Showing papers on "Obstacle published in 1995"

Obstacle warning system for a vehicle

Abstract: An obstacle warning system for a vehicle includes a distance measuring device for emitting a transmission wave or laser light in a given angular range in a direction of a width of the vehicle in a scanning manner, and for detecting a distance between the vehicle and an obstacle in correspondence with a scan angle on the basis of a reflected wave or reflected light from the obstacle A relative position calculating device calculates a relative position of the obstacle with respect to the vehicle on the basis of the distance detected by the distance measuring device and a corresponding scan angle A radius calculating device calculates a radius of an estimated relative curved path of the vehicle with respect to the obstacle on the basis of relative positions of at least two points of the obstacle which are calculated by the relative position calculating device A warning area setting device sets a given warning area on the basis of the width of the vehicle and the radius calculated by the radius calculating device A warning device executes a given warning process if the obstacle remains in the warning area for a given period of time

Sliding mode control for gradient tracking and robot navigation using artificial potential fields

Abstract: This paper introduces a sliding mode control strategy for tracking the gradient of an artificial potential field. The control methodology is applicable to fully actuated holonomic robotic systems with n-degrees of freedom. The controller yields exact tracking of the gradient lines and is invariant with respect to parametric uncertainty and disturbances in system dynamics. A detailed case study for mobile robots introduces the equilibrium point placement method for designing harmonic planar potential fields for circular obstacle security zones. Diffeomorph mappings can be utilized for more complex obstacle security zones. The gradient of the harmonic potential field is shown to always lead away from the obstacle security zone and to continuously approach the goal point. >

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.

Fluid-solid interaction: acoustic scattering by a smooth elastic obstacle

Abstract: A bounded three-dimensional elastic obstacle is surrounded by an unbounded inviscid compressible fluid. Acoustic waves are scattered by the obstacle; the problem is to find the scattered waves and the response of the obstacle. This problem is formulated mathematically; existence and uniqueness theorems are proved. Various systems of boundary integral equations over the interface between the fluid and the solid are derived and analysed. These systems include a system obtained by a straightforward direct method and a smaller system for a single vector field.

Gravity current flow over obstacles

Abstract: When a gravity current meets an obstacle a proportion of the flow may continue over the obstacle while the rest is reflected back as a hydraulic jump. There are many examples of this type of flow, both in the natural and man-made environment (e.g. sea breezes meeting hills, dense gas and liquid releases meeting containment walls). Two-dimensional currents and obstacles, where the reflected jump is in the opposite direction to the incoming current, are examined by laboratory experiment and theoretical analysis. The investigation concentrates on the case of no net flow, so that there is a return flow in the (finite depth) upper layer. The theoretical analysis is based on shallow-water theory. Both a rigid lid and a free surface condition for the top of the upper layer are considered. The flow may be divided into several regions: the inflow conditions, the region around the hydraulic jump, the flow at the obstacle and the flow downstream of the obstacle. Both theoretical and empirical inflow conditions are examined; the jump conditions are based on assuming that the energy dissipation is confined to the lower layer; and the flow over the obstacle is described by hydraulic control theory. The predictions for the proportion of the flow that continues over the obstacle, the speed of the reflected jump and the depth of the reflected flow are compared with the laboratory experiments, and give reasonable agreement. A shallower upper layer (which must result in a faster return velocity in the upper layer) is found to have a significant effect, both on the initial incoming gravity current and on the proportion of the flow that continues over the obstacle.

BIE and material differentiation applied to the formulation of obstacle inverse problems

Abstract: In this paper, we consider the problem of identifying, by means of boundary element methods and nonlinear optimization, a cavity or obstacle of unknown location and shape embedded in a linearly acoustic or elastic medium. The unknown shape is classically sought so as to achieve a best fit between the measured and computed values of some physical quantity, which is here the scattered acoustic pressure field. One is usually led to the minimization of a cost function J . Classical nonlinear optimization algorithms need the repeated computation of the gradient of the cost function with respect to the design variables as well as the cost function itself. The present paper emphasizes the formulation and effectiveness of the adjoint problem method for the gradient evaluation. First, the hard obstacle inverse problem for 3-D acoustics is considered. For a given J , the adjoint problem is established, and the gradient of J is then formulated in terms of both primary and adjoint states. Next, the adjoint variable approach is extended to the case of a penetrable obstacle in a 3-D acoustical medium, and also for a traction-free cavity in a 3-D elastic medium. Explicit formulae for the gradient of J with respect to shape variations, which appear to be rather compact and elegant, are established for each case. The formulation is incorporated in an unconstrained minimization algorithm, in order to solve numerically the inverse problem. Numerical results are presented for the search of a rigid bounded obstacle embedded in an infinite 3-D acoustic medium, where the measurements are taken to be values of the pressure field on a remote measurement surface, the obstacle being illuminated by monochromatic plane waves. They demonstrate the efficiency of the proposed method. Some computational issues (accuracy, CPU time, influence of measurements errors) are discussed. Finally, for the sake of completeness, the direct differentiation approach is also treated and new derivative BIE formulations are established.

Obstacle detecting system for vehicles

Abstract: An obstacle detection system for vehicles detects kinetic attributes relative to a vehicle equipped with the system of an object present in a forward path of travel of the vehicle, sets a presumed zone into which the object is expected to have entered at a lapse of a specified period based on the kinetic attributes, and proves an object detected at a lapse of the specified period as the object previously detected if the object of second detection is determined as one having moved into the presumed zone and an obstacle precarious to the vehicle.

Running control system of robot and method thereof

Abstract: A running control system of a mobil robot performs a fuzzy inference according to a position error, directional error and instantaneous directional angle detected in the travel of the robot, so that the robot can travel accurately to a target point and perform operations such as cleaning and monitoring. An obstacle detecting unit detects whether or not there is an obstacle within a prescribed area to be traveled by the robot and for detecting a distance to the obstacle.

An integrated obstacle detection framework for intelligent cruise control on motorways

Abstract: This paper deals with the development and implementation of a purely visual obstacle detection framework for autonomous driving on motorways. Our activities are embedded in the SMART VEHICLE subproject of the ESPRIT project CLEOPATRA. The aim of SMART VEHICLE is the development of a visually controlled intelligent cruise control (ICC) for a prototype passenger car, the Mercedes-Benz research car VITA II. The vision modules are operating concurrently on a net of digital signal processors with multiple video inputs. Our obstacle detection framework bases on the application of highly adapted machine-vision elements such as robust symmetry measuring, neural net-based adaptive object recognition, real-time tracking of multiple vehicles, and inverse-perspective stereo image matching (IPM). We will show detailed results from extensive closed-loop autonomous driving on public motorways and we will present the final HPC hardware system which is part of the application computer of VITA II.

Obstacle accommodation motion planning

Abstract: A new robot path planning methodology, called obstacle accommodation, has been introduced for robots in cluttered environments. This methodology does not attempt to avoid physical contact between the robot and obstacles. Instead, it controls the contact to prevent damage to the robot. Obstacle accommodation represents a new robotic paradigm in which obstacles can contact robots at unspecified positions, i.e., a contact point can be at any point on any link. Obstacle accommodation requires analysis in kinematics, motion planning, dynamics, and control. This paper deals with the development of the kinematic constraints and with motion planning under these constraints. We begin by providing a general formulation of the motion constraints due to contact with obstacles. Next, a new inverse kinematics is presented that provides joint motion for robots under contact constraints. Finally, the new motion planning algorithm for robot motion in a cluttered environment is provided. The motion planning algorithm is verified by two examples, one on a linkage robot and the other on a mobile robot. >

Robot motion planning among moving obstacles

Abstract: This thesis presents a new approach for planning a robot's trajectory that avoids static and moving obstacles and minimizes motion time, subject to robot dynamics and actuator constraints. This approach consists of first computing a coarse trajectory that avoids the obstacles and satisfies an approximation of the actuator constraints. Then this trajectory is used as the initial guess of a dynamic optimization that satisfies obstacle avoidance, robot dynamics and the true actuator limits. The first step of the approach is based on the concept of Velocity Obstacle (VO) that defines, at every instant in time, the set of colliding velocities between the robot and the obstacles. The VO set is computed using the relative velocity between the robot and each obstacle, and is instrumental in determining the set of robot velocities avoiding all obstacles and satisfying approximate system dynamics and actuator limits. Within this set, the best avoidance maneuver is chosen heuristically so that the trajectory resulting from the sequence of maneuvers reaches the goal and minimizes motion time. The second step of the approach consists of refining the trajectory with a dynamic optimization that minimizes motion time, subject to the true robot's dynamics, actuator constraints, and time varying obstacle constraints. The dynamic optimization is based on Pontryagin's Minimum Principle and uses a gradient descent method. These two steps lead to the implementation of a powerful and flexible planner that combines the advantages of heuristics with those of dynamic optimization. Heuristics in fact, captures the non-analytic aspects of motion planning, such as sequence of obstacle avoidance, conservative or aggressive maneuvers, and so on, thus characterizing the global structure of the trajectory. Dynamic optimization on the other hand, ensures feasibility and optimality of the trajectory thus guaranteeing its local correctness. This approach is demonstrated for planning the motions of an automated vehicle in an Intelligent Vehicle Highway System (IVHS) scenario, and of an articulated robot moving in a dynamic environment. This motion planner is suitable to a wide range of applications. The Velocity Obstacle method is very fast and, although approximate, it can be used for real time planning. The Dynamic Optimization is computationally intensive, but yields optimal solutions, which can be used when off-line planning is acceptable.

Drive assist system

Abstract: PROBLEM TO BE SOLVED: To suppress annoyance of a driver by providing a drive assist system automatically controlling notification and a vehicle behavior in response to the presence of a steady obstacle even if the steady obstacle is present and the driver inevitably approaches the obstacle whenever parking or starting a vehicle around a parking area.SOLUTION: A drive assist system comprises: an approach detection unit 71 detecting an obstacle within a set distance; a behavior control unit 73 forcibly braking an own vehicle if the approach detection unit 71 detects the obstacle; an arrangement storage unit 66 storing therein a previous picked-up image picked up around a target parking area; a picked-up-image acquisition unit 61 acquiring a current picked-up image picked up around the target parking area at a time of parking the vehicle in the target parking area or leaving the target parking area; and an obstacle identification unit 70 identifying a nonsteady obstacle around the target parking area on the basis of a difference between the previous picked-up image stored in the arrangement storage unit 66 and the current picked-up image acquired by the picked-up-image acquisition unit 61, the approach detection unit 71 setting the set distance for a steady obstacle smaller than the set distance for the nonsteady obstacle.

Time-optimal obstacle avoidance

Abstract: This paper presents a method for generating near-time optimal trajectories in cluttered environments for manipulators with invariant inertia matrices. For one obstacle, the method generates the time-optimal trajectory by minimizing the time-derivative of the return (cost) function for this problem, satisfying the Hamilton-Jacobi-Bellman (HJB) equation. For multiple obstacles, the trajectory is generated using the pseudo return function, which is an approximation of the return function for the multi-obstacle problem. The pseudo return function avoids one obstacle at a time, producing near-optimal trajectories that are guaranteed to avoid the obstacles and satisfy the actuator constraints. An example with circular obstacles demonstrates close correlation between the near-optimal and optimal paths, requiring computational efforts that are suitable for on-line implementations.

An analytic approach to moving obstacle avoidance using an artificial potential field

Abstract: This paper proposes a unified method for moving obstacle avoidance of a robot The method incorporates the artificial potential field (APF) concept into view-time based motion planning where the driving force is generated at every interval of the view-time The view-time is defined as the time set from one sampling time instant to the next The velocity and acceleration of the moving obstacle is assumed to be monitored or priorly known at each sampling time At each sampling time, an accessible region that will be swept by the obstacle in the next view-time is predicted from the velocity, acceleration, and dynamic constraints of the obstacle Then, an APF which exerts repulsive force on the robot is constructed around the accessible region During the view-time, the force induced by the artificial potential field drives the robot away from the accessible obstacle trajectories in real-time The dynamic constraints of the robot are also considered Application of the described procedure at each successive sampling time from the initial to final location yields the collision-free trajectory for moving obstacle avoidance

Direct Obstacle Detection and Motion from Spatio-Temporal Derivatives

Abstract: Autonomous vehicles need a means of detecting obstructions on its path, to avoid collision In this paper, a novel approach to obstacle detection is presented A camera moves on a visible ground plane with the optical axis parallel to the ground Camera motion parameters are linearly related to first order spatio-temporal derivatives of the taken image sequence; image flow is not needed Motion is robustly estimated using RANSAC An error measure for each image point corresponds to the likelihood of an obstacle in that point

Obstacle detecting device for vehicle

Abstract: PURPOSE:To heighten reliability in detecting an obstacle by properly estimating the relative relationship between the obstacle and one's own vehicle when the obstacle becomes undetectible by radar devices. CONSTITUTION:When an obstcle becomes undetectible by radar devices 1 and 2, a position of the obstacle is estimated by an estimating means 6 according to information so far. In that case, an estimating method by the estimating means 6 is changed according to a disappearance cause of the obstacle N.

Path deciding method for unmanned mobile investigating machine

Abstract: PURPOSE:To ensure the safe traveling of an unmanned mobile investigating machine in a short time processing by deciding an obstacle evading path based on the local map data generated for emergency evasion of obstacles if a prescribed range is sensed in the traveling direction of the investigating machine and an obstacle is detected on a planned local path. CONSTITUTION:A mobile investigating machine 1 senses only once the geographical features in a comparatively wide range set in the front traveling direction of the machine 1 by a three-dimensional topographical sensor 4 and then produces a local map by an external environment recognizing means 41. A local path planning means 42 plans a local path in a range of the local map. Thus the machine 1 travels on this planned path. If an obstacle is overlooked on the local path in a traveling state of the machine 1, only the nearby areas are sensed by the sensor 4 with high accuracy. Then the emergency obstacle evading local map data are generated by the means 41, and an obstacle evading path is decided by the means 42 based on the map data. Thus it is possible to simplify the path deciding processing and to ensure the safe traveling of the machine 1 by sensing in the small frequency the wide ranges in the traveling direction of the machine 1 and also sensing only the nearby areas with high accuracy.

Autonomous moving device

Abstract: PROBLEM TO BE SOLVED: To prevent an autonomous moving device from falling into dead lock state by trying to avoid parties each other when the device meets a person and to enable an avoiding operation when the person stops by stopping the device onstandby for fixed time when an obstacle is the person and starting the avoiding operation when the obstacle still exists even after the lapse of fixed time. SOLUTION: When any one of ultrasonic sensors 1 detects an obstacle and there is no output from an infrared sensor 2 corresponding to that ultrasonic sensor 1, it is judged that the obstacle is not a person, and an avoiding command is outputted. When there is any output from that infrared sensor 2, on the other hand, it is judged that the obstacle is a person, and a stopping command is outputted for time T. When the ultrasonic sensor 1 detects no obstacle after the lapse of time T, speed and steering angle commands are outputted from a course planning part 5 together with an ordinary traveling command. When any ultrasonic sensor 1 detects the obstacle, on the other hand, the avoiding command is outputted.

Sensory based motion planning with global proofs

Abstract: A sensory based algorithm DistBug, that is guaranteed to reach the target in an unknown environment or report that the target is unreachable, is presented. The algorithm is reactive in the sense that it relies on range data to make local decisions, and does not create a world model. The algorithm consists of two behaviors (modes of motion): straight motion between obstacles and obstacle boundary following. Simulation results as well as experiments with a real robot are presented. The condition for leaving obstacle boundary is based on the free range in the direction to the target. This condition allows the robot to leave the obstacle as soon as the local conditions guarantee global convergence. Range data is utilized for choosing the turning direction when the robot approaches an obstacle. A criterion for reversing the boundary following direction when it seems to be the wrong direction is also introduced. As a direct result of these local decisions, a significant improvement in the performance was achieved.

Obstacle detecting device and warning device for automobile

Abstract: PURPOSE:To secure the cooperation for detection of obstacles in accordance with the traveling state of an automobile and also to change the report contents in accordance with the state of each obstacle CONSTITUTION:The size and the position of an obstacle existing in the front of an automobile are detected based on the image information given from an image sensor 1 Meanwhile the distance between the obstacle and the automobile and the direction of the obstacle are detected by the laser light emitted from a laser diode 3 Then a deciding part 5 changes the cooperative relation between both detecting operations in accordance with the traveling state of the automobile So that the obstacle identifying accuracy is improved in accordance with the traveling state of the automobile Furthermore a control part 6 gives a warning to the driver to properly evade the danger based on the identifying result

On-line deadlock-free path-planning algorithms by means of a sensor-feedback tracing

Abstract: In the sensor-based path-planning, a mobile robot always finds a deadlock-free path towards the goal if such the path exists in an uncertain world, otherwise it automatically sees that there is no deadlock-free path in the world. All the previous sensor-based path-planning algorithms keep two terminations as their deadlock-free characteristic under the following assumptions: 1) a robot faithfully traces an uncertain obstacle at a constant distance; and 2) a robot exactly recognizes its position. However, in general, a mobile robot with the non-holonomic system cannot faithfully trace an uncertain obstacle. Thus in this paper, we discuss deadlock-free characteristics of those algorithms after removing the first assumption in the presence of sensing and control errors. Then we propose some robust versions from the previous algorithms and also give proofs of their deadlock-free characteristics by a non-contact obstacle tracing with some errors.

Forward monitoring device for vehicle

Abstract: PURPOSE: To correctly determine the existence/abscence of possibility of a collision by determining designated conditions according to the obstacle bypass time and the arrival time of a car running on the opposite lane to determine the existence/abscence of possibility of a collision of a driver's own vehicle in a device adapted to determine the existence/abscence of possibility of a collision of the driver's own vehicle according to the forward projected image and the speed of the driver's own vehicle. CONSTITUTION: A forward monitoring device for a vehicle comprises a CCD camera 2 for image-picking up the forward image of a driver's own vehicle 1 and a car speed sensor 4. Obstacles such as a stopped vehicle and a low-speed leading vehicle are extracted from the forward projected image to detect the obstacle size and the distance between the driver's own vehicle and the obstacle. The estimated length of the obstacle in the direction of depth is calculated according to a designated table concerging a general obstacle from the width and height of the obstacle sizes, and the larger length is selected among the detected length and the general lengths to be taken as the length of the obstacle. Subsequently, from the obstacle length and the distance between the driver's own vehicle and the obstacle, the obstacle bypass time for avoiding a collision of the driver's own vehicle with the obstacle and passing the same is calculated, and the calculated time is compared with the arrival time of a car running on the opposite lane to determine the existence/abscence of possibility of a collision of the driver's own vehicle, and a warning buzzer 6 or the like is controlled.

Analytical solution for configuration space obstacle computation and representation

Abstract: Objects within the robot's work space impose constraints on the motion of the robot. We present a novel approach to represent these kinematic motion constraints in the robot's configuration space. Two fundamental problems such as efficiency and completeness have also been investigated. By introducing the concept of pseudo kinematics for the robot, we demonstrate that the kinematic motion constraints in the robot's configuration space can be analytically and completely described by a set of parametric equations. These parametric equations result from mapping the boundary of the obstacle from the work space into the configuration space using the inverse pseudo kinematics. The technique is generalized for an n-degrees of freedom manipulator operating in a 3-D work space. The closed form representation for a C-space obstacle substantially reduces the computation time needed to obtain a C-space obstacle, thus making it possible to implement on-line collision-free motion planning schemes. Simulations results are presented for computing C-space obstacles in the 3D configuration space.

Dynamic obstacle avoidance

Abstract: Techniques to allow simulated entities to avoid static terrain, such as trees, buildings, rivers, etc., have been in use in Distributed Interactive Simulation (DlS) environments for many years. Avoidance of objects in motion, “dynamic obstacles”, is much more complex. Although simple dynamic obstacle collision avoidance has been implemented in other systems, the resulting behavior is usually less than realistic. The Institute for Simulation and Training (1ST) has investigated techniques to allow simulated entities to make reasonably intelligent and realistic maneuvers intended to avoid dynamic (and static) objects. The goal has been to find new methods which will yield improved collision avoidance behavior without excessive computational cost. As a result of this work, 1ST has developed a novel approach to attack the DIS dynamic obstacle avoidance (DOA) problem by combining two disparate motion planning approaches: potential fields and grid based route planning.

Outside environment recognition device for vehicle

Abstract: PURPOSE: To measure the relative positional relation between an obstacle and a travel road section line with high precision by measuring the relative positional relation between the travel section line and obstacle according to the travel road section line, the obstacle position, and distance information. CONSTITUTION: An image processing part 12 extracts the travel road section line or a road border line and the obstacle position from an image obtained by a CCD camera 10. The output of a radar unit 14 as an obstacle distance information detecting means is sent to a signal processing part 16. The signal processing part 16 converts radar information obtained from the radar unit 14, i.e., the distance and direction to the obstacle (from this vehicle) into coordinates on an image pickup plane by using initial camera parameters. Further, an in-travelling road position measurement part 18 measures (recognizes) the in-travelling road position of the obstacle, or the relative positional relation between the obstacle and travel road section line, to be more concrete, from the travel road section line and obstacle position obtained by the image processing part 12 and the obstacle information (distance and direction) obtained by the signal processing part 16.

End position display device for vehicle

Abstract: PURPOSE:To grasp the relative positional relation with an obstacle not visible easily, easily and accurately, by controlling the display of the image of an end mark display body depending on the distance of the end position and the obstacle detected by a distance detecting means. CONSTITUTION:A control circuit 7 controls a display unit 1 depending on the detecting signal from a corner sonar 6, the radiating light from the display unit 1 is reflected at a point D on a windshield 5 through a plane mirror 2 and a toroidal concave mirror 3, and it is injected to the eye position E of a driver. The corner sonar 6 is provided at the front end position of a vehicle lower than a front end display mark image 4, and when an obstacle is detected, the control circuit 7 takes in this output signal, controls a display control lights circuit 8, and flashes or lights the display unit 1. In this case, by changing the flashing cycle of the display unit 1 according to the distance between the top end position of the vehicle and the obstacle, the length of the distance with the obstacle can be recognized. In such a way, the positional relation with an obstacle can be grasped easily even though the obstacle is at a place lower than the bonnet.

Obstacle sensor for automobile

Abstract: PURPOSE:To heighten the detection accuracy by detecting an obstacle efficiently when a possibility of contact between a driver's own automobile and an obstacle is discriminated. CONSTITUTION:A proceeding path estimate means 8 estimates a proceeding path on which a driver's own automobile travels afterward based on a traveling state such as a steering angle and a car velocity of the driver's own automobile. A traveling path detection means 14 by using a CCD camera 11 detects a road on which the driver' s own automobile travels. An obstacle discrimination means 15 discriminates the avoidance necessity of the obstacle detected by a scan radar 4 for detecting the obstacle in existence in a prescribed area based on a proceeding path estimated by the proceeding path estimate means 8 and a traveling path sensed by a traveling path detection means 14. The obstacle discrimination means 15 lets the degree of the avoidance necessity of the obstacle in existence in the area where the proceeding path and the traveling path are overlapped to be highest and makes the degree of the avoidance necessity of the obstacle sequentially low in order of an area in the traveling path and on the outside of the proceeding path, an area in the proceeding path and on the outside of the traveling path and other obstacle detection area than the area.

Unmanned apparatus for farm working

Abstract: PROBLEM TO BE SOLVED: To provide an unmanned apparatus for farm working, equipped with a positional moving means, etc, comprising a driving system, etc, capable of averting an obstacle and continuing operations and improved in safety for the apparatus or humans SOLUTION: This unmanned apparatus for farm working is obtained by installing a positional moving means 1 comprising a driving system and a steering system, a farm working means 4 such as a tillage device, a global positioning system(GPS) receiving means 3 for calculating the position of the own machine from radio waves transmitted from a GPS satellite and an automatic controlling means 2 capable of controlling the positional moving means 1 so as to collate a travel passage automatically indexed from the preinputted travel passage or a farm working area with the own position obtained from the GPS receiving means 3 and correct the position and controlling the farm working means 4 so as to perform operations in the preinputted farm working area Furthermore, the apparatus is provided with an obstacle sensor for sensing an obstacle in the forward direction and the positional moving means 1 and the farm working means 4 are controlled so as to avert the obstacle or stop the operations thereof with the automatic controlling means 2 when the obstacle is present in the forward direction

Obstacle detection apparatus

Abstract: PURPOSE:To precisely detect a distance and a direction up to an obstacle existing around a car by a method wherein at least one ultrasonic-wave transmitter and a plurality of ultrasonic-wave receivers are installed on the four sides, the front, rear, right and left sides of the car CONSTITUTION:Ultrasonic waves at different frequencies are sent from four sides of a car (an own vehicle) 3 from sonar sensors 5, 8, 11, 14, ultrasonic waves reflected by an obstacle (other vehicles or the like) are received by remaining sonar sensors 4, 6, 7, 9, 10, 12, 13, 15, and the transmission time and the reception time of the ultrasonic waves are sent to a microcomputer 18 The microcomputer 18 computes the direction and the distance of the obstacle existing around the own vehicle 3 on the basis of the wave-transmission time and the wave-reception time of the ultrasonic waves When the obstacle is recognized inside a three-dimensional space, the sensors 5, 8, 11, 14 are changed over for wave-reception after the ultrasonic waves have been transmitted