External Disturbance Torque Research Articles

Asymmetric full-state constrained attitude control for a flexible agile satellite with multiple disturbances and uncertainties

In this paper, an asymmetric full-state constrained attitude control method for a flexible agile satellite with multiple disturbances and uncertainties is proposed. Both the attitudes and angular velocities of the flexible agile satellite are guaranteed in the asymmetric/symmetric bounds by utilizing the time-varying integral barrier Lyapunov function (TVIBLF) and constant integral barrier Lyapunov function (IBLF) respectively. Compared with the existing error-based barrier Lyapunov functions, the asymmetric TVIBLF does not need error transformation, relaxes the conservation of the initial requirements, and has more compatibility. Furthermore, the proposed asymmetric TVIBLF can deal with the asymmetric time-varying constraints without loss of generality. In addition, the high-frequency flexible vibrations, inertial uncertainties, and unknown external disturbance torques affected on the agile satellite are considered respectively. On one hand, a modal observer is utilized to suppress the high-frequency flexible vibration effects on the attitudes. On the other hand, the inertial uncertainties and unknown external disturbance torques are estimated with a multi-variable nonlinear disturbance observer. Therefore, both the asymmetric full-state constrained performances and robustness of the attitude control system for the flexible agile satellite are achieved. The stability of the closed-loop system is proved and numerical simulations have validated the effectiveness of the proposed method.

Geometric extended state observer on [formula omitted] with fast finite-time stability: Theory and validation on a multi-rotor vehicle

This article presents an extended state observer for a vehicle modeled as a rigid body in three-dimensional translational and rotational motions. The extended state observer is applicable to a multi-rotor aerial vehicle with a fixed plane of rotors, modeled as an under-actuated system on the state-space TSE(3), the tangent bundle of the six-dimensional Lie group SE(3). This state-space representation globally represents rigid body motions without singularities. The extended state observer is designed to estimate the resultant external disturbance force and disturbance torque acting on the vehicle. It guarantees stable convergence of disturbance estimation errors in finite time when the disturbances are constant, and finite time convergence to a bounded neighborhood of zero errors for time-varying disturbances. This extended state observer design is based on a Hölder-continuous fast finite time stable differentiator that is similar to the super-twisting algorithm, to obtain fast convergence. Numerical simulations are conducted to validate the proposed extended state observer. The proposed extended state observer is compared with other existing research to show its advantages. A set of experimental results implementing disturbance rejection control using feedback of disturbance estimates from this extended state observer is also presented.

Deep learning based fuzzy-MPC controller for satellite combined energy and attitude control system

Combined Energy and Attitude Control System (CEACS) reduces the size and mass budgets of typical satellites and consequently, increases their payload capacity. CEACS uses flywheels for a dual purpose, i.e., as both energy storage and attitude control device. This maiden work attempts to introduce a novel Deep-Learning capability of the fuzzy-Model Predictive Control (FMPC) controller for CEACS. The design approach for the fuzzy-MPC controller uses the Takagi-Sugeno (T-S) fuzzy model of satellite attitudes and computes the control torque through a parallel distribution compensation (PDC) approach. However, the MPC controller offers a high computational burden, and it becomes a significant problem for smaller satellites having limited computational power. Therefore, in this research work, a novel Deep-Learning-based fuzzy-MPC controller (D-FMPC) is designed for the CEACS attitude regulation subject to higher initial angles, actuator constraints, parametric uncertainties, and external disturbance torques. Here, the deep-layer neural network is trained offline with the MPC controller data to replicate the FMPC controller, thus ensuring its controllability. Numerical results validate that the D-FMPC controller successfully mimics the FMPC controller and produces the desired pointing accuracy effectively with smooth transient response and without violating the attitude control actuator constraints. The results also validate that the D-FMPC controller offers significantly reduced computational burden than the FMPC controller. Therefore, the novel Deep-Learning solution provides a feasible platform for applying more complicated and sophisticated attitude control techniques for the CEACS attitude regulation in small satellites as an example.

PMSM Speed Control Using an Enhanced State Feedback Controller and Linear Quadratic Regulator for Effective Drive System

This paper introduced an effective method for regulating and controlling the speed of PMSMs (permanent magnet synchronous motors) by linearizing the non-linear and time-varying equations that model the PMSM dynamics. This method was achieved by utilizing an improved state feedback controller along with a linear quadratic regulator (LQR) to determine an optimal performance index. In order to assess external load torque disturbances in the system, a disturbance observer (DO) method was employed. Additionally, a sliding mode observer was utilized in conjunction with the disturbance observer to control motor speed. Simulations were conducted to compare the state feedback controller with a conventional PI- controller. The results showed that the state feedback controller achieved a robust as well as improved speed and torque dynamic performance with a reduced steady-state error percentage of 24.17% and 23.51%, as compared to 38.0% and 38.37% obtained using a PI-controller. The derived state feedback matrix (K), based on Ackerman’s rule, demonstrated that the entire system is controllable and that the performance index is marginally stable. All simulations were achieved in MATLAB/SIMULINK 2021 version.

A New Nonlinear Dynamic Speed Controller for a Differential Drive Mobile Robot.

A disturbance/uncertainty estimation and disturbance rejection technique are proposed in this work and verified on a ground two-wheel differential drive mobile robot (DDMR) in the presence of a mismatched disturbance. The offered scheme is the an improved active disturbance rejection control (IADRC) approach-based enhanced dynamic speed controller. To efficiently eliminate the effect produced by the system uncertainties and external torque disturbance on both wheels, the IADRC is adopted, whereby all the torque disturbances and DDMR parameter uncertainties are conglomerated altogether and considered a generalized disturbance. This generalized disturbance is observed and cancelled by a novel nonlinear sliding mode extended state observer (NSMESO) in real-time. Through numerical simulations, various performance indices are measured, with a reduction of 86% and 97% in the ITAE index for the right and left wheels, respectively. Finally, these indices validate the efficacy of the proposed dynamic speed controller by almost damping the chattering phenomena and supplying a high insusceptibility in the closed-loop system against torque disturbance.

Low cost high performance self-starting sensorless single phase induction motor drive

<p><span lang="EN-US">The present paper is directed to achieve a low-cost high-performance self-starting single phase induction motor (SPIM) drive system. A phase shifted pulse width modulation (PWM) trains feeding the motor will replace the starting and running capacitors. Adaptive sliding mode control, enhance with model reference adaptive control (MRAC), is implemented to achieve high performance sensorless SPIM drive. The obtained results confirm the feasibility of the proposed system in starting and fast tracking the reference speed with nearly zero percentage overshoot and zero steady-state error. Moreover, the proposed SPIM drive system is robust to external load torque disturbances and insensitive to system parameter variations. Extensive simulations have been conducted to confirm the validity of the proposed system.</span></p>

Adaptive generalized super twisting sliding mode control for PMSMs with filtered high-gain observer

This paper proposes a novel adaptive-gain generalized super twisting algorithm for permanent magnet synchronous motors. The stability of this algorithm is strict proof using the Lyapunov method. Both controllers of the speed-tracking loop and the current regulation loop are designed according to the proposed adaptive-gain generalized super twisting algorithm. Dynamically adjusted gains in the controllers can improve the transient performance and system’s robustness while reducing chattering. A filtered high-gain observer is applied in the speed-tracking loop to estimate the lumped disturbances, including parameter uncertainties and external load torque disturbances. The estimates feeding forward to the controller further improve the robustness of the system. Meanwhile, the linear filtering subsystem reduces the sensitivity of the observer to the measurement noise. Finally, experiments are constructed using the adaptive gain generalized super twisting sliding mode algorithm and the fixed gain one, showing the effectiveness and advantages of the proposed control scheme.

Linear Parameter Varying Controller Design For Satellite Attitude Control*

This paper presents a systematic linear parameter varying (LPV) control approach for the 3-axis attitude control of an Earth-observation satellite in a sun-synchronous orbit. The dynamics of the satellite depend on the orientation of the solar array which completes a full rotation every orbit, thus it is used as a scheduling parameter in the design. The satellite has two additional flexible appendages; these are 2 scatterometers. The control objective is to precisely track a given reference attitude using reaction wheels, while rejecting external torque disturbances and sensor noise. The design follows a mixed-sensitivity approach, applying a recently introduced weighting scheme. It allows traceable and effective controller tuning by using a low number of physically interpretable weights. The controller is synthesised by solving the induced L2-norm of the closed-loop interconnection of the controller and weighted plant. Scheduling with the solar array orientation leads to an LPV notching behaviour in the controller that effectively mitigates the effects of the array's most prominent flexible modes. This behaviour enables increased performance, when compared to a linear time invariant controller, while maintaining robustness. The pointing performance of the synthesised controller over the complete satellite lifecycle is verified using the European Space Agency's standards for spacecraft attitude control.

Extended state observer based current-constrained controller for a PMSM system in presence of disturbances: Design, analysis and experiments

Considering overcurrent and total disturbances, i.e. measurement noise, parameter uncertainties, external load torque disturbance etc., a composite current-constrained control method based on non-cascade single-loop speed regulation control structure is adopted for permanent magnet synchronous motor system (PMSMs). First, a tracking state space model is proposed to transfer the matched and mismatched disturbances into a uniform matched disturbance. Second, a third-order extended state observer (ESO) is developed to satisfactorily attenuate the effect of the total disturbances with their estimation values via feedforward compensation, since a tracking differentiator (TD) is designed to arrange the transition process for the reference input signal to balance the contradiction between overshoot and quick response. Third, a composite ESO-based current-constrained controller with a penalty mechanism of q-axis current, constructed by a special nonlinear gain, is designed to deal with the overcurrent of the PMSMs speed regulation. In addition, a finite time bounded stability theory is introduced to analyze the proposed closed-loop speed regulation system. A bench mark experimental set-up based on NI CompactRIO 9045 and LabVIEW for a PMSMs is designed to verify and compare the performances of the proposed composite controller against conventional PID controller. Finally, the simulation and experiment results demonstrate the effectiveness and superiority of the proposed controller.

Particle swarm optimization based high performance four switch BLDC motor drive

The present publication is directed to utilize particle swarm optimization (PSO) algorithm based PI controller for adjusting the speed of brushless DC motor fed via four switch three phase inverter. The inverter topology reduces the cost and complexity of the drive system. High performance response during transient and steady state conditions is achieved by optimizing the controller gains using POS algorithm. The obtained results confirm the validity of the proposed drive configuration in providing the features of fast dynamic response (the settling time is about 0.025 s), with minimized percentage overshot, and approximately zero steady state error. Moreover, the drive system shows robustness feature when subjected to external load torque disturbances.

Research on UDE control based on load torque compensation of PMSM

In order to solve the problem that the traditional uncertainty and disturbance estimator (UDE) control needs to increase the filter order to keep good performance when facing rapid disturbance changes, thus lead to cost increase in implementing the system, a speed control strategy of permanent magnet synchronous motor (PMSM) driver based on reduced order observer compensation is proposed. The designed control strategy is robust to the system with internal parameter variation and external torque disturbance. Through the compensation of load torque, the pressure of UDE controller is relieved, and then the tracking error of high-frequency component in load torque is eliminated, and the control performance of the system is improved more effectively. This paper proves the superiority of the new compound controller through comparison of simulation. results

Intelligent Control of Uncertain PMSM Based on Stable and Adaptive Discrete-Time Neural Network Compensators

In this paper, stable and adaptive neural network compensators are proposed to control the uncertain permanent magnet synchronous motor (PMSM). Firstly, the overall uncertainties caused by mathematical modelling, parameters variation during operation and external load torque disturbances are modelled. Secondly, a new motion control scheme, where (d-q) current loops are dotted by two on-line tuning neural network compensators (NNCs), is used to compensate these uncertainties. As a result, the speed control loop is processed easily by proportional integral (PI) controller. Stability of the closed-loop system is also designed according to the Lyapunov stability. Compared to classical vector control, the simulations of PMSM system at different speeds including nominal, low and high speed, with and without uncertainties, show the effectiveness of the proposed control scheme.

Optimal design of adaptive robust control for a planar two-DOF redundantly actuated parallel robot

An adaptive robust control combined with a multi-objective parameter optimization method for a parallel robot under unknown uncertainty is proposed. In the active joint space, the model of the parallel robot can be obtained by combining the closed-chain constraint force and the open-chain system’s dynamic equation. Based on the Udwadia–Kalaba theory, the closed-chain constraint force imposed by the end effector can be calculated if no uncertainty. If there is uncertainty, we propose an adaptive robust control, based on a set of feasible design parameters, which guarantees deterministic performances, including uniform boundedness and uniform ultimate boundedness. To seek the optimal choice of the design parameters, among the feasible pool. We examine the system performance, which includes the transient performance, the steady state performance, and the control cost. By a fuzzy-theoretic D-operation, a performance index is formulated. The problem of choosing the optimal control parameters is equivalent to the problem of finding the minimum value of the performance index. An illustrative example demonstrates the superiority of the adaptive robust control. Mass uncertainty and external disturbance torque are introduced to test the effectiveness of the proposed control strategy.

Disturbance-observer based prescribed-performance fuzzy sliding mode control for PMSM in electric vehicles

This paper investigates the problem of accurate speed tracking control of electric vehicles powered by permanent magnet synchronous motor (PMSM) under external load torque disturbance. Firstly, the dynamic model of PMSM is given, and the controller is designed based on backstepping control. Secondly, a second-order sliding mode differentiator is used to approximate the derivative of virtual control law and solve the problem of explosion of complexity. Considering the load disturbance of PMSM in the actual operation due to road roughness, a novel disturbance observer is proposed to the estimate the load disturbance. In addition, in order to achieve prescribed tracking error performance, the prescribed-performance control is proposed to guarantee the tracking error within a given prescribed boundary. Finally, the finite-time stability of the system is proved, the simulation and real-time implementation results verify the effectiveness of the designed controller.

A backstepping disturbance observer control for multirotor UAVs: theory and experiment

This paper presents a backstepping disturbance observer based control (DOBC) for trajectory tracking motion control of multirotor Unmanned Aerial Vehicles (UAVs). Two disturbance observers (DO) estimate external force and torque disturbances acting on the UAV. A nonlinear backstepping dynamic state feedback is proposed which uses the DO estimates to achieve exponential stability for the closed-loop tracking error under constant disturbances. The stability analysis accounts for the entire nonlinear vehicle model which includes translational and rotational dynamics. Software-in-the-loop simulation and experimental results are presented showing the effectiveness of the proposed method using the commonly used PX4/Pixhawk development framework.

Maximum torque per ampere and maximum power per ampere sliding mode control for interior permanent magnet synchronous motors

This paper presents novel maximum torque per ampere (MTPA) and maximum power per ampere (MPPA) sliding mode control (SMC) approaches for interior permanent-magnet synchronous motors (IPMs). We first derive the first-order SMC methods to improve the field-oriented control's resiliency against the external perturbations, extraneous noise and modelling uncertainties. After that, we propose the higher-order SMC to significantly reduce the chattering phenomenon, which is inherent in the first-order sliding mode method. Based on the comparison studies, the conventional proportional-integral-derivative based field oriented control shows sluggish response and is more sensitive to parameter perturbations and external torque disturbances. By introducing the novel SMC methods, both the speed and torque regulation performance of interior permanent magnet synchronous motor can be greatly improved. Computer simulation studies have demonstrated the superior performance of the first-order and higher-order sliding mode controllers for interior permanent magnet synchronous motor speed and torque regulation applications.

Design of a robust controller for a rotary motion control system: disturbance compensation approach

This paper proposes a design of a robust controller for a rotary motion control system that includes a PID controller, a disturbance observer, and a friction compensator. Friction force versus angular velocity has been measured, and viscous, Coulomb friction and stiction components have been identified. With nominal PID (proportional- integral-derivative) controller, we have observed adverse effects due to friction such as excessive steady-state errors, oscillations, and limit-cycles. By adding a friction model as an augmented nonlinear dynamics of a plant, we are able to conduct a simulation study of a motion control system that matches very well with experimental results. The disturbance observer (DOB) based on simple and effective robust control theory has been implemented to make the rotary motion control system “robust” against inertia/load variations, external torque disturbances, and some of friction forces. Further performance enhancement of the DOB-based robust motion control system has been achieved by adding the friction compensator and experimentally verified.

Finite-time formation tracking control with collision avoidance for quadrotor UAVs

In this paper, the distributed finite-time formation tracking control problem with collision avoidance is investigated for multiple quadrotor Unmanned Aerial Vehicles (UAV) subject to external disturbances. Firstly, two finite-time observers are designed to estimate the external disturbance force and torque without upper bound, respectively. Then, utilizing the precisely observed information deriving from the observers, a novel sliding mode surface-like variable based distributed position formation tracking control strategy and a fast terminal sliding mode based attitude tracking control strategy are proposed, respectively. It achieves that the multiple quadrotor UAVs can track the desired trajectory in a specific formation configuration within the safe distance and avoid dynamic obstacles. Meanwhile, the rapid attitude synchronization and tracking is also achieved. The entire multiple UAVs distributed formation tracking closed-loop control system are proved to be globally fast finite-time stable by using Lyapunov-like analysis. Finally, the effective and fine performance of the proposed schemes are demonstrated by a numerical simulation example with a group of quadrotor UAVs.

Control Design of Nonlinear Spacecraft System Based on Feedback Linearization Approach

In this paper, based on simple quadratic matrix algebra, feedback linearization and neural network methods, the kinematics and almost perturbation decoupling and tracking performances of nonlinear spacecraft attitude control represented by improved Rodriguez parameters are studied. A nonlinear robust attitude controller is proposed to ensure the global stability and the almost disturbance decoupling performance without any learning or adaptation rules used in neural network approach and without having to solve the complex Hamilton-Jacobi equation of H-infinity control approach. This study presents an example that cannot be solved by the first paper on the problem of almost disturbance decoupling, to illustrate the point that this method can easily solve the tracking and almost disturbance decoupling performance. In addition, we propose a novel algorithm and two theorems that design a controller with almost disturbance decoupling and tracking performances. On the basis of meeting the standards we proposed, we successfully carried out some simulations on the spacecraft system to solve the effects of external disturbance torques.

Adaptive Sliding Mode Control for Spacecraft Proximity Operations Based on Dual Quaternions

This paper proposes an adaptive sliding mode control law based on dual quaternions for six-degree-of-freedom proximity operations between a chaser and a target spacecraft. Dual quaternion, a new parameterization to simultaneously describe the translation and the rotation of a rigid body, is used to model the relative motions during proximity operations. The novelty of the proposed sliding mode controller is that, by exploring the similarity between dual quaternions and quaternions, the sliding surface is designed based on basic dual quaternion algebra without introducing the logarithm of dual quaternions. The unwinding phenomenon is taken into consideration in the design of the sliding surface. The uncertainties in the mass property (i.e., the mass and the inertia matrix) of the chaser and external disturbance forces and torques (bounded but unknown) exerted on the chaser are considered. The closed-loop stability of the relative translational and relative rotational motions is proven using the Lyapunov method. The chattering effect of the sliding mode control is alleviated by replacing the sign function with the sigmoid function. With this modification, the sliding variable can only converge to a neighborhood of the ideal sliding mode. Simulation results are provided to demonstrate the performance of the proposed controller.