Conventional Sliding Mode Observer Research Articles

An Adaptive-Gain Sliding Mode Observer with Precise Compensation for Sensorless Control of PMSM

In this paper, we propose a sensorless control strategy for permanent magnet synchronous motors (PMSMs) based on an adaptive-gain sliding mode observer (ASMO) with precise compensation. Firstly, the observer adopts a saturation function with a continuous boundary layer as the switching function to avoid the delay effect of the low-pass filter. In addition, the adaptive-gain method is designed based on a conventional sliding mode observer (SMO) with constant-gain and a saturation function. The adaptive-gain mathematical model is simplified by establishing a nonlinear feedback channel of an SMO. Secondly, in order to improve the practicability and facilitate debugging, the explicit stability condition of an ASMO is deduced according to Lyapunov’s second method. According to the proposed adaptive method, the chattering caused by the mismatch of the sliding-mode gain is suppressed, and the observable speed range is also improved. Thirdly, the position estimation delay problem of an SMO with a continuous switching function is analyzed in detail from the perspective of frequency characteristics. Then, a precise compensation method is proposed for the delay problem, which greatly improves the position estimation accuracy and the control performance. Finally, the correctness of the theory and the feasibility of the ASMO with precise compensation for the sensorless control of PMSMs are verified by experiments.

Sensorless control of SPMSM based on an adaptive sliding mode observer with optimized phase-locked loop structure

To improve the speed and position detection accuracy of surface-mount permanent magnet synchronous motor (SPMSM) vector control and reduce unnecessary chattering of the system, this paper proposes a sensorless control strategy of SPMSM based on an adaptive sliding mode observer (ASMO) with optimized phase-locked loop (OPLL) structure. First, in order to overcome the chattering of system caused by discontinuous switching characteristic of signum function in conventional sliding mode observer (CSMO), a continuous saturation function is selected as the switching function. The ASMO adopts the system state-related adaptive gain function to adjust the switching gain value of the system in real time, which overcomes the slow response speed or severe chattering of the system caused by the constant switching gain of CSMO. Second, to reduce the phase delay between the rotor position estimation value and the actual value caused by the adoption of low-pass filter (LPF) and the position estimation error caused by arctangent function method, an OPLL method is designed for accurate estimation of rotor position and speed. Finally, the effectiveness and feasibility of the proposed improved SMO algorithm is verified by simulation and experiments on an SPMSM with rated power of 2 kW.

A robust observer based on the nonlinear descriptor systems application to estimate the state of charge of lithium-ion batteries

A robust observer based on nonlinear descriptor systems is applied to estimate lithium-ion batteries’ state of charge (SOC). We creatively take the relationship between the battery’s open circuit voltage (OCV) and SOC as a nonlinear algebraic constraint, thereby modeling the battery as a nonlinear descriptor system. This model can effectively trade off accuracy and complexity. The robust convergence, even in the presence of uncertainties, is proven through a combination of the Lyapunov stability theorem and linear matrix inequality (LMI) techniques. Experimental results showcase the effectiveness of the proposed SOC estimation technique, offering enhanced convergence speed, estimation accuracy, and robustness compared to conventional sliding mode observers.

Design of sensorless permanent magnet synchronous motor controller based on improved sliding mode observer

Because PMSM needs to install a position sensor in practical application, and the buffeting issue in sensorless control stems from an old SMO (sliding mode observer), an improved SMO is proposed. Stemming from the improvement of the switching function and low-pass filter of the traditional SMO, the chattering problem of the conventional SMO is optimized. Considering the reality that the traditional PI control strategy unable to respond accurately and quickly in the case of current coupling, the current complete decoupling integrates the traditional PI control method is adopted. It can speed up system response and improve system performance. The experimental consequence demonstrates that the improved SMO can effectively restrain the chattering phenomenon and realize the fast and precise control of the PMSM.

Research on sensorless control of HSPMSM based on a discrete full-order sliding mode observer

To address the inaccuracy of the observed rotor position caused by the large estimated back-electromotive force harmonics of the high-speed permanent magnet synchronous motor (HSPMSM) under the conventional sliding mode observer, this paper presents an adaptive full-order sliding mode observer for back-electromotive force (EMF) based on the accurate mathematical model of the HSPMSM in the discrete-time domain. The accuracy of the sliding mode observer is improved under high-speed operating conditions by using the proposed method. To further reduce the harmonic component of the observed back EMF, a synchronous fundamental frequency extraction filter (SFEF) is used to obtain the back EMF, and then, the extracted observed EMF is fed in;to the normalized phase-locked loop to obtain the rotor position. The simulation results in Matlab are presented to demonstrate the feasibility and effectiveness of the proposed method.

Vector Control of PMSM Based on Improved Sliding Mode Observer and Controller

This paper presents a sensorless speed control method of permanent magnet synchronous motor (PMSM) applying sliding-mode control theory, to enhance the observation precision and improve robustness of control system. Firstly, an improved full-order sliding mode observer (FSMO) with sigmoid function is gifted to weaken the high-frequency (HF) chattering caused by conventional sliding mode observer (SMO). The quadrature phase-locked loop (PLL) is used to calculate high-precision rotor location and speed, avoiding the use of filter. Then the nonsingular fast terminal sliding mode controller (NFTSMC) in speed controller is introduced to replace traditional proportional integral (PI) controller to improve the dynamic performance of control system. The outcomes verify that the presented control method enhances the overall observation precision, suppresses HF chattering, and increases dynamic and stable state response of PMSM.

Robust synergetic control of electric vehicle equipped with an improved load torque observer

Abstract For environmental reasons, a great effort was focused on the improvement of the steady-state performance and dynamic performance of electric vehicles (EV). The EV is one of the cleanest and most ecological transport solutions. Accurate knowledge of EV load torque signals is important information for controlling and improving EV active safety. The estimation of load torque in EV drive contributes to cost reduction and solves many of the implementation problems encountered: lack of space, and severe environment. On this basis, in this research, our contribution contains two parts. The first part is the conception of a new scheme of control based on synergetic control (SC) for the speed of an EV propelled by a Six-Phase Permanent Magnet Synchronous Motor (PMSMs) is developed. This control technique offers a fast response, decreases the size of modeled system, and asymptotic stability of the closed-loop system in a vast domain. The second part deals with the synthesis of the sliding mode observer (SMO) to estimate load torque, compensate for strong disturbances and achieve high servo precisions. Moreover, reducing the chattering is inherent in the conventional SMO, we have proposed to replace the switching observer term Ksign with a smooth function and super twisting algorithm. The obtained simulation results proved the high performance assured by the synergetic control such as robustness and dynamic performance, and good estimation accuracy with free chattering even in strong noises.

An improved Sliding Mode Observer for parameter estimation in induction motor drive with optimised gains

ABSTRACT This paper represents the online parameter identification and continuous updating in the controller of Induction Motor Drives (IMD). The online measure of parameters improves the operation of the speed estimator, particularly nearer to the zero speed, and also computes the adaptive slip angular frequency. The parameter of speed estimation is performed by the improved Optimized Constant Rate Reaching Law (OCRRL)-based sliding mode observer (SMO), and electrical parameters of stator resistance, mutual inductance, and rotor time constant estimation is performed by Improved Adaptive SMO (IASMO). To enhance the monitoring reliability driven by parameter mismatches, an Online Parameter Estimation Control (OPEC) is presented. Lyapunov’s stability function is used to develop OPEC’s motor parameter adaptive rule. The conventional SMO suffers from the problem of higher chattering phenomena at the sliding surface, especially at very low and zero speeds. An improved OCRRL-based SMO dissolves this issue. Further, to enhance the performance by eliminating the time required for manual tuning of gains of observers in IASMO and PI controllers in Indirect Field Oriented Control (IFOC) are obtained by the Grey Wolf Optimization (GWO) technique. The effectiveness and performance of the proposed observers are tested and verified for possible operating conditions.

A Stroke Estimation Method for Linear Oscillatory Machine Using an Improved Sliding Mode Observer

For the linear compressor system driven by a linear oscillatory machine (LOM), the piston stroke is very important to realize the high working efficiency for the whole system. In order to obtain precise and reliable piston stroke signals without using the position sensor, this article proposes a stroke estimation method for the LOM using an improved sliding mode observer (SMO). For the improved SMO, the integral sliding surface is chosen to reduce the chattering phenomenon and the steady-state error of the system, and a novel reaching law is introduced to construct the sliding control law, which can further reduce the influence of the sliding chattering. Due to the piston stroke being obtained by integrating the back electromotive force (EMF) as estimated by the improved SMO, the pure integration saturation problem will occur due to that the measured current and voltage signals always contain some dc components. In order to cope with this problem, a self-adaptive bandpass filter is designed, which can obtain a filtered signal with almost no amplitude and phase deviation by adaptively adjusting its center frequency. Simulation and experimental results confirm that the proposed improved SMO has higher stroke estimation accuracy than the back EMF integration and the conventional SMO.

PMSM Adaptive Sliding Mode Controller Based on Improved Linear Dead Time Compensation

Aiming at the issue of the sliding mode observer (SMO) being sensitive to the motor model parameters at low speeds, a rotor position observation method based on resistance adaptive SMO and considering the influence of inverter dead time is designed in this paper. In this method, the online resistance identification is introduced into the conventional SMO, the resistance parameters of the SMO are modified in real-time, and the online resistance identification algorithm is designed by using the Lyapunov function. An enhanced linear dead time compensation method is proposed to improve the resistance adaptive SMO and eliminate the voltage error between the estimated and the actual motor models in order to address the impact of inverter dead time on the voltage parameters in the estimation model at low speeds. Simulation results show that the online resistance identification and dead time compensation can significantly improve the accuracy of sensorless speed control at low speeds, and the dead time compensation can also improve the accuracy of online resistance identification.

A Novel SPMSM Sensorless Drive Using Discrete-Time Synchronous-Frequency Adaptive Observer Under Low Frequency Ratio

To improve the stability and accuracy of the estimated position using the conventional sliding mode observer (CSMO) under low frequency ratio (LFR), this article proposes a novel discrete-time synchronous-frequency adaptive observer (SFAO) for surface-mounted permanent magnet synchronous motor (SPMSM) sensorless drives. The proposed SFAO has merits of high amplitude and zero-phase lag of resonant controller at synchronous frequency. The sign function and the low-pass filter (LPF) of CSMO in the proposed observer can be removed and conducive to dispel the inherent chattering of the CSMO as well as phase shift produced by the LPF. Then, taking into account the digital control delay and discretization truncation error, an exact complex-vector discrete-time model in the stationary coordinate is developed. Based on that, the direct discrete-time domain design approach is utilized in the proposed observer, which can be devised by pole placement directly on complex <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">z</i> -domain to assure the stability and position estimation accuracy under LFR. Finally, the availability of the proposed discrete-time SFAO scheme is verified via experiments on a 2.1-kW SPMSM drive.

Speed Estimation of PMSM Based on a Super-Twisting Slide Mode Observer

To limit the high-frequency chattering originating from the conventional sliding mode observer in a PMSM sensorless control system of vacuum pumps and reduce the steady-state error caused by the phase lag of the coordinate system on the estimated speed, a speed estimation algorithm was proposed based on the super-twisting sliding mode observer. Then, the proposed algorithm was applied to observe an electromotive force. To this end, the Lyapunov function was established to analyze the stability of the current dynamic error equation. In this regard, the estimated phase lag of the rotating coordinate system was considered to study the influence of the speed estimation error. Moreover, a speed estimation algorithm considering the d-axis estimation of back electromotive force is proposed. The performed analyses show that the speed estimation algorithm based on a super-twisting sliding mode observer has promising estimation accuracy. It is concluded that the proposed algorithm can be effectively applied to suppress high-frequency chattering in the system, reduce the influence of phase lag in the estimation coordinate system on the speed estimation error, remove the low-pass filter and phase compensation module, and improve the accuracy of speed estimation.

Sliding mode observers for robust fault estimation in linear parameter varying systems

AbstractA linear parameter varying sliding mode fault reconstruction scheme is proposed. Compared with other conventional sliding mode observer designs, the estimate emerges quite naturally from the equations governing the sliding motion, and although the process may be viewed as a filtering of the discontinuous injection, there is no phase lag introduced in the process. A semi‐analytic solution to the proposed linear parameter varying sliding mode observer is first discussed. This motivates the structure of the linear matrix inequality formulation which is proposed, and clarifies the class of systems to which the approach is applicable. The linear matrix inequality problem set up minimizes the induced gain between the fault estimate and external disturbances, whilst ensuring linear quadratic performance of the underpinning sliding motion. The proposed scheme has been validated using the Japan Aerospace Exploration Agency's Multi‐Purpose Aviation Laboratory aircraft‐in‐the‐loop platform to demonstrate the design efficacy.

Disturbance estimation for robotic systems using continuous integral sliding mode observer

AbstractThis article presents a novel force‐sensor‐less method for the estimation of external forces for a general class of second‐order robotic systems. The method is based on the integral sliding mode observer (ISMO) which serves as a second‐order differentiator for the position measurement of the system. As a result, the system states and disturbance are estimated without explicitly using force and velocity measurements. To apply the ISMO to the general second‐order systems, a proper assumption is proposed to address their nonlinearity and discontinuity. The boundary‐layer method is applied to ensure that the virtual inputs of the observer are continuous such that the chattering phenomenon is attenuated. A Lyapunov‐based method is used to analyze the influence of the boundary layers on the convergence of the state‐ and disturbance‐estimation errors. This influence, mainly determined by the boundary‐layer scalars, is given in analytical forms as a reference for parameter selection. The method is evaluated by numerical simulation on a robot manipulator system and compared with a conventional sliding mode observer (SMO). The validation of the performance of the continuous ISMO indicates its generalizability to general second‐order robotic systems. Also, the advantage of continuous ISMO over the conventional SMO is reflected by its small estimation errors and superior responsiveness. In general, the proposed method in this paper may interest those who are seeking solutions for haptic robotic tasks without using force sensors.

Adaptive Sliding Mode Observer-Based Sensorless Control for SPMSM Employing a Dual-PLL

In order to get rid of the chattering problem of a sliding mode observer, this article presents an adaptive sliding mode observer (ASMO)-based sensorless control for surface-mounted permanent-magnet synchronous machines (SPMSMs). In the conventional sliding mode observer, a large gain is required to ensure the sliding motion stability. However, it leads to undesired chattering and degrades the position estimation accuracy. With the proposed ASMO strategy, the observer gain can be dynamically adjusted according to the back electromotive force (EMF), and it is applicable in wide speed range with improved estimation accuracy. Then, a dual-phase-locked loop (DPLL) is improved to extract accurate rotor position information under dynamic process in both positive and negative rotating directions of the SPMSM. Finally, the effectiveness of the proposed method has been verified by simulation and experiment on a Higale platform with a 0.2-kW SPMSM.

Current Decoupling Control of Linear Synchronous Motor Based on an Improved Sliding Mode Observer

This paper proposes an improved sliding mode observer (ISMO) for the current decoupling control of the linear synchronous motor (LSM) to improve the dynamic performance of the LSM system. The proposed ISMO is based on variable power and exponential terms. By comparing the convergence time of the proposed ISMO and the conventional sliding mode observer (CSMO), we find that the ISMO can achieve a high convergence rate than the CSMO with the appropriate parameter options. Because the ISMO is established based on the extended state equation of the lumped disturbances, which includes the current coupling interferences and parameter variation disturbances, the ISMO-based decoupling control (ISMO-DC) can suppress these two types of disturbances simultaneously. The stability analysis based on the Lyapunov stability theory guarantees the convergence of the proposed ISMO. The experimental results verify the effectiveness of the proposed method in achieving a better decoupling control performance for the LSM system.

High-Order Terminal Sliding-Mode Observer for Chattering Suppression and Finite-Time Convergence in Sensorless SPMSM Drives

Due to the advantages of strong robustness and fast convergence, the sliding-mode observer (SMO) is considered as an effective approach for sensorless surface-mounted permanent magnet synchronous motor (SPMSM) drives. However, the inherent chattering and none finite-time convergence are still challenging problems in SMO application. To address these problems, this article proposed a high-order terminal SMO (HOTSMO) for SPMSM position estimation. First, a terminal sliding-mode surface is designed to achieve finite-time convergence of state variables. Second, a high-order sliding-mode control law is presented to achieve chattering suppression. Compared with the conventional SMO, the studied HOTSMO can achieve high estimation accuracy without sacrificing strong robustness of SMO. The effectiveness of the studied scheme is experimentally verified on a 4.4-kW ARM-based SPMSM platform.

An Enhanced SMO-Based Permanent-Magnet Synchronous Machine Sensorless Drive Scheme With Current Measurement Error Compensation

This article establishes an enhanced sliding-mode observer (SMO) with current measurement error compensators for the speed and position estimation in the permanent-magnet synchronous machine (PMSM) sensorless drive scheme. First, hyperbolic tangent switching function-based SMO with a self-adjusted shape coefficient is realized using a fuzzy logic controller (FLC) to not only eliminate the low-pass filter (LPF) and angular compensator in the conventional SMO, but also to reduce chatter caused by the constant boundary layer thickness. On the basis of Lyapunov's second theory, reachable and stable conditions of the enhanced SMO are founded. Then, as the current controller in the PMSM sensorless drive system needs to detect phase currents using current sensors, inevitable measurement errors exist. Two major kinds of current measurement errors, namely, the offset error and the scaling error, are analyzed. Their influences on the current fluctuations and corresponding compensation strategies are given in detail. By integrating current compensators into the enhanced SMO, a practical PMSM sensorless field-oriented control (FOC) scheme is constructed. The effectiveness of the enhanced SMO and current compensators is validated separately by comparative experiments. Final results indicate satisfactory chatter reduction and current ripple suppression performance of the proposed method.

Sliding Mode Observer with Adaptive Parameter Estimation for Sensorless Control of IPMSM

To improve the observation accuracy and robustness of the sensorless control of an interior permanent magnet synchronous motor (IPMSM), a sliding mode observer based on the super twisting algorithm (STA-SMO) with adaptive parameters estimation control is proposed, as parameter mismatches are considered. First, the conventional sliding mode observer (CSMO) is analyzed. The conventional exponential approach law produces a large chattering phenomenon in the back EMF estimation, which causes a large observation error when filtering the chattering through the low-pass filter. Second, a high-order approach law of the super twisting algorithm is introduced to observe the rotor position and speed estimation, which uses the integral function to eliminate the chattering of the sliding mode. Third, an adaptive parameter estimation control (APEC) is presented to enhance the observation accuracy caused by parameter mismatches; the motor parameter adaptive law of the APEC is designed by Lyapunov’s stability law. Finally, the proposed method not only reduces both the chattering and the low-pass filter, but it also enhances accuracy and robustness against parameter mismatches, as discussed through simulations and experiments.

Sensorless Predictive Control of SPMSM-Driven Light EV Drive Using Modified Speed Adaptive Super Twisting Sliding Mode Observer With MAF-PLL

Sensor reduction is a key sought after requirement for a surface mounted permanent magnet synchronous motor (SPMSM) electric vehicle (EV) drive to improve reliability and to reduce its cost. However, achieving a smooth and successful wide speed range using sensorless control is still a challenge. This article presents a modified higher order sliding mode observer (SMO)-based position sensorless predictive current control for wide range speed operation of an SPMSM-driven light EV. For reducing chattering and singularity phenomenon in conventional SMO, a modified speed adaptive super twisting SMO with moving average filter phase-locked loop (PLL) is deployed to accurately estimate the position and speed of SPMSM. Moreover, optimal switching pulses are provided to a voltage source inverter using time delay-compensated finite control set-model predictive current controller, eliminating the need of proportional integral controllers and modulators. Simulated performance of the control scheme is presented in MATLAB Simulink and its hardware implementation is executed using an SPMSM EV drive laboratory test setup. A comprehensive study of different PLL-based SMOs is carried out and the effectiveness of proposed system against conventional and other methods is demonstrated experimentally. It is observed that this method allows seamless sensorless operation at 3.95% of rated speed.