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Development of a self-localising system for determining the exact position and orientation of mobile floor bound system based on multi-sensor data fusion

Driverless transport vehicles (FTF) and mobile robots serve the auomated transport of goods and must navigate automatically without human intervention. Traditionally FTF were track based using either and optical guiding beam or induction guide wire. This approach is very inflexible, so today FTF use mostly virtual guidepaths. Mobile robots usually have a greater degree of autonomy than FTF and navigate freely, without physical or virtual guidepaths. For this navigation FTF and mobile robots require knowledge of their own position and orientation with reference to a two dimensional coordinate system within the deployment environment.

Locating of mobile systems outdoors can be realised via satellite positioning systems, like GPS. In environments with insufficient GPS information, like indoors or areas shaded by buildings, determining the position with GPS is not possible. Different locating technologies need to be found for such environments.

One possible approach for determining position, using Auto-ID technology, is grid navigation. Passive RFID transponders are attached to or embedded in the floor. Future-Shape GmbH has developed NaviFloor®, a floor covering with embedded FRID transponders. By embedding the RFIF underlay in a synthetic resin floor it becomes suitable for high loadings, such as that caused by heavy FTF. RFID readers in the FTF or mobile robot can read the ID of any RFID transponder within reach. By knowing all RFID transponder positions in the deployment environment the FTF or mobile robot can determine it's own position. Direct detection of orientation is not possible with this technology. Only after reading two transponders can the orientation be roughly determined.

For FTF navigation using RFID transponders up to now, the orientation at start needs to be determined manually and entered into the FTF controller. Reconciliation of the orientation during travel using RFID transponders, requires additional sensors (wheel sensors, gyroscope), as well as precise knowledge of the kinematics of the FTF in combination with the geometry and positioning of the RFID aerials. Customisation needs to be done for each FTF type and implemented in the vehicle controller. This customisation effort currently prevents greater spread of the NaviFloor®.

Aim of the project is the development of a modular localisation device, that can determine the exact position and orientation of mobile floor bound systems like driverless transport vehicles or mobile robots, outdoors using GPS and indoors using NaviFloor®. The device should work independently of the FTF's or mobile robot's sensors. Key is the separation of the FTF localisation hardware and controller hardware, to minimise the integration efforts for the FTF manufacturer.

A device was developed, together with Future-Shape GmbH, that contains integrated GPS and RFID reader, as well as further sensors for determining orientation and precise position interpolation. Suitable fusion of the sensor data with the RFID reader data will enable precise determination of orientation and position.

The localisation system is primarily meant for use with FTF or mobile robots. However, any other mobile object that can have a reader attached near the floor will be supported. This could be forklift trucks, shopping trolleys, electrical wheelchairs, hospital beds or other valuable devices or objects whose location needs to be captured automatically.