Electro-hydraulic System Research Articles

Optimized-Based Fault-Tolerant Control of an Electro-Hydraulic System with Disturbance Rejection

In this article, the design and implementation of a fault-tolerant controller are proposed for an electro-hydraulic actuator (EHA) in the presence of disturbances and actuator faults. The existence of nonlinearities, uncertainties, and a bias fault (i.e., internal leakage fault) in the system dynamics significantly decreases the desired performance. The nonlinear disturbance observers (NDO) are constructed to handle the adverse influences caused by the above disadvantages. The whole fault-tolerant control (FTC) scheme consists of two design loops: an inner force control loop and an outer position control loop. The inner loop is based on an optimized backstepping framework to achieve the optimal performance, whilst the problem of uncertainties and disturbances is dealt with using a terminal sliding mode directly designed from the position tracking error. It is shown by theoretical analysis that system stability is ensured under faulty conditions. Finally, simulation results and comparison studies are conducted to further verify the effectiveness of the proposed approach.

Redundancy Control of Anti-lock Braking System Based on Electro-hydraulic Braking System

Redundancy Control of Anti-lock Braking System Based on Electro-hydraulic Braking System

Environmentally Friendly Thanks to Electrohydraulics

To reduce CO2 emissions, energy-efficient electrohydraulic systems, such as Bucher’s new Smart PowerPacks, offer a solution

Actuator failure compensation-based command filtered control of electro-hydraulic system with position constraint

In this article, the design and experimental evaluation of a fault-tolerant controller are introduced for a double-rod electro-hydraulic actuator subjected to actuator faults and disturbances. The internal leakage fault is captured as a bias fault, whilst the faults in servo-valve and supply failure are considered as a partial loss of effectiveness (LOE) fault. The design obstacles caused by the disturbances and bias fault are suppressed by nonlinear disturbance observers (NDO) while an asymmetric barrier Lyapunov function is used to ensure the non-violated boundary of the output position. To tackle the LOE fault, the development of an enhanced adaptive compensation technique for actuator fault-tolerant control (FTC) is then constructed. Moreover, to mitigate the “explosion of complexity” in the traditional backstepping design, the command-filtered control is utilized to elaborate the FTC scheme. It is shown by theoretical analysis that system stability is ensured under faulty conditions. Finally, simulation/experiment results and comparison studies are performed to further verify the effectiveness of the proposed approach.

Adaptive sliding mode control for tunnel boring machine cutterhead telescopic system with uncertainties

PurposeThis paper aims to present an adaptive sliding mode control (ASMC) for tunnel boring machine cutterhead telescopic system with uncertainties to achieve a high-precision trajectory in complex strata. This method could be applied to solve the problems caused by linear and nonlinear model uncertainties.Design/methodology/approachFirst, an integral-type sliding surface is defined to reduce the static tracking error. Second, a projection type adaptation law is designed to approximate the linear and nonlinear redefined parameters of the electrohydraulic system. Third, a nonlinear robust term with a continuous approximation function is presented for handling load force uncertainty and reducing sliding mode chattering. Moreover, Lyapunov theory is applied to guarantee the stability of the closed-loop system. Finally, the effectiveness of the proposed controller is proved by comparative experiments on a scaled test rig.FindingsThe linear and nonlinear model uncertainties lead to large variations in the dynamics of the mechanism and the tracking error. To achieve precise position tracking, an adaptation law was integrated into the sliding mode control which compensated for model uncertainties. Besides, the inherent sliding mode chattering was reduced by a continuous approximation function, while load force uncertainty was solved by a nonlinear robust feedback. Therefore, a novel ASMC for tunnel boring machine cutterhead telescopic system with uncertainties can improve its tracking precision and reduce the sliding mode chattering.Originality/valueTo the best of the authors’ knowledge, the ASMC is proposed for the first time to control the tunnel boring machine cutterhead telescopic system with uncertainties. The presented control is effective not only in control accuracy but also in parameter uncertainty.

Parameter Matching and Performance Analysis of a Master-Slave Electro-Hydraulic Hybrid Electric Vehicle

To improve the battery state of charge (SOC) of the electric vehicle (EV), this paper proposes a master–slave electro-hydraulic hybrid electric vehicle (MSEH-HEV). The MSEH-HEV uses a planetary row as the core transmission component to realize the interconversion between mechanical energy, hydraulic energy and electrical energy. Meanwhile, this paper introduces the six working modes in vehicle operation, matches the parameters of key components to the requirements of the vehicle’s performance and designs a rule-based control strategy to dominate the energy distribution and the operating mode switching. The research uses AMESim and Simulink to perform a co-simulation of the MSEH-HEV, and the superiority of MSEH-HEV is testified by comparing it with an AMESim licensed EV. The simulation results show that in the Economic Commission for Europe (ECE) and the Extra Urban Driving Cycle (EUDC), the MSEH-HEV has a 15% reduction in battery consumption, and the motor peak torque is greatly reduced. Moreover, a fuzzy control strategy is designed to optimize the rule-based control strategy. Ultimately, the optimized strategy further reduces the motor torque while maintaining the battery SOC. In this paper, the applicable research consists of the necessary references for the design matching of future electro-hydraulic hybrid electricity systems.

An independent steering driving system to realize headland turning of unmanned tractors

Headland turning is one of the factors that affect the efficiency of automatic tractors. The tractor turns in headland following a curved trajectory based on the minimum turning radius and drives into the next row, in most cases. However, the efficiency of the tractor with this turning method is limited by the steering angle range of the front wheels. In this paper, an auxiliary wheel is designed to achieve efficient headland turning by equipping a 360° steering auxiliary wheel at the front of the tractor, which includes auxiliary wheel structure, hydraulic drive system and electro-hydraulic servo controller. The designed electro-hydraulic system can realize automatic steering, lifting and driving of the auxiliary wheel. Finally, field experiments are conducted to verify the superiority of the proposed auxiliary wheel turning method compared with the existing turning methods. Experimental results show that the auxiliary wheel turning method improved the efficiency of the automatic tractor in headland by 50%, 80% and 50% respectively in terms of time efficiency, travel distance and appropriation of space compared with the conventional turning method.

Dynamic Response Analysis of Control Loops in an Electro-Hydraulic Servo Pump Control System

An electro-hydraulic servo pump control system realizes the basic action of a hydraulic cylinder by controlling the servo motor, which effectively improves the problems of a traditional valve control system such as high energy consumption, low power-to-weight ratio, and poor anti-pollution ability. However, the static accuracy and dynamic performance of an electro-hydraulic servo pump control system are limited due to the electro-hydraulic coupling and flow nonlinearity. Based on this, in this paper, we establish a mathematical model of an electro-hydraulic servo pump control system. Starting from the internal control mechanism of the system, the Simulink simulation model is established to analyze the dynamic response of the system current loop, speed loop, position loop, and pressure loop. The system parameters are obtained by combining the system dynamic analysis and component technology samples. The position/force control model of the electro-hydraulic servo pump control system is built for simulation, and the experimental platform is built for experimental verification. The results show that the system position/force control can achieve good dynamic response and steady-state accuracy after the parameters are determined based on the dynamic analysis of control loops.

Tracking error constraint-based adaptive dynamic surface control of electro-hydraulic manipulator system

Tracking error constraint-based adaptive dynamic surface control of electro-hydraulic manipulator system

A Study on the Electro-Hydraulic Coupling Characteristics of an Electro-Hydraulic Servo Pump Control System

Electro-hydraulic servo pump control belongs to an electro-hydraulic coupling motion control system, which involves the mutual penetration and integration of mechanical, hydraulic, electrical, control, and other disciplines, as well as the time-varying, uncertain, multisource, and multifield problems of the internal and external excitation of the system, which makes the electro-hydraulic servo pump control system have the characteristics of a complex model, strong coupling, nonlinearity, and time-variation, resulting in the low accuracy and poor dynamic characteristics of the system. This paper takes a servo motor quantitative pump hydraulic cylinder load as the main dynamic line; divides the electro-hydraulic servo pump control system into a motor pump unit, a hydraulic transmission unit and a power output unit; analyzes its electromechanical coupling characteristics, pressure flow coupling characteristics, and mechanical–hydraulic coupling characteristics, respectively; studies the multiparameter characteristics of the system under the electromechanical–hydraulic coupling conditions; and summarizes the influence laws between the parameters. Finally, through a MATLAB/Simulink simulation, it provides a theoretical basis and guidance for high-performance control of the system.

Self-Anti-Disturbance Control of a Hydraulic System Subjected to Variable Static Loads

A hydraulic system’s lubricating oil is subject to serialized variable static loads with performance. An improved self-turbulent flow algorithm, based on the real-time acquisition and monitoring of lubricating oil static pressure in a hydraulic system to simulate variable static loads, is proposed. A mathematical model of the electrohydraulic servo control system for lubricating oil static pressure acquisition is presented, and the self-turbulent flow controller is designed for numerical analysis. The self-anti-disturbance control strategy for the lubricating oil static pressure of an electrohydraulic servo system is discussed, which is used for quadratic optimization, pole placement, PID, and self-turbulent flow control, and the lubricating oil static pressure simulation model of self-turbulent flow control is constructed by a SIMULINK module. The numerical simulation results indicate that the overshoot is significantly reduced. The proposed self-anti-disturbance control algorithm is verified by experiments, and the lubricating oil static pressure acquisition followability and monitoring accuracy are greatly improved. Variable hydraulic lubricating oil static pressure acquisition and monitoring can be effectively and stably adjusted by a predesigned electrohydraulic servo control system in the field of power hydraulic fluid lubrication.

Intelligent Control Strategy of Electrohydraulic Drive System for Raising Boring Power Head

The power head is the key part of the rock breaking work of the raise boring machine. Because the power head cannot adjust speed in time with the change in complex rock stratum, it leads to high failure rate, low work efficiency, and even accidents, so it is urgent to improve the controllability of the power head. In this paper, the electrohydraulic coupling mathematical model of the power head is established using the characteristic equations of dynamics and hydraulic components, and the control strategy of the fractional electrohydraulic drive system of the power head is proposed; genetic algorithm (GA), particle swarm optimization (PSO), and whale optimization algorithm (WOA) are used to adjust the parameters of FOPID, so as to improve the control effect of electrohydraulic system. The results show that the step response of WOA-FOPID control strategy is also better than that of genetic algorithm (GA) and particle swarm optimization (PSO). It can reach a stable state in 0.02 seconds, and the overshoot is only 0.12137%. The test verifies the correctness of the adaptive control and simulation results of the power head, which can effectively improve the adaptability of the power head to complex coal seams.

Terminal sliding mode observer based–asymptotic tracking control of electro-hydraulic systems with lumped uncertainties

Since the existence of lumped uncertainties caused by uncertain parameters and unmeasured external load, the disturbance suppression is always a significant issue in research of electro-hydraulic system (EHS). In this paper, a type of terminal sliding mode observer (TSMO) is introduced for EHS, based on which the disturbances can be converged in a finite time. Then, based on TSMO, a controller is designed via recursive backstepping method to realize the displacement tracking control of EHS. Finally, simulated results are given to verify the feasibility of the proposed theoretical conclusions and a series of contrast experimental results are also given to illustrate the better performance of TSMO and proposed control strategy than others.

Synchronized control of multiple electrohydraulic systems with terminal sliding mode observer under parametric uncertainty and external load

The leader-following synchronization control strategy is proposed for multiple electro-hydraulic systems (MEHS) to realize all the follower outputs of electrohydraulic systems synchronized to a virtual leader demand. Due to existed lumped uncertainties generated by some uncertain errors of hydraulic parameters and unascertainable external load disturbance, the synchronization control performance of MEHS will be degraded by using many common controllers. In this study, a terminal sliding mode observer (TSMO) is adopted in the MEHS to estimate the lumped uncertainties such that guarantees uncertainty estimated errors convergence to zero in a finite time. Then a synchronized controller of MEHS is designed by backstepping iteration and Lyapunov technique to guarantee the output cylinder position of every EHS tracking the virtual leader demand. Finally, the feasibility and effectiveness of the designed TSMO and the proposed synchronized control strategy are verified via simulation and experiment.

Evaluation of compliance with the current standards requirements regarding the anti-lock braking system effectiveness of an electric vehicle with mixed braking support

Introduction (statement of the problem and relevance). In accordance to the current standards the requirements were assessed: for the braking process efficiency of M1vehicles category using an antilock braking system (ABS) and the combined possibility control of two actuators - electric machines installed in the vehicle driving wheels as well as the electro-hydraulic modulation pressure unit in the hydraulic circuit of the working brake cylinders.The purpose of the study was to evaluate the effectiveness of the newly developed ABS algorithm in accordance with current standards and additional requirements.Methodology and research methods. The braking process computer simulation of a M1 vehicle category equipped with four electric motors and an electro-hydraulic braking system was carried out. As a result of calculations, the obtained braking parameters were to be compared and evaluate according to the requirements of UN Regulation No. 13H, as well as evaluate the braking efficiency parameters.Scientific novelty and results. The effectiveness of the developed control algorithm for the ABS actuators (electro-hydraulic unit and electric machines in the drive wheels) has been proven in terms of meeting the requirements of UN Regulation No. 13H. Studies showed an efficiency improvement of the ABS operating due to the proposed algorithm, when compared to foreign-produced analogues.The practical significance of the work is the proof of the developed algorithm efficiency for M1 electric vehicles category.

Modeling and simulation of electro-hydraulic telescopic elevator system controlled by programmable logic controller

Traditional hydraulic <span>cylinders are widely used in industry as load lifting tools. There is difficulty in employing these cylinders in narrow installation space like building elevators as well as they require a long working stroke, so solving this problem requires using the telescopic hydraulic cylinder instead. This cylinder is a unique hydraulic cylinder design that uses a sequence of decreasing diameters to create a long operating stroke in a compact-retracted form. In this work, the Auto Station software is used to build a telescopic hydraulic cylinder model that includes hydraulic elements such as double-acting hydraulic telescopic cylinders, pump, valves, pipeline, and filter, as well as electrical parts such as programmable logic controller (PLC), push-bottoms, and position sensors. The proposed model is operated by a PLC controller and has three floors with an overall height of around 300 cm for lifting a 100 kg payload. The accuracy and validity of this model in lifting big weights were demonstrated by the analytical findings of characteristic curves for cylinder position and velocity. This model can be used a basic reference to analyze and construct hydraulic cylinders with any number of stages. The findings of simulations reveal that a quick change in pressure due to phase change causes multi-phase vibration.</span>

Characteristics study of electro-hydraulic load-sensing control system for mobile machines

The hydro-mechanical load-sensing control is an efficient system solution to working function of mobile machines since the system pressure always adapts to the highest load pressure. The main issue of this system is its instability problem caused by hydro-mechanical feedback control. Moreover the pressure margin between system and load pressure set by the load-sensing compensator is usually fixed and has less control flexibility. Therefore, an electro-hydraulic load-sensing control system occurs, where the load pressure is sensed by pressure transducer and load-sensing control is achieved electronically. It eliminates the hydro-mechanical feedback control loop and has more control flexibility. The previous studies mainly focus on the system function, controller design and system efficiency. However the quantitative analysis of system characteristics has not yet been studied. Therefore, in this paper a method is provided to investigate the influences of pump displacement dynamics and preset pressure margin on system control performance. A hydraulic load-sensing control test rig is developed. Results show a good agreement between simulation and test results. The pressure margin fluctuation is reduced by using a pump with faster displacement dynamics and a larger cut-off frequency of load velocity control is obtained with a larger preset pressure margin however this results in lower system efficiency.

Optimization of the Quality of the Automatic Transmission Shift and the Power Transmission Characteristics

We have established a simulation platform for the machine–electro-hydraulic coupling system of the transmission system and the control system to study the root causes of the problems of large shifting impact and slow change of the machine tool transmission system. The dynamic analysis of the gear shift work of the gearbox was carried out, and the main factors affecting its shift instability were studied. With the impact and sliding power as the optimization goals, the shift quality is optimized based on the multi-objective genetic algorithm. Through the shift experiment, it was found that the power interruption phenomenon during the shift process was eliminated after optimization, and the quality of the shift was improved. Simulated planetary row wheel gear meshing force was found in the same gear, and the second planetary row gear meshing force was the largest among the planetary rows. The stress of the node near the top of the tooth is greater than the stress of the node near the node circle and the root of the tooth, and the two sides of the tooth top are relatively larger than the intermediate stress. The dynamic simulation model of the planetary gearbox system with rigid–soft hybrid can obtain the stress distribution of the solar wheel at the maximum impact moment and the stationary stage, as well as the dynamic stress of the key nodes of the solar wheel, which lays the foundation for the fatigue strength and life prediction of the gear system.

A Novel Trajectory Adjustment Mechanism-Based Prescribed Performance Tracking Control for Electro-Hydraulic Systems Subject to Disturbances and Modeling Uncertainties

This paper proposes a novel active disturbance compensation framework for exactly positioning control of electro-hydraulic systems (EHSs) subject to parameter deviations, unknown dynamics, and uncertain external load without velocity measurement mechanism. In order to accurately estimate and then actively compensate for the effects of these uncertainties and disturbances on the system dynamics, a combination between an extended sliding mode observer (ESMO) and a linear extended state observer (LESO) is firstly established for position control of EHSs. In addition, an inherited nonlinear filter-based trajectory planner with minor modifications is utilized to overcome the barriers of inappropriate desired trajectories which do not consider the system kinematic and dynamic constraints. Furthermore, for the first time, the command filtered (CF) approach and prescribed performance control (PPC) are successfully coordinated together and dexterously integrated into the backstepping framework to not only mitigate the computational cost significantly and avoid the “explosion of complexity” of the traditional backstepping design but also satisfy the predetermined transient tracking performance indexes including convergence rate, overshoot, and steady-state error. The stabilities of the observers and overall closed-loop system are rigorously proven by using the Lyapunov theory. Finally, comparative numerical simulations are conducted to demonstrate the advantages of the proposed approach.

Adaptive sliding mode control of switched linear systems using disturbance observer based on the RBF neural network

This study deals with analyze of an adaptive sliding model controller for a class of switched linear systems in the context of model reference adaptive control (MRAC) using RBF neural network (RBFNN) with the aid of disturbance observer (DO). For this purpose, adaptive laws and switching rules are designed. These are constructed based on tracking error and sliding mode control, together with using time-dependent switching conceptualizations. A DO is used to estimate the external disturbance with an adaptive RBFNN which is applied to obtain the external disturbance upper bound estimation, combined with an adaptive sliding mode control (ASMC) under the identic Lyapunov stability framework. The switching rules are based on dwell time (DT) and average dwell time (ADT) switching. The ASMC updates the system dynamics so that it assures the proposed closed-loop switched linear system stability via fast switching, resulting in the form of globally uniformly ultimately bounded (GUUB) stability. The convergence of the process of updating the weights in the adaptive RBFNN and the boundedness of updated estimates of weights are satisfied. Achieving the state tracking, robustness, reducing the chattering problem and anti-disturbance performance are the main objectives. Moreover, switching rules based on the mode-dependent approaches have been developed, which can allow faster switching as compared to switching rules based on the DT and ADT. Finally, to evaluate the efficiency of the obtained theoretical results, the controller and the proposed method have been tested on the electro-hydraulic system (EHS).