Sequencing tasks to minimize the effects of near-coincident faults in TMR controller computers

Although Triple Modular Redundancy (TMR) has been widely used to mask the effects of a single faulty module, it cannot tolerate coincident faults in multiple modules caused by a common source, such as an environmental disruption or malfunction of a shared component. We propose a method to eliminate or alleviate the effects of (near) coincident faults by sequencing tasks on different modules in a TMR system. Specifically, we develop an effective sequencing of tasks to simply place an "optimal" distance (in the sense of minimizing the mean number of faulty tasks due to TMR failures) between the copies of a task to be executed on different modules. Several examples are presented, showing significant improvements in reducing TMR failures with the proposed task sequencing.