Surgical instrument drive systems with cable-tightening system

A surgical instrument drive system configured to perform a function of a surgical end effector, wherein said surgical instrument drive system comprises:

• a shaft assembly configured to be inserted into and attached to an attachment interface;
• a pulley drive system, comprising:
• a first cable driver;
• a second cable driver;
• a pulley;
• and
• a cable attached to said first cable driver and said second cable driver, wherein said cable is supported by said pulley and actuatable by said first cable driver and said second cable driver;
• an actuation member comprising a linear rack portion;
• and
• a bracket attaching said actuation member to said pulley drive system, wherein said pulley drive system is configured to move said actuation member through an actuation stroke between a home position and a fully-actuated position by way of said bracket, and wherein said bracket comprises:
• a mounting portion fixedly attached to said cable;
• and
• a pawl engaged with said linear rack portion to hold said actuation member relative to said bracket, wherein said pawl is configured to ratchet relative to said linear rack portion while said actuation member is held in position to allow said bracket to move relative to said actuation member to eliminate previously induced cable slack in the pulley drive system by tensioning the cable of the pulley drive system with one of said first cable driver or said second cable driver.