Methods and systems for robot-assisted surgery

1 . A method for preventing a robotic arm from colliding with a patient, comprising:

tracking at least one of a position and orientation of a robotic arm with an end effector relative to a patient using a motion tracking system, the end effector including a cannula configured to allow one or more instruments to removably pass through the cannula below an epidermal surface of the patient;

tracking a position and an orientation of the patient with one or more patient markers with the motion tracking system;

generating a boundary surface based on identifying at least a portion of the epidermal surface of the patient, wherein the boundary surface comprises a virtual three-dimensional surface above the epidermal surface of the patient;

preventing the end effector from crossing the boundary surface;

detecting the position of the patient relative to the robotic arm; and

controlling the robotic arm to take a remedial action based on the position of the patient relative to the robotic arm.

2 . The method of claim 1 , wherein the boundary surface is offset from the epidermal surface by a predetermined amount.

3 . The method of claim 1 , further comprising registering an image dataset and the boundary surface within a patient coordinate system.

4 . The method of claim 3 , wherein the robotic arm executes a control loop that repeatedly reads joint parameters of the robotic arm while monitoring tracking data of the patient from the motion tracking system indicating a current position and orientation of the robotic arm within the patient coordinate system.

5 . The method of claim 1 , wherein end effector is controlled to be prevented from crossing the boundary surface by modifying at least one of a velocity, acceleration, and torque of the robotic arm as a function of proximity to the boundary surface.

6 . The method of claim 1 , further comprising identifying the at least a portion of the epidermal surface of the patient in an image dataset of an anatomy of the patient, wherein the image dataset comprises at least one of a three-dimensional x-ray CT reconstruction and a three-dimensional MRI dataset.

7 . The method of claim 1 , further comprising defining a target location below the epidermal surface of the patient.

8 . The method of claim 7 , further comprising maintaining the end effector of the robotic arm pointed along a trajectory intersecting with the target location.

9 . The method of claim 8 , further comprising allowing movement of the robotic arm to advance the end effector along the trajectory toward the target location.

10 . The method of claim 9 , wherein the cannula is further defined as being configured to allow one or more instruments to removably pass through the cannula to the target location along the trajectory.

11 . The method of claim 1 , wherein the remedial action comprises at least one of: immediately stopping all current and/or planned movements of the robotic arm, preventing hand guiding of the robotic arm, triggering an audio and/or visual alarm, controlling the robotic arm to move away from the patient, and entering a compliant mode characterized by an increased sensitivity and/or responsiveness of the robotic arm to an applied force.