Atherectomy system , comprising: a drive shaft ; a rotational member coupled to a first end of the drive shaft ; a motor coupled to a second end of the drive shaft to rotate the rotational member , and a control unit configured to control a motor state of the motor , the control unit comprising: a controller ; a motor state estimator in communication with the controller ; and a reference schedule component in communication with the controller and the motor state estimator , the reference schedule component is configured to provide an output to the controller based on an input from the motor state estimator , wherein the input to the reference schedule component from the motor state estimator is a motor speed, wherein the controller is configured to output a control signal for actively braking the motor until it stops rotating based on the output received from the reference schedule component when the input to the reference schedule component from the motor state estimator reaches or goes beyond a threshold level, and wherein the control unit is configured to adjust the motor state of the motor to actively brake the motor until it stops rotating by reducing an amount of voltage provided to the motor in response to a detected stall condition in the rotational member , wherein the stall condition is detected when the speed of the motor reaches or goes below the threshold level, wherein the reference schedule component includes a reference schedule that relates the motor state to a reference value for the motor state in such a way that when the speed of the motor reaches or goes below the threshold level, the difference between a back electromotive force voltage and a target voltage rapidly transitions from positive to negative. a drive shaft ; a rotational member coupled to a first end of the drive shaft ; a motor coupled to a second end of the drive shaft to rotate the rotational member , and a control unit configured to control a motor state of the motor , the control unit comprising: a controller ; a motor state estimator in communication with the controller ; and a reference schedule component in communication with the controller and the motor state estimator , the reference schedule component is configured to provide an output to the controller based on an input from the motor state estimator , wherein the input to the reference schedule component from the motor state estimator is a motor speed, a controller ; a motor state estimator in communication with the controller ; and a reference schedule component in communication with the controller and the motor state estimator , the reference schedule component is configured to provide an output to the controller based on an input from the motor state estimator , wherein the input to the reference schedule component from the motor state estimator is a motor speed, wherein the controller is configured to output a control signal for actively braking the motor until it stops rotating based on the output received from the reference schedule component when the input to the reference schedule component from the motor state estimator reaches or goes beyond a threshold level, and wherein the control unit is configured to adjust the motor state of the motor to actively brake the motor until it stops rotating by reducing an amount of voltage provided to the motor in response to a detected stall condition in the rotational member , wherein the stall condition is detected when the speed of the motor reaches or goes below the threshold level, wherein the reference schedule component includes a reference schedule that relates the motor state to a reference value for the motor state in such a way that when the speed of the motor reaches or goes below the threshold level, the difference between a back electromotive force voltage and a target voltage rapidly transitions from positive to negative. <EOS>