An optimal control of Reverse Osmosis (RO) plant is studied in this paper utilizing the auto tuning concept in conjunction with PID controller. A control scheme composing an auto tuning stochastic technique based on an improved Genetic Algorithm (GA) is proposed. For better evaluation of the process in GA, objective function defined newly in sense of root mean square error has been used. Also in order to achieve better performance of GA, more pureness and longer period of random number generation in operation are sought. The main improvement is made by replacing the uniform distribution random number generator in conventional GA technique to newly designed hybrid random generator composed of Cauchy distribution and linear congruential generator, which provides independent and different random numbers at each individual steps in Genetic operation. The performance of newly proposed GA tuned controller is compared with those of conventional ones via simulation. Keywords—Genetic Algorithm, Auto tuning, Hybrid random number generator, Reverse Osmosis, PID controller.

Auto Tuning PID Controller based on Improved Genetic Algorithm for Reverse Osmosis Plant

This paper presents both offline and online optimization techniques for the control of a multiple high voltage direct current link power system. A frequency control scheme based on classical proportional-integral-derivative controllers is proposed and optimally tuned offline using particle swarm optimization. The performance of this scheme is compared with the performance of a centralized model predictive control (MPC) scheme, and a distributed MPC scheme that uses only local communications. The results illustrate that a significant performance improvement can be achieved using distributed MPC instead of classical control, illustrating the potential of distributed MPC for use in future power networks.

Optimal Coordination of a Multiple HVDC Link System Using Centralized and Distributed Control

In this paper, model based design of PID controllers is proposed for higher-order oscillatory systems. The proposed method has no limitations regarding systems order, time delays and oscillatory behavior. The reduced model is achieved based on third-order modeling and selection of coefficients through the use of frequency responses. The tuning of the PID parameters are obtained from a reduced third-order model; the procedure seems to be simple and effective, and improved performance of the overall system can be achieved. Three simulation examples and one real-time experiment are included to demonstrate the effectiveness and applicability of the proposed method to systems with oscillatory behavior.

Tuning PID controllers for higher-order oscillatory systems with improved performance.

This paper presents a novel cost-effective automatic resonance tracking scheme with maximum power transfer for piezoelectric transducers (PTs). The conventional approaches compensate the PT with complex power factor correction schemes or drive it in resonance using intricate loops with limited operating range. The proposed tracking scheme is based on a bandpass filter (BPF) oscillator, exploiting the PT's intrinsic resonance point through a sensing bridge. It guarantees automatic resonance tracking and maximum electrical power converted into mechanical motion, regardless of process variations and environmental interferences. Thus, the proposed BPF oscillator-based scheme was designed for an ultrasonic vessel sealing and dissecting system, where accurate PT displacement regulation over a wide range of loads is required. An amplitude control for a switching power stage was developed to regulate the output mechanical motion and provide different power levels for the specific surgical functions such as sealing and dissecting. A proportional–integral compensator was developed to ensure stable operation under various loading conditions. The sealing and dissecting functions were verified experimentally in chicken tissue and glycerin.

An Automatic Resonance Tracking Scheme With Maximum Power Transfer for Piezoelectric Transducers

The aim of this study is to evaluate the feasibility of using harmonic cancellation for a therapeutic ultrasound transducer excited by a switched-mode power converter without an additional output filter. A switching waveform without the third harmonic was created by cascading two switched-mode power inverter modules at which their output waveforms were pi/3 phase-shifted from each other. A PSPICE simulation model for the power converter output stage was developed. The simulated results were in good agreement with the measurement. The waveform and harmonic contents of the acoustic pressure generated by a 1-MHz, self-focused piezoelectric transducer with and without harmonic cancellation have been evaluated. Measured results indicated that the acoustic third harmonic- to-fundamental ratio at the focus was small (-48 dB) with harmonic cancellation, compared to that without harmonic cancellation ( -20 dB). The measured acoustic levels of the fifth harmonic for both cases with and without harmonic cancellation also were small (-46 dB) compared to the fundamental. This study shows that it is viable to drive a piezoelectric ultrasound transducer using a switched-mode power converter without the requirement of an additional output filter in many high-intensity focused ultrasound (HIFU) applications.

A harmonic cancellation technique for an ultrasound transducer excited by a switched-mode power converter

In this paper we uses a software pack, which allows to adjust PID controller automatically in real time way in the case of changes parameters of used object. PID settings are optimized in real time by using genetic algorithm and are compared with generally accepted quality indicators for control systems like rise time, % overshoot and settling time of step response or such coefficient like oscillations frequency, reduced damping and gain of second order object. A digital signal processor (DSP) is a specialized microprocessor designed specifically for digital signal processing generally in real time applications requiring high computation. The simulation results were verified by some laboratory test.

On-line PID controller tuning using genetic algorithm and DSP PC board

This paper presents the control method of the high-frequency-generator for supplying a sandwich-type piezoelectric ceramic transducers used in ultrasonic cleaning systems. This method makes it possible to obtain an optimal US cleaning system by varying the resonant frequency of the transducers. A power generator with the new control method was built and tested. The generator developed consists of a resonant MOSFET transistor converter, a group of sandwich-type piezoelectric ceramic transducers, and a full-bridge inverter circuit. Experimental results for the test conducted using the generator developed are given.

Series resonant converter with sandwich-type piezoelectric ceramic transducers

Sandwich type piezoelectric ceramic transducers are the most frequently applied source of ultrasounds in technical cleaning system. They have the ability to radiate in an ultrasonic medium, e.g. water, with maximum acoustic power when the vibration is activated by a current whose frequency equals the mechanical resonance frequency of the transducer. In resonant inverters the transducer units are part of the oscillating circuit, for which equivalent electrical circuit consist of connection in parallel: Co end RLC. Genetic algorithm is used to optimization of structure and parameters piezoelectric ceramic transducer. Genetic algorithm have been shown to be effective in the resolution of difficult problems. The resonant frequency of the real circuit varies during the operation in function of many parameters, among others, the most important are temperature, time, the column of cleaning factor, and the surface of the cleaned elements. In this situation, to obtain the maximum value of the converter efficiency, its important role of control system to assure the optimal mechanical resonant frequencies of converter.

Series Resonant Converter with Piezoelectric Ceramic Transducers and Fuzzy Logic Control with Genetic Optimization

In this paper the genetic algorithm is used to optimization of parameters the equivalent electrical circuit of piezoelectric ceramic. Sandwich type piezoelectric ceramic transducer are the source of power ultrasounds when the vibration is activated by a voltage inverter. The output frequency of inverter most by equals the mechanical resonance frequency of the transducer and most by tuning with very high precise. In real circuits the mechanical resonant frequency is function of many parameters of piezoelectric material. The equivalent electrical circuit of transducer transforms this parameters in electrical value. This electrical circuit consist of connection in parallel: Co end RLC elements and this units are part of the oscillating circuit of inverter. The values of equivalent electrical circuit varies during the operation of transducer in function extending parameters, among others, the most important are temperature and time. In this situation to obtain the optimal value of the output voltage frequency of inverter most by know electrical parameters equivalent circuit of transducer. In the resolution of difficult problems to by effective the genetic algorithm.

Genetic identification of parameters the sandwich piezoelectric ceramic transducers for ultrasonic systems

This paper deals with fuzzy logic control of inverter fed synchronous motor. In this paper mathematical model of the motor drive system and stability condition of fuzzy logic control algorithm are represented. The essential fuzzy logic control configuration system consists of an internal current regulation loop and an external speed regulation loop. PID controller generally controls the speed and current loop in these systems. To control a inverter fed synchronous machine a host computer and a special microprocessor system with dSPACE 1104 central unit as a microcontroller is used. Most important results of our investigation is to find a simply mathematical model of our motor drive system. Then stability conditions are determined for current and speed controller. The simulated results were compared during the laboratory test on 600 W synchronous motor.

P. Fabijanski

Papers

On-line PID controller tuning using genetic algorithm and DSP PC board

Series resonant converter with sandwich-type piezoelectric ceramic transducers

Series Resonant Converter with Piezoelectric Ceramic Transducers and Fuzzy Logic Control with Genetic Optimization

Genetic identification of parameters the sandwich piezoelectric ceramic transducers for ultrasonic systems

A very simple fuzzy control system for inverter fed synhronous motor