Dynamics analysis and design methodology of roll-resistant hydraulically interconnected suspensions for tri-axle straight trucks
Introduction
Vehicle suspensions are designed to isolate the passenger compartment from roadway irregularities, as well as control and distribute the vertical tire-loads for numerous driving conditions [1], [2]. Therefore, the suspension design involves the selection of optimal spring/damper parameters to provide a better compromise between ride, road holding and handling performances [3], [4], [5], [6]. The controlled (semi-active and active) suspensions have been recently developed to achieve better compromise [7], [8], [9], while the passive suspensions still predominate in modern society due to inevitable drawbacks involved in these controlled suspensions [10], [11]. Therefore, some alternative passive suspension systems are considered desirable to enhance design compromise. Because suspension performances are determined by four fundamental modes [12], e.g. bounce, pitch, roll and articulation, such suspensions should possess the abilities to independently enhance some modes without sacrificing the others.
Additionally, full vehicle ride and handling motions are strongly coupled in roll motion induced by maneuvers, road disturbances and crosswind [6], [13], especially in the case of heavy trucks with high center of gravity (CG) [14]. According to Winkler et al. [15], both higher roll stiffness and roll damping improve the roll stability. Therefore, anti-roll suspensions and similar assist systems are developed to improve the roll stability, such as stabilizer bar (passive) and anti-roll bar (semi-active or active). However, the stabilizer bar, without implementing roll damping, degrades the ride comfort and increases dynamic tire forces [16], [17]. Meanwhile, the wide application of active anti-roll bars is limited as result of power demand, complexity and reliability, as well as weight and cost [10], [11].
Interconnected suspensions (ISs) have been recently reported to be as one of typical alternative solutions to overcome these drawbacks, which is defined as a suspension that a displacement at one wheel station can give rise to forces at other wheel stations [18]. Compared to conventional suspensions, ISs have many advantages and can be realized by either mechanical, hydraulic, air or hydropneumatic (hydro gas) [19]. Mechanical implementation can be realized using a simple and robust system, but it is difficult to provide individual damping [20], [21]. Air connections put higher requirement on sealing and need more installation space than fluid connections. Hydropneumatic connections require larger working area and thus greater installation space. In this study, hydraulically interconnected suspensions (HISs) combing with mechanical springs are proposed for heavy trucks to overcome the above mentioned drawbacks, which own both the functionalities of conventional and interconnected suspensions, simultaneously. In this system, the single or double acting hydraulic cylinders are interconnected via hydraulic circuits. Accumulators and damper valves are incorporated in these circuits. The mechanical springs share the vehicle load, and HISs provide additional stiffness and damping for specified modes.
To the author׳s knowledge, so far a limited number of theoretical studies have been carried out for HIS systems [21], [22], [23]. For instance, Ortiz [21] conceptually integrated mechanical/hydraulic schematic to provide separate spring and damping for pitch/bounce and roll/articulation. Mace [22] presented a theoretical study for a family of existing passive HIS systems using network theory and system synthesis methodologies. Cao et al. [23] investigated the static and dynamic properties of interconnected hydro-pneumatic suspensions using a generalized analytical model. Zhang et al. [24] derived the impedance of hydraulic subsystem for two-axle sport utility vehicles with transfer impedance matrix method. Our previous work [19] studied the dynamic characteristics of tri-axle trucks with pitch-resistant HIS systems based on established dynamic equations of motion of coupling system. Researchers also evaluated the HIS system with experimental results [20], [25], [26], [27]. All obtained results indicated that HIS systems can improve the roll stability without sacrificing ride comfort, and achieve better weight distribution during maneuvers [21], [22], [23], [24], [25], [26], [27], [28], [29]. For an up-to-date review of HIS, the readers can refer to two recently published papers by Cao et al. [10] and Smith et al. [30]. However, it can be seen that the most of above studies assumed ideal interconnections, and thus ignored the pressure loss, so the dynamics of the interconnecting mechanisms were not thoroughly investigated and so it is difficult to qualitatively study the influence of hydraulic physical parameters on the full-vehicle performance. Furthermore, most researchers focused on the performances improvements from HIS system for two-axle vehicles [21], [22], [23], [24], [25], [26], [27], [28], [29], [30], [31], [32], [33], especially sport utility vehicles [24], [25], [26], [27], [28], [29], [31], [32], [33]. In particular there are barely reported studies on the dynamic characteristics of tri-axle straight trucks equipped with HIS system. Different from two-axle vehicles, the typical tri-axle straight trucks are classified into two types, and straight trucks, which correspond to trucks with dual-steering and dual-driven axles, respectively. It means that there are totally six wheel hops for motions of these wheel stations with respect to rigid frame. Therefore, the conventional method [22], [34], which is based on two-axle vehicles, should be extended to obtain displacement or force modes of suspension systems and wheel stations. This extension is especially important for tri-axle trucks with HIS systems when aiming to improve ride/handling performances with method of individually setting mode stiffness/damping. Additionally, the HIS system used for tri-axle straight truck is generally realized by six interconnected actuators. Compared to four interconnected actuators for two-axle vehicles, the interconnections among six actuators yield more complex configurations [32]. As a result, it is required to propose a new configuration of fluidic interconnections for HIS system, in order to independently enhancing roll mode stiffness/damping in this study.
In this paper, a new roll-resistant HIS system is proposed to improve performances of tri-axle straight truck. The equations of motion of coupling system are developed by incorporating the hydraulic strut forces into the mechanical subsystem as externally applied forces, which are derived with transfer impedance matrix method. Based on the obtained dynamic equations, the mode forces of vehicle body and wheel stations for tri-axle straight truck are obtained, and the additional mode stiffness/damping yielded by hydraulic system are presented to evaluate the capacities of this HIS system to independently adjust roll mode stiffness/damping. The dynamic responses between trucks with HIS system and conventional suspension are further compared. And a parametric design method is finally employed to tune the stiffness and damping related parameters of hydraulic system.
Section snippets
Model development
The tri-axle straight truck studied in this paper has one steering axle and two driven axles. The steering axle is connected to rigid frame via leaf spring suspension. While the suspension system for two rear driven axles is inverted semi-elliptic spring centrally pivoted tandem axle bogie suspension [35]. Based on our previous work [36], this bogie suspension can be modeled using a new simplified model, as shown in Fig. 1. In this study, a typical full truck model comprising the lumped sprung
Suspension characteristics
As aforementioned, the suspension modes determine the suspension characteristics. For the vehicle system, the suspensions connect the wheel stations to the vehicle body, and undertake the functions as mentioned above. Therefore, the vehicle-body mode stiffness and damping and tire modal forces are employed to explore the characteristics of the suspensions with the HIS systems. In the following discussions, the full vehicle system is assumed to possess right-left symmetry. All right-side
Responses and design methodology
The stiffness/damping alterations of the suspension systems are embodied in the responses of the vehicles subject to random excitations. In this study, the dynamic characteristics are investigated in terms of weighted sprung mass acceleration (SMA), pitch/roll angular displacements (PAD/RAD), suspension working space (SWS) and tire mode force (TMF). Cole [37] stated that modal analysis method can be used as an alternative method to investigate the vibration characteristics. Thus, in this study,
Results and discussions
In this study, two models named TUCS and THIS are used to represent the trucks with uncoupled conventional suspension and the proposed HIS systems, respectively. All the physical parameters used for simulation can be obtained from [19], [36]. In this study, the dynamic responses are shown to investigate the benefits from the HIS system in terms of the performance indexes defined by Eqs. (21), (22). Applying the proposed tuning method, comprehensive discussions are then followed to illustrate
Conclusions and future work
This paper has proposed a new roll-resistant HIS system to improve the roll dynamics of the truck body. The dynamic equations for the HIS system have been derived with impedance transfer matrix method. Based on the derived equations, the additional mode stiffness/damping rates provided by the HIS system are quantitatively described in terms of the physical parameters of the hydraulic system. It can be found that (1) the difference and summation of the top and the corresponding bottom piston
Acknowledgments
This research was partly supported by the National Natural Science Foundation of China (11232004) and International Science & Technology Cooperation Program of China (2015DFA13060), and also by the National Natural Science Foundation of China (51175157).
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2021, Information SciencesCitation Excerpt :The electro-hydraulic actuator is widely used due to low cost, less bulky and high reliability [6]. Furthermore, the interconnected electro-hydraulic actuator with double-acting asymmetric cylinder among wheel stations has been proven to be able to independently improve any one of the suspension bounce/pitch and roll/warp modes in our previous research works [7]. For these interconnected electro-hydraulic actuators, the inflow/outflow to the asymmetric cylinder chamber of each actuator installed on each wheel station is simultaneously regulated by multiple servo-valves.
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2021, Mechanical Systems and Signal ProcessingCitation Excerpt :Smith et al. [14] further proposed a 9-DOF vehicle model and conducted the comparison of the handling performances between the vehicle fitted with a HIS system and a conventional independent suspension through the simulations of a fishhook maneuver and the condition that one side of the vehicle traversed a half-sine bump. Ding et al. [15–17] proposed roll- and pitch-resistant HIS systems for the tri-axle heavy truck and two-axle vehicle to obtain a desired roll or pitch vibration reduction with slight impact on the bounce motion. Xu et al. [18] proposed a roll and pitch independently tuned HIS system and evaluated the ride and handling performance by carrying out the time domain analyses of a generalized 14-DOF vehicle model under different road excitations and steering/braking maneuvers.
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2020, Mechanical Systems and Signal ProcessingCitation Excerpt :He investigated dynamic characteristics, corresponding natural frequencies, mode shapes and dynamic responses of the system and indicated that the presented technique can significantly enhance the mode damping of the truck, while it can effectively increase the natural frequencies of roll modes. Moreover, Ding and Zhang [33,34] conducted further studies for three-axle trucks to explicitly describe auxiliary mode stiffness/damping of the vehicle body and wheel state forces based on physical parameters of the hydraulic system. The main attention of the anti-roll HIS system is to provide a nonlinear roll stiffness in addition to a roll damping for the enhancement of the roll stability of monomeric vehicles, as confirmed different theoretical researches [18–21,23,25,29,32–34] and experimental validations [22,24,26–28,30,31].