Dual Actuator Research Articles

Lifetime assessment of structural adhesive joints by combining effects of mechanical load, humidity, moisture and UV: design of a test rig

ABSTRACTThis research covers the design of a novel dual-actuator servo-electric test rig for conducting mixed mode fracture testing of adhesively bonded specimens under changing environmental conditions. Typically, fracture testing of such specimens is directly performed on a dual actuator test rig after artificial ageing in a climate chamber. As the cumulated effects of mechanical and environmental loading cannot simply be decoupled, there is a need for combining a climate chamber with a mechanical loading test rig. The resulting rig enables static and dynamic mechanical testing in an ageing environment combining temperature, humidity and UV effects. The test rig will be used to study and validate mixed mode criteria of, amongst others (T)DCB-samples subjected to extreme combined environmental factors. The introduction of this paper extensively discusses documented research on the effects of moisture, temperature and UV radiation on adhesives and adhesive bonds. Based on the specimens to be tested, the requirements of the test rig are defined. In this paper, the necessity for the combined complete test setup, its design and functionalities are described. In order to demonstrate the accuracy of the test rig concerning measured load and displacement, validation tests are presented.

Design and analysis of a nested structure micro-displacement amplification mechanism for a galfenol-based actuator

In this paper, two galfenol rods are arranged in a nested structure to amplify the micro-displacement of an actuator. First, a finite element model of the actuator is developed to analyze the magnetization process of the actuator for different material of the sleeves. Secondly, the mathematical model of the actuator is established using the theory of magnetization, magnetostriction, and structural dynamics to describe the output displacement characteristics of the actuator at different frequencies; the hysteretic behavior of the actuator is taken into consideration and is modeled according to Jiles–Atherton hysteresis model. The experiments and results show that the output displacement of the dual galfenol rods-based actuator is significantly larger than that of a single galfenol rod-based actuator under the same experimental conditions, in addition to that, the proposed nested structure exhibits the advantages of occupying small volume and maintaining response dynamics even at high frequencies. Finally, using the established mathematical model, studies are carried out to analyze the feasibility of further amplification of the output displacement using more than two galfenol rods in a nested structure.

Flexible Gait Enhancing Mechatronics System for Lower Limb Assistance (GEMS L-Type)

This paper presents a novel wearable walking assistance device for the elderly, designed to aid them in their physical gait. In compliance with human motion and the human body, the device not only fits tightly to the lower body of a wearer, but also transmits the assisting torque to the hip/knee joint efficiently and comfortably. To overcome the poor wearability and assistive performance of conventional wearable walking assistance devices, three novel mechanisms are proposed: first, a dual reduction actuator, which makes the mechanism more compact with minimal resistance, second, compliant joints, which adapt to human motion regardless of the wearing state, wearing position, and three-dimensional human joint motions, and third, a flexible foot/ankle mechanism, which helps in rigidly transmitting the assisting force only to the forefoot. The developed wearable walking assistance device based on these mechanisms was validated through experiments.

Design and simulation of an ultrasonic linear motor with dual piezoelectric actuators

In this study, an ultrasonic linear motor with dual piezoelectric (PZT) actuators is developed. A traveling wave motion is generated on the stator by a double-sided excitation of the stator of the ultrasonic linear motor, which drives the slider that is connected to the stator. The development and design processes are described. In this paper, the principle of using an ultrasonic motor to drive a traveling wave type is presented. The structure for the ultrasonic linear motor is then demonstrated with its dimensions, driving conditions and material parameters, so that Computer-Aided Engineering (CAE) can be used to simulate the driving performance. The simulation results show the differences to the characteristics that are achieved by adjusting the critical parameters, such as the PZT boned positions, the excitation frequency and the preload, in order to derive the best design. A prototype that uses the best parameter design is presented, and a method to improve development processes is presented in the final section.

Experimental validation of the Direct Strength Method for shear spans with high aspect ratios

Shear behaviour of cold-formed steel beams with an aspect ratio (shear-span/web-depth) of 1.0 has been studied thoroughly, mainly using central point load tests. However, for beams with higher aspect ratios, the effect of bending causes a reduction of shear capacity and alters the failure modes. This paper introduces a new test setup, the dual actuator test rig, which is equipped with two actuators moving independently at customizable displacement rates to control and minimize applied bending moments in the shear spans of interest. Shear strength close to pure shear capacity can be therefore reached even at an aspect ratio of 2.0. Experimental series recently performed at the University of Sydney on channel section members using the new test configuration is presented. The experimental results together with other available experimental data are combined and used to validate and re-calibrate the Direct Strength Method design formulae incorporated in the AISI S100:2016 Specification and the AS/NZS 4600:2018 Standard.

Design a composite piezoelectric motor using face-shear and longitudinal resonance vibration

A new flexural-wave of a piezoelectric composite motor constructed with d14 and d13 is developed. The piezoelectric motor using dual d14 mode is firstly designed with an output head located in the middle of the structure, which is able to produce two-way motion. However, it is found that the longitudinal deflection is not large enough to preserve appropriate contact with the slider and normal contact force. A composite structure of single-piece ceramic that combines the d14 mode for mainly contributing face-shear deformation and the d13 mode for generating additional longitudinal deflection is thus considered to build. Polarization method is introduced for the composite actuator. Characterization on the detected domain change by Piezoresponse Force Microscopy (PFM) verifies the sequentially poled ceramic workable. The degeneracy process is carried out by using the modal and harmonic analysis of ANSYS simulation to search for a suitable common driving frequency can generate desired deformation. Both analytical and experimental results are in a good agreement. Displacement and speed as well as force output are measured to examine the performance of both actuators. In comparison the dual d14 actuator with the composite d14 + d13 actuator on the condition of nearly same size, the latter one performs better for increasing the longitudinal deflection efficiently. Moreover, by adjusting the phase difference of the driving signal to each the d14 and d13 mode, various types of elliptical motion profile are gained, which provides more options for output performance.

Preliminary Validation of a Cable-Driven Powered Ankle–Foot Orthosis With Dual Actuation Mode

Motor weakness at the ankle joint is a major contributor to locomotor deficits in stroke, as the ankle provides the largest propulsive moment during walking, compared to the knee and the hip joints. In this paper, a novel lightweight powered ankle–foot orthosis (AFO), named Stevens ankle–foot electromechanical (SAFE) orthosis, is presented and evaluated. The prominent feature of the SAFE orthosis relies on its two alternative actuation modes (AMs): 1) fully active and 2) semi-active. The former mode utilizes two BLDC motors to provide ankle plantar- and dorsi-flexion torques, whereas the latter replaces the motor on the dorsiflexion side with a set of linear springs. This design allows direct investigation of how the introduction of a passive antagonistic element may affect the performance of a powered AFOs. Experimental results from both bench-top tests and human walking tests indicate that the performance of the two AMs are comparable in terms of device transparency and torque tracking. Implications of these results for the design of future powered AFOs are discussed in this paper.

A Piezoelectric and Electromagnetic Dual Mechanism Multimodal Linear Actuator for Generating Macro- and Nanomotion.

Fast actuation with nanoprecision over a large range has been a challenge in advanced intelligent manufacturing like lithography mask aligner. Traditional stacked stage method works effectively only in a local, limited range, and vibration coupling is also challenging. Here, we design a dual mechanism multimodal linear actuator (DMMLA) consisted of piezoelectric and electromagnetic costator and coslider for producing macro-, micro-, and nanomotion, respectively. A DMMLA prototype is fabricated, and each working mode is validated separately, confirming its fast motion (0~50 mm/s) in macromotion mode, micromotion (0~135 μm/s) and nanomotion (minimum step: 0~2 nm) in piezoelectric step and servomotion modes. The proposed dual mechanism design and multimodal motion method pave the way for next generation high-precision actuator development.

Disturbance-Estimation Based Adaptive Backstepping Fault-Tolerant Synchronization Control for a Dual Redundant Hydraulic Actuation System With Internal Leakage Faults

In this paper, a fault-tolerant synchronization control (FTSC) algorithm is proposed to deal with the position tracking control problem for a dual redundant hydraulic actuation system (DRHAS) working on active/active (A/A) mode and suffering from internal leakage faults, large disturbances, and force fighting between actuators. Specifically, two reference trajectories are introduced and a novel nonlinear model for the DRHAS is developed to facilitate the synthesis of position tracking control and force synchronization control. Then, a nonlinear FTSC algorithm is proposed by incorporating adaptive control and disturbance rejection control into the backstepping design. In which, a simple reconfiguration mechanism based on faulty parameters online adaptation is adopted to accommodate the faults. The matched and unmatched disturbances in both actuators are estimated by constructing four extended state observers (ESOs) and are compensated in a feedforward way. The stability analysis indicates that the proposed control algorithm can ensure prescribed tracking performance for the system under internal leakage faults and time-varying disturbances, and can make the tracking error of the faulty system converge to zero asymptotically under constant disturbances. Finally, the effectiveness of the proposed control algorithm is verified through comparative simulations.

Unusually fast and large actuation from multilayer polyelectrolyte thin films

Polymers responsive to external stimuli (e.g., electric field, chemical vapor, light) are of great interest for smart materials such as sensors and soft robotics. A vapor-driven multilayer polymer actuator, capable of fast and large-scale actuation, is described here. This Janus-like actuator is prepared with two polyelectrolyte multilayer systems (polyethylenimine (PEI)/poly(acrylic acid) (PAA) and polyurethane (PU)/poly(acrylic acid) (PAA)) using layer-by-layer assembly (LbL). The differing hydrophilicity of these two nanocoatings results in different swelling behavior in water and organic solvents, which leads to vapor-responsive mechanical motion. The bending/curling degree of this polymeric actuator can be precisely controlled by changing the thickness ratio of the two layers. A vapor sensor was constructed to demonstrate the environmental detection ability of this unique actuator.

Dual Quasi-Halbach Linear Tubular Actuator With Coreless Moving-Coil for Semiactive and Active Suspension

This paper proposes the application of a specific topology of coreless linear tubular actuator for semiactive and active suspension systems. The actuator consists of two quasi-Halbach arrays of permanent magnets, inner and outer, and a moving-coil armature. Some of the advantages of this actuator for the proposed applications include low moving mass, low ripple of force, reduced magnetic losses, and high force density. The paper also introduces a new method for determining actuator requirements to operate with an active and/or semiactive suspension system and presents the application of the proposed approach to a harmonically base excited single degree-of-freedom suspension system. Additionally, the electromagnetic model for magnetic field distribution, open-circuit induced voltage, and axial force and force ripple was developed and validated by means of finite-element analysis and with experimental results obtained from a prototype.

Interferometric trigger method with dual piezoelectric transducers for digital holographic interferometry

Recently, it has become necessary to detect cracks in structures such as buildings and bridges. Phase-shifting digital holography is one valuable method that can be used to measure the strain distribution on the surface of an object. However, to simplify the optical measurement setup, more compact equipment is required. An interferometric trigger method with dual piezo actuators for phase shifting is proposed. This method is useful for designing a head discrete-type measurement system that uses phase-shifting digital holography with multiple imaging sensors. The ability to phase shift using the proposed trigger method was confirmed with the reconstruction of an object and an experiment that was performed to measure the displacement distribution.

Adaptive Robust Fault-Tolerant Synchronization Control for a Dual Redundant Hydraulic Actuation System with Common-Mode Fault

This paper investigates the fault-tolerant synchronization control (FTSC) problem for a dual redundant hydraulic actuation system (DRHAS), which works on active/active (A/A) mode and suffers from a kind of common-mode fault (CMF), i.e., internal leakage faults occurring in both hydraulic actuator (HA) channels simultaneously due to a common cause. Firstly, in order to follow the position command and synchronize the force outputs of the two channels, a desired trajectory generator derived from the dynamics of the control surface is employed. Then, considering model uncertainties and nonlinear dynamics of the plant, an FTSC controller is designed based on adaptive robust control (ARC) theory and backstepping technology. The controller parameters, closely related to the fault parameters, are updated online to make the controller adapt to the fault condition only when the system performance degradation exceeds a prescribed tolerable level. It has been verified that the proposed FTSC scheme can guarantee the bounded stability of output tracking error system under common-mode fault. Finally, simulation results under two scenarios demonstrate the effectiveness of the proposed FTSC scheme.

Coupled actuators with a mechanically synchronized phase during MR elastography: A phantom feasibility study

AbstractIntroductionMagnetic resonance elastography (MRE) is an MR imaging method for the quantification of spatial stiffness of soft tissues using mechanically induced dynamic shear waves. In some applications, the penetration of shear waves can be limited through attenuation and shadowing of the waves. In order to increase the actuator performance, we present a dual driver approach to compensate for shear wave attenuation and to achieve better coverage over the entire region of interest.Materials and Methods(a) We designed pneumatic turbines that created a sinusoidal centrifugal force due to an eccentric weight. Two turbines were connected in‐phase with each eccentric weight having the same angular position relative to its pivot point. (b) We developed a tissue elasticity mimicking abdominal phantom. (c) The phantom served as a test object to investigate the feasibility to generate shear waves at two surface origins with the dual actuator system and to compare it against a single actuation setup.Results and DiscussionA stable phase relationship of the shear waves generated by the turbines was achieved as the positions of the eccentric weights were mechanically fixed. The abdominal phantom yielded sufficient MR signal. Liver and rib cage were clearly visible in MR imaging. The shear waves generated by the dual turbine propagated through the region of interest. Our turbine design is reproducible through 3D printing and can be integrated into existing clinical equipment for 1.5 T and 3 T scanners.

Spacecraft attitude control and vibration suppression integration based on single gimbal magnetically suspended control moment gyroscope pyramid configuration

For the sake of improving the agility and super-static performance of spacecraft, this paper puts forward an idea for using single gimbal magnetically suspended control moment gyroscope pyramid configuration to realize dual control of attitude maneuver and micro-vibration suppression of spacecraft, in which gyro gimbal rotation is used to realize fast attitude maneuver and magnetic suspension rotor deflection is used to realize high-precision micro-vibration suppression of spacecraft; the switching design of spacecraft attitude/vibration controller realizes the coordinated operation of gyro gimbal and magnetic suspension motor, showing the control advantage of dual actuators. This strategy not only speeds up the attitude maneuver process of spacecraft, improving the dynamic response, but also reduces the attitude stabilization adjustment time as well as improves the stabilization precision, ensuring the fast vibration suppression after attitude maneuver. In addition, this method has strong robustness ensuring the smooth implementation of spacecraft attitude control and vibration suppression integration in the case of parameter change. The simulation results show the effectiveness and superiority of this strategy.

Mixed-mode crack propagation tests of composite bonded joints using a dual-actuator load frame – Constant and variable GII/GI conditions

The increasing use of high-performance composite materials in primary structures is boosting the interest in structural bonding since it allows for higher mechanical performances under static and fatigue loading conditions. The design of highly efficient bonded structures, however, requires the capability of being able to correctly characterize the bonded joints which usually present multiple failure mechanisms. In this work, crack propagation experiments are performed under mixed mode conditions on composite bonded specimens using a dual actuators loading frame. Three different test protocols are developed and implemented in order to investigate the debonding failure envelope in the GI-GII space. At first, a constant displacement rate is imposed on both the actuators. According to the simple beam theory analysis, large mode mixity ratio variation is expected during the test under such loading condition. As a result, large variation of fracture energy is measured during the test, and crack path bifurcations are observed. Then, two different strategies are proposed to keep the mode mixity ratio constant during the test. When keeping GII/GI ratio constant during the test, stable fracture energy values are recorded all along the crack propagation path with identical fractured surface aspect.

Dual actuation micro-mirrors

This paper investigates the performance of cantilever-type micro-mirrors under electromagnetic, electrostatic and dual actuation. We developed and validated a two-DOFs model of the coupled bending-torsion motions of the mirror and used it in conjunction with experiments in air and in vacuum to compare all three actuation methods. We found that electromagnetic actuation is the most effective delivering a scanning range of ± out of a geometrically allowable range of ± at a current amplitude i = 3 mA and a magnetic field of B = 30 mT. Electrostatic actuation, whether alone or in conjunction with electromagnetic actuation, limited the stable angular range to smaller values (as small as ) due to the presence of spurious piston motions. This is an innate characteristic of micro-scale electrostatic actuation, the electrostatic force and the undesirable piston motion grow faster than the electrostatic torque and the desired angular displacement as the voltage is increased and they limit the stable angular range. Finally, we found that the dual actuation can be used to design two-DOF mirrors where electromagnetic actuation drives angular motion for optical beam steering and electrostatic actuation drives piston motion to control the mirror focus.

Composite Polymeric Membranes with Directionally Embedded Fibers for Controlled Dual Actuation.

In this paper, preparation method and actuation properties of an innovative composite membrane composed of thermo- and pH-responsive poly(N-isopropylacrylamide-co-acrylic acid) fibers (average diameter ≈ 905 nm) embedded within a passive thermoplastic polyurethane (TPU) matrix at different angles with degree of alignment as high as 98% are presented. The composite membrane has a gradient of TPU along the thickness. It has the capability of temperature- and pH-dependent direction-, and size-controlled actuation in few minutes. The stresses generated at the responsive fiber and nonresponsive matrix provide actuation, whereas the angle at which fibers are embedded in the matrix controls the actuation direction and size. The temperature has no effect on actuation and actuated forms at pH 7 and above, whereas the size of the actuated forms can be controlled by the temperature at lower pH. The membranes are strong enough to reversibly lift and release ≈426 times weight of their own mass (2.47 g metal ring is lifted by a 5.8 mg membrane). Soft actuators are of interest as smart scaffolds, robotics, catalysis, drug release, energy storage, electrodes, and metamaterials.

An efficient, compact and low-cost Dual Cylinder Hydrostatic Actuator (DCHA)

Pump-controlled systems are highly efficient alternatives to the high throttling losses of valve-controlled systems. Closed-circuit systems have been widely adopted for rotary loads, but the asymme...

Potential of dual spray injectors for optimising the noise emission of gasoline partially premixed combustion in a 2-stroke HSDI CI engine

This paper evaluates the potential advantages of introducing a new injector concept with a dual set of orifices in a 2-stroke engine operating with gasoline partially premixed combustion (PPC gasoline), specially in terms of combustion noise reduction. The injector is based on a configuration with two concentric needle valves and dual actuators, which allows to switch among two independent crowns of holes. The first set of orifices is controlled by the primary needle valve while an additional needle valve manages the secondary holes crown. Moreover, both valves are coupled with the two actuators separately, providing enhanced selective control over injection with an extra degree of freedom. In this investigation, a combination of Computational Fluid Dynamics (CFD) simulations and the Design of Experiments (DoE) technique is proposed with the specific purpose of optimizing this new injector configuration. In addition to determining the most convenient design, this method is extremely useful to establish cause/effect relationships between the injection design parameters and their impact on the engine performance and emissions. Results show how this solution could increase the operating range of the PPC gasoline concept by improving the combustion stability while acoustic emissions are reduced.