Showing papers on "Any-angle path planning published in 2002"
10 Dec 2002
TL;DR: This work builds a path planning system based on RRTs that interleaves planning and execution, first evaluating it in simulation and then applying it to physical robots, and demonstrates that ERRT is significantly more efficient for replanning than a basic RRT planner.
Abstract: Mobile robots often must find a trajectory to another position in their environment, subject to constraints. This is the problem of planning a path through a continuous domain Rapidly-exploring random trees (RRTs) are a recently developed representation on which fast continuous domain path planners can be based. In this work, we build a path planning system based on RRTs that interleaves planning and execution, first evaluating it in simulation and then applying it to physical robots. Our planning algorithm, ERRT (execution extended RRT), introduces two novel extensions of previous RRT work, the waypoint cache and adaptive cost penalty search, which improve replanning efficiency and the quality of generated paths. ERRT is successfully applied to a real-time multi-robot system. Results demonstrate that ERRT is significantly more efficient for replanning than a basic RRT planner, performing competitively with or better than existing heuristic and reactive real-time path planning approaches. ERRT is a significant step forward with the potential for making path planning common on real robots, even in challenging continuous, highly dynamic domains.
317 citations
Patent•
[...]
13 Aug 2002
TL;DR: In this paper, a switching fabric includes one or more fast paths for handling lightweight, common data operations and at least one control path for handling other data operations, and a locking mechanism is described for controlling access to data shared by the control paths.
Abstract: Described are techniques used in a computer system for handling data operations to storage devices. A switching fabric includes one or more fast paths for handling lightweight, common data operations and at least one control path for handling other data operations. A control path manages one or more fast paths. The fast path and the control path are utilized in mapping virtual to physical addresses using mapping tables. The mapping tables include an extent table of one or more entries corresponding to varying address ranges. The size of an extent may be changed dynamically in accordance with a corresponding state change of physical storage. The fast path may cache only portions of the extent table as needed in accordance with a caching technique. The fast path may cache a subset of the extent table stored within the control path. A set of primitives may be used in performing data operations. A locking mechanism is described for controlling access to data shared by the control paths.
240 citations
Patent•
13 Aug 2002
TL;DR: In this paper, a switching fabric includes one or more fast paths for handling lightweight, common data operations and at least one control path for handling other data operations, and a locking mechanism is described for controlling access to data shared by the control paths.
Abstract: Described are techniques used in a computer system for handling data operations to storage devices. A switching fabric includes one or more fast paths for handling lightweight, common data operations and at least one control path for handling other data operations. A control path manages one or more fast paths. The fast path and the control path are utilized in mapping virtual to physical addresses using mapping tables. The mapping tables include an extent table of one or more entries corresponding to varying address ranges. The size of an extent may be changed dynamically in accordance with a corresponding state change of physical storage. The fast path may cache only portions of the extent table as needed in accordance with a caching technique. The fast path may cache a subset of the extent table stored within the control path. A set of primitives may be used in performing data operations. A locking mechanism is described for controlling access to data shared by the control paths.
198 citations
TL;DR: Three optimisation algorithms namely: Dijkstra, A∗, and Genetic algorithms that are used to find multi-criteria paths in construction sites based on transportation and safety-related cost are compared and critically analysed.
152 citations
TL;DR: In this article, an interference detection technique is used to generate the configuration space and two levels of heuristic search are performed within the C-space to identify lift paths that satisfy the planning requirements.
Abstract: Planning the lift path for a mobile crane involves the generation and selection of a suitable lift path through three-dimensional space while considering the degrees of freedom of the crane, its lifting capacity and potential site obstacles. This paper presents work done toward applying configuration space (C-space) and search concepts to develop a tool to identify lift paths that satisfies the planning requirements. An interference detection technique is used to generate the C-space and two levels of heuristic search are performed within the C-space. The first search is a heuristic depth search to determine the obstacle-free lift paths. The second search performs a more detailed optimization of the path within a constrained search space. The tool developed here can be used within the AutoCAD environment and is based on program modules developed using AutoLisp and external programs. Test findings indicate that the approach is capable of generating good paths in complex situations within reasonable time. Directions for further research are indicated.
82 citations
01 Aug 2002
TL;DR: In this article, the authors considered a variant of the constrained shortest path problem, where the constraints come from a set of forbidden paths (arc sequences) that cannot be part of any feasible solution.
Abstract: We consider a variant of the constrained shortest path problem, where the constraints come from a set of forbidden paths (arc sequences) that cannot be part of any feasible solution. Two solution approaches are proposed for this variant. The first uses Aho and Corasick's keyword matching algorithm to filter paths produced by a k-shortest paths algorithm. The second generalizes Martins' deviation path approach for the k-shortest paths problem by merging the original graph with a state graph derived from Aho and Corasick's algorithm. Like Martins' approach, the second method amounts to a polynomial reduction of the shortest path problem with forbidden paths to a classic shortest path problem. Its significant advantage over the first approach is that it allows considering forbidden paths in more general shortest path problems such as the shortest path problem with resource constraints.
79 citations
10 Dec 2002
TL;DR: Some algorithms that may be considered as an extension of probabilistic planning techniques to the problem at hand of planning collision-free motions for a redundant robot whose end-effector must travel along a given path.
Abstract: We consider the problem of planning collision-free motions for a redundant robot whose end-effector must travel along a given path. Although collision avoidance is one of the main reasons for introducing kinematic redundancy in manipulators, the planning methods so far proposed for this particular problem are neither efficient nor complete. In this paper, we introduce some algorithms that may be considered as an extension of probabilistic planning techniques to the problem at hand. All the algorithms are based on the same simple mechanism for generating random samples of the configuration space that are compatible with the end-effector path constraint. Experimental results illustrate the performance of the planners.
58 citations
01 Jul 2002
TL;DR: It is shown that a simple method based on shortest path routing for which primary paths are selected first is more effective than a greedy approach that minimizes, for each call arrival, the number of wavelengths used by the primary and backup path jointly.
Abstract: We propose a new protection scheme, which we term partial path protection (PPP), to select end-to-end backup paths using local information about network failures. PPP designates a different restoration path for every link failure on each primary path. PPP also allows reuse of operational segments of the original primary path in the protection path. A novel approach used in this paper is that of a dynamic call-by-call model with blocking probability as the performance metric, this model is in contrast with traditional capacity-efficiency measurement for batch call arrivals. Additionally, we show that a simple method based on shortest path routing for which primary paths are selected first is more effective than a greedy approach that minimizes, for each call arrival, the number of wavelengths used by the primary and backup path jointly.
53 citations
20 May 2002
TL;DR: In this article, the authors consider the application of evolutionary algorithms to the motion of an unmanned air vehicle (UAV) through a field of obstacles at uncertain locations, where the locations of the obstacles that form the obstructions in these environments may only be known with limited accuracy.
Abstract: Evolutionary algorithms (EA) have been successfully used to compute near-optimal paths through obstructed, dynamically changing environments. The locations of the obstacles that form the obstructions in these environments may only be known with limited accuracy. Explicitly accounting for this uncertainty can result in the survival of “best” paths which differ from those that would be favored in a purely deterministic environment. In this paper, we consider the application of evolutionbased path planning to the motion of an unmanned air vehicle (UAV) through a field of obstacles at uncertain locations. Specifically, we focus on the “cost function” utilized by the evolutionary algorithm to judge the likelihood of a given path successfully traversing the uncertain environment. We first show a method for computing a cost function based on the exact probability of intersection of the vehicle with an obstacle. A more computationally tractable approximation technique for this cost function is then derived. Both cost functions are compared to the weighted graph search technique found in much of the literature on path planning.
47 citations
Patent•
22 May 2002TL;DR: In this paper, a method and system for finding shared risk diverse paths is disclosed, which includes receiving route information at a node and running a shortest path algorithm to identify a first path.
Abstract: A method and system for finding shared risk diverse paths is disclosed. The method includes receiving route information at a node and running a shortest path algorithm to identify a first path. A shared risk metric is assigned to links and nodes with the first path. The method further includes running the shortest path algorithm with the shared risk metrics assigned to identify a second path and comparing the first and second paths. New shared risk metrics are assigned to links and nodes in the second path if the first and second paths are not diverse. The second path then becomes the first path and the algorithm is repeated.
47 citations
TL;DR: An efficient method to select a minimal set of testable paths in scan designs, such that every line in the circuit is covered by at least one of the longest testable path that contain it (if there are any).
Abstract: We propose an efficient method to select a minimal set of testable paths in scan designs, such that every line in the circuit is covered by at least one of the longest testable paths that contain it (if there are any). The proposed path selection approach is based on a stepwise path expansion procedure that uses delay information and compact information about untestable paths to select longest paths while avoiding untestable paths. Techniques called delay analysis and delay-constrained path expansion are used to speedup the selection of paths to test. Compared to earlier approaches, the proposed approach is fast and it is guaranteed to find testable paths. Experimental results for ISCAS89 benchmark circuits using standard scan and broadside testing are presented to demonstrate the effectiveness of the proposed method.
[...]
TL;DR: The algorithm is developed and an application to robot path planning in configuration space, where the graph topology, transition costs, or start/goals may change simultaneously, is discussed.
Abstract: A* graph search effectively computes the optimal solution path from start nodes to goal nodes in a graph, using a heuristic function. In some applications, the graph may change slightly in the course of its use and the solution path then needs to be updated. Very often, the new solution will differ only slightly from the old. Rather than perform the full A* on the new graph, we compute the necessary OPEN nodes from which the revised solution can be obtained by A*. In this "Differential A*" algorithm, the graph topology, transition costs, or start/goals may change simultaneously. We develop the algorithm and discuss when it gives an improvement over simply reapplying A*. We briefly discuss an application to robot path planning in configuration space, where such graph changes naturally arise.
19 May 2002
TL;DR: This work presents Friend Assisted Path Discovery, a social oriented path discovery scheme that needs to have or to build a summarized view of the network topology, but does not require explicit collaboration of nodes for acquiring path.
Abstract: Terminode routing, defined for potentially very large mobile ad hoc networks, forwards packets along anchored paths. An anchored path is a list of fixed geographic points, called anchors. Given that geographic points do not move, the advantage to traditional routing paths is that an anchored path is always "valid". In order to forward packets along anchored paths, the source needs to acquire them by means of path discovery methods. We present two of such methods: Friend Assisted Path Discovery assumes a common protocol in all nodes and a high collaboration among nodes for providing paths. It is a social oriented path discovery scheme. Geographic Maps-based Path Discovery needs to have or to build a summarized view of the network topology, but does not require explicit collaboration of nodes for acquiring path. The two schemes are complementary and can coexist.
11 May 2002
TL;DR: This paper presents a novel analysis of the probabilistic roadmap method (PRM) for path planning in terms of computing the transitive closure of a relation over a probability space and gives a bound interms of the number of intermediate points for some path and the probability of choosing a point from a certain set.
Abstract: This paper presents it novel analysis of the probabilistic roadmap method (PRM) for path planning. We formulate the problem in terms of computing the transitive closure of a relation over a probability space and give a bound in terms of the number of intermediate points for some path and the probability of choosing a point from a certain set. Explicit geometric assumptions are not necessary to complete this analysis and consequently it provides some unification of the previous work as well as generalizing new path planning problems, two of which, 2k-DOF kinodynamic point robots and deformable robots with force field control, are presented in this paper.
07 Aug 2002
TL;DR: The algorithm is based on the Dubins' theorem to simplify the problem model, the genetic algorithm to search the best path, a special hierarchical structure of chromosome to denote a possible path in the environment, the special genetic operators for each module, and a penalty strategy to "punish" the infeasible chromosomes during searching.
Abstract: In this paper, a new hierarchical genetic algorithm for path planning in a static environment with obstacles is presented. The algorithm of path planning in this paper is inspired by the Dubins' theorem regarding shortest paths of bounded curvature in the absence of obstacles. The algorithm is based on the Dubins' theorem to simplify the problem model, the genetic algorithm to search the best path, a special hierarchical structure of chromosome to denote a possible path in the environment, the special genetic operators for each module, and a penalty strategy to "punish" the infeasible chromosomes during searching. The performance results presented have shown that the approach is able to produce high quality solutions in reasonable time.
12 May 2002
TL;DR: The algorithm is based on the Dubins' theorem to simplify the problem model, the genetic algorithm to search the best path, a special hierarchical structure of the chromosome to denote a possible path in the environment, the special genetic operators for each module, and a penalty strategy to "punish" the infeasible chromosomes during searching.
Abstract: In this paper, a new hierarchical genetic algorithm for path planning in a static environment with obstacles is presented. The algorithm of path planning in this paper is inspired by the Dubins' theorem regarding shortest paths of bounded curvature in the absence of obstacles. The algorithm is based on the Dubins' theorem to simplify the problem model, the genetic algorithm to search the best path, a special hierarchical structure of the chromosome to denote a possible path in the environment, the special genetic operators for each module, a penalty strategy to "punish" the infeasible chromosomes during searching. The performance results presented have shown that the approach is able to produce high quality solutions in reasonable time.
05 Nov 2002
TL;DR: Considering the surrounding environment, the path planning was conducted to ensure stable navigation of the mobile robot for two main parts, choosing the shortest path and the feature point for the global path planning by utilizing cell decomposition method off-line computation.
Abstract: Given a certain target point, the mobile robot's navigation could be mainly considered about two areas, 'how fast and accurate' and 'how safe'. Such problems regarding the velocity and stability have close relationship with the path in which the mobile robot navigates. Therefore, in this paper, considering the surrounding environment, the path planning was conducted to ensure stable navigation of the mobile robot for two main parts. First, the shortest path and the feature point for the global path planning was chosen by utilizing cell decomposition method off-line computation. Second, to control the movement and path between the feature points, Potential field method, which acutely responds to the surrounding environment on-line computation, is used. In order to detect the given path and avoid obstacles, the navigation algorithm was composed by using two fuzzy logic control.
03 Sep 2002
TL;DR: The author improves previous designs, and comes up with the so-called Q matrices that serve well in the A* algorithm for best-path planning under route constraints, and employs matrices for capturing the route constraints.
Abstract: The author examines methods for a special class of path planning problems in which the routes are constrained. General search algorithms assume that we can move around in the traffic network freely, so they extend the partial paths from the very last location to each of its neighbors to form more partial paths. The best partial paths are then selected to expand, unless die selected partial path happens to he a solution. Without proper guidance, this strategy way lead to inefficient planning algorithms when the way one can move around in the networks Is constrained. This scenario could happen in public transportation system where passengers cannot order drivers to change the routes of public buses to meet individual travel needs. A few recently proposed path-planning algorithms for public transportation systems capture the route constraints by matrices. Although they work for some applications, they are not perfect for cooperating with traditional algorithms; for best-path planning. Applying special properties of matrix multiplication, the author also employs matrices for capturing the route constraints. The author improves previous designs, and comes up with the so-called Q matrices that serve well in the A* algorithm for best-path planning under route constraints.
10 Dec 2002
TL;DR: To efficiently compute harmonic functions for constrained motion planning, the paper presents a hierarchical and dynamic method that works on a non-regular grid decomposition of configuration space.
Abstract: Robot path planning copes with the planning of a collision-free path for the robot from an initial configuration to a goal configuration. The potential field method is one of the main approaches to path planning, and the use of harmonic functions allows the definition of potential fields without local minima and with the ability to be incrementally updated. Constrained motion planning copes with the planning of motions in cluttered environments with low clearances and high uncertainties. The robust, adaptive and reactive behavior of the harmonic functions approach suits the requirements of constrained motion planning. To efficiently compute harmonic functions for this purpose, the paper presents a hierarchical and dynamic method that works on a non-regular grid decomposition of configuration space.
07 Nov 2002
TL;DR: This paper represents a novel smooth trajectory planning algorithm which uses the natural behavior model of a mobile robot and is applicable to the real time dynamic configuration spaces, because of simplicity and low computational time.
Abstract: This paper represents a novel smooth trajectory planning algorithm which uses the natural behavior model of a mobile robot (MR). The shortest path in the free configuration space is obtained by using the visibility graph method. It is modified according to dynamic constraints which are implicitly included in natural behavior of the mobile robot. The modified path becomes a smooth, easily trackable near time and distance optimal trajectory. For every point of it, translating/steering velocities and accelerations and reaching times are known. It is applicable to the real time dynamic configuration spaces, because of simplicity and low computational time.
Patent•
31 Jan 2002TL;DR: In this paper, a method for defining hardware routing paths for networks having IP and MPLS paths generally comprises assigning a path ID for each path within a path group, and comparing all path IDs in each path group and assigning a common hardware resource to groups having matching path IDs.
Abstract: A method for defining hardware routing paths for networks having IP and MPLS paths generally comprises assigning a path ID for each path within a path group. The path ID for each path is an IP address and the path group contains all IP paths, all MPLS paths, or both IP and MPLS paths. The path ID for each MPLS path is a unique IP multicast address. The method further includes comparing all path IDs in each path group and assigning a common hardware resource to groups having matching path IDs.
Patent•
20 Feb 2002
TL;DR: In this article, the authors proposed a space path control program capable of maintaining connection between a terminal and a base station even when interference of paths takes place in the MIMO (Multi Input Multi Output) system where a PDMA (Path Division Multiple Access) base station makes communication with a single terminal via a plurality of paths.
Abstract: PROBLEM TO BE SOLVED: To provide a wireless apparatus, a wireless communication system, a space path control method, and a space path control program capable of maintaining connection between a terminal and a base station even when interference of paths takes place in the MIMO (Multi Input Multi Output) system where a PDMA (Path Division Multiple Access) base station makes communication with a single terminal via a plurality of paths. SOLUTION: In a mobile communication system compatible with the MIMO system, each of terminals/base stations properly applies switching control to a communication operation in a space path among a plurality of kinds of operations on the basis of communication quality information in the space path where a reception error is detected. In the first operation, one path is left and the other paths are interrupted. In the second operation, path diversity is performed. In the third operation, the modulation factor of the path is decreased. A DSP executes the operations above. COPYRIGHT: (C)2003,JPO
TL;DR: A new method of constructing hierarchical path planning algorithms based on a novel application of the A* control strategy, called Meta A*, is introduced, which suggests that the Meta A* based planners find paths faster and consume less memory than the other two algorithms.
Abstract: Usually it is impossible to know in advance how coarsely robot movements can be discretized in order to find a collision-free path from an initial robot position to a desired goal position in a presence of obstacles. Our solution to the problem is to introduce a new method of constructing hierarchical path planning algorithms. It is based on a novel application of the A* control strategy, called here Meta A*.
We test four hierarchical path planning algorithms, two of which are based on Meta A*, using five simulated robot workcells. The simulations suggest that the Meta A* based planners, on average, find paths faster and consume less memory than the other two algorithms.
01 Jan 2002
TL;DR: A Critical Path Profiler for efficiently finding the critical dependence path through the complete execution of a program, intended to be used for profile-based compiler and processor optimizations.
Abstract: Modern processors come close to executing as fast as true dependencies allow. The particular dependencies that constrain execution speed constitute the critical path of execution. To optimize the performance of the processor, we either have to reduce the critical path or execute it more efficiently. In both cases, it can be done more effectively if we know the actual path. This paper describes a Critical Path Profiler for efficiently finding the critical dependence path through the complete execution of a program. It is intended to be used for profile-based compiler and processor optimizations. Unlike other critical-path based tools which analyze dependences along a single most-likely path (trace), this one analyzes dependences along every taken path through the code. We present data on the SPEC benchmark suite gathered through the profiler and experiment with potential uses for the profiler as a static critical-path predictor.
Patent•
18 Mar 2002
TL;DR: In this paper, an obstacle map updating part of a path planning device receives obstacle information 331, a current position, and destination information from an obstacle grid calculation part OG to prepare (update) an obstacle maps.
Abstract: PROBLEM TO BE SOLVED: To prepare a travel path plan efficiently in a short time without performing unnecessary observation and distance image calculation processing when moving a robot device to destination. SOLUTION: An obstacle map updating part 223 of a path planning device 221 receives obstacle information 331, a current position, and destination information from an obstacle grid calculation part OG to prepare (update) an obstacle map. At this time, a line of sight control part 222 controls a line of sight so that a line of sight of the robot device 1 is directed in the direction of destination. A path planning part 224 plans a path by regarding an unobserved region and a free space region as a travel possible region based on the obstacle map prepared in the obstacle map updating part 223. A path evaluation part 225 evaluates the path planned in the path planning part 224, outputs the path from the path planning part 224 based on the results of evaluation, outputs the results indicating that preparation is impossible, and adjusts line of sight control by the line of sight control part 222. COPYRIGHT: (C)2003,JPO
07 Aug 2002
TL;DR: Simulation results indicate the effectiveness of the proposed algorithm from the viewpoints of planning quality and calculation cost.
Abstract: The author has proposed the rearrangement planning methodology of multiple movable objects by an autonomous mobile robot. In the problem settlement, several objects should be moved from initial configuration to each destination through the robot's handling operation. The proposed algorithm has the following characteristics: (1) introduction of a real-time search methodology for application to sensor-based robots, (2) description of motion primitives-transit movement, transfer movement to the destination, transfer movement to temporal positions, (3) motion generation of each primitive with the standard motion planning methodology, and (4) proposal of an efficient heuristic function by using the solution of the stacker crane problem and the concept of the precedence graph. Simulation results indicate the effectiveness of the proposed algorithm from the viewpoints of planning quality and calculation cost.
07 Nov 2002
TL;DR: This paper proposes a hierarchical global path planning approach for autonomous underwater vehicle in ocean that consists of successive decomposition of the robot's workspace and searching for a path at each level of decomposition.
Abstract: Proposes a hierarchical global path planning approach for an autonomous underwater vehicle in an ocean. This approach consists of successive decomposition of the robot's workspace and searching for a path at each level of decomposition. In the process of heuristic search, the evaluation function takes into account both the energy cost and the length of paths. The approach proves to be flexible and practicable, and can reduce memory consumption significantly.
10 Dec 2002
TL;DR: A heuristic, limited path Dijkstra's algorithm (LPDKS), is presented by extension of the conventional DijkStra's algorithm by maintaining a limited number of nondominated paths, say X non-dominated paths, for each node.
Abstract: Multi-constrained path problem (MCPP) alms to find a path in a network that satisfies multiple additive path constraints, it has many applications such as route guidance in intelligent transportation systems and quality of service (QoS) routing in integrated networks for voice, data, and multimedia communications. It is well known that MCPP is NP-complete and heuristic or approximate algorithms are required to solve it suboptimally. A heuristic, limited path Dijkstra's algorithm (LPDKS), is presented by extension of the conventional Dijkstra's algorithm by maintaining a limited number of nondominated paths, say X non-dominated paths, for each node. Three key design problems are investigated for this new algorithm, i.e., how to maintain X non-dominated paths for each node when there are more paths available, how to decide which path to extend first, and how to determine X. We propose path deletion heuristics and path order heuristic to deal with the first two problems, and provide a heuristic value of X that can have very high probability to find a feasible path when one exists. The complexity analysis and extensive experiments are given to show the performance of the proposed algorithm.
07 Nov 2002
TL;DR: The need for the use of simulation for site layout analysis is identified and the potential application of mathematical optimisation techniques for the selection of site paths is investigated.
Abstract: This paper presents an optimisation application to support the construction site planning task by finding efficient paths between two site locations based on a combination of safety, transportation cost, and visibility criteria. These criteria can be combined or individually optimised by mathematical search algorithms, namely Dijkstra and A*, in order to present site planners with the safest path, the shortest distance path, the most visible path, and the paths that reflect a combination of low risks, short distance, and high visibility measures between two site locations. This paper identifies the need for the use of simulation for site layout analysis, in particular, it investigates the potential application of mathematical optimisation techniques for the selection of site paths.
12 Aug 2002
TL;DR: A stochastic search technique to identify low risk paths that satisfy a constraint on the transit time and is compared with the related problem of finding the fastest bounded-risk path, and the potential use of dynamic graph algorithms to quickly find new paths as the risk bound is varied.
Abstract: We have been developing path planning techniques to look for paths that balance the utility and risk associated with different routes through a minefield. Such methods will allow a battlegroup commander to evaluate alternative route options while searching for low risk paths. A risk management framework can be used to describe the relative values of different factors such as risk versus time to objective, giving the commander the capability to balance path safety against other mission objectives. We will describe our recent investigations of two related path planning problems in this framework. We have developed a stochastic search technique to identify low risk paths that satisfy a constraint on the transit time. The objective is to generate low risk paths quickly so that the user can interactively explore the time-risk tradeoff. We will compare this with the related problem of finding the fastest bounded-risk path, and the potential use of dynamic graph algorithms to quickly find new paths as the risk bound is varied.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.