File:Fig JointAxes.jpg

Summary

Both antennal joints of the stick insect Carausius morosus are simple rotary joints (hinge joints). Left: One joint is located between head (H) and scape (S), the other between scape and pedicel (P). Middle: When one joint is immobilised, movement of the other joint causes the antennal tip to move along a circular line, i.e., a cross-section of a sphere. The axis perpendicular to this cross-section is the joint axis. In stick insects, the joint axes are non-orthogonal and slanted with respect to the body coordinate frame. Right: The non-orthogonal axis orientation results in out-of-reach zones. By assuming unrestrained rotation around both joint axes, the antennal workspace and its out-of-reach zones can be visualised as a torus with holes. Theoretically, increased positioning accuracy can be traded off by increasingly large out-of-reach-zones. [modified from Mujagic et al., 2007, Naturwissenschaften by Volker Dürr, Biological Cybernetics, Bielefeld University, Germany]

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