Multimodal tuning of a vibrating ring using laser ablation

Abstract This paper investigates laser ablation as a mechanism for fine tuning the flexural modes of vibration of a slightly imperfect suspended ring. A theoretical analysis of the effect of ablation on the natural frequencies of both in-plane and out-of-plane flexural modes is developed. Contributions made to the frequency shift from the reduced mechanical stiffness and reduced mass, as a result of ablation, are included. A specific cyclic symmetric relationship between the modes of vibration and the ablation configuration permitting multimodal tuning is developed. This relationship is expanded for the particular case of flexural modes of order 2 and 3, which are commonly used in vibrating ring gyroscope designs. For vibrating ring gyroscopes, tuning between certain flexural modes of vibration greatly increases the sensitivity of the device to applied rates of rotation. Therefore, a fine-tuning mechanism is highly desirable. An experimental examination of multimodal tuning using laser ablation is performed. In-plane modes of order 2 and out-of-plane modes of order 3 are investigated. Stiffness reduction as a possible method for modifying the natural frequencies of the out-of-plane modes of vibration is explored.