No-load Speed Research Articles

Characterization and Control of a Pneumatic Motor for MR-conditional Robotic Applications.

Magnetic Resonance (MR) guided interventional robots have recently been developed for a variety of surgeries, such as biopsy, ablation, and brachytherapy. The actuators and encoders that power and track such robots must be MR-conditional. In this paper, we propose an MR-conditional pneumatic motor with an integrated and custom-built fiber-optical encoder that provides powerful and accurate actuation. The motor is coupled with a modular plastic gearbox that provides a variety of gear ratio options so that the motor can be adapted to application requirements. With a 100:1 gear reduction at 0.55 MPa, the motor achieves 460 mNm stall torque and 370 rpm no-load speed, which leads to the peak output power of 6W. The motor has the bandwidth of approximately 1.1 Hz and 3.5 Hz when connected to 8 m and 0.2 m air hoses, respectively. The motor was tested in a 3T MRI scanner. No image artifact was observed and maximum signal to noise ratio (SNR) variation was less than 5%. Different from most of the existing MR-conditional pneumatic actuators, the proposed motor shape is more like the traditional electric motors, which offers more flexibility in the MR-conditional robot design.

Development of a bi-directional standing wave linear piezoelectric actuator with four driving feet

A bi-directional standing wave linear piezoelectric ultrasonic actuator with four driving feet is proposed in this work. Two sandwich type transducers operated in longitudinal-bending hybrid modes are set parallelly. The working mode of the transducer is not simple hybrid vibrations of a longitudinal one and a bending one, but a special coupling vibration mode contained both longitudinal and bending components. Two transducers with the same structure and unsymmetrical boundary conditions are set parallelly to accomplish the bi-directional driving: the first transducer can push the runner forward, while the other one produces the backward driving. In the experiments, two voltages with different amplitudes are applied on the two transducers, respectively: the one with higher voltage serves as the actuator, whereas the other one applied with lower voltage is used to reduce the frictional force. The prototype achieves maximum no-load speed and thrust force of 244 mm/s and 9.8 N. This work gives a new idea for the construction of standing wave piezoelectric ultrasonic actuator with bi-directional driving ability.

A novel piezoelectric actuator with two operating modes

A novel piezoelectric actuator with two operating modes is proposed and tested in this work, whose unique feature is that it has different mechanical output performances under two bending resonance frequencies. The proposed actuator is fabricated by bonded eight pieces of lead zirconate titanate ceramic plates on an aluminum alloy beam symmetrically. When the ceramic plates are excited by signals with resonance frequency of the first bending mode of the actuator, two bending vibrations will be superimposed to form elliptical movements on the two driving tips, which is the first operating mode. The other operating mode can be realized easily by changing the working frequency to the second bending mode of the actuator. These two operating modes are calculated and compared in detail. The prototype achieves a maximum no-load speed of 171 mm/s and maximum thrust force of 0.6 N using the first operating mode, whereas these two values are increased to be about 208 mm/s and 0.76 N under the second operating mode. The weight of the proposed piezoelectric actuator is about 17.7 g, and the maximum force weight ratio is tested to be about 42.9 N/kg.

A novel plate type linear piezoelectric actuator using dual-frequency drive

In this paper, a novel rectangular structure linear piezoelectric actuator that utilizes two lower order decoupled vibration modes is developed and investigated. A noticeable trait of the linear piezoelectric actuator is that it can realize bi-directional motion by changing the vibration mode of the stator with different exciting frequencies. Modal and harmonic analysis of the stator are performed by the finite element method to determine the actuator structure and dimensions and stablished that the driving tip trajectories are diagonal lines. The direction of the actuator is controlled by the orientation of the diagonal motion generated at the driving tip. When the diagonal motion is inclined right as the driving tip approaches the linear guide, it will move the linear guide right. Correspondingly, the linear guide will move to the left, if the diagonal motion inclines left. In addition, a prototype linear piezoelectric actuator is fabricated and experimented. The results of the experiments indicate that the actuator has good mechanical output characteristics. Typical output of the prototype is no-load speed of 504 mm s−1 and maximum mechanical load of 6.5 kg.

Bio-inspired piezoelectric linear motor driven by a single-phase harmonic wave with an asymmetric stator.

A novel, bio-inspired, single-phase driven piezoelectric linear motor (PLM) using an asymmetric stator was designed, fabricated, and tested to avoid mode degeneracy and to simplify the drive mechanism of a piezoelectric motor. A piezoelectric transducer composed of two piezoelectric stacks and a displacement amplifier was used as the driving element of the PLM. Two simple and specially designed claws performed elliptical motion. A numerical simulation was performed to design the stator and determine the feasibility of the design mechanism of the PLM. Moreover, an experimental setup was built to validate the working principles, as well as to evaluate the performance, of the PLM. The prototype motor outputs a no-load speed of 233.7 mm/s at a voltage of 180 Vp-p and a maximum thrust force of 2.3 N under a preload of 10 N. This study verified the feasibility of the proposed design and provided a method to simplify the driving harmonic signal and structure of PLMs.

A piezoelectric motor driven by a single-phase signal

This paper aims to present a proof-of-concept for a novel piezoelectric motor using a single-phase driving signal. The stator is constructed by bonding a Terfenol-D plate and a piezoelectric ceramic (PZT) plate onto the outer surface of a metal base. The PZT plate based on d31 effect is used to simultaneously excite two in-plane bending modes of the stator. Similarly, the Terfenol-D plate can also be used to excite the two bending modes. By superposition of the two bending modes, elliptical motions of the stator surface points are generated. The working modes and vibration characteristics of the motor are analyzed by finite element analysis software. The resonance frequencies of the two bending modes are tuned to be close by additional mass. The dimensions of the stator are optimized to maximize the output displacement. To confirm the feasibility of the proposed design, a prototype motor is fabricated and tested. The size of the prototype motor is about 11.2×10.7×28.0 mm3. The tested resonance frequencies of the two bending modes are 16.0820 kHz and 16.3476 kHz respectively. The maximum no-load speed is 85 rpm. The applied driving voltage is 100 Vo-p (peak voltage) at a frequency of 16.34 kHz.

Design and manufacturing of ultrasonic motor with in-plane and out-of-plane bending vibration modes of rectangular plate with large contact area

Ultrasonic motor working with coupled in-plane and out-of-plane vibration modes of rectangular plate is proposed and experimentally investigated. Thanks to its unique configuration, proposed motor provides large contact area between stator and rotor of motor which can reduce wear and enhance motor life-time. The proposed motor is designed using finite element method and according to the design, a prototype is fabricated and its working characteristics such as speed, normal and driving force and working frequency are measured. Overall dimension of designed prototype is 49×14×2mm, working frequency of motor is 49.6kHz, no-load speed and stall force of motor are 122rpm and 0.32mNm at 50V, respectively.

Dual traveling wave rotary ultrasonic motor with single active vibrator

Traveling wave rotary ultrasonic motor with double vibrators can improve the output performance effectively. However, the rotor has to be energized through a slip ring, which increases the complexity and reduces the reliability. Inheriting the concept of two traveling waves propagating in the stator and rotor, a dual traveling wave rotary ultrasonic motor energized only in the stator is proposed. By analyzing the oscillatory differential equation and the contact particles motion, a traveling wave is found in the rotor and the drive mechanism of dual traveling wave is studied. With the resonant rotor adopted, the consistent eigenfrequencies are calculated by finite element method and verified by an impedance analyzer. The performance experiment presents that the dual traveling wave rotary ultrasonic motor is superior to the motor with single traveling wave. The no-load speed is 60 rpm and the stalling torque is 0.85 Nm. Additionally, compared with a reported motor with double vibrators, the proposed motor presents the better output performance and the simpler design.

Influence of the input parameters on the efficiency of plaster sanding with alundum abrasive discs

The paper presents test results concerning the relationship between selected input parameters and the process efficiency for the sanding of plaster surfaces with alundum abrasive discs. The input parameters under study were the size of the abrasive grains, the force exerted by the plaster sample pressing against the abrasive disc and the no-load rotational speed of the abrasive disc. The experimental data illustrating the relationship between the process efficiency and the particular input parameters were used to select the optimum plaster sanding conditions.

Linear ultrasonic motor for absolute gravimeter

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 1.4m/s and maximal thrust of 43N, meeting the requirements for absolute gravimeters.

A method for assessing the wear of sanding abrasive discs differing in the type of grains (SiC, Al2O3(95A))

This paper describes a method for studying the wear of abrasive mesh discs differing in the type of grains employed to sand plaster. The tests were conducted at a specially developed and constructed setup. The investigations involved analysing the influence of the basic input parameters (the size of the abrasive grains covering the disc surface, the force exerted by the plaster sample pressing against the abrasive disc and the no-load speed of the abrasive disc) on the efficiency of the sanding process. The paper also describes the structural details of the experimental setup.

A Symmetrical Hybrid Driving Waveform for a Linear Piezoelectric Stick-Slip Actuator

A symmetrical hybrid driving waveform (SHDW) is proposed in this paper, which includes a symmetrical saw-tooth driving waveform and a sinusoidal friction regulation waveform, and the sinusoidal friction regulation waveform is applied to the shrinkage period of the symmetrical saw-tooth driving waveform. In other words, the proposed SHDW can be achieved when the waveform symmetry of the hybrid driving method is 50%. The SHDW can effectively drive the designed symmetrical linear piezoelectric stick-slip actuator, and the motion direction is also easily regulated. The excitation principle of the actuator excited by the SHDW is explained in detail. A prototype is fabricated and the experimental investigations of the actuator characteristics are carried on. The higher velocity and the larger driving capacity are realized using by the SHDW relative to the asymmetrical hybrid driving waveform. Testing results show that the prototype excited by the SHDW can obtain the peak no-load speeds of 0.41 and 0.39 mm/s in the forward and reverse directions when the saw-tooth driving waveform voltage is 10 $\text{V}_{\text {p-p}}$ for 800 Hz and the sinusoidal friction regulation waveform voltage is 2 $\text{V}_{\text {p-p}}$ for 39 kHz. The step efficiencies can reach 92% and 90%. The driving capacities can reach 10.52 and 9.85 [(mm/s)g/mW] with the load of 70 g under the locking force of 0.1 N. The actuator excited by the SHDW will make it ideal for miniature information technology devices.

A type of dual-rotor hybrid ultrasonic motor based on vibration of four side panels

Based on vibration of four side panels, a type of dual-rotor hybrid ultrasonic motor without using the torsional piezoelectric ceramics polarized along the circumferential direction is presented. The first longitudinal and the first bending vibration modes of the four side panels are used to indirectly excite the first longitudinal and the second torsional vibration modes of the stator cylinder. There are rectangle piezoelectric ceramics bonded on both sides of the four side panels, which are uniformly distributed along the circumference of the stator cylinder. One pair of panels on the opposite side is used to indirectly excite the first longitudinal vibration mode of the stator cylinder, and the other pair is used to indirectly excite the second torsional vibration mode. The simulation results, using finite element method software Workbench, reveal the operating principles, and the optimal structure is proposed. The appearance size of the prototype is 27.2 mm × 27.2 mm × 70 mm, while the outer diameter of the stator cylinder is 20 mm. The working frequency of the prototype measured in experiment is 44.7 KHz, which is consistent with the numerical results. According to the major mechanical measurement at 450 Vp−p operating voltage and 3.46 N preload, the stalling torque of the prototype is 8 mN·m and the no-load speed is 140 r/min. The experimental results indicate that the motor can operate in the first longitudinal and the second torsional coupled vibration modes transformed from the first longitudinal and the first bending vibration modes of four side panels.

An energy harvesting type ultrasonic motor

An energy harvesting type ultrasonic motor is presented in this work. The novel motor not only can drive and/or position the motion mechanism, but also can harvest and convert the vibration-induced energy of the stator into electric energy to power small electronic devices. In the new motor, the stator is a sandwich structure of two PZT rings and an elastic metal body. The PZT ring bonded on the bottom surface is used to excite the stator metal body to generate a traveling wave with converse piezoelectric effect, and the other PZT ring bonded on top surface is used to harvest and convert the vibration-induced energy of the stator into electric energy with direct piezoelectric effect. Finite element method is adopted to analyze the vibration characteristics and the energetic characteristic. After the fabrication of a prototype, the mechanical output and electric energy output abilities are measured. The maximum no-load speed and maximum output torque of the prototype are 117rpm and 0.65Nm at an exciting voltage with amplitude of 134 Vp-p and frequency of 40kHz, and the maximum harvesting output power of per sector area of the harvesting PZT is 327mW under an optimal equivalent load resistance of 6.9kΩ.

A piezoelectric motor operated under the superposition of the second and third bending modes of a sandwich transducer

ABSTRACTA rotary piezoelectric motor was proposed, in which the second and third bending vibrations of a transducer were superimposed to produce reverse elliptical movements on the two driving tips. The second bending mode was used to overcome the preload, whereas the third bending mode was used to rotate the rotor. The frequency tuning process of the two bending modes was discussed. The working frequency, the maximum no-load speed, the maximum torque and the maximum efficiency of the prototype were tested to be 23.8 kHz, 130 r/min, 2.96 N·m and 16.8%, respectively.

A novel standing wave linear piezoelectric actuator using the longitudinal-bending coupling mode

A novel standing wave linear piezoelectric actuator is proposed and tested by using a sandwich transducer operated in longitudinal-bending coupling mode. The vibration mode used in this work is neither longitudinal mode nor bending mode, but a longitudinal-bending hybrid one, which is generated simultaneously by only one group of PZT ceramic elements. The exciting principle of this coupling mode is discussed, and then realized by designing a standing wave piezoelectric actuator. When the 1st longitudinal and 3rd bending modes of the transducer have colse resonance frequencies and unsymmetrical boundary condition is applied, the desired longitudinal-bending coupling mode can be generated by a sine signal, which finally produces oblique elliptical movement on the end tip of the transducer. The design and analysis work is accomplished by finite elements method (FEM), and verified by a scanning laser Doppler vibrometer after the fabrication of a prototype. The proposed standing wave linear piezoelectric actuator achieves maximum no-load speed and thrust force of about 891.3mm/s and 39.2N under voltage of 400VP-P and working frequency of 29.4kHz.

Design of an ultrasonic motor with multi-vibrators

This paper presents and verifies a new idea for constructing an ultrasonic motor (USM). The stator contains several vibrators fabricated by bonding piezoelectric ceramics (PZTs) to a metal base. When two alternating current (AC) voltages with a 90° phase difference are applied to the PZTs, longitudinal and bending modes are excited in the vibrator. The bending vibrations of the vibrators are stacked to form the torsional vibration of the stator, ultimately generating longitudinal-torsional composite vibration. Both vibrators and the stator are excited to the resonance state. A standing wave is formed by superposition of longitudinal and torsional modes. The proposed motor is an in-plane vibration motor because the vibrations of the stator are in the circumferential plane. The finite element method (FEM) is used to validate the feasibility of the proposed motor. The fabricated stator contains five vibrators. The tested resonance frequencies of longitudinal and torsional modes are 44.42 kHz and 43.83 kHz, respectively. The stall torque is 0.3 N·m and no-load speed is 45 r/min. The highest efficiency is 30%. The applied driving voltage is 100 Vo-p (peak voltage) at 43.9 kHz. The designed motor is a parallel-actuated integral motor. It allows the vibrators to operate synchronously, and overcomes asynchronous issues that occur in traditional multi-vibrator motors.

Development of an ultrasonic linear motor with ultra-positioning capability and four driving feet

This paper presents a novel linear piezoelectric motor which is suitable for rapid ultra-precision positioning. The finite element analysis (FEA) was applied for optimal design and further analysis, then experiments were conducted to investigate its performance. By changing the input signal, the proposed motor was found capable of working in the fast driving mode as well as in the precision positioning mode. When working in the fast driving mode, the motor acts as an ultrasonic motor with maximum no-load speed up to 181.2mm/s and maximum thrust of 1.7N at 200Vp-p. Also, when working in precision positioning mode, the motor can be regarded as a flexible hinge piezoelectric actuator with arbitrary motion in the range of 8μm. The measurable minimum output displacement was found to be 0.08μm, but theoretically, can be even smaller. More importantly, the motor can be quickly and accurately positioned in a large stroke.

Resonant-type inertial impact motor with rectangular pulse drive

In this paper, a resonant-type piezoelectric inertial motor driven by rectangular pulse is developed. The rectangular pulse drive methodology is explained and its influence on output displacement of the stator is discussed in relation to four factors: frequency ratio, duty ratio, vibration amplitude ratio, and phase difference. A bending stator with second harmonics at its double fundamental resonant frequency is designed to generate saw-tooth type displacements under a rectangular pulse. It is composed of an aluminum plate (20mm×4mm×2mm) sandwiched between two piezoelectric plates (10mm×4mm×0.73mm). Experiments show that with optimized duty ratios, both the rotation speed and stall torque can be enhanced. The rotation direction of the rotor can be reversed by changing the duty ratio. The maximum no-load angular speed reaches 300rpm with driving voltage of 60Vpp at the fundamental resonant frequency of 35.3kHz in both directions. Using a preload of 1.07N, stall torque reaches 1220μNm driven at 80Vpp and 35.3kHz. The maximum efficiency of the motor is 2.1%, which is higher than that of the previously reported piezoelectric inertial rotary motors. The proposed inertial motor features simple mechanical and electrical design, which makes it ideal for miniature electro-mechanical device applications.

Compact Traveling Wave Micromotor Based on Shear Electromechanical Coupling

A compact traveling wave piezoelectric micromotor is proposed based on ${d_{15}}$ shear electromechanical coupling. A single bulk lead zirconate titanate is employed as the stator, which offers a comparatively small length-to-width ratio. The system construction is simplified and favorable for further miniaturization. The wobbling motion of stator generates traveling waves on the surface when the first- or second-order bending mode is stimulated by a rotating electric field, and thus to move the rotor with friction in clockwise or counterclockwise directions. The vibration property is analyzed in detail and design optimization is conducted. A research prototype with a size of 0.75 mm $\times$ 0.75 mm $\times$ 1.55 mm has been developed and an experimental rig with adjustable payload is built up for the performance test. Experimental result proves that the proposed motor can work in wide frequency bands of more than 10 kHz for both the first- and second-order bending modes. The system can achieve no-load speed of 1850 r/min and maximum torque of at least 2 $\mu$ N $\cdot$ m at no more than 60 ${{\rm {V}}_{{\rm {pp}}}}$ , which is very competitive compared to other micromotors. The developed piezoelectric micromotor has potential applications in small-sized systems such as micromedical robots, etc.