Journal of Control
Year:2016 | Volume:10 | Issue:3 |Papers Count:6

The fault tolerant controller (FTC) issue is one of the most important subjects in the system theory and control engineering which has many practical and industrial applications. In This paper, a new FTC has been designed in order to detect and compensate the sensors faults of permanent magnet synchronous motor (PMSM). To achieve this goal, sliding mode controller (SMC) and PMSM vector control have been used. In the faulty conditions, in order to achieve control purposes, two sliding mode observers (SMO) estimate the speed and currents of motor. The observers create virtual sensors for the feedback control. If sensors face with a condition that cause any fault, the FTC detects the fault and the virtual sensors are immediately used for sensorless control of motor. The stability of the closed-loop system has been investigated by the Lyapunov stability theory. Simulation results confirm good performance of the proposed FTC for PMSM.

Radome causes refraction of the incoming rardar wave in radar-guided interceptors, thus having a destabilizing effect on the guidance loop, especially at high altitudes. Therefore, a compensator is required to maintain the stability of the guidance loop and causes minimum miss distance in the presence of radome error. From the control perspective, Radome causes an unwanted feedback that is not similar to the conventional feedback loops, in which output must follow a desired control signal. In this paper, the desired closed-loop response is determined first, then a novel approach is proposed to shape the frequency response of the feedforward path so that the stability and performance requirements are satisfied. Frequency response is shaped by linear matrix inequality (LMI) tools and v-gap metric is used to select the best frequency response. Simulation results show that the designed compensator drastically decreases the miss distance, while the stability is guaranteed.

This paper investigates the problem of robust stabilization of uncertain singular systems with time-varying delay in the presence of model uncertainties and input amplitude constraint. Here, the purpose of robust stabilization is to design a saturated state feedback such that the closed-loop system is regular, impulse free and stable for all admissible uncertainties. The timedelay has been considered to be time-varying with known lower and upper bound. The problem of stabilization is studied in two cases. First, the robust stabilization problem is considered for the singular systems with time-varying delay in the presence of actuator saturation and model uncertainties. In this case, the existence conditions of robust stabilizing delay-independent state feedback controller are given via the linear matrix inequalities. Additionally, an estimation of the domain of attraction of the closed-looped system is proposed in the related theorem. In the second case, delay-dependent criteria for robust stability of uncertain time-delay singular systems withconstrained input is given in two theorems. These theorems investigate delay-independent stability conditions via the linear matrix inequalities for constant and time-varying delay. Also, the domain of attraction for the closed-looped system is estimated in this case, too. Finally, practical and numerical examples are given and simulation results verify the theoretical achievements of paper.

There are two approaches to guarantee zero steady-state error in step reference tracking and step disturbance rejection in model predictive controllers. In the first scheme, which is more prevalent, integrator is added to the model of the system. In generalized predictive control and dynamic matrix control, this structure is used. In second scheme, the desired steady-state value of control signal is used in cost function of predictive controller. Due to substantial characteristics of second scheme, in this paper it is tried to propose an analytically tuning method for these predictive controllers. Besides, many industrial processes can be effectively described with first-order plus dead time models. Hence, in this paper these models are used to provide predictions. Using these models and considering the constraints are inactive, the closed-loop transfer function is derived and a deep study on the closed-loop system and its robustness are given. Finally, the simulation results are used to evaluate the efficiency of the proposed tuning method.

In this paper, estimation of second order polynomial systems’ domain of attraction (DA) via rational Lyapunov function is investigated. One of the methods for estimating DA is to find the greatest level set. In this study, in order to obtain the greatest level set, cost function based on increasing the region enclosed to the level set has been offered instead of using shape factor.Estimating DA has been converted into solving bilinear matrix inequality optimization problem.Capacity of this method compared to other methods in recent studies has been shown through some examples.

In this paper the problem of vehiclular platoons control with time delay and switching topology is considered. Due to data transmitions and sensors mesuarements, time delay should be investigated insystem’s modeling and controller design. Changes in communication topology may cause the internal and string instability of the vehicular platoons. Based on constant spacing policy, a robust controller is designed to provide internal and string stability of the vehicular platoons. By using Lyapunov-Krassovski and Lyapunov-Razumikhn theorems, two new approaches are presented to perform the internal stability of the proposed switched linear time-delay system. In continuance, a new theorem is presented to attain conditions satisfying string stability. Several simulation studies are provided to show the effectiveness of the proposed approaches.