Proceedings of the 9 th International Symposium on Mechatronics and its Applications (ISMA13), Amman, Jordan, April 9-11, 2013 IDENTIFICATION OF PIEZOELECTRIC ULTRASONIC TRANSDUCERS FOR MACHINING PROCESSES Tarek Tutunji 1 , Ashraf Saleem 2 , Mohammad Salah 3 , and Naseer Ahmad 2 1 Department of Mechatronics Engineering, Philadelphia University, Amman, Jordan 2 Department of Mechanical Engineering, Taibah University, Al-Madinah Al-Monawara, Saudi Arabia 3 Department of Mechatronics Engineering, Hashemite University, Zarqa, Jordan ABSTRACT Smart or active materials expand or deform as a response to external pressure, temperature, or electromagnetic field. The most commonly used active material in actuators is piezoelectric as it relates the electric field to mechanical compression and elongation. However, mathematical modeling of such actuators is tedious and complicated because of the nonlinear behavior. Therefore, there is a need to employ appropriate identification algorithms in order to capture the modeling process of such actuators. In this paper, ultrasonic transducer that is used in ultrasonically assisted machining is adopted as a case study. A component-based model for the piezoelectric is derived and the dynamic response is analyzed. Then, two identification techniques, ARX and ANN, are used to obtain models that mimic the system’s dynamic response with minimal error. 1. INTRODUCTION The direct piezoelectric effect is the ability of certain materials to generate electric charge in proportion to externally applied force. The inverse piezoelectric effect is their ability to expand under an electric field. Due to these phenomena, piezoelectric materials can be used as both actuators and sensors. Applications include micromanipulation such as suppression of oscillations, micro-robot, micro-pump, and micro-gripper [1]. Piezomotors usage as actuators is based on the conversion of high frequency mechanical oscillations into continuous motion. Advantages of piezomotors are large torque, high resolution, excellent controllability, small time constant, compactness, high efficiency, silent operation, and no electromagnetic induction. Researchers have been very active in the area of identification and control of piezoelectric material. Ru et al. [2] have derived a mathematical model to describe the hysteresis effect and tested an adaptive control approach for micro- positioning experiment. Juhasz et al. [3] described a method for parameter identification of embedded piezoelectric actuators for the use in a real-time FPGA system. In both of these papers, the applied voltage had a frequency range in hertz. Other researchers investigated the identification of the piezoelectric structure properties [4] and developed models for damage identification [5]. Another interesting application is the Ultrasonic Assisted Tuning (UAT) which is a machining technique that is being used to machine hard-to-cut alloys. In this technique, a high frequency vibration (about 20kHz) is superimposed on the movement of the cutting tool that results in a reduction of the required cutting force by 60% [6]. In this work, component-based model is developed for piezoelectric ultrasonic transducer. This transducer converts electric energy into ultrasonic vibration waves by applying external voltage on the piezoelectric stack. The vibration waves travel through the transducer material in the form of deformation and stress waves. The stress wave is then concentrated at the cutting tip to intensify the effort. As mentioned earlier, modeling of such system is complicated and therefore system identification techniques are used in this work in order to predict an appropriate model for the system based on recorded input-output data. The rest of the paper is organized as following: Section 2 presents the component-based model of the system. Section 3 provides two different identification methods. Results are discussed in Section 4 and Section 5 concludes the paper. 2. COMPONENT BASED-MODELING Component-based modeling is an approach where the system is decomposed into its basic components which can be developed and tested individually. Therefore, a component is defined as an entity or subsystem which is designed to perform certain functions and tasks and can be used as a building block in the design or modeling of a larger system. In the context of this study, the ultrasonic transducer is divided into two basic components as shown in Figure 1: 1- PZT component: this component represents the piezoelectric rings which are considered the driving force for the actuator. This component has three inputs and two outputs as depicted in Figure 1. 2‐ Mass-Spring-Damper (MSD) component: this component represents a mass that is connected with two springs and two dampers as shown in Figure 1. This component has four inputs and two outputs. For ultrasonic transducer two MSD components are required to model the concentrator. 1 x 1 x  2 x 2 x  o x o x  L x L x  Figure 1. Proposed component-based model for piezoelectric ultrasonic transducers ISMA13-1