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Piezoelectric transducers are widely used for generating an elliptical motion in vibration-assisted machining and in a piezoelectric actuator. In this study, an analytical model of a V-shaped piezoelectric ultrasonic transducer with a flexible joint is proposed. The analytical model is used to optimize the structure, predict the performance, and design the controller and drive circuit. The longitudinal-bending mode is utilized for generating an elliptical motion at a drive foot. A vibration model of the V-shaped transducer is proposed. The vibration resonance frequency and mode shape are obtained by solving a set of differential equations of the balance force and continuous displacement. The energy method is then used to derive the displacement response based on Hamilton-Lagrange equations. Finally, three prototypes are fabricated to validate the model effectiveness. The resonance frequency, displacement response, and electric response of the analytical model are consistent with the experimental results. The results show that the vibration amplitude in the tangential direction X at the drive foot increases with the increase of the phase difference φ , and the amplitude in the normal direction Y decreases with the decrease of the phase difference φ. As the coupling angle θ increases, the amplitude in the tangential direction X increases and the amplitude in the normal direction Y decreases. [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]

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]

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]

In the field of plastic forming, ultrasonic vibration has the advantages of small forming force and high forming quality, and it has been introduced into a single-point incremental plastic forming technique with high flexibility and high precision. The ultrasonic vibration single-point incremental compound forming technology with all the above advantages has been achieved. To reveal the variation tendency of the forming force under ultrasonic vibration and single-point incremental coupling, the process parameters (layer spacing, tool head radius, and feed rate) and vibration parameters (frequency and amplitude) on the forming force of the composite technology were quantitatively analyzed by theory, simulation, and experiment. The simulation and experimental results showed that ultrasonic vibration can significantly reduce the forming force of the composite technology. Compared with the simulation results, the theoretical results are not only closer to the experimental results but also have a shorter computation time and better prediction effect on the forming force. The change in the process parameters has a linear effect on the forming force, the nonlinearity of the vibratory parameters influences the forming force, and the frequencies and amplitudes in a suitable range allow the forming force to reach a minimum value. These conclusions have some significance for further studies on the ultrasonic vibratory single-point incremental composite forming technology. [ABSTRACT FROM AUTHOR]