High-precision Position Control Research Articles

Dynamic simulation and adaptive heave compensation control of a wave-compensated gangway under random wave excitation

For high-precision position control of wave-compensated gangways under random wave excitation, the kinematic model is established based on the Denavit–Hartenberg parametric method. Desired motion parameters for each degree of freedom (DOF) are solved through multi-DOF motion decoupling calculations. The telescopic arm, pitching arm, and slewing seat are simplified as mechanical-hydraulic motor-driven systems or cylinder-driven systems. The nonlinear dynamic models for each system are deduced based on their structural composition and adaptive motion controllers are designed with the desired motion parameters as control targets. The gangway base's heave motion under random wave excitation is reconstructed and the electromechanical-hydraulic coupling dynamic model of the wave-compensated gangway under random wave excitation is coupled. Comparative testing with the traditional Proportional-Integral-Derivative control method shows that the displacement stabilization accuracy of the telescopic arm's tip in the x-axis and y-axis directions under the condition of scale 4 wave improved by 93.05% and 97.38%, respectively. This research provides a technical reference and reliable approach for dynamic analysis and high-precision control of wave-compensated gangways.

Vibration-attitude integrated control of large membrane diffraction space telescope

The development of telescopes with large apertures is driven by the increasing demand for higher imaging resolution and coverage. Large membrane diffraction space telescopes are particularly attractive due to their lightweight nature, ease of folding and unfolding, and high-precision imaging capabilities. However, their substantial size and flexibility make them susceptible to long-duration, low-frequency vibrations during attitude maneuvers, which degrade attitude and imaging accuracy and risk instrument damage. Consequently, an urgent need exists for a high-precision integrated control scheme. In this paper, the integrated control of vibration and attitude in a large space telescope is studied using cable actuators and control moment gyroscopes (CMGs). Since cables can only withstand limited tension, the unilateral and constrained characteristics of the control input are taken into account during the control design process. Firstly, a rigid-flexible coupling dynamic model of the space telescope is established using the velocity variation principle with hybrid coordinates. Additionally, a two-body astrodynamic model is developed to assess the impact of gravity gradient torque. Next, combining the computational torque method and H∞ control theory, an integrated control scheme is proposed, which achieves vibration and attitude control during maneuvers. Then, this paper optimizes the cable actuator positions via the discrete particle swarm optimization (PSO) algorithm and plans various attitude maneuver paths. Finally, numerical simulations are adopted to demonstrate the effectiveness of the control scheme. The results show that this integrated control scheme swiftly suppresses structural vibrations during attitude maneuvers, enabling high-precision attitude control of the space telescope.

Design of an active wing-folding biomimetic flapping-wing air vehicle

In nature, birds and bats dynamically alter their wing shapes to suit various flight environments and tasks. This paper focuses on the design and validation of a biomimetic flapping-wing aerial vehicle, named FlexiWing, which features a unique mechanism for active wing deformation. This mechanism allows the wings to adjust their shapes flexibly in response to flight demands, significantly enhancing attitude control and maneuverability.’ ‘This study began with an in-depth exploration of biomimetic principles, focusing particularly on how birds and bats achieve precise control during flight through active wing deformation. Subsequently, we present a detailed account of the design and fabrication process of the active folding biomimetic flapping-wing aerial vehicle, including the design of mechanical mechanisms and material selection. Utilizing lightweight nylon materials and hollow carbon fiber rods, we successfully constructed a mechanically foldable wing structure. To achieve precise control over the aircraft’s movement, an embedded control system was designed, comprising an onboard embedded flight controller and ground-based equipment. The onboard controller uses a high-performance ESP32-C3 processor and a JY901 inertial measurement unit to acquire real-time attitude information of the aircraft. The control system incorporates Wi-Fi communication technology, enabling operators to send commands via a remote control or personal computer to manage flight modes and attitudes. Ultimately, a series of flight experiments were conducted to validate the performance of FlexiWing. The results demonstrate that FlexiWing exhibits remarkable maneuverability and stability, capable of achieving high-precision attitude control through active wing folding, making it adaptable to complex environments and tasks.’

Event-Triggered Supercavitating Vehicle Terminal Sliding Mode Control Based on Non-Recursive Observation

Supercavitating vehicles present significant issues in controller design due to their multiphase flow-coupling characteristics. This study addresses force analysis and the construction of a 6-degree-of-freedom mathematical model for a supercavitating vehicle. A terminal sliding mode control law is intended to guarantee the quick tracking of the command signal for high-precision attitude control. To drastically lower the frequency of actuation and communication, a mechanism to trigger events is also introduced into the control link. A disturbance observer, which estimates system uncertainty using a non-recursive differentiator, improves the robustness of the system. The Lyapunov approach is used to prove that the system is stable. Numerical simulation results validate that the proposed method enhances control accuracy and robustness. The event-trigger mechanism reduces the execution frequency to 18.59%, effectively reducing the communication burden.

РОЗРОБКА СИСТЕМИ КЕРУВАННЯ КРОКОВИМ ДВИГУНОМ НАВЧАЛЬНОЇ ТРАНСПОРТНОЇ ЛІНІЇ

Stepper motors have long been successfully used in a variety of industrial and special equipment. The advantage of stepper motors is that a high degree of motion control can be achieved. Stepper motors are controlled using microprocessor systems. However, in this case, the stepper motor is controlled by the program loaded into the microcontroller. There is often a need to dynamically change the operation parameters of the stepper motor - speed of rotation, direction and magnitude of the angle of rotation, etc. The work is devoted to the development of the stepper motor control system of the educational transport line, implemented at the Department of Automation of Production Processes of the Ukrainian State University of Science and Technology. The system allows you to dynamically change system parameters using either a personal computer (PC) by sending the appropriate commands to the system via the COM port, or by using a tablet by sending the appropriate commands to the system via Bluetooth. Such a system can be used both in the educational process to practice standard stepper motor control techniques and microcontroller programming skills, and in industrial systems that require high-precision mechanism position control.

The Angular Momentum Unloading of the Asymmetric GEO Satellite by Using Electric Propulsion with a Mechanical Arm

A high-precision attitude control satellite uses an angular momentum exchange device such as a flywheel or a control moment gyro as the actuator for attitude stability control. Once the accumulation of angular momentum exceeds the upper limit of the angular momentum exchange device, the satellite will lose its attitude control ability. Therefore, it is necessary to unload the angular momentum exchange device to ensure the attitude control ability of the satellite platform. The angular momentum accumulation of GEO(Geosynchronous Orbit, GEO) satellites with asymmetric structure can reach 40 Nms per day, and the accumulation speed is more than 20 times that of GEO satellites with symmetrical structure. Therefore, it is necessary to carry out angular momentum unloading for GEO satellites with asymmetric structure every day. The previous method of angular momentum unloading using electric propulsion has weak unloading capacity, which is not suitable for angular momentum unloading of asymmetric satellites. This paper presents a method of angular momentum unloading using a four-joint mechanical arm plus an electric thruster. Large angular momentum unloading with near-zero burn-up can be achieved through the thrust generated by station keeping. In addition, the problem of attitude and orbit coupling control can be solved by controlling the thrust direction of the electric thruster with a mechanical arm.

Attitude maneuver planning and robust tracking control for flexible satellite

AbstractIn this paper, we investigate the attitude manoeuver planning and tracking control of the flexible satellite equipped with a coilable mast. Due to its flexible beamlike structure, the coilable mast experiences bending and torsional modal vibrations in multi-direction. The complex nonlinear coupling and other external disturbances significantly impact the achievement of high-precision attitude control. To overcome these challenges, a robust attitude tracking controller is proposed for easy implementation by the Attitude Determination and Control System (ADCS). The controller consists of a disturbance compensator, feedforward controller and output feedback controller. The compensator, based on a Nonlinear Disturbance Observer (NDO), effectively compensates for the cluster disturbances caused by vibrations, environmental factors and parameter perturbations. The feedforward controller tracks the desired path in the nominal satellite model. Furthermore, the output feedback controller enables large-angle manoeuver control of the satellite and evaluates the suppression effect of the controlled output on the observation error of cluster disturbances used the${L_2}$-gain. Simulation results demonstrate that the proposed controller successfully achieves high-precision attitude tracking control during large-angle manoeuvering.

Decoupling modeling design and high-precision position control of fast steering mirror

For a two-axis fast steering mirror (FSM) based on the flexible chain structure support and voice coil motor drive, the two axes are strongly coupled. This strong coupling may decrease the system positioning accuracy. In this study, the electric kinematics model associated with the voice coil motor and the motion and frequency equations associated with the flexible chain structure were analysed. A comprehensive system model was established considering shaft coupling, a digital controller with compensation coupling was designed, and the method of active compensation was used for decoupling. The experimental results showed that compared with the traditional non-decoupling control algorithm, the decoupling control method decreased the coupling degree from 7% to 0.8% and reduced the positioning accuracy error from 1.5% to 0.3%.

Design of anti-unwinding attitude coupling controller for flexible spacecraft using positive position feedback control

Flexible vibration has a great impact on flexible spacecraft attitude control, which will reduce the pointing accuracy of the spacecraft platform and bring severe challenges to the design of a high-precision attitude control system for flexible spacecraft. Aiming at the problem of attitude and vibration coupling control of flexible spacecraft, an anti-unwinding attitude coupling controller using the positive position feedback (PPF) control is proposed in this paper. The model compensation control term is constructed based on the prior information to improve the tracking performance. The proposed attitude coupling control method can effectively suppress the flexible vibration while achieving more accurate attitude control. The obtained closed-loop system under the proposed control scheme is asymptotically stable, which is proved by the Lyapunov stability theory. The numerical simulation illustrates that the proposed method can effectively improve the attitude control accuracy of the flexible spacecraft and is capable of large-angle attitude maneuver control because of its prominent performance in attitude tracking and its unwinding-free performance.

High-Precision Position Control of PMLSM Using Fast Recursive Terminal Sliding Mode With Disturbance Rejection Ability

High-Precision Position Control of PMLSM Using Fast Recursive Terminal Sliding Mode With Disturbance Rejection Ability

УПРАВЛЕНИЕ ТРАЕКТОРИЕЙ ПОЛЕТА БЕСПИЛОТНОГО ЛЕТАТЕЛЬНОГО АППАРАТА ПРИ РАЗЛИЧНОЙ КОНФИГУРАЦИИ ИСТОЧНИКОВ НАВИГАЦИОННОЙ ИНФОРМАЦИИ

In real conditions of application for high-precision positioning and trajectory control of unmanned aerial vehicles (UAVs) when flying along a route, insufficient noise immunity and operating accuracy of satellite navigation system receivers are manifested. In this regard, it is relevant to study possible methods and means of providing high-precision navigation definitions based on complex processing of signals from various sources of navigation information when solving the problem of displaying a UAV in a terminal set. The article presents the results of developing a UAV trajectory control algorithm based on methods of statistical optimal control theory, the implementation of which will improve the accuracy of maintaining a given flight route. The characteristics for analyzing errors in maintaining the flight path are considered. The results of modeling and research of the characteristics of the trajectory control algorithm for various configurations of navigation information sources (NIS) are presented and the dependence of the accuracy of maintaining a given UAV flight route on errors in estimating navigation parameters is shown.

A Two-Layer Trajectory Tracking Control Scheme of Manipulator Based on ELM-SMC for Autonomous Robotic Vehicle

With the development of autonomous driving technology, some special vehicles should also be developed into autonomous driving vehicles. The robotic vehicles are widely used in engineering operations, and the robotic manipulator is a common tool mounted on robotic vehicles. The autonomous driving of robotic vehicles requires not only automatic movement, but also the automation of the robotic manipulator drive system. Therefore, this paper proposes an adaptive trajectory tracking control of manipulator based on sliding mode control (SMC), which can more accurately describe the joint space movement of the manipulator system under multi task coupling and external interference. Considering the multi-tasking situation, the influence of obstacle avoidance and base tilt on the trajectory of manipulator is investigated by using extreme learning machine (ELM), and the framework of machine learning is established. The output based on ELM-SMC is used as the bottom-layer control. Then an effective trajectory compensation method is proposed as the top-level control to avoid the error accumulation in the periodic repeated operation of the manipulator. Finally, the application effect of trajectory error tracking and compensation of manipulator in complex tasks of dynamic environment is verified by simulation and experiments, which lays a foundation for the stability control of manipulator in practical complex engineering applications. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Note to Practitioners</i> —The motivation of this paper is to solve the problem of poor trajectory tracking control accuracy of the manipulator caused by the change of the direction of the manipulator base. It is suitable for the high-precision position control of the manipulator assembled on the mobile robotic vehicle. Nowadays, the autonomous driving technology is developing rapidly, and the automation of traffic will be widely popularized in the future. Therefore, we should not only pay attention to the autonomous driving function of passenger vehicles, but also give consideration to the autonomous driving technology of robotic vehicles applied in engineering. It not only needs to complete the driving function, but also needs to ensure the reliable operation of the manipulator. In this paper, we mathematically deduce the control model of the manipulator. Then, we use SMC as the trajectory tracking control method of the manipulator, and use ELM to estimate the trajectory error caused by the end trajectory of the manipulator in the non-horizontal state of the base. Furthermore, we propose an optimization algorithm to optimize the compensation coefficient of cubic spline and give a reasonable compensation scheme. Through simulation and experiments, it is preliminarily verified that the schemes proposed in this paper are feasible, but they lack the application verification in the actual robotic vehicles, and the model fitting part of machine learning is completed with the help of the host computer, and the calculation ability of the controller of the actual manipulator may also be the limitation of completing this scheme.

Neural Network Learning Algorithms for High-Precision Position Control and Drift Attenuation in Robotic Manipulators

In this paper, different learning methods based on Artificial Neural Networks (ANNs) are examined to replace the default speed controller for high-precision position control and drift attenuation in robotic manipulators. ANN learning methods including Levenberg–Marquardt and Bayesian Regression are implemented and compared using a UR5 robot with six degrees of freedom to improve trajectory tracking and minimize position error. Extensive simulation and experimental tests on the identification and control of the robot by means of the neural network controllers yield comparable results with respect to the classical controller, showing the feasibility of the proposed approach.

Trajectory control of a hydraulic system using intelligent control approach based on adaptive prediction model

Electro-hydraulic actuators (EHAs) have become a preferred alternative to traditional hydraulic actuators with valve control systems due to their numerous advantages, making them an ideal choice for applications requiring high-precision force or position control. However, the highly complex nonlinear nature of EHAs makes modelling and controlling them a challenging task. To address this challenge, a new position control approach has been proposed for an EHA system using a combination of a feedforward online-tuning PID (FOPID) controller and an adaptive grey predictor (AGP), known as the feedforward online-tuning adaptive grey predictor (FOAGP). The FOPID controller is constructed based on PID controller and fuzzy logic algorithm to control the EHA system towards referred trajectory, while an updating rule that consists of robust checking terms optimizes its parameters online to minimize control error. The AGP predictor is an important aspect of the proposed approach. It consists of a self-tuning step size mechanism, which estimates the performance of the plant to tune the parameters of the controller and create an additive control signal that is used to counteract environment noises and perturbations. This approach significantly improves control performance by reducing the effect of disturbances and sensor noises on the system. The FOAGP approach was tested in simulation to investigate its effectiveness. The results showed that the proposed approach outperformed other existing control methods, with a higher accuracy and better control performance. One of the significant advantages of the FOAGP approach is its ability to learn and adapt to changing system dynamics. The learning mechanism used in the FOPID controller allows the system to optimize its parameters online, which is especially useful in systems with varying operating conditions. The AGP predictor also continuously adjusts its parameters to accurately estimate the system output, making it an effective tool for controlling EHAs. The proposed approach offers a significant improvement in control performance, making it a better alternative to traditional control methods. This approach can be applied to various EHA systems, including those used in aerospace, automobile, and robotic applications, among others.

Sliding-mode control of electro-hydraulic positioning tracking system combining K-observer and nonlinear disturbance observer

High-precision position control of hydraulic systems is of great significance in industrial applications. However, unknown external force disturbance, measurement noise, and other uncertain nonlinearities widely exist in electro-hydraulic servo systems, which severely degrade the system performance. To handle this problem, a sliding-mode controller based on K-observer with nonlinear disturbance observer is proposed for electro-hydraulic position systems in this article. The nonlinear disturbance observer is to estimate and eliminate the time-varying external force disturbance. The sliding-mode controller based on K-observer is to reach low gain observation of states and improve the system performance by reducing the chattering of the sliding-mode algorithm. The proposed controller is proved to be stable by the Lyapunov stability criterion. Comparative experiments support that the controller has high precision and strong robustness.

Research on High-Precision Position Control of Valve-Controlled Cylinders Based on Variable Structure Control

During the operation of valve-controlled cylinder position systems, there are some problems, such as uncertainty and time-varying of the system parameters, imprecise modeling, and external interference. These problems will affect the position loading accuracy and safety reliability of the electro-hydraulic position servo system. This paper used the position servo system of a valve-controlled cylinder as the research object, and a mathematical model was established. Then, a sliding mode variable structure controller and dynamic soft variable structure controller were designed, and the Grey Wolf algorithm was used to adjust the controller parameters. The control effect of the two controllers in the valve-controlled cylinder system was verified with a simulation and experiment. The results showed that compared with the sliding mode variable structure controller, the dynamic soft variable structure controller had higher control precision and better stability and avoided the chattering phenomenon.

An anti-rolling control method of rudder fin system based on ADRC decoupling and DDPG parameter adjustment

To achieve high-precision attitude control of ships, the output delay, state coupling, and controller parameter maladjustment of the rudder fin joint anti-rolling system are studied. A predictive anti-rolling method based on active disturbance rejection control (ADRC) and deep deterministic policy gradient (DDPG) is proposed. The external forces on the ship are analyzed, and a three-degree-of-freedom mathematical model considering rolling, yawing, and pitching is established. The model is decoupled using the idea of ADRC total disturbance for the state coupling problem, then the pitch ADRC controller and the roll-yaw predictive observer are designed respectively. In pitch ADRC, the nonlinear extended state observer (NLESO) is used to observe the total disturbance between models. And the total disturbance observations are feedforward compensated to the error control law. As a result, the rapidity of reference output tracking and robustness of total disturbance are realized. The roll-yaw predictive observer solves the output delay by feeding the predicted output back to the controller instead of the actual output. To ensure the accuracy of the prediction output, the DDPG algorithm is introduced to modify the parameters of the prediction observer in real-time. Finally, state constraints are added to solve the rudder angle and fin angle control laws. This method can perform control, parameter adjustment, and solution online and continuously. The wave disturbance test based on the experimental ship shows that the anti-rolling effect of the method is improved by 10% compared with the previous study. Under the condition of a small overshoot, the new expected value can be tracked quickly.

Research on Control Strategy of Electro-Hydraulic Lifting System Based on AMESim and MATLAB

Given the influence of flow instability, parameter uncertainty, and unpredictable disturbances in electro-hydraulic lifting systems, high-precision position control for electro-hydraulic lifting systems is challenging to achieve. This study proposes an observer–sliding mode control strategy to improve the control accuracy of the tractor electro-hydraulic lifting system. Firstly, the principle of the electro-hydraulic hoisting system is analyzed. Secondly, a mathematical model of the electro-hydraulic hoisting system is established, and the electro-hydraulic hoisting system is reduced to design an observer to achieve a real-time evaluation of the unknown system state and disturbance. The observer and the sliding mode control are then integrated into a controller to improve system response. Theoretical analysis demonstrates that the controller ensures that the actuator can achieve the desired control effect even under disturbing effects. Finally, a joint AMESim–MATLAB simulation and conducting pilot studies are carried out to compare the observer–sliding mode control with PID (Proportion–Integral–Derivative) control and sliding mode control. At the same time, in the process of the simulation and test, the symmetric structure as the electro-hydraulic lifting system was used to build a ploughing depth simulation system (changes in the hydraulic cylinder thrust simulate changes in ploughing depth values). The results show that the proposed observer–sliding mode control strategy can achieve a better position and pressure tracking and parameter change robustness than PID control and sliding mode control.

Adaptive Fixed-Time Position Precision Control for Magnetic Levitation Systems

A novel adaptive fixed-time controller (AFTC) based on disturbance compensation technology is proposed to achieve high performance position precision control for magnetic levitation system in this paper. Firstly, the dynamic model of the magnetic levitation system is established and a fixed-time controller (FTC) is designed to realize the closed-loop control. However, this approach usually requires a large switching gain to suppress interference, resulting in chattering. In view of this, the generalized proportional integral observer (GPIO) is introduced to estimate and compensate the time-varying interference, which can not only improve the anti-interference ability, but also reduce the chattering by choosing a smaller switching gain. Nevertheless, these two performance improvements come at the cost of the dynamic response rate. In order to improve steady state performance without sacrificing dynamic performance, an adaptive fixed-time controller based on GPIO is proposed, which has a significant advantage because of the adjustable switching gain. Specifically, when the system state is far from the sliding mode surface, a larger switching gain is adjusted to improve the convergence rate. When the system state is close to the sliding mode surface, a smaller switching gain is adjusted to reduce chattering. Simulation and experimental results demonstrate the superiority of the proposed AFTC-GPIO method qualitatively and quantitatively. Note to Practitioners–As a highly nonlinear system easily affected by external disturbances and system uncertainty, high precision position control of magnetic levitation system is a great challenge. In this paper, based on the accurate estimation of lumped time-varying interference by GPIO, an adaptive fixed time sliding mode controller is designed to suppress the disturbance and achieve the high precision control. Traditional sliding mode control inevitably has to choose between improving convergence rate and suppressing chattering, and the dynamic and steady performance of the system cannot be considered simultaneously. In view of this issue, this paper combines sliding mode control with adaptive control, and an adaptive and adjustable switching gain is designed, so that the system has the performance of fast convergence and small chattering. Simulation and experimental results verify the effectiveness of the proposed method. The reported AFTC-GPIO idea can also be extended to control of other types of systems.

Research on transfer case clutch accurate position control of on-demand four-wheel drive systems

<p indent="0mm">The on-demand four-wheel-drive system has been widely used because of its simple structure and low cost. The core component of the on-demand four-wheel-drive system in this study is a transfer case based on an electronically controlled multi-plate wet clutch. Its actuator consists of a worm gear driven by a permanent magnet synchronous motor and a helical booster mechanism. The actuator can control the position of the clutch pressure plate to change the drive torque transmitted to the front axle, and adjusting the front axle torque significantly affects the handling stability and dynamics. Therefore, the precise position control of the transfer clutch is of great significance. In this paper, a model of the PMSM actuator system and load is first established, which provides the basis for the design of the controller. Then, explicit model predictive controllers for current tracking control and position tracking control are designed based on the model. Finally, typical working condition position tracking simulations and experiments are carried out. The results show that the proposed position control algorithm can achieve relative accuracy of 1%, which can meet the requirements of the real-time online high-precision position control of an on-demand four-wheel-drive system.