experimental system is also performed to validate the practical application of the proposed method on ear surgery.

A ring-shaped, linear piezoelectric ultrasonic motor operating in E01 mode

Linear piezoelectric ultrasonic motors based on multimodal coupling are widely used for generating precision actuations; however, multimodal decoupling often occurs when environment temperature changes, which may result in actuation failure. In this work, a miniature, ring-shaped, linear piezoelectric ultrasonic motor operating in a single, in-plane E01 mode (zero node line along the circumference and one node line along the diameter direction) is proposed. Experimental results show that it can produce a maximum driving force of 2.7 N, a no-load moving speed of ∼56 mm/s, and a high positioning resolution of 0.1 μm in open-loop control. Advantages of simple structure, controllable micrometer-scale displacement, and large bidirectional working stroke indicate that the proposed linear motor has great potential for industrial applications, especially for precise actuations.

3DOF Ultrasonic Motor With Two Piezoelectric Rings.

A novel design of a multiple degrees of freedom (multi-DOF) piezoelectric ultrasonic motor (USM) is presented in the paper. The main idea of the motor design is to combine the magnetic sphere type rotor and two oppositely placed ring-shaped piezoelectric actuators into one mechanism. Such a structure increases impact force and allows rotation of the sphere with higher torque. The main purpose of USM development was to design a motor for attitude control systems used in small satellites. A permanent magnetic sphere with a magnetic dipole is used for orientation and positioning when the sphere is rotated to the desired position and the magnetic field synchronizes with the Earth’s magnetic dipole. Also, the proposed motor can be installed and used for robotic systems, laser beam manipulation, etc. The system has a minimal number of components, small weight, and high reliability. Numerical simulation and experimental studies were used to verify the operating principles of the USM. Numerical simulation of a piezoelectric actuator was used to perform modal frequency and harmonic response analysis. Experimental studies were performed to measure both mechanical and electrical characteristics of the piezoelectric motor.