Attitude-constrained reorientation control for spacecraft based on extended state observer

The pitching axis is the main axis of a satellite camera and is used to control the pitch posture of satellite cameras. A control strategy based on extended state observer (ESO) is designed to obtain a fast response speed and highly accurate pitching axis control system and eliminate disturbances during the adjustment of pitch posture. First, a sufficient condition of stabilization for ESO is obtained by analyzing the steady-state error of the system under step input. Parameter tuning and disturbance compensation are performed by ESO. Second, the ESO of speed loop is designed by the speed equation of the pitching axis of satellite cameras. The ESO parameters are obtained by pole assignment. By ESO, the original state variable observes the motor angular speed and the extended state variable observes the load torque. Therefore, the external load disturbances of the control system are estimated in real time. Finally, simulation experiments are performed for the system on the cases of nonload starting, adding external disturbances on the system suddenly, and the load of system changing suddenly. Simulation results show that the control strategy based on ESO has better stability, adaptability, and robustness than the PI control strategy.

Electro-hydraulic position servo system of valve-controlled symmetrical cylinder (EPSSVCS) is a very important and widely used electro-hydraulic servo system, the performance of which is often affected by friction nonlinearity and external random disturbances together with unmodeled dynamic factors such as parameter uncertainty in practical work. To improve the tracking performance of the system, a backstepping sliding mode control algorithm (BSMC) based on an extended state observer was presented in this paper. Firstly, a nonlinear mathematical model of the EPSSVCS was established which takes into account the composite disturbance induced by the systematic friction nonlinearity, external disturbances and unmodeled dynamic factors. Then, an extended state observer (ESO) was designed which can effectively estimate the velocity, acceleration, and composite disturbance of the valve-controlled cylinder online. Furthermore, a kind of BSMC was presented based on the online ESO estimates and the displacement feedback signals. The control law was given and the system stability was proved. The analysis results showed that the output signal of the system can effectively track the input signal under the influence of typical external disturbances and unmodeled dynamic factors, which illustrated the effectiveness of the established nonlinear mathematical model and the stability of the designed control system. Moreover, by taking the parameters of the electro-hydraulic servo system of a certain type of CNC machine tool as a real example, the proposed algorithm (BSMC) was compared with the conventional PID control algorithm, the backstepping sliding mode control algorithm (BSC), and the adaptive robust control algorithm (ARC), and the results verified the superiority of the BSMC. This work may provide a useful reference for the research in the field of related control systems.

In this paper, a command filter-based backstepping controller is proposed for robust height and attitude tracking for small unmanned helicopter with flapping dynamics. Firstly, the helicopter model is divided into height subsystem and attitude subsystem, which are presented in strict feedback form. Then a second-order command filter is applied to obtain the derivative of virtual control laws and introduce amplitude and rate limits into control signals, thus the explosion of differentiation terms problem during backstepping process is solved, and actuators saturation is avoided. Meanwhile, the extended state observer (ESO) is designed to estimate and compensate the total uncertainty, which includes parametric uncertainties and external disturbances. Furthermore, globally bounded stability of the closed-loop helicopter system is proved by using Lyapunov theory. Finally, simulation results illustrate the applicability of the proposed controller in the presence of uncertain terms in the model.

An anti-windup compensate algorithm for active disturbance rejection mechanism is proposed in this paper. This paradigm extends the traditional anti-windup scheme to the Active Disturbance Rejection Control (ADRC) mechanism, to deal with the input saturation nonlinearity and meanwhile reject the disturbance automatically by using Extended State Observer (ESO) . The output of anti-windup compensator is treated as a part of unknown disturbances and is introduced into the ESO, which can online observe both internal and external disturbances (parameter uncertainties and model mismatches). The controller input is yielded by using a nonlinear feedback combination, and it is used to compensate the integrator windup caused by the saturation nonlinearity element. On the other hand, in order to determine the parameters of the ESO and the anti-windup compensator feedback gain, the ℒ 2 gain is adopted. The effectiveness and the robustness against model and parameter uncertainties of the proposed method is verified by an example of the seeker platform.

This paper considers the path following problem of underactuated marine surface vessel in the presence of model uncertainty and external disturbances. A robust control strategy is proposed by employing the dynamic surface control and extended state observer. The key features of the presented control strategy include that, first, the extended state observer is proposed to estimate the model uncertainty and external disturbances of the underactuated marine surface vessel; second, in order to avoid the calculation of derivatives of virtual control signals, the dynamic surface control is used to design the robust control laws based on the output of the extended state observer. All regular paths are feasible by introducing the Serret-Frenet Line-of-Sight guidance. Uniformly ultimately bounded can be obtained based on the proposed control strategy by using Lyapunov theory. Simulation results demonstrate the effectiveness of the proposed control strategy.

To regulate uncertainties in system dynamics and external disturbances, a robust controller is proposed for a plant with time-varying uncertainty. The design is based on the concept of extended state observer (ESO) with repetitive controller (RC). In real time estimation and mitigation of the total effect of various uncertainties, ESO based RC is particularly effective against a wide range of parameter variations, model uncertainties, and large disturbances. With only two tuning parameters, the controller provides a simple and user friendly solution to complex engineering problems in practice. The comparison results verified the effectiveness of the ESO based RC over state observer (SO) based RC.

Preassigned finite-time attitude control for spacecraft based on time-varying barrier Lyapunov functions

Anti-disturbance backstepping control for air-breathing hypersonic vehicles based on extended state observer

Based on input-output stability theory, a multi-input multi-output indirect adaptive fuzzy tracking control method for satellite attitude systems with parametric uncertainty and external disturbance is presented. First, a nonlinear controller is designed based on the satellite precision model, and stability of the closed-loop system is analyzed; then, because of contained the parametric uncertainty and external disturbance in the model, an adaptive fuzzy controller is constructed through using fuzzy logic system to approximate the uncertain section. Last, it is proved that the proposed controller can make the satellite track to the located place, and force the tracking error to converge to a small neighborhood of the origin. Simulation results show the satisfied control accuracy and robustness to the model uncertainty.

This paper proposed a finite-time backstepping control for a robotic manipulator under the presence of actuator fault, saturation constraints, output constraints, and external disturbance to obtain requirements about the robustness, fast convergence, and high accuracy tracking performance. To manage the above challenges, the proposed control is designed on a transformed model with the backstepping approach and extended state observer. The transformed model is resulted from converting a constrained system based on a transformation technique. So, it provides an ability for the proposed control to obtain the prescribed performance of the output response. Additionally, an extended state observer is conducted to deal with the lumped uncertainties in the system. The essential characteristic of the proposed control is no required knowledge of the actuator faults and external disturbance to be available. Furthermore, fractional-order terms are added in the control laws to enhance the rate of output responses. To demonstrate the advantages of the proposed control in terms of global asymptotic stability, the Lyapunov approach is used to verify the whole controlled system in theory. The proposed control is applied to a 2-degree of freedom (DOF) manipulator and simulated by MATLAB Simulink. Its simulation results are compared to other state-of-the-art methods to exhibit the effectiveness of the proposed control.

To provide high output force and to reduce the installation space, the electro-hydrostatic actuator (EHA) usually adopts asymmetric cylinder. However, comprehensive effects produced by its asymmetric flow, parameter uncertainties and unknown disturbance make it difficult to achieve high-accuracy position control. This paper proposed an integral sliding mode backstepping control (ISMBC) based on extended state observer for the asymmetric EHA. Firstly, the principle of the EHA was analyzed and an EHA model was built. Furthermore, the state space equation of the EHA was established based on flow distribution analysis. Two extended state observers (ESO) were designed to achieve real-time estimation of the unmeasured system states, unmatched and matched disturbances. The backstepping method was used to compensate the matched and unmatched disturbance, and an integrated sliding mode controller was developed to eliminate the static error and to improve the response ability. Theoretical analysis indicates that the controller can guarantee the desired tracking performance for the actuator under time-varying unmatched disturbances, and can make the tracking error asymptotically converge to zero under constant matched disturbances. Finally, simulations were performed with the designed controller, backstepping controller and proportional–integral–derivative (PID) controller, respectively. Thereafter, detailed comparisons of the control performances were provided. The results show that the proposed controller can achieve better position tracking and stronger robustness in parameter changing compared with the backstepping controller and PID controller.

This study proposes a novel Disturbance Observer based Adaptive Backstepping Sliding Mode Controller (DOABS-SMC) to overcome the adverse effects of parametric uncertainties and external disturbances on a single-phase inverter in stand-alone power supply mode in addition to improving the tracking time of the output voltage. Firstly, the dynamical model of the inverter in stand-alone power supply mode is established with parametric uncertainties. Thereafter, a traditional Backstepping controller (BSC) is combined with disturbance observers (DO) to remove the adverse effects of the disturbances and confirm the system's stability. To ensure the robustness of the controller, an SMC is combined with the BSC to further improve the performance of the controller. The effectiveness of the proposed controller is then experimentally verified by comparing it with traditional BSC and PID controllers. The results indicated that the proposed controller's performance is better than the other ones under the parametric disturbances and changing load.

The suspension gap of the electromagnetic suspension maglev train is around 8 mm. In practice, it is found that the system gap fluctuations are amplified due to the inner coupling of the suspension module system in the maglev train. In addition, maglev trains are affected by load disturbances and parameter perturbations during operation. These uncertainties reduce the ride comfort. Therefore, it is necessary to propose a novel control strategy to suppress inner coupling while reducing the influence of uncertainties on the system. In this paper, a control strategy based on feedback linearization and extended state observer (ESO) is proposed to address this challenge. Firstly, the suspension module system model is established with parameter uncertainties and external disturbances. Additionally, the inner coupling of the suspension module is represented in this model. Subsequently, the feedback linearization method based on differential geometry theory is applied to reduce the effect of inner coupling. Meanwhile, the system uncertainties are transformed into equivalent disturbances by this method. Afterward, a linear ESO is designed to estimate the equivalent disturbances. Finally, a state feedback controller is used to achieve stable suspension and compensate for the disturbances. Simulation and experimental results show that the proposed decoupled control strategy significantly suppresses the influence of inner coupling and uncertainties on the system compared with the traditional PID control strategy.

This paper presents a sliding mode synchronization controller (SMSC) based on extended state observer (ESO) for the dual-drive system in gantry-type machine tools (GTMT). This controller achieves not only excellent tracking accuracy but also high synchronization performance. Firstly, a sliding mode synchronization controller is designed for the dual-drive system based on a simplified mode. Then, in order to handle the difficulties associated with the parameter uncertainties, external disturbances and coupling effects of the dual-drive system, a linear extended state observer (LESO) is designed. In this active disturbance rejection control (ADRC) technology, the total disturbances are treated as an extended state of the system and compensated with the disturbance observed value. Moreover, Rigorous theoretical analysis is performed to show that the proposed control method is able to achieve asymptotical tracking and synchronization performance for the dual-drive system in GTMT. Finally, Simulation studies are carried out and the results show that the proposed control strategy performs an improved tracking and synchronization motion control in comparison to the independent axis P-PI control approach.

The accuracy of the line-of-sight of aviation photoelectric optoelectronic stabilization platforms is limited by two factors: external disturbance and sensor noise. An extended state observer (ESO) can effectively improve their anti-interference ability. However, due to the serious problem of gyroscope noise, further improvement of an ESO's disturbance suppression effect is limited. This article proposes a control structure that combines a Kalman filter (KF) and ESO, effectively improving upon the interference suppression ability of a traditional ESO under the influence of noise. Firstly, an ESO was used to observe the lumped disturbance of the system, and then, the observed disturbance was compensated for in the control loop. Secondly, based on the compensation servo control system, the state equation of the system was reconstructed using a Kalman filter. Finally, the reconstructed filtered state variables were iterated onto the universal state observer, achieving the observation of disturbances while filtering out sensor noise. Under the conditions of a laboratory flight simulation turntable, the line-of-sight stability accuracy level was improved under disturbance excitation. It can be seen that the combination of a Kalman filter and extended disturbance observer proposed in this project improves the ESO's anti-interference ability under the influence of noise.