Terminal Sliding Mode Observer Research Articles

Robust flux observer and robust block controller design for interior permanent magnet synchronous motor under demagnetisation fault

This paper deals with rotor flux-linkage estimation in interior permanent magnet synchronous motor. In most applications, the rotor flux is considered as a known constant. However, sharp transients, high loads and high temperatures may cause demagnetisation which has dominant impact on the motor performance. As a result, estimating the rotor flux-linkage can be helpful to detect and manage demagnetisation faults. To estimate the rotor flux-linkage, a novel integral terminal sliding mode observer is proposed. The observer uses stator currents as state variables which can tolerate well against the motor uncertainties. To keep the motor performance during the demagnetisation fault, a sliding mode block control strategy is proposed for the interior permanent magnet synchronous motor for a first time. The suggested robust controller is composed of a speed control loop and two stator current control loops. Comprehensive simulations are carried out to show the effectiveness of the proposed observer and controllers.

A Novel Online Parameter Estimation Method for Indirect Field Oriented Induction Motor Drives

This paper presents a novel online parameter estimation method to overcome the negative influence of parameter mismatch on the field orientation and then on the performance of the indirect field oriented induction motor drives. This method allows for parallel estimation of the rotor resistance and the mutual inductance, which tend to deviate from their nominal values resulting from changes in temperature and flux level. In the case of electrical vehicles or wind power generators, the parameter deviation degrades the drive performance in two ways: calculation of the current reference from the torque command issued by the power control unit and calculation of the slip frequency for the indirect field orientation. Moreover, the mutual inductance estimation is more critical in these wide speed range applications than in general industry field. This proposed estimation method is implemented through a model reference adaptive system about the rotor flux. The reference model comes from two sliding-mode observers (SMOs): a terminal SMO and a linear SMO, implemented in series. The adjustable model is undertaken by the current model of rotor flux. The analysis and design presented in this paper are confirmed both through numerical simulation and experiments.

A Novel Disturbance Estimation Scheme for Formation Control of Ocean Surface Vessels

To achieve high-accuracy formation control of multiple ocean surface vessels, the external disturbance acting on each vessel should be accommodated. In this paper, a novel disturbance estimation scheme is presented to solve this problem, and to provide the future formation controller design with precise estimation information. This approach is developed in the theoretical framework of a terminal sliding mode observer. The proposed observer is able to precisely estimate external disturbance after finite time. It is shown by Lyapunov stability analysis that the estimation error for external disturbance will converge to zero after finite time. A fast and precise estimation for external disturbance is achieved. Numerical example is further presented to validate the effectiveness of the developed disturbance estimation approach.

Position Sensorless Control of BLDC Motors Based on Global Fast Terminal Sliding Mode Observer

The brushless DC motor (BLDCM) has many advantages. As a result, it is widely used in electric vehicle (EV) drive systems. To improve the reliability of the motor control system, a position sensorless control strategy based on a sliding mode observer (SMO) is proposed. The global fast terminal sliding mode observer (GFTSMO) is proposed to enhance the control performance of the SMO control system. The advantages of the linear sliding mode and the nonsingular terminal sliding mode (NTSM) are combined in the control strategy. The convergence speed of the system state is enhanced. The motor commutation point is obtained with the observation of the back EMF, and the instantaneous torque value of the motor is calculated. Therefore, the position sensorless control of the BLDCM is realized. Experimental results show that the proposed control strategy can improve the convergence speed, dynamic characteristics and robustness of the system.

Adaptive Fuzzy Terminal Sliding-Mode Observer with Experimental Applications

In this paper, conventional gradient-descent-based adaptive fuzzy observer is improved by using the terminal sliding-mode theory for a class of nonlinear systems. The improvement is made in two ways: first, the switching term of the sliding-mode approach is added to the state of the observer. Second, the measurement error of the system is designed as the input of the observer instead of measured state. The stability of the observer and boundedness of the parameters are proved using Lyapunov approach. Contributions of the paper are summarized as follows: (i) the robustness and convergence properties of newly proposed observer are improved, (ii) the proposed adaptive fuzzy terminal sliding-mode observer, conventional adaptive fuzzy observer, adaptive neural-network observer, and Euler filtering approaches are compared in terms of their ability to estimate velocities of three real-time experimental systems reliably. The performance of the designed observers is discussed with root mean squared-error criterion where the proposed adaptive fuzzy terminal sliding-mode observer provided much accurate state estimation results than classical observers.

Data‐driven identification approach for thruster misalignment angles of rigid satellite

The problem of thruster misalignment angles identification on-line and in real-time is addressed in this study. A data-driven approach is proposed to identify the parameter of satellite's thruster misalignment angles. The satellite considered is represented by Euler angles. As the finite available data is met for on-orbital satellite, the proposed approach is designed by using the techniques of nonlinear observer and data-driven solution simultaneously. As a stepping stone, a terminal sliding-mode observer is developed to estimate the deviation torque introduced by thruster misalignment. It is shown by Lyapunov stability analysis that, precise estimation with zero error is guaranteed with finite-time convergence. Based on such estimated value, a data-driven solution is then synthesised to identify the misalignment angles of the thruster. The performance using the proposed identification methodology is evaluated through a numerical example.

Fault reconstruction of thruster for autonomous underwater vehicle based on terminal sliding mode observer

The motion modeling and thruster fault reconstruction for autonomous underwater vehicle (AUV) system are addressed in this paper. Considering the modeling uncertainty of the AUV motion model given by dynamics analysis method, we present an AUV motion modeling method based on RBF neural networks. Since there is asymptotic convergence problem in the process of using traditional sliding mode observer to estimate the state signal, which cannot be measured directly by sensor, the fault signal cannot be reconstructed timely. Therefore, a Terminal sliding mode observer is presented to ensure each estimated state signal converge in a finite time. According to the output of Terminal sliding mode observer, the equivalent output injection method is used to reconstruct thruster fault. Finally, the feasibility and effectiveness of the proposed approach is demonstrated with pool experiments of the experimental prototype.

A Rotor Position/Speed Identification Method of Permanent Magnet Synchronous Motor for Low Speed Operating Condition and Parameter Perturbation

Accurate positioning of the motor requires high control performance for low-speed operation and motor’s parameter perturbation. In the AC motor vector control technology, the nonsingular higher-order terminal sliding mode observer of Insertion Permanent Magnet Synchronous Motor (IPMSM) is put forward based on the object current and voltage values to obtain the rotor position and speed signa. The accurate and reliable identification of the motor rotor position and speed is realized to provide the necessary information of rotor position and speed for high performance vector control system. In order to improve the dynamic response of the observer and overcome the parameter perturbation, the nonsingular terminal sliding mode control is used in the present study. Compared with the general sliding mode control, the chattering phenomenon is reduced by using the high-order sliding mode control technology features. The algorithm is applied to the theodolite micro shafting control system with sensorless IPMSM, which paves the way for theodolite precise target localization. The experiment results show that the method can accurately identify the motor rotor position and speed with strong robustness, good steady precision and dynamic performance.

Reaction Wheel Fault Compensation and Disturbance Rejection for Spacecraft Attitude Tracking

A novel attitude tracking control scheme is proposed for rigid spacecraft to simultaneously compensate for reaction wheel faults and reject external disturbances. The reconstruction of the reaction wheel faults and disturbances is treated as a problem of observing the state of a linear system with unknown inputs. A terminal sliding mode observer is proposed to reconstruct the reaction wheel faults and disturbances. A Lyapunov-based analysis shows that the observer asymptotically converges to the actual faults and disturbances with a finite time convergence. Then, with the reconstructed faults and disturbance information, a compensation control law is developed to guarantee that the desired attitude trajectories are followed in finite time. The key feature of the proposed control strategy is that it globally asymptotically stabilizes the system, even in the presence of reaction wheel faults and external disturbances. The attitude tracking performance using the proposed compensation control is evaluated through a numerical example.

Spacecraft Attitude Fault Tolerant Control with Terminal Sliding-Mode Observer

AbstractA velocity-free attitude fault tolerant control scheme is presented to stabilize spacecraft attitude. A terminal sliding-mode observer is developed to reconstruct system states. With the reconstructed attitude and angular velocity, a control law is synthesized without any knowledge on actuator faults. The controller guarantees all the signals of the closed-loop attitude system to be uniformly ultimately bounded even in the presence of actuator fault and external disturbance. The control power is rigorously ensured to be within the maximum magnitude of output torque. An illustrative example is presented to evaluate the control performance.

Nonsingular terminal sliding-mode observer design for interior permanant magnet synchronous motor drive at very low-speed

A nonsingular high-order terminal sliding-mode observer of interior permanent magnet synchronous motor (IPMSM) is presented, of which the state variable is the current of rotor-oriented d-q reference frame, to obtain the accurate information about angular speed and rotor position for high-performance vector control system. A nonsingular terminal sliding-mode observer is used to improve dynamic response of the observer speed and robustness of the current observer, and the high-order sliding mode method is adopted to estimate the chattering phenomenon of the conventional sliding-mode. Meanwhile, to obtain the regulator parameters of speed and current loop, an integral-feedback method of estimating the rotor speed is adopted, and the inner current loop is realized using a decoupling and diagonal internal model control algorithm. Experimental results of 2 MW PMSM drive system show that the proposed method can accurately estimate the position and speed of the rotor, and the system has good dynamic and static performances.

Terminal sliding mode observers for a class of nonlinear systems

This paper proposes a terminal sliding mode observer for a class of nonlinear systems to achieve finite time convergence for all error states. Compared to standard sliding mode observers which only enable finite time convergence of the output error, the observer in this paper makes use of fractional powers to reduce other non-output errors to zero in finite time. A 2-degree-of-freedom robotic manipulator is used to demonstrate the effectiveness of the proposed observer.

Hybrid Terminal Sliding-Mode Observer Design Method for a Permanent-Magnet Synchronous Motor Control System

This paper proposes a hybrid terminal sliding-mode observer based on the nonsingular terminal sliding-mode (NTSM) and the high-order sliding-mode (HOSM) for the rotor position and speed estimation in the permanent-magnet synchronous motor control system. An NTSM manifold is utilized to realize both fast convergence and better tracking precision. In addition, a derivative estimator is used to obtain the derivative of the sliding-mode function. Meanwhile, an HOSM control law is designed to guarantee the stability of the observer and eliminate the chattering, so that smooth back-electromotive-force (EMF) signals can be obtained without a low-pass filter. According to the back-EMF equations, the rotor position and speed of the motor can be calculated. Simulation and experimental results are presented to validate the proposed method.