Collision avoidance system for the RP survey and visual inspection train in the CERN large hadron collider

Abstract

This Final Year Project focused on producing a working prototype of a collision avoidance system for the retractable Radio-Protection (RP) arm, in the Train Inspection Monorail (TIM), located in European Organization for Nuclear Research (CERN)’s Large Hadron Collider (LHC) Tunnel. This retractable arm is deployed in specific regions in the tunnel, after the beams have been dumped, to take radiation and oxygen level measurment around LHC equipment. In turn, these measurements allow the CERN Radiation Protection Group to assess any health hazards inside the LHC tunnel, before access to it is permitted to the maintenance personnel. This prototype uses a series of eight distance measurement sensors based on the Infrared (IR) Time-of-Flight (ToF) technology, which scans a safety volume underneath the TIM and raises an alarm once this volume is breached. Namely, the TeraRanger One (TR1) IR ToF distance measurement sensor, is used, which is interfaced via the TeraRanger Hub (TRH), by TeraBee. A Cortex-M microcontroller, is mounted on the TRH, which in turn is connected to the distance measurement sensors via a multiplexed Universal Synchronous/Asynchronous Receiver/Transmitter (USART) connection among all eight sensors. The Micro Controller Unit (MCU) also provides an interface for the user maintaining the collision avoidance system, via a second, dedicated USART connection. The MCU’s Direct Memory Access (DMA) functionalities are also used to transfer the data from the TR1, directly into memory. Sensor characterisation tests were also devised and performed. The sensor characterisation tests obtained calibration results, by which the accuracy of the TR1 sensors was improved, established any effects that prolonged use of the TR1 might have on the distance measurement, due to components heating up over time, as well as the effects on the distance measurements, when the Field-of-View (FOV) of the TR1 was partially covered. For the specific role of aiding in the data acquisition during the sensor characterisation tests, a testing rig was designed and constructed. This was designed to ensure that the distance from the sensor array to the surface being scanned, was always known during testing.