nan Zulfatman

Modeling and controller design of an industrial hydraulic actuator system in the presence of friction and internal leakage

This paper presents a robust controller scheme and its capabilities to control the position tracking performance of an electro-hydraulic actuator system. Sliding mode control with fixed and varying boundary layer is proposed in the scheme. It is aimed to compensate nonlinearities and uncertainties caused by the presence of friction and internal leakage. Its capabilities are verified through simulations in Matlab Simulink environment. The friction was represented by the LuGre model and the internal leakage was assumed to change. The results indicate that the scheme successfully improves the robustness and the tracking accuracy of the system. This improvement offers a significant contribution in the control of modern equipment positioning applications.

On-line identification of an electro-hydraulic system using recursive least square

This paper presents experimental on-line identification of an electro-hydraulic system represented by a discrete time model. A recursive least square (RLS) method is used to estimate the unknown parameters of the system based on auto regression with exogenous input (ARX) model. Residual analysis is used for model validation. Results are presented which show variations in parameters of the electro-hydraulic system.

PID controller design for an industrial hydraulic actuator with servo system

Electro-hydraulic system (EHS) consists of several dynamic parts which are widely used in motion control application. These dynamic parts need to be controlled to determine direction of the motion. Mathematical model of EHS is required in order to design a controller for the system. In this paper, system identification technique is used for system modeling. Model of the system is estimated by using System Identification Toolbox in Matlab. This process began with collection of input and output data from experimental works. The data collected is used for model estimation. Auto Regressive with eXogeneous input (ARX) model is chosen as model structure of the system. Based on the input and output data of the system, best fit criterion and correlation analysis of the residual is analyze to determine the adequate model for representing the EHS system. By using Ziegler-Nichols tuning method, PID controller is designed for the model chosen through simulation in Simulink. In order to verify this controller, it is applied to the real time system and the performance of the system is monitored. The result obtained shows that the output of the system with controller in simulation mode and experimental works is almost similar. The output of the system also tracked the input given successfully.

Open-loop and closed-loop recursive identification of an electro-hydraulic actuator system

This paper presents experimental work on recursive identification of an electro-hydraulic system that represented by a discrete-time model in open-loop and closed-loop configurations. A recursive least square (RLS) method is used to estimate the unknown parameters of the system based on auto regression with exogenous input (ARX) model. Residual analysis is utilized for a model validation. Results are presented which show variations in parameters of the electro-hydraulic system. From the results obtained, position tracking for electro-hydraulic system can be implemented by using conventional proportional-integral-derivative (PID) controller with the aim of the modeling validation.

Position tracking control of an electro-hydraulic servo system using sliding mode control

This paper evaluates the position tracking performance of an electro-hydraulic hydraulic servo (EHS) system using sliding mode control (SMC). The EHS system is established in modelling process by consider its nonlinearities with a friction model. The control strategy is derived from developed dynamics equation and stability of the control system is theoretically proven by Lyapunov theorem. Simulation results demonstrate the proposed controller is highly robust and capable to cope with the uncertainties and disturbances occur during the position tracking control. It is also shows that the proposed controller can achieve better tracking performance compared with conventional PID controller.

Two-degree-of-freedom robust control for a non-minimum phase electro-hydraulic system

Electro-hydraulic actuator (EHA) system inherently suffers from uncertainties, nonlinearities and time-varying in its model parameters which makes the modeling and controller designs are more complicated. The main objective of this paper is to perform a robust control design using discrete-time sliding mode control (DSMC) with two-degree-of-freedom control strategy. The proposed controller consists of feedback and feedforward combination which capable to reduce phase lag during the trajectory tracking of EHA system. The feedforward controller is developed by implementing the zero phase error tracking control (ZPETC) technique which the main difficulty arises from the nonminimum phase system with no stable inverse. Finally, a chaotic trajectory tracking is performed in the experimental works to show the robustness of DSMC controller and performance comparison is made with Linear-Quadratic-Regulator (LQR) and Proportional-Integral-Derivative (PID) controllers. The findings show that the proposed controller with ZPETC outperforms the LQR and PID controllers in terms of tracking accuracy.

Smooth control action of sliding mode for a class of electro-hydraulic actuator

This paper presents a sliding mode control scheme to control a class of electro-hydraulic actuator system. A reaching law and varying boundary layers approaches are proposed in the scheme. The reaching law is aimed to solve the effect of chattering and minimize the reaching time. While, varying boundary layers algorithm is applied to ensure position tracking accuracy and smooth control action. The system is presented with the inclusion of friction and internal leakage in the system model. The proposed controller abilities are investigated through simulations works in Matlab Simulink environment based on the existing system parameters. The results indicate that the proposed scheme successfully reduces the reaching time, eliminates the chattering effect, improves the tracking accuracy, and results a smooth control action. In general, this improvement offers a significant contribution for accuracy in modern equipments positioning applications.

Point-to-point trajectory tracking with two-degree-of-freedom robust control for a non-minimum phase electro-hydraulic system

Electro-hydraulic actuator (EHA) system inherently suffers from uncertainties, nonlinearities and time-varying in its model parameters which makes the modeling and controller designs are more complicated. The main objective of this paper is to perform a robust control design using discrete-time sliding mode control (DSMC) with two-degree-of-freedom (2-DOF) control strategy. The proposed controller consists of feedback and feedforward combination which capable to reduce phase lag and steady state error during the trajectory tracking of EHA system. The feedforward controller is developed by implementing the zero phase error tracking control (ZPETC) technique which the main difficulty arises from the nonminimum phase system with no stable inverse. A point-to-point trajectory is used in the experimental works to evaluate the performance of the DSMC. Experimental results reveal that the DMSC with 2-DOF control structure is highly robust and capable to deal with the uncertainties and disturbances occur during the position tracking control for different point of trajectories. It is also shows that the proposed controller can achieve better tracking performance as compared to conventional LQR and PID controller.

Two-time scales matrix decomposition for wastewater treatment plant

The purpose of this work is to identify two-time scales matrix decomposition of wastewater treatment plant. Wastewater plant is naturally aim to remove suspended substances, organic material and phosphate before releasing to recipients. Initially, the MIMO system is excited with generalized binary noise signals and estimated with robust numerical subspace state-space system identification. The performance of identified models is then validated by variance accounted for. Next, the block diagonalisation procedures are implemented in decoupling the system with two-time property into slow and fast subsystem. It was observed that the identified model possess two-time scales behaviors presented by separated clusters of eigenvalues. Besides, similar dynamic responses were obtained by decoupled systems compared to actual full model at lower frequency that is highly demanded in control design application. The study leads to future improvement on wastewater control strategies.