The electrification of vehicles has caused a great change in the characteristics of noise, vibration and harshness. A rangeextended electric vehicle has complicated noise and vibration problems because it behaves both like a traditional vehicle and like a battery electric vehicle as well as having its own specific noise, vibration and harshness properties. Therefore, increasing attention should be paid to these issues. This paper is intended as a contribution to the current research on the noise, vibration and harshness of a range-extended electric vehicle. The electric driveline, the auxiliary power unit and the accessories, including the power steering pump, the electric vacuum pump and the air conditioner compressor, are tested and their noise, vibration and harshness performances are analysed. The results indicate that the highfrequency noise of the electric driveline and the vibrations of the auxiliary power unit and the air conditioner compressor are crucial noise, vibration and harshness issues of a range-extended electric vehicle. Some improvement methods are implemented or proposed for better comfort in the passenger compartment. Application of a material which is sound insulating and sound absorbing proved to be an effective countermeasure. The design and refinement of a vibration isolation system for the auxiliary power unit and the air conditioner compressor are of great importance. A reduction in the low-frequency torsional resonance of the auxiliary power unit shaft during a start-stop process is a new problem compared with that of a conventional engine. It is necessary to find a well-balanced compromise between the expected acoustic feedback and the power demand.
A perforated resonator can attenuate the broadband noise generated by the air intake system of a turbocharged engine. This paper mainly focuses on the sound transmission theory of a perforated resonator with a multi-chamber. The numerical decoupling method for a perforated resonator with a single chamber is extended to a perforated resonator with a multi-chamber in order to calculate the transmission loss. To verify the modified algorithm, a two-microphone method is adopted to measure the transmission loss of the resonator. The measurement uncertainty of the experiment is discussed further. The experimental and analytical results on the resonator are presented, and good agreement is found. To determine the optimal structural parameters of the resonator in order to match the given target, a modified algorithm obtained by using the non-linear least-squares method is proposed for the resonator, and a detailed analysis of the selection of the design variables and optimization modes with different design variables is carried out. The optimized results show that all optimization modes can meet the target curve. Therefore, it provides multiple solutions for researchers to determine flexibly the best solution. Finally, a robustness analysis is carried out to show that the variations in the structural parameters have little effect on the transmission loss. It is expected that the research methods and conclusions of the study can provide theoretical support and application guidance for the sound design of a turbocharged engine air intake system.
Sudden torque changes and torque fluctuations caused by a traction motor in HEV (hybrid electric vehicle) can result in a driveline oscillation. This paper focuses on the HEV launch vibration in pure electric mode while only the electric motor is generating output torque. A relevant mathematical model has been built based on the working principle. According to the model, the torsional vibration characteristics of the electric propulsion system have been analyzed. Two active control methods, feed-forward control (FFC) and pole placement (PP) have been applied to suppress the HEV launch vibration. However, such longitudinal vibration may still be perceived by passengers, though they can attenuate the vibration to some extent. Therefore another method, wave superposition control strategy (WSCS), has been proposed to suppress the vibration more effectively. In order to prove the control effectiveness of WSCS, all these three active control methods have been applied in simulation for a comprehensive comparison of the vibration suppression effect. Simulation results demonstrate that compared with FFC and PP, WSCS minimizes the overshoot of wheel angular acceleration (WAA) most and doesn't have much effect on the system response quickness, which can be regarded as the most effective control method.
Because of the higher requirements for vehicle comfort and people's increasing ecological consciousness, research on the interior noise in a vehicle has received wide concern, among which structure-borne noise is hard to diagnose and control. To solve the problem, the transfer path analysis method of powertrain structure-borne noise has been systematically analysed. By introduction of the powertrain source-path-receiver model, this method enables us to estimate and study the vibro-acoustic transfer functions and their operational forces. Since structure-borne noise is composed of multiple paths, the aim of this paper is to discuss different synthesis methods for this noise. On the basis of previous discussion, the transfer path analysis test of a certain vehicle is carried out, and the transfer function and operational data at idle and second-gear wide-open throttle are obtained. The test data are processed and an acoustic contribution analysis of the target is performed using LMS software. The results of analysis show that the right-hand side mount represents the main contribution path. Then the match principle of the bracket dynamic stiffness of the powertrain isolation system is proposed. On the basis of the transfer path analysis results and the above principle, the bracket on the body side of the right-hand side mount is improved by combination of the experimental transfer path analysis and the finite element method. The test results show that the A-weighted sound pressure level of the interior noise at idle and second-gear wide-open throttle are reduced by 2.9 dB(A) and 4 dB(A) respectively after improvement. Also there is no obvious booming noise at second-gear wide-open throttle. It is expected that this paper can help automotive noise, vibration and harshness engineers to perform trouble shooting and sound design.
An active engine mount (AEM) is an effective technology to improve a vehicle’s noise, vibration, and harshness performance. This paper mainly focuses on the combination experiment and finite element analysis (FEA) for parameter identification of AEMs. Notably, a novel test rig is designed to identify all specific parameters involved in the AEM. Firstly, the static and dynamic stiffness of the main rubber spring are calculated based on structure FEA method. The equivalent piston area and upper chamber volumetric stiffness are also estimated through fluid–structure interaction analysis. Inertia track parameters, involving inertia and linear and nonlinear resistance of the fluid, are identified by a simplified fluid model. These common hydraulic engine mount parameters are all experimentally validated through the original test rig. Besides, the particular components of the electromagnetic AEM, namely actuator parameters, are further estimated by experimental identification utilizing the experimental apparatus. The novel test bench, which exhibited high accuracy, good tightness, and strong versatility, not only simplifies the structure and process of identification plant for passive engine mount parameters, but accommodates the particular AEM ones. The combination method assimilates both the efficiency of FEA and the accuracy of experiment, facilitating the structure design and renovation of AEMs.
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