Showing papers on "Obstacle avoidance published in 1984"

Impedance Control: An Approach to Manipulation

Abstract: Manipulation fundamentally requires a manipulator to be mechanically coupled to the object being manipulated. A consideration of the physical constraints imposed by dynamic interaction shows that control of a vector quantity such as position or force is inadequate and that control of the manipulator impedance is also necessary. Techniques for control of manipulator behaviour are presented which result in a unified approach to kinematically constrained motion, dynamic interaction, target acquisition and obstacle avoidance.

Obstacle avoidance using an octree in the configuration space of a manipulator

Abstract: An automatic system for planning safe trajectories for a computer controlled manipulator among obstacles is a key component of robot assembly operations. This paper describes an algorithm transforming cartesian obstacles into obstacles in the space of the first three joints of a manipulator with six revolute joints (e.g. a ACMA-CRIBIER V80), and giving a hierarchical description of the free space by mean of an octree. Such a description is very useful in testing for collision between the arm of the manipulator end obstacles since it is represented by a point in this space.

Motion Planning with Six Degrees of Freedom

Abstract: : The motion planning problem is of central importance to the fields of robotics, spatial planning, and automated design. In robotics we are interested in the automatic synthesis of robot motions, given high-level specifications of tasks and geometric models of the robot and obstacles. The Mover's problem is to find a continuous, collision-free path for a moving object through an environment containing obstacles. This thesis describes the first known implementation of a complete algorithm (at a given resolution) for the full six degree of freedom Movers' problem. The algorithm transforms the six degree of freedom planning problem into a point navigation problem in a six-dimensional configuration space (called C-Space). The C-Space obstacles, which characterize the physically unachievable configurations, are directly represented by six-dimensional manifolds whose boundaries are five dimensional C-surfaces. Implementing the point navigation operators requires solving fundamental representational and algorithmic questions: we will derive new structural properties of the C-space constraints and show how to construct and represent C-surfaces and their intersection manifolds. Originator-Supplied keywords include: Motion planning, Configuration space, Generalized Voroni diagram, Piano mover's problem, Computational geometry, Path planning, Robotics, Spatial reasoning, Geometric modelling, Obstacle avoidance, Geometric planning, Collision avoidance.

Minimum distance collision-free path planning for industrial robots with a prismatic joint

Abstract: A collision-free path is a path which an industrial robot can physically take while traveling from one location to another in an environment containing obstacles. Usually the obstacles are expanded to compensate for the body width of the robot. For robots with a prismatic joint, which allows only a translational motion along its axis, additional problems created by the long boom are handled by means of pseudoobstacles which are generated by real obstacle's edges and faces. The environment is then modified by the inclusion of pseudoobstacles which contribute to the forbidden regions. This process allows the robot itself again to be represented by a point specifying the location of its end effector in space. An algorithm for determining the shortest distance collision-free path given a sequence of edges to be traversed has been developed for the case of stationary obstacles.

A Scheme for Collision Avoidance with Minimum Distance Traveling for Industrial Robots

Abstract: Maneuvering an industrial robot to avoid a collision with obstacles in real time involves not only the fast obstacle detection and descripton, but also fast decision making. The problem is complicated since no a priori knowledge about obstacles is assumed. In addition, they may appear in the robot's path unexpectedly. To detect and describe the three-dimensional obstacles, stereo cameras are used to collect environmental images. Through the top view of the workspace, the cameras furnish the silhouette as well as heights of obstacles. To speed up the image processing, the pixel array is grouped into patches and the maximum height of each patch is determined. TO simplify the obstacle description in the computer, a “pillar” model of the bounding polyhedra is constructed. Fast decision making is accomplished by structuring a finite number of possible collision avoidance paths. Path feasibility is determined at the “module aisle” level while optimization is performed at the subpath level so that the magnitude of processing effort is reduced from the order of 6 to 3 × 6.

An Autonomous Vehicle Navigation Algorithm

Abstract: We present a simple heuristic-based navigation algorithm for autonomous vehicle con-trol. We assume sensor input in the form of a range scan of distances to closest obstacles at a variety of angles in the vehicle's field of view. The algorithm works within a 2-dimensional model of the world to solve the problem of obstacle avoidance : find a collision-free path from START to GOAL.

Planning of straight line manipulator trajectory in Cartesian space with torque constraints

Abstract: Most of the existing off-line trajectory planning schemes focus on the requirements that the trajectory must be smooth and continuous. This paper, based on discrete time trajectory analysis, extends these concepts and includes the manipulator dynamics in the planning of straight line trajectory in the Cartesian space. The planning of straight line trajectory is performed in the Cartesian space and requires optimization in the jointvariable space. An iterative forward and backward search algorithm coupled with a modified forward search algorithm are developed to determine the joint values at each control set point on the given straight line within the bounds imposed by the smoothness and torque constraints. These sets of joint position, velocity and acceleration will be used as referenced inputs to the manipulator controller for the joint-variable space control [1] or can be used to determine the corresponding Cartesian position, velocity, and acceleration on the straight line for the Cartesian space control. The proposed straight line trajectory planning will be useful for obstacle avoidance and the resolved motion adaptive control [2].

The application of distance functions to the optimization of robot motion in the presence of obstacles

Abstract: An approach to robotic path planning, which allows optimization of useful performance indices in the presence of obstacles, is given. The main idea is to express obstacle avoidance in terms of the distances between potentially colliding parts. Mathematical properties of the distance functions are studied and under certain conditions the derivatives of the distance functions are characterized. The results lead to a general formulation of path planning problems and suggest numerical procedures for their solution. A simple numerical example involving a 3-degree of freedom cartesian manipulator is described.

An Autonomous Roving Vehicle for the Planet Mars

Abstract: : The early efforts were directed chiefly toward deployment, structural, and suspension problems, and resulted in a storage-battery-powered vehicle that served as a test bed for later developments. The next phase involved the development of a primitive vision system for detecting obstacles. This consisted of a pulsed laser source and single photodetector both mounted on the same mast. As the mast is rotated, they scan the terrain ahead at fixed elevation angles such that a ground reflection should be received for relatively flat terrain. Azimuth angles for which no ground reflection is received are presumed to contain boulders or craters. This information is processed and used to guide the vehicle by means of telemetry and a remote computer. Results of extensive testing of this vehicle are summarized. A more sophisticated vision system was subsequently developed that continues to use triangulation as a basic feature, but scans the terrain ahead in two dimensions. The improved telemetry system and other hardware and software improvements are discussed, along with some fixed-position test results for this vision system. Some suggestions for the direction of future efforts are included. Problems that were not addressed in this work are obstacle avoidance and navigation for distances over three meters, and autonomous power sources suitable for extended travel.