Cobot implementation of virtual paths and 3D virtual surfaces

Abstract—Cobots are devices for human/robot interaction, in which axes of motion are coupled to one another by computer-controlled continuously variable transmissions rather than individually driven by servomotors. We have recently built a cobot with a three-dimensional workspace and a 3-rev-olute parallelogram-type mechanism. Here we present control methods for the display of virtual surfaces and for free mode in which the cobot end-point moves as if it were unconstrained. We provide experimental results on the performance of the free, virtual path, and virtual surface controllers. Index Terms—Cobot, haptics, human/robot collaboration, intelligent as-sist device (IAD), nonholonomic, virtual constraint. I