Self-excited Dynamic Active Antenna

摘要

This paper proposes the Self-excited Dynamic Active Antenna (SDAA) that can detect a contact location between an insensitive flexible beam and an object through observation of the fundamental frequency of the beam in contact with the object. The main part of the SDAA is composed of a flexible beam, one permanent magnet and two electromagnets. The permanent magnet is attached to a part of the beam and two electromagnets are positioned at both sides of the permanent magnet with a small gap. These magnets not only contribute to exciting the motion but also changing the boundary condition of the beam. We analyze the relationship between the displacement of the permanent magnet and the induced force, and show the linear spring-like behavior of the magnetic force. We also show that the contact position is uniquely determined by utilizing two fundamental natural frequencies before and after changing the boundary condition, whereas both the fundamental and the second natural frequencies are required for localizing the contact point under the conventional type of Dynamic Active Antenna. We present the basic working principle of the SDAA and show some experimental results to verify the idea.