Method of determining the shape of a bendable instrument

Abstract

Embodiments of the invention relate to methods of positioning a bendable instrument by moving at least two control elements first and second amounts to bend the instrument to a position; measuring the first and second amounts; and determining the position, shape or configuration of the instrument from the first and second amounts.

1 . A method of determining the shape a bendable instrument, comprising: 
 moving at least two control elements first and second amounts without bending the instrument;    measuring the first and second amounts; and    determining the shape of the instrument from the first and second amounts.    
     
     
         2 . The method according to  claim 1  wherein the moving step is accomplished without using an actuator connected to a control element.  
     
     
         3 . The method according to  claim 1 , wherein the moving step removes slack from the at least two control elements before the measuring step.  
     
     
         4 . The method according to  claim 3  wherein the removing step is performed by applying a known drive command to an actuator.  
     
     
         5 . The method according to  claim 4  wherein the drive command is insufficient to change the position of the instrument.  
     
     
         6 . The method according to  claim 3  wherein the removing step is performed using a tension measurement taken in a connector that couples an actuator to one of the at least two control elements.  
     
     
         7 . The method according to  claim 3  wherein the removing step is performed using a feedback loop that receives input from a sensor.  
     
     
         8 . The method according to  claim 7  wherein the input from a sensor is related to a tension measurement of a control element.  
     
     
         9 . The method according to  claim 7  wherein the sensor is located on or in the bendable instrument.  
     
     
         10 . The method according to  claim 7  wherein the sensor is located on or in a connector that joins the bendable instrument to an actuator.  
     
     
         11 . The method according to  claim 7  wherein the sensor is located on or in an actuator connected to a control element.  
     
     
         12 . The method according to  claim 3  wherein further comprising: 
 removing the slack from the at least two control elements during a first time period at a first force limit before removing the slack from the at least two control elements during a second time period at a second different force limit.    
     
     
         13 . The method according to  claim 12  wherein the first force limit is less than the second force limit.  
     
     
         14 . The method according to  claim 12  wherein the velocity of slack removal during the first time period is greater than the velocity of slack removal during the second time period.  
     
     
         15 . The method according to  claim 1  wherein the determining step comprises using a look up table that correlates the first and second amounts to the instrument shape.  
     
     
         16 . The method according to  claim 1  wherein the determining step comprises using a modeled kinematic relationship between first and second amounts and the instrument shape.  
     
     
         17 . The method according to  claim 1  wherein the determining step uses a calculated position delta of the at least two control elements.  
     
     
         18 . The method according to  claim 1  wherein the determining step uses a calculated position delta of complementary control elements within the at least two control elements.  
     
     
         19 . The method according to  claim 1  wherein the determining step uses a calculated position delta of a pair of opposing control elements within the at least two control elements.  
     
     
         20 . The method according to  claim 1  the measuring step further comprising: 
 moving a control element not being used to bend the instrument; and    determining a calculated position delta for the control element not being used to bend the instrument.    
     
     
         21 . The method according to  claim 20  wherein the determining step uses the calculated position delta for a control element not being used to bend the instrument.  
     
     
         22 . The method of  claim 1  further comprising: 
 positioning the bendable instrument within a lumen before the moving step.    
     
     
         23 . The method according to  claim 1  wherein the moving step is performed by a lumen acting on the instrument.  
     
     
         24 . The method according to  claim 22  further comprising: 
 using the determining step to determine the shape of the lumen.