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Byline: Waleed F. Faris, Zohir BenLahcene, Sany Izan Ihsan This paper deals with dynamics and control policies analysis of semi-active suspension systems for off-road vehicles. Three configurations of these vehicles; two-axle, three-axle and four-axle have been studied and their performances are compared. The application of several control policies of semi-active suspension system, namely skyhook; ground-hook and hybrid controls have been analysed and compared with passive systems. The results show that the hybrid control policy yields better comfort than a passive suspension, without reducing the road-holding quality or increasing the suspension displacement. The hybrid control policy is also shown to be a better compromise between comfort, road-holding and suspension displacement than the skyhook and ground-hook control policies. Skyhook control generally improves sprung mass responses while at the same time increasing unsprung mass responses. On the other hand, ground-hook control generally improves unsprung mass responses at the expense of the sprung mass responses. Results show an improvement in ride comfort and vehicle handling using four-axle over three-axle and two-axle when emphasis is placed on the response of the vehicle body acceleration, suspension and tyre deflection.

Byline: Faried Hasbullah, Waleed F. Faris The application of the linear quadratic regulator (LQR) and fuzzy logic controller (FLC) in the field of active vibration isolation for a vehicle suspension system is presented to overcome the limitation of passive suspension system and the performances of the two active controllers are compared with the passive system. Results show that the performance of the LQR controller is better than the FLC at the expense of control force. The performances of both active controllers are better than the passive system in terms of settling time.

Byline: Waleed F. Faris, Fazidah Saad Generally, the vehicle engine mounting system consists of an engine as the vibration source and several mounts connected to the vehicle structure. The modern engine mounting systems have been successfully used to isolate the driver and passenger from both noise and vibration generated by the engine. However, there is still a need to improve the performance of engine mounting systems because of the requirements of vibration and noise level isolation for passenger cars and also because of the modern car designs that need lighter bodies and more power-intensive engines. Such a weight reduction and increased power requirements will often have adverse effects on vibratory behaviour that it will increase the vibration and noise level. This study is focusing on the current elastomeric engine mounts of different geometry and will also characterise the dynamic properties of elastomeric engine mount. This will be done by having parametric study of different engine mountings. The analysis of engine mounting rubber components should be accompanied by the vibration analysis of the engine mount system. This research opens up a passage to researchers to study and improve the elastomeric engine mount.

Byline: Nabilah Ramli, Hishamuddin Jamaluddin, Shuhaimi B. Mansor, Waleed F. Faris Principal component analysis (PCA) is employed in this study to reduce the size of the neural network input node. Neural network is used to identify the ground vehicle aerodynamic derivatives based on a recorded simple harmonic motion of a ground vehicle model. The study involves the identification using neural network with and without the input optimisation by PCA. Both studies are compared with the identification results from a conventional method, and it is shown that the neural network can approximate functions based on principal components extracted as well as a full-size neural network can.

Byline: Zahir Ahmad Hanouf, Waleed F. Faris The main focus of this paper is the study of the relationship between components of vibration and noise inside the passenger cabin of a production vehicle. The noise inside automobiles is largely composed of contributions from the engine, ground and wind. The engine and tyres successively transfer the vibration via the structural connections to the body panels, which then propagates through the air to the interior of the car cabin. The analysis technique is based on the signal analysis method of sound pressure level and vibration response, and the modal analysis method of vehicle structural components. Firstly, the results were obtained by the noise contour test, which is a contour of sound pressure level, done over the horizontal cross-sectional plane inside the cabin. This was carried out under the random excitation, to predict the dominating noise frequencies. Secondly, the vibration response on the front suspension in the vertical direction under the engine excitation was studied. Finally, the modal analysis was used to determine the dynamic characteristics of every component of the vehicle body panels; this would contribute to the interior noise. It was found that the interior noise of the car vehicle is mainly caused by the excessive bending mode vibration of the front suspension and twisting mode vibration of the cross-roof beam.

Byline: Waleed F. Faris, Zohir BenLahcene, Sany Izan Ihsan Handling and ride quality are affected by many factors, including high-frequency vibrations, body booming, body roll and pitch motion, vertical motion by the suspension system and frequency vibration transmitted from the road input excitations. This article focuses on the most significant vibration source that affects handling and ride quality, which is the suspension system. Passive suspension has been taken as the starting point of this work, in which we discuss the model in context. Semi-active suspension systems are introduced with the aim of exploring the performance of the system compared with passive suspension. Several control policies of semi-active systems, namely, skyhook, ground-hook and hybrid controls, are presented. Their ride comfort, suspension displacement and roadholding performances are analysed and compared with passive systems. The analysis covers both transient and steady-state responses in the time domain and transmissibility response in the frequency domain. The results show that the hybrid control policy yields better comfort than a passive suspension, without reducing the road-holding quality or increasing the suspension displacement for a typical off-road vehicle. The hybrid control policy is also shown to provide a better compromise between comfort, road-holding and suspension displacement than the skyhook and ground-hook control policies.

Byline: Waleed F. Faris, Sany Izan Ihsan, Mehdi Ahmadian Vehicle models used to evaluate performance and dynamic behaviour are either discrete models, which includes quarter, half, and full car models, or continuous models using finite element modelling. In this work our focus will be on discrete models, which have more popularity with ground vehicle analysts owing to their shorter computational time and lower cost compared with continuous models. In this paper, ride comfort, suspension displacement and road-holding performances are compared for three different models – quarter (Q), half (H) and full (F) car models. In each model, semi-active system controls, namely skyhook, groundhook and hybrid controls, are used along with the conventional passive system. The analysis covers both transient and steady-state responses in the time domain and transmissibility response in the frequency domain. Results show that while the responses give generally the same trend, the simpler model gives significantly higher responses.

Byline: Waleed F. Faris, Sany Izan Ihsan, Mehdi Ahmadian Several control policies of semi-active system, namely skyhook, groundhook and hybrid controls are presented using a half-car model, as a continuation of the previous work on quarter-car model. Their ride comfort, suspension displacement and road-holding performances are analysed and compared with passive system. The analysis covers both transient and steady state responses in time domain and transfer function in frequency domain. The results show that the hybrid control policy yields better comfort than a passive suspension, without reducing the road-holding quality or increasing the suspension displacement for typical passenger cars. The hybrid control policy is also shown to be a better compromise between comfort, road-holding and suspension displacement than the skyhook and groundhook control policies.

Byline: Fadly Jashi Darsivan, Waleed F. Faris, Wahyudi Martono The application of the Extended Minimal Resource Allocation Network (EMRAN) in the field of active vibration isolation for an automotive engine system is presented. As the source of disturbance the engine is mounted on a two passive mounts in parallel with an active force actuator. EMRAN is implemented to control the force actuator and to isolate this disturbance. The characteristic of EMRAN and the criteria for growing and pruning of hidden layers are presented. EMRAN's capability is compared with a PID controller and NARMA-L2 neural controller and shows superior performance in rejecting sinusoidal disturbances and achieving the chassis's vibration isolation.

Byline: S.I. Ihsan, Waleed F. Faris, M. Ahmadian Several control policies of semi-active systems, namely skyhook, groundhook and hybrid controls, are presented. Their ride comfort, suspension displacement and road-holding performances are analysed and compared with passive systems. The analysis covers both transient and steady-state responses in the time domain and transmissibility response in the frequency domain. The results show that the hybrid control policy yields better comfort than a passive suspension, without reducing the road-holding quality or increasing the suspension displacement for typical passenger cars. The hybrid control policy is also shown to be a better compromise between comfort, roadholding and suspension displacement than the skyhook and groundhook control policies.