Fast Positioning Research Articles

Simulation of a Gas Electron Multiplier Detector for Hard X-Ray Imaging with a Novel Nano Converter

One of the most marvelous applications of GEM is hard X-ray imaging. For increasing the detection efficiency, a photoconverter is usually required. In this work a novel nanostructure photo converter is proposed. Simulation results show that the combination of fast position sensitive gas detector with nanophoto converter can be improved the detection efficiency by one order of magnitude in comparison to the bulk one, which is more benefic for hard X-ray medical imaging applications.

3D scalp extraction and reconstruction of MRI brain images

A new scalp extraction method for Magnetic Resonance Imaging(MRI) brain images in 3D was proposed for the requirements of image guided surgery on fast and accurate positioning in craniotomy.Firstly,anisotropic diffusion filtering was used to reduce noises,and the brain parenchyma image was got by the medical software of BrainSuite3.Afterwards,the brain parenchyma was removed and the threshold of scalp from non-brain-image was calculated.Thirdly,outside surface was extracted by mathematical morphology.Finally,combined with the gray value of scalp,the scalp was reconstructed by Marching Cube(MC) algorithm.The experiments show that this method can extract scalp effectively and the precision reaches sub-pixel's level by connecting threshold,mathematical morphology and MC algorithm.

Fast Position and Accurate Segmentation Algorithms for Detecting Surface Defects of the Thermal-State Heavy Rail Based on Machine Vision

Color imaging in the hot rolled condition provides the better reaction of heavy rail on surface defects. In this paper, it proposes a series of novel algorithms of accurate position and segmentation of surface defects of heavy rail. An image acquisition device is designed on the adjustable camera bracket with the linear array CCD, and based on the correlation among pixels at the image level, a fast positioning method is developed for searching the Region Of Interesting (ROI) of the surface defects. Using the Mean-Shift image filtering algorithm which features multi-parameter kernel function, amendments to the sampling point weights and regional search with the nearest neighbor sampling points, accurate segmentation of the identification character is easily achieved by K-means clustering. Experiments show that this algorithm for the identification of the heavy rail surface defects is proven to be more rapid in testing the inclusions, cracks and oxide skin defects with a good promotional value.

Initial Friction Compensation Using Rheology-Based Rolling Friction Model in Fast and Precise Positioning

This paper presents an initial friction compensation by a disturbance observer which is designed on the basis of a rolling friction model (RFM) for the fast and precise positioning of ball-screw-driven table systems. Rolling friction in the table drive mechanism behaves as a nonlinear elastic component in the microdisplacement region, deteriorating the fine settling performance. The effects of the rolling friction on the positioning, therefore, should be compensated to provide the desired control performance. In the compensator design, a feedback control with a disturbance observer allows the plant system to behave as a nominal one with a robust stability and compensates for the effects of nonlinear friction on the positioning performance. The disturbance observer, however, inherently includes an estimation delay at the starting motion due to low-pass filters and delay components. In this paper, therefore, an RFM is adopted as an initial value compensation of the disturbance observer to compensate for the initial friction behavior, providing the delay-free estimation. The proposed compensation method has been verified by numerical simulations and experiments using a prototype for industrial positioning devices.

Sliding Mode Control for BLDC Electromechanical Actuator Based on DSP

This paper deals with the design, simulation and implementation of a digital sliding mode controller for brushless DC motor-based electromechanical actuator. Firstly, a mathematic model of the actuator is drawn from its structure. Secondly, sliding mode control algorithm with the approach to weaken chattering is designed for the system, and simulations are carried out under Matlab/Simulink environment. Thirdly, the SMC algorithm is implemented on TMS320F2812 digital signal processor platform along with extensive experiments. Lastly, results of simulation and experiment are compared and discussed, showing that the proposed approach can achieve accurate and fast position tracking in the presence of load disturbance and plant parameter variations.

P 233. Robot-assisted and image-guided randomized TMS mapping of human and primate hand muscle

Introduction Coil positioning is a crucial factor for transcranial magnetic stimulation (TMS). Manual positioning of flat TMS coil against the curved head allows for errors in translation and rotation. As scalp markings are an ineffective way to ensure consistency in coil positioning, image-guided neuronavigation is used to reduce errors. However, as manual neuronavigation increases time for coil positioning it is less suitable when the coil has to be moved between pulses during TMS mapping. The use of a robot for coil positioning may overcome these drawbacks of manual neuronavigation. Objectives We aimed at assessing the practicability and efficacy of the using a robot for a neuronavigated TMS mapping of the cortical representation of the first dorsal interosseus (FDI) of humans and rhesus monkey. Materials and methods For FDI mapping, 12 supra-threshold stimuli (120% RMT) were applied in a randomized order to each grid point of a 7 × 7 grid with a spacing of 10 mm in 8 subjects (mean age 26 y, 6 male) with a Magstim 200 stimulator and a standard 70 mm figure-8 coil. Surface EMG was recorded from contralateral FDI. An Adept Viper s850 robotic arm moved the coil to each grid point on an MRI-based head model in a random order. An IR camera obtained actual positional data of the head. This allowed tracking of head movements and respective online movement compensation by the robot. Centers of gravity were projected onto the brain surface and co-registered to an MNI152 T1 1 mm brain template. A similar setup was used for FDI mapping in a male adult rhesus monkey on a 4x5 grid with 5 mm spacing. TMS was applied with a Magstim 25 mm figure-8 coil. The mapping was performed during multiple sessions during which the monkey’s head was attached to a frame with frontal and occipital head posts. Relaxation of FDI was rewarded with water after each pulse. Results TMS Mapping sessions took about 80–90 min in each subject with a pulse interval of 8 s. Preparations lasted about 20 min. A closely spaced TMS representation of FDI could be identified in each subject within the precentral gyrus. The shape of the representation area resembled ovals with a mean maximum MEP amplitude of 1.35 mV (SD: 0.52). Mean stereotaxic coordinates of the centers of gravity were (−36, −12, 67) in MNI152 space. In the animal experiment, the monkey adapted to the setup within 4 weeks. The preparation time for each session was about 10 min. Across all sessions muscle relaxation was present during 64% of the pulses. The pulse interval was 13.4 s. Four repetitions of a complete grid could be recorded in a single session of about 45 min duration. MEPs from contralateral FDI were elicited from a highly defined elliptical area (1 × 1.5 cm) within the precentral gyrus. Conclusion Due to the combination of fast high-precision coil positioning and online head tracking, robot-assisted and image-guided TMS is exquisitely suited to perform randomized TMS mappings in the human with acceptable preparation times. In addition, this method allows for precise TMS mapping of the considerably smaller rhesus brain where high-precision coil positioning with a high inter-session reliability is required for multiple session mappings with grid sizes in the millimeter scale.

Gender-specific associations between functional autonomy and physical capacities in independent older adults: Results from the NuAge study

BackgroundEven with healthy and active aging, many older adults will experience a decrease in physical capacities. This decrease might be associated with diminished functional autonomy. However, little is known about the physical capacities associated with functional autonomy in older women and men. ObjectiveThis study aimed to examine gender-specific associations between functional autonomy and physical capacities in independent older women and men. MethodsSecondary analyses were carried out using cross-sectional data from 652 women and 613 men who participated in the NuAge longitudinal study. The “functional autonomy measurement system” (SMAF) was used to evaluate functional autonomy. The physical capacities measured (tests used) were: biceps and quadriceps strength (Microfet dynamometer), grip strength (Martin vigorimeter), unipodal balance, changing position & walking (timed up and go), normal & fast walking (four-meter walking speed) and changing position (chair stand). Correlation and multiple linear regression analyses adjusted for age, depressive symptoms and body composition were performed. ResultsOn average, participants were aged 73 years and had mild to moderate functional autonomy loss. In women, after controlling for age, depressive symptoms and body composition, greater functional autonomy was best explained by faster changing position & walking skills and superior biceps strength (R2=0.46; p<0.001). After controlling for depressive symptoms, faster changing position & walking skills and better unipodal balance best explained greater functional autonomy in men (R2=0.21; p<0.001). ConclusionAccording to these results, physical capacities are moderately associated with functional autonomy among independent older adults, especially women.

A microstrip silicon telescope for high performance particle tracking

Bent crystals are thin silicon/germanium devices that act as a bulk dipole magnet and thus are able to deflect relativistic charged particle beams with high efficiency (up to 98%). To study their behavior on extracted beamlines in terms of deflection capability and efficiency, a fast and high position resolution telescope is needed such as the INSULAB telescope.It consists in several modules equipped with double or single side silicon detectors readout by different ASICs. The Data Acquisition system is designed to work with pulsed beams minimizing the dead time to allow the collection of a large statistics in a short time. It is based on custom VME readout/memory boards for the data storage and 12 bit ADC custom boards for the signal digitization; the present maximum DAQ rate is 6kHz.A detailed description of the detectors, the ASICs and the readout system together with the results obtained at the SPS H4 and PS T9 CERN beamlines in terms of spatial resolution and charge sharing are presented.

Investigation on the Data Processing Method for High-Precision Alignment of PM Fibers

The extinction ratio is the characteristic parameter of polarization-maintaining (PM) fiber couplers. The detection accuracy of polarization angle is related to the extinction ratio, and affects the thin-diameter PM fiber coupler performances greatly. A series of image processing steps including median filtering, adaptive image morphology, and maximum variance threshold segmentation method are used to get the outline of optical fibers. The minimum squares method is used to get the maximum intensity of the light. The experimental data is processed using the Fourier filtering method and influences of the manufacturing error and random errors of fibers are reduced. By fitting the experiment data with cubic spine method, and its mean square error of fitting is 0.05458, then the polarization angle of the PM fiber is determined. Experiments show that this method can precisely determine the fast axis position of PM fibers, and it can achieve the high precision alignment of 80 um PM fibers.

Numerical Control System Based on Permanent Magnet Linear Synchronous Motor

Linear servo system is an important part of numerical control machine tool, and its performance and quality will directly decide and affect the rapidity, stability and accuracy of numerical control device. The servo system made up of linear motor can realize zero transmission between motor and worktable with various advantages as fast response, high efficiency and position tracking precision. In this paper, the permanent magnet linear synchronous motor is used as actuator, and according to the idea of space vector decoupling control, the linear servo control structure is established based on position proportion adjustment and speed IP adjustment. On such backgrounds, the paper studies the iterative learning control method so as to realize the perfect position tracking ability and robust performance of the system. Chinese Library Classification: TG659

Fast and precise positioning using sequential adaptive feedforward compensation for disturbance

SummaryThis paper presents a performance improvement for trajectory tracking for fast‐response and high‐precision positioning using sequential adaptive compensation for disturbances. A mathematical disturbance model formulated and parametrized by an iterative learning process can estimate the actual disturbance, and the model can be sequentially adapted using the recursive least squares method so that it shows adaptivity to disturbance variations. The proposed positioning control approach involving disturbance modeling and compensation has been verified by experiments using a linear motor‐driven table system. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 184(4): 52–63, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22280

Fast Precise Positioning of Circular Mark in Automatic Optical Inspection

Captured circular marks are deformed sometimes when Automatic Optical Inspection (AOI) is used to detect various defects on Printed Circuit Boards (PCB), which may affect the precision of inspection. A new accurate positioning method of circular marks is proposed to solve the problem by obtaining the center of the most round ellipse based on the criterion that the ratio of the difference between the length and width of its circumscribed rectangle and the width of the rectangle is less than 0.1. The simulation tests show that, if the mark has much more deformations, the center positioning error of the proposed algorithm is about 0.013 pixels, and the running time is less than 40ms. Therefore, the proposed method provides good characteristics such as speediness, strong anti-interference ability and robustness.

Fast Position and Accurate Segmentation Algorithms for Detecting Surface Defects of the Thermal-State Heavy Rail Based on Machine Vision

Fast Position and Accurate Segmentation Algorithms for Detecting Surface Defects of the Thermal-State Heavy Rail Based on Machine Vision

Coordination Fault Diagnosis Based on RBF

In large-scale complex system, The establishment of a fast, accurate fault diagnosis system is more difficult because there exist many uncertain elements between the fault cause and the fault sign .A fault diagnosis system is established based on RBF cloud neural network ,the RBR (rule-based reasoning) and the CBR (case-based reasoning).The fault diagnosis system not only has the advantages of self-learning, high accuracy, randomness, fuzziness, etc ,and has the advantages of independently of mathematical model ,rich knowledge representation, mighty problem solving ability, etc. Theoretical analysis and simulation results show that the system is feasible and effective for fast and accurate fault positioning of complex systems.

Ambiguity-Free Method for Fast and Precise GNSS Differential Positioning

AbstractMethods based on integer ambiguity determination, such as the least-squares ambiguity decorrelation adjustment (LAMBDA) method, are currently used for precise global navigation satellite system (GNSS) differential positioning. In the present paper, the author proposes an ambiguity-free method based on a dedicated mixed (stochastic/deterministic) optimization algorithm that, unlike the LAMBDA method, is capable of providing reliable and accurate results using few observation epochs (e.g., 1-cm accuracy with just two epochs), having the additional advantages of insensitivity to cycle slips and impossibility of wrong ambiguity fixation. In addition, it is demonstrated that the application of the linear (deterministic) part of this algorithm yields the correct baseline results much more easily and quickly than methods requiring integer ambiguity determination, provided the initial approximate coordinates are accurate to a few centimeters. However, the use of ambiguity-free methods requires that the in...

Improvement of Settling Performance by Mode-Switching Control With Split Initial-Value Compensation Based on Input Shaper

This paper presents a novel initial-value-compensation (IVC) technique for mode-switching-control approaches in the fast and precise positioning of mechatronic systems. Parameter perturbations in plant mechanism and/or actuator generally deteriorate the positioning performance. In order to realize the desired positioning performance with robust property against the perturbations, the mode-switching control with the IVC is one of the promising approaches, where the timing of the mode switching and the time interval of the IVC critically affect the compensation performance. However, the shortening in the IVC operation interval causes an increase in the input amplitude, which leads to deterioration of the positioning performance due to saturation in control input. In this paper, therefore, a split IVC based on input-shaping techniques is applied to prevent the input amplitude from being saturated and to provide adaptiveness and robustness against unknown parameter perturbations. The effectiveness of the proposed approach has been verified by experiments using a prototype of galvanoscanners.

Control performance simulation of a space robotic joint by estimation of motor fast shaft position and speed via a seven-state nonlinear Kalman Filter

This paper presents the results of a control performance simulation for a robotic joint, sized for space applications, via a seven-state nonlinear Kalman Filter. This leads to better estimation of joint mechanical state and in particular the motor fast shaft position and speed which are directly used for the commutation and speed control functions. In the presented simulation the sensor information assumed available to the Kalman Filter are the ones normally available in the drive electronics, like currents and voltages, motor windings temperatures and speed information of the joint output shaft, downstream the reducer, derived from an output shaft absolute position sensor. The general technique to utilize a Kalman Filter estimator to support the reconstruction of the motor shaft mechanical state have been already proposed in different variants and could be considered for robotic applications in hostile environments where active electronics, inclusive hall sensors, installed in the robotic arm should be reduced to the minimum and where the need to keep the arm design as light and as simple as possible suggests to reduce the number of components into the joint to the minimum. Possible scenarios are represented by Moon and Mars robotic exploration where the extreme environmental conditions of certain areas and the convenience to keep the mass of the robotic arm as low as possible suggest the use of techniques similar to the one discussed.

Phase Resistance Feedback Control and Displacement-Resistance Model for Thick SMA Actuator

The purpose of this study is to design and control a thick shape memory alloys (SMA) actuator to achieve fast position control with two connected SMA wires. In the past, research had focused on position and force control of thin SMA wires, because they can be cooled fast in air and as it is easy to obtain fast response speeds for SMA actuators in this manner. However, the cooling time increases for thick SMA wires, making it difficult to obtain fast position responses. Phase resistance feedback control (PRFC) minimizes cooling time by shortening the long latency time of thick SMA wires. Compared with binary control, experimental results here show that a rate increase of 18% is achieved using this new method. A new displacement-resistance model which normalizes both resistance and displacement is used to estimate the total output displacement of this new SMA actuator.

Control strategies for the index finger of a tendon-driven hand

To understand how versatile dexterity is achieved in the human hand and to achieve it in a robotic form, we have constructed an anatomically correct testbed (ACT) hand. This paper focuses on the development of control strategies for the index finger motion and implementation of joint passive behavior in the ACT hand. A direct muscle position control and a force-optimized joint control are implemented for position tracking through muscle force control. The relationships between the muscle and joint motions play a critical role in both of the controllers and we implemented a Gaussian process regression technique to determine these relationships. Our experiments demonstrate that the direct muscle position controller allows for fast position tracking, while the force-optimized joint controller allows for the exploitation of actuation redundancy in the finger critical for this redundant system. We demonstrate that by implementing a passive force–length relationship at each muscle we are able to precisely match joint stiffness of the metacarpophalangeal (MCP) joint of the ACT to that of a human MCP joint. We also show the results from improved position tracking when implemented in the presence of passive muscle control schemes. The control schemes for position tracking and passive behavior are inspired by human neuromuscular control, and form the building blocks for developing future human-like control approaches.

航空相机镜筒全程快速无超调位置控制

To eliminate the overshoot of lensbarrel of an aerial camera in process of position control,a tracking differentiator was used to process step signals and to design a position transient process to control accurately the lensbarrel position without overshoots.First,the theory of the tracking differentiator was described and its characteristics were expatiated.And then,by taking position step response with a 90° input as an example,the transient process was designed and compared with that of no transient process design.Experiment results show that the position overshoot of lensbarrel can be eliminated completely through the appropriate transient process design,and the regulation time is reduced also.In the case of 90° step input,the system overshoot is reduced from 24.4% to zero and the regulation time is shorten by 28.8%.Furthermore,the fast position control of the lensbarrel was realized with non-overshoot in omnirange,in which the least square method was used to fit a curve of step input and a speedability parameter in transient process.The optimum parameter of the transient process was calculated according to the step input in control process.This method has been used in the lensbarrels of aerial cameras,and it obtains a good effect and provides significant and practical values for improving the dynamic performance of systems.