Search

This paper proposes a dynamic numerical model for the bonded-type ultrasonic motor considering the load transfer in the adhesive interlayer between the piezoceramics and the host structure. The finite element method and an extended shear-lag theory are used to derive the dynamic equation. The effectiveness of this model is validated by comparing the dynamic response of the stator in frequency and time domains between simulation and experimental results, with a maximum relative error of less than 4%. The dynamic load transfer in the adhesive interlayer is analyzed when the stator is excited electrically, and the results show that the interfacial load transfer is concentrated near the bonding edges. The effects of partially bonded piezoceramics on the dynamic characteristics of the motor are investigated, where two partially bonded conditions including edge and inner debonded cases are considered. The results indicate that both the inner and edge debonded conditions could reduce the vibration amplitude of the stator and then reduce the output performance of the motor. [ABSTRACT FROM AUTHOR]

In this paper, a wear model is established for a V-shaped linear ultrasonic motor. The influence of the change in the dynamic friction coefficient and the roughness parameters of the contact surface of the stator/slider on the output performance of the motor is considered in this model. The wear mechanism of the motor and the variation rules of the morphology of the contact surface during the operation of the motor are studied, as well as the relation of the wear height of the driving tip with the preload force and the relation of the preload force with the resonance frequency of the stator. The accuracy of the model is verified by numerical simulation and experimental methods. A test platform for friction and wear experiments is constructed, and the wear characteristics and the output performance of the motor are tested. The obtained results indicated that the model can accurately predict the dynamic changes during the wear process and the service life and output performance of the motor. [ABSTRACT FROM AUTHOR]

A compact slider for linear ultrasonic motors (LUMs) to improve the ability of LUMs for precision positioning is proposed in this article. The compact slider can avoid the effect of variable stiffness of the traditional slider on ultra-precision positioning, which consists of two pieces of ceramic with little lubricating oil on the sliding interface. Based on contact theory and lubrication theory, the contact mechanism and the lubricating state between the slider and the support plate are analyzed. Subsequently, a dynamic model for LUMs considering the lubricating state and the ultrasonic vibration condition is obtained. Furthermore, the output speed and output force of the motor are analyzed under the influence of film lubrication. Moreover, some experiments are designed to test the feasibility and effectiveness of the compact slider for precision positioning. The results indicate that the compact slider is more effective in inhibiting the fluctuation of the output speed compared to the traditional slider, and it can improve the displacement resolution of LUMs up to 7 nm. [ABSTRACT FROM AUTHOR]

For achieving high speed and large thrust, Langevin-type ultrasonic motors (LTUM) are generally operated under high voltage. However, high voltage causes the current harmonics of piezoelectric material nonlinear phenomena, which will decrease the efficiency, the output force, and the accuracy of LTUMs. In this study, the nonlinearity of current harmonics of LTUM are described and analyzed by a novel nonlinear equivalent circuit model using Lagrange equations. Thereafter, based on a nonlinear tuning method, a specific driver circuit is suggested to suppress the current harmonics. Experimental results validate that the time response of the current is consistent with that of the model and furtherly demonstrate that the total harmonic current distortion decreases by 68% utilizing the proposed nonlinear tuning method under 500 Vpp. • A nonlinear dynamic model and simple identification method of a Langevin-type ultrasonic motor are proposed to describe the current harmonics. • A nonlinear tuning method and drive circuit are developed to suppress current harmonics under high voltage. • Experiment results demonstrate that the time response of the current was consistent with that of the model. [ABSTRACT FROM AUTHOR]

Highlights • A general purpose method to model the complete dynamic response of the linear ultrasonic motors is presented. • The whole-machine model is solved at a low computational cost so that can be run on an average computer. • A linear ultrasonic motor with V-shaped stator is systematically investigated as an example. • An optimization method of electrical input parameters are designed by using this model. Graphical abstract Abstract A general purpose dynamic modeling method of linear ultrasonic motors (LUMs) is presented in this paper. The proposed model considers all the LUMs elements, including the stator, the mover and the contact between stator and mover. For the stator, a model in modal space was derived based on finite element method. The mover was analytically modeled with considering the complex contact between the stator and mover. The stator-mover intermittent contact problem was mathematically described by the normal and tangential contact model. Interpenetration-dependent penalty and continuous functions approximating to Coulomb friction were used to tangential contact and normal contact, respectively. A hybrid overall dynamic model was built by assembling all these models and solved at a low computational cost. The model enables us to understand the dynamic behavior of LUMs, including the vibration of stator, the contact process, the output performance of the mover and the interactive coupling between each element. The effectiveness of the developed model was validated in a LUM with V-shaped stator by comparing with available measurement results. Furthermore, this model was combined with the particle swarm algorithm to find the optimal electrical input parameters. It is believed that the proposed modeling method is useful for the performance evaluation and input parameters' optimization of LUMs. [ABSTRACT FROM AUTHOR]

In order to meet the demand of a linear ultrasonic motor with large thrust in narrow space, a novel Π-type linear ultrasonic motor with double driving feet is proposed. In this paper, the structure of a stator is designed. The working mode and structure size are determined by finite element simulation. To amplify the amplitude of driving foot, an optimization design for the stator is performed. After that, a novel pre-load device that separates from the stator is put forward, which can not only improve the output but also help to improve the operation stability and prolong the life of motor. Additionally, a prototype of the proposed motor with the novel pre-load device was fabricated and the performance tests were implemented. The experimental results show that the suggested motor has structural stability and high dynamic performance, such as a no-load speed of 273 mm/s and 238 mm/s in two directions, corresponding to a maximal thrust of 80 N and 110 N. [ABSTRACT FROM AUTHOR]

The effects of surface roughness are not considered in the traditional motor model which fails to reflect the actual contact mechanism between the stator and slider. An analytical model for calculating the tangential force of linear ultrasonic motor is proposed in this article. The presented model differs from the previous spring contact model, the asperities in contact between stator and slider are considered. The influences of preload and exciting voltage on tangential force in moving direction are analyzed. An experiment is performed to verify the feasibility of this proposed model by comparing the simulation results with the measured data. Moreover, the proposed model and spring model are compared. The results reveal that the proposed model is more accurate than spring model. The discussion is helpful for designing and modeling of linear ultrasonic motors. [ABSTRACT FROM AUTHOR]

Thanks to their compactness and suitability for vacuum applications, linear ultrasonic motors are considered as substitutes for classical electromagnetic motors as driving elements in absolute gravimeters. Still, their application is prevented by relatively low power output. To overcome this limitation and provide better stability, a V-type linear ultrasonic motor with a new clamping method is proposed for a gravimeter. In this paper, a mechanical model of stators with flexible clamping components is suggested, according to a design criterion for clamps of linear ultrasonic motors. After that, an effect of tangential and normal rigidity of the clamping components on mechanical output is studied. It is followed by discussion of a new clamping method with sufficient tangential rigidity and a capability to facilitate pre-load. Additionally, a prototype of the motor with the proposed clamping method was fabricated and the performance tests in vertical direction were implemented. Experimental results show that the suggested motor has structural stability and high dynamic performance, such as no-load speed of 1.4 m/s and maximal thrust of 43 N, meeting the requirements for absolute gravimeters. [ABSTRACT FROM AUTHOR]

In this paper, an integrated model is developed to analyze the fundamental characteristics of a modal-independent linear ultrasonic motor with double piezoelectric vibrators. The energy method is used to model the dynamics of the two piezoelectric vibrators. The interface forces are coupled into the dynamic equations of the two vibrators and the moving platform, forming a whole machine model of the motor. The behavior of the force transmission of the motor is analyzed via the resulting model to understand the drive mechanism. In particular, the relative contact length is proposed to describe the intermittent contact characteristic between the stator and the mover, and its role in evaluating motor performance is discussed. The relations between the output speed and various inputs to the motor and the start-stop transients of the motor are analyzed by numerical simulations, which are validated by experiments. Furthermore, the dead-zone behavior is predicted and clarified analytically using the proposed model, which is also observed in experiments. These results are useful for designing servo control scheme for the motor. [ABSTRACT FROM AUTHOR]

Ultrasonic motor (USM) is an electromechanical coupling system with ultrasonic vibration, which is driven by the frictional contact force between the stator (vibrating body) and the rotor/slider (driven body). Stick-slip motion can occur at the contact interface when USM is operating, which may affect the performance of the motor. This paper develops a physically-based model to investigate the complex stick-slip-separation dynamics in a bimodal standing wave ultrasonic motor. The model includes both friction nonlinearity and intermittent separation nonlinearity of the system. Utilizing Hamilton׳s principle and assumed mode method, the dynamic equations of the stator are deduced. Based on the dynamics of the stator and the slider, sticking force during the stick phase is derived, which is used to examine the stick-to-slip transition. Furthermore, the stick-slip-separation kinematics is analyzed by establishing analytical criteria that predict the transition between stick, slip and separation of the interface. Stick-slip-separation motion is observed in the resulting model, and numerical simulations are performed to study the influence of parameters on the range of possible motions. Results show that stick-slip motion can occur with greater preload and smaller voltage amplitude. Furthermore, a dimensionless parameter is proposed to predict the occurrence of stick-slip versus slip-separation motions, and its role in designing ultrasonic motors is discussed. It is shown that slip-separation motion is favorable for the slider velocity. [ABSTRACT FROM AUTHOR]

• An analytical model for predicting the wear and performance of a linear piezoelectric ultrasonic motor is presented. • The effects of temperature and surface roughness on wear are considered in the proposed model. • A test platform is conducted and the simulation results are in good agreement with the experimental data. 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. [ABSTRACT FROM AUTHOR]

A vibro-impact system is proposed to investigate the normal motion and impact of the driving foot of the linear ultrasonic motors based on longitudinal and bending modes. Using coefficient of restitution (CoR) method a dynamical model is developed to simulate the normal impacts between the stator and mover taking into account the preload and vibration of barycenter of the stator. Furthermore, the sticking motions that can occur are simulated when the stator impacts the mover via a Lagrange multiplier. It is shown that the sticking motions occurring in the system are affected by some factors like CoR, preload and stiffness of the preload spring in clamping parts. Results indicate that a friction material with a higher hardness, modest preload and stiffness of the preload spring can weaken sticking motion in the system. [ABSTRACT FROM AUTHOR]

• A thermal-mechanical-electric coupling dynamic model is developed for a V-shaped linear ultrasonic motor. • The influence of surface roughness on the temperature rise of the motor is taken into account in the model. • The model can be used to predict the output characteristics of the motor. In this paper, a thermal-mechanical-electric coupling dynamic model is developed for a V-shape linear ultrasonic motor. The impact of surface roughness of stator/slider on the motor temperature rise as well as the temperature dependence of the stator material parameters are considered in this model. The relationship between the resonant frequency of the stator and the temperature is investigated, and the variation relation of motor parameters with regard to the temperature is discussed. The validity of the model is verified by numerical simulation and experimental results. Based on the proposed model, the influences of surface roughness of stator/slider, driving voltage, driving frequency and pre-pressure on motor temperature and velocity are studied and analyzed, and the comparison between the measuring data and the previous reported model with constant parameters are conducted. The results denote that the established model under different input parameters can be more accurately to predict the dynamic changes of temperature and velocity of the motor, which will be a valuable guide for the improvement of precise control and long-term stable operation of the motor. [ABSTRACT FROM AUTHOR]

In this study, a large thrust linear ultrasonic motor using an L-shaped stator is described. The stator is constructed by two mutually perpendicular rectangular plate vibrators, one of which is mounted in parallel with the slider to make the motor structure to be more compact. The symmetric and antisymmetric modes of the stator based on the first order bending vibration of two vibrators are adopted, in which each resonance mode is assigned to drive the slider in one direction. The placement of piezoelectric ceramics in a stator could be determined by finite element analysis, and the influence of slots in the head block on the vibration amplitudes of driving foot was studied as well. Three types of prototypes (non-slotted, dual-slot, and single-slot) were fabricated and experimentally investigated. Experimental results demonstrated that the prototype with one slot exhibited the best mechanical output performance. The maximum loads under the excitation of symmetric mode and antisymmetric mode were 65 and 90 N, respectively. [ABSTRACT FROM AUTHOR]

This article presents a high-efficient thermal analysis methodology and outlines a set of useful design guidelines for high-power linear ultrasonic motors. A thermal network modeling technique is introduced to rapidly calculate the temperature rise for a typical high-power linear ultrasonic motor with a V-shaped stator. First, a six-terminal equivalent circuit for Langevin piezoelectric transducer considering the prestress bolt loss and all three losses in piezoelectrics is proposed to calculate the stator loss. Then, the calculated losses along with the friction loss are used as inputs into the developed thermal network model to calculate the temperature rise of critical parts of the motor. Furthermore, an analytical mechanical model combined with the proposed thermal network is established to calculate the temporal–spatial distribution of the stator thermal stress for evaluating its fatigue under the heating-up process. Finally, some experimental measurements and finite-element simulations are conducted to validate the theoretical analyses. [ABSTRACT FROM AUTHOR]

Single-mode linear ultrasonic motors (SMLUMs) have the advantages of excellent accuracy, long travel distance, single vibration mode and simple driving scheme, which have been applied in precision positioning and micro/nano manipulation actuators. However, it is still challenging to accurately and efficiently analyze such motors due to their complicated electro-mechanical coupling behaviors under contact-based operating conditions. This paper proposed an improved equivalent circuit model for a single-mode linear ultrasonic motor considering the real contact-based operating conditions, where a new actuation mode of the V-shape transducer is adopted. The electro-mechanical coupling characteristics of the stator under contact-based boundary condition is modeled by a modified admittance-type equivalent circuit, where the variable contact stiffness and loss are characterized between the stator and the mover. The friction drive mechanism is modeled by a thyristor rectifying circuit to characterize the intermittent actuation characteristics, and the nonlinear relationship between the motor characteristics and the contact-based operating conditions is initially characterized from the circuit viewpoint. The merits and the applications of the circuit-based model are exemplified by parameter identification and modification, losses segregation, admittance characteristics analysis and output and control characteristics evaluation for such SMLUMs. [Display omitted] • The real contact-based operating conditions are considered in equivalent circuit modeling. • The friction drive mechanism is initially characterized and clarified from circuit viewpoint. • A circuit-based method is proposed to conduct segregation and evaluation of various losses. • The motor output and control characteristics can be evaluated by the proposed model. [ABSTRACT FROM AUTHOR]

• A novel miniature I-shaped piezoelectric linear ultrasonic motor with two vibrators is proposed and investigated in this paper. • One noticeable feature of this ultrasonic motor is that the first-order flexural vibration modes of two rectangular plate vibrators are employed as the foundational modes to form the transverse and vertical motions at the driving tip. • The output characteristics of this ultrasonic motor are analyzed by finite element method and verified by experiments. • The dimension of the motor is 39.8 × 17.6 × 6 mm3 and the weight is only 18.2 g, the typical outputs of the prototype are maximum speed of 364 mm/s, maximum thrust of 500 g and thrust-weight ratio of 24.47. • This linear ultrasonic motor has the advantages in structure design and miniaturization, and it possesses good potential for application in future devices, such as micromanipulators and robots, aircrafts and space exploration vehicles, lightweight automatic weapons, etc. In this study, a novel miniature I-shaped linear ultrasonic motor is proposed. The motor is constructed by two rectangular piezoelectric vibrators which are mounted in parallel with the slider to make the structure look like the letter "I". The symmetric and antisymmetric modes of the motor based on the first-order flexural vibrations of the two vibrators are chosen as the working modes. The finite element method is adopted to optimize the structure and study the vibration behavior of the motor. A prototype of the proposed linear ultrasonic motor is fabricated and its mechanical characteristics are tested. The dimension of the stator is 39.8 × 17.6 × 6 mm3 and the weight of the prototype is only 18.2 g. The typical outputs of the prototype are maximum speed of 364 mm/s, maximum thrust of 500 g and thrust-weight ratio of 24.47. The experimental results confirm that the developed linear ultrasonic motor has the advantages of structural design and miniaturization. [ABSTRACT FROM AUTHOR]