Driving the arms live
At the start of a match the game prepares the hardware: home the rails, move apart, both arms to rest. It drives the carriages together for the charge and apart for the return, plays each beat on both arms, and waits on the arms’ own busy flags rather than on timers. The screen beat is stretched to the real motion — an overhead chop is 4.5 s of arm time, not the 1.4 s the screen would take on its own.
A mock daemon carrying the real motion timings lets the whole thing be rehearsed with no hardware attached. In rehearsal the screen never released before the arms, with a worst margin of +23 ms.
Players choose their own openers and finishing flourishes. The En garde opener runs before the first beat; the Samurai finish runs after the knockout, with the winner raining blows while the loser collapses. Both stream the rail carriages in time with the arm motions.
The arms sit on stepper rails and charge in to 19.5 inches of each other.
Calibration, by hand
The arms’ servo calibrations live in the repo, in calib/. We calibrated the SO-100 by holding it at the zero pose and sweeping every joint to its stops, then checked the zero points against physical references — the arm leaning fully back on its board, the upright square pose, the blade sitting on top of the gripper — before we trusted the taught moves on the real arm.
Designed in simulation
The hardware
We printed a fencing gripper for the arms: a sword holder that takes swappable 6 and 8 inch blades in five styles — fang, katana, rapier, falchion and crystal — plus a shield, a gauntlet and a sword-breaker talon for the wrist. For the tilt itself we printed a plate with one of each 8 inch blade, plus the gauntlet and talon wrists.
