Joint constraints

Joint constraints are rotational constraints on the joints of an artificial system.^[1] They are used in an inverse kinematics chain, in fields including 3D animation or robotics.^[2] Joint constraints can be implemented in a number of ways, but the most common method is to limit rotation about the X, Y and Z axis independently. An elbow, for instance, could be represented by limiting rotation on X and Z axis to 0 degrees, and constraining the Y-axis rotation to 130 degrees.

To simulate joint constraints more accurately, dot-products can be used with an independent axis to repulse the child bones orientation from the unreachable axis. Limiting the orientation of the child bone to a border of vectors tangent to the surface of the joint, repulsing the child bone away from the border, can also be useful in the precise restriction of shoulder movement.

References

^ "Joint constraints and multibodies". nphysics.org. Retrieved 2020-06-08.
^ Knoop, S.; Vacek, S.; Dillmann, R. (December 2005). "Modeling joint constraints for an articulated 3D human body model with artificial correspondences in ICP". 5th IEEE-RAS International Conference on Humanoid Robots, 2005. pp. 74–79. doi:10.1109/ICHR.2005.1573548. ISBN 0-7803-9320-1. S2CID 15067294.

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[1] "Joint constraints and multibodies". nphysics.org. Retrieved 2020-06-08.

[2] Knoop, S.; Vacek, S.; Dillmann, R. (December 2005). "Modeling joint constraints for an articulated 3D human body model with artificial correspondences in ICP". 5th IEEE-RAS International Conference on Humanoid Robots, 2005. pp. 74–79. doi:10.1109/ICHR.2005.1573548. ISBN 0-7803-9320-1. S2CID 15067294.

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