Range-based underwater target localization using an autonomous surface vehicle: Observability analysis

This paper provides a Cramer-Rao lower bound (CRLB) on range, cross range, speed and heading tracking accuracy for a class of maneuvering target trajectories using nonlinear noisy range and bearing measurements when both the target and the sensor platform are moving. It is assumed that there are no missing or false measurements. This analysis is valid only for single target two-dimensional tracking scenarios. The target trajectory is assumed to have a constant velocity with a single coordinated turn maneuver. Hence, the target trajectory has three legs where the first and last ones are straight and level trajectories. Therefore, these two legs are characterised by their initial target position and velocity. The second trajectory leg is assumed to be a constant velocity-coordinated turn (CV-CT) maneuver where maneuver start time, maneuver duration and turn rate are the unknown parameters. Hence, the overall target trajectory is characterised by the sufficient statistics which are the initial target position and velocity in the horizontal (x, y) plane, maneuver start time, maneuver duration and maneuver turn rate. First, the CRLB on the accuracy of the sufficient statistics is obtained by deriving Fisher information matrices (FIMs) from partial derivatives of range and bearing measurements with respect to sufficient statistics for different target trajectory legs. Then, the CRLB is derived for the tracking accuracy on parameters of interest, namely, target range, cross range, speed and heading by taking partial derivatives of these parameters with respect to the sufficient statistics. A single target tracking example is provided where the CRLB on tracking accuracy is illustrated with different radar measurement sampling periods. This example also provides the Cramer-Rao lower bound on estimation error on other parameters of interest, namely the maneuver start time and duration.

Vergence eye movements are the inward (convergence) or outward (divergence) turning of the eyes which allows humans to view objects in depth. Previous studies on the dynamics of convergence and divergence eye movements have produced varied, sometimes contradictory, results. Four subjects were studied and tracked four degree disparity step changes for convergence and divergence at different initial target positions. Here we report that the dynamics of divergence movements not only differ from convergence movement, but depend on the initial vergence position. Velocities of divergence eye movements in response to targets that were initially near to the subject were approximately twice that of responses to initially distant targets. Hence, while convergence responses are fairly similar irrespective of the initial position, divergence dynamic properties are dependent on the initial stimulus position. It is speculated that the differences observed in divergence may be the result of a difference in the underlying neural controller potentially a difference in the magnitude of the fusion initiating component. Preliminary data using independent component analysis (ICA) shows the divergence system contains a step and pulse where the amplitude of the pulse is dependent on the initial stimulus position

On optimal search plans to detect a target moving randomly on the real line

1. The introduction of a period of darkness between the disappearance of an initial fixation target and the appearance of a peripheral saccade target produces a general reduction in saccadic reaction time (SRT)-known as the gap effect- and often very short latency express saccades. To account for these phenomena, premotor processes may be facilitated by release of visual fixation and advanced preparation of saccadic programs. The experiments described in this paper were designed to test the relevance of the ocular fixation disengagement and oculomotor preparation hypotheses by identifying the influence of different factors on SRTs and the occurrence of express saccades in the monkey. 2. The SRTs of two monkeys were measured in two behavioral paradigms. A peripheral saccade target appeared at the time of disappearance of a central fixation target in the no-gap task, whereas a 200-ms period of no stimuli was interposed between the fixation target disappearance and the saccade target appearance in the gap task. The distribution of SRTs in these tasks was generally bimodal; the first and second mode was composed of express and regular saccades, respectively. We measured the mean SRT, mean regular saccade latency, mean express saccade latency, and percentage of express saccades in both tasks. We also estimated the gap effect, i.e., the difference between the SRTs in no-gap trial and the SRTs in gap trials. 3. Once the animals were trained to make saccades to a single target location and produce express saccades, SRTs in both no-gap and gap trials displayed a broad tuning with respect to the spatial location of the trained target when the target location was varied randomly in a block of trials. Express saccades were made only to a restricted region of the visual field surrounding the trained target location. A gap effect was present for nearly all target locations tested, irrespective of express saccade occurrence. Finally, the probability of generating an express saccade at the trained target location decreased with the introduction of uncertainty about target location. 4. The occurrence of express saccades increased with the duration of the visual and nonvisual (gap) fixation that the animal was required to maintain before the onset of a saccade target. The gap duration was effective in reducing the mean SRT for gaps < or = 300 ms, and it was more influential than comparable variation in the visual fixation duration. 5. The occurrence of express saccades made to targets of identical eccentricity increased when the initial eye fixation position was shifted eccentric in a direction opposite to the saccade direction. Concomitantly, mean SRT decreased by approximately 2 ms for each 1-deg change in initial eye fixation position. 6. The occurrence of express saccades depended upon contextual factors, i.e., on both the behavioral task (no-gap or gap) and the latency of the saccade that the monkey executed to the same target in the preceding trial. The highest percentage of express saccades was observed after an express saccade in a no-gap trial, whereas the lowest percentage was obtained after a regular saccade in a gap trial. 7. These findings indicate that training-dependent express saccades are restricted to a specific spatial location dictated by the training target, and their incidence is facilitated by high predictability of target presentation, long-duration foreperiod, absence of visual fixation, eccentric initial eye position opposite to the saccade direction, and express saccade occurrence in the previous trial. The release of fixation afforded by the gap accounts for the general gap effect, but has only a modulatory influence on express saccade generation. We conclude that advanced motor preparation of saccadic programs generally reduces SRT and is primarily responsible for the occurrence of express saccades, which therefore may be caused mainly by neuronal changes restricted to a specific locus-coding for the trained movemen

Handcycling performance is dependent on the physiological economy of the athlete; however, handbike configuration and the biomechanical interaction between the two are also vital. The purpose of this study was to examine the effect of crank length manipulations on physiological and biomechanical aspects of recumbent handcycling performance in highly trained recumbent handcyclists at a constant linear handgrip speed and sport-specific intensity. Nine competitive handcyclists completed a 3-minute trial in an adjustable recumbent handbike in four crank length settings (150, 160, 170 & 180mm) at 70% peak power output. Handgrip speed was controlled (1.6m·s-1 ) across trials with cadences ranging from 102 to 85rpm. Physiological economy, heart rate, and ratings of perceived exertion were monitored in all trials. Handcycling kinetics were quantified using an SRM (Schoberer Rad Messtechnik) powermeter, and upper limb kinematics were determined using a 10-camera VICON motion capture system. Physiological responses were not significantly affected by crank length. However, greater torque was generated (P<.0005) and peak torque occurred earlier during the push and pull phase (P≤.001) in longer cranks. Statistical parametric mapping revealed that the timing and orientation of shoulder flexion, shoulder abduction, and elbow extension were significantly altered in different crank lengths. Despite the biomechanical adaptations, these findings suggest that at constant handgrip speeds (and varying cadence) highly trained handcyclists may select crank lengths between 150 and 180mm without affecting their physiological performance. Until further research, factors such as anthropometrics, comfort, and self-selected cadence should be used to facilitate crank length selection in recumbent handcyclists.

An analysis of the physical demands of international female soccer match-play and the physical characteristics of elite players

Purpose This paper aims to study the turning strategies for the bounding quadruped robot with an active spine and explore the significant role of the spine in the turning locomotion. Design/methodology/approach Firstly, the bounding gait combining the pitch motion of the spine with the leg motion is presented. In this gait, the spine moves in phase with the front legs. All the joints of the legs and spine are controlled by cosine signals to simplify the control, and the initial position and oscillation amplitude of the joints can be tuned. To verify the effectiveness of the proposed gait, the spine joints are set with different initial positions and oscillation amplitudes, and the initial position and oscillation amplitude of the leg joints are tuned to make the virtual model do the best locomotion in terms of the speed and stability in the simulation. The control signals are also used to control a real robot called Transleg. Then, three different turning strategies are proposed, including driving the left and right legs with different strides, swaying the spine in the yaw direction and combining the above two methods. Finally, these strategies are tested on the real robot. Findings The stable bounding locomotion can be achieved using the proposed gait. With the spine motion, the speed of the bounding locomotion is increased; the turning radius is reduced; and the angular velocity is increased. Originality/value A simple and flexible planning of the bounding gait and three turning strategies for the bounding quadruped robot are proposed. The effectiveness of the proposed bounding gait, along with the beneficial effect of the spine motion in the yaw direction on the turning locomotion is demonstrated with the computer simulations and robot experiments. This will be instructive for the designing and actuating of the other quadruped robots.

The article presents a kinematic analysis of a ten-link gear-lever differential transmission mechanism (GLDTM) consisting of a lever contour antipalallelogram, which transmits rotational motion and torque from the drive shaft to the drive shaft for machines with symmetrically driven roller centers. The kinematic analysis of the mechanism is carried out in order to determine the angular and linear speeds and accelerations of the links of the mechanism, depending on the angular speed of the driving link (gear) and the linear speed and acceleration of the center of rotation of the free working shaft. The kinematic analysis was carried out according to the centroid theory by the method of the instantaneous center of rotation of the links.

In the current vehicle design, mechanical handbrake is widely used as a low-configuration model and often proposed as cost reduction scheme, and because of its frequent use during the driving and the need to meet the convenience of users of different stature, to make sure the comfort layout of mechanical handbrake is still of great importance in the design process. Based on the actual operation process of the user, this paper decomposes the process into nine comfort variables that users can easily perceive, including the initial position of the handbrake, the pull-up position of the handbrake, the horizontal angle of the initial position, the horizontal angle of the pull-up track of the handbrake, the pull-up stroke of the handbrake, the horizontal angle after the pull-up of the handbrake, the distance between the operating point of the handbrake and the human body in Y direction, the Y inclination angle of the handbrake, and the gap between the centerline of the arm and the hand pillow after the handbrake is pulled. In this paper the comfort variables are discussed based on theoretical human body analysis and large database analysis, then summarized into relative comfort range, after verification on the adjustable physical bench, we finally get a comprehensive recommended range of handbrake layout comfort parameters. The final research conclusion can be effectively uesd to guide the project development, to improve the quality of project development, and to ensure the man–machine comfort of product design.KeywordsMechanical handbrakeComfort layoutInitial position of handbrakePull-up position of handbrakeHorizontal angle of initial positionHorizontal angle of pull-up track of handbrakePull-up stroke of handbrakeHorizontal angle after pull-up of handbrakeDistance between operating point of handbrake and human body Y directionInclination angle of Y direction of handbrakeGap between centerline of arm and hand pillow after pull-up of handbrake

In this work we have studied what mechanisms might possibly underlie arm trajectory modification when reaching toward visual targets. The double-step target displacement paradigm was used with inter-stimulus intervals (ISIs) in the range of 10---300 ms. For short ISIs, a high percentage of the movements were found to be initially directed in between the first and second target locations (averaged trajectories). The initial direction of motion was found to depend on the target configuration, and on D: the time difference between the presentation of the second stimulus and movement onset. To account for the kinematic features of the averaged trajectories two modification schemes were compared: the superposition scheme and the abort-replan scheme. According to the superposition scheme, the modified trajectories result from the vectorial addition of two elemental motions: one for moving between the initial hand position and an intermediate location, and a second one for moving between that intermediate location and the final target. According to the abort-replan scheme, the initial plan for moving toward the intermediate location is aborted and smoothly replaced by a new plan for moving from the hand position at the time the trajectory is modified to the final target location. In both tested schemes we hypothesized that due to the quick displacement of the stimulus, the internally specified intermediate goal might be influenced by both stimuli and may be different from the location of the first stimulus. It was found that the statistically most successful model in accounting for the measured data is based on the superposition scheme. It is suggested that superposition of simple independent elemental motions might be a general principle for the generation of modified motions, which allows for efficient, parallel planning. For increasing values of D the inferred locations of the intermediate targets were found to gradually shift from the first toward the second target locations along a path that curved toward the initial hand position. These inferred locations show a strong resemblance to the intermediate locations of saccades generated in a similar double-step paradigm. These similarities in the specification of target locations used in the generation of eye and hand movements may serve to simplify visuomotor integration.

Unmanned Surface Vehicle (USV) has been gaining more marine applications nowadays. However, the USV is vulnerable to excessive rolling motions induced by water waves, and this phenomenon may cause significant downtime to the operations of USV and engender detrimental effects to the on-board instrument and sensors. Active control system had been proposed to compensate the rolling stability issue but most of the proposed devices were expensive. This paper developed a gyrostabiliser on USV model to compensate the excessive rolling motion. Gyrostabiliser consists of rotor, gimbal and spinning axes, which commonly used for measuring or maintaining orientations and angular velocities. The gyrostabiliser was mounted vertically inside the USV model. Experiments were conducted to obtain the ideal gains of gyrostabiliser’s controller, to investigate the differences between active- and passive-gyrostabiliser, and to identify the induced pitch effect of the vertical gyrostabiliser to the USV model. The roll angle of the USV was measured by gyro sensor, whereas the precession motor and flywheel motor were controlled by a non-encoder Direct-Current (DC) motor. A proportional controller of the gyrostabiliser was implemented through Arduino Integrated Development Environment (IDE) to ensure optimal performance of gyrostabiliser in precession speed and direction control. The results showed that both active- and passive-gyrostabiliser managed to mitigate the roll angle of USV from +/- 15° back to less than 1° and reached steady state within 2.32 seconds and 2.60 seconds, respectively. The active gyrostabiliser had advantage to return to zero precession angle while the passive gyrostabiliser accumulated 30° precession angle in the experiment. The induced pitch angle by the gyrostabiliser had been found in an insignificant magnitude for the case study. The outcomes of this paper lead to an alternative for improving the robustness of USV in rolling reduction.

On convergence results for nonlinear cyclic pursuit strategies

Received signal strength (RSS)-based localization techniques have gained much attention in location-based services (LBSs). However, the coexistence of unknown path loss exponent (PLE), uncertain sensor positions, and impulsive noise poses serious challenges to localization accuracy. To address the problem, we first model the impulsive noise as a Mixture of Gaussian (MoG) distribution with unknown parameters. Thus, the noise model and the channel model can be refined using the observed data under the variational Bayesian inference (VBI) framework, which is defined as the model refinement learning. We then propose a corresponding online target localization procedure with the refined noise distribution, PLE and sensor positions. The Bayesian Cramer-Rao bound (BCRB) is finally derived in terms of all unknown parameters. Simulation results together with real experiment demonstrate that the proposed VBI algorithm can effectively learn the true noise distribution, and the developed localization method exhibits robust localization performance in various scenarios.

Protection performance assessments of two types of sheath voltage limiters in 220kV single point bonded cable system

Particle sedimentation is a fundamental process encountered in various industrial applications. In this study, we used immersed boundary lattice Boltzmann method and discrete element method (IBM-LBM-DEM) to investigate two-particle sedimentation. A lattice Boltzmann method was used to simulate fluid flow, a discrete element method was used to simulate particle dynamics, and an immersed boundary method was used to handle particle–fluid interactions. Via the IBM-LBM-DEM, the particles collision process in fluid or between rigid walls can be calculated to capture the information of particles and the flow field more efficiently and accurately. The numerical method was verified by simulating settling of a single three-dimensional particle. Then, the effects of Reynolds number (Re), initial distance, and initial angle of particles on two-particle sedimentation were characterized. A specific focus was to reproduce, analyze, and define the well-known phenomenon of drafting-kissing-tumbling (DKT) interaction between two particles. Further kinematic analysis to define DKT is meaningful for two-particle sedimentation studies at different particle locations. Whether a pair of particles has experienced DKT can be viewed from time plots of the distance between the particles (for kissing), the second-order derivative of distance to time (for drafting), and angular velocities of particles (for tumbling). Simulation results show that DKT’s signatures, including attraction, (near) contact, rotation, and in the end, separation, is only completely demonstrated when particles have nearly vertically aligned initial positions. Hence, not all initial positions of particles and Reynolds numbers lead to DKT and not all particle–particle hydrodynamic interactions are DKT. Whether particle–particle interaction is attractive or repulsive depends on the relative positions of particles and Re. Collision occurs when Re is high and the initial angle is small (&lt;20°), almost independent of the initial distance.