Fiber Bragg grating based tunable sensitivity goniometer

Abstract

Goniometer has found extensive usage in diverse applications, primary being medical field in which it is employed for obtaining the range of motion of joints during physical therapy. It is imperative to have a dynamic system to measure the range of motion which will aid for a progressive therapeutic treatment. Hence in the present study, a novel goniometer for real time dynamic angle measurement between two surfaces with the aid of a Fiber Bragg Grating sensor is proposed. The angular rotation between the two surfaces will be identified by the two arms of the Fiber Bragg Grating Goniometer (FBGG), which is translated to the rotation of the shaft which holds these arms together. A cantilever beam is fixed onto the base plate whose free end is connected to the rotating shaft. The rotating shaft will actuate a mechanism which will pull the free end of the cantilever resulting in strain variation over the cantilever beam. The strain variation on the cantilever beam is measured by the Fiber Bragg Grating sensor bonded over it. Further, the proposed FBGG facilitates tunable sensitivity by the discs of varying diameters on the rotating shaft. Tunable sensitivity of the FBGG is realised by the movement of these discs by varying circumferential arc lengths for the same angular movement, which will actuate the pull on the cantilever beam. As per the requirement of the application in terms of resolution and range of angular measurement, individual mode of sensitivity may be selected.