Laser Position Sensor Research Articles

Actuator and Contact Force Modeling of an Active Soft Brace for Scoliosis.

Scoliosis is an abnormality of the spinal curvature that severely affects the musculoskeletal, respiratory, and nervous systems. Conventionally, it is treated using rigid spinal braces. These braces are static, rigid, and passive in nature, and they (largely) limit the mobility of the spine, resulting in other spinal complexities. Moreover, these braces do not have precise control over how much force is being applied by them. Over-exertion of force may deteriorate the spinal condition. This article presents a novel active soft brace that allows mobility to the spine while applying controlled corrective forces that are regulated by varying the tensions in elastic bands using low-power light weight twisted string actuators (TSAs). This article focuses on the actuator and contact force modeling of the active soft brace (ASB). The actuator modeling is required to translate the twisting of string in terms of contraction of the string’s length, whereas the contact force modeling helps in estimating the net resultant force exerted by the band on the body using single point pressure/force sensors. The actuators (TSAs) are modeled as helix geometry and validated using a laser position sensor. The results showed that the model effectively tracked the position (contraction in length) with root mean square error (RMSE) of 1.7386 mm. The contact force is modeled using the belt and pulley contact model and validated by building a custom testbed. The actuator module is able to regulate the pressure in the range 0–6 Kpa, which is comparable to 0–8 Kpa pressure regulated in rigid braces. This makes it possible to verify and demonstrate the working principle of the proposed active soft brace.

Improvement of metrological characteristics of calibrating units of flow measuring devices

The paper presents an analysis of the operation of mass and volumetric calibration devicesused for calibrating flow meters of liquid media in various industries, including model testing ofhydraulic machines in specialized hydraulic turbine laboratories. The aim of the work is shown,which is to analyze the characteristics of deflecting devices and to determine the ways of decreasingthe errors arising therefrom.It was determined that the largest specific weight in the total error of determining the massand volumetric fluid flow rate is the error of the deflecting device, which depends on its dynamiccharacteristics. The system for determining the profile of the liquid flow that fills the measuringtank was improved. A device to control the position of the liquid flow and a method of determiningthe time of filling the measuring tank, taking into account the use of modern laser sensors installedon the measuring tank, is proposed.It is shown that the use of laser position sensors with intersecting beams makes it possible toreduce the measurement error of the measuring tank filling time caused by both low sensitivity offlow position control devices and asymmetry of the flow entering the deflecting device.

A new algorithm for pick‐and‐place operation

PurposeThis paper aims to represent a novel framework for optimization of robotic handling from disarray to structure where the products are randomly distributed on a surface, the initial location of the products are known (with the aid of image processing, laser position sensors, etc.) and there is a set of final positions for the products.Design/methodology/approachPick‐and‐place is one of the main solutions especially for the food products where the products are prone to damage, have adhesive surfaces and the grippers can be complicated. The aim of this paper is to maximize the utilization of the pick‐and‐place robotic system. In order to do so the handling process is modelled mathematically and the pick‐and‐place problem is formulated based on assignment problem where Hungarian algorithm is utilized to minimize the total distance travelled by the robot. Furthermore, a simulation program is developed to demonstrate the possible improvements of the algorithm in comparison with the existing algorithms.FindingsUtilizing the proposed algorithm can significantly increase the utilization of robots in the pick‐and‐place operation.Originality/valueThe new optimization algorithm can be applied to any industry with pick‐and‐place where time efficiency and maximum utilization matters.

DEVELOPMENT OF A TARGET POSITIONING SYSTEM BASED ON A LASER POSITION SENSOR FOR HIGH-EFFICIENCY WAVELENGTH-DISPERSIVE PIXE ANALYSIS

A precise target positioning system based on a laser position sensor was developed for a high-efficiency wavelength dispersive PIXE analysis. The absolute position and the target surface profile were clearly observed using this position sensor, which was rigidly connected to the target vacuum chamber. By using a thin proton beam ( width = 2 mm ) and a small target (width = 1 mm), the optimum target position for the measurement of chlorine ( Cl ) Kβ X-ray could be determined from X-ray detection yields measured at various target positions. We found that the relationship between the X-ray detection yield and the target position can be explained by the target size as well as the incident proton beam width. After precise adjustment of the target position using the above system, target samples with two different Cl compounds, NaCl and NH 4 Cl , were successfully distinguished from the difference in the measured profiles of Kβ X-ray spectra.

2 DOF resolution adjustment laser position sensor

A low cost sensor system is envisaged that has 2 distinct routes for resolution enhancement in position detection. The main area for application of the sensor design would be in the food processing and packaging industry where position resolution of the end effector is in the millimetre to sub-millimetre range. The sensor concept consists of a grid of laser light detectors attached to the stationary base and a grid of lasers attached to the mobile end effector. The photo detectors on the base provide one level for position detection enhancement, that is, the density of the sensor array. The second degree of freedom in improvement comes from the strategic positioning of a set of lasers attached to the end effector.

Modeling of NC Machine Tool Thermal Error Based on Adaptive Best-fitting WLS-SVM

In order to eliminate the influence of thermal error of NC machine on the machining precision, a novel method based on adaptive best-fitting weighted least squares support vector machine (WLS-SVM) is utilized to implement error compensation. In order to construct the thermal error model of machine tool, a series of experiments are carried out to acquire the data of a XK713 NC milling machine, including temperature on different positions and the thermal deformation of spindle. By smart temperature sensors and laser position sensors, the temperature and thermal error of the machine tool are collected respectively. First the parameters of WLS-SVM are optimized by a method called adaptive best-fitting parameter search algorithm. Then the samples are trained and the weighted coefficients are calculated according to the error variables. The regression model is constructed finally. Test results show that WLS-SVM is an effective method for error modeling which can be used for the thermal error compensation. It is superior to unweighted least squares support vector machine (LS-SVM) method and traditional least squares (LS) method.

Pulse compression using segmented grating in Gekko MII system, ILE

A segmented (tiled) grating array is now investigated as a new compressor system for the reason of manufacturing cost of large aperture single grating. However the considerable freedom of motion of segment arises new difficulties on pulse compression and focusing. We constructed a real compressor system using a segmented grating for 15cm aperture laser beam at Gekko MII 100TW laser system, ILE, for investigating several alignment techniques. In order to produce clean pulse shape and focused pattern generated by misalignments or line density mismatching between segment gratings, we applied the image rotation technique as a compressor arrangement. In addition to reduce uncertainness of motion of all optics, we introduced several sensor/detector such as laser level meter or position sensor. It is also shown that a capacitance detector can keep the perfect flatness of segmented grating surface. Using these techniques we demonstrated pulse compression close to Fourier transform limit.

Feasibility of Whole-Body MR with T2- and T1-weighted Real-time Steady-State Free Precession Sequences during Continuous Table Movement to Depict Metastases

The purpose of the study was to prospectively evaluate a whole-body magnetic resonance (MR) imaging protocol to help depict metastases by using unenhanced T2-weighted and contrast material-enhanced T1-weighted real-time sequences during continuous table movement. The study was conducted after approval of the local institutional review board and written informed consent were obtained. In 11 patients with positron emission tomographic (PET) scans positive for tumors and known metastases, whole-body MR imaging, including T2- and T1-weighted sequences, was performed before and after contrast material administration. A high-precision laser position sensor was used to register the table position for off-line multiplanar reformations of the acquired transverse whole-body data sets. Seventy-three of 75 metastases detected by using PET/computed tomography were correctly diagnosed by using MR imaging. Metastases with a diameter exceeding 5 mm could be visualized in all anatomic regions.

Integration of Ground-Penetrating Radar and Laser Position Sensors for Real-Time 3-D Data Fusion

Full-resolution 3-D ground-penetrating radar (GPR) imaging of the near surface should be simple and efficient. Geoscientists, archeologists, and engineers need a tool capable of generating interpretable subsurface views at centimeter-to-meter resolution of field sites ranging from smooth parking lots to rugged terrain. The authors have integrated novel rotary laser positioning technology with GPR into such a 3-D imaging system. The laser positioning enables acquisition of centimeter accurate x, y, and z coordinates from multiple small detectors attached to moving GPR antennas. Positions streaming with 20 updates/s from each detector are fused in real time with the GPR data. The authors developed software for automated data acquisition and real time 3-D GPR data quality control on slices at selected depths. Industry standard (SEGY) format data cubes and animations are generated within an hour after the last trace has been acquired. Such instant 3-D GPR can be used as an on-site imaging tool supporting field work, hypothesis testing, and optimized excavation and sample collection in the exploration of the static and dynamic nature of the shallow subsurface

Whole‐body magnetic resonance imaging featuring moving table continuous data acquisition with high‐precision position feedback

A novel setup for whole-body MR imaging with moving table continuous data acquisition has been developed and evaluated. The setup features a manually positioned moving table platform with integrated phased-array surface radiofrequency coils. A high-precision laser position sensor was integrated into the system to provide real-time positional data that were used to compensate for nonlinear manual table translation. This setup enables continuous 2D and 3D whole-body data acquisition during table movement with surface coil image quality. The concept has been successfully evaluated with whole-body steady-state free precession (TrueFISP) anatomic imaging in five healthy volunteers. Seamless coronal and sagittal slices of continually acquired whole-body data during table movement were accurately reconstructed. The proposed strategy is potentially useful for a variety of applications, including whole-body metastasis screening, whole-body MR angiography, large field-of-view imaging in short bore systems, and for moving table applications during MR-guided interventions.

Human interface and vibration control of robotic manipulator suspended from ceiling

A robotic manipulator, suspended from a ceiling of a general house, with an easily operated human interface and vibration-reduction control of a suspended hand, is proposed in this paper. A bedridden user can easily manipulate his/her belongings by using the robotic manipulator. The human interface is a laser pointer. When a bedridden user wishes to pick up a target object, the user exposes the target object to the laser beam spot by manipulating a joystick lever. Then, the user pushes a switch on the joystick lever. After this simple operation, the robotic hand moves automatically to the target object following a laser beam trajectory, and the user can capture the object. The robotic manipulator used in our research does not require ‘oor installation on a ‘oor because it is installed on the ceiling of a house. Two linear motion actuators are fixed on the ceiling, and the carriage is moved horizontally. The robotic hand is suspended from the carriage. An active vibration-reduction control system is designed to decrease the suspended hand vibrations. The swings of the suspended hand are detected by a hand-swing detection system using a laser position sensor. The validity of the proposed robotic manipulator has been confirmed by the experimental and simulation results.

A smart boring tool for process control

A mechatronic metal cutting tool has been developed to improve the accuracy and flexibility of line boring machining in the automotive industry. Laser position sensors and piezoelectric actuator were integrated into the rotating body of the boring tool. To compensate the boring bar droop and effects of cutting forces, a fast tool servo utilizing feedback control of the boring tool insert position was designed and embedded in the rotating tool assembly. In addition to position control, a self-monitoring algorithm that utilizes disturbance estimator has been put together in the controller. Experimental results demonstrated that the developed cutting process controller improves the accuracy of the boring tool as well as reliably detects the process failures, such as tool tip breakage, without additional monitoring equipment.

Moving boundary capillary electrophoresis with concentration gradient detection

A rugged and inexpensive Schlieren optics detection system consisting of a laser, focusing lens and light beam position sensor was combined with moving boundary electrophoresis performed in a 10 cm × 20 μm I.D. capillary. This system facilitated rapid analysis and universal detection of sample components. The laser beam, which is focused directly into the separation capillary, probes the refractive index gradients produced by the arrival of new boundaries. The frontal injection method used in this approach introduces samples into the capillaries without discrimination and provides higher sensitivities because of the lack of dilution during the separation process compared with the zone technique. A specially designed cartridge accommodates a short piece of the separation capillary and reservoirs for buffer and sample. The separation in this method is completed usually within 30 s. During this short separation time only a small dispersion associated with diffusion of analytes along the flow direction occurs, which ensures that high gradients are generated in the detection volume. The detection limits in this approach are sub-micromolar concentrations of analyte injected for low-molecular-weight compounds such as sucrose. This system has been applied to the separation of amino acids and carbodydrates.

Variably shaped electron beam lithography system, EB55: I. System design

The precision electron beam exposure system EB55 has been developed for direct wafer writing of submicron patterns. This paper describes the system architecture, design approach, and system specifications. The system utilizes a variably shaped beam column with a spot size ranging from 0.5 to 5.1 μm square, which is adjustable in 0.02 μm increments. Pattern data, compressed by a pattern data preparation software, is supplied to the high-speed digital control unit, where it is expanded to provide control data at a 320 ns shot rate to an analog unit. The analog unit provides deflection current and voltage to the electrostatic deflection plates and magnetic deflection coils with 0.02 μm resolution. Pattern accuracy is maintained by deflection distortion correction and overlay techniques. The deflection error is measured within 0.02 μm accuracy over a 2.6 mm square field with a mark detector and laser position sensor and corrected by a digital correction unit. Overlay accuracy is assured by registering to fiducial marks on the wafer and measuring wafer deformation to determine field adjustments. The exposure time per wafer is about 41 min with 0.5 μm minimum linewidth and ±0.1 μm overlay accuracy (3σ) using 20 μC/cm2 resist sensitivity and 8×108 shots per wafer. In this case, the writing time, the registration time, and the stage move time are 32, 3, and 6 min, respectively.

A Seebeck effect position sensor for CO2 laser beam alignment

A new concept for a laser position sensor is presented. The device utilizes the Seebeck effect in semiconductors. Results using a Si detector show position linearity and energy linearity of the device signal. A theoretical model explaining the operation of the device is outlined. Applications to pulsed laser beam alignment are discussed.