Model-Based Approach for a Control System for Ultrasonic Systems Using Mechanical Sensors

Ultrasonic vibration assistance can significantly enhance the performance of manufacturing processes and reduce process limitations. Changing external loads during manufacturing, e.g., process forces or heat flow, require a continuous adjustment of the system’s operating frequency. Conventional approaches based on the readily available electrical signals of the ultrasonic transducer, like a phase-locked-loop approach, are effective but not ideal as the electrical signals are gathered far from the cutting edge. Since the resonance frequencies of the electrical and mechanical resonant circuit do not necessarily match, using signals based on mechanical quantities close to the cutting edge, like acceleration, might offer benefits regarding the current vibration behavior of the system. Therefore, a better control of the ultrasonic system during operation can be provided. In this work a control model for an ultrasonic system using signals based on the acceleration at the cutting edge is designed and evaluated. The data for the modeling of the ultrasonic system is obtained from experiments using an existing system. Two control algorithms, phase-locked-loop and autoresonant control, are modeled and adapted for using mechanical quantities as the input for the control model. The results show the differences between the resonance frequencies of the electrical and the mechanical resonant circuit. The findings support the benefits of using a control algorithm based on mechanical quantities to better control the process. Furthermore, larger displacements at the tool could be achieved using acceleration in the proposed control algorithms.