Review on Stable Motion Control Methods of Whole Body for Hydraulic Quadruped Robots

Introduction: The performance of the hydraulic quadruped robots has not yet reached the level of quadrupeds. The whole-body stable motion control method of the hydraulic quadruped robot is the key to determining the motion ability. The paper summarizes the current development status of hydraulic quadruped robots and whole-body control methods, and the advantages of existing and future development trends of the main control methods, with a focus on related research papers. Methods: The various typical hydraulic quadruped robots and their characteristics that have been published are summarized in this study. Additionally, the whole-body stable control methods of hydraulic quadruped robots are summarized, and the characteristics of various control methods are analyzed, especially the widely used model predictive control method and whole-body control method. Moreover, a few research results on hybrid control methods are introduced. Results: By summarizing the research results of hydraulic quadruped robots, it is evident that different control methods have different characteristics. The single control method is suitable for simple control tasks of hydraulic quadruped robots on flat road surfaces. Discussion: Due to the nonlinearity and time-varying parameters of hydraulic drive, hydraulic drive errors are inevitably present. There are still shortcomings in the development of hydraulic quadruped robots, such as energy utilization efficiency, lightweight design of structures, joint servo drive, and intelligent control. Conclusion: In order to achieve stable control and industrial application of hydraulic quadruped robots, the control methods of whole body are summarized and analyzed. And it is pointed out that the future research work of hydraulic quadruped robots mainly focuses on the lightweight design of the system and the study of intelligent control algorithms with stronger adaptability.