Conclusions Measurements of iron losses on SMC ring samples of different sizes showed that the total loss per mass unit was depending on the component size.. Introduction The modern appl
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Total Ring Losses
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Figure 13 Ring samples 1A, 1B, and 2–5 Measured and simulated total loss at different frequencies
using a modified conductivity and established factors for the hysteresis loss
The correspondence between measured and calculated values is good From Table 5 it can also be seen that the values of hysteresis loss are very close between the different ring samples
Total loss comparison
Simulations of total losses were carried out using the modified measured conductivity to simulate the eddy currents Hysteresis losses were calculated from simulated B-field and the built-in iron loss model, using the established values of Kh andα The measured and
simulated losses for ring samples 1A, 1B, and 2-5 are summarized in Fig 13 It can be seen that the simulated values corresponds quite well with measurements
An evaluation of the three logical series gave no extra information except that bigger components have higher eddy current losses What can be noticed is that regardless the ring
or components size the simulated and measured results are very close to each other except the small ring samples where the eddy currents are slightly underestimated
Conclusions
Measurements of iron losses on SMC ring samples of different sizes showed that the total loss per mass unit was depending on the component size Bigger SMC components have higher eddy current losses
It is also shown that it is possible for SMC materials to find factors for eddy current and hysteresis losses resulting in good agreement between FEA simulations and measure-ments
Trang 2III-3.2 Loss Calculations for Soft Magnetic Composites 433
References
[1] P Jansson, A Jack, “Magnetic Assessment of SMC materials” Twenty first Conference on Properties and Applications of Magnetic Materials, Chicago, May 13–15, 2000
[2] JMAG-Studio from the Japan Research Institute Ltd Engineering Technology Division 16, Kudan Building 2F, 1-5-3, Kudanminami, Chiyoda-ku, Tokyo 102-0074, Japan
Trang 3III-3.3 ELECTROACTIVE MATERIALS: TOWARD NOVEL ACTUATION CONCEPTS
B Nogarede, Jean-Fran¸cois Rouchon and Alexis Renotte
Electrodynamics–EM3 Research group, Laboratoire d’Electrotechnique et d’Electronique Industrielle INPT-ENSEEIHT, UMR-CNRS n◦5828, 2 rue Charles Camichel,
31071 Toulouse, France
Bertrand.Nogarede@leei.enseeiht.fr, Jean-Francois.Rouchon@leei.enseeiht.fr,
Alexis.Renotte@leei.enseeiht.fr
Abstract After a brief recapitulation of diverse physical processes which can be used in
elec-tromechanical energy conversion, the present article proposes a survey of the modern stakes of electrodynamics in the range of centimetric or decimetric dimensioned actuators The potential of the new technologies considered is evaluated through different examples of novel actuators which aim at meeting the increase of the performances or the expansion of required functionalities in the face of varied types of applications An experimental study concerning friction drag reduction for a supersonic aircraft is briefly dealt with at the end of the article The aim is the control of turbulent streaks with spanwise traveling wave A piezoelectric demonstrator was designed for wind tunnel testing at different configurations of frequency and wave-length
Introduction
The modern applications of electromechanics is characterized by a more and more inten-sive integration of actuator and sensor functions within mechanisms allying high mass performances and advanced functionalities Recently accomplished progress in the field
of electroactive materials (piezoelectric, electrostrictive ceramics, magnetostrictive alloys, shape memory alloys) reveal a very promising field of innovation aiming at ending up in high mass performance devices with a high functional integration level besides [1] The present article proposes a non-exhaustive survey of new electrodynamic device stakes in the face of diverse types of emerging applications
A wide variety of exploitable effects
In the centimetric dimensional field considered, the design of electroactive actuators con-stitutes a real technological brake Let it be underlined that this potential essentially hangs
on the possibility of generating high specific efforts (driving constraints to the order of 40 MPa in the PZT piezoelectric ceramics or to the order of 100 MPa in shape memory alloys)
in a reduce bulk (the energy conversion is operated in the very volume of the materials) Of course, the amplitude of the elementary displacements produced by the transducers remains limited (relative strain to the order of 1,000 parts per million for multi-layer piezoelectric
2006 Springer.
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Figure 1 Comparison of the various electromechanical effects in terms of specific energy [3].
ceramics and of 8,000 ppm in the case of shape memory alloys [2]) Nevertheless, the possibility of cumulating these microdisplacements in space (e.g., by using the flexion
of a beam), or in time (thanks to the transmission of a high frequency vibratory move-ment by intermittent contact) gives rise to remarkable performances in terms of specific power
Thus, as illustrated in Fig 1, the comparison of the intrinsical performances associated with the main exploitable processes clearly shows the potential represented by the use of these novel materials
Toward an intensive functional integration
Modern electromechanical applications, notably in the field of servo-control or devices for electric assistance, are often characterized by the need to integrate the functions of a mechanical speed reducer, eventually associated with a brake, so as to reduce the global bulk of the device One can try to integrate the driving and reducing functions into one and the same structure thanks to the exploitation of new actuation concepts [4]
The mechanism in Fig 2, which corresponds to the active part of a motorized hand prosthesis, with two degrees of mobility (wrist bending, grasping) clearly brings out the
Figure 2 Hand prosthesis mechanism prototype driven by two rotating mode piezomotors [5].
Trang 5III-3.3 Electroactive Materials: Toward Novel Actuation Concepts 437
Figure 3 Quasistatic operating piezoelectric actuator with its electronic supply.
potential represented by piezoelectric motor technology for this type of use [5]: two driving functions can be lodged instead of the classical mechanism with a sole degree of freedom worked by a direct current micromotor (for globally reduce bulk) whereas unobtrusive noise, the precision of positioning and the off-supplied locking which characterize piezoelectric drives (here two rotating mode motors), are all advantages to consider
High torque–low speed actuator for direct drive
At the same time the approach which leads to a better integration of speed reducing functions
in electric drives, the emergence of new needs to satisfy specifications of the high-effort-at-low-speed type, under more and more severe mass and bulk constraints (notably in space and aeronautic fields) favors the development of actuator using a direct drive of the mechanical load (absence of reduction stages in the cinematic chain)
Fig 3 illustrates these possibilities through a new design of rotating piezoactuator which operates in quasistatic mode (clamp stator deformed by multi-layer PZT ceramics) intended for the direct drive of an aeronautic fuel gate and dimensioned to develop a maximum torque
of 10 Nm (maximum speed to the order of 5 rpm), for a total mass of 1.5 kg
Actuator combining several degrees of freedom
The new functionalities resulting from the simultaneous management of several degrees
of freedom within a same mechanism (robotized microsurgery, micropositioning for mi-croelectronics or near field microscopics [6]) also give the research scientist a particularly rich field of investigation Opposed to the approach which aims at combining the different
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Figure 4 Piezoelectric planar translator–straight line driving (b), left turn (a), and right turn (c) [7].
motion required within relatively complicated multi-axes mechanisms, it is rather a matter here of imagining actuator structures which are intrinsically built to manage the different displacement required jointly As an example, the case of the piezoelectric actuator schema-tized in Fig 4 could be quoted Its working principle lies in the one-phased excitation of a bending standing wave The adjustment of the supply frequency then enables the control of the trajectory of the mobile on a flat surface The centimetric demonstrator achieved proves
to be relatively interesting from the point of view of performance in so far as it enables the displacement of a 2 kg mass at a speed of 10 mm/s [7].
Seeking original functionalities: distributed actuation for air flow control
The emerging field of the electroactive flow control constitutes a particularly revealing example of the need for electromechanical functions of a distributed nature [8,9]
The field of active flow control raises many relevant questions like internal or exter-nal noise control, hybrid laminarity, wave drag control, or friction drag control A low-ering of a few percent of friction drag could provide a non-negligible reduction of fuel consumption
Several control techniques can be considered in order to decrease friction drag: passive techniques by optimization of wing geometry, and active ones by injecting external energy into the flow In these cases, two major orientations can be distinguished: on one hand there
Trang 7III-3.3 Electroactive Materials: Toward Novel Actuation Concepts 439
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Figure 5 Numerical simulation of streaks agglomeration [10].
is local action at microscopic scale, and on the other hand global action on several structures Numerical studies have demonstrated the benefit of a transverse traveling wave on the drag force [10]
As illustrated in Fig 5, the results obtained show a 30% reduction of drag force, by agglomeration of high and low velocity streaks In the context of a French research program concerning future supersonic aircraft, a specific research project involving ONERA, AIR-BUS France, The Institut de M´ecanique des Fluides de Toulouse, and the EM3 group of INPT/LEEI (coordinator of the program) has been initiated The aim of the project is to ex-perimentally reproduce the same effect by using a “smart wall”, able to generate transverse traveling wave [11]
Fig 6 shows the principle of the developed test bench which is based on the use of a multi-bladed structure (PALM concept)
The most popular scenario about turbulence enhancement begins with the formation of high and low speed streaks in the near-wall region, after advection of streamwise swirls An autonomous cycle of turbulence regeneration appears, due to the creation of new structures
on those that already exist These streaks have great span wise gradient of streamwise velocity, which explains the appearance of vertical vorticity The vertical and spanwise vorticity is redirected in the streamwise direction creating new turbulent structures That is why we consider reducing friction drag by inducing progressive waves of spanwise velocity,
to vanish artificially created streaks in a Blasius boundary layer [12]
In order to produce transverse traveling waves of at least 1 mm amplitude, a vibrating airfoil, whose surface must be able to move, has to be realized In this aim, a system of 24 located actuators, distributed on the airfoil, was chosen The specifications for the required
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Figure 6 Multi-bladed piezoelectric actuator for turbulence reduction: the PALM concept.
deformation were defined One other main goal is to produce an adaptive structure in order
to study as many different configurations as possible
Actuator is based on multi-layer piezoceramics stacks from Morgan Matroc Electro ceramics (5 × 5 × 47 mm3, 1,000 ppm strain, 770 N max blocked force) In order to obtain large displacement in static use, the ceramic movement is amplified with a lever arm principle, as shown in Fig 7 The application point of the ceramic is located 1.1 mm above the middle of the flexion blade, so when the ceramic lengthens it produces the flexion of the blade, and makes the upper beam rotate The rotation angle is so small that the movement
of the upper beam can be assimilated to a translation
To use the ceramics at their maximum power rate, a mechanical device, which produces
a 2.5-mm displacement for half of the maximum ceramic displacement, was designed
Figure 7 FEM modal analysis: first resonant mode of the actuator.
Trang 9III-3.3 Electroactive Materials: Toward Novel Actuation Concepts 441
Figure 8 Standing wave on a perturbed laminar boundary layer.
The mechanical structure is made of Duralumin, whose plasticity limit is 75 MPa The ceramic is linked with the structure through a linear contact allowing its rotation Modal analysis reveals a first resonance mode at 33 Hz
When applying 200 V on the ceramic, a 2.52-mm displacement of the upper beam is measured Tests was made with a laser beam vibrometer insulated from external vibrations which allows us to measure displacements to the order of 1μm Dynamic tests revealing that the first resonance mode comes at 40 Hz were also performed
The first mode frequency is slightly higher than predicted by the FEM study, because the structure is strengthened by the ceramic, which was not simulated in the FEM study Actuators are pair-controlled, in order to eliminate every unintentional phase shifting The active power consumption of a pair of actuators at 20 Hz is about 120 mW, for a reactive power of 2.85 VAR, due to ceramic capacitance
First wind tunnel tests
After validating the actuator behavior, a prototype was realized for experimentation in a wind tunnel Several measurement methods have been employed: hot wire velocity measurement and particle image velocimetry (PIV)
The hot wire measurement data describing the effect of different control frequencies of
a standing spanwise wave are shown in Fig 8
At frequencies of 7 and 13 Hz, certain streaks are reduced Even though friction drag seems to be enhanced, the produced effect depends on the frequency The first results obtained are promising, even though deeper investigations are required to precisely quantify the benefit of the produced waves on the flow
Conclusion
The field of exploitable physical processes is considerably enlarged, notably thanks to the development of electroactive materials of the performances, the working capacities, and the flexibility of implementation pave the way to new designs of converters Exploited
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within motors or actuators, this technology makes it possible to envisage substantial gains
in terms of force mass ratio The growing need to control the physical processes of the more and more distributed kind naturally induces the research scientists to imagine devices with distributed drive, drawing direct benefit from the possibilities of structural integration which electroactive materials provide by principle In this context active flow control corresponds
to a very promising investigation area
References
[1] T Sashida, T Kenjo, An Introduction to Ultrasonic Motors, Oxford: Clarendon Press, 1993 [2] S Gangbing, K Brian, N.A Brij, Active position control of a shape memory alloy wire actuated beam, Smart Mater Struct., Vol 9, pp 711–716, 2000
[3] B Nogarede, “Machines ´electriques: Conversion ´electrom´ecanique de l’´energie”, Trait´e de G´enie Electrique, Techniques de l’Ing´enieur, D3410, 2000.
[4] C Henaux, G Pons, B Nogarede, “A Novel Type of Permanent Magnet Actuator: the HYPO-MAG Structure”, ICEM’2000, Espoo (Finland), August 28–30, 2000
[5] B Nogarede, C Henaux, J.-F Rouchon, F L´eonard, R Briot, L Petit, P Gonnard, B Lemaire-Semail, F Giraud, Ph Kapsa, “Mat´eriaux ´electroactifs et g´enie biom´edical: ´etude d’une proth`ese de la main actionn´ee par une motorisation pi´ezo´electrique”, MGE’2000, Lille, d´ecembre 13–14, 2000
[6] N Bonnail, D Tonneau, H Dallaporta, G.-A Capolino, “Dynamic Response of a Piezoelectric Actuator at Low Excitation Level in the Nanometer Range”, ICEM’2000, Espoo (Finland), August 28–30, 2000
[7] F Galiano, B Nogarede, Un nouveau concept d’actionneur pi´ezo´electrique plan monophas´e `a onde stationnaire, Revue Internalionale de G´enie Electrique, Vol 2, N◦/Ref 4/1999 [8] R.G Loewy, Recent developments in smart structures with aeronautical applications, Smart Mater Struct., Vol 6, pp R11-R42, 1997
[9] E Stanewsky, Adaptive wing and flow control technology, Prog Aerosp Sci., Vol 37, pp 583–667, 2001
[10] V Du, G Karniadakis, Drag reduction in a wall bounded turbulence via a transverse travelling wave, J Fluid mech., Vol 457, pp 1–34, 2002
[11] B Nogarede, V Monturet, D.Harribey, A Bottaro, H Boisson, P Konieckzny, A.Sevrain, J.P Chretien, A Sagansan, “D´eveloppement et ´evaluation de nouvelles technologies d’actionneurs r´epartis pour le supersonique”, 1ier Colloque National sur la Recherche A´eronautique sur le Supersonique, Paris, f´evrier 6–7, 2002
[12] P Konieczny, A Bottaro, V Monturet, B Nogarede, “Active Control of Near-Wall Coherent Structures”, FEDSM’2002, Joint US ASME-European Fluids Engineering Summer Confer-ence Montreal, Quebec (Canada), July 14–18, 2002