Yves Langeron

A modeling framework for deteriorating control system and predictive maintenance of actuators

Abstract Actuators play a central role in industrial automation systems. They are costly, and therefore studying their dependability needs all attention. Usually, an actuator is inserted in a feedback control system, and its mission is to implement a control action delivered by a controller. In this paper, a monotonic actuator deterioration is considered and it is assumed that a relationship exists between the control action and the physical actuator׳s deterioration. A modeling framework is proposed including a non-decreasing stochastic degradation process driving the inability for an actuator to fully implement its role. The prognosis of the actuator׳s residual useful lifetime is derived and used to update the controller׳s setting. The controller reconfiguration completes the maintenance corrective and preventive actions. This new action is suggested as an alternative for maintenance strategy.

Actuator Lifetime Management in Industrial Automation

Abstract The aim of this paper is to combine the deterministic behavior of a feedback control system with an inner stochastic degradation process. For that, a modeling framework is proposed with an intrinsic deterioration caused by the control input law and its variations. As a consequence, when degrading the actuator has a loss of effectiveness to carry out this command. Two system missions are studied - slow and fast missions - with a Markov chain allowing to parameterize the sojourn times in the different system states. Finally, a basic PID controler commonly used in industrial automation is assessed regarding performances and lifetime aided with Monte Carlo simulations.

Joint maintenance and controller reconfiguration policy for a gradually deteriorating control system

This paper tackles the maintenance decision-making of gradually deteriorating control systems. The main feature of these systems is their ability within a closed-loop to drive actuators in order to set the controlled process in a given state. Usually, the existing literature deals with the diagnosis of faults of a control system and the means to recover system performances after their appearance. The controller reconfiguration is one of these means. The root cause of a fault is rarely argued nor its occurrence time. Before designing maintenance policies, this paper proposes a stochastic modeling framework of a degrading control system focusing on the actuator deterioration. It is based on the assumption of a close relationship between the controller setting, the actuator deterioration and finally its faulty situations. These latter are related to given degradation thresholds. Due to the stochastic nature of the deterioration, the thresholds hitting times are random. The obtained model allows the conditional reliability of the actuator to be assessed and then the prognosis of its residual useful life (RUL). This RUL is finally used to achieve two maintenance policies based upon the reconfiguration of the controller which is therefore considered as a new maintenance action.