On Coupled Flexural and Torsional Oscillations of a Vibrating Beam Gyroscopic System

Gyroscopes are commonly used to measure the angle of rotation and its rate of change in several critical systems like airplanes. Therefore, there is a never-ending desire for researchers to increase measurement precision of these devices. In order to achieve this goal, some new gyroscopes have been invented recently. Especially, advent of micro manufacturing has appeared some sophisticated to more pre´cised gyroscopic systems. The widely-used gyroscopes are vibrating beam gyroscopes; however they face a very important drawback, called cross-coupling error. In presence of the secondary base rotations, significant errors will be produced in measurement of the gyroscope output. In order to deal with this issue, this paper addresses a novel gyroscopic system, called rocking-mass gyroscope. It is consist of four beams attached to a rigid substrate, undergoing coupled flexural and torsional vibrations with a finite mass attached in the middle. This configuration is such that, it does not encounter the same problems as vibrating beam gyroscopes. This configuration makes the vibration analysis very complicated. Despite this fact, a thorough analysis is performed in this paper. Using Extended Hamilton’s principle, eight governing partial differential equations of motion along with their corresponding boundary conditions are derived. Further attempt is made to find the closed-form frequency equation of the system. Solving this equation needs high computational costs and gives the natural frequencies of the system. In spite of this fact, the system is analysed in the frequency domain using an exact method in full detail, for two cases of fixed and rotating base support. Furthermore, a detailed parameter sensitivity analysis is carried out to determine the effects of different parameters on the natural frequencies of the system. The contributions of this research are very important from two viewpoints. Firstly, determination of natural frequencies and resonance conditions are essential for design of the system, and design of appropriate control strategies. Secondly, frequency domain analysis forms the basis of time domain analysis, followed by exact mode superposition method.