112MAINTENANCE10. Theory10.1 how the pid loop worksThe following diagram demonstrates the correlation between the variables in the PID Loop.Derivative ProportionalIntegralSet PointReading-e(t) Yd(t) Yp(t)Yi(t)Yt(t) Ys(t)+ + ScaleA/D PowerAmplifierBrakeCoilTSC LoadCellAmplifierAmplifierTORQUESPEEDSpeedCorrectionYswb(t)orHD & PBWBIIR FilterFigure 10–1 System Block Diagram10.1.1 SCale faCTorS for HySTereSiS, eDDy-CurrenT anD powDer Brake DynaMoMeTerSYt(t) Ys(t)ScaleToRqUE: TSC1 & TSC2 Ys(t) = Yt(t) / 1.90775 * 2 (hb brake)Ys(t) = Yt(t) / 1.0908 * 2 (all others)SPEED: TSC1 & TSC2 Ys(t) = Yt(t) * 5599.19 / MAx SPEED10.1.2 SpeeD CorreCTion for wB (eDDy-CurrenT Brake) DynaMoMeTerYs(t) Yswb(t)Speed CorrectionThe Wb Dynamometer follows the same scaling as the hYST and Pb with the addition of onecalculation for both torque and speed. This calculation is due to the fact that for a given current thetorque changes with speed. This is referred to as speed correction.Yswb(t) = (Ys(t) + Ys(t) / speed correction factor) / 2
