Showing papers on "Motion planning published in 1984"

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.

Path Relaxation: Path Planning for a Mobile Robot

Abstract: Path Relaxation is a method of planning safe paths around obstacles for mobile robots. It works in two steps: a global grid search that finds a rough path, followed by a local relaxation step that adjusts each node on the path to lower the overall path cost. The representation used by Path Relaxation allows an explicit tradeoff among length of path, clearance away from obstacles, and distance traveled through unmapped areas.

Re-definition of the robot motion control problem: Effects of plant dynamics, drive system constraints, and user requirements

Abstract: The objective of this paper is a redefinition of the robot control problem, based on realistic (1) models for the industrial robot as a controlled plant, (2) end effector trajectories consistent with manufacturing applications, and (3) the need for end-effector sensing to compensate for uncertainties inherent to most robotic manufacturing applications. Based on extensive analytical and experimental studies, realistic robot dynamic models are presented that have been validated over the frequency range 0 to 50 Hz. These models exhibit a strong influence of drive system flexibility, producing lightly damped poles in the neighborhood of 8 Hz, 14 Hz, and 40 Hz, all unmodeled by the conventional rigid body multiple link robot dynamic approach. The models presented also quantify the significance of nonlinearities in the drive system, in addition to those well-known in the linkage itself. Realistic simulations of robot dynamics and motion controls demonstrate that existing controls coupled with effective path planning produce dynamic path errors that are acceptable for most manufacturing applications. Major benefits are projected, with examples cited, for use of end-effector sensors for position, force, and process control that compensate for uncertainties encountered on the factory floor.

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.

Automatic planning of fine motions: Correctness and completeness

Abstract: In this paper we explore a method for automatic planning of robot fine-motion programs, first described in [Lozano-Perez, Mason, and Taylor 1983]. The primary result is a variation that is shown to be "bounded-complete"-the method obtains a solution whenever a solution consisting of a bounded number of motions exists.

On the Motion of Objects in Contact

Abstract: There is an increasing use of computers in the design, manufacture and manipulation of physical objects. An important aspect of reasoning about such actions concerns the motion of objects in contact. The study of problems of this nature requires not only the ability to represent physical objects but the development of a framework or theory in which to reason about them. In this paper such a development is investigated and a fundamental theorem concerning the motion of objects in contact is proved. The simplest form of this theorem states that if two objects in contact can be moved to another configuration in which they are in contact, then there is a way to move them from the first configuration to the second configuration such that the objects remain in contact throughout the motion. This result is proved when translation and rotation of objects are allowed. The problem dealing with more generalized types of motion is also discussed. This study has obvious applications in compliant motion and in motion planning.

On the Piano Movers' Problem. V. The Case of a Rod Moving in Three- Dimensional Space Amidst Polyhedral Obstacles,

Abstract: This paper, a fifth in a series, solves some additional 3-D special cases of the „piano movers” problem, which arises in robotics. The main problem solved in this paper is that of planning the motion of a rod moving amidst polyhedral obstacles. We present polynomial-time motion-planning algorithms for this case, using the connectivity-graph technique described in the preceding papers. We also study certain more general polyhedral problems, which arise in the motion planning problem considered here but have application to other similar problems. Application of these techniques to the problem of planning the motion of a general polyhedral body moving in 3-space amidst polyhedral obstacles is also described.

Path relaxation: path planning for a mobile robot

Abstract: Path Relaxation is a method of planning safe paths around obstacles for mobile robots It works in two steps: a global grid search that finds a rough path, followed by a local relaxation step that adjusts each node on the path to lower the overall path cost The representation used by Path Relaxation allows an explicit tradeoff among length of path, clearance away from obstacles, and distance traveled through unmapped areas

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.

Reducing Multiple Object Motion Planning To Graph Searching

Abstract: In this paper we study the motion planning problem for multiple objects where an object is a 2-dimensional body whose faces are line segments parallel to the axes of $R^{2}$ and translations are the only motions allowed. Towards this end we analyze the structure of configuration space, the space of points that correspond to positions of the objects. In particular, we consider CONNECTED, the set of all points in configuration space that correspond to configurations of the objects where the objects form one connected component. We show that CONNECTED consists of faces of various dimensions such that if there is a path in CONNECTED between two 0-dimensional faces (vertices) of CONNECTED then there is a path between them along 1-dimensional faces (edges) of CONNECTED. It is known that if there is a motion between the configurations. Thus by the result of this paper the existence of a motion between two vertices of CONNECTED implies a motion corresponding to a path along edges of CONNECTED. Hence we have reduced the motion planning problem from a search of a high dimensional space to a graph searching problem. Searching the graph of vertices and edges of CONNECTED for a path has a prohibitive worse-case complexity because of the large number of vertices and edges. However, if the search generates edges and vertices only as they are needed, a practical and efficient algorithm may be possible using some effective heuristic. From this result it is shown that motion planning for rectangles in a rectangular boundary is in PSPACE. Since it is known that the problem is PSPACE-hard we conclude it is a PSPACE-complete problem.

Planning Collision-Free Paths for Robotic Arm Among Obstacles

Abstract: A theory for planning collision-free paths of a moving object among obstacles is described. Using the concepts of state space and rotation mapping, the relationship between the positions and the corresponding collision-free orientations of a moving object among obstacles is represented as some set of a state space. This set is called the rotation mapping graph (RMG) of that object. The problem of finding collision-free paths for an object translating and rotating among obstacles is thus transformed to that of considering the connectivity of the RMG. Since the connectivity of the graph can be solved by topological methods, the problem of planning collision-free paths is easily solved in theory. Using this theory, a topological method for planning collision-free paths of a rod-object translating and rotating among obstacles is presented. If a nonrigid robotic arm is viewed as a composite rod with some degrees of freedom, the planning of collision-free paths of a robotic arm can be solved in a similar way to a rod.

Effect of uncertainty on continuous path planning for an autonomous vehicle

Abstract: This paper describes one approach to the problem of path planning for an autonomous vehicle (an automaton) moving in two-dimensional space filled with obstacles. The approach is based on continuous processing of incoming local information about the environment. A continuous computational model for the environment and for the vehicle operation is presented. Information about the environment (the scene) is assumed to be incomplete except that at any moment the vehicle knows the coordinates of its target as well as its own coordinates. The vehicle is presented as a point; obstacles can be of any shape, with continuous borderline and finite size. Algorithms guaranteeing reaching the target (if the target is reachable), and tests for target reachability are presented. The efficiency of the algorithms is evaluated in terms of perimeters of obstacles met by the vehicle. It is shown that with the exception of some rather unusual initial positions of the vehicle relative to the obstacles, one of the presented algorithms guarantees an optimal path.

Motion Planning with Six Degrees of Freedom. Revision

Abstract: : The motion planning problem is of central importance to the fields of robotics, spatial planning, and automated design An implemented algorithm is presented for the 'classical' formulation of the three-dimensional Movers' problem: Given an arbitrary rigid polyhedral moving object 'p' with three translational and three rotational degrees of freedom, find a continuous, collision free path taking 'p' from some initial configuration to a desired goal configuration 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 By characterizing these surfaces and their intersection collision-free paths may be found by the closure of three operators which (i) slide along 5-dimensional level C-surfaces parallel to C-Space obstacles; (ii) slide along 1- to 4-dimensional intersections of level C-surfaces; and (iii) jump between 6-dimensional obstacles

Algorithm of navigation for a mobile robot

Abstract: This study describes the theoretical and practical aspects of the design and computer simulation of a heuristic based navigation algorithm. An algorithm is developed which provides a convenient testing system for generalized navigation strategies on a fixed map which may be known or unknown to a system. A variety of maps are simulated and the navigation results are compared.

Multilevel Path Planning For Autonomous Vehicles

Abstract: A system that performs automatic path planning for an autonomous land vehicle is described. It uses three levels of planning: a mission planner, a long range planner, and a local planner. The system relies both on a digital database and sensor-based information to plan a route, and it has been implemented as a software simulation for robotic vehicles.

An Efficient Minimum-Time Robot Path Planning under Realistic Conditions

Abstract: In this paper, we have developed a method for minimum-time path planning in joint space subject to realistic constraints. This method differs from others in that: (i) an absolute path deviation at each corner point of the path can be specified, (ii) local upper bounds on joint accelerations are derived from the arm dynamics so as to nearly fully utilize robot's capabilities, and (iii) a set of Local optimization problems--one at every local corner point--are employed to replace the global minimum-time problem, thus making the minimum-time path planning problem simpler. As a demonstrative example, we have applied the method to the path planning of the first three joints of the Unimation PUMA 600 series manipulator. The example has indeed shown significant improvements in the total traveling time in addition to the computational simplicity obtained from the decomposition of the global problem into a set of local problems.

Experience with Visual Robot Navigation

Abstract: The CMU Mobile Robot Lab is studying issues in the development of autonomous vehicles, including path planning, motion determination, and obstacle detection from video and sonar data We have built a simple testbed vehicle and a visual navigation system designed to maneuver to a pre-defined location in a static environment The visual system is based on algorithms developed by Moravec for the Stanford Cart [10] At each Cart position, these algorithms used stereo correspondence in nine camera images to triangulate the distance to potential obstacles Motion of the vehicle was determined by tracking these obstacles over time This paper discusses several issues in the on-going evolution from the Cart to our present system These issues have led to the use of fewer images per step, to the use of more constraint in the correspondence process, and toward the use of a different motion solving algorithm that better embodies the rigidity property inherent in the problem

A computer simulation study of omnidirectional supervisory control for rough-terrain locomotion by a multilegged robot vehicle

Abstract: This dissertation presents motion planning algorithms to provide omnidirectional control of a multilegged robot vehicle over rough-terrain using a three-axis joystick. The algorithms have been developed through computer simulation using a graphics device. They are based on the development of the kinematics of legged locomotion over rough terrain. The hexapod vehicle model used is for the Adaptive Suspension Vehicle (ASV) which is presently under construction at The Ohio State University. In order to implement periodic gaits for omnidirectional control, the notion of the constrained working volume has been introduced on the basis of reachability of the leg. The optimal cycle period is selected in such a way that at least one leg fully utilizes its constrained working volume. For control of the body motion over rough terrain, the local terrain surface is estimated by using six points of estimation based on the measurements from the six legs. Also, a simple body regulation plan has been designed which results in the body attitude adjusting to the terrain slope and the body height decreasing with greater slope. In order to control the leg motion in the transfer phase, a simple parallelogrammatic type of foot trajectory has been developed. It allows the proximity sensors to detect the potential footholds and to control the footlift height during the transfer phase. Also, the adjustment of the position and dimensions of the constrained working volume to increase the stability of the vehicle over sloped terrain has been implemented. The algorithms have been implemented in PASCAL on the PDP-11/70 minicomputer. The evaluation of the control algorithms for the ASV is also given.

The Configuration Space Approach to Robot Path Planning

Abstract: Graphically simulated configuration maps are used to plan manipulator paths in two-dimensions. Configuration maps represent a transformation of the Cartesian workspace into the manipulator joint coordinates, identifying both the free space and the space occupied by obstacles. Visual examination of the configuration map allows simulation users to plan collision-free paths by maneuvering the manipulator point along a series of path line segments which connect starting and final manipulator configurations. A PUMA 600 revolute manipulator experimentally verifies one such path planned through a congested workspace.

Robot path planning using dynamic programming

Abstract: This paper presents a solution to the problem of minimizing the cost of moving a robotic manipulator along a specified geometric path subject to input torque/force constraints, taking the coupled, nonlinear dynamics of the manipulator into account. The proposed method uses dynamic programming (DP) to find the positions, velocities, accelerations, and torques that minimize cost. Since the use of parametric functions reduces the dimension of the state space from 2n for an n-jointed manipulator to two, the DP method does not suffer from the "curse of dimensionality". While maintaining the elegance of the path planning methods in [1], [11], the DP method offers the advantages that it can be used in the general case where (i) the actuator torque limits are dependent on one another, (ii) the cost functions can have an arbitrary form, and (iii) there are constraints on the jerk, or derivative of the acceleration. As a numerical example, the path planning method is simulated for a two-jointed robotic manipulator. The example considers first the minimum-time problem, comparing the solution with that of the phase plane plot method in [11]. Secondly, the sensitivity of the path solutions to the grid size is examined. Finally, the DP method is applied to cases with interactions between joint torque bounds and with cost functions other than minimum-time, demonstrating its power and flexibility.

Interaction Between Subsystems Of Vision And Motion Planning In Unmanned Vehicles With Autonomous Intelligence

Abstract: A structure of preprocessing is described corresponding to a planner strata of the "perception-cognition" interaction within the machine intelligence for an autonomous mobile vehicle. A terraine is represented via a polygonal map. Algorithms are described which transform such a map into a database which can be used by PLANNER to solve motion planning problem.© (1984) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Sensor‐based obstruction avoidance technique for a mobile robot

Abstract: This article describes a sensor-based obstruction avoidance technique. This technique, if implemented on the on-board computer of a mobile robot, would enable the robot to move through an unknown environment. The proposed approach is driven by sensory data. The robot thus senses and adapts to the changes in the environment. The software also does path planning. As more information about the environment is obtained the robot's path planning capabilities improve. Illustrative examples are used to describe the algorithms.

The Flight Planning - Flight Management Connection

Abstract: Airborne flight management systems are currently being implemented to minimize direct operating costs when flying over a fixed route between a given city pair. Inherent in the design of these systems is that the horizontal flight path and wind and temperature models be defined and input into the airborne computer before flight. The wind/temperature model and horizontal path are products of the flight planning process. Flight planning consists of generating 3-D reference trajectories through a forecast wind field subject to certain ATC and transport operator constraints. The inter-relationships between flight management and flight planning are reviewed, and the steps taken during the flight planning process are summarized.

Automatic Synthesis of Robot Programs from CAD Specifications

Abstract: Industrial robots require more and more advanced programming tools. After “teaching by showing” techniques, manipulator-level programming languages for describing tasks by sequences of robot operations have emerged, and they to-day become widespread in industry. However, writting manipulators-level programs is not easy. This difficulty arises the need for higher level languages called task-level languages, for describing assembly tasks as sequences of goal spatial relationships between objects. Translating such a description into a manipulator-level program requires to solve three main problems: grasp planning, path planning, and fine motion planning. This paper surveys recent progress toward solving these problems. Task-level languages may deeply transform the way we will program robots in the future, and they contribute to better CAD/CAM integration.

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.

On Motion Planning with Uncertainty. Revised.

Abstract: : Robots must successfully plan and execute tasks in the presence of uncertainty. Uncertainty arises from errors in modelling, sensing, and control. Planning in the presence of uncertainty constitutes one facet of the general motion planning problem in robotics. This problem is concerned with the automatic synthesis of motion strategies from high level task specifications and geometric models of environments. In order to develop successful motion strategies, it is necessary to understand the effect of uncertainty on the geometry of object interactions. Object interactions, both static and dynamic, may be represented in geometrical terms. This thesis investigates geometrical tools for modelling and overcoming uncertainty. The thesis describes an algorithm for computing backprojections of desired task configurations. Task goals and motion states are specified in terms of a moving object's configuration space. Backprojections specify regions in configuration space from which particular motions are guaranteed to accomplish a desired task. The backprojection algorithm considers surfaces in configuration space that facilitate halt.