Electro-hydraulic Actuator System Research Articles

Integrated Electrohydraulic Control Actuation System with Centralized Power Plant for the Reusable Launch Vehicle Technology Demonstrator

An electrohydraulic control actuation system for actuating eight aerodynamic control surfaces of the two-stage technology demonstrator of the Indian reusable launch vehicle (RLV-TD) was developed, validated by extensive testing in various test beds, simulation runs and flight proven in the RLV-TD HEX-01 mission flight on 23 May 2016. A centralized hydraulic power generating unit (HPU) was used for powering the eight actuators located in two stages. The network of plumbings and control components of this actuation system were required to be laid out over the entire length and breadth of the vehicle measuring 17 m in length, to distribute the hydraulic power to all the actuators. The hydraulic actuation system had to work for the longest ever duration of 833 s for an Indian launch vehicle. Many challenges arose due to a single HPU for two stages, long complex network of plumbings, longest ever operating duration, thermal issues, second-stage structure resembling an aircraft, limited occupancy for operations at the launch pad, limited power source, etc. Necessary provisions were incorporated in the design to successfully overcome them. This article describes the development of the control actuation system.

Computationally Efficient Non-linear Electro-hydraulic Actuation System Model for Real-time Simulation

An electro-hydraulic actuation system with critically lapped servovalve and pressurized return line is exposited. The dynamic equations governing the behavior of various components are explained; using these nonlinear equations, a simulation model is developed in Simulink® software for the purpose of controller design and verification. Model requires very small integration step size as the equations involved are stiff. A relationship between the various pressures in the system is derived, and a simplified method for the nonlinear modeling of electro hydraulic actuating system is developed using these relationships. The simplified model is computationally efficient as the integration step-size is large compared to the original model. The computationally efficient model finds application in real-time hardware-in-loop simulation (HILS).

Design of Servo Scheme and Drive Electronics for the Integrated Electrohydraulic Actuation System of RLV-TD

Reusable Launch Vehicle-Technology Demonstrator (RLV-TD) is a system which has the ability to carry a payload from the earth’s surface to the outer space more than once. The control actuation forms the major component of the control system and it actuates the control surfaces of the RLV-TD based on the control commands. Eight electro hydraulic actuators were used in RLV-TD for vectoring the control surfaces about their axes. A centralised Hydraulic Power Generating Unit (HPU) was used for powering the eight actuators located in two stages. The actuation system had to work for the longest ever duration of about 850 s for an Indian launch vehicle. High bandwidth requirement from autopilot was met by the servo design using the nonlinear mathematical model. Single Control Electronics which drive four electrohydraulic actuators was developed for each stage. High power electronics with soft start scheme was realized for driving the BLDC motor which is the prime mover for hydraulic pump. Many challenges arose due to single HPU for two stages, uncertainty of aero load, higher bandwidth requirements etc. and provisions were incorporated in the design to successfully overcome them. This paper describes the servo design and control electronics architecture of control actuation system.

Robustness Analysis of an Optimized Controller via Particle Swarm Algorithm

This paper deals with an evaluation on the effectiveness of the robust controller in terms of its robustness towards the changes in the electro-hydraulic actuator (EHA) system parameters. It is well known that the defects exposed in this system are the existence of disturbances, parameters variation, and uncertainties in nature that yielding great difficulties in the development of system controller and the modelling of EHA system. Such difficulties simultaneously vitiating system performance and imposed if inappropriate control strategy is employed. A nonlinear EHA system model is established and the proposed controller which is sliding mode controller (SMC) is implemented in the simulation studies. The proposed control strategy has been compared with the conventional proportional-integral-derivative (PID) controller concerning its robustness characteristic with the variation in the system supply pressure in which the controller variables are obtained through particle swarm optimization (PSO) algorithm. The finding shows that the SMC that utilized the PSO algorithm parameters are capable to produce smaller robustness index values, which demonstrated better robustness characteristic in confront with the variation of the system parameter.

A model-based design approach for an optimal electro-hydraulic system within automatic transmissions

Fast and precise actuation plays a key role to reach challenging drivability targets of an automatic transmission. Electro-hydraulic actuation systems are mainly used to fulfill the demanding requirements in state-of-the-art applications. Additionally to control tasks, the electro-hydraulic system is responsible for the cooling and lubrication of gears, clutches and other parts of the transmission. The focus of this article is to optimize a hydraulic layout design, satisfying various demands from lubrication, cooling, transmission efficiency as well as production costs. The presented approach analyses the different requirements in detail and derives corresponding rules for possible hydraulic layouts. A standard automotive test cycle is used to illustrate and quantify the design considerations of the different topologies. Additionally, worst-cases scenarios are considered to take into account cases that are not covered explicitly in the provided test cycle.The system costs and the average power consumption of the hydraulic layout are shown to be the two essential optimization criteria finally left for the design decision. With respect to essential optimal criteria a corresponding multi-objective optimization is performed and the optimal solutions are discussed.

Mathematical Modeling and Fuzzy Adaptive PID Control of Erection Mechanism

This paper describes an application of fuzzy adaptive PID controller to erection mechanism. Mathematical model of erection mechanism was derived. Erection mechanism is driven by electro-hydraulic actuator system which is difficult to control due to its nonlinearity and complexity. Therefore fuzzy adaptive PID controller was applied to control the system. Simulation was performed in Simulink software and experiment was accomplished on laboratory equipment. Simulation and experiment results of erection angle controlled by fuzzy logic, PID and fuzzy adaptive PID controllers were respectively obtained. The results show that fuzzy adaptive PID controller can effectively achieve the best performance for erection mechanism in comparison with fuzzy logic and PID controllers.

Sliding Mode Controller Design with Optimized PID Sliding Surface Using Particle Swarm Algorithm

This article deals with an evaluation on the designed controller named as sliding mode control (SMC) which sliding surface of the controller has been integrated with proportional-integral-derivative (PID) controller. The control scheme is established from the derived dynamic equation which stability is proven through Lyapunov theorem. In the performance assessment on the designed PID sliding surface, the controller parameter is first obtained through conventional tuning method known as Ziegler-Nichols (ZN), which is then compared with the particle swarm optimization (PSO) computational tuning algorithm. From the observation of the simulation results, the PSO tuning algorithm showing outperform performances compared to the conventional ZN tuning method in term of trajectory tracking on the electro-hydraulic actuator (EHA) system.

The Effects of Parameter Variation in Open-Loop and Closed-Loop Control Scheme for an Electro-hydraulic Actuator System

It is well known that the EHA system is exposed to the disturbances,uncertainties,and parameter variations which are caused by the changes in operating conditions for instance,total moving mass,supply pressure,servo-valve gain,bulk modulus,leakage coefficient,and friction.These problems pose to a great challenge in modelling and controller development for an EHA system.Degradation of the desired performance can be imposed if an improper control strategy is utilized.This paper discusses the fundamental study on the significant effect that leads to degradation of EHA system performance due to variation in the system parameters.A nonlinear EHA system model is developed and implemented in the simulation studies in open-loop and closed-loop control configuration.The finding shows that the servovalve gain resulted the most influential parameters to the EHA system performance as compared to the total moving mass and supply pressure parameters.In order to overcome these issues,the utilized controller should be robust enough to overcome the entire operating range that against such disturbances,uncertainties,and parameter variations.Therefore,a nonlinear and the intelligent control approach may be necessary to be designed in order to overcome these difficulties.

Composite adaptive dynamic surface control of nonlinear systems in parametric strict-feedback form

In this paper, a composite adaptive dynamic surface control scheme is developed for a class of parametric strict-feedback nonlinear systems. The proposed composite adaptation law uses both the surface error and the estimation error to update the parameters. In addition, by using the dynamic surface control technique, the problem of the explosion of complexity in the adaptive backstepping design is avoided. It is proved that the proposed scheme guarantees uniform ultimate boundedness of all signals in the closed-loop system with arbitrary small surface error by adjusting the design parameters. Simulation results demonstrate the effectiveness of the proposed approach for an electrohydraulic actuator system.

Adaptive semi-parallel position/force-sensorless control of electro-hydraulic actuator system using MR fluid damper

The focus of this paper is to develop a semi-parallel control method using an inversion of identification model of a magnetorheological (MR) fluid damper along with a smart predictor controller (SPC) for a damping system using that damper and an electrohydraulic actuator (EHA) in order to realize the real time position/force control of the industrial task requiring interaction with the environment. The inverse model of MR fluid damper is established base on a self-tuning Lyapunov-based fuzzy (STLF) model. This STLF model is designed in the form of a center average fuzzy interference system, of which the fuzzy rules are planted based on the Lyapunov stability condition. In addition, in order to optimize the STLF model, the back propagation learning rules are used to adjust the fuzzy weighting net. Meanwhile, the SPC is constructed using a nonlinear PID controller (NPID) base on feedforward neural network and a smart Grey-Markov predictor (SGMP). Here, the NPID controller is built to drive the system to desired targets. Additionally, a learning mechanism with robust checking conditions is implemented into the NPID in order to optimize online its parameters with respect to the control error minimization. Besides, the SGMP with self-tuning ability of the predictor step size takes part in, first, estimating the system.

Nonlinear modeling and PID control through experimental characterization for an electrohydraulic actuation system: system characterization with validation

The physical model of an electrohydraulic actuation system has been obtained. To arrive at the closure of the model, experimental models for actuator friction and the characteristics of the proportional valves have been constructed. The variation of discharge through the proportional valve has shown the metered ports to be nonmatched that has been taken care of by estimating two separate coefficients for the main flow path and one leakage coefficient. An algebraic friction model retaining all the features of the existing differential model has been developed. All these nonlinear subsystem models have been integrated together in MATLAB/SIMULINK frame to predict the actuation dynamics. The variations of the predicted and experimental displacements of the piston against different command signals have been found to be quite close to each other.

Lessons learned from using some bio-inspired optimizers for real-time controller design for a low-cost electrohydraulic system

Well-designed searching procedures following natural processes have been developed for finding optimized solutions of complex systems. Here, a comparison of performances of some optimizers, namely differential evolution, genetic algorithm, bacterial foraging and artificial bee colony technique, have been carried out for designing a fuzzy-feedforward real-time controller of an electrohydraulic motion actuation system. The first two optimizers execute dominatingly exploratory search, while the latter two execute a combination of exploratory search with intensified exploitive search in prospective regions, thus providing faster convergence. The optimized controller has been designed by minimizing a response error integral for some standard displacement demands of the highly nonlinear system. The strong nonlinearities in the system arise from the friction of low-cost industry-grade cylinder and large deadband of rugged proportional valve. The convergences to the minimum of zero for a number of nonlinear functions have also been demonstrated for all the optimization processes. These optimizers with faster convergence rate have been shown to be robust against arbitrary demands like variable frequency sinusoidal demands and sinusoidal demands with superimposed log concave-convex variations.

Continuous–Discrete Time-Observer Design for State and Disturbance Estimation of Electro-Hydraulic Actuator Systems

In this paper, a continuous–discrete time observer which simultaneously estimates the unmeasurable states and the uncertainties for the electro-hydraulic actuator (EHA) system is presented. The main feature of the proposed observer is the use of an intersample output predictor which allows the users to increase the frequency acquisition of the piston position sensor without affecting the convergence performance. The stability analysis of the proposed observer is proved using Lyapunov function adapted to hybrid systems. To show the efficiency of our proposed observer, numerical simulations and experimental validation involving a control application, which combines the designed observer and a proportional–integral (PI) controller for the purpose of piston position tracking problem, are presented.

CONTROLLER PARAMETER OPTIMIZATION FOR AN ELECTRO-HYDRAULIC ACTUATOR SYSTEM BASED ON PARTICLE SWARM OPTIMIZATION TECHNIQUE

Motion control applications are widely applied in the industrial field with the assistance of electro-hydraulic actuator (EHA) system. EHA system is well known to be disclosed to the parameter variations, disturbances and uncertainties which are affected by the changes in the operating conditions such as friction, internal and external leakage. The complexity and nonlinear characteristic of the EHA system leads to a great challenge for controller development and system modelling. The performance of the utilized controller can be improved in order to achieve its best capability. In this paper, the basic knowledge in optimization of the proportional-integral-derivative (PID) controller through Gradient Descent (GD) and Particle Swarm Optimization (PSO) techniques are discussed. The PID parameters obtained through Ziegler-Nichols (ZN) tuning method has been optimized by using the GD method and is compared with PSO optimization technique via MATLAB/Simulink software. The findings show significant improvement in positioning tracking performance when the developed optimization technique is applied. Therefore, the issues degrading the EHA system performance have been reduced.

Fractional-order control of active suspension actuator based on parallel adaptive clonal selection algorithm

In current study, a new approach for vehicle active suspension actuator control is reported. For this approach, a nonlinear model for an electro-hydraulic servo actuator and quarter suspension system is established. An Oustaloup recursive approximation (ORA) Fractionalorder proportional–integral–derivative (FOPID) controller is designed to control the displacement of the actuator, and controller parameters are optimized based on error integral criteria using the Parallel adaptive clonal selection algorithm (PACSA). The research indicates that PACSA can tune parameters of the FOPID controller accurately and efficiently, and the tuned FOPID controller performs better in terms of response speed and tracking accuracy than a regular Proportional–integral–derivative (PID) controller. The performance of the active suspension system that uses the FOPID actuator is obviously superior to that of the active suspension system that uses a PID actuator and a passive suspension system.

Development and validation of electro-hydraulic camless free-piston engine

The scavenging system in two stroke engine is very important, therefore an electro-hydraulic camless variable valves actuation is developed and the effect of the exhaust valve character change on HFPE engine performance is investigated. Firstly the HFPE working principle and the control strategy are analyzed, and then a 3D CFD model is built by AVL_FIRE software, the piston displacement is obtained by 0D simulation. The simulation results are verified by the ideal scavenging model. The specific distributions of flow field are by plane cut. Further the scavenging parameters, such as trapping ratio, delivery ratio and scavenging efficiency, are analyzed with different intake pressure. In order to optimize the scavenging performance, the scavenging efficiency is affected by intake port height and the exhaust valve timing. Therefore the laws of higher scavenging efficiency are obtained. Experiment is necessary for validating the electro-hydraulic camless variable valves actuation system design. The specific prototype test bench is introduced for experimental study. In addition, the factors that affect variable valves actuation system are tested. Finally, the engine operation results are obtained and the engine performance is analyzed further.

Actuation dynamic modeling and characterization of an electrohydraulic system

The physical model of an electrohydraulic actuation system with pressure-reducing cylinder end cushioning has been obtained. In order to arrive at the closure of the model, experimental models for actuator friction and the characteristics of the relief, non-return and proportional valves have been constructed. The variation in discharge through the proportional valve with both pressure and command signal has been modeled by training a neural network with experimental data. For the characterization of the discharge through the proportional valve, besides square root of the pressure drop in each metered orifice, polynomial forms of command signal for the discharge coefficients have been used. Such a direct characterization of the discharge with the command signal eliminates the orifice opening as an intermediate variable. A simple friction model that retains all the features of the existing complex models has been developed. Parameters such as maximum dynamic friction and the corresponding velocity have been introduced for this purpose. All these nonlinear subsystem models have been integrated together in MATLAB/Simulink frame to predict the actuation dynamics. The variations in the predicted and experimental displacements of the piston against different command signals have been found to be quite close to each other.

Designing an optimized model-free controller for improved motion tracking by rugged electrohydraulic system

Electrohydraulic actuation systems with proportional valves and industry-grade cylinders have widespread use due to their low cost and ease of maintenance. Achieving good tracking of output position of the piston in such a system by a proper controller design is the objective of this study. Due to various parameter uncertainties and complex nonlinearities like piston friction, valve deadband and flow characteristics, the variation of oil property with working temperature and air entrapment volume, the implementation of a model-based control becomes quite difficult for such systems. A notable contribution of this work is to couple a model-free fuzzy controller with a feedforward controller with all the parameters estimated by a real-coded genetic algorithm. Also, the optimizer has been used for identifying an appropriate fuzzy structure that is easy to implement in real time. A comprehensive experimental study has revealed the best fuzzy structure to be achieved through a Gaussian fuzzification of linear combination of the position and velocity errors as the input and singleton membership function for the output voltage actuating the proportional valve. Excellent responses with good disturbance rejection capability and energy efficiency have been achieved. These responses have emerged superior to those achieved in a similar system with different controller structures and in systems with much costlier components.

PID PARAMETERS OPTIMIZATION USING PSO TECHNIQUE FOR NONLINEAR ELECTRO HYDRAULIC ACTUATOR

Electro-hydraulic actuator (EHA) system inherently suffers from uncertainties, nonlinearities and time- varying in its model parameters which cause the modeling and controller designs are more complicated. Proportional Integral Derivative (PID) control scheme has been proposed and the main problem with its application is to tune the parameters to its optimum values. This study will look into an optimization of PID parameters using particle swarm optimization (PSO). Simulation study has been done in Matlab and Simulink.

Improved dynamic model of electro- hydraulic servo and actuator system for steam turbine in power systems

Accuracy system model and its parameters are of great importance in stability and security evaluation or simulation for power systems. The electro-hydraulic servo and actuator is one of the most important components in the system. A mathematical model for the electro-hydraulic servo and actuator system developed on the working principle of each component has model parameters with clear physical meanings that can be obtained from field test data. The model is validated by data from four reheat turbines with different digital electro-hydraulic (DEH) control systems. Simulations show that the model agrees well with the test data when the servo cards are either proportional or proportional integral controllers. The results also show that the IEEE model parameters can be derived by this model.