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Selected
papers from the latest issue:
Transparent force sensing arrays with low power consumption using liquid crystal arrays
16 November 2012,
09:50:02
Publication year:
2012
Source:Sensors and Actuators A: Physical
Chia-Yi Huang, Liang Lou, Aaron J. Danner, Chengkuo Lee
A transparent force sensing array with low power consumption is developed from a 3×3 liquid crystal (LC) array. As force is applied to the LC array, the force-dependent capacitance curve of a sensor pixel under a higher voltage will shift to larger capacitance. Accordingly, the force range of the LC array can be divided into many sub-ranges at one of the capacitance values. The number of the input voltage is equal to that of the output capacitance in each of the sub-ranges, and the voltage-to-capacitance number is small (large) in the high (low)-force sub-range. The sensing array measures force in terms of the voltage-to-capacitance number. The transparent force sensing array shows potential as a touch panel, while it is immune to the need of rectifying the nonlinear relation between the applied force and the output capacitance using complex algorithm via high-end microcontrollers.
Source:Sensors and Actuators A: Physical
Chia-Yi Huang, Liang Lou, Aaron J. Danner, Chengkuo Lee
A transparent force sensing array with low power consumption is developed from a 3×3 liquid crystal (LC) array. As force is applied to the LC array, the force-dependent capacitance curve of a sensor pixel under a higher voltage will shift to larger capacitance. Accordingly, the force range of the LC array can be divided into many sub-ranges at one of the capacitance values. The number of the input voltage is equal to that of the output capacitance in each of the sub-ranges, and the voltage-to-capacitance number is small (large) in the high (low)-force sub-range. The sensing array measures force in terms of the voltage-to-capacitance number. The transparent force sensing array shows potential as a touch panel, while it is immune to the need of rectifying the nonlinear relation between the applied force and the output capacitance using complex algorithm via high-end microcontrollers.
Highlights
► Finding: The force-dependent capacitance curve of a sensor pixel under a higher voltage will shift to higher capacitance. ► Application: A transparent force sensing array with low power consumption is developed from the 3×3 liquid crystal (LC) array. ► Extended application: The transparent LC array has potential to be developed into touch panels with low power consumption for next generation operating systems.A Novel Dual Stator-Ring Rotary Ultrasonic Motor
16 November 2012,
09:50:02
Publication year:
2012
Source:Sensors and Actuators A: Physical
Xiaolong Lu, Junhui Hu, Lin Yang, Chunsheng Zhao
In this work, a novel dual stator-ring rotary ultrasonic motor is proposed, designed, fabricated and characterized for raising driving torque of the rotary ultrasonic motor operating in the flexural vibration mode. It uses four bending mode Langevin transducers, which are evenly distributed between its two identical stator rings, to excite the 9th order flexural mode travelling waves in the two stator-rings and drive its two rotors. Driving bars assembled at the center of Langevin transducers are employed to excite two 9th order flexural standing waves spatially and temporally orthogonal to each other in each stator-ring, and form the travelling wave. Results of vibration measurement are used to confirm the operating principle, and the finite element method is used to design the motor size in order that the motor can operate in resonance. The appearance size of the motor is 80mm×80mm×53mm, stator outer diameter is 60mm, and operating frequency is around 39kHz. The major mechanical and thermal characteristics of the motor have been measured. At the room temperature and 250 V0-p operating voltage, its stalling torque is 1.6 Nm, no-load speed is 120rpm, and output power reaches the maximum (= 5.5W) with a driving torque of 0.9 Nm and speed of 54rpm. At ambient temperature of 100°C, the motor still has stalling torque of 0.9 Nm and no-load speed of 79rpm for a operating voltage of 250 V0-p, which means that this motor can operate in relatively high temperature environment.
Source:Sensors and Actuators A: Physical
Xiaolong Lu, Junhui Hu, Lin Yang, Chunsheng Zhao
In this work, a novel dual stator-ring rotary ultrasonic motor is proposed, designed, fabricated and characterized for raising driving torque of the rotary ultrasonic motor operating in the flexural vibration mode. It uses four bending mode Langevin transducers, which are evenly distributed between its two identical stator rings, to excite the 9th order flexural mode travelling waves in the two stator-rings and drive its two rotors. Driving bars assembled at the center of Langevin transducers are employed to excite two 9th order flexural standing waves spatially and temporally orthogonal to each other in each stator-ring, and form the travelling wave. Results of vibration measurement are used to confirm the operating principle, and the finite element method is used to design the motor size in order that the motor can operate in resonance. The appearance size of the motor is 80mm×80mm×53mm, stator outer diameter is 60mm, and operating frequency is around 39kHz. The major mechanical and thermal characteristics of the motor have been measured. At the room temperature and 250 V0-p operating voltage, its stalling torque is 1.6 Nm, no-load speed is 120rpm, and output power reaches the maximum (= 5.5W) with a driving torque of 0.9 Nm and speed of 54rpm. At ambient temperature of 100°C, the motor still has stalling torque of 0.9 Nm and no-load speed of 79rpm for a operating voltage of 250 V0-p, which means that this motor can operate in relatively high temperature environment.
Highlights
► A dual stator-ring ultrasonic motor with bending mode Langevin transducers is proposed. ► The motor has larger torque than the conventional UM with identical diameter. ► The motor is fit for the operation in high temperature environment.A laser calibration system for in-situ dynamic characterization of temperature sensors
16 November 2012,
09:50:02
Publication year:
2012
Source:Sensors and Actuators A: Physical
A. Garinei, E. Tagliaferri
Dynamic calibration of temperature sensors is of crucial importance in many applications where temperature changes quickly. Response time qualification testing of sensors is usually performed by sensor manufacturers by plunge tests into flowing water. “Loop Current Step Response” (LCSR) technique, self-heating index and noise analysis techniques are the current methods used for in-situ dynamic characterization of temperature sensors. The dynamic calibration technique using laser as an excitation source has been developed for many applications. Here, a portable dynamic calibration system for in-situ calibration is proposed. A high brilliance laser diode heating system is used to generate both step change and ramp change in temperature so as to measure the dynamic response of the sensor. Laboratory tests performed in different environments show the reliability and the advantages of the proposed system. The laser calibration performed with the new portable device gave good results with accuracy levels in comparison with currently available techniques.
Source:Sensors and Actuators A: Physical
A. Garinei, E. Tagliaferri
Dynamic calibration of temperature sensors is of crucial importance in many applications where temperature changes quickly. Response time qualification testing of sensors is usually performed by sensor manufacturers by plunge tests into flowing water. “Loop Current Step Response” (LCSR) technique, self-heating index and noise analysis techniques are the current methods used for in-situ dynamic characterization of temperature sensors. The dynamic calibration technique using laser as an excitation source has been developed for many applications. Here, a portable dynamic calibration system for in-situ calibration is proposed. A high brilliance laser diode heating system is used to generate both step change and ramp change in temperature so as to measure the dynamic response of the sensor. Laboratory tests performed in different environments show the reliability and the advantages of the proposed system. The laser calibration performed with the new portable device gave good results with accuracy levels in comparison with currently available techniques.
Stick-Slip and Slip-Slip Operation of Piezoelectric Inertia Drives – Part I: Ideal Excitation
16 November 2012,
09:50:02
Publication year:
2012
Source:Sensors and Actuators A: Physical
Matthias Hunstig, Tobias Hemsel, Walter Sextro
Piezoelectric inertia motors, also known as “stick-slip drives”, use the inertia of a body to drive it in small steps by means of a friction contact. While these steps are classically assumed to involve stiction and sliding, the motors can also operate in “slip-slip” mode without any phase of static friction. This contribution provides a systematic investigation and performance comparison of different stick-slip and slip-slip modes of operation. Different criteria for comparing the motional performance of inertia motors are defined: Steady state velocity, smoothness of motion, and start-up time. Using the example of a translational inertia motor excited by an ideal displacement signal, it is found that the maximum velocity reachable in stick-slip operation is limited principally, while continuous slip-slip operation allows very high velocities. For the investigated driving signals, the motor velocity is proportional to the square root of the actuator stroke. The motor performance with these ideal signals defines an upper boundary for the performance of real motors.
Source:Sensors and Actuators A: Physical
Matthias Hunstig, Tobias Hemsel, Walter Sextro
Piezoelectric inertia motors, also known as “stick-slip drives”, use the inertia of a body to drive it in small steps by means of a friction contact. While these steps are classically assumed to involve stiction and sliding, the motors can also operate in “slip-slip” mode without any phase of static friction. This contribution provides a systematic investigation and performance comparison of different stick-slip and slip-slip modes of operation. Different criteria for comparing the motional performance of inertia motors are defined: Steady state velocity, smoothness of motion, and start-up time. Using the example of a translational inertia motor excited by an ideal displacement signal, it is found that the maximum velocity reachable in stick-slip operation is limited principally, while continuous slip-slip operation allows very high velocities. For the investigated driving signals, the motor velocity is proportional to the square root of the actuator stroke. The motor performance with these ideal signals defines an upper boundary for the performance of real motors.
Highlights
► Ideal excitation signals for maximum velocity of inertia motors are defined. ► Performance criteria for inertia motors are defined. ► Inertia motors can only achieve very high velocities in continuous slip-slip mode. ► Ideal performance defines an upper boundary for the performance of real motors.Analytical closed-form solutions for size-dependent static pull-in behavior in electrostatic micro-actuators via Fredholm integral method
16 November 2012,
09:50:02
Publication year:
2012
Source:Sensors and Actuators A: Physical
Hossein Rokni, Rudolf J. Seethaler, Abbas S. Milani, Shahrokh Hosseini-Hashemi, Xian-Fang Li
In this paper, a novel method is proposed for the first time to obtain static pull-in voltages with fringing field effects in electrostatically actuated cantilever and clamped-clamped micro-beams where the mid-plane stretching and the residual axial load are taken into account for clamped-clamped boundary conditions. The non-classical Euler–Bernoulli beam model containing one material length scale parameter is adopted to effectively capture the size effect. In the solution procedure, the governing fourth-order differential equation of variable coefficients is converted into a Fredholm integral equation. By adopting the first natural mode of the cantilever and clamped-clamped micro-beams as a deflection shape function, the resulting equation is solved for the static pull-in voltages. The accuracy of the present analytical closed-form solution is verified through comparing with the experimentally measured and numerical data conducted in the published works. From the experimental data available in the literature, the value of the material length scale parameter for the (poly)silicon is estimated to be in the order of magnitude of 10−1 μm. Then, the effect of the material length scale parameter on the pull-in voltages of the cantilever and clamped-clamped micro-beams is investigated. The results indicate that the tensile residual stress can extend the validity range of the classical continuum mechanics to lower beam thicknesses. It is also found that microcantilever beams are more sensitive to the size effect than their corresponding clamped-clamped micro-beams.
Source:Sensors and Actuators A: Physical
Hossein Rokni, Rudolf J. Seethaler, Abbas S. Milani, Shahrokh Hosseini-Hashemi, Xian-Fang Li
In this paper, a novel method is proposed for the first time to obtain static pull-in voltages with fringing field effects in electrostatically actuated cantilever and clamped-clamped micro-beams where the mid-plane stretching and the residual axial load are taken into account for clamped-clamped boundary conditions. The non-classical Euler–Bernoulli beam model containing one material length scale parameter is adopted to effectively capture the size effect. In the solution procedure, the governing fourth-order differential equation of variable coefficients is converted into a Fredholm integral equation. By adopting the first natural mode of the cantilever and clamped-clamped micro-beams as a deflection shape function, the resulting equation is solved for the static pull-in voltages. The accuracy of the present analytical closed-form solution is verified through comparing with the experimentally measured and numerical data conducted in the published works. From the experimental data available in the literature, the value of the material length scale parameter for the (poly)silicon is estimated to be in the order of magnitude of 10−1 μm. Then, the effect of the material length scale parameter on the pull-in voltages of the cantilever and clamped-clamped micro-beams is investigated. The results indicate that the tensile residual stress can extend the validity range of the classical continuum mechanics to lower beam thicknesses. It is also found that microcantilever beams are more sensitive to the size effect than their corresponding clamped-clamped micro-beams.
Highlights
► A novel method is proposed to obtain pull-in voltages in electrostatic micro-actuators. ► Value of material length scale parameter for (poly)silicon is in the order of magnitude of 10−1 μm. ► Microcantilevers are more sensitive to the size effect than their corresponding clamped-clamped beams. ► Clamped-clamped micro-beams under tensile residual stress are less sensitive to the size effect than their counterparts under compressive stress.MEMS Solid Propellant Thruster Array with Micro Membrane Igniter
16 November 2012,
09:50:02
Publication year:
2012
Source:Sensors and Actuators A: Physical
Jongkwang Lee, Taegyu Kim
A microigniter with improved membrane for MEMS solid propellant thruster array is proposed. Although existing igniters using dielectric SiNx membranes consume low power, they cannot withstand shocks during the propellant charging process. A glass wafer is selected as the material for the igniter. A glass membrane is fabricated by the anisotropic wet etching of photosensitive glass. Platinum is used for the ignition coil. A 30∼40-μm thick glass membrane exhibited sufficient strength to withstand accidental impacts during the propellant charging process. Further, the microigniter using the glass membrane had an appropriate power consumption to ignite the solid propellant. The thermal, electrical, and mechanical characteristics of the fabricated microigniter were measured. The proposed microigniter provided the sufficient heat for the propellant to be ignited with the given electric power. The fracture pressure of the glass membrane was thrice higher than the conventional microigniter. A solid propellant lead styphnate was filled into the microigniter without any additional processes. Ignition tests with fully assembly MEMS thrusters were performed successfully. Thus, it is demonstrated that a simpler, robust, and low-cost fabrication process of an igniter that performs well when assembled into a micro solid propellant thruster (MSPT) array is possible.
Source:Sensors and Actuators A: Physical
Jongkwang Lee, Taegyu Kim
A microigniter with improved membrane for MEMS solid propellant thruster array is proposed. Although existing igniters using dielectric SiNx membranes consume low power, they cannot withstand shocks during the propellant charging process. A glass wafer is selected as the material for the igniter. A glass membrane is fabricated by the anisotropic wet etching of photosensitive glass. Platinum is used for the ignition coil. A 30∼40-μm thick glass membrane exhibited sufficient strength to withstand accidental impacts during the propellant charging process. Further, the microigniter using the glass membrane had an appropriate power consumption to ignite the solid propellant. The thermal, electrical, and mechanical characteristics of the fabricated microigniter were measured. The proposed microigniter provided the sufficient heat for the propellant to be ignited with the given electric power. The fracture pressure of the glass membrane was thrice higher than the conventional microigniter. A solid propellant lead styphnate was filled into the microigniter without any additional processes. Ignition tests with fully assembly MEMS thrusters were performed successfully. Thus, it is demonstrated that a simpler, robust, and low-cost fabrication process of an igniter that performs well when assembled into a micro solid propellant thruster (MSPT) array is possible.
Highlights
► Microigniter with improved membrane for MEMS solid propellant thruster array is proposed. ► A 30∼40-μm thick glass membrane exhibited sufficient strength to withstand accidental impacts during the propellant charging process. ► Heating characteristics with the given electric power of the proposed microigniter were 20% lower than those of the conventional microigniter. ► Fracture pressure of the glass membrane was thrice as high as that of the conventional microigniter.Preparation on transparent flexible piezoelectric energy harvester based on PZT films by laser lift-off process
16 November 2012,
09:50:02
Publication year:
2012
Source:Sensors and Actuators A: Physical
Young Ho Do, Woo Suk Jung, Min Gyu Kang, Chong Yun Kang, Seok Jin Yoon
The piezoelectric energy generation properties of transparent flexible devices (TFD) based on PbZr0.52Ti0.48O3 (PZT) films, which were fabricated by laser lift-off (LLO) process, were studied for a piezoelectric energy harvester. Through the introduction of indium-tin-oxide (ITO) and polyethylene terephthalate (PET) substrates, TFDs were implemented, respectively. The TFDs based on PZT films generated an AC-type output signal and output power of 8.4 nW/cm2, at periodically bending and releasing motion. In addition, inverted output signals were observed when the manufactured TFDs were connected to the measuring equipment in reverse and were bended to the reverse direction, demonstrating that the generating signals originated from the piezoelectric effect of TFDs. The experimental results clearly showed that the TFDs based PZT film have potential for use in next generation of electronic devices applications such as flexible devices, transparent electronics, and energy harvester.
Source:Sensors and Actuators A: Physical
Young Ho Do, Woo Suk Jung, Min Gyu Kang, Chong Yun Kang, Seok Jin Yoon
The piezoelectric energy generation properties of transparent flexible devices (TFD) based on PbZr0.52Ti0.48O3 (PZT) films, which were fabricated by laser lift-off (LLO) process, were studied for a piezoelectric energy harvester. Through the introduction of indium-tin-oxide (ITO) and polyethylene terephthalate (PET) substrates, TFDs were implemented, respectively. The TFDs based on PZT films generated an AC-type output signal and output power of 8.4 nW/cm2, at periodically bending and releasing motion. In addition, inverted output signals were observed when the manufactured TFDs were connected to the measuring equipment in reverse and were bended to the reverse direction, demonstrating that the generating signals originated from the piezoelectric effect of TFDs. The experimental results clearly showed that the TFDs based PZT film have potential for use in next generation of electronic devices applications such as flexible devices, transparent electronics, and energy harvester.
NEMS-based heterodyne self-oscillator
16 November 2012,
09:50:02
Publication year:
2012
Source:Sensors and Actuators A: Physical
G. Jourdan, E. Colinet, J. Arcamone, A. Niel, C. Marcoux, L. Duraffourg
We report a novel NEMS-based heterodyne self-oscillator. By using a downmixing detection scheme, the NEMS motion piezoresistive signal at 20MHz is shifted down to few tens of kHz, thus avoiding the negative impact of stray capacitances. This technique allows the NEMS self-oscillator to benefit from its major advantages: a high Dynamic Range and a high Signal to Background Ratio. However in this form, the signal cannot be directly inserted in a standard oscillator feedback loop since the output signal is neither proportional, nor at the same frequency as the NEMS actuation signal. This paper describes a novel heterodyne architecture so that self oscillation motion of the NEMS builds up with excellent frequency stability. By providing a high dynamic range and high signal to background ratio, this feedback loop architecture represents an efficient way to track NEMS resonance frequency in real time, as required in sensing applications like mass sensors.
Source:Sensors and Actuators A: Physical
G. Jourdan, E. Colinet, J. Arcamone, A. Niel, C. Marcoux, L. Duraffourg
We report a novel NEMS-based heterodyne self-oscillator. By using a downmixing detection scheme, the NEMS motion piezoresistive signal at 20MHz is shifted down to few tens of kHz, thus avoiding the negative impact of stray capacitances. This technique allows the NEMS self-oscillator to benefit from its major advantages: a high Dynamic Range and a high Signal to Background Ratio. However in this form, the signal cannot be directly inserted in a standard oscillator feedback loop since the output signal is neither proportional, nor at the same frequency as the NEMS actuation signal. This paper describes a novel heterodyne architecture so that self oscillation motion of the NEMS builds up with excellent frequency stability. By providing a high dynamic range and high signal to background ratio, this feedback loop architecture represents an efficient way to track NEMS resonance frequency in real time, as required in sensing applications like mass sensors.
Highlights
► A NEMS based resonator with suspended piezoresistive nanogauges generates an electrical signal through a heterodyne transduction scheme. ► A feedback loop integrating a RF mixer enables to fit the output frequency of the NEMS to the required frequency at the NEMS input. ► Feedback loop requirements to generate self sustained motion of the NEMS are experimentally studied. ► Frequency stability of the heterodyne oscillator complies with the resonance frequency stability obtained in open loop for a similar motion amplitude.Volatile Detection System using Piezoelectric Micromechanical Resonators Interfaced by an Oscillator Readout
16 November 2012,
09:50:02
Publication year:
2012
Source:Sensors and Actuators A: Physical
J. Pettine, M. Patrascu, D.M. Karabacak, M. Vandecasteele, V. Petrescu, S.H. Brongersma, M. Crego-Calama, C. Van Hoof
In this paper, we demonstrate the implementation of a real–time volatile detection system using an electronic readout interfacing a functionalized piezoelectric micromechanical resonator for frequency shift tracking. The readout circuit is based on a trans-impedance sustaining amplifier and it is assembled from off–the–shelf components. The 2.08 MHz oscillator system achieves a measured Allan deviation of 3Hz at 10ms integration time. Exposure to varying concentrations of ethanol in a controlled dry nitrogen flow yielded a normalized sensitivity of -7.48×10−6/ppm. These results pave the way towards compact and portable measurement systems capable of ppm–level detection resolution for low–molecular weight volatile compounds.
Source:Sensors and Actuators A: Physical
J. Pettine, M. Patrascu, D.M. Karabacak, M. Vandecasteele, V. Petrescu, S.H. Brongersma, M. Crego-Calama, C. Van Hoof
In this paper, we demonstrate the implementation of a real–time volatile detection system using an electronic readout interfacing a functionalized piezoelectric micromechanical resonator for frequency shift tracking. The readout circuit is based on a trans-impedance sustaining amplifier and it is assembled from off–the–shelf components. The 2.08 MHz oscillator system achieves a measured Allan deviation of 3Hz at 10ms integration time. Exposure to varying concentrations of ethanol in a controlled dry nitrogen flow yielded a normalized sensitivity of -7.48×10−6/ppm. These results pave the way towards compact and portable measurement systems capable of ppm–level detection resolution for low–molecular weight volatile compounds.
Highlights
► A real-time volatile detection system combining a MEMS piezoelectric resonator and an off-the-shelf electronic readout is presented. ► We demonstrate a linear sensitivity to ethanol in dry nitrogen conditions of -15.6Hz/ppm. ► The minimum measured Allan deviation is 3Hz with three sigma confidence level. ► The system theoretical limit of detection to ethanol in dry nitrogen is 0.2ppm.Towards In-Vivo Differentiation of Brain Tumor versus Normal Tissue by Means of Torsional Resonators
16 November 2012,
09:50:02
Publication year:
2012
Source:Sensors and Actuators A: Physical
Diethelm Johannsmann, Arne Langhoff, Berthold Bode, Konstantinos Mpoukouvalas, Axel Heimann, Oliver Kempski, Patra Charalampaki
It was tested to what extend torsional acoustic resonators can serve to in-vivo differentiate between healthy and tumorous brain tissue. The resonators employed consist of crystalline quartz. They are cylindrically shaped. The resonance frequency at the fundamental is 78kHz. The best correlation between the shifts of resonance frequency and resonance bandwidth, on the one hand, and the state of the tissue, on the other, was found when analyzing ratios of the shifts in resonance frequency and resonance bandwidth. These ratios are independent of contact area. Taking data on the fundamental mode as well as the third overtone further improved the efficiency and precision of the technique. These results suggest that torsional resonators can serve as diagnostic tools in neurosurgery.
Source:Sensors and Actuators A: Physical
Diethelm Johannsmann, Arne Langhoff, Berthold Bode, Konstantinos Mpoukouvalas, Axel Heimann, Oliver Kempski, Patra Charalampaki
It was tested to what extend torsional acoustic resonators can serve to in-vivo differentiate between healthy and tumorous brain tissue. The resonators employed consist of crystalline quartz. They are cylindrically shaped. The resonance frequency at the fundamental is 78kHz. The best correlation between the shifts of resonance frequency and resonance bandwidth, on the one hand, and the state of the tissue, on the other, was found when analyzing ratios of the shifts in resonance frequency and resonance bandwidth. These ratios are independent of contact area. Taking data on the fundamental mode as well as the third overtone further improved the efficiency and precision of the technique. These results suggest that torsional resonators can serve as diagnostic tools in neurosurgery.
Highlights
► Torsional acoustic resonators have been used on living animals to distinguish between tumorous and healthy tissue. ► If the specimens are accessible well, one finds that the tumorous tissue is stiffer than the healthy tissue. ► Taking ratios between shifts of frequency and bandwidth improves the correlation between tissue state and sensor output.Magnetic Tuning of a Kinetic Energy Harvester Using Variable Reluctance
16 November 2012,
09:50:02
Publication year:
2012
Source:Sensors and Actuators A: Physical
I.N. Ayala-Garcia, P.D. Mitcheson, E.M. Yeatman, D. Zhu, J. Tudor, S.P. Beeby
In this paper we present a new technique for tuning the resonant frequency of an energy harvester using a variable reluctance device which changes the strain in a cantilever beam to alter its spring constant. In order for energy harvesting devices to be able to operate reliably in many applications they must be able to generate energy as the input excitation frequency changes. Most harvesters are resonantly tuned mass-spring-damper devices and therefore it is important that their resonant frequency is tuneable during operation. Several mechanical methods have previously been demonstrated for accomplishing this task which operates by altering the stress in a cantilever beam by altering the distance between a fixed tuning magnet and a magnet on the moving cantilever. Here, we demonstrate a new actuation method for manipulating the stress in a beam. The actuation mechanism alters the magnetic reluctance between the cantilever mounted and the fixed magnet. The investigation has highlighted the importance of the design of the magnetic circuit and choice of materials in order to avoid eddy current damping and asymmetrical forces. The method presented here has demonstrated a maximum tunable frequency range of 11.1Hz and may be more suitable for microfabrication than the previously reported techniques due to the reduced tuning force which makes microfabricated actuators feasible.
Source:Sensors and Actuators A: Physical
I.N. Ayala-Garcia, P.D. Mitcheson, E.M. Yeatman, D. Zhu, J. Tudor, S.P. Beeby
In this paper we present a new technique for tuning the resonant frequency of an energy harvester using a variable reluctance device which changes the strain in a cantilever beam to alter its spring constant. In order for energy harvesting devices to be able to operate reliably in many applications they must be able to generate energy as the input excitation frequency changes. Most harvesters are resonantly tuned mass-spring-damper devices and therefore it is important that their resonant frequency is tuneable during operation. Several mechanical methods have previously been demonstrated for accomplishing this task which operates by altering the stress in a cantilever beam by altering the distance between a fixed tuning magnet and a magnet on the moving cantilever. Here, we demonstrate a new actuation method for manipulating the stress in a beam. The actuation mechanism alters the magnetic reluctance between the cantilever mounted and the fixed magnet. The investigation has highlighted the importance of the design of the magnetic circuit and choice of materials in order to avoid eddy current damping and asymmetrical forces. The method presented here has demonstrated a maximum tunable frequency range of 11.1Hz and may be more suitable for microfabrication than the previously reported techniques due to the reduced tuning force which makes microfabricated actuators feasible.
Highlights
► We present a novel tuning mechanism for vibration energy harvesting. ► The tuning mechanism uses variable reluctance to alter the mechanical frequency. ► The paper demonstrates a useable tuning range for practical applications. ► Design issues are identified: eddy currents, tuning force and reliability.Magnetostrictive vibrator utilizing iron-cobalt alloy
16 November 2012,
09:50:02
Publication year:
2012
Source:Sensors and Actuators A: Physical
Jiang Guo, Shin-ya Morita, Yutaka Yamagata, Toshiro Higuchi
In this paper, a novel magnetostrictive vibrator with a unique and integrated design is proposed and developed by using a kind of iron-cobalt alloy (Permendur). Permendur is a giant magnetostrictive material (GMM) with magnetostriction exceeding 70ppm, Young's modulus of 210GPa, high relative permeability and sufficient force for actuation, which shows a good performance as actuator material and has been drawn a lot of attention. The magnetostrictive vibrator has four legs around which the coils are wound. The legs can be pushed (expansion) and pulled (contraction) respectively through controlling the input currents of the coils. The actuation principle of the magnetostrictive vibrator is illustrated and the lateral vibrating motion can be generated by using a pair of opposing coils, whereas 2D vibrating motion could be obtained by using two pairs of opposing coils. The finite element method (FEM) is used to analyze the vibrating motion and optimize the concrete shape. Through some fundamental experiments, the characteristics of the magnetostrictive vibrator have been evaluated. For the application, it has been successfully used as a vibrating polisher in the ultra-precision finishing of micro-optic molds.
Source:Sensors and Actuators A: Physical
Jiang Guo, Shin-ya Morita, Yutaka Yamagata, Toshiro Higuchi
In this paper, a novel magnetostrictive vibrator with a unique and integrated design is proposed and developed by using a kind of iron-cobalt alloy (Permendur). Permendur is a giant magnetostrictive material (GMM) with magnetostriction exceeding 70ppm, Young's modulus of 210GPa, high relative permeability and sufficient force for actuation, which shows a good performance as actuator material and has been drawn a lot of attention. The magnetostrictive vibrator has four legs around which the coils are wound. The legs can be pushed (expansion) and pulled (contraction) respectively through controlling the input currents of the coils. The actuation principle of the magnetostrictive vibrator is illustrated and the lateral vibrating motion can be generated by using a pair of opposing coils, whereas 2D vibrating motion could be obtained by using two pairs of opposing coils. The finite element method (FEM) is used to analyze the vibrating motion and optimize the concrete shape. Through some fundamental experiments, the characteristics of the magnetostrictive vibrator have been evaluated. For the application, it has been successfully used as a vibrating polisher in the ultra-precision finishing of micro-optic molds.
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