Feasibility Assessment of Novel Multi-Mode Camshaft Design Through Modal Analysis

Camshafts in internal combustion engines are critical components not only for mechanical functionality but also for dynamic performance and vibration characteristics. This study aims to present a comprehensive modal analysis of the camshaft by integrating both computational and experimental approaches, followed by the design of an innovative multi-mode camshaft mechanism that enhances fuel efficiency and optimizes engine performance. First, a computational model of the camshaft is built with a proper mesh structure with a mesh size of 2 mm. Modal analysis is performed on the computational model, and the critical modal parameters of the camshaft are obtained. Second, modal tests are performed on the camshaft, which reveal an error of 15% on the computationally predicted natural frequencies. Third, a model updating procedure is applied to improve the accuracy of the computational model. The critical material properties are determined based on a sensitivity analysis, and the structural optimization process is performed accordingly. The optimized model solution is compared to the experimental data, and the computational model is validated based on both natural frequencies and mode shapes. The comparison of experimentally and computationally estimated natural frequencies reveal a difference below 2%. Mode shapes are compared based on Modal Assurance Criteria (MAC), and it is determined that the values of the elements in the main diagonal of the MAC matrix are around 0.9. Finally, the validated model is used as a basis for an innovative camshaft mechanism. The proposed mechanism offers enhanced flexibility by integrating multiple valve actuation methods, including Variable Valve Timing (VVT), Variable Valve Lift (VVL), Variable Valve Duration (VVD), Cylinder Deactivation, and Skip Cycle methods into a single camshaft for the first time in the literature. Modal analysis is performed on the proposed multi-mode design, and it is observed that the modified design resembles the modal properties of the original design.