Low-cost experimental apparatus for motion tracking based on image processing and camera calibration techniques
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Low‑cost experimental apparatus for motion tracking based on image processing and camera calibration techniques Rodrigo M. Amarante1 · André L. C. Fujarra2 Received: 4 March 2020 / Accepted: 28 July 2020 © Springer Nature Switzerland AG 2020
Abstract The present work focuses on the use of a low-cost equipment to monitor static and dynamic tests as an alternative to expensive commercial devices. First, we describe a procedure for cameras calibration and image processing in order to establish a less invasive (than other common instrumentation, such as strain gauges) and much cheaper motion capture method (than commercial tracking systems). Following, two cameras and one personal computer (with an image acquisition board) are used as the monitoring apparatus for tracking the movements of a flexible cable under harmonic excitation at its top end. The experimental results are then compared with numerical simulations, showing a fairly good agreement and the same level of precision as that obtained with one of the most used motion capture system in laboratories. The proposed experimental methodology correctly identifies the displacements, frequencies, and dynamic geometric behavior of the flexible model in all directions. Although commercial solutions are faster, since data processing and cameras calibration take place in real time, the acquisition cost of the suggested equipment is most affordable for small industries, educational institutions and projects with restrict budget on kinesiology, physiology, dentistry, facial recognition and mechanics, among others. Keywords Tests monitoring · Flexible cable · Low cost · Camera calibration · Digital image processing
1 Introduction Recently, many areas of knowledge developed in an unprecedented way in the history of science, partly due to technological advances and increased processing power of computers. One of these areas is the Digital Image Processing (DIP). In the DIP field, several algorithms were developed to extract information from images (or frames) obtained by digital cameras (or camcorders), as discussed by Gonzalez and Woods in [1]; Ekstrom in [2]; and Ravi and Ashokkumar in [3], just to name a few important works. In addition to the DIP, cameras calibration is a mandatory procedure, performed to determine a mathematical relation between the coordinate systems of the image and
the object of interest. There are many calibration techniques and some of them are presented and compared by Zollner and Sablatnig in [4]; Kwon in [5]; Hieronymus in [6]; and Abdel-Aziz et al in [7], for example. Among the camera calibration methods, Zollner and Sablatnig [4] mention that the Direct Linear Transformation, a technique proposed by Abdel-Aziz and Karara (refer to [7]), is efficient, presents a high convergence level for multi-vision purposes and a great accuracy in 3D reconstruction, so that this method is used in the present work. The use of optical monitoring systems has the advantage of being a minimally invasive and is as an alternative to the classic instrumentatio
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