Hydropneumatic suspension systems combine the excellent properties of gas springs with the favourable damping properties of hydraulic fluids. The advantages of these systems are particularly appropriate for mobile applications, such as agricultural and construction equipment as well as passenger cars, trucks and busses. Based on his 20 years of experience with this technology, Dr. Bauer provides in this book an extensive overview of hydropneumatic suspension systems. Starting with a comparison of different types of suspension systems, the author subsequently describes the theoretical background associated with spring and damping characteristics of hydropneumatic systems. Furthermore, he explains the design of the most important system components and gives an overview of level control systems, various special functions, patents and design examples. Finally, an outlook for future hydropneumatic suspension systems is discussed. Compared to the first edition, this new edition puts an additional focus on damping functions as well as applications / projects and contains various additional details such as proportional valves, all-wheel suspension or dediated power supply. Furthermore, suspension testing has been added as a new chapter.

A four-degrees-of-freedom roll plane model of a heavy highway vehicle is developed to investigate the ride and anti-roll properties of two different hydropneumatic strut designs, unconnected and interconnected in the roll plane. Three different interconnections, involving flows across different chambers of the right- and left-compact struts, are realized for the analyses. The analytical models are solved to derive the static and dynamic properties of various unconnected and interconnected configurations in terms of vertical spring rate, effective vertical mode damping, effective roll stiffness and roll mode damping. From the results it is concluded that roll plane interconnection of the suspension struts offers considerably potential for enhancing the anti-roll properties, with insignificant influence on the vertical ride properties. The analytical models are further analyzed under deterministic and random vertical road and roll moment arising from directional maneuvers. The relative performance potentials of interconnected suspensions are presented in terms of vertical and roll acceleration transmissibility under a harmonic excitation transient vertical and roll responses under a transient road bump and roll moment excitations, and power spectral densities and RMS values of the sprung mass responses to random road excitation.

Vehicle suspension design and dynamics analysis play a key role in enhancement of automotive system performance. Despite extensive developments in actively-controlled suspensions, their commercial applications have been limited due to the associated high cost and weight. Alternative designs in either passive or semi-active suspensions are highly desirable to achieve competitive vehicle performance with relatively lower cost and greater reliability. This dissertation research proposes two hydro-pneumatic suspension strut designs, including a twin-gas-chamber strut, and systematically investigates various concepts in roll- and pitch-coupled suspensions employing hydraulic, pneumatic and hybrid fluidic interconnections between the wheel struts. The proposed strut designs, including single- and twin-gas-chamber struts, offer larger working area and thus lower operating pressure, and integrate damping valves. Nonlinear mathematical models of the strut forces due to various interconnected and unconnected suspension configurations are formulated incorporating fluid compressibility, floating piston dynamics, and variable symmetric and asymmetric damping valves, which clearly show the feedback damping effects of the interconnections between different wheel struts. The properties and dynamic responses of the proposed concepts in roll- and pitch-coupled suspension struts are evaluated in conjunction with in-plane and three-dimensional nonlinear vehicle models. The validity of the vehicle models is demonstrated by comparing their responses with the available measured data. The analyses of the proposed coupled suspensions are performed to derive their bounce-mode, anti-roll, anti-pitch and warp-mode properties, and vehicle dynamic responses to external excitations. These include road roughness, steering and braking, and crosswinds. The results suggest that the fluidically-coupled passive suspension could yield considerable benefits in enhancing vehicle ride and handing performance. Furthermore these offer superior design flexibility. The suspension struts offer a large number of coupling possibilities in the three-dimensions, some of which however would not be feasible, particularly for commercial vehicles where suspension loads may vary considerably. A generalized analytical model for a range of interconnected suspensions is thus developed, and a performance criterion is formulated to assess the feasibility of a particular interconnection in a highly efficient manner. The handling and directional responses of a three-dimensional vehicle model employing X-coupled hydro-pneumatic suspension are evaluated under split-? straight-line braking and braking-in-a-turn maneuvers. The results clearly show that the X-coupled suspension offers enhanced anti-roll and anti-pitch properties while retaining the soft vertical ride and warp properties. Fundamental pitch and vertical dynamics of a road vehicle are also considered to derive a set of essential design rules for suspension design and tuning for realizing desirable pitch performance.