Ratcheting for master alignment of a teleoperated minimally invasive surgical instrument
Inventors
Itkowitz, Brandon D. • DiMaio, Simon P. • Nowlin, William C. • Niemeyer, Günter D. • Mintz, David S.
Assignees
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Publication Number
US-8903549-B2
Publication Date
2014-12-02
Expiration Date
Abstract
A minimally-invasive surgical system includes a slave surgical instrument having a slave surgical instrument tip and a master grip. The slave surgical instrument tip has an alignment in a common frame of reference and the master grip, which is coupled to the slave surgical instrument, has an alignment in the common frame of reference. An alignment error, in the common frame of reference, is a difference in alignment between the alignment of the slave surgical instrument tip and the alignment of the master grip. A ratcheting system (i) coupled to the master grip to receive the alignment of the master grip and (ii) coupled to the slave surgical instrument, to control motion of the slave by continuously reducing the alignment error, as the master grip moves, without autonomous motion of the slave surgical instrument tip and without autonomous motion of the master grip.
Core Innovation
A teleoperated minimally invasive surgical system aligns a slave surgical instrument tip with a master control in a common frame of reference using an alignment system. The alignment system replaces master-powered alignment with an unpowered master grip and a ratcheting control scheme that receives master-grip and slave-tip orientations and aligns them in the common frame, while avoiding autonomous motion of either the master or the slave.
The system determines and maintains alignment by quantifying an alignment error, including an orientation misalignment represented by a relative rotation matrix RΔ and a scalar angle error θe. After movement of the master control from a first alignment to a second alignment, the alignment system determines a second alignment error as a difference between the alignment of the slave instrument tip and the second alignment of the master control, both in the common frame of reference.
The system stores information characterizing the second alignment error in place of the stored information characterizing the first alignment error only if the second alignment error is less than the first alignment error. The ratcheting control scheme is implemented to continuously reduce the alignment error while constraining motion and optionally introducing a control-loop error, and described embodiments select among multiple orientation solutions to choose the closest match.
Claims Coverage
The patent includes two independent claims: one directed to a surgical system and one directed to a method of operating the surgical system. Across these claims, the main inventive features are centered on computing first and second alignment errors in a common frame of reference and conditionally updating stored alignment error only when the new error is smaller, together with alignment behavior that tracks master motion via a ratcheting control system for a slave instrument tip.
Conditional replacement of stored alignment error
The alignment system stores information characterizing a second alignment error in place of stored information characterizing a first alignment error only if the second alignment error is less than the first alignment error.
First and second alignment errors in a common frame of reference
The alignment system characterizes a first alignment error as a difference between an alignment of the slave instrument tip and a first alignment of the master control, and determines a second alignment error as a difference between the alignment of the slave instrument tip and a second alignment of the master control after movement of the master control from the first alignment to the second alignment, with both alignments being in a common frame of reference.
Ratchet-style master-to-slave relative alignment based on updated errors
The method determines and stores a first alignment error, determines a second alignment error after movement of the master control from the first alignment to the second alignment, and stores information characterizing the second alignment error in place of the stored first alignment error only if the second alignment error is less than the first alignment error.
Control system updates drive slave instrument tip alignment
The method further includes determining, by a control system, a second alignment error and generating an updated common-frame alignment for the slave surgical instrument tip based on the comparison of the second alignment error and the first alignment error.
Both independent claims share the same core mechanism: compute a first alignment error and a second alignment error in a common frame of reference and conditionally replace the stored alignment error only when the second alignment error is less than the first. The method claim further grounds the conditional error update in control-system operation that drives slave instrument tip alignment based on the updated, lower-error alignment.
Stated Advantages
Avoids autonomous motion of either the master or the slave.
Continuously reduce the alignment error while constraining motion.
Select among multiple orientation solutions to choose the closest match.
Documented Applications
Teleoperated minimally invasive surgical system.
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