A cable robot positions a tool by changing several cable lengths together. This interactive example shows four corner drives around a rectangular frame and a shared point attachment. Move the target or change the frame dimensions to inspect the resulting free-span lengths.
Cable Robot Interactive Calculator
Set frame dimensions and a target measured from the lower-left anchor. Autoplay travels from an illustrative home point to that target and back. Result cards give selected-target lengths; the animation panel gives the live lengths.
Equation Used
- Rectangular planar frame with four ideal point anchors. X is measured rightward and Y upward from the lower-left corner.
- All four cables terminate at one point. A real rigid platform needs its own attachment offsets and orientation model.
- Target lengths remain in the cards while the animation reports its current position and lengths.
- A boundary or corner target is shown geometrically even if actual hardware would collide or lose useful tension.
- The diagram compresses extreme aspect ratios to stay legible; numerical lengths always use the original entered dimensions.
The four original length equations are retained. This is a planar point-attachment geometry calculator, not a tension or payload-capacity solver.
How coordinated cable motion positions a tool
Winches pay out or take up cables attached to a moving tool or platform. Fraunhofer IPA’s documented systems show cable connections on a structural platform and dedicated winch units. Those photographs establish the physical components; the example here is a simpler, four-cable planar point model.
The animation changes all four free spans as the shared attachment moves. It replaces moving dots on stationary lines with actual tool travel. Frame members, corner drive housings and a tool symbol identify the parts. The drive housings are illustrative: their drum dimensions and cable routing are outside the calculation.
What this example can demonstrate
The tool is useful for exploring how target position and anchor spacing change required cable lengths. It can also illustrate why a controller must coordinate several winches for a single tool movement.
The linked Fraunhofer references describe handling and manufacturing research with cable-driven robots. This example does not reproduce a particular IPAnema robot or its capabilities.
Four distances, not a tension calculation
Let the rectangular anchor frame have width W and height H. With the origin at the lower-left anchor, the target is x = Wpx/100 and y = Hpy/100.
The four distances are TL = √[x² + (H − y)²], TR = √[(W − x)² + (H − y)²], BR = √[(W − x)² + y²], and BL = √[x² + y²]. These are the existing calculator equations.
They describe straight segments to a shared point. A finite platform requires separate cable attachment coordinates. Cable tension, gravity, pretension, sag, stretch and pulley routing require additional models. A set of calculable lengths does not prove a pose can be held.
Try a target away from the centre
For a 10 m wide, 6 m high frame, the centre target is (5, 3) m. All four free spans are √34, or about 5.83 m.
Set X to 20% and Y to 75%. The target becomes (2, 4.5) m: TL is 2.50 m, TR is 8.14 m, BR is 9.18 m and BL is 4.92 m. The cards retain those target results while autoplay shows the coordinated approach and return.
At the lower-left corner, BL becomes zero. That is a valid distance calculation but a degenerate hardware configuration, so the animation reports the boundary condition rather than claiming feasibility.
What the illustration includes and omits
The frame has visible structure, four corner drives and a common moving attachment. Cable lines stay attached throughout motion and their lengths are calculated at each frame.
Real machines have routing hardware, finite attachment spacing and tension constraints. The small tool symbol here represents a point; it is not a collision envelope. The moving sequence and drum rotation are educational illustrations, not a commanded speed profile or winding design.
Questions about the cable robot model
Why do the result cards differ from the moving diagram?
The cards give lengths at the selected target. The drawing lists lengths at the current animated position.
Does changing frame height affect every cable?
It changes the anchor and target geometry. At some special positions a particular cable can remain unchanged, but the equations always use the entered frame dimensions.
Can this calculate cable tensions or payload capacity?
No. It calculates four distances only. Load balance, cable stiffness and feasible positive tensions are not solved.
Why is an extreme frame shape compressed on screen?
The display keeps the components readable. The warning identifies that presentation choice; the numerical calculations still use the entered dimensions.
Building or designing a mechanism like this?
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