Admittance compensation for surgical tool

Abstract

The disclosed embodiments relate to systems and methods for a surgical tool or a surgical robotic system. An actuator or a motor of a tool driver is configured to operate a joint of a tool. One or more processors are configured to receive an initial joint command for the joint of the tool, determine a joint torque based on motor torque of the motor or actuator as well as motor to joint torque mapping, calculate a tip force based on an effective length associated with the joint and based on the joint torque, compare the tip force to a predetermined threshold, calculate an admittance control compensation term in response to the tip force exceeding the predetermined threshold, and generate a command for the motor or actuator based on the admittance control compensation term and the initial joint command.

We claim: 
     
         1 . A controller for operation of a joint of a tool in a surgical robotic system, the controller comprising:
 one or more processors configured to:
 perform a comparison of a tip force at the joint to a predetermined threshold; 
 calculate an admittance control compensation term in response to the comparison of the tip force and the predetermined threshold; and 
 modify an initial command for a motor based on the admittance control compensation term. 
   
     
     
         2 . The controller of  claim 1 , wherein the one or more processors are configured to:
 calculate the tip force based on an effective geometry associated with the joint and based on a joint torque.   
     
     
         3 . The controller of  claim 2 , wherein the joint is a closure joint. 
     
     
         4 . The controller of  claim 3 , wherein the effective geometry is a length of a jaw for the closure joint. 
     
     
         5 . The controller of  claim 2 , wherein the joint is a roll joint. 
     
     
         6 . The controller of  claim 5 , wherein the effective geometry is a length of the roll joint. 
     
     
         7 . The controller of  claim 1 , wherein the admittance control compensation term is based on an inverse of mechanical impedance of at least a portion of the tool. 
     
     
         8 . The controller of  claim 7 , wherein the mechanical impedance is a degree of resistance to motion for the tool. 
     
     
         9 . The surgical robotic system of  claim 1 , the one or more processors configured to:
 receive sensor data for a current position of the motor for the joint of the tool, wherein the command for the motor is based, in part, on the sensor data.   
     
     
         10 . The controller of  claim 1 , wherein the command for the motor based on the admittance control compensation term improves safety at the tip of the tool. 
     
     
         11 . The controller of  claim 1 , the one or more processors configured to:
 calculate a tip force saturation value in response to the comparison of the tip force to the predetermined threshold, wherein the admittance control compensation term is based on the tip force saturation value.   
     
     
         12 . The controller of  claim 1 , the one or more processors configured to:
 receive the initial command including a desired position or angle.   
     
     
         13 . A controller for operation of a joint of a tool in a surgical robotic system, the controller comprising:
 one or more processors configured to:
 perform a comparison of a tip force at the joint to a predetermined threshold; and 
 calculate an admittance control compensation term in response to the comparison of the tip force and the predetermined threshold. 
   
     
     
         14 . The controller of  claim 13 , one or more processors configured to:
 receive an initial command including a desired position or angle, wherein the initial command is modified based on the admittance control compensation term.   
     
     
         15 . The controller of  claim 14 , wherein the one or more processors are configured to:
 receive sensor data for a current position of the joint of the tool, wherein the initial command for the joint is modified based, in part, on the sensor data.   
     
     
         16 . The controller of  claim 13 , wherein the one or more processors are configured to:
 calculate the tip force based on a length associated with the joint and based on a joint torque, wherein the joint is a closure joint or a roll joint.   
     
     
         17 . The controller of  claim 13 , wherein the admittance control compensation term is based on an inverse of mechanical impedance of at least a portion of the tool. 
     
     
         18 . The controller of  claim 17 , wherein the mechanical impedance is a degree of resistance to motion for the tool. 
     
     
         19 . A method comprising:
 performing a comparison of a tip force at a joint of a surgical instrument to a predetermined threshold;   calculating an admittance control compensation term in response to the comparison of the tip force and the predetermined threshold; and   modifying an initial command for the joint based on the admittance control compensation term.   
     
     
         20 . The method of  claim 19 , further comprising:
 calculating the tip force based on a length associated with the joint and based on a joint torque, wherein the joint is a closure joint or a roll joint.