Current Issue : October - December Volume : 2014 Issue Number : 4 Articles : 4 Articles
Combinatorial optimization has been used in different research areas. It has been employed successfully in software testing fields\nto construct minimum set of combinations (i.e., in terms of size) which in turn represents the minimum number of test cases. It\nwas also found to be a successful approach that can be applied to solve other similar problems in different fields of research. In line\nwith this approach, this paper presents a new application of the combinational optimization in the design of PID controller for DC\nservomotor.The design of PID controller involves the determination of three parameters. To find optimal initial PID parameters,\ndifferent tuning methods have been proposed and designed in the literature. The combinatorial design is concerned with the\narrangement of finite set of elements into combinatorial set that satisfies some given constraints. Consequently, the proposed\nmethod takes the interaction of the input parameters as a constraint for constructing this combinatorial set. The generated sets\nare then used in the proposed tuning method. The method proved its effectiveness within a set of experiments in a simulated\nenvironment....
The vibration of SRMobtains less attention for in-wheel motor applications according to the present research works. In this paper,\nthe vertical component of SRM unbalanced radial force, which is named as SRMvertical force, is taken into account in suspension\nperformance for in-wheel motor driven electric vehicles (IWM-EV). The analysis results suggest that SRMvertical force has a great\neffect on suspension performance.The direct cause for this phenomenon is that SRM vertical force is directly exerted on the wheel,\nwhich will result in great variation in tyre dynamic load and the tyre will easily jump off the ground. Furthermore, the frequency\nof SRMvertical force is broad which covers the suspension resonance frequencies. So it is easy to arouse suspension resonance and\ngreatly damage suspension performance. Aiming at the new problem, FxLMS (filtered-X least mean square) controller is proposed\ntoimprove suspensionperformance.TheFxLMScontroller isbasedonactive suspension systemwhichcangenerate the controllable\nforce to suppress the vibration caused by SRM vertical force. The conclusion shows that it is effective to take advantage of active\nsuspensions to reduce the effect of SRM vertical force on suspension performance....
The Joint Architecture for Unmanned Systems (JAUS) is a communication standard that allows for interoperability between\nUnmanned Vehicles (UVs). Current research indicates that JAUS-compliant systems do not meet real-time performance guidelines\nnecessary for internal systems in UVs. However, there is a lack of quantitative data illustrating the performance shortcomings of\nJAUS or clear explanations on what causes these performance issues or comparisons with existing internal communication systems.\nIn this research, we first develop a basic C++ implementation of JAUS and evaluate its performance with quantitative data and\ncompare the results with published performance data of Controller Area Network (CAN) to determine the feasibility of the JAUS\nstandard. Our results indicate that the main reason of JAUS�s poor performance lies in the latency inherent in the hierarchical\nstructure of JAUS and the overhead of User DatagramProtocol (UDP) messages, which has been used with JAUS and is slower than\nthe high-speed CAN. Additionally, UDP has no schedulingmechanism, whichmakes it virtually impossible to guarantee messages\nmeeting their deadlines. Considering the slow and nondeterministic JAUS communication fromsubsystems to components, which\nis JAUS Level 3 compliance, we then propose a solution by bringing Ethernet for Control Automation Technology (EtherCAT) to\nadd speed, deterministic feature, and security. The JAUS-EtherCAT mapping, which we called a JEBridge, is implemented into\nnodes and components. Both quantitative and qualitative results are provided to show that JEBridge and JAUS Level 3 compliance\ncan bring not only interoperability but also reasonable performance to UVs....
A state estimator and various model-based control systems have been designed for a real anaerobic digestion (AD) pilot reactor\nfed with dairy manure. The model used is a modified Hill model which is a relatively simple dynamical AD process model. The\nstate estimator is an Unscented Kalman Filter (UKF) which uses only methane gas flow measurement to update its states. The\nmodel and the state estimates are used in different control systems. One of the control systems aims at controlling the methane gas\nflow to a setpoint. Simulations indicate that the setpoint tracking performance of a predictive control system is considerably better\ncomparing with PI control, while disturbance compensation is not much better. Consequently, assuming the setpoint is constant,\nthe PI controller competes well with the predictive controller. A successful application of predictive control of the real reactor is\npresented. Also, three different control systems aiming at retaining the reactor at an operating point where the volatile fatty acids\n(VFA) concentration has a maximum, safe value are designed. A simulation study indicates that the best control solution among\nthe three alternatives is PI control based on feedback from estimated VFA....
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