This paper deals with friction-induced vibration of a disc brake system with a constant friction coefficient. A linear, lumped, and distributed parameter model to represent the floating caliper disc brake system is proposed. The complex eigenvalues are used to investigate the dynamic stability, and, in order to verify simulations which are based on the theoretical model, an experimental modal test and dynamometer test are performed. The comparison of experimental and theoretical results shows good agreement, and the analysis indicates that modal coupling due to friction forces is responsible for disc brake squeal. Also, squeal type instability is investigated, using a parametric analysis. This indicates which parameters have influence on the propensity of brake squealing. This is helpful for validating the analysis model and establishing confidence in the experimental results of the modified system. These results may also be useful during system development or diagnostic analysis.
Human hearing is very sensitive to sound, so a subjective index of sound quality is required. Each situation of sound evaluation is composed of Sound Quality (SQ) metrics. When substituting the level of one frequency band, we could not see the tendency of substitution at the whole frequency band during SQ evaluation. In this study, the Design of Experiments (DOE) is used to analyze noise from an automotive Heating, Ventilating, and Air Conditioning (HVAC) system. The frequency domain is divided into 12 equal parts, and each level of the domain is given an increase or decrease due to the change in frequency band based on the "loud" and "sharp" sound of the SQ analyzed. By using DOE, the number of tests is effectively reduced by the number of experiments, and the main result is a solution at each band. SQ in terms of the "loud" and "sharp" sound at each band, the change in band (increase or decrease in sound pressure) or no change in band will have the most effect on the identifiable characteristics of SQ. This will enable us to select the objective frequency band. Through the results obtained, the physical level changes in arbitrary frequency domain sensitivity can be determined.
A dynamic model of a gaseous-fuel engine is developed in order to design an engine control system. This model includes estimation methods of dynamic characteristics to be affected by components in mixture. An effective air mass ratio is defined as air mass flow divided by mixture mass flow, and is proposed to predict variations of the air flow, manifold pressure and the air-fuel ratio according to the water vapour and the gaseous fuel in the mixture. The dynamic engine model is validated with a liquefied petroleum gas (LPG) engine-dynamometer under steady and transient operating conditions. Experimental results from an LPG gaseous-fuel engine show that estimation of the airflow and the air-fuel ratio based upon the effective air mass ratio is more accurate than that of a normal engine model.
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