Obstacle

About: Obstacle is a research topic. Over the lifetime, 9517 publications have been published within this topic receiving 94760 citations. The topic is also known as: impediment & barrier.

High speed robot control and obstacle avoidance using dynamic potential functions

Abstract: Time-optimal control of robot motion for dynamically decoupled manipulators is described in terms of potential functions. Avoidance of moving obstacles is incorporated via protective potential functions. An energy interpretation of the potential functions leads to rules for construction of avoidance functions and logical operations among them. Simple expressions for combining obstacle fields with an obstacle-free time-optimal solution result in the minimum safe influence of obstacles. Simulation results are given demonstrating high-speed target interception in the presence of obstacles.

Navigational control apparatus and method for autonomus vehicles

Abstract: A navigational apparatus and method is provided for autonomous vehicles having digitally controlled drive means for driving the vehicle along a line in either forward or rearward direction and for turning the vehicle either clockwise or counterclockwise with zero turning radius. The navigational apparatus includes obstacle sensors connected to the vehicle for producing an obstacle signal in response to contact or other desired proximity between an obstacle and a vehicle as the vehicle is driven through a work area. The work area comprises a substantially horizontal planar work surface bounded on all sides by an obstacle. The navigational apparatus also includes a search memory storage device connected to the vehicle for storing a two-dimensional memory array comprising a sufficient number of array elements to represent the work area to a desired resolution and with each array element representing a unique work area increment within the work area. A data processing device connected to the vehicle communicates with the memory storage device to produce a plurality of drive signals capable of directing the vehicle's drive motors to drive the vehicle from an origin work area increment into successive work area increments until the entire work area is explored. The obstacle sensors produce obstacle signals when the vehicle encounters an obstacle in the work area and these obstacle signals are used by the data processor to navigate the vehicle around the obstacles.

Real-time estimation and tracking of optical flow vectors for obstacle detection

Abstract: Optical flow contains information about the motion of a camera relative to its environment and about the three-dimensional structure of the imaged scene. In this contribution we use that information to detect obstacles in front of a moving vehicle. Since the detection is based on motion no a-priori knowledge about obstacle shape is required. Optical flow vectors are estimated from spatio-temporal derivatives of the gray value function which are computed at video frame rate by the custom-designed hardware MiniVISTA. To eliminate outliers and to speed up obstacle detection by data reduction the estimated vectors are clustered before they are passed to the obstacle test. The purpose of the obstacle test is to separate moving objects from the stationary environment and to separate elevated objects from the ground plane. In continuation of our previous work, obstacle detection is regarded as a state estimation problem. This enables us to enlarge the motion stereo basis by applying a Kalman filter to track optical flow vectors over subsequent image frames. Experimental results obtained from image sequences recorded with our experimental vehicle are presented.

Steady motion around a symmetrical obstacle moving along the axis of a rotating liquid

Abstract: An investigation by G. I. Taylor, of the steady motion of an obstacle along the axis of a rotating fluid, is extended in this paper. It is shown that Taylor's particular solution is just one of an infinity of functions comprising the general solution. The theory is applied to motions in a rotating cylinder of fluid. A critical Rossby number is derived, below which the flow around the obstacle is wave-like. When the Rossby number is greater than the critical value, the flow consists only of a local perturbation that dies out rapidly on both sides of the obstacle. Various other critical numbers exist, below which additional modes of oscillation become dynamically possible. An experiment was designed to test the theoretical results of this paper. An obstacle was moved along the axis of a long cylinder of rotating water. The resulting flow patterns were observed visually and photographically. The three-dimensional wave motions which occurred in the experiment were unquestionably the same as those in ...

Autonomous obstacle avoidance and maneuvering on a vision-guided MAV using on-board processing

Abstract: We present a novel stereo-based obstacle avoidance system on a vision-guided micro air vehicle (MAV) that is capable of fully autonomous maneuvers in unknown and dynamic environments. All algorithms run exclusively on the vehicle's on-board computer, and at high frequencies that allow the MAV to react quickly to obstacles appearing in its flight trajectory. Our MAV platform is a quadrotor aircraft equipped with an inertial measurement unit and two stereo rigs. An obstacle mapping algorithm processes stereo images, producing a 3D map representation of the environment; at the same time, a dynamic anytime path planner plans a collision-free path to a goal point.