Adaptive robust precision control of an active spray boom suspension with disturbance estimation

When the boom sprayer works in the field, the boom must be parallel to the undulating ground or crop canopy. Aiming at the problem of low control accuracy and poor stability caused by parameter uncertainties and time-varying disturbances in the electro-hydraulic active boom suspension system, this paper proposes an adaptive robust precision control algorithm based on disturbance estimation. Firstly, the dynamic analysis modeling method is adopted to establish the nonlinear dynamic model and mechanism geometric equation of the pendulum active and passive suspension. Then, the controller was designed based on the nonlinear model of the suspension system. The proposed controller uses the backstepping design method to integrate the disturbance observer into the adaptive robust controller, which can effectively deal with the parameter uncertainties and time-varying disturbances in the suspension system model. Finally, a large number of experiments were carried out by taking a 28 m large boom active suspension driven by a single-rod hydraulic pressure as an example. Using an established rapid control prototype of a large boom suspension, a variety of control algorithm comparison experiments were carried out, and a 6-DOF motion platform was used to simulate the motion coupling interference of the sprayer chassis. The experiment results illustrate the high-performance characteristics of the proposed controller and improve the tracking performance of the active pendulum suspension system under various parameter uncertainties and time-varying disturbances.

TRACKING CONTROL OF WHEELED MOBILE ROBOT WITH MODEL UNCERTAINTIES AND INPUT DISTURBANCE: A NOVEL APPROACH WITH DISTURBANCE ESTIMATION AND ARBITRARY CONVERGENCE TIME CONTROLLER

Xe tự hành đã được sử dụng rộng rãi trong thực tế và chúng thu hút được nhiều sự quan tâm từ những nhà nghiên cứu do tính ràng buộc không tích phân được, tính phi tuyến và tải bất định của chúng. Trong bài báo này một phương pháp điều khiển bám mới được đề xuất cho xe tự hành với mô hình bất định và có nhiễu đầu vào. Phương pháp mới này dựa trên một bộ quan sát nhiễu đầu vào và bộ điều khiển có thời gian đáp ứng tùy ý. Bất định của mô hình và nhiễu đầu vào sẽ được bù bằng bộ quan sát nhiễu trong khi đó sai lệch tốc độ sẽ tiến đến không trong một khoảng thời gian xác lập cho trước bởi bộ điều khiển thời gian hữu hạn tùy ý, bộ điều khiển này sẽ cải thiện chất lượng điều khiển của hệ kín. Tính hiệu quả của phương pháp được kiểm chứng thông qua mô phỏng số.

Nonsmooth control based on finite-time disturbance estimator for the translational oscillator with a rotational actuator system with nonvanishing disturbances

In this article, the stabilization and disturbance estimation of the translational oscillator with a rotational actuator with nonvanishing disturbances are considered. Different from existing methods, a disturbance estimator is designed to eliminate the effects of unexpected external disturbances. As far as we know, this article presents the first finite-time disturbance-estimator-based nonsmooth control scheme for the translational oscillator with a rotational actuator system. Specifically, first, a series of changes of coordinates is made for the model of the translational oscillator with a rotational actuator system. Then, a disturbance estimator is presented to estimate uncertain disturbances and a nonsmooth control scheme is designed to ensure the convergence of all the states. Furthermore, rigorous theoretical analysis is given. Finally, simulation tests are carried out and the obtained results demonstrate that the designed approach exhibits better control performance and stronger robustness than the existing methods.

Unscented Kalman filter for airship model uncertainties and wind disturbance estimation

An airship is lighter than an air vehicle with enormous potential in applications such as communication, aerial inspection, border surveillance, and precision agriculture. An airship model is made up of dynamic, aerodynamic, aerostatic, and propulsive forces. However, the computation of aerodynamic forces remained a challenge. In addition to aerodynamic model deficiencies, airship mass matrix suffers from parameter variations. Moreover, due to the lighter-than-air nature, it is also susceptible to wind disturbances. These modeling issues are the key challenges in developing an efficient autonomous flight controller for an airship. This article proposes a unified estimation method for airship states, model uncertainties, and wind disturbance estimation using Unscented Kalman Filter (UKF). The proposed method is based on a lumped model uncertainty vector that unifies model uncertainties and wind disturbances in a single vector. The airship model is extended by incorporating six auxiliary state variables into the lumped model uncertainty vector. The performance of the proposed methodology is evaluated using a nonlinear simulation model of a custom-developed UETT airship and is validated by conducting a kind of error analysis. For comparative studies, EKF estimator is also developed. The results show the performance superiority of the proposed estimator over EKF; however, the proposed estimator is a bit expensive on computational grounds. However, as per the requirements of the current application, the proposed estimator can be a preferred choice.

Global adaptive neural backstepping control of a flexible hypersonic vehicle with disturbance estimation

Purpose This paper aims to discuss the precise altitude and velocity tracking control of a hypersonic vehicle, a global adaptive neural backstepping controller was studied based on a disturbance observer (DOB). Design/methodology/approach The DOB combined with a radial basis function (RBF) neural network (NN) was used to estimate the disturbance terms that are generated by the flexible modes of the hypersonic vehicle system. A global adaptive neural method was introduced to approximate the unknown system dynamics, with robust control terms pulling the system transient states back into the neural approximation domain externally. Findings The globally uniformly ultimately bounded for all signals of a closed-loop system can be guaranteed by the proposed control algorithm. Additionally, the command filtered backstepping methods can avoid the explosion of the complexity problem caused by the backstepping design process. In addition, the effectiveness of the proposed controller can be verified by the simulation used in this study. Research limitations/implications Normally lateral dynamics issue should be discussed in the process of control system designed, the lateral dynamics are not included in the nonlinear dynamic model of hypersonic vehicle used in this paper, merely the longitudinal flight dynamics are discussed in this paper. Originality/value The flexible states in rigid modes are considered as the disturbance of the system, which is estimated by structuring DOB with NN approximations. The compensating tracking error and prediction error are used in the update law of RBF NN weight. The differential explosions complexity derived from the backstepping procedure is dealt with by using command filters.

Disturbance Observer-Based Chattering-Attenuated Terminal Sliding Mode Control for Nonlinear Systems Subject to Matched and Mismatched Disturbances

This work presents a new disturbance observer-based chattering-attenuated terminal sliding mode control for a class of nonlinear systems in the presence of both mismatched and matched disturbances. A nonlinear disturbance observer is typically employed to accurately estimate mismatched disturbances. In this study, a terminal sliding mode control was designed, based on the disturbance estimation results, to counter the effects of disturbances and ultimately stabilize the target system. The utilization of a chattering-attenuated full-order terminal sliding mode structure satisfactorily resolves both chattering and singularity problems in controller design. It was shown by theoretical analyses that both the disturbance estimation error and the system state converge to the equilibrium point in finite time. Two simulation studies, namely a numerical example and an application to an electro hydrostatic actuator system, were conducted to examine the characteristics and to verify the effectiveness of the proposed algorithm.