This Major Research Instrumentation (MRI) grant provides funding for the development of a high-precision noncontact vibration measurement system. Fast and accurate noncontact full-field measurement of dynamical systems is important for research and development in many engineering fields. The PIs will develop a high-precision noncontact vibration measurement system using new high-speed high-resolution digital cameras and the principal investigators' novel noncontact measurement and image processing techniques. This system will have a measurement accuracy that is one order better than those of currently available camera-based motion analysis systems. The approach is to utilize commercial off-the-shelf hardware components of an existing system of an industry partner who has successfully developed camera-based motion analysis systems, and to develop and integrate auxiliary hardware and image processing software to provide advanced measurement capabilities. This camera-based measurement instrument has the potential to transform the way dynamic deformation measurements are performed.
The noncontact, high-precision, high-speed and full-field measurement capabilities of the proposed system will open up new possibilities for research on mechanical and civil structures, system dynamics, aerospace structures, animal locomotion, human motion analysis, computer graphics, and many other areas. In addition, this system will be a valuable educational tool both in the developmental phase, where two graduates and one undergraduate will actively participate, and in the operational phase, where the equipment will be used by undergraduate and graduate students to collect and analyze dynamics and mechanics of deformable physical systems for their research and design projects. Moreover, this instrumentation will be used to develop new methods to detect problems with on-earth and in-space structural systems, develop ways to mitigate effects on society from natural hazards, and detect potential threats to national security.
based on the use of today’s consumer-grade off-the-shelf digital cameras, new image processing techniques, fast and accurate camera calibration process, and an advanced measurement theory for static/dynamic testing of structures (see Fig. 1). The developed camera calibration process consists of a closed-form solution for first estimation and then a refinement based on nonlinear optimization. It is easy to calibrate cameras without elaborate setup and expensive calibration tools having two or three orthogonal planes of high precision. The technique only requires the camera to observe a planar pattern (e.g., a checkerboard) shown at one or more orientations by arbitrarily moving the planar pattern or the camera. Moreover, methods for development and use of forward and backward lens distortion models are derived, and a set of experimentally validated camera calibration steps is recommended. The capabilities and measurement accuracy of the proposed methodology are validated by numerical simulations and experimental verifications using an old Eagle-500 motion analysis system and a new Vicon system. The proposed system overcomes several limitations of existing camera-based motion analysis systems and provides better measurement accuracy. The system has the potential to transform the way dynamic deformation measurements being performed. It can advance 3D computer vision one step away from laboratory environments toward real-world applications. The noncontact, high-precision, high-speed, full-field measurement capabilities of the system will open up new possibilities for research and development in several areas in mechanical, aerospace and civil engineering, computer science, animal science, and other fields. From all the theoretical developments and experimental verifications based on the use of two Canon EOS-7D cameras (Fig. 1), a set of specifications on auxiliary hardware and software for a new camera system were requested and implemented in the newly purchased Vicon motion analysis system (Fig. 2). The Vicon system has an adjustable and easy-to-setup hardware configuration and allows significant changes by the user for its experimental setup, camera calibration and image processing. The Vicon MX-T160 camera’s sensor has a resolution of 16.3 (4704x3456 ) megapixels, which is much higher than the resolution of Eagle-500 camera’s sensors of 1.3 (1280x1024) megapixels. Moreover, the user is allowed to access the original distributions of grey values of all images captured by each camera to enable the development of in-house software for 3D reconstruction. Figures 3 and 4 demonstrate that the Vicon camera system can provide accurate full-field dynamic measurements for a whirling cable and a spinning thin rod. Figure 5 shows that the Vicon camera system can be used to evaluate the accuracy of in-house wireless sensors for a horse lameness evaluation system. Figure 6 shows that the Vicon camera system can be used to measure the complex dynamics of a multi-functional compound bow. All these three-dimensional full-field measurements are uniquely enabled by this accurate noncontact static/dynamic measurement system.
