Aggressive tapping, a gentle caress, a deliberate tap. These are emotionally distinct interactions and I wanted the robot to respond to them differently.

The question was: how much hardware does that actually require?

I started with the simplest possible input, a single capacitive touch sensor. One sensing point. One time series of capacitance values.

Then I extracted basic features from each touch event: duration, peak value, mean, minimum, rise rate, fall rate, and area under the curve.

What I didn't expect was this

The three touch classes aggressive, caress, tap, separate cleanly in feature space. Especially on rise_rate and fall_rate (log scale). The information was always encoded in the shape of the signal. How fast the capacitance climbs. How fast it falls. How long it lingers.

A caress is slow in both directions. An aggressive touch hits hard and releases sharply. A tap is brief and decisive.

Needed such happiness for the recent hard days