Robotic surgical system with joint motion controller adapted to reduce instrument tip vibrations

Abstract

A robotic surgical system has a robot arm holding an instrument for performing a surgical procedure, and a control system for controlling movement of the arm and its instrument according to user manipulation of a master manipulator. The control system includes a filter in its forward path to attenuate master input commands that may cause instrument tip vibrations, and an inverse filter in a feedback path to the master manipulator configured so as to compensate for delay introduced by the forward path filter. To enhance control, master command and slave joint observers are also inserted in the control system to estimate slave joint position, velocity and acceleration commands using received slave joint position commands and torque feedbacks, and estimate actual slave joint positions, velocities and accelerations using sensed slave joint positions and commanded slave joint motor torques.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a top view of an operating room employing a robotic surgical system utilizing aspects of the present invention.

FIG. 2 illustrates a simplified side view of a robotic arm assembly that is usable with various aspects of the present invention.

FIG. 3 illustrates a block diagram of a master/slave control system utilizing aspects of the present invention.

FIG. 4 illustrates a block diagram of a slave joint controller utilizing aspects of the present invention.

FIG. 5 illustrates a block diagram of a slave joint observer usable in a control system utilizing aspects of the present invention.

FIG. 6 illustrates a block diagram of a master command observer usable in a control system utilizing aspects of the present invention.

FIG. 7 illustrates a block diagram of a first filter/derivative function usable in a control system utilizing aspects of the present invention.

FIG. 8 illustrates a block diagram of a second filter/derivative function usable in a control system utilizing aspects of the present invention.

FIG. 9 illustrates a frequency diagram for a fixed attenuation filter usable in a control system utilizing aspects of the present invention.

FIG. 10 illustrates a frequency diagram for a dual frequency notch filter usable in a control system utilizing aspects of the present invention.

FIG. 11 illustrates a frequency diagram for a combination filter usable in a control system utilizing aspects of the present invention.

FIG. 12 illustrates a frequency diagram for an inverse fixed attenuation filter usable in a control system utilizing aspects of the present invention.

FIG. 13 illustrates a frequency diagram for an inverse dual frequency notch filter usable in a control system utilizing aspects of the present invention.

FIG. 14 illustrates a frequency diagram for an inverse combination filter usable in a control system utilizing aspects of the present invention.

Claims

1. A robotic surgical system comprising: a surgical instrument;a robotic arm assembly holding the surgical instrument;a master manipulator; anda controller configured to control movement of the surgical instrument in response to user operation of the master manipulator in such a manner that vibrations experienced at a tip of the surgical instrument are reduced by filtering an output of the master manipulator that may induce the vibrations while at least partially compensating in a feedback path to the master manipulator for delay induced by such filtering so as to enhance stability of such control.

2. The robotic surgical system according to claim 1, wherein the controller includes a control system to control movement of the robotic arm assembly in response to the user operation of the master manipulator, wherein the control system includes a filter for filtering the vibrations, and an inverse filter to at least partially compensate for delay caused by the filter in the control system.

3. The robotic surgical system according to claim 2, wherein the filter is characterized by attenuating high frequency signals above a cut-off frequency more than low frequency signals below the cut-off frequency.

4. The robotic surgical system according to claim 2, wherein the filter is further characterized by attenuating a resonant frequency signal caused by resonance of a mechanical structure supporting the robotic arm assembly so as to resemble a notch filter.

5. The robotic surgical system according to claim 2, wherein the filter is further characterized by attenuating a resonant frequency signal caused by resonance of the robotic arm assembly so as to resemble a notch filter.

6. The robotic surgical system according to claim 2, wherein the filter is implemented in a forward path of the control system for transmitting slave command signals from the master manipulator to the robotic arm assembly and the inverse filter is implemented in a feedback path of the control system for transmitting force feedback indications from the robotic arm assembly to the master manipulator.

7. The robotic surgical system according to claim 2, wherein the filter is implemented such that a Laplace transform of the filter has an equal number of dominant poles and zeroes.

8. The robotic surgical system according to claim 2, wherein the filter is implemented such that the dominant poles of a Laplace transform of the filter are real and the dominant zeroes of the Laplace transform of the filter are complex.

9. The robotic surgical system according to claim 2, wherein the filter is implemented such that the dominant poles of the Laplace transform of the filter are less in magnitude than a resonant frequency of a mechanical structure associated with the robotic arm assembly.

10. The robotic surgical system according to claim 2, wherein an input of the filter includes at least one of a commanded position, commanded velocity, and commanded acceleration.

11. The robotic surgical system according to claim 10, wherein an output of the filter includes a filtered value for the commanded position, and a filtered value for the commanded velocity.

12. The robotic surgical system according to claim 11, wherein the output of the filter further includes a filtered value for the commanded acceleration.

13. The robotic surgical system according to claim 11, wherein the filter is digitally implemented as a state space balanced realization of the filter.

14. The robotic surgical system according to claim 11, wherein the commanded position is a position of a joint in the robotic arm assembly.

15. The robotic surgical system according to claim 2, wherein the control system further comprises a slave joint observer having: inputs including a sensed slave joint position of a slave joint in the robotic arm assembly, and a motor drive command for driving a slave joint motor adapted to move the slave joint; and outputs including at least estimated values for a position of the slave joint and a velocity of the slave joint.

16. The robotic surgical system according to claim 15, wherein the outputs of the slave joint observer further includes an estimated value for an acceleration of the slave joint.

17. The robotic surgical system according to claim 15, wherein the slave joint observer has a disturbance observer structure and the outputs of the slave joint observer further includes an estimated value for an external load being applied to the slave joint motor.

18. The robotic surgical system according to claim 15, wherein the motor drive command is generated by a slave feedback control law based on at least one of the differences between corresponding of the filtered values for the commanded joint position and commanded joint velocity, and estimated values for the slave joint position and velocity.

19. The robotic surgical system according to claim 15, wherein part of the motor drive command is generated by a slave feedforward control law based on at least one of the filtered values for the commanded position, velocity, and acceleration.

20. The robotic surgical system according to claim 2, further comprising a master command observer having: inputs including a commanded joint position and a master motor drive feedback value; and outputs including estimated values for the commanded position and velocity.

21. The robotic surgical system according to claim 20, wherein the master command observer outputs further including an estimated value for the command acceleration.

22. The robotic surgical system according to claim 21, wherein the master command observer has a disturbance observer structure and the outputs of the master command observer further includes an estimated value for an external load applied to the master manipulator.

23. The robotic surgical system according to claim 2, wherein the inverse filter receives at least one of an estimated slave joint position, velocity and acceleration, and generates a filtered value for the at least one of the estimated slave position, velocity and acceleration.

24. The robotic surgical system according to claim 23, wherein the master motor drive feedback value is generated by a master feedback control law based on at least one of the differences between corresponding of the estimated values for the commanded position, velocity and acceleration, and outputs of the inverse filter.

25. The robotic surgical system according to claim 24, wherein part of the master motor drive command is generated by a master feedforward control law based on at least one of the filtered values for the commanded position, velocity and acceleration.

26. In a controller for controlling movement of a robotic arm assembly in response to user manipulation of a master manipulator, a control system for controlling rotation of a slave joint of the robotic arm assembly, the control system comprising: a filter in a forward control path defined as being from the master manipulator to a motor coupled to the slave joint, wherein the filter attenuates frequency content of a joint position command generated from user manipulation of the master manipulator so that vibrations experienced at a tip of a surgical instrument held by the robotic arm assembly are reduced; andan inverse filter in a feedback path defined as being from a slave joint sensor to the master manipulator, wherein the slave joint sensor senses movement of the slave joint and the inverse filter provides a phase lead in the feedback path so as to at least partially compensate for a phase lag caused by the filter.

27. The control system according to claim 26, wherein the filter is implemented so that a Laplace transform of the filter has an equal number of dominant poles and dominant zeroes, and attenuates the a high frequency band.

28. The control system according to claim 26, wherein the filter has a notch filter characteristic that significantly attenuates vibrations at a resonant frequency of the robotic arm assembly.

29. The control system according to claim 26, wherein the filter is implemented so that a Laplace transform of the filter has an equal number of dominant poles and dominant zeroes.

30. The control system according to claim 26, wherein the filter and inverse filter are digitally implemented as state space representations.

31. The control system according to claim 30, further comprising: a slave joint observer for generating estimated values for a current position, velocity and acceleration of the joint using a joint position value indicated by the joint sensor and a torque command to the motor.

32. The control system according to claim 30, wherein the slave joint observer has a disturbance observer structure and the outputs of the slave joint observer further includes an estimated value for an external torque applied to the slave joint.

33. The control system according to claim 31, wherein the filter generates filtered values for the joint position command, and filtered values for joint velocity and acceleration commands generated using the joint position command.

34. The control system according to claim 33, wherein a command to drive the motor is generated using differences between corresponding outputs of the filter and the slave joint observer.

35. The control system according to claim 31, wherein the inverse filter generates inverse filtered values using the outputs of the slave joint observer.

36. The control system according to claim 35, further comprising: a master command observer for generating estimated joint position, velocity, and acceleration commands using the joint position command and a force feedback indication for the master manipulator.

37. The control system according to claim 36, wherein the master command observer has a disturbance observer structure, and further generates the force feedback indication.

38. The control system according to claim 37, wherein the force feedback indication is indicative of differences between corresponding outputs of the inverse filter and the master command observer.

39. A method for controlling the movement of a slave joint in a robotic arm assembly, comprising: generating filtered position, velocity and acceleration slave joint commands so as to command movement of the slave joint while reducing vibrations experienced on a tip of a surgical instrument held by the robotic arm assembly;generating a motor command signal using the filtered position, velocity and acceleration slave joint commands;providing the motor command signal to a motor coupled to the slave joint;receiving sensed positions of the slave joint;generating estimated positions, velocities and accelerations of the slave joint using the sensed positions of the joint and the slave motor command signal; andupdating the slave motor command signal using a function of the differences between corresponding of the filtered position, velocity and acceleration slave joint commands and the estimated positions, velocities and accelerations of the slave joint.

40. The method according to claim 39, further comprising: generating filtered estimated positions, velocities and accelerations of the slave joint in a manner so as to at least partially compensate for any delay caused by the filtering of the position, velocity and acceleration slave joint commands and to enhance stability in controlling the movement of the slave joint.

41. The method according to claim 40, further comprising: generating a master feedback signal using differences between corresponding of estimated position, velocity and acceleration slave joint commands and the filtered estimated positions, velocities and accelerations of the slave joint.

42. The method according to claim 41, further comprising: generating the estimated position, velocity and acceleration joint commands using a joint position command generated from user manipulation of a master manipulator and the master feedback signal.

43. A method for reducing vibrations on a tip of a surgical instrument held by a robotic arm assembly without degrading stability of a control system controlling movement of a slave joint of the robotic arm assembly, the method comprising: attenuating a first signal indicating slave joint position commands generated from user manipulation of a master manipulator at frequencies beyond a cut-off frequency so that vibrations on the tip of the surgical instrument held by the robotic arm assembly are reduced at those frequencies; andamplifying a second signal indicating a position of the slave joint at frequencies above the cut-off frequency while providing phase lead to the second signal so as to at least partially compensate for delay caused by the attenuation of the first signal and stably generate a feedback signal provided to the master manipulation.