Performance Of Ultrasonic Motor Research Articles

Geometric parameters optimization on storage performance degradation of ultrasonic motor based on simulation analysis

The performance of ultrasonic motor will drift due to material degradation and other reasons during long-term storage, which will directly affect the working performance after storage. Aiming at the optimization design of geometric parameters for performance storage degradation, this paper takes the piezoelectric constant d31 of ceramic chip and the elastic modulus of colloid as the characterization parameters of product storage degradation, and takes the stator tooth spacing and the thickness of rubber layer as the analysis objects of product geometric parameters optimization, and proposes a simulation analysis method based on finite element model. Through the analysis of the simulation results, it is found that the increase of the stator tooth spacing will lead to the increase of the change rate of the 5-wave modal frequency with the degradation of the material properties, and the decrease of the overall change rate of the amplitude. However, properly reducing the thickness of the adhesive layer can effectively reduce the influence of the degradation of the piezoelectric properties of the ceramic chip and the hardening of the gel on the frequency response characteristics of the stator of the ultrasonic motor under long-term storage.

Improving output performance of ultrasonic motor by coating MoS2 on the stator

To improve the wear resistance of frictional interface of ultrasonic motors (USM), a new tribological pair was designed. The phosphor bronze stator surface of USM urgently needs modification to match with aluminum alloy rotor surface that was treated by micro-arc oxidation (MAO). The tribological properties of stator coating, MoS2 and WS2, were compared at the material level. The strengthening mechanism of stator coating was interpreted by extracting microscopic information from molecular dynamics (MD) results. The results showed that new tribological pair significantly enhance the output performance and energy conversion efficiency, particularly the MoS2 coating. When the preload was 280 N, input voltage was 500 V, and frequency was 36.2 kHz, the maximum efficiency of MoS2 reached to 46.12%.

The influence of laser surface texture on the tribological properties of friction layer materials in ultrasound motors

Ultrasonic motors are typically driven by the dry friction force between the rotor and the stator; the friction pairs’ high friction coefficient and low wear rate are two essential elements for improving the operational stability with longer service life. In this research article, high-precision microgroove arrays were manufactured on the surfaces of the stator and rotor of the TRUSM60 ultrasonic motor using laser machining. Dry friction and wear tests between the stator and the rotor were carried out with pin-on-disc using HSR-2M high-speed reciprocating friction and wear tester to determine the tribological properties of the ultrasonic motor. According to a different distribution of microgrooves on the two contact surfaces, the influence of smooth surface, single-sided texture, and double-sided texture on the friction pair's friction performance were discussed. The results show that the textured surface can substantially increase the coefficient of friction of the contact surface and reduce the rate of wear. The one-sided textured phosphor bronze surface with a microgroove width of 200μm and an area ratio of 20% had the highest coefficient of friction of 0.334 and a friction increase rate of 36.3%. Similarly, the single-sided textured Polyimide surface attained the highest friction coefficient of 0.355 and friction increase rate of 44.9% when the groove width is 150μm and the area ratio is 30%. A higher friction coefficient of the double-sided texture can be obtained through reasonable parameter configuration than the single-sided texture. The included angle of 0° between the two textured surfaces produced the highest friction coefficient of 0.368 and the wear rate of the phosphor bronze and polyimide surfaces were 2.01 × 10−4 mm3/N-m and 1.949 × 10−3 mm3/N-m, respectively. The result provides an essential benchmark for enhancing the tribological performance of ultrasonic motors and increasing the output torque.

Super-Resolution Velocity Reconstruction and Control of Ultrasonic Motors.

Accurate and fast velocity feedback signal is essential for the velocity control of ultrasonic motors (USMs). However, the low operating velocity of USMs results in a long velocity detection dead time (VDDT) of incremental encoders, which seriously restricts the dynamic control performance of USMs. Therefore, this article presents a super-resolution velocity control (SRVC) scheme based on the velocity reconstruction for the USM. First, the mathematical model of the USM is derived from the mechanical characteristics and the electromechanical coupling characteristics. Then, the velocity reconstruction method is proposed by combining the model estimated velocity and the encoder measured velocity. The closed-loop control scheme using the reconstructed velocity is implemented by a self-designed driving circuit. Experimental results show the velocity reconstruction method not only can break through the limitation of the encoder resolution to reduce the VDDT but also has a high-velocity accuracy. Furthermore, compared with the existing encoder-based control scheme, the proposed SRVC scheme has a faster velocity response under different loads.

Improving the performance of ultrasonic motors in low-pressure, variable-temperature environments

Ultrasonic motor (USM) performance is dependent on the tribological characteristics of the interface between a stator and rotor, which are sensitive to ambient environments and driving parameters. Thus, the effects of vacuum and temperature on the mechanical output performance and energy conversion efficiency of a traveling wave rotary ultrasonic motor 60 (TRUM-60) with a novel micro-dimpled PI-based friction material and optimized input parameters were systematically investigated for the first time. The degree of vacuum had a negligible effect on the performance of the TRUM-60, whereas temperature influenced its mechanical output torque, rotational speed, and output power. The results can aid in the design of USM devices for aerospace applications.

Pre-pressure influences on the traveling wave ultrasonic motor performance: A theoretical analysis with experimental verification

In order to improve the output performance of the rotating traveling wave ultrasonic motor and study the optimal pre-pressures under different loads, the theoretical calculation and experimental verification on a TRUM-70H ultrasonic motor were carried out. The dynamic model of an ultrasonic motor is established, and the influence of pre-pressure on the mechanical properties of the ultrasonic motor is analyzed. Taking the TRUM-70H ultrasonic motor as the object of study, the relationship between the optimum pre-pressure and the load torque is analyzed. A multi-functional testing platform for an ultrasonic motor is built to verify the theoretical derivation results, and the reason for the error is also pointed out. According to the conclusion, the pre-pressure should be selected according to the load when the ultrasonic motors are assembled. The results show that there is a coupling relationship between the pre-pressure and the load torque on the speed of the ultrasonic motor. In the effective working range of the ultrasonic motor, the optimum pre-pressure is approximately linearly positively correlated with the load torque. When the pre-pressure is set according to the actual load demand during assembly, the output efficiency of the ultrasonic motor can be improved.

Rotor optimization for the improvement of ultrasonic motor performance

The rotor deformation of an ultrasonic motor is an important factor affecting its performance. However, little research focuses on the relationship between the rotor deformation and motor performance. This paper provides an approach to improve the ultrasonic motor's output properties by changing the rotor's size from the view of proper rotor deformation and better stress distribution on the interface. First, a thin shell structure is introduced to study the deformation of the rotor. A finite element model of the motor is built in COMSOL Multiphysics software for the contact analysis of the stress distribution. Then, the optimized ranges of parameters are determined by simulation. Frictional experiments are conducted to verify the feasibility of the rotor under the optimized size. Finally, the performance experiments of a stator corresponding to different sizes of rotor are carried out. The experimental results show that the speed, the power and the efficiency of the optimized rotor are all increase. These results prove the effectivity of the new approach to improving the performance of the ultrasonic motor.

Improving the wear resistance of PTFE-based friction material used in ultrasonic motors by laser surface texturing

Abstract For improving wear resistance of PTFE-based material and performances of ultrasonic motors, 1-Dimple and 3-Dimple textures were fabricated on stator surface based on observations of transfer material. The worn surface and wear debris were observed to investigate the effect of textures on wear behavior. Meanwhile, performances of the motor were tested. The wear rate of PTFE material sliding against 3-Dimple stator decreased by 52.5%, the average speed of the motor was improved by 20.6%, and the maximum efficiency of 3-Dimple stator reached 32.7%. The beneficial effect of dimples was to make the contact surface discontinuous, thereby reducing the adhesion force between stator and PTFE material, which prevented severe adhesive wear of PTFE-based material and improved the motor performances.

Ultrasonic motor performance influenced by lubricant properties

Functional lubrication has been shown to be a promising method for improving the performance of ultrasonic motors (USMs). However, the complex lubrication mechanisms have not been studied and the effect of lubricant properties on motor performance remains unknown. In this paper, both low-traction fluids and high-traction fluids with a wide viscosity range are applied, and the lubricating effects are investigated in hybrid transducer-type ultrasonic motors. The results clearly show that high-traction fluids have significant superiority to low-traction fluids in terms of motor efficiency and reduction of friction loss at the entire range of the applied preload. A high friction coefficient in boundary lubrication regime and efficient modulation in friction are confirmed to be essential for achieving high-performance lubricated USMs. It is also found that the motor performance is independent of lubricant viscosities in the tested range, irrespective of lubricant types. The reasons for the distinct lubricating effects with the two types of lubricants are analyzed in detail, which leads to the criteria of selecting lubricants and more understanding in the lubrication mechanisms in USMs.

Electrochemical micromachining of microgroove arrays on phosphor bronze surface for improving the tribological performance

A high friction coefficient and a low wear rate of contacted surfaces are essential elements to friction pairs between the stator and the rotor in ultrasonic motors. It has been shown that surface textures have a significant effect on improving the tribological performance of friction pairs. In this paper, microgroove arrays are introduced to the stator surface for improving the tribological performance of friction pairs between the stator and the rotor in ultrasonic motors. Microgrooves were fabricated on a phosphor bronze surface by through-mask electrochemical micromachining (TMEMM). Parameters, namely, the electrolyte inlet pressure, applied voltage, pulse duty cycle, and frequency, were varied to investigate their influences on the dimensions and morphology of the microgrooves. Results showed that the width and depth of the microgrooves were strongly affected by the applied voltage and frequency, while the morphology of the microgrooves was dependent on the electrolyte inlet pressure and the pulse duty cycle. Compared with a smooth surface, the friction coefficient increased from 0.245 to 0.334 and less abrasion was obtained when a surface was textured with microgrooves of which the width and depth were 185.6 and 57.6 μm, respectively. Microgroove arrays might play an important role in enhancing the performance of ultrasonic motors.

Tribological performance of ceramics in lubricated ultrasonic motors

Small ultrasonic motors are driven by the oscillation of piezoelectric transducers. They are primarily applied to equipment components that require precise movements, such as drivers for auto-focus lenses in cameras, and actuators in robots and positioning devices. While lubrication has been proven effective in improving the performance of ultrasonic motors, the friction materials still play a significant role. In this study, the suitability of four different engineering ceramics, which included alumina (Al2O3), zirconia (ZrO2), silicon carbide (SiC), and silicon nitride (Si3N4), were investigated in the self-mated configuration. By testing the candidate materials in the actual ultrasonic motor configuration, the main wear mechanisms of these ceramics were identified under lubricated conditions, with fracture being the most dominant contributor to their wear. Among the four tested ceramics, ZrO2 was found to be the most promising material as it exhibited the mildest wear and a satisfactory level of friction. The obtained results also indicate that the fracture toughness of ceramics is more critical than their hardness. This study provides guidelines for selecting friction materials that can be used in long-lived, lubricated ultrasonic motors.

Improved linear ultrasonic motor performance with square-wave based driving-tip trajectory

This paper proposes the application of a non-sinusoidal periodic excitation voltage to induce a near-square-wave driving tip trajectory in linear ultrasonic motors (LUSMs). A square-wave-based trajectory can deliver superior frictional force to the moving stage in the forward stroke of the driving tip motion and reduced frictional force during the return stroke. This would reduce lost power in the periodic driving tip motion, thereby, increasing the output force and power of the LUSM. An implementation procedure is suggested to achieve the near-square-wave driving tip trajectory. The proposed approach is illustrated through realistic finite-element-based simulations using a bimodal LUSM configuration.

Ultrasonic Motor’s H-Bridge Control Circuit Using Phase-Shift PWM Method

Ultrasonic motor is a special kind of actuator for motion control system. Because of the peculiar mechanism of ultrasonic motor, control circuit is needed for the operation of ultrasonic motor. The performance of ultrasonic motor depends on the topology and modulation method of control circuit. A novel type of control circuit for ultrasonic motor, H-bridge control topology using phase-shift PWM method, is proposed in this paper. Two kinds of implementary circuits are designed and analyzed. On the basis of the new designed circuit, the difference of performances between the phase-shift H-bridge circuit and push–pull circuit is analyzed. The experimental results proved that, the performance of the proposed control circuit is good.

Effects of wear of friction material on performance of ultrasonic motor

Friction material is one of the key components in an ultrasonic motor. The wear of the material affects the contact friction and output performance of the motor. A method which utilizes the equivalent wear of friction material to simulate the wear during operation is proposed based on the wear characteristics of the ultrasonic motor’s contact interface. A relationship between wear and performances of the ultrasonic motor is constructed. The influences of wear on output performance, friction coefficient of the contact interface, and wear morphology are researched in the experiments. According to the experiment’s results, with wear of friction material (decreasing thickness), the output performance of the ultrasonic motor presents a downward trend, the friction coefficient between contact interfaces decreases gradually, the friction-reducing ratio between contact interfaces increases gradually, and the wear between contact interfaces decreases. The results are helpful to understand operating performance, design, and select friction material of ultrasonic motor.

Dynamic Takagi‐Sugeno Model for the Control of Ultrasonic Motor

Model of ultrasonic motor is the foundation of the design of ultrasonic motor′s speed and position controller. A two‐input and one‐output dynamic Takagi‐Sugeno model of ultrasonic motor driving system is worked out using fuzzy reasoning modeling method in this paper. Many fuzzy reasoning modeling methods are sensitive to the initial values and easy to fall into local minimum, and have a large amount of calculation. In order to overcome these defects, equalized universe method is used in this paper to get clusters centers and obtain fuzzy clustering membership functions, and then, the unknown parameters of the conclusions of fuzzy rules are identified using least‐square method. Different experimental data that are tested with different operational conditions are used to examine the validity of the fuzzy model. Comparison between experimental data and calculated data of the model indicates that the model can well describe the nonlinear characteristics among the frequency, amplitude of driving voltage and rotating speed. The proposed fuzzy model can be used to analyze the performance of ultrasonic motor driving system, and also can be used to design the speed and position controller of ultrasonic motor.

Effects of Piezoelectric Ceramic on the Stator Performances of Ultrasonic Motor

The piezoelectric ceramic(PZT) is one of the key elements of the ultrasonic motor stator,its performance greatly affects the output characteristics of the ultrasonic motor.In order to research the effects of PZT on the output characteristics of ultrasonic motor,the electromechanical coupling dynamics model of the free stator is built by using finite element method.Based on the model,the effects of the thickness,polarization partition format and polarization inhomogeneity of the PZT on the stator dynamic performance are studied.And the energy evaluation method of the effects of the PZT on the stator dynamic characteristics is proposed.Meanwhile,The theoretical model of temperature characteristics of the ultrasonic motor stator is built by using Newton cooling law and heat capacity theory.Based on the model,the effect of dielectric loss of PZT material on the temperature characteristics of the stator is researched.The results show that the stator modal frequency increases with the enhancement of PZT thickness,while the vibration amplitude of the stator surface particle decreases with the increase of PZT thickness.Meanwhile,the stator modal frequency when PZT is in open circuit condition is greater than that when PZT is in short circuit condition.Based on the research results,a prototype of traveling-wave type ultrasonic motor with 10.4 mm diameter is produced,experiments show that the maximum torque of the motor is 9.5 mN·m,the no-load speed is about 1 000 r/min.The research results are helpful to the industrialization of the ultrasonic motor.

Finite element modelling of a rotating piezoelectric ultrasonic motor

The evaluation of the performance of ultrasonic motors as a function of input parameters such as the driving frequency, voltage input and pre-load on the rotor is of key importance to their development and is here addressed by means of a finite element three-dimensional model. First the stator is simulated as a fully deformable elastic body and the travelling wave dynamics is accurately reproduced; secondly the interaction through contact between the stator and the rotor is accounted for by assuming that the rotor behaves as a rigid surface. Numerical results for the whole motor are finally compared to available experimental data.

An electric contact method to measure contact state between stator and rotor in a traveling wave ultrasonic motor

Performances of ultrasonic motor (USM) depend considerably on contact state between stator and rotor. To measure the contact state in a traveling wave ultrasonic motor (TWUSM), a special test method is necessary. This paper develops a new method named electric contact method to measure contact state of stator and rotor in traveling wave type USM. The effects of pre-load and exciting voltage (amplitude) of stator on contact state between stator and rotor are studied with this method. By a simulating tester of friction properties of TWUSM, the variations of stalling torque and no-load speed against the pre-load and the exciting voltage have been measured. The relative contact length that describes the contact characteristic of stator and rotor is proposed. The relation between the properties of TWUSM and the contact state of stator and rotor are presented. Additionally, according to a theoretical contact model of stator and rotor in TWUSM, the contact lengths at given conditions are calculated and compared with the experimental results.

Effect of the Rotor/Stator Interface Condition Including Contact Type, Geometry, and Material on the Performance of Ultrasonic Motor

The purpose of this paper is to show the dynamic contact characteristics and the motor performance of several types of ultrasonic motors. First, we compare the performance of “intermittent” and “traveling” contact type ultrasonic motors by using the locally deforming rotor model. We show that the motor performances are the same when the shape of the stator’s amplitude, and the rotor’s interpenetration are the same. Then, we show that the performance of these two types of motors are different according to the effects of inertia and actual three dimensional displacement by using the FE (finite element) analysis. Finally, the effects of the teeth and a surface layer at the contact interface on the performance of the ultrasonic motor, including T-N (torque-speed) characteristics and friction loss, are analyzed.