Assistance Characteristics and Control Strategy of Electro-Hydraulic Power Steering Systems on Commercial Vehicles

Electro-hydraulic power steering system (EHPS) maintains the advantages of Hydraulic power steering system (HPS) and Electric power steering system (EPS).It is even more superior than this two. In the foreseeable future, this system will have a certain development space. Assistant characters analysis was carried out in this paper. Control strategy based on steering states and feedback control strategy were designed too. Besides, aiming at the emergency steering conditions, steering angular velocity additional controlling strategy was brought out. Under emergency steering conditions, steering angular velocity additional controlling strategy will be applied. Additional steering moment will be calculated to ensure the assistant follow steering rapidly. Comparing the assist characteristic of Electro-hydraulic power steering system and Hydraulic power steering system, referring to existing research results, ideal assistant characteristic curve of Electro-hydraulic power steering system was included. During the design process, ensured the Electro-hydraulic power steering system assistant characteristic curve had the characteristics of Hydraulic power steering system, and only the parabolic assistant characteristic curve was studied. After the characteristic parameters are determined, fit the curve basing on the ideal assistant characteristic. Electro-hydraulic power steering system control strategy was designed by combining logic threshold control strategy and feedback control strategy. Logic threshold control strategy aimed to distinguish steering conditions while feedback control strategy controlled steering assist.