Method and system for engagement of a surgical tool with actuators of a tool drive in a surgical robotic system

1. A surgical robotic system for engaging a robotic surgical tool with a tool drive, the system comprising:

a robotic surgical tool having one or more tool disks at a proximal end and an end effector at a distal end;

a tool drive mounted at a distal end of a surgical robotic arm, wherein the tool drive comprises one or more drive disks each driven by a rotary motor, each drive disk configured to be attached to a tool disk of the surgical tool to impart motion to the end effector;

a control unit comprising one or more processors configured to:

detect that the surgical tool is attached to the tool drive;

for each drive disk

actuate the drive disk through the rotary motor;

detect, during the actuation, that the drive disk is engaged to a tool disk based on sensed changes in motor status, including that a velocity of the rotary motor drops below a velocity threshold and a torque of the rotary motor rises above a torque threshold, wherein the torque threshold is a value between i) a minimum torque for the rotary motor to overcome friction between the drive disk and the tool disk before engagement and ii) a maximum torque for the rotary motor to produce; and

report engagement of the surgical tool when engagement of all of the drive disks to their tool disks has been detected.

2. The system of claim 1 , wherein the velocity of the rotary motor dropping below the velocity threshold corresponds to the rotary motor being stopped.

3. The system of claim 1 , wherein the changes in motor status are caused by at least one of: the end effector reaching a joint limit, an external force on the end effector, a motion constraint due to another motor of the tool drive being activated, and a combination thereof.

4. The surgical robotic system of claim 3 wherein the tool disk is winding a cable, and the rotary motor reaches a physical constraint against further rotation of the drive disk, wherein the physical constraint is caused by a second drive disk that is also winding the cable or holding a position of the cable.

5. The surgical robotic system of claim 1 , wherein the sensed changes in motor status are caused by the rotary motor reaching a physical constraint against further rotation of the drive disk.

6. The surgical robotic system of claim 5 , wherein the tool disk is winding a cable, and the physical constraint comprises a movement constraint caused by a second drive disk that is also winding the cable or holding a position of the cable.

7. The surgical robotic system of claim 6 , wherein the drive disk and the tool disk comprise one or more pairs of coupling features wherein each pair of coupling features becomes interlocked to each other to rotate as one when mechanical engagement is achieved.

8. The surgical robotic system of claim 1 wherein the control unit is further configured to:

activate the rotary motor of the tool drive to rotate the drive disk at a first velocity, and

activate the rotary motor of the tool drive to rotate the drive disk at a second velocity lower than the first velocity when the rotary motor or drive disk reaches a threshold angle away from a reference position, wherein the reference position corresponds to a known calibrated engagement position.

9. The surgical robotic system of claim 1 wherein the drive disk and the tool disk comprise one or more pairs of coupling features wherein each pair of coupling features becomes interlocked to each other to rotate as one when mechanical engagement is achieved.

10. A method performed by a processor of a surgical robotic system for engaging a surgical tool with a tool drive of the surgical robotic system, the method comprising the following operations performed by the processor:

activating an actuator of the tool drive to rotate a drive disk wherein the drive disk is to be mechanically engaged with a tool disk in the surgical tool;

while the actuator is activated, which causes rotation of the drive disk, measuring a plurality of operating parameters of the actuator including motor torque and motor velocity; and

detecting when the drive disk becomes mechanically engaged with the tool disk based on the measured operating parameters of motor torque and motor velocity satisfying a condition, by determining that measured torque of the actuator exceeds a threshold torque and measured velocity of the actuator is below a threshold velocity, wherein the threshold torque is i) greater than friction between the drive disk and the tool disk during rotation without mechanical engagement and ii) less than a maximum torque for the actuator.

11. The method of claim 10 , wherein the condition represents the actuator reaching a physical constraint against further rotation of the drive disk.

12. The method of claim 11 , wherein the physical constraint comprises a predefined motion constraint of the surgical tool, wherein the tool disk is winding a cable, and wherein the physical constraint comprises a movement constraint caused by a second drive disk that is also winding the cable or holding a position of the cable.

13. The method of claim 11 , wherein the plurality of motor operating parameters are measured by one or more sensors.

14. The method of claim 10 , wherein the drive disk and the tool disk comprise one or more pairs of coupling features wherein each pair of coupling features becomes interlocked to each other to rotate as one, when mechanical engagement is achieved.

15. The method of claim 10 , further comprising:

activating the actuator of the tool drive to rotate the drive disk at a first velocity; and

activating the actuator of the tool drive to rotate the drive disk at a second velocity lower than the first velocity when the actuator reaches within a threshold angle away from a reference position, wherein the reference position corresponds to a known calibrated engagement position.

16. The method of claim 10 , further comprising:

detecting that the drive disk has failed to mechanically engage with the tool disk; and

generating a notification for an operator of the surgical robotic system indicating an unsuccessful engagement.

17. The method of claim 10 wherein determining that the measured. velocity of the actuator is below the threshold velocity corresponds to velocity of the actuator being zero.

18. A method performed by a processor of a surgical robotic system for engaging a surgical tool with a tool drive of the surgical robotic system, the method comprising the following operations performed by the processor:

activating a motor of the tool drive to rotate a drive disk wherein the drive disk is to be mechanically engaged with a tool disk in the surgical tool;

while the motor is activated, which causes rotation of the drive disk, measuring motor current and motor voltage of the motor; and

detecting when the drive disk becomes mechanically engaged with the tool disk based on the measured motor current and the measured motor voltage satisfying a condition in which the measured motor current exceeds a current threshold and the measured motor voltage is below a voltage threshold, wherein the current threshold represents motor torque that is it greater than friction between the drive disk and the tool disk during rotation without mechanical engagement and ii) less than a maximum torque for the motor.

19. The method of claim 18 , wherein the condition represents the motor reaching a physical constraint against further rotation of the drive disk.

20. The method of claim 19 , wherein the physical constraint comprises a motion constraint of the surgical tool, wherein the tool disk is winding a cable, and wherein the physical constraint comprises a movement constraint caused by a second drive disk that is also winding the cable or holding a position of the cable.

21. The method of claim 20 , wherein the measured motor current and the measured motor voltage are measured by one or more sensors.

22. The method of claim 18 , further comprising:

activating the motor of the tool drive to rotate the drive disk at a first velocity; and then activating the motor of the tool drive to rotate the drive disk at a second velocity lower than the first velocity when the drive disk reaches within a threshold angle away from a reference position, wherein the reference position corresponds to a known calibrated engagement position.

23. The method of claim 18 wherein the measured motor velocity voltage being below the voltage threshold velocity corresponds to velocity of the actuator motor being zero.