Parallel mechanism with kinematically redundant actuation
A parallel mechanism comprises legs with kinematically redundant actuation for a parallel mechanism. Each of these legs comprises a first sub-leg and a second sub-leg each with a proximal end and a distal end. A link has a proximal end and a distal end. A joint with a rotational degree of freedom (DOF) is between and common to the distal ends of the sub-legs, and the proximal end of the link. A joint provides two or more rotational DOFs at the distal end of the link and connects the distal end of the link to one end of the parallel mechanism. Joints in the sub-legs provide DOFs to the sub-legs and connect the proximal ends of the sub-legs to the other end of the parallel mechanism. A degree of actuation (DOA) is provided for each of the sub-legs to control movement of the link.
1. A leg with kinematically redundant actuation for a parallel mechanism comprising:
a first sub-leg and a second sub-leg, each said sub-leg comprising a proximal end and a distal end;
a link having a proximal end and a distal end, the link lying in a link plane;
a revolute joint having a joint axis and being between and common to the distal ends of each of the first sub-leg and the second sub-leg, and the proximal end of the link, the joint axis projecting out of the link plane;
at least one joint providing at least two rotational degrees of freedom (DOFs) at the distal end of the link and adapted to connect the distal end of the link to one end of the parallel mechanism, said at least one joint providing at least two rotational DOFs having a center lying in said link plane, said center being separated from the joint axis by a length;
joints in the first sub-leg and the second sub-leg to provide DOFs to the sub-legs, with at least one of said joints in each of the first sub-leg and the second sub-leg connecting the proximal end of a respective one of the sub-legs to another end of the parallel mechanism; and
at least one degree of actuation (DOA) for each of the first sub-leg and the second sub-leg to control movement of the link.
2. The leg according to claim 1 , wherein said joints in the first sub-leg and the second sub-leg include:
a translational DOF joint in each said sub-leg between its proximal end and its distal end, the DOA for each said sub-leg actuating the translational DOF joint, and at least one joint providing two rotational DOFs at the proximal end of each said sub-leg.
3. The leg according to claim 1 , wherein said joints in the first sub-leg and the second sub-leg include:
a rotational DOF joint in each said sub-leg between its proximal end and its distal end,
a rotational DOF joint at the proximal end of each said sub-leg, the DOA for each said sub-leg actuating the rotational DOF joint at the proximal end, and
a common rotational DOF joint connected to the other end of the parallel mechanism, the rotational DOF joints at the proximal ends of the sub-legs being concurrently mounted onto the common rotational DOF joint.
4. The leg according to claim 3 , wherein the sub-legs lie in a plane and a rotational
axis of the common rotational DOF joint lies in said plane.
5. The leg according to claim 1 , wherein said joints in the first sub-leg and the second sub-leg include:
a rotational DOF joint at the proximal end of each of the sub-legs,
a translational DOF joint upon which is mounted said rotational DOF joint at the proximal end of each of the sub-legs, the DOA for each said sub-leg actuating the translational DOF joint, and
a common rotational DOF joint connected to the other end of the parallel mechanism, the translational DOF joints at the proximal ends of the sub-legs being concurrently mounted onto the common rotational DOF joint.
6. The leg according to claim 1 , wherein the link and the sub-legs lie in a common plane being said link plane, with an axis of rotation of the revolute joint between and common to the distal ends of the sub-legs being normal to the common plane.
7. A spatial parallel mechanism comprising:
a platform;
a base;
at least three of the legs with kinematically redundant actuation according to claim 1 , each connected at opposed ends to the platform and to the base; and
at least three single legs extending between the one end and the other end of the spatial parallel mechanism, each single leg comprising
at least one distal joint providing at least two rotational DOFs connecting a distal end of the single leg to the spatial parallel mechanism,
joints to provide DOFs to the single leg with at least one of said joints in each of the single leg connecting a proximal end of the single leg to the spatial parallel mechanism, and
at least one DOA for each of the single leg to actuate movement at one of said joints;
wherein the DOAs of the legs with kinematically redundant actuation and of the single legs are actuated to selectively displace the platform along at least one of six DOFs.
8. The spatial parallel mechanism according to claim 7 , wherein said joints in each said single leg include:
a translational DOF joint between the proximal end and the distal end of each said single leg, the DOA for each said single leg actuating the translational DOF joint, and
at least one proximal joint providing two rotational DOFs at the proximal end of each said single leg.
9. The spatial parallel mechanism according to claim 7 , wherein the proximal end of the legs with kinematically redundant actuation and of the single legs are connected to the base, and the distal ends of the legs with kinematically redundant actuation and of the single legs are connected to the platform.
10. A leg with kinematically redundant actuation for a parallel mechanism comprising:
a first sub-leg and a second sub-leg, each said sub-leg comprising a proximal end and a distal end;
a link having a proximal end and a distal end, the link lying in a link plane;
a revolute joint having a joint axis and being between and common to the distal ends of each of the first sub-leg and the second sub-leg, and the proximal end of the link, the joint axis projecting out of the link plane;
at least one joint providing at least two rotational degrees of freedom (DOFs) at the distal end of the link and adapted to connect the distal end of the link to one end of the parallel mechanism, said at least one joint providing at least two rotational DOFs, the one joint having a center point lying in said link plane, said center point being separated from the joint axis by a length;
joints in the first sub-leg and the second sub-leg to provide DOFs to the sub-legs, with at least one of said joints in each of the first sub-leg and the second sub-leg connecting the proximal end of a respective one of the sub-legs to another end of the parallel mechanism; and
at least one degree of actuation (DOA) for each of the first sub-leg and the second sub-leg to control movement of the link.
11. The leg according to claim 10 , wherein said joints in the first sub-leg and the second sub-leg include:
a translational DOF joint in each said sub-leg between its proximal end and its distal end, the DOA for each said sub-leg actuating the translational DOF joint, and
at least one joint providing two rotational DOFs at the proximal end of each said sub-leg.