Controlling software remote centers of motion for computer-assisted systems subject to motion limits

A method of driving a plurality of joints of a repositionable structure, the method comprising:

• while a remote center of motion (RCM) of the repositionable structure is set at a first position, receiving a command to move an instrument supported by the repositionable structure with a commanded motion;
• determining whether driving the plurality of joints to move the repositionable structure in accordance with the commanded motion while maintaining the RCM at the first position would violate a limit of the repositionable structure;
• in response to determining that driving the plurality of joints to move the repositionable structure in accordance with the commanded motion while maintaining the RCM at the first position would violate the limit:
• determining an alternative motion of the plurality of joints based on the commanded motion and the first position, wherein driving the plurality of joints in accordance with the alternative motion would not violate the limit, and would move the RCM to a second position different from the first position, and
• driving the plurality of joints in accordance with the alternative motion;
• after the RCM has moved from the first position and while the RCM is at a current position, receiving a second command to move the repositionable structure with a second commanded motion;
• and
• in response to a determination that driving the plurality of joints to move the repositionable structure in accordance with the second commanded motion allows the RCM to move closer to the first position while not violating the limit, driving the plurality of joints to move the repositionable structure in accordance with the second commanded motion and to move the RCM closer to the first position.

One or more non-transitory machine-readable media comprising a plurality of machine-readable instructions which, when executed by one or more processors associated with a computer-assisted system comprising a repositionable structure, the repositionable structure comprising a plurality of joints, are adapted to cause the one or more processors to perform a method comprising:

• while a remote center of motion (RCM) of the repositionable structure is set at a first position, receiving a command to move an instrument supported by the repositionable structure with a commanded motion;
• determining whether driving the plurality of joints to move the repositionable structure in accordance with the commanded motion while maintaining the RCM at the first position would violate a limit of the repositionable structure;
• in response to determining that driving the plurality of joints to move the repositionable structure in accordance with the commanded motion while maintaining the RCM at the first position would violate the limit:
• determining an alternative motion of the plurality of joints based on the commanded motion and the first position, wherein driving the plurality of joints in accordance with the alternative motion would not violate the limit, and would move the RCM to a second position different from the first position, and
• driving the plurality of joints in accordance with the alternative motion;
• after the RCM has moved from the first position and while the RCM is at a current position, receiving a second command to move the repositionable structure with a second commanded motion;
• and
• in response to a determination that driving the plurality of joints to move the repositionable structure in accordance with the second commanded motion allows the RCM to move closer to the first position while not violating the limit, driving the plurality of joints to move the repositionable structure in accordance with the second commanded motion and to move the RCM closer to the first position.