Theoretical and Experimental Vibration Analyses of the Steering Wheel of a Heavy Commercial Vehicle

In this study, the components of a particular heavy commercial truck that affect the steering wheel vibration are identified and the most common sources of this vibration are examined. Then, modal analyses and impact hammer tests are implemented to determine the root causes of the vibration. Finally, finite element modeling is applied, and all the results of the analyses are compared to present design improvement recommendations for the reduction in steering wheel vibration, which can be applicable in new projects.

Satellite architecture and preliminary in-orbit experiment of Taiji-1

Taiji-1 is China’s first in-orbit technology validating satellite related to spaceborne gravitational wave (GW) detection. The satellite was launched at 600km sun synchronized orbit on 31 August 2019. It has accomplished its mission goals while all subsystems have validated their key technologies in orbit. The subsystems include optical metrology system (OMS), drag-free attitude control system (DFACS), thermal control subsystem, high-quality microgravity satellite platform and so on. This paper presents system architecture of Taiji-1 analyzing in-orbit experimental results of thermal stability, reaction wheel vibration contributing to the noise of gravitational reference sensor (GRS) measurement noise, and the center-of-mass (CoM) of GRS calibration.

EFFECTIVE PROFILE ESTIMATION FOR TRACTOR DYNAMICS ON AGRICULTURAL TERRAINS

For tractor operation on deformable terrains, accurate terrain profiles are critically needed to determine the dynamic tractor response, which is affected by the terrain roughness. Effective profiles for tractors operating on agricultural terrains were identified in this study. A novel technique, called independent component analysis (ICA), was used to estimate the effective profiles. ICA can use a known system dynamic response (observed signals) to identify road-induced excitation. In this context, tractor wheel vibration signals were used as observed signals, and the ICA method was used to estimate the source signals, which are the effective profiles of the terrain. The proposed approach was validated by comparing the estimated profiles with those measured by a profiling apparatus in the time and frequency domains. The calculated root mean square error RMSE and the relative error Ef between the measured and estimated profiles showed that the proposed approach can be used to accurately estimate road profiles. A group of grass-field roughness data was taken as an example to compare the characteristics of the original and effective profiles, and the parameters of the effective profiles, such as the RMS, roughness index C and waviness W were found to noticeably change during the interaction between the tractor wheel and the terrain soil.

Investigation of the generation mechanism of squeal noise under non-negative damping conditions

The traditionally known generation mechanism of squeal noise is generally agreed to be the negative damping theory, which is represented by the negative slope of friction creepage curve. Recently, however, it was found that squeal noise still can be generated when the negative slope is eliminated. To investigate this phenomenon, water-based and oil-based friction modifiers are applied on a test rig to create non-negative damping conditions. The adhesion ratios at various rolling speeds are measured, and it is found that the negative slopes of friction curves can be eliminated when using friction modifiers, but squeal noise still exists. To investigate this phenomenon, a model involving the effect of vertical dynamics on squeal noise is developed in this research. The results show that the involvement of vertical dynamics has negligible effect on wheel vibration velocity when the friction creepage curve has a negative slope. When the friction creepage curve has a zero or positive slope, however, the results show that a stable lateral vibration still can be generated when vertical dynamics is involved. The generation mechanism of wheel squeal involving vertical dynamics is illustrated from the perspective of power input. Furthermore, the sound pressure levels of squeal noise are simulated using this model and the results correlate well with experimental measurements. Therefore, the results indicate that the vertical dynamics may be the reason why squeal noise still exists under non-negative damping conditions.

Design, Dimensioning and Simulation of Inerters for the Reduction of Vehicle Wheel Vibrations—Case Studies

For the last two decades, a novel mechanical system has received increasing attention—the inerter. An inerter is a system that can store mechanical energy for a rather short amount of time and behaves analogously to a capacitor in electrical engineering. Until today, only a few inerter applications have been reported. In a vehicle suspension, an inerter can be used to reduce wheel vibrations. This paper demonstrates the application potential of the novel mechanical system and describes the design and dimensioning of an inerter for the reduction of these kind of wheel vibrations for two completely different vehicle concepts. The first application concerns a Formula Student race car in which the main objective represents the maximization of the mechanical grip to improve lap times. For the inerter dimensioning in a racing car, lightweight design is a major issue. The second application is an agricultural tractor in which the focus is on the reduction of the ground pressure to protect the environment as well as on a very robust and compact realization of the inerter. A detailed simulation of both cases allows a qualitative and quantitative assessment of the wheel vibration reduction potential. In both applications, a considerable improvement potential could be identified which amounts, in the case of the race car, to a reduction of wheel oscillation of about 21% and for the tractor to a wheel vibration reduction potential of up to 54%.

Understanding the effect of elastic wheels on an urban railway system using a new wheel–rail coupling vibration model

In order to control the wheel–rail coupling vibration of an urban railway system, a combined elastic wheel damping structure is proposed where the key parameters that determine the structural damping and thereby control the vibration of the railway system are explored. The vertical acceleration of the elastic wheels is obtained for a range of stiffness coefficients as the wheel moves on an irregular track, which is calculated by the [Formula: see text] method in the time domain. The results show that the vertical acceleration changes with a V-shaped trend, with an increase of wheel stiffness coefficient, which allows the optimum stiffness coefficient for minimum vertical acceleration of the elastic wheel to be obtained. It is observed that when attempting to suppress wheel vibration, an elastic wheel with a larger stiffness coefficient is needed as the degree of track irregularity reduces. This paper provides new insights into the effect of wheel elasticity on vibration characteristics, and thereby provides directions to improve ride quality and passenger comfort.

Optimized Perforation Schemes in Railway Wheels Toward Acoustic Radiation Mitigation

Rolling noise emitted by railway wheels is a problem that affects human health and limits the expansion of the railway network. It is caused by the wheel vibration due to the wheel-rail contact force, and it is important in almost all the vehicle velocity range. The minimization of noise radiation associated with changes on the wheel web is discussed in this work, focusing on potential shape modifications in existing wheels in the form of a perforation distribution over the web. Such a post-manufacturing technique is a cost-effective solution that can be performed in a relatively short term. The implemented objective function is directly related to the overall radiated sound power, which is minimized using a genetic algorithm-based optimizer. In the acoustic model, radiation efficiencies are approximated to unity, the accuracy of this assumption being also studied in the work. The results reflect that an optimized distribution of perforations on the web of a railway wheel can reduce the total sound power level, by about 5 dB(A) and 2 dB(A) for curved and straight web, respectively. The mitigation of the radiated sound power is due to the fact that certain wheel vibration modes are modified and shifted to other frequencies where they are less excited. Finally, the relevance of the cross-sectional curvature of the web is explored by studying two different web geometries, suggesting that it can strongly influence the noise mitigation effects of the perforation pattern.

Research on a Multinode Joint Vibration Control Strategy for Controlling the Steering Wheel of a Commercial Vehicle

The vibration degree of a steering wheel has important reference significance for drivers to evaluate the ride comfort of the whole vehicle. To solve the jitter problem of the steering wheel of a commercial vehicle at idle speed, this work proposes a multinode joint vibration control strategy (MDVC) based on the associated vibration path of the steering wheel. Based on the analysis of the associated vibration transfer paths of the steering wheel, the whole vehicle was divided into a system comprising several nodes. For the decomposed node system, taking the vibration transmission path associated with the target as the research direction, the vibration reduction design of each node system is analyzed step by step. After exploring the possible causes of abnormal vibration of the steering wheel through experimental tests, the abnormal node structure interval was determined. By further extracting the structural model of the steering system from the vehicle, the hammering method was applied to test its modal and related frequency. Furthermore, an improved structure of steering support was also designed, and its fitting degree and modal characteristics were analyzed and compared to the original scheme. The following test results show that the structure improvement greatly reduces the vibration level of the steering wheel, meets the ideal design requirements of the steering wheel vibration reduction, and provides the possibility of weighing the correlation between these hierarchical node systems in whole vehicle.