Research On Mapping And Navigation For Tokamak Transfer Cask

Tokamak Transfer Cask System(TCS) is an important part of International Thermonuclear Experimental Reactor(ITER), it can transfer component between the tokamak building and the hot cell building under the environment with radiation, poison, and high temperature instead of human. TCS is a kind of Automatic Guided Vehicle, which belongs to wheeled mobile robot, its navigation system must be reliable and highly accurate. Navigation based on map is one of the main solutions to indoor environment navigation. In regard to TCS and its working environment, this paper proposes two mapping methods. Then navigation experiments are conducted on the TCS platform.First, different map representations are analyzed, on the situation of complex junctions, part of the environment information may be covered and moving objects may disturb the measurement, this paper proposes a heterogeneous mapping method based on landmarks. During mapping, the localization results based on landmark map can help the contour map building which is based on ICP-SLAM. This method can reduce computation complexity of ICP-SLAM and avoid getting in local minimum. Localization experiment results show that the localization result by heterogeneous map can obtain effective result when either the landmarks are covered or there are moving objects disturbance.Second, magnetic guidance based on magnet markers is a widely used method in AGV navigation, with regard to the magnet map used in magnet navigation, RTK-GPS is usually used for building magnet map. But this method cannot reach an expected precision and may cost lots of time and effort, and there is no GPS signal in indoor environment. So SLAM can be a solution to build magnet map. After analyzing different solutions to SLAM problem and comparing their advantages and disadvantages in different problems, a mapping method based on Graph-SLAM is proposed. Errors in measurement and computation may cause failure in SLAM loop closure, but Graph-SLAM solves the problem by loop closure detection and graph optimization. One of the main problems of Graph-SLAM is the loop closure detection in the measured environment. However, the magnet coordinates, which are the result of Graph-SLAM, can offer reliable and accurate loop closure constraints in return. The experiment result shows the feasibility of this mapping method.Last, TCS navigation system is designed for the specific characteristics of thermonuclear experimental environment, including the selection and parameters analysis of sensors, controllers, and actuator on TCS. Then do navigation experiments based on heterogeneous map and based on electromagnetic guide line respectively. Experimental results show the navigation accuracy is high enough, the system can meet the accuracy and reliability requirements in the thermonuclear experimental environment.