Actuator Setup Research Articles

Development of a bio-MEMS device for electrical and mechanical conditioning and characterization of cell sheets for myocardial repair.

Here we propose a bio-MEMS device designed to evaluate contractile force and conduction velocity of cell sheets in response to mechanical and electrical stimulation of the cell source as it grows to form a cellular sheet. Moreover, the design allows for the incorporation of patient-specific data and cell sources. An optimized device would allow cell sheets to be cultured, characterized, and conditioned to be compatible with a specific patient's cardiac environment in vitro, before implantation. This design draws upon existing methods in the literature but makes an important advance by combining the mechanical and electrical stimulation into a single system for optimized cell sheet growth. The device has been designed to achieve cellular alignment, electrical stimulation, mechanical stimulation, conduction velocity readout, contraction force readout, and eventually cell sheet release. The platform is a set of comb electrical contacts consisting of three-dimensional walls made of polydimethylsiloxane and coated with electrically conductive metals on the tops of the walls. Not only do the walls serve as a method for stimulating cells that are attached to the top, but their geometry is tailored such that they are flexible enough to be bent by the cells and used to measure force. The platform can be stretched via a linear actuator setup, allowing for simultaneous electrical and mechanical stimulation that can be derived from patient-specific clinical data.

UsBot: A Modular Robotic Testbed for Programmable Self-Assembly

We present the design, characterization, and experimental results for a new modular robotic system for programmable self-assembly. The proposed system uses the Hybrid Cube Model (HCM), which integrates classical features from both deterministic and stochastic self-organization models. Thus, for instance, the modules are passive as far as their locomotion is concerned (stochastic), and yet they possess an active undocking routine (deterministic). The robots are constructed entirely from readily accessible components and unlike many existing robots, their excitation is not fluid mediated. Instead, the actuation setup is a solid state, independently programmable, and highly portable platform. The system is capable of demonstrating fully autonomous and distributed stochastic self-assembly in two dimensions. It is shown to emulate the performance of several existing modular systems and promises to be a substantial effort towards developing a universal testbed for programmable self-assembly.

Thickness-Dependent Swelling Behavior of Vapor-Deposited Smart Polymer Thin Films.

In this contribution, the temperature-dependent swelling behavior of vapor-deposited smart polymer thin films is shown to depend on cross-linking and deposited film thickness. Smart polymers find application in sensor and actuator setups and are mostly fabricated on delicate substrates with complex nanostructures that need to be conformally coated. As initiated chemical vapor deposition (iCVD) meets these specific requirements, the present work concentrates on temperature-dependent swelling behavior of iCVD poly(N-isopropylacrylamide) thin films. The transition between swollen and shrunken state and the corresponding lower critical solution temperature (LCST) was investigated by spectroscopic ellipsometry in water. The films’ density in the dry state evaluated from X-ray reflectivity could be successfully correlated to the position of the LCST in water and was found to vary between 1.1 and 1.3 g/cm3 in the thickness range 30–330 nm. This work emphasizes the importance of insights in both the deposition process and mechanisms during swelling of smart polymeric structures.

Vortex Actuation via Electric Ducted Fans: an Experimental Study

The presented work investigates the potential of utilizing commercially available Electric Ducted Fans (EDFs) as adhesion actuators, while providing a novel insight on the analysis of the adhesion nature related to negative pressure and thrust force generation against a target surface. To this goal, a novel EDF-based Vortex Actuation Setup (VAS) is proposed for monitoring important properties such as adhesion force, pressure distribution, current draw, motor temperature etc. during the VAS’ operation when placed in variable distances from a test surface. In addition, this work is contributing towards the novel evaluation of different design variables and modifications to original EDF structures, with the goal of analyzing their effect on the prototype VAS, while optimizing its adhesion efficiency for its future incorporation in a wall-climbing robot for inspection and repair purposes.

Numerical Investigations on Tollmien–Schlichting Wave Attenuation Using Plasma-Actuator Vortex Generators

Recently, plasma actuators have been employed to control laminar-to-turbulent transition in Blasius flow by exciting counter-rotating longitudinal vortices. Due to the resulting momentum redistribution, the vortices generate a spanwise modulation of the flow with regions of high and low streamwise velocity, which are commonly denoted as streaks. In the case of moderate amplitudes, the streaks yield a stabilization of the flow by reducing the amplification of Tollmien–Schlichting waves, and hence delayed transition. In the present work, two fundamentally different actuator setups are investigated: a symmetrical one, exciting counter-rotating vortices; and a nonsymmetrical one, exciting corotating vortices. The differences between these setups are discussed in detail, and the respective stabilization of the flow is scrutinized.

High-contrast imaging at small separations: impact of the optical configuration of two deformable mirrors on dark holes

The direct detection and characterization of exoplanets will be a major scientific driver over the next decade, involving the development of very large telescopes and requires high-contrast imaging close to the optical axis. Some complex techniques have been developed to improve the performance at small separations (coronagraphy, wavefront shaping, etc). In this paper, we study some of the fundamental limitations of high contrast at the instrument design level, for cases that use a combination of a coronagraph and two deformable mirrors for wavefront shaping. In particular, we focus on small-separation point-source imaging (around 1 $\lambda$/D). First, we analytically or semi-analytically analysing the impact of several instrument design parameters: actuator number, deformable mirror locations and optic aberrations (level and frequency distribution). Second, we develop in-depth Monte Carlo simulation to compare the performance of dark hole correction using a generic test-bed model to test the Fresnel propagation of multiple randomly generated optics static phase errors. We demonstrate that imaging at small separations requires large setup and small dark hole size. The performance is sensitive to the optic aberration amount and spatial frequencies distribution but shows a weak dependence on actuator number or setup architecture when the dark hole is sufficiently small (from 1 to $\lesssim$ 5 $\lambda$/D).

Design and Analysis of a Novel 3D Decoupled Manipulator Based on Compliant Pantograph for Micromanipulation

A novel 3D compliant manipulator for micromanipulation is introduced based on pantograph linkage. The proposed manipulator provides decoupled 3DOF translational motions. The key design feature is the use of parallelograms, which maintain the orientation of the end-effector fixed. The proposed manipulator provides advantages over its counterparts in the literature. It has significantly higher workspace to size ratio if its pantograph acts as a magnification device. On the other hand, it has higher resolution if its pantograph acts as a miniaturizing device. This provides great flexibility in the design process to account for the limited variety of the micro-actuators and the large variety of the micro-scale tasks in terms of workspace and resolution. Thus, the proposed system possesses the characteristics of gearing (speed up or speed down). A suitable choice of flexure hinges and material is done. The position and velocity kinematic analysis are carried out. Analytical expressions are derived for singularity-free-workspace boundaries in terms of physical constraints of the flexure joints. Dexterity analysis is performed to evaluate the design performance. A synthesis methodology of the proposed manipulator is developed. A finite element analysis is carried out and a prototype is manufactured to validate the conceptual design. Simulation and experimental results have successfully demonstrated the linearity and consistency between input and output displacements with acceptable parasitic motions. Moreover, the manipulability of the proposed manipulator is found to be configuration independent. Also, the manipulator could have isotropic performance over its workspace for certain actuator setup.

High-Resolution Altitude Profiles of the Atmospheric Turbulence with PML at the Sutherland Observatory

The direct detection and characterization of exoplanets will be a major scientific driver over the next decade, involving the development of very large telescopes and requires high-contrast imaging close to the optical axis. Some complex techniques have been developed to improve the performance at small separations (coronagraphy, wavefront shaping, etc). In this paper, we study some of the fundamental limitations of high contrast at the instrument design level, for cases that use a combination of a coronagraph and two deformable mirrors for wavefront shaping. In particular, we focus on small-separation point-source imaging (around 1 $\lambda$/D). First, we analytically or semi-analytically analysing the impact of several instrument design parameters: actuator number, deformable mirror locations and optic aberrations (level and frequency distribution). Second, we develop in-depth Monte Carlo simulation to compare the performance of dark hole correction using a generic test-bed model to test the Fresnel propagation of multiple randomly generated optics static phase errors. We demonstrate that imaging at small separations requires large setup and small dark hole size. The performance is sensitive to the optic aberration amount and spatial frequencies distribution but shows a weak dependence on actuator number or setup architecture when the dark hole is sufficiently small (from 1 to $\lesssim$ 5 $\lambda$/D).

Discrete Composite Control of Piezoelectric Actuators for High-Speed and Precision Scanning

The scanning accuracy of piezoelectric mechanisms over broadband frequencies is limited due to inherent dynamic hysteresis. This phenomenon has been a key bottleneck to the use of piezoelectric mechanisms in fast and precision scanning applications. This paper presents a systematic model identification and composite control strategy without hysteresis measurement for such applications. First, least squares estimation using harmonic signals is applied to achieve the Preisach density function. Next, the hysteresis output is estimated, such that the non-hysteretic dynamics can be identified. The discrete composite control strategy is proposed with a feedforward-feedback structure. The feedforward controller is the primary component designed for the performance. The secondary proportional-integral (PI) feedback controller is employed to suppress disturbances for robustness. Finally, the identification and composite control strategy is implemented with a dSPACE 1104 board for a real piezoelectric actuator setup. The experimental results indicate that adequate scanning performance can be sustained at a rate higher than the first resonant frequency.

Design of a Twin Hull Based USV with Enhanced Maneuverability

This paper provides an overview of the development of a catamaran-like autonomous surface vessel. The vessel is intended to serve as an experimental platform to study algorithms for control, sensor data fusion as well as path planning and collision avoidance. The mechanical design, the electronics and software architecture is described together with the sensor and actuator setup. The propulsion system comprises of two azimuth thrusters with limited azimuth angles. This concept provides additional degrees of freedom resulting in an overactuated control system. A mathematical model of the vessel has been adapted and implemented for model based control strategies, simulation and hardware in the loop testing. In this paper some results of the parameter identification process are presented. For the overactuated system a control allocation algorithm has been developed.

Numerical Modeling Aspects of Dielectric Elastomer Actuators

AbstractIn modern actuator technology dielectric elastomers are considered as new materials to realize smart actuators which are known as dielectric elastomer actuators (DEAs). In comparison to piezoceramics actuators, DEAs offer the possibility to achieve large deformations with low actuation forces. This property motivates the implementation as artificial muscles since the deformation‐force behavior is similar. Other application fields are pumps, deformable surfaces in aerospace, robotics and haptic feedback.The present work introduces the fundamental concepts to describe the electromechanical coupling in the concept of continuum mechanics for finite deformations.As a benchmark a 3D sandwich actuator setup is taken into account to analyze the mechanical compression stability of the elastomer structure, see [1, 2]. This structure is also considered to study the influence of inhomogeneities in the deformation behavior. For this purpose piezoceramic and air inclusions are considered in the finite element mesh.As a last numerical example an elastomer tube with three pairs of electrodes is simulated numerically to motivate the use of dielectric elastomers as peristaltic pumps. (© 2012 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)

INFLUENCE OF SINTERING CONDITIONS ON DOPED PZT CERAMICS FOR BASE-METAL ELECTRODE MULTILAYER ACTUATORS

The influence of sintering atmosphere and copper addition on the microstructural and piezoelectric properties of Mn -doped lead zirconate titanate ceramics (PZT) was investigated. This ceramic powder densifies below 1000°C, enabling the use of copper inner electrodes for a multilayer actuator setup. To simulate the influence of oxidized inner electrodes during sintering, different CuO contents (0 and 1 mol.%) were mixed to the precalcined Mn -doped PZT powder. Ceramic discs were sintered at 950°C in air and analogously in N2 , or in steam containing N2 (25 vol.% water vapor content). The electrical characterization of the discs showed that the piezoelectric properties are influenced by the CuO addition as well as by the sintering atmospheres. The large signal piezoelectric constant [Formula: see text] shows an improvement of at least 20% when CuO is added. CuO acts as a sintering aid, and especially when the ceramics are fired in steam-containing N2 , anomalous grain growth occurs.

Control performance of a road vehicle with four independent single-wheel electric motors and steer-by-wire system

This article presents a motion controller for a road vehicle equipped with a steer-by-wire system and four independent electric rim-mounted drives. The motion controller separates the control law from the specific actuator setup by the usage of virtual global control variables acting on the vehicle centre of gravity. A control allocation algorithm distributes the virtual control variables to the available actuators. An approximation of the real actuator dynamics is used to analyse the performance of different motion controller types in the linear and nonlinear driving regions. In addition, a vehicle state observer consisting of a traction force observer and an unscented Kalman filter is discussed to analyse the control behaviour in the case of a real sensor setup.

Improved tracking and switching performance of an electro-pneumatic positioning system

For robotic systems that use on/off (solenoid) pneumatic actuators, a sliding mode control law for precise position control and low switching (open–close) activity of the valves is presented in this paper. Given a pneumatic actuator with two chambers and four solenoid valves, there are sixteen possible input combinations defined directly from the state of the four on/off valves present in the system; however, only seven of these discrete operating modes are considered both functional and unique. Therefore, we introduce a novel seven-mode sliding controller that minimizes the position tracking error using modes that have both the necessary and sufficient amounts of drive energy and, thus, involve reduced switching activity. An analysis of the closed-loop system stability is carried out. The performance of the proposed control design is experimentally verified on a single pneumatic actuator setup comprising of two chambers with four on/off valves.

Effect of organo-clay on the dielectric relaxation response of silicone rubber

Dielectric elastomers are light weight, low-cost, highly deformable and fast response smartmaterials capable of converting electrical energy into mechanical work or vice versa.Silicone rubber is a well-known dielectric elastomer which is used as actuator, and in orderto enhance the efficiency of this smart material, compounding of silicone rubber withvarious fillers can be carried out. The effect of organically modified montmorillonite(OMMT) nano-clay on improvement of dielectric properties, actuation stress andits relaxation response was considered in this study. OMMT was dispersed inroom temperature vulcanized (RTV) silicone rubber, and a composite film wascast. Using an in-house actuation set-up, it was shown that the actuation stressfor a given electric field intensity is higher for composites than that for pristinesilicone rubber. Also, the time-dependent actuation response of the samples wasevaluated, and it was shown that the characteristic relaxation time of the actuationstress for composites is less than for the pristine rubber as a result of OMMTaddition.

Thermally driven piezoresistive cantilevers for shear-force microscopy

In this article we will present architecture, properties and application of a novel scanning probe microscopy (SPM) piezoresistive cantilever with thermal deflection actuator. This microprobe with an integrated planar microtip is utilized in shear-force microscopy (ShFM) in which the cantilever microtip vibrates parallel to the surface. We will describe the calibration procedure of sensitivity of cantilever piezoresistive deflection detection, thermal actuation and experimental setup of the developed measurement system. We will also present results of topography measurements of highly oriented pyrolytic graphite (HOPG) and Hafnia alvei bacteria culture surface using developed ShFM system.

Magnetic resonance elastography with a phased‐array acoustic driver system

Dynamic MR elastography (MRE) quantitatively maps the stiffness of tissues by imaging propagating shear waves in the tissue. These waves can be produced from intrinsic motion sources (e.g., due to cardiac motion), from external motion sources that produce motion directly at depth in tissue (e.g., amplitude-modulated focused ultrasound), and from external actuators that produce motion at the tissue surface that propagates into the tissue. With external actuator setups, typically only a single transducer is used to create the shear waves, which in some applications might have limitations due to shadowing and attenuation of the waves. To address these limitations, a phased-array acoustic driver system capable of applying independently controlled waveforms to each channel was developed and tested. It was found that the system produced much more uniform illumination of the object, improving the quality of the elastogram. It was also found that the accuracy of the stiffness value of any arbitrary region of interest could be improved by obtaining maximal shear wave illumination with the phased array capability of the system.

Photon-pressure-induced test mass deformation in gravitational-wave detectors

A widely used assumption within the gravitational-wave community has so far been that a test mass acts like a rigid body for frequencies in the detection band, i.e. for frequencies far below the first internal resonance. In this paper, we demonstrate that localized forces, applied for example by a photon pressure actuator, can result in a non-negligible elastic deformation of the test masses. For a photon pressure actuator setup used in the gravitational-wave detector GEO 600, we measured that this effect modifies the standard response function by 10% at 1 kHz and about 100% at 2.5 kHz.

A novel artificial sphincter prosthesis driven by a four-membrane silicon micropump

In this paper we present the state of the art of our artificial sphincter project. A novel silicon micropump has been designed recently for this system that features a four-membrane actuator set-up. The four-membrane micropump can transport fluid bidirectional with a maximum flow rate of 4.1 ml/min and can build up a back pressure of 60 kPa. The total size of the micropump is 30 mm × 12 mm × 1 mm. The novel pump is modeled by a lumped-parameter approach and compared to our three-membrane design. The main advantage of an additional membrane is a reduction of the driving frequency of the micropump while the flow rate remains the same compared to a three-membrane model. Consequently, the power consumption of the micropump can be reduced. A reliability analysis shows that the four-membrane micropump is more reliable then our previous design. The micropump was integrated into the artificial sphincter prosthesis. The first in vivo experiment is described and the measured data of the prosthesis implanted in a mini pig are given.

Experimental and Analytical Identification of a Delamination Using Isolated PZT Sensor and Actuator Patches

Delaminations in laminated composite structures are usually invisible or difficult to detect by visual inspection, and thus, cost-effective and reliable non-destructive techniques and approaches need to be developed to detect such failures for structural health monitoring. In this study, a dynamic analytical model is developed to detect a through-the-width delamination embedded in a cantilever laminated composite beam. This beam is surface-bonded with an isolated piezoelectric lead-zirconate-titanate (PZT) sensor and a PZT actuator. The PZT actuator located near the fixed end of the composite beam is used to excite the beam system using a sinusoidal input voltage. The PZT sensor with a striped electrode pattern is bonded on the top surface of the beam section embedded with a delamination and is used to monitor the output voltages recorded from the electrode strips. To study the feasibility of the present model for delamination identification, an experimental investigation is conducted to detect an embedded delamination using this PZT sensor and actuator setup. A comparison of the first three frequencies and the output voltage distribution for the case of the first frequency between the predicted and measured results is carried out, and good agreement between them is noted. Numerical study using the present analytical model reveals that the output voltage distribution along the PZT sensor is closely related to the magnitude and frequency of the sinusoidal input voltage.