Mohd Noh Karsiti

Starting of a free-piston linear engine-generator by mechanical resonance and rectangular current commutation

Starting a free-piston linear engine-generator (LG) involves reciprocating a freely moving piston-magnet-translator assembly between two oppositely placed engine cylinders for combustion to occur. The machine is operated as a brushless linear motor to produce the required motion. However, due to the very large peak compression force during starting, limited current rating of stator coils and insufficient motor force constant, it is not possible to push the translator end to end in a single stroke. A strategy is proposed which utilizes the air-spring quality of the engine cylinders prior to combustion. Energizing the coils with fixed DC voltage and open-loop, rectangular commutation of injected current, sufficiently high motoring force is produced to reciprocate the translator in small amplitudes initially. Due to repeated compression-expansion of the engine cylinders and constant application of motoring force in the direction of natural bouncing motion, the translatorpsilas amplitude and speed is expected to grow - due to mechanical resonance - to finally reach the required parameters for combustion. This work discusses the starting problem and its mechanical aspects for a specific LG configuration, builds a mechanical model of LG and presents simulation results on the viability of the starting strategy using different values of constant-magnitude motoring force.

Modeling, parameters identification, and control of an electronic throttle control (ETC) system

The modeling, parameters identification, and linear and nonlinear feedback control designs of an electronic throttle control (ETC) system is considered. A commercially available ETC system made by Bosch is selected for our investigation. The unknown parameters identified are used in designing linear and nonlinear controllers. Simulations and extensive experiments were conducted. A real-time linear controller was implemented with the xPC Target. The ETC model is then extended to a separately excited nonlinear DC motor model. The nonlinear controller is designed using the input-output feedback linearization technique; the extension proves to be of solid theoretical value. The results presented in this paper can be considered as an interesting and important case study encompassing system modeling, parameters identification, linear and nonlinear controller designs, and real-time control. The techniques and methodology developed are applicable to similar and/or other types of systems.

A testbed for control schemes using multi agent nonholonomic robots

Multi agent robots performing tasks together have significant advantages over a single robot. Applications of multi agent robots can be found in the fields of tele-surgery, hazardous waste cleanup, mine and ores detection and harvesting of agriculture fields. This paper presents the control analysis and develops a testbed to simulate different feedback control strategies using multi agent nonholonomic robots. Each multi agent robot communicate with other robots using Bluetooth piconet. The multi agent robot system is modeled in Simulink and simulation results are presented. The nonlinear feedback control strategy improves the system performance by minimizing the mean of the error. Furthermore, the nonlinear strategy globally asymptotically stabilizes the system using Lyapunov stability theory compared to the linear feedback strategy. The work presented here is an initial study concerning the design of feedback controllers for multi agent nonholonomic robots.

Rectangular current commutation and open-loop control for starting of a free-piston linear engine-generator

Starting a free-piston linear engine-generator consists of reciprocating a freely moving piston-magnet-translator assembly between two oppositely placed engine cylinders to initiate combustion. To provide for the reciprocating force, the machine is operated as a brushless linear motor. A starting strategy is proposed which utilizes the air-spring quality of the engine cylinders prior to combustion: by energizing the coils with fixed DC voltage and by open-loop, rectangular commutation of injected current, sufficiently high motor force is produced to reciprocate the piston-magnet assembly in small amplitudes initially. Due to repeated compression-expansion of the engine cylinders and constant application of motoring force in the direction of natural bouncing motion, the translatorpsilas amplitude and compression pressure is expected to grow - due to mechanical resonance - to finally reach the required parameters for combustion. This work discusses the electrical aspects of the starting strategy, considers control possibilities, builds a model of the electrical subsystem and presents simulation and validation tests of the integrated model for starting investigation.

Visual-based fuzzy navigation system for mobile robot: Wall and corridor follower

This paper presents the development of a visual-based fuzzy navigation system that enables a mobile robot in moving through a corridor or following a wall. The system employs a camera to detect the existence of walls on the left, the right, and the front of the robot. A mamdani-type fuzzy logic controller uses the information gathered by the camera to determine the turning angle and the speed of the robot. The fuzzy system is tested using an OpenGL-based 3D simulator that capable in animating the movement of the robot as well as generating the images captured by the camera. The results of the test confirm that the controller shows a good performance in navigating the robot.

Use of wavelets in marine controlled source electromagnetic method for geophysical modeling

Wavelets gained significant attention in science and engineering disciplines due to their remarkable data analyzing capabilities. Wavelets are also used for finding numerical solution of various engineering and geophysical problems. Marine controlled source electromagnetic (CSEM) method is a relatively new geophysical technique used to explore petroleum reserves from shallow and deep water. This work attempts to use periodic and non-periodic wavelets in CSEM for modeling of geophys- ical problem. This is results in a solution with multi-scale approximations using multiresolution analysis (MRA) algorithm. In this work, Daubechies wavelets are used, as the basis functions for solving the wave equation of marine CSEM, because of their orthonormality and compact support. Accuracy of the proposed method for marine CSEM is determined by comparing the results with the analytical solution for isotropic problem as well as those obtained using finite element (FE) method. Nu- merical results show that the governing equations for aforementioned geophysical method yield less obscure results than that of finite element method, for both bounded and unbounded domains. Furthermore, the proposed wavelet based numerical method produces multi-scale approximation that would prove useful for further analysis and data processing.

Observer based feedback control strategies for collaborative robots

This paper presents observer based feedback control strategies for nonholonomic collaborative robots. The collaborative robot system uses the leader-follower formation controller. The observer based feedback strategies are presented for the leader robot. The control inputs for the follower robot are derived based on input-output linearization techniques. The system is modeled using Simulink and simulation results are presented. From the simulation results, it can be seen that the error for observer based feedback controller converges rapidly to zero. Furthermore, the observer based feedback controller results in a K-exponentially stable system. The work presented here is an initial study concerning the design of observer feedback controllers for nonholonomic collaborative robots.

High accuracy traffic light controller for increasing the given green time utilization

Traffic congestion has become one of the main complications in the urban cities according to the growing number of vehicles in those cities, outdated technologies used on the streets of those cities, unsuitable road design, and several other reasons. So, that has urged the need for a more precise traffic light controlling system; the one that will help in preserving high stability at all levels of demand. This paper introduces a dynamic traffic light phase plan protocol for single-isolated intersections. The developed controlling method was compared with four other methods and showed a good performance in terms of reducing the average and maximum queue lengths, optimizing the given green time amount as needed, and increased the intersections throughput (increased the given green time utilization). In addition, it maintained a good traffic light stability at all levels of demand.

Phase angle adjustment for phase advance control of brushless DC motor

Brushless direct current (BLDC) motor is widely used in small and medium side electric vehicles as it exhibit highest specific power and thermal efficiency compared with induction motor. The permanent magnets in the rotor create a constant magnetic flux, which limit the motor top speed. As the back electromotive force (EMF) voltage increases proportionally with motor rotational speed and it approaches the amplitude of the input voltage, the phase current amplitude will reach zero. By advancing the phase current, it is possible to extend the maximum speed of the BLDC motor beyond the rated top speed. This will allow smaller BLDC motor to be used in small electric vehicles and in larger applications will allow the use of BLDC motor without the use of multispeed transmission unit for high speed operation. Adjusting the phase angle will affect the speed of the motor as the each coil is energized earlier than the corresponding rise in back emf of the coil. Preliminary test results indicated that the motor top speed can be increased at least by 40 percent over the baseline speed at no load condition.

Input-Output Exact Feedback Linearization for Depth Positioning of Spherical URV

In this paper, depth positioning of a spherical URV which utilizes variable ballast as actuator is presented. Since the model of this system is nonlinear therefore feedback linearization is utilized in this depth positioning. The idea of feedback linearization is to algebraically transform nonlinear systems dynamics into (fully or partly) linear ones, so that linear control techniques can be applied. This method can stabilize the equilibrium point of this system which is unstable in open loop system. From the control analysis and simulation results, it can be observed that the asymptotical stabilization is achieved by tracking the error. Hence, feedback linearization can also be applied for tracking a trajectory of desired depth position.