Electro-hydraulic Actuator System Research Articles

Efficiency and Performance of Optimized Robust Controllers in Hydraulic System

Common applications involved hydraulic system in real-time including heavy machinery, air-craft system, and transportation. Real-time applications, however, are notorious to suffered with nonlinearities due to unavoidable mechanical structures. Thus, control system engaged to manipulate and minimize the effect resulting from the nonlinearities. In this paper, few control approaches are executed in the Electro-Hydraulic Actuator (EHA) system. The control approaches including the generally used Proportional-Integral-Derivative (PID) controller, the reinforced Fractional-Order (FO) PID controller, the Sliding Mode Controller (SMC), and the enhanced hybrid SMC-PID controller. In order to obtain proper parameter of each controller, the Particle Swarm Optimization (PSO) technique is applied. The output data are then analysed based on the performance indices in terms of the consumption of the energy and the error produced. The performance indices including Root Mean Square Error/Voltage (RMSE/V), Integral Square Error/Voltage (ISE/V), Integral Time Square Error/Voltage (ITSE/V), Integral Absolute Error/Voltage (IAE/V), and Integral Time Absolute Error/Voltage (ITAE/V). It is observed in the results, based on the performance indices in terms of error and voltage, the hybrid SMC-PID capable of generating better outcomes with reference to tracking capabilities and energy usage.

Output Feedback Control for Active Suspension Electro-Hydraulic Actuator Systems With a Novel Sampled-Data Nonlinear Extended State Observer

In this paper, an output feedback controller based on a novel sampled-data nonlinear extended state observer (SDNLESO) is proposed for an active suspension electro-hydraulic actuator (ASEHA) system to address the heavy nonlinearities, model uncertainties and sampled-data behavior. The designed controller only requires little prior knowledge about the controlled system for the purpose of position tracking. The SDNLESO, integrating a novel nonlinear extended state observer and an output predictor, is developed to simultaneously and continuously estimate the unmeasurable states and total disturbance for an error dynamic system rather than the original ASEHA system, where the actual discrete displacement tracking error between measurement output and the reference signal serves as the observer input. Then, a compensated controller is synthesized based on the obtained estimates, which is robust against the matched and mismatched disturbances of the system while being able to ensure an expected transient tracking performance and final tracking accuracy. By constructing weighted error system and using the geometric homogeneity theory, the SDNLESO convergence is proven, while the maximum allowable sampling period is derived theoretically for guiding the selection of the actual sampling interval. Moreover, the closed-loop system stability and the tracking error exponential convergence are guaranteed within the Lyapunov framework. Finally, a number of practical experiments are carried out on the ASEHA system test platform. The results show that the proposed control method is applicable and valid for nonlinear and uncertain ASEHA system despite the existence of a large actuator area ratio.

Extended High Gain Observer-Based Sliding Mode Control for an Electro-hydraulic System with a Variant Payload

This paper presents a robust control regarding position control of an electro-hydraulic rotary actuator (EHRA) system under the presence of the lumped uncertainties such as the variant payload, the unknown friction, and the uncertain parameters. The proposed control is developed on a high order sliding mode control (HOSMC) and an extended high gain observer (EHGO). In detail, the HOSMC is derived to not only reduce the chattering effect but also guarantee the stability for the EHRA. In addition, the EHGO is used as a disturbance estimator to compensate the lumped uncertainties. Consequently, it helps to improve control performance. Furthermore, the stability and robustness of the whole system are theoretically proved by a Lyapunov approach. The proposed control is practically implemented through both the co-simulation between AMESIM and MATLAB, and the experiments. The results are compared to other controllers to exhibit the effectiveness of the proposed control with the lumped uncertainties.

Improved Position Tracking Performance of Electro Hydraulic Actuator Using PID and Sliding Mode Controller

This paper focuses on the position control of low-velocity servo controlled electro hydraulic actuator system in order to increase the system productivity. To overcome the nonlinearities and uncertainties caused by friction and internal leakages, an efficient sliding mode control (SMC) is designed based on the selection of appropriate sliding surface and control law. The solution is a model-based position control and it is shown that the proposed design procedure is simple and efficient. The controller is designed with approximated first-order dynamics of the system. To express the performance of the proposed control scheme, the designed control strategy is compared with conventional proportional integral derivative (PID) control. The simulation and experimental comparisons between the PID and SMC demonstrate that SMC has smooth and stable response than PID in tracking performance and robustness.

Development and Control of an Electro-Hydraulic Actuator System for an Exoskeleton Robot

Exoskeleton robots have been developed in various fields and are divided into electric and hydraulic exoskeletons according to the actuator type. In the case of hydraulic robots, because a unidirectional pump is applied, there are limitations to the wearer’s walking. In addition, robot systems are complicated, because a directional control valve is required to change the direction of the actuator. To solve these problems, we designed the electro-hydraulic actuator (EHA) system which has both the hydraulic and electric advantages. The EHA system consists of a hydraulic bidirectional pump, a motor, a hydraulic cylinder, and various valves. For the development of the piston pump, we analyzed the gait cycle and considered the flow rate and pulsation rate. In order to reduce the size and weight of the EHA system, the valves were made from one manifold, and the hydraulic circuit was simplified. We verified that the developed EHA system is applicable to robots through position and force control experiments. Because the hydraulic system is nonlinear, we designed a sliding mode control (SMC) and compared it with the proportional integral derivative (PID) controller.

Comparison of Fractional Order PID Controller and Sliding Mode Controller with Computational Tuning Algorithm

The industry processes involving punching, lifting, and digging usually require high precision, high force and long operating hours that increase the prestige in the usage of the electrohydraulic actuator (EHA) system. These processes with the companion of the EHA system usually possess high dynamic complexities that are hard to be controlled and require well-designed and powerful control system. Therefore, this paper will involve the examination of the designed controllers which is applied to the EHA system. Firstly, the conventional proportional-integral-derivative (PID) controller which is the famous controller in the industry is designed. Then, the improved PID controller, which is known as the fractional order PID (FO-PID) controller is designed. After that, the design of the gradually famous robust controller in the education field, which is the sliding mode controller (SMC) is performed. Since the controller's parameters are essentially influencing the performance of the controller, the meta-heuristic optimization method, which is the particle swarm optimization (PSO) tuning method is applied. The variation in the system's parameter is applied to evaluate the performance of the designed controllers. Referring to the outcome analysis, the increment of 59.3% is obtained in the comparison between PID and FOPID, while the increment of 67.13% is obtained in the comparison of the PID with the SMC controller. As a conclusion, all of the controllers perform differently associated with their own advantages and disadvantages.

Impedance Control of Hydraulic Actuation Systems With Inherent Backdrivability

The demand for high-performance impedance control in electro-hydraulic actuation systems is a mainstream issue in the robot actuation research community. Although various nonlinear model-based impedance controllers have been developed and showed good performance in recent years, they remain hindered by the high cost of force sensors, and accurate internal dynamics models need to be derived to overcome the non-backdrivability and complex dynamics of hydraulic systems. As a solution to these problems, this paper presents an impedance control approach for hydraulic systems that require no external force sensors or chamber pressure sensors with a pressure control servovalve or backdrivable servovalve. First, we show that a backdrivable servovalve brings inherent backdrivability to hydraulic systems, such that high-performance impedance control can be implemented without requirement of force sensors and exact knowledge on the dynamics of hydraulic chambers, owing to its torque-source property and low effective valve inertia on the link side. Second, utilizing the obtained backdrivability, we develop a passivity-guaranteed impedance controller. A momentum-based external torque observation algorithm is incorporated to render desired impedance over a wide range, without using force/torque sensor. The performance of the proposed backdrivable servovalve and impedance controller was verified through extensive experimental results.

Optimization of PID for industrial electro-hydraulic actuator using PSOGSA

The Electro-hydraulic actuator (EHA) systems known to be extremely nonlinear due to its dynamic characteristics and these existing nonlinearities and uncertainties yield to the constraint in the control of EHA system, which influences the position tracking accuracy and affect the occurrences of leakage and friction in the system. The purpose of this work is to develop the mathematical model for the industrial electrohydraulic actuator, then to design a controller by proportional-integral-derivative (PID) and optimize the parameters using Particle Swarm Optimization - Gravitational Search Algorithm (PSOGSA). A few controllers such as conventional PID (CPID) and model reference adaptive control (MRAC) designed for comparison. The performance of PID, PID-PSOGSA and modern controller MRAC will be compared in order to determine the most efficient controller. Despite all controllers are capable to provide good performance, PID-PSOGSA control methods generate good response compared to PID and MRAC in term of positioning.

Performance Evaluation of Fractional Order Pid and Sliding Mode Control with Optimization Tuning Access

The statistical analyses in the past showing the important properties of the electrohydraulic actuator (EHA) system, especially in the growth of the world economy. Dealing with the existing drawback in the EHA system, various types of control schemes have been introduced in the past. In this paper, to produce a more insightful view of the performance and the capabilities of the controller, three different types of controllers have been designed and compared. The favourite controller in the industry field, which is the proportional-integral-derivative (PID) controller will be first introduced. Follow by the improved PID controller, named Fractional Order (FO-PID) controller will be designed. Then, the prominent robust controller in the control field, called sliding mode controller (SMC) will be established. Instead of obtaining the controller’s parameters without any appropriate technique, the well-known tuning technique in computer science, named particle swarm optimization (PSO) will be utilized. Referring to the performances produced by these controllers, it can be concluded that the SMC is capable to generate most desired control performance that produced the highest accuracy with the smallest error in the analyses.

Simulation and Experimental Study of a Diesel Engine Based on an Electro-Hydraulic FVVA System Optimization

Abstract Variable valve timing technologies for internal combustion engines are used to improve power, torque, reduce emissions, and increase fuel efficiency. First, the paper presents a new electrohydraulic full variable valve actuator (FVVA) system which can control the seating velocity of engine valve flexibly. Second, based on the NSGA-II genetic algorithm, the paper outlines a multi-objective optimization strategy and designs the parameters of the FVVA system to make the system easier to implement. Third, the paper builds the combined FVVA engine simulation model. The combined simulation and experimental results are executed to validate the designed FVVA engine. The simulation results show that brake power is improved between 1.31% and 4.48% and the torque is improved by 1.32–4.47%. Brake thermal efficiency and volumetric efficiency also show improvement. Experimental results have good agreement with the simulation results. The research results can provide a basis for engine modification design.

Hydraulically actuated horizontal axis wind turbine pitch control by model free adaptive controller

In the present work a model free fuzzy feedforward PID controller has been developed for pitch control application of the horizontal axis wind turbine through electrohydraulic pitch actuation system. The controller has been designed to achieve maximum power tracking and protect from high wind gusts even with fault in the actuating system. Electrohydraulic pitch actuating system has high power to weigh ratio, self-lubricating property, good controllability etc. as its merit of application. Nonlinear mathematical model of small horizontal axis wind turbine along with proportional valve controlled electrohydraulic pitch actuating system has been developed. The BEM theory has been used to estimate aerodynamic load on the turbine blade and pitch for maximum power capture by the turbine with the variation of the wind speed. The present model has been validated with experimental results. The performance of the proposed fuzzy feedforward PID controller has been investigated with various test signals as well as predicted pitch demand from wind data for maximum power tracking and to save from high wind gusts. The performance index of proposed fuzzy feedforward PID controller has been found as 0.08606, 0.08849 and 0.09809 with normal leakage, high leakage and very high leakage respectively.

Application of Electro-Hydraulic Actuator System to Control Continuously Variable Transmission in Wind Energy Converter

The wind energy conversion system (WEC) has been increasingly proposed to capture wind energy producing electrical power in high efficiency. One of the most important factors that has significant influence on the overall efficiency is the performance of generators in a fixed-speed wind turbine. The efficiency of the generator strongly depends on the operating speed. Therefore, the generator should be controlled to operate at the rated speed to increase the overall efficiency. In this paper, a continuously variable transmission (CVT) was employed to maintain the speed of the generator by controlling the transmission ratio. By employing a position control system based on an electro-hydraulic actuator (EHA), the speed ratio could be tuned continuously to keep the generator at rated speed. Here, an adaptive fuzzy sliding mode control (AFSC) was developed to control the proposed EHA CVT. Mathematical analysis was also carried out to investigate the global stability of the system. Finally, experiments were conducted to evaluate the performance of the proposed WECs.

Design and Performance of Nonlinear Control for an Electro-Hydraulic Actuator Considering a Wearable Robot

In the development of a wearable robot, compact volume size, high energy efficiency, and a high load capacity linear actuator system are necessary. However, conventional hydraulic actuator systems are difficult to apply to wearable robots. Also, they have nonlinearities because of the presence of hydraulic fluid in a single rod cylinder. Electric linear actuators resolve the problems of hydraulic systems. However, due to their low load capacity, they are not easy to apply to wearable robots. In this paper, a pump-controlled electro-hydraulic actuator (EHA) system that considers the disadvantages of the hydraulic actuator and electric actuator is proposed for a wearable robot. Initially, a locking circuit design is considered for the EHA to give the system load holding capacity. Based on the developed model, the adaptive sliding mode control (ASMC) scheme is designed to resolve the nonlinearity problem of changes in the dynamic system. The ASMC scheme is then modeled and verified with Simulink. In order to verify the performance of the proposed adaptive control with the model, experiments are conducted. The proposed EHA verifies that the ASMC reaches the target value well despite the existence of many model uncertainties.

Optimization of Modified Sliding Mode Control for an Electro-Hydraulic Actuator System with Mismatched Disturbance

Optimization of Modified Sliding Mode Control for an Electro-Hydraulic Actuator System with Mismatched Disturbance

Optimization of Modified Sliding Mode Control for an Electro-Hydraulic Actuator System with Mismatched Disturbance

Optimization of Modified Sliding Mode Control for an Electro-Hydraulic Actuator System with Mismatched Disturbance

Einfluss von Triebstrang, Fahrwerk und Reifen-Boden-Kontakt auf Lastschaltvorgänge in Standardtraktoren

Today, electro-hydraulic gearshift actuation systems offer a wide range of opportunities to optimize power shift behavior and therefore handling comfort of tractors. However, the parameter application process is very time consuming, especially with regard to increasing comfort demands. To reduce the time consumption and to increase the repeatability of the parameter application process, it is promising to transform the process from field tests to test benches. One main requirement for the transformation is to adjust the dynamic drivetrain behavior on the bench until it is comparable with tractor field operations. Therefore, it is necessary to understand the influence of the tire-soil contact, the chassis design and the drivetrain design on power shift operations. Within this article, the influences are analyzed with the help of a complete tractor simulation model which is based on a CLAAS Axion 800 Hexashift. The resulting effects are evaluated by tractor driving speed, transmission output speed and transmission output torque.

Performance analysis of electro-hydraulic actuator based on optimal control algorithm

When designing the controller to improve the performance of the system, energy consumption are often neglected. Therefore we use the LQR control method to add energy considerations to the objective function to optimize the performance of the system. In this paper, an optimal control algorithm is proposed for Electro-Hydraulic Actuator (EHA) system. Firstly EHA system is modelled by bond-graph methodology. Then, design the controller to improve both the performance and efficiency of EHA system. The simulation results verify the optimization and stability of system by the optimal controller.

Electro Hydrostatic Actuator System Based on Active Stabilizer System for Vehicular Suspension Systems

The suspension systems of vehicles are being actively researched to improve steering stability and ride comfort of vehicles. Among these, the active stabilizer system exhibits improved steering stability and ride comfort during the turning of a vehicle by controlling the vehicle body roll through actuators mounted on the front and rear stabilizer bars. This paper proposes an active stabilizer system of the electrohydraulic drive type, which addresses the disadvantages of the conventional hydraulic drive type whose active stabilizer system has poor ride comfort and causes excessive energy loss due to the system structure. In this study, the electrohydraulic actuator system model is designed, and the dynamic characteristics of the vehicle are analyzed with a simple proportional-integral-derivative (PID) controller for controlling the roll angle of the vehicle through the active stabilizer depending on the application of the designed system. The designed hydraulic model and system are evaluated based on the dynamic characteristics of a vehicle fitted with the active stabilizer of the electrohydraulic drive type and analyzed using the interface-analysis method between MATLAB/Simulink and CarSim. Furthermore, the results of the simulation are compared with those from the bench test to evaluate the performance.

Ant Colony Optimization Based Type-2 Fuzzy Force-Position Control for Backhoe Excavator Robot

This paper proposes the design and simulation of Interval Type-2 Fuzzy Logic Control using MATLAB/Simulink to control the position of the bucket of the backhoe excavator robot during digging operations. In order to reach accurate position responses with minimum overshoot and minimum steady state error, Ant Colony Optimization (ACO) algorithm is used to tune the gains of the position and force parts for the force-position controllers to obtain the best position responses. The joints are actuated by the electro-hydraulic actuators. The force-position control incorporating two-Mamdani type-Proportional-Derivative-Interval Type-2 Fuzzy Logic Controllers for position control and 3-Proportional-Derivative Controllers for force control. The nonlinearity and uncertainty in the model that inherit in the electro hydraulic actuator system are also studied. The nonlinearity includes oil leakage and frictions in the joints. The friction model is represented as a Modified LuGre friction model in actuators. The excavator robot joints are subjected to Coulomb, viscous and stribeck friction. The uncertainty is represented by the variation of bulk modulus. It can be shown from the results that the ACO obtain the best gains of the controllers which enhances the position responses within the range of (19, 23 %) compared with the controllers tuned manually.

Nonlinear modeling of an electrohydraulic actuation system via experiments and its characterization by means of neural network

The friction and end-cushioning effects in the actuator have been taken care in consideration in the modeling of the actuation method related to an electrohydraulic system. A much simpler friction model that retains all the features of the existing models has been developed for this purpose. In addition, a systematic experimental characterization procedure has been proposed that has been utilized in a supplementary manner for the development of the elaborate nonlinear system model. An artificial neural-network model has been constructed by training with experimental data keeping in mind the variation of discharge through the proportional valve with pressure and command signal. All the nonlinear subsystem models thus obtained have been incorporated simultaneously in MATLAB/SIMULINK to monitor the actuation dynamics. The variations of the theoretical and investigated (via experiments) displacements of the piston against different command signals have been found to be quite close to each other.