JOURNAL OF NONLINEAR SYSTEMS IN ELECTRICAL ENGINEERING
Year:2018 | Volume:4 | Issue:1-2 |Papers Count:6

In this paper, a new nonlinear model is identified for magnetorheological (MR) damper based on the bouc-wen model. This model which includes the hysteresis loop is linear with respect to the input current. This advantage makes it easy to use the proposed model in semiactive suspension systems as the inverse model. For better comparison, a polynomial model developed in the prevalent papers is also designed. The performance evaluation of two models shows that the proposed bouc-wen model has higher accuracy in the smaller velocity range. At the rest of the paper, an LQR controller designed for calculation of the active suspension force is integrated with the two identified inverse models. The simulation studies are carried out for active and semi-active suspension systems on a standard road. The results show that the simplified nonlinearbouc-wen model has better performance in controlling the semi active suspension system compared to the other models. In high amplitude velocities of the damper, the performance of two models is close to each other.

In this paper, joint effect of transmitter and receiver IQ imbalance under insufficient and sufficient cyclic prefix (CP) is studied. The case of insufficient CP length results in interblock-interference (IBI) between the OFDM symbols. For compensation of this effect and other impairments, simultaneously, per-tone equalization (PTEQ) structure implementation is necessary. Regarding to the topology of this structure and required high length filters, the system computations will be very high, even using simplest adaptive algorithms. In this paper, firstly wavelet packet transform (WPT) is applied to branches of PTEQ structure to increase the convergence speed of adaptive algorithms. Then it is proposed to use the selective coefficient update (SCU) based on packets entropy on each branch of this structure to decrease the computations. In this way, not only the large amount of calculations will be eliminated but also systems operation will not be affected. Also, to further increase of convergence speed and computation reduction, using the data selective update (DSU) along with SCU is proposed. This kind of filtering (DSU) increases the algorithms convergence speed because of using adaptive noise dependent step size. Simultaneous using of two DSU and SCU methods besides the expedition and denoising characteristics of WPT makes suitable the proposed algorithm for using in real time systems. Simulation results show that this algorithm not only causes considerably reduction on the amount of calculations, but also does not affect the normal operation of algorithm. In addition, it is capable to compensate the joint channel and IQ imbalance distortions.

Damping of electromechanical oscillation ensures the improvement of power system operation. The occurance of a fault in the transmission system impacts the transmitted power and buses voltages. To mitigate or eliminate these fluctuations, power system stabilizer (PSS) is generally exploited. To optimize the overall system performance the pss parameters design is solved as an optimization problem with nonlinear objective function using cuckoo optimization algorithm (COA). For comparison of the results, the problem is also solved by using cuckoo search (CS). The optimal stabilizer leads to reduce significantly the active power oscillations. The designed PSS is tested and analyzed on the two-area four-machine power system under different operating conditions. Moreover, the multi-machine system performance analysis shows that the COA based PSS is superior to the CS based PSS.

In this paper, the fractional order sliding mode control is used to design an aircraft autopilot. This method aims at reducing the chattering phenomenon and has smoother control signal than conventional sliding mode. Fractional order control uses fractional integrator and derivative to improve integer order control methods. The sliding surface and sliding mode control law are proposed to reduce the chattering phenomenon, while the closed-loop stability is guaranteed. Using this algorithm, a robust autopilot against aerodynamic coefficients uncertainties is designed for an aircraft and the proposed control law is utilized to stabilize the closed loop system by the Lyapunov stability theorem. The proposed autopilot is applied to the aircraft model and our simulation results illustrate the reduction of chattering phenomenon.

In this paper, electric power production using airborne systems (kites) has been investigated. In the first step, an appropriate model is extracted to describe the behavior of airborne systems. Based on this model, a new path planning algorithm is proposed for the airborne system in the traction phase. Then, in order to achieve the proper operation, tracking the desired path and thus extracting optimal wind energy, a robust controller based on the sliding mode approach is designed in the presence of variations in atmospheric parameters and uncertainties in the system model. In the proposed method, the control strategy is obtained based on the speed vector angle of the airborne. In the proposed approach, six target points are used for the path designing of the kite motion in the traction phase, which increases the precision and flexibility of the designed path. Furthermore, the effect of adjusting the shape of the flight path of the airborne system during the traction phase on the system performance and extraction of the maximum wind force is also investigated.

In this paper, a finite-time stabilized guidance law is proposed in the presence of measurement noises. The measurement noise affects on the guidance system stability and/or performance. Hence, in the presence of measurement noise, the guidance law must be modified in a way that the noise effect on the guidance system response be reduced. By using the stochastic stability theory, a modified guidance law, dependent on the measurement nois variance, is proposed such that the line of sight angle rate is stabilized in a finite time. After a finite-time, no force is applied to the vehicle actuators. Then, the line of sight angle would be constant. The proposed method is used in a two-dimensional numerical example. The effectiveness of the suggested method is shown in the simulation results.