Translational Trajectory Research Articles

An Indirect Adaptive Control Approach to Image Based Visual Servoing for Translational Trajectory Tracking

In this work, it is considered an image based visual servoing control problem, for uncertain robot manipulators. Visual feedback is provided by a fixed monocular camera with uncertain parameters, for the purpose of tracking translational trajectories of a spherical target, both the trajectory on image plane and depth. Based on a cascade structure, the proposed adaptive visual servoing is combined with an adaptive motion control strategy. Stability and passivity properties are analyzed with the Lyapunov method. Simulation results illustrate and highlight performance of the proposed controller.

Trajectory statistical solutions for the 3D Navier–Stokes equations: The trajectory attractor approach

In this article, we construct the trajectory statistical solution for the 3D incompressible Navier–Stokes equations via the natural translation semigroup and trajectory attractor. In our construction, the trajectory statistical solution is an invariant space–time probability measure which is carried by the trajectory attractor of the natural translation semigroup defined on the trajectory space, and the trajectory statistical solution possesses the invariant property under the acting of the translation semigroup.

Imaging in the acute brain injured state; Ethical considerations

Serious brain injury has a 30% mortality rate, and survivors are commonly disabled and require ongoing care. In Canada, deaths are preceded by decisions to limit care in 70% of cases, and some decisions are made too early for accurate prognostication (Turgeon, 2011). Neurologists have an ethical obligation to provide next-of-kin with accurate diagnostic and prognostic information to inform their decision making. Functional magnetic resonance imaging (fMRI) offers the prospect of improving prediction of outcomes in patients with an indeterminate prognosis, but more evidence is required. Conducting fMRI research involving acutely brain injured patients in the intensive care unit (ICU) is practically difficult and raises ethical issues (Weijer, 2016). Early in the translational trajectory, fMRI ought to be considered a nontherapeutic intervention, and the risks of such interventions must be minimized. Transporting critically ill patients outside the ICU has rates of serious adverse events of 4.2–8.9% and cardiac arrest of 0.34–1.6% (Weijer, 2016). To minimize the incremental risks of research participation, nontherapeutic fMRI scans should be paired with clinically indicated imaging. Informed consent in this setting poses difficult challenges (Bruni, 2019). Informed consent must be obtained from the surrogate decision maker (SDM). SDMs should be approached by a third party who can dedicate substantial time to the consent process, and fMRI should be identified clearly as a nontherapeutic procedure. [1]Bruni T. et al.J Med Ethics. 2019 Feb 25; (pii: medethics-2018-104867)Google Scholar; [2]Turgeon A.F. et al.CMAJ. 2011; 183: 1581-1588Google Scholar; [3]Weijer C. et al.Brain. 2016; 139: 292-299Google Scholar

Intersections between Translation and Book History: Reflections and New Directions

This article identifies points of intersection between the histories of translation and of the book by focusing on the way the two fields have approached textual transmission. After reflecting on the fundamentally complementary aims and methodologies of book and translation historians, it explores the increasingly close relationship between the two histories, and identifies some next steps and possible future areas of intersection. The article also argues that further synergism between translation and book history will make it possible for us to achieve a deeper understanding of the translational and transnational trajectories of texts.

Compressed sensing-based reconstruction for computed tomography with translational trajectory

ABSTRACTThis study newly demonstrates a compressed sensing (CS)-based reconstruction scheme for computed tomography (CT) with a translational trajectory. CT with a translational trajectory has many potential applications in the field of non-destructive testing (NDT) and medicine. For example, in the X-ray inspection of a large civil engineering structure, the movements of the source and detector are strictly limited, and a simple straight CT trajectory is preferable. This method could also be applied in X-ray inspection lines in factories and airports. In the medical field, this method would complement the tomosynthesis in mammography. When using a translational trajectory, the dispersion of the fan- or cone-beam creates projection data with the angular information of the sample object. However, the angular information inevitably becomes insufficient when using a translational trajectory, which degrades the reconstruction accuracy. In this case, CS is considered suitable for reconstruction because it has been successfully used for reconstructions from sparse-view and limited-angle data. For reconstruction from the translational trajectory projection, a new concept of directional difference (DD) regularization was proposed. An algorithm was developed based on the alternating direction method of multipliers (ADMM) algorithm to solve the regularization problem. Numerical reconstruction experiments from noisy projection data were conducted and the results were compared with those from other reconstruction methods. The convergence performance of the total variation (TV), DD, and mixed TV-DD regularization methods were examined. The proposed DD and TV-DD methods showed better performance than the TV only regularization. Reconstruction from Monte-Carlo simulated projection data was also demonstrated.

Quality-assured research environments for translational cancer research.

In order to secure high‐quality cancer care for increasing numbers of cancer patients in the upcoming decades, the complete continuum of cancer research and cancer care needs a thorough overhaul, with more emphasis on prevention and early detection, and a greater focus on the development of innovative treatments that are also scrutinised for effectiveness and quality‐of‐life aspects. Therefore, under‐resourced research areas, such as primary prevention, early diagnosis/secondary prevention (Song et al., 2018; Wild et al., 2015) and outcomes research (Cavers et al., 2017), should be given more emphasis, whereas basic, preclinical and clinical cancer research requires more innovation and effective collaboration to develop more effective treatments at an affordable cost. Innovative collaborative research in this translational trajectory requires the participation of well‐resourced and well‐organised institutions that are committed to high scientific and ethical standards. Offering focused funding to distinct segments of this research continuum concomitant with incentives to aspire to high‐quality standards is the most effective route to achieve these goals. Therefore, a rigorous quality assessment system for institutions operating in this research continuum is a high priority.

Spatial thermal dose delivery in atmospheric pressure plasma jets

Atmospheric pressure plasma jets (APPJs) are increasingly used in plasma medicine and materials processing applications. Reproducible and effective operation of APPJs requires regulating the cumulative effects of plasma on a target substrate in the face of variabilities and exogenous disturbances. This article investigates spatial delivery of thermal effects—thermal dose—of plasma using a kHz-excited APPJ in helium translated over a dielectric substrate. A dose metric is presented for quantifying the cumulative, nonlinear thermal effects of plasma along the translation trajectory of the APPJ. An optimization-based feedback control strategy is proposed for real-time regulation of thermal dose delivery using spatial measurements of substrate temperature. Experimental investigation reveals that feedback control is crucial for achieving spatially uniform dose delivery.

Effects of Nonlinear Propagation of Focused Ultrasound on the Stable Cavitation of a Single Bubble

Many biomedical applications such as ultrasonic targeted drug delivery, gene therapy, and molecular imaging entail the problems of manipulating microbubbles by means of a high-intensity focused ultrasound (HIFU) pressure field; namely stable cavitation. In high-intensity acoustic field, bubbles demonstrate translational instability, the well-known erratic dancing motion, which is caused by shape oscillations of the bubbles that are excited by their volume oscillations. The literature of bubble dynamics in the HIFU field is mainly centered on experiments, lacking a systematic study to determine the threshold for shape oscillations and translational motion. In this work, we extend the existing multiphysics mathematical modeling platform on bubble dynamics for taking account of (1) the liquid compressibility which allows us to apply a high-intensity acoustic field; (2) the mutual interactions of volume pulsation, shape modes, and translational motion; as well as (3) the effects of nonlinearity, diffraction, and absorption of HIFU to incorporate the acoustic nonlinearity due to wave kinematics or medium—all in one model. The effects of acoustic nonlinearity on the radial pulsations, axisymmetric modes of shape oscillations, and translational motion of a bubble, subjected to resonance and off-resonance excitation and various acoustic pressure, are examined. The results reveal the importance of considering all the involved harmonics and wave distortion in the bubble dynamics, to accurately predict the oscillations, translational trajectories, and the threshold for inertial (unstable) cavitation. This result is of interest for understanding the bubble dynamical behaviors observed experimentally in the HIFU field.

Asymptotic regularity of trajectory attractor and trajectory statistical solution for the 3D globally modified Navier–Stokes equations

We first prove the existence and regularity of the trajectory attractor for a three-dimensional system of globally modified Navier–Stokes equations. Then we use the natural translation semigroup and trajectory attractor to construct the trajectory statistical solutions in the trajectory space. In our construction the trajectory statistical solution is an invariant Borel probability measure, which is supported by the trajectory attractor and is invariant under the action of the translation semigroup. As a byproduct of the regularity of the trajectory attractor, we obtain the asymptotic regularity of the trajectory statistical solution in the sense that it is supported by a set in the trajectory space in which all weak solutions are in fact strong solutions.

Translational and rotational motion planning for spacecraft close proximity using sampling-based methods

For autonomous spacecraft close proximity under environments containing multiple obstacles and complicated constraints, incrementally rapid planning approaches stemming from sampling-based methods are investigated in this paper. Exploring planners are separately developed for the impulsive maneuvered translation and the piecewise constant controlled rotation, which, however, is constrained by the pointing limits coupling with relative positions during the proximity. Using a cost-informed parent-connecting strategy originating from dynamic programming as well as a sweeping growth fashion balanced between tree-based and graph-based methods, an asymptotically optimal unidirectional exploration method is proposed to search energy-efficient translational trajectory without collision. As for the rotation planning, the pointing constraints are taken as virtual obstacles in the state-space augmented with time horizon planned by the translation and, accordingly, a bidirectional exploration method is developed to generate constraint-satisfied slew paths with fast convergence rate. Numerical experiments indicate that the proposed sampling-based methods can rapidly return asymptotic optimal translation trajectory and rotation path satisfying collision avoidance and sensor field-of-view constraints.

Periodic Trajectory Planning Beyond the Static Workspace for 6-DOF Cable-Suspended Parallel Robots

This paper proposes a dynamic trajectory planning technique for six-degree-of-freedom (6-DOF) cable-suspended parallel robots (CSPRs). First, a passive mechanical system that is equivalent to the CSPR is introduced to provide insight and facilitate the design of trajectories that can extend beyond the robot's static workspace. The tilt-and-torsion angle convention is used to develop the mathematical model and impose restrictions for the rotational component of the trajectories. The dynamic differential equations that govern the translational component of the trajectories are shown to become linear under some conditions. Natural frequencies of an equivalent passive linear system of constant-stiffness springs are, thus, obtained and the set of linear differential equations associated with this system is integrated to produce a general solution for natural, periodic trajectories. This approach is used to produce pure translation trajectories and more complex motion that includes changes in position and orientation. An experimental implementation is also presented using a 6-DOF prototype and a supplementary video file is included to demonstrate the results.

Numerical analysis of ship motion under linear and nonlinear waves

Simulating physical phenomena by applying mathematical and numerical modeling has been increasingly used during the different stages of research and development and innovation projects. The purpose of this study is to present results about translational motion (x, y, z), angular motion (α, β, γ) and trajectories obtained using a numerical model developed to study ship dynamics under the influence of linear and nonlinear waves. The results indicated that translational motion, surge and sway, is mostly influenced by thrust in the studied scenario. The translational motion (heave) displayed curves which can be related with wave patterns before 0.1 hr. The angular motion distributions displayed a variation that can be related with wave forces. However, at 0.4 hr the curves depicted smaller variations that is explained by the increased engine thrust pattern. In both simulations, the distance of 20.582 km and 20.342 km for linear and nonlinear simulations were calculated, respectively. Once both simulations yielded similar values for travel distance, the wave patterns used in this study were shown to generate variations at the displacement from 0 to 0.4 hr. After 0.4 hr, the ship displacement depicted linear curves but the engine thrust was able to overcome the external forces.

Minimum-energy cornering trajectory planning with self-rotation for three-wheeled omni-directional mobile robots

A minimum-energy cornering trajectory planning with self-rotation algorithm is investigated for three-wheeled omni-directional mobile robots (TOMRs). First, an generalized minimum-energy point-to-point trajectory planning algorithm is studied, which is obtained using Pontryagin’s minimum principle, a practical cost function as the energy drawn from the batteries to motors, and the accurate TOMR dynamic model including actuator dynamics and the Coriolis force. By analyzing the co-state equation, the minimum-energy rotational velocity trajectory is presented in analytic form. Also a novel algorithm for the minimum-energy translational velocity trajectory is investigated. Second, the minimum-energy cornering trajectory planning algorithm with self-rotation is developed. Simulation results show that the minimum-energy cornering trajectory can save energy up to 15.20%compared with the conventional control using trapezoidal velocity profiles, and up to 3.96 % compared with the loss-minimization control using the armature loss as the cost function. Also a resolved-acceleration controller is implemented to show an actual performance.

Theory of Kinematic Motion Control of a Rigid Body

The authors present a review of the works on the theory of kinematic control of the rotational (angular) motion of a rigid body and spatial motion of a free rigid body, which is a composition of the rotational and translational (trajectory) movements of a rigid body. The theory is based on the use of the quaternion and biquaternion kinematic models of the rigid body motion. They also provide a review of the papers devoted to the problems of construction of the optimal laws of change of the angular momentum of a dynamically symmetric rigid body and rigid body with an arbitrary mass distribution, which ensures its optimal translation from an arbitrary initial angular position to the desired final angular position. These tasks occupy an intermediate position between the kinematic and dynamic problems of control of the rotational rigid body motion and play an important role in the theory of control of orientation of the spacecraft using the rotating flywheels. The theory of kinematic motion control has various topical applications in the space flight mechanics, inertial navigation, and mechanics of robotics.

Integrated Guidance and Feedback Control of Underactuated Robotics System in SE(3)

An integrated guidance and feedback control scheme for steering an underactuated vehicle through desired waypoints in three-dimensional space, is developed here. The underactuated vehicle is modeled as a rigid body with four control inputs. These control inputs actuate the three degrees of freedom of rotational motion and one degree of freedom of translational motion in a vehicle body-fixed coordinate frame. This actuation model is appropriate for a wide range of underactuated vehicles including spacecraft with internal attitude actuators, vertical take-off and landing (VTOL) aircraft, fixed-wing multirotor unmanned aerial vehicles (UAVs), maneuverable robotic vehicles, etc. The guidance problem is developed on the special Euclidean group of rigid body motions, SE(3), in the framework ofgeometric mechanics, which represents the vehicle dynamics globally on this configuration manifold. The integrated guidance and control algorithm selects the desired trajectory for the translational motion that passes through the given waypoints, and the desired trajectory for the attitude based on the desired thrust direction to achieve the translational motion trajectory. A feedback control law is then obtained to steer the underactuated vehicle towards the desired trajectories in translation and rotation. This integrated guidance and control scheme takes into account known bounds on control inputs and generates a trajectory that is continuous and at least twice differentiable, which can be implemented with continuous and bounded control inputs. The integrated guidance and feedback control scheme is applied to an underactuated quadcopter UAV to autonomously generate a trajectory through a series of given waypoints in SE(3) and track the desired trajectory in finite time. The overall stability analysis of the feedback system is addressed. Discrete time models for the dynamics and control schemes of the UAV are obtained in the form of Lie group variational integrators using the discrete Lagrange-d’Alembert principle. Almost global asymptotic stability of the feedback system over its state space is shown analytically and verified through numerical simulations.

Kinematic analysis of an electric stair-climbing wheelchair

<p>This paper presents the functional design and the kinematic synthesis of the last version of an electric stair-climbing wheelchair. The proposed device represents the latest evolution of the ‘Wheelchair.q’ project and introduces several improvements over previous designs. This updated solution has greater stability during stair-climbing operation and satisfy the safety requirements introduced by ISO 7176-28:2012, “Requirements and test methods for stair-climbing devices”. The main improvement presented, concerns the regularity of the user trajectory during stair-climbing, which ensures a more comfortable perception. This result has been achieved through the introduction of a cam mechanism between the frame connected to the locomotion unit and the seat frame, which properly manages the seat orientation. With an appropriate cam profile it is possible to compensate the oscillations introduced on the wheelchair during the climbing sequence and allow the user to obtain a translational trajectory. The proposed design and its working principle are firstly described and illustrated through schematic and graphic representations. A brief explanation of the procedure for obtaining the cam profile is also given. Two different architectures for the cam mechanism are then compared and the advantages and disadvantages for each solution are identified. Finally, the kinematic wheelchair performances are tested through a simulation obtained in the MSC-ADAMS multibody environment.</p>

Local Corner Smoothing Transition Algorithm Based on Double Cubic NURBS for Five-axis Linear Tool Path

A five-axis tool path is often composed of a linear path that has a tangential discontinuity so that the tangential velocity will be abrupt or be equal to zero at the corner of the adjacent segments. Therefore, it greatly affects the machining efficiency and quality. Thus, a corner smoothing transition algorithm based on double cubic NURBS, which is curvature-continuous and satisfies the given accuracy constraint, is proposed to smooth the local corner at the adjacent five-axis linear path. On the basis of the smoothing transition model, the parametric synchronization between the smoothed double NURBS trajectories and the remaining two linear segments are respectively constructed to realize the smoothing variation along the tool tip translational trajectory and tool axis rotational trajectory. The simulation and examples show that the proposed transition algorithm can satisfy the error constraints, reduce the feedrate fluctuation, and improve the machining quality.

Trajectory Generation for Three-Degree-of-Freedom Cable-Suspended Parallel Robots Based on Analytical Integration of the Dynamic Equations

This paper proposes a trajectory generation technique for three degree-of-freedom (3-dof) planar cable-suspended parallel robots. Based on the kinematic and dynamic modeling of the robot, positive constant ratios between cable tensions and cable lengths are assumed. This assumption allows the transformation of the dynamic equations into linear differential equations with constant coefficients for the positioning part, while the orientation equation becomes a pendulum-like differential equation for which accurate solutions can be found in the literature. The integration of the differential equations is shown to yield families of translational trajectories and associated special frequencies. This result generalizes the special cases previously identified in the literature. Combining the results obtained with translational trajectories and rotational trajectories, more general combined motions are analyzed. Examples are given in order to demonstrate the results. Because of the initial assumption on which the proposed method is based, the ratio between cable forces and cable lengths is constant and hence always positive, which ensures that all cables remain under tension. Therefore, the acceleration vector remains in the column space of the Jacobian matrix, which means that the mechanism can smoothly pass through kinematic singularities. The proposed trajectory planning approach can be used to plan dynamic trajectories that extend beyond the static workspace of the mechanism.

How do researchers decide early clinical trials?

Launch of clinical investigation represents a substantial escalation in commitment to a particular clinical translation trajectory; it also exposes human subjects to poorly understood interventions. Despite these high stakes, there is little to guide decision-makers on the scientific and ethical evaluation of early phase trials. In this article, we review policies and consensus statements on human protections, drug regulation, and research design surrounding trial launch, and conclude that decision-making is largely left to the discretion of research teams and sponsors. We then review what is currently understood about how research teams exercise this discretion, and close by laying out a research agenda for characterizing the way investigators, sponsors, and reviewers approach decision-making in early phase research.

Collision Detection and Trajectory Planning for Palletizing Robots Based OBB

This paper proposes an algorithm for Collision detection between two convex polyhedra (Boxes). It is assumed that the Palletizing robot’s end effector grasped the Box in accurate incremental method, by compare the distances between objects in same space . The detections proposed by ignorance of time consumption, and make comparisons between performances of theories discussed this problem, like Axes Aligned Bounded Boxes (AABB) and Sphere theories. Oriented Bounded Boxes (OBB) theory is chosen because unspecified orientation of objects which meets the requirements for detecting collisions with accuracy and handling transformations. Transformation assumptions are based on Z-Y-Z Euler’s angles representation. The key factor for detecting collision between two OBB convex polyhedra is the Separating Axes Theorem (SAT). The trajectory algorithm presents incremental distance computation by implementing translation and spherical trajectory. The checking and simulations in C++ language and Auto CAD software, attests that implementations in both show accuracy results.