Page - 210 - in Proceedings - OAGM & ARW Joint Workshop 2016 on "Computer Vision and Robotics“

2. PlatformStructure The construction of the redundantly actuated parallel platform (see Fig. 1) is quite simple. It is a planarmechanismwithδ=2degreesof freedom.Redundantlyactuatedmeans, that theplatformhas moreactuators (m=3) thandegreesof freedom.Altogether therearen=6 joints. However, the main dimension of the experimental test platform is 610 x 610 x 170mm and the distance between themotors is 400mm. Each link of an arm is l = 200mm long. The general Figure1.Platformwiththreearms(motor,activelink,passive link) indifferentcolors Motor1 Motor2 Motor3 l l l l l l EE qa1 qa2 qa3 qp1 qp2 qp3 Figure2. Jointcoordinatesof theredundantac- tuatedparallelmechanism purpose, the highmodularity, can be noticed bymany features of the platform. Base of this planar parallelmanipulator is a fourmillimeter steel platewith twelveholepatterns. On theseholepatterns motor sockets are centeredandmounted.On theonehand,weare able toposition themotor sockets ondifferent location tryingvariousmotor constellations. On theother hand, a symmetrical disposal of two, three or four arms (each consisting of two links), is possible. Themounting concept, used for the platform, has the advantage to exchange arms (e.g. with flexible links instead of rigid ones) quickly. Todistinguisharms fromeachother, theyhavegotdifferent colors (red,gray,black). ThearmsaredrivenbybrushlessmaxonmotorsEC-i40withapowerof100W. 3. DynamicModeling The repetitive use of identical link combination (e.g. motor, active link, passive link) in parallel manipulators is a typical characterization. Thereforemodeling of arms bymeans of subsystems is obvious. 3.1. SubsystemModeling Themost important advantage of modeling a system by subsystems is the flexibility to add com- ponents such as additional actuated kinematic chains connecting themovingplatformwith the base platform. Furthermore it iseasy toamendthemodel if inorder torepresentdifferentphenomenasuch aselasticityof links,gearbacklashorgearelasticities,whichwillbedone in thenear future. 210