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120
Planning in Information Space for Quadrotor Helicopter in a GPS-denied Environment
- Robotics and Automation, 2008. Proceedings. ICRA'08. IEEE International Conference on
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On the probabilistic foundations of probabilistic roadmap planning
- In Proc. Int. Symp. on Robotics Research
, 2005
"... Probabilistic roadmap (PRM) planners [5, 16] solve apparently difficult motion planning problems where the robot’s configuration space C has dimensionality six or more, and the geometry of the robot and the obstacles is described by hundreds of thousands of triangles. While an algebraic planner woul ..."
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Cited by 61 (11 self)
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Probabilistic roadmap (PRM) planners [5, 16] solve apparently difficult motion planning problems where the robot’s configuration space C has dimensionality six or more, and the geometry of the robot and the obstacles is described by hundreds of thousands of triangles. While an algebraic planner would be overwhelmed by the high cost of computing an exact representation of the free space F, defined as the collisionfree subset of C, a PRM planner builds only an extremely simplified representation of F, called a probabilistic roadmap. This roadmap is a graph, whose nodes are configurations sampled from F with a suitable probability measure and whose edges are simple collision-free paths, e.g., straight-line segments, between the sampled configurations. PRM planners work surprisingly well in practice, but why? Previous work has partially addressed this question by identifying and formalizing properties of F that guarantee good performance for a PRM planner using the uniform sampling measure (e.g.,
Sampling-Based Motion Planning Using Predictive Models
, 2005
"... Robotic motion planning requires configuration space exploration. In high-dimensional configuration spaces, a complete exploration is computationally intractable. Practical motion planning algorithms for such high-dimensional spaces must expend computational resources in proportion to the local co ..."
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Cited by 47 (4 self)
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Robotic motion planning requires configuration space exploration. In high-dimensional configuration spaces, a complete exploration is computationally intractable. Practical motion planning algorithms for such high-dimensional spaces must expend computational resources in proportion to the local complexity of configuration space regions. We propose a novel motion planning approach that addresses this problem by building an incremental, approximate model of configuration space. The information contained in this model is used to direct computational resources to difficult regions, effectively addressing the narrow passage problem by adapting the sampling density to the complexity of that region. In addition, the expressiveness of the model permits predictive edge validations, which are performed based on the information contained in the model rather then by invoking a collision checker. Experimental results show that the exploitation of the information obtained through sampling and represented in a predictive model results in a significant decrease in the computational cost of motion planning.
Finding narrow passages with probabilistic roadmaps: The small step retraction method
- in Proc. IEEE/RSJ Int. Conf. on Intelligent Robots & Systems
, 2005
"... Abstract: Probabilistic Roadmaps (PRM) have been successfully used to plan complex robot motions in configuration spaces of small and large dimensionalities. However, their efficiency decreases dramatically in spaces with narrow passages. This paper presents a new method – smallstep retraction – tha ..."
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Cited by 36 (3 self)
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Abstract: Probabilistic Roadmaps (PRM) have been successfully used to plan complex robot motions in configuration spaces of small and large dimensionalities. However, their efficiency decreases dramatically in spaces with narrow passages. This paper presents a new method – smallstep retraction – that helps PRM planners find paths through such passages. This method consists of slightly “fattening ” robot’s free space, constructing a roadmap in fattened free space, and finally repairing portions of this roadmap by retracting them out of collision into actual free space. Fattened free space is not explicitly computed. Instead, the geometric models of workspace objects (robot links and/or obstacles) are “thinned ” around their medial axis. A robot configuration lies in fattened free space if the thinned objects do not collide at this configuration. Two repair strategies are proposed. The “optimist ” strategy waits until a complete path has been found in fattened free space before repairing it. Instead, the “pessimist ” strategy repairs the roadmap as it is being built. The former is usually very fast, but may fail in some pathological cases. The latter is more reliable, but not as fast. A simple combination of the two strategies yields an integrated planner that is both fast and reliable. This planner was implemented as an extension of a pre-existing single-query PRM planner. Comparative tests show that it is significantly faster (sometimes by several orders of magnitude) than the pre-existing planner. 1.
Sampling-based roadmap of trees for parallel motion planning
- IEEE Trans. Robot
, 2005
"... Abstract — This paper shows how to effectively combine a sampling-based method primarily designed for multiple query motion planning (Probabilistic Roadmap Method- PRM) with sampling-based tree methods primarily designed for single query motion planning (Expansive Space Trees, Rapidly-Exploring Rand ..."
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Cited by 36 (11 self)
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Abstract — This paper shows how to effectively combine a sampling-based method primarily designed for multiple query motion planning (Probabilistic Roadmap Method- PRM) with sampling-based tree methods primarily designed for single query motion planning (Expansive Space Trees, Rapidly-Exploring Random Trees, and others) in a novel planning framework that can be efficiently parallelized. Our planner not only achieves a smooth spectrum between multiple query and single query planning but it combines advantages of both. We present experiments which show that our planner is capable of solving problems that cannot be addressed efficiently withPRM or single-query planners. A key advantage of our planner is that it is significantly more decoupled thanPRM and sampling-based tree planners. Exploiting this property, we designed and implemented a parallel version of our planner. Our experiments show that our planner distributes well and can easily solve high-dimensional problems that exhaust resources available to single machines and cannot be addressed with existing planners. Index Terms — Motion planning, sampling-based planning, parallel
Using Workspace Information as a Guide to Non-Uniform Sampling in Probabilistic Roadmap Planners
, 2005
"... The probabilistic roadmap (PRM) planner is a popular method for robot motion planning problems with many degrees of freedom. However, it has been shown that the method performs less well in situations where the robot has to pass through a narrow passage in the scene. This is mainly due to the unifor ..."
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Cited by 34 (2 self)
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The probabilistic roadmap (PRM) planner is a popular method for robot motion planning problems with many degrees of freedom. However, it has been shown that the method performs less well in situations where the robot has to pass through a narrow passage in the scene. This is mainly due to the uniformity of the sampling used in the planner; it places many samples in large open regions and too few in tight passages. Cell decomposition methods do not have this disadvantage, but are only applicable in low-dimensional configuration spaces. In this paper, a hybrid technique is presented that combines the strengths of both methods. It is based on a robot independent cell decomposition of the free workspace guiding the probabilistic sampling more toward the interesting regions in the configuration space. The regions of interest (narrow passages) are identified in the cell decomposition using a method we call watershed labeling. It is shown that this leads to improved performance on difficult planning problems in two- and three-dimensional workspaces.
An obstacle-based rapidly-exploring random tree
- in Proc. IEEE International Conference on Robotics and Automation (ICRA
, 2006
"... Abstract — Tree-based path planners have been shown to be well suited to solve various high dimensional motion planning problems. Here we present a variant of the Rapidly-Exploring Random Tree (RRT) path planning algorithm that is able to explore narrow passages or difficult areas more effectively. ..."
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Cited by 32 (4 self)
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Abstract — Tree-based path planners have been shown to be well suited to solve various high dimensional motion planning problems. Here we present a variant of the Rapidly-Exploring Random Tree (RRT) path planning algorithm that is able to explore narrow passages or difficult areas more effectively. We show that both workspace obstacle information and C-space information can be used when deciding which direction to grow. The method includes many ways to grow the tree, some taking into account the obstacles in the environment. This planner works best in difficult areas when planning for free flying rigid or articulated robots. Indeed, whereas the standard RRT can face difficulties planning in a narrow passage, the tree based planner presented here works best in these areas. I.
Resampl: A region-sensitive adaptive motion planner
- TRACTS IN ADVANCED ROBOTICS
, 2006
"... Automatic motion planning has applications ranging from traditional robotics to computer-aided design to computational biology and chemistry. While randomized planners, such as probabilistic roadmap methods (prms) or rapidly-exploring random trees (rrt), have been highly successful in solving many h ..."
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Cited by 30 (7 self)
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Automatic motion planning has applications ranging from traditional robotics to computer-aided design to computational biology and chemistry. While randomized planners, such as probabilistic roadmap methods (prms) or rapidly-exploring random trees (rrt), have been highly successful in solving many high degree of freedom problems, there are still many scenarios in which we need better methods, e.g., problems involving narrow passages or which contain multiple regions that are best suited to different planners. In this work, we present resampl, a motion planning strategy that uses local region information to make intelligent decisions about how and where to sample, which samples to connect together, and to find paths through the environment. Briefly, resampl classifies regions based on the entropy of the samples in it, and then uses these classifications to further refine the sampling. Regions are placed in a region graph that encodes relationships between regions, e.g., edges correspond to overlapping regions. The strategy for connecting samples is guided by the region graph, and can be exploited in both multi-query and single-query scenarios. Our experimental results comparing resampl to previous multi-query and single-query methods show that The general motion planning problem consists of finding a valid path for an object from a start configuration
OOPS for Motion Planning: An Online Open-source Programming System
- IN IEEE INTL. CONF. ON ROBOTICS AND AUTOMATION
, 2007
"... The success of sampling-based motion planners has resulted in a plethora of methods for improving planning components, such as sampling and connection strategies, local planners and collision checking primitives. Although this rapid progress indicates the importance of the motion planning problem ..."
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Cited by 26 (7 self)
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The success of sampling-based motion planners has resulted in a plethora of methods for improving planning components, such as sampling and connection strategies, local planners and collision checking primitives. Although this rapid progress indicates the importance of the motion planning problem and the maturity of the field, it also makes the evaluation of new methods time consuming. We propose that a systems approach is needed for the development and the experimental validation of new motion planners and/or components in existing motion planners. In this paper, we present the Online, Open-source, Programming System for Motion Planning (OOPSMP), a programming infrastructure that provides implementations of various existing algorithms in a modular, object-oriented fashion that is easily extendible. The system is open-source, since a community-based effort better facilitates the development of a common infrastructure and is less prone to errors. We hope that researchers will contribute their optimized implementations of their methods and thus improve the quality of the code available for use. A dynamic web interface and a dynamic linking architecture at the programming level allows users to easily add new planning components, algorithms, benchmarks, and experiment with different parameters. The system allows the direct comparison of new contributions with existing approaches on the same hardware and programming infrastructure.
Quantitative analysis of nearest-neighbors search in high-dimensional sampling-based motion planning
- IN WORKSHOP ON ALGO. FOUND. OF ROBOT
, 2006
"... We quantitatively analyze the performance of exact and approximate nearest-neighbors algorithms on increasingly high-dimensional problems in the context of sampling-based motion planning. We study the impact of the dimension, number of samples, distance metrics, and sampling schemes on the efficie ..."
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Cited by 23 (6 self)
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We quantitatively analyze the performance of exact and approximate nearest-neighbors algorithms on increasingly high-dimensional problems in the context of sampling-based motion planning. We study the impact of the dimension, number of samples, distance metrics, and sampling schemes on the efficiency and accuracy of nearest-neighbors algorithms. Efficiency measures computation time and accuracy indicates similarity between exact and approximate nearest neighbors. Our analysis indicates that after a critical dimension, which varies between 15 and 30, exact nearest-neighbors algorithms examine almost all the samples. As a result, exact nearest-neighbors algorithms become impractical for sampling-based motion planners when a considerably large number of samples needs to be generated. The impracticality of exact nearest-neighbors algorithms motivates the use of approximate algorithms, which trade off accuracy for efficiency. We propose a simple algorithm, termed Distance-based Projection onto Euclidean Space (DPES), which computes approximate nearest neighbors by using a distance-based projection of high-dimensional metric spaces onto low-dimensional Euclidean spaces. Our results indicate DPES achieves high efficiency and only a negligible loss in accuracy.