Method for improving the start up of an ultrasonic system under zero load conditions
First Claim
1. A method for improving start up performance of an ultrasonic surgical system under zero load conditions, comprising the steps of:
- applying a drive signal from an ultrasonic generator to a hand piece/blade;
adjusting a circuit located in the generator;
performing a first search to locate a target angle;
increasing a drive frequency of the drive signal;
maintaining the target angle at a constant value;
monitoring properties of the drive signal at the increased drive frequency to calculate a differential value; and
adjusting the circuit using the calculated differential value.
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Abstract
The start up performance of an ultrasonic system under zero load conditions is improved by setting a phase set point in a frequency control loop such that, at start up under zero load conditions, the phase set point intersects a point on a phase-frequency response curve which has a low positive slope. This intersection point on the phase-frequency response curve changes as the load is increased and the system Q is decreased. The controller “seeks” a target 0° impedance phase angle. The frequency of the ultrasonic generator is set to an off-resonance frequency which is lower than the resonance of any known hand piece/blade combination. In order for the drive voltage to not exceed the physical limit of the system, the drive current is set to a low level. The drive frequency is then smoothly increased in steps until the target 0° impedance phase delta is located.
152 Citations
20 Claims
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1. A method for improving start up performance of an ultrasonic surgical system under zero load conditions, comprising the steps of:
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applying a drive signal from an ultrasonic generator to a hand piece/blade;
adjusting a circuit located in the generator;
performing a first search to locate a target angle;
increasing a drive frequency of the drive signal;
maintaining the target angle at a constant value;
monitoring properties of the drive signal at the increased drive frequency to calculate a differential value; and
adjusting the circuit using the calculated differential value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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