A closed loop robust control system for electrosurgical generators

Electrosurgical generators (ESU) are commonly utilized in medical surgeries for arc cutting and coagulation. The ESU unit is primarily composed of a high-power and high-frequency single-phase inverter. A probe is connected at the output of the inverter, which forms an arc between the patient tissues and its output terminal. The ESU unit is operated in three operational modes, including constant power mode, constant current mode, and constant voltage mode. For clean dissection, the unit is operated in constant power mode, for tissue vaporization it is operated in constant voltage mode, and for thermal coagulation constant current mode is utilized. In all the three modes, the power, voltage, and current are required to be limited to the specified values so that the undesirable effects such as thermal damage or tissue-charring phenomena should not occur. This chapter is focused on the introduction of ESU unit followed by the basic configuration of the unit, mathematical modeling, and closed-loop control system derivation. Fractional order robust control system based on variable structure method is derived for both inverter and buck converter stages of the ESU device. The results obtained using numerical simulations are presented and a comparative performance analysis is done for the ESU device with both fractional order and integer order control system.