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- AJIT

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According to GM..

A self-actuating device includes a member inphysical communication with a vehicle surface andan actuator. The member is configured to have atleast a first form and a second form, wherein one of

the first form and the second form is configured tostow the member and the other of the first form andthe second form is configured to present themember. The actuator is in operable communication

with the member. The actuator is actuated uponreceipt of an activation signal and is effective totransition the member from one of the forms toanother of the forms.

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LVDT-based self-actuating displacement

transducer

A novel linear actuator with inherent sensingcapabilities is developed from a linear variabledifferential transformer (LVDT). By superposition ofdc currents upon high-frequency excitation signals,

the coils of the LVDT are capable of exerting apush/pull force on the armature while retaining theoriginal displacement-sensing function. LC resonantcircuits and active bandpass filters are designed toeffectively isolate the sensing signals from the dcenergizing sources. Linearity and sensitivity of thedevice are largely preserved compared to the original

LVDT.

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For actuation, it is found that the magneticforce on the armature can be maximized byenergizing a specific combination of thethree coils according to armature positions.A simple control algorithm is developed forclosed-loop control. It is implemented withan 8-bit microcomputer. Real-time testing

shows that rest-to-rest control can beachieved with positioning errors of 0.02-0.04 mm and settling time below 0.2s .

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THE AKIYAMA PROBE

It features a symmetrical arrangement of a U-shaped siliconcantilever attached to the two prongs of a quartz tuning fork.The tuning fork serves as an oscillatory force sensor thatgoverns the tip vibration frequency as well as the amplitudeand ensures a high mechanical Q-factor. The force constant of

the probe is determined by the cantilever and can be adjustedindependently from the resonance frequency.The Akiyama-probe requires neither optical detection, nor anexternal shaker. A-Probe occupies only a small volume above

the sample. These features make it very attractive for creatinga new generation of scanning probe microscopy (SPM)instruments.

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THE AKIYAMA PROBE

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Mercury vapor detection with a self-sensing,

resonating piezoelectric cantilever

A microcantilever with an integrated piezoelectric filmis demonstrated as a mercury vapor detector. Thecantilever is self-sensing and self-actuating, andtherefore does not need alignment of an external,optical detection system. This gives the new sensorsystem an advantage in array applications. Mercuryvapor, when adsorbed onto gold on the cantilever,

causes the stiffness, and therefore the naturalfrequency, of the cantilever to increase as a result ofmercury gold amalgamation. This shift is detectedusing the piezoelectric portion of the cantilever in

conjunction with a bridge circuit and amplifier

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For frequency-modulation atomic forcemicroscopy (FM-AFM) which has three electrodes:

an actuating electrode, a sensing electrode, and aground electrode. By applying an ac signal on theactuating electrode, the cantilever is set to vibrate.If the frequency of actuation voltage closely

matches one of the characteristic frequencies ofthe cantilever, a sharp resonance should beobserved. The vibration of the cantilever in turngenerates a current on the sensing electrode.

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The arrangement of the electrodes is such thatthe cross-talk capacitance between the actuatingelectrode and the sensing electrode is less than1016 F, thus the direct coupling is negligible. Toverify the principle, a number of samples were

made. Direct measurements with a NanosurfeasyPPL controller and detector showed that foreach cantilever, one or more vibrational modes canbe excited and detected. Using classical theory ofelasticity, it is shown that such novel cantileverswith proper dimensions can provide optimizedperformance and sensitivity in FM-AFM with verysimple electronics.

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