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ABSTRACT: Distance measurement using an ultrasonic wave is suitable for environment recognition in autonomous mobile robots. Ultrasonic distance measurement with the pulse-echo method is based on determining the time-of-flight (TOF) of the reflected echoes. The pulse-echo method with pulse compression, the cross-correlation method, can improve the distance resolution and the signal-to-noise ratio (SNR) of the reflected echo. However, cross correlation of the cross-correlation method requires the high-cost digital signal processing. A sensor signal processing method of cross correlation using a delta-sigma modulated single-bit digital signal has been proposed. Cross correlation by single-bit signal processing reduces the calculation cost of cross correlation. Furthermore, cross correlation by single-bit signal processing improves the time resolution of digital signal processing. In this paper, the distance resolution of cross correlation by single-bit signal processing is evaluated by computer simulations and experiments of ultrasonic distance measurement. Distance measurement from the high-time-resolution cross-correlation function obtained by single-bit signal processing realized high distance resolution from experimental results, despite the low calculation costs.
Robotics and Automation, 2009. ICRA '09. IEEE International Conference on; 06/2009
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ABSTRACT: Ultrasonic distance measurement is based on determining the time of flight of ultrasonic wave. The pulse compression technique
that obtains the cross-correlation function between the received signal and the reference signal is used to improve the resolution
of distance measurement. The cross-correlation method requires high-cost digital signal processing. This paper presents a
cross-correlation method using a delta–sigma modulated single-bit digital signal. Sensor signal processing composed of the
cross-correlation between two single-bit signals and a post-moving average filter is proposed and enables reducing the cost
of digital signal processing.
Key wordsUltrasonic distance measurement-Pulse compression technique-Delta–sigma modulation-Cross-correlation-Moving average filter
12/2008: pages 317-322;
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ABSTRACT: A flat plane slider for a surface acoustic wave (SAW) motor has been enabled by using a chemically reduced lithium niobate stator. Since a slider with no projections or the flat plane slider can drive with higher preload than a slider with projections, it is expected to obtain a higher output force. In this paper, driving properties such as a no-load speed characteristic and output force characteristic of the flat plane slider was measured. The SAW motor with the flat plane slider achieved 18 N high output force and 0.9 m/s no-load speed.
Micro-NanoMechatronics and Human Science, 2008. MHS 2008. International Symposium on; 12/2008
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ABSTRACT: A procedure for modeling the frictional heating and electricity of a surface acoustic wave (SAW) motor is proposed. The frictional heat is developed during friction drive when sliding occurs at the frictional interface; the heat is conducted into the solids, resulting in an increase in temperature. The spatial distribution of the heat source was associated with the contact pressure distribution, and the heat conduction from the heat source was formulated. Owing to the piezoelectricity and pyroelectricity of the stator used in the present study, the elastic deformation and temperature increase produce the electric fields. The electric fields in the stator were determined with respect to each cause. Electric discontinuity at the boundary between the stator and the slider, moreover, produces electrostatic force, which was calculated using a Maxwell stress tensor. All the analyses revealed the underlying physical fields in addition to the mechanical fields of the SAW motor. By the use of those analytical methods, the frictional properties of the SAW motor were discussed. We pointed out that another physical phenomenoniquestcontact electrificationiquestcould arise at the contact interface. The electrostatic force due to contact electrification had sufficient strength to change the friction property, which corresponded to the variation of the friction coefficient from 0.1 to 1.
IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control 11/2008; · 1.69 Impact Factor
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ABSTRACT: A 2-layer modeling method of friction drive of a surface acoustic wave motor is proposed. The surface layer accounts for the previously proposed point-contact friction drive model, which was generalized to correspond spatially to the underlying layer that is comprised of a 3-D elasticity field. A method to determine stiffness through the use of analytical solutions of 3-D contact problems bridges the 2 layers. Because the determined stiffness expresses the accuracy of the results regarding either layer, the validity of the results concerning the stiffness and the resulting stress field was evaluated by comparison with the results of finite element analysis. Furthermore, we executed numerical simulations by using the friction drive model, which were compared with the measured displacements of the frictional surface of the slider. The simulation accurately represented the normal displacement of the frictional surface; the modeling procedure in the normal direction was found to be reliable. However, because the friction coefficient drastically changes the tangential displacement, we could not discuss the reliability of the modeling procedure in the tangential direction. A thorough discussion of the friction drive would thus require further investigation of the friction phenomena.
IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control 11/2008; · 1.69 Impact Factor
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ABSTRACT: The surface acoustic wave motor in this study utilized transparent lithium niobate for a stator. We then measured the normal and tangential displacements of the frictional surface of the slider via the transparent stator by means of 2 laser Doppler vibrometers. We thoroughly inspected the measurement conditions and indicated that the measured data were reliable and usable for subsequent precise analyses of the friction drive. The driving conditions for the measurements were a driving frequency of 9.61 MHz and a wave vibration amplitude of 20 nm. The start-up transients of the motor for a duration of 10.4 mus were measured. The measurements showed that the frictional surface of the slider displaced in both the normal and tangential directions followed each wave vibration. The displacements increased with the wave's vibration amplitude: they increased to 10 nm in both directions, in response to the transient increase of the wave's vibration amplitude to 20 nm, under the 15 N preload condition. Moreover, the slider surface rotated in the same direction as the wave surface and its trajectories were a tilted elliptical orbit. Since the surface of the wave rotated in an upright elliptical orbit, the result indicated that the tangential displacement of the slider surface was delayed in relation to that of the wave. The delay was in the range from 30deg to 60deg under the 15 N preload condition.
IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control 10/2008; · 1.69 Impact Factor
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ABSTRACT: The mechanics of the friction drive of a surface acoustic wave motor were investigated by means of contact mechanics theory. As a means to control the contact condition, the motor's slider had projections on its frictional surface. Assuming the projection was a rigid circular punch and the slider body was an elastic half-space allowed application of contact mechanics formulae to the analyses of the friction drive. Because the projection contacted the Rayleigh wave vibration, the projection's responses were considered dynamic; thus, the dynamics were also analyzed in the same framework of contact mechanics formulae. Moreover, the analyses were applied to measurements of the projection's displacement to examine the detailed mechanics during the friction drive. We calculated the contact/frictional forces based on the measurement and indicated the necessity of further investigation of the surface acoustic wave motor's friction drive, because the usual friction law was unable to explain the measurement.
IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control 10/2008; · 1.69 Impact Factor
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ABSTRACT: Recently, our laboratory has explored the possibility of using lead zirconate titanate [PZT] polycrystalline film deposited hydrothermally on titanium substrate to fabricate a small actuator and ultrasound sensor. Hydrothermally deposited PZT polycrystalline films have piezoelectricity without a poling process, and it is easy to deposit PZT polycrystalline films on substrates that are tiny or complexly shaped. We confirmed that hydrothermally synthesized PZT polycrystalline films have wideband frequency characteristics with sensitivities in the megahertz band. It is thought that miniature ultrasound probes with wide- frequency band characteristics can be fabricated using hydrothermally synthesized PZT polycrystalline films. In our last report we assessed methods to produce a miniature ultrasound probe and transceiver characteristics. Here, the reception and transmission directivities of such a probe were measured at 5, 10, 15, and 20 MHz. The results showed that, except at 5 MHz, the theoretical and experimental values agreed. The difference at 5 MHz is attributed to the effect of the resonance frequency of the diameter direction.
Ultrasonics Symposium, 2007. IEEE; 12/2007
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ABSTRACT: Design criteria for the stable and durable operation of a surface acoustic wave motor were discussed. The low electric conductivity coupled with pyroelectricity of lithium niobate stator hindered the stable friction drive operation. We indicated that the conductivity improved lithium niobate, by chemical reduction, would then eliminate the unstable reason i.e. the contact electrification. The severe failure of the stator surface sets the limit to the durability of the surface acoustic wave motor. Owing to the chemical inertness of lithium niobate, the surface failure of the stator was arisen from the mechanical stresses developed by the indentation and sliding of the projections placed at the slider surface. The sharp edge of projections, as fabricated, easily causes the failure. Thereby, wearing off procedure before the operation is proposed as only feasible method, if the projections are necessary. Nevertheless, the optimum geometry to prevent surface failure was deduced as flat plane.
Advanced intelligent mechatronics, 2007 IEEE/ASME international conference on; 10/2007
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ABSTRACT: Stability of friction drive of a surface acoustic wave motor has been improved by adopting chemically reduced lithium niobate. Through experimental and analytical investigations, we clarified the low electric conductivity coupled with pyroelectricity of lithium niobate stator hindered the stable friction drive operation. We indicated that the conductivity improved LN, by chemical reduction, would then prevent the unstable reasons, i.e., the contact electrification and meniscus stiction.
Solid-State Sensors, Actuators and Microsystems Conference, 2007. TRANSDUCERS 2007. International; 07/2007
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ABSTRACT: Surface acoustic wave motor has already shown a superior potential. However, the efficiency from the electrical input to mechanical output is still low. To improve the efficiency, an energy circulation driving method has been proposed and demonstrated. In this method, the traveling SAW is initially excited by two phases power source of IDTs. The excited traveling wave propagates the stator. Then the wave is received by one unidirectional IDT, to convert into electric energy; the energy is circulated to the front of the stator and transduced to traveling wave again. It is very important that the circulated wave and the initially excited wave are added in phase to efficiently excite the Rayleigh wave. On the other hand, it has been found that Rayleigh wave beneath the slider is scattered, so that the phase of the wave shifts from the designed value. This phase shift affects on the addition of the waves. Phase shift decreases the efficiency of the motor. So we need to know the characteristics of the phase shift in order to design the motor with high efficiency. From several experimental results, it has been found that the phase shift is related to the projections parameter of the slider. The relationship between the slider projections contact, friction phenomenon and the phase shift was investigated by numerical simulation using the finite element method. Two dimensional FEM analysis in time domain was carried out to simulate the wave propagation from driving points through a preloaded silicon slider. Contact and friction simulation was applied to the boundary condition between the stator and the slider projections. As the result, we obtained values of phase shift down to -5 degrees up to 100 degrees. Large preload and large contact areas caused large phase shift. These results were close to the experimental results
Ultrasonics Symposium, 2006. IEEE; 11/2006
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ABSTRACT: In this study, in order to apply the hydrothermally synthesized piezoelectric polycrystalline films to the medical miniature 1-dimensional array type ultrasound probes with resonance frequency of 10 MHz, the hydroxyapatite was employed as the material for the substrate. After sputtering of pure titanium on the surface of hydroxyapatite substrate, the titanium film was etched using photo-etching method to form 1-dimensional titanium film electrodes array with element pitch of 75 mum, element width of 40 mum and element length of 4mm in order to scan ultrasound beam electronically by sector scan mode using phased array technique. We tried to deposit PZT poly-crystalline film hydrothermally on the titanium film electrodes. The deposited PZT poly-crystalline film has thickness of about 10 mum on the 1-dimensional array titanium electrode pattern. We could succeed trial fabrication of the miniature 1-dimensional array type ultrasound probe. The sputtered and etched titanium film electrodes were used as the electrodes for signal lines of the 1-dimensional array type ultrasound probe. Furthermore, a gold electrode was deposited as a common ground electrode all over the surface of 1-dimensional hydrothermally synthesized PZT poly-crystalline film vibrators. Transmitted ultrasound pulse from 10 MHz commercial ultrasound probe was received by the trially fabricated 1-dimensional array type ultrasound probe with hydrothermally synthesized PZT poly-crystalline film vibrators
Ultrasonics Symposium, 2006. IEEE; 11/2006
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ABSTRACT: Recently, the PZT poly-crystalline film deposited on titanium substrate by hydrothermal method has been studied actively for development of a small actuator and ultrasonic sensor in our laboratory. The PZT poly-crystalline films were deposited on a titanium substrate in KOH solution used as mineralizer which included Pb ion, Ti ion, and Zr ion under high temperature (about 150degC) and high pressure (about 4 kPa). We reported on the needle type miniature hydrophone and the ultrasonic transducer with hydrothermally synthesized PZT poly-crystalline films in 2005 IEEE International Ultrasonics Symposium in Rotterdam. It has confirmed that the hydrothermally synthesized PZT poly-crystalline films showed wide band frequency characteristics in MHz band of the sensitivities. It is thought that miniature ultrasonic probe with wide frequency band characteristics of sensitivities can be fabricated by using the hydrothermally synthesized PZT poly-crystalline films. The miniature ultrasonic probes were fabricated by hydrothermally deposited PZT poly-crystalline film on an end of the titanium wire with diameter of 0.6 mm and length of 50mm. The performances of trially fabricated ultrasound probes were measured. Ultrasonic imaging experiments using a target in water were performed with the trially fabricated ultrasonic probe with hydrothermally synthesized PZT films. As a result, it was confirmed that this probe has a center frequency of 16 MHz, a bandwidth of 80%, and distance resolution more than 80 micrometers. We will report about the structure and performance of the fabricated ultrasound probe with hydrothermally synthesized PZT poly-crystalline film and the results of imaging experiments under water
Ultrasonics Symposium, 2006. IEEE; 11/2006
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ABSTRACT: A high intensity and high frequency ultrasound radiation ultrasonic transducer was fabricated by the hydrothermal deposition technique of lead zirconate titanate polycrystalline thick film. This ultrasonic transducer had a 45 micron meters thick hydrothermal PZT layer on a 50 micron meters thick titanium substrate, and an active area was 5 mm times 5 mm. The piezoelectric constant d33 of this PZT thick film was 44 pm/V and the acoustic impedance was about 8 Mrayl. This prototype ultrasonic transducer radiated a sound pressures of over 100 kPa at over 20 MHz in degassed water using a thickness vibration mode of the PZT film. The radiated sound pressures was measured using a commercial hydrophone that was proofed of the receiving sensitivity at 1 MHz to 60 MHz. The hydrophone was held 40 mm in front of a surface of the prototype transducer. This measuring point was a central ultrasonic beam axis from the prototype transducer. An applied voltage to the prototype ultrasonic transducer was 40 V at ten cycles burst waveform of sine wave when measuring the radiated sound pressure. Additionally, when a driving signal was 20 MHz continuous sine waves, cavitations and an acoustic streaming was generated along a line of the central ultrasonic beam axis. The observation of generated cavitations when the continuous high intensity ultrasonic radiation from the transducer was conducted with the KI oxidation method. The cavitations was measured by measuring the oxidation reaction from the generating of cavitations in a KI solution. A volume of the KI solution for the measurement of cavitations was 50 ml
Ultrasonics Symposium, 2006. IEEE; 11/2006
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ABSTRACT: This paper presents a new oversampling architecture for implementing phase-tracking loop that is commonly utilized for position sensors such that synchro, resolver, and incremental encoder. This architecture consists of the cascade connection of three stage: coarse-quantizing and oversampling modulation, direct signal processing, and decimation filtering. It is expected that the oversampling strategy and the signal processing increase the resolution of detecting phase as well as oversampling A/D converters. This paper shows a simplest design of the signal processing circuit and some simulation results
Circuits and Systems, 2006. ISCAS 2006. Proceedings. 2006 IEEE International Symposium on; 06/2006
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ABSTRACT: Potential of surface acoustic wave (SAW) motor has been investigated during the past decade. A substrate of 128 degrees y-rotated lithium niobate was used for a stator of a SAW motor. Interdigital transducer (IDT) electrodes were fabricated by the vacuum evaporation and the lithography. These processes are familiar for SAW device fabrication and also MEMS field. Material of slider is now silicon substrate for the processes of lithograph and dry etching to fabricate surface texture. Up to now, several typical performances have been measured at several operating conditions and several kinds of SAW motors by the authors. In this paper, we tried feed back control by introducing a nonlinear function which compensates the motor response.
Industrial Electronics Society, 2005. IECON 2005. 31st Annual Conference of IEEE; 12/2005
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Ultrasonics Symposium, 2005 IEEE; 10/2005
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Ultrasonics Symposium, 2005 IEEE; 10/2005
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ABSTRACT: Steering angle over 20 degrees two-axis optical beam steering prototype that employs a mirror on a two-axis gimbal is developed, which takes advantage of two-dimensional planner surface acoustic wave actuator. For the actuation of 20 degrees of tilt angle, 10 ms duration of driving power input is required for actuation, then additional 10 ms for mirror structure's damping produced complete angle holding. Note that any power supply is unnecessary to hold the angle. The resolution of the angle was 0.003 degree because of high-resolution ability of the actuator. The beam steering prototype showed 10<sup>4</sup> dynamic range of angle positioning ability.
Solid-State Sensors, Actuators and Microsystems, 2005. Digest of Technical Papers. TRANSDUCERS '05. The 13th International Conference on; 07/2005
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ABSTRACT: A new technique that uses a DSM signal in a common technique for digitally synthesizing an arbitrary waveform, which is generally known as direct-digital synthesis (DDS), is described in this paper. In this way, the DDS frequency resolution is not restricted to the phase resolution in DDS and requires no phase truncation technique. As a simulation result, a low-pass filtered output waveform is smooth at a lower frequency with respect to the clock frequency. At lower frequencies, this technique leads to a higher spurious-free-dynamic-range than that of an ideal linear interpolator output with the same phase resolution. Therefore, the proposed combination of DSM signal and basic DDS is able to realize high frequency resolution and high spectral-purity at a lower frequency band using a small circuit.
Circuits and Systems, 2005. ISCAS 2005. IEEE International Symposium on; 06/2005
