Expressions for a servo robot head

Servo heads show feeling through timing more than shape: how fast the head turns, whether the lids lead or follow, when it nods. The engine works out a performance on 20 channels and turns it into degrees per servo, clamped to the limits you set, so the head moves like a character rather than a pan-tilt mount.

Mapping channels to servos

Each servo gets a channel, a centre, a range and hard minimum and maximum angles: {name: "lid left", channel: "lidUpL", center: 30, range: 60, min: 0, max: 90}. Mirrored servos take invert: true. Presets cover pan and tilt; pan, tilt and roll; a head with two antennas; and a nine-servo animatronic head. Eyes lead and the head follows a little later, which is also kinder to small servos than snapping everything at once. Test at low power first; the limits are there to protect your mechanism.

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