Alberto Vale

A motion planning methodology for rhombic-like vehicles for ITER remote handling operations

Abstract The Transfer Cask System (TCS) is one of the adopted Remote Handling (RH) components to operate on the International Thermonuclear Experimental Reactor (ITER). During maintenance operations, the TCS is expected to move between specified locations in different levels of the Tokamak Building (TB), transporting heavy and highly activated components while meeting competing safety requirements. This paper proposes a complete motion planning methodology, covering path optimization and trajectory evaluation for static but tightly constrained scenarios. The optimization scheme is inspired on the elastic bands method, and takes into account geometric and kinematic robot considerations.

Trajectory optimization for autonomous mobile robots in ITER

The Cask and Plug Remote Handling System (CPRHS) is one of the remote handling systems that will operate in the International Thermonuclear Experimental Reactor (ITER), transporting heavy and highly activated in-vessel components between the Tokamak Building and the Hot Cell Building, the two main buildings of the nuclear facility. The CPRHS has similar dimensions as an autobus, maximum weight of 100 tons, with kinematics of a rhombic-like vehicle (two drivable and steerable wheels) and has to move in cluttered environments. Two main approaches for trajectory optimization were developed and implemented aiming at providing smooth paths that maximize the clearance to obstacles taking into account the flexibility of rhombic-like vehicles: line guidance (same path for both wheels) and free roaming (different paths for each wheel). The line guidance approach includes maneuvers when necessary and the ability of maximizing the common parts of different paths used in the most of the nominal operations. Free roaming is mainly used when line guidance is not possible, namely in rescue operations. Both approaches were implemented in a standalone application that receives 2D CAD models of the buildings and returns the best trajectories, including a report of the most risky points of collision and the swept volume of the vehicle along the missions. This paper also presents the main results of these approaches applied in the models of the real scenarios, crucial to proceed with the construction of the Tokamak Building. Conclusions and future work are presented and discussed. Path planning for mobile robots in cluttered environments with high safety constrains as in nuclear facilities like ITER.Line guidance and free roaming path planning methodologies for vehicles with rhombic-like kinematics.Integration of multiple maneuvers in path planning.Methodology that maximizes the common parts of different trajectories.

Performance analysis of fast marching-based motion planning for autonomous mobile robots in ITER scenarios

Operations of transportation in cluttered environments require robust motion planning algorithms. Specially with large and heavy vehicles under hazardous operations of maintenance, such as in the ITER, an international nuclear fusion research project. The load transportation inside the ITER facilities require smooth and optimized paths with safety margin of 30 cm. The transportation is accomplished by large rhombic-like vehicles to exploit its kinematic capabilities. This paper presents the performance analysis of a motion planning algorithm to optimize trajectories in terms of clearance, smoothness and execution time in cluttered scenarios. The algorithm is an upgraded version of a previous one used in ITER, replacing the initialization implemented using Constrained Delaunay Triangulation by the Fast Marching Square. Exhaustive simulated experiments have been carried out in different levels of ITER buildings, comparing the performance of the algorithm using different metrics. Path planning in International Thermonuclear Experimental Reactor (ITER) is studied.Fast marching-based path initialization provides high smoothness and clearance paths.Path length and obstacle clearance are improved with an optimization procedure.Path smoothness is decreased only the necessary to satisfy the requirements.Final paths are optimal, smooth and collision-free, demanded ITER scenarios.

Path optimization for rhombic-like vehicles: An approach based on rigid body dynamics

This paper proposes a new path optimization method to improve feasibility and optimality of rough collision-free paths provided by global planners. Inspired on the dynamics of rigid bodies, this method redefines the elastic bands framework to explicitly handle vehicle geometric constraints and explore the high maneuvering ability of rhombic vehicles. The proposed method was tested as a post optimization technique on global path solutions planned for a large transporter that will operate in the International Thermonuclear Experimental Reactor (ITER). Presented results show the proficiency of this method on handling feasible and reliable paths in cluttered scenarios such as those in ITER.

Optimizing range finder sensor network coverage in indoor environment

Abstract This document states a method to optimize the coverage of a range finder multisensor network on an indoor environment. The problem arose from the need of a localization system for autonomous mobile robots, integrated with the building. The common approach for a localization system consists on sensors in the vehicle itself. In this case the vehicle is only an actuator and the sensory part is installed on the building. The localization system performance depends on the sensor placement, to enhance it, the sensor network must maximize the covered area. To solve the problem, an algorithm that maximizes the coverage areas is proposed. Given a scenario map, obtains the optimal coverage area multisensor placement. This paper presents also some results and proposals to future approaches to the problem.

Feature extraction and selection for mobile robot navigation in unstructured environments

Abstract Feature extraction and selection are important steps in the construction of a map to support the navigation of mobile robots in outdoor environments. The large amount of data acquired by the on-board sensors has to be reduced to retain only the crucial information for the navigation purpose. This procedure should be robust given the rough, dynamic and unpredictable conditions provided by outdoor scenarios. The paper discusses the use of different types of features and proposes a feature selection criteria aiming at building a topological map of the environment. The approach was tested with real data acquired in different types of outdoor scenarios.

Four path following controllers for rhombic like vehicles

This paper addresses the path following problem of a wheeled mobile robot with rhombic like kinematics (two drivable and steerable wheels) operating in cluttered environments. Four path following controllers are developed to steer the kinematic model of a rhombic like vehicle (RLV) along a desired path: three are based on feedback laws derived at a kinematic level with geometrical inspiration; the fourth is a nonlinear controller built upon a kinematic model of the vehicle using Lyapunov functions. By fully exploiting the kinematic capabilities of this type of vehicles, all the developed controllers are capable of performing under two situations: when both wheels follow the same path, or when each wheel follows a different path. Simulated and experimental results are presented in the paper to illustrate the performance of the controllers. The main conclusions of these controllers are summarized, leading to a possible application in the vehicles that will operate in the remote handling missions of the International Thermonuclear Experimental Reactor (ITER).

Fast Marching in motion planning for rhombic like vehicles operating in ITER

Rhombic like vehicles are characterized for high maneuverability in cluttered environments. This type of vehicles will be used on remote handling operations of maintenance in the International Thermonuclear Experimental Reactor (ITER). Previous work was done in motion planning using Constrained Delaunay Triangulation for rhombic like vehicles operating in ITER. This paper shows that the integration of Fast Marching Square improves the motion planning methodology, decreasing also the computational effort, which can be applied not only in ITER but also in other complex and cluttered environments. Simulated results are presented comparing the initial and the improved motion planning.

Behavior of digital and analog controller devices for manual driving of rhombic like vehicles

This paper describes a study of different remotely operated driving modes applied to rhombic like vehicles using the digital buttons and the analog sticks of a generic game controller device (e.g., joysticks and gamepads). The performance of the different modes was evaluated using a software simulator and a 2D model of the Tokamak building of ITER. Several experiments were performed taking into account relevant parameters, such as the distance to the obstacles and accelerations. An optimal approach for a real implementation with a rhombic like vehicle prototype is proposed and discussed.

State Variables Estimation Using Particle Filter: Experimental Comparison with Kalman Filter

Within the probabilistic methods for the state estimation of a dynamic system, the particle filter approach is an innovative technique which is focusing the attention of current researches. Particle filtering succeeds in applying to different type of systems (linear and non-linear) and noise models. This paper presents a comparison between the results obtained using the particle Filter and the Kalman Filter for estimating the orientation and velocity of a DC motor. Real experiments are also presented.