Despite the significant advances in path planning methods, problems involving highly constrained spaces are still challenging. In particular, in many situations the configuration space is a non-parametrizable variety ...
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ISBN:
(纸本)9783642174513
Despite the significant advances in path planning methods, problems involving highly constrained spaces are still challenging. In particular, in many situations the configuration space is a non-parametrizable variety implicitly defined by constraints, which complicates the successful generalization of sampling-based path planners. In this paper, we present a new path planning algorithm specially tailored for highly constrained systems. It builds on recently developed tools for Higher-dimensional Continuation, which provide numerical procedures to describe an implicitly defined variety using a set of local charts. We propose to extend these methods to obtain an efficient path planner on varieties, handling highly constrained problems. The advantage of this planner comes from that it directly operates into the configuration space and not into the higher-dimensional ambient space, as most of the existing methods do.
This paper presents a technique for planning and controlling bevel-tip steerable needles towards a target location in 3-D anatomy under the guidance of partial, noisy sensor feedback. Our approach minimizes the probab...
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ISBN:
(纸本)9783642174513
This paper presents a technique for planning and controlling bevel-tip steerable needles towards a target location in 3-D anatomy under the guidance of partial, noisy sensor feedback. Our approach minimizes the probability that the needle intersects obstacles such as bones and sensitive organs by (1) explicitly taking into account motion uncertainty and sensor types, and (2) allowing for efficient optimization of sensor placement. We allow for needle trajectories of arbitrary curvature through duty-cycled spinning of the needle, which is conjectured to make a needle path small-time locally "trackable" [13]. This enables us to use LQG control to guide the needle along the path. For a given path and sensor placement, we show that a priori probability distributions of the needle state can be estimated in advance. Our approach then plans a set of candidate paths and sensor placements and selects the pair for which the estimated uncertainty is least likely to cause intersections with obstacles. We demonstrate the performance of our approach in a modeled prostate cancer treatment environment.
Self-reconfigurable robots have an intriguingly flexible design, composing a single robot with many small modules that can autonomously move to transform the robot's shape and structure. Scaling to a large number ...
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ISBN:
(纸本)9783642174513
Self-reconfigurable robots have an intriguingly flexible design, composing a single robot with many small modules that can autonomously move to transform the robot's shape and structure. Scaling to a large number of modules is necessary to achieve great flexibility, so each module may only have limited processing and memory resources. This paper introduces a novel distributed locomotion algorithm for lattice-style self-reconfigurable robots which uses constant memory per module with constant computation and communication for each attempted module movement. Our algorithm also guarantees physical stability in the presence of gravity. By utilizing some robot modules to create a static support structure, other modules are able to move freely through the interior of this structure with minimal path planning and without fear of causing instabilities or losing connectivity. This approach also permits the robot's locomotion speed to remain nearly constant even as the number of modules in the robot grows very large. Additionally, we have developed methods to overcome dropped messages between modules or delays in module computation or movement. Empirical results from our simulation are also presented to demonstrate the scalability and locomotion speed advantages of this approach.
A body of effort has been devoted to developing efficient algorithms for kinematics and dynamics computation of robotic mechanisms, and has been successfully applied to control and simulation of complex mechanisms inc...
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ISBN:
(纸本)9783642147432
A body of effort has been devoted to developing efficient algorithms for kinematics and dynamics computation of robotic mechanisms, and has been successfully applied to control and simulation of complex mechanisms including industrial manipulators and humanoid robots. Thanks to such effort, as well as the recent progress in the computation power, it is becoming, more realistic to apply these algorithms to human body dynamics modeling and simulation. On the other hand, the human body has a number of different properties from robotic systems in its complexity, actuators. and controllers. This paper describes our attempt towards building a precise human body dynamics model for its motion analysis and simulation. In particular, we present how the algorithms developed in robotics are combined with physiological models and data to address the difficulties of handling real human body.
A framework for force and visual control of robot manipulators in contact with a partially known environment is proposed. The environment is modelled as a rigid object of known geometry but of unknown and time-varying...
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ISBN:
(纸本)9783642147432
A framework for force and visual control of robot manipulators in contact with a partially known environment is proposed. The environment is modelled as a rigid object of known geometry but of unknown and time-varying pose. An algorithm or online estimation of the object pose is adopted;based on visual data as well as on force measurements. This information is used by a force/position controller. The resulting control scheme has a inner/outer structure where the outer loop performs pose estimation and the inner loop is devoted to interaction control.
This paper presents HybridSLAM: an approach to SLAM which combines the strengths and avoids the weaknesses of two popular mapping strategies: FastSLAM and EKF-SLAM. FastSLAM is used as a front-end, producing local map...
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ISBN:
(纸本)9783642003110
This paper presents HybridSLAM: an approach to SLAM which combines the strengths and avoids the weaknesses of two popular mapping strategies: FastSLAM and EKF-SLAM. FastSLAM is used as a front-end, producing local maps which are periodically fused into an EKF-SLAM back-end. The use of FastSLAM locally avoids linearisation of the vehicle model and provides a high level of robustness to clutter and ambiguous data association. The use of EKF-SLAM globally allows uncertainty to be remembered over long vehicle trajectories, avoiding FastSLAM's tendency to become over-confident. Extensive trials in randomly-generated simulated environments show that HybridSLAM significantly out-performs either pure approach. The advantages of HybridSLAM are most pronounced in cluttered environments where either pure approach encounters serious difficulty. In addition, the HybridSLAM algorithm is experimentally validated in a real urban environment.
Analysis and control of underactuated mechanical systems in the nonzero velocity setting remains a challenging problem. In this paper, we demonstrate the utility of a recently developed alternative representation of t...
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ISBN:
(纸本)9783642003110
Analysis and control of underactuated mechanical systems in the nonzero velocity setting remains a challenging problem. In this paper, we demonstrate the utility of a recently developed alternative representation of the equations of motion for this large class of nonlinear control systems. The alternative representation gives rise to an intrinisic symmetric form. The generalized eigenvalues and eigen-vectors associated with the symmetric form are used to determine control inputs that will drive a class of mechanical systems underactuated by one control to rest from an arbitrary initial configuration and velocity. Finally, we illustrate the stopping algorithm by presenting numerical simulation results for the planar rigid body, snakeboard and planar rollerblader.
We consider a target tracking problem in which, in addition to sensing some information about the position of a mobile target, the tracker must also ensure that the privacy of that target is preserved, even in the pre...
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ISBN:
(纸本)9783642003110
We consider a target tracking problem in which, in addition to sensing some information about the position of a mobile target, the tracker must also ensure that the privacy of that target is preserved, even in the presence of adversaries that have complete access to the tracker's sensor data. This kind of problem is important for many kinds of robot systems that involve communication systems or agents that cannot be fully trusted. In this paper, we (1) introduce a formal, quantitative definition for privacy, (2) describe algorithms that allow a robot to maintain conservative estimates of its performance in terms of tracking and privacy, (3) give strategies for the tracker to maximize its tracking performance;subject to constraints on the allowable privacy levels, and (4) present an implementation of these methods along with some experimental results.
A mobile robot equipped with a single camera can take images at different locations to obtain the 3D information of the environment for navigation. The depth information perceived by the robot is critical for obstacle...
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ISBN:
(纸本)9783642003110
A mobile robot equipped with a single camera can take images at different locations to obtain the 3D information of the environment for navigation. The depth information perceived by the robot is critical for obstacle avoidance. Given a calibrated camera, the accuracy of depth computation largely depends on locations where images have been taken. For any given image pair, the depth error in regions close to the camera baseline can be excessively large or even infinite due to the degeneracy introduced by the triangulation in depth computation. Unfortunately, this region often overlaps with the robot's moving direction, which could lead to collisions. To deal with the issue, we analyze depth computation and propose a predictive depth error model as a function of motion parameters. We name the region where the depth error is above a given threshold as an untrusted area. Note that the robot needs to know how its motion affect depth error distribution beforehand, we propose a closed-form model predicting how the untrusted area is distributed on the road plane for given robot/camera positions. The analytical results have been successfully verified in the experiments using a mobile robot.
This article addresses SLAM and navigation frame using low-cost sensor systems as a practical solution in an indoor environment. It is divided into three major modules according to their functionality: 1) initial mapp...
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ISBN:
(纸本)9783642147432
This article addresses SLAM and navigation frame using low-cost sensor systems as a practical solution in an indoor environment. It is divided into three major modules according to their functionality: 1) initial mapping by VR-SLAM (Vision and Range sensor-SLAM) while exploring an unknown environment, 2) task-based navigation to guarantee safe motion under dynamic environmental changes and 3) failure recovery to improve system reliability. These modules work with a stereo camera, ultrasonic and infrared sensors combined. In this article, we will describe the navigation frame, especially, focusing on VR-SLAM.
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