No-load Speed Research Articles

A multi-degree-of-freedom clamping type traveling-wave ultrasonic motor

This paper proposes a multi-degree-of-freedom (multi-DOF) ultrasonic motor with four stators clamping a spherical rotor. The stator surface teeth are inclined at a certain angle, using the inclined surface to contact the rotor and transfer energy. The motor frame is exquisitely designed in which substrates hold four identical stators to drive the rotor to achieve a multi-DOF rotation. COMSOL Multiphysics performs the stator's modal analysis and harmonic response analysis to illustrate the vibration mode and frequency response. A prototype is fabricated to verify the operating principle and conduct the performance tests. The experimental results indicate that the motor can reach a no-load speed of 100r/min, and the stalling torque is 150mNm under a preload of 113 N. The results also denote the motor has a high load-carrying capacity with a maximum load torque of 143mNm and accurate operation with a maximum error of 0.15 mm.

Multi-Axis Electric Stepper Motor

Multi-axis stepper motors offer a compact solution to actuate multiple degrees of freedom in a mechanical system by a single device. This research presents an electric stepper motor with three coaxial shafts driven by a single stator. The motor dimensions are 42 × 42 × 44 mm$^3$ (excluding output shafts), its mass is 0.326 kg and it includes three rotors of height 7 mm and different number of teeth. The maximum torque for one rotor at low speed and 1 A current is 0.10 N m, which is comparable to that of a conventional stepper motor with similar rotor size. When multiple rotors are driven simultaneously, then the total power has to be distributed over the three rotors, resulting in 42% lower torque on average. The maximum no-load speed is 4000 revolutions per minute. The coaxial output shaft configuration poses significant challenges but also unique opportunities in actuating multiple joints of a robotic system. In many applications, the mechanical design can be redesigned to make effective use of the multi-motor design. An example of a three-DOF robot arm is demonstrated that can be efficiently driven by the proposed motor.

Evaluation method for acoustic underwater propulsion systems.

Acoustic underwater propulsion systems based on bulk acoustic waves and surface acoustic waves have been studied. In this study, an acoustic propulsion system that consists of a 2.065-MHz thickness-vibration-mode lead-zirconate-titanate ultrasonic transducer is evaluated. A prototype swimmer is designed and fabricated. The admittance difference of the transducer in water and air is investigated. The vibration amplitude of the transducer is measured to evaluate transducer performance. The acoustic radiation force is calculated to describe acoustic propulsion. The zero-speed propulsion (ZSP) force and no-load speed (NLS) are measured in water. Swimmer movement starts at a NLS of 6.1 mm/s and a ZSP force of 0.2 mN for an input voltage and input power of 12.4 V peak to peak and 0.4 W, respectively. Although the average efficiency of the acoustic propulsion system is 69% in water, the overall movement efficiency of the swimmer is less than 1% because of fluid resistance and wire traction. Based on admittance, acoustic propulsion calculations, ZSP force, NLS measurements, and efficiency analysis, an evaluation method is proposed for optimizing swimmers with an acoustic underwater propulsion system. Small size, high power density, and simple structure of an acoustic propulsion system with an ultrasonic transducer make such systems suitable for applications such as pipeline inspection and repair.

Preload Optimization Method for Traveling-Wave Rotary Ultrasonic Motor

Preload optimization is very important for ultrasonic motors’ design and application. In this paper, a novel method for a traveling-wave rotary ultrasonic motor is proposed. Firstly, based on linear regression and the analytic hierarchy process (AHP), the mapping between the drive characteristics, mechanical characteristics, speed stability, and preload of the traveling-wave-type rotary ultrasonic motor was established. Then, the characteristic curves of stalling torque, no-load speed, maximum efficiency, and speed stability with the change of preload method were measured with a new test platform. Finally, three traveling-wave rotary ultrasonic motors with optimized preload were used in a cooperative manipulator for validation. The experimental results showed that when the preload was optimized from 200 N to 310 N, the stalling torque of the motor increased by 20.7%, the maximum efficiency increased by 15.3%, the standard deviation of the speed decreased by 53.8%, and the no-load speed decreased by 5.5%. Therefore, it can be seen that the new preload optimization approach can significantly improve the performance indexes of ultrasonic motors and meet the practical requirements of direct-drive cooperative manipulators in engineering applications. The new preload optimization method offers advantages in motor output performance compared to conventional methods.

Resonant-type inertial impact piezoelectric motor based on a cam locking mechanism.

A new resonant-type inertial impact piezoelectric motor based on a cam locking mechanism was designed, assembled, and tested. The motor is composed of a stator, a rotor, and other auxiliary components. The cam clamping foot of the stator in contact with the inner surface of the rotor forms a cam locking mechanism, which can make the resonant vibration of the stator effective in a half cycle. By receiving sinusoidal signals, the stator generates bending deformation due to the regular deformation of the piezoelectric plate, which drives the cam clamping foot to move and subsequently causes the rotor to rotate. COMSOL5.4 finite element analysis software was used to design the structure of the piezoelectric motor, and an experimental device was built to evaluate and verify the performance of the motor. The maximum no-load speed of the prototype reached 21.61 rpm and the maximum load torque of the motor was 84 N mm under a driving voltage of 360Vp-p and a driving frequency of 388Hz. The motor achieved a net efficiency of 5.6% under a preload torque of 2 N mm with the same condition. The maximum resolution of the motion angle of the new motor prototype was 0.0748° with a driving voltage of 160Vp-p and the same frequency.

A CFRP/PZT laminated piezoelectric motor with high force density

This work presents a laminated piezoelectric (PZT) motor to achieve high force density, high strength, and compact structure. The oscillator consists of vibration units and a driving foot. Each of the vibration units is formed by symmetrically bonding two PZT ceramics on a carbon fiber-reinforced plastic (CFRP) layer to improve its strength. The oscillator works in hybrid mode of the first longitudinal vibration (L1) and second bending vibration (B2). The finite-element method is adopted to tune the resonance frequencies of the two modes, and the vibration characteristics are experimentally analyzed. The strength test shows that the presence of the CFRP layer can increase the overall strength of the oscillator by 28% compared with a pure PZT motor. To evaluate the performance, the load characteristics of the fabricated prototype (with a size of 39 × 10 × 4.6 mm3 and weight of 10.6 g) are tested on a designed testbed. The single-phase driving method is used to drive the motor, and the best performance is obtained at the B2-mode frequency. The maximum thrust force, no-load speed, and output power reach 17 N, 335 mm s−1, and 775 mW, respectively, at a drive voltage of 100 Vp. Meanwhile, a thrust density of 1604 N kg−1 and an output power density of 73.11 W kg−1 are achieved. The thrust density is much higher than that of the other motors that operate in the same modes.

Design and performance analysis of a novel mechanical flux-adjusting interior permanent magnet motor

In this paper, a novel mechanical flux-adjusting interior permanent magnet (MFA-IPM) motor is proposed. The key is to employ an additional mechanical flux-adjusting (MFA) device attached to one side of the rotor, which can achieve flexible adjustment of the air-gap flux and obtain a wide speed range. This system with appropriate gears uses centrifugal force to set the cylindrical PMs in a required position. The topology and working principle of the MFA-IPM motor are introduced. Then, the dynamic performance prediction between the deformation length of spring and the rotation angles of PMs is obtained by the dynamic simulation. Moreover, the electromagnetic characteristics of the proposed MFA-IPM motor and a conventional IPM motor are analysed and compared based on finite element analysis, including no-load performances, inductances, electromagnetic torque, flux-weakening ability and speed range, as well as demagnetization evaluation. Finally, a prototype MFA-IPM motor is fabricated and tested. Both the simulation and experimental results indicate the validity and feasibility of the MFA-IPM motor.

3D printing and dynamic modeling of a polymer-based bimodal piezoelectric motor

Owing to characteristics of single-step fabrication and rapid prototyping, 3D printing have potential applications in processing piezoelectric motors with complex structures. In this paper, a 3D printed resin-based bimodal piezoelectric motor is proposed. Four slots of the motor are designed to reduce the influence of large damping caused by polymer’s viscoelastic and enhance mechanical properties. Considering the viscoelasticity and internal structure of the stator, a dynamic model based on the proposed motor is developed. Furthermore, parameters of these slots are optimized using the Taguchi method. Prototypes are fabricated and experimentally investigated. The results demonstrate that the first longitudinal mode and the second bending mode are 17 765 Hz and 18 006 Hz respectively, which are consistent with the analytical model results. Under the voltage of 300 Vpp, the maximum no-load speed and maximum driving load of the slotted motor are 200 r min−1 and 20 g with a speed of 6 r min−1, respectively. Compared with the motor without slots, the speed and load capacity are increased by 25% and 33%. Therefore, the motor with slots exhibits better mechanical output performance.

Driving strategy for minimal energy consumption of an ultra-energy-efficient vehicle in Shell Eco-marathon competition

The paper focuses on the different driving strategies (driving cycles) for minimisation of the energy consumption of an ultra-energy-efficient electric vehicle developed by students for Shell Eco-marathon competition. The vehicle runs on hydrogen fuel and completes a set track with a 1420 m length and zero vertical deviation which is used for the 2019 European edition of the contest. A dynamic simulation model of the vehicle is developed taking into account vehicle resistance forces. A simplified model of the propulsion system is also described and used in the simulation. The propulsion system consists of a hydrogen fuel cell with a 1 kW rated power output, electric motors, electric converters, motor controllers and transmission. Furthermore, a strategy overview is proposed by which the vehicle complies with all necessary strategy limitations deriving from the competition rules. The various driving strategies, that comply with the competition average speed and differ from one another by the number of motors and transmission ratio, are simulated. The optimisation is done by changing the maximal and the minimal no-load speeds of the vehicle. A comparison of the energy usage is therefore conducted based on these strategies and the optimal one is chosen. In conclusion, additional driving strategies are proposed, in case more vehicle manoeuvrability or simpler driving style are desired during the race.

A Dumbbell Shaped Piezoelectric Motor Driven by the First-Order Torsional and the First-Order Flexural Vibrations

A piezoelectric motor driven by the first-order torsional and first-order flexural (T/F) vibrations is designed, fabricated, and tested in this study. The actuating force is generated by the torsional vibration of the dumbbell-shaped vibrator, while the elliptical motion shape is adjusted with the flexural vibration. The rotor, pressed onto the vibrator’s lateral surface, is frictionally driven with the vibrator. Here, the torsional vibration, the shear modes of piezoelectric ceramics, and the driving method may contribute to high torque and high output power. To test the feasibility of our proposal, first, a prototype of the T/F vibrator is built and its vibration properties are explored. As predicted, the torsional and flexural vibrations are excited on the vibrator. Then, the load characteristics of the piezoelectric motor are investigated. The maximal torque, the no-load rotation speed, and maximal output power are 4.3 Nm, 125 r/min, and 16.9 W, respectively. The results imply that using the first-order torsional and the first-order flexural vibrations is a feasible method to achieve high torque and high output power of piezoelectric motors.

Field-Testing of Biodiesel (B100) and Diesel-Fueled Vehicles: Part 1—No Load and Highway Driving Emissions, and Acceleration Characteristics

AbstractBiodiesel has emerged as a sustainable renewable transport fuel worldwide. This study investigated the use of biodiesel (B100) and mineral diesel in two identical unmodified vehicles to realistically assess different aspects of biodiesel’s compatibility with modern common rail direct injection (CRDI) diesel engines. Exhaustive experimental results from this series of tests are divided into four segments and no-load engine speed emissions, highway driving emissions, and acceleration characteristics of biodiesel and diesel-fueled vehicles are included in this first paper of the series of four papers. First, the emissions were measured at different engine speeds at no load, when the vehicles were stationary. Thereafter, the real highway driving emissions were measured at different vehicle speeds using on-board emission analyzers. CO and HC emissions from biodiesel fueled stationary vehicle were negligible but relatively higher than mineral diesel-fueled stationary vehicle. NOx emissions increased with increasing engine speed at no-load condition for both stationary vehicles and smoke opacity was also very low for most engine speeds at no load. Among real highway driving emissions, CO and HC from biodiesel-fueled vehicles were ∼13% and ∼30% lower than mineral diesel-fueled vehicles, respectively, at varying vehicle speeds. Emissions of CO2 were not too different in these two vehicles but NOx emissions from biodiesel-fueled vehicle were ∼32% higher than mineral diesel-fueled vehicle. Smoke opacity from biodiesel-fueled vehicle was lower by ∼80% than mineral diesel-fueled vehicle and it didn’t increase with increasing vehicle speed. Acceleration characteristics of biodiesel-fueled vehicle were as good as diesel-fueled vehicle up to a speed of 90 kmph using stock electronic control unit (ECU), however, beyond 90 kmph vehicle speed, the acceleration of biodiesel-fueled vehicle was noticeably lower than baseline mineral diesel-fueled vehicle. This underlines the need for ECU recalibration before the large-scale implementation of biodiesel in existing diesel vehicles.

Novel piezoelectric rotary motor on the basis of synchronized switching control.

A novel piezoelectric rotary motor (PRM) on the basis of synchronized switching control was designed, fabricated, and tested to achieve high speed, high efficiency, and high torque. The new motor mainly consists of a vibrator working in the resonance state as the driving element of the PRM and a clutch working in the quasi-static state to control the shaft for unidirectional rotation. The finite element method software COMSOL Multiphysics 5.4 was used to design the structure of the motor and determine the feasibility of the design mechanism of the PRM. Moreover, an experimental setup was built to validate the working principles and evaluate the performance of the PRM. The prototype motor outputted a no-load speed of 7.21 rpm and a maximum torque of 54.4 N mm at a vibrator driving voltage of 120 Vp-p and a clutch driving voltage of 200 Vp-p. The motor achieved a net efficiency of 15.6% under the preload torque of 3 N mm. The average stepping angle of the motor with no-load was 0.068°, when the voltages applied to the clutch and the vibrator were 200 Vp-p and 120 Vp-p, respectively, with the frequency of 512 Hz.

Rod drive type ultrasonic linear motor with quadruped stator

Piezoelectric motors exhibit advantages such as high force density and linear motion with simple and compact configuration compared to electromagnetic motors. Among them, an inchworm mechanism provides high holding force and thrust, and high positioning accuracy. However, the drawback is its complicated structure combining multiple transducers. On the other hand, an ultrasonic linear motor with quadruped stator can achieve the inchworm movement by using a single rectangular plate transducer, which is advantageous for miniaturization. In this study, we propose a novel ultrasonic linear motor that drives a slider rod inside the quadruped stator to realize a compact linear motion system. A prototype was fabricated and an excitation of each vibration mode and a bidirectional drive was confirmed via experiments. Maximum no-load speed of 258 mm s−1 and maximum thrust of 490 mN were obtained with total length of the stator transducer of 20 mm and its weight of 4.9 g.

A novel multifunctional piezoelectric composite device for mechatronics systems by using one single PZT ring

Piezoelectric ceramics are fascinating function materials and have good electromechanical coupling properties that can be used to develop various types of composite devices. Recently, piezoelectric composite devices with multifunctional demands have been extensively desired due to the remarkable developments of mechatronics systems. This paper focuses on developing a novel multifunctional composite device by using one single PZT ring, in which a piezoelectric actuator, a sensor and an energy harvester are embedded. The composite device is mainly composed of a rotary rotor and a piezoelectric vibrator, the piezoelectric vibrator is formed by a metal elastomer mechanically bonded together with a piezoelectric ceramic ring. The piezoelectric ceramic ring is polarized into three regions to produce the actuating, sensing and energy harvesting functions. The mathematical model of the composite device was derived and validated by experiment. A prototype was fabricated and the experiments including the mechanical, energetic and transient characteristics were performed and discussed. The results indicate that the composite device reaches the maximum torque, no-load speed and mechanical power of 0.674 Nm, 118 rpm and 2.65 W when it is excited by a voltage signal with amplitude 67 V and frequency 40 kHz; the results also show that the maximum extracted power of the composite device reaches 305 mW when the load resistance is 11.6 kΩ, the composite device has a rapid response speed with startup time less than 5 ms and shutdown time less than 1 ms.

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.

Design of two-way self-moving linear ultrasonic motor

This paper designsa two-way self-moving linear ultrasonic motor. The ultrasonic motor is composed of a diamond-shaped metal elastic body, a piezoelectric ceramic piece and a parallel guide rail. There is a slight gap between the driving foot and the parallel guide rail on both sides of the metal elastic body, and the grounded aluminum tube is sandwiched between the diamond-shaped metal elastic body. By exciting the piezoelectric ceramic sheets on both sides of the elastic body, the first-order bending vibration mode is excited to realize the bidirectional movement of the motor. Based on the analysis of the working principle of the ultrasonic motor, the finite element harmonic response analysis of the ultrasonic motor was carried out. A prototype is made for mechanical properties experiments. Experiments show that under the excitation of 200Vpp, the forward and reverse frequency of the ultrasonic motor is 18.18KHz and 18.07KHz, and the forward and reverse no-load speed is 43.76mm/s and 43.14mm/s. The no-load speed is close to.

A Micro Piezoelectric Motor With Multiple Excitation Modes and Methods

To widen the performance of piezoelectric motors, this paper demonstrates a micro piezoelectric motor having multiple driving ways. The stator includes a hollow polygon bar and two groups of PZT plates. PZT plates are symmetrically bonded onto a brass base, and used to actuate the vibration modes of the stator. The symmetrical design enables the motor to operate in two types of vibration modes. The working modes are the second/third-order in-plane bending modes, and can be excited by different ways. Elliptical motion of stator surface points is generated by superposition of two bending modes with the same order. To investigate the feasibility of multi-mode and multi-motivation mechanisms, vibration behaviors of stator driving particles are simulated using ANSYS software. The structural parameters of the stator are strictly designed to harmonize the eigenfrequencies of the vibration modes. The calculated results reveal that the motor performance can be adjusted by selecting different operating modes and excitation ways. The motor performances under various excitation ways and driving modes are also investigated experimentally to validate the proposed design. The dimension of the fabricated prototype motor is 8.3 mm$\times 7.2$ mm$\times 15.0$ mm. The maximum torques are respectively 8.3 cN$\cdot \text{m}$ and 13.3 cN$\cdot \text{m}$ under single-phase and two-phase excitation voltages, when the motor operates in the second-order bending modes. The corresponding no-load speeds are respectively 40 rpm and 47 rpm. The maximum torque and speed under the third-order bending modes are much smaller than that under the second-order bending modes.

A Novel Dual-Rotor Ultrasonic Motor for Underwater Propulsion

Micro underwater vehicles (MUVs) have been highlighted recently for underwater explorations because of their high maneuverability, low price, great flexibility, etc. The thrusters of most conventional MUVs are driven by electromagnetic motors, which need big mechanical transmission parts and are prone to being interrupted by the variance of ambient electromagnetic fields. In this paper, a novel dual-rotor ultrasonic motor with double output shafts, compact size, and no electromagnetic interference is presented, characterized, and applied for actuating underwater robots. This motor was composed of a spindle-shaped stator, pre-pressure modulation unit, and dual rotors, which can output two simultaneous rotations to increase the propulsion force of the MUV. The pre-pressure modulation unit utilized a torsion spring to adjust the preload at the contact faces between the stator and rotor. The working principle of the ultrasonic motor was developed and the vibration mode of the stator was analyzed by the finite element method. Experimental results show that the no-load rotary speed and stalling torque of the prototype ultrasonic motor were 110 r/min and 3 mN·m, respectively, with 150 V peak-to-peak driving voltage at resonance. One underwater robot model equipped with the proposed ultrasonic motor-powered thruster could move at 33 mm/s immersed in water. The dual-rotor ultrasonic motor proposed here provides another alternative for driving MUVs and is appropriate for developing specific MUVs when the electromagnetic interference issue needs to be considered.

Simple bidirectional linear ultrasonic motor driven by single-phase signal

A novel standing wave linear ultrasonic motor with a single source of sinusoidal wave is presented for exciting first-order longitudinal and second-order bending coupling working modes. First, on the basis of a kinematics analysis of the composite piezoelectric beam, the initial motor structure size is created, and the frequency difference of the two working modes of the motor with the initial sizes is 10,950.8 Hz. Second, the initial motor design is optimized according to the subproblem approximation algorithm to obtain the final motor size. The frequency difference in the optimized motor becomes 121.2 Hz. Third, transient analysis of the optimized motor is carried out, and the motion trajectory of the driving foot is an oblique ellipse. Switching the drive electrodes can realize the bidirectional movement of the motor. Finally, the motor prototype is fabricated, and its vibration characteristics and mechanical properties are tested. The maximum no-load motor speed at 96.6 kHz is 168.5 mm/s. The performance in the forward and backward directions is identical according to a test of no-load velocity versus voltage. With 150 Vpp voltage and 10 N preload, the motor’s maximum output thrust is approximately 0.9 N with a moving speed of 16.6 mm/s at 96.6 kHz. The overall motor mass is approximately 3.4 g. Thus, the thrust-to-weight ratio reaches 27.01.

Ring-shaped traveling wave ultrasonic motor for high-output power density with suspension stator

A ring-shaped traveling wave ultrasonic motor with a suspension stator is proposed for improving output power density. Piezoelectric stacks working in d33 mode are involved in the stator, whereas piezoelectric plates employed in classic ring-shaped traveling wave motors often work in d31 mode. Spring-mass systems are used to suspend the stator from the base that supports the motor and provide preload force. The volume of piezoelectric material and the power density of the motor can be easily increased through the suspension structure. Large vibration amplitude of the stator can be generated on the coupling surface. Simulink analysis and finite element analysis are conducted to verify the theory and determine the optimum parameters of the suspension stator with four piezoelectric stacks. The maximum free vibration amplitude of 4.25 µm of the stator is observed, which is nearly 4.7 times of that without suspension. The prototype can work at a maximum no-load speed of 62 rpm and produce a stall torque of 49.5 mN m under a driving signal of 30 Vpp when the mass block is 0.30 g. Furthermore, the higher output power can be expected because more extra stacks can be added in this suspension structure.