Current Heading Research Articles

Estimating orientation in natural scenes: A spiking neural network model of the insect central complex.

The central complex of insects contains cells, organised as a ring attractor, that encode head direction. The 'bump' of activity in the ring can be updated by idiothetic cues and external sensory information. Plasticity at the synapses between these cells and the ring neurons, that are responsible for bringing sensory information into the central complex, has been proposed to form a mapping between visual cues and the heading estimate which allows for more accurate tracking of the current heading, than if only idiothetic information were used. In Drosophila, ring neurons have well characterised non-linear receptive fields. In this work we produce synthetic versions of these visual receptive fields using a combination of excitatory inputs and mutual inhibition between ring neurons. We use these receptive fields to bring visual information into a spiking neural network model of the insect central complex based on the recently published Drosophila connectome. Previous modelling work has focused on how this circuit functions as a ring attractor using the same type of simple visual cues commonly used experimentally. While we initially test the model on these simple stimuli, we then go on to apply the model to complex natural scenes containing multiple conflicting cues. We show that this simple visual filtering provided by the ring neurons is sufficient to form a mapping between heading and visual features and maintain the heading estimate in the absence of angular velocity input. The network is successful at tracking heading even when presented with videos of natural scenes containing conflicting information from environmental changes and translation of the camera.

Neural representation of goal direction in the monarch butterfly brain

Neural processing of a desired moving direction requires the continuous comparison between the current heading and the goal direction. While the neural basis underlying the current heading is well-studied, the coding of the goal direction remains unclear in insects. Here, we used tetrode recordings in tethered flying monarch butterflies to unravel how a goal direction is represented in the insect brain. While recording, the butterflies maintained robust goal directions relative to a virtual sun. By resetting their goal directions, we found neurons whose spatial tuning was tightly linked to the goal directions. Importantly, their tuning was unaffected when the butterflies changed their heading after compass perturbations, showing that these neurons specifically encode the goal direction. Overall, we here discovered invertebrate goal-direction neurons that share functional similarities to goal-direction cells reported in mammals. Our results give insights into the evolutionarily conserved principles of goal-directed spatial orientation in animals.

A comparison of regression models for the ice loads measured during the ice tank test

To evaluate the time-domain positioning performance of arctic marine structures, it is necessary to generate an ice load appropriate for the current position and heading of the structure. The position and orientation angle of a floating body continuously change with time. Therefore, an ice load is required for any attitude in the time-domain simulation. In this study, we present a fundamental technique for analyzing ice loads in the frequency domain based on data measured at various angles in the ice-water tank experiment. We perform spectral analysis instead of general FFT to analyze the ice load, which has the characteristics of a random signal. To generate the necessary ice load in the time domain, we must first interpolate the measured data in the frequency domain. Using the Blackman-Tukey method, we estimate the spectrum for the measured data, then process the data to generate the training set required for machine learning. Based on the results, we perform regression analysis by applying four representative techniques, including linear regression, random forest, or neural network, and compare the results with MSE. The deep neural network method performed best, but we provide further discussion for each model.

Integration of optic flow into the sky compass network in the brain of the desert locust.

Flexible orientation through any environment requires a sense of current relative heading that is updated based on self-motion. Global external cues originating from the sky or the earth's magnetic field and local cues provide a reference frame for the sense of direction. Locally, optic flow may inform about turning maneuvers, travel speed and covered distance. The central complex in the insect brain is associated with orientation behavior and largely acts as a navigation center. Visual information from global celestial cues and local landmarks are integrated in the central complex to form an internal representation of current heading. However, it is less clear how optic flow is integrated into the central-complex network. We recorded intracellularly from neurons in the locust central complex while presenting lateral grating patterns that simulated translational and rotational motion to identify these sites of integration. Certain types of central-complex neurons were sensitive to optic-flow stimulation independent of the type and direction of simulated motion. Columnar neurons innervating the noduli, paired central-complex substructures, were tuned to the direction of simulated horizontal turns. Modeling the connectivity of these neurons with a system of proposed compass neurons can account for rotation-direction specific shifts in the activity profile in the central complex corresponding to turn direction. Our model is similar but not identical to the mechanisms proposed for angular velocity integration in the navigation compass of the fly Drosophila.

Bionic Magnetic Compass Algorithm Based on Radical Pair Theory

Vector magnetometers play an essential role in aerial and marine navigation due to their advantages of low cost, portability, and high sensitivity. However, the unstable magnetic field anomaly restricts the performance improvement of the magnetic compass. The existing methods have done a lot of optimization and improvement work, but the test results are less than expected in a dynamic environment. In order to solve this problem, a bionic magnetic compass algorithm based on the theory of “radical pairs” in birds was proposed. This article finds the stability convergence of the magnetic compass deviation (MCD) at the critical angle. The theoretical analysis and experiment results show that the heading accuracy at the critical angle is trustworthy. Then, the MCD distribution and the magnetic heading correction model are established. Finally, the current magnetic heading is corrected according to the angle difference between the critical angle and the current heading. The sea trial shows that compared with the traditional compensation algorithm, the reservoir environment is improved by 83.1%, and the effect in real ocean environment is improved by 30.12% and 58.49%.

Attractive serial dependence in heading perception from optic flow occurs at the perceptual and postperceptual stages.

Previous work has revealed that the heading perception from optic flow can be either attracted to the straight-ahead direction showing a center bias or repelled away from the previously seen heading (i.e., repulsive serial dependence) after ruling out the center bias accounting for perceptual errors. Recent studies have debated whether the serial dependence occurs at the perceptual or postperceptual stages (e.g., working memory). Our current study reexamined the serial dependence in heading perception and investigated whether the serial dependence occurred at perceptual or postperceptual stages. Additionally, an ideal observer model was developed to explore whether observers optimally combined the straight-ahead direction and previous and current headings to perceive headings. Our results showed that after ruling out the center bias, the perceived heading was biased toward the previous heading, suggesting an attractive serial dependence in heading perception. This attractive serial dependence occurred at both perceptual and postperceptual stages. Importantly, the perceived heading was well predicted by an ideal observer model, suggesting that observers could optimally combine their perceptual observations (current heading) with their prior information about the straight-ahead direction and previous headings to estimate their heading.

Experimental studies on the effects of draft condition, current heading and mooring stiffness on vortex-induced motions of a Tension-Leg Platform

The paper presents experimental studies on the effects of draft conditions, current headings and mooring stiffnesses on the Vortex-Induced Motion (VIM) responses of a Tension-Leg Platform (TLP) with four circular columns. The nominal transverse and yaw amplitudes, and the corresponding spectra obtained by fast Fourier Transform (FFT) and continuous wavelet transform (CWT) are analyzed to examine the characteristics of the motion responses. Four current headings in the range of 0° to 45° are adopted in the model test. The results show that the maximum response amplitude in both transverse and yaw directions are achieved at 0° current incidence. For the transverse response, the maximum nominal amplitude decreases and the lock-in range narrows as the current heading increases. The spectral analyses for the transverse and yaw motions at 0° current heading show that the dominant peak frequencies increase as the reduced velocity increases. It is observed that the low-frequency spectral peak of the in-line motion amplitude spectra increases as reduced velocity increases. A color band or a ribbon concentrates stably around the frequency of f<0.05 in the wavelet analysis. It is primarily caused by the initial acceleration of the model in the towing tank. The absolute values of correlations between the spring tensions and the transverse motion of the platform are much larger than those between the spring tensions and the in-line or yaw motions. Moreover, it is found that the VIM trajectories of the TLP are primarily always along the direction perpendicular to the current heading.

Development of a Portable Interface System Sharing the Positioning and Heading Information to Support a Berthing Vessel

The study develops a portable interface system to inform berthing operators of the position and heading in relation to the quay when berthing a large vessel equipped with distance-measuring instruments. A portable interface system is indispensable for preventing collisions and improving the efficiency of berthing operations because it allows operators to intuitively grasp the movement status of the vessel based on the distance data measured during berthing. These data can not only be converted into the current position and heading of the vessel relative to the quay, but can also be visualized to predict the movement and speed of the vessel in a few seconds. Therefore, we developed a visualization system using Rviz, a 3D model visualization tool for a robot operating system, and verified the necessity for an interface system through simulations and experiments using a model vessel. Furthermore, we extended the function of the visualization interface using a wireless network, developed a web application to display the vessel’s positioning information on multiple operators’ terminals, and verified the drawing stability at 10 Hz using the extended application.

A Human Gait Tracking System Using Dual Foot-Mounted IMU and Multiple 2D LiDARs.

This paper proposes a human gait tracking system using a dual foot-mounted IMU and multiple 2D LiDARs. The combining system aims to overcome the disadvantages of each single sensor system (the short tracking range of the single 2D LiDAR and the drift errors of the IMU system). The LiDARs act as anchors to mitigate the errors of an inertial navigation algorithm. In our system, two 2D LiDARs are used. LiDAR 1 is placed around the starting point, and LiDAR 2 is placed at the ending point (in straight walking) or at the turning point (in rectangular path walking). Using the LiDAR 1, we can estimate the initial headings and positions of each IMU without any calibration process. We also propose a method to calibrate two LiDARs that are placed far apart. Then, the measurement from two LiDARs can be combined in a Kalman filter and the smoother algorithm to correct the two estimated feet trajectories. If straight walking is detected, we update the current stride heading and the foot position using the previous stride headings. Then, it is used as a measurement update in the Kalman filter. In the smoother algorithm, a step width constraint is used as a measurement update. We evaluate the stride length estimation through a straight walking experiment along a corridor. The root mean square errors compared with an optical tracking system are less than 3 cm. The performance of proposed method is also verified with a rectangular path walking experiment.

大数据分析在智能釆摘机器人路径规划中的应用

In order to solve the problem of autonomous movement of intelligent picking robot, a method for big data analysis is proposed. The data collected by laser ranging sensor, CCD camera and electronic compass are analyzed to determine the current robot position and heading. The walking route for the robot is preset of the orchard. The sign for the digital tube is installed, so the coordinates for the sign are known. Electronic compass is used to determine the heading angle of robot. The CCD camera captures the sign image, and adopts the methods of image graying, image segmentation, image corrosion and image thinning to extract the digital tube image data on the sign. Fuzzy control method is used to identify digital tube numbers on the ground sign, and CCD camera scans whether there are obstacles in front of the road at the same time. The laser ranging sensor completes two tasks: ① detecting the sign distance and direction angle of the distance, and calculating the current position and heading angle of the robot through the coordinates of the sign; (2) detect the distance from obstacles, and start the obstacle avoidance system when it is less than 1m. The path planning system of picking robot based on big data analysis relies on a variety of sensors, and has a strong ability to perceive orchard environment, and it has high ability of path planning.

Enhancing Security of ADS-B Systems with Encryption Algorithm in the Smart Ocean

Liu, Z.; Ling, M.; Zhu, T.; Xu, D.; He, Y., and Liu, Z., 2020. Enhancing security of ADS-B systems with encryption algorithm in the smart ocean. In: Hu, C. and Cai, M. (eds.), Geo-informatics and Oceanography. Journal of Coastal Research, Special Issue No. 105, pp. 181–184. Coconut Creek (Florida), ISSN 0749-0208.The smart ocean is an influencer concept incorporating digitalized associated ocean and seaboard cities. The construction of an omni-bearing smart ocean requires urban resilience, and the application of smart means can greatly improve a city's emergency response capability in the face of dangerous events. Aviation security is a non-negligible point in the construction of the smart ocean. The automatic dependent surveillance-broadcast (ADS-B) in the aircrafts is used to broadcast and transmit navigating data, including the call sign of aircraft, altitude in the airspace, current heading of destination, and other locating messages. This paper studies ADS-B security threats such as distributed denial of service attacks and proposes the use of an encryption algorithm to process ADS-B plaintext to improve urban resilience of the smart ocean.

Effects of the position of pipe-type appendages on the flow induced motions, energy transformation, and drag force of a TLP

Flow-induced motions (FIM) can cause fatigue damage to the mooring and riser systems of deepwater offshore structures, especially for cylindrical platforms, such as Tension Leg Platform(TLP). Previous experimental and numerical studies have showed conservative FIM prediction compared to the field measurements, due to many significant factors such as the Reynolds number, the nonuniformity of the incident current, the unsteadiness of the current velocity and platform heading, the coupled current and wave presence. Besides, the appendages covering the hull surface of platforms also played an important role in the smaller FIM responses of the field measurements. In order to specifically examine the influence of position of pipe-type appendages, this paper experimentally investigated the FIM of a TLP with different positions of appendages at 0°-incidence and compared the FIM responses, energy transformation, and average drag coefficients with those of the bare hull. An air-bearing system and a horizontal mooring system were employed to provide vertical pretension and horizontal restoring forces, respectively, and to ensure the low-friction horizontal motions. The results showed that for 0°-incidence whatever the appendages position, the transverse and yaw motions were all mitigated and the TLP with appendages-45° was the most effective configuration, with a reduction of 55% for the transverse motion and 52% for the yaw motion, mainly owing to the changes of the boundary layer separation point. However, the analysis of energy transformation indicated the development trend of the galloping phenomenon for the TLP with appendages-45°. In addition, the influence of the FIM behavior on the drag force of the TLP at 0° 22.5° and 45°-incidences was also studied. It showed that the FIM could contribute to larger drag force and the increase of drag force is the most significant at 0°-incidence, with a value of around 39%.

Wayfinding and acquisition of spatial knowledge with navigation assistance.

Integrated visualizations for assisted navigation were investigated that support both wayfinding and spatial learning. Participants navigated a predefined route with assistance through a virtual environment, visiting five target locations. Wayfinding accuracy was assessed. After wayfinding, self-to-object knowledge was measured with pointing tasks, and object-to-object knowledge was measured with an allocentric configurational task. Self-to-object knowledge was supported through self-to-targets-visualizations that provided information about the egocentric straight-line directions between the navigator and target locations. Both the acquisition of object-to-object knowledge as well as self-to-object knowledge was supported through comprehensive map visualizations. Alignment (rotations of the visualization according to changes of heading in the environment) appeared supportive for the acquisition of self-to-object knowledge with self-to-targets visualizations. Alignment was not effective with comprehensive maps. Wayfinding was impeded if visualizations were not aligned with the current heading. Individual differences in perspective taking ability played a strong role for wayfinding accuracy with misaligned visualizations. It is concluded that visualizations are encoded egocentrically for wayfinding purposes in the context of assisted navigation. Accordingly, the acquisition of self-to-object spatial knowledge can be supported through appropriate visualizations. (PsycINFO Database Record (c) 2020 APA, all rights reserved).

Development Navigation, Guidance & Control Program for GPS based Autonomous Ground Vehicle (AGV) using Soft Computing Techniques

In this chapter, an introduction of navigate a vehicle autonomously, the control action of the system must know at least two things, its own current position and direction of movement. Location can be find by either from an outside system source with technology such as the Global Positioning System (GPS), or by calculation of mathematical equation a followed path from a known source point with the use of electronic compasses, inclinometers, and rotational counters. However, under any scheme, the outcome is to somehow generate the positional information of the vehicle so that the vehicle could be guided to follow a path and reach the target. In addition of this, the direction sensing devices are also used for getting the values of current heading of vehicle so that it could be steered to move towards target location. GPS has advantage over other position detection mechanism that it also provides an estimate of vehicle’s current heading based on the previous two positional coordinates. While the current heading provided by GPS is not accurate enough under some conditions, it is envisaged to accommodate GPS as the only sensor for guiding the autonomous vehicle to follow the trajectory in outdoor applications

Single-Neuron Representations of Spatial Targets in Humans.

The hippocampus and surrounding medial-temporal-lobe (MTL) structures are critical for both memory and spatial navigation, but we do not fully understand the neuronal representations used to support these behaviors. Much research has examined how the MTL neurally represents spatial information, such as with "place cells" that represent an animal's current location or "head-direction cells" that code for an animal's current heading. In addition to behaviors that require an animal to attend to the current spatial location, navigating to remote destinations is a common part of daily life. To examine the neural basis of these behaviors, we recorded single-neuron activity from neurosurgical patients playing Treasure Hunt, a virtual-reality spatial-memory task. By analyzing how the activity of these neurons related to behavior in Treasure Hunt, we found that the firing rates of many MTL neurons during navigation significantly changed depending on the position of the current spatial target. In addition, we observed neurons whose firing rates during navigation were tuned to specific heading directions in the environment, and others whose activity changed depending on the timing within the trial. By showing that neurons in our task represent remote locations rather than the subject's own position, our results suggest that the human MTL can represent remote spatial information according to task demands.

Sensory perception plays a larger role in foraging efficiency than heavy-tailed movement strategies

Animals must balance their rates of energetic intake and expenditure while foraging. Several mathematical models have been put forward as energetically optimal foraging strategies when the food environment is sparse (i.e., the distance between food patches in the environment is much larger than the distance from which the forager can perceive food). In particular, Lévy walks with a power law exponent approaching 1 are considered optimal for destructive foragers. However, these models have yet to explore the role of sensory perception in foraging success as the distance between food patches approaches the distance from which the forager can perceive food. Here, we used an agent-based modeling approach to address this question. Our results concur that lower values of the power law exponent (i.e. values approaching 1) result in the most food found, but in contrast to previous studies, we note that, in many cases, lower exponents are not optimal when we consider food found per unit distance traveled. For example, higher values of the exponent resulted in comparable or higher foraging success relative to lower values when the forager's range of sensory perception was restricted to an angle ± 30° from its current heading. In addition, we find that sensory perception has a larger effect on foraging success than the power law exponent. These results suggest that a deeper examination of how animals perceive food sources from a distance may affect longstanding assumptions regarding the optimality of Lévy walk foraging patterns, and lend support to the developing theoretical shift towards models that place increasing emphasis on how organisms interact with their environments.

Examining the Perception and Effectiveness of a System Awareness Briefing During Cruise Flight

Automation has increased the safety of air transportation by assisting pilots during periods of high workload and during critical phases of flight. However, an unintended consequence of automation proliferation has been the reduction in attention resulting from its use. Prior research has shown that during periods of high automation and low workload, pilots’ minds begin to wander and occupy themselves with thoughts other than the current task at hand. This research involved conducting four separate studies addressing the following research questions: 1) Would the use of a system awareness briefing result in the general public being more willing to fly on commercial airlines? 2) Do student pilots support the use of a system awareness briefing? and 3) Does a system awareness briefing actually improve pilot awareness of automation and aircraft parameters during cruise flight? The results from Studies 1 and 2 indicated participants preferred flying with a pilot who was using the system awareness briefing compared to a pilot not using the briefing. The findings from Study 3 did not reveal any significant differences between pilots who used the system awareness briefing versus those that did not. In Study 4, pilots who used the system awareness briefing were more accurate in reporting current heading, fuel flow, and electrical volts, compared to pilots who did not use the briefing. They also reported that they felt more situational awareness compared to the control group. Keywords: system awareness briefing; experimental research; automation; training

Parametric study on the vortex-induced motions of semi-submersibles: Effect of rounded ratios of the column and pontoon

The vortex-induced motions (VIMs) of semi-submersibles have emerged as an important issue in offshore engineering, as they pose a threat to safe and reliable operations and severely affect the fatigue lives of risers and mooring systems. The VIM response depends on the shape of the submerged structure and thus is significantly influenced by the design parameters related to the columns and pontoons. Numerical simulations by the detached Eddy simulation method are validated by experimental data and then used for parametric analysis of the VIM performance of various semi-submersibles with different column rounded ratios (Rc/L) and pontoon rounded ratios (Rp/Lp). The results show that the transverse amplitudes of a semi-submersible with circular columns at a 0° current heading are twice as large as those at a 45° current heading. However, the semi-submersible with rounded square columns shows more significant transverse motions at a 45° current heading than at a 0° current heading. Furthermore, at the 45° current heading, the transverse amplitudes of the semi-submersibles show a rapid increase as the column radius increases in the range of Rc/L&amp;lt;0.1. The peak values remain roughly the same for 0.1≤Rc/L≤0.2 and then decrease as the column radius increases (Rc/L≥0.3). In addition, the effect of the pontoon shape on the transverse response is negligible for semi-submersibles with sharp square columns, while for semi-submersibles with rounded square columns or circular columns, the sharp rectangular pontoons greatly mitigate the VIM response.

Experimental investigation into the influences of pontoon and column configuration on vortex-induced motions of deep-draft semi-submersibles

Deep-draft design of semi-submersibles improves vertical motions but leads to critical vortex-induced motions (VIM) attributable to fluctuating loads on columns. As characteristic components, both columns and pontoons produce complex wake interference and thus have significant influences on the VIM of semi-submersibles. This paper presents an experimental study on VIM of deep-draft semi-submersibles (DDS) to examine the effects of pontoons and column configuration. There were four test models including four-pontoon DDS, two-pontoon DDS, four-square-column structure and four-rhombic-column structure with no pontoons. A number of current headings and reduced velocities were considered. The main results reveal that the two-pontoon DDS can generate larger lift forces in comparison with the four-pontoon DDS; consequently, the transverse motion amplitudes at high reduced velocities are larger. However, the four-square-column structure with no pontoons shows the most significant transverse and yaw responses owing to the largest excitation forces induced by the well-established wake. On the other hand, similar trend and values in the transverse response are observed for the four-square-column structure at the 45° current heading and for the four-rhombic-column structure at the 0° current heading. The incidence angle related to columns has more significant effect on the VIM of DDS than that related to the platform.

Marine Current Meter Calibration Using GNSS Receivers, a Comparison with Commercial Method

Getting information from marine current requires that accurate and calibrated current meter is used. Current meter calibration is carried out in accordance with specific standard in calibration laboratories. To evaluate the performance and health of a current meter, one should compares velocity and heading it with a velocity and heading reference. In this paper, the innovative method for evaluate velocity and heading resulted from impeller marine current meter is presented. In this method, current meter is to be attached to buoy that is installed on it tow GNSS receivers; and by towing it in a lake, simultaneous velocity and heading of the current meter are recorded. Also data position of buoy by GNSS is recorded. Accurately calculated velocity and heading of buoy by using GNSS data to be used as a criterion to evaluate the current meter velocity and heading. Finally, the calibration equation that is known as the final result of the calibration process was determined for velocity and heading of current meter with reasonable accuracy. Also, current meter is tested in this paper evaluated commercial method in calibration laboratory. The results were compared with the results of the proposed method. The results indicated the success of the GNSS-based method for the Performance analysis of a marine current meter.