High Control Accuracy Research Articles

Integral Nonsingular Terminal Sliding Mode Control of Hydraulic Servo Actuator Based on Extended State Observer

Hydraulic servo actuator always suffers from various disturbance and uncertainties, which makes it difficult to design a higher performance controller. In this paper, an integral nonsingular terminal sliding mode controller based on extended state observer (ESO‐INTSM) is proposed to improve the robust performance of hydraulic servo actuator. The ESO is designed to estimate not only the parametric uncertainties but also the model disturbance. Based on the observed states of ESO, the proposed controllers could enable hydraulic servo actuator to track the desired motion trajectories. The stability of the synthesized controller is proved via Lyapunov analysis, which is very important for high‐accuracy tracking control of hydraulic servo actuator. Simulation and experimental results demonstrate that the proposed control strategy can effectively attenuate the adverse influence caused by the uncertainties and apparently improve the tracking accuracy.

Разработка цифровых алгоритмов управления приводами мехатронной системы реверсивной клети толстолистового прокатного стана

Expanding the plate mill product range implies the improvement of control algorithms for the mechatronics control system drives of the reversing stands. The most important objectives include increasing the accuracy of geometric dimensioning and tolerancing, as well as improving the profile and surface flatness of rolled pro­ducts. The structure explaining the automatic ROLL-GAP CONTROL concept is provided, which allows controlling the thickness and gap between SMS-Demag AG rolls. This concept is implemented in the '5000' mill stand of Magnitogorsk Iron and Steel Works. The structural diagram of the automatic gauge control system (AGS) is presented. The functional diagram of the hydraulic gap control (HGC) system is presented, which includes a fast proportional control channel and a relatively slow integral position control channel. The principle of automatic thickness control is discussed, implemented in the automatic gauge control (AGC) system of the mill stand TCS controller. The diagram and dependences are prepared for the calculation of the nonlinear thickness controller parameters. The functions of the RAC regulator are described, intended for compensation of the tensile difference (gap spacing) at the mill stand sides. The dynamic impact compensation system functions are considered. The removal of the roll bending and deformation control signals is substantiated. The disadvantages of AGC are noted for sheets with a thickness below 10 mm. The most dangerous case is the tearing of metal fragments from the rear sheet side caused by the incorrect operation of the gauge control system. A method for hydraulic gap control is proposed based on the fast increase of the roll gap in the rear part of the rolled sheet during the last passage when rolling thin sheets. The results of experimental studies made on the '5000' mill are presented. The efficiency of the proposed control method has been confirmed. The oscillograms of signals are presented characterizing thickness variations. HGC and AGC systems with the proposed adjustments are proven to provide high-accuracy hydraulic position control and thickness control along the sheet length and width.

Інформаційний простір об’єкту в системах ідентифікації

The article focuses on the issues of determining the information space of an object in identification problems, and the information set is considered as a set of data obtained by observing the variables of an object in the normal operation of the system and a priori data on the structure of the object. In order to manage, you should use the necessary information to assess the current situation and develop recommendations that ensure the most effective implementation of the objectives of the management of the situation. The choice of a model when solving control problems and studying continuous processes is due to both the conditions of implementation and the requirements of adequacy. In conditions of uncertainty, algorithms and methods of information analysis of data of different structures come to the fore. To solve the problem of control in conditions of uncertainty, methods of the theory of adaptive systems are used, which make it possible to ensure high accuracy of control when changing the dynamic properties of an object; to optimize the operating modes of the object in conditions of changing characteristics; improve the reliability of the system; unify individual control subsystems and their blocks; reduce the time required to develop and prove the system. Adaptive methods are used to solve problems in which there is no information about the nature and conditions of the object's functioning, as well as in the case of impossibility or insufficient complete formalization of a priori data. The process of synthesis of an adaptive system can be divided into stages. First, the purpose of management is formed and requirements are set for the structure of the mathematical model of the object. For this, a priori and / or experimental information is used. In a more general case, the synthesis of the system is associated with the solution of the problem of structural identification. At the second stage, the structure of the control device is determined. Next, an algorithm for adapting the controller parameters is selected. At the final stage, the adopted algorithm is substantiated.

Increased shielding of a Direct Energy Deposition process to enable Deposition of reactive materials; an investigation into Deposition of 15-5 PH Stainless Steel, Inconel 718 and Ti-6Al-4V

Hybrid additive and subtractive machining combines the flexibility of additive manufacturing (AM) with the high precision and geometrical accuracy of computer numerical control (CNC) machining. Of the many metal AM strategies blown powder direct energy deposition (DED) is the method most commonly chosen for incorporation into hybrid additive and subtractive platforms. Due to the necessity for coolant during machining operations, these platforms are usually not sealed environments meaning the deposition of reactive metals such as titanium to acceptable standards is not possible due to oxygen absorption from the surrounding environment. The research presented focuses on the investigation of the effect of a series of shielding methods in the geometry and microstructure of the materials deposited in a hybrid-manufacturing platform. The ultimate objective is to select the method with the biggest potential to enable the deposition of reactive materials with the aim of successfully depositing low oxygen content titanium, enabling the creation of Ti-6Al-4V at grade 5 and grade 23. To achieve this, bath and bag shielding strategies were compared with the standard through nozzle shielding when depositing in 15-5 PH stainless steel, Inconel 718 and Ti-6Al-4V. Based on the results of the post machining analysis the oxygen content of a multi-layer titanium sample was found to be 0.079%, lower than the maximum limit for grade 23 Ti-6Al-4V.

Uniform robust exact differentiator-based output feedback adaptive robust control for DC motor drive systems

This paper studies a high-accuracy motion control method named output feedback adaptive robust control for a dc motor with uncertain nonlinearities and parametric uncertainties, which always exist in physical servo systems and deteriorate their tracking performance. As only position signal is measurable, a uniform robust exact differentiator (URED) for the unmeasurable states and adaptive control for the parametric uncertainties are integrated in the model compensation term; and the robust control is applied to handle uncertain nonlinearities and stabilize the system. Then, the stability of the closed-loop system is proved theoretically. Finally, simulation and experimental results are studied for a dc motor system to prove the control performance of the proposed control method.

Automatic Control of Ship Motion Conducting Search in Open Waters

Abstract In this work a search operation support system is presented, which is an additional autopilot function block. Its task is to lead a vessel included in the search by the SAR services to the datum position on the basis of the data entered by the operator into the system and then automatically to search the indicated area according to the newly defined search pattern. The set goal can be achieved thanks to the autopilot that guides the ship along a given trajectory consisting of straight lines and arcs. High control accuracy is provided by the IMC control system using a relatively simple non-linear ship model. The simulation tests of the tanker model confirmed that the indicated search area can be precisely checked in a shorter time than when using the expanding square search pattern.

Design and control of a novel rotary shape memory alloy actuator for two degree of freedom underwater vectored thruster

Underwater vectored propulsion thruster is normally actuated by a step motor or a hydraulic system. The traditional actuators show an inherent shortcoming in energy consumption per volume, low space utilization and structure complexity. Shape memory alloy (SMA) based actuator is considered as a strong competitor to the traditional one, however high torque output and long movement distance to acquire high control accuracy and wide operating range still remain a big challenge. In this work, we developed an SMA-based underwater vectored thruster consisting of two motion rings and their rotary SMA actuators. Two SMA wires combined with supplementary rotation parts are utilized to drive the rotation of each motion ring. The rotary SMA actuator outputs torque that can change the angular position of underwater thruster, and the maximum angle and the response speed can be reached 38° and 1.6° s−1. The experimental results verify the feasibility of applying the rotary actuator to underwater device. Modeling the SMA rotary actuator system helps understanding the rotary process of underwater vectored thruster. Based on the system model, a control scheme integrated with an anti-windup Proportion Integral Differential (PID) controller is proposed. Its performance is compared with that of the integrating angle feedback without an anti-windup block through the simulation method. With the proposed anti-windup PID controller, the results show that the overshoot can be eliminated and the steady error is decreased to 0.01% and 0.9% at 10° and 25° respectively, reflecting that the anti-windup PID controller significantly improves the system controlling performance.

Data Driven Model-Free Adaptive Control Method for Quadrotor Trajectory Tracking Based on Improved Sliding Mode Algorithm

In order to solve the problems of dynamic modeling and complicated parameters identification of trajectory tracking control of the quadrotor, a data driven model-free adaptive control method based on the improved sliding mode control (ISMC) algorithm is designed, which does not depend on the precise dynamic model of the quadrotor. The design of the general sliding mode control (SMC) algorithm depends on the mathematical model of the quadrotor and has chattering problems. In this paper, according to the dynamic characteristics of the quadrotor, an adaptive update law is introduced and a saturation function is used to improve the SMC. The proposed control strategy has an inner and an outer loop control structures. The outer loop position control provides the required reference attitude angle for the inner loop. The inner loop attitude control ensures rapid convergence of the attitude angle. The effectiveness and feasibility of the algorithm are verified by mathematical simulation. The mathematical simulation results show that the designed model-free adaptive control method of the quadrotor is effective, and it can effectively realize the trajectory tracking control of the quadrotor. The design of the controller does not depend on the kinematic and dynamic models of the unmanned aerial vehicle (UAV), and has high control accuracy, stability, and robustness.

Attitude dynamic tracking control of an agile satellite using a fixed-structured H∞ synthesis method

It is a challenging control problem for an agile satellite to observe a rapidly moving target with high dynamic tracking precision. This paper presents a robust and high-accuracy attitude control law for an agile satellite with flexible solar arrays. Model uncertainties caused by vibration of flexible appendages are described as an uncertainty weighting function in the framework of robust H∞ control. However, using the traditional H∞ synthesis method, the resulting dynamic output-feedback controller is not suitable for practical implementation due to its complicated structure and high order. To deal with this issue, an H∞ controller with a fixed proportional-integral-derivative (PID) structure is proposed, and the PID control gains are determined by solving a set of linear matrix inequalities with minimizing the H∞ norm of the feedback control system. Moreover, a feedforward compensator is included to further improve the dynamic performance of the system, achieving a faster response with a smaller dynamic tracking error. Simulations are carried out to demonstrate that the proposed control system can achieve high-precision and rapid maneuver tracking performance for abruptly changing attitude command signals in presence of modeling uncertainties.

A bioelectric neural interface towards intuitive prosthetic control for amputees

Objective. While prosthetic hands with independently actuated digits have become commercially available, state-of-the-art human-machine interfaces (HMI) only permit control over a limited set of grasp patterns, which does not enable amputees to experience sufficient improvement in their daily activities to make an active prosthesis useful. Approach. Here we present a technology platform combining fully-integrated bioelectronics, implantable intrafascicular microelectrodes and deep learning-based artificial intelligence (AI) to facilitate this missing bridge by tapping into the intricate motor control signals of peripheral nerves. The bioelectric neural interface includes an ultra-low-noise neural recording system to sense electroneurography (ENG) signals from microelectrode arrays implanted in the residual nerves, and AI models employing the recurrent neural network (RNN) architecture to decode the subject’s motor intention. Main results. A pilot human study has been carried out on a transradial amputee. We demonstrate that the information channel established by the proposed neural interface is sufficient to provide high accuracy control of a prosthetic hand up to 15 degrees of freedom (DOF). The interface is intuitive as it directly maps complex prosthesis movements to the patient’s true intention. Significance. Our study layouts the foundation towards not only a robust and dexterous control strategy for modern neuroprostheses at a near-natural level approaching that of the able hand, but also an intuitive conduit for connecting human minds and machines through the peripheral neural pathways.Clinical trial: DExterous Hand Control Through Fascicular Targeting (DEFT). Identifier: NCT02994160.

Dynamic Analysis of DFIG Fault Detection and Its Suppression Using Sliding Mode Control

In this article, a fault detection method based on chaos is proposed for doubly fed induction generator (DFIG). First, the nonlinear differential equation of the DFIG is established by the stator flux-oriented vector control method, and then, the motion state of the DFIG is proved by the 0–1 test algorithm. Second, the motion state of the DFIG is analyzed under normal and fault conditions. Due to some failures that may occur in the normal operation of the DFIG, the motion state of the DFIG system may enter chaos from the cycle, which is mainly manifested by the violent oscillation of the rotor current and speed. At this time, the system is in an extremely unstable operating condition. Thereby, a new sliding mode control rate is mentioned to suppress chaotic behavior. Its stability is analyzed by constructing the Lyapunov function to ensure that the system state can quickly and stably converge to the given value. After that, the simulation model of the system is built. The simulation results show that sliding mode control can make the DFIG get out of the chaotic state quickly. And, the sliding mode control has the characteristics of fast fault elimination and high control accuracy. In addition, the traditional sliding mode approach rate is compared with the proposed new sliding mode approach rate. It proves that the proposed new approach rate can achieve better control effect.

Radiation protection risk control method of nuclear power project based on sequence optimization

In order to protect the construction safety of nuclear power project and improve the radiation protection effect of nuclear power project, this paper introduces the sequence optimization algorithm to study the risk control method of nuclear power project radiation protection. The radiation risk level of nuclear power project is divided by sequential optimization algorithm, and the control structure of radiation protection risk of nuclear power project is optimized. In this paper, the radiation protection risk detection procedure is used to improve the radiation protection risk detection process of nuclear power engineering, so as to enhance the control effect of radiation protection risk of nuclear power engineering. In order to verify the protective effect of this method, a comparative experiment was designed. The results show that the radiation protection risk control method based on sequence optimization has high control accuracy in the practical application process, which fully meets the research requirements.

Simulation modelling in design of a city transit vehicle with electromagnetic suspension

Intensive development of city transit vehicles with electromagnetic suspension of the last decade raises the significance of their optimal design problems. In this paper, the simulation model of an electromagnetic suspension system of the city transit vehicle created in Simulink is presented. The model is featuring feedback applied to determine the magnitude of the magnetic flux. The main parameters of the electromagnet were evaluated while creating the model. The presented model was used to obtain the air gap regulator settings. An adaptive control system ensuring low energy consumption at low speed and high gap control accuracy at high speed could lead to the realization of the stable and efficient suspension system.

Active Disturbance Rejection Control of Valve-Controlled Cylinder Servo Systems Based on MATLAB-AMESim Cosimulation

The valve-controlled cylinder position servo system has the advantages of large output force and large power. As characteristics of nonlinearity and uncertainty exist in the hydraulic servo system, it is difficult for the traditional PID control to meet the requirements of high precision and control. The active disturbance rejection control (ADRC) considers the uncertainty of the system and external disturbances as the total disturbance. In this paper, the valve-controlled cylinder servo system is designed based on ADRC, its working principle is described, and its mathematical model and cosimulation model based on MATLAB-AMESim are established. In the case of constant load, variable load, and long pipeline, the comparative simulation of ADRC and PID is carried out. The simulation results show that the ADRC can effectively suppress the disturbance of the internal parameter changes and external load changes of the hydraulic system and has strong robustness and high control accuracy. This study provides a reference for the application of ADRC in electrohydraulic servo systems.

Control of a New Cycling Rehabilitation Robot Based on Fuzzy PID

For completing the standardized rehabilitation training of the affected limb based on the lower limb rehabilitation training robot system, it is designed that a lower limb rehabilitation robot control system based on fuzzy PID control method to realize stable and accurate control of the rehabilitation training process. First of all, this paper analyzes the ranges of motion of human hip and knees, and a single degree of freedom lower limb rehabilitation training robot system based on the belt transmission principle is designed. Then the fuzzy PID control is analyzed. And the Matlab is used to simulate the passive rehabilitation mode of the lower limb rehabilitation training robot system under different control strategies. The designed rehabilitation training test shows that the control system of the lower limb rehabilitation robot based on the fuzzy PID control method has a small speed overshoot, high control accuracy and smoother operation.

Nonlinear differential and integral sliding mode control for wave compensation system of ship-borne manipulator

Ship-borne manipulator system is extremely unstable under the complex marine environment, which seriously threatens the safety of operating equipment and operators. In this paper, the dynamics and robust control of wave compensation system for ship-borne manipulator are studied. First, based on the oil circuit variable amplitude control of ship-borne manipulator, the coupling dynamic model of valve-controlled cylinder parallel accumulator is established. Then, since traditional sliding mode needs high-order derivative of feedback angle, it is difficult to implement traditional sliding mode in real hardware system. To solve these problems, a nonlinear differential and integral sliding mode control strategy is proposed. The integral term is introduced to reduce the influence of unmodeled disturbance and parameter perturbation. The stability analysis proves that the system state can track the desired target signal, and the tracking error e( t) tends to zero. In addition, in order to weaken the phenomenon of system chattering, this paper introduces a nonlinear differential control to increase the damping coefficient of the system. The simulation and experimental results show that the control law has good dynamic performance, high control accuracy, and strong anti-disturbance ability without chattering phenomenon. It is of great significance to improve the efficiency and safety of ship-borne manipulator operation, and this paper also provides useful reference for wave compensation system of other marine equipment.

Prescribed performance based model-free adaptive sliding mode constrained control for a class of nonlinear systems

To tackle the trajectory tracking problem and achieve high control accuracy in many actual nonlinear systems with unknown dynamics, a novel prescribed performance based model-free adaptive sliding mode constrained control (SMCC) strategy is studied which relies on the input/output data of plant rather than the specific model information via a pseudo partial derivative (PPD) parameter. Firstly, two approaches are introduced for PPD estimation, i.e., an observer-based adaptive algorithm, and an algorithm based on the stochastic configuration network approximating the controlled plant model, upon which the realtime control including PPD construction are carried out. Then, the prescribed performance is introduced in the model-free adaptive SMCC scheme as a prescribed range for the output tracking error. Meanwhile, an anti-windup compensation signal is employed to suppress the actuator saturation that commonly exists in many actual nonlinear systems. In addition, the stability analysis of the control system is presented to verify the rationality of the prescribed performance. Finally, simulations are carried out for both a linear induction motor and a battery energy storage system to demonstrate the effectiveness of the proposed control strategy.

Precise robust motion control of cell puncture mechanism driven by piezoelectric actuators with fractional-order nonsingular terminal sliding mode control

A novel robust controller is proposed in this study to realize the precise motion control of a cell puncture mechanism (CPM) driven by piezoelectric ceramics (PEAs). The entire dynamic model of CPM is constructed based on the Bouc–Wen model, and the nonlinear part of the dynamic model is optimized locally to facilitate the construction of a robust controller. A model-based, nonlinear robust controller is constructed using time-delay estimation (TDE) and fractional-order nonsingular terminal sliding mode (FONTSM). The proposed controller does not require prior knowledge of unknown disturbances due to its real-time online estimation and compensation of unknown terms by using the TDE technology. The controller also has finite-time convergence and high-precision trajectory tracking capabilities due to FONTSM manifold and fast terminal sliding mode-type reaching law. The stability of the closed-loop system is proved by Lyapunov stability theory. Computer simulation and hardware-in-loop simulation experiments of CPM verify that the proposed controller outperforms traditional terminal sliding mode controllers, such as the integer-order or model-free controller. The proposed controller can also continuously output without chattering and has high control accuracy. Zebrafish embryo is used as a verification target to complete the cell puncture experiment. From the engineering application perspective, the proposed control strategy can be effectively applied in a PEA-driven CPM.

Model and design of real-time control system for aerial variable spray.

The dosage sprayed upon per unit area is an important index to measure the effects of pesticide application. Owing to the fact that parameters such as flight height, flight speed, and spray swath can change at any given time, it is impossible to ensure a consistent amount of pesticide application per unit area during the course of aerial variable spray. In order to ensure a consistent amount of pesticide application per unit area, a set of control models of aerial variable spray using an unmanned aerial vehicle (UAV) was proposed, and the corresponding control system was developed based on the technology of aerial variable spray. According to the change of flight parameters, this system was able to adjust the opening degree of solenoid valve through the control model of aerial variable spray. After that, the amount per unit time would change to ensure a consistent amount of pesticide application per unit area, which effectively avoided the phenomenon of uneven pesticide application and improved the accuracy. According to the actual demand for the area in need of pesticide application, the operator can manually control the amount of pesticide applied and change the dosage sprayed upon per unit area to achieve a better effect. Through field tests, it was verified that the system has high accuracy of variable control. The deviation range was between 0.11% and 9.79%, which met the demands of agricultural aviation pesticide application. Furthermore, the system had strong stability for working continuously for more than 6 h at 30°C to meet the environmental requirements of pesticide application via UAV. All the data related to the pesticide application were stored in this system, which provided a reference for the further study of the precision technology in pesticide application. The model proposed in this paper also provided a theoretical basis for the technology development of aerial variable spray.

A Novel Grid-Connected Current Control Method Based on Frequency Adaptive Proportional Resonance

In this paper, a novel quasi-proportional resonance (quasi-PR) controller for grid-connected current control is proposed. For the traditional quasi-PR controller, the performance decreases in cases when a large gird frequency deviation is going through. To solve the problem, a frequency adaptive structure is applied in the current control method to achieve online correction on the resonance frequency, so that a high control accuracy is maintained and the robustness of the control system is enhanced. The feasibility of the proposed method has been verified by experimental results.