Conventional Electromagnetic Motors Research Articles

Permanently magnetized elastomer rotating actuator using traveling waves

We report a soft actuator that generates continuous rotation of an object placed on it by electromagnetically exciting circular travelling waves in a soft disk. The disk, that serves as the stator, is made of a stretchable composite consisting of segments of silicone elastomer in which hard ferromagnetic particles are embedded. Inspired by piezoelectric traveling wave rotary actuators, the disk’s 16 sections are driven by underlying printed circuit board coils to create a flexural traveling wave on the disk’s surface. The rotor can be any object directly placed on the stator: the traveling wave in the stator leads by friction to the rotation of the rotor. Unlike conventional electromagnetic motors that rely on a precisely controlled gap between stator and rotor, a concept incompatible with soft robotics, our device exploits the contact between rotor and stator and the associated dry friction to generate torque. Rotation speeds of over 6 rpm were obtained for a partially rice-filled balloon, 30 cm diameter, weighing 17 g. We report detailed speed and performance metrics when rotating plastic disks. With this rotating actuator, we demonstrate an innovative way to transmit torques and rotations within soft structures.

Motion Accuracy of Pneumatic Stepper Motor-Driven Robotic System Developed for MRI-Guided High-Intensity Focused Ultrasound Treatment of Prostate Disease

The latest advancement in high-intensity focused ultrasound (HIFU) treatment technology integrates magnetic resonance imaging (MRI) guidance for precise treatment of prostate disease. As conventional electromagnetic motors are not applicable for utilization within MRI scanners, we have developed a prototype robotic system driven by pneumatic stepper motors to control the movement of the HIFU transducer within an intrarectal probe during MRI-guided HIFU treatment procedures. These pneumatic stepper motors were constructed entirely from MRI-compatible plastic materials. Assessment of the robotic system’s MRI compatibility was conducted utilizing a 3.0T MRI scanner, revealing no discernible MRI image distortion with a minor decrease in the signal-to-noise ratio (2.8%) during the motor operation. The robotic system enabled the transducer to move inside the probe with two degrees of freedom, allowing both linear and rotational motion. The positional accuracy of the transducer movement was assessed, yielding ±0.20 and ±0.22 mm accuracies in the forward and backward linear movements, respectively, and ±0.79° and ±0.74° accuracies in the clockwise and counterclockwise rotational motions, respectively. Emulation of authentic HIFU procedures involved creating a two-dimensional array of thermal lesions in a tissue-mimicking phantom, achieving positional accuracy within ±1 mm for the generated HIFU focal spots. The prototype robotic system incorporating pneumatic stepper motors fabricated entirely from MRI-compatible plastic materials has demonstrated the requisite positional accuracy necessary for effective HIFU treatment of prostate disease, indicating substantial promise for future clinical application.

Enhanced SLF radiation efficiency in a piezoelectrically driven magnetic pendulum transmitter

Long-wave radio station based on an electrically small antenna and mechanical transmitter based on a rotating permanent antenna are commonly used for super low frequency (SLF, 30–300 Hz) communication. The current challenge is the difficulty in developing both an efficient and a miniaturized SLF transmitter. Enlightened by the advantages of piezoelectric motor over conventional electromagnetic motor in terms of efficiency and the output torque in low frequency band, we propose a piezoelectrically driven magnetic pendulum transmitter by combining a magneto-mechano-electric (MME) cantilever and a swinging magnet in this work. The magnetic force coupling between the MME cantilever and the swinging magnet is optimized by changing the thickness and the attached position of the used Metglas laminates. The experimental results show that the piezoelectrically driven magnetic pendulum transmitter has a working frequency of 57 Hz, and a flux density of 149 f Tpk at 100 m distance could be expected with a low power consumption of 40.64 mW. When driving the same magnet with an electromagnetic motor, however, the required power consumption reaches 4.2 W for 57 Hz magnetic field radiation. By dividing the induced magnetic moment over the consumed power, the effective radiation efficiency of our proposed piezoelectrically driven SLF magnetic pendulum transmitter significantly increased from 0.55 to 17.4. This proof-of-concept work is believed to open a dimension for the design and the application of efficient SLF mechanical transmitter in the future.

Special Issue on State-of-the-Art Actuators: Design, Analysis, Control, Materials, Systems, and Applications

Actuators are components that are essential to the moving, manipulating, or deforming of objects. Historically, conventional electromagnetic motors as well as pneumatic and hydraulic actuators have been developed to sophistication. In the past several decades, however, many other kinds of actuators based on novel principles have also been proposed. These have employed physical or/and chemical effects, such as piezoelectric, electrostatic, or giant magnetostrctive effects, as well as thermal expansion, phase transformation, or ion mobility in polymers. Not only the novel actuators but also conventional ones have been continually evolving in astounding ways. These actuators have been embedded not only in conventional machines but also in smart ones, such as artificial muscles for robots and power assist systems, electric vehicles, and machine tools. By combining the actuators with the Internet of Things (IoT), they are also used to test equipment. In addition, there is no doubt that the technologies involved in the development of novel actuators and the improvement of their efficiency are key to the achievement of Sustainable Development Goals (SDGs), as actuators currently consume a huge aggregate amount of energy. In sum, actuators have the potential to be central to the development of innovative machines. This special issue features one review, six research papers, and three technical papers on the most recent advances in various types of actuators. These papers cover topics that include magnetic levitation technologies for precision motion control, electromagnetic motors, fluid power actuators, electrostatic actuators embedded in micro-electromechanical systems, and an ultrasonic motor, plus their applications. All the papers were refereed through careful peer reviews. I believe that this special issue will help the readers to enhance their understanding and knowledge of actuators and their applications. I would like to express my sincere appreciation to the excellent contributions of all the authors, and I appreciate the incisive efforts of reviewers in producing this special issue.

Self-shaping building skin: Comparative environmental performance investigation of shape-memory-alloy (SMA) response and artificial-intelligence (AI) kinetic control

This paper presents the first controlled experimental investigation on the environmental performance of self-shaping adaptive façade, which is a kinetically-responsive building skin activated by smart material. Although adaptive façade is an emerging subject in architectural design and research, its effectiveness has been rarely addressed in terms of building performance. Thus, in this study, we investigated indoor temperature and daylight illuminance of a thermo-responsive skin actuated by shape-memory alloy (SMA). For comparative analysis in a controlled situation, two identical lab-scale (1:20) building models with kinetic louver shading were designed, representing a south-oriented living room of 3.4 m✕5.2 m. The shadings were climate-adaptively operated by a conventional electromagnetic motor (baseline) and an SMA actuator (test case), respectively, for the same time period. The mechanical characterization and simulation of SMA-bias coil spring actuation were studied, and an artificial neural networks (ANNs) model was employed for the baseline's optimal dynamic control to approximate the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) Standard for thermal comfort (19.4–27.8 °C) and a minimum illuminance level of 500 lx. The study's findings indicate that SMA actuation is effective for controlling indoor daylight intensity, thereby improving overall indoor environmental conditions. Nevertheless, the climate-responsive self-shaping was not as instantaneous as the optimal kinetic control. Average performance was probabilistically different; however, a significant correlation was found in illuminance variation.

Flexural Deflection Prediction of Piezo-Composite Unimorph Actuator Using Material Orthotropy and Nonlinearity of Piezoelectric Material Layer

Layered piezo-composite unimorph actuators have been studied by many research teams to provide active vibration control of thin-walled aerospace structures, control the shapes of aircraft wing airfoils, and control the fins of small missiles, because they require less space and provide better frequency responses than conventional electro-magnetic motor actuator systems. However, due to the limited actuation strains of conventional piezo-composite unimorph actuators with poly-crystalline piezoelectric ceramic layers, they have not been implemented effectively as actuators for small aerospace vehicles. In this study, a lightweight piezo-composite unimorph actuator (LIPCA-S2) was manufactured and analyzed to predict its flexural actuation displacement. It was found that the actuated tip displacement of a piezo-composite cantilever could be predicted accurately using the proposed prediction model based on the nonlinear properties of the piezoelectric strain coefficient and elastic modulus of a piezoelectric single crystal.

Piezoelectric Devices in the Sustainable Society

Our 21st century faces to a “sustainable society”, which enhances (a) usage of non-toxic materials, (b) disposal technology for existing hazardous materials, (c) reduction of contamination gas, (d) environmental monitoring system, (e) new energy source creation, and (f) energy-efficient device development in the piezoelectric area. With reducing their size, the electromagnetic components reduce their efficiency drastically. Thus, piezoelectric transducers with much less losses are highly sought recently. Piezoelectric devices seem to be all-around contributors and a key component to the above mentioned five R&D areas. Some of the efforts include: (a) Since the most popular piezoelectric lead zirconate titante ceramics will be regulated in European and Asian societies due to their toxicity (Pb2+ ion), lead-free piezoelectrics have been developed. (b) Since hazardous organic substances can easily be dissolved by the ultrasonic irradiation in water, a new safe disposal technology using piezoelectric transducers has been developed. (c) We demonstrated an energy recovery system on a hybrid car from its engine’s mechanical vibration to the rechargeable battery. (d) Micro ultrasonic motors based on piezoelectrics demonstrated 1/20 reduction in the volume and a 20-time increase in efficiency of the conventional electromagnetic motors. This paper introduces leading piezoelectric materials, devices, and drive/control methods, relating with the above “sustainability” technologies, aiming at further research expansion in this area.

Modelling and parametric design of a pneumatic soft stepper motor

This paper presents model-based design of a Pneumatic Soft Stepper Motor (PSSM). This motor is inspired by the conventional electromagnetic stepper motors and the Wankel rotary engines, leveraging the principles of pole difference and pressure eccentricity. It is actuated by sequential inflation and deflation of the soft chambers on inner circumference of the stator to apply eccentric pressure on teeth of the rotor, and thus to produce the rotation torque. From equilibrium of the drive and load torques, the Switching Phase Space (SPS) model is constructed to describe rotation behaviors of the PSSM. Based on the model, the parameter design is discussed when considering the torque and speed characteristics of the motor in different drive modes (wave-drive, half-step and full-step drives) and with different inflating pressures. Furthermore, the model-based design rules are verified by FEM simulations.

A novel piezoelectric inertial rotary motor for actuating micro underwater vehicles

With developments of micro-machining and advanced functional materials, smart actuators have been developed and applied in various micro underwater vehicles (MUVs) or micro underwater robots. Since there is a tradeoff between the miniature size and output performance for MUVs driven by traditional electromagnetic motors, piezoelectric motors with features of compact structure, large force or torque at small size and no electromagnetic interference provide another promising alternative for actuating MUVs. However, there is a few research to explore the possibility of utilizing piezoelectric motors to realize underwater actuations. In this paper, a novel piezoelectric inertial rotary motor is designed to power the underwater vehicle, which is capable of forward swimming, rotating, rising and diving. This motor consists of two rotors and one disk type stator. One piece of piezoelectric wafer adhered to the bottom face of the stator’s metal disk is used to excite the radial in-plane vibration mode of stator’s outer ring, which is converted into the revolved motion of the inner tube through the connection beams. To utilize the inertial driving mechanism, the motor works at a “slip-slip” mode by the saw-tooth type driving signal. One prototype motor with the appearance size of Φ 20 mm × 20 mm and weight of 3.6 g is designed, fabricated and characterized. Experimental results show that the prototype motor could rotate at a steady speed of 2200 r/min with 150 Vp-p driving voltage. In addition, the motor also performs well with a slightly decrease of operating speed in underwater environments when the silver electrode is coated by waterproof material. Consequently, sealing ring is not necessary for the proposed motor as immersed in water, which is different with conventional electromagnetic motors and enables the actuation unit to be smaller. And then, the prototype motor is coupled with a propeller to build a thruster, which could output the steady speed and maximum propulsion force of 1200 r/min and 4.6 mN, respectively. Finally, the thruster is installed in a spherical swimming robot, and the velocity of the robot could reach 80 mm/s. With merits of simple structure, compact size and great waterproof feasibility, the proposed piezoelectric inertial motor opens a new avenue for developing advanced and flexible MUVs.

Continuous high-performance drive of rotary traveling-wave ultrasonic motor with water cooling

It is known that rotary traveling-wave ultrasonic motors (RTUSMs) have several inherent advantages over conventional electromagnetic motors. However, the practical applications of RTUSMs are limited in the field of transitory servo drive. The underlying reason is that the temperature rise caused by internal losses has a significant influence on the motor characteristics, which gives rise to substantial performance degradation and poor operational reliability. To explore the feasibility of RTUSMs in the applications of continuous motion drive, we propose to maintain the output performance by directly suppressing the working temperature rise. Based on convective heat transfer, a water-cooling motor base was designed to remove heat from the stator. The motor base was fabricated by embedding a simple pipeline structure and connected to a commercial PC water-cooling radiator. The experimental results show that the RTUSM60 motor maintains an output power of 3.3W and a temperature rise of 22°C during 48-h continuous operation with water cooling. Due to the effective suppression of temperature rise, the motor can work with a stable output power of 2.35W even under the load torque of 0.9Nm.

A novel in-plane mode rotary ultrasonic motor

Ultrasonic motors have the merits of high ratio of torque to volume, high positioning precision, intrinsic holding torque, etc., compared to the conventional electromagnetic motors. There have been several potential applications for this type of motor in aerospace exploration, but bearings and bonding mechanism of the piezoelectric ring in the motors limit the performance of them in the space operation conditions. It is known that the Langevin type transducer has excellent energy efficiency and reliability. Hence using the Langevin type transducer in ultrasonic motors may improve the reliability of piezoelectric motors for space applications. In this study, a novel in-plane mode rotary ultrasonic motor is designed, fabricated, and characterized. The proposed motor operates in in-plane vibration mode which is excited by four Langevin-type bending vibrators separately placed around a ring-shaped stator. Two tapered rotors are assembled to the inner ring of the stator and clamped together by a screw nut. In order to make the motor more stable and convenient to fix, a thin cylindrical support is placed under the stator ring. Due to its no-bearing structure and Langevin transducer excitation, the prototype ultrasonic motor may operate well in aeronautic and astronautic environments.

A novel piezohydraulic aerospace servovalve. Part 1: design and modelling

Servovalves are compact, accurate and high-bandwidth modulating valves widely used in aerospace, defence, industrial and marine applications. However, manufacturing costs are high due to high part count and tight tolerances required, particularly in the first stage of the valve, and due to manual adjustments required as part of the set-up process. In this research, a novel servovalve concept is investigated that has the potential to be more cost-effective. In particular, for the first time, a piezoelectric first-stage actuator is developed to move a servovalve spool using the deflector jet principle; this is especially suited to aerospace actuation requirements. In the new valve, the conventional electromagnetic torque motor is replaced by a multilayer bimorph piezoelectric actuator. The bimorph deflects a jet of fluid to create a pressure differential across the valve spool; hence the spool moves. A feedback wire is used to facilitate proportional spool position control via mechanical feedback. The bimorph is directly coupled to the feedback wire and is immersed in hydraulic fluid. A high-order non-linear model of the valve has been developed and used to predict valve static and dynamic characteristics and is described in this article. This makes use of stiffness constants derived analytically for the bimorph-feedback wire assembly and cross-referenced to finite element analysis predictions. The model of the flow force acting on the deflector is an approximation of the force characteristic found from computation fluid dynamic analysis. The measured characteristics of the prototype valve are in good agreement with the simulation results and prove that the operational concept is viable.

A Novel Ultrasonic Motor Driver Based on Two Phase PWM Signals

An ultrasonic motor (USM) has been widely used in many applications since it has several advantages over the conventional electromagnetic motor, such as high torque at low speeds, no electromagnetic interference, and high holding torque without power supply. However, in order to achieve high efficiency, its electrical drive system presents unique challenges, especially in producing two-phase signal (high frequency, high voltage, phase difference of two-phase signal) input to a low impedance capacitive motor. In this paper, a novel drive system based on microcontroller (ATmega16) has been proposed for ultrasonic motor. Drive system includes power drive circuit and control system. Power drive circuit is combined from Push-Pull Inverter to provide high-frequency two-phase voltages. A microcontroller was used to control ultrasonic motor drive system. PWM signals were generated and then directly applied to the MOSFET drivers for speed control of ultrasonic motor. The frequency and phase difference of two phase PWM signals can be directly changed by microcontroller. Detailed experimental results are provided to demonstrate the successful of the proposed drive system.

Comparative Assessment of Several Nutation Motor Types

A new type of pneumatic stepping motor, named a nutation motor, has been developed. By using a simple mechanism in a compact body, this motor can generate high torque. The nutation motor consists of three small linear pneumatic actuators and a gear-reduction mechanism that transforms their motion into rotation of the output shaft. Driving each pneumatic actuator sequentially with pneumatic digital signals results in nutation of the input bevel gear, which causes the output shaft to rotate. In this paper, the structure, working principle, and theoretical characteristics of a pneumatic nutation motor are presented. The design and fabrication of five prototype models and the results of experimental evaluations are also reported in detail. The prototype motors range in size from 10 to 50 mm in diameter and from 11.5 to 49 mm in length. It was found that the torque/volume ratios of the pneumatic nutation motors were about 2-29 times larger than those of a typical conventional electromagnetic geared motor.

Ultrasonic motors: Their models, drives, controls and applications

In the last decades piezoelectrically driven ultrasonic motors have become alternative actuators to the conventional electromagnetic motors especially for precise and accurate servo positioning applications. Different types of ultrasonic motors have been constructed and manufactured. Several drive systems have been designed, implemented and proposed for these motors. A variety of control techniques have been applied to them. The research given in this study covers bases of the ultrasonic motors. Theoretical background, modeling, drive systems, control techniques and applications of the ultrasonic motors have been introduced. Firstly, the general overview has been given. Then, modeling studies focused on performance estimation and analysis of ultrasonic motors have been examined. Afterwards, drive systems and control techniques of ultrasonic motors have been investigated. Furthermore, an example drive and control system has been presented. This drive system has been designed as to be controlled digitally. In addition, the important industrial and research applications of these motors have been included. The presented study has been arranged as a review of ultrasonic motors. The important points of specifications, models, drive systems and control methods of the ultrasonic motors have been emphasized.

Robots will be of service with muscles, not motors

PurposeAims to project how electroactive polymer will replace conventional electromagnetic motor driven solutions for service and industrial robots.Design/methodology/approachPresents the ability of electro active polymer to provide higher power density for robot actuation over conventional approaches. Laboratory tests by DARPA compared electroactive polymer with conventional electromagnetic methodologies as well as shape memory alloy and piezo solutions.FindingsTests by DARPA and SRI International showed significant power density advantages for electroactive polymer artificial muscles (EPAM). Robot prototypes and well as early commercial prototypes developed by Artificial Muscle, Inc. in pumps, valves, and actuators prove superior performance over other actuation solutions.Originality/valueIntroduces a new low cost, low power consumption, light weight, and silent method for actuation for robots and other motion control devices.

Vibration analysis of stepping piezoelectric micro-motor using wiggle mode

Piezoelectric ultrasonic motor, a fractional horsepower motor, is different from conventional electromagnetic motor. It combines the features such as lightweight package, high driving torque at low speed, quick response, low consume, zero backlash, self-braking at zero power, no electromagnetic disturbance and noise, and high heat-stability in wicked environment. In this paper, we propose a new type of stepping piezoelectric micro-motor using wiggle vibration mode and three-dimensional contacts between the rotor and stator. Micro-vibration behavior and vibration mode shape of the prototype have been investigated using advanced POLYTEC PSV-300-F laser Doppler vibrometer. The piezoelectric micro-motor has potential applications for camera auto focus lenses, medical apparatus, micro-robots, micro-satellites, precise positioning, micro-machining, aerospace instruments, laser communication, etc. Here, using such two piezoelectric motors an improved manipulator with two degrees of freedom has been realized.

Compact piezoelectric ultrasonic motors

This paper reviews recent developments of compact ultrasonic motors using piezoelectric resonant vibrations. Following the historical background, ultrasonic motors using the standing and traveling waves are introduced. Driving principles and motor characteristics are explained in comparison with the conventional electromagnetic motors.

A high-power electrostatic motor using skewed electrodes

This paper describes a new type of high-power electrostatic motor equipped with skewed electrodes. The authors have developed several types of high-power electrostatic motors. Among them, the dual excitation multiphase electrostatic drive (DEMED) has the best performance in terms of power. Its power/weight ratio is almost the same as that of the most advanced conventional electromagnetic motors. However, DEMED exhibits a large force ripple leading to such disadvantages as low controllability, high noise, and vibration. To overcome these disadvantages, the authors have proposed to apply the skew technique to DEMED and have analyzed the effects of skewing the electrodes. The analysis has shown that appropriate skewing can reduce the force ripple considerably. In this paper, we further analyze the shape of the electrodes. A new type of motor incorporating the results of the analysis is fabricated and tested. Using the new DEMED with skewed electrodes (V-DEMED), the slider motion becomes much smoother, noise and vibration are reduced, and efficiency improves, without compromising the thrust force. © 1998 Scripta Technica, Electr Eng Jpn, 125(3): 50–58, 1998

Piezoelectric ultrasonic motors: overview

This paper reviews recent developments of ultrasonic motors using piezoelectric resonant vibrations. Following the historical background, ultrasonic motors using standing and traveling waves are introduced. Driving principles and motor characteristics are explained in comparison with conventional electromagnetic motors. After a brief discussion on speed and thrust calculation, finally, reliability issues of ultrasonic motors are described.