Method for passively decoupling torque applied by a remote actuator into an independently rotating member

A minimally invasive robotic surgical assembly comprising:

• a base;
• a main shaft assembly rotationally mounted to the base, the main shaft assembly including a main shaft, an end effector supported by the main shaft, and a first end effector drive shaft drivingly coupled to the end effector;
• a main shaft drive rotationally driving the main shaft relative to the base;
• a first input drive shaft transmitting a first input torque;
• and
• a first transmission having a first input link rotationally coupled to the first input drive shaft, a first output link rotationally coupled with the first end effector drive shaft, and a first base link, the first transmission providing a first gear ratio between the first input link and the first output link so as to transmit a first output torque to the main shaft assembly in response to the first input torque, a first end effector torque being transmitted by the first end effector drive shaft to the end effector in response to the first output torque, the first base link rotationally coupled with the main shaft by a second gear ratio such that the first base link, in response to the first input torque, transmits a first counteracting torque to the main shaft that is opposite in direction from the first output torque such that the first counteracting torque inhibits rotational driving of the main shaft assembly by the first output torque.