CHARM facility remotely controlled platform at CERN: A new fault-tolerant redundant architecture

Many power electronics applications require high tolerance to faults such as short circuit or open circuit of the control signals. One such application is the CERN High energy AcceleRator Mixed-field (CHARM) facility, where maintenance may be precluded for long periods of time due to radiation and, therefore, high reliability is necessary. A redundant interconnection architecture for the control signals is proposed, where each signal is individually processed by different CPUs and transmitted through separate interconnection lines. During normal operation, the CPUs are synchronized and produce the same signals. The purpose of the proposed hardware and firmware strategy is to allow the actuator to continue operating even in case of fault; regardless of the fault type (open circuit, short circuit to ground or to positive supply), a fault on one of the parallel lines would not inhibit the correct operation of the remaining line. This solution can be used to control the movements of a target system using a remote joystick in a safe environment. The architecture features reliable transmission of PWM signals driving a half-bridge power converter. Moreover, it is possible to extend it to any type of converter such as three-phase bridges, three-level NPC, or buck-boost converters. Simulations and experimental results show a good agreement, proving the effectiveness of the proposed fault tolerant circuitry.