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Piezoelectric films have good elasticity and microstructure stability, which are the basis of the piezoelectric nanogenerator to adapt to various application scenarios and run stably for a long time. In this paper, Polyurethane (PU) is introduced into PVDF nanofibers to obtain blend nanofiber film with elasticity and microstructure stability. The tensile and compression moduli of the nanofiber films are effectively controlled by changing the mass ratio of PU to PVDF. By the impact of a 5.6 g ball falling freely from a height of 16 cm, the piezoelectric output of nanofiber film with an optimized mass ratio of 35/65 is 3.58 V. The maximum peak current and power surface densities are 0.286 μA and 0.18 μW cm−2, respectively. The piezoelectric response of the nanofiber film remained stable before and after 9 cycles of 10 % compressive strain. A simulated vehicle tire pressure fluctuation energy collection device is fabricated by using the blend nanofiber film. The peak-to-peak piezoelectric response is about 0.32 V. This unique property opens up another way to harvest mechanical energy from gas pressure fluctuation. The development of PU/PVDF blend nanofiber film show inestimable application potential as a mechanical energy harvesting device for gas or liquid pressure fluctuation. [Display omitted] • The piezoelectric properties of PU/PVDF composite nanofiber film were investigated. • PU enhances the strain toughness of PU/PVDF composite nanofiber film. • The PU/PVDF composite nanofiber nanogenerator has good stability. • A mechanical energy harvesting device for gas pressure fluctuation. [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]