Truss-Walking Robotic Arm | mysimulator.uk

Gait Controls

Fixture spacing 2.4 m

Carried payload mass 0 kg

Joint damping ratio ζ 0.18

Swing duration 3.0 s

Live Telemetry

Both feet anchored

Distance walked

0.00 m

Steps completed

Tip oscillation

0.0 mm

Reach margin

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How it works

The ISS's Canadarm2 has an identical Latching End Effector (LEE) at both ends. To travel further than its own length it doesn't move a base — it walks: one LEE stays grappled to a Power/Data Grapple Fixture (PDGF) while the other end swings free, reaches the next fixture down the truss, and latches. Then the roles swap. Each cycle relocates the whole arm by one fixture spacing, hand-over-hand, indefinitely.

The free end's path is solved with planar two-link inverse kinematics (law of cosines), given upper-arm length L₁, forearm length L₂, and target distance d to the next fixture:

cos(θ_elbow) = (d² − L1² − L2²) / (2 L1 L2)
θ_shoulder   = atan2(target) − atan2(L2 sinθe, L1 + L2 cosθe)

A step is only geometrically possible while d ≤ L1 + L2 — the "reach margin" readout below turns negative when the fixture spacing exceeds the arm's total reach, and the swing aborts.

Because a space manipulator is a long, lightly-damped structure, driving a joint to a stop doesn't stop the tip instantly — residual structural flexibility rings down as a damped harmonic oscillator:

x(t) = A·e^(−ζωn t)·cos(ωd t),   ωn = √(k / m_eff),   ωd = ωn√(1 − ζ²)

Heavier payloads lower the effective stiffness-to-mass ratio ω_n, so the tip rings longer and with more amplitude before it's safe to trigger the latch — mirroring why real free-flying/free-floating space manipulators impose a mandatory settling wait before every grapple, not just a position tolerance.

Latched end effector Swinging end effector Unused grapple fixture

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