ARDC Lab · University of Minnesota
Rotating a cable robot’s payload
without tangling its cables
A cable-driven parallel robot positions its payload with cables. Turn the payload and those cables converge on each other, so yaw runs out long before the workspace does. This is the mechanism that removes that limit, from bench prototype to full scale.
- 30–40°yaw before the cables collide
- 360°continuous, with the mechanism
The Initial Idea
The Main Consideration: Continuous Rotation
The first build put a planetary yaw drive under the payload frame, and a magnetic encoder on the yaw axis itself rather than on the motor, so the controller reads the angle that matters for the closed-loop-control.
It was modelled with true mass and inertia properties, which meant the bench article behaved like the real payload rather than like a lightweight mock-up.
- 3:1planetary reduction (36/12)
- 360°continuous rotation
- 10 kgpayload, limited by 3D-printed parts
On the robot
It exists, and it turns
Filmed on the lab’s cable-driven parallel robot.
Scaling up
The version that could actually be afforded
Scaling the prototype meant machining almost every part. The redesign replaced the custom gearbox and machined holders with off-the-shelf gears, pillow-block bearings and extrusion. Now we have exactly one custom part, the shaft-to-payload attachment.
- ↓65%cost, $1500–2000 to $500–700
- 7 → 1custom parts
- 5:1reduction, up from 3:1
- 50 kgpayload, up from 10 kg
Drag the slider to pull the assembly apart.
Full-scale walkthrough
The finished design
A pass over the full-scale payload: the 1 inch 1144 carbon-steel shaft, the carbon-steel gear pair, the bearing pillow mounts, and the ODrive motor that drives it all.