Fail-safe output modules for electronic control systems

In order to obtain a safety electronic control system, a widely used solution is the massive redundancy approach (i.e., duplication, triplication, etc. of the system), which results in very expensive solutions. This paper presents a method to make the outputs of an electronic control system fail-safe, with a reduced hardware overhead and a reduced cost. The method, based on the use of dynamic logic, is suitable for implementation in digital electronic control systems and, in particular, in PLCs of low or medium range.