Target Motion Research Articles

Are attentional momentum and representational momentum related?

ABSTRACT In attentional momentum, detection of a target further ahead in the direction of an ongoing attention shift is faster than detection of a target an equal distance in an orthogonal direction. In representational momentum, memory for the location of a previously viewed target is displaced in the direction of target motion. Hubbard [Hubbard, T. L. (2014). Forms of momentum across space: Representational, operational, and attentional. Psychonomic Bulletin & Review, 21(6), 1371–1403; Hubbard, T. L. (2015). The varieties of momentum-like experience. Psychological Bulletin, 141(6), 1081–1119] hypothesized that attentional momentum and representational momentum might be related or reflect the same mechanism or similar mechanisms. Two experiments collected measures of attentional momentum and representational momentum. In Experiment 1, attentional momentum based on differences between detecting targets opposite or orthogonal to a cued location was not correlated with representational momentum based on M displacement for the final location of a target. In Experiment 2, attentional momentum based on facilitation in detecting a gap on a probe presented in front of the final target location was not correlated with representational momentum based on a weighted mean of the probabilities of a same response in probe judgments of the final target location. Implications of the findings for the relationship of attentional momentum and representational momentum, and for theories of momentum-like effects in general, are considered.

Dynamic grasping of manipulator based on realtime smooth trajectory generation

For safe and effective grasping in a dynamic environment, planning algorithms need real-time to deal with changing the target’s movement and obstacles. This paper proposes a new sequential Sense-Plan-Act (SeqSPA) dynamic grasping framework to generate a robot’s real-time and smooth grasping trajectory. Specifically, we cluster all stable grasps of the target, transform the clustering centers into pregrasps, and predict the future motion of the moving objects by using the observed values. The trajectory optimization algorithm constructing the approximative joint space gradient field can generate a smooth trajectory for a 6-DOF industrial robot arm within 2 ms. Our method generates trajectories for multiple pregrasps and selects the time-optimal trajectory for execution. Simulation comparison and actual experiments verify that our framework can immediately respond to environmental changes and efficiently find a grasping trajectory of the near-optimal time. The trajectory optimization algorithm in the framework can also be used alone to generate a real-time grasping trajectory when the prediction module cannot accurately predict the target motion.

Energy‐compatible modulating functions for the stochastic generation of fully non‐stationary artificial accelerograms and their effects on seismic site response analysis

AbstractThe reliability of non‐linear dynamic analysis aimed to predict the seismic performance of structural and geotechnical systems, as well as their dynamic interaction, is significantly affected by the selection of suitable input motions. Several procedures for selecting actual earthquake records compatible with the seismic hazard at the site of interest and for evaluating synthetic accelerograms consistent with a seismological framework are available in the literature. However, the degree of uncertainty affecting these approaches might lead to unreliable performance predictions especially for strongly non‐linear problems, such as those involving the response of soils to cyclic and dynamic loading. In this vein, the paper presents a procedure for generating fully non‐stationary ground motions ensuring energy compatibility with a target motion. Two different approaches have been introduced: i) the time window method based on the central finite difference approach and ii) the simplified intensity‐compatible approach in which a closed form expression is provided to evaluate a modulating function that depends on the Arias intensity and on the strong motion duration of a target motion. To highlight the reliability and the accuracy of the proposed procedure, several sets of spectrum‐compatible artificial accelerograms, generated starting from a rock outcropping motion, were used as input motions in a series of one‐dimensional site response analyses. The analysis results are presented and discussed in the paper highlighting the influence of the main features of the proposed generation procedure on the variability of the computed site response.

Location and tracking of environmental pollution sources under multi-UAV vision based on target motion model

In computer vision, the detection and tracking of moving objects has become a hot topic today. The target tracking technology in this paper refers to the visual tracking of the ground moving target by the aircraft during the flight. Since both the aircraft and the target are moving, there are background and two motion vectors composed of the target and the background in the acquired image. Therefore, this paper proposed a research on the location and tracking of environmental pollution sources under multi-UAV vision based on the target motion model. This paper first introduced the UAV target tracking technology, and analyzed the development history and types of UAVs in detail. Then, based on the increasingly serious environmental pollution, this paper proposed to use UAV sensing technology to locate the pollution source. Finally, in the experimental part, this paper tested the UAV flight platform, and carried out the actual operation and positioning of the pollution source. The final experimental results showed that within 0 ~ 360 s, the attitude angle obtained by the gradient descent method had no divergence phenomenon, which could effectively reduce the error caused by the integration; the inclination angle deviation of the two groups of experimental equipment was within ±2.5°, the roll angle deviation was within ±3°, and the deviation angle was relatively large at some moments, but the average deviation was only 0.8°.

A simple method to measure the gating latencies in photon and proton based radiotherapy using a scintillating crystal.

In respiratory gated radiotherapy,low latency between target motion into and out of the gating window and actual beam-on and beam-off is crucial for the treatment accuracy. However, there is presently a lack of guidelines and accurate methods for gating latency measurements. To develop a simple and reliable method for gating latency measurements that work across different radiotherapy platforms. Gating latencies were measured at a Varian ProBeam (protons, RPM gating system) and TrueBeam (photons, TrueBeam gating system) accelerator. A motion-stage performed 1cm vertical sinusoidal motion of a marker block that was optically tracked by the gating system. An amplitude gating window was set to cover the posterior half of the motion (0-0.5cm). Gated beams were delivered to a 5mm cubic scintillating ZnSe:O crystal that emitted visible light when irradiated, thereby directly showing when the beam was on. During gated beam delivery, a video camera acquired images at 120Hz of the moving marker block and light-emitting crystal. After treatment, the block position and crystal light intensity were determined in all video frames. Two methods were used to determine the gate-on (τon ) and gate-off (τoff ) latencies. By method 1, the video was synchronized with gating log files by temporal alignment of the same block motion recorded in both the video and the log files. τon was defined as the time from the block entered the gating window (from gating log files) to the actual beam-on as detected by the crystal light. Similarly, τoff was the time from the block exited the gating window to beam-off. By method 2, τon and τoff were found from the videos alone using motion of different sine periods (1-10s). In each video, a sinusoidal fit of the block motion provided the times Tmin of the lowest block position. The mid-time, Tmid-light , of each beam-on period was determined as the time halfway between crystal light signal start and end. It can be shown that the directly measurable quantity Tmid-light - Tmin =(τoff +τon )/2, which provided the sum (τoff +τon ) of the two latencies. It can also be shown that the beam-on (i.e., crystal light) duration ΔTlight increases linearly with the sine period and depends on τoff - τon : ΔTlight =constant•period+(τoff - τon ). Hence, a linear fit of ΔTlight as a function of the period provided the difference of the two latencies. From the sum (τoff +τon ) and difference (τoff - τon ), the individual latencies were determined. Method 1 resulted in mean (±SD) latencies of τon =255±33ms, τoff =82±15ms for the ProBeam and τon =84±13ms, τoff =44±11ms for the TrueBeam. Method 2 resulted in latencies of τon =255±23ms, τoff =95±23ms for the ProBeam and τon =83±8ms, τoff =46±8ms for the TrueBeam. Hence, the mean latencies determined by the two methods agreed within 13ms for the ProBeam and within 2ms for the TrueBeam. A novel, simple and low-cost method for gating latency measurements that work across different radiotherapy platforms was demonstrated. Only the TrueBeam fully fulfilled the AAPM TG-142 recommendation of maximum 100ms latencies.

Range-Doppler Based Moving Target Image Trace Analysis Method in Circular SAR

The single channel Circular Synthetic Aperture Radar (CSAR) has the advantage of continuous surveillance of a fixed scene of interest, which can provide high frame rate image sequences to detect ground moving targets. Recent image-sequence-based CSAR moving target detection methods utilize the fact that the target signal moves fast in the image sequence. Knowledge of the target’s image trace(moving trace in the image sequence, which is equal to a target signature’s morphology in a full aperture CSAR image) can help design better detection methods. However, previous signature morphology studies are based on linear track geometry assumptions, which cannot handle CSAR’s nonlinear track. Hence, this paper proposes a new image trace method based on the range-Doppler principle. The proposed method can deduct the exact analytic function of an arbitrary moving target’s image trace in CSAR. The method assumes radar operates in side-looking mode and that the target moves on the ground plane. It combines the range-Doppler equations(i.e., iso-range and iso-Doppler relation) and Cartesian transformation between the ground and radar coordinate system to obtain the parametric functions of the image trace. Based on the method, three types of target motion (including linear and nonlinear motion) are analyzed. The proposed method is validated with both simulated and real data.

Sperm whale distribution and seasonal density in the Faroe Shetland Channel

Results from previous surveys suggest that an area of the northeast Atlantic, the Faroe Shetland Channel, is important for cetaceans. This study utilised passive acoustic survey techniques to evaluate the density of sperm whales in the Channel. Two-week surveys were carried out during oceanographic cruises in May and October 2001, and May 2002. A two hydrophone array was towed behind the vessel throughout the majority of the survey routes and was monitored by a two-person team and by software designed to automatically detect and measure bearings to whales. Distances of individual sperm whales from the trackline were determined using target motion analysis. Standard line transect techniques were applied to calculate the density of whales during surveys. The effects of sea conditions and survey vessel on the ability to detect whales were tested; the encounter rate and effective stripwidth (esw) were estimated independently for each sea state and for each of the vessels. A total of 79 individual whales were detected, and their distances from the trackline were calculated. As a probable result of insufficient sample size and a small effects size, neither the esw nor the encounter rates varied significantly with sea state or between the two survey vessels. The density of sperm whales during each of the surveys was estimated to be 2.05, 0.52 and 1.75 whales per 1,000km2 for the May 2001, October 2001 and May 2002 surveys respectively. Sperm whales were distributed across the majority of the Faroe Shetland Channel. This study has provided the basis for meaningful hypothesis generation in future studies and to gain a better understanding of the factors underlying the spatial and temporal distribution patterns of sperm whales in this area; data on oceanographic, biological and anthropogenic determinants should now be examined.

Adaptive second order sliding mode guidance law for missile-target interception with fuzzy logic system

This paper presents the design of a 3D missile guidance law based on a second order sliding mode control technique employing an adaptive tuning law and a fuzzy gain scheduling. At the outset, the super-twisting sliding mode guidance law is obtained to overcome the chattering phenomenon. Then, without the knowledge about the bounds of disturbances, an adaptive law is used to determine the control gains. The results are enhanced using a fuzzy module that provides the controller parameters according to a set of linguistic rules. Finally, a comparative set of simulation results are given. To verify the performance and effectiveness of the proposed guidance law, we compare the performances of the traditional sliding mode (SM) guidance law, the traditional super-twisting sliding mode (STWSM) guidance law, the adaptive super-twisting sliding mode (ASTWSM) guidance law and the adaptive fuzzy super-twisting, sliding mode (AFSTWSM) guidance law. The simulation scenarios consider fundamental target movements. The results demonstrate that the proposed adaptive guidance laws display better performance in terms of miss distance, intercept time, and final closing velocity compared the alternatives considered in this study.

Towards fast adaptive replanning by constrained reoptimization for intra-fractional non-periodic motion during robotic SBRT.

Periodic and slow target motion is tracked by synchronous motion of the treatment beams in robotic stereotactic body radiation therapy (SBRT). However, spontaneous, non-periodic displacement or drift of the target may completely change the treatment geometry. Simple motion compensation is not sufficient to guarantee the best possible treatment, since relative motion between the target and organs at risk (OARs) can cause substantial deviations of dose in the OARs. This is especially evident when considering the temporally heterogeneous dose delivery by many focused beams which is typical for robotic SBRT. Instead, a reoptimization of the remaining treatment plan after a large target motion during the treatment could potentially reduce the actually delivered dose to OARs and improve target coverage. This reoptimization task, however, is challenging due to time constraints and limited humansupervision. To study the detrimental effect of spontaneous target motion relative to surrounding OARs on the delivered dose distribution and to analyze how intra-fractional constrained replanning could improve motion compensated robotic SBRT of the prostate. We solve the inverse planning problem by optimizing a linear program. When considering intra-fractional target motion resulting in a change of geometry, we adapt the linear program to account for the changed dose coefficients and delivered dose. We reduce the problem size by only reweighting beams from the reference treatment plan without motion. For evaluation we simulate target motion and compare our approach for intra-fractional replanning to the conventional compensation by synchronous beam motion. Results are generated retrospectively on data of 50patients. Our results show that reoptimization can on average retain or improve coverage in case of target motion compared to the reference plan without motion. Compared to the conventional compensation, coverage is improved from 87.83 % to 94.81 % for large target motion. Our approach for reoptimization ensures fixed upper constraints on the dose even after motion, enabling safer intra-fraction adaption, compared to conventional motion compensation where overdosage in OARs can lead to 21.79 % higher maximum dose than planned. With an average reoptimization time of 6 s for 200 reoptimized beams our approach shows promising performance for intra-fractional application. We show that intra-fractional constrained reoptimization for adaption to target motion can improve coverage compared to the conventional approach of beam translation while ensuring that upper dose constraints on VOIs are notviolated.

Reproducibility of surface-based deep inspiration breath-hold technique for lung stereotactic body radiotherapy on a closed-bore gantry linac.

Tumor motion and delivery efficiency are two main challenges of lung stereotactic body radiotherapy (SBRT). The present work implemented the deep inspiration breath hold technique (DIBH) with surface guided radiation therapy (SGRT) on closed-bore linacs and investigated the correlation between SGRT data and internal target position. Thirteen lung SBRT patients treated in DIBH using a closed-bore gantry linac and a ring-mounted SGRT system were retrospectively analysed. Visual coaching was used to achieve DIBH with a±1mm threshold window in the anterior-posterior direction. Three kV-CBCTs were added to the treatment workflow and examined offline to verify intra-fraction tumor position. Surface-based DIBH was analysed using SGRT treatment reports and an in-house python script. Data from 73 treatment sessions and 175kV-CBCTs were studied. Correlations between target and surface positions were studied with Linear Mixed Models. Median intra-fraction tumor motion was 0.8mm (range: 0.7-1.3 mm) in the anterior-posterior direction, 1.2mm (range: 1-1.7 mm) in the superior-inferior direction, and 1mm (range: 0.7-1.1 mm) in the left-right direction, with rotations of <1° (range: 0.6°-1.1°) degree in all three directions. Planned target volumes and healthy lung volumes receiving 12.5Gy and 13.5Gy were reduced on average by 67% and 54%, respectively. Lung SBRT in DIBH with the ring-mounted SGRT system proved reproducible. The surface monitoring provided by SGRT was found to be a reliable surrogate for internal target motion. Moreover, the implementation of DIBH technique helped reduce target volumes and lung doses.

Study on Maneuvering Target Trajectory Simulation and Tracking Based on IMM algorithm

On the background of air defense missile which use radar command guidance, this article focuses on the maneuvering target trajectory simulation and tracking problem by considering possible maneuvering modes and target overload. Taking Serpentine maneuvering (S maneuvering) as an example, the target trajectory is simulated based on overload using stepwise design method, and data are measured through sensor models. Since single model cannot model the maneuvering target motion exactly, the estimation is addressed by combining the interacting multiple model algorithm and unscented Kalman filter algorithm, so as to study the applications of maneuvering target trajectory simulation and tracking in air defense missile systems. The effectiveness of the algorithm is demonstrated with simulated data.

Robust Passive Proximity Detection Using Wi-Fi

Indoor target detection through motion sensing based on Wi-Fi signals has gained much attention recently. However, most of the existing motion detection approaches can only detect motion in a large coverage area without knowing the distance of the target motion from the transmitter (Tx)/receiver (Rx). Passive positioning techniques can provide the location of a target, which, however, requires high deployment efforts without robust performance. In this article, we present a novel technique for detecting motion in proximity by exploring the physics behind the indoor radio frequency (RF) multipath propagation. We discover that motion in the proximity of the Rx/Tx produces distinct time dispersion over the radio channel at the Rx/Tx side. By exploring two novel metrics and linking them with the distance of the motions to antennas, we are able to precisely distinguish motions in nearby proximity from the motions far away. Extensive experiments in various real-world scenarios demonstrate that the proposed scheme can achieve true positive rates (TPRs) greater than 95% and 99% in distance-based and room-level proximity detection, respectively, while maintaining the corresponding false positive rates (FPRs) less than 5% and 0.5%. The detection delays for a detection distance of 2 m are within 0.6 s, which verifies the responsiveness of the proposed scheme.

Single-Position Passive Location of a Moving Target with Consideration of the Evolutionof the Period and Level of the Pulsed Radio Signal

Single-Position Passive Location of a Moving Target with Consideration of the Evolutionof the Period and Level of the Pulsed Radio Signal

Research on the method of searching and tracking of the time-sensitive target through the mega-constellation

The time-sensitive target has the characteristics of high-speed motion and an uncertain model, which present challenges to the observation process. Aiming at the problem of searching and tracking the time-sensitive target in a region, the scheduling method of the mega-constellation based on grids coding is proposed in this paper. Above all, the observation problem is assessed, after which the grids coding model of observation resources and tasks is constructed. Afterwards, the dynamic updating process of probability is established as a Markov state transition, taking into consideration the movement of the time-sensitive target during the searching phase, and the dynamic prediction model of target position for target tracking is founded, which takes into account the unpredictability of the time-sensitive target model. Ultimately, the mega-constellation searching technique is developed with the enhancement of information entropy of covering grids as the objective function. Based on the optimal acquisition probability of grids, a method for determining the field-of-view center grid code is established to realize cooperative tracking. It is proved by experiments that, the continuous tracking of time-sensitive targets can be realized and the percentage of searches achieved within half an hour is greater than 92%, which is 10% to 35% higher than the conventional methods.

Autonomous Spacecraft Rendezvous Using Tube-Based Model Predictive Control: Design and Application

As the concentration of large space debris increases, how rendezvous maneuvers involving these typically non-cooperative, freely tumbling bodies are planned and executed is evolving. The rendezvous must be carefully planned, employing up-to-date in situ data to identify the inertial and motion parameters of the target body, and executed in a manner that accounts for the remaining uncertainty in these parameters. This paper presents an extension of the Tumbling Rendezvous via Autonomous Characterization and Execution (TRACE) pipeline used in the ROAM/TumbleDock Astrobee experiment campaign, which sequences the target state estimation, motion planning, controller design, and maneuver execution tasks while additionally providing logical loop-back avenues to previous tasks, increasing the chances of a successful maneuver. The pipeline’s performance is analyzed in simulation, utilizing target state estimates generated in a previous activity on a dedicated on-ground test bed; online motion planning, based on nonlinear programming and warm-started using a trajectory library generated offline with a novel graphics-processing-unit-based method; and tube-based model predictive control to robustly track the planned trajectory. Tube-based model predictive control is an actively evolving subject, distributed over multiple publications and various research interests. The necessary theory and considerations for practical implementation of the method are consolidated; its use, features, and limitations in the proposed task are demonstrated.

A detection probability guaranteed energy-efficient scheduling mechanism in large-scale WSN

In intrusion detection wireless sensor network (WSN), ensuring detection performance and prolonging network lifetime are two equally important but contradictory pursuits. In this paper, we propose a node scheduling scheme jointly considering the detection probability, energy consumption, and energy balance to ensure the detection performance and maximize the network lifetime. We mathematically transform the scheduling process into an optimization problem and further propose a novel mechanism called greedy-like step-by-step trimming heuristic algorithm (GLSTA) to obtain the optimal task nodes set. By gradually trimming unnecessary nodes, GLSTA intelligently eliminates redundancy and obtains a task set that can save energy and balance the residual energy of nodes. Moreover, we propose a dual cluster head (OCH-DCH, organization cluster head-data cluster head) scheme to realize the smooth update of the cluster due to the target movement. Simulation results show that the rounds of half nodes death of GLSTA are extended by at least 28.6% compared with existing mechanisms.

Transposition of functioning muscles in complex treatment of adult patients with injuries of the bracheric plexus (literature review)

Introduction. Injuries to the brachial plexus are one of the most severe types of injuries to the nerves of the upper limb, and variants with the separation of the roots from the spinal cord represent a very difficult category of injuries to treat. Among patients who have received such injuries, there is a very high incidence of disability, since it is possible to achieve only partial restoration of the function of the upper limb. Recently, the method of transposition of functioning muscles has been growing in popularity due to its reliability and relatively short recovery time of function.The purpose of the work is to analyze the literature data on the possibility of using the method of transposition of functioning muscles in the complex treatment of victims with brachial plexus injuries.The authors have searched PubMed and RSCI databases over the past 25 years for keywords: peripheral nerve damage, tendon transposition, transposition of functioning muscles, nerve injury, brachial plexus injury, spinal cord root avulsion. In the selected 23 most relevant papers, the muscles used for transposition, indications and timing of operations, results and complications were analyzed, compared with other methods of surgical treatment of brachial plexus injuries. The analysis of studies has shown that the transposition of functioning muscles allows in most cases to restore the target movement to the useful level of M3–M4 on the MRC scale, is a more reliable method and allows achieving better results, especially in patients with severe complete injuries of the brachial plexus. An important disadvantage of free hip thin muscle transplantation operations is the risk of microanastomosis thrombosis, which requires detailed preoperative planning and good microsurgical technique of the operating team.Conclusion. Free transplantation of 2 functioning muscles is currently the method of choice for restoring upper limb movements in patients with complete brachial plexus injuries.

A Novel Approach to the Characterization of Stretching and Folding in Pursuit Tracking with Chaotic and Intermittent Behaviors

Detection of Stretching And Folding (SAF) traits in a time series is still controversial and of great interest. Also, visuo-manual tracking studies did not pay attention to SAF in hand motion trajectories. This research aims to find out the relevance of SAF to the discontinuities in chaotic dynamics of hand motion through target tracking tasks. Specifically, a new method is constructed based on this relation in which SAF can extract accurately trajectories in both time domain and phase space. Consequently, we designed experiments to track sinusoidal and trapezoidal target movements shown on a monitor. In these experiments, fourteen participants were instructed to move the joystick handle by wrist flexion-extension movements. Results confirm intermittency in significant human motor control behavior which results in discontinuities in hand motion trajectories. The relation between SAF and these discontinuities is realized by chaotic and intermittent behaviors of tracking dynamics. Verification of the method’s accuracy is also carried out by taking advantage of the Poincaré section. Our method can provide insight into the dynamical behaviors of chaotic and intermittent systems involving mechanisms in human motor control. It can be applied to general systems with intermittent behavior and other systems with modification.

Estimation of a moving broadband sound target motion velocity based on spectrum standard deviation

Traditional Doppler velocity estimation method usually requires radiant noise in a high energy line spectrum, which is often less effective for a target without an obvious line spectrum. Considering a moving target radiating a broadband signal whose spectrum has a regular undulating structure and the presence of Doppler shifts will make the structure of the spectrum more complex, we propose a method of Doppler-warping transform combined with the spectrum standard deviation to estimate the velocity of the target. The received signal after the Doppler-warping transform by the correct motion parameters will restore the undulating structure of the sound source signal spectrum, resulting in a significant increase in standard deviation. The Doppler-warping transform result is related to the motion parameters. Therefore, parameters, such as the velocity of a moving target, can be obtained by this method. Both the simulation and the car and motorboat experiment results suggest the effectiveness of this method.

Super-resolution in brain positron emission tomography using a real-time motion capture system

Super-resolution (SR) is a methodology that seeks to improve image resolution by exploiting the increased spatial sampling information obtained from multiple acquisitions of the same target with accurately known sub-resolution shifts. This work aims to develop and evaluate an SR estimation framework for brain positron emission tomography (PET), taking advantage of a high-resolution infra-red tracking camera to measure shifts precisely and continuously. Moving phantoms and non-human primate (NHP) experiments were performed on a GE Discovery MI PET/CT scanner (GE Healthcare) using an NDI Polaris Vega (Northern Digital Inc), an external optical motion tracking device. To enable SR, a robust temporal and spatial calibration of the two devices was developed as well as a list-mode Ordered Subset Expectation Maximization PET reconstruction algorithm, incorporating the high-resolution tracking data from the Polaris Vega to correct motion for measured line of responses on an event-by-event basis. For both phantoms and NHP studies, the SR reconstruction method yielded PET images with visibly increased spatial resolution compared to standard static acquisitions, allowing improved visualization of small structures. Quantitative analysis in terms of SSIM, CNR and line profiles were conducted and validated our observations. The results demonstrate that SR can be achieved in brain PET by measuring target motion in real-time using a high-resolution infrared tracking camera.