Modeling and Simulation of a Dual-mode Electrohydraulic Fully Variable Valve Train for Four-stroke Engines

Pak Kin Wong,L. M. TAM,K. LI 한국자동차공학회 2008 International journal of automotive technology Vol.9 No.5

In modern four-stroke automotive engine technology, variable valve timing and lift control offer potential benefits for making a high-performance engine. In this paper, a novel design named dual-mode electrohydraulic fully variable valve train (EHFVVT) for both engine intake and exhaust valves is introduced. The system is mainly controlled by either proportional flow control valves or proportional pressure relief valves, and hence two different families of valve displacement patterns can be achieved. The construction of the mathematical model of the valve train system and its dynamic analysis are also presented in this paper. Experimental and simulation results show that the dual-mode electrohydraulic variable valve train can achieve fully variable valve timing and lift control, and has the potential to eliminate the traditional throttle valve in the gasoline engines. With the proposed system, the engine performance at various speeds and loads will be significantly improved.

Analysis of automotive rolling lobe air spring under alternative factors with finite element model

Pak Kin Wong,Zhengchao Xie,Jing Zhao,Tao Xu,Feng He 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.12

Air springs are widely used in automotive suspensions for their superior performance in terms of low friction motion, adjustable loadcarrying capacity and user-friendly ride height control. However, it has posed great difficulties in constructing an accurate model as wellas the analysis of the influence of alternative factors, such as cord angle, cord diameter and initial pressure. In this paper, a numericalmodel of the rolling lobe air spring (RLAS) is built by using finite element method and compared with an existing analytical model. Anexperiment with respect to the vertical stiffness of the RLAS is carried out to validate the accuracy of the proposed model. Evaluationresult reveals that the existing analytical model cannot represent the performance of the RLAS very well, whereas the accuracy of thenumerical model is very good. With the verified numerical model, the impacts of many alternative factors on the characteristics of theRLAS are analyzed. Numerical results show that the newly proposed model is reliable to determine the vertical characteristic and physicaldimensions of the RLAS under the alternative factors.

DESIGN AND CONTROL OF AN AUTOMOTIVE VARIABLE HYDRAULIC DAMPER USING CUCKOO SEARCH OPTIMIZED PID METHOD

Jing Zhao,Pak Kin Wong,Zhengchao Xie,Xinbo Ma,Xingqi Hua 한국자동차공학회 2019 International journal of automotive technology Vol.20 No.1

The semi-active suspension (SAS) system has been one of the most attractive topics due to its simplicity and effectiveness in the control of vehicle dynamics. This research proposes a cuckoo search optimized proportional-integral– derivative (CS-PID) strategy for the damping force control of the semi-acive suspension system in order to improve vehicle ride quality. Firstly, a quarter-car suspension model with air spring and variable hydraulic damper (VHD) is developed. By constructing the detailed analytical model and describing the working process, the regulating mechanism and external characteristics of the VHD are presented. Subsequently, the CS-PID strategy is designed to generate the desired damping force according to the vehicle states in real-time, followed with the evaluation of the proposed strategy. Finally, the experimental tests are carried out to verify the accuracy of the VHD model and examine the feasibility of the proposed strategy. The numerical simulation reveal that the proposed control strategy is effective in improving the vehicle performance and the experimental results show that the CS-PID strategy can be successfully implemented in the suspension system for practical use.

Analysis of Co-Relation Between Objective Measurement and Subjective Assessment for Dynamic Comfort of Vehicles

Ao Di,Wong Pak Kin,Huang Wei,Mei Xing Tai,Cao Yu Cong,Zhao Jing 한국자동차공학회 2020 International journal of automotive technology Vol.21 No.6

The assessment of vehicle dynamic comfort to human body vibration varies from person to person. Even though the dynamic comfort rating can be obtained by placing measurement devices over the cabin, passengers may have dissimilar sensations. For many car manufacturers, both subject and objective measurements are used together at development of new cars. To effectively assess the dynamic comfort of vehicle, this research explores the correlation between the objective measurement of the whole body vibration, hand-transmitted vibration and subjective assessment. The whole body vibration is measured from the backrest, seat surface and vehicle floor, whereas the hand-transmitted vibration is measured from the steering wheel. Four different vehicles are driven at various speeds on five types of pavements. Both simple linear regression and polynomial regression models based on Stevens’s power law from psychophysics are built to correlate the subjective and objective data. The regression results show that (1) the seat surface is more reliable than other positions for assessing the human body vibration; (2) the hand transmitted vibration on rough roads is more trustful for dynamic comfort evaluation than on smooth roads; (3) the overall dynamic comfort value is the most reliable index for dynamic comfort evaluation.

A New Adaptive Region of Interest Extraction Method for Two-Lane Detection

Chen Yingfo,Wong Pak Kin,Yang Zhi-Xin 한국자동차공학회 2021 International journal of automotive technology Vol.22 No.6

As a key environment perception technology of autonomous driving or driver assistance systems, lane detection is to ensure vehicles to drive safely in corresponding lane. However, existing lane detection algorithms for two-lane detection focus on using various filtering methods to reduce the impact of useless information, resulting in low accuracy and low efficiency. In this paper, a novel Adaptive Region of Interest (A-ROI) extraction method is proposed to improve the accuracy and real-time performance of the two-lane detection algorithm. Three key technologies are introduced to solve the problems. First, A-ROI, which only focuses on the lane where the vehicle is located, is applied to the Bird’s-Eye-View image obtained by using Inverse Perspective Mapping (IPM). Next, based on Bayesian framework and Likelihood models, a lane feature extraction method with a lane-like feature filter is used for edge detection. Finally, an improved Random Sample Consensus (RANSAC) algorithm is introduced by using a filter that can remove noisy lane data. The performance of the proposed A-ROI method together with the improved lane detection method is evaluated via simulation of various scenarios. Experimental results show the proposed method has better accuracy and real-time performance than the traditional lane detection methods.

Modeling and analysis of rotating plates by using self-sensing active constrained layer damping

Zhengchao Xie,Pak Kin Wong,Ian Ian Chong 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.10

This paper proposes a new finite element model for active constrained layer damped (CLD) rotating plate with self-sensing technique. Constrained layer damping can effectively reduce the vibration in rotating structures. Unfortunately, most existing research models the rotating structures as beams that are not the case many times. It is meaningful to model the rotating part as plates because of improvements on both the accuracy and the versatility. At the same time, existing research shows that the active constrained layer damping provides a more effective vibration control approach than the passive constrained layer damping. Thus, in this work, a single layer finite element is adopted to model a three-layer active constrained layer damped rotating plate. Unlike previous ones, this finite element model treats all three layers as having the both shear and extension strains, so all types of damping are taken into account. Also, the constraining layer is made of piezoelectric material to work as both the self-sensing sensor and actuator. Then, a proportional control strategy is implemented to effectively control the displacement of the tip end of the rotating plate. Additionally, a parametric study is conducted to explore the impact of some design parameters on structure’s modal characteristics.

Data-Based Identification of the Tire Cornering Properties Via Piecewise Affine Approximation

Sun Xiaoqiang,Hu Weiwei,Cai Yingfeng,Wong Pak Kin,Chen Long 한국자동차공학회 2021 International journal of automotive technology Vol.22 No.3

The piecewise affine (PWA) model represents an attractive model structure for approximating nonlinear systems. In this paper, a procedure for obtaining the PWA model of the tire nonlinear cornering properties is introduced. In this approach, the highly nonlinear dynamic of the tire cornering properties is well approximated by a set of affine maps which relate inputs and outputs. These maps are defined in disjunctive regions in the regression space, itself composed of system inputs and outputs. The tire cornering properties tests are firstly carried out through a high-performance flat-plate test bench, thus the experimental data which can accurately reflect the tire cornering properties is obtained. On this basis, the PWA identification of the tire cornering properties is composed of the data clustering, the parameter estimation of the affine submodels and the calculation of the hyperplane coefficient matrices, which are respectively achieved by means of fuzzy c-means clustering, weighted least-squares and support vector machines. Finally, to verify the PWA model accuracy in approximating the tire nonlinear cornering properties, the comparison between the simulation results of the PWA identification model and the experimental data is conducted and the comparison results are analyzed.

Design and performance research of a hydro-pneumatic suspension with variable damping and stiffness characteristics

Chunfang Yin,Xuhui Zhai,Xiaoqiang Sun,Shaohua Wang,Pak Kin Wong 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.10

This research proposes a novel hydro-pneumatic suspension structure based on high-speed on-off solenoid valves, which can realize two spring force modes and four damping force modes. The basic working principles of the HPS with multiple output force modes are analyzed to establish the damping and stiffness features mathematical models. Based on the parameters taken from a mine dump truck, the stiffness coefficient and damping coefficient of the proposed HPS are matched firstly, then the initial charging pressure of accumulators and the diameter of throttle valves are determined. Finally, the validity of the proposed model is demonstrated by comparing the force-displacement and the force-velocity responses of the model with the corresponding measured experimental data under a broad range of excitations.

Knockout of Lmod2 results in shorter thin filaments followed by dilated cardiomyopathy and juvenile lethality

Pappas, Christopher T.,Mayfield, Rachel M.,Henderson, Christine,Jamilpour, Nima,Cover, Cathleen,Hernandez, Zachary,Hutchinson, Kirk R.,Chu, Miensheng,Nam, Ki-Hwan,Valdez, Jose M.,Wong, Pak Kin,Granzie Proceedings of the National Academy of Sciences 2015 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF Vol.112 No.44