Linear Position Sensor Research Articles

Linear Tracking for 3-D Medical Ultrasound Imaging

As the clinical application grows, there is a rapid technical development of 3-D ultrasound imaging. Compared with 2-D ultrasound imaging, 3-D ultrasound imaging can provide improved qualitative and quantitative information for various clinical applications. In this paper, we proposed a novel tracking method for a freehand 3-D ultrasound imaging system with improved portability, reduced degree of freedom, and cost. We designed a sliding track with a linear position sensor attached, and it transmitted positional data via a wireless communication module based on Bluetooth, resulting in a wireless spatial tracking modality. A traditional 2-D ultrasound probe fixed to the position sensor on the sliding track was used to obtain real-time B-scans, and the positions of the B-scans were simultaneously acquired when moving the probe along the track in a freehand manner. In the experiments, the proposed method was applied to ultrasound phantoms and real human tissues. The results demonstrated that the new system outperformed a previously developed freehand system based on a traditional six-degree-of-freedom spatial sensor in phantom and in vivo studies, indicating its merit in clinical applications for human tissues and organs.

A Novel Image Motion Compensation Method for the Pendular Aeronautical Camera

This paper puts forward an improved image motion compensation method according to the complex mechanical system and expensive cost problem when the pendular aeronautical camera uses multiple sensors to compensate image motion. This method can only use a linear position sensor to obtain a linear output voltage signal and a sinusoidal output voltage signal, thus a linear position sensor can not only complete image motion compensation function but also complete pendulum sweep range positioning. Finally the experiments has proved that the method this paper has chosen not only simplifies the mechanical system design and reduces the aerial camera cost, but also can meet the accuracy and real-time requirements of various pendular aeronautical camera or space camera.

Thin Film of Giant Magnetoresistance (GMR) Material Prepared by Sputtering Method

In recent decades, a new magnetic sensor based on magnetoresistance effect is highly researched and developed intensively. GMR material has great potential as next generation magnetic field sensing devices. It has also good magnetic and electric properties, and high potential to be developed into various applications of electronic devices such as: magnetic field sensor, current measurements, linear and rotational position sensor, data storage, head recording, and non-volatile magnetic random access memory. GMR material can be developed to be solid state magnetic sensors that are widely used in low field magnetic sensing applications. A solid state magnetic sensor can directly convert magnetic field into resistance, which can be easily detected by applying a sense current or voltage. Generally, there are many sensors for measuring the low magnetic field, such as: fluxgate sensor, Hall sensor, induction coil, GMR sensor, and SQUID sensor. Compared to other low magnetic field sensing techniques, solid state sensors have demonstrated many advantages, such as: small size (<0.1mm2), low power, high sensitivity (~0.1Oe) and good compatibility with CMOS technology. The thin film of GMR is usually prepared using: sputtering, electro deposition or molecular beam epitaxy (MBE) techniques. But so far, not many researchers reported the manufacture of thin film of GMR by dc-Opposed Target Magnetron Sputtering (dc-OTMS). In this paper, we inform the development of GMR thin film with sandwich and spin valve structures using dc-OTMS method. We have also developed organic GMR with Alq3 as a spacer layer.

Development and testing of a snow interceptometer to quantify canopy water storage and interception processes in the rain/snow transition zone of the North Cascades, Washington, USA

[1] Tree canopy snow interception is a significant hydrological process, capable of removing up to 60% of snow from the ground snowpack. Our understanding of canopy interception has been limited by our ability to measure whole canopy water storage in an undisturbed forest setting. This study presents a relatively inexpensive technique for directly measuring snow canopy water storage using an interceptometer, adapted from Friesen et al. (2008). The interceptometer is composed of four linear motion position sensors distributed evenly around the tree trunk. We incorporate a trunk laser-mapping installation method for precise sensor placement to reduce signal error due to sensor misalignment. Through calibration techniques, the amount of canopy snow required to produce the measured displacements can be calculated. We demonstrate instrument performance on a western hemlock (Tsuga heterophylla) for a snow interception event in November 2011. We find a snow capture efficiency of 83 ± 15% of accumulated ground snowfall with a maximum storage capacity of 50 ± 8 mm snow water equivalent (SWE). The observed interception event is compared to simulated interception, represented by the variable infiltration capacity (VIC) hydrologic model. The model generally underreported interception magnitude by 33% using a leaf area index (LAI) of 5 and 16% using an LAI of 10. The interceptometer captured intrastorm accumulation and melt rates up to 3 and 0.75 mm SWE h−1, respectively, which the model failed to represent. While further implementation and validation is necessary, our preliminary results indicate that forest interception magnitude may be underestimated in maritime areas.

Design of Compensation Coils for EMI Suppression in Magnetostrictive Linear Position Sensors

This paper presents recent development on magnetostrictive linear position sensors (MLPS). A new compensation coil structure improves the EMI suppression and accuracy considerably. Furthermore, experimental results indicate that the new structure can improve the accuracy to ±0.13 mm nearly double the ±0.2 mm obtained with traditional structures. As another design continuation after the differential waveguide structure, this new structure is a practical and reliable implementation technique for the commercialization of MLPS.

Integration of Triaxial Hall-Effect Sensor Technology for Gear Position Sensing in Commercial Vehicle Transmissions

The proliferation of microprocessor architecture onboard transmission control modules has seen sensors play a crucial role in feedback control. This paper presents a linear position sensor module with a Hall-effect element for gear position sensing in a commercial vehicle transmission. Finite-element analysis model of the sensor performance has been performed, and the model has been validated against experimental data from the sensor prototype. The significance of this paper is that a low-cost linear position sensor module has been developed with high linearity, high output resolution (37.5 μm), and high accuracy (0.25 mm) for gear position sensing. The complete sensor system is designed for ease of manufacturing and application in harsh transmission environments, such as high-temperature profiles ranging from -40 °C to +135 °C.

Development of Sensors Based on Giant Magnetoresistance Material

In this review we discuss development of sensors based on giant magnetoresistance (GMR) material.The GMR material has high magnetic and electrical properties, therefore it has great potential as next generation magnetic field sensing devices. During the last decade, intensive research efforts have been expended to develop sensors based on giant magnetoresistance (GMR) material, both based on inorganic materials and organic materials. Many application of GMR sensor, such as: current sensor, linear and rotational position sensor, head recording, and biosensor, are reviewed.

Simulation of Whisker Sensor in Robotic Assisted Beating Cardiac Surgery

A novel method was presented to measure the motion of the heart with the whisker sensor in robotic assisted beating cardiac surgery. The whisker sensor is a flexible, high-precision，low stiffness contact sensor designed for real-time accurate measuring heart motion. The sensor tip can be in continuous contact with the surface of the heart, which can actively cancel the relative motion between the surgical instruments and the surgical site on the beating heart. The proposed highly sensitive sensor employs a linear position sensor connected to two flexible cantilever beams that are attached orthogonally with a ridged joint. The theoretical formula was derived from the mechanical model which established based on the classical mechanics of materials．Finally，finite-element simulations were done with the ANSYS to prove the feasibility and validity of the method.

Design and Analysis of a Differential Waveguide Structure to Improve Magnetostrictive Linear Position Sensors

Magnetostrictive linear position sensors (MLPS) are high-precision sensors used in the industrial field for measuring the propagation time of ultrasonic signals in a waveguide. To date, MLPS have attracted widespread attention for their accuracy, reliability, and cost-efficiency in performing non-contact, multiple measurements. However, the sensor, with its traditional structure, is susceptible to electromagnetic interference, which affects accuracy. In the present study, we propose a novel structure of MLPS that relies on two differential waveguides to improve the signal-to-noise ratio, common-mode rejection ratio, and accuracy of MLPS. The proposed sensor model can depict sensor performance and the relationship of sensor parameters. Experimental results with the new sensor indicate that the new structure can improve accuracy to ±0.1 mm higher than ±0.2 mm with a traditional structure. In addition, the proposed sensor shows a considerable improvement in temperature characteristics.

Impedance characteristics analysis of the non‐contact magnetic type position sensor

AbstractThe mechanical contact‐type potentiometer that has been conventionally used as a position sensor is known to have the problems of contact reliability and lifetime. Therefore, we have developed a noncontact linear position sensor using impedance change based on displacement. In this paper, we evaluate the AC magnetization characteristics of the core material used for such a sensor, and investigate how to use the complex magnetic permeability in three‐dimensional finite element analysis. In addition, the impedance characteristics of the noncontact magnetic position sensor are calculated using the measured complex magnetic permeability of the core. The validity of our method is verified by comparing the measurements of the prototype to calculated values. © 2011 Wiley Periodicals, Inc. Electron Comm Jpn, 94(3): 33–40, 2011; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/ecj.10302

Fundamental Study on Developing Eddy Current Linear Encoders

This paper presents the results obtained from a fundamental study on eddy-current linear encoders. We propose eddy current linear encoders as a replacement for optical and magnetic encoders. Eddy current linear encoders are linear displacement and position sensors that are used in eddy-current tests. Linear displacement and position are detected by counting cracks on a scale from the change in the induced voltage of the detecting coil. They are expected to have unique advantages in reducing costs and enabling shields and gaps to be used between the detector and scale. We report experimental results on the output characteristics of an eddy current linear encoder and the characteristics of the gap between the coil and scale. The effects of the ferrite core, the effects of ferrite size, and the output characteristic of a 1-mm pitch scale obtained by simulation are also reported.

Modeling Shrinkage Response to Tensile Stresses in Wood Drying III. Stress—Tensile Set Correlation in Short Pieces of Lumber

This article reports on the correlation between tensile stresses, temperature, and target moisture content in short pieces of lumber based on relationships developed on experiments made on small wood strips subjected to different types of restraints. Linear motion position sensors were placed around a tested specimen using a frame connected to a support body. A wireless moisture and temperature monitoring system was used to record wood moisture and temperature changes. All measurements were performed perpendicular to fiber grain while drying at 40, 60, and 80°C in an environment set for a target moisture content of 5%; the experiments were stopped when the average moisture content of the lumber was around 10%. High stress values were obtained for specimens dried at 60°C and a low relative humidity, whereas a high reduction in stress level could be obtained for 80°C. The findings are intended to be used in further studies of the shrinkage process as an indicator of the tensile stresses generated in the early stages of wood drying.

Giant Room Temperature Magnetoimpedance in La<SUB>0.7</SUB>Ba<SUB>0.15</SUB>Sr<SUB>0.15</SUB>MnO<SUB>3</SUB> and Development of a Sensitive Position Detector

Observation of room temperature giant magnetoimpedance in La0.7Ba0.15Sr0.15MnO3 compound having nanometric grain size is reported under low magnetic field and over the frequency range between 50 KHz and 15 MHz. Both the resistive and reactive components of impedance increase with increasing frequency due to skin effect of the metallic state below T(C). Above a critical frequency (1 MHz), a sharp increase in both R and X and hence Z is observed. The applied magnetic field influences the impedance by affecting the penetration depth via the transverse permeability and gives rise to large magnetoimpedance (approximately 70%) at low fields up to 0.1 T. Magnetoimpedance of La0.7Ba0.15Sr0.15MnO3 compound display major change (approximatley 61%) between 0.02 and 0.035 T and appears to originate due to the spin alignment of the charge carriers across the grain boundaries. At fields > 0.1 T, magnetoimpedance displays near saturation, corresponding to the completion of the spin alignment across the grain boundaries. An unique scaling behavior has been observed for field dependence of magnetoimpedance at various frequencies, which could be well accounted by a phenomenological model. Feasibility of the development of a sensitive linear position sensor is also demonstrated.

Nanoprecision MEMS Capacitive Sensor for Linear and Rotational Positioning

This paper presents a microelectromechanical systems (MEMS) capacitive position sensor for nanopositioning applications in Probe storage systems. The objective of the sensor system design is to develop a high-precision <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">X</i> - <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Y</i> linear and rotational position sensor with a minimum sensor area and a large range of movements at high speed. To achieve this, first, a simple sensor noise model scalable with a sensor area was developed, in which all the parasitic capacitances are taken into account. Furthermore, a signal-processing solution was developed to compensate for the nonlinearities caused by rotational disturbances and, at the same time, to generate a rotational position signal for active rotation-control purposes. A MEMS capacitive sensor prototype was constructed with the design of a 13-mum pitch, a 300-mum peak-to-peak linear stroke, and a 3.46-mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> sensor area at a 3-mum gap. The measured sensor noise was 0.2 nm 1sigma, which corresponds to 12 mudeg 1sigma for the fabricated prototype sensor, at 25-kHz bandwidth. Furthermore, the signal linearity was significantly enhanced by the proposed sensor signal processing, with a measured sensor signal nonlinearity of 0.78% for an 80-mum peak-to-peak stroke at 200 Hz. Finally, the capacitive sensor-based dynamic closed-loop <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">X</i> - <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Y</i> linear and rotational position control of an electromagnetic scanner was successfully demonstrated.

Improving the Accuracy of Magnetostrictive Linear Position Sensors

Magnetostrictive (MS) sensors are based on the transmission of ultrasonic signals in a waveguide and constitute an interesting alternative to optical encoders for long-range absolute high-precision measurement of linear position. Despite their inherent conceptual simplicity, many aspects of the sensor design must be considered to achieve an accuracy in the 10-mum range. This paper describes research in a new kind of MS linear position sensor, focusing on the enhancement of the processes of generation, transmission, and reception of the ultrasonic waves, with the aim of obtaining high measurement accuracy. Empirical results obtained with a sensor prototype indicate an improvement of six times over the precision of standard MS sensors.

Electronic Control of a Motorcycle Suspension for Preload Self-Adjustment

This paper describes the application of electronics to the control of the rear suspension of a motorcycle. The aim of the system is to make the suspension work around its optimal operating point, so that the safety and comfort of the vehicle can be improved. In fact, variations of the load carried by the vehicle determine a change of the suspension spring compression that moves the operating point away from the optimal value. Spring compression can also be changed by varying the suspension preload. The electronic system described here reveals load changes and automatically adjusts the motorcycle suspension preload in order to compensate the load variation and keep the suspension to its optimal operating point. The system is based on a linear position sensor that monitors the actual stroke of the suspension and a microcontroller that executes the control algorithm and drives the preload actuator. Road tests carried out on a motor scooter equipped with the system show its correct functionality and demonstrate the achievement of a better operation of the suspension with simple hardware and cost affordable for the two-wheel market.

Nano-Positioning of a Electromagnetic Scanner with a MEMS Capacitive Sensor

This paper presents the control design and experimentation of a prototype electromagnetic scanner with an integrated capacitive linear and rotational position sensor for small form factor probe storage. An array of probe heads is to be precisely positioned in X/Y linear and rotation directions so that high areal density (>1 terabit/in2) and high data throughput can be achieved. The scanner has X/Y motion capabilities with a linear stroke of about 300 µm. It can also generate rotational motion with offset actuators to compensate for disturbances, mechanical tolerance and nonlinearities. System characterization, modeling, MIMO control design and simulation, and preliminary experimental results are presented. The feasibility of rotation control with the developed capacitive sensor and offset actuators is experimentally confirmed.

Impedance Characteristics Analysis of the Non-Contact Magnetic Type Position Sensor

The mechanical contact type potentiometer that has been conventionally used as a position sensor, is pointed out the problems of contact reliability, life time, and so on. Therefore, we are developing the non-contact magnetic type linear position sensor using impedance change according to the displacement.In this paper, we evaluate AC magnetization characteristic of the core material used for a sensor, and investigate how to use complex magnetic permeability in the three-dimensional finite element analysis. In addition, the impedance characteristic of the non-contact magnetic type position sensor is calculated using the measured complex magnetic permeability of the core. As a result, we obtained the validity of the method that compares the measurements of the prototype to calculated value.

Antialiasing Encoder Interface With Sub-Nyquist Sampling

A technique is presented for reconstructing absolute position or angle from time-sampled outputs of incremental encoders. Unlike existing techniques, the new method is able to track analog quadrature outputs with frequency contents higher than the Nyquist frequency. The algorithm is described in detail, and both the existing and new methods are tested using a linear position sensor and a high-speed hydraulic actuator. The results from these tests demonstrate aliasing and incorrect tracking for the existing algorithm and correct tracking for the new algorithm. The technique is an excellent complement to resolution-enhancing encoder interfaces that sample raw analog encoder outputs

A high accuracy magnetostrictive linear position sensor

Magnetostrictive (MS) linear position sensors, which operate by measuring the time of flight of ultrasonic signals propagating in a waveguide, are one of the possible technologies for long range, absolute and high precision measurement. However, their accuracy is still far from the micrometer level achieved by standard differential sensors like optical encoders. This paper describes work in progress in a novel kind of MS linear position sensor, and considers the optimization of the processes of generation, transmission and reception of the ultrasonic waves in order to obtain higher precision. Preliminary results with the new sensor indicate a considerable improvement over the accuracy of standard MS sensors.