Index: firmware/App/Services/PIControllers.c
===================================================================
diff -u -rf8395d7271a1fbcb2e577ce48b9327b16d2b97e0 -r316e7117180362d54af53818822694c4f936e550
--- firmware/App/Services/PIControllers.c	(.../PIControllers.c)	(revision f8395d7271a1fbcb2e577ce48b9327b16d2b97e0)
+++ firmware/App/Services/PIControllers.c	(.../PIControllers.c)	(revision 316e7117180362d54af53818822694c4f936e550)
@@ -136,7 +136,7 @@
         controller->referenceSignal = referenceSignal;
         controller->measuredSignal = measuredSignal;
         // calculate error signal
-        controller->errorSignal = fabs( referenceSignal ) - ( referenceSignal < 0.0 ? ( measuredSignal * -1.0 ) : measuredSignal );
+        controller->errorSignal = referenceSignal-measuredSignal;//fabs( referenceSignal ) - ( referenceSignal < 0.0 ? ( measuredSignal * -1.0 ) : measuredSignal );
         controller->errorSum += controller->errorSignal;
         // anti-windup
         controller->errorSumBeforeWindUp = controller->errorSum;