User`s manual

41
Magtrol Model DSP6001 Dynamometer Controller
Chapter 5 – PID Settings
SETUP
5.3 HOW THE PID LOOP WORKS
The following diagram demonstrates the correlation between the variables in the PID LoOp.
Derivative Proportional
Integral
Set Point
Reading
-
e(t) Yd(t) Yp(t)
Yi(t)
Yt(t)
Ys(t)
+ +
Scale
A/D
Power
Amplifier
Brake
Coil
TSC
Load
Cell
Amplifier
Amplifier
TORQUE
SPEED
Speed
Correction
Yswb(t)
or
HD & PB
WB
IIR Filter
Figure 5–1 System Block Diagram
5.3.1 SCaLe faCtorS for HyStereSiS, eDDy-CUrrent anD powDer Brake DynaMoMeterS
Yt(t) Ys(t)Scale
TORQUE: TSC1 Ys(t) = Yt(t) / 1.725 * 2
TSC2 Ys(t) = Yt(t) / 1.725 * 2 * 1.6623
SPEED: TSC1 & TSC2 Ys(t) = Yt(t) * 5319.93 / MAX SPEED
5.3.2 SpeeD CorreCtion for wB (eDDy-CUrrent Brake) DynaMoMeter
Ys(t) Yswb(t)Speed Correction
The WB Dynamometer follows the same scaling as the HYST and PB with the addition of one
calculation for both torque and speed. This calculation is due to the fact that for a given current the
torque changes with speed. This is referred to as speed correction.
Yswb(t) = (Ys(t) + Ys(t) / speed correction factor) / 2
The speed correction factor is calculated on each entry into the PID loop equations.
Speed Correction Factor = - 0.0001 * x * 2 + 0.0203 * x + 0.005 limited to 0.051 to 1
where x = RPM / NOMINAL SPEED * 100
NOMINAL SPEED is set by the user and obtained from the data sheets for the dynamometer or
brake.