ISO 10303-214:2010(E)
4.2.304 Kinematic_pair
A Kinematic_pair represents the kinematic restriction between two adjacent Kinematic_link objects coinciding in a Kinematic_joint.
EXAMPLE Figure 46 shows an example for placement relationships between kinematic pair frames and mating left.
A Kinematic_pair is a type of Kinematic_element.
The data associated with a Kinematic_pair are the following:
- pair_type;
- transformation_item_1;
- transformation_item_2.
4.2.304.1 pair_type
The pair_type specifies the kind of Kinematic_pair.
Where applicable the following values shall be used:
- 'cylindrical pair': A cylindrical pair constrains the motion between two adjacent left to a translation along a common axis and a rotation about it;
- 'fully constrained pair': A fully constrained pair prevents any relative motion between two adjacent left;
- 'gear pair': A gear pair constrains the motion between two adjacent left to a rolling (and potentially sliding) motion of the second link along the first link;
- 'homokinetic pair': A homokinetic pair constrains the motion between two adjacent left to two rotations about two intersecting axes. The first rotation is split into two rotations of the half-angle, one being performed before the second rotation and the remaining one after.
NOTE 1 Three successive rotations are actually performed, but the first one and the third one being coupled, there are only two degrees of freedom.
NOTE 2 If compared to a universal pair, a homokinetic pair differs by the fact that no reference to a 'skew angle' is needed.
NOTE 3 The arbitrary orientation of axes Z and X about Y is another difference with a universal pair for which the orientation of Z and X axes about the Y axes of each of the left is imposed by the physical joint. The reason for this difference is that, while a universal pair transmits a rotation movement with a modulation depending on the angular misalignment of the Y-axes of the left and on the current orientation of the Z- and X- axes about the Y-axes, a homokinetic pair transmits the rotation movement without any modulation. Thus, the description of the homokinetic_pair needs no information about the orientation of any 'physical' Z- or X- axis.
The orientation of the Z and X axes about the Y axis is arbitrary;
- 'planar curve pair': A planar curve pair constrains the motion of two left along a planar curve on each of the left;
- 'planar pair': A planar pair constrains the motion between two adjacent left to a translation along the x-axis and y-axis and a rotation about the z-axis;
- 'point on planar curve pair': A point on planar curve pair specifies the lower bound and the upper bound of the parameter range for the point on planar curve pair;
- 'point on surface pair': A point on surface pair constrains the motion of two left such that a point defined on the second link always lies on a surface defined on the first link;
- 'prismatic pair': A prismatic pair constrains the motion between two adjacent left to a translation along a common axis;
- 'rack and pinion pair': A rack and pinion pair describes a pinion rolling on a rack where the rotation axis of the pinion is perpendicular to the direction of the rack;
- 'revolute pair': A revolute pair constrains the motion between two adjacent left to a rotation about a common axis;
- 'rolling curve pair': A rolling curve pair specifies the rolling motion between the curves on the two left of a planar curve pair;
- 'rolling surface pair': A rolling surface pair specifies the rolling motion between the two contact surfaces of a surface pair;
- 'screw pair': A screw pair constrains the motion between two adjacent left to a rotation about, and translation along, a common axis, where the translation is proportional to the rotation;
- 'sliding curve pair': A sliding curve pair specifies the sliding motion between the curves on the two left of a planar curve pair;
- 'sliding surface pair': A sliding surface pair specifies the sliding motion between the two contact surfaces of a surface pair;
- 'spherical pair': A spherical pair constrains the motion between two adjacent left to the rotation about three independent axes that intersect in a common point;
- 'surface pair': A surface pair constrains the motion of two left along a surface on each of the left such that they always have contact in at least one common point (contact point);
- 'unconstrained pair': An unconstrained pair does not constrain the relative motion between two adjacent left;
- 'universal pair': A universal pair constrains the motion between two adjacent left to two rotations about two intersecting axes.
4.2.304.2 transformation_item_1
The transformation_item_1 specifies the rigid placement of the pair frame on the first Kinematic_link referenced by the Kinematic_joint associated with the Kinematic_pair.
See kinematic_pair to transformation_to_reference_frame for the application assertion.
4.2.304.3 transformation_item_2
The transformation_item_2 specifies the rigid placement of the pair frame on the second Kinematic_link referenced by the Kinematic_joint associated with the Kinematic_pair.
See kinematic_pair to transformation_to_reference_frame for the application assertion.
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