Theoretical research often leads to fascinating discoveries: in this case the tripteron, a 3-DOF translational parallel mechanism. The prototype was first developed through mathematical derivations (systematic type synthesis) based on screw theory. This unique and patented robot enables linear displacements in all directions. It is in fact equivalent to serial Cartesian robots. But since it is a parallel robot, it offers numerous other advantages, including the positioning of its actuators on the base, which reduces the moving inertia and thus allows rapid movements.
Moreover, the tripteron has very simple kinematics, which are actually the same as those of serial Cartesian robots. Also, this robot is isotropic and fully decoupled, i.e. each of the actuators is controlling one Cartesian degree of freedom, independently from the others. This robot thus has no singularities within its workspace and its dexterity is always optimal.
The figures below also indicate that it is possible to orient the linear actuators in different directions, for example in a parallel or co-planar manner rather than orthogonally. The prototype developed in our laboratory is of the type 3-PRRR.
Akin to the tripteron, the quadrupteron was also developed through systematic type synthesis. Ressembling the tripteron on many ways, the unique feature of the quadrupteron is mainly its 4 DOFs. In addition to the three translations, one rotation along the vertical axis is possible. The prototype thus has three legs of the type PRRU and one leg of type PRRR.
The quadupteron reproduces the same movements, although with an increased dexterity, as the well-known SCARA robot (Selective Compliant Assembly Robot Arm), i.e., the Schönflies motions. The quadrupteron is isotropic in translation. The singularities are only present in two orientations, ±90 degrees, which cannot be reached since the workspace is ±60 degrees (which is already very attractive).
The design of the prototype was achieved through a variety of studies in order to reduce the presence and size of the singularities and to optimize the deterity and workspace.