This paper concerns the development of a set of simulating models able to assess gear sets. The m... more This paper concerns the development of a set of simulating models able to assess gear sets. The modeled gear set is an intermediate gear drive, a component of the drive line of a military armored tracked vehicle. It is responsible of transferring the power from the vehicle’s engine to the hydraulic torque converter of the hydro-mechanical transmission of the vehicle. The intermediate gear drive has been modeled with the aid of a specialized simulation module of Matlab® programming environment. The components of the intermediate gear drive make energetic network, able to reproduce both the physical structure and the real working mode within the basic system. The paper concludes by comparing the dynamic performances of the tracked vehicle for both the options: with the basic layout of the intermediate gear drive and the suggested one within the developed simulating operations.
Military vehicles have to travel, at least from time to time, on the national road network. Whene... more 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
The paper presents a possible method to diagnose a mechanical fault of an automotive system. Seve... more The paper presents a possible method to diagnose a mechanical fault of an automotive system. Several experimental tests have been developed aiming at determining the actual performances of a military vehicle's braking system. During data processing procedures, some unusual but also systematic noises occurred. As a main issue at this point, the source of the noise should have been identified and filtered if necessary. In this respect, a thorough analysis was developed, starting with a frequency analysis. In the end, the mechanical fault has been identified and the useful signal could be separated from the accompanying noise.
The simulation procedure has always been considered as a giant leap forward, especially in the fi... more The simulation procedure has always been considered as a giant leap forward, especially in the field of basic designing of a product. There is nothing new underneath the basic concept, but the scientific and technical progress always brings up new techniques that improve simulation in its whole. When we talk about a vehicle, especially about a military one, we consider that it is much cheaper to simulate a process involving the weapon system than performing countless tests that are rather expensive. In this respect, we tried to develop a simulation mathematical model, check its accuracy with a set of extensive tests, prove it reliability and further extrapolate the behavior of the simulated model to a larger number of military vehicles of the same kind. It could help in various fields, such as diagnose (by comparing the simulated results with the real ones got from a faulty vehicle) or automatically regulating some functions (an intelligent vehicle, having an implemented, simulated model, that is able to feel the status of a subsystem in real time and regulate its behavior, accordingly). Hence, the paper presents a model that simulates the longitudinal dynamics of a tracked vehicle. It has been issued using Simulink module of Matlab programming environment. It aims at pointing out the performances of the vehicle. The models interface is friendly and its structure is modular. The main modules of the model are the engine, the torque converter, the transmission and the track. The engine and the torque converter are modeled using the experimental maps obtained by the tests that have been previously developed by the manufacturer. The main principle of the equations that describe the system is to set a balance among the forces (both active and resistive) that load the vehicle. The inputs of the model are the technical and dimensional features, provided by the manufacturer or experimentally determined. The output of the model is a dynamic behavior. Comparing the results with the experimental data eventually validates or invalidates the model. But the results were excellent, so the model was validated. Also, the results proved that the developed model is able to predict the performances of the take-off stage of the tracked vehicle.
This paper presents an analysis for the longitudinal loop power flow of a 4x4 driven vehicle type... more 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.
Present paper aims at revealing a way to determine the cinematic misfit within a 4x4 vehicle’s in... more Present paper aims at revealing a way to determine the cinematic misfit within a 4x4 vehicle’s inter-axle driveline, which is eventually the reason of the self-generated torque occurrence. We used experimental methods to determine the magnitude of the cinematic misfit. Within this frame, we used a vehicle that has a longitudinal (inter-axle) differential and we locked it, actually forcing the longitudinal transmission to work without differentiating the angular speeds on its output shafts. On the other hand, the tire radii were different, inducing the above-mentioned cinematic misfit that we were looking for. We also present the way we fit the transducers on the vehicle’s driveline components to measure the needed parameters. The paper also presents some theoretical considerations regarding the occurrence of the cinematic misfit and its way of generating closed power loops within the vehicle’s transmission.
This work is dealing with the self-generated torque that occurs within a 4WD military special aut... more This work is dealing with the self-generated torque that occurs within a 4WD military special automotive drivetrain. The mathematical model stated in this paper is confirmed by the means of multiple tests developed in real conditions. The tests were developed in order to reveal both transversal and longitudinal self-generated torque within the drivetrain, on different road surfaces. The present paper also introduces some new concepts, such is for instance the insensitive domain of a self-locking (or a progressively locking) differential. With the aid of this concept we can easier deal with the self-generated torque that is due to the increased internal friction of the differential. Moreover, a general, comprehensive theory can be further issued that could classify the self-locking differentials according to their internal friction and their locking coefficient variation.
This paper is a result of a research focused on statistical vehicles dynamics. Its main purpose i... more This paper is a result of a research focused on statistical vehicles dynamics. Its main purpose is to establish mathematical description of vehicle dynamics based on statistically sufficient experimental data and using statistical instruments. The results are analytical expressions and graphical representations that can be used in situations other than those the data were obtained. Experimental research program objective was to obtain a variety of data to define the dynamics of a vehicle. It involved a large number of tests, more than 100, on different runways, pavement, mosaic tiles or asphalt. They were performed in various weather conditions, sunny and warm weather or rain or sleet and snow. The driving style varied between normal and sport ones. The experimental data were used in obtaining mathematical models that define certain dependency between dynamic parameters. There were issued multiple linear regressions with one resulting parameter. If we analyzed the models we issued we notice that the more factorial parameters are involved, the higher the accuracy of the model we get.
This paper presents an analysis that aims at identifying the interdependence between the wheels s... more This paper presents an analysis that aims at identifying the interdependence between the wheels slip and the self-generated torque that occurs at the inter-axle level of a 4x4 automobiles driveline. We consider that this paper has a high degree of novelty since it succeeds in establishing causality relationships between different automotive typical parameters. Moreover, the paper provides the specific mathematical, theoretical equations as well as an example of a generalized mathematical model derived from time or frequency analysis.The theoretical mathematical elements consist of terms referring to the rigid wheels kinematics and specific working conditions of the vehicle when it runs with tire radii differences at the inter-axle level. To achieve the goal of our work we developed a large experimental research work that involved an extended instrumentation of an all-wheel driven military vehicle in such a manner that allowed getting information concerning different shafts torque and angular speed. The vehicle has transfer case, involving a longitudinal differential. The tests were developed with the locking device of the differential working in the engaged mode. Aiming at revealing the connection between the tire radii and the self-generated torque, we have subjected the vehicle to different tire radii running modes. The rolling radius of the wheels that were on the same axle was the same. The bigger the tire radii difference the bigger the self-generated torque; hence the interdependence started to reveal itself as far as the tire slip also followed the behavior of the self-generated torque. In order to determine the wheels slip we also measured the vehicles speed with a GPS. The results are graphically presented.Following the results of the data processing stage, we concluded that the interdependence between wheels slip and the self-generated torque exists and a relationship between these two phenomena can be mathematically expressed, using a generalized model. We consider that a kind of model like this proves its utility in simulating similar conjectures; thus, the experimental research effort can be significantly reduced either by lacking either in torque measuring or wheels slip measuring. Such a determination could have a positive impact by optimizing the vehicle exploitation or even its modernization.
Present paper focuses on the power circuits within planetary gearboxes, providing an original mat... more 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.
The paper presents a possible method to diagnose a mechanical fault of an automotive system. Star... more The paper presents a possible method to diagnose a mechanical fault of an automotive system. Starting from the point of view that every fault of a mechanical system should introduce an abnormal component within the signal that describes the time history of a mechanical parameter we tried to find a way to reveal it.We were performing some tests involving a military vehicle with respect to the performances of its braking system. The tests were aiming at identifying a way to bring up-to-date the old weapon system from the braking systems point of view. During these tests we observed some anomalies concerning the pressure evolution within the braking cylinders of the vehicle. Some unusual but also systematic noises occurred. As a main issue at this point, the source of the noise should have been identified and filtered if necessary. We had to decide whether the noisy component of the signal is just a noise that should be removed by filtering the signal or it is a physical component of the mechanical parameter itself (not noise but a useful information).These procedures take time and they also request accurate knowledge as well as fine expertise in automotive testing. Since our Dept. has a long and rich practice in this respect, we assumed to processing data and give them a thorough interpretation. So, the first thing we did was to perform a frequency analysis, using classical methods. Usually, a simple frequency analysis cant provide information about a time variation of the frequency spectra due to the Fourier Transforms behavior, since it freezes the signal in time. A much more accurate analysis is the time-frequency analysis. However, observing both the amplitude and power spectra can lead to a useful conclusion. We concluded that the noise we met within the signal is due to the brake drums loss of circular shape (they turned into an oval, the process being known as ovalization). Hence, we cant talk about a noise as it is usually defined.
This paper is the result of a research program which focused on the statistical dynamics of vehic... more This paper is the result of a research program which focused on the statistical dynamics of vehicles. Most of the inputs of man-machine-field system have a random variation, so a systemic and statistical analysis of vehicle dynamics is obvious. In our study, data were obtained by measuring the dynamic parameters of vehicles and engines. Testing program aimed to capture a large range of operating regimes. To analyze the data the authors have used neural networks. There was adopted aNNARX(NeuralNetworkAuto-Regressive with eXogene inputs) model with 4 inputs, 5 hidden units and 1 output. It can be concluded that the development of mathematical modeling using non-linear neural network can ensure the desired accuracy, conveniently is obtained by increasing the number of neurons in the hidden laws.
Military heavy vehicle drivers experience low-frequency vibrations that are associated with fatig... more Military heavy vehicle drivers experience low-frequency vibrations that are associated with fatigue, drowsiness, and other adverse health effects. The existing research papers focus on performing different types of analysis, but few use advance signal processing tools based on recurrence plot representation; therefore, the main goal of this paper is to assess the whole-body vibration (WBV) and hand-arm vibration (HAV) exposure of a driver, comparing armoured personnel carriers and cargo destined vehicles. For this purpose, the power of a signal distributed over its frequency was analysed using power spectral density (PSD) and diagonal line quantification (DLQ) analysis. According to the results, in the case of the cargo vehicle, the driver experienced vibration dose values of frequency weighted acceleration above the limits during all three experimental tests, with a maximum value of 26.802 m/s2, whereas the results in the case of the armoured personnel carrier are below the 5 m/s2 ...
In the case where one intends to reveal the torque distribution onto the elements of a planetary ... more In the case where one intends to reveal the torque distribution onto the elements of a planetary gearbox, issuing a virtual model is previously needed. This model should replicate both the physical structure and the real working behavior. The torque is transmitted along the gearbox through the intermediary of three simple planetary mechanisms by successively locking different components with the aid of some multi-plate clutches. The simulation of the friction element’s engagement is achieved by introducing a physical signal that replaces the pressure of the hydraulic command system. The pressure evolution has been previously experimentally determined, during the vehicle’s taking-off procedure. The friction elements are modeled considering their three working stages: fully disengaged, partially engaged and fully engaged. The torque distribution is modeled starting from the energy conservation law as well as the torque balance law.
This paper is a result of a research focused on statistical vehicles dynamics. Its main purpose i... more This paper is a result of a research focused on statistical vehicles dynamics. Its main purpose is to establish mathematical description of vehicle dynamics based on statistically sufficient experimental data and using statistical instruments. The results are analytical expressions and graphical representations that can be used in situations other than those the data were obtained. Experimental research program objective was to obtain a variety of data to define the dynamics of a vehicle. It involved a large number of tests, more than 100, on different runways, pavement, mosaic tiles or asphalt. They were performed in various weather conditions, sunny and warm weather or rain or sleet and snow. The driving style varied between normal and sport ones. The experimental data were used in obtaining mathematical models that define certain dependency between dynamic parameters. There were issued multiple linear regressions with one resulting parameter. If we analyzed the models we issued w...
The working characteristic features of a process can be synthetically expressed as a mathematical... more The working characteristic features of a process can be synthetically expressed as a mathematical model. For the technical systems, this model can be obtained based on the mathematical expressions that describe the working way of the system’s components. The 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. The paper makes an analysis using modelling and simulating techniques of a special clutch servomechanism. The modern simulation software allows studying the complex automotive systems; at the same time allows the fast variation of the system’s parameters and the study of all modifications that appear within the working system.Some of dynamic charts are presented and improvement of the dynamic performances methods are given.
IOP Conference Series: Materials Science and Engineering, 2022
The present paper aims to analyze the influence of certain parameters specific to the distributio... more The present paper aims to analyze the influence of certain parameters specific to the distribution systems on a truck engine performance. The research is focused on how the change in the shape of lobes of a camshaft can influence the vehicle functional parameters. It was considered a non-variable fuel distribution system which represents by itself the controlling part, needed to move the poppet valves in order to ensure engine operating cycles. There have been compared results obtained in the case of different profiles of lobes, taking into account the accelerations during movements, in order to obtain minimum inertia of the distribution system components. By increasing the total height of the lobes, it was observed an increase in engine power and torque. Also, the intake air efficiency was improved by approximately 4%. Furthermore, engine fuel consumption reached higher levels in the case of the modified camshaft, in order to increase engine power.
IOP Conference Series: Materials Science and Engineering, 2022
The present paper aims to analyse the possibility to prevent machine failure due to bearing fault... more The present paper aims to analyse the possibility to prevent machine failure due to bearing faults, with the use of frequency analysis. The experimental research consisted in mounting a simple mechanical transmission, integrating an electric motor, a rigid coupling, a driven shaft, two pillow block bearings and a uniaxial accelerometer (connected to a data acquisition board), which was tested at two constant motor speeds. Follow-up, with the use of recorded data, it was plotted the envelope spectrum of bearing functioning, based on BPFO, BPFI, FTF and BSF harmonics, which were later used to determine on which element of the bearing is the defect located, or if the bearing lacks proper greasing.
This paper concerns the development of a set of simulating models able to assess gear sets. The m... more This paper concerns the development of a set of simulating models able to assess gear sets. The modeled gear set is an intermediate gear drive, a component of the drive line of a military armored tracked vehicle. It is responsible of transferring the power from the vehicle’s engine to the hydraulic torque converter of the hydro-mechanical transmission of the vehicle. The intermediate gear drive has been modeled with the aid of a specialized simulation module of Matlab® programming environment. The components of the intermediate gear drive make energetic network, able to reproduce both the physical structure and the real working mode within the basic system. The paper concludes by comparing the dynamic performances of the tracked vehicle for both the options: with the basic layout of the intermediate gear drive and the suggested one within the developed simulating operations.
Military vehicles have to travel, at least from time to time, on the national road network. Whene... more 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
The paper presents a possible method to diagnose a mechanical fault of an automotive system. Seve... more The paper presents a possible method to diagnose a mechanical fault of an automotive system. Several experimental tests have been developed aiming at determining the actual performances of a military vehicle's braking system. During data processing procedures, some unusual but also systematic noises occurred. As a main issue at this point, the source of the noise should have been identified and filtered if necessary. In this respect, a thorough analysis was developed, starting with a frequency analysis. In the end, the mechanical fault has been identified and the useful signal could be separated from the accompanying noise.
The simulation procedure has always been considered as a giant leap forward, especially in the fi... more The simulation procedure has always been considered as a giant leap forward, especially in the field of basic designing of a product. There is nothing new underneath the basic concept, but the scientific and technical progress always brings up new techniques that improve simulation in its whole. When we talk about a vehicle, especially about a military one, we consider that it is much cheaper to simulate a process involving the weapon system than performing countless tests that are rather expensive. In this respect, we tried to develop a simulation mathematical model, check its accuracy with a set of extensive tests, prove it reliability and further extrapolate the behavior of the simulated model to a larger number of military vehicles of the same kind. It could help in various fields, such as diagnose (by comparing the simulated results with the real ones got from a faulty vehicle) or automatically regulating some functions (an intelligent vehicle, having an implemented, simulated model, that is able to feel the status of a subsystem in real time and regulate its behavior, accordingly). Hence, the paper presents a model that simulates the longitudinal dynamics of a tracked vehicle. It has been issued using Simulink module of Matlab programming environment. It aims at pointing out the performances of the vehicle. The models interface is friendly and its structure is modular. The main modules of the model are the engine, the torque converter, the transmission and the track. The engine and the torque converter are modeled using the experimental maps obtained by the tests that have been previously developed by the manufacturer. The main principle of the equations that describe the system is to set a balance among the forces (both active and resistive) that load the vehicle. The inputs of the model are the technical and dimensional features, provided by the manufacturer or experimentally determined. The output of the model is a dynamic behavior. Comparing the results with the experimental data eventually validates or invalidates the model. But the results were excellent, so the model was validated. Also, the results proved that the developed model is able to predict the performances of the take-off stage of the tracked vehicle.
This paper presents an analysis for the longitudinal loop power flow of a 4x4 driven vehicle type... more 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.
Present paper aims at revealing a way to determine the cinematic misfit within a 4x4 vehicle’s in... more Present paper aims at revealing a way to determine the cinematic misfit within a 4x4 vehicle’s inter-axle driveline, which is eventually the reason of the self-generated torque occurrence. We used experimental methods to determine the magnitude of the cinematic misfit. Within this frame, we used a vehicle that has a longitudinal (inter-axle) differential and we locked it, actually forcing the longitudinal transmission to work without differentiating the angular speeds on its output shafts. On the other hand, the tire radii were different, inducing the above-mentioned cinematic misfit that we were looking for. We also present the way we fit the transducers on the vehicle’s driveline components to measure the needed parameters. The paper also presents some theoretical considerations regarding the occurrence of the cinematic misfit and its way of generating closed power loops within the vehicle’s transmission.
This work is dealing with the self-generated torque that occurs within a 4WD military special aut... more This work is dealing with the self-generated torque that occurs within a 4WD military special automotive drivetrain. The mathematical model stated in this paper is confirmed by the means of multiple tests developed in real conditions. The tests were developed in order to reveal both transversal and longitudinal self-generated torque within the drivetrain, on different road surfaces. The present paper also introduces some new concepts, such is for instance the insensitive domain of a self-locking (or a progressively locking) differential. With the aid of this concept we can easier deal with the self-generated torque that is due to the increased internal friction of the differential. Moreover, a general, comprehensive theory can be further issued that could classify the self-locking differentials according to their internal friction and their locking coefficient variation.
This paper is a result of a research focused on statistical vehicles dynamics. Its main purpose i... more This paper is a result of a research focused on statistical vehicles dynamics. Its main purpose is to establish mathematical description of vehicle dynamics based on statistically sufficient experimental data and using statistical instruments. The results are analytical expressions and graphical representations that can be used in situations other than those the data were obtained. Experimental research program objective was to obtain a variety of data to define the dynamics of a vehicle. It involved a large number of tests, more than 100, on different runways, pavement, mosaic tiles or asphalt. They were performed in various weather conditions, sunny and warm weather or rain or sleet and snow. The driving style varied between normal and sport ones. The experimental data were used in obtaining mathematical models that define certain dependency between dynamic parameters. There were issued multiple linear regressions with one resulting parameter. If we analyzed the models we issued we notice that the more factorial parameters are involved, the higher the accuracy of the model we get.
This paper presents an analysis that aims at identifying the interdependence between the wheels s... more This paper presents an analysis that aims at identifying the interdependence between the wheels slip and the self-generated torque that occurs at the inter-axle level of a 4x4 automobiles driveline. We consider that this paper has a high degree of novelty since it succeeds in establishing causality relationships between different automotive typical parameters. Moreover, the paper provides the specific mathematical, theoretical equations as well as an example of a generalized mathematical model derived from time or frequency analysis.The theoretical mathematical elements consist of terms referring to the rigid wheels kinematics and specific working conditions of the vehicle when it runs with tire radii differences at the inter-axle level. To achieve the goal of our work we developed a large experimental research work that involved an extended instrumentation of an all-wheel driven military vehicle in such a manner that allowed getting information concerning different shafts torque and angular speed. The vehicle has transfer case, involving a longitudinal differential. The tests were developed with the locking device of the differential working in the engaged mode. Aiming at revealing the connection between the tire radii and the self-generated torque, we have subjected the vehicle to different tire radii running modes. The rolling radius of the wheels that were on the same axle was the same. The bigger the tire radii difference the bigger the self-generated torque; hence the interdependence started to reveal itself as far as the tire slip also followed the behavior of the self-generated torque. In order to determine the wheels slip we also measured the vehicles speed with a GPS. The results are graphically presented.Following the results of the data processing stage, we concluded that the interdependence between wheels slip and the self-generated torque exists and a relationship between these two phenomena can be mathematically expressed, using a generalized model. We consider that a kind of model like this proves its utility in simulating similar conjectures; thus, the experimental research effort can be significantly reduced either by lacking either in torque measuring or wheels slip measuring. Such a determination could have a positive impact by optimizing the vehicle exploitation or even its modernization.
Present paper focuses on the power circuits within planetary gearboxes, providing an original mat... more 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.
The paper presents a possible method to diagnose a mechanical fault of an automotive system. Star... more The paper presents a possible method to diagnose a mechanical fault of an automotive system. Starting from the point of view that every fault of a mechanical system should introduce an abnormal component within the signal that describes the time history of a mechanical parameter we tried to find a way to reveal it.We were performing some tests involving a military vehicle with respect to the performances of its braking system. The tests were aiming at identifying a way to bring up-to-date the old weapon system from the braking systems point of view. During these tests we observed some anomalies concerning the pressure evolution within the braking cylinders of the vehicle. Some unusual but also systematic noises occurred. As a main issue at this point, the source of the noise should have been identified and filtered if necessary. We had to decide whether the noisy component of the signal is just a noise that should be removed by filtering the signal or it is a physical component of the mechanical parameter itself (not noise but a useful information).These procedures take time and they also request accurate knowledge as well as fine expertise in automotive testing. Since our Dept. has a long and rich practice in this respect, we assumed to processing data and give them a thorough interpretation. So, the first thing we did was to perform a frequency analysis, using classical methods. Usually, a simple frequency analysis cant provide information about a time variation of the frequency spectra due to the Fourier Transforms behavior, since it freezes the signal in time. A much more accurate analysis is the time-frequency analysis. However, observing both the amplitude and power spectra can lead to a useful conclusion. We concluded that the noise we met within the signal is due to the brake drums loss of circular shape (they turned into an oval, the process being known as ovalization). Hence, we cant talk about a noise as it is usually defined.
This paper is the result of a research program which focused on the statistical dynamics of vehic... more This paper is the result of a research program which focused on the statistical dynamics of vehicles. Most of the inputs of man-machine-field system have a random variation, so a systemic and statistical analysis of vehicle dynamics is obvious. In our study, data were obtained by measuring the dynamic parameters of vehicles and engines. Testing program aimed to capture a large range of operating regimes. To analyze the data the authors have used neural networks. There was adopted aNNARX(NeuralNetworkAuto-Regressive with eXogene inputs) model with 4 inputs, 5 hidden units and 1 output. It can be concluded that the development of mathematical modeling using non-linear neural network can ensure the desired accuracy, conveniently is obtained by increasing the number of neurons in the hidden laws.
Military heavy vehicle drivers experience low-frequency vibrations that are associated with fatig... more Military heavy vehicle drivers experience low-frequency vibrations that are associated with fatigue, drowsiness, and other adverse health effects. The existing research papers focus on performing different types of analysis, but few use advance signal processing tools based on recurrence plot representation; therefore, the main goal of this paper is to assess the whole-body vibration (WBV) and hand-arm vibration (HAV) exposure of a driver, comparing armoured personnel carriers and cargo destined vehicles. For this purpose, the power of a signal distributed over its frequency was analysed using power spectral density (PSD) and diagonal line quantification (DLQ) analysis. According to the results, in the case of the cargo vehicle, the driver experienced vibration dose values of frequency weighted acceleration above the limits during all three experimental tests, with a maximum value of 26.802 m/s2, whereas the results in the case of the armoured personnel carrier are below the 5 m/s2 ...
In the case where one intends to reveal the torque distribution onto the elements of a planetary ... more In the case where one intends to reveal the torque distribution onto the elements of a planetary gearbox, issuing a virtual model is previously needed. This model should replicate both the physical structure and the real working behavior. The torque is transmitted along the gearbox through the intermediary of three simple planetary mechanisms by successively locking different components with the aid of some multi-plate clutches. The simulation of the friction element’s engagement is achieved by introducing a physical signal that replaces the pressure of the hydraulic command system. The pressure evolution has been previously experimentally determined, during the vehicle’s taking-off procedure. The friction elements are modeled considering their three working stages: fully disengaged, partially engaged and fully engaged. The torque distribution is modeled starting from the energy conservation law as well as the torque balance law.
This paper is a result of a research focused on statistical vehicles dynamics. Its main purpose i... more This paper is a result of a research focused on statistical vehicles dynamics. Its main purpose is to establish mathematical description of vehicle dynamics based on statistically sufficient experimental data and using statistical instruments. The results are analytical expressions and graphical representations that can be used in situations other than those the data were obtained. Experimental research program objective was to obtain a variety of data to define the dynamics of a vehicle. It involved a large number of tests, more than 100, on different runways, pavement, mosaic tiles or asphalt. They were performed in various weather conditions, sunny and warm weather or rain or sleet and snow. The driving style varied between normal and sport ones. The experimental data were used in obtaining mathematical models that define certain dependency between dynamic parameters. There were issued multiple linear regressions with one resulting parameter. If we analyzed the models we issued w...
The working characteristic features of a process can be synthetically expressed as a mathematical... more The working characteristic features of a process can be synthetically expressed as a mathematical model. For the technical systems, this model can be obtained based on the mathematical expressions that describe the working way of the system’s components. The 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. The paper makes an analysis using modelling and simulating techniques of a special clutch servomechanism. The modern simulation software allows studying the complex automotive systems; at the same time allows the fast variation of the system’s parameters and the study of all modifications that appear within the working system.Some of dynamic charts are presented and improvement of the dynamic performances methods are given.
IOP Conference Series: Materials Science and Engineering, 2022
The present paper aims to analyze the influence of certain parameters specific to the distributio... more The present paper aims to analyze the influence of certain parameters specific to the distribution systems on a truck engine performance. The research is focused on how the change in the shape of lobes of a camshaft can influence the vehicle functional parameters. It was considered a non-variable fuel distribution system which represents by itself the controlling part, needed to move the poppet valves in order to ensure engine operating cycles. There have been compared results obtained in the case of different profiles of lobes, taking into account the accelerations during movements, in order to obtain minimum inertia of the distribution system components. By increasing the total height of the lobes, it was observed an increase in engine power and torque. Also, the intake air efficiency was improved by approximately 4%. Furthermore, engine fuel consumption reached higher levels in the case of the modified camshaft, in order to increase engine power.
IOP Conference Series: Materials Science and Engineering, 2022
The present paper aims to analyse the possibility to prevent machine failure due to bearing fault... more The present paper aims to analyse the possibility to prevent machine failure due to bearing faults, with the use of frequency analysis. The experimental research consisted in mounting a simple mechanical transmission, integrating an electric motor, a rigid coupling, a driven shaft, two pillow block bearings and a uniaxial accelerometer (connected to a data acquisition board), which was tested at two constant motor speeds. Follow-up, with the use of recorded data, it was plotted the envelope spectrum of bearing functioning, based on BPFO, BPFI, FTF and BSF harmonics, which were later used to determine on which element of the bearing is the defect located, or if the bearing lacks proper greasing.
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Papers by Radu Vilau