Parallel kinematic mechanisms with decoupled rotational motions

Abstract

A parallel kinematic mechanism apparatus includes a frame, a handle and an input joint that connects having at least two independent and functionally parallel paths for transmission of motion coupling the handle to the frame. A first path includes a first intermediate body connected to the frame by a first connector and to the handle by a third connector while the second path that is independent from the first path includes a second intermediate body that is connected to the frame by a second connector and to the handle by a fourth connector. The first connector and the fourth connector both allow rotation in a first rotational direction and restrict rotation in a second rotational direction and the second and third connectors allow rotation in the second rotational direction and restrict rotation in the first rotational direction.

What is claimed is: 
     
         1 . A parallel kinematic (PK) mechanism having at least pitch and yaw rotational degrees of freedom between a handle and a frame, the PK mechanism comprising:
 a frame;   a handle;   an input joint having at least two independent paths for transmission of motion coupling the handle to the frame, wherein the at least two independent paths comprise a first path and a second path;   a first intermediate body in the first path that is connected to the frame by a first connector comprising a first pivot joint and to the handle by a third connector comprising a third pivot joint;   a second intermediate body in the second path that is connected to the frame by a second connector comprising a second pivot joint, and to the handle by a fourth connector, wherein the fourth connector comprises a flexible torsion shaft;   wherein the first connector and the fourth connector both allow rotation in a pitch rotational direction and restrict rotation in a yaw rotational direction;   further wherein the second and third connectors allow rotation in the yaw rotational direction and restrict rotation in the pitch rotational direction.   
     
     
         2 . The parallel kinematic mechanism of  claim 1 , wherein the flexible torsional shaft transmits rotation about its center axis, which corresponds to the yaw direction, while remaining compliant in bending in the pitch rotational direction. 
     
     
         3 . The parallel kinematic mechanism of  claim 1 , wherein the flexible torsional shaft is rigidly connected to the handle at a first end of the flexible torsional shaft, and rigidly connected to the second intermediate body at a second end of the flexible torsional shaft. 
     
     
         4 . The parallel kinematic mechanism of  claim 1 , wherein the first and second intermediate bodies comprises pulleys. 
     
     
         5 . The parallel kinematic mechanism of  claim 1 , wherein the first path constrains rotation about a roll axis that is orthogonal to both the pitch and yaw axes. 
     
     
         6 . A parallel kinematic (PK) mechanism having at least pitch and yaw rotational degrees of freedom between a handle and a frame comprising:
 a frame;   a handle;   an input joint having at least two independent paths for transmission of motion coupling the handle to the frame, wherein the at least two independent paths comprise a first path and a second path;   a first intermediate body comprising a pitch mount in the first path that is connected to the frame by a first connector comprising a pivot joint and to the handle by a third connector comprising a first slider joint;   a second intermediate body comprising a yaw mount in the second path that is connected to the frame by a second connector comprising a pivot joint and to the handle by a fourth connector comprising a second slider joint;   wherein the first connector and the fourth connector both allow rotation in a pitch rotational direction and restrict rotation in a yaw rotational direction, and wherein the second connector and the third connector both allow rotation in the yaw rotational direction and restrict rotation in the pitch rotational direction,   further wherein the first slider joint and the second slider joint allow the handle or the member rigidly extending from the handle to translate along a roll axis that is orthogonal to both the pitch and yaw axes.   
     
     
         7 . The parallel kinematic mechanism of  claim 6 , wherein the first intermediate body comprises a pulley rigidly coupled to the pitch mount and wherein the second intermediate body comprises a yaw pulley rigidly coupled to the yaw mount. 
     
     
         8 . The parallel kinematic mechanism of  claim 6 , wherein the pitch mount of the first intermediate body comprises a first slot forming the first slider joint within which the handle or member rigidly extending from the handle may slide; and further wherein the yaw mount of the second intermediate body comprise a second slot forming the second slider joint within which the handle or the member rigidly extending from the handle may slide. 
     
     
         9 . The parallel kinematic mechanism of  claim 6 , further wherein the handle or the member rigidly extending from the handle is constrained from rotating within the first and second slider joint about a roll axis that is orthogonal to both the pitch and yaw axes. 
     
     
         10 . A parallel kinematic (PK) mechanism having at least pitch and yaw rotational degrees of freedom between a handle and a frame comprising:
 a frame;   a handle;   an input joint having at least two independent paths for transmission of motion coupling the handle to the frame, wherein the at least two independent paths comprise a first path and a second path;   a first intermediate body comprising a pitch mount in the first path that is connected to the frame by a first connector comprising a pivot joint and to the handle by a third connector comprising a first slider joint;   a second intermediate body comprising a yaw mount in the second path that is connected to the frame by a second connector comprising a pivot joint and to the handle by a fourth connector comprising a second slider joint;   wherein the first connector and the fourth connector both allow rotation in a pitch rotational direction and restrict rotation in a yaw rotational direction, and wherein the second connector and the third connector boht allow rotation in the yaw rotational direction and restrict rotation in the pitch rotational direction,   further wherein the handle or the member rigidly extending from the handle is constrained from rotating within the first and second slider joint about a roll axis that is orthogonal to both the pitch and yaw axes   
     
     
         11 . The parallel kinematic mechanism of  claim 10 , wherein the first intermediate body comprises a pulley rigidly coupled to the pitch mount and wherein the second intermediate body comprises a yaw pulley rigidly coupled to the yaw mount. 
     
     
         12 . The parallel kinematic mechanism of  claim 10 , wherein the pitch mount of the first intermediate body comprises a first slot forming the first slider joint within which the handle or member rigidly extending from the handle may slide; and further wherein the yaw mount of the second intermediate body comprise a second slot forming the second slider joint within which the handle or the member rigidly extending from the handle may slide.