A discrete model-based event PID controller solution and stability evaluation

A simple tuning method for multiloop PID controllers will be presented in this article. The method is suited for PID algorithms with no proportional and derivative kick. This tuning method is derived from a controller synthesis method with a control performance specification of 5% overshoot on servo response. Depending on the interaction natures of the multiloop systems, tuning based on the diagonal elements of the model or further detuning may be necessary. For systems with a relative gain array [RGA(λii)] < 1, a detuning factor based on this information is proposed. The information needed for controller tuning purposes is the dynamic model parameters of the diagonal elements and the process gain information of the off-diagonal elements. The tuning method procedure is very simple and straightforward, utilizing only nth identification tests with n as the number of the interacting control loops. The tuning method can easily be applied to various industrial situations with almost no need for a priori process knowledge.

This thesis focuses on the development and analysis of general methods for the design of optimal discrete PID control strategies for multivariable glass furnace processes, where standard genetic algorithms (SGAs) are applied to optimise specially formulated objective functions. Furthermore, a strong emphasis is given on the realistic model parameters identi cation method, which is illustrated to be applicable to a wide range of higher order model parameters identi cation problems. A complete, realistic and continuous excess oxygen model with nonlinearity effect was developed and the model parameters were identified. The developed excess oxygen model consisted of three sub-models to characterise the real plant response. The developed excess oxygen model was evaluated and compared with real plant dynamic response data, which illustrated the high degree of accuracy of the developed model. A new technique named predetermined time constant approximation was proposed to make an assumption on the initial value of a predetermined time constant, whose motive is to facilitate the SGAs to explore and exploit an optimal value for higher order of continuous model's parameters identi cation. Also, the proposed predetermined time constant approximation technique demonstrated that the population diversity is well sustained while exploring the feasible search region and exploiting to an optimal value. In general, the proposed method improves the SGAs convergence rate towards the global optimum and illustrated the effectiveness. An automatic tuning of decentralised discrete PID controllers for multivariable processes, based on SGAs, was proposed. The main improvement of the proposed technique is the ability to enhance the control robustness and to optimise discrete PID parameters by compensating the loop interaction of a multivariable process. This is attained by adding the individually optimised objective function of glass temperature and excess oxygen processes as one objective function, to include the total effect of the loop interaction by applying step inputs on both set points, temperature and excess oxygen, at two different time periods in one simulation. The effectiveness of the proposed tuning technique was supported by a number of simulation results using two other SGAs conventional tuning techniques with 1st and 2nd order control oriented models. It was illustrated that, in all cases, the resulting discrete PID control parameters completely satisfied all performance specifications. A new technique to minimise the fuel consumption for glass furnace processes while sustaining the glass temperature is proposed. This proposed technique is achieved by reducing the excess oxygen within the optimum thermal efficiency region within 1.7% to 3.2%, which is approximately equal to about 10% to 20% of excess air. Therefore, by reducing the excess oxygen set point within the optimum region, 2.45% to 2%, the fuel consumption is minimised from 0:002942kg/sec to 0:002868kg/sec while the thermal efficiency of the glass temperature is sustained at the desired set point (1550K). In addition, a reduction in excess oxygen within methane combustion guidelines will assure that undesirable emissions are in control throughout the combustion process. The efficiencies of the proposed technique were supported by a number of simulation results applying the three SGAs controller tuning techniques. It was illustrated that, in all cases, the fraction of excess oxygen reduction results in a great minimisation of fuel consumption over long plant operating periods.

This paper describes the design, simulation, optimisation and implementation of a 1-Degree-of-Freedom (1-DOF) discrete PID controller for the buck converter working in Continuous Conduction Mode (CCM) based on Field Programmable Gate Array (FPGA) device. The converter operates at a switching frequency of 500 KHz. The elaborated PID control algorithm takes advantage of the conjugation of Xilinx ISE digital designing environment with MATLAB/Simulink simulation and testing environment, through Xilinx System Generator toolbox. This results in a faster and efficient design flow. First the PID controller is designed using Simulink Control Design Toolbox or ‘sisotool’ from MATLAB to generate the required set of compensator coefficients to meet the start-up and the transients characteristics. The controller is then realized using Xilinx System Generator (XSG) Blockset. The design example certifies the validity of the classical discrete 1-DOF PID controller as an efficient, more compact and reliable control method for rapid system prototyping for designs developed using the MATLAB/Simulink environment.

In order to meet the needs of modern high-performance aircraft, the fuzzy PID control strategy was used to design the electromechanical actuator control system. This control strategy combines the advantages of fuzzy control and PID control, and has better adaptability to time-varying complex systems. The electromechanical actuator control system adopted the three-loop structure, and current loop, speed loop and position loop were built on the platform of MATLAB / Simulink. Considering that the discrete universe fuzzy PID control algorithm has good real-time performance with small online computation, the fuzzy PID controller in discrete universe was designed in the position loop and the system was simulated. The simulation results show that the dynamic and steady performance of discrete universe fuzzy PID control is better than that of traditional PID control, and it is more suitable for electromechanical actuator system.

This paper concerns a tuning method for PID controller using optimization subject to constraints on derivatives of control input. To evaluate the control performance, the responses to load disturbance and reference input changes are presented compared to those by the partial model matching method. Moreover, it is found that the PID controller tuned by this optimization technique is somewhat robust and effective enough for practical applications.

In this paper, we introduce a procedure to assess the performance of three particular systems, when the orders of the integrator and differentiator of a fractional PID controller are changed in a range of values. At first, a conventional tuning method for PID controllers is used, and then, the orders are changed individually. The dynamical response is analyzed in transient state as well as when a load disturbance is introduced.

Stability of Networked Control System (NCS) with discrete time-driven PID controllers

Practical implementation of the fractional order PID (FOPID) controller for FLHex robot leg position control system with comparison of selected performance indexes for different controller's coefficients. In the case of systems such as the FLHex mobile robot, where multiple PID controllers are used, more advanced control algorithms such as FOPID controller can improve quality of control and energy consumption, which is extremely important in the case of mobile robots. Presented comparison of FOPID controllers with varied coefficients in case of leg underwater movement for step sequence setpoint shown differences in parameters of averaged step response, integrals of the squared error (ISE) and integrals of energy consumption (IEC).

PID control is widely used to control stable processes, however its application to unstable processes is less common. In the paper, the formulas are derived to tune PID controller for unstable processes with time delay to meet sensitivity specification. It adopts two feedback loop design technique, and obtains a tuning method for PID controller with setpoint weighting which can overcome structural limitation of the typical PID controller for unstable processes. With the proposed PID tuning method, a loop transfer function with desired sensitivity specification is obtained, which guarantees both robustness and performance. Simulation examples are given to show good performance of the proposed tuning method.

Variable-order fuzzy fractional PID controller

An analytical approach for tuning fractional PID controllers based on the frequency response of the system is addressed in this paper. Fractional PID controller inherits all advantages of conventional PID controllers and also has additional degrees of freedom. Based on their frequency response a new method of tuning is proposed in this paper, which is inspired from the previous works associated with this topic. Then the same method is validated by applying for attitude control of Reusable launch vehicle. The robustness study of the whole system is also carried out.

The article considers different types of controllers and regulators used in industry, laboratories and for daily tasks. In practice, the most commonly used controllers are discrete state controllers, PID controllers, fuzzy and neural controllers. The last two use more sophisticated concepts, such as artificial intelligence. Controllers can be divided into feed-forward and feedback controllers. The feed-forward controller works by giving a result based on waiting for the next step, while the feedback controller works to give an observable result that changes the processing value of the later step. PID controllers are very popular in the design of a ship's main power plant. There is considered a schematic diagram of the PID controller. The description of the ship model in the Simulink environment is presented, the specified model of the diesel engine, the mechanical regulator, areas of restrictions of the engine are illustrated. The model of the turbocharger is analyzed in detail. It consists of a turbine resting on the exhaust gases coming out of the cylinders, due to which the compressor starts and compresses the air at the inlet to the cylinders. There is given the equation formed by the ratio of integral to time. In accordance with the original model of the diesel engine Diesel Engine Module, the nominal efficiency is defined. A model of shaft dynamics based on Newton's second law for rotation is considered. The actual Simulink model is illustrated, which introduces transmission losses and saturation associated with the load capacity of the engine. The model uses three designs of propellers. The characteristics of the propellers on the container ship MSC Caitlin, the tanker “Ivan Poddubny” and the ferry “Olympiad” are given. The general model of the propeller is made and resistance of calm water is simulated. The additional model of wave resistance is presented.

This paper compares two approaches to tune PI controllers in a multivariable process. A modified Direct Synthesis method extends the technique to a multivariable system. Results show that the modified Direct Synthesis technique relies on model accuracy and suitability of the desired transfer function and process model. The effectiveness of this technique may break down when these conditions are not met. Genetic algorithms provide a method based on the evolution of species via natural selection. The GA method allows the use of a specific structure, such as PI controller, and then gets the best possible results for that structure. The concept has been adapted into an optimization technique that can be used to find the best controller parameters to meet user defined transient specifications for a complex process. Thus, the robustness of the method allows it to outperform the former technique. Simulation results are shown to illustrate the comparisons between these two methods and the effectiveness of Gas.

The complexity and severe nonlinearity of multi-machine power systems make it difficult to design a control input for voltage regulation using modern control theory. This paper presents a model-based PID control scheme for the regulation of the bus voltage to a desired value. To this end, a fourth-order linear system is constructed using input and output data obtained using the TSAT (Transient Security Assessment Tool); the input is assumed to be applied to the grid through the STATCOM (STATic synchronous COMpensator) and the output from the grid is a bus voltage. On the basis of the model, it is identified as to which open-loop poles of the system make the response to a step input oscillatory. To reduce this oscillatory response effectively, a model-based PID control is designed in such a way that the oscillatory poles are no longer problematic in the closed loop. Simulation results show that the proposed PID control dampens the response effectively.

In a sampled-data control circuit the regulator can be designed in the frequency domain taking into account that by sampling and applying a zero order hold the system behaves as if additional dead-time had occurred in the system. Discrete PID controllers considering this effect are designed with pole cancellation technique.