Hydro-gas Suspension Research Articles

Development of sprung mass non-linear mathematical model of pitch dynamics with trailing arm suspension

Military vehicles are required to negotiate drastic ride environments. Therefore, the vibration magnitudes which are transmitted to the vehicle chassis through the suspension system due to dynamic vehicle-terrain interactions, are usually large. Hence, it is necessary to study the vibrations that are transmitted to the sprung mass as it negotiates different types of terrain at different speeds. The present study is focused on the development of sprung mass non-linear pitch dynamics mathematical model of a military vehicle with a trailing arm torsion bar suspension system. The trailing arm kinematics and dynamics are incorporated into the non-linear governing equations of motion of the sprung and unsprung masses which consider the effects of sprung mass large pitch angular motions. The model is solved by coding in Matlab. The sprung mass non-linear pitch dynamics mathematical model is validated with an equivalent multi-body dynamics model which is developed by using MSC.ADAMS. This mathematical model would play a key role to fine-tune the vehicle and suspension parameters as well as comparatively evaluate the performance of the hydro-gas suspension system. The model can further be extended to include the military vehicle weapon recoil effects which can cause considerable magnitudes of vehicle pitch. Apart from simulating ride dynamics of the entire vehicle, the influence of movement with crane payload on the military recovery vehicle pitch dynamics can also be brought out as a useful extension of this mathematical model.

MODELING AND ANALYSIS OF HYDRO-GAS SUSPENSION UNIT

ABSTRACTHydro-gas suspension systems cushion shocks and damp oscillations of vehicle hullwhen it moves on uneven terrain. The hydro-gas suspension provides the vehiclewith proper ride comfort due to non-linear characteristics of hydro-gas units. Thehydro-gas suspension system can store a large amount of potential energy;accordingly, it can withstand higher shocks than the torsion bar suspension.Consequently, it is preferred to be used in the design of vehicle suspension. In thispaper, a mathematical model for hydro-gas unit used in BMR wheeled vehicle isestablished to evaluate its characteristics using Matlab /Simulink program. Themathematical model is validated experimentally using the data measured for the unitin laboratory using MTS (793) damper test system. The unit is tested using an inputsine wave excitation by a frequency and amplitude corresponding to real roadconditions.

Modeling of Hydrogas Unit for Tracked Vehicle Suspension

Tracked vehicles equipped with conventional suspension are limited in their ability to achieve high mobility. This limitation is due to the linear characteristics and the consequent poorer ride performance [1-3]. Hydro gas suspension due to their inherent non-linear behavior can provide higher mobility and better ride comfort performance [4]. This paper aims to evaluate the characteristics of hydro-gas suspension system and apply this nonconventional system for the armored fighting carrier BMP-1. To achieve this goal, theoretical and experimental studies were carried out. The theoretical study includes modeling of the hydro gas suspension unit mathematically and validation of the developed model using MATLAB/SIMULINK. The experimental measurements are carried out to validate the results obtained from the model. The force, created inside the hydro gas unit during its action, includes the elastic and damping forces, the variation of such force with displacement and velocity of moving part are recorded (obtained). This variation is used as input parameters in the equation of oscillation of vehicle hull to study its vibration response. The obtained results show that the proposed hydro gas suspension system is more acceptable than the conventional one.

Ride dynamics mathematical model for a single station representation of tracked vehicle

Tracked vehicles are exposed to severe ride environment due to dynamic terrain-vehicle interactions. Hence it is essential to understand the vibration levels transmitted to the vehicle, as it negotiates different types of terrains at different speeds. The present study is focused on the development of single station representation of tracked vehicles with trailing arm hydro-gas suspension systems, simulating the ride dynamics. The kinematics of hydro-gas suspension system have been derived in order to determine the non-linear stiffness characteristics at various charging pressures. Then, incorporating the actual suspension kinematics, non-linear governing equations of motion have been derived for the sprung and unsprung masses and solved by coding in Matlab. Effect of suspension non-linear dynamics on the single station ride vibrations have been analyzed and validated with a multi-body dynamics model developed using MSC.ADAMS. The above mathematical models would help in estimating the ride vibration levels of the tracked vehicle, negotiating different types of terrains at various speeds and also enable the designers to fine-tune the suspension characteristics such that the ride vibrations are within acceptable limits. The mathematical ride model would also assist in development of non-linear ride vibration model of full tracked vehicle and estimate the sprung mass dynamics.

Proportional Integral Derivative Control of Hydro-Gas Suspension Unit for Tracked Vehicles

High-speed tracked vehicles traversing off-road terrains are subjected to ride vibrations of low frequency and large amplitude. This causes bodily discomfort to the operator and limits the mobility and performance of the vehicle. The damping of the terrain vibrations is achieved by a Hydro-Gas Suspension Unit (HGSU) with inbuilt damper and hydraulic actuator piston mechanism. The present studies have been carried out to develop a quarter-car dynamic model of passive and active suspensions for improving the HGSU characteristics using proportional integral derivative controller. Performance of the active suspension system has been compared with the passive suspension system through simulations using MATLAB/SIMULINK software.

Semi-active hydro-gas suspension system for a tracked vehicle

A semi-active hydro-gas suspension is proposed for a tracked vehicle to improve ride comfort performance, without compromising the road holding and load carrying capabilities of the passive suspension. This is achieved through an active damper used in parallel with a gas spring. The suspension damper parameters are varied by a control mechanism based on sky-hook damping theory, which alters the flow characteristics. A damper prototype has been developed, tested for its flow characteristics, after which it has been integrated into an existing hydro-gas suspension system. An analytical model has been proposed from first principles rather than developing a phenomenological model based on experimental characteristics. This model is validated with experiments carried out on a suspension test rig. In order to compare the performance with the original passive system, an in-plane vehicle model is developed and the simulations clearly show that the semi-active system performance is superior to the passive system.

Hydro-gas suspension system for a tracked vehicle: Modeling and analysis

Tracked vehicles fitted with torsion bar suspensions are limited in their ability to achieve high mobility. This limitation is due to the linear characteristics and the consequent poorer ride performance. Hydro-gas suspensions due to their inherent non-linear behavior can provide higher mobility and better ride comfort performance. The hydro-gas suspension model has usually been developed from experimental force–displacement characteristics, which requires availability of suspension hardware. In this paper, a hydro-gas suspension system is modeled using polytropic gas compression model to represent the spring characteristics, while the damper orifices are modeled using hydraulic conductance. The analytical model is then validated with experiments individually for spring and damper flow characteristics and then as a suspension-wheel assembly in a test rig. The validated suspension model is incorporated in an in-plane model. Using this model, simulation is carried out for sinusoidal inputs of different wavelengths, amplitudes and vehicle speeds. The simulation model is validated with data measured on a vehicle traversing an APG course. The proposed model agrees very well with the measured data. Based on the validated model, studies on the influence of suspension parameters on the ride comfort of a tracked vehicle are carried out.

Optimisation of Kinematics for Tracked Vehicle Hydro Gas Suspension System

The modern-day armoured fighting vehicles (AFVs) are basically tracked vehicles equipped with hydro gas suspensions, in lieu of conventional mechanical suspensions like torsion bar and coil spring bogie suspensions. The uniqueness of hydro gas suspension is that it offers a nonlinear spring rate, which is very much required for the cross-country moveability of a tracked vehicle. The AFVs have to negotiate different cross-country terrains like sandy, rocky, riverbed, etc. and the road irregularities provide enumerable problems during dynamic loadings to the design of hydro gas suspension system. Optimising various design parameters demands innovative design methodologies to achieve better ride performance. Hence, a comprehensive kinematic analysis is needed. In this study, a methodology has been derived to optimise the kinematics of the suspension by reorienting the cylinder axis and optimising the loadtransferring leverage factor so that the side thrust on the cylinder is minimised to a greater extent. The optimisation ultimately increases the life of the high-pressure and high-temperature piston seals, resulting in enhanced system life for better dependability.

Assessment of tracked vehicle suspension system using a validated computer simulation model

A non-linear, in-plane computer simulation model of a typical high-mobility tracked vehicle is developed for suspension dynamic analysis and ride quality assessment. The Langrangian model formulation of the tracked vehicle is derived considering an arbitrary rigid terrain profile and constant vehicle speed. The model incorporates detailed representations of a trailing arm suspension system and dynamic wheel-track-terrain interactions. The computer model predictions are validated against field measurements, which were gathered from tests of an armoured personnel carrier traversing a discrete half-round bump and a random course. A parametric sensitivity analysis was carried out using the validated computer model in order to assess the influence of conventional suspension parameters on the ride performance of the test vehicle. In addition, the ride performance potentials of an alternate hydrogas suspension configuration were investigated.