Electro-hydraulic Actuator System Research Articles

Robust precision control for a class of electro-hydraulic actuator system based on disturbance observer

This paper presents a new robust control scheme for a class of electro-hydraulic actuator using dynamic sliding mode control associated with nonlinear disturbance observer. Switching-gain of the sliding mode is designed to be adaptable on the estimated disturbance. A switching-gain adaptation mechanism is proposed to obtain as small as possible switching-gain to minimize chattering effect. The scheme is developed to guarantee the tracking precision of the system with robust and smooth control actions in the existence of uncertainties and the changes of external disturbance. Capability of the proposed scheme is enhanced by varying boundary layers algorithm to assist the scheme to return to its ability in a larger change of external disturbance. Capability and effectiveness of the proposed scheme are validated through experiment, where the results indicate that the proposed scheme ensures the tracking precision of the system with robust and smooth control actions in a large change of external load disturbance. Moreover, smooth control actions that are produced by the proposed control scheme offer a significant efficiency of energy in the control of electro-hydraulic actuator systems.

Position and Speed Double Closed Loop Control Performance of Electro-Hydraulic Actuator System Research Based on AMESim

In the paper, we research on a preparatory electro-hydraulic actuator product, using the simulation software AMESim to research work to analyze the system performance. We research position in closed loop servo actuator system, generally only considered the requirements of the position. While the speed trajectory and precision control did not do high demand. The position of the system by increasing the speed control strategy module, the system meets the requirements of the position. At the same time, we can achieve speeds start-up operation, stable operation and stopped operation of the three phases according to the requirement following a given trajectory; simultaneously can carry out detailed system performance analysis and research. Simulation results show that increasing position speed control strategy module of the system get very good effect. It can realize the speed control system and satisfy the system output displacement and speed steady-state performance and dynamic response.

Clutch fill control of an automatic transmission for heavy-duty vehicle applications

In this paper an integrated clutch filling phase control for gearshifts on wet clutch transmissions is developed. In a clutch-to-clutch shift of an automatic transmission, in order to obtain smooth gearshift, it should synchronize the oncoming clutch and the off-going clutch timely as well as precise pressure control for the engagement of the oncoming clutch. However, before the oncoming clutch pressure starts to increase, the initial cavity of the clutch chamber has to be filled first. The filling time and stability of the fill phase are very important for the clutch control. In order to improve the shift quality of the automatic transmission which is equipped on heavy-duty vehicles, the electro-hydraulic clutch actuation system is analysed and modelled. A new fill phase control strategy is proposed based on the system analysis as well as the control parameters are optimized according to the variation of the oil temperature and engine speed. The designed strategy is validated by a simulation work. The results demonstrate that the proposed control strategy and parameters modified method can transit the shift process from the fill phase to the torque phase effectively.

Application of Draw Wire Sensor in the Tracking Control of An Electro Hydraulic Actuator System

A draw wire sensor is considered as a contact measurement method. It is normally used to measure the speed and position of a system. A draw wire sensor is convenient especially when a low cost solution and a small sensor dimension are desired. The objective of this paper is to describe the application of draw wire sensor in control tracking of electro hydraulic actuator system. This research started with the modelling of electro hydraulic actuator system by using system identification approach. During the data taking process, an experiment is conducted using electro hydraulic actuator test bed. A draw wire sensor is attached to the load of electro hydraulic actuator system to measure the output displacement when the system is injected with the desired input signal. Draw wire sensor is measuring the output displacement in millimeters and then the signal is converted to voltage reading regarding to the given input signal. The input and output signal is collected and is used in system identification technique to obtain the best mathematical model that can represent the electro hydraulic actuator system. Once a model is obtained, a Self Tuning Controller (STC) with Generalize Minimum Variance Control (GMVC) strategy is designed to control the tracking performance of the electro hydraulic actuator system. The designed controller is tested in simulation and experiment mode. Then, the output result from both modes is compared. The results show that the output performance from both modes are almost similar. Thus, this research had shown that a draw wire sensor has a significant role in capturing an accurate output data from electro hydraulic actuator system even with or without the controller.

A Comparative Study of Linear ARX and Nonlinear ANFIS Modeling of an Electro-Hydraulic Actuator System

The existence of a high degree of nonlinearity in Electro-Hydraulic Actuator (EHA) has imposed a challenge in development of a representable model for the system such as that significant control performance can be proposed. In this work, linear Autoregressive with Exogenous (ARX) model and nonlinear Adaptive Neuro-Fuzzy Inference System (ANFIS) model of an EHA system are obtained based on the mathematical model of the system. Linear ARX modeling technique has been widely applied on EHA system and satisfying result has been obtained. On the other hand, ANFIS modeling technique can model nonlinear system at high accuracy. Both models are validated offline using data set obtained and using different stimulus signals when doing online validation. Offline validation test shows that ANFIS model has 99.37% best fitting accuracy, which is more accurate than 93.75% in ARX model. ARX model fails in some online validation tests, while ANFIS model has been consistently accurate in all tests with RMSE lower than 0.25.

Electro-Hydraulic Actuator System Control via Pole Assignment Controler and Minimum Variance Controller

Precise control is necessary in controlling electro-hydraulic actuator system (EHAS). However due to its nonlinearities and uncertainties, controlling hydraulic actuator system had become a challenging task that need to be solved. A proper controller can be designed when an accurate model of a system is defined. In this paper, the process to obtain an EHAS system’s model by using system identification approached is presented. System identification is chosen because this technique only requires input and output data from system in order to obtain system model. An ARX model is chosen as a model structure for EHAS. A pole assignment controller and minimum variance controller (MVC) is later been designed based on the obtained model. The simulation result shows that both controllers manage to regulate at the desired input signal. However MVC controller prove to provide a better output performance compared to pole assignment controller by minimizing the phase lagging and having a better rise time.

Cascaded sliding mode force control for a single-rod electrohydraulic actuator

This paper investigates the force control problem of a single-rod electrohydraulic actuator system based on sliding mode strategy. On the basis of the force tracking error dynamics, in order to facilitate the controller design, the whole system is divided into a linear subsystem and a nonlinear subsystem. By forcing the output of nonlinear subsystem to track the expected fictitious input of linear subsystem, and specifying suitable sliding mode functions for nonlinear subsystem and linear subsystem respectively, the cascaded sliding mode controller is created according to the reaching law approach. The stability of the closed-loop system is proved. Simulation results verify the effectiveness of the proposed cascaded sliding mode force control method for the single-rod electrohydraulic actuator system.

Identification and Design of Closed loop Hydraulic system with 4/3 Servo valve

Fluid power actuators play a vital role in the field of mechatronics. The controlling of electrohydraulic actuation system is important in the view of nonlinearity characteristics of hydraulic valves. In order to control the operation of valves, the controller should be designed as well as identification of the system is necessary to know the behavior of the system. This paper provides the derivation of transfer function for a electrohydraulic servo system by using transient response of the cylinder with respect to different set point with different loads .The performance of the system is analyzed using open loop without load, open loop with load, closed loop with load and it is observed that the performance of the system works better using closed loop. Also, in this paper the identification of the electrohydraulic servo system is done using transient response parameters and using Bode plot. It has been found that the poles & zeros of the system determined by the transient response & Bode’s Plot are nearly equal. For the transfer function derived from different conditions such as open loop, closed loop, with variable loads, the PID controller is also designed and the performance characteristics hold good with theoretical aspects

Optimization of PID Parameters in Electro-Hydraulic Actuator System Using Genetic Algorithm

Electro-Hydraulic Actuator (EHA) replaces centralized hydraulic system by a local compact actuator system. It is gaining more attention due to its compactness and reliability. The control method should be appropriate to achieve accurate position control and stability. The EHA system model is developed in AMESim software and Proportional-Integral-Derivative (PID) control is used for position tracking of the cylinder. Design Exploration facility of AMESim software provides a platform to optimize PID parameters using Genetic Algorithm (GA). Simulation results show that position tracking with no overshoot and less settling time.

Design of Self-Tuning Fuzzy Control and Fault Tolerant Error Control Coding Based on Graphic User Interface for Smart Hybrid Powerpack

The Smart Hybrid Powerpack (SHP) is an electro-hydraulic system which combines the system of Electro Hydraulic Actuator (EHA) and advanced technologies such as network fault tolerance and intelligent control. EHA system has been famous in the industry because that the EHA acts as a power-shift which shifts the power from high-speed electric motor to the high-force of hydraulic cylinder by bi-directional piston pump. If errors in the plant and network occur in the SHP, the system will cause serious malfunctions. To reduce plant noises and network errors, this paper shows the intelligent control method comparing Self-tuning fuzzy with fuzzy control and network fault tolerant error control coding in the SHP. In the intelligent control part, the simulation result shows good performance to reduce plant noises by the self-tuning fuzzy than fuzzy control. In the network fault tolerant error control coding part, proposed scheme also shows good performance by CRC code and Reed-Solomon (R-S) code in two channel (CRT) method than one channel only. We developed LabVIEW Graphic User Interface (GUI) to show these simulation results. Using this GUI, we can save time to experiment and get benefit of guidance to make real program.

Adaptive Backstepping Control of an Electrohydraulic Actuator

This paper presents an adaptive position control for a pump- controlled electrohydraulic actuator (EHA) based on an adaptive backstepping control scheme. The core feature of this paper is the combination of a modified backstepping algorithm with a special adaptation law to compensate all nonlinearities and uncertainties in EHA system. First of all, the mathematical model of the EHA is developed. The position control is then formulated using a modified backstepping technique and the uncertainties in hydraulic system are adapted by employing a special Lyapunov function. The control signal consists of an adaptive control signal to compensate the uncertainties and a simple robust structure to ensure the robustness corresponding to a bounded disturbance. Experimental results proved strongly the ability of the proposed control method.

Robust H ∞ sliding mode control with pole placement for a fluid power electrohydraulic actuator (EHA) system

In this paper, we exploit the sliding mode control problem for a fluid power electrohydraulic actuator (EHA) system. To characterize the nonlinearity of the friction, the EHA system is modeled as a linear system with a system uncertainty. Practically, it is assumed that the system is also subject to the load disturbance and the external noise. An integral sliding mode controller is proposed to design. The advanced techniques such as the H∞ control and the regional pole placement are employed to derive the optimal feedback gain which can be calculated by solving a necessary and sufficient condition in the form of linear matrix inequality. A sliding mode control law is developed such that the sliding mode reaching law is satisfied. Simulation and comparison results show the effectiveness of the proposed design method.

Research on the New Missile Electro-Hydraulic Actuation System Based on Two-Stage Speed Control Mode

The performance of missile guidance and penetration ability is determined by the missile actuation system. According to the development trend of high performance and energy saving, the new missile electro-hydraulic actuation system based on two-stage speed control mode is presented in this paper, and then the operating principle and process are discussed in detail. Finally the accurate mathematical model of the new actuation system is established, and the influence of the different basic speed on the power loss and the dynamic performance are analyzed. The simulation results show that the purposes of maintaining the dynamic performance and reducing the zero-control current are achieved. Therefore, the new proposed scheme has a certain practical significance for the future development of the missile electro-hydraulic actuation system.

Research on the New Missile Actuation System with Dual Independent Closed-Loop

With the development of the advanced precision-guided missile and anti-missile system, high precision, high penetration ability and Low energy consumption have become an important direction for the missile. A new missile electro-hydraulic actuation system with dual independent closed-loop is put forward with the trend of high performance and energy-saving, and then the operating principle and process are discussed. Finally the accurate mathematical model is established, and the influence of the different basic pressure on the dynamic performance is analyzed. The simulation results show that the new proposed scheme has made great improvements in reducing the zero-control current of the system, but the efficiency and performance of the actuation system should be considered integrated due to the decrease of the dynamic performance, so it is practical for the future development of the missile electro-hydraulic actuation system.

System Identification of Electro-Hydraulic Actuator System using ANFIS Approach

Precise control of an electro-hydraulic actuator (EHA) system has been an interesting subject due to its nonlinearities and uncertainties characteristics. Suitable controller can be designed when the precise model of the system is available. Adaptive Neuro-Fuzzy Inference System (ANFIS) modeling technique has proven can model various nonlinear systems at high accuracy. The objective of this paper is to obtain an ANFIS model from EHA system stimulus-response data with less complicated model structure and fewer system parameters. The validation of ANFIS model is done using various data sets which contain different operating region and limited data set, where data set is reduced to small operating region. Results show that ANFIS model can estimate the response nonlinear EHA system with more than 97% high best-fitting accuracy, with simple structure, under different operating region condition.

ANFIS modeling of Electro-Hydraulic Actuator system through physical modeling and FCM gap statistic in initial FIS determination

The Adaptive Neuro-Fuzzy Inference System (ANFIS) modeling technique has shown the ability to model nonlinear system at high accuracy. The initial Fuzzy Inference System (FIS) is required before ANFIS parameters' training. The generation of initial FIS requires the number of inputs, number of clusters and cluster centers to be determined. Instead of determining the above parameters by heuristic approach, the number and variable of inputs of an Electro-Hydraulic Actuator (EHA) system are determined through mathematical derivation of the system. The number of clusters for each input is determined via fuzzy gap statistic, which applies Fuzzy C-means (FCM) instead of k-means of gap statistic in calculating the within cluster dispersion. FCM clustering also provides the center of each cluster identified. Information of the input variables and cluster numbers as well as cluster centers are used to obtain initial FIS. ANFIS hybrid training algorithm is used to train the initial FIS for parameters. The result shows that the model obtained using ANFIS approach can estimate the EHA's system response at high precision.

Robust Position Tracking Control of an Electro-Hydraulic Actuator in the Presence of Friction and Internal Leakage

This paper proposes an improved robust position controller for the electro-hydraulic actuator system using the varying boundary layered sliding mode control scheme. The proposed scheme has the ability to improve the position tracking performance of the actuator in the presence of friction and internal leakage. The former is represented using the LuGre model while later is modelled as a turbulent flow. To evaluate the effectiveness of the proposed method, MATLAB simulations are carried out under friction and leakage effects. Its performance is compared with the conventional PID and fuzzy PID (FPID) methods. Finally, an experimental rig that comprises of a single-rod and double acting hydraulic cylinder is set up to validate the proposed idea. The software development is carried out in the DSpace 1104 environment using a TMS320F240 digital signal processor. The superiority of the proposed method over the PID and FPID in terms of tracking position is highlighted by simulation and experimental results.

Thermal Analysis of a Fluid Immersed Brushless DC Motor for Aerospace Applications

In this paper, the thermal behavior of a 12kW, 12000rpm, wet-type Permanent Magnet Brushless DC motor (BLDC) with skydrol oil inside designed for electro-hydraulic actuation system (EHA) was analyzed. A 3-D computational fluid dynamics (CFD) model has been built. The influence of skydrol hydraulic oil in thermal behavior at both low-speed and high-speed conditions was discussed. The results confirm that the skydrol oil passing through the motor has different impact on the thermal performance in different conditions.

Position Control of Electro-hydraulic Actuator System Using Fuzzy Logic Controller Optimized by Particle Swarm Optimization

The position control system of an electro-hydraulic actuator system (EHAS) is investigated in this paper. The EHAS is developed by taking into consideration the nonlinearities of the system: the friction and the internal leakage. A variable load that simulates a realistic load in robotic excavator is taken as the trajectory reference. A method of control strategy that is implemented by employing a fuzzy logic controller (FLC) whose parameters are optimized using particle swarm optimization (PSO) is proposed. The scaling factors of the fuzzy inference system are tuned to obtain the optimal values which yield the best system performance. The simulation results show that the FLC is able to track the trajectory reference accurately for a range of values of orifice opening. Beyond that range, the orifice opening may introduce chattering, which the FLC alone is not sufficient to overcome. The PSO optimized FLC can reduce the chattering significantly. This result justifies the implementation of the proposed method in position control of EHAS.

Modeling and Robust Discrete-Time Sliding-Mode Control Design for a Fluid Power Electrohydraulic Actuator (EHA) System

This paper studies the design of a robust discrete-time sliding-mode control (DT-SMC) for a high precision electrohydraulic actuator (EHA) system. Nonlinear friction in the hydraulic actuator can greatly influence the performance and accuracy of the hydraulic actuators, and it is difficult to accurately model the nonlinear friction characteristics. In this paper, it is proposed to characterize the frictions as an uncertainty in the system matrices. Indeed, the effects of variations of the nonlinear friction coefficients are considered as norm-bounded uncertainties that span a bounded region to cover a wide range of the real actuator friction. For such a discrete-time dynamic model, for the EHA system with system uncertainty matrices and a nonlinear term, a sufficient condition for existence of stable sliding surfaces is proposed by using the linear matrix inequality approach. Based on this existence condition, a DT-SMC is developed such that the reaching motion satisfies the discrete-time sliding mode reaching condition for uncertain systems. Simulation and experimental studies on the EHA system illustrate the effectiveness and applicability of the proposed method.