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The purpose of this paper is to solve problems about cab’s low-frequency shaking in the direction of forward motion when vibratory roller operates. To solve this problem, a modal test for a single-drum vibratory roller is carried out by the Belgium LMS dynamic testing which is used to identify the model parameters and find out the natural frequency of the vehicle. A Finite Element Analysis (FEA) simulation is carried out to find out the reasons causing the cab’s low-frequency shaking. The model simulation results are found to be in good agreement with the experimental results. Finally, the design parameters of cab’s isolation system are optimized to reach the maximum value of the first-order natural frequency in order to avoid resonance vibration for cab at low frequency and reduce cab’s low-frequency shaking.

This paper presents the effect of in-wheel motor (IWM) suspension system on electric vehicle (EV) ride comfort. To analyze the impact on the vehicle ride comfort caused by IWM suspension system, a dynamic model of quarter vehicle is established with the combination of IWM and road surface roughness excitations. The weighted root-mean-square (r.m.s.) acceleration of the vertical vehicle body (awbz) according to the international standard ISO 2631-1 (1997) is selected as an objective function to analyze the effect of IWM suspension system when the road surface and IWM mass conditions change. The study results indicate that the effect of IWM suspension system on the EV ride quality is significant and the value of awbz reduces by 8.6 % in comparison to without IWM suspension system. The IWM suspension system has significantly improved the EV ride quality when the road surface and IWM mass conditions change.

This study presents a method to improve vehicle ride comfort using additional damping coefficient values for an internal combustion engine (ICE) rubber mounting system. To analyze the effect of the adding damping coefficient values into the rubber mounting system on vehicle ride comfort, a full-vehicle vibration model with 10 degrees of freedom is established under the combination of road surface roughness and ICE excitations. The damping coefficient values are added into ICE rubber mounting system which are respectively analyzed and evaluated according to the international standard ISO 2631-1 (1997). The study results do not only evaluate the influence of the adding damping coefficients on vehicle ride comfort but also suggest the optimal design solution for ICE mounting system to improve vehicle ride comfort.

This study proposes a three-dimensional vibration model of bus with 10 DOF (degree of freedom) based on Dragan Sekulić model to analyze the suspension parameters directly influenced ride comfort. The suspension parameters which include the stiffness and damping parameters are analyzed based on the weighted r.m.s. (root-mean-square) acceleration responses of the space of a driver, passenger in the middle part of the bus and passenger in the rear overhang according to ISO 2631-1:1997. The results show that both stiffness and damping parameters of vehicle suspension have important influences on ride comfort. Especially, the stiffness and damping values of vehicle suspension are within the value ranges (0.5k0 ≤ k ≤ 0.75 k0) and (0.5c0 ≤ c ≤ 0.75c0) to improve the ride comfort of driver and passengers.

The construction machinery market has required increasingly not only on working capacity but also ride comfort quality, therefore it has required increasing toward researchers and manufacturers. The main objective of this paper proposes and evaluates the performance of semi-active hydraulic cab mount system (SHCMs) of a double-drum vibratory roller in the direction of enhancing vehicle ride comfort under different operating conditions. Firstly, a nonlinear dynamic model of passive hydraulic cab mount system (PHCMs) is established to determine its vertical force which is connected with a dynamic model of vehicle - ground surface interaction. And then, a fuzzy logic controller (FLC) is designed to control the value of the damping force of SHCMs. Both the differential equations of motion and FLC are implemented in the MATLAB/Simulink environment. Finally, the ride performance of SHCMs is evaluated under different conditions according to ISO 2631: 1997 (E) standard. The obtained results show that the values of objective functions with SHCMs significantly reduce in comparison with PHCMs under different operating conditions.

The purpose of this work is to evaluate the performance of novel hydrfo-pneumatic suspension system (HPSs) in comparison with traditional hydro-pneumatic fsuspension system (HPSs) of a heavy truck in the direction of improving vehicle ride comfort. Firstly, the nonlinear dynamic models of the traditional and novel HPS systems are set up to determine the vertical forces. And then, the vertical forces are connected with a 3-D nonlinear dynamic model of heavy truck with 10 degrees of freedom under random excitation of road surface. The root mean square (RMS) acceleration responses of the vertical cab, pitch and roll angles of the cab (awzcb, awfcb and awtcb) based on the International Standard ISO 2631-1: 1997 are chosen as objective functions. The study results show that the awzcb, awfcb and awtcb values with novel HPSs reduce by 28.27%, 28.32% and 6.89% in comparison with traditional HPSs when vehicle moves on ISO class D road surface at vehicle speed of 50 km/h and full load. Finally, the ride performance of novel HPSs is verified and compared and evaluated with traditional HPSs under different operating conditions and the evaluation results are also indicated that the ride performance of a novel HPSs is better than the traditional HPSs under survey conditions.

The goal of this paper is to find out the optimal parameters of cab’s isolation system to improve the ride comfort of the vibratory roller. A half-vehicle ride dynamic model of a single drum vibratory roller is established under various operating conditions. The design parameters of cab’s isolation system are optimized by the root mean square (rms) values of acceleration responses of the vertical driver’s seat (aws) and cab’s pitch angle angle (awcphi) according to the ISO 2631:1997(E) standard. A genetic algorithm (GA) and a multi-objective optimization algorithm are used for searching for the optimal design parameters of cab’s isolation systems. The study results indicate that the aws and awcphi values with GA optimal parameters reduce by 31.88% and 31.27%, respectively in comparison with the original parameters of cab’s isolation systems when the vehicle moves on the ISO class D road surface at the vehicle speed v = 5 km/h, which shows that the performance of the optimal parameters of cab’s isolation system is better than that of cab’s original isolation system in improving the ride comfort of a single drum vibratory roller at all operating conditions.

The objective of this study is to analyze the effects of suspension design parameters of a semi-trailer truck on vehicle ride comfort as well as road surface friendliness. A half-dynamic vehicle model with 12° of freedom is established under random road excitation. The weighted root mean square (RMS) of acceleration responses of the vertical driver’s seat, cab’s pitch and dynamic load coefficient (DLC) is chosen as an objective function which uses Matlab/Simulink software to simulate the vehicle dynamics model and calculate the objective functions. The effects of suspension design parameters of a semi-trailer truck such as stiffness and damping coefficients on the objective functions are analyzed respectively. The results show that the effects of the stiffness and damping parameters in the suspension systems on the vehicle ride comfort as well as road surface friendliness are very obvious. The worse the vehicle ride comfort as well as road surface friendliness is, the greater the stiffness of the suspension systems is. However, the vehicle ride comfort improves with the increase of the damping of the suspension systems. Therefore, the study provides a theoretical basis for the suspension system design of semi-trailer trucks.

The objective of this study was to evaluate influence of heavy truck operating condition on dynamic load coefficient. A three-dimensional nonlinear dynamic model of heavy with 15 DOF (degree of freedom) was established based on Zhou Changfeng model for simulation and analysis. The tire dynamic load and dynamic load coefficient (DLC) was chosen as objective function which uses Matlab/Simulink software to simulate the full vehicle dynamics model with nonlinear rubber suspension and calculate the objective function. The influence of the different operating conditions such as road surfaces, vehicle speeds, sprung mass on dynamic load coefficient was analyzed. The results show that the influence of the road surface roughness, vehicle speed and vehicle sprung mass on the DLC values of wheel at 3rd axle as well as road friendliness is very obvious. Especially, this study proposes that the speed limits for AD250 articulated dump truck are vmax ≤ 30 km/h for the road surface condition of the ISO level D, vmax ≤ 20 km/h for the road surface condition of the ISO level E.

The purpose of this paper is to analyze the performance of the hydro-pneumatic suspension system (HPSs) of a mining dump truck on ride comfort under operating conditions. To achieve goals, a 3-D full-vehicle vibration model of a mining dump truck with 10 degrees of freedom is set up to analyze the effects. A nonlinear mathematical model is set up based on the nonlinear characteristics of the HPSs to determine their vertical force which is connected with a 3-D full-vehicle vibration model. The effects of operating conditions on a heavy truck ride comfort are respectively analyzed through the values of the root mean square of acceleration responses of the vertical cab, pitch and roll angles of cab (awc, awphi and awteta). The analysis results indicate that the survey conditions have a great influence on vehicle ride comfort. Especially, the values of awc, awphi and awteta with the poor road surface condition respectively reduce by 43.1%, 45.9% and 61.8% compared to the very poor road surface condition at vehicle speed of 30 km/h and full load.

A series of 65 intracranial tumours operated on, and followed by, the same surgical team during 7 years is presented as a retrospective analysis (1987–1994). Among these patients, only 38 had a diagnosis based upon computed tomography (CT) scan because it was not until 1991 that the first CT scanner was set up in Ho Chi Minh City. Many patients were drowsy or comatose prior to operation due to lack of specialists' intervention or tardy diagnosis and evacuation from remote provincial hospitals. All operations were satisfactory despite the lack of many essential instruments. The histological diagnosis followed the classification proposed by Zulch KJ.1 Intratumoural calcification has in no case been seen on X-rays or on histological specimens. Operative mortality rate was nil. Although not all the patients with malignant tumours could be followed up, the data available concerning their survival time and the quality of life seems similar to that observed in other reports.