Mechanical Output Characteristics Research Articles

Design and performance analysis of a compact dual-motor underwater vector propulsion system

Vector propulsion systems enhance the limited three-dimensional motion capabilities of conventional systems at low speeds. However, their requirement for multiple prime movers increases the underwater robot’s power capacity, impacts its size and mass and compromises long endurance capabilities. To solve this problem, a compact dual-motor underwater vector propulsion system is proposed in this paper. It employs a nozzle, adjustable in a two-dimensional plane, to produce an adjusting force, and a propeller, perpendicular to this plane, for main thrust, achieving three-dimensional motion. The innovation lies in a dual-shaft motor with each shaft featuring a one-way bearing. The synchronized direction of rotation of the two one-way bearings is opposite. This configuration enables the motor to drive the propeller during forward rotation and the nozzle during reverse rotation, achieving a two-in-one drive motor and reducing prime movers. Additionally, using nozzles for attitude regulation overcomes the limitation of conventional propulsion systems. An analytical model defines mechanical output characteristics. Computational fluid dynamics analyze hydrodynamic characteristics. The prototype’s underwater experiments confirm its ability to generate main thrust and a two-dimensional planar adjusting force, enabling three-dimensional motion.

Modulating NH4+ in vanadium oxide framework for high-efficient aqueous NH4+ storage

Aqueous energy storage systems have garnered significant attention due to their inherent advantages, including low cost, high eco-sustainability, and enhanced safety profiles. Nonmetal ion as a charge carrier is a fascinated paradigm shift just recently. Vanadium-based materials for ammonium ion (NH4+) storage have received considerable interest and have been demonstrated to serve as highly efficient NH4+ (de)intercalation host materials. However, tuning their structure for enhanced NH4+ storage presents significant challenges. Herein, we report a strategy for the pre-intercalation of NH4+ in vanadium oxide framework to study on the influence of the amount of ammonium ions on their NH4+ storage properties. The results from the experiments and density functional theory (DFT) calculations demonstrate that the appropriate quantity of pre-inserted ammonium ions boosts the (de)intercalation of NH4+ and exhibits the superior electrochemical properties. Moreover, excessive pre-inserted ammonium ions in vanadium oxide framework occupy the active sites for storing NH4+, whereas insufficient pre-inserted ammonium ions in vanadium oxide framework do not support the interlayer space enough for rapid (de)intercalation of NH4+. All results elucidate that modulating NH4+ in vanadium oxide framework enables highly efficient aqueous ammonium ion storage for supercapacitors (SCs). At 0.5 A·g−1, the specific capacitance of 341F·g−1 (171 mAh·g−1) and stable cycle performance of nearly 100 % after 10,000 cycles are achieved. The assembled hybrid supercapacitor exhibits the capacitance with 330 mF·cm−2 at 1 mA·cm−2, and energy density with 13.7 Wh·kg−1 at 22.1 W·kg−1, complemented by commendable mechanical durability and energy output characteristics. The profound insights gleaned from this study illuminate the strategic modulation of NH4+ ions, unveiling the vast potential of vanadium-based materials for efficient NH4+ storage applications.

Development of a bipedal piezoelectric actuator with flexible mechanism based on the frog-leg inspiration

A new piezoelectric actuator with flexible mechanism using stick-slip principle based on the frog-leg inspiration is developed in this work. It utilizes bipedal design, and the slider can be driven by only one foot or two feet alternately, which depends on the exciting situation of the used two PZT stacks. The extension of the PZT stack can be transmitted into the vertical and horizontal deformations on two driving feet due to the frog-leg inspiration. They are used to press and actuate the slider. The configuration of this actuator is presented and its working principle is illustrated. Finite element simulation is carried out to investigate the statics performance. A prototype of the proposed actuator is fabricated and series of mechanical output characteristics are measured. The results demonstrated that the proposed actuator obtained the output velocity of 4.23 mm/s when the voltage and frequency were 100 V and 400 Hz. The maximum vertical loading capacity was 9 N under the voltage of 100 V. The corresponding results in this work validated the feasibility of the proposed bipedal piezoelectric actuator with flexible mechanism based on the frog-leg inspiration.

Design, simulation, and experimental investigation on a novel multi-drive pattern three-degree-of-freedom rotary piezoelectric motor

Three-degree-of-freedom (3-DOF) rotary piezoelectric motors often suffer from low positioning accuracy, complex excitation signals, and uneven preloading, limiting their application in precision drive systems. To address these issues, this study proposes a novel multi-drive pattern 3-DOF rotary piezoelectric motor, comprising a sandwich-type hollow cylindrical stator, a spherical rotor, and a pre-tightening structure. The proposed motor can operate in both inertial and traveling wave drive patterns. In the inertial drive pattern, the first-order and the third-order bending vibration modes of the stator are simultaneously excited by a sawtooth wave signal, generating a saw-tooth displacement on its driving feet to rotate the rotor around the x or y-axis. In the traveling wave drive pattern, two mutually orthogonal first-order bending vibration modes of the stator are simultaneously stimulated by two sinusoidal signals, generating a traveling wave on its driving feet to rotate the rotor around the z-axis. Initially, finite element analysis is used to simulate the operating principle of the stator and determine its geometric dimensions. Subsequently, a prototype of the sandwich-type hollow cylindrical stator is fabricated, and its vibration characteristics are tested to confirm the validation of the proposed operating principle and the correctness of the finite element simulation. Finally, a prototype of the proposed 3-DOF rotary piezoelectric motor is assembled, and its mechanical output characteristics are experimentally evaluated. Experimental results indicate that when the excitation voltage is 200 Vpp, the no-load rotary velocities of the motor prototype in three rotation directions are 79 r min−1, 76 r min−1, and 101 r min−1, respectively, start/stop response times are 10 ms/8.6 ms, 13.4 ms/6.2 ms, and 15.5 ms/7.7 ms, respectively, and the angular displacement resolutions are 7.4 μrad, 8 μrad, and 11.4 μrad, respectively. The proposed motor exhibits high mechanical integration, 3-DOF rotation, few excitation signals, adjustable pre-tightening force, and high positioning accuracy advantages, holding the potential applications in fields such as robotic technology and space pointing mechanisms.

Development and evaluation of a new piezoelectric stick-slip actuator using stair type flexure hinge

A new piezoelectric stick-slip actuator using stair type flexure hinge is proposed and developed in this work. It’s spirited by referencing the reported “Z-shaped” flexure hinge in the literatures and the idea of asymmetric structure. In this design, the PZT stack can generate elongation displacement under the excitation of sawtooth signal, and then the elongation can be transmitted into the vertical and horizontal displacements on the driving tip by the stair type flexure hinge. The slider is pressed by the vertical displacement and driven by the horizontal displacement, respectively. The working principle of the proposed actuator is clarified. The statics characteristics are investigated by the theoretical and simulation methods. Finally, the mechanical output characteristics of the developed prototype are tested. The maximum output velocity is 8.5 mm/s when the voltage and frequency are 100 V and 720 Hz. The maximum output force is tested as 2.6 N when the preloading force is 3 N. The experiment results validate the feasibility of the proposed piezoelectric stick-slip actuator based on stair type flexure hinge.

Design of a linear-rotary ultrasonic motor for optical focusing inspired by the bionic motion principles of the earthworms

ABSTRACT Multi-motor configuration of multi-DOF (degree of freedom) optical system is a major source of redundant structure, putting a limitation on the simple and miniaturized design. Thus, a novel two-DOF ultrasonic motor (USM) is proposed to provide a feasible method of application in the lens autofocus of the optical system. The proposed USM operates by one longitudinal mode and two orthogonal bending modes, which is inspired by the bionic motion principle of the earthworms. The frequency degeneration among the three working modes is performed, and the working principle of the USM is verified via the FEM simulation. A prototype of the two-DOF USM is fabricated, and its mechanical output characteristics are tested. The experimental results indicate that the prototype achieves the maximum rotary and linear speeds of 3319.6 rpm and 57.6 mm/s, respectively. Furthermore, we demonstrate the result of a simple focusing experiment using the prototype and obtain a series of clear pictures, which verifies the feasibility of application in the optical focusing system.

Theoretical modeling and experimental investigation on a novel screwed-type piezoelectric focusing mechanism for space cameras

Traditional focusing mechanisms for space cameras are driven by a stepper motor with transmission parts, holding the disadvantages of complex structure, low space utilization, electromagnetic interference, and difficulty in self-locking. In order to overcome the above defects, a novel screwed-type piezoelectric focusing mechanism is proposed for space cameras. A screwed-type piezoelectric actuator with a hollow tube stator and rotor is proposed to directly drive a focusing lens to achieve a variation in the focal length. The stator with internal thread operates with two orthogonal bending vibrations and drives the rotor with thread to achieve linear motion by friction. An axial pre-pressure adjustment structure is designed to improve the output performance of the screwed-type piezoelectric actuator in a weightless environment. In order to reveal the dynamic characteristics of the stator and to determine its physical dimensions, an electromechanical coupling model is created using the transfer matrix method. A prototype of the stator is fabricated, and its vibration characteristics were tested to confirm the correctness of the developed theoretical model. In addition, the mechanical output characteristics of the screwed-type piezoelectric actuator prototype are experimentally evaluated. The experimental results shown that: 1. The maximum axial load weight to actuator weight ratio reaches 4.8 under peak-to-peak excitation voltages of 100 Vp-p; and 2. the actuator prototype can operate in high-temperature (100 °C) and high-vacuum (1.5 × 10-3 Pa) environments. Finally, the feasibility of the screwed-type piezoelectric focusing mechanism is experimentally demonstrated. The minimum displacement resolution of the mechanism prototype reaches 5.01 μm when the duty ratio is 1.20%, and the mechanism focuses on the image located at 3300 mm. The proposed piezoelectric focusing mechanism can realize high-precision linear positioning without transmission parts, and can realize self-locking without power, presenting the potential application in space cameras.

MXene based mechanically and electrically enhanced film for triboelectric nanogenerator

The development of triboelectric nanogenerator (TENG) technology which can directly convert ambient mechanical energy into electric energy may affect areas from green energy harvesting to emerging wearing electronics. And, the material of triboelectric layer is critical to the mechanical robustness and electrical output characteristics of the TENGs. Herein, a MXene enhanced electret polytetrafluoroethylene (PTFE) film with a high mechanical property and surface charge density is developed. The MXene/PTFE composite film was synthesized by spraying and annealing treatment. With the doping of MXene, the crystallinity of composite film could be tuned, leading to an enhancement in the tensile property of 450% and reducing the wear volume about 80% in the friction test. Furthermore, the as-fabricated TENG with this composite film outputs 397 V of open-circuit voltage, 21 µA of short-circuit current, and 232 nC of transfer charge quantity, which are 4, 6, and 6 times higher than that of the TENG made by pure PTFE film, respectively. Therefore, this work provides a creative strategy to simultaneously improve the mechanical property and electrical performance of the TENGs, which have great potential in improving device stability under a complex mechanical environment.

Investigation of an Automobile magnetorheological damper with asymmetric mechanical characteristics

In order to reduce the cost of sensors in automotive magnetorheological suspension systems and improve system reliability, a structural design scheme of automotive magnetorheological dampers with asymmetric mechanical characteristics is proposed. In this structure, the rebound damping coefficient with or without the action of the magnetic field will be greater than the compression damping coefficient, which solves the influence of the traditional magnetorheological damper limited by its own adjustable range, and continuously outputs the passive damper under different working conditions. According to the structural design plan, the mechanical output characteristics of the system are analysed theoretically, and the prototype machine is processed and tested. The research results show that the designed magnetorheological damper has the working characteristics of continuously outputting asymmetric damping force, which verifies the effectiveness of the design ideas and methods.

Integrated Shock Absorber With Both Tunable Inertance and Damping

Inerter is a two-terminal mass element and the applied force is proportional to the relative acceleration between the terminals. According to the second class of mechanical-electrical analogy, the inerter corresponds exactly to the capacitor in the electric network. Aiming at improving the limited vibration isolation performance using constant inertance of conventional inerter, a new semi-active inerter based on smart material, magnetorheological (MR) fluid, is proposed in this paper. Further, according to the design concept of “functional integration”, the MR inerter, an MR damper and a spiral spring are integrated to realize a new integrated inerter-spring-damper (IISD) with both adjustable inertance and damping characteristics. The MR inerter consists of a ball screw, an MR clutch, MR fluid, excitation coils, an excitation shell, a flywheel, a flywheel shell, a connector, upper and lower covers, bearings and seals. The tunable inertance is achieved by adjusting the excitation current in the excitation coils to change the operating state of the MR clutch. The MR damper and the spiral spring provide variable damping and constant stiffness, respectively. The mathematical model of the IISD is established. The adjustment principle of inertance is verified by numerical simulation, and the mechanical output characteristics of the IISD are analyzed. Besides, the 1/4 vehicle suspension model based on the proposed IISD is built by using MATLAB/SimMechanics. The frequency response and unit impulse response characteristics of the suspension are obtained via the comfort-oriented virtual experiment. The simulation results show that the suspension with the IISD has a 23.0% higher performance than the conventional suspension in vehicle body acceleration, and the suspension deflection and dynamic tire load are also improved.

An insight into the flexible drive mechanism in short cylinder ultrasonic piezoelectric vibrator.

In this study, a resonant type piezoelectric vibrator for driving a flexible body is proposed and its driving principle is discussed. The flexible body driven in this article is rigid in the longitudinal direction and flexible in the transverse direction, such as in metal straps and metal wires. The exciting signals used in the piezoelectric transducer in the horizontal and vertical directions are both sinusoidal signals, possessing a phase shift of π/2. Two third-order orthogonal bending in-plane modes of the same frequency were effectively excited, and an elliptic motion formed on the end plane of the vibrator toothed structure. A flexible body was then effectively driven by friction under a certain amount of tension. The proposed vibrator was designed using the finite element method, and the flexible drive models were established, while the output force in the contact friction was analyzed. The vibration characteristics of the vibrator were tested in order to obtain the resonance frequencies and responses. An experimental system was then established to test the mechanical output characteristics. The results demonstrate that the difference in thickness, tension force, and surface roughness between the flexible bodies confer great influence on driving. With a thickness of 0.01 mm, 0.02 mm, and 0.03 mm, the flexible metal strap velocity was found to be 24 mm/s, 43.64 mm/s, and 10.43 mm/s under the corresponding proper tension, smooth surface, and voltage of 200Vp-p, respectively.

A Rotary Traveling Wave Ultrasonic Motor With Four Groups of Nested PZT Ceramics: Design and Performance Evaluation.

This study proposes a rotary traveling wave ultrasonic motor utilizing the B (0, 5) axial bending mode of a ring-shaped stator. The proposed motor had a compact structure as only four groups of piezoelectric (PZT) ceramics were nested into the stator to produce a bending traveling wave, a new design method was proposed utilized less PZT ceramics to reduce the volume and to improve the mechanical output characteristics. The operating principle of the proposed motor was illustrated. The finite element analysis was performed to obtain the vibration modes and the motion trajectories of the stator. A prototype was manufactured to validate the operating principle. The two standing waves and the motion trajectories of the driving tips were measured. The results denoted that this motor obtained an output speed of 53.86 r/min under a preload of 0.69 N when the frequency and voltage were 24.86 kHz and 250 Vp-p, the maximum stall torque was tested as about [Formula: see text] under the preload of 3.14 N. Finally, this study was compared with a previous design and it was found that the volume was reduced markedly; furthermore, the no-load speed, the efficiency, the torque density and the power density were improved significantly.

Development of a novel spherical stator multi-DOF ultrasonic motor using in-plane non-axisymmetric mode

A novel spherical stator multi-DOF ultrasonic motor using in-plane non-axisymmetric mode was proposed. The stator and the rotor of the motor adopt a piezoelectric ceramic spherical shell and two metal hemispherical shells, respectively, which is beneficial to realize high symmetry and miniaturization of the whole motor. The motor adopts the pair combination of three orthogonal in-plane non-axisymmetric modes to generate three types of elliptical motions at eight driving feet, which can rotate the rotor around X, Y and Z axes, respectively. Finite element method was used in the design of the proposed motor including searching for reasonable modes by modal analysis and verifying the uniform driving of the eight driving feet by transient analysis. A prototype was fabricated to verify the working principles, designs and simulations. The mechanical output characteristics around X, Y and Z axes were measured under different excitations, pre-tightening forces and loading conditions. The no-load rotary velocities of the prototype were 200 r/min, 198 r/min and 250 r/min and the maximum load torques were 10.8 mN·m, 11.0 mN·m and 12.3 mN·m around X, Y and Z axes, respectively. The spherical stator multi-DOF ultrasonic motor could be applied to robot visual driving systems as its merits of compact size and high velocity.

Disc type piezoelectric motor with two coaxial rotors

A small disc type piezoelectric motor was developed that can be used for micro flying vehicles. The operating principle of the motor is based on radial-bending type hybrid vibrations. The stator of the motor is a bimorph disc with the special quadrilateral shaped waveguides in the inner circumference of the disc. Waveguides are aligned with the tangential direction of the contacting ring. Such configuration of the actuator allows transforming radial vibrations of the disc into rotational vibrations of the contacting ring. Elliptical motion of the contact points is obtained by superposition of radial and bending vibration modes. The motor has two truncated cone-shaped rotors. Although the actuator is asymmetrical, two coaxial shafts of the motor can be rotated in both directions depending on the phase of excitation signals. Moreover, the proposed piezoelectric motor allows controlling the rotation speed of the rotors in different directions depending on the amplitude of the applied voltage. Numerical and experimental investigation of the piezoelectric motor was performed to validate the operating principle and to analyze vibrations of the contact points. Electrical and mechanical output characteristics of the piezoelectric motor were measured. The motor achieved a maximum no load rotational speed of 7108 rpm at 15 V while maximum torque is 0.0647 mN m.

Mechanical and energetic characteristics of an energy harvesting type piezoelectric ultrasonic actuator

Piezoelectric ultrasonic actuators (PUA) are fascinating and precision-controlled actuators in some mechatronics systems. This study proposed an energy harvesting type piezoelectric ultrasonic actuator (H-PUA) and investigated its mechanical and energetic characteristics. The proposed H-PUA has a sandwich-type stator composed of a metal body, an exciting piezoelectric (PZT) ring and a harvesting PZT ring. The exciting PZT ring bonded on the bottom surface of the stator was used to produce a traveling wave, and the harvesting PZT ring bonded on the top surface of the stator was used to harvest the vibration-induced energy of the stator and convert it into electric energy. Sensitivity analysis method was used to optimize the stator structure. Finite element analysis using ANSYS software was performed for both the mechanical and energetic characteristics of the new actuator. A prototype H-PUA was fabricated and subsequently used to test the mechanical and energetic characteristics. When the rotor torque is zero and the pre-pressure is 100 N, the prototype H-PUA has mechanical output characteristics of no-load speed 112 rpm and stalling torque 0.78 Nm when the exciting voltage amplitude is 152 V0−p with frequency 36.0 kHz. The maximum harvesting output power of a sector area of the harvesting PZT ring reaches 54 mW when it is connected to an optimized load resistance 11 kΩ. Experiments have shown that the harvesting output energy can fully meet with the power supply demands of some low-power (i.e., mW/μW level) mechatronics systems, such as LED.

A Two-DOF Ultrasonic Motor Using a Longitudinal–Bending Hybrid Sandwich Transducer

A two-degrees-of-freedom (two-DOF) ultrasonic motor, which could output linear motions with two-DOF by using only one longitudinal–bending hybrid sandwich transducer, is proposed and tested in this paper. The motion in the horizontal ( X ) direction is achieved by the hybrid of the second longitudinal and fifth bending vibrations of the motor, while the motion in the vertical ( Y ) direction is gained by the composition of two orthogonal fifth bending vibrations. The proposed ultrasonic motor is designed and the principles for the two-DOF driving were analyzed. Then, the simulation analyses of the motor are accomplished to verify the described principles. Finally, a prototype is fabricated and its mechanical output characteristics are tested. The results indicate that the maximum no-load velocities of the motor in horizontal and vertical directions are 572 and 543 mm/s under the preload of 100 N and the voltage of 300 Vp-p, respectively. The maximum output forces in horizontal and vertical directions are 24 and 22 N when the preload is 200 N. The simulation and experiment results verify the feasibility of the proposed two-DOF ultrasonic motor.

A novel fixable cylindrical ultrasonic motor

A novel cylindrical ultrasonic motor easy to be fixed is proposed in this article. There are threaded holes on the bottom of stator used for fixing, distinguishing it from other cylindrical stators. The bottom is machined as a round lug boss. Its radius is smaller than the inner radius of the stator in order not to affect the excitation of vibration mode. The finite element analysis was accomplished to verify the working principle. Based on the analysis, a prototype was fabricated and measured. The mechanical output characteristics were obtained by experiments. The maximal velocity of the proposed motor is 170 r/min at the operating frequency of 31.6 kHz.

A novel U-shaped stepping linear piezoelectric actuator with two driving feet and low motion coupling: Design, modeling and experiments

Abstract A U-shaped stepping piezoelectric actuator featuring low motion coupling is proposed, fabricated and tested. The actuator contains four similar piezoelectric actuation units (PAUs): two of them are used as the clamping units, while the other two act as the pushing units. The sliders and brackets supporting the clamping units can strongly suppress the motion coupling. The actuator can move the runner twice in each cycle with the operating principle similar to an inchworm. Static models are developed to calculate the step length and clamping force of the proposed actuator. A prototype is fabricated and its mechanical output characteristics are measured. The measured step length and clamping force agree well with the calculated results by the static model. The operating principle is verified by the experiment results, and the motion coupling ratio is 4%. The output speed linearly depends on the voltage applied on the pushing units, which indicates that the proposed actuator is very suitable for speed control. The working frequency has positive effect on the speed in range from 0.05 Hz to 6.25 Hz, whereas negative effect is found over 6.25 Hz. The prototype achieves a maximum thrust force of 189.7 N and a maximum speed of 273.4 μm/s.

Multi‐DOF Ultrasonic Actuators for Laser Beam Positioning

A novel design concept of multi‐degree‐of‐freedom (multi‐DOF) piezoelectric actuator is introduced in the paper. The main idea is to connect two identical piezoelectric transducers by hyperelastic material in order to increase the total number of degrees‐of‐freedom of the system. Such design principle also allows to separate vibrations of two piezoelectric transducers and to control them independently. The ring‐ and cylinder‐type piezoelectric transducers were used to design two multi‐DOF ultrasonic actuators for precise laser beam positioning. Reflecting mirror is mounted on the top of the actuator and is preloaded by magnetic force. Both disc‐ and cylinder‐type actuators can realize up to six degrees‐of‐freedom, i.e., to rotate the mirror about three axes employing one transducer and to position mirror in the plane by using another transducer. Bidirectional rotation and translation motion of the mirror are obtained by switching excitation signals between different electrodes of the transducers. Both the numerical simulation and physical prototype were used to verify operating principle of the actuators. Numerical investigation of the piezoelectric actuator was performed to investigate modal‐frequency and harmonic response analysis while experimental study was performed to measure electrical and mechanical output characteristics of the piezoelectric actuator. A mathematical model of contacting force control was proposed, and numerical verification was performed when the mirror need to be rotated according to the specific motion trajectory.

Working Mechanism of Nonresonance Friction in Driving Linear Piezoelectric Motors with Rigid Shaking Beam

A kind of nonresonance shaking beam motors is proposed with the advantages of simple structure, easy processing, and low cost due to its wide application prospects in precision positioning technology and precision instruments. The normal vibration model between the stator and slider is divided into contact and noncontact types to investigate the nonresonance friction drive principle for this motor. The microscopic kinematics model for stator protruding section and the interface friction model for motor systems during both operating stages are established. Accordingly, the trajectory of the stator protruding section consists of two different elliptical motions, which differ from those of resonance-type motors. The output characteristic of the nonresonance shaking beam motor is proposed under steady working conditions with reference to the research method of standing-wave-type ultrasonic motors. Numerical analysis is used to simulate the normal vibration and mechanical output characteristics of the motor. Experimental and theoretical data fitting validates the numerical analysis results and allows the future optimization of nonresonance-type motors.