CHANGELOG.md

@@ -16,6 +16,12 @@ will consitute of a breaking change warranting a new major release:
 
 # [unreleased]
 
+# [v7.5.5] 2024-01-22
+
+## Fixed
+
+- Calculation of error quaternion was done with inverse of the required target quaternion.
+
 # [v7.5.4] 2024-01-16
 
 ## Fixed

mission/controller/acs/Guidance.cpp

@@ -418,7 +418,9 @@ void Guidance::comparePtg(double currentQuat[4], double currentSatRotRate[3], do
                           double targetSatRotRate[3], double refQuat[4], double refSatRotRate[3],
                           double errorQuat[4], double errorSatRotRate[3], double &errorAngle) {
   // First calculate error quaternion between current and target orientation
-  QuaternionOperations::multiply(currentQuat, targetQuat, errorQuat);
+  double invTargetQuat[4] = {0, 0, 0, 0};
+  QuaternionOperations::inverse(targetQuat, invTargetQuat);
+  QuaternionOperations::multiply(currentQuat, invTargetQuat, errorQuat);
   // Last calculate add rotation from reference quaternion
   QuaternionOperations::multiply(refQuat, errorQuat, errorQuat);
   // Keep scalar part of quaternion positive