Adaptive control in this example means when the line is stopped, the tension regulator output is multiplied by zero (no effect). As the line speed increases, the gain increases until it is at its maximum at design speed. The units of the adapted regulator output (Control Variable or CV) are in FPM or MPM.
This makes sense in that the % difference in speeds between traction points creates a tension. At low speed, less FPM or MPM speed difference is required to obtain the same % speed difference.
Results were very good using this adaptive tension regulator gain.
This was not done decades ago for two reasons. One was that analog multipliers and dividers were very expensive and prone to drift over time. The other was that if a line runs near design speed all the time, adaptive gain is not needed.