Sensors in Proactive Maintenance – A case of LTCC pressure sensors

Pressure sensors are the third most widely used category of physical sensors in the system maintenance [1]. Beside system control the pressure measurements can be used to reveal physical changes in a system. If the pressure values go outside the expected range, there is a possibility of damaging system parts. In safety-critical systems special measures are taken to provide robust and reliable operation even in the case of sensor failures [7]. Such solutions either introduce hardware or software redundancy, or make the monitoring more complex by enabling it to work better with incomplete data. Not all sensors can be made redundant because of space and cost constraints and the impact of individual sensors on system operation is analysed in order to identify their significance [5]. For the systems that are not necessarily safety-critical but still require reliable operation various possible maintenance scenarios with respect to both reliability and economic criteria are considered. For example, a method used to study the effect of equipment aging under different maintenance strategies is described in [13]. Accurate and reliable sensor measurements are prerequisite for efficient system maintenance, which is also one of the goals of the ECSEL JU project MANTIS – Cyber Physical System based Proactive Collaborative Maintenance [11], and the work reported in this paper. Proactive maintenance (PM) is a maintenance strategy which attempts to anticipate machine failures and similar problems and provides solutions before they occur [3]. The proactive approach benefits from the traditional preventive and predictive maintenance practice and upgrades them by root cause analysis, and predictive algorithms based on cyber physical system models [2, 9, 10]. The proactive maintenance can yield considerable savings over conventional predictive/ preventive maintenance programs [4, 14]. Pressure sensors enable monitoring of operating conditions and the wear-out of the critical parts of the mechanical system for which proactive maintenance is performed. Yet, it should be noted that the sensors themselves are not ideal components, but physical devices including sensing elements, electronic components, connections and housings that are aging and degrading [12, 15], and in general may need to be maintained. To improve the reliability of a system, it is essential to ensure reliable operation of the sensors involved, i.e., the correct interpretation of their responses in the different periods of their life-cycles. In this regard, it is prudent to track and monitor their health conditions. In the presented case study, we concentrate on how the operating mode affects their ageing and identify measures that could be taken in defining the maintenance strategy. Marina SAnto ZArnik Franc novAk Gregor PAPA