Showing papers on "Collision avoidance published in 2001"

Mixed integer programming for multi-vehicle path planning

Abstract: This paper presents a new approach to fuel-optimal path planning of multiple vehicles using a combination of linear and integer programming. The basic problem formulation is to have the vehicles move from an initial dynamic state to a final state without colliding with each other, while at the same time avoiding other stationary and moving obstacles. It is shown that this problem can be rewritten as a linear program with mixed integer/linear constraints that account for the collision avoidance. A key benefit of this approach is that the path optimization can be readily solved using the CPLEX optimization software with an AMPL/Matlab interface. An example is worked out to show that the framework of mixed integer/linear programming is well suited for path planning and collision avoidance problems. Implementation issues are also considered. In particular, we compare receding horizon strategies with fixed arrival time approaches.

A versatile and safe mobility assistant

Abstract: The Bremen autonomous wheelchair implements obstacle avoidance plus driving and routing assistance in a shared-control system. This article shows how the tasks of reliably detecting obstacles in the environment and safely avoiding these obstructions are solved.

Decentralized collision avoidance, deadlock detection, and deadlock resolution for multiple mobile robots

Abstract: This paper describes a method for coordinating the independently planned trajectories of multiple mobile robots to avoid collisions and deadlocks among them. Whenever the distance between two robots drops below a certain value, they exchange information about their planned trajectories and determine whether they are in danger of a collision. If a possible collision is detected, they monitor their movements and, if necessary, insert idle times between certain segments of their trajectories in order to avoid the collision. Deadlocks among two or more robots occur if a number of robots block each other in a way such that none of them is able to continue along its trajectory without causing a collision. These deadlocks are reliably detected. After a deadlock is detected, the trajectory planners of each of the involved robots are successively asked to plan an alternative trajectory until the deadlock is resolved We use a combination of three fully distributed algorithms to reliably solve the task They do not use any global synchronization and do not interfere with each other.

Human Performance Models and Rear-End Collision Avoidance Algorithms

Abstract: Collision warning systems offer a promising approach to mitigate rear-end collisions, but substantial uncertainty exists regarding the joint performance of the driver and the collision warning algorithms. A simple deterministic model of driver performance was used to examine kinematics-based and perceptual-based rear-end collision avoidance algorithms over a range of collision situations, algorithm parameters, and assumptions regarding driver performance. The results show that the assumptions concerning driver reaction times have important consequences for algorithm performance, with underestimates dramatically undermining the safety benefit of the warning. Additionally, under some circumstances, when drivers rely on the warning algorithms, larger headways can result in more severe collisions. This reflects the nonlinear interaction among the collision situation, the algorithm, and driver response that should not be attributed to the complexities of driver behavior but to the kinematics of the situation. Comparisons made with experimental data demonstrate that a simple human performance model can capture important elements of system performance and complement expensive human-in-the-loop experiments. Actual or potential applications of this research include selection of an appropriate algorithm, more accurate specification of algorithm parameters, and guidance for future experiments.

Activity of descending contralateral movement detector neurons and collision avoidance behaviour in response to head-on visual stimuli in locusts.

Abstract: We recorded the activity of the right and left descending contralateral movement detectors responding to 10-cm (small) or 20-cm (large) computer-generated spheres approaching along different trajectories in the locust's frontal field of view. In separate experiments we examined the steering responses of tethered flying locusts to identical stimuli. The descending contralateral movement detectors were more sensitive to variations in target trajectory in the horizontal plane than in the vertical plane. Descending contralateral movement detector activity was related to target trajectory and to target size and was most sensitive to small objects converging on a direct collision course from above and to one side. Small objects failed to induce collision avoidance manoeuvres whereas large objects produced reliable collision avoidance responses. Large targets approaching along a converging trajectory produced steering responses that were either away from or toward the side of approach of the object, whereas targets approaching along trajectories that were offset from the locust's mid-longitudinal body axis primarily evoked responses away from the target. We detected no differences in the discharge properties of the descending contralateral movement detector pair that could account for the different collision avoidance behaviours evoked by varying the target size and trajectories. We suggest that descending contralateral movement detector properties are better suited to predator evasion than collision avoidance.

Formation surveillance and collision avoidance

Abstract: A formation collision avoidance system includes a Traffic Alert and Collision Avoidance System (TCAS) having a passive mode and an active mode. The passive mode enables several members of an aircraft formation to fly without actively interrogating using TCAS while only one or few formation members are actively interrogating. Formation members in passive mode maintain awareness of current air and ground traffic conditions using networked surveillance information provided over a communications link between formation members in active mode and formation members in passive mode. The networked surveillance information includes positional and intent information of current air/ground traffic obtained from ADS-B broadcasts and replies to the actively interrogating members of the formation. The communications link utilizes Station Keeping Equipment (SKE) already existing on certain aircraft.

Collision avoidance method for multiple autonomous mobile agents by implicit cooperation

Abstract: This paper proposes a collision avoidance method, called the cooperative collision avoidance method, for an environment consisting of multiple autonomous mobile agents. We also consider tasks such as map exploration and object collection, in addition to the collision avoidance. The method is based on local measurements and local planning at every sampling period in real-time. The proposed method is an extension of the conventional velocity obstacle (VO) method which provides collision detection among moving agents. The proposed method utilizes the uniformity of agents enabling the agents to share information of collisions without explicit communication. Sharing collision information allows agents to cooperate implicitly with each other to avoid collision by using the common VO approach. Furthermore, we introduce a velocity index which evaluates velocities to achieve good task performance and collision avoidance simultaneously. Finally, the efficiency of the cooperative collision avoidance method is demonstrated by analyses and simulations on examples.

Radar-assisted collision avoidance/guidance strategy for planar flight

Abstract: We propose a radar-assisted collision avoidance/guidance strategy (RACAGS) for flight vehicles on low altitude missions. The task of obstacle avoidance and guidance are integrated in a single collision avoidance/guidance strategy. The avionic aids and computational requirements are modest as the strategy mainly depends on range-map and inertial system information. The strategy is first implemented in a planar scenario and then extended to three-dimensional and nominal trajectory following flight scenarios. Several simulation studies are presented for illustration.

Nonholonomic stabilization with collision avoidance for mobile robots

Abstract: This paper presents a motion planner and nonholonomic controller for a mobile robot, with global collision avoidance and convergence properties. An appropriately designed (dipolar) potential field is combined with discontinuous state feedback. A new class of Lyapunov functions is introduced and used for nonholonomic navigation. The obstacle avoidance and global asymptotic stability properties are verified through simulations.

Method for reducing transmit power for traffic alert and collision avoidance systems and airborne collision avoidance systems

Abstract: The present invention provides a method for efficient use of the transmit power of a Traffic Alert Collision Avoidance System (TCAS) that allows enhanced surveillance range and limits radio frequency (RF) interference in crowded airspace. The method reduces power density in crowded airspace by modifying Mode S, Mode A and Mode C interrogations. During Mode S broadcasts, tracking interrogation power is reduced as a function of range. Further transmit power reduction is achieved by broadcasting a variable power density whisper-shout interrogation technique for Mode A/C aircraft when garbling is detected. If garbling is observed during a medium whisper-shout interrogation sequence, the method of the present invention attempts to clear the garbling by using focused high-density whisper-shout steps but only in the ranges where garbling was detected. Formation members can account for other formation members that are TCAS equipped using a special E-TCAS Broadcast Interrogation. The presence of other E-TCAS will be used in the RF interference limiting calculations. Aircraft flying in formation further minimize broadcast power by sharing information between the formation leader and formation aircraft.

Collision protection system for automotive vehicles comprises measurement sensors, a data processing system and means for controlling a vehicle to prevent a collision

Abstract: The collision protection system calculates the separation distances between a vehicle and an obstacles in the surroundings are measured and used to calculate the available driving space. Additional values relating to the actual vehicle movement, such as speed, direction, deceleration, etc., are measured and used in conjunction with the vehicle dimensions to calculate the required space in the forwards direction. This is compared with the available space and if necessary collision avoidance measures are implemented. An Independent claim is made for a device for avoiding collisions of a motor vehicle with measurement means, data processing means and means for controlling the vehicle to prevent a collision.

Visual display of ground collision avoidance device for aircraft

Abstract: The invention concerns a device designed to be installed on board an aircraft to provide eventual warning data corresponding to a risk of collision between the aircraft and the landform. The device comprises an assist-module (4) designed to use static and dynamic parameters of the aircraft with a database of the relief of the terrain flown over (3), and a visual display module (5) for displaying (55) a representation of the relief over a displayed domain, and inserting therein a particular signalling of possible warnings in particular based on a detected landing/take-off phase state.

Collision avoidance by observing pedestrians' faces for intelligent wheelchairs

Abstract: With the increase in the number of senior citizens, there is a growing demand for human-friendly wheelchairs as mobility aids. One of the main issues in the robotic wheelchair research is autonomous obstacle avoidance for safety. However, this is difficult because most moving obstacles in the real world are human beings. They sometimes change their motion abruptly. The paper presents an intelligent wheelchair that can avoid collisions with such human pedestrians safely and comfortably for each other. We assume that the information whether or not a pedestrian has noticed the wheelchair and which direction he/she wants to go can appear in the face direction. Thus our intelligent wheelchair is continuously observing the pedestrian's face in its front area, realizing smooth passing by changing its collision avoidance strategy based on the face information and the range data from the ultrasonic sensors. Experimental results show the effectiveness and comfortableness of the proposed method.

Modelling free flight with collision avoidance

Abstract: Free flight has been proposed as a future alternative to the current policy in air traffic management (ATM) where aircraft follow predefined corridors. In free flight pilots can choose their own optimal routes, altitudes and velocities but are also responsible for the safe and fair resolution of trajectory conflicts. This would require a safe distributed control system were the trajectories that aircraft follow are as optimal as possible respecting sufficient safety distances. We model aircraft behaviour using non-determinism in such a way that reachability analysis provides the optimal trajectories of the aircraft. We compare the obtained results with the conflict resolution solutions proposed in the literature.

Collision prediction and avoidance amidst moving objects for trajectory planning applications

Abstract: A methodology for computing a collision-free trajectory for mobile robots amidst moving objects is presented. This planner is based on a technique for computing the minimum translational distance between two mobile objects. This distance is then used for predicting and avoiding a collision. The computation of this distance is based on the application of the GJK algorithm to a particular subset of the Minkowski difference set of the involved objects. This subset states the separation or penetration distance between two objects along their given motions. When a collision is predicted, a collision-free intermediate temporal-position is generated avoiding such a collision.

Collision avoidance system for use by motor vehicles equipped with an inter-vehicle communications system so that if a vehicle comes too close or is moving too quickly a warning is triggered in both of the vehicles involved

Abstract: Method for avoidance of collisions amongst road traffic wherein signals transmitted by an inter-vehicle communication system are detected and if a vehicle is approaching with a critical velocity, a reaction is triggered in both of the concerned vehicles. Independent claims are made for: a collision avoidance warning device, with a receiver that detects signals from other vehicles in an inter-vehicle communication system and analyses them to detect a critical approach of another vehicle in order to trigger a warning in both the concerned vehicles; and a method for generation of a security zone around a number of moving vehicles that are transmitting inter-vehicle communications signals. The zone can be extended to creation of an electronic buffer zone along the edges of pavements, etc. that generates a warning to pedestrians, cyclists, etc.

Optimal collision avoidance and formation switching on Riemannian manifolds

Abstract: The problems of optimal collision avoidance and optimal formation switching for multiple agents moving on a Riemannian manifold are studied. It is assumed that the underlying manifold admits a group of isometries, with respect to which the Lagrangian function is invariant. A reduction method is used to derive optimality conditions for the solutions. Some examples are presented.

The design of fuzzy collision-avoidance expert system implemented by h ∞ - autopilot

Abstract: Collision avoidance is one of the urgent topics on ship voyage at sea. Experts’ experience is still essential when a ship is in the danger of colliding with the others nowadays although a lot of electronic voyage supported apparatuses have been equipped on ships. To include these experts’ experiences to resolve the problems of collision, we design a fuzzy collision-avoidance expert system that includes a knowledge base to store facts and rules, an inference engine to simulate experts’ decision and a fuzzy interface device. Either a quartermaster or an autopilot system can then implement the avoidance action proposed in the research. To perform the ship task of collision-avoidance effectively, a robust autopilot system that is based on the state space H∞ control methodology is designed to steer a ship safely for various outer surroundings at sea in performing course keeping, course-changing and route-tracking more robustly. The integration of fuzzy collision-avoidance and H∞ autopilot systems is then proposed in this paper.

Examination of drivers' collision avoidance behavior using conventional and antilock brake systems

Abstract: Antilock braking systems (ABS) have been introduced on many passenger car and light truck makes/models in recent years. In general, ABS appear to be very promising safety devices when evaluated on test tracks. Under many pavement conditions, ABS allow a driver to stop a vehicle more quickly and to maintain steering control even during situations of extreme panic braking. Brake experts anticipated that the introduction of ABS on passenger vehicles would reduce both the incidence and severity of crashes. However, a number of crash data analyses performed in recent years by NHTSA, automobile manufacturers, and others indicate that the introduction of ABS has not reduced the frequency of crashes as expected. This paper examines drivers' collision avoidance behavior using both conventional brakes and ABS in order to better understand this phenomenon.

Effects of Multiple Auditory Alerts for in-Vehicle Information Systems on Driver Attitudes and Performance:

Abstract: In-vehicle information systems might introduce a variety of sounds to alert drivers to situations ranging from imminent collisions to the arrival of email. This study examined the effects of auditory alerts on driver performance and attitudes. Sixteen participants drove eight driving scenarios over a period of two days in which they were exposed to email alerts and collision avoidance warnings. In each scenario, four email alert tones sounded, one occurring 300 ms before a collision avoidance tone. Two collision avoidance tones sounded in each scenario, one associated with a braking lead vehicle and the other a false alarm. The results show that annoyance is an important sound characteristic that can affect workload. The results also indicate that urgency is a sound characteristic that affects driving performance. In addition, the strong effect of sound parameters on annoyance suggest that Edworthy's urgency mapping principle should be complemented by an annoyance tradeoff principle.

A method for collision avoidance and collision mitigation

Abstract: The present invention relates to a method for avoiding vehicle collisions and collision mitigation. The method comprises the steps of predicting the probability density function (11, 12, 13, 14) for the position of a vehicle at several future occasions and predicting the probability density function (21, 22, 23, 24) for at least one additional object at several future occasions. Further the method comprises the step of forming the joint probability density function for the relative positions of the vehicle and object at several future occasions and integrating over the area in which the vehicle and object are in physical conflict.

Sensor-friendly vehicle and roadway systems

Abstract: Sensor-friendly vehicle and roadway systems consist of complementary signal sensor and reflector or transmitter technologies, which provide information about the threat of a collision. These technologies can be composed into cooperative collision avoidance systems, which can supplement or replace single vehicle-based systems. Experiments were run on the four most promising technologies to determine their performance and reliability; the four technologies were passive license plates with enhanced radar return, roadside obstacle-mounted radar-reflecting corner cubes, fluorescent paint for lane and obstacle marking, and light emitting diode brake-light messaging. These technologies all focus on improving the signal-to-noise ratio of the collision avoidance sensor. We believe that experimental results indicate that further proof-of-concept refinements are needed, but in general these systems represent technologically sound, cooperative vehicle-roadway components and that sensor friendly systems could eventually translate into a significant benefit in terms of lives saved.

Dynamic collision avoidance for redundant multi-robot systems

Abstract: This paper presents a new approach to the online planning of collision-free robot motions and evasive actions for redundant multi-robot/multi-obstacle environments. The approach, based on the collision avoidance methodology CARE (collision avoidance in real-time environments) presented by Rossmann (1993), is a local planning approach which considers the shortest distance and relative velocity between objects. This results in an intuitively comprehensible model to determine the potential collision and provides the basis of a new way of treating collision free path-planning as an optimization problem. This optimization problem is solved in real-time and provides a mathematically exact solution of the path-planning problem by considering all the static and dynamic obstacles in the environment.

Planning a collision avoidance model for ship using genetic algorithm

Abstract: Using genetic algorithms to plan the safe path for ship in congested traffic situation, a new gene vector is proposed. The gene vector is composed of the position and speed of our ship, as well as a noise model. The noise model describes the influence on a maneuvering ships system of wind, sea waves and the other natural factors. To test and verify the new gene vector, the equipment installed on "Shioji Maru" (the training ship of our university) have been applied to an automatic collision avoidance system. In the experimental system, the ARPA (Automatic Radar Plotting Aids) system was used to collect information on the navigational obstacles around our ship. The information was processed. Useful information, especially that related to target ships, was extracted and used to derive a stochastic predictor that can predict the future position and degree of future collision threat in sufficient time. The information relating to our own ship was detected with GPS and other sensors. These data were introduced to a GA optimum controller. The optimum or semi-optimum path was evolved from a set of possible safe paths based on the fitness function. Many experiments have been done and the results are presented.

Collision Avoidance in Multi-Robot Environment based on Local Communication

Abstract: In this paper, we propose a new collision avoidance method among multiple autonomous mobile robots. Generally, it is difficult to apply conventional collision avoidance methods to robots in multi-robot environment because those methods are only applicable to a single robot environment. For this problem, we propose a new method using the LOCISS (LOcally Communicable Infrared Sensory System) by which a robot is able to communicate with other robots locally to exchange information necessary for their mutual collision avoidance. To realize the collision avoid ance based on these information, we introduce a learning method by which a robot is able to acquire the behavior adaptively and autonomously. A learning curriculum is divided into multiple layers to reduce a number of situation for the learning. Finally, we implemented this system to execute acquired behaviors, so that robots can avoid other robots and obstacles at the same time. It is confirmed by conducting experiments that this method is effective in the multi-robot environment.

The Effect of Rear-End Collision Warnings on on-Going Response:

Abstract: Rear-end collisions are a major concern for highway safety, and considerable effort is being expended to address the frequency of these types on collisions. One possible solution is to warn drivers just before a collision is to occur, so that they can attempt to avoid it. One concern is that warnings may interfere with an avoidance response the driver may have already initiated. This simulator study examined how drivers respond to a rear-end collision when they receive a warning as they begin to release the accelerator. Contrary to expectations, the warning enhanced rather than undermined collision avoidance performance. Receiving a warning as the accelerator was released reduced the accelerator-brake reaction time by 50%. These data suggest that RECAS warnings are unlikely to interfere with a driver's ongoing response.

Driver Choice of Headway with Auditory Warnings

Abstract: Two major causes of rear-end collisions are driver distraction and the tendency for some drivers to maintain insufficient headways with other vehicles. Previous research into in-vehicle collision avoidance systems has focused on warning drivers in near-collision situations with short headways (e.g., less than 1 second). The current study focused on mid-range headways and on warning distracted drivers to maintain safe following distances. Subjects performed a simulated car-following task in which the lead vehicle periodically decelerated. The lead vehicle was otherwise programmed to maintain a minimum following distance of 2 seconds—although the subjects could drive more slowly to leave a longer headway. On trips with an auditory headway warning, the subjects tended to leave larger headways, particularly on trips in which they performed a secondary task as well.