Patent ID: 8197502

Claim:
A method of maintaining a constant movement of a cutting blade of an ultrasonic waveguide, which comprises: providing: an ultrasonic transducer operable to convert a received motional current into a movement of a cutting blade of an ultrasonic waveguide, the ultrasonic transducer having a first capacitance in a parallel configuration with a series configuration of a resistance, an inductance, and a second capacitance, wherein the motional current flows through the series configuration; a measurement circuit connected in a parallel configuration with the ultrasonic transducer and comprising a third capacitance in a parallel configuration with the first capacitance; supplying current through a set of connection points of the parallel configuration with a variable power source to, thereby, create the motional current in the ultrasonic transducer, the variable power source being coupled to the third capacitance and the ultrasonic transducer; and regulating the motional current with a current controller by varying an output of the power source based upon a product of the current flowing through the third capacitance multiplied by a ratio between a value of the first capacitance and a value of the third capacitance subtracted from a total current flowing into the ultrasonic transducer, thereby maintaining a substantially constant rate of movement of the cutting blade across a variety of cutting loads.