Method for detecting a disturbance as an energy applicator of a surgical instrument traverses a cutting path

A method for detecting a disturbance as an energy applicator of a surgical instrument traverses a cutting path, the method being implemented on at least one computing device having a non-transitory computer-readable storage medium with an executable program stored thereon, said method comprising the steps of:

• executing the program stored on the computer-readable storage medium, wherein the program instructs the at least one computing device to:
• determine actual torques for each active joint of an actuated arm mechanism supporting the surgical instrument;
• calculate expected torques for each active joint of the actuated arm mechanism, wherein the expected torques are calculated based on an angular position of each active joint and a commanded joint angle for each active joint;
• determine estimated backdrive torques based on the expected torques and the actual torques, wherein the estimated backdrive torques indicate a disturbance along the cutting path;
• convert the estimated backdrive torques to a backdrive force having a force component and a torque component;
• filter the backdrive force by:
• comparing an absolute value of the magnitude for each component of the backdrive force with a threshold;
• setting to zero each component of the backdrive force that has an absolute value less than the threshold;
• and calculating a filtered backdrive force based on the differences between the threshold and the components of the backdrive force having an absolute value greater than the threshold;
• and
• generate an external force based on the filtered backdrive force and a sensor force derived from a force/torque sensor mounted to an end effector coupled to the surgical instrument.