Showing papers on "Obstacle avoidance published in 2001"
TL;DR: A new framework for segmentation of sonar images, tracking of underwater objects and motion estimation, applied to the design of an obstacle avoidance and path planning system for underwater vehicles based on a multi-beam forward looking sonar sensor is described.
Abstract: This paper describes a new framework for segmentation of sonar images, tracking of underwater objects and motion estimation. This framework is applied to the design of an obstacle avoidance and path planning system for underwater vehicles based on a multi-beam forward looking sonar sensor. The real-time data flow (acoustic images) at the input of the system is first segmented and relevant features are extracted. We also take advantage of the real-time data stream to track the obstacles in following frames to obtain their dynamic characteristics. This allows us to optimize the preprocessing phases in segmenting only the relevant part of the images. Once the static (size and shape) as well as dynamic characteristics (velocity, acceleration,...) of the obstacles have been computed, we create a representation of the vehicle's workspace based on these features. This representation uses constructive solid geometry (CSG) to create a convex set of obstacles defining the workspace. The tracking takes also into account obstacles which are no longer in the field of view of the sonar in the path planning phase. A well-proven nonlinear search (sequential quadratic programming) is then employed, where obstacles are expressed as constraints in the search space. This approach is less affected by local minima than classical methods using potential fields. The proposed system is not only capable of obstacle avoidance but also of path planning in complex environments which include fast moving obstacles. Results obtained on real sonar data are shown and discussed. Possible applications to sonar servoing and real-time motion estimation are also discussed.
274 citations
12 Jun 2001
TL;DR: In this article, the authors present and apply the mobile robot path planning technique which integrates the artificial potential field approach with simulated annealing to mobile robots to avoid local minima.
Abstract: The artificial potential field methods provide simple and effective motion planners for practical purposes. However, there is a major problem with the artificial potential field approach. It is the formation of local minima that can trap the robot before reaching its goal. The avoidance of local minima has been an active research topic in potential field path planning. As one of the powerful techniques for escaping local minima, simulated annealing has been applied to local and global path planning. In this paper, the authors present and apply the mobile robot path planning technique which integrate the artificial potential field approach with simulated annealing to mobile robots.
212 citations
TL;DR: The Bremen autonomous wheelchair implements obstacle avoidance plus driving and routing assistance in a shared-control system that solves the tasks of reliably detecting obstacles in the environment and safely avoiding these obstructions.
Abstract: The Bremen autonomous wheelchair implements obstacle avoidance plus driving and routing assistance in a shared-control system. This article shows how the tasks of reliably detecting obstacles in the environment and safely avoiding these obstructions are solved.
146 citations
21 May 2001
TL;DR: The principles of these control enhancements will raise dramatically the level of safety and precision that a surgeon can achieve, but those principles can also be applied to a wide variety of teleoperation applications.
Abstract: Concerns telerobotic microsurgery. Existing systems offer tremor elimination and scaling of motions. This article goes beyond the strict master/slave scheme to the enhancement of the operator's capabilities during teleoperation. It is focused on the implementation of three types of constraints for the operators' movements: constrained movement (along a curve or on a predefined surface); virtual obstacle avoidance; and geometric constraints to limit the robots workspace. Constraints for the operator's movements can be implemented mechanically. Our approach uses a haptic master robot, and consists in adding constraint forces to its control scheme. Constraint forces are computed according to attractive or repulsive potential fields placed around constraints. This article presents the principles of these control enhancements which, we believe, will raise dramatically the level of safety and precision that a surgeon can achieve, but those principles can also be applied to a wide variety of teleoperation applications.
107 citations
TL;DR: Simulations and experimental results demonstrate the effectiveness and applicability of the proposed internet control architecture for internet-based personal robot, which is insensitive to the inherent internet time delay.
Abstract: This paper proposes a novel direct internet control architecture for internet-based personal robot, which is insensitive to the inherent internet time delay. The personal robot can be controlled using a simulator provided at a local site. Since the internet time delay is affected by the number of nodes and the internet loads, it is variable and unpredictable so that a large internet delay makes some control inputs distorted. The proposed control architecture guarantees that the personal robot can avoid obstacles and reduce the path error and the time difference between a virtual robot at the local site and a real robot at the remote site. This architecture is extended for an uncertain environment. Simulations and experimental results in the real internet environment demonstrate the effectiveness and applicability of the proposed internet control architecture.
99 citations
TL;DR: In this article, a navigation and guidance system (NGS) with real-time path planning and obstacle avoidance capabilities was developed for the autonomous underwater vehicle RAIS, which is designed to accomplish two missions: pre-deployment survey of sea bottom, and visual inspection of pipelines.
Abstract: This paper describes a navigation and guidance system (NGS) with real-time path planning and obstacle avoidance capabilities that has been developed for the autonomous underwater vehicle RAIS. The vehicle is designed to accomplish two missions: pre-deployment survey of sea bottom, and visual inspection of pipelines. In the first mission, the NGS must be able to track a predefined path while avoiding the unplanned occurrence of obstacles. In the second mission, the NGS must track a pipeline by locally reconstructing its location from visual information; also in this case, the unplanned occurrence of obstacles must be handled. Furthermore, the NGS must properly take into account the presence of ocean current and some drastic constraints due to sensor and actuator characteristics. Numerical and hardware-in-the-loop simulations have been developed to verify the effectiveness of the proposed NGS.
93 citations
TL;DR: In this paper, the authors give the basic considerations for building mobile micro-robots and the major scaling effects are presented and their impact on micro-system design, as well as the scaling laws.
Abstract: Design of mobile micro-robot (MMR) is still a challenge due to the restricted availability of basic components. However, the number of highly integrated microelectronic and micromechanical components is growing fast. Nevertheless, its integration to a micro-system requires a good knowledge of all the interactions between sensor, actuator, computation and energy source. Often compromises between performance and power consumption have to be found. This paper gives the basic considerations for building mobile micro-robots. The major scaling effects are presented and their impact on micro-system design is discussed. The mobile micro-robot Alice (Fig. 1), having the size of a sugar cube, is presented and discussed in the context of scaling laws. It has an autonomy of around 10 hours and is able to navigate based on simple behaviors like obstacle avoidance or wall following.
93 citations
TL;DR: The neuro-fuzzy approach, shown in this paper, is able to extract a set of fuzzy rules set from aSet of trajectories provided by a human, which guide the mobile robot towards the target in different cases.
90 citations
10 Sep 2001
TL;DR: A biologically inspired, minimalistic model for visual flight control in an autonomous agent that robustly indicates the sign of attitude angles, self-rotation, obstacle direction and altitude deviation is presented.
Abstract: Flying insects use highly efficient visual strategies to control their self-motion in three-dimensional space. We present a biologically inspired, minimalistic model for visual flight control in an autonomous agent. Large, specialized receptive fields exploit the distribution of local intensities and local motion in an omnidirectional field of view, extracting the information required for attitude control, course stabilization, obstacle avoidance, and altitude control. In open-loop simulations, recordings from each control mechanism robustly indicate the sign of attitude angles, self-rotation, obstacle direction and altitude deviation, respectively. Closed-loop experiments show that these signals are sufficient for three-dimensional flight stabilization with six degrees of freedom.
87 citations
25 Aug 2001
TL;DR: Describes the technologies of cooperative driving with automated vehicles and inter-vehicle communications in the Demo 2000 cooperative driving, aiming at the compatibility of safety and efficiency of road traffic.
Abstract: Describes the technologies of cooperative driving with automated vehicles and inter-vehicle communications in the Demo 2000 cooperative driving. Cooperative driving, aiming at the compatibility of safety and efficiency of road traffic, here means that automated vehicles drive by forming a flexible platoon over a couple of lanes with a short inter-vehicle distance while performing lane changing, merging, and leaving the platoon. The vehicles for the demonstration are equipped with automated lateral and longitudinal control functions with localization data by the DGPS and the inter-vehicle communication function with 5.8 GHz DSRC designed for dedicated use in the demonstration. In order to show the feasibility and potential of the technologies, the demonstration was held in November, 2000 on a test track with 5 automated vehicles. The scenario included stop and go, platooning, merging and obstacle avoidance.
79 citations
Patent•
1 Jun 2001
TL;DR: In this article, the authors proposed a method for working out an avoidance path comprising two parts: a first jinking part with an initial heading such that the threatening aircraft adopts a path relative to the threatened aircraft tangent, on one side or the other, to the edges of the angle under which the aircraft sees a protective circle drawn around a threatened aircraft with a radius equal to an accepted minimum distance, and a second part for returning to the initial route.
Abstract: The invention concerns the production of an avoidance path in the horizontal plane enabling an aircraft to resolve a route conflict with another aircraft bringing about a risk of collision in the next 5 to 10 minutes and which minimises the negative consequences, on the aircraft flight plan, of the resulting diversion. The invention concerns a method for working out an avoidance path comprising two parts: a first jinking part with an initial heading such that the threatening aircraft adopts a path relative to the threatened aircraft tangent, on one side or the other, to the edges of the angle under which the threatening aircraft sees a protective circle drawn around the threatened aircraft with a radius equal to an accepted minimum distance, and a second part for returning to the initial route. Said method for working out an avoidance path can be carried out by a flight management computer which, once the evasive course has been accepted by the aircraft crew, continues to monitor said avoidance path by the automatic pilot system.
TL;DR: In the present work, fuzzy logic based implementation of the single-sided reflex is considered and the use of perceptional symmetry allows perception–action mapping with reduced sensor space dimensions.
29 Oct 2001
TL;DR: A semi-autonomous control method for omnidirectional wheelchairs that provides a collision avoidance function using external sensors and is shown to be effective by changing the impedance of the joystick essentially creating resistance against moving the joystick in the dangerous direction.
Abstract: An omnidirectional wheelchair is highly maneuverable in narrow or crowded areas such as residences, offices and hospitals. A semi-autonomous control method for omnidirectional wheelchairs is proposed. In addition to allowing the normal joystick commands of the wheelchair operator, this method provides a collision avoidance function using external sensors. The proposed method does not employ unexpected autonomous movements conflicting with the operator's joystick commands, because this tends to create discomfort for users and can be dangerous for infirm patients. Instead, the proposed method merely alerts the operator to the presence of an obstacle; this is accomplished by changing the impedance of the joystick essentially creating resistance against moving the joystick in the dangerous. direction. The wheelchair's motion remains controlled only by the operator's joystick commands, while a collision is avoided successfully. The effectiveness of the proposed method is shown by experiments with an onmidirectional wheelchair.
Book•
1 May 2001
TL;DR: This chapter describes the GuideCane system, including the mechanical, electronic, and software components, followed by a description of the intuitive user-machine interface.
Abstract: This chapter gives an overview of existing devices for the guidance of visually impaired pedestrians and discusses the properties of the white cane and of conventional electronic travel aids. Also described are the disadvantages of using a standard mobile robot for this purpose. Next follows a description of the NavBelt, a computerized travel aid for the blind that is based on advanced mobile robot obstacle avoidance technology. The NavBelt is worn by the user like a belt and, via a set of stereo earphones, provides acoustic signals that guide the user around obstacles. One limitation of the NavBelt is that it is exceedingly difficult for the user to comprehend the guidance signals in time to allow fast walking. This problem is effectively overcome by a newer device, called GuideCane. The GuideCane uses the same mobile robotics technology as the NavBelt but it is a wheeled device pushed ahead of the user via an attached cane. When the GuideCane detects an obstacle it steers around it. The user immediately feels this steering action and can follow the GuideCane's new path easily and without any conscious effort. This chapter describes the GuideCane system, including the mechanical, electronic, and software components, followed by a description of the intuitive user-machine interface. The chapter ends with a discussion of the GuideCane's novel information transfer approach and its advantages and disadvantages in practical term.
21 May 2001
TL;DR: A method in which data generated by crosstalk is actually used to generate more reliable and accurate object detection by assigning a unique code to the signals emitted by each sonar, so that the source sonar can be identified even if its signal's echo is received by another sonar.
Abstract: One problem oftentimes observed with arrays of multiple ultrasonic sensors (sonars) in obstacle detection and avoidance systems is crosstalk. The paper presents a method in which data generated by crosstalk is actually used to generate more reliable and accurate object detection. This is accomplished by assigning a unique code to the signals emitted by each sonar, so that the source sonar can be identified even if its signal's echo is received by another sonar. Using geometric interpolation between the various sonars increases the accuracy of the measurements, overcoming their limited resolution. Experimental results show the potential of our system for mobile robotics obstacle detection and avoidance, as well as for localization using map-matching techniques.
18 Sep 2001
TL;DR: Care-O-bot is the prototype of a multifunctional home care system to be used by elderly people in order to live independently in their homes, and the way to use it as a walking aid has been adapted to conventional walking aid systems.
Abstract: This work presents the intelligent walking aid system Care-O-bot. Care-O-bot is the prototype of a multifunctional home care system, to be used by elderly people in order to live independently in their homes. In order to enable easy manipulation of the robot platform, the way to use it as a walking aid has been adapted to conventional walking aid systems. The robot drives in reaction to input forces given by the user, for example if the user "pushes" the robot forward, it will start moving in the required direction. As an improvement to conventional walking aid systems, intelligent behaviours, as for example autonomous obstacle avoidance and path planning are included.
29 Oct 2001
TL;DR: This paper presents a motion planner and nonholonomic controller for a mobile robot, with global collision avoidance and convergence properties, using an appropriately designed (dipolar) potential field combined with discontinuous state feedback.
Abstract: This paper presents a motion planner and nonholonomic controller for a mobile robot, with global collision avoidance and convergence properties. An appropriately designed (dipolar) potential field is combined with discontinuous state feedback. A new class of Lyapunov functions is introduced and used for nonholonomic navigation. The obstacle avoidance and global asymptotic stability properties are verified through simulations.
1 Jan 2001
TL;DR: Inspired by the visual navigation of flying insects, a model of vision-based navigation using Elementary Motion Detectors (EMDs) is presented, showing that goal-directed navigation can be potentially achieved by simple visual processing, and that the design flexibility of this approach leads to high adaptivity to the given task-environment.
Abstract: In nature, flying insects are capable of surprisingly good navigation, despite the small size and relative simplicity of their brains. Recent experimental research in biology has uncovered a number of different ways in which insects use cues derived from optical flow for navigational purposes, such as obstacle avoidance, safe landing and dead-reckoning. Inspired by the visual navigation of flying insects, this paper presents a model of vision-based navigation using Elementary Motion Detectors (EMDs). The performance tests with an autonomous flying robot successfully demonstrate goal-directed navigation in an unstructured environment, as well as obstacle avoidance and course stabilization behaviors. Further investigation in the simulation shows that goal-directed navigation can be potentially achieved by simple visual processing, and that the design flexibility of this approach leads to high adaptivity to the given task-environment.
TL;DR: In this paper, two different strategies for the problem of the optimal trajectory planning of robot manipulators in the presence of fixed obstacles are presented. Androulaki et al. proposed two strategies: the first strategy is related to the situation where the trajectory must pass through a given number of points and the second strategy corresponds to the case where only the initial and final points are given.
Abstract: This paper presents two different strategies for the problem of the optimal trajectory planning of robot manipulators in the presence of fixed obstacles. The first strategy is related to the situation where the trajectory must pass through a given number of points. The second strategy corresponds to the case where only the initial and final points are given. The optimal traveling time and the minimum mechanical energy of the actuators are considered together to build a multiobjective function. The trajectories are defined using spline functions and are obtained through offline computation for online operation. Sequential unconstrained minimization techniques (SUMT) have been used for the optimization. The obstacles are considered as three-dimensional objects sharing the same workspace performed by the robot. The obstacle avoidance is expressed in terms of the distances between potentially colliding parts. Simulation results are presented and show the efficiency of the general methodology used in this paper.
29 Oct 2001
TL;DR: This paper presents an intelligent wheelchair that can avoid collisions with such human pedestrians safely and comfortably for each other, and demonstrates the effectiveness and comfortableness of the proposed method.
Abstract: With the increase in the number of senior citizens, there is a growing demand for human-friendly wheelchairs as mobility aids. One of the main issues in the robotic wheelchair research is autonomous obstacle avoidance for safety. However, this is difficult because most moving obstacles in the real world are human beings. They sometimes change their motion abruptly. The paper presents an intelligent wheelchair that can avoid collisions with such human pedestrians safely and comfortably for each other. We assume that the information whether or not a pedestrian has noticed the wheelchair and which direction he/she wants to go can appear in the face direction. Thus our intelligent wheelchair is continuously observing the pedestrian's face in its front area, realizing smooth passing by changing its collision avoidance strategy based on the face information and the range data from the ultrasonic sensors. Experimental results show the effectiveness and comfortableness of the proposed method.
TL;DR: The aim is to develop robust controllers in the sense that neuro-controllers evolved in a simulator show comparably good behavior when loaded to a real robot acting in a physical environment.
TL;DR: The success of the neural network approach shows that the sonar signals do contain sufficient information to differentiate all target types, but the previously reported methods are unable to resolve this identifying information.
TL;DR: In this article, the authors present an overview of a research program that aims to apply machine vision for guiding a small, unmanned helicopter during inspection of overhead electrical distribution lines, which is the underlying motivation for the work described here.
Abstract: Gives an overview of a research programme that aims to apply machine vision for guiding a small, unmanned helicopter during inspection of overhead electrical distribution lines. Briefly discusses the background and requirements for aerial inspection of power lines and states the advantages of using a remotely piloted vehicle (RPV). Identifies the main obstacle to the use of RPVs in this application as the ’‘see and avoid” principle, which arises from regulatory requirements; it is the underlying motivation for the work described here. Machine vision and automated path planning offer a potential solution. Gives a brief tutorial of the principles involved and describes research in image processing and rapid path planning aimed at detecting and avoiding obstacles in the airspace of a small RPV. Also presents experimental results from a laboratory test rig which was constructed to assess the methods.
30 Mar 2001
TL;DR: The development and implementation of an approach using genetic algorithms for finding optimum paths for a group of mobile robots located at arbitrary starting positions to a given number of targets in a known multi-obstacle environment is considered.
Abstract: We present the development, simulation and testing of a new approach using genetic algorithms for planning optimum paths for a group of mobile robots to be moved from arbitrary starting positions to final a number of targets in a known multi-obstacle 3D environment. The factors considered for fording optimum paths for the group of mobile robots are the size and location of obstacles in the environment and the topographical elevations of the environment. First, a digital picture of the environment is transformed into a grid map by a graphic simulator. The obstacles are mapped according to their location, shape and size. The ground elevations are represented using a color-coding scheme. The resulting grid map of the environment contains information about initial positions of the robots, target positions, obstacle locations and ground elevation. Hence, the location and size of obstacles and altitudes of the elevation of the environment are presented in the map. The genetic algorithm modules takes information about the environment from the grid map and search for optimum paths to move a group of mobile robots to the specified targets.
Patent•
11 Oct 2001TL;DR: In this paper, a specific configuration detecting element was proposed to detect an obstacle having an upper structure, thus providing efficient avoidance of an obstacle in the presence of a radar and an obstacle sensor in a space different from the radar device.
Abstract: An autonomous moving apparatus moving to a destination while detecting and avoiding an obstacle includes a radar device for scanning a horizontal plane in its travelling direction to thereby detect a position of an obstacle and an obstacle sensor for detecting an obstacle in a space different from the scanning plane of the radar device. The apparatus moves to the destination under such control as to avoid the obstacle based on detection information from the radar device and the obstacle sensor from a detection output provided by a specific-configuration detecting element for detecting a present specific configuration from scanning information by the radar device. By providing such a specific-configuration detecting element that detects a specific configuration based on the scan information by the radar device that can accurately know about position information, it is possible to guess an obstacle having an upper structure, thus providing efficient avoidance.
TL;DR: An optimal control framework for this general class of problems in robotics is developed, and analytic solutions for the local and global versions of the general optimal control problem are derived.
Abstract: A large class of problems in robotics, e.g., trajectory tracking with obstacle avoidance, compliant motion control, and complex assembly, can be formulated as a least-squares tracking problem on the Euclidean group subject to constraints on the state and/or control. We develop an optimal control framework for this general class of problems, and derive analytic solutions for the local and global versions of the general optimal control problem. Our formalism can be viewed in some sense as an extension to the Euclidean group of the linear quadratic regulator subject to state equality constraints. Examples from force-guided complex assembly and tracking with obstacle avoidance are given.
18 Oct 2001
TL;DR: An implementation of fuzzy logic for control of type (2-0) mobile robots with fuzzy controllers for trajectory tracking and obstacle avoidance and simulation results are compared to those of a nonlinear control algorithm.
Abstract: Presents an implementation of fuzzy logic for control of type (2,0) mobile robots. The kinematics model of the robot is briefly outlined. Then, fuzzy controllers for trajectory tracking and obstacle avoidance are described. Simulation results are compared to those of a nonlinear control algorithm.
1 Jan 2001
TL;DR: In this article, an approach for outdoor robot navigation using Distance Transform Methodology (DT) is presented for indoor robot navigation and can also be used to perform obstacle avoidance simultaneously, where the distance transform method is used for both path planning and obstacle avoidance.
Abstract: This paper presents an approach for outdoor robot navigation using Distance Transform Methodology (DT). DT has been used in path planning for indoor robot research and can also be used to perform obstacle avoidance simultaneously. However, when it comes to outdoor robot navigation, the operating environment becomes too large and DT becomes inefficient when performing both the tasks of path planning and obstacle avoidance. Usually both tasks have to be decoupled and DT is normally only used for path planning. The newly proposed DT methodology solves this problem by optimising the DT algorithm and reducing the processing area. Simulation and actual tests had also been carried out on an autonomous mobile robot to verify that the DT methodology can integrate both the tasks of path planning and obstacle avoidance and yield encouraging results in outdoor navigation.
29 Oct 2001
TL;DR: A first step towards application in a more realistic scenario such as a typical office environment where the robot perceives its environment via a set of sonar sensors and simple geometric representations of the corridor and obstacles are extracted from the perceptual information.
Abstract: The dynamical system approach to behaviour based robotics provides a sound mathematical framework to behaviour design and integration. So far this approach has been used in various simulation work and in simple real world settings. This paper is a first step towards application in a more realistic scenario such as a typical office environment. The robot perceives its environment via a set of sonar sensors. Simple geometric representations of the corridor and obstacles are extracted from the perceptual information. Obstacle avoidance and corridor following are implemented as the basic behaviours, which allow the robot to navigate safely through its environment. The robot can reliably distinguish between passages that are either wide enough to pass or too narrow to be traversed. Coordination among the primitive behaviours allows the robot to cope with more complex situations, such as a corridor that is blocked by obstacles, in a flexible manner.
TL;DR: In this paper, a method of collision avoidance planning using automatic dependent surveillance-broadcast (ADS-B) and dynamic programming (DP) is proposed for the aircraft case using DP applied to the moving obstacle case.
Abstract: This paper proposes a method of collision avoidance planning using automatic dependent surveillance-broadcast (ADS-B) and dynamic programming (DP). It in essence allows air traffic control (ATC) within the cockpit for remote or uncontrolled airspace and is a step toward Free Flight. This paper reviews the approach to collision avoidance in the aircraft industry and to similar problems in other industries. DP is one solution method used in other industries for the problem of path planning to avoid collisions with fixed obstacles. The solution proposed here for the aircraft case uses DP applied to the moving obstacle case. The problem is first simplified by assuming fixed obstacles for the cost minimisation algorithms. These fixed obstacles are then moved with time and the minimisation process is started again. Although this method works well in most cases, situations can be constructed where this method fails, allowing a collision. A modified approach is proposed, where the movement of obstacles is included more explicitly in the cost minimisation algorithm. This modification allows solutions which are complete and ensures safe maneuvres and should be considered as an aid to the Traffic alert and Collision Avoidance System (TCAS).