diff --git a/include/unitree_arm_sdk/model/ArmModel.h b/include/unitree_arm_sdk/model/ArmModel.h
index 1882a4a..51b37ff 100644
--- a/include/unitree_arm_sdk/model/ArmModel.h
+++ b/include/unitree_arm_sdk/model/ArmModel.h
@@ -59,7 +59,7 @@ Mat6 CalcJacobian(Vec6 q);
  * Inputs: q: joint angles
  *         qd: joint velocities
  *         qdd: joint accelerations
- *         Ftip: Spatial force applied by the end-effector
+ *         Ftip: Spatial force applied by the end-effector [rpyxyz]
  * Returns: required joint forces/torques
  */
 Vec6 inverseDynamics(Vec6 q, Vec6 qd, Vec6 qdd, Vec6 Ftip);
@@ -168,4 +168,4 @@ private:
     double _theta2Bias;
 };
 }
-#endif
\ No newline at end of file
+#endif