Prototype Actuator Research Articles

Considerations on the implementation and modeling of an active mass driver with electric torsional servomotor

The current trend in full-scale applications of active mass drivers for mitigating buildings׳ vibrations is to rely on the use of electric servomotors and low friction transmission devices. While similar full-scale applications have been recently documented, there is still the need for deepening the understanding of the behavior of such active mass drivers, especially as it concerns their reliability in the case of extreme loading events. This paper presents some considerations arisen in the physical implementation of a prototype active mass driver system, fabricated by coupling an electric torsional servomotor with a ball screw transmission device, using state-of-the-art electronics and a high speed digital communication protocol between controller and servomotor drive.The prototype actuator is mounted on top of a scaled-down five-story frame structure, subjected to base excitation provided by a sliding table actuated by an electrodynamic shaker. The equations of motion are rigorously derived, at first, by considering the torque of the servomotor as the control input, in agreement with other literature work. Then, they are extended to the case where the servomotor operates under kinematic control, that is, by commanding its angular velocity instead of its torque, including control-structure-interaction effects.Experiments are carried out by employing an inherently stable collocated skyhook control algorithm, proving, on the one hand, the control effectiveness of the device but also revealing, on the other hand, the possibility of closed-loop system instability at high gains. Theoretical interpretation of the results clarifies that the dynamic behavior of the actuator plays a central role in determining its control effectiveness and is responsible for the observed stability issues, operating similarly to time delay effects. Numerical extension to the case of earthquake excitation confirms the control effectiveness of the device and highlights that different controllers essentially provide similar performances in the mitigation of the structural response.

Shape Memory Epoxy Foams and Composites: Ribes_foam2 Experiment on Spacecraft “Bion-m1” and Future Perspective

Shape memory epoxy foams and composites were tested in April 2013, on board the BION-M1 spacecraft through the Soyuz-2 launch vehicle, with the aim to study their behaviour in microgravity for future applications. The on-orbit Ribes_Foam2 experiment consisted in the heating of three samples in various configurations having different shapes (a prototype of actuator, a sheet of composite laminate and parallelepiped) packed on ground, to evaluate the shape recovery capabilities in the space environment. As expected, micro-gravity does not affect the ability of the samples to recover their shape in these configurations but it poses limits for the heating system design because of the difference in heat transfer on earth and on orbit. In this work, the main results of the experiment are discussed. They have provided useful information for the development of actuators and deployable structure, highlighting future perspectives.

Screw-type actuator driven by piezoelectric transducers

The significant features of screw transmission are effort-saving and self-locking. Based on this, a screw-rod-type actuator is proposed, which is driven by a nut swung spirally together with piezoelectric transducers. The actuator consists of three parts: a nut fastened to a hollow cylinder, a precise screw rod, and two orthogonal piezoelectric vibrators worked on d33 mode. The screw rod is forced to rotate and translate by traveling wave within the helical surface of nut, which is generated by two vibrators. First, the actuator’s running mechanism is preliminarily illustrated. Second, modal analysis and optimal design of the stator are performed through finite element method. Finally, the prototype actuator is manufactured and tested. The experimental results have proven that this driving manner is feasible, and the main characteristics are as follows: the stable working frequency is about at 9.5 kHz, and the maximum no-load speed and output force are approximately 61 r/min and 2.1 N, respectively, under 300 Vpp.

Experimental Validation of a Cogging Torque Assisted Valve Actuation System for Internal Combustion Engines

Electromechanical valve actuation (EVA) is an emerging technology that aims to optimize valve trains, allowing for significant improvements to engine performance, efficiency, and emissions. Recently, a simulation study introduced a novel cogging-torque-assisted motor-driven (CTAMD) valve actuation system. The actuator design emphasized a large output cogging torque that removed the need for conventional valve springs. The cogging torque developed by this actuator allows for highly efficient energy recovery that is superior to comparable systems that make use of mechanical springs. This paper experimentally validates the simulation study with a prototype actuator constructed using the specifications suggested in the previous simulation. The characterization procedure of the prototype is discussed and close agreement is found between the simulated and experimental motor parameters. Furthermore, this paper details a control system that minimizes Ohmic loss while providing fast transition times and low seating velocities. Finally, experimental results are displayed and compared to the simulated results as well as other EVA systems to validate the conjectured speed and efficiency of the CTAMD system.

Design of Voice Coil Type Linear Actuator for Hydraulic Servo Valve Operation

In this study, we proposed governing equations for voice coil type linear actuator for valve operation. We draw up governing equations which are composed by combination of electromagnetic theories and empirical knowledge, and deduct the values of major design factors by use of them. We suggested the governing equations to determine the values of design parameters of linear actuator as like bobbin size, length of yoke and plunger and turn number of coil. And we also calculated the life test time of linear actuator for verification of reliability of the prototype. In addition, for reducing the life test time, the acceleration model of linear actuator is proposed and the acceleration factor is calculated considering the field operating conditions. Finally we have proven the propriety of the governing equations by accelerated life test using the valve assembly adopted the voice coil type linear actuator prototype.

EFFECT OF ELECTRICAL CABLE ON MOVEMENT-RANGE OF AGNETIC ACTUATOR SYSTEM CAPABLE OF INSPECTION IN A PIPE

This paper proposes a magnetic actuator system of a new type capable of inspection in a complex pipe by means of a new motion principle. Using plural vibration components, the magnetic actuator is able to move in the complex pipe. A magnetic actuator of the reversible type, due to opening and closing of a compound material by using elongation and contraction of four shape-memory-alloy (SMA) coils, was fabricated. In this paper, the influence of the electrical cable length on the moving characteristics of the magnetic actuator is discussed. Twenty electrical cables of 0.12 mm diameter were used in this paper. The experimental result shows that the prototype actuator was able to climb at 15.3 mm/s in the straight pipe when pulling a load mass of 50 g. In addition, the result demonstrated that the magnetic actuator system was able to inspect the complex pipe over a distance of 10 m. This actuator system can inspect a complex pipe with an inside diameter from 40 mm to 50 mm. In addition, the actuator system was able to inspect the pipe with a simple apparatus of three amplifiers and one signal generator.

Development of a new ultrasonic actuator based on Langevin bending transducer

A new ultrasonic actuator based on a bending-type Langevin piezoelectric transducer has been developed. An actuator consists of a half-wavelength Langevin transducer and an aluminum plate that is mounted in the middle of the transducer. The driving tip is located at the bottom of the aluminum plate. Piezoceramic rings with opposite polarity within each half of the ring are divided into two groups. Two harmonic signals with shifted phases by π/2 are used to excite the first bending mode of the Langevin transducer and aluminum plate. Elliptical trajectory of the contact point motion is obtained by combining these two bending modes. Numerical modelling was carried out to analyze harmonic response of the actuator and to investigate the trajectories of the contact point motion. Optimization of the aluminum plate design was performed to maximize the parameters of elliptical motion of the driving tip. A prototype actuator was fabricated, and output characteristics were measured. The results of numerical and experimental study are discussed.

Design and implementation of a novel two stage mechanical–magnetic variable stiffness actuator (M²-VSA)

This paper presents the design and implementation of a novel joint-based magnetic actuator for robotic manipulators using variable stiffness mechanism. This new actuator prototype, namely M2-VSA, is developed as an improvement over previous actuators in its class. The robotic arm with M2-VSA joint can safely interact with human operators and work in hazardous conditions. The main novelty in this work is the use of magnetic force in accompanying with springs in a novel arrangement to adjust the joints’ stiffness and mitigate the effect of impact. The theoretical framework and advantages of the design are discussed in detail. Experimental studies through various tests show the effectiveness and efficiency of mechanical–magnetic joint as a safe mechanism in environments where human and robotics have interaction.

Modelling, simulation and characterization of a linear shape memory actuator with compliant bow-like architecture

The design of shape memory alloy actuators typically compromises between force and stroke, the two properties being inversely proportional to one another for any given shape memory alloy element. This article presents a bow-like compliant actuator aimed at improving the specific performance of shape memory wires on both accounts. Conceptually, the actuator is formed by two straight elastic beams mutually hinged at the ends with a pre-stretched shape memory alloy wire in between. Heating of the alloy shortens the wire, which in turn makes the beams to buckle outwards in a symmetric double-arched configuration. The transverse displacement of the beams amplifies the contraction of the wire while producing a favourable output force. This article develops a simple, though accurate, analytical model of the actuator upon which a step-by-step design procedure is built. The theoretical findings are compared with the outcome of a finite element simulation for a case study and with the test data gathered from a physical prototype actuator.

An orientation measurement method based on Hall-effect sensors for permanent magnet spherical actuators with 3D magnet array.

An orientation measurement method based on Hall-effect sensors is proposed for permanent magnet (PM) spherical actuators with three-dimensional (3D) magnet array. As there is no contact between the measurement system and the rotor, this method could effectively avoid friction torque and additional inertial moment existing in conventional approaches. Curved surface fitting method based on exponential approximation is proposed to formulate the magnetic field distribution in 3D space. The comparison with conventional modeling method shows that it helps to improve the model accuracy. The Hall-effect sensors are distributed around the rotor with PM poles to detect the flux density at different points, and thus the rotor orientation can be computed from the measured results and analytical models. Experiments have been conducted on the developed research prototype of the spherical actuator to validate the accuracy of the analytical equations relating the rotor orientation and the value of magnetic flux density. The experimental results show that the proposed method can measure the rotor orientation precisely, and the measurement accuracy could be improved by the novel 3D magnet array. The study result could be used for real-time motion control of PM spherical actuators.

ARES, a variable stiffness actuator with embedded force sensor for the ATLAS exoskeleton

Purpose – The purpose of this study is to present a variable stiffness actuator, one of whose main features is that the compliant elements simultaneously allow measuring of the torque exerted by the joint. Conceived as a force-controlled actuator, this actuator with Adjustable Rigidity and Embedded Sensor (ARES) is intended to be implemented in the knee of the ATLAS exoskeleton for children to allow the exploitation of the intrinsic dynamic during the locomotion cycle. Design/methodology/approach – A set of simulations were performed to evaluate the behavior of the actuator mechanism and a prototype of the variable impedance actuator was incorporated into the exoskeleton’s knee and evaluations of the torque measurements capabilities along with the rigidity adjustments were made. Findings – Mass and inertia of the actuator are minimized by the compact design and the utilization of the different component for more than one utility. By a proper match of the compliance of the joint and the performed task, good torque measurements can be achieved and no bandwidth saturation is expected. Originality/value – In the actuator, the compliant elements simultaneously allow measuring of the torque exerted by the join. By a proper match of the compliance of the joint and the performed task, good torque measurements can be achieved and no bandwidth saturation is expected.

A Prototype of Magnetic Actuator Based on Generalized Magnetoelectric Phenomena: Experiments and Analysis

This paper reports on a prototype of magnetic actuator which is based on generalized magnetoelectric (ME) phenomena. The tested sample was made up of a vertical piezoelectric bender coated with a silver plate and electric wire. Due to the coupling of the piezoelectric layer and Lorentz force in the metal part of the sample, piezoelectric bender’s torsion deformation can be induced by Lorentz force, and thus piezoelectric voltage appeared on the sample. Then, generalized magnetoelectric effect appeared when ac magnetic flux was across the thickness of the beam. Finally, without applying a power source on the specimen, a room temperature magnetic field actuator can be developed by using this piezoelectric beam, from which magnetoelectric voltage coefficient as high as 81.8 mV/cm-Oe can be obtained. In the experiments, the magnetoelectric voltage of piezoelectric beam can be controlled by adjusting ac current, so it is promising to be put into the application of magnetic field sensing and actuating technology.

Haptic Actuator Design Using PMN-PT Ceramic

The study is aimed to design the haptic actuator powered by piezoelectric actuation. Prototype actuator consists mainly of two metallic plate joined with rubbers. PMN-PT ceramics are connected to each of one side of metallic plate and tungsten mass joined at centre of plate to control resonance frequency and vibration force of prototype actuator. This prototype actuator has evaluated 3D finite element method simulation program and has conducted an experiment. The result of experiment has shown vibration acceleration with frequency. This actuator has given 0.15∼0.25 g of vibration acceleration at 180∼230 Hz.

Design of an impact drive actuator using a shape memory alloy wire

This paper introduces an impact drive mechanism (IDM) that utilizes the rapid contraction property of shape memory alloy (SMA) wire. In this study, possible structures for an SMA-wire-based IDM actuator are investigated, and a prototype actuator comprising a main body, an inertia body, an SMA wire, and a bias spring is developed. To verify the applicability of the prototype actuator as a positioning device, driving experiments were conducted under various conditions. The experimental results demonstrated that the prototype actuator enables bidirectional step-like movement with several step sizes by changing the profile of applied voltage, such as amplitude, duty cycle, and frequency. In addition, we developed PI-controller-based position control systems by using these three parameters as control input; the control characteristics and potential applications of each method were discussed. These results implied that the SMA-wire-based IDM actuator has the potential to be used as a new linear actuator in sub-millimeter order driving.

Design and experiment performances of an inchworm type rotary actuator

A piezo-driven rotary actuator by means of inchworm principle is proposed in this paper. Six piezo-stacks and flexure hinges are used to realize large rotation ranges with high accuracy both in the forward and backward motions. Four right-angle flexure hinges and two right-circular flexure hinges are applied in the stator. The motion principle and theoretical analysis of the designed actuator are discussed. In order to investigate the working characteristics, a prototype actuator was manufactured and a series of experiment tests were carried out. The test results indicate that the maximum rotation velocity is 71,300 μrad/s; the maximum output torque is 19.6 N mm. The experiment results confirm that the designed actuator can obtain large rotation motion ranges with relatively high output torques and different rotation speeds on the condition of different driving voltages and frequencies.

CONCEPT AND REALISATION OF AUTOMATED ROOM CLIMATE CONTROL

The paper deals with technical problems of automated decentralised indoor climate control in residential buildings. The lead value for the realisation of the control system is the objective thermal comfort. The measurement system to be designed works as a network between a large variety of different sensors and actuators. A comprehensive and flexible EIB networked instrumentation using cheap commercial and prototype sensors and actuators has been created and tested in a realistic test environment. In the paper, the conditions for a modern room climate control are discussed and the technical base for data acquisition system containing several different data collection channels is presented. Extensive measurements with the reliable, fully redundant data acquisition system showed its applicability in residential buildings. Based on the presented concept, different systems configurations can be realised. Following the results, a low­cost decentralised automated room climate control system is able to become a new standard in low­energy buildings, opening a huge market potential.

Synchronization Control Scheme for Antenna Pointing Control System Based on Hybrid Linear Actuator

To overcome the limitations of the independent stacked hybrid actuator with multiple sensors, a new hybrid linear actuator combines the advantages of both technologies: piezo actuator for extremely high accuracy and motorized stage for long travel ranges. A hybrid linear actuator prototype has been developed for testing in our satellite tracking antenna pointing control system. For the maximum absolute positioning accuracy, host positioning controller depends only on one common position sensor for both the coarse and fine positioning at the same time. Synchronization control scheme shows promising results for extremely small steps, high repeatability and good linearity over long travel ranges.

Variable recruitment fluidic artificial muscles: modeling and experiments

We investigate taking advantage of the lightweight, compliant nature of fluidic artificial muscles to create variable recruitment actuators in the form of artificial muscle bundles. Several actuator elements at different diameter scales are packaged to act as a single actuator device. The actuator elements of the bundle can be connected to the fluidic control circuit so that different groups of actuator elements, much like individual muscle fibers, can be activated independently depending on the required force output and motion. This novel actuation concept allows us to save energy by effectively impedance matching the active size of the actuators on the fly based on the instantaneous required load. This design also allows a single bundled actuator to operate in substantially different force regimes, which could be valuable for robots that need to perform a wide variety of tasks and interact safely with humans. This paper proposes, models and analyzes the actuation efficiency of this actuator concept. The analysis shows that variable recruitment operation can create an actuator that reduces throttling valve losses to operate more efficiently over a broader range of its force–strain operating space. We also present preliminary results of the design, fabrication and experimental characterization of three such bioinspired variable recruitment actuator prototypes.

Design, simulation, and testing of a magnetorheological fluid–based haptic actuator for mobile applications

This article presents a novel design of a miniature haptic actuator based on magnetorheological fluids for mobile applications with the aim of providing various haptic sensations to users in mobile devices. The primary design goal for a haptic actuator for mobile applications is to miniaturize its size while achieving large forces and low power consumption. To this end, this study proposes to design the actuator’s piston head (or plunger) in cone shape and activate multiple modes of magnetorheological fluids. A prototype actuator was designed and fabricated based on a simulation model. Using a dynamic test frame, the performance of the prototype actuator was evaluated in terms of the force (resistive force) produced by the prototype. The results show that the small actuator (10 mm × 10 mm × 6.5 mm) produced a maximum resistive force of about 5 N and the force rate of nearly 80% at 0.3 W. This change in resistive force or the force rate is sufficient to provide several steps of force variation that is explicitly perceivable for operators, depending on the input power. The results demonstrate a feasibility of using the proposed actuator’s applications in mobile devices, conveying realistic haptic sensations to users.

Comparative investigation of permanent magnet linear oscillatory actuators used in orbital friction vibration machine

The paper describes the alternative designs and performances of a single-phase moving-magnet linear oscillating actuator (LOA) which has been developed for orbital friction welding. The influences of the pole ratio on the performance of the LOAs are investigated and the optimal parameters have been identified with reference to the thrust force characteristics. It can be illustrated that a quasi-Halbach magnetized LOA, in which the magnets are assembled on a nonmagnetic mover yoke, represents the best electromagnetic performances. Finally, the predicted thrust force-current characteristic of quasi-Halbach magnetized LOA is validated by measurements on a prototype actuator.