Sliding Mode Observer

The proposed control approach has the advantage of not requiring a position sensor which is cumbersome and expensive. The simulation results prove the efficiency and the robustness of the sliding mode observer. Moreover, when the PD control is associated to the sliding mode observer it allows the elimination of the motor oscillations.

This paper is an extension of the results disseminated in the most recent international conference paper relating to the real time implementation of a sliding mode observer (SMO) state estimator, integrated in a direct current (DC) servomotor angular speed control system [1]. The main goal of the extended version paper is to investigate new directions for improving the SMO state estimator performance in terms of state estimation accuracy and robustness to the changes in the noise levels, initial conditions values of the estimates, input disturbance and modeling errors uncertainties. The improved version of the SMO estimator is a fuzzy version of SMO (FSMO), a real helpful tool for our future developments in the real time control applications field, namely several real time fault detection and isolation (FDI) control strategies based on various estimation techniques. The purpose of

Abstract—To enhance the accuracy of estimated rotor position for sensorless controlled permanent magnet synchronous motor, the strategy based on sliding mode observer (SMO) with dual second order generalized integrator (DSOGI) is proposed. The SMO is utilized to estimate the back electromotive force (EMF). Considering the estimated back-EMF harmonics resulting from both flux spatial harmonics and inverter nonlinearities, the DSOGI is applied to eliminate multiple orders harmonics and extract the fundamental wave of the estimated back-EMF for calculating the rotor position. Therefore, the DSOGI can effectively reduce the influence of the estimated back-EMF harmonics and improve the accuracy of rotor position estimation. In addition, the software quadrature phase-locked loop with back-EMF normalization is utilized to calculate the rotor position in order to eliminate the influence of the changed back-EMF magnitude at different speed. Finally, to illustrate the effectiveness of the proposed strategy, the experimental platform of an open-winding permanent magnet brushless motor is built. The comparison results verified that the drive system performance of both steady state and dynamic state is improved.

Since the switching signals of the sliding mode observer contain the back EMF of the motor, it is possible to obtain the speed and position of the motor directly from the switching signals[6]. Undesirably, the chattering problem is present due to the discontinuous controls (sgn function) in sliding mode observer and make it the major factor for the high system oscillation. For overcoming a such problem, the low pass filter with cutoff frequency ω n is used but it produces the delay time

In this paper a new method has been presented to modeling of doubly-fed induction generator (DFIG)based wind turbine, and a new scheme of sliding mode observer of Double Fed Induction Generator, based on theestimation of the value of the rotor resistance. The estimation of the rotor resistance is based on the use of theerror between real and estimated value of DFIG in faulty condition, this will have to improve the performances ofrobustness and stability and precision for the sliding mode observer. The results show that the proposed, even inpresence of rotor resistance variation. The FTC control strategy has been validated steady-state conditions byMatlab/simulink.

ABSTRACT:.A sensorless control scheme is presented for induction motor with core loss and anon linear model is developed in well known (α, β) stationary reference frame, where the core is represented with a resistance in parallel with a magnetization inductance. An optimal rotor flux modulus is calculated by minimizing copper and core loss. This flux modulus is forced to be tracked by the induction motor along with a desired rotor velocity by means of sliding mode observer by using the super twisting algorithm. The rotor velocity is estimated by two methods. The first consist of a super twisting sliding mode observer for rotor fluxes with the purpose of retrieving the back-electromotive force components by means of the equivalent control method. The second method is based on a generalization of the phase – locked loop methodology. PI controller is used in both the technique. The robustness of the system is checked by varying the stator, rotor and core resistances.

Since the early 70’s, the model-based fault diagnosis technique has attracted the attention of many researchers in the field of control engineering [5-7]. The main idea of such approaches is to build a residual signal as a signal to indicate the fault occurrence. These signals are produced using a comparison between the estimated parameters and the real parameters. There are many different approaches to generate a residual signal, such as a parity space approach, observer-based approaches [8] and the approaches based on advanced observers such as sliding mode [9, 10]. Each of these approaches has their own advantages and disadvantages. In [11], the existence conditions and design algorithm of sliding mode observer for linear descriptor systems is investigated. In the proposed method, a sliding mode observer is used for fault reconstruction. But no fault detection methods is described. [12] shows how model-based fault detection and diagnosis methods together with few available measurements can be applied for fault detection in automobiles. In [13], different fault-tolerance principles with various forms of redundancy are considered, resulting in fail-operational, fail-silent, and fail-safe systems. Fault-detection methods are discussed for use in low-cost components, followed by a review of principles for fault-tolerant design of sensors, actuators, and communication in a brake-by-wire system with electronic pedal and electric brakes.

This paper proposes a sliding mode control scheme for effective speed tracking by obtaining ripple free torque through the inner loop current control for a BLDC motor. Sliding mode observer is a parameter for estimating the phase to phase trapezoidal back- EMF in sensor less mode. BLDC motor drive uses one or more sensors giving positional information to keep synchronization. Such implementation results in a higher drive cost due to sensor wiring and implementation in the motor. This project shows that the torque and speed control of three phase BLDC motors. Using sliding mode observer it is used to estimate the back EMF for sensorless operation. This project proposes, a space vector pulse width modulation(SVPWM) technique is employed to obtain the required output voltage in the line side of the inverter to control the BLDC motor speed and the same was simulated using MATLAB software.

For the stabilization of anoptical switch, it is necessary to dynamically estimate the switch position and velocity. Because, when the switch is near the completely closed or open situation, there is no position information available as a feedback for the control system. Thus, state observers have been introduced to overcome this problem. In [3] a simple nonlinear observer is used to estimate the state variables for a system with Lipschitz nonlinearity in the output characteristics. In this paper, two sliding mode observers are proposed to estimate the state variables for an uncertain nonlinear system. The main advantages of the sliding mode observer are robustness against disturbances/unmodeled dynamics, insensitivity to parameter variations, compact implementation and efficiency for the standard output system.

This article proposes an innovative strategy to the problem of non-linear estimation of states for electrical machine systems. This method allows the estimation of variables that are difficult to access or that are sim- ply impossible to measure. Thus, as compared with a full-order sliding mode observer, in order to reduce the execution time of the estimation, a reduced-order discrete-time Extended sliding mode observer is proposed for on-line estimation of rotor flux, speed and rotor resistance in an induction motor using a robust feedback linearization control. Simulations results on Matlab-Simulink environment for a 1.8 kW induction motor are presented to prove the effectiveness and high robustness of the proposed nonlinear control and observer against modeling uncertainty and measurement noise.

performance of sensor and sensorless IFO IM drives. In case of operation of drives with sensors, has good dynamic performance at high and medium speed operation. Where as at low speed operation, the performance of the drive is not satisfactory. To get satisfactory performance even at low speeds sensorless controlled IM drives with MRAS and Sliding mode observer is designed. Sensorless control has good dynamic response compared to drives with sensor. In a sensorless induction motor drive, A Stator current observer is designed based on the second-order sliding mode which is used as the reference model of the MRAS estimator. The phase angle error between the actual and estimated rotor flux vectors is used to tune the adaptive model of MRAS estimator. The sliding mode observer is insensitive to variation of stator resistance, rotor resistance and perturbation when the states arrive the sliding mode. By making full use of auxiliary sliding-mode surfaces, the proposed observer successfully reduces the chattering behavior. Furthermore, in order to improve the near zero speed operation, a parallel adaptive identification of stator resistance is designed based on derivatives of rotor flux and stator current.

In this paper a sliding mode observer is proposed to reconstruct the states of uncertain nonlinear systems from available output measurements. The proposed approach is robust for synchronization despite the difference between transmitter and receiver parameters and their initial conditions. We have applied this approach on three systems, Lorenz, Rössler and Chuaיs circuit. With reference to the simulation results, it is shown that the correct estimation of real system can be obtained. The effectiveness of the proposed method is investigated through some examples that show a significant performance improvement.

This paper presents a robust sixth-order Discrete-time Extended Sliding Mode Observer (DESMO) for sensorless control of PMSM in order to estimate the currents, speed, rotor position, load tor- que and stator resistance. The satisfying simulation results on Simulink/Matlab environment for a 1.6 kW PMSM demonstrate the good performance and stability of the proposed ESMO algorithm against parameter variation, modeling uncertainty, measurement and system noises.

This paper is organized as follows. Section 2 shows the dynamic model of induction motor. Sliding mode observer will be described in Section 3. The proposed solution will be presented in Section 4. In Section 5, results of simulation tests are reported. Finally, Section 6 draws conclusions.

Abstract—This letter presents a fault detection method for modular multilevel converters (MMC) which is capable of lo- cating a faulty semiconductor switching device in the circuit. The proposed fault detection method is based on a sliding mode observer (SMO) and a switching model of a half-bridge, the approach taken is to conjecture the location of fault, modify the SMO accordingly and then compare the observed and measured states to verify, or otherwise, the assumption. This technique requires no additional measurement elements and can easily be implemented in a DSP or micro-controller. The operation and robustness of the fault detection technique are confirmed by simulation results for the fault condition of a semiconductor switching device appearing as an open-circuit.

This paper presents a sliding mode observer for sensorless operation of SRM (switched reluctance motor) drive. Design of such an observer depends mainly on the nonlinear model of SRM. In this technique, neither extra hardware nor huge memory space arenot required but it only requires active phase measurements. Furthermore, PI (proportional integral) are suggested to operate individually along with the SMO (sliding mode observer) to cover a full speed range of sensor less controller. Both controller schemes operate in PWM (pulse width modulation) control mode. The proposed observer is implemented and using Matlab/Simulink. All results obtained with simulation are presented.

Abstract The problem of fault detecting subject to external disturbances has been a topic of considerable interest. In this paper, a sliding mode observer for fault detection and isolation is applied to a continuous reactor. Additionally, a general review has been done on dynamic model of continuous reactor along with detailed study of the mathematical model of these kinds of systems. Then, sliding mode observer is investigated with detailed comment. In order to isolate and estimate the possible actuator faults a bank of Sliding Mode Observer (SMO) is designed. Also a simple canonical form for sliding mode observer is presented. A design procedure is described and linear simulation results are presented to demonstrate the approach.

Observer design for nonlinear dynamic systems is a significant and interesting research area, and it has a lot of potential applications in control engineering, fault reconstruction, state estimation, and signal tracking [27–39]. Because the fractional derivative of a com- pound function has a very complicated form, most of the current observers which were designed for classical nonlinear systems cannot be used to fractional ones directly. With respect to fractional-order linear systems, observers were designed in Refs. [40–42]. Up to now, there was only little work that considered the observer design for fractional-order nonlinear systems. In Ref. [36], a sliding mode observer was given based on state estima- tion. An observer was proposed by using a scalar transmitted signal in Ref. [43]. A frac- tional observer with non-fragile structure was proposed in Ref. [44], and a fractional-order observer was introduced to cope with second-order multi-agent systems in Ref. [45]. Some other results can be found in Refs. [46–49].

In this work an exponential reaching law based SMC based controller was presented to handling load torque disturbances affecting a BLDC drive. To estimate the unknown load torque a sliding mode observer was designed that was effectual in give a fast response even in variable load conditions with a maximum delay of 0.01 seconds. Finally the developed SMC scheme was compared with a PI based speed controller and the advantage of the SMC scheme in relation to handling load disturbances while operating as a variable speed drive is summarized. Finally it was concluded that in chattering persisted in the output response which can be eliminated by employing a low pass filter. In future work the work can be tested on hardware platform by use of fast DSP processors.

This study has been contributed to some challenging issues in control of nonlinear stochastic systems. Sliding mode mechanism has been properly referred to accommodate the un-measurable (but observable) system states and therefore to design the controller. An adaptive sliding mode observer is designed to reconstruct the unmeasured system states with measurable output, and a sliding mode control law is constructed by synthesizing the estimated system states from the observer. The convergence of ASMO designed is proved and its estimation error is mean-square exponential ultimately bounded. The overall closed-loop nonlinear stochastic systems can be guaranteed to be globally asymptotically stabilized in probability with the design strategy.