Military vehicles have to travel, at least from time to time, on the national road network. Whenever that happens, the legal requirements have to be met with respect to the systems that contribute to the traffic safety. One of these systems is the braking system. On the other hand, most of the military vehicles arent that up-to-date that the rest of the traffic partners are. Therefore, a military automotive engineer should have at hand a fast method to diagnose the technical status of the braking system even the checked vehicle is rather old. It would be also even better if the faulty party were accurately identified. The paper aims at providing a method helps the diagnosing teams to quickly compare the behaviour of an actual vehicle braking system status with a general model that had been acquired by tests. Since nobody provided that kind of information during 70s, our model derived from a large number of tests that have been performed on good technical condition vehicles. Key words: vehicle braking system, parametric models, data-based models.
Present paper focuses on the power circuits within planetary gearboxes, providing an original mathematical model. This model is an excellent instrument to analyze and determine the torque, angular speed, power factors, global gear ratios and efficiency distribution. The analysis itself has been developed for the second-gear, forward-motion of the gearbox. The analysis provides the mathematical model of the gearboxs way of working both in the static and dynamic modes. The method starts with issuing the equivalent graph (network structure) of the gearbox. Using this model, the gearbox is associated to a power driveline network that both transforms and guides the power flow to the final transmission of the vehicle. Using the network structural model, the gearbox turns into a general nodal diagram (graph). Our study concerned both the static and dynamic modes. It consists in a mathematical determination of the cinematic (angular speed) and dynamic (torque) factors that charge the gearboxs components. The mathematical model takes into account the power losses and the inertia occurring within the entire network and their influences upon the general power distribution. Using the model, we could get accurate results of the torque and power distribution. Moreover, the model provides the map of the power distribution when the gearbox works in its second gear, emphasizing the difference between the analysis performed for the two above mentioned working regimes (static and dynamic). The results can be further used as entry points for a much more complex mathematical model that describes the dynamic features of the vehicle.
Military vehicles have to travel, at least from time to time, on the national road network. Whenever that happens, the A military vehicle doesnt have to meet all the requirements of a civilian vehicle. Moreover, its lifecycle is much longer than a civilian vehicles one. This is the reason a military vehicle doesnt have to meet all the requirements that a civilian one has to. Nevertheless, traffic security asks for periodical checks of the braking, steering and other systems. In this respect, we have been contracted to develop a method to assess the braking systems parameter of a certain class of military vehicles. When an assessment is involved, we usually develop a basic mathematical model to be the basic feature for further investigation. Since for the old vehicles there are no database, we have created two models, one by numerical simulation and the other one by processing the experimental data. Should be mentioned that prior to use one of them for further analysis, we had to check for the models accuracy. Data have been achieved using a very up-to-date measuring system. Moreover, the data was subject to filtering procedures, taking into account the noises of the system and different other measuring errors. We have tested several vehicles that were in good technical condition. All in all, we have tried to create a reliable database that should stand back from a trusting point of view. The working characteristic features of a process can be synthetically expressed as a mathematical model. For the technical systems, this model can be obtained either based on the mathematical expressions that describe the working way of the systems components or on data-base grounds that have been previously achieved throughout experimental research. As far as the validation of the mathematical model is concerned, the modelling error should be kept under tight control. Therefore, the researcher has to permanently determine the difference between either the simulated and measured output parameters. Eventually, the validated mathematical model can be used to analyse the dynamic performances of the system or a proper way to improve them, as far as the actual evolution of the system is accurately enough described. Key words: vehicles, braking system, theoretical models, data based models, modelling error
This paper presents an analysis for the longitudinal loop power flow of a 4x4 driven vehicle type taking into consideration the influence of the running track. The goal set up by this paper is to experimentally verify the existence of a certain dependency between the longitudinal loop power flow and the type of the running track the vehicle is moving on. Such a determination could have a positive impact by optimizing the vehicle exploitation or even its modernization. The loop power-flow is the result of the self-generated torque within the automobiles transmission, which is, at its turn, a consequence of cinematic misfits during the rolling process of the wheels. The mathematical model stated in this paper is confirmed by the means of multiple tests developed in real conditions. In order to carry out experimental research we used an all-driven, wheeled military APC, reconnaissance vehicle. The longitudinal power flow was determined with the vehicle moving in straight motion but having different rolling radius between the axles. The rolling radii of the wheels of the same axle were the same. The difference between the rolling radii was set to 0.03 m then to 0.05 m. The vehicle traveled on tarmac then on grass. The transmission of a vehicle that is susceptible in generating loop power-flow can be updated to decrease and technically eliminate it. Prior to such an update, a thorough analysis of the transmission working regimes should be performed, especially of those regimes that are most probable to generate loop power-flow. The paper presents the equipment used to perform the measurements and the way it was mounted on the vehicle. It also presents the values for the longitudinal power flow, recorded for both rolling radii differences. The results are presented in graphic display. Eventually, the paper presents the longitudinal power flow taking into account the difference between the rolling radii and its dependency towards the running tracks type. This study can be extended to all the 4WD automobiles, which have special traction control devices. The results obtained were processed in order to underline the power loops within the longitudinal transmission. Thus, important and interesting results could be drawn.
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