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Showing papers on "Obstacle avoidance published in 1992"


Journal ArticleDOI
01 Oct 1992
TL;DR: A methodology for exact robot motion planning and control that unifies the purely kinematic path planning problem with the lower level feedback controller design is presented.
Abstract: A methodology for exact robot motion planning and control that unifies the purely kinematic path planning problem with the lower level feedback controller design is presented. Complete information about a freespace and goal is encoded in the form of a special artificial potential function, called a navigation function, that connects the kinematic planning problem with the dynamic execution problem in a provably correct fashion. The navigation function automatically gives rise to a bounded-torque feedback controller for the robot's actuators that guarantees collision-free motion and convergence to the destination from almost all initial free configurations. A formula for navigation functions that guide a point-mass robot in a generalized sphere world is developed. The simplest member of this family is a space obtained by puncturing a disk by an arbitrary number of smaller disjoint disks representing obstacles. The other spaces are obtained from this model by a suitable coordinate transformation. Simulation results for planar scenarios are provided. >

1,912 citations


Journal ArticleDOI
TL;DR: The understanding of some invertebrate sensory-motor systems has now reached a level able to provide valuable design hints and this approach brings into prominence the mutual constraints in the designs of a sensory and a motor system, in both living and non-living ambulatory creatures.
Abstract: Airborne insects are miniature w ing-flapping aircraft the visually guided manoeuvres of which depend on analogue, ‘fly-by-wire’ controls. The front-end of their visuomotor system consists of a pair of com pound eyes which are masterpieces of integrated optics and neural design. They rely on an array of passive sensors driving an orderly analogue neural network. We explored in concrete terms how motion-detecting neurons might possibly be used to solve navigational tasks involving obstacle avoidance in a creature whose wings are exquisitely guided by eyes with a poor spatial resolution. We designed, simulated, and built a complete terrestrial creature which moves about and avoids obstacles solely by evaluating the relative motion between itself and the environment. The compound eye uses an array of elementary motion detectors (emds) as smart, passive ranging sensors. Like its physiological counterpart, the visuomotor system is based on analogue, continuous-time processing and does not make use of conventional computers. It uses hardly any memory to adjust the robot’s heading in real time via a local and intermittent visuomotor feedback loop. This paper shows that the understanding of some invertebrate sensory-motor systems has now reached a level able to provide valuable design hints. Our approach brings into prominence the mutual constraints in the designs of a sensory and a motor system, in both living and non-living ambulatory creatures.

501 citations


Journal ArticleDOI
TL;DR: It is argued that the overall approach provides a unifying paradigm for practical, domain-independent stereo ranging, with high reliability and near real-time performance for low-resolution image pairs.
Abstract: NASA scenarios for lunar and planetary missions include robotic vehicles that function in both teleoperated and semi-autonomous modes. Under teleoperation, on-board stereo cameras may provide 3-D scene information to human operators via stereographic displays; likewise, under semi-autonomy, machine stereo vision may provide 3-D information for obstacle avoidance. In the past, the slow speed of machine stereo vision systems has posed a hurdle to the semi-autonomous scenario; however, recent work at JPL and other laboratories has produced stereo systems with high reliability and near real-time performance for low-resolution image pairs. In particular, JPL has taken a significant step by achieving the first autonomous, cross-country robotic traverses (of up to 100 meters) to use stereo vision, with all computing on-board the vehicle. Here, we describe the stereo vision system, including the underlying statistical model and the details of the implementation. The statistical and algorithmic aspects employ random field models of the disparity map, Bayesian formulations of single-scale matching, and area-based image comparisons. The implementation builds bandpass image pyramids and produces disparity maps from the 60×64 level of the pyramids at rates of up to two seconds per image pair. All vision processing is done in one 68020 augmented with Datacube image processing boards. We argue that the overall approach provides a unifying paradigm for practical, domain-independent stereo ranging. We close with a discussion of practical and theoretical issues involved in evaluating and extending the performance of the stereo system.

268 citations


Proceedings ArticleDOI
12 May 1992
TL;DR: The authors address the issue of collision avoidance in unknown or partially modeled environments using a capacitative sensor system which can detect obstacles up to 400 mm away and enable the robot arm to avoid a conductive post and a concrete block.
Abstract: The authors address the issue of collision avoidance in unknown or partially modeled environments using a capacitative sensor. An eight channel capacitance-based sensor system which can detect obstacles up to 400 mm away has been developed. This sensor can detect both conductive and nonconductive obstacles of arbitrary color and shape. The sensor hardware was reliable and inexpensive, and may be fabricated using flexible printed circuit boards to provide whole-arm and joint protection for any robot or manipulator. Simple collision avoidance control algorithms have been implemented on a two-link robot arm. The sensor and control system enable the robot arm to avoid a conductive post and a concrete block. >

118 citations


Proceedings ArticleDOI
12 May 1992
TL;DR: The authors describe a practical path planner for nonholonomic robots in environments with obstacles based on building a one-dimensional, maximal clearance skeleton through the configuration space of the robot.
Abstract: The authors describe a practical path planner for nonholonomic robots in environments with obstacles. The planner is based on building a one-dimensional, maximal clearance skeleton through the configuration space of the robot. Rather than using the Euclidean metric to determine clearance, a special metric which captures information about the nonholonomy of the robot is used. The robot navigates from start to goal states by loosely following the skeleton. The resulting paths taken by the robot are of low complexity. Much of the computation can be done offline for a given robot, making for an efficient planner. The focus is on path planning for mobile robots, particularly the planar two-axle car, but the underlying ideas may be applied to planners for other nonholonomic robots. >

97 citations


DissertationDOI
01 Jan 1992
Abstract: The term "hyper-redundant" refers to robotic manipulators and mobile robots with a very large, possibly infinite, number of actuatable degrees of freedom. These robots are analogous in morphology and operation to snakes, worms, elephant trunks, and tentacles. This thesis presents a novel kinematic framework for hyper-redundant manipulator motion planning and task implementation. The basis of this formulation is the use of a "backbone reference set" which captures the essential macroscopic geometric features of hyper-redundant robots. In the analytical part of this work, the backbone representation is developed and used to solve problems in obstacle avoidance, locomotion, grasping, and "optimal" end effector placement. The latter part of this thesis deals with the design and implementation of a thirty-degree-of-freedom planar hyper-redundant manipulator which is used to demonstrate these novel kinematic and motion planning techniques. Design issues such as robustness with respect to mechanical failure, and design for easy assembly and repair are also addressed. The analytical and design concepts are combined to illustrate tasks for which hyper-redundant robotic mechanisms are well suited.

88 citations


Proceedings ArticleDOI
12 May 1992
TL;DR: The authors introduce a novel formulation of subtask performance for redundant manipulators that uses the singularity robust inverse (SRI) in conjunction with a homogeneous-like joint velocity component to perform an additional subtask such as obstacle avoidance.
Abstract: The authors introduce a novel formulation of subtask performance for redundant manipulators. This formulation uses the singularity robust inverse (SRI), which is effective in yielding feasible joint motions in single regions, in conjunction with a homogeneous-like joint velocity component to perform an additional subtask such as obstacle avoidance. This novel inverse kinematic scheme enables the manipulator to overcome singularities (or, more accurately, avoid infeasible joint motions at or near singular configurations) and avoid obstacles in addition to the main motion task. The attractive aspect of this scheme is that it results in the satisfaction of two subtasks without requiring two explicit subtask criteria. This is because one of the subtasks, i.e., feasible joint motion, is implicitly incorporated in the particular solution in the form of the SRI. As depicted in simulations, the proposed formulation proves to be an effective inverse kinematic solution in singular regions of the manipulator workspace. >

72 citations



Patent
Ishikawa Shigeki1
06 Apr 1992
TL;DR: In this paper, the authors used fuzzy inference to estimate the distance and angle from a predetermined path and the obstacle-free space ahead of the machine to avoid collisions with obstacles. But they did not consider the obstacle avoidance.
Abstract: The present apparatus, control system, and method for navigating is used to navigate a mobile machine accurately along a traced path so that the machine avoids collisions with obstacles. Intermediate control outputs are generated not only in accordance with a signal indicative of a distance and angle from a path to be traced according to a navigation procedure for path tracing, but also in response to a signal related to the obstacle-free space ahead of the machine according to a navigation procedure for obstacle avoidance. Weighting coefficients respective for the two procedures are generated by fuzzy inference based on signals indicating the distance and angle from the predetermined path and signals related to the obstacle-free space ahead of the machine. Final control outputs are computed in accordance with the two intermediate outputs and the two weighting coefficients. Regardless of the number of obstacles a mobile machine comes across while moving along a path, and of whether or not they are moving, the mobile machine can avoid them reliably and smoothly.

54 citations


Journal ArticleDOI
TL;DR: This paper is concerned with a particular aspect of the resolution of this redundancy, which is its utilization to optimize the system's position and configuration during task commutations when changes occur in both task requirements and task constraints.
Abstract: Mobile manipulators are attracting significant interest in the industrial, military, and public service communities because of the potential they provide for increased efficiency in material handling and manipulation tasks. Corresponding interest has arisen in the robotics research community since the combination and coordination of the mobility of an autonomous platform with the robotic motion of a manipulator introduce complex analytical problems. One such problem arises from the particular kinematic redundancy which characterizes practical mobile manipulators. This paper is concerned with a particular aspect of the resolution of this redundancy, which is its utilization to optimize the system's position and configuration during task commutations when changes occur in both task requirements and task constraints. Basic optimization schemes are developed for cases when load and position constraints are applied at the end-effector. Various optimization criteria are investigated for task requirements including obstacle avoidance, maneuverability and several torque functions. The problem of optimally positioning the platform for execution of a manipulation task requiring a given reach is also treated. Emphasis is then placed on the multi-criteria optimization methods which are necessary to calculate the commutation configurations in sequences of tasks with varying requirements. Sample results are presented for a system involving a three-link planar manipulator on a mobile platform. The various optimization schemes are discussed and compared, and several directions (in particular the novel use of minimax optimization pioneered here for redundancy resolution) are outlined for further extensions of the methods to the general problem of motion planning and control of redundant robotic systems with combined mobility and manipulation capabilities.

53 citations


Journal ArticleDOI
TL;DR: This work addresses the implementation issues of sensor-based motion planning system for a robot arm manipulator operating among unknown obstacles of arbitrary shape that includes infrared based proximity sensitive skin covering the arm body, computer hardware for signal processing and motion planning, and an interface between the planning and arm control systems.

Proceedings ArticleDOI
16 Dec 1992
TL;DR: A novel strategy for coordination of multiple autonomous robots by using genetic algorithms (GAs) is presented, which is applied to both the selfish planning and the coordinative planning of multiple mobile robots.
Abstract: A novel strategy for coordination of multiple autonomous robots by using genetic algorithms (GAs) is presented. When a mobile robot moves from a point to a goal point, it is necessary to plan an optimal or feasible path for it, avoiding obstructions in its way and minimizing costs such as time, energy, and distance. This planning is referred to as selfish planning. When many robots move in the same space, it is necessary to select the most reasonable path so as to avoid collisions with other robots and to minimize the cost. This planning is referred to as coordinative planning. The GAs are search algorithms based on the mechanics of natural selection and natural genetics. The GAs are applied to both the selfish planning and the coordinative planning of multiple mobile robots. >

Proceedings ArticleDOI
H.R. Beom, Hansol Cho1
07 Jul 1992
TL;DR: A sensor-based path planning method which utilizcs fuzzy logic and neural network for obstacle avoidancc of a mobile robot in uncertain environments and has a merit that the fuzzy rules €or obstacle avoidance can be easily constructed for more cornplcx environments.
Abstract: Abslmct-This paper proposes a sensor-based path planning method which utilizcs fuzzy logic and neural network for obstacle avoidancc of a mobile robot in uncertain environments. In order to acquire the information about the environment around the mobile robot, the ultrasonic sensors mounted on the front of mobile robot are used. The neural network, whose inputs arc preprocessed by ultrasonic sensor readings, informs the mobile robot of the situation of environment in which mobile robot is at the present instant. Then, according to the situatiou class, the fuzzy rules are fired to make a decision on the mobilc robot action. This structure has a merit that the fuzzy rules €or obstacle avoidance can be easily constructed for more cornplcx environments. In addition, this method can be implcrncoted real time sincc the number of fuzzy rules used to avoid the obstacles is small. The fuzzy rules are constructed based on the human reasoning and are tuned by iterative simulations. The cffectivcness of the proposed avoidance method is vcrilicd by a series of simulations. Path planning is one of tlie most vital task in navigation of autonomous niobiic robot. Path planning for mobile robot may be tlivitletl illto two categories: One is the global path planning based on a priori complete inforniation about the environment antl the other is the local path pliinning based on sensory information i n uncertain environnient where the size, shape and loc,atioii of ol)stacles are UllIi1lo\v11. nietliotl incliitlcs configuration space Voronoi diiigraiii[2] and potential field out i n oft-line iii:aiinc:r. 1-Iowever, this metliod is not suitable for ntivigiition i n coiiiples and dynamically changing environment where uiiliiiown obstacles niiiy be located on a priori planned path. Thus, this inc~thotl niust be followed by sensor-based local path planning, so ciilletl obstacle avoidance, carried out in on-line nianncr. Local pittli plxnning utilizes tlie information provided by sensor suc,li as ultrasonic sensor, vision, laser range finder, proximity sensor and binnper switch R.A.Brooks[4] applied tlie for(;c-fielti concept to obstacle avoidance problem for mobile robot equipped with ultrasonic, sensors whose readings are used to compute the I-esultant repulsive force. Borenstein and I


Journal ArticleDOI
01 May 1992-Robotica
TL;DR: A real-time obstacle avoidance algorithm for autonomous mobile robots that is more efficient and more robust than other sensor-based algorithms and will guarantee a solution for the obstacle avoidance problem.
Abstract: A real-time obstacle avoidance algorithm is proposed for autonomous mobile robots. The algorithm is sensor-based and consists of a H-mode and T-mode. The algorithm can deal with a complicated obstacle environment, such as multiple concave and convex obstacles. It will be shown that the algorithm is more efficient and more robust than other sensor-based algorithms. In addition, the algorithm will guarantee a solution for the obstacle avoidance problem. Since the algorithm only takes up a small computational time, it can be implemented in real time.

Proceedings ArticleDOI
07 Jun 1992
TL;DR: A hybrid-network method for obstacle avoidance in the truck-backing system of D. Nguyen and B. Widrow (1989) and a neural network technique for vehicle navigation and control in the presence of obstacles has been developed.
Abstract: A hybrid-network method for obstacle avoidance in the truck-backing system of D. Nguyen and B. Widrow (1989) is presented. A neural network technique for vehicle navigation and control in the presence of obstacles has been developed. A potential function which peaks at the surface of obstacles and has its minimum at the proper vehicle destination is computed using a network structure. The field is guaranteed not to have spurious local minima and does not have the property of flattening-out far from the goal. A feedforward neural network is used to control the steering of the vehicle using local field information. The network is trained in an obstacle-free space to follow the negative gradient of the field, after which the network is able to control and navigate the truck to its target destination in a space of obstacles which may be stationary or movable. >

Proceedings ArticleDOI
29 Jun 1992
TL;DR: A novel approach to obstacle detection using optical flow without recovering range information has been developed and a linear relationship, plotted as a line and called a reference flow line, has been found, which can be used to detect discrete obstacles above or below the reference terrain.
Abstract: A novel approach to obstacle detection using optical flow without recovering range information has been developed. This method can be used for ground vehicles to navigate through man-made roadways or natural outdoor terrain or for air vehicles to land on known or unknown terrain. A linear relationship, plotted as a line and called a reference flow line, has been found. This reference flow line can be used to detect discrete obstacles above or below the reference terrain. Slopes of surface regions are also computed. The approach is simple, fast, and robust because: (1) the only required information is one component of the optical flow, (2) each image line can be processed in parallel, and (3) the error sources involved are reduced to a minimum. An initial experiment using noisy synthetic data is also included to demonstrate the applicability and robustness of the method. >

Journal ArticleDOI
Barry A. Roberts1, Bir Bhanu1
TL;DR: The approach to obstacle detection employs motion analysis of imagery collected by a passive sensor during vehicle travel to generate range measurements to world points within the field of view of the sensor.
Abstract: Recent work on INS integrated motion analysis is described. Results were obtained with a maximally passive system of obstacle detection (OD) for ground-based vehicles and rotorcraft. The OD approach involves motion analysis of imagery acquired by a passive sensor in the course of vehicle travel to generate range measurements to world points within the sensor FOV. INS data and scene analysis results are used to enhance interest point selection, the matching of the interest points, and the subsequent motion-based computations, tracking, and OD. The most important lesson learned from the research described here is that the incorporation of inertial data into the motion analysis program greatly improves the analysis and makes the process more robust.

Journal ArticleDOI
TL;DR: This paper describes the theory and an experiment of a velocity potential approach to path planning and avoiding moving obstacles for an autonomous mobile robot by use of the Laplace potential and verifies the effectiveness of the navigation function for obstacle avoidance in a real world.
Abstract: This paper describes the theory and an experiment of a velocity potential approach to path planning and avoiding moving obstacles for an autonomous mobile robot by use of the Laplace potential. This new navigation function for path planning is feasible for guiding a mobile robot avoiding arbitrarily moving obstacles and reaching the goal in real time. The essential feature of the navigation function comes from the introduction of fluid flow dynamics into the path planning. The experiment is conducted to verify the effectiveness of the navigation function for obstacle avoidance in a real world. Two examples of the experiment are presented; first, the avoidance of a moving obstacle in parallel line-bounded space, and second, the avoidance of one moving obstacle and another standing obstacle. The robot can reach the goal after successfully avoiding the obstacles in these cases.

Proceedings ArticleDOI
12 May 1992
TL;DR: Evaluation of the guidance and control system with a 3-dimensional graphical helicopter simulation suggests that the guidance has the potential for providing good and meaningful flight trajectories.
Abstract: The authors describe the implementation of a full-function guidance and control system for automatic obstacle avoidance in helicopter nap-of-the-earth (NOE) flight. The guidance function assumes that the helicopter is sufficiently responsive so that the flight path can be readily adjusted at NOE speeds. The controller, basically an autopilot for following the derived flight path, was implemented with parameter values to control a generic helicopter model used in the simulation. Evaluation of the guidance and control system with a 3-dimensional graphical helicopter simulation suggests that the guidance has the potential for providing good and meaningful flight trajectories. >

Journal ArticleDOI
TL;DR: In environments described with two-dimensional convex polygonal cells, it is shown that maneuvering can be completely handled with geometric reasoning and allows not only precise calculation of the trajectories within the convex cells, but also extremely fast path-planning computation.

Journal ArticleDOI
TL;DR: It is shown that it is possible to avoid obstacles without recovering depth and a detailed algorithm is provided for obstacle avoidance using the spatiotemporal derivatives of the image intensity function as input.
Abstract: Is it possible to perform nontrivial visual tasks without using passive ranging? Is it necessary to create, using vision, an accurate 3-D description of the outside world to recognize, navigate, and manipulate? Could a visual system perform obstacle avoidance without reconstructing the depth of the scene in view, but through the recognition of a collision in some amount of time that is quite small and not far into the future? In this article, it is shown that it is possible to avoid obstacles without recovering depth and a detailed algorithm is provided for obstacle avoidance using the spatiotemporal derivatives of the image intensity function as input. © 1992 John Wiley & Sons, Inc.

Proceedings ArticleDOI
12 May 1992
TL;DR: A computationally efficient method to achieve reflexive collision avoidance that incorporates task-space-based attraction to a hand goal, while the reflexes permit use of kinematic redundancy for obstacle avoidance.
Abstract: A computationally efficient method to achieve reflexive collision avoidance is described. The system consists of four parallel, asynchronous control layers: a conventional servo tracking controller, a reactive trapezoidal velocity profiler, a joint-by-joint reflexive collision avoidance layer, and a guiding potential-function layer. The lowest two layers guarantee that the robot will not overshoot any joint-space position setpoint. The higher two layers compute successive set points based on a continuous, online inspection of configuration space. The guiding potential-function layer incorporates task-space-based attraction to a hand goal, while the reflexes permit use of kinematic redundancy for obstacle avoidance. In many cases, no explicit path planning is required to achieve competent, collision-free motion to a task-space goal while moving in a cluttered environment. Experimental results are described for the physical implementation of the system on the first four joints of a kinematically redundant robot. >

01 Jan 1992
TL;DR: In this paper, the authors discuss the technologies required for automating rotorcraft nap-of-the-earth flight, where the use of natural obstacles for masking from the enemy is intentional and the danger of undesirable obstacles such as enemy traps is real.
Abstract: This paper discusses the technologies required for automating rotorcraft nap-of-the-earth flight, where the use of natural obstacles for masking from the enemy is intentional and the danger of undesirable obstacles such as enemy traps is real. Specifically, the automatic guidance structure is modeled by three decision-making levels: the far-field mission planning and the mid-field terrain-masking trajectory shaping are both driven by prestored terrain data, whereas the nearfield obstacle detection/avoidance is driven by real-time on-board sensor data. This paper summarizes the far-field and mid-field accomplishments, and reports on the status of the more-recent efforts in obstacle detection and avoidance development. Obstacle detection is based primarily on passive imaging sensors for the desirable properties of covertness and wide field of view, although active sensors are included in the structure to provide the much needed high resolution for thin-wire detection.

Proceedings ArticleDOI
12 May 1992
TL;DR: A method for mobile robot motion planning is presented for both two- and three-dimensional robots, based on complex variable theory and conformal mapping, which gives the robot the capability of avoiding obstacles more efficiently, smoothly, and at a constant curvilinear velocity.
Abstract: A method for mobile robot motion planning is presented for both two- and three-dimensional robots. For the two-dimensional case, the algorithm is based on complex variable theory and conformal mapping. The method gives the robot the capability of avoiding obstacles more efficiently, smoothly, and at a constant curvilinear velocity. In order to establish the structure of the proposed velocity feedback obstacle avoidance scheme, several issues are addressed and successfully resolved. First, an analytical solution is derived for the case of circular obstacles. Second, the algorithm uses conformal mapping to establish the solution for an arbitrarily shaped obstacle based on the derived solution for a circular obstacle. The use of complex variable methodology with the objectives of exploiting the powerful technique of uniformal mapping constitutes the fundamental characteristic of the proposed technique. Third, by analogy, a solution to 3-D space-flying and subsea robots is also derived. >

Proceedings ArticleDOI
12 May 1992
TL;DR: A formulation that makes possible the integration of collision prediction and avoidance stages for mobile robots moving in general terrains containing moving obstacles is presented and local asymptotic stability is proved if the velocity of the moving obstacle is bounded.
Abstract: A formulation that makes possible the integration of collision prediction and avoidance stages for mobile robots moving in general terrains containing moving obstacles is presented. A dynamic model of the mobile robot and the dynamic constraints are derived. Collision avoidance is guaranteed if the distance between the robot and a moving obstacle is nonzero. A nominal trajectory is assumed to be known from off-line planning. The main idea is to change the velocity along the nominal trajectory so that collisions are avoided. A feedback control is developed and local asymptotic stability is proved if the velocity of the moving obstacle is bounded. Simulation results verify the value of the proposed strategy. >


Journal ArticleDOI
TL;DR: An efficient method for computing the minimum distance and predicting collisions between moving objects is presented, incorporated in the framework of an in-line motion planning algorithm to satisfy collision avoidance between a robot and moving objects modelled as convex polyhedra.

Proceedings ArticleDOI
01 Nov 1992
TL;DR: This paper describes a vision-based method for avoiding obstacles using the concepts of visual looming and fixating motion, which is simple, independent of the size of the 3-D object and its range and involves simple quantitative measurements.
Abstract: This paper describes a vision-based method for avoiding obstacles using the concepts of visual looming and fixating motion. Visual looming refers to the expansion of images of objects in the retina. Usually, this is due to the decreasing distance between the observer and the object. An increasing looming value signifies an increasing threat of collision with the object. The visual task of avoiding collision can be further simplified by purposive control of visual fixation at the objects in front of the moving camera. Using these two basic concepts real time obstacle avoidance in a tight perception-action loop is implemented. Three-dimensional space in front of the camera is divided into zones with various degrees of looming-based threat of collision. For each obstacle seen by a fixating camera, looming and its time derivative are calculated directly from the 2-D image. Depending on the threat posed by an obstacle, a course change is dictated. This looming based approach is simple, independent of the size of the 3-D object and its range and involves simple quantitative measurements. Results pertinent to a camera on a robot arm navigating between obstacles are presented.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Journal ArticleDOI
01 Nov 1992-Robotica
TL;DR: An algorithm for kinematic motion planning of redundant planar robots, having revolute joints, in an unknown dynamic environment is presented and cases of link overlap have been avoided by considering each link as a body which is sensed as an obstacle by every other link of the same manipulator.
Abstract: An algorithm for kinematic motion planning of redundant planar robots, having revolute joints, in an unknown dynamic environment is presented. Distance ranging sensors, mounted on the body of each manipulator link, are simulated here to estimate the proximity of an obstacle. The sensory data is analyzed through a fuzzy controller which estimates whether a collision is imminent, and if so, employs a geometric approach to compute the joint movements necessary to avoid the collision. Obstacles can sometimes move uncompromisingly in the environment attempting a deliberate collision. Strategies to deal with such cases are presented and recovery procedures to circumvent the obstacle from tight corners are suggested. Cases of link overlap have been avoided by considering each link as a body which is sensed as an obstacle by every other link of the same manipulator. Suitable examples are presented to demonstrate the algorithm.