This Cable Robot Can Move Objects Around a Large Room with Ease

The layout and actuation of a robot is, of course, a result of its intended purpose. If a robot needs to travel long distances without a tether, it’s best to give it some wheels or tracks. If a robot needs to work precisely within a relatively small area, such as with a CNC machine or 3D printer, then linear rails are ideal. But with the use of some clever math, more unusual designs are possible. That’s the case with Hackaday.io user Tom’s innovative cable robot.

This robot works by suspending the end effector from cables coming from three points on the ceiling. By adjust the length of those cables, the end effector can be moved around the room. Calculating the length of the cables is a simple trigonometry problem, similar to how triangulation is used to calculate the position of something based on its distance from known locations. But to accurately position the end effector, the lengths of those cables have to be exact. The method that Tom used to accomplish that is what makes this robot particularly interesting.

The robot’s end effector is actually suspended from six cables that are divided into three groups of two cables running in parallel. Using two cables from each point keeps the end effector stable. Those cables are wrapped around drums that are turned by stepper motors. Importantly, those are designed so that the cables only spool in a single layer. That keeps the diameter constant, and ensures that the cable length calculations are accurate. The calculations and the movement are controlled by EMC2 software, which is traditionally used for CNC machines.

As Tom demonstrates, the robot works quite well. It has enough repeatability that it’s able to pick up beer cans and then stack them on a table across the room. That said, he does see room for improvement. He believes that servo motors might perform better than stepper motors in this situation, and that the drive mechanism could be switched from chains to GT2 timing belts. Even so, this robot is quite impressive already.