An approach for the model based monitoring of piezoelectric actuators

Piezoelectric actuators are used in a wide range from mechatronic applications like fuel injection to the field of smart structures for micropositioning or noise and vibration suppression. However, due to increasing demands for reliability and safety of technical systems, fault diagnosis and structural health monitoring become important. Therefore, the on-line diagnosis of piezo actuators is an essential challenge when developing smart structural systems for industrial as well as automotive or aerospace applications.Model based monitoring systems can provide detailed information about the current status of a technical system [Börner M, Straky H, Weispfenning T, Isermann R. Model based fault detection of vehicle suspension and hydraulic brake systems. Mechatronics 2002;12:999–1010]. In this work, an approach for model based monitoring of piezoelectric actuators is examined. The main idea is to use the measurement of the electrical impedance of the actuator to receive information about possible damages. Because of the electromechanical coupling, this measure includes information about the electrical parameters as well as the mechanical parameters of the actuator. At hands of a simulation, basic studies on damage scenarios of electromechanically coupled systems are accomplished.Methods for model based fault diagnosis of the system are developed and implemented with the help of adaptive digital filters [Mayer D, Herold S, Atzrodt H. Structural health monitoring of smart structures using pattern recognition and adaptive digital filters. In: Proceedings of the second European workshop on structural health monitoring. Munich: DesTech Publications Inc.; 2004. p. 1099–1105]. These should provide parametric models of the input impedance function, possibly on-line in parallel to the operation of the piezo transducer in a vibration control system. The signal processing algorithms are developed taking into account the possibility of implementation of a real-time capable embedded standard hardware, i.e. the computational effort of the diagnostic system. Measurements on piezoelectric stack actuators used in smart systems for vibration decoupling help to improve the simulation. The monitoring system is implemented on rapid prototyping controller hardware and is tested in an experiment on monitoring of the piezoelectric actuators.