Articulating including antagonistic controls for articulation and calibration

Abstract

A method of homing a drive input of a robotic surgical tool includes recording and storing a home position of the drive input in a memory included in the robotic surgical tool, establishing a slow zone for the drive input encompassing a known angular magnitude away from the home position, storing the slow zone in the memory, rotating the drive input toward the home position, and slowing a rotation speed of the drive input upon reaching the slow zone.

What is claimed is: 
     
         1 . A method of homing a drive input of a robotic surgical tool, comprising:
 recording and storing a home position of the drive input in a memory included in the robotic surgical tool;   establishing a slow zone for the drive input encompassing a known angular magnitude away from the home position;   storing the slow zone in the memory;   rotating the drive input toward the home position; and   slowing a rotation speed of the drive input upon reaching the slow zone.   
     
     
         2 . The method of  claim 1 , wherein rotating the drive input toward the home position includes:
 mounting the robotic surgical tool to a tool driver of a robotic manipulator, the tool driver including a driver matable with the drive input, and a motor that drives the driver in rotation to thereby rotate the drive input;   sending an input signal to the motor to operate the driver and thereby rotate the drive input; and   measuring rotational motion of the motor with a rotary encoder communicably coupled to the motor and thereby determining an angular position of the drive input.   
     
     
         3 . The method of  claim 1 , further comprising detecting a torque spike with one or more torque sensors when the drive input reaches the home position. 
     
     
         4 . The method of  claim 1 , wherein recording and storing the home position of the drive input in the memory comprises:
 calibrating the robotic surgical tool during manufacture of the robotic surgical tool and thereby determining an absolute angular position at which the drive input reaches the home position; and   storing the absolute angular position in the memory as the home position.   
     
     
         5 . The method of  claim 1 , wherein the drive input requires rotation of two or more full revolutions prior to reaching the home position, the method further comprising
 establishing the slow zone for each full revolution of the drive input; and   slowing the rotation speed of the drive input upon reaching each slow zone.   
     
     
         6 . The method of  claim 1 , wherein slowing the rotation speed of the drive input upon reaching the slow zone comprises:
 rotating the drive input at a first speed when the drive input is not rotationally oriented within the slow zone; and   rotating the drive input at second speed slower than the first speed when the drive input is rotationally oriented within each slow zone.   
     
     
         7 . A homing system for a robotic surgical tool including a drive housing and a drive input rotatably mounted to the drive housing, the homing system comprising:
 a memory included in an internal computer forming part of the drive housing, the memory having stored therein:
 a home position of the drive input; and 
 a slow zone established for the drive input that encompasses a known angular magnitude away from the home position; and 
   a computer system in communication with the memory and in further communication with a motor operable to rotate the drive input and a rotary encoder operable to determine an angular position of the drive input,   wherein the computer system causes the motor to reduce a rotation speed of the drive input upon reaching the slow zone.   
     
     
         8 . The homing system of  claim 7 , further comprising one or more torque sensors operatively coupled to the motor and in communication with the computer system, wherein the one or more torque sensors detect a torque spike when the drive input reaches the home position. 
     
     
         9 . The homing system of  claim 7 , wherein the home position of the drive input is 180° and the slow zone comprises a buffer of 40° ranging before and after the absolute angular position of 180°. 
     
     
         10 . The homing system of  claim 7 , wherein the drive input requires rotation of two or more full revolutions prior to reaching the home position, and wherein the slow zone comprises a corresponding slow zone for each full revolution of the drive input. 
     
     
         11 . The homing system of  claim 10 , wherein computer system is programmed to slow the rotation speed of the drive input upon reaching each slow zone. 
     
     
         12 . The homing system of  claim 7 , wherein the drive input is rotated at a first speed when the drive input is not rotationally oriented within the slow zone, and wherein the drive input is rotated at second speed slower than the first speed when the drive input is rotationally oriented within each slow zone. 
     
     
         13 . A robotic surgical tool, comprising
 a drive housing having first and second drive inputs rotatably coupled thereto, the drive housing being mountable to a tool driver of a robotic manipulator, and the tool driver including first and second drivers matable with the first and second drive inputs;   a shaft extending from the drive housing and terminating at an end effector;   a wrist joint interposing the shaft and the end effector;   a first drive member extending from the drive housing and terminating at the wrist joint, the first drive member being operatively coupled to the first drive input such that actuation of the first driver moves the first drive member along the shaft; and   a second drive member extending from the drive housing and terminating at the wrist joint, the second drive member being operatively coupled to the second drive input such that actuation of the second driver moves the second drive member along the shaft,   wherein the wrist joint is rotated a first rotational direction by actuating the first driver and thereby pushing the first drive member distally while simultaneously actuating the second driver and thereby pulling the second drive member proximally, and   wherein the wrist joint is rotated a second rotational direction by actuating the first driver and thereby pulling the first drive member proximally while simultaneously actuating the second driver and thereby pushing the second drive member distally.   
     
     
         14 . The robotic surgical tool of  claim 13 , wherein the first and second drivers maintain equal tension or compression in the first and second drive members until commanded to rotate the wrist joint in either the first or second rotational directions. 
     
     
         15 . The robotic surgical tool of  claim 14 , wherein the tension or compression applied by the first and second drivers is dependent upon an articulation angle of the joint. 
     
     
         16 . The robotic surgical tool of  claim 13 , wherein the wrist joint includes physical limits past which the wrist joint cannot physically rotate, the homing system further comprising:
 a computer system in communication with first and second motors arranged to drive the first and second drivers, respectively,   wherein the computer system is programmed to operate the first and second motors at a first speed when an instantaneous angle of the wrist joint is within a defined safe limit away from the physical limits, and   wherein the computer system is programmed to operate the first and second motors at a second speed lower than the first speed when the instantaneous angle of the wrist joint is outside the defined safe limit and near the physical limits.   
     
     
         17 . The robotic surgical tool of  claim 16 , wherein the first and second motors decelerate at a constant speed when transitioning between the first and second speeds. 
     
     
         18 . A system for controlling antagonistic translation of a pair of drive members in a surgical tool, the surgical tool being mountable to a robotic manipulator having a first driver operable to translate the first drive member and a second driver operable to translate the second drive member,
 wherein, upon receiving a desired articulation angle input, the system determines a first driver position command and a second driver position command at which the first and second drivers will cause translation of the first and second drive members, respectively, to achieve the desired articulation angle input,   wherein the first driver command causes the first drive member to translate a distance in a proximal direction and the second driver command causes the second drive member to translate the distance in a distal direction, and   wherein the distance is modified by a correction factor.   
     
     
         19 . The system of  claim 18 , wherein the correction factor is an empirically determined constant of the surgical tool. 
     
     
         20 . The system of  claim 18 , wherein the correction factor is a product of a constant and a function, and wherein the function is selected from the group consisting of a linear function, a sinusoidal function, an exponential function, a polynomial function, and any combination thereof.