Hydro-pneumatic Suspension Research Articles

Statistical Linearization Analysis of a Hydropneumatic Suspension System With Nonlinearity

Hydropneumatic suspension has the characteristics of nonlinear stiffness, nonlinear friction damping, and nonlinear hydraulic damping, and therefore, it has been widely applied to heavy vehicles. A hydropneumatic suspension with a special structure was proposed and studied in this paper. The nonlinear quarter-vehicle model was built by using Newton’s laws according to its configuration. Then, this nonlinear mathematic model was linearized through the statistical linearization method on the basis of random vibration theory. Next, the transfer functions of the suspension system subjected to random road excitation were built according to the statistical linearization model and the power density spectrum approach. In addition, the responses of vehicle body acceleration, tire relative dynamic load, and suspension deflection with respect to the wideband random excitation due to road roughness were obtained according to the James formula. Next, the influences of the equivalent damping ratio and the equivalent frequency ratio on vehicle riding comfort, riding safety, handing stability, and suspension reliability were analyzed through simulations. These results provided the basic principles for selecting the reasonable hydropneumatic suspension parameters.

An Improved Rollover Index Based on BP Neural Network for Hydropneumatic Suspension Vehicles

The 3-DOF rollover model has been established by the Lagrangian second-class equation, taking the road inclination angle, the steering strategy, and the hydropneumatic suspension characteristics into consideration. A 3-layer BP (backpropagation) neural network is applied to predict the road inclination angle and to optimize the rollover model in real-time. The number of the hidden layer neurons for the BP network is also discussed. The numerical calculation of the optimized rollover model is in good agreement with the full-scale vehicle test. Different rollover indexes are compared, and the results indicate that the rollover index of dynamic LTR optimized by the BP neural network can evaluate the rollover tendency more accurately in the ramp steering test and the snake steering test. This study provides practical meanings for developing a rollover warning system.

Statistical Linearization of Nonlinear Stiffness in Hydropneumatic Suspension

Hydropneumatic springs are the elastic components of a vehicle’s suspension. As the nonlinear characteristic of the spring is difficult to express accurately, the statistical linearization method is introduced to analyze the dynamic response of the hydropneumatic spring. The nonlinear stiffness of a hydropneumatic spring is approximated by a quadratic polynomial at the static equilibrium position. Parameters of the hydropneumatic spring, road roughness and vehicle velocity are provided and analytical functions for equivalent stiffness and the dynamic equilibrium position are worked out in this paper. The analytical functions are validated through numerical simulation and are shown to be more accurate than those validated by existing methods. The method proposed here could be used in the design and analysis of hydropneumatic suspensions in future.

Assessment Study of the Design and Characteristic of Front-axle Hydro-pneumatic Spring of the Tractor

The paper discussed the improvement of design and characteristics of front-axle hydro-pneumatic spring of the tractor. For the experimental purposes, tractor with the model number of CF700 and the vibrational differential equation was established and also the three degrees of freedom vibration model of the front-axle suspension tractor was built up. According to the requirements of the tractor model number CF700 for front-axle suspension parameters, hydro-pneumatic spring with the controllable stiffness and damping was designed. The stiffness and damping non-linear mathematical model of hydro-pneumatic spring was established and the structural parameters of hydro-pneumatic spring were calculated. The performance of hydro-pneumatic springs was studied by simulation and the static and dynamic characteristics of the hydro-pneumatic spring were studied in the experiment. From the investigated results shows that the stiffness characteristics of hydro-pneumatic spring were studied and the static stiffness of hydro-pneumatic spring in equilibrium position was 72.6 kN.m-1. The influence of proportional valve current size, the opening of the throttle valve size and excitation frequency to the output force of hydro-pneumatic spring was studied by dynamic experiment. Further, from the results, it was showed that the designed hydro-pneumatic spring can adjust output force on a wide range of sizes. However, from the investigated results, it was concluded that the study provides an important basis for the later development of the semi-active hydro-pneumatic suspension of tractor front axle suspension.

A novel integrated suspension tilting system for narrow urban vehicles

Narrow vehicles are proposed to resolve urban transportation issues such as congestion, parking, fuel consumption and pollution. They are characterized by a high ratio of centre of gravity height over track width. Such vehicles are vulnerable to rollover and stability issues when negotiating curves at a normal operating speed. Therefore, the tilting capability is crucial to such vehicles. Existing solutions, which mechanically connect the wheel module on both sides and synchronize their movement, still have room for further improvement. The extra links for synchronization not only take up space on compact urban vehicles, but also introduce additional mass to the light-weighted body. The novel tilting mechanism introduced in this work utilizes hydraulics to replace mechanical connections to generate the tilting motion. An interconnected hydro-pneumatic suspension system is adopted to provide the desired bump and roll stiffness for narrow urban vehicle applications. Two independently controlled hydraulic pumps are connected to the hydraulic suspensions to provide the tilting, as well as riding height change capabilities. The integration of the tilting system with suspension reduces the system weight and packing size, both of which are vital to the success of narrow urban vehicles. All the functionalities are illustrated, modelled and examined in the simulation studies, which prove the feasibility of the proposed system on narrow urban vehicle applications resulting in more functionalities with lower complexity and weight.

Research on dynamic behaviors of wheel loaders with different layout of hydropneumatic suspension

The traditional wheel loader is built without any axle suspension and experiences severe vibration. Three different layouts of hydropneumatic suspension, namely, unconnected strut (UCS), interconnected in roll plane (IC-R) and interconnected in roll and pitch plane (IC-RP), are installed on the wheel loader to improve ride comfort. This study mainly focuses on the damping effect of different layouts of suspensions and investigates whether the suspensions will affect the driving and operation stability of the wheel loader. The multibody model of the wheel loader with hydropneumatic suspension is developed by RecurDyn in co-simulation with MATLAB/Simulink. Detailed analysis was performed as the wheel loader was traveling on a C-class road, turning on a flat road, and scooping and unloading crushed rocks. Results showed that (1) the three layouts of suspensions can greatly reduce the vector sum of weighted acceleration; (2) the UCS suspension affects both the driving and operation stability of the wheel loader, and the IC-R suspension affects the operation stability when the wheel loader scoops and unloads crushed rocks, (3) the IC-RP suspension with anti-roll and anti-pitch functions has little effect on the driving and operation stability of the wheel loader.

Tire wear estimation based on nonlinear lateral dynamic of multi-axle steering vehicle

This paper presents a novel nonlinear dynamic model of a multi-axle steering vehicle to estimate the lateral wear amount of tires. Firstly, a 3DOF nonlinear vehicle dynamic model is developed, including dynamic models of the hydropneumatic suspension, tire, steering system and toe angle. The tire lateral wear model is then built and integrated into the developed vehicle model. Based on the comparison of experimental and simulation results, the nonlinear model is proved to be better than a linear model for the tire wear calculation. In addition, the effects of different initial toe angles on tire wear are analyzed. As simulation results shown, the impact of the dynamic toe angle on the tire wear is significant. The tire wear amount will be much larger than that caused by normal wear if the initial toe angle increases to 1° - 1.5°. The results also suggest that the proposed nonlinear model is of great importance in the design and optimazation of vehicle parameters in order to reduce the tire wear.

Research and simulation of anti - rollover technology of harvester

The structural characteristics of our country’s corn harvester are narrow-track, high centroid and existence of eccentric distance, so rollover accident is easily to occur when going up and down the hills mountainous and hilly regions for complex terrain. In the previous paper, we introduced the Hydro-Pneumatic Suspension to prevent the roller of the harvester, and took ADAMS simulation on the left and right roller, and obtained that the use of Hydro-Pneumatic Suspension can improve the side angle of the harvester for 5°. At the same time, we continue to use the Hydro-Pneumatic Suspension as the key part of the anti-roller system of the harvester. In the uphill and downhill case of the harvester, we respectively simulated the anti-roller performance on the traditional harvester and the harvester installing the Hydro-Pneumatic Suspension. Finally, we got that the anti-roller angle of the harvester installed Hydro-Pneumatic Suspension is obviously higher than the traditional harvester, which indicates that the anti-rollover performance of the harvester installed Hydro-Pneumatic Suspension is better than the traditional harvester. The data obtained from this experiment will provide technical support for the following structure optimization of the harvester.

Tracked Vehicle Performance Evaluation using Multi Body Dynamics

The objective of the study was to shorten the design cycle and evaluate the performance of infantry fighting vehicle using advanced multi body dynamics (MBD) environment before physical prototypes built. The MBD model is built with tracked vehicle module consisting of tracks (Links), sprocket, Support rollers, and hydro pneumatic suspension with suitable connections. Hull, turret are characterised by mass and inertial properties. The dynamic analysis was carried out for different field conditions i.e. trench crossing, step and ramp climbing, etc., to extract the hull forces at joints, power required to manuever, track tension forces to determine overall vehicle stability and look for possible design modifications. Recommendations were then suggested for power train, number of track segments, tensioner force, etc to ensure proper behavior during different manuevers. The MBD results are used in FEA to determine structural response in terms of stress, deformation, fatigue etc., and reflects in design modification before physical prototype made and are validated with base level analytical results.

취약면적법과 DMEA를 활용한 지상전투차량 유공압 현가장치의 취약성 평가

취약면적법과 DMEA를 활용한 지상전투차량 유공압 현가장치의 취약성 평가

ANALYSIS OF HYDRO-PNEUMATIC SUSPENSION SYSTEM FOR RALLY TRUCK AND TO CHECK ITS FEASIBILITY FOR COMMERCIAL DELIVERY VANS

The suspension system is the main part of the vehicle, where the shock absorber is designed mechanically to handle shock impulse and dissipate kinetic energy. The basic study of hydro pneumatic suspension system is carried out for GINAF rally truck which has been as a part of this project to get a basic idea regarding the system and applicability in commercial vans. As spring is basic element of any suspension system, study and analysis of the spring is carried out. Optimization of the spring for the generalized suspension is done and checked in modal as well as structural analysis in ANSYS. And found that the newly designed spring is feasible for Conventional as well hydro pneumatic suspension system. Applicability of this newly designed hydro pneumatic suspension is checked for Indian commercial delivery vehicle and stresses are found way under the maximum failure limit. Feasibility of hydro pneumatic suspension system including all the requirements has been checked in this project against wear, bumping etc. Also Feasibility of the whole system has been checked for front as well as rear wheels differently and found suitable.

Numerical analysis of a dual-chamber hydro-pneumatic suspension using nonlinear vibration theory and fractional calculus

A dual-chamber hydro-pneumatic suspension, a modified version of the traditional hydro-pneumatic suspension, can provide enhanced isolation performance. In this article, we use two very different t...

Suspension System Dynamics Modeling and Simulation Analysis

A dynamic model of 7-DOF wheeled vehicles was established using the Lagrange's theorem, vibration response of vehicle body’s vertical, pitching, lateral directions and unsprung mass can be carried on simultaneously based on the model. The random road spectrums of standard road surface and typical off-road terrain were deduced separately, pavement structure analysis in time and frequency domain was also completed. Systematical dynamic programming computation was conducted using random road spectrums as input. Optimal iteration algorithms were adopted to match and optimize the elastic-damping characteristics of suspension systems, and the variation laws of suspension damping ratio under different road conditions and vehicle speeds were obtained, which provides theoretical basis for determination of hydro-pneumatic suspension composite characteristic in prototype vehicle.

Effects of Entrapped Gas within the Fluid on the Stiffness and Damping Characteristics of a Hydro-Pneumatic Suspension Strut

Effects of Entrapped Gas within the Fluid on the Stiffness and Damping Characteristics of a Hydro-Pneumatic Suspension Strut

Investigation of Semi-Active Hydro-Pneumatic Suspension for a Heavy Vehicle Based on Electro-Hydraulic Proportional Valve

Hydro-pneumatic suspension is widely used in heavy vehicles due to its nonlinear characteristics of stiffness and damping. However, the conventional passive hydro-pneumatic suspension can’t adjust parameters according to the complicated road environment of heavy vehicles to fulfill the requirements of the vehicle ride comfort. In this paper, a semi-active hydro-pneumatic suspension system based on the electro-hydraulic proportional valve control is proposed, and fuzzy control is used as the control strategy to adjust the damping force of the semi-active hydro-pneumatic suspension. A 1/4 semi-active hydro-pneumatic suspension model is established, which is co-simulated with AMESim and MATLAB/Simulink. The co-simulation results show that the semi-active hydro-pneumatic suspension system can significantly reduce vibration of the vehicle body, and improve the suspension performance comparing with passive hydro-pneumatic suspension.

Hydro-Pneumatic Suspension System Hybrid Reliability Modeling Considering the Temperature Influence

Hydro-pneumatic suspension systems have been widely used in many fields for their variable stiffness characteristics that effectively improve the comfort and operation stability of a vehicle. However, due to poor environmental conditions, hydro-pneumatic suspension is frequently subjected to the influence of transient impact and environmental temperature changes, which results in sealing failure and gas leakage problems and reduces the reliability of the system. In this paper, a method combining parametric modeling and probability analysis is adopted to establish the reliability model of a hydro-pneumatic suspension system considering the influence of temperature variations. First, the working principle and failure mode of the hydro-pneumatic suspension system are analyzed, and then the reliability of the hydro-pneumatic suspension system is defined. On this basis, for the key failure modes of the hydro-pneumatic suspension system, a reliability model based on the allowable height and a reliability model based on the allowable stiffness are established. The system reliability model of the hydro-pneumatic suspension system is obtained synthetically. Finally, the single-chamber hydro-pneumatic suspension system is selected as the experimental object. Comparative tests of different design parameters of the hydro-pneumatic suspension system under temperature effect are conducted. The accuracy is verified for the failure mode analysis and reliability model of the hydro-pneumatic suspension system.

Research on the Effects of Hydropneumatic Parameters on Tracked Vehicle Ride Safety Based on Cosimulation

Ride safety of a tracked vehicle is the key focus of this research. The factors that affect the ride safety of a vehicle are analyzed and evaluation parameters with their criteria are proposed. A multibody cosimulation approach is used to investigate the effects of hydropneumatic parameters on the ride safety and aid with design optimization and tuning of the suspension system. Based on the cosimulation environment, the vehicle multibody dynamics (MBD) model and the road model are developed using RecurDyn, which is linked to the hydropneumatic suspension model developed in Lab AMESim. Test verification of a single suspension unit is accomplished and the suspension parameters are implemented within the hydropneumatic model. Virtual tests on a G class road at different speeds are conducted. Effects of the accumulator charge pressure, damping diameter, and the track tensioning pressure on the ride safety are analyzed and quantified. This research shows that low accumulator charge pressure, improper damping diameter, and insufficient track tensioning pressure will deteriorate the ride safety. The results provide useful references for the optimal design and control of the parameters of a hydropneumatic suspension.

A Semiactive and Adaptive Hybrid Control System for a Tracked Vehicle Hydropneumatic Suspension Based on Disturbance Identification

The riding conditions for a high-speed tracked vehicle are quite complex. To enhance the adaptability of suspension systems to different riding conditions, a semiactive and self-adaptive hybrid control strategy based on disturbance velocity and frequency identification was proposed. A mathematical model of the semiactive, self-adaptive hybrid suspension control system, along with a performance evaluation function, was established. Based on a two-degree-of-freedom (DOF) suspension system, the kinematic relations and frequency zero-crossing detection method were defined, and expressions for the disturbance velocity and disturbance frequency of the road were obtained. Optimal scheduling of the semiactive hybrid damping control gain (csky, cground, chybrid) and self-adaptive control gain (cv) under different disturbances were realized by exploiting the particle swarm multiobjective optimization algorithm. An experimental study using a carefully designed test rig was performed under a number of typical riding conditions of tracked vehicles, and the results showed that the proposed control strategy is capable of accurately recognizing different disturbances, shifting between control modes (semiactive/self-adaptive), and scheduling the damping control gain according to the disturbance identification outcomes; hence, the proposed strategy could achieve a good trade-off between ride comfort and ride safety and efficiently increase the overall performance of the suspension under various riding conditions.

Modeling and analysis of the vibration characteristics of a new type of in-arm hydropneumatic suspension of a tracked vehicle

We investigated the nonlinear elastic characteristic of an in-arm hydropneumatic suspension unit (ISU) as well as the damping characteristic of the controllable vane absorber. Due to the strong nonlinear characteristic of the ISU, simplify is needed to accurately model the vehicle. Based on the theory of multibody dynamics, a virtual prototype of the tracked vehicle was built, which includes the hydraulic system, the multi-dynamics of running gears and a road surface model. The virtual prototype is validated using both a static balancing test and a stiffness characteristics test. By simulating the road impact loading of the tracked vehicle when travelling on a trapezoidal US military road, the changes of the pitch angle and the acceleration of seats and centroid of the tracked vehicle was analyzed for two different damping ratios. We also determined key ride indicators for different speeds. The stiffness and damping characteristics of the ISU were tested in a bench experiment.

Effectiveness evaluation of hydro-pneumatic and semi-active cab suspension for the improvement of ride comfort of agricultural tractors

Advances have been made to agricultural tractors to improve their ride comfort. However, the ride comfort of tractors is relatively low compared to that of passenger vehicles. Many researchers have developed various types of suspension for tractors. While most studies have focused on the geometry of the suspension, few studies have been carried out on the development of a control algorithm for tractor suspension.In this paper, to improve the ride comfort of an agricultural tractor, a hydro-pneumatic suspension model with a semi-active suspension control is developed with computer simulation, and the effectiveness of the suspension is evaluated before the vehicle is equipped with the suspension and placed into production.An optimal control algorithm for the semi-active suspension of the tractor is developed using a linear quadratic Gaussian. In the simulation, a hydro-pneumatic suspension system model is developed using SimulationX and is applied to a full vehicle model using MATLAB/Simulink. The suspension is assessed by experiments and simulations. The ride comfort using the ride comfort index according to ISO 2631 is evaluated by comparing a vehicle with a passive cab suspension to that with a hydro-pneumatic suspension applied with the semi-active control.