Adjustment of complex impedance to compensate for lost power in an articulating ultrasonic device

An ultrasonic surgical instrument comprising:

• an ultrasonic electromechanical system comprising an ultrasonic transducer coupled to an articulatable ultrasonic blade via a flexible ultrasonic waveguide;
• and
• a generator to supply power to the ultrasonic transducer, wherein the generator comprises a control circuit configured to:
• sweep the articulatable ultrasonic blade through a range of articulation angles from a first articulation angle to a second articulation angle at one or more predetermined angular increments;
• activate the ultrasonic transducer at an energy level at each of the one or more predetermined angular increments;
• measure a complex impedance of the ultrasonic transducer at each of the one or more predetermined angular increments;
• record a set of complex impedance measurements at each of the one or more predetermined angular increments;
• generate reference complex impedance characteristic patterns as a function of the one or more predetermined angular increments;
• store the reference complex impedance characteristic patterns in a memory or a database;
• determine a third articulation angle of the articulatable ultrasonic blade;
• adjust the complex impedance of the ultrasonic transducer to compensate for power lost as a function of the one or more predetermined angular increments;
• and
• adjust a power applied to the ultrasonic transducer based on the third articulation angle.