EOD Robot Arm: Bomb-Disposal Manipulator Kinematics

Target Device

Distance from turret 1.10 m

Azimuth (turret yaw) 0°

Grip force setpoint 14 N

Set the target, then run the sequence.

Live Telemetry

Shoulder θ₁

0.0°

Elbow θ₂

0.0°

End-effector error

— m

Grip force

0.0 N

How it works

The arm is a planar 2-link manipulator (shoulder–elbow) carried on a turret that rotates to face the target, exactly like real EOD platforms (Andros, PackBot, Wheelbarrow). Given the horizontal reach r and vertical drop v from the shoulder pivot to the target, the elbow angle follows from the law of cosines:

d  = √(r² + v²)
cosθ₂ = (d² − L₁² − L₂²) / (2·L₁·L₂)
θ₂ = acos(cosθ₂)                     (elbow bend)
θ₁ = atan2(v, r) − atan2(L₂sinθ₂, L₁+L₂cosθ₂)   (shoulder pitch)

A third, wrist joint is servoed to θ₃ = −(θ₁ + θ₂), which keeps the claw pointing straight down regardless of shoulder/elbow pose — the standard trick for a planar arm whose last link must stay vertical.

The turret yaw is simply atan2 of the target's lateral offset, so the whole arm plane is re-oriented to face the device before the 2-link solve runs.

Grip force loop: once the claw contacts the object it doesn't just slam shut — a proportional feedback loop closes the jaws while grip force ramps toward the operator's setpoint (F(t+dt) = F(t) + k·(F_set − F(t))·dt), the same reason a real EOD operator dials in a low clamp force before lifting a pressure-sensitive device: too much force risks triggering it, too little drops it.

Real-world relevance: this is the same forward/inverse-kinematics + force-feedback pattern used by every teleoperated bomb-disposal manipulator to place a disruptor charge or lift a suspect package without a human anywhere near it.

EOD manipulator arm Suspect device

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