Multi-Ply Strap Drive Trains for Robotic Arms

A robotic arm comprising:

• a linkage assembly including first, second, third, and fourth links pivotally coupled in series together at first, second, and third joints to define a parallelogram with an insertion axis, wherein
• the first link includes a first joint pulley rigidly coupled thereto,
• the second link includes a third joint pulley rigidly coupled thereto, the third joint pulley concentric with but independent of the second joint pulley to pivot independently,
• the third link includes a second joint pulley rigidly coupled thereto, and
• the fourth link includes a fourth joint pulley rigidly coupled thereto;
• a strap drive train including first and second sets of straps coupled to the linkage assembly, the first set of straps connect the first joint pulley to the second joint pulley in a one-to-one ratio, and the second set of straps connect the third joint pulley to the fourth joint pulley in a one-to-one ratio, wherein
• a first end of a second strap of the second set of straps is wrapped around the third joint pulley in an opposite direction to a first end of a first strap of the second set of straps,
• a second end of the second strap wrapped around the fourth joint pulley in an opposite direction to a second end of the first strap,
• the first strap rides over a first idler pulley, and
• the second strap is reverse bent over a second idler pulley concentric with but independent of the first idler pulley to pivot in an opposite direction;
• and
• wherein as the linkage assembly is moved about a pitch axis, the first set of straps ensures the third link maintains the same angle relative to the first link, and the first and second sets of straps ensures the fourth link maintains the same angle relative to the second link.

A robotic arm comprising:

• a serial linkage pivotally coupled in series together including
• an offset yaw link having a first joint pulley rigidly coupled thereto,
• a drive link having a second joint pulley rigidly coupled thereto,
• a bent link having a third joint pulley rigidly coupled thereto and first and second idler pulleys, the third joint pulley independent of and concentric with the second joint pulley, the first idler pulley independent of and concentric with the second idler pulley, wherein the bent link includes a bend configured to provide a compact robotic arm with an improved range of pitch, and
• an instrument holder link having a fourth joint pulley rigidly coupled thereto;
• a strap drive train including
• a first strap and a second strap in the drive link coupled between the first joint pulley and the third joint pulley;
• a third strap in the bent link coupled between the second joint pulley and the fourth joint pulley over the first idler pulley;
• a fourth strap in the bent link coupled between the second joint pulley and the fourth joint pulley reverse bent over the second idler pulley with ends of the fourth strap wrapped around the second and fourth joint pulleys in an opposite direction to that of ends of the third strap;
• and
• wherein the serial linkage and the strap drive train to constrain the motion of a shaft of a tool to a center of rotation.

A robotic arm comprising:

• a linkage assembly including a plurality of links pivotally coupled in series together at one or more joints to slidingly support a tool along an insertion axis, the plurality of links including a first pulley and a second pulley;
• at least one strap coupled between the first pulley and the second pulley to drive the linkage assembly;
• and
• a strap tensioning system coupled to the at least one strap, the strap tensioning system to tension the at least one strap.