John Ehlers:

• Take EMA of price (better, a 3 Pole filter).
• Take the difference (delta) between Price and its EMA.
• Take an EMA of delta (or a 3 Pole filter):
  • Smoothing will help reduce whipsaws.
  • Ideally, smoothing introduces no major trend mode lag because delta is detrended.
• Add the smoothed delta to EMA for a zero lag curve.
• Add 2*(smoothed delta) to EMA for a smoother predictive line.