Aminudin Abu

Study of Model Predictive Control for Path-Following Autonomous Ground Vehicle Control under Crosswind Effect

We present a comparative study of model predictive control approaches of two-wheel steering, four-wheel steering, and a combination of two-wheel steering with direct yaw moment control manoeuvres for path-following control in autonomous car vehicle dynamics systems. Single-track mode, based on a linearized vehicle and tire model, is used. Based on a given trajectory, we drove the vehicle at low and high forward speeds and on low and high road friction surfaces for a double-lane change scenario in order to follow the desired trajectory as close as possible while rejecting the effects of wind gusts. We compared the controller based on both simple and complex bicycle models without and with the roll vehicle dynamics for different types of model predictive control manoeuvres. The simulation result showed that the model predictive control gave a better performance in terms of robustness for both forward speeds and road surface variation in autonomous path-following control. It also demonstrated that model predictive control is useful to maintain vehicle stability along the desired path and has an ability to eliminate the crosswind effect.

Bio-corrosion behavior and mechanical characteristics of magnesium-titania-hydroxyapatite nanocomposites coated by magnesium-oxide flakes and silicon for use as resorbable bone fixation material

This study was aimed to improve of the corrosion resistance and mechanical properties of Mg/15TiO2/5HA nanocomposite by silicon and magnesium oxide coatings prepared using a powder metallurgy method. The phase evolution, chemical composition, microstructure and mechanical properties of uncoated and coated samples were characterized. Electrochemical and immersion tests used to investigate the in vitro corrosion behavior of the fabricated samples. The adhesion strength of ~36MPa for MgO and ~32MPa for Si/MgO coatings to substrate was measured by adhesion test. Fabrication a homogenous double layer coating with uniform thicknesses consisting micro-sized particles of Si as outer layer and flake-like particles of MgO as the inner layer on the surface of Mg/15TiO2/5HA nanocomposite caused the corrosion resistance and ductility increased whereas the ultimate compressive stress decreased. However, after immersion in SBF solution, Si/MgO-coated sample indicates the best mechanical properties compared to those of the uncoated and MgO-coated samples. The increase of cell viability percentage of the normal human osteoblast (NHOst) cells indicates the improvement in biocompatibility of Mg/15TiO2/5HA nanocomposite by Si/MgO coating.

Enhancing the yaw stability and the manoeuvrability of a heavy vehicle in difficult scenarios by an emergency threat avoidance manoeuvre

This study aims to investigate the switching model predictive control strategy for a heavy-vehicle system in order to coordinate the actuator between active rear steering and differential braking control manoeuvres for emergency threat avoidance in difficult environments. We present the controller performances for the lateral dynamic behaviour, the yaw stability and the manoeuvrability of a vehicle when subjected to a sudden threat or disturbance such as a gust of wind, a road bank angle or a split-μ road surface in order to enable a fast safe lane-change trajectory to be followed. The vehicle was driven at a medium forward speed and a high forward speed in order to investigate the effectiveness of the proposed approach in avoiding the threat, maintaining the stability and enablinge a fast safe lane-change trajectory to be followed. We compared two different controllers (a model predictive controller and a switching model predictive controller) for two different control manoeuvres (active rear steering with differential braking control and active rear steering with direct yaw moment control). The simulation results demonstrate that the proposed switching model predictive control method provides an improved fast safe lane-change manoeuvre in a threat avoidance scenario for both control manoeuvres. It also demonstrated that the proposed active rear steering with differential braking control is more useful for maintaining the stability of the vehicle in a threat avoidance scenario with disturbance effects than is active rear steering with direct yaw moment control.

Practical Control Method for Two-Mass Rotary Point-To-Point Positioning Systems

Motion control systems play an important role in industrial engineering applications such as advanced manufacturing systems, semiconductor manufacturing system, computer numerical control (CNC) machining and robot systems. In general, positioning system can be classified into two types, namely point-to-point (PTP) positioning systems and continuous path (CP) control system (Crowder R.M, 1998). PTP positioning systems, either of one-mass or multi-mass systems, is used to move an object from one point to another point either in angular or linear position. For example, in application with one-mass system, such as CNC machines, PTP positioning is used to accurately locate the spindle at one or more specific locations to perform operations, such as drilling, reaming, boring, tapping, and punching. In multi-mass systems application, such as in spot-welding robot, which has a long arm for linear system or long shaft in rotary system, PTP positioning is used to locate the manipulator from one location to another.

The effectiveness of two-versus three-start helical strakes in suppressing VIV of flexible cylinder

The proposed paper investigates experimentally the effectiveness of strakes in suppressing the vortex-induced vibration (VIV) of a long flexible cylinder by varying the number of helix of the strakes, which differ from the previous studies that only focus on short rigid cylinder. The experiment was conducted in the towing tank with constant velocity under subcritical Reynolds number (0.14x104 - 1.37x104) by using a poly vinyl chloride cylinder with aspect ratio of 162. CCD cameras were installed to capture the amplitude vibration while the variation of tension was measured by using tension load-cell. The drag force coefficient and the cross-flow and in-line frequency response were obtained from the strain gauges. The purpose of the present study is to identify the main deficiency and advantage of a two-start helical strakes compare to a three-start helical strakes in reducing the VIV of a low mass ratio flexible riser. The experimental result shows that the two-start helical strakes perform well in mitigating the VIV in low reduced velocity range. However, its effectiveness in suppressing the vibration amplitude of flexible cylinder is far smaller than the three-start helical strakes. Substantial amplitude mitigation is found for the three-start helical strakes, but with significant amplification of drag at high reduced velocity, which is unfavourable. On the other hand, although the mean drag coefficient is slightly higher for the two-start helical strakes in the lock-in region, the drag force response is more consistent and independent to the velocity changes at high reduced velocity.

Modelling behaviour for magneto rheological motorcycle suspension system

This paper discusses the performance of Magneto-rheological (MR) for motorcycle suspension. Previous studies on the application of the MR fluids may improve the performance and decrease the vibration in systems such as building structure and automobile. The promising future of the application of MR has become the motivation for the present work. Hence, the MR motorcycle suspension system is designed to bring safety and comfort to both rider and passenger. The designed system is also contributed to the improvement of the handling ability to the vehicle. The effectiveness between the MR motorcycle suspension and the conventional passive system is demonstrated by computer simulation. The result showed that MR suspension system could eliminate external disturbance which obtain much better ride quality and handling performance to the motorcycle.

On Theoretical of Transmission Loss in Exhaust Muffler System

Exhaust muffler system iscommonly used to reduce noise associated with internal combustion engine exhausts.This paper presents a numerical analysis of transmission loss for exhaust muffler by using transfer matrix method. The objective of this study is to develop the computer program to predict the transmission loss of muffler.The influence of cross sectional area of pipe, effect of muffler length and temperature towards the transmission loss of muffler is discussed as well in present study. The efficiency and capabilities of the computing transmission loss is compared to the experiment results obtained from the previous established research paper.

Improvement on Ride Comfort of Quarter-Car Active Suspension System Using Linear Quadratic Regulator

The goal of this paper is to investigate the performance of an active suspension system via linear quadratic regulator (LQR) control and proportional–derivative–integral (PID) control. This project presents the mathematical models of the two degrees of freedom of a quarter-car active suspension system. This project introduces the design of a controller performance used for an active suspension system. The equations of motion of the quarter-car active suspension system model are developed. In the passive suspension system, there are huge oscillations or vibrations that occur in the suspension system. This phenomenon will lead to uncomfortable ride among the passengers or the driver. Besides, it takes longer time to reduce the vibration. Therefore, a good controller design must be able to reduce the vibration and produce a fast settling time. This project is focused on designing a controller for active suspension system by using MATLAB and Simulink software for both PID and LQR controllers to enhance the performance of ride comfort. This research also aims to study the effect of disturbances such as road bump and holes to the response time of the vibration of the vehicle. The result shows that the response of LQR control gives the best output performances in minimizing the vibration and gives faster settling time than that of the PID control.

Prediction on the Performance of Helical Strakes Through Fluid-Structure Interaction Simulation

Fluid-structure interaction (FSI) is used in the study to predict the vortex-induced vibration (VIV) of a cylinder that is fitted with helical strakes. The aims is to predict the characteristic of VIV after the installation of helical strakes on a cylinder. Two-way coupling through commercial fluid and structural solvers is utilized to develop the simulation. Helical strakes of height, h = 0.10D and pitch, p = 10D is used together with cylinder of diameter, D = 0.018 m. Three different velocities are tested. The amplitude, frequency, fluctuating lift response and vorticity contour are presented. The present study shows capability of FSI in reproducing the VIV characteristic of cylinder fitted with helical strakes. However, improvement is required especially at low reduced velocity as the values are deviated.

The effect of changing disk parameters on whirling frequency of high speed rotor system

The requirement for efficiency improvement of machines has caused machine rotor to be designed to rotate at high speeds. It is known that whirling natural frequency of a shaft changes with the change of shaft speed and the design needs to avoid points of resonance where the whirling frequency equals the shaft speed. At high speeds, a shaft may have to carry a huge torque along and this torsional effect has been neglected in past shaft analyses. Whirling behaviour of high speed rotating shaft is investigated in this study with consideration of the torsional effect of the shaft. The shaft system under study consists of a shaft, discs and two bearings, and the focus is on the effect of the disc parameters. A finite element formulation is developed based on Nelsons 5 degrees of freedom (DOF) per node element that includes the torsional degree of freedom. Bolotins method is applied to the derived Mathieu-Hill type of equation to get quadratic eigenvalues problem that gives the forward and backward frequencies of the shaft. Campbells diagrams are drawn in studying the effect of discs on the whirling behaviour of the shaft. It is found that the addition of disks on the shaft decreases the whirling frequency of the shaft and the frequency is lower for mass located at the centre of the shaft compared to the one located near to the end. The effect of torsional motion is found to be significant where the difference between critical speed of 4DOF and 5DOF models can be as high as 15%.