Surgical robot with passive end effector

1. A surgical system comprising:

a passive end effector including,

a base configured to attach to an end effector coupler of a robot arm positioned by a surgical robot,

a first mechanism extending along a first plane, the first mechanism extends between a rotatable connection to the base and a rotatable connection to a second mechanism, and

a second mechanism extending along a second plane, the second mechanism extends between a rotatable connection to the first mechanism and a rotatable connection to a tool attachment mechanism,

wherein the first and second mechanisms pivot about the rotatable connections to constrain movement of the tool attachment mechanism to a range of movement within a working plane, the tool attachment mechanism being configured to connect to a surgical saw having a saw blade configured to oscillate for cutting, the saw blade extending along the working plane, and

wherein the first plane is positioned vertically above the second plane and the second plane is positioned vertically above the working plane.

2. The surgical system of claim 1 , further comprising:

a tracking system configured to determine a pose of an anatomical structure that is to be cut by the saw blade and to determine a pose of the saw blade,

wherein the surgical robot includes

a robot base,

the robot arm is connected to the robot base and configured to position the passive end effector,

at least one motor operatively connected to move the robot arm relative to the robot base, and

at least one controller connected to the at least one motor and configured to determine a pose of a target plane based on a surgical plan defining where the anatomical structure is to be cut and based on the pose of the anatomical structure, and

generate steering information based on comparison of the pose of the target plane and the pose of the surgical saw, wherein the steering information indicates where the passive end effector needs to be moved to position the working plane of the passive end effector so the cutting plane of the saw blade is aligned with the target plane.

3. The surgical system of claim 2 , wherein the at least one controller is further configured to

control movement of the at least one motor based on the steering information to reposition the passive end effector so the cutting plane of the saw blade becomes aligned with the target plane and the saw blade becomes positioned a distance from the anatomical structure to be cut that is within the range of movement of the tool attachment mechanism of the passive end effector.

4. The surgical system of claim 2 , wherein the at least one controller is further configured to

provide the steering information to a display device for display to guide operator movement of the passive end effector so the cutting plane of the saw blade becomes aligned with the target plane and so the saw blade becomes positioned a distance from the anatomical structure, which is to be cut, that is within the range of movement of the tool attachment mechanism of the passive end effector.

5. The surgical system of claim 4 , wherein the at least one controller is further configured to

configuring the steering information for display on a head-mounted display device having a see-through display screen that displays the steering information as an overlay on the anatomical structure that is to be cut to guide operator movement of the passive end effector so the cutting plane of the saw blade becomes aligned with the target plane and the saw blade becomes positioned the distance from the anatomical structure within the range of movement of the tool attachment mechanism of the passive end effector.

6. The surgical system of claim 5 , wherein to configure the steering

information for display on the head-mounted display device the at least one controller generates a graphical representation of the target plane that is displayed as an overlay anchored to and aligned with the anatomical structure that is to be cut, and

generates another graphical representation of the cutting plane of the saw blade that is displayed as an overlay anchored to and aligned with the saw blade.

7. The surgical system of claim 5 , wherein to configure the steering information for display on the head-mounted display device the at least one controller generates a graphical representation a depth of cut made by the saw blade into a graphical representation of the anatomical structure being cut.

8. The surgical system of claim 2 , wherein the tracking system is configured to determine the pose of the anatomical structure that is to be cut by the saw blade based on determining a pose of tracking markers that are attached to the anatomical structure, and is configured to determine a pose of the surgical saw based on determining a pose of tracking markers on at least one of the surgical saw and the passive end effector.

9. The surgical system of claim 2 , wherein the tracking system is configured to determine the pose of the surgical saw based on rotary position sensors configured to measure rotational positions of the first and second mechanisms during movement of the tool attachment mechanism within the working plane.