So this seems to be a little similar to SAR, only that SAR moves the stop a little closer in every bar, irrespective of whether there is a drop in price or not.

Supertrend (supertrend[sts, per] ) will also move the stop closer, when prices go sideways and volatility (ATR) decreases. The sensitivity of this effect depends on the number of bars (per) that the ATR component is looking back. The distance of the stop is adjusted by the multiplication factor sts. Best results are usually obtained when the supertrend is not used as an immediate stop, but when you check after each bar whether the supertrend line  has been cut by the closing price.