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The traditional dynamic models of linear ultrasonic motor (LUSM) do not consider the influences of the preload force and the roughness of the contact surface of stator/slider on the performance of the motor, which unable to effectively describe the dynamic behavior of the motor. In this paper, a dynamic model is established for a V-shaped LUSM considering the influence of the preload force and the roughness of the contact surface of stator/slider on the dynamic behavior of the motor. The contact mechanism of the stator/slider and the influence of preload force on the stator parameters are studied and analyzed. The effectiveness of the developed model is verified by comparing with the analytical model that ignored the effect of the preload force on the stator parameters. The experimental results shown that the developed model can accurately reflect the dynamic characteristics of the motor, and the model will be helpful for the function prediction and precise control of the motor. [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]

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]

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]

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]