Index: firmware/App/Services/PIControllers.c
===================================================================
diff -u -rab304e2ca6e3e40ed8cb12650e9855ae0b9649d8 -rd3671cad1447db7ad496ad6282324ef7570c5625
--- firmware/App/Services/PIControllers.c	(.../PIControllers.c)	(revision ab304e2ca6e3e40ed8cb12650e9855ae0b9649d8)
+++ firmware/App/Services/PIControllers.c	(.../PIControllers.c)	(revision d3671cad1447db7ad496ad6282324ef7570c5625)
@@ -155,7 +155,7 @@
         controller->referenceSignal = referenceSignal;
         controller->measuredSignal = measuredSignal;
         // calculate error signal
-        controller->errorSignal = fabs( referenceSignal ) - ( referenceSignal < 0.0 ? ( measuredSignal * -1.0 ) : measuredSignal );
+        controller->errorSignal = referenceSignal - measuredSignal;
         controller->errorSum += controller->errorSignal;
         // anti-windup
         controller->errorSumBeforeWindUp = controller->errorSum;