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206
Reciprocal Velocity Obstacles for RealTime MultiAgent Navigation
 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION
, 2008
"... In this paper, we propose a new concept  the "Reciprocal Velocity Obstacle"  for realtime multiagent navigation. We consider the case in which each agent navigates independently without explicit communication with other agents. Our formulation is an extension of the Velocity Obstacle c ..."
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Cited by 104 (22 self)
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In this paper, we propose a new concept  the "Reciprocal Velocity Obstacle"  for realtime multiagent navigation. We consider the case in which each agent navigates independently without explicit communication with other agents. Our formulation is an extension of the Velocity Obstacle concept, which was introduced for navigation among (passively) moving obstacles. Our approach takes into account the reactive behavior of the other agents by implicitly assuming that the other agents make a similar collisionavoidance reasoning. We show that this method guarantees safe and oscillationfree motions for each of the agents. We apply our concept to navigation of hundreds of agents in densely populated environments containing both static and moving obstacles, and we show that realtime and scalable performance is achieved in such challenging scenarios.
Inevitable collision states  a step towards safer robots
 Advanced Robotics
, 2004
"... Abstract — An inevitable collision state for a robotic system can be defined as a state for which, no matter what the future trajectory followed by the system is, a collision with an obstacle eventually occurs. An inevitable collision state takes into account both the dynamics of the system and the ..."
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Cited by 86 (15 self)
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Abstract — An inevitable collision state for a robotic system can be defined as a state for which, no matter what the future trajectory followed by the system is, a collision with an obstacle eventually occurs. An inevitable collision state takes into account both the dynamics of the system and the obstacles, fixed or moving. The main contribution of this paper is to lay down and explore this novel concept (and the companion concept of inevitable collision obstacle). Formal definitions of the inevitable collision states and obstacles are given. Properties fundamental for their characterisation are established. This concept is very general and can be useful both for navigation and motion planning purposes (for its own safety, a robotic system should never find itself in an inevitable collision state!). The interest of this concept is illustrated by a safe motion planning example.
Safe Motion Planning in Dynamic Environments
 in Proceedings of the IEEE International Conference on Intelligent Robots and Systems (IROS
, 2005
"... This paper addresses the problem of motion planning (MP) in dynamic environments. It is first argued that dynamic environments impose a realtime constraint upon MP: it has a limited time only to compute a motion, the time available being a function of the dynamicity of the environment. Now, given t ..."
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Cited by 77 (7 self)
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This paper addresses the problem of motion planning (MP) in dynamic environments. It is first argued that dynamic environments impose a realtime constraint upon MP: it has a limited time only to compute a motion, the time available being a function of the dynamicity of the environment. Now, given the intrinsic complexity of MP, computing a complete motion to the goal within the time available is impossible to achieve in most real situations. Partial Motion Planning (PMP) is the answer to this problem proposed in this paper. PMP is a motion planning scheme with an anytime flavor: when the time available is over, PMP returns the best partial motion to the goal computed so far. Like reactive navigation scheme, PMP faces a safety issue: what guarantee is there that the system will never end up in a critical situation yielding an inevitable collision? The answer proposed in this paper to this safety issue relies upon the concept of Inevitable Collision States (ICS). ICS takes into account the dynamics of both the system and the moving obstacles. By computing ICSfree partial motion, the system safety can be guaranteed. Application of PMP to the case of a carlike system in a dynamic environment is presented.
Coordinating Multiple Robots with Kinodynamic Constraints along Specified Paths
, 2005
"... This paper focuses on the collisionfree coordination of multiple robots with kinodynamic constraints along specified paths. We present an approach to generate continuous velocity profiles for multiple robots; these velocity profiles satisfy the dynamics constraints, avoid collisions, and minimize t ..."
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Cited by 68 (9 self)
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This paper focuses on the collisionfree coordination of multiple robots with kinodynamic constraints along specified paths. We present an approach to generate continuous velocity profiles for multiple robots; these velocity profiles satisfy the dynamics constraints, avoid collisions, and minimize the completion time. The approach, which combines techniques from optimal control and mathematical programming, consists of identifying collision segments along each robot's path, and then optimizing the robots' velocities along the collision and collisionfree segments. First, for each path segment for each robot, the minimum and maximum possible traversal times that satisfy the dynamics constraints are computed by solving the corresponding twopoint boundary value problems. The collision avoidance constraints for pairs of robots can then be combined to formulate a mixed integer nonlinear programming (MINLP) problem. Since this nonconvex MINLP model is difficult to solve, we describe two related mixed integer linear programming (MILP) formulations, which provide schedules that give lower and upper bounds on the optimum; the upper bound schedule is designed to provide continuous velocity trajectories that are feasible. The approach is illustrated with coordination of multiple robots, modeled as double integrators subject to velocity and acceleration constraints. An application to coordination of nonholonomic carlike robots is described, along with implementation results for 12 robots.
Reactive Path Deformation for Nonholonomic Mobile Robots
, 2004
"... This paper presents a novel and generic approach of path optimization for nonholonomic systems. The approach is applied to the problem of reactive navigation for nonholonomic mobile robots in highly cluttered environments. A collisionfree initial path being given for a robot, obstacles detected whi ..."
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Cited by 66 (6 self)
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This paper presents a novel and generic approach of path optimization for nonholonomic systems. The approach is applied to the problem of reactive navigation for nonholonomic mobile robots in highly cluttered environments. A collisionfree initial path being given for a robot, obstacles detected while following this path can make it in collision. The current path is iteratively deformed in order to ge away from obtacles and satisfy the nonholonomic constraints. The core idea of the approach is to perturb the input functions of the system along the current path in order to modify this path, making an optimization criterion decrease.
Reciprocal nbody Collision Avoidance
 INTERNATIONAL SYMPOSIUM ON ROBOTICS RESEARCH
, 2009
"... In this paper, we present a formal approach to reciprocal nbody collision avoidance, where multiple mobile robots need to avoid collisions with each other while moving in a common workspace. In our formulation, each robot acts fully independently, and does not communicate with other robots. Based o ..."
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Cited by 65 (22 self)
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In this paper, we present a formal approach to reciprocal nbody collision avoidance, where multiple mobile robots need to avoid collisions with each other while moving in a common workspace. In our formulation, each robot acts fully independently, and does not communicate with other robots. Based on the definition of velocity obstacles, we derive sufficient conditions for collisionfree motion by reducing the problem to solving a lowdimensional linear program. We test our approach on several dense and complex simulation scenarios involving thousands of robots and compute collisionfree actions for all of them in only a few milliseconds. To the best of our knowledge, this method is the first that can guarantee local collisionfree motion for a large number of robots in a cluttered workspace.
Aggregate Dynamics for Dense Crowd Simulation
"... Figure 1: Some examples of large, dense crowds simulated with our technique. (a) 100,000 pilgrims moving through a campsite. (b) 80,000 people on a trade show floor. (c) 25,000 pilgrims with heterogeneous goals in a mosque. Large dense crowds show aggregate behavior with reduced individual freedom o ..."
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Cited by 47 (7 self)
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Figure 1: Some examples of large, dense crowds simulated with our technique. (a) 100,000 pilgrims moving through a campsite. (b) 80,000 people on a trade show floor. (c) 25,000 pilgrims with heterogeneous goals in a mosque. Large dense crowds show aggregate behavior with reduced individual freedom of movement. We present a novel, scalable approach for simulating such crowds, using a dual representation both as discrete agents and as a single continuous system. In the continuous setting, we introduce a novel variational constraint called unilateral incompressibility, to model the largescale behavior of the crowd, and accelerate interagent collision avoidance in dense scenarios. This approach makes it possible to simulate very large, dense crowds composed of up to a hundred thousand agents at nearinteractive rates on desktop computers.
ClearPath: Highly Parallel Collision Avoidance for MultiAgent Simulation
 ACM SIGGRAPH/EUROGRAPHICS SYMPOSIUM ON COMPUTER ANIMATION
, 2009
"... We present a new local collision avoidance algorithm between multiple agents for realtime simulations. Our approach extends the notion of velocity obstacles from robotics and formulates the conditions for collision free navigation as a quadratic optimization problem. We use a discrete optimization ..."
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Cited by 44 (11 self)
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We present a new local collision avoidance algorithm between multiple agents for realtime simulations. Our approach extends the notion of velocity obstacles from robotics and formulates the conditions for collision free navigation as a quadratic optimization problem. We use a discrete optimization method to efficiently compute the motion of each agent. This resulting algorithm can be parallelized by exploiting dataparallelism and threadlevel parallelism. The overall approach, ClearPath, is general and can robustly handle dense scenarios with tens or hundreds of thousands of heterogeneous agents in a few milliseconds. As compared to prior collision avoidance algorithms, we observe more than an order of magnitude performance improvement.
Motion planning in dynamic environment: Obstacles moving along artitrary trajectories
 In Workshop on Autonomous navigation in Dynamic Environments, Int. Conference on Robotics and Automation
, 2005
"... This paper generalizes the concept of velocity obstacles [3] to obstacles moving along arbitrary trajectories. We introduce the nonlinear velocity obstacle, which takes into account the shape, velocity and path curvature of the moving obstacle. The nonlinear vobstacle allows selecting a single av ..."
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Cited by 38 (1 self)
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This paper generalizes the concept of velocity obstacles [3] to obstacles moving along arbitrary trajectories. We introduce the nonlinear velocity obstacle, which takes into account the shape, velocity and path curvature of the moving obstacle. The nonlinear vobstacle allows selecting a single avoidance maneuver (if one exists) that avoids any number of obstacles moving on any known trajectories. For unknown trajectories, the nonlinear vobstacles can be used to generate local avoidance maneuvers based on the current velocity and path curvature of the moving obstacle. This elevates the planning strategy to a second order method, compared to the first order avoidance using the linear vobstacle, and zero order avoidance using only position information. Analytic expressions for the nonlinear vobstacle are derived for general trajectories in the plane. The nonlinear vobstacles are demonstrated in a complex traffic example. 1
A short paper about motion safety,”
 in Int. Conf. on Robotics and Automation. IEEE,
, 2007
"... AbstractMotion safety for robotic systems operating in the real world is critical (especially when their size and dynamics make them potentially harmful for themselves or their environment). Motion safety is a takenforgranted and illdefined notion in the Robotics literature and the primary cont ..."
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Cited by 37 (10 self)
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AbstractMotion safety for robotic systems operating in the real world is critical (especially when their size and dynamics make them potentially harmful for themselves or their environment). Motion safety is a takenforgranted and illdefined notion in the Robotics literature and the primary contribution of this paper is to propose three safety criteria that helps in understanding a number of key aspects related to the motion safety issue. A number of navigation schemes used by robotic systems operating in the realworld are then evaluated with respect to these safety criteria. It is established that, in all cases, they violate one or several of them. Accordingly, motion safety, especially in the presence of moving objects, cannot be guaranteed (in the sense that these robotic systems may end up in a situation where a collision inevitably occurs later in the future). Finally, it is shown that the concept of Inevitable Collision States introduced in [1] does respect the three abovementioned safety criteria and therefore offers a theoretical answer to the motion safety issue.