The effect of operation is directly determined by the vibration amplitude of the ultrasonic scalper

which is a key control parameter on the treatment for the patient by using the power ultrasonic medical instrument.Because the vibration amplitude of the scalper changes with multiple factors such as environmental temperature

time variance nonlinear load and static state press

a vibration amplitude control technique is needed for obtaining the stable vibration amplitude in the power ultrasonic medical system. This paper analyzes the equivalent electromechanical model of the ultrasonic vibration system made up of a longitudinal composite bar high-power transducer

a horn and a scalper

and presents the vibration amplitude control approach based on the self-modifying PID fuzzy controller for the power ultrasonic medical instrument.Compared with the PID controller

the self-modifying PID fuzzy controller has two merits: avoidance of the limit circle oscillation and elimination of the system residual error.Finally

it states the design procedure.The experiments show that the robustness and the control accuracy of the power ultrasonic system can be improved by using the self-modifying PID fazzy control technique.