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.
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.
Abstract. We present an electrical caterpillar autonomous robot demonstrator, which consists of two independent tracks with an operational platform, a system with photovoltaic panels for converting solar energy into electricity, and a system for connecting different devices to the robot chassis. One goal is to reduce operational costs in terms of fulfilling the missions and maintaining safe human operations in unfriendly environments. Other goals, imbedded in the demonstrator's design, are: mobility, lowered energy consumption, the usage of ecological energy, and an increased energetic independence. These characteristics would allow the development of a class of robots that may be used in unfriendly and isolated areas, in which solar energy is adequate. Yet another goal is to develop a database documenting how the demonstrator operates under various conditions.
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