Autonomous correction of alignment error in a master-slave robotic system

Patent metadata

Field	Value
Publication number	US-10327856-B2
Application number	US-201615542356-A
Country	US
Kind code	B2
Filing date	Jan 8, 2016
Priority date	Jan 9, 2015
Publication date	Jun 25, 2019
Grant date	Jun 25, 2019

Abstract

In some embodiments, correcting an alignment error between an end effector of a tool associated with a slave and a master actuator associated with a master in a robotic system involves receiving at the master, master actuator orientation signals (R MCURR ) representing the orientation of the master actuator relative to a master reference frame and generating end effector orientation signals (R EENEW ) representing the end effector orientation relative to a slave reference frame, producing control signals based on the end effector orientation signals, receiving an enablement signal for selectively enabling the control signals to be transmitted from the master to the slave, responsive to a transition of the enablement signal from not active state to active state, computing the master-slave misalignment signals (R Δ ) as a difference between the master actuator orientation signals (R MCURR ) and the end effector orientation signals (R EENEW ), and adjusting the master-slave misalignment signals (R Δ ) to reduce the alignment difference.

First claim

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method of correcting an alignment error between an end effector of a tool associated with a slave and a master actuator associated with a master in a master-slave robotic system in which an orientation of the end effector is remotely controlled by an orientation of the master actuator by producing and transmitting control signals at the master for controlling the slave, the method comprising:
causing a processor associated with the master to receive master actuator orientation signals (R MCURR ) representing the orientation of the master actuator relative to a master reference frame;
causing the processor to generate end effector orientation signals (R EENEW ) representing the end effector orientation relative to a slave reference frame, in response to:
said master actuator orientation signals (R MCURR );
master base orientation signals (R MBASE ) representing previous-saved values of said master actuator orientation signals (R MCURR ); and
slave base orientation signals (R EEBASE ) representing previous-saved values of said end effector orientation signals (R EENEW );

causing the processor to produce control signals based on said end effector orientation signals, for transmission from the master to the slave;
causing the processor to receive an enablement signal for selectively enabling said control signals to be transmitted from the master to the slave whereby the master transmits said control signals to the slave when said enablement signal is active and does not transmit said control signals to the slave when said enablement signal is not active and such that when said enablement signal is active, changes in the orientation of the master actuator cause corresponding changes in the orientation of the end effector and such that when said enablement signal is not active, changes in the orientation of the master actuator do not cause corresponding changes in the orientation of the end effector;
when said enablement signal transitions from said not active state to said active state, causing the processor to:
save said values of said master actuator orientation signals (R MCURR ) as said master base orientation signals (R MBASE ) to create said previous-saved values of said master actuator orientation signals (R MCURR ); and
save said values of said end effector orientation signals (R EENEW ) as said slave base orientation signals (R EEBASE ) to create said previous-saved values of said end effector orientation signals (R EENEW );

causing the processor to detect a difference; between the master actuator orientation signals (R MCURR ) and the end effector orientation signals (R EENEW ), the difference representing a difference in physical alignment between the tool and the master relative to their respective reference frames, the causing comprising computing a difference rotation matrix that carries the end effector orientation signals into the master actuator orientation signals according to the relation:
R EE _ TO _ MASTER =R EENEW −1 R MCURR
Where: R EENEW −1 is an inverse matrix of the end effector orientation signal R EENEW represented by a 3×3 matrix; and
R MCURR is the master actuator orientation signal at a current time step represented by a 3×3 matrix;

in response to detecting said difference, causing the processor to adjust said saved slave base orientation signals (R EEBASE ) to ultimately have the same values as said saved master base orientation (R MBASE ) values so that subsequent generations of said end effector orientation signals (R EENEW ) cause said control signals to cause said tool to satisfy an alignment criterion; and
causing the processor to determine an angle of rotation associated with the difference rotation matrix according to the relation:
φ EE _ TO _ MASTER =a cos(0.5 trace( R EE _ TO _ MASTER )−1).

2. The method of claim 1 further comprising causing said processor to autonomously adjust said saved slave base orientation (R EEBASE ) signals.

3. The method of claim 1 further comprising causing the processor to determine whether the angle of rotation associated with the difference rotation matrix (R EE _ TO _ MASTER ) meets a criterion.

4. The method of claim 3 further comprising causing the processor to determine an angular speed of rotation of the difference rotation matrix (R EE _ TO _ MASTER ) which represents the difference in rotation between the previous-saved master handle orientation signals and the current master handle orientation signals.

5. The method of claim 4 further comprising causing the processor to determine whether the angular speed of rotation of the difference rotation matrix meets a criterion.

6. The method of claim 5 further comprising causing the processor to determine a misalignment axis and an incremental correction angle by which the slave base orientation signals (R EEBASE ) is to be rotated about the misalignment axis.

7. The method of claim 6 further comprising causing the processor to:
generate a correction rotation matrix for adjusting the current slave base orientation (R EEBASE ) signals by the incremental correction angle in a misalignment plane; and
adjust said current slave base orientation (R EEBASE ) signals with the correction matrix.

8. The method of claim 7 further comprising causing the processor to produce new end effector orientation signals (R EENEW ) using said adjusted current slave base orientation (R EEBASE ) signals and causing the processor to generate said control signals using said new end effector signals (R EENEW ).

9. A non-transitory computer readable medium encoded with codes for directing a processor to execute the method of claim 1 .

10. A method of correcting an alignment error between an end effector of a tool associated with a slave and a master actuator associated with a master in a master-slave robotic system in which an orientation of the end effector is remotely controlled by an orientation of the master actuator by producing and transmitting control signals at the master for controlling the slave, the method comprising:
causing a processor associated with the master to receive master actuator orientation signals (R MCURR ) representing the orientation of the master actuator relative to a master reference frame;
causing the processor to generate end effector orientation signals (R EENEW ) representing the end effector orientation relative to a slave reference frame, in response to:
said master actuator orientation signals (R MCURR ); and
master-slave misalignment signals (R Δ ), representing a product of previously saved values of said master actuator orientation signals (R MCURR ) and said end effector orientation signals (R EENEW );

causing the processor to produce control signals based on said end effector orientation signals, for transmission from the master to the slave;
causing the processor to receive an enablement signal for selectively enabling said control signals to be transmitted from the master to the slave whereby the master transmits said control signals to the slave when said enablement signal is active and does not transmit said control signals to the slave when said enablement signal is not active and such that when said enablement signal is active, changes in the orientation of the master actuator cause corresponding changes in the orientation of the end effector and such that when said enablement signal is not active, changes in the orientation of the master actuator do not cause corresponding changes in the orientation of the end effector;
when said enablement signal transitions from sai

Assignees

• Titan Med Inc

Inventors

• Kralicky Joseph
• Cameron Peter

Classifications

• A61B2034/306

  Wrists with multiple vertebrae · CPC title

• Y10S901/31

  Gripping jaw · CPC title

• B25J11/008

  Manipulators for service tasks · CPC title

• A61B34/37 Primary

  Leader-follower robots (A61B34/35 takes precedence) · CPC title

• A61B34/74

  Manipulators with manual electric input means · CPC title