US Patent 9486233 Tissue resecting systems and methods

A tissue resecting system includes an assembly having first and second tubular members. An electrical motor drive and controller moves the second member to resect tissue received in a window of the first member. A tachometer sends motor drive rotational signals to the controller, and the controller modulates a motor voltage in response to the signals from the tachometer both to drive the second member at a predetermined speed and to calculate resistance to driving the second member at the predetermined speed.