Supervisory controller synthesis and implementation for safety PLCs

Abstract

The development of supervisory controllers for cyber-physical systems is a laborious and error-prone process. Supervisor synthesis enables control designers to automatically synthesize a correct-by-construction supervisor from a model of the plant combined with a model of the control requirements. From the supervisor model, controller code can be generated which is suitable for the implementation on a programmable logic controller (PLC). Supervisors for industrial systems that operate in close proximity to humans have to adhere to strict safety standards. To achieve these standards, safety PLCs (SPLCs) are used. For SPLC implementation, the supervisor has to be split into a regular part and a safety part. In previous work, a method is proposed to automatically split a supervisor model for this purpose. The method assumes that the provided plant model is a collection of finite automata. In this paper, the extension to extended finite automata is described. Additionally, guidelines are provided for modeling the plant and the requirements to achieve a favorable splitting. A case study on a rotating bridge is elaborated which has been used to validate the method. The case study spans all development steps, including the implementation of the resulting supervisor to control the real bridge.

Analysis and Control of Partially Observed Discrete-Event Systems via Positively Constructed Formulas

“…Moreover, the representation of DESs with the help of PCFs allows one to use information coming from the environment, as well as data on the functioning of the system itself, in the process of constructing the logical inference. This feature may help greatly in problems of supervisory controller synthesis and implementation for safety PLCs (programmable logic controllers) [48], where extended finite-state automata (EFA) are exploited. Transitions in an EFA may contain guards (i.e., logical conditions) over the variables and updates (i.e., assignments) to the variables.…”

Supervisor Synthesis: Bridging Theory and Practice

“…A simulator enables interactive visualization-based simulation of the behavior of the controlled plant. Efficient PLC code can be generated automatically [20]; this code conforms to the IEC 61131-3 standard.…”

On the application of the calculus of positively constructed formulas for the study of controlled discrete-event systems

“…Представление ДСС с помощью ПОФ позволяет использовать в процессе построения логического вывода информацию, поступающую из окружающей среды, а также данные о функционировании самой системы. Эта функция может существенно помочь в задачах синтеза и реализации супервизоров для программируемых логических контроллеров (ПЛК) [29], где используются расширенные автоматы с конечным числом состояний (РКА). Переходы в РКА могут содержать условия (например, логические условия) на переменные и действия (например, обновление) на переменные.…”