Reachable Points Research Articles

A multi-chamber soft robot for transesophageal echocardiography: continuous kinematic matching control of soft medical robots.

This research investigates designing a continuum soft robot and proposing a kinematic matching control to enable the robot to perform a specified medical task, which in this paper is the transesophageal echocardiography (TEE). A multi-chamber soft robot was designed and fabricated based on the molding of separate layers. The method of transformation matrices was used to develop the kinematic models, and a control method using Jacobian matrices was proposed to manipulate the robot. A prototype was made based on a multi-chamber multi-layer design. The system contains three segments that can be actuated independently to mimic the active bending part of the respective probe. Kinematic models were developed. Negative pressure (vacuum) was used as actuation input. An open-loop controller inspired by a redundancy resolution technique was proposed to make the soft robot tip follow the desired path, i.e.the path of the rigid ultrasound probe. It is concluded that the soft solution can perform the required task as the reachable points of the TEEtip cover the proposed robot workspace and the proposed control can be used for maneuvering in arbitrary trajectories.

Adaptive map matching based on dynamic word embeddings for indoor positioning

Map matching has been widely used in various indoor localization technologies. However, conventional map matching technologies based on probabilistic models, such as particle filter (PF), still have a series of limitations, such as underutilization of map information, poor generalization, and relatively low precision. To improve the performance of PF-based map matching technique, this paper proposes MapDem, a novel map matching model fusing dynamic word embeddings and Variational Autoencoder (VAE) to improve matching performance significantly. The key to our approach is to extract map information using dynamic word embeddings to represent each reachable point on the map as word vectors with allowable oriented trajectory information. The same point has different representations on different trajectories so that MapDem can adaptively learn the contextual information of map for position estimation. Unlike traditional particle filters, MapDem focuses on the learning of particle sets distribution by a statistical model, Variational Autoencoder (VAE), followed by estimating position with combined current and previous sequence information. Extensive experiments have been conducted with 610 trajectories in three real-world scenarios. Numerical results demonstrate the adaptability of MapDem which works equally well in all three different scenarios, outperforming traditional particle filters by 18% on average.

REPRODUCTION OF SPACE: ÜÇKUYULAR MARKET UNDER VIADUCT

Lefebvre defines markets as places of exchange where people and goods come face to face and also underlines that the market has had a central position throughout history which shapes gathering place. (Lefebvre, 2011) Üçkuyular market places, which was taken under viaduct around 2016, is an important center of İzmir which takes place every Sunday and becomes specialized with fresh fruits and vegetables selling including other fields (clothing, charcuterie, fish market). Strategically markets establish at reachable points with both vehicle and foot. Üçkuyular as a region serves transfer center for metro, bus, ferry, dolmush for districts and tram in the near future. However, with sudden decision of municipality location of Üçkuyular market will move from its place to under viaducts of highway. In this paper, it is aimed to examine how these kinds of decisions were taken free from users with ignoring “right to the city”.

Functional workspace of a novel single incision surgical robotics platform

The enabling potential of robotics continues to increase in abdominal surgery, including gynecology.1 The functionality of a robotics platform is more than just the extent of the workspace that the end effectors can reach, but also the usability (or manipulability) of the end effectors at every reachable point in that workspace. A novel robotics platform has been developed that allows all the articulation to occur inside the abdomen through 2 arms inserted through a small vaginal incision in the rectouterine space. After insertion while extended, the two robotic arms can then retroflex back towards the point of entry to perform procedures such as a hysterectomy with the standard fundus to cervix surgical workflow. This study measured the manipulability of this new robotic platform throughout its entire reachable workspace in the abdomen by first generating a set of 200,000 configurations of the robot arms and secondly calculating the manipulability index according to robotics literature.2 The results show that, due to the shoulder, elbow and wrist joints of the arms that perform all of their articulation after entry, the reachable workspace encompasses the entirety of the average male and female abdomen from the para-aortic nodes to the pelvic floor, across from abdominal sidewall to sidewall and from the abdominal wall to vertebrae. Because the wrist joints have unlimited rotation and the shoulder and elbow joints allow the arms to function as they cross over each either, the manipulability index remains high (high usability) within the abdominal cavity and particularly around anatomy of interest such as the uterus and adnexa, lymph nodes, gall bladder, inguinal canal and appendix. The design of this new robotic technology has the potential to provide surgical treatment to a broad array of abdominal anatomy through a single transvaginal entry point.

A Network-Based Model of Passenger Transfer Flow between Bus and Metro: An Application to the Public Transport System of Beijing

In a multimodal public transport network, transfers are inevitable. Planning and managing an efficient transfer connection is thus important and requires an understanding of the factors that influence those transfers. Existing studies on predicting passenger transfer flows have mainly used transit assignment models based on route choice, which need extensive computation and underlying behavioral assumptions. Inspired by studies that use network properties to estimate public transport (PT) demand, this paper proposes to use the network properties of a multimodal PT system to explain transfer flows. A statistical model is estimated to identify the relationship between transfer flow and the network properties in a joint bus and metro network. Apart from transfer time, the number of stops, and bus lines, the most important network property we propose in this study is transfer accessibility. Transfer accessibility is a newly defined indicator for the geographic factors contributing to the possibility of transferring at a station, given its position in a multimodal PT network, based on an adapted gravity-based measure. It assumes that transfer accessibility at each station is proportional to the number of reachable points of interest within the network and dependent on a cost function describing the effect of distance. The R-squared of the regression model we propose is 0.69, based on the smart card data, PT network data, and Points of Interest (POIs) data from the city of Beijing, China. This suggests that the model could offer some decision support for PT planners especially when complex network assignment models are too computationally intensive to calibrate and use.

Real-Time Trajectory Generation and Reachability Determination in Autorotative Flare

Autorotation maneuvers inherently offer little margin for error in execution and induce high pilot workload, particularly as the aircraft nears the ground in an autorotative flare. Control augmentation systems may potentially reduce pilot workload while simultaneously improving the likelihood of a successful landing by offering the pilot appropriate cues. This paper presents an initial investigation of a real-time trajectory generation scheme for autorotative flare based on time-to-contact theory. The algorithm exhibits deterministic runtime performance and provides a speed trajectory that can be tracked by a pilot or inner-loop controller to bring the vehicle to a desired landing point at the time of touchdown. A low-order model of the helicopter dynamics in autorotation is used to evaluate dynamic feasibility of the generated trajectories. By generating and evaluating trajectories to an array of candidate landing points, the set of reachable landing points in front of the aircraft is determined. Simulation results are presented in which the trajectory generator is coupled with a previously derived autorotation controller. Example cases and trade studies are conducted in a six degree-of-freedom simulation environment to demonstrate overall performance as well as robustness of the algorithm to variations in target landing point, helicopter gross weight, and winds. The robustness of the reachability determination portion of the algorithm is likewise evaluated through trade studies examining off-nominal flare entry conditions and the effects of winds.

Volumetric uncertainty bounds and optimal configurations for converging beam triple LIDAR

We consider the problem of quantifying uncertainty for converging beam triple LIDAR when the input uncertainty follows a uniform distribution. We determine expressions for the range (i.e. set of reachable points) for the reconstructed velocity vector as a function of any particular setting of the nominal input parameters and determine an explicit lower (and upper) bound on the (averaged) volume (with respect to Lebesgue measure), in R3, of that range. We show that the size of any such bound is inversely proportional to the absolute value of the triple scalar product of the unit vectors characterizing the Doppler measurement directions (optimized over the uncertainty region) in R6 associated with the nominal angle settings under consideration. This leads to the conclusion that the nominal LIDAR configurations that minimize output uncertainty ought to be those in which the value of the triple scalar product of the Doppler unit vectors is at its largest.

Development of a Robotic End-Effector for Apple Tree Pruning

HighlightsAn end-effector with two degrees of freedom (2R) was developed for pruning apple trees.A rational 2×2 relationship (R2 = 0.93) was found for ‘Fuji’ apple tree branch diameter and cutting force.Simulation showed that the cutter can be aligned in a wide range of orientations in a spherical workspace.The developed end-effector was able to cut branches up to 12 mm in diameter.Abstract. Robotics and automation technologies are now used extensively in agriculture, while production operations for tree fruit crops still largely depend on manual labor. Manual pruning is a labor-intensive and costly task in apple production. Robotic pruning is a potential solution, but it involves several challenges due to the unstructured work environment. This study focused on designing an end-effector prototype for pruning considering the maneuvering, spatial, mechanical, and horticultural requirements. Branch cutting force was measured with a thin force sensor to provide guidelines for the end-effector design. The test results indicated the relationship between the force required to cut different diameter branches with an R2 value of 0.93. The end-effector was developed using two rotary motors, a pneumatic cylinder, and a pair of bypass shear blades. A three-directional linear manipulator system and a control system were built for moving the end-effector to targeted locations. A mathematical model was developed for simulation of the workspace utilization and reachable points of the end-effector. The simulation results indicated that the end-effector can be aligned in a wide range of orientations of the cutter. Field tests were conducted for validation of the simulation results and performance assessment of the end-effector. The results indicated that the end-effector with the current parameter settings successfully cut branches up to 12 mm in diameter and was able to cut branches in a wide range of possible orientations in a given 3D space. The robotic end-effector developed in this study is a core component of an automated pruning system for fruit trees. In future work, an integrated manipulator system will be developed for branch accessibility with collision-free trajectories. Keywords: Malus × domestica (Borkh.), Pruning end-effector, Reachable-points simulation, Tree pruning.

Pair component categories for directed spaces

The notion of a homotopy flow on a directed space was introduced in Raussen (Appl Categ Struct 15(4):355–386, 2007) as a coherent tool for comparing spaces of directed paths between pairs of points in that space with each other. If all directed maps along such a 1-parameter deformation preserve the homotopy types of path spaces, such a flow and the parameter maps are called inessential. For a directed space, one may consider various categories whose objects are pairs of reachable points to which a functor associates the space of directed paths between them. The monoid of all inessential maps acts on such a category by endofunctors leaving the associated path spaces invariant up to homotopy. We construct a pair component category as quotient category: it has as objects pair components along which the homotopy type is invariant—for a coherent and transparent reason. This paper follows up Fajstrup et al. (J Homotopy Relat Struct 12(1):81–108, 2004); Goubault and Haucourt (Appl Categ Struct 15(4):387–414, 2007); Raussen (Appl Categ Struct 15(4):355–386, 2007) and removes some of the restrictions for their applicability. At least in several examples, it gives reasonable results for spaces with non-trivial directed loops. If one uses homology equivalence instead of homotopy equivalence as the basic relation, it yields an alternative to computable versions of “natural homology” introduced in Dubut et al (in: Automata, languages, and programming. 42nd International Colloquium, ICALP 2015, Kyoto, Japan, July 6–10, 2015. Proceedings. Part II, 171–183, Springer, Berlin 2015) and elaborated in Dubut (Directed homotopy and homology theories for geometric models of true concurrency. Ecole normale superieure Paris-Saclay 2017). It refines, for good and for evil, the stable components introduced and investigated in Ziemianski (Appl Categ Struct 27:217–244, 2019).

Kinematic Synthesis of a Serial Robotic Manipulator by Using Generalized Differential Inverse Kinematics

In this paper, we propose an optimization method to determine the design parameters comprising joint displacement parameters in a serial manipulator having small degrees of freedom realizing an approximated target trajectory. Using generalized differential kinematics, we can achieve efficient optimization without solving the inner-loop optimization required to obtain the reachable points.

Distorted distance perception to reachable points in people with chronic shoulder pain

Perception is not simply a carbon copy of the real world, but is subject to distortions that may reflect protective drive. This study aimed to investigate whether people with chronic shoulder pain show perceptual distortions of space and body that may promote protective behavior. Eighty-four people with shoulder pain and 51 healthy controls participated. Participants estimated (1) distances to points on a cork-board within and outside reaching distance, and (2) the perceived length of their own arms. A novel measure of movement-related pain was also used to determine whether movement-related pain relates to perceptual distortion. Overall, distance and arm length estimates did not differ between groups, nor did participants perceive their arms to be of different length. However, a moderate correlation between movement-related pain and the index of distance perception was found within the pain group, specifically for distance estimates to points within reach. Our results suggest that distorted perception is not a typical consequence of chronic shoulder pain; however, that it may occur in cases where pain is strongly linked to movement. Our findings have implications for understanding avoidance of movement in people with persistent pain.

A New Coverage Flight Path Planning Algorithm Based on Footprint Sweep Fitting for Unmanned Aerial Vehicle Navigation in Urban Environments

This paper presents a new coverage flight path planning algorithm that finds collision-free, minimum length and flyable paths for unmanned aerial vehicle (UAV) navigation in three-dimensional (3D) urban environments with fixed obstacles for coverage missions. The proposed algorithm significantly reduces computational time, number of turns, and path overlapping while finding a path that passes over all reachable points of an area or volume of interest by using sensor footprints’ sweeps fitting and a sparse waypoint graph in the pathfinding process. We devise a novel footprints’ sweep fitting method considering UAV sensor footprint as coverage unit in the free spaces to achieve maximal coverage with fewer and longer footprints’ sweeps. After footprints’ sweeps fitting, the proposed algorithm determines the visiting sequence of footprints’ sweeps by formulating it as travelling salesman problem (TSP), and ant colony optimization (ACO) algorithm is employed to solve the TSP. Furthermore, we generate a sparse waypoint graph by connecting footprints’ sweeps’ endpoints to obtain a complete coverage flight path. The simulation results obtained from various scenarios fortify the effectiveness of the proposed algorithm and verify the aforementioned claims.

Geographic wayfinders and space-time algebra

Time Geography is a framework for describing reachable points in a (static) spatio-temporal environment. While originally devised to facilitate reasoning about an individual's or a population's living conditions, it was later adapted to many other applications. A wayfinder is an entity that moves through a space-time continuum with possible obstacles. We show how to model the pertinent notions in relational algebra (and, more abstractly, in modal semirings) with box and diamond operators. Admissible or undesired regions can be described as Boolean combinations of primitive regions such as the set of all points reachable by forward or backward movement from a given region or starting point. To derive results about the region blocked by the union of two regions we introduce an abstract algebraic view of coordinates that is largely independent of dimensional and metric aspects and thus very general. Moreover, the approach lends itself quite well to machine-supported proofs.

Optimizing a Long-Lived Transaction with Verification Function

We have considered a method called Enhanced Rollback Migration Protocol, which potentially has the effects of compressing the period of compensations in a long-lived transaction, since before. In general, a compensation transaction can recover an irregular status of a long-lived transaction into the original status without holding unnecessary resources by making its consistency tentatively loose. However, it has also been pointed out that there is a difficulty of maintaining the isolation between a pair of transactions when executed in parallel. In particular, this could be more prominent under modernized scalable cloud environments. Thus, there is a proposal for concurrency control for the service level. However, there is still another risk that more computer resources will be consumed than actually necessary and an unnecessary stagnation of the processing will be caused if concurrency control is naively applied without careful consideration. Therefore, we need to implement a functionality which can optimize the processing of a long-lived transaction by selecting a suitable method between concurrency control and compensation transactions. In this paper, we propose a method in which optimistic concurrency control is applied for long-lived transactions. Furthermore, a pair of verification phases is carried out. At the beginning from a safe point, an attempt of verification is done. Then if the difficulty of isolation on a long-lived transaction executed under a competitive situation is estimated, concurrency control for the service level is applied. Alternatively, a long-lived transaction without any concurrency control is executed. At the next reachable safe point, another attempt of verification is performed. Then if a failure of serialization is detected, a set of compensation transactions is invoked to recover the original long-lived transaction by returning to the first safe point. We evaluated this approach by using numerical simulations and confirmed the basic features. This approach can realize optimizing and enhancing the performance of a long-lived transaction. We regard this approach applicable even to the modernized scalable cloud environments.

Algorithm of uniform filling of nonlinear dynamic system reachable set based on maximin problem solution

In this paper we propose an algorithm of obtaining reachable points that uniformly fill the volume of the reachable set, and thus, result in a point cloud uniformly approximating a set even with a small number of points. To solve the task of finding each additional point is to solve the maximin optimal control problem. The design of the method allows considering reachable sets not only of two-dimensional systems but of multidimensional ones as well. The computational experiments conducted with the use of the proposed algorithm confirm the efficiency of the approach.

Guidance-Control System of a Quadrotor for Optimal Coverage in Cluttered Environment with a Limited Onboard Energy: Complete Software

In this paper, a Guidance-Control System (GCS) for optimal coverage planning, using a quadrotor, in damaged area is considered. The quadrotor is assumed to visit a set of reachable points, defined manually by the user or automatically generated, following the shortest path while avoiding the no-fly zones. The problem is solved by using a two-stage proposed algorithm. In the first stage, a novel tool for cluttered environments based on optimal Rapidly-exploring Random Trees (RRT) approach, called Multi-RRT* Fixed Node (RRT*FN), is developed to define the shortest paths from each point to its neighbors. By means of the pair-wise costs between points provided by the first-stage algorithm, in the second stage, the overall shortest path is obtained by solving a Traveling Salesman Problem (TSP) using Genetic Algorithms (GA). Taking into consideration the limited onboard energy, multi-rounds for the coverage planning are assumed as an alternative by adapting our problem as a Vehicle Routing Problem (VRP). This latter is solved using the savings heuristic approach. The guidance module is supported by an efficient controller that minimizes the consumed energy and allows a damped response (i.e. without overshoot). It is a reference model based control strategy called Interconnection Damping Assignment-Passivity Based Control (IDA-PBC). The effectiveness of the overall system is demonstrated via numerical simulations and confirmed experimentally with very promising results.

Computation of State Reachable Points of Second Order Linear Time-Invariant Descriptor Systems

This paper considers the problem of computing the state reachable points (from the origin) of a linear constant coefficient second order descriptor system. A new method is proposed to compute the reachable set in a numerically stable way. The original descriptor system is transformed into a strangeness-free system within the behavioral framework followed by a projection that separates the system into different order differential and algebraic equations while keeping the original state variables. This reformulation is followed by a first order formulation that avoids all unnecessary smoothness requirements. For the resulting first order system, it is shown that the computation of the image space of two matrices, associated with the projected system, is enough to numerically compute the reachable set. Moreover, a characterization is presented of all the inputs by which one can reach an arbitrary point in the reachable set. These results are used to compute two different types of reachable sets for second order systems. The new approach is demonstrated through a numerical example.

Null controllable sets and reachable sets for nonautonomous linear control systems

Under the assumption of lack of uniform controllability for a family of time-dependent linear control systems, we study the dimension, topological structure and other dynamical properties of the sets of null controllable points and of the sets of reachable points. In particular, when the space of null controllable vectors has constant dimension for all the systems of the family, we find a closed invariant subbundle where the uniform null controllability holds. Finally, we associate a family of linear Hamiltonian systems to the control family and assume that it has an exponential dichotomy in order to relate the space of null controllable vectors to one of the Lagrange planes of the continuous hyperbolic splitting.

A fewest-turn-and-shortest path algorithm based on breadth-first search

Many cognitive studies have indicated that the path simplicity may be as important as its distance travelled. However, the optimality of paths for current navigation system is often judged purely on the distance travelled or time cost, and not the path simplicity. To balance these factors, this paper presented an algorithm to compute a path that not only possesses fewest turns but also is as short as possible by utilizing the breadth-first-search strategy. The proposed algorithm started searching from a starting point, and expanded layer by layer through searching zero-level reachable points until the endpoint is found, and then deleted unnecessary points in the reverse direction. The forward searching and backward cleaning strategies were presented to build a hierarchical graph of zero-level reachable points, and form a fewest-turn-path graph (G*). After that, a classic Dijkstra shortest path algorithm was executed on the G* to obtain a fewest-turn-and-shortest path. Comparing with the shortest path in Baidu map, the algorithm in this work has less than half of the turns but the nearly same length. The proposed fewest-turn-and-shortest path algorithm is proved to be more suitable for human beings according to human cognition research.

MIS approach analyzing the controllability of switched boolean networks with higher order

Controllability of higher order switched Boolean control networks (SBCNs) is investigated in this paper. Two algebraic forms of higher order SBCNs are derived. A necessary and sufficient condition of controllability for higher order SBCNs is obtained. An algorithm is derived to calculate the corresponding control and switching-law which drive a point to a given reachable point. Then we talk about the compatibility between our main results and other systems. Finally, two illustrative examples are given to show the validity of the main results.