Smooth Velocity Profile Research Articles

An optimal model-based trajectory following architecture synthesising the lateral adaptive preview strategy and longitudinal velocity planning for highly automated vehicle

ABSTRACTAutomated driving has received a broad of attentions from the academia and industry, since it is effective to greatly reduce the severity of potential traffic accidents and achieve the ultimate automobile safety and comfort. This paper presents an optimal model-based trajectory following architecture for highly automated vehicle in its driving tasks such as automated guidance or lane keeping, which includes a velocity-planning module, a steering controller and a velocity-tracking controller. The velocity-planning module considering the optimal time-consuming and passenger comforts simultaneously could generate a smooth velocity profile. The robust sliding mode control (SMC) steering controller with adaptive preview time strategy could not only track the target path well, but also avoid a big lateral acceleration occurred in its path-tracking progress due to a fuzzy-adaptive preview time mechanism introduced. In addition, an SMC controller with input–output linearisation method for velocity tracking is built and validated. Simulation results show this trajectory following architecture are effective and feasible for high automated driving vehicle, comparing with the Driver-in-the-Loop simulations performed by an experienced driver and novice driver, respectively. The simulation results demonstrate that the present trajectory following architecture could plan a satisfying longitudinal speed profile, track the target path well and safely when dealing with different road geometry structure, it ensures a good time efficiency and driving comfort simultaneously.

Abstract 5059: Cancer cell invasion dynamics in microchannels during stromal cell coculture

Abstract Metastasizing cancer cells must escape their tumor microenvironment and invade into surrounding healthy stromal tissue. During this process, they must balance intercellular crosstalk with ECM degradation, physical force generation, and cytoskeletal rearrangement. To mimic this process in vitro, PDMS microchannels fabricated with photolithography and replica molding were used to examine the interaction of cancer cells with healthy stromal cells during physical confinement in three dimensional environments. A focus was placed on understanding the variations in invasion behavior between healthy cells and cancer cells, then attempting to explain these differences by cell mechanical properties and gene expression. Distinct differences in cancer cell invasion characteristics were observed between wide 10 μm channels and narrow 3 μm channels, with the latter exhibiting smooth velocity profiles and increased channel permeation. Live cell actin staining, ECM protein alteration, and chemical inhibition of both Rac1 and RhoA mechanical pathways were all used to better understand these differences, leading to the conclusion that the actin cytoskeleton is greatly altered during invasion into very confined channels. To better understand the role of stromal cells in this process, both indirect and direct coculture of MDA MB-231 basal breast cancer cells and stromal cells were performed in microchannel chips with the aid of live cell permeable tracking dyes. To reflect a diverse range of stromal cell types, cocultures were performed with MCF 10A non-tumorigenic breast epithelial cells, macrophage-differentiated THP-1 monocytes, and HN-CAFs (head and neck carcinoma-associated fibroblasts). Both the cancer cells and the stromal cells exhibited increases in invasion speed upon direct co-culture of the two cancer cell lines, both in wide and narrow channels. The use of stromal cell-conditioned media as well as observed differences in migration speed and persistence when unconfined provided further understanding of the complex processes underlying cancer cell and stromal cell invasion. Citation Format: Andrew W. Holle, Verena Kast, Ralf Kemkemer, Joachim Spatz. Cancer cell invasion dynamics in microchannels during stromal cell coculture. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 5059.

The Initiation of Smooth Pursuit is Delayed in Anisometropic Amblyopia.

PurposeSeveral behavioral studies have shown that the reaction times of visually guided movements are slower in people with amblyopia, particularly during amblyopic eye viewing. Here, we tested the hypothesis that the initiation of smooth pursuit eye movements, which are responsible for accurately keeping moving objects on the fovea, is delayed in people with anisometropic amblyopia.MethodsEleven participants with anisometropic amblyopia and 14 visually normal observers were asked to track a step-ramp target moving at ±15°/s horizontally as quickly and as accurately as possible. The experiment was conducted under three viewing conditions: amblyopic/nondominant eye, binocular, and fellow/dominant eye viewing. Outcome measures were smooth pursuit latency, open-loop gain, steady state gain, and catch-up saccade frequency.ResultsParticipants with anisometropic amblyopia initiated smooth pursuit significantly slower during amblyopic eye viewing (206 ± 20 ms) than visually normal observers viewing with their nondominant eye (183 ± 17 ms, P = 0.002). However, mean pursuit latency in the anisometropic amblyopia group during binocular and monocular fellow eye viewing was comparable to the visually normal group. Mean open-loop gain, steady state gain, and catch-up saccade frequency were similar between the two groups, but participants with anisometropic amblyopia exhibited more variable steady state gain (P = 0.045).ConclusionsThis study provides evidence of temporally delayed smooth pursuit initiation in anisometropic amblyopia. After initiation, the smooth pursuit velocity profile in anisometropic amblyopia participants is similar to visually normal controls. This finding differs from what has been observed previously in participants with strabismic amblyopia who exhibit reduced smooth pursuit velocity gains with more catch-up saccades.

Characterization and Theoretical Analysis of Rapidly Prototyped Capillary Action Autonomous Microfluidic Systems

Capillary action arising from surface tension-based forces has been demonstrated to be an effective means of passively actuating various fluids through simple and sophisticated microfluidic channel networks. Systems based on this technique are advantageous compared with standard pumping strategies, as they have zero power requirements, are readily integrated into the overall fluidic chip design, and can be fabricated rapidly in a single manufacturing step. This paper comprehensively investigates time lapsed average velocity profiles of various capillary action microfluidic systems, including channels and pumping structures, and compares experimental data against prominent, competing, and flow-based theoretical models. We demonstrate that the average meniscus flow velocity of CO 2 laser ablated capillary systems can be adequately predicted and characterize smooth fluidic velocity profiles in simple microchannels and complex interlinking channel pump/filling structures. Such systems offer a useful, rapid, and low cost alternative to traditional fluidic actuation and flow control systems such as those found in on-chip based biological and chemical analysis.

Instability of plane shear flows

This paper obtains the existence of unstable modes of the Rayleigh equation with smooth or piecewise smooth steady states. In the reasoning, we employ a crucial tool that displays the asymptotic distribution of eigenvalues of non-symmetric Sturm–Liouville operators. For flows with piecewise smooth velocity profiles, we propose a new framework for eigenvalue problems with interior singularities. Examples are presented to show the scope of our criteria.

Bio-inspired Trajectory Planning for Robot Catching Movements Based on Tau Theory

A bio-inspired trajectory planning method for robot reaching movement to catch an object is presented. The method is based on the Tau theory which has been established by cognitive science researchers from studying the natural motion patterns when animals(including humans) approaching and catching a target object. Based on the Tau theory, two fundamental motion strategies, namely, the Tau coupling strategy and the intrinsic Tau-g guidance strategy have been analyzed. In order to solve the problem that the initial acceleration value is nonzero in the intrinsic Tau-g guidance strategy, a new strategy, namely, the intrinsic constant jerk Tau guidance strategy is presented. The trajectory planning formulae based on the Tau theory are derived. Trajectory planning, kinetics analysis, dynamic analysis, computer simulation and experiments are performed on a 3-DOF planar manipulator. The results show that, by using the proposed method, the end-effector can achieve reaching the target position and attitude at the same definite time with good continuity of joint velocity and acceleration, and the trajectory in Cartesian space is a straight path with a smooth bell-shaped velocity profile.

Modeling and improvement of dynamic contour errors for five-axis machine tools under synchronous measuring paths

In this paper, a contour error model of the tool center point (TCP) for a five-axis machine tool is proposed to estimate dynamic contour errors on three types of measuring paths. A servo tuning approach to achieve five-axis dynamic matching is utilized to improve contouring performance of the cutting trajectory. The TCP control function is developed to generate measuring trajectories where five axes are controlled simultaneously to keep the TCP at a fixed point. The interpolation method of the rotary axes with S-shape acceleration/deceleration (ACC/DEC) is applied to plan smooth five-axis velocity profiles. The contour error model for five axes is derived by substituting five-axis motion commands into servo dynamics models. The steady state contour error (SSCE) model is demonstrated to illustrate three particular dynamic behaviors: the single-circle with amplitude modulation, double-circle effect and offset behavior. Furthermore, the model is also utilized to investigate the behaviors of dynamic contour errors change in 3D space. The factors that affect dynamic contour errors, including the initial setup position, feedrate and five-axis servo gains, are analyzed. With the developed servo tuning process under the measuring paths (CK1, CK2 and CK4), the contour errors caused by servo mismatch are reduced remarkably. Finally, experiments are conducted on a desktop five-axis engraving machine to verify the proposed methodology can improve dynamic contouring accuracy of the TCP significantly.

Study of a Newtonian Fluid through Circular Channels with Slip Boundary Taking into Account Electrokinetic Effect

We study the slip flow of fluids driven by the combined effect of electrical force and pressure gradient. The underlying boundary value problem is solved through the use of Fourier series expansion in time and Bessel function in space. The exact solutions and numerical investigations show that the slip length and electrical field parameters have significant effects on the velocity profile. By varying these system parameters, one can achieve smooth velocity profiles or wave form profiles with different wave amplitude and frequency. This opens the way for optimizing the flow by choosing the slip length, the electrical field, and electrolyte solutions.

Kelvin–Helmholtz instability with a free surface

The well-posedness of the hydrostatic equations is linked to long wave stability criteria for parallel shear flows. We revisit the Kelvin--Helmholtz instability with a free surface. In the wall-bounded case, the flow is unstable to all wave lengths. Short wave instabilities are localized and independent of boundary conditions. On the other hand, long waves are shown to be stable if the upper boundary is a free surface and gravity is sufficiently small. We also consider smooth velocity profiles of the base flow rather than a velocity jump. We show that stability of long waves for small gravity generally holds for monotone profiles U(y). On the other hand, this need not be the case if U is not monotone.

Crustal and uppermost mantle S velocity structure under Hi-CLIMB seismic array in central Tibetan Plateau from joint inversion of surface wave dispersion and receiver function data

Trade-off between the depth of an interface and the average velocity above the interface is well known in receiver function inversion. To resolve model ambiguity, surface wave dispersion data, which are sensitive to vertical shear velocity average, are commonly combined with P receiver functions in the inversion. In this paper, we design a joint inversion scheme using the neighborhood searching algorithm to solve shear velocity structure of the crust and uppermost mantle with receiver function and surface wave dispersion data. Two sets of stretched splines are implemented in the inversion to obtain smooth velocity profiles, separated by a specifically defined Moho discontinuity. We apply this method to the dense Hi-CLIMB seismic array in the central Tibetan Plateau (TP). The Indian crust is observed to subduct and underplate the Tibetan crust between the Yarlung-Zangbo suture and the Bangong-Nujiang suture, at the latitude of about 31.5°N. The crust thickens from about 50km below the Indian foreland to over 75km south of Bangong-Nujiang suture and turns shallower at around 65km under the Qiangtang block. We identify two zones with complicated Moho structure beneath the northern Lhasa block and southern Qiangtang block, indicating highly deformed Moho morphology, and beneath the Himalaya block associated with the underthrusting of the Indian Plate, respectively. A low velocity zone is present in the mid-crust in most parts of the profile under the TP with up to more than 10% velocity reduction. The low velocity structure is not continuous, forming discontinuous patches rather than channels, calling for a revision of the channel flow model.

The transition algorithm based on parametric spline curve for high-speed machining of continuous short line segments

A numerical control (NC) program generated by a complex CAD/CAM system mainly composes a number of short line segments. For continuous short line segment machining, the traditional machining approach and the direct transitional approach cause the oscillations of the federate and affect machining efficiency. Moreover, the arc transitional approach enhances machining efficiency, but it brings about the greater machining error. To increase the smoothness of velocity profile and machining efficiency of continuous short line segment machining, this paper presents a parametrical cubic spline curve transitional approach with the S-shaped jerk-limited acceleration and deceleration with look-ahead. The trajectory error of the transitional curve is deduced according to the correlative factors, the preconditions of the transitional curve are put forward and analyzed, the mathematical model of the parametrical cubic spline curve is constructed, and the constraint conditions of the transforming velocity are built. In addition, the velocity control method is adopted for the smoother velocity profile. Thus, the machining productivity is dramatically increased and the velocity profile is more smoothness. The simulative and experimental results verify the feasibility and validity of the proposed approach.

Precise seismic-wave velocity atop Earth's core: No evidence for outer-core stratification

Earth's outer core is composed of liquid Fe and Ni alloyed with a ∼10% fraction of light elements such as O, S, or Si. Secular cooling and compositional buoyancy drive vigorous convection that sustains the geodynamo, but critical details of light-element composition and thermal regime remain uncertain. Seismic velocities can provide important observational constraints on these parameters, but global reference models such as Preliminary Reference Earth Model ( PREM), IASP91 and AK135 exhibit significant discrepancies in the outermost ∼200 km of the core. Here, we apply an Empirical Transfer Function method to obtain precise arrival times for SmKS waves, a whispering-gallery mode that propagates near the underside of the core–mantle boundary. Models that fit our data are all characterized by seismic velocities and depth gradients in the outermost 200 km of the core that correspond best with PREM. This similarity to PREM, which has a smooth velocity profile that satisfies the adiabatic Adams and Williamson equation, argues against the presence of an anomalous layer of light material near the top of the core as suggested in some previous studies. A new model, AE09, is proposed as a slight modification to PREM for use as a reference model of the outermost core.

Velocity Control Method for Continuous Short Line Segment High-Speed Machining Based on Transition of Parametric Spline

To enhance the velocity profile’s smoothness and machining efficiency of continuous short line segments, a velocity smooth control algorithm was presented based on the transition of cubic parametric spline curves. The transitional mathematical model was constructed, and an improved S-shaped jerk-limited acceleration/deceleration algorithm with look-ahead was adopted for smoother velocity profiles. The simulation and experiment results showed that machining efficiency was greatly improved, and smoother velocity profile was achieved, which approved the feasibility and validity of the proposed method.

Two modes of error processing in reaching

Several processes are devoted to error reduction for the production of purposeful actions. When motor responses deviate from their goal, online corrections can be performed either under voluntary control with additional sub-movements or under fast automatic control with smooth velocity profiles. When errors cannot be corrected online and are repeated over trials, subsequent responses can be improved iteratively through adaptation, a progressive adjustment of motor commands that acts to reduce the magnitude of error. It has been argued that reaching adaptation results essentially from a conflict between actual sensory feedback and expected sensory feedback. Here, we specifically compare two innovative hand-reaching paradigms that provide the subject with undistorted hand sensory feedback. Both paradigms induce motor planning errors unknown to the subjects. Experiment 1 yields a continuous retinal and visuomotor feedback which allows fast and complete automatic online corrections. In experiment 2, all visual feedback is eliminated during movement execution. This prevents online correction and provides information on hand-to-target visual error at movement end only. Despite a reiterated motor planning error and an automatic online correction of the whole error, experiment 1 shows a complete lack of adaptation. In contrast, experiment 2 which yields the same motor planning error exhibits a robust and generalized adaptation, although devoid of limb inter-sensory mismatch. These results demonstrate independence between the induced motor adaptation and automatic online correction, both characterized by the lack of any cognitive interference. Despite these quite different processes acting upon either motor planning or motor control, the general structure of the movement kinematics remains unaltered. A putative visuomotor cerebro-cerebellar network accounting for our results is proposed.

Response to Intensive Upper Extremity Therapy by Individuals with Ataxia from Stroke

Objective: This study investigated whether or not individuals with ataxia from stroke improve their upper extremity motor function with intense motor practice. Method: Three individuals with ataxia from chronic stroke completed modified constraint-induced movement therapy (CIMT) protocols. Stroke Participants 1 and 2 completed 60 hours and Stroke Participant 3 completed 30 hours of graded task practice while being asked to wear a mitt on the nonparetic arm for 90% of waking hours. Outcome measures were the upper extremity subscale of the Fugl-Meyer Motor Assessment, Wolf Motor Function Test, Motor Activity Log, and kinematics of reaching. Results: All stroke participants improved on either the Fugl-Meyer or the Wolf tests and increased their daily use of the paretic upper extremity. Participants 1 and 2 also improved on all kinematic measures: maximum velocity and time to maximum velocity increased, while index of curvature, number of peaks in the velocity profile, and trunk movement decreased. Participant 3 improved on some kinematic measures (smoother velocity profile, increased time to maximum velocity, decreased number of peaks in the velocity profile) but not all (decreased maximum velocity, increased index of curvature). Conclusion: Individuals with ataxia from stroke can improve their motor function with intense motor practice.

Marginally unstable Holmboe modes

Marginally unstable Holmboe modes for smooth density and velocity profiles are studied. For a large family of flows and stratification that exhibit Holmboe instability, it is shown that the modes with phase velocity equal to the maximum or the minimum velocity of the shear are marginally unstable. This allows us to determine the critical value of the control parameter R (expressing the ratio of the velocity variation length scale to the density variation length scale) above which Holmboe instability is present, Rcrit=2. Furthermore, systems for which the parameter R is very close to this critical value Rcrit are examined. For this case, an analytical expression for the dispersion relation of the complex phase speed c(k) in the unstable region is derived. The growth rate and the width of the region of unstable wavenumbers has a very strong (exponential) dependence on the deviation of R from the critical value. Two specific examples are examined and a physical interpretation of the results is described.

Lens‐Aided Multi‐Angle Spectroscopy (LAMAS) Reveals Small‐Scale Outflow Structure in Quasars

Spectral differences between lensed quasar image components are common. Since lensing is intrinsically achromatic, these differences are typically explained as the effect of either microlensing, or as light path time delays sampling intrinsic quasar spectral variability. Here we advance a novel third hypothesis: some spectral differences are due to small line-of-sight differences through quasar disk wind outflows. In particular, we propose that variable spectral differences seen only in component A of the widest separation lens SDSS J1004+4112 are due to differential absorption along the sight lines. The absorber properties required by this hypothesis are akin to known broad absorption line (BAL) outflows but must have a broader, smoother velocity profile. We interpret the observed C IV emission-line variability as further evidence for spatial fine structure transverse to the line of sight. Since outflows are likely to be rotating, such absorber fine structure can consistently explain some of the UV and X-ray variability seen in AGNs. The implications are many: (1) Spectroscopic differences in other lensed objects may be due to this lens-aided multi-angle spectroscopy (LAMAS). (2) Outflows have fine structure on size scales of arcseconds, as seen from the nucleus. (3) Assuming either broad absorption line region sizes proposed in recent wind models, or typically assumed continuum emission region sizes, LAMAS and/or variability provide broadly consistent absorber size scale estimates of ~1015 cm. (4) Very broad smooth absorption may be ubiquitous in quasar spectra, even when no obvious troughs are seen.

Meshing for velocity modeling and ray tracing in complex velocity fields

In seismic processing, velocity fields are commonly represented on finely sampled Cartesian grids. Attractive alternatives are unstructured grids such as meshes composed of triangles or tetrahedra. Meshes provide a space-filling framework that enables editing of velocity models while facilitating numerical tasks such as seismic modeling and inversion. In this paper, we introduce an automated process to generate meshes of subsurface velocity structures for highly resolved velocity fields without providing additional external constraints such as horizons and faults. Our analysis shows that these new meshes can represent both smooth and discontinuous velocity profiles accurately and with less computer memory than grids.

Effect of gravity and angular velocity on an automatic ball balancer

The effects of gravity and an angular velocity profile on the performance of an automatic ball balancer (ABB) are studied in this paper. In order to investigate these effects, a physical model of a Jeffcott rotor with an ABB is adopted in this study, in which gravity as well as the angular acceleration is considered. With the polar coordinates, the non-linear equations of motion are derived by using Lagrange's equation. These equations include gravity, the angular acceleration, and the angular jerk. Based on the equations derived, time responses are computed by using the generalized α method. The effects of gravity on the balancing performance are analysed. For various angular velocity profiles, the ABB performance is also evaluated. The analysis of results shows that the balancing of the rotor with an ABB can be achieved regardless of gravity. It is also shown that a smooth velocity profile results in less vibration compared with a non-smooth velocity profile.

On the design of slider-crank mechanisms. Part II: multi-phase path and function generation

A method to design slider-crank mechanisms to achieve multi-phase path and function generation applications typically accomplished by adjustable planar four-bar mechanisms is presented. The benefit of this method is twofold. First, multiple phases of prescribed coupler curve points or crank and follower displacement angles are achievable using a mechanism with fewer moving parts than the planar four-bar mechanism. Second, the slider-crank mechanism can achieve these phases of prescribed values without any physical or automated adjustments of its moving pivots between phases. A slider path that enables the slider-crank to achieve two phases of prescribed coupler curve points or crank and follower displacement angles is designed by using seventh order polynomials to connect the moving pivot paths of the follower link of the adjustable planar four-bar mechanism. This polynomial generates smooth radial displacement, velocity, acceleration and jerk profiles with boundary conditions that can be prescribed. The example problems in this work considers a two-phase moving pivot adjustment of a planar four-bar mechanism.