Constant Speed Motion Research Articles

Platooning of Position-Controlled Vehicles on a Curved Path under Communication Losses and Delays

<div>This article offers an algorithmic solution for moving a homogeneous platoon of position-controlled vehicles on a curved path with varying speeds and in the presence of communication losses and delays. This article considers a trajectory-based platooning with the leader–following communication topology, where the lead vehicle communicates its reference position and orientation to each autonomous follower vehicle. A follower vehicle stores this communicated information for a specific period as a virtual trail of the lead vehicle starting from the lead vehicle’s initial position and orientation. An algorithm uses this trail to find the follower vehicle’s reference position and orientation on that trail, such that the follower vehicle maintains a constant distance from the lead vehicle. The proposed algorithm helps form a platoon where each vehicle can traverse a curve with varying speeds. In contrast, in the existing literature, most of the solutions for vehicle platooning on a curved path demonstrate constant speed motion. This article considers delayed information as lost. Therefore, the communication losses and delays are considered as packet drops. The algorithm uses estimates of the lost information of the lead vehicle’s trail to generate the reference path for the follower vehicles. Analysis of the algorithm shows a relationship between the platoon’s performance and the extent of packet drops. Simulation results agree with the relationship.</div>

Effect of Acute Psychological Stress on Speed Perception: An Event-Related Potential Study

The present study tested the intrinsic ERP features of the effects of acute psychological stress on speed perception. A mental arithmetic task was used to induce acute psychological stress, and the light spot task was used to evaluate speed perception. Compared with judgments in the constant speed and uniform acceleration motion, judgments in the uniform deceleration motion were made more quickly and with higher accuracy; attention control was higher and peaked later; and there was longer N2 peak latency, larger N2 peak amplitude, and lower mean amplitude of the late negative slow wave (SW). Under stress, the reaction time was significantly shorter. The N2 peak amplitude and SW mean amplitude were significantly higher, attention control was higher and appeared earlier, and there was a greater investment of cognitive resources. The type of movement and evoked stress also interacted to predict behavioral and ERP measures. Under acute stress, judgments made in the uniform deceleration motion condition elicited lower N2 peak latency, higher attention control, and later peak attention. The results suggest that judgments of the speed of decelerating motion require a lower investment of cognitive resources than judgments of other kinds of motion, especially under acute stress. These findings are best interpreted in terms of the interaction of arousal and attention.

Analysis of Strategies Used by Students in Solving Motion Problems According to the Presentation of the Problem

In this research, it was aimed to analyze the problem solving strategies used during solving problems related to constant speed and constant acceleration motion, which are often used in graphs, according to the presentation of the problem (text and graph).The research was carried out with 119 students studying in the 11th grade. In the research conducted in a case study pattern, data were collected using the problem solving strategies scale used in Physics at the high school level and open-ended questions about problems presented in two different ways. Scores from the scale were analyzed through the SPSS 25 program, and data from open-ended questions were analyzed by content analysis. According to the results obtained from the scales, it was determined that the problem-solving strategies used by students did not differ according to the presentation of the problem, but there was a difference in the stages of understanding the problem and organizing the problem according to the results obtained from open-ended questions. According to these results, it can be said that the way the problem is presented mostly affects the stage of understanding the problem. The understanding phase affects the solution process and the time required for the solution.

Postdiction: When Temporal Regularity Drives Space Perception through Prestimulus Alpha Oscillations.

In postdiction, the last stimulus of a sequence changes the perception of the preceding stimuli. Postdiction has been reported in all sensory modalities, but its neural underpinnings remain poorly understood. In the rabbit illusion, a sequence of nonequidistant stimuli presented isochronously is perceived as equidistantly spaced. This illusion might be driven by an internal prior favoring a constant-speed motion. Here, we hypothesized that prestimulus alpha oscillations (8–12 Hz), known to correlate with perceptual expectations and biases, would reflect the degree to which perceptual reports are influenced by a constant-speed prior. Human participants were presented with ambiguous visual sequences while being recorded simultaneously with MEG and EEG: the same sequences yielded an illusory perception in about half the trials, allowing contrasting brain responses elicited by identical sequences causing distinct percepts. As a proxy of an individual’s prior, we used the percentage of perceived illusion and the detection criterion, assuming that a strong constant-speed prior would result in a higher rate of illusory percepts. We found that high frontoparietal alpha power was associated with perceiving the sequence according to the individual’s prior: participants with high susceptibility to the illusion would report the illusion, while participants with low susceptibility would report the veridical sequence. Additionally, we found that prestimulus alpha phase in occipitoparietal regions dissociated illusion from no-illusion trials. We interpret our results as suggesting that alpha power reflects an individual’s constant-speed prior, whereas alpha phase modulates sensory uncertainty.

Collision Avoidance for an Unmanned Aerial Vehicle in the Presence of Static and Moving Obstacles

A new collision-avoidance procedure for an unmanned aerial vehicle (UAV) in the presence of static and moving obstacles is presented. The proposed procedure is based on a new form of local parameterized guidance vector fields, called collision-avoidance vector fields, which produce smooth and intuitive maneuvers around obstacles. These vector fields are generated from a decomposition of UAV kinematics and a proximity-based velocity modulation. The proposed kinematic decomposition encodes both collision avoidance and constant-speed motion for the UAV. As such, the resulting maneuvers follow nominal collision-free paths, which are referred to as streamlines of the collision-avoidance vector fields, with constant speed. Next, in accordance with the computed guidance vector fields, different collision-avoidance controllers that generate collision-free maneuvers are developed. Furthermore, it is shown that any tracking controller with convergence guarantees can be used with the avoidance controllers to track the streamlines of the collision-avoidance vector fields. Finally, numerical simulations demonstrate the efficacy of the proposed approach and its ability to avoid collisions with static and moving pop-up threats in different practical scenarios.

Quantitative evaluation by measurement and modeling of the variations in dose distributions deposited in mobile targets.

The objective of this study is to quantitatively evaluate variations of dose distributions deposited in mobile target by measurement and modeling. The effects of variation in dose distribution induced by motion on tumor dose coverage and sparing of normal tissues were investigated quantitatively. The dose distributions with motion artifacts were modeled considering different motion patterns that include (a) motion with constant speed and (b) sinusoidal motion. The model predictions of the dose distributions with motion artifacts were verified with measurement where the dose distributions from various plans that included three-dimensional conformal and intensity-modulated fields were measured with a multiple-diode-array detector (MapCheck2), which was mounted on a mobile platform that moves with adjustable motion parameters. For each plan, the dose distributions were then measured with MapCHECK2 using different motion amplitudes from 0-25 mm. In addition, mathematical modeling was developed to predict the variations in the dose distributions and their dependence on the motion parameters that included amplitude, frequency and phase for sinusoidal motions. The dose distributions varied with motion and depended on the motion pattern particularly the sinusoidal motion, which spread out along the direction of motion. Study results showed that in the dose region between isocenter and the 50% isodose line, the dose profile decreased with increase of the motion amplitude. As the range of motion became larger than the field length along the direction of motion, the dose profiles changes overall including the central axis dose and 50% isodose line. If the total dose was delivered over a time much longer than the periodic time of motion, variations in motion frequency and phase do not affect the dose profiles. As a result, the motion dose modeling developed in this study provided quantitative characterization of variation in the dose distributions induced by motion, which can be employed in radiation therapy to quantitatively determine the margins needed for treatment planning considering dose spillage to normal tissue.

Conceptual Design and Trajectory Planning of a Precision Repetitive-Scanning Stage With Separated Drive Unit for Energy Saving

Precision repetitive-scanning stages, which exist in lithographic reticle systems, scanning probe microscopes, and scanning electrodischarge machines, have been widely used in modern precision industry. To design such stages, energy consumption has become one of the most important criteria due to energy crisis and practical heat-reduction request. Considering the motion characteristics of such stages, it would lead to an energy-saving nature if the accelerated and constant-speed motions are driven by two separated drive units (SDUs). Inspired by this thought, we propose a novel concept of precision repetitive-scanning stage especially equipped with a separate permanent-magnet drive unit for accelerated motion. In order to exploit the function of SDUs for achieving high energy-saving performance, a modified repetitive-scanning trajectory is proposed. For this trajectory, complete analytic formulas allowing real-time planning are provided to match the permanent-magnet drive force, which results in a sufficient utilization of the SDUs’ drive ability. Finally, a precision repetitive-scanning stage prototype is set up. Comparative experimental results demonstrate that the proposed structural concept and its matched trajectory can significantly save energy without any motion accuracy deterioration. Essentially speaking, the proposed conceptual design and trajectory planning strategy provide a good guidance for precision repetitive-scanning system on energy saving, which could be applied to industry of semiconductor manufacturing, precision detection, microfabrication, and so on.

Eddy current damper for passive reaction force compensation of a linear motor motion stage

This article presents an eddy current damper of a passive reaction force compensation mechanism for a linear motor motion stage. The reaction force compensation mechanism with a movable magnet track and eddy current damper resolves problems with the existing spring-based reaction force compensation mechanism such as resonance, design freedom, and difficulty of assembly and manufacturing. A simplified mathematical model of the eddy current damper is derived considering the sinusoidal magnetic flux density distribution and effective width of the eddy current damper, which shows important design factors of the eddy current damper–based reaction force compensation mechanism. Then, force of the eddy current damper according to the constant speed motion of the magnet track is investigated using multi-physical finite element analysis and is verified by experiments. Finally, the passive reaction force compensation with movable magnet track and eddy current damper is identified by experiments, and the finite element analysis of the eddy current damper is verified with free and forced vibration responses.

Interacting multiple model for improving the precision of vehicle-mounted global position system

To improve the precision of low-cost, vehicle-mounted global position system (GPS), this paper presents the multi-source information fusion algorithm of vehicle navigation, which is based on the interacting multiple model (IMM). Considering vehicle kinematics and dynamic characteristics, as well as its braking capacity in extreme accelerating situations, this study establishes the clothoid model, which shows longitudinal and lateral constant speed motion, and the Adaptive Current Statistics (ACS) model, which shows the acceleration of a vehicle. Through the parametric estimation of interactivity, filtering, and updating of probability, the vehicle trajectory is predicted within a period of time, and high-precision dead-reckoning is therefore achieved. Comparative analysis shows that the above algorithm can improve the precision of vehicle-mounted GPS/inertial navigation system.

Efficient Path Planning Algorithm for Additive Manufacturing Systems

Recent additive manufacturing technologies, such as 3-D printing and printed electronics, require constant speed motion for consistent material deposition. In this paper, a new path planning algorithm is developed for an \(XY\) -motion stage with an emphasis on aerosol printing. The continuous aerosol stream provided by the printing nozzle requires constant velocity in relative motion of a substrate to evenly deposit inks. During transitioning between print segments, a shutter prevents the aerosol from reaching the substrate, therefore wasting material. The proposed path planning algorithm can control motion of an \(XY\) stage for an arbitrary printing path and desired velocity while minimizing material waste. Linear segments with parabolic blends (LSPBs) trajectory planning is used during printing, and minimum time trajectory (MTT) planning is used during printer transition. Simulation results show that combining LSPB with MTT can minimize the printing time while following the desired path.

Simple timing generation along workspace paths for nonredundant robotic limbs

This article focuses on the relation between workspace path geometry and the timing along the path, obtained via simple timing generators yielding constant end-link speed motion, natural motion, and two types of globally optimized joint velocity motions. The generators are designed within the Singularity-Consistent framework developed originally to tackle motion control in the vicinity of kinematic singularities. A comparative study highlights how performance expressed in terms of various kinematic and dynamic criteria of local (peak joint velocity and torque) and global (joint velocity/torque uniformity and total mechanical power) nature is influenced by the curvature of the path image in configuration space and by the vicinity of singular configurations. Results from simulations with a simple planar 2R limb and a spatial 3R positioning limb following linear and circular paths are presented.

Constant Speed Motion Simulation and Error Analysis of Planar Non-Circular Curve Parts

The relative direction for a constant speed can be determined according to the planar non-circular curve parts. To establish the mathematical model, a constant speed motion simulation system is designed. The parameters of (vH=5mm/s, δ<3") is commonly used for the simulation system to simulate the movement of drawing the error curve. The results show that by controlling the movement of the plane curve parts in mathematical model can derive the basic constant speed, the relative error of constant speed is less than 3%, it provides a reliable bias when apply to production practice.

Does visually induced self-motion affect grip force when holding an object?

Accurate control of grip force during object manipulation is necessary to prevent the object from slipping, especially to compensate for the action of gravitational and inertial forces resulting from hand/object motion. The goal of the current study was to assess whether the control of grip force was influenced by visually induced self-motion (i.e., vection), which would normally be accompanied by changes in object load. The main task involved holding a 400-g object between the thumb and the index finger while being seated within a virtual immersive environment that simulated the vertical motion of an elevator across floors. Different visual motions were tested, including oscillatory (0.21 Hz) and constant-speed displacements of the virtual scene. Different arm-loading conditions were also tested: with or without the hand-held object and with or without oscillatory arm motion (0.9 Hz). At the perceptual level, ratings from participants showed that both oscillatory and constant-speed motion of the elevator rapidly induced a long-lasting sensation of self-motion. At the sensorimotor level, vection compellingness altered arm movement control. Spectral analyses revealed that arm motion was entrained by the oscillatory motion of the elevator. However, we found no evidence that grip force used to hold the object was visually affected. Specifically, spectral analyses revealed no component in grip force that would mirror the virtual change in object load associated with the oscillatory motion of the elevator, thereby allowing the grip-to-load force coupling to remain unaffected. Altogether, our findings show that the neural mechanisms underlying vection interfere with arm movement control but do not interfere with the delicate modulation of grip force. More generally, those results provide evidence that the strength of the coupling between the sensorimotor system and the perceptual level can be modulated depending on the effector.

Effect Of A Video-Based Laboratory On The High School Pupils’ Understanding Of Constant Speed Motion

Among the physical phenomena studied in high school, the kinematical concepts are important because they constitute a precondition for the study of subsequent concepts of mechanics. Our research aims at studying the effect of a computer-assisted scientific investigation on high school pupils’ understanding of the constant speed motion. Experimentation took place in a high school physics classroom. A repeated measures analysis of variance shows that, during the implementation of this strategy, the pupils’ understanding of kinematical concepts increased in a significant way. In conclusion, we specify advantages and limits of the study and give future research directions concerning the design of a computer-assisted laboratory in high school physics.

T-cell movement on the reticular network

The idea that the apparently random motion of T cells in lymph nodes is a result of movement on a reticular network (RN) has received support from dynamic imaging experiments and theoretical studies. We present a mathematical representation of the RN consisting of edges connecting vertices that are randomly distributed in three-dimensional space, and models of lymphocyte movement on such networks including constant speed motion along edges and Brownian motion, not in three-dimensions, but only along edges. The simplest model, in which a cell moves with a constant speed along edges, is consistent with mean-squared displacement proportional to time over intervals long enough to include several changes of direction. A non-random distribution of turning angles is one consequence of motion on a preformed network. Confining cell movement to a network does not, in itself, increase the frequency of cell–cell encounters.

Second order numerical scheme for motion of polygonal curves with constant area speed

We study polygonal analogues of several moving boundary problems and their time discretization which preserves the constant area speed property. We establish various polygonal analogues of geometric formulas for moving boundaries and make use of the geometric formulas for our numerical scheme to analyse general constant area speed motion of polygons. Accuracy and efficiency of our numerical scheme are checked through numerical simulations for several polygonal motions such as motion by curvature and area-preserving advected flow etc.

Finite Difference Solution of Response Time Delay of Magneto-rhelological Damper

Magneto-rhelological(MR) dampers are devices that employ rheological fluids to modify their mechanical properties. Their mechanical simplicity, high dynamic range, lower power requirements, large force capacity, robustness and safe manner of operation in cases of failure have made them attractive devices for semi-active real-time control in civil, aerospace and automotive applications. Time response characteristic is one of the most important technical performances of MR dampers, and response time directly affects the control frequency, application range and the actual effect of MR dampers.In this study, one kind of finite difference solution for predicting the response time of magneto-rheological dampers from "off-state" to "on-state" is put forward. A laminar flow model is used to describe the flow in the MR valve, and a bi-viscous fluid flow model is utilized to describe the relationship of shear stress and shear rate of MR fluid. An explicit difference format is used to discretize the Novior-Stoks equation, and stability condition of this algorithm is built by Von-Neumann stability criterion. The pressure gradient along the flow duct is solved by a dichotomy algorithm with iteration, and the changing curve of the damping force versus time of MR damper is obtained as well. According to the abovementioned numerical algorithm, the damping forces versus time curves from "off-state" to "on-state" of a cylindrical piston type MR damper are computed. Moreover, the MR damper is installed in a material test system(MTS), the magnetic field in the wire circles of the MR damper is "triggered" when the MR damper is imposed to do a constant speed motion, and the damping force curves are recorded. The comparison between numerical results and experimental results indicates that this finite difference algorithm can be used to estimate the response time delay of MR dampers.

Measuring the circular motion of small objects using laser stroboscopic images

Measuring the circular motion of a small object, including its displacement, speed, and acceleration, is a challenging task. This paper presents a new method for measuring repetitive and/or nonrepetitive, constant speed and/or variable speed circular motion using laser stroboscopic images. Under stroboscopic illumination, each image taken by an ordinary camera records multioutlines of an object in motion; hence, processing the stroboscopic image will be able to extract the motion information. We built an experiment apparatus consisting of a laser as the light source, a stereomicroscope to magnify the image, and a normal complementary metal oxide semiconductor camera to record the image. As the object is in motion, the stroboscopic illumination generates a speckle pattern on the object that can be recorded by the camera and analyzed by a computer. Experimental results indicate that the stroboscopic imaging is stable under various conditions. Moreover, the characteristics of the motion, including the displacement, the velocity, and the acceleration can be calculated based on the width of speckle marks, the illumination intensity, the duty cycle, and the sampling frequency. Compared with the popular high-speed camera method, the presented method may achieve the same measuring accuracy, but with much reduced cost and complexity.

Observability Measures and Their Application to GPS/INS

In this paper, two observability measures are introduced for a discrete linear system. The degrees of observability of both the system and its subspaces can be examined with these measures. The measures are well conditioned to perturbation and applicable to multi-input/multi-output time-varying systems. The relations among observability, observability measures, error covariance, and the information matrix are presented. It is shown that the measures have direct connections with the singular value decomposition of the information matrix. In contrast to the error covariance, the measures are determined by the system model and independent of the initial error covariance. An example of the observability analysis of the Global Positioning System/inertial navigation system is given. The measures are confirmed to be less sensitive to the system model perturbation. It is also shown that the vertical component of the gyro bias can be considered unobservable with a tactical-grade inertial measurement unit for a horizontal constant-speed motion.

B-picture coding in AVS video compression standard

This paper first gives a brief overview of the Chinese audio–video coding standard (AVS 1 1 The China audio-video coding standard (AVS) referred in this paper all indicates AVS-Part 2. It targets at a better trade-off between coding efficiency and complexity for high-definition video coding. ) especially on prediction modes of motion compensation for B-picture. Furthermore, two techniques adopted by AVS about how to improve motion compensation for B-picture coding are discussed in detail. The first one is the proposed symmetrical mode that replaces the conventional bi-directional mode, in which only one motion vector is coded and another is derived from the coded one with the assumption of approximate constant-speed motion. It can achieve a better trade-off between prediction accuracy and the bits for coding motion information. The second one is the improved temporal direct mode. It not only solves the problem in AVS on how to correctly derive reference index under the constraint of two reference buffers for both P- and B-pictures but also improves the accuracy of derived motion vectors in temporal direct mode with division-free operations. In experimental results, the proposed symmetrical mode and the improved temporal direct mode were integrated into the H.264/MPEG-4 AVC reference software to exhibit their performances. Furthermore, the B-picture coding performance in AVS is also evaluated using different GOP coding structures.