Sallehuddin Mohamed Haris

Vision-Based Mobile Robot Navigation Using Image Processing and Cell Decomposition

In this paper, we present a method to navigate a mobile robot using a webcam. This method determines the shortest path for the robot to transverse to its target location, while avoiding obstacles along the way. The environment is first captured as an image using a webcam. Image processing methods are then performed to identify the existence of obstacles within the environment. Using the Cell Decomposition method, locations with obstacles are identified and the corresponding cells are eliminated. From the remaining cells, the shortest path to the goal is identified. The program is written in MATLAB with the Image Processing toolbox. The proposed method does not make use of any other type of sensor other than the webcam.

Advances in the control of mechatronic suspension systems

The suspension system is a key element in motor vehicles. Advancements in electronics and microprocessor technology have led to the realization of mechatronic suspensions. Since its introduction in some production motorcars in the 1980s, it has remained an area which sees active research and development, and this will likely continue for many years to come. With the aim of identifying current trends and future focus areas, this paper presents a review on the state-of-the-art of mechatronic suspensions. First, some commonly used classifications of mechatronic suspensions are presented. This is followed by a discussion on some of the actuating mechanisms used to provide control action. A survey is then reported on the many types of control approaches, including look-ahead preview, predictive, fuzzy logic, proportional-integral-derivative (PID), optimal, robust, adaptive, robust adaptive, and switching control. In conclusion, hydraulic actuators are most commonly used, but they impose high power requirements, limiting practical realizations of active suspensions. Electromagnetic actuators are seen to hold the promise of lower power requirements, and rigorous research and development should be conducted to make them commercially usable. Current focus on control methods that are robust to suspension parameter variations also seems to produce limited performance improvements, and future control approaches should be adaptive to the changeable driving conditions.

A MATLAB Toolbox for Finding Stabilizing Controllers for a Class of Switched Systems

This paper presents a MATLAB toolbox that computes stabilizing state feedback controllers for a class of switched systems where the system dynamics switch interchangeably between several subsystems. The subsystems considered here are restricted to second order linear systems. The toolbox finds controllers that stabilize the system under arbitrary switching, where this is ensured by first determining the existence of a common Lyapunov function. To find the common Lyapunov function, the toolbox makes use of an algorithm that is less computationally demanding compared to methods based on solving linear matrix inequalities.

Steady-State Integral Proportional Integral Controller for PI Motor Speed Controllers

The output of the controller is said to exceed the input limits of the plant being controlled when a control system operates in a non-linear region. This process is called the windup phenomenon. The windup phenomenon is not preferable in the control system because it leads to performance degradation, such as overshoot and system instability. Many anti-windup strategies involve switching, where the integral component differently operates between the linear and the non-linear states. The range of state for the non-overshoot performance is better illustrated by the boundary integral error plane than the proportional–integral (PI) plane in windup inspection. This study proposes a PI controller with a separate closed-loop integral controller and reference value set with respect to the input command and external torque. The PI controller is compared with existing conventional proportional integral, conditional integration, tracking back calculation, and integral state prediction schemes by using ScicosLab simulations. The controller is also experimentally verified on a direct current motor under no-load and loading conditions. The proposed controller shows a promising potential with its ability to eliminate overshoot with short settling time using the decoupling mode in both conditions.

New Formulation for the Estimation of Monthly Average Daily Solar Irradiation for the Tropics: A Case Study of Peninsular Malaysia

In order to investigate a potential use of concentrating solar power technologies and select an optimum site for these technologies, it is necessary to obtain information on the geographical distribution of monthly average daily solar irradiation over an area of interest. In this study, three different models (Paltridge, Daneshyar, and modified Daneshyar) for the estimation of solar irradiation were discussed, and it turns out that the best result belongs to modified daneshyar method. This modification was necessary in order to accommodate tropical climate condition. The modifications are made by the inclusion of altitude, monthly total number of cloudy days, and variation of Sun-Earth distance. Data were analyzed for one year starting from January till December 2009. The annual average daily solar radiation for Peninsular Malaysia, during one year, has been between 13.67 MJ·m−2·day−1 and 17.18 MJ·m−2·day−1. The highest solar irradiation was estimated as 19.28 MJ·m−2·day−1 in the month of January, while the lowest was 10.53 MJ·m−2·day−1 recorded in November. The northern region has the highest potential for solar energy application due to its high solar irradiation throughout the year.

Topological and Topographical Optimization of Automotive Spring Lower Seat

The design of a suspension system emphasizes weight reduction in this high-computation technology era. Understanding that the reduction of suspension mass can lead to cost and material reduction is important; moreover, the riding performance of the vehicle should be improved. Topology and topography structure optimization for the spring lower seat is performed to reduce the weight of a passenger car spring lower seat design under stress and structure compliance constraints. Topology optimization is performed to identify the density of the required elements, whereas topography optimization is utilized to strengthen the structure of the lower seat by applying bead parameters in the model. Based on topology optimization, the mass of the model is improved by a reduction of 36.5%. Topography optimization is subsequently performed to fine-tune the topology-optimized model. Beads are added to the model to strengthen the stiffness of the structure. The topography-optimized model has successfully increased compliance by 27% compared with the sole topological optimized design. With the combination of topology and topography optimization techniques, the weight of coil spring lower seat has been successfully reduced while preserving the strength. Suitable sheet materials are proposed to match the optimized coil spring lower seat design.

Using the pressure transmission coefficient of a transmitted wave to evaluate some of the mechanical properties of refractory metals

Refractory metals have attracted increasing interest in recent years because of their use in many high-temperature applications. However, the characteristics of these metals calculated using loaded tests (such as tensile strength tests) differ considerably from those calculated using one of the most famous methods in NDT which is called time of flying of the wave (TOF).The present study presents two solutions based on calculating the pressure transmission coefficient (PTC) of the transmitted wave between the test sample and magnesium metal. The first is based on the development of a highly accurate algorithm that lowers the cost by determining the acoustic impedance of the test specimen to calculating mechanical properties. Up to 26 theoretical tests were done (10 of these tests for refractory materials) according to their known mechanical properties to verify the accuracy of the algorithm. The convergence in results ranged from 92% to 99%. The second solution was designed to solve the same problem for specimens with a thickness of less than 1mm. Eight experimental tests were done (five using refractory materials) to verify the accuracy of the second solution, with the convergence in the results ranging from 94% to 97%. The relationships of the Vrms measured from the oscilloscope with the PTC and with the Fourier transform spectrum were derived. The results of this research were closer to the standard mechanical properties for refractory metals compared with several recent acoustic tests.

Influence of a silver epoxy dopant on the performance of broken piezoelectric ceramic transducer based on an analytical model

Over the past decade, an unprecedented increase in the types of, the methods of using, and the demand for piezoelectric ceramic transducers (PCTs) has been observed in the market. These factors increase the probability of PCTs being subjected to breakage. Therefore, this study proposes a simple, low-cost procedure which uses available components to repair and reinstall five broken PCTs and then tests them as emitters and receivers in bulk and surface wave detection. An SM211 PCT with a 7.2 MHz frequency, a high damping and electromechanical coupling coefficient, and two silver electrodes were selected for the experiment. A Mason circuit was used for the procedure, the Laplace transform was used as a mathematical analysis method, and MATLAB was the technical computing language used to model the new transfer function for this type of PCT. This study proved that silver electrodes are a significant load on PCTs, particularly at high frequencies. Very good identity correlations between this mathematical and the experimental responses of the standard PCT were obtained. Later this mathematical model was used to prove the explanations provided by this research. The response of the standard PCT was compared with that of the samples of PCT that have been repaired (SPCTR). Through this comparison, many conclusions were obtained, and several recommendations were made, which can be taken advantage of by people who are interested in this field of research. Such recommendations include analyzing the response of SPCTR and explaining the types of ultrasonic tests in which SPCTR can be used.

Depth estimation from monocular vision using image edge complexity

Autonomous robotic arm motion requires the use of a control system in order to prevent collisions with the targeted object. Generally, in translational motion, as the camera approaches an object, the degree of complexity of the edges of the object image will change. This principle can be used to estimate the distance to a targeted object. This work introduces a novel statistical method, named Moment of Zoomed-Algorithm Kurtosis (MoZAK), which is based on the I-kaz method, as an indicator for motion system control. The MoZAK parameter, ℒc which represents the degree of complexity of image edges, is used to indicate if further actuation of the motor, or otherwise, is required. The method is compared to conventional statistical methods (standard deviation and kurtosis). Results indicate that the MoZAK method presents a viable distance estimator compared to conventional statistical methods.

Design and development of lower limb exoskeletons: A survey

Abstract Research into the development of the lower limb exoskeleton (LLE) has been on-going since the 1960s. Although this field has long been explored, the technological progress has been very slow. Many exoskeletons were stopped in their tracks toward commercialization at the research stage itself. Therefore, this paper is aimed at systematically reviewing the design and development of multiple joint LLEs. The discussion focuses on the application of LLEs for augmentation, muscle weakness or gait recovery and rehabilitation. Details of aspects such as the control strategy, actuator, safety and design, including compactness, noise, heavy structural weight, cost, mimicking of natural walking, and power sources, will be discussed. Finally, issues concerning the design and development of LLEs will also be presented.