Variable Universe Research Articles

An Approach to Improve the Performance of Simulated Annealing Algorithm Utilizing the Variable Universe Adaptive Fuzzy Logic System

This paper focuses on improving the standard form of the classical simulated annealing algorithm (CSAA). A novel method of improving the performance of CSAA by the variable universe adaptive fuzzy logic system (VUAFLS) is studied. We develop the VUAFLS to adjust the annealing temperature, which is a very important parameter governing the performance of CSAA, and this algorithm is named VUAFLS-CSAA. The main innovations of VUAFLS-CSAA lie in the application of VUAFLS containing the fast cooling mechanism and reheating mechanism relative to the characteristic of the sustained temperature fall of CSAA. Compared with the conventional method for controlling annealing temperature, VUAFLS-CSAA can control the annealing temperature more effectively, leading to the high efficiency of CSAA. The performance of the proposed method is evaluated and compared with CSAA through two examples. One is the image restoration problem, and the other is the traveling salesman problem (TSP). The experimental result indicates that the new method proposed in this paper can improve the efficiency of CSAA by tremendously shortening the iteration optimization process. And at the same time, the successful application of the new method for tackling two different problems demonstrates the generality of this method. In addition, techniques that can further improve the performance of CSAA are discussed.

The Motion Path Study of Measuring Robot Based on Variable Universe Fuzzy Control

For the problem of measuring robot requires a higher positioning, firstly learning about the error overview of the system, analysised the influence of attitude, speed and other factors on systematic errors. Then collected and analyzed the systematic error curve in the track to complete the planning process. The last adding fuzzy control in both cases, by comparing with the original system, can found that the method based on fuzzy control system can significantly reduce the error during the motion.

Approximation performance of the nonlinear hybrid fuzzy system based on variable universe

Variable universe is through a group of nonlinear contraction expansion factors online timely to adjust the input domain, so that the input domain is subdivided as detailed as possible at surrounding the expected control points. It is characteristic of constant rules, quick response, and high stability precision. In this paper, a nonlinear hybrid fuzzy system was established by introducing adjusting parameters to combine Mamdani fuzzy system and Takagi–Sugeno (T–S) fuzzy system. The input–output expression of the nonlinear hybrid fuzzy system based on variable universe was deduced according to the hybrid inference rules and contraction expansion factors. Furthermore, the second-order approximation of the nonlinear hybrid fuzzy system based on variable universe on the second-order continuously differentiable function was proved by multiple Taylor formula and maximum norm, and a sufficient condition for the approximation of the nonlinear hybrid fuzzy system was disclosed when adjusting parameters and approximation accuracy are known. Finally, the simulation example confirmed that the established nonlinear hybrid fuzzy system based on variable universe has better approximation performance than other systems under different adjusting parameter meanings.

A novel tensor product model transformation-based adaptive variable universe of discourse controller

In this paper, a tensor product (TP) model transformation-based variable universe of discourse (VUD) controller is presented for a class of under-actuated nonlinear systems. First, the under-actuated nonlinear system is transformed into a parameter-varying weighted polytopic system by TP model transformation. Next, the VUD approach is extended to the TP model case; in this model, the gains of the error and error derivative in the VUD are calculated by linear matrix inequalities rather than traditional linear methods, such as the linear quadratic regulator or the Lyapunov equation. The TP model transformation-based VUD (TPVUD) is augmented with a σ-adaptive strategy to improve the controller׳s performance. To demonstrate the advantages of the developed control method, numerical simulations are carried out on a parallel-type double inverted pendulum and an aeroelastic wing system. Moreover, experimental results are employed to test the effectiveness of TPVUD on a laboratory-scale three-dimensional (3-D) crane system.

MR-SAS variable universe fuzzy control in steering situation based on wheelbase preview

In order to make the vehicle meet the requirements of complex conditions, the dynamic model of 1/2 vehicle magneto-rheological (MR) semi-active suspension (SAS) based on wheelbase preview in steering situation was established, and the variable universe adaptive fuzzy controller based on fuzzy neural network (FNN) was designed. The universe size of the system fuzzy controller can be adjusted automatically by FNN controller according to system deviation, avoided subjectivity of universe division, improved the fuzzy control accuracy. The damping of MR damper can be adjusted by controlling the current size, so the vehicle will remain the ride comfort and safety in steering situation, and the vehicle dynamic performance can be improved. Through the comparison of simulation, the vehicle performance of variable universe FNN control system based on wheelbase preview were superior to passive system and fuzzy control system and without preview system in the same situation.

Design and Application of Variable Universe Fuzzy Controller Based on Cat Swarm Optimization

A novel variable universe fuzzy controller based on cat swarm optimization (CSO-VUFC) is proposed to regulate the temperature of the reactor system, which is characterized by nonlinearity, large time delay, and uncertainty. In CSO-VUFC, firstly, corresponding contraction-expansion factors with the function form were, respectively, introduced for the input and output fuzzy universes of the controller. Then, cat swarm optimization was used to optimize the relevant parameter values in the contraction-expansion factor function to achieve the intelligence optimization of the contraction-expansion factors, based on the system performance test function as an evaluation index; the contradiction between the universe adjustment and control accuracy of the fuzzy controller will be effectively solved to achieve the online self-adjustment of the universe. The simulation results indicate that the variable universe adaptive fuzzy control method based on the cat swarm optimization has the features of high precision adjustment, short transient time, and hard real-time.

Modelling and Experimental Study on Active Energy-Regenerative Suspension Structure with Variable Universe Fuzzy PD Control

A novel electromagnetic active suspension with an energy-regenerative structure is proposed to solve the suspension’s control consumption problem. For this new system, a 2-DOF quarter-car model is built, and dynamics performances are studied using the variable universe fuzzy theory and the PD control approach. A self-powered efficiency concept is defined to describe the regenerative structure’s contribution to the whole control consumption, and its influent factors are also discussed. Simulations are carried out using software Matlab/Simulink, and experiments are conducted on the B-class road. The results demonstrate that the variable universe fuzzy control can recycle more than 18 percent vibration energy and provide over 11 percent power for the control demand. Furthermore, the new suspension system offers a smaller body acceleration and decreases dynamic tire deflection compared to the passive ones, so as to improve both the ride comfort and the safety.

Research on Approaching Error Boundary of Variable Universe Adaptive Fuzzy Controller

To confirm the fuzzy rules satisfying given approaching error of variable universe adaptive fuzzy controller, this paper designs a universal approaching error boundary of adaptive fuzzy controller. With explicating the structure of variable universe adaptive fuzzy controller, the approaching error boundary of Single-Input and Single-Output or Multi-Input and Multi-Output fuzzy control system should be ascertained respectively for physical condition. The model simulation results indicate the better performance of the new method in comparison with the traditional controller with more accuracy and practicability.

Enhancing working performance of active magnetic bearings using improved fuzzy control and Kalman-LMS filter

This paper develops a novel control approach to enhance working performance of eight-pole radial active magnetic bearings (AMB). In the proposed method, the improved fuzzy proportional-integral-derivative (PID) control based on variable universes of proportional scaling is designed firstly to obtain better identification performance and flexibility of AMB control. Then, a Kalman filter is implemented to estimate the rotor displacement to reduce the noise disturbance and undesirable parameter adjustments caused by fuzzy control scheme. Finally, the least mean square (LMS) filter is connected with fuzzy control to compensate the unknown mass unbalance which might induce serious vibrations of AMB facilities. The simulation results show that the improved fuzzy PID control plays better performance than PID control in overshoot control, and the transient time of improved fuzzy PID is much shorter compared to conventional fuzzy PID. Meanwhile, the impacts of noise disturbance can be significantly limited by connecting with Kalman filter, and the maximum steady-state error can be decreased to about 85%. It is also shown that the LMS filter algorithm can effectively compensate the unknown mass unbalance in relatively short time without affecting the stability of AMB system.

High-Frequency Volatility Estimation and the Relative Importance of Market Microstructure Variables: An Autoregressive Conditional Intensity Approach

In this paper we use an autoregressive conditional intensity approach to estimate local high-frequency volatility, and examine to what extent a large universe of market microstructure variables affects local volatility. Our findings support a sequential information arrival hypothesis on the high-frequency level since we show that contemporaneous trading volume is negatively, and lagged trading volume is positively related to local volatility. The use of a penalized likelihood method allows us to obtain a ranking in terms of the relative importance of all market microstructure variables considered. We find that, in a descending order, contemporaneous volume, bid-ask spread, absolute order imbalance, absolute order flow and absolute quote difference carry the most important information for local volatility modelling.

Pressure Regulation of Multi-level Gas Tank by Variable Universe Fuzzy Self-tuning Control

Pressure Regulation of Multi-level Gas Tank by Variable Universe Fuzzy Self-tuning Control

The Throne of King Tutankhamun as Egyptian Environmental System

The ancient Egyptian, since the very beginning, associated with the surrounding environment, representing in the Nile, earth and heaven, including the sun, moon and stars. The sun rises and sets. The size of the moon varies across passages of disappearance, growth and completeness. The Nile level varies throughout the year during the flood that regularly occurs. The continuity of such image gave the ancient Egyptian the sense and feeling of the unity of the variable universe. The ancient Egyptian's concept of the universe represents in two straight and crossed meanings. The first meaning extends in the form of a line with the flow of the Nile in its course from the south to the north, cross-cutting with the second meaning, stretching throughout the sky with the sun's daily journey from the east to the west. Therefore, the Egyptian designer remains controlling the surrounding environment, which makes him fond of the idea of eternity and renewal. The ancient Egyptian always refers to the eternal truth (renewal and continuity). The land of Egypt constitutes the source of truth, whereas it remains forever, moreover it is the whole universe. Hence, all the ancient Egyptian's products reflect such idea. The temple embodies the story of creation on the land of Egypt, so what about furniture? Particularly the furniture in the complete and mature image was represented in the Throne of King Tutankhamun. The significance of research is defined through attempting to answer the following questions: - Is the furniture represented in the throne of King Tutankhamun reflection for the same Truth (renewal and continuity)? - Is the throne of the king Tutankhamun expression of the land of Egypt? - Does the throne of King Tutankhamun hold an Egyptian integral environmental system? - Can we through the environmental system reach determinants, in order to rely on, Designing furniture, to grant the same wealth and cultural exchange?

Enhanced approximation capabilities of the fuzzy systems using variable universes of discourse

The fuzzy systems with variable universe of discourse (VUD) have received increasing attention due to their fine control performance. VUD fuzzy systems are ones in which universes of discourse can be online tuned by means of a set of nonlinear contraction–expansion factors. One advantage of the VUD fuzzy systems lies in that higher control accuracy can be obtained without the aid of integral elements. Another advantage of the VUD fuzzy systems is that the number of fuzzy rules can be reduced significantly for a given application, compared with the fuzzy system based on fixed universes of discourse. Utilizing the multivariable Taylor’s expansion formula, it is proven that the VUD fuzzy system possesses higher approximating power as the input variables approach the equilibrium point. The approximation error converges to zero when the input variables reach the equilibrium point. It is also proven that the same approximating power can be obtained even when two fuzzy sets are applied on any universe of discourse. In addition, a sufficient condition is given for the VUD fuzzy systems as approximators for any given accuracy. Two examples show that the approximating capability of the VUD fuzzy systems can significantly outperform the fuzzy systems with fixed universes of discourse and that the shape of membership functions can influence the approximation effect. This paper provides researchers with some explanations why the VUD fuzzy systems hold the two advantages mentioned above from the standpoint of the functions approximation theories.

Asymmetric Variable Universe Adaptive Landing Fuzzy Controller for Carrier-Based Aircraft

During the process of aircraft landing, the control manners of carrier-based aircraft are always used to study. This is one of the important ways to avoid pilot-aircraft adverse coupling. In order to keep the accuracy of landing, this paper presents an improved asymmetric variable universe adaptive landing fuzzy controller with Safe Flight Area during approach for carrier-based aircraft. By means of universe-conversion factors and contraction–expansion factors, universe of discourse can be modified online, and fuzzy rules can reproduce automatically to adapt to the modified universe of discourse. The model simulation results indicate the better performance of the new method in comparison with the traditional controller with more accuracy and practicability.

A Variable Universe Self-Tuning Fuzzy-PI Speed Controller for Induction Motor with DTC-SVM

In the paper, To control the speed of induction motor drive with DTC-SVM, A variable universe self-tuning fuzzy-PI(VUFPI) controller was designed based on the concept of variable universe to generate the torque reference value, Two inputs of the fuzzy controller are speed error and error change rate, the output of the fuzzy controller are adjustment parameters (,) of PI controller parameters (Kp, Ki), the input and output variable universe of fuzzy controller were regulated by scale factor which is calculated according to error grade, The simulation results show that the proposed method has fast response speed and lower torque ripple.

Research on Fuzzy-adaptive PID Control with Correction Factor of Electric Power Steering System

According to the power assisted control strategy of Electric Power Steering system (EPS), fuzzy-adaptive PID control with correction factor is proposed. The present method can not only change parameters of PID in dynamic process but also keep the form of rules and variable universe of discourse according to the control error. This control strategy overcomes the disadvantages that the flxed parameters cannot meet the requirement of the real-time control of EPS system. It can also improve the control precision. The simulation results show fuzzy-adaptive PID control with correction factor improves transient response and follow-up characteristic e‐ciently compared with traditional PID control and fuzzy-adaptive PID control.

Wire Tension Force Variable Universe Fuzzy Control in Fixed Abrasive Wire Saw Manufacturing

The structural characteristics of the tensioning device in the wire saw manufacturing equipment is introduced. Based on the characteristic of the strainer, the principle of variable universe fuzzy control is adopted to deal with the controlling objects. The design of two stage fuzzy controller and its parameters are discussed. The system simulation shows that the control scheme can make the tension within the stable range.

Adaptive Variable Universe of Discourse Fuzzy Sliding Mode Control

This paper proposes adaptive variable universe of discourse fuzzy sliding mode control for efficient compensation of unbounded disturbances and reduced chattering. Classical sliding mode control is robust to bounded uncertainties and disturbances. The disadvantages of classical sliding mode control are high frequency chattering and poor performance in case of unbounded disturbances. Chattering phenomena is minimized using adaptive fuzzy sliding mode control but fuzzy fixed universe of discourse makes it in-efficient for time varying unbounded disturbances and uncertainties. This article investigates a variable universe of discourse fuzzy logic system for unbounded disturbances. Fuzzy universe of discourse for membership functions of input and output parameters is tuned online using an adaptive empirical law derived from the error dynamics. Performance of proposed control is verified using extensive simulations.

Application of Variable Universe Fuzzy Control PID in Temperature Command of the Animal Building

Temperature is a universe and significant data in production and scientific experiment, effective measurement and control of the temperature are widely applied in every part of national economy. Therefore, temperature control has great significance; relevant requirements regarding temperature control are also higher and higher. Temperature command system for animal house is a complex system with features of time varying, nonlinear, inaccurate model and unknown operating circumstance, temperature controlled by air-conditioner is less accurate and will affect the stability of the system performance. Regarding existing problems of long responding time, less stability and other disadvantages of the conventional PID control, we hereby raise a new approach of variable universe fuzzy PID control which is characterized with quick responding speed, better stability and stronger anti-interruption performance. Through the application of variable universe fuzzy control theory, which combined with the advantages of conventional PID and variable universe fuzzy control, forming the calculation of self-applied variable universe fuzzy control PID. Improve the accuracy of fuzzy inference by variable universe control theory, and realize the online tuning of PID data through fuzzy inference. Stimulate on Matlab, relevant stimulation results revealed that the control ways is clearly superior than conventional PID control, therefore effectively improve the dynamic property, stability precision and robustness, the system has better future of industrial application.

Designing fuzzy controllers with variable universes of discourse using input–output data

Using field data from sensors to construct a fuzzy controller based on variable universe of discourse (VUD) is an open question that is often encountered in real-world applications. The basic structure of a VUD fuzzy controller is given in this paper. To use subconscious knowledge, the input/output data from sensors, a novel method is proposed for designing a VUD fuzzy controller. Firstly, the central points of the input fuzzy sets are distributed equidistantly and those of the output fuzzy sets are regarded as undetermined parameters. Then, an improved recursive least square algorithm is presented to identify these unknown parameters, and a cut-off condition is applied to end the recursive computation. Finally, simulation examples show that the VUD fuzzy controller constructed by the identification algorithm can satisfactorily approximate original input/output data and that it can achieve a better effect on a rotary single inverted pendulum than a general fuzzy controller.