Permanent Magnet Synchronous Motor Servo Research Articles

Rapid phase current sampling in a permanent magnet synchronous motor servo system utilizing flexible memory controller bus

Background The permanent magnet synchronous motor (PMSM) servo system, integral to robots and other high-precision motion control applications, has its performance directly influenced by the current loop in the PMSM servo system. Though the theoretical adjustment time of the current loop can approach the electrical time constant of PMSM in order of magnitude, constraints such as control frequency make the adjustment time significantly larger than this theoretical limit. Methods This paper introduces a PMSM servo system using a flexible memory controller (FMC) bus for rapid phase current sampling. It leverages an independent current sampling module, equipped with an external analog-to-digital (AD) conversion chip for precise sampling of the output phase current of the PMSM. The sampling precision is 16-bit with a range of 0-3V. The sampled signal is preprocessed by a field-programmable gate array (FPGA), with the phase current data finally transmitted to the primary control chip through the FMC bus. Results By implementing this rapid current sampling architecture, we have successfully reduced the current sampling time by 95.4% while maintaining sampling accuracy. This scheme also substantially shortens the microcontroller unit’s (MCU) interrupt response time, potentially enhancing the current loop's control frequency, ultimately increasing the current loop bandwidth to 20kHz. Conclusions In conclusion, the proposed PMSM servo system with rapid current sampling significantly enhances the performance of the current loop. This advancement in sampling efficiency and control frequency offers substantial improvements for high-precision motion control applications, making it a valuable contribution to the field.

Research on trajectory tracking control method for agricultural robot permanent magnet synchronous motor servo system based on improved EMD threshold wavelet filtering

In agricultural robots, trajectory tracking can be affected by disturbances such as road slopes or bumps, leading to sudden changes in path curvature and reduced control accuracy. To address this issue, we propose a servo motor drive control method based on an improved Empirical Mode Decomposition (EMD) threshold. A mathematical model integrating the drive and control of the servo motor is established, and the driving performance of the servo motor is analyzed. By detecting the speed and position of the servo motor, the specified three-phase current values for motor drive control are derived. The actual current of the motor is collected using Hall current sensors and denoised with an improved EMD threshold wavelet filtering method. Within the servo motor drive control model, the system calculates the difference between the given three-phase current values and the actual motor current, and this difference is then used to adjust the motor control via an input linear amplifier, ensuring integrated drive control. Simulation and experimental results show that the proposed trajectory tracking control method for the agricultural robot’s permanent magnet synchronous motor servo system exhibits high control accuracy, strong anti-interference ability, and good performance, making it more suitable for practical applications.

A Novel Nonsingular Fast Terminal Sliding Mode Control with Sliding Mode Disturbance Observer for Permanent Magnet Synchronous Motor Servo Control

This article proposes a novel nonsingular fast terminal sliding mode control (N-NFTSMC) with a sliding mode disturbance observer (SDOB) for permanent magnet synchronous motor (PMSM) servo control. Firstly, to reduce the chattering issue, a new sliding mode reaching law (NSRL) is proposed for the N-NFTSMC. Secondly, to further improve the dynamic tracking accuracy, we introduce a sliding disturbance observer to estimate unknown disturbances for feedforward compensation. Comparative simulations via Matlab/Simulink 2018 are conducted using the traditional NFTSMC and N-NFTSMC; the step simulation results show that the chattering phenomenon was suppressed well via the N-NFTSMC scheme. The sine wave tracking simulation proves that the N-NFTSMC has better dynamic tracking performance when compared with traditional NFTSMC. Finally, we carry out experiments to validate that the N-NFTSMC adequately suppresses the chattering issue and possesses better anti-disturbance performance.

A Fractional-Order ADRC Architecture for a PMSM Position Servo System with Improved Disturbance Rejection

This paper proposes an active disturbance rejection control (ADRC) architecture for a permanent magnet synchronous motor (PMSM) position servo system. The presented method achieved enhanced tracking and disturbance rejection performance with a limited observer bandwidth. The model-aided extended state observer (MESO)-based ADRC was designed for the current, speed, and position loops of the PMSM position servo system. By integrating known plant information, the MESO improved disturbance estimation with a limited observer bandwidth without amplifying the noise. Additionally, a fractional-order proportional-derivative (FOPD) controller was designed as the feedback controller for the speed loop to further enhance the disturbance rejection. A simulation and experimental tests were conducted on a PMSM servo platform. The results demonstrate not only that the proposed method achieved superior tracking performance but also that the position error of the proposed strategy decreases to 2.25% when the constant disturbance was input, significantly improving the disturbance rejection performance.

A Novel Friction Compensation Method Based on Stribeck Model With Fuzzy Filter for PMSM Servo Systems

Friction deteriorates speed and position control accuracy of high-precision machine tools and causes distortion phenomenon when the speed crosses zero. In this paper, a new compensation method based on static Stribeck model (SB) combined with fuzzy low-pass filter (SBFF) is studied for friction compensation of permanent magnet synchronous motor (PMSM) servo systems. First, models of the servo system, the Stribeck, and the LuGre are established. Then, it is theoretically derived that the hysteresis effect of the LuGre model (LG) can be equivalent to a low-pass filter term compared to the SB. Based on this, the relationship between the filter time constant and the motor reference speed can be derived. To further improve the friction compensation effect near zero speed and to weaken the delay generated by the filter during the non-zero-speed range, fuzzy logic is introduced to adjust the filter time constant according to the reference speed variation. Through simulations and experiments, compensation strategies based on the LG feedforward, SB feedforward, SBFF feedforward and SBFF feedback are compared, and the robustness of the proposed SBFF feedforward compensation method over entire speed range is verified as well.

Implementation Process Simulation and Performance Analysis for the Multi-Timescale Lookup-Table-Based Maximum Power Point Tracking under Variable Irregular Waves

The efficacy of the multi-timescale lookup-table-based maximum power point tracking (MLTB MPPT) in capturing energy at various fixed sea states has already been demonstrated. However, it remains imperative to conduct a more comprehensive evaluation of the MPPT tracking performance under varying sea states in practical scenarios. Additionally, it is crucial to engage in an in-depth analysis of the dynamic process and energy loss/consumption associated with MLTB MPPT implementations. This paper focuses on the implementation process simulation and performance analysis for the MLTB MPPT under variable irregular waves. Firstly, the structure of the wave power controller based on a MLTB MPPT algorithm is described in detail, as well as that of a controlled plant, known as a novel inverse-pendulum wave energy converter (NIPWEC). Secondly, mathematical models for the MLTB MPPT are developed, taking into account the efficiency of each link. In this paper, we present simplified modelling methods for both permanent magnet synchronous generator (PMSG) vector control and permanent magnet synchronous motor (PMSM) servo control. Finally, the tracking performance of the MLTB MPPT in the presence of variable irregular waves is comprehensively analyzed by simulating the implementation process and comparing it with two other MPPT algorithms, i.e., the frequency- and amplitude-control-based MPPT and the lookup-table-based internal mass position adjustment combined with the optimal fixed damping search. Results show that the MLTB MPPT (Method 2) is a competitive algorithm. Besides, a significant portion (>12%) of the time-averaged absorbed power is actually lost during the power generation process. On the other hand, the power required for a mass-position-adjusting mechanism is relatively small (approximately 0.2 kW, <1.5%). The research findings can offer theoretical guidance for optimizing the operation of NIPWEC engineering prototypes under actual sea conditions.

Low order speed harmonic suppression in FOC-PMSM based on the closed-loop transfer mechanism of injected voltage

In the field oriented control (FOC) permanent magnet synchronous motor (PMSM) servo system, torque ripple impairs motor performance. Harmonic injection methods can suppress torque ripple by injecting additional voltage harmonic to offset the existing speed harmonic. However, since FOC is a closed-loop motion control strategy, the transfer path from injected voltage harmonic to speed harmonic is affected by FOC, especially in very low frequency. Due to the influence of FOC on the transfer function, the relation between the injected voltage harmonic and speed harmonic varies with operating conditions and motor control parameters. It causes the existing harmonic injection methods ineffective to suppress low order speed harmonics. To solve the problem, in this paper, the closed-loop transfer mechanism of injected voltage harmonics is analyzed and the closed-loop transfer function is derived. Based on the derived closed-loop transfer function, a low order speed harmonic suppression method is proposed. With the derived transfer function, the proposed method can adapt to the variations of the relation between low order injected voltage harmonic and speed harmonic under different operation conditions. Finally, the accuracy of the derived closed-loop transfer function and the effectiveness of the proposed low order speed harmonic suppression method are evaluated by experiment.

Fast terminal sliding mode control of agricultural robots with permanent magnet synchronous motor servo systems based on an extended state observer for path tracking

In response to the challenges in mobile robot path tracking using model predictive control, where the predictive model weakens the controller’s ability to respond to sudden changes in the reference path curvature and heading, this paper proposes a composite control strategy suitable for agricultural robots. The strategy combines the maximum torque per ampere control and an Extended State Observer (ESO). The paper initially establishes a mathematical model for a Permanent Magnet Synchronous Motor (PMSM) considering aggregated disturbances. It designs a position tracking controller based on a non-singular terminal sliding mode and convergence law. This controller, employing a non-cascaded structure, replaces traditional position and velocity loop controllers and is proven to be stable with finite-time convergence through Lyapunov’s theorem. To enhance the system’s disturbance rejection capabilities further, the paper introduces an ESO to estimate system disturbances and applies it for feedforward compensation. The paper concludes by providing stability proof for the overall PMSM servo system in agricultural robots. Finally, the paper conducts simulations and experimental verifications based on the designed controller, demonstrating that the controller exhibits excellent path tracking performance, fast convergence, and robustness against external disturbances.

A Feedrate Planning Method in CNC System Based on Servo Response Error Model

Reducing servo response error and further making reduction on contour error is crucial for high-precision computer numerical control (CNC) machine tools. For a permanent magnet synchronous motor (PMSM) servo system, there is always a response lag in feedrate tracking, which would introduce response error into the machining trajectory. Therefore, it is necessary to improve the performance of feedrate planning and interpolation for trajectory path. In this paper, a novel contour error compensation strategy is proposed. Compared with the mainstream methods, the proposed method offers a simplified alternative to existing contour error estimation techniques. Through a three-closed-loop control structure of a PMSM servo system, a response error model is founded. Afterwards, an improved S-model feedrate planning method is introduced according to the servo response error compensation. This predicted error is subsequently compensated in each interpolation cycle, resulting in a reduction of contour error. Finally, simulations and experiments are performed to demonstrate that the contour error can be reduced in both the ‘∞’-shaped Non-Uniform Rational B-Spline (NURBS) curve path and the butterfly-shaped NURBS curve path using the proposed method.

Additive-state-decomposition-based model predictive tracking control for PMSM servo system with multiple disturbances

This paper presents an additive-state-decomposition-based model predictive tracking control and disturbance rejection method for a permanent magnet synchronous motor (PMSM) servo system subject to unknown parameter perturbations, unmodeled dynamics, and time-varying load torque. The basic idea of this method is to equivalently decompose the original system into a primary system for handling the tracking control subproblem and a secondary system for dealing with the robust stabilization subproblem. A model predictive controller is designed for the primary system to achieve high-accuracy tracking of the reference speed. As for the secondary system, a novel high-order generalized extended state observer (HGESO) is constructed to estimate the multiple disturbances simultaneously, and a state feedback control law incorporating a disturbance compensator is developed to eliminate the adverse effect of the multiple disturbances on the system output. By combining the control inputs of the two subsystems together, the control objectives of the original system can be achieved. Both the stability criterion and design procedure of the closed-loop control system are developed. Finally, hardware-in-the-loop-based comparative experiments are conducted to demonstrate that the proposed method effectively suppresses the influence of the multiple disturbances on motor speed tracking accuracy and that the control system has both satisfactory dynamic performance and robustness.

Disturbance and Uncertainty Attenuation for Speed Regulation of PMSM Servo System Using Adaptive Optimal Control Strategy

This paper proposes an adaptive optimal control scheme to minimize the effect of disturbances and uncertainties of permanent magnet synchronous motor (PMSM). In the speed regulation loop, an adaptive speed controller is designed, which not only regulates the speed perfectly but also is robust against wide range variation of parameters and external disturbance of PMSM. Unlike the traditional speed controller, the proposed controller includes an adaptive law to compensate the distorted model parameters and disturbances in real-time, enhancing speed performance. The stability of the proposed speed controller is fully proven by using Lyapunov theory. Meanwhile, a PI-type optimal current controller is established in the inner control loop to achieve the current tracking and limitation. By easily selecting appropriate performance indexes, the proposed controller can balance between control input magnitude and current tracking error. Finally, the validity of the proposed control scheme is verified through simulations and experiments. For a comparative study, four different control strategies, that is, the proposed control, super twisting sliding mode control, PI control and disturbance observer-based control, are carried out to demonstrate the superiority of the proposal.

Sliding-Mode-Based Robust Output Regulation and Its Application in PMSM Servo Systems

A robust output regulation of a control system aims at disturbance rejection and reference tracking in the presence of uncertainties. Technically, the control design contains two mechanisms: the compensation of nontrivial steady states caused by disturbances and/or reference trajectories and the stabilization of an error system relative to steady states. Feedforward compensation and the internal model (including an approximate integrator) are the two main techniques for the former, while the latter is on a case-by-case basis. This article studies an alternative sliding-mode-based approach that can address the two mechanisms simultaneously, thanks to the new concept of sliding-mode-based output zeroing manifold. This concept bridges the two widely studied areas: robust output regulation and sliding-mode control. The approach is also verified by its application in permanent magnet synchronous motor servo systems.

Design of single neuron super-twisting sliding mode controller for permanent magnet synchronous servo motor

Aiming at the control system of permanent magnet synchronous servo motor which is easily affected by external disturbance and parameter uncertainty, a single neuron sliding mode combining single neuron adaptive algorithm and super-twisting sliding mode (STSM) control is proposed. The STSM control is used to overcome the chattering problem in the traditional sliding mode control, and the proportional control and the STSM control are combined to enhance the robustness of the control system. In order to improve the dynamic performance of the system and enhance the anti-disturbance ability of the system, the single neuron adaptive control adopted can adjust the relevant parameters of the designed sliding mode controller online. The simulation and experimental results show that the designed improved sliding mode controller can effectively suppress the chattering of the control system, realize the fast following and no overshoot of the control system, and enhance the robustness of the system.

A novel adaptive PD-type iterative learning control of the PMSM servo system with the friction uncertainty in low speeds.

High precision demands in a large number of emerging robotic applications strengthened the role of the modern control laws in the position control of the Permanent Magnet Synchronous Motor (PMSM) servo system. This paper proposes a learning-based adaptive control approach to improve the PMSM position tracking in the presence of the friction uncertainty. In contrast to most of the reported works considering the servos operating at high speeds, this paper focuses on low speeds in which the friction stemmed deteriorations become more obvious. In this paper firstly, a servo model involving the Stribeck friction dynamics is formulated, and the unknown friction parameters are identified by a genetic algorithm from the offline data. Then, a feedforward controller is designed to inject the friction information into the loop and eliminate it before causing performance degradations. Since the friction is a kind of disturbance and leads to uncertainties having time-varying characters, an Adaptive Proportional Derivative (APD) type Iterative Learning Controller (ILC) named as the APD-ILC is designed to mitigate the friction effects. Finally, the proposed control approach is simulated in MATLAB/Simulink environment and it is compared with the conventional Proportional Integral Derivative (PID) controller, Proportional ILC (P-ILC), and Proportional Derivative ILC (PD-ILC) algorithms. The results confirm that the proposed APD-ILC significantly lessens the effects of the friction and thus noticeably improves the control performance in the low speeds of the PMSM.

An EPCH Control Strategy for Complex Nonlinear Systems with Actuator Saturation and Disturbances

This paper presents a novel error port-controlled Hamiltonian (EPCH) strategy with adaptive gains for a class of complex nonlinear systems subject to actuator saturation and disturbances. Considering the actuator saturation phenomenon in real complex systems, a new smooth saturation function with hyperbolic tangent is adopted to deal with the limitations between the actuator and the control signal. A nonlinear disturbance observer (NDOB) is utilized to compensate the influence of model parameter uncertain, noise, measurement error, external disturbance and other factors in real complex systems. To enhance the accuracy of position control and tracking control for the target, we propose a novel EPCH strategy, which adopts adaptive gain and variable damping technology in the damping injection link. Finally, the permanent magnet synchronous motor (PMSM) servo system is applied to verify the proposed method. The strategy proposed compared with port-controlled Hamiltonian based on disturbance observer, port-controlled Hamiltonian based on load torque estimator and other methods has better control performances by simulation results.

A Novel Two-Phase Mode Switching Control Strategy for PMSM Position Servo Systems With Fast-Response and High-Precision

In this article, a novel mode switching control (MSC) strategy is proposed containing a fast-response phase and a high-precision settling phase to meet the requirement of high-quality point-to-point permanent magnet synchronous motor servo systems. In the fast-response stage, an adaptive trajectory planning method is developed to program the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</i> -axis current profile online based on the reference for the motor to reach the neighborhood of the reference position in minimum time. The chattering in the conventional time-optimal control is overcome and the idea that skipping speed and position loop with preplanned <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</i> -axis current trajectory is first attempted. After switching, the high-precision settling stage that is responsible for improving the transient performance in terms of reducing the overshoot and settling time is built with the proposed robust composite nonlinear feedback (RCNF) control law. This RCNF method cancels the overall disturbance through an extended state observer. The switching condition for the proposed MSC controller is clarified. Afterward, the whole closed-loop system's stability is strictly proved. Experiments are then conducted based on different scenarios to prove the effectiveness and robustness of the proposed MSC method.

A Singular Perturbation Approach-Based Non-Cascade Sliding Mode Control for Surface-Mounted PMSMs

Motivated by the fact that electrical transients are rather fast compared with mechanical response, the traditional cascade control structure constituted by the inner current and outer speed loops is usually employed in the permanent magnet synchronous motors (PMSMs) servo control community. According to the above-mentioned time-scale characteristic of the PMSMs drive systems, this technique addresses the problems of the non-cascade sliding mode control (SMC) strategy for the surface-mounted PMSMs. Firstly, by appropriately introducing the singular perturbation theory, the corresponding mathematical equations are modeled as a singular perturbation system. Meanwhile, a composite sliding mode surface is constructed based on the Lyapunov equation, such that the system stability can be also guaranteed. Then, according to the exponential reaching law, a standard non-cascade SMC law is designed. Furthermore, an optimal nonlinear function-based tracking differentiator (TD) is presented to smooth the reference velocity value, while providing differential signals. As a result, a novel TD-based SMC strategy is synthesized by incorporating a nonlinear function, thus improving the inherent chattering phenomenon. Finally, a surface-mounted PMSM servo system is performed to illustrate the advantages and effectiveness of the proposed approaches. The main contribution of this paper is to present an alternative non-cascade SMC framework based on the singular perturbation approach, which provides a novel control structure for a PMSM speed regulation system.

Anti-Disturbance Integrated Position Synchronous Control of a Dual Permanent Magnet Synchronous Motor System

In order to solve the problem that the position synchronous performance of dual permanent magnet synchronous motor servo system is easily affected by parameter perturbation and load disturbance, an anti-disturbance integrated position synchronous control strategy of dual permanent magnet synchronous motor system is proposed. Firstly, the integral mathematical model of a dual permanent magnet synchronous motor system is established. After that, the third-order linear extended state observer is constructed to observe and compensate for disturbance in order to improve the anti-disturbance performance of the position loop. At the same time, a cross-coupled position synchronous compensator is added to improve the synchronous performance of the system, and through the Bode diagram analysis method in the frequency domain, the system stability and anti-disturbance performance are researched. Finally, the effectiveness of the proposed algorithm is verified by experimental research.

Dual-Time-Scale Sliding Mode Control for Surface-Mounted Permanent Magnet Synchronous Motors

The permanent magnet synchronous motors (PMSMs) as the completely symmetrical three-phase machines, which are usually driven by symmetrical voltage signals. Unfortunately, a PMSM system usually suffers from the different lumped disturbances, such as internal parametric perturbations and external load torques, the speed regulation problem should be addressed within the different operation situations. Characterizing by the current variation speed of the motor winding is much faster than that of the mechanical dynamic velocity, a dual-time-scale sliding mode control (SMC) method for the surface-mounted PMSMs is proposed in this paper. Firstly, the mathematical model of PMSMs is established in the two-phase synchronous rotating orthogonal reference coordinate system, and the slow and fast variation subsystems are obtained based on the quasi-steady-state theory. Secondly, a tracking differentiator (TD)-based and exponential reaching law-based sliding mode controllers are individually designed within dual-time-scale, respectively. As a result, the eventual SMC strategy is presented, and the stability of control system is analyzed by applying the Lyapunov stability theory. The main contribution of this study is to present an alternative control framework for the PMSMs servo system, where the dual-time-scale characteristic is involved, and thus a non-cascade control structure that different from the traditional drive strategy is proposed in the motor community. Finally, the model of whole system is built and carried out on the simulation platform. Research results demonstrate that the presented servo control system can accurately track the reference angle velocity signal, while the strong robustness and fast response performance are guaranteed in the presence of external disturbances. In addition, the three-phase current transient response values are completely symmetrical with the rapid adjustment characteristic.

Improved sliding mode control for permanent magnet synchronous motor servo system

In this study, an improved sliding mode control (ISMC) method combining continuous non-singular terminal sliding mode (CNTSM) and linear active disturbance rejection control (LADRC) for permanent magnet synchronous motor (PMSM) servo system is proposed to improve the performance of PMSM. Based on the mathematical model of PMSM, combined with SMC theory and LADRC theory, CNTSM controller based on continuous function is proposed to solve the singularity of terminal sliding mode (TSM) control. In order to solve the contradiction between the convergence performance of sliding mode control and the ability of chattering suppression, fuzzy control is introduced to adjust the gain of sliding mode controller in real time. LADRC is developed to ensure the current starting conditions of the motor and improve the robustness. Moreover, the asymptotic stability of the system is guaranteed by the Lyapunov theorem and it is verified by the AISim MBD servo motor experimental platform. Experiments show that the algorithm has good tracking performance and robustness.