Noise & Vibration Worldwide

This study proposes three vibration isolator modes of the seat designed by horizontal-parallel isolator (HPI), vertical-parallel isolator (VPI), and negative-stiffness isolator (NSI) for improving the vehicle seat’s comfort. The influence of the dynamic parameters of three vibration isolator models is then analyzed based on their three dynamic models. Their dynamic parameters have been then optimised for comparing the isolation performance of HPI, VPI, and NSI based on root-mean-square (RMS) accelerations in the vertical, pitch, and roll directions of the driver’s seat. Research shows that driver comfort has been insignificantly affected by dimensions whereas driver comfort has been greatly affected by dynamic parameters of three vibration isolator modes. Based on the optimized parameters of HPI, VPI, and NSI, the vertical comfort of the driver with the NSI has been improved better than that of both the HPI and VPI, conversely, the pitch comfort and roll comfort of the driver with the VPI has been improved better than that of both the HPI and NSI. In order to improve the comfort of the driver in three directions, the VPI should be combined with the NSI to design the seat isolator of vehicles.

In this paper, the experimental study of the asphalt paver is performed to assess the effect of the vibrational screed system’s operating parameters on the asphalt paver’s working performance. Then, the nonlinear dynamic models of the vibrational screed system and tamper system are built to assess in detail the effect of the working parameters of the vibrational screed system and optimise its working parameters to ameliorate the asphalt paver’s working performance. Both the vertical acceleration and angular acceleration of the vibrational screed system computed via their Root Mean Square (RMS _a ) value have been selected as the evaluation indexes. Results showed that the acceleration at the measured points has been unevenly distributed on the vibrational screed system’s length, thus, the working performance of the asphalt paver is quite low. With the vibrational screed system’s working parameters optimised, the average value of RMS _a with optimisation is increased by 7.67% whereas the average deviation of RMS _a between the measurement points with optimisation is greatly reduced by 34.2% in comparison without optimisation. Consequently, the working performance of the asphalt paver has obviously ameliorated.

The progression and refinement of traction electric motors play a pivotal role in the enhancement of vehicles. With constant advancements in power efficiency, diagnostic tools, and reliability, electric traction motors are becoming more economical in terms of operational costs. This article underscores the significance of methods used in assessing the technical proficiency of traction electric motors, coupled with their testing techniques. The vibration characteristics of these motors serve as a prime criterion in assessing their quality throughout their lifecycle – from design and manufacturing to operation. A groundbreaking proposition made in this article is the evaluation of electric traction motors’ health based on their vibration acceleration within an expansive frequency range of 5 Hz to 10 kHz. This contrasts the conventional approach which focuses on vibration speed in a restricted frequency spectrum up to 1000 Hz, as outlined by current standards. Such permissible vibration classes are essential in ensuring the high-quality design, technical finesse, and dependability of traction electric motors. Exceeding these vibration thresholds can result in rapid wear and tear, diminishing the motor’s reliability and lifespan. Hence, motors that surpass these permissible vibrations are not advised for vehicular use. Additionally, the article sheds light on requisite equipment controls for accurately gauging vibrations and noise levels in electric motors. Delving deeper into the nuances, the methods for mounting vibration transducers and electric motors on testing platforms are elucidated. These methods are pivotal in obliterating any hindrances that could impede the precise measurement of vibrations induced by an electric motor.

The aim of this article is to study the effects of evolution in defect size on vibration of a ball bearing by simulation of a ball bearing by developing a 2-DOF mathematical model and to compare the vibration responses of defective bearings obtained for two widely used defect functions, viz., rectangular function and half-sine wave function. MATLAB codes are developed to prepare a mathematical model of a ball bearing and to solve the differential equations of the model using the Runge-Kutta method. In the model, the mass supported by the bearing is considered as a lumped mass, and the contact between the races and the balls is considered as a series of springs, whose spring stiffness is obtained by using Hertz’s contact deformation theory. This model considers the contact deformation between the balls and the races and the additional displacement between the balls and the inner race due to radial clearance and defect geometry. The maximum possible radial displacement of the ball into the defect is obtained analytically and graphically from the race-ball-defect geometry. First, the impulses generated due to an outer race defect in the ball bearing are modeled using two different defect functions separately and their vibration responses are compared. Secondly, the effects of increase in defect length on vibration of the bearing are simulated separately for two defect functions, and then their responses are compared and analyzed. The results show that when the defect is modeled with a rectangular defect function, the vibration responses obtained are greater than when the defect is modeled with a half-sine wave defect function. And, vibration responses increase rapidly up to a certain level of defect length and then decrease with a further increase in defect length. The vibration analysis performed for different defect lengths can provide good support to vibration analysts and researchers.

This paper proposes a new control scheme that is composed by the sliding mode control(SMC) with three-dimensional ceiling control to reduce the multi-dimensional vibration of the vehicle’s seat. The seat suspension system is made of a kind of 3-RPS parallel mechanism, in which each limb is mainly composed by the spherical pair, spring, piston rod, damping fluid and rotary pair. Based on the single-open-chain theory, Position and Orientation Characteristics (POC) set of a 3-RPS seat mechanism was analyzed to verify its movement law. Three-dimensional seat system mathematical model was established, and the SMC and ceiling control were combined to obtain the required force. The ceiling control belongs to an ideal control method, it could provide the reference for the SMC. The comparisons between the SMC and passive seat suspension system were done when the vehicles were walking or working on E, F and G-roads. The results show that the transient amplitudes of seat acceleration outputs were reduced with the proposed control scheme. The research in this work can be extended and applied for other vehicles and improve their performance.

In the whole power system, the importance of the transformer is self-evident, if its fault is bound to cause adverse effects on the whole power system. However, the previous fault diagnosis method is not only time-consuming and laborious, but also has great danger, once it is not handled properly, it may also pose a threat to the life safety of operators. At this time, the transformer fault diagnosis mode based on voice print follows and becomes a big tool for fault diagnosis. However, the surrounding environment of the transformer is changeable and noisy, which will cause interference to the voice print signal and affect the fault diagnosis result. In this regard, this paper will start from this key point and solve this unfavorable factor by using different denoising technologies and feature extraction technologies. The final empirical results show that the improved wavelet threshold technology has the best denoising ability, and the feature parameters obtained under the transformer sound frequency cepstrum coefficient (TFCC) feature extraction technology can better improve the fault diagnosis accuracy. It can solve the problem of low fault diagnosis rate of transformer in different environments, and can be used in practical engineering.

Three-wheeled vehicles may be a better choice as compared with four-wheeler cars provided they are properly designed to improve the rollover stabilities and ride comfort. The design modifications need improvement in geometry and suspension. This article presents the dynamic behavior of three-wheeled vehicle equipped with an inerter-based dynamic absorber and compares the same with the conventional suspension system. The performance parameters analyzed are vertical-lateral acceleration, front & rear suspension deflection, and front & rear dynamic tyre loads. The analytical rigid body model is formulated by assigning 9 degrees of freedom to the system for the evaluation of performance parameters to compare the inerter-based absorber suspension with the conventional passive suspension system.

This work proposes a three-degrees-of-freedom Human-Vehicle-Road model to study the system’s dynamic as a response to road-induced excitations and evaluate the effect of vibrations on ride comfort. The study of the dynamic responses of the system is concerned only with the vertical motion of the passenger, sprung mass, and the tire when subjected to different excitation profiles. The model of the human is developed based on literature and then coupled to a quarter-car model using analytical methods. The mathematical model that describes the motion of the system is derived using Newton’s law of motion. The numerical simulations of the mathematical model using MATLAB provide the basis for the ride comfort analysis. The effects of the bump geometry are also studied in terms of the amplitude of each displacement, velocity, acceleration, and transmitted force. The ride comfort analysis is based on the ISO 2631 and BS6841 standards. The new concept of bump rotation is introduced and discussed in comparison with previous results. The investigation of the angle of rotation is presented as a totality of case studies where the bump is rotated with respect to the x-axis from 0 to 75° which is equivalent to a longer bump while maintaining the same height. The dynamic response for all rotation angles is collected to show that longer bumps have better performance because they reduce the forces transmitted to the system while maintaining the required level of discomfort to control the speeds of vehicles on roads. The ride comfort analysis concludes that the cycloidal bump has better performance as a speed control device.