Automotive suspension system modelling and controlling

In both academic and industrial fields, suspension system modelling and associated control design influence vehicle response. Ideal hydraulic force models have been used in active suspension studies for decades, but few studies have investigated hydraulic effects, which are the core of system force generation. Accurate mathematical subsystem modelling is essential in representing physical subsystems and enhancing design estimation control. This thesis details the mathematical modelling of both passive and active suspension and controller design for a quarter-car test rig. When using a conventional passive model, a significant difference between the experimental and simulation results was found for improved modelling of body movements. This led to an investigation in how to resolve this issue, accordingly, the consideration of a new term (friction force) was researched. Establishing a nonlinear friction force became a vital aspect of this work. In addition, emphasis was placed on hydraulic modelling and unknown model parameters that were experimentally identified. This experimental work is unique and helpful for advancing knowledge of any system. A new approach to implementing the friction force was used to identify the system through the transformation of a ¼ car model to one Degree of Freedom (DOF) and two-DOF models. This reduced the model complexity and allowed the parameters to be identified from a series of transfer functions linking vehicle parts and the hydraulic models. Simulation and experimental results were then compared. The hydraulic component model is crucial to the formulation of accurate active control schemes. Full-state feedback controls were realised by Pole-Assignment (PA) and Linear Quadratic (LQ) optimal method. Simulation results suggest that even though the performance of active suspension designed by the PA method is superior to that of passive suspension, it still possesses a design constraint, similar to a passive system, as the design is a compromise between the effects of natural frequency and transmissibility. With a different design concept, the LQ method provided a better solution as it reduced energy consumption by 65% and effectively shifts the dominant natural frequency to a very low-frequency range. Thus, allowing the damping rate to be increased to its critical value with the smallest effect on transmissibility. iv It was estimated for experimental work that the identified model with the LQ controller might be used to predict the dynamic responses of the actual system within a certain range of the design parameters due to the considerable difference between the initial condition of the test rig and the linearised operating design. The servovalve produced issues that did not allow validation of the controller. Both simulation and experimental results, with several conditions, showed consistent agreement, between experimental and simulation output, consequently confirming the feasibility of the newly approved model for passive and active suspension systems that accounted for the actual configuration of the test rig system. These models, that subsequently implemented the nonlinear friction forces that affect the linear supported body bearings, are entirely accurate and useful. The nonlinear friction model captures most of the friction behaviours that have been observed experimentally. Additionally, the models of the nonlinear hydraulic actuators, covered by the dynamic equation for the servovalve, are moderately precise and practical. The suggested Proportional Integral (PI) control successfully guided the road hydraulic actuator and validated the control strategy. The suggested PA and LQ controllers for active systems successfully guided the system to achieve the targets. Ride comfort and handling response are close to that expected for the passive suspension system with road disturbances, whereas there were clear response enhancements for the active system

Factors Influencing Customer Satisfaction towards E-shopping in Malaysia

Online shopping or e-shopping has changed the world of business and quite a few people have decided to work with these features. What their primary concerns precisely and the responses from the globalisation are the competency of incorporation while doing their businesses. E-shopping has also increased substantially in Malaysia in recent years. The rapid increase in the e-commerce industry in Malaysia has created the demand to emphasize on how to increase customer satisfaction while operating in the e-retailing environment. It is very important that customers are satisfied with the website, or else, they would not return. Therefore, a crucial fact to look into is that companies must ensure that their customers are satisfied with their purchases that are really essential from the ecommerce’s point of view. With is in mind, this study aimed at investigating customer satisfaction towards e-shopping in Malaysia. A total of 400 questionnaires were distributed among students randomly selected from various public and private universities located within Klang valley area. Total 369 questionnaires were returned, out of which 341 questionnaires were found usable for further analysis. Finally, SEM was employed to test the hypotheses. This study found that customer satisfaction towards e-shopping in Malaysia is to a great extent influenced by ease of use, trust, design of the website, online security and e-service quality. Finally, recommendations and future study direction is provided. Keywords: E-shopping, Customer satisfaction, Trust, Online security, E-service quality, Malaysia

Performance analysis for wireless G (IEEE 802.11G) and wireless N (IEEE 802.11N) in outdoor environment

This paper described an analysis the different capabilities and limitation of both IEEE technologies that has been utilized for data transmission directed to mobile device. In this work, we have compared an IEEE 802.11/g/n outdoor environment to know what technology is better. The comparison consider on coverage area (mobility), throughput and measuring the interferences. The work presented here is to help the researchers to select the best technology depending of their deploying case, and investigate the best variant for outdoor. The tool used is Iperf software which is to measure the data transmission performance of IEEE 802.11n and IEEE 802.11g

Performance Analysis For Wireless G (IEEE 802.11 G) And Wireless N (IEEE 802.11 N) In Outdoor Environment

This paper described an analysis the different capabilities and limitation of both IEEE technologies that has been utilized for data transmission directed to mobile device. In this work, we have compared an IEEE 802.11/g/n outdoor environment to know what technology is better. the comparison consider on coverage area (mobility), through put and measuring the interferences. The work presented here is to help the researchers to select the best technology depending of their deploying case, and investigate the best variant for outdoor. The tool used is Iperf software which is to measure the data transmission performance of IEEE 802.11n and IEEE 802.11g