Method for handling an operator command exceeding a medical device state limitation in a medical robotic system
A medical robotic system has a robotic arm holding a medical device, and a control system for controlling movement of the arm according to operator manipulation of an input device. If the medical device is being commanded to a state exceeding a limitation by a threshold amount, then the control system disengages control of the medical device by the input device, servos the arm so that it remains in its current state, servos the input device so that it is set at a position such that a force being applied on the input device remains at its current level, requests the operator to lighten hold of the input device, sets a parameter associated with the input device upon detecting such lightened hold so that the medical device is commanded to a different state that does not exceed the limitation, and reengages control of the medical device by the input device.
1. A method implemented by a processor for handling an operator command received from a master input device to command a slave manipulator, the method comprising:
using the processor to automatically determine whether the slave manipulator is being commanded by the operator command to a commanded state of the slave manipulator that is greater than or equal to a threshold value which is less than a limit of the slave manipulator; and
if the slave manipulator is determined by the processor as being commanded to the commanded state that is greater than or equal to the threshold value which is less than the limit of the slave manipulator, then using the processor to automatically:
cause control of the slave manipulator by the master input device to be disengaged,
cause the slave manipulator to remain at a current state of the slave manipulator,
cause the master input device to remain at a current state of the master input device, and
alter a parameter that affects a functional relationship between the current state of the master input device and the commanded state of the slave manipulator so that the current state of the master input device commands a different commanded state that is not greater than or equal to the threshold value which is less than the limit of the slave manipulator, and
after altering the commanded state to the different commanded state, cause the control of the slave manipulator by the master input device to be re-engaged so that the different commanded state is applied to the slave manipulator.
2. The method according to claim 1 , wherein the limit of the slave manipulator is a kinematic limit of a joint of the slave manipulator, and wherein using the processor to determine whether the slave manipulator is being commanded to the commanded state that is greater than or equal to the threshold value which is less than the limit of the slave manipulator comprises determining the commanded state of the joint by using forward kinematics of the master input device and inverse kinematics of the slave manipulator.
3. The method according to claim 2 , wherein movement of the slave manipulator results in movement of a medical device coupled to the slave manipulator, and wherein using the processor to determine whether the slave manipulator is being commanded to the commanded state of the joint that is greater than or equal to the threshold value which is less than the limit of the slave manipulator comprises determining the commanded state by transforming movement of the master input device relative to a first reference frame to desired movement of the medical device relative to a second reference frame and applying inverse kinematics of the slave manipulator.
4. The method according to claim 2 , wherein using the processor to determine whether the slave manipulator is being commanded to the commanded state of the slave manipulator that is greater than or equal to the threshold value which is less than the limit of the slave manipulator comprises determining whether the commanded state of the slave manipulator exceeds or is equal to at least one of a position threshold value which is before a position limit of the joint and a velocity threshold value which is before a velocity limit of the joint.
5. The method according to claim 1 , wherein using the processor to determine whether the slave manipulator is being commanded to the commanded state of the slave manipulator that is greater than or equal to the threshold value which is less than the limit of the slave manipulator comprises determining whether the commanded state of the slave manipulator is greater than or equal to the threshold value which is less than a singularity of the slave manipulator.
6. The method according to claim 1 , wherein if the slave manipulator is determined by the processor as being commanded to the commanded state that is greater than or equal to the threshold value which is less than the limit of the slave manipulator, then using the processor to automatically:
cause a message to be provided to the operator of the master input device to instruct the operator to lighten hold of the master input device, and
determine that the lightened hold of the master input device by the operator has been detected,
after causing control of the slave manipulator by the master input device to be disengaged, but before altering the commanded state to the different commanded state and causing the control of the slave manipulator by the master input device to be re-engaged.
7. The method according to claim 6 , wherein using the processor to cause the message to be provided to the operator of the master input device to lighten hold of the master input device comprises commanding a pre-recorded audio message to be played on speakers hearable by the operator.
8. The method according to claim 6 , wherein using the processor to cause the message to be provided to the operator of the master input device to lighten hold of the master input device comprises commanding a vibration on the master input device so as to indicate to the operator to lighten hold of the master input device.
9. The method according to claim 6 , wherein using the processor to cause the message to be provided to the operator of the master input device to lighten hold of the master input device comprises causing the message to be displayed on a computer screen viewable by the operator.
10. The method according to claim 1 , wherein using the processor to cause control of the slave manipulator by the master input device to be disengaged and the slave manipulator to remain at the current state of the slave manipulator comprises: using the processor to cause control of the slave manipulator by the master input device to be interrupted and cause the slave manipulator to be held in place by control feedback at the current state of the slave manipulator by a control system controlling the slave manipulator.
11. The method according to claim 1 , further comprising:
generating a modified commanded state so that the modified commanded state is a version of the commanded state that has been modified so as not to exceed the limit of the manipulator; and
generating a force feedback indicative of a difference between the commanded state and the modified commanded state;
wherein using the processor to automatically alter a parameter that affects a functional relationship between the current state of the master input device and the commanded state of the slave manipulator so that the current state of the master input device commands a different commanded state that is not greater than or equal to the threshold value which is less than the limit of the slave manipulator, comprises: altering the parameter until the different commanded state is less than or equal to the modified commanded state while generating the force feedback so that the force feedback is indicative of a difference between the different commanded state and the modified commanded state.