Motorized surgical handpiece and controller for regulating the handpiece motor based on the inductively sensed determination of motor rotor position

Abstract

A surgical tool system including a handpiece with a motor for driving a cutting accessory. The system includes a control unit for applying energization signals to the windings internal to the handpiece motor. At start-up and low speeds, the rotational position of the rotor relative to the static windings is determined based on inductances of the windings. At high speeds, the rotational position of the winding is determined based on the back electromotive forces developed across the windings.

1 - 56 . (canceled)  
   
   
       57 . A powered surgical tool system comprising: 
 a surgical handpiece including: a brushless, sensorless motor having a plurality of windings and a rotor; a coupling assembly that releasably holds a cutting accessory to said rotor; and    a drive assembly connected to said handpiece for selectively applying energization signals to said motor windings based on the position of said rotor relative to said windings, wherein said drive assembly is configured to: 
 when said motor is at a speed is at or below a threshold rate, determine the position of said motor rotor relative to said windings based on inductance sensing of the position of said rotor; and  
 when said motor is at a speed above the threshold rate, determine the position of said motor rotor relative to said windings based on a process other than inductance sensing of the position of said rotor.  
   
   
   
       58 . The powered surgical tool system of  claim 57 , wherein said motor is at a speed above the threshold rate, said drive assembly determines the position of said motor rotor relative to said windings by monitoring the back electromotive force developed across said windings.  
   
   
       59 . The powered surgical tool system of  claim 57 , wherein said drive assembly, when performing inductance sensing of motor rotor position is configured to: 
 measure the current flow through each winding; and    determine said rotor position based on the measurements of winding current flow measurements.    
   
   
       60 . The powered surgical tool system of  claim 57 , wherein said drive assembly, when performing inductance sensing of motor rotor position is configured to: 
 measure the current flow through each winding;    normalize the plurality of winding current flow measurements; and    determine said rotor position based on the normalized measurements of winding current flow measurements.    
   
   
       61 . The powered surgical tool system of  claim 57 , wherein said driver, when performing inductance sensing of motor rotor position is configured to: 
 negate the application of energization signals to said windings that result in the rotation of said rotor;    measure current flow through each said winding during periods when voltage pulses are applied across each winding;    determine through which winding there is the greatest current flow;    based on the winding through which there is the greatest current flow, determine rotor position.    
   
   
       62 . The powered surgical tool system of  claim 57 , wherein said driver, when performing inductance sensing of motor rotor position is configured to: 
 negate the application of energization signals to said windings that result in the rotation of said rotor;    measure current flow through each said winding during periods when voltage pulses are applied across each winding;    compare the measured winding current flows to a model of winding current flows; and    based on the comparison of the measured winding current flows to the model of winding current flows, determine rotor position.    
   
   
       63 . The powered surgical tool system of  claim 57 , wherein said driver is configured to perform inductance sensing of motor rotor position at motor start up.  
   
   
       64 . A method of energizing a powered surgical tool having a motor that includes: a plurality of windings; a rotor that is rotated in response to currents being applied to the windings; and a coupling assembly for releasably holding a cutting accessory to the rotor, said method including the steps of: 
 at motor start-up, determining the position of the rotor relative to the windings based on inductance sensing of the windings as the windings are affected by rotor position;    selectively applying currents to the windings based on the inductively sensed determination of rotor position so as to cause rotation of the rotor;    continuing to determine the position of the rotor by inductance sensing of the windings and applying currents to the windings based on the inductively sensed determination of rotor position until the rotor rotates at a speed above a threshold speed;    when the rotor speed is above the threshold speed, determining the position of the rotor relative to the windings based on the monitoring of the back electromotive force that develops across the windings; and    selectively applying the current to the windings based on the back electromotive force-based determination of rotor position;    
   
   
       65 . The method of energizing a powered surgical tool of  claim 64 , wherein, in said steps of determining the rotor position by inductance sensing of the winding, the current flows through the windings are measured.  
   
   
       66 . The method of energizing a powered surgical tool of  claim 64 , wherein, in said steps of determining the rotor position by inductance sensing: 
 the current flow through each winding is measured;    the measured winding current flows are normalized; and    rotor position is based on the normalized measurements of the winding current flows.    
   
   
       67 . The method of energizing a powered surgical tool of  claim 64 , wherein, in said steps of determining the rotor position by inductance sensing: 
 the application of energization signals to the windings to cause rotation of the rotor is negated;    a voltage pulse is applied across each winding and the current flow through each winding during the application of the voltage pulse is measured; and    rotor position is determined by determining through which winding the current flow is greatest.    
   
   
       68 . The method of energizing a powered surgical tool of  claim 64 , wherein, in said steps of determining the rotor position by inductance sensing: 
 the application of energization signals to the windings to cause rotation of the rotor is negated;    a voltage pulse is applied across each winding and the current flow through each winding during the application of the voltage pulse is measured; and    rotor position is determined by comparing the measured winding current flows to a model of winding current flows, the model indicating the relationship of the current flows through the windings to rotor position.    
   
   
       69 . The method of energizing a powered surgical tool of  claim 64 , wherein, 
 in said steps of determining rotor position by inductance sensing, current flows through the windings are measured:    if, as a result of the current flow measurements, it is determined that the rotor has moved from an initial position to a shifted position, determining if the shifted position is an adjacent position;    if the shifted position is in an adjacent position, determining that the rotor is in the adjacent position; and    if the shifted position is not an adjacent position, determining if the current flow is above a threshold level;    if the current flow is above the threshold level, determining that the rotor is in the shifted position; and    if the current flow is below the threshold level, determining that the rotor has remained in the initial position.    
   
   
       70 . A surgical tool system, said system including: 
 a surgical handpiece having: a motor with windings and a rotating rotor; and a coupling assembly for releasably holding a coupling assembly to said rotor so that the cutting accessory is actuated by said rotor; and    a drive circuit that selectively applies energization signals to said windings so as to cause rotation of said rotor, said drive circuit including: 
 an inductance measuring circuit for measuring the inductance of said windings; and  
 a processor connected to said inductance measuring circuit for receiving therefrom signals representative of the winding inductances, said processor circuit configured to: based on the measurements of winding inductance, determine the position of said rotor relative to said windings; and based on the rotor position, selectively apply energization signals to said windings.  
   
   
   
       71 . The surgical tool system of  claim 70 , wherein said processor is further configured to: 
 based on the inductance sensed determined positions of said rotor, determine rotor speed; and    when the rotor speed is above a threshold value, use a means other than winding inductance sensing to determine rotor position.    
   
   
       72 . The surgical tool system of  claim 70 , wherein: 
 said drive circuit includes a circuit for detecting the back electromotive forces developed across said windings; and    said processor receives from said back electromotive force detection circuit signals representative of the back electromotive forces developed by said windings, and is further configured to: 
 based on the inductance sensed determined positions of said rotor, determine rotor speed; and  
 when the rotor speed is above a threshold value, determine rotor position based on the back electromotive forces developed across said windings.  
   
   
   
       73 . The surgical tool system of  claim 70 , wherein said inductance measurement circuit is configured to measure current flows through said windings.  
   
   
       74 . The surgical tool system of  claim 70 , wherein: 
 said inductance measurement circuit is configured to measure current flows through said windings; and    said processor is configured to determine rotor position by determining the relative inductances of said windings.    
   
   
       75 . The surgical tool system of  claim 70 , wherein: 
 said inductance measurement circuit is configured to measure current flows through said windings; and    said processor is configured to determine rotor position by comparing the measured winding current flows to a model of winding current flows, the model indicating for different sets of winding current flows, the position of said rotor.    
   
   
       76 . The surgical tool system of  claim 70 , wherein: 
 integral with said handpiece is a memory, said memory containing data for normalizing inductance generated current flow measurements through said windings;    said inductance measurement circuit is configured to measure current flows through said windings; and    said processor is configured to: receive from said handpiece memory the data for normalizing inductance generated current flow measurements; and determine rotor position based on the current flow measurements made by said inductance sensing circuit, wherein said processor normalizes the current flow measurements based on the data for normalizing inductance generated current flow measurements and uses the normalized current flow measurements to determine rotor position.    
   
   
       77 . The surgical tool system of  claim 70  wherein: 
 said inductance measurement circuit is configured to measure current flows through said windings; and    said processor is configured to: 
 based on winding inductance current measurements determine if it appears that said rotor has moved from an initial position to a shifted position;  
 if said rotor has so moved positions, determine if the shifted position is an adjacent position;  
 if the shifted position is an adjacent position, determine that said rotor is in the adjacent position; and  
 if the shifted position is not am adjacent position, determining if the current flow is above a threshold level;  
 if the current flow is above the threshold level, determining that the rotor is in the shifted position; and  
 if the current flow is below the threshold level, determining that the rotor has remained in the initial position.