Nonlinear Parameter Identification and Suspension Performance Analysis of Hydropneumatic Suspension Based on Polynomial Modeling

The necessity of increasing the efficiency of timber transportation to consumers by timber trucks equipped with traditional dependent suspensions has been substantiated. The analysis of articles made by foreign scientists in the field of research of characteristics of hydropneumatic suspensions of vehicles is presented. A promising design of a modular-type hydropneumatic suspension is proposed. The goal of the work is formulated to develop mathematical and simulation models for the functioning of the proposed construction of a hydropneumatic suspension of a modular type to assess the influence of the main dependences of the nature of oscillations of a timber truck in time on the values of volume, pressure and temperature of air in the cavity of the pneumatic cylinder of the suspension structure. Developed and investigated mathematical and on its basis simulation models of the functioning of the hydropneumatic suspension. The dependences of the vibration frequencies of the body of a timber truck equipped with a hydropneumatic suspension on the vibration spectrum, as well as the time dependence of the volume, pressure and temperature of the air in the pneumatic cylinder when driving over a random uneven surface and single irregularities, are obtained.

In the development of heavy-duty vehicles, the design of hydro-pneumatic suspension (HPS) is important for improving various aspects of vehicle performance, such as comfort and stability. An HPS with gas–oil emulsion is advantageous with respect to cost and design compared to that with a separated chamber, because it shares a chamber with gas and oil. This paper presents an optimisation procedure for obtaining the optimal design of HPS with gas–oil emulsion for heavy-duty vehicles. The HPS model is developed from a mathematical analysis of the gas–oil emulsion, and a parameter study is performed to confirm the design sensitivity of the spring and damping characteristics. A full vehicle model with HPS is constructed to analyse the vehicle performance. The necessity of this vehicle model is shown by comparing its results with those of a simplified vehicle model. To alleviate the problem of excessive computational effort caused using the full vehicle model, surrogate models with respect to performance are developed for the design optimisation of HPS. By performing a multi-objective optimisation of the HPS design, a Pareto front considering the contradiction between the comfort and stability of the performances is obtained.

To enhance the ride comfort of the active hydro-pneumatic suspension and ensure system stability during an engineering vehicle’s operation, this study focuses on a dual-chamber hydro-pneumatic spring. It derives the relationship between the nonlinearity of the damping force and stiffness characteristics of the hydro-pneumatic spring and the vehicle body displacement. A control strategy is proposed to optimize the active disturbance rejection controller (ADRC) using a BP neural network. The neural network’s self-learning capability is employed for dynamic tuning of the ADRC parameters, thereby dampening body vibrations and achieving a stable condition. A two-degree-of-freedom dynamics model for a hydro-pneumatic suspension, along with a road input model, is constructed using MATLAB/Simulink. An optimized ADRC, leveraging a BP neural network, is integrated into the hydro-pneumatic suspension system. The vertical acceleration of the vehicle body and the dynamic load of the tire are adopted as evaluation indices. Through simulation analysis, the performance of the optimized algorithm is compared with that of an active suspension system controlled by both passive control and ADRC control. It is demonstrated that this optimization algorithm effectively reduces the vehicle body’s vertical acceleration and the tire’s dynamic load, thereby validating the efficacy of the control strategy.

In order to improve the vibration reduction performance of a special vehicle, a mathematical model with 13 DOF of the special vehicle is established by reasonable simplification. The vehicle dynamics simulation model is established based on the multi-body system dynamics software Simpack; the model of hydro-pneumatic suspension is established in AMEsim; a random road excitation model is established in Simulink. Through multi-software co-simulation, the vibration reduction performance of ipsilateral coupled hydro-pneumatic suspension and hybrid connected hydro-pneumatic suspension of a special vehicle is compared and analyzed. The results show that the hybrid connected hydro-pneumatic suspension system can improve the driving stability of the vehicle and improve the anti-roll and anti-pitch ability.

Most references on hydropneumatic suspension analysis regard it as harden Duffing spring and take the white noise as the system input, which is quite different from real physical model. It will introduce considerable errors to the analytical result compared with the numerical simulation which makes it impossible to give a good depiction of the hydropneumatic suspension dynamics. In this paper, the dynamic response of the hydropneumatic suspension is worked out using statistical linearization based on 2 DOFs nonlinear suspension model. The damping of the suspension and the tire stiffness are both regarded as linear components and the real road roughness spectrum is used to work out the system input. The explicit analytical equivalent stiffness, dynamic mean value offset from statistic equilibrium position and the sprung acceleration varied with parameters of hydropneumatic spring, road roughness and vehicle velocity are worked out by substituting the nonlinear stiffness of hydropneumatic spring with its first three terms Tyler series at the static equilibrium position using James formula. The comparison of the numerical simulation and analytical result both on statistical parameters and distribution shows the validity of the analysis. The explicit form provides a concise and valid method on hydropneumatic suspension design and optimization.

The capability of a variable stiffness and damping (VSVD) suspension system via a magnetorheological (MR) damper on improving vehicle lateral stability is investigated in this paper. First, a type of the VSVD suspension system is briefly introduced with the application of variable damping to realize the capability of VSVD. Then, variable damping via the MR damper is extended, and the characteristics of damping force are presented with the Bouc-Wen model. Then, the proposed VSVD system is inserted into a full vehicle model as a front suspension system to control tire normal forces. A control strategy composed of a fuzzy controller that the output is wheel slip ratio and a simple on/off controller to model the application of VSVD is developed to illustrate its ability in improving vehicle stability. It is shown from simulation that VSVD can increase tire normal forces and make vehicles present better performance on lateral stability.

<div class="htmlview paragraph">Humans are most sensitive to low frequency whole body vibrations often associated with roadways. As a result, improvement of vibration characteristics is an important aspect of vehicle design. While much research has been performed on active suspensions and their role in ride quality, comparatively little has been performed on seat dynamics. This paper develops a method of selecting optimal seat dynamic seat parameters with respect to ride quality. A nine degree of freedom dynamic vehicle simulation model is presented. An optimization procedure, using absorbed power as the objective function, then minimizes rider discomfort by manipulating the seat dynamic parameters. A two degree of freedom seat model yields four design variables, including seat suspension stiffness and damping and seat cushion stiffness and damping. The optimization problem is solved for several road inputs and two different vehicle models. The road inputs include actual road profiles, as well as common road test elements like sine waves and chuck holes. The vehicle models include a typical passenger car and utility-type vehicle. The results indicate that cushion and suspension stiffness and suspension damping are the most important factors influencing ride quality. The objective function was found to be relatively insensitive to cushion damping. The most critical parameter was determined to be the seat suspension damping. Design charts are provided which may be used in an active seat suspension application.</div>

Hydro-pneumatic suspension is widely used for its desirable nonlinear stiffness and damping characteristics. However, with the presence of parameter uncertainties and inherent nonlinearities, traditional controllers often yield unsatisfactory control effects in practical applications. Therefore, a novel stability control method for active hydro-pneumatic suspension is proposed in this paper. First, a nonlinear mathematical model of the hydro-pneumatic suspension considering the seal friction and a full vehicle dynamics model is established. Second, the vertical, roll, and pitch motions of the vehicle body are collaboratively controlled by establishing three active disturbance rejection sliding mode controllers (ADRSMC) in parallel with each other. The lumped disturbances caused by the model nonlinearities and uncertainties are estimated by the extended state observer (ESO), integrating these into the sliding mode control (SMC) law to enable adaptive system response. Finally, the effectiveness of the proposed control method is verified under the bump and random road surfaces. The results demonstrate that the proposed ADRSMC has better performance than the ADRC method and SMC, significantly improving the vehicle stability.

SUMMARY The high weight and critical conditions of wheel load distribution shown by crane vehicle supported on a special chassis, suggest hydro-pneumatic suspensions as most suitable so that they should replace the conventional mechanical types. The Instituto Tecnologico de Aragon, Zaragoza (Spain) in the collaboration with Industrias Luna S.A., Huesca (Spain) has been working on the analysis of hydro-pneumatic suspensions using bond graph techniques, different alternatives to their use being presented in this paper.

Torsional vibration modelling of powertrains is hindered by the lack of understanding of tyre low-frequency torsional stiffness and damping characteristics. Torsional here means rotation about the wheel (spin) axis so that the rotation of the wheel hub is different from that of the periphery of the tyre. This paper explains a simple, practical test rig design that can be used to determine a tyre's torsional characteristics via simple modelling. The model assumes a complex stiffness that allows the damping type to be determined as a function of the frequency. The measurement of some torsional stiffness and damping characteristics of a small pneumatic tyre while under load and rolling is presented. The tyre was excited torsionally and, from the results obtained, the tyre's torsional stiffness and damping characteristics were calculated. The investigations were concerned with the low-frequency characteristics. It was found that there was a large torsional vibration associated with the tread pattern. Over the frequency range tested (10–50Hz), it was found that the damping is more accurately represented as hysteretic and not viscous when lightly loaded. The effects of rotational speed, preload, and inflation pressure on the stiffness and damping were also investigated. The damping type for the tyre (hysteretic or viscous) was found to vary depending on the loading and excitation. Tyre properties were then included in a lumped-inertia, frequency-domain powertrain model and the steady-state response predicted. The results indicated that the viscous or hysteretic damping assumption has significant effects on the predicted frequency response of the powertrain. The need for further studies investigating the damping characteristics of automotive tyres in torsion is therefore recommended.

This paper presents the optimization of suspension characteristics under the condition of curved track railway vehicles. Reducing lateral acceleration on curved track is an issue for high-speed railway vehicles. In terms of curved track running environments, reducing the lateral vibration of railway vehicles is critical to safety and curving performance. The properties of lateral damping and stiffness of both primary and secondary suspension show effect on wheel-set, bogie and car-body. Analysis for reducing the lateral vibration of rail vehicles with respect to the characteristics of both primary and secondary suspension has been developed using ADAMS/Rail. Response Surface Method has been chosen for the purpose of verifying correlation effects among design parameters. Also, this paper suggests the method for designing optimal suspension of railway vehicles on curved track. The optimization result indicates decrement of lateral acceleration on wheel-set by 3% and bogie by 1% on curved track. Finally, this paper comes to the conclusion that suspension system of railway vehicle (KTX I) is properly designed when regarding lateral vibration of railway vehicle on diverse curved track condition.

By using the corrugation formatting and developing model we successfully fixed the formatting and developing mechanism of rail corrugation on curved track. The frequency of corrugation is governed by the vertical dynamic system of the wheelset including the contact stiffness between rail and wheel, but not by the torsional dynamic system of the wheelset. From the simulation results we find that, (1) reducing the wheelset mass and static wheel load, (2) increasing the radius difference between inside/outside wheels in curving, the damping of axle suspension and axle torsional stiffness, are useful means to reduce corrugation. However, reducing axle suspension stiffness has almost no influence on the reduction of corrugation, because the contact stiffness between rail and wheel is much greater than the suspension stiffness.

The suspension characteristics of a 10 ton truck with a highly non-linear leaf spring suspension have been investigated. The acceleration transmissibility frequency response characteristics of the truck were first investigated. Results showed that whereas the bounce (sprung mass) resonant frequency was quite close to that expected, the wheel-hop (unsprung mass) resonant frequencies were roughly twice that expected. As no obvious mechanism for this effect was evident, the static stiffness characteristics of the suspension were measured in an attempt to understand this phenomenon. A simple plot of the resulting suspension-generated force against suspension deflection showed that two distinct stiffness regimes were present; the first, which was associated with small suspension deflections of between 2 and 4 mm, was significantly greater than the second, which was associated with larger suspension deflections. A state-variable linear 5 degree-of-freedom spring mass damper model of the vehicle was created within MATLAB in an attempt to predict the frequency response characteristics of the vehicle. The state-variable model predictions were close to those seen experimentally for the sprung mass at frequencies below 3 Hz, but were quite incorrect for both the sprung and unsprung masses above this frequency. The state-variable model was then used again with increased values of suspension stiffness and results showed that using these higher values led to a more accurate predicted response for both the sprung and unsprung masses above 3 Hz, whereas below this frequency their responses were clearly incorrect. Comparison of experimental and predicted results showed that the vehicle frequency response was dominated above 3 Hz by the low suspension deflection-high stiffness regime identified in the static stiffness results, whereas below this frequency, the high suspension deflection- low stiffness regime tended to dominated the response. To overcome the problem of the transition from the low to the high stiffness regimes when predicting the frequency response characteristics, a non-linear model was created using MATLAB and SIMULINK. Results showed that the model was able to capture this transition, with resulting frequency response curves for both the sprung and unsprung masses being very similar to the experimental results. Further refinements to the model were able to account for additional discrepancies between predictions and experimental results. The non-linear nature of the spring stiffnesses, resulting in a very useful hysteresis damping effect at the sprung mass resonant frequency, meant that for most normal road conditions the vehicle would ride on a near solid suspension. The apparent advantages of the extra damping would therefore be o set by a significant decrease in ride quality, and this was especially evident in respect to road noise and vibration-a finding borne out in practice. This paper establishes the principal characteristics of the truck suspension and goes on to describe the linear state-variable and non-linear models created to simulate the frequency response characteristics of the vehicle suspension.

Triplet shear tests are commonly used to evaluate the strength of masonry shear walls. A conventional approach involves identifying the parameters of the Mohr-Coulomb failure criterion. Although numerous studies have proposed numerical models capable of reproducing the global experimental response, the present work distinguishes itself by coupling full-field displacement measurements obtained through Digital Image Correlation (DIC) with the identification of nonlinear material parameters within a consistent inverse framework. DIC measurements were used to prescribe experimentally measured boundary conditions in finite element simulations. A Finite Element Model Updating (FEMU) strategy was then implemented to identify the model parameters. A prior sensitivity analysis showed that displacement fields exhibited limited influence on the targeted parameters for the adopted constitutive model, which justified a force-based identification procedure. The methodology was applied to four triplet shear tests. The results demonstrated the capability of the mesoscopic model to reproduce the observed mortar joint response. Both elastic and nonlinear parameters were identified, and their associated uncertainties were quantified.

A new method based on dynamic response sensitivity is proposed for the identification of local nonlinear system. The unknown local nonlinear hysteresis parameters are identified together with linear structural parameters. The sensitivities of structural dynamic response with respect to unknown parameters are derived. The identification equation is set up based on Taylor’s first order approximation, and is solved with the damped least-squares method. A four-story shearing system with rubber isolation bearing of nonlinear hysteresis model is studied to validate the proposed method. Numerical simulation with noisy measured accelerations shows that the proposed method can accurately identify both linear and nonlinear parameters of the system. This method provides a new approach for detecting local nonlinear structures with incomplete measured output information.