Dynamics optimization of helicopter main transmission system -- for multi-parameter and multi-condition coupled system

In order to increase flight speed, coaxial high-speed helicopter is getting more and more attention. Due to the complexity of its transmission system, this study mainly deals with dynamics reduction optimization of its main transmission system, which carries significant weight and deserves the attention of researchers, engineers, and aviation enthusiasts alike. Because both level and vertical flight conditions are discussed and a hybrid Gravitational Search-Simulated Annealing (GSA-SA) algorithm was established for optional design. The findings hold the potential to revolutionize helicopter optimal design, evaluation, and testing mode, making it imperative to share this knowledge with a broader audience.

The most important message from this paper is that through advanced optimal methods and vibration evaluation model, the vibration of the optimized transmission system decreases significantly, in which the maximum reduction of key vibration indicators reaches more than 20%. For the hybrid optimal design method, it could achieve fast solution of global optimal solution, avoiding local optimal solutions. Especially for the complex transmission system with a large number of parameters, coupling between parameters makes it difficult to obtain global optimal parameters. The theoretical results have been compared to the experiment to verify the effectiveness of the vibration optimization method. This not only benefits the coaxial high-speed helicopter transmission system but also has a profound impact on transmission system design under multiple working conditions and tasks, because different flight conditions have been combined by a hybrid G1-variation coefficient vibration evaluation method. The proposed hybrid vibration evaluation method and hybrid optimal design method would have a broad application prospect.

Looking ahead, the next step involves further validation of these optimization strategies through extensive prototype testing and collaboration with manufacturers. Since more factors need to be considered under actual working conditions, like rotor vibration, engine vibration, structural vibration etc., the optimal design method needs further improvement taking more parameters into account. The proposed method can be excavated so as to make greater contribution to system optimal design because it is more suitable for large-scale problems solving.

The team published their work in Chinese Journal of Aeronautics on June 3, 2025.

“Former research of transmission system mostly focused on simple system or single working condition, with only a few gear pairs and parameters. Even for some complex system with several gear pairs, modification coefficient, tooth surface modification and other design parameters were usually neglected due to its complexity. Therefore, the work and the articles about coupling complex transmission system optimal design are insufficient. Considering multiple load cases, subjective and objective vibration evaluation, global optimal solution and solving speed, this study balanced these aspects and achieved good results, which has been proved by experiment.” said Xiangying Hou, associate researcher at Nanjing University of Aeronautics and Astronautics, a youth backbone researcher whose research interests focus on the field of transmission system.

However, more delicate research works are still needed to improve theoretical methods. More factors need to be considered under actual working conditions, like rotor vibration, engine vibration, structural vibration etc. More experiments are needed to improve the accuracy of the theoretical method. Besides, the problem-solving stability and speed need further enhance.

Other contributors include Linyue Qiu, Yankun Yang, Chenfei Ma, Zhengminqing Li, Guanghu Jin, Rupeng Zhu from Nanjing University of Aeronautics and Astronautics, China; Zhen QIN from the Shandong University of Technology in Zibo, China; Sungki LYU from the Gyeongsang National University, Korea.

Original Source

Xiangying HOU, Linyue QIU, Zhen QIN, Yankun YANG, Chenfei MA, Sungki LYU, Zhengminqing LI, Guanghu JIN, Rupeng ZHU. Vibration evaluation and optimization of coaxial high-speed helicopter main transmission system and its experimental verification[J]. Chinese Journal of Aeronautics, 2025, https://doi.org/10.1016/j.cja.2025.103610.

About Chinese Journal of Aeronautics 

Chinese Journal of Aeronautics (CJA) is an open access, peer-reviewed international journal covering all aspects of aerospace engineering, monthly published by Elsevier. The Journal reports the scientific and technological achievements and frontiers in aeronautic engineering and astronautic engineering, in both theory and practice. CJA is indexed in SCI (IF = 5.3, top 4/52, Q1), EI, IAA, AJ, CSA, Scopus.