Real-world Terrain Research Articles

A Constraint-Aware Heuristic Path Planner for Finding Energy-Efficient Paths on Uneven Terrains

Motions of mobile robots need to be optimized to minimize their energy consumption to ensure long periods of continuous operations. Shortest paths do not always guarantee the minimum energy consumption of mobile robots. Moreover, they are not always feasible due to climbing constraints of mobile robots, especially on steep terrains. We utilize a heuristic search algorithm to find energy-optimal paths on hilly terrains using an established energy-cost model for mobile robots. The terrains are represented using grid-based elevation maps. Similar to A*-like heuristic search algorithms, the energy-cost of traversing through a given location of the map depends on a heuristic energy-cost estimation from that particular location to the goal. Using zigzag-like path patterns, the proposed heuristic function can estimate heuristic energy-costs on steep terrains that cannot be estimated using traditional methods. We proved that the proposed heuristic energy-cost function is both admissible and consistent. Therefore, the proposed path planner can always find feasible energy-optimal paths on any given terrain without node revisits, provided that such paths exist. Results of tests on real-world terrain models presented in this paper demonstrate the promising computational performance of the proposed path planner in finding energy-efficient paths.

Evaluation of wimax admission control algorithms in mobile voip scenarios with batch arrivals and nbldpc fec

Abstract This paper presents results of assessing quality of VoIP conversations in WiMAX networks using the nbLDPC (non-binary Low- Density Parity-Check) FEC in mobility scenarios that are based on the real world terrain charactristics around simulated BS. System under test (SUT) is instrumented with three Call Admission Control (CAC) mechanisms (namely EMAC, ARAC and nsc-ARAC). These algorithms are evaluated against controlling the VBR traffic that comes with burst arrivals. The first algorithm relies on calculating simple exponential weighted moving average (EWMA) of the overall resource consumption whereas the other two ARAC algorithms perform calculations discerning between the new, the ongoing and the finishing connections thus providing more accurate resource estimations (but the ARAC tracks the history of requests as well). In order to evaluate their performance authors rely on a cell-level based simulation environment that relies on the cooperative use of well known simulators - ns2 and Matlab. Previous work in the field is enhanced by improving the fidelity of proposed IEEE 802.16 simulator. Authors demonstrate the influence of increasing number of arrivals per one batch as well as testing the "zero hour" scenario (system saturation). In order to include nbLDPC codes in SUT’s mobile channels, a method called Link-To-System interface (L2S) has been implemented.

BigDog-Inspired Studies in the Locomotion of Goats and Dogs

Collision-based expenditure of mechanical energy and the compliance and geometry of the leg are fundamental, interrelated considerations in the mechanical design of legged runners. This article provides a basic context and rationale for experiments designed to inform each of these key areas in Boston Dynamic's BigDog robot. Although these principles have been investigated throughout the past few decades within different academic disciplines, BigDog required that they be considered together and in concert with an impressive set of control algorithms that are not discussed here. Although collision reduction is an important strategy for reducing mechanical cost of transport in the slowest and fastest quadrupedal gaits, walking and galloping, BigDog employed an intermediate-speed trotting gait without collision reduction. Trotting, instead, uses a spring-loaded inverted pendulum mechanism with potential for storage and return of elastic strain energy in appropriately compliant structures. Rather than tuning BigDog's built-in leg springs according to a spring-mass model-based virtual leg-spring constant , a much stiffer distal leg spring together with actuation of the adjacent joint provided good trotting dynamics and avoided functional limitations that might have been imposed by too much compliance in real-world terrain. Adjusting the directional compliance of the legs by adopting a knee-forward, elbow-back geometry led to more robust trotting dynamics by reducing perturbations about the pitch axis of the robot's center of mass (CoM). BigDog is the most successful large-scale, all-terrain trotting machine built to date and it continues to stimulate our understanding of legged locomotion in comparative biomechanics as well as in robotics.

Terrain Synthesis from Digital Elevation Models

In this paper, we present an example-based system for terrain synthesis. In our approach, patches from a sample terrain (represented by a height field) are used to generate a new terrain. The synthesis is guided by a user-sketched feature map that specifies where terrain features occur in the resulting synthetic terrain. Our system emphasizes large-scale curvilinear features (ridges and valleys) because such features are the dominant visual elements in most terrains. Both the example height field and user's sketch map are analyzed using a technique from the field of geomorphology. The system finds patches from the example data that match the features found in the user's sketch. Patches are joined together using graph cuts and Poisson editing. The order in which patches are placed in the synthesized terrain is determined by breadth-first traversal of a feature tree and this generates improved results over standard raster-scan placement orders. Our technique supports user-controlled terrain synthesis in a wide variety of styles, based upon the visual richness of real-world terrain data.

Virtually Successful: Defeating the Dropout Problem through Online School Programs

GISELLE, an aspiring ballerina, took Illinois Virtual High School (IVHS) courses during her junior year and the following summer in order to graduate early and spend what would have been her senior year touring the country with her ballet troupe. (1) Now, having graduated from her high school, she is taking IVHS Advanced Placement classes to improve her chances of getting into the college of her choice. Leslie missed all her courses in the second half of her sophomore year because she was pregnant. She was highly motivated to get her diploma but had a lot of courses to make up, a baby to care for, and no money for child care at night, when her school offered credit-recovery courses. In her junior and senior years, she took courses through the Michigan Virtual High School (MVHS) half time in addition to her regular courses. Thanks to the flexible scheduling of MVHS, she was able to do the coursework while caring for her baby and graduated on time, with honors. She is currently enrolled in a community college and plans to finish her college degree by taking courses part time. A quiet and slightly built youngster, Sidney was a social outcast among the tough, macho youths in his classes and was consistently bullied and harassed. Despite the inhospitable environment for learning, he managed to complete all the necessary courses for high school graduation except one English course, which was offered at his school at night. His mother, fearful of the youth gangs in the area, refused to let Sidney attend night school, so he enrolled in the English class through the Florida Virtual School (FLVS) and is completing the work from his home computer. He is scheduled to graduate with his class. IVHS, MVHS, and FLVS personnel confirm that these are not isolated success stories. Rather, they are typical of the reports coming out of these programs, as well from many of the other 19 statewide virtual schools around the U.S. (2) Students venture down the electronic paths of an online-learning cyberworld so that they may better negotiate the increasingly complex and demanding real-world terrain of contemporary life. Virtual schools--programs that offer regular school courses in distance-education formats--slipped onto the American education scene under the radar of most educators about a decade ago. Utah's Electronic High School, FLVS, and the Concord Consortium's Virtual High School began operations in the mid-1990s. Today, many people may still not be aware that virtual schooling is one of the fastest-growing areas in K-12 education. In its 2005 report, the National Center for Education Statistics found that, as of 2003, 36% of U.S. school districts had students participating in virtual courses for a total of more than 300,000 students. (3) And this number is projected to explode in the coming decade. Many students enroll in online programs to take advanced courses or to accelerate the pace of their study, as Giselle did; many others seek credit-recovery courses like those that allowed Leslie and Sidney to earn their high school diplomas. But there are a variety of other reasons as well. Students turn to virtual schools when their own school lacks the resources to offer the courses they want or need, or when physical handicaps or disciplinary problems prevent them from attending a face-to-face classroom, or simply because they want the flexibility--or sometimes the invisibility--that they feel virtual courses offer. Home-schooled students are also a growing part of the consumer base for virtual courses. So why, in light of their obvious popularity and value, do many policy makers, educators, and parents view virtual schools with suspicion that approaches alarm? Objections both political and philosophical surround the topic of virtual schools. Claims and counterclaims swirl around issues of funding, credit, certification, and even whether or not the whole idea of learning without the teacher and student being in the same room is socially desirable or morally acceptable. …

Multidimensional Scaling Analysis of Terrain Features Relevant for Simulating Low-Altitude Flight

Multidimensional scaling was used to identify the features of real–world terrain that are salient to pilots during low–altitude, high–speed flight. Subjects were ten United States Air Force and Air National Guard pilots experienced in low–altitude flight. The stimuli were 17 short (five–seconds duration) videotape segments depicting low–altitude, high–speed flight over a variety of real–world terrains. Pilots rated pairs of terrains with respect to similarity of terrain features relevant for visual low–altitude flight. Similarity ratings were submitted to a multidimensional scaling analysis using ALSCAL. A two–dimensional solution revealed dimensions corresponding to 1) the presence/absence of hills and ridges and 2) the presence/absence of large objects clustered into groups. Results suggest that designers of flight simulators should focus on representing hills and ridges, and large trees and buildings with high perceptual fidelity.

The Integration Of MapsHow Mathematica Is Used In The Modelling Of Geo-Objects

Traditionally, geographic maps are drawn on some material, e.g. paper, but in the last twenty five years maps have been digitised for storage and use in computerised information systems. These so called Geo-Information Systems (abbreviated as GIS) are now dominant in all kinds of geo-disciplines. Computerised maps from a certain region are much more easy to combine then paper maps. However there is still a problem: how do we combine maps from a certain region with different themes in order to query these maps as a whole? This is called the map integration problem. Beside querying multiple map themes map integration is important in using updates from a certain map that are relevant to another map. This paper discusses our experiences in building a prototype of a map integrator in Mathematica. 1 The Modelling of Geo-Objects Real world terrain objects, or geo-objects, are modelled according to their thematic aspect and their geometric aspect. The geometric aspect of geo-objects is described by edges and nodes: an edge being a straight connection between two nodes. Beside edges and nodes there are faces, a face being the area surrounded by a closed series of edges (see the picture below). i