Atherectomy motor control system

Abstract

An atherectomy system includes a drive mechanism that is adapted to rotatably actuate an atherectomy burr and a controller that is adapted to regulate operation of the drive mechanism. In some cases, the drive mechanism includes a drive cable that is coupled with the atherectomy burr and a drive motor that is adapted to rotate the drive cable. The controller is adapted to receive an indication of an increase in torque experienced at the atherectomy burr and is further adapted to, in response, regulate operation of the drive mechanism such that the increase in torque results in a noticeable reduction in speed of the drive mechanism such that a user of the atherectomy system notices the reduction in speed and is alerted to the increase in torque.

What is claimed is: 
     
         1 . An atherectomy system, comprising:
 a drive mechanism adapted to rotatably actuate an atherectomy burr, the drive mechanism comprising a drive cable coupled with the atherectomy burr and a drive motor adapted to rotate the drive cable in a rotational direction; and   a controller adapted to regulate operation of the drive mechanism in accordance with a speed reference;   the controller adapted to receive an indication of an increase in torque experienced at the atherectomy burr;   when the controller receives an indication of an increase in torque experienced at the atherectomy burr, the controller is further adapted to command the drive motor to drive the drive mechanism at a reduced speed by changing the speed reference in order to produce a reduction in speed of the drive mechanism greater than what would otherwise normally occur in response to the increase in torque while continuing to rotate the drive mechanism in the same rotational direction, thereby providing a user with notice of the increase in torque.   
     
     
         2 . The atherectomy system of  claim 1 , wherein the speed reference changeable between a nominal positive value, a negative value and zero. 
     
     
         3 . The atherectomy system of  claim 2 , wherein when the atherectomy burr becomes stuck, the controller is further adapted to:
 increase the torque provided by the drive mechanism until a torque threshold is reached; and   direct the drive mechanism to reverse by changing the speed reference to the negative value in order to unwind energy in the drive mechanism.   
     
     
         4 . The atherectomy system of  claim 1 , further comprising a user interface operably coupled to the controller so that the controller is able to display information regarding performance of the drive mechanism. 
     
     
         5 . The atherectomy system of  claim 1 , wherein the controller comprises:
 a reference circuit that is adapted to receive a speed signal and output the reference signal;   a control circuit that is adapted to receive the reference signal from the reference circuit and generate a resulting control effort signal; and   a drive circuit that is adapted to receive the control effort signal from the control circuit and regulate operation of the drive mechanism accordingly.   
     
     
         6 . The atherectomy system of  claim 5 , wherein the control circuit comprises a Proportional controller. 
     
     
         7 . The atherectomy system of  claim 5 , wherein the control circuit comprises a Proportional Integral Derivative (PID) controller. 
     
     
         10 . The atherectomy system of  claim 5 , wherein the reference circuit is adapted to default to the nominal positive value for the reference signal upon startup of the atherectomy system. 
     
     
         11 . The atherectomy system of  claim 5 , wherein the reference circuit is adapted to add an offset value to the reference signal in order to accurately hold speed of the drive mechanism during a no-load situation. 
     
     
         12 . An atherectomy system, comprising:
 a drive mechanism adapted to rotatably actuate an atherectomy burr, the drive mechanism comprising a drive cable coupled with the atherectomy burr and a drive motor adapted to rotate the drive cable in a rotational direction; and   a controller adapted to regulate operation of the drive mechanism in accordance with a speed reference;   the controller adapted to, in response to an increasing torque as a result of a stuck atherectomy burr;
 increase torque until a predetermined threshold is reached; and 
 set the speed reference to a negative value in order to unwind energy stored in the drive mechanism. 
   
     
     
         13 . The atherectomy system of  claim 12 , wherein the controller is further adapted to receive an indication of an increase in torque experienced at the atherectomy burr before the atherectomy burr becomes stuck, and the controller is further adapted to command the drive motor to drive the drive mechanism at a reduced speed by changing the speed reference in order to produce a reduction in speed of the drive mechanism greater than what would otherwise normally occur in response to the increase in torque while continuing to rotate the drive mechanism in the same rotational direction, thereby providing a user with notice of the increase in torque. 
     
     
         14 . The atherectomy system of  claim 12 , wherein the controller comprises:
 a reference circuit that is adapted to receive a speed signal and output the reference signal;   a control circuit that is adapted to receive the reference signal from the reference circuit and generate a resulting control effort signal; and   a drive circuit that is adapted to receive the control effort signal from the control circuit and regulate operation of the drive mechanism accordingly.   
     
     
         15 . The atherectomy system of  claim 12 , wherein the controller comprises a Proportional controller. 
     
     
         16 . The atherectomy system of  claim 12 , wherein the controller comprises a Proportional Integral Derivative (PID) controller. 
     
     
         17 . An atherectomy system, comprising:
 a drive motor operably coupled to a drive cable;   an atherectomy burr operably coupled to the drive cable;   a control system operably coupled to the drive motor, the control system including:
 a feedback loop adapted to monitor performance of the drive motor and output a control effort signal; and 
 a drive circuit adapted to receive the control effort signal and regulate operation of the drive motor in accordance with the control effort signal; 
 wherein the control system is further adapted to provide a reduction in motor speed of the drive motor that is greater than what would otherwise normally occur in response to an increasing torque experienced at the atherectomy burr, thereby actively rotating the atherectomy burr in a same rotational direction at a reduced speed. 
   
     
     
         18 . The atherectomy system of  claim 17 , wherein the feedback loop includes:
 a reference circuit for determining a speed reference; and   a Proportional Integral Derivative (PID) controller operably coupled to the reference circuit for receiving the speed reference, the PID controller adapted to utilize the speed reference, a Proportional (P) gain value, an Integral (I) gain value and a Derivative (D) gain value in determining the control effort signal.   
     
     
         19 . The atherectomy system of  claim 18 , wherein the feedback loop is adapted to add an offset value to the reference signal in order to accurately hold speed of the drive motor during a no-load situation. 
     
     
         20 . The atherectomy system of  claim 17 , wherein when the atherectomy burr becomes stuck, the control system is further adapted to:
 increase the torque provided by the drive motor until a torque threshold is reached; and   direct the drive motor to reverse in order to unwind energy in the drive cable.