# How are Interference Avoidance and Collision Avoidance different?

Someone told me when explaining about a controller module named CollisionDetector that it only checks self-interference and moves accordingly without detecting collision. To me both sounds the same. How are they different?

Self-interference refers to instances where something like a robot arm (with many degrees of freedom) may attempt to move in a path that crosses part of its own body. Your CollisionDetector is likely keeping track of the joint angles in a planned arm movement and seeing if any of them result in such a condition. The robot doesn't need any information about its environment to do this, just a reliable measurement of its own position (and possibly the shape of whatever it may be gripping).
• Thanks. Now I understand that real confusion to me came from the fact that people around my community also use self-collision check, which I presume is equivalent to self-interference. – IsaacS Feb 9 '14 at 15:05