Surgical manipulator

• US 8,444,631 B2
• Filed: 12/22/2008
• Issued: 05/21/2013
• Est. Priority Date: 06/14/2007
• Status: Active Grant

• Current Assignee: Macdonald Dettwiler and Associates Limited
• Original Assignee: Macdonald Dettwiler and Associates Limited
• Inventors: Yeung, Benny Hon Bun, Gregoris, Dennis, Bednarz, Bronislaw, Gray, Michael A.
• Primary Examiner(s): Yao, Sam
• Assistant Examiner(s): Downey, John R
• Application Number:
  US12/318,151
• Publication Number:
  US 20090163929A1
• Time in Patent Office: 1,611 Days
• Field of Search: 606/1, 414/5, 414/6, 414/680, 414729-741, 4147441-7443, 901 14- 16, 901/19, 901/21, 901/23, 901/28, 901/29
• US Class Current: 606/1
• CPC Class Codes: A61B 2034/305 Details of wrist mechanisms at distal ends of robotic arms
• CPC Class Codes: A61B 2034/715 Cable tensioning mechanisms for removing slack
• CPC Class Codes: A61B 2090/064 for measuring force, pressure or mechanical tension
• CPC Class Codes: A61B 34/30 Surgical robots
• CPC Class Codes: A61B 34/37 Master-slave robots A61B34/35 takes precedence
• CPC Class Codes: A61B 34/71 Manipulators operated by drive cable mechanisms
• CPC Class Codes: A61B 46/10 specially adapted for instruments, e.g. microscopes
• CPC Class Codes: A61B 90/361 Image-producing devices, e.g. surgical cameras
• CPC Class Codes: B25J 9/047 the pivoting axis of the first arm being offset to the vertical axis
• CPC Class Codes: B25J 9/104 with cables, chains or ribbons

Abstract

The present invention provides a surgical manipulator including a manipulator arm, an end-effector held by the robotic arm, surgical tools held by the end-effector and manipulator joints, particularly right-angle drive devices for transmitting rotational motion in one axis to a perpendicular axis.

Claims

1. A surgical manipulator, comprising:

a) a base and a first right angle drive mechanism mounted on said base, a shoulder-roll drive mechanism located in said base for rotating said first right-angle drive mechanism about a shoulder-roll axis,

said first right-angle drive mechanism including a first input pulley and a first output pulley and a first bi-directional coupling mechanism,

a first drive mechanism, having a first rotational drive axis, coupled to said first input pulley for rotating said first input pulley about a first input axis, said first input axis being coincident with said first rotational drive axis, wherein rotation of said first input pulley is translated into rotation of said first output pulley by said first bi-directional coupling mechanism about a shoulder-yaw axis which is perpendicular to, and intersecting with, said first input axis;

b) a second right-angle drive mechanism coupled to said first right-angle drive mechanism including a second input pulley and a second output pulley and second bi-directional coupling mechanism,

a second drive mechanism, having a second rotational drive axis, coupled to said second input pulley for rotating said second input pulley about a second input axis, said second input axis being coincident with said second rotational drive axis, wherein rotation of said second input pulley is translated into rotation of said second output pulley by said bi-directional coupling mechanism about a shoulder-pitch axis which is perpendicular to, and intersecting with, said second input axis;

c) a robotic lower arm being mounted at one end thereof to said second output pulley so that when said second output pulley is rotated, said robotic lower arm rotates about said shoulder-pitch axis,

a third right-angle drive mechanism mounted in said robotic lower arm, said third right-angle drive mechanism including a third input pulley and a third output pulley and a third bi-directional coupling mechanism,

a third drive mechanism, having a third rotational drive axis, coupled to said third input pulley for rotating said third input pulley about a third input axis, said third input axis being coincident with said third rotational drive axis, wherein rotation of said third input pulley about said third input axis is translated into rotation of said third output pulley by said bi-directional coupling mechanism about an elbow-pitch axis perpendicular to, and intersecting with, said third input axis;

d) a robotic fore arm mounted on said third output pulley of said third right-angle drive mechanism so that when said third output pulley is rotated, said robotic fore arm rotates about said elbow-pitch axis,

a fourth right-angle drive mechanism mounted in said robotic fore arm, said fourth right-angle drive mechanism including a fourth input pulley and a fourth output pulley, and a fourth bi-directional coupling mechanism,

a fourth drive mechanism, having a fourth rotational drive axis, coupled to said fourth input pulley for rotating the fourth input pulley about a fourth input axis, said fourth input axis being coincident with said fourth rotational drive axis, wherein rotation of said fourth input pulley about said fourth input axis is translated into rotation of said fourth output pulley by said bi-directional coupling mechanism about a wrist-pitch axis perpendicular to, and intersecting with, said fourth input axis;

e) a robotic wrist mounted on said fourth output pulley of said fourth right-angle drive mechanism so that when said fourth output pulley is rotated, said robotic wrist rotates about said wrist-pitch axis,

said robotic wrist including an actuation mechanism coupled to a wrist output shaft for rotating said robotic wrist output shaft about a wrist-roll axis; and

f) an end-effector mounted to said wrist output shaft, said end-effector including gripping means for releasibly gripping a surgical tool wherein, when said actuation mechanism is engaged, said end-effector is rotated about said wrist-roll axis.

2. The surgical manipulator according to claim 1 wherein components of said surgical manipulator including said base, said first, second, third and fourth right-angle drive mechanisms, said robotic lower arm, said robotic forearm, said robotic wrist, and said end effector include mechanical quick release mechanisms for quick assembly and disassembly of said surgical manipulator and include quick electrical connections so that when said components are assembled said components are electrically connected.

3. The surgical manipulator according to claim 2 wherein said components of said manipulator are modular components and configured to be quickly removed and replaced with different but similar modular components which can be of a different size, shape, orientation or sequence of said modular components.

4. The surgical manipulator according to claim 1 wherein said shoulder-roll drive mechanism includes a spur-gear mechanism mounted in said base and including a pinion anti-backlash gear meshed with a driven gear, a motor for rotating said pinion gear which in turn rotates said driven gear and therefore the first right angle drive mechanism about a shoulder-roll axis, and including a motor brake.

5. The surgical manipulator according to claim 1 wherein said end-effector includes

a main body portion including a frame having an interface configured to be attached to said robotic wrist, a tool-yaw motor mounted on said frame, a tool-actuation motor mounted on said frame,

a tool holder mounted on said frame and being detachable therefrom, said tool holder being configured to hold said surgical tool,

a tool-actuation mechanism mounted on said frame and being detachable therefrom, said tool-actuation mechanism being configured to engage a piston on said surgical tool, said tool-actuation mechanism being coupled to said tool-actuation motor,

and a tool-yaw drive mechanism mounted on said frame and being detachable therefrom, said tool-yaw drive mechanism being coupled to said tool-yaw motor, wherein upon activation of said tool-yaw drive mechanism said surgical tool rotates about said tool-yaw axis and wherein upon activation of said tool-actuation mechanism said piston is linearly retracted or linearly extended with respect to said end-effector thereby activating a tool portion of said surgical tool.

6. The surgical manipulator according to claim 5 wherein said interface includes a base block which interfaces to said robotic wrist, and wherein said end-effector includes a tool-tip force-moment sensor which is a single mechanical linkage between said frame and said base block, and wherein said tool-tip force-moment sensor mounted to said end-effector is configured to sense tool forces and moments at a tip of the surgical tool, and wherein said end-effector includes a tool-actuation force sensor mounted thereon configured to measure actuation forces on a tip of the surgical tool, said surgical manipulator including hand controller means being configured to be operated by a surgeon, and including a communication system coupling said hand controller means to said surgical manipulator for translating movement of said hand controller means to scaled movement of said surgical manipulator, and wherein said communication system coupling said hand controller means to said surgical manipulator is configured to communicate said forces and moments to said hand controller means providing haptic feedback to a surgeon.

7. The surgical manipulator according to claim 6 wherein said tool-actuation motor is a linear actuator having an output shaft which moves up and down along a major axis of the linear actuator and at a distal end portion of said output shaft an actuator bar is connected at a first end portion thereof, said actuator bar having a second end portion supported by a vertical guide rod and including an interface which couples to said tool-actuation mechanism, wherein said actuator bar transmits vertical motion of the output shaft to the tool-actuation mechanism which is mounted at the second end of the bar such that said vertical motion provides a tool-actuation axis of motion for the end-effector, and wherein said tool-actuation mechanism includes a pair of pivoting fingers pivotally mounted to a support member with matched end portions configured to engage and hold a portion of a piston on the surgical tool.

8. The surgical manipulator according to claim 5 wherein said tool-yaw mechanism includes a frame on which is mounted a pair of outer idler pulleys, a middle idler pulley and a drive pulley, including a toothed belt being routed on said outer idler pulleys, said middle idler pulley and said drive pulley, said toothed belt being configured to engage a toothed pulley on said surgical tool, on two opposite ends of a diameter of said toothed pulley, and wherein bi-directional rotation of said toothed belt driven by said drive pulley, converts tangential forces to rotary motion of said surgical tool, and wherein said frame has an open front-framed architecture and a toothed belt routing configuration on said outer idler pulleys and said middle idler pulley configured to allow the surgical tool to be ejected/replaced from the open front of the end-effector, and wherein said frame includes sheet metal flexures supporting said outer idler pulleys so that said outer idler pulleys can be passively spread out enough to completely disengage the surgical tool thereby eliminating any frictional effects, and wherein when engaged with said surgical tool, the metal flexures allow a constant preload to the toothed belt during tool yawing but can also manually collapse, when no surgical tool is present, for facilitating toothed belt replacement.

9. The surgical manipulator according to claim 8 wherein said tool holder includes a support body having an elongate channel having a size suitable to receive therein a cylindrical tool body of said surgical tool, and wherein said cylindrical tool body is made of a magnetic material, and wherein said support body includes at least one magnet embedded therein adjacent to said elongate channel for magnetically restraining said magnetic cylindrical tool body, wherein said support body is made of a material which allows the surgical tool to rotate with minimal friction within said support body when rotated by said tool-yaw mechanism, wherein said surgical tool includes flanges on the body of the surgical tool for locating and constraining the surgical tool axially within said channel in said support body due to a close axial fit with the support body;

wherein said tool holder includes a tool release mechanism including a pair of tool-ejection wings pivotally mounted on said support body with a portion of each wing located in said channel behind said tool body and configured such that once said tool-ejection wings are compressed on outer surfaces thereof, said tool-ejection wings pivot in a scissor action, to strip the tool body away from said at least one magnet responsively ejecting said tool from said tool holder.

10. The surgical manipulator according to claim 9 including a tool changer mechanism comprising a tool storage and tool change tray, said tool change tray including a support structure for holding the surgical tools and including engaging features arrayed on said tool change tray configured to simultaneously spread said pulleys apart, engage the pivoting fingers located on said tool-actuation mechanism, and engage said ejection-wings located on said tool holder thereby releasing said surgical tool from said end-effector, wherein said support structure for holding the surgical tools and said engaging features arrayed on said tool change tray include first and second pair of pins fixed in vertical arrangement to said tool tray being positioned and spaced apart such that they engage said pulleys on said tool-yaw mechanism and spread said pulleys apart when said end-effector engages said passive tool changer when picking up a surgical tool or releasing a surgical tool, and including a third pair of pins positioned on said tool change tray with respect to said first and second pairs of pins such that the third pair of pins engage pivoting fingers located on said tool-actuation mechanism responsively pivoting said fingers out of engagement with said piston on said surgical tool, said tool change tray including mating ejection latches mounted on the tool tray which line up with said ejection-wings located on said tool holder, which mating ejection latches include a spring-loaded pliers-like mechanism to provide a cushioned tool-ejection;

wherein each surgical tool includes identifying means mounted thereon, and wherein said tool changer includes a tool-identification sensor for said identifying means, wherein said identifying means includes a radio frequency (rf) tag and, and wherein said reading means includes an rf receiver, wherein said identifying means includes a bar code, and wherein said reading means includes a bar code reader.

11. The surgical manipulator according to claim 1 wherein said surgical manipulator is a first surgical manipulator, including at least a second surgical manipulator and configured to be a structural mirror image of said first surgical manipulator, said first surgical manipulator being configured for left handed operation and said at least a second surgical manipulator being configured for right handed operation to allow the surgical tools attached to respective end-effectors to be brought into close proximity with each other in a surgical site on a patient.

12. The surgical manipulator according to claim 1 wherein each right-angle drive mechanism includes

a housing and wherein said drive mechanism includes a harmonic drive mounted on said housing and connected to said input pulley for rotation about said input axis;

an output shaft being connected to said output pulley, said output pulley being mounted in said housing for rotation about an output axis, said input and output pulleys being mounted in said housing and positioned with respect to each other such that said input and output axes are perpendicular to, and intersecting with each other;

each bi-directional coupling mechanism for coupling said input pulleys and said output pulleys comprising

a cable drive mounted in said housing, said cable drive including,

at least one flexible cable, said input and output pulleys each including at least one cable guide for receiving therein said at least one flexible cable,

idler means for guiding said at least one flexible cable between said input and output pulleys,

wherein when the input pulley rotates in one direction about said input axis, said at least one flexible cable pulls the output pulley and output shaft to rotate in one direction about said output axis, and when the input pulley rotates in the other direction about said input axis, said at least one flexible cable pulls the output pulley and output shaft to rotate in an opposite direction about said output axis.

25. A surgical manipulator system, comprising;

a) at least first and second surgical manipulators according to claim 11;

b) left and right hand controllers with the right hand controller being associated with the first surgical manipulator and the left hand controller being associated with the second surgical manipulator, said at least first and second hand controllers being configured to be operated by a surgeon;

c) communication system coupling said left and right hand controllers to said at least first and second surgical manipulators for translating movement of said left and right hand controllers to scaled movement of said at least first and second surgical manipulators; and

d) a vision system focused on a work area including an area of a patient to be operated on and focused on the end-effectors and associated surgical tools attached to said at least two surgical manipulators, said vision system including display means for displaying images of said work area to a surgeon.

26. The surgical system according to claim 25 configured for teleoperation wherein said surgeon is located remotely from a patient.

27. The surgical system according to claim 26 wherein said end-effector includes a tool-tip force-moment sensor mounted to said end-effector and configured to sense tool forces and moments at a tip of the surgical tool, and wherein said end-effector includes a tool-actuation force sensor mounted thereon configured to measure actuation forces on a tip of the surgical tool, and wherein said communication system coupling said left and right hand controllers to said at least first and second surgical manipulators is configured to communicate said forces and moments to said left and right handed controllers providing haptic feedback to a surgeon.

13. A surgical manipulator, comprising:

a) a base and a first right-angle drive mechanism mounted on said base, a shoulder-roll drive mechanism located in said base for rotating said first right-angle drive mechanism about a shoulder-roll axis,

said first right-angle drive mechanism including a first input pulley and a first output pulley and a first bi-directional coupling mechanism,

a first drive mechanism, having a first rotational drive axis, coupled to said first input pulley for rotating said first input pulley about a first input axis, said first input axis being coincident with said first rotational drive axis, wherein rotation of said first input pulley is translated into rotation of said first output pulley by said first bi-directional coupling mechanism about a shoulder-pitch axis which is perpendicular to, and intersecting with, said first input axis;

b) a robotic lower arm being mounted at one end thereof to said first output pulley so that when said first output pulley is rotated, said robotic lower arm rotates about said shoulder-pitch axis,

a second right-angle drive mechanism mounted in said robotic lower arm, said second right-angle drive mechanism including a second input pulley and a second output pulley and a second bi-directional coupling mechanism,

a second drive mechanism, having a second rotational drive axis, coupled to said second input pulley for rotating said second input pulley about a second input axis, said second input axis being coincident with said second rotational drive axis, wherein rotation of said second input pulley is translated into rotation of said second output pulley by said second bi-directional coupling mechanism about an elbow-pitch axis which is perpendicular to, and intersecting with, said second input axis;

c) a robotic fore arm mounted on said second output pulley of said second right-angle drive mechanism so that when said second output pulley is rotated, said robotic fore arm rotates about said elbow-pitch axis,

a third right-angle drive mechanism mounted in said robotic fore arm, said third right-angle drive mechanism including a third input pulley and a third output pulley and a third bi-directional coupling mechanism,

a third drive mechanism, having a third rotational drive axis, coupled to said third input pulley for rotating said third input pulley about a third input axis, said third input axis being coincident with said third rotational drive axis, wherein rotation of said third input pulley is translated into rotation of said third output pulley by said third bi-directional coupling mechanism about an wrist-pitch axis perpendicular to, and intersecting with, said third input axis;

d) a fourth right-angle drive mechanism mounted on said third output pulley of said third right-angle drive mechanism, said fourth right-angle drive mechanism including a fourth input pulley and a fourth output pulley and a fourth bi-directional coupling mechanism,

a fourth drive mechanism, having a fourth rotational drive axis, coupled to said fourth input pulley for rotating said fourth input pulley about a fourth input axis, said fourth input axis being coincident with said fourth rotational drive axis, wherein rotation of said fourth input pulley is translated into rotation of said fourth output pulley by said fourth bi-directional coupling mechanism about a wrist-yaw axis perpendicular to, and intersecting with, said fourth input axis;

e) a robotic wrist mounted on said fourth output pulley of said fourth right-angle drive mechanism so that when said fourth output pulley is rotated, said robotic wrist rotates about said wrist-yaw axis,

said robotic wrist including an actuation mechanism coupled to a wrist output shaft for rotating said robotic wrist output shaft about a wrist-roll axis; and

f) an end-effector mounted to said wrist output shaft, said end-effector including gripping means for releasibly gripping a surgical tool wherein, when said actuation mechanism is engaged, said end-effector is rotated about said wrist-roll axis.

14. The surgical manipulator according to claim 13 wherein components of said surgical manipulator including said base, said first, second, third and fourth right-angle drive mechanisms, said robotic lower arm, said robotic forearm, said robotic wrist, and said end effector include mechanical quick release mechanisms for quick assembly and disassembly of said surgical manipulator and include quick electrical connections so that when said components are assembled said components are electrically connected.

15. The surgical manipulator according to claim 14 wherein said components of said manipulator are modular components and configured to be quickly removed and replaced with different but similar modular components which can be of a different size, shape, orientation or sequence of said modular components.

16. The surgical manipulator according to claim 14 wherein said shoulder-roll drive mechanism includes a spur-gear mechanism mounted in said base and including a pinion anti-backlash gear meshed with a driven gear, a motor for rotating said pinion gear which in turn rotates said driven gear and therefore the first right angle drive mechanism about a shoulder-roll axis, and including a motor brake.

17. The surgical manipulator according to claim 13 wherein said end-effector includes

a main body portion including a frame having an interface configured to be attached to said robotic wrist, a tool-yaw motor mounted on said frame, a tool-actuation motor mounted on said frame,

a tool holder mounted on said frame and being detachable therefrom, said tool holder being configured to hold said surgical tool,

a tool-actuation mechanism mounted on said frame and being detachable therefrom, said tool-actuation mechanism being configured to engage a piston on said surgical tool, said tool-actuation mechanism being coupled to said tool-actuation motor,

and a tool-yaw drive mechanism mounted on said frame and being detachable therefrom, said tool-yaw drive mechanism being coupled to said tool-yaw motor, wherein upon activation of said tool-yaw drive mechanism said surgical tool rotates about said tool-yaw axis and wherein upon activation of said tool-actuation mechanism said piston is linearly retracted or linearly extended with respect to said end-effector thereby activating a tool portion of said surgical tool.

18. The surgical manipulator according to claim 17 wherein said interface includes a base block which interfaces to said robotic wrist, and wherein said end-effector includes a tool-tip force-moment sensor which is a single mechanical linkage between said frame and said base block, and wherein said tool-tip force-moment sensor mounted to said end-effector is configured to sense tool forces and moments at a tip of the surgical tool, and wherein said end-effector includes a tool-actuation force sensor mounted thereon configured to measure actuation forces on a tip of the surgical tool, said surgical manipulator including hand controller means being configured to be operated by a surgeon, and including a communication system coupling said hand controller means to said surgical manipulator for translating movement of said hand controller means to scaled movement of said surgical manipulator, and wherein said communication system coupling said hand controller means to said surgical manipulator is configured to communicate said forces and moments to said hand controller means providing haptic feedback to a surgeon.

19. The surgical manipulator according to claim 18 wherein said tool-actuation motor is a linear actuator having an output shaft which moves up and down along a major axis of the linear actuator and at a distal end portion of said output shaft an actuator bar is connected at a first end portion thereof, said actuator bar having a second end portion supported by a vertical guide rod and including an interface which couples to said tool-actuation mechanism, wherein said actuator bar transmits vertical motion of the output shaft to the tool-actuation mechanism which is mounted at the second end of the bar such that said vertical motion provides a tool-actuation axis of motion for the end-effector, and wherein said tool-actuation mechanism includes a pair of pivoting fingers pivotally mounted to a support member with matched end portions configured to engage and hold a portion of a piston on the surgical tool.

20. The surgical manipulator according to claim 17 wherein said tool-yaw mechanism includes a frame on which is mounted a pair of outer idler pulleys, a middle idler pulley and a drive pulley, including a toothed belt being routed on said outer idler pulleys, said middle idler pulley and said drive pulley, said toothed belt being configured to engage a toothed pulley on said surgical tool, on two opposite ends of a diameter of said toothed pulley, and wherein bi-directional rotation of the toothed belt driven by the drive pulley, converts tangential forces to rotary motion of said surgical tool, and wherein said frame has an open front-framed architecture and a toothed belt routing configuration on said outer idler pulleys and said middle idler pulley configured to allow the surgical tool to be ejected/replaced from the open front of the end-effector, and wherein said frame includes sheet metal flexures supporting said outer idler pulleys so that said outer idler pulleys can be passively spread out enough to completely disengage the surgical tool thereby eliminating any frictional effects, and wherein when engaged with said surgical tool, the metal flexures allow a constant preload to the toothed belt during tool yawing but can also manually collapse, when no surgical tool is present, for facilitating toothed belt replacement.

21. The surgical manipulator according to claim 20 wherein said tool holder includes a support body having an elongate channel having a size suitable to receive therein a cylindrical tool body of said surgical tool, and wherein said cylindrical tool body is made of a magnetic material, and wherein said support body includes at least one magnet embedded therein adjacent to said elongate channel for magnetically restraining said magnetic cylindrical tool body, wherein said support body is made of a material which allows the surgical tool to rotate with minimal friction within said support body when rotated by said tool-yaw mechanism, wherein said surgical tool includes flanges on the body of the surgical tool for locating and constraining the surgical tool axially within said channel in said support body due to a close axial fit with the support body;

wherein said tool holder includes a tool release mechanism including a pair of tool-ejection wings pivotally mounted on said support body with a portion of each wing located in said channel behind said tool body and configured such that once said tool-ejection wings are compressed on outer surfaces thereof, said tool-ejection wings pivot in a scissor action, to strip the tool body away from said at least one magnet responsively ejecting said tool from said tool holder.

22. The surgical manipulator according to claim 21 including a tool changer mechanism comprising a tool storage and tool change tray, said tool change tray including a support structure for holding the surgical tools and including engaging features arrayed on said tool change tray configured to simultaneously spread said outer pulleys apart, engage the pivoting fingers located on said tool-actuation mechanism, and engage said ejection-wings located on said tool holder thereby releasing said surgical tool from said end-effector, wherein said support structure for holding the surgical tools and said engaging features arrayed on said tool change tray include first and second pair of pins fixed in vertical arrangement to said tool tray being positioned and spaced apart such that they engage said outer pulleys on said tool-yaw mechanism and spread said outer pulleys apart when said end-effector engages said passive tool changer when picking up a surgical tool or releasing a surgical tool, and including a third pair of pins positioned on said tool change tray with respect to said first and second pairs of pins such that the third pair of pins engage pivoting fingers located on said tool-actuation mechanism responsively pivoting said fingers out of engagement with said piston on said surgical tool, said tool change tray including mating ejection latches mounted on the tool tray which line up with said ejection-wings located on said tool holder, which mating ejection latches include a spring-loaded pliers-like mechanism to provide a cushioned tool-ejection;

wherein each surgical tool includes identifying means mounted thereon, and wherein said tool changer includes a tool-identification sensor for said identifying means, wherein said identifying means includes a radio frequency (rf) tag and, and wherein said reading means includes an rf receiver, wherein said identifying means includes a bar code, and wherein said reading means includes a bar code reader.

23. The surgical manipulator according to claim 13 wherein said surgical manipulator is a first surgical manipulator, including at least a second surgical manipulators and configured to be structural mirror images of each other, said first surgical manipulator being configured for left handed operation and said at least a second surgical manipulator being configured for right handed operation to allow the surgical tools attached to respective end-effectors to be brought into close proximity with each other in a surgical site on a patient.

24. The surgical manipulator according to claim 13 wherein each right-angle drive mechanism includes

a housing and wherein said drive mechanism includes a harmonic drive mounted on said housing and connected to said input pulley for rotation about said input axis;

an output shaft being connected to said output pulley, said output pulley being mounted in said housing for rotation about an output axis, said input and output pulleys being mounted in said housing and positioned with respect to each other such that said input and output axes are perpendicular to, and intersecting with each other;

each bi-directional coupling mechanism for coupling said input pulleys and said output pulleys including

a cable drive mounted in said housing, said cable drive including,

at least one flexible cable, said input and output pulleys each including at least one cable guide for receiving therein said at least one flexible cable,

idler means for guiding said at least one flexible cable between said input and output pulleys,

wherein when the input pulley rotates in one direction about said input axis, said at least one flexible cable pulls the output pulley and output shaft to rotate in one direction about said output axis, and when the input pulley rotates in an opposite direction about said input axis, said at least one flexible cable pulls the output pulley and output shaft to rotate in an opposite direction about said output axis.