Height-posture and load coupling control methodology of URAPM and its application in active suspension control of multi-axle vehicles

Abstract

Unidirectional redundant actuated parallel mechanism (URAPM) is the physical prototype of active suspension system, truck crane outrigger system, etc. As the number of adjustment mechanisms (AMs) increases to more than three, the difficulty of height-posture control of the upper component (UC) increases considerably. The AMs load control is also tough but highly underappreciated, which in turn causes height-posture disturbance. In this work, a convenient height-posture and bearing load coupling control methodology and its application in the active suspension system are presented. Firstly, by characterizing the force-deformation coupling relationship of the URAPM, a basic geometry and load coupling control model is proposed. And for the desired bearing load control, different optimal load allocation algorithms are developed and evaluated. Secondly, coupling control models for the flexible load control under stationary height-posture, and the flexible height-posture control under balancing load are constructed respectively. Finally, bench tests based on a six-legged URAPM (equivalent to a three-axle active suspension vehicle) validate the proposed method can achieve high precision, high convergence, and most attractively, the height-posture and load coupling adjustment with few iterations, thus demonstrating its good application prospect in low-speed off-road maneuvering of multi-axle vehicles and other related fields.