DESIGN AND TUNING OF THE LYAPUNOV BASED NONLINEAR POSITION CONTROL OF ELECTROHYDRAULIC SERVO SYSTEMS

A complete study of the development of a nonlinear backstepping controller for an electrohydraulic servo system is shown in this paper. The authors present an optimized nonlinear mathematical model used as fundamental for computer simulation. A proposed nonlinear controller is suitable for research of behavior of the complete system in control. Special attention is paid to the selection of tuning parameters. Using the experience of earlier studies of the state-space controller where the additional feedback signals such as velocity and acceleration signal increase the frequency and damping factor of the system, the results were proved by computer simulation. The results show that by appropriate selection of tuning parameters the system can achieve the best reference signal tracking performance with a small tracking error. The proposed approach seems to be adequate not only for step reference signals but also for ramp and sinusoidal reference signals. However, the parameters of the backstepping controller can be optimized manually to achieve the best results required

Optimization of Modified Sliding Mode Controller for an Electro-hydraulic Actuator System with Mismatched Disturbance

This paper presents the design of the modified sliding mode controller (MSMC) for the purpose of tracking the nonlinear system with mismatched disturbance. Provided that the performance of the designed controller depends on the value of control parameters, gravitational search algorithm (GSA), and particle swarm optimization (PSO) techniques are used to optimize these parameters in order to achieve a predefined system’s performance. In respect of system’s performance, it is evaluated based on the tracking error present between reference inputs transferred to the system and the system output. This is followed by verification of the efficiency of the designed controller in simulation environment under various values, with and without the inclusion of external disturbance. It can be seen from the simulation results that the MSMC with PSO exhibits a better performance in comparison to the performance of the similar controller with GSA in terms of output response and tracking error

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

This paper presents a modified sliding mode controller (MSMC) for tracking purpose of electro-hydraulic actuator system with mismatched disturbance. The main contribution of this study is in attempting to find the optimal tuning of sliding surface parameters in the MSMC using a hybrid algorithm of particle swarm optimization (PSO) and gravitational search algorithms (GSA), in order to produce the best system performance and reduce the chattering effects. In this regard, Sum square error (SSE) has been used as the objective function of the hybrid algorithm. The performance was evaluated based on the tracking error identified between reference input and the system output. In addition, the efficiency of the designed controller was verified within a simulation environment under various values of external disturbances. Upon drawing a comparison of PSOGSA with PSO and GSA alone, it was learnt that the proposed controller MSMC, which had been integrated with PSOGSA was capable of performing more efficiently in trajectory control and was able to reduce the chattering effects of MSMC significantly compared to MSMC-PSO and MSMC-GSA, respectively when the highest external disturbance, 10500N being injected into the system's actuator

DESIGN OF ADAPTIVE BACKSTEPPING WITH GRAVITATIONAL SEARCH ALGORITHM FOR NONLINEAR SYSTEM

Adaptive backstepping controller is designed for tracking purpose of nonlinear system with unknown parameter is injected to it. Gravitational search algorithm (GSA) is integrated with the designed controller in order to automatically tune its control parameters and adaptation gain since the tracking performance of the controller relies on these parameters. Performance evaluation is observed based on the tracking output and the tracking error between reference input and the system’s output. The effectiveness of the adaptive backstepping controller is verified by looking at the lowest amount value of Sum of Squared Error (SSE) attained from the simulation process. The results show that the system’s output follow the reference input given with remarkably small tracking error

Commande nonlinéaire et non différentiable d'un système électrohydraulique

Cette these traite la modelisation, 1'identification et la commande des systèmes electrohydrauliques et leur integration dans des processus industriels tels que la suspension active des vehicules. Le travail est reparti sur trois phases. Dans une premiere etape une etude est menee sur le modele mathematique d'un systeme electrohydraulique generique et la commande utilisee en temps real, qui est basee sur l'approche du backstapping nonlineaire. L'amphase est essentiellement sur la disposition des parametres du controleur et la façon dont ils influencent la dynamique de I'erreur. Malgre que le backstepping assure la stabilite asymptotique globale du systeme, les parametres du controleur affectent néanmoins considerablement la saturation et l'allure du signal de commande et par consequent, la dynamique de l'erreur. Le backstapping est un choix incontestable parce qu'il constitue une technique nonlineaire puissante et robuste. Les resultats experimentaux, obtenus a ce stade, sont compares a ceux d'un controleur PED, afin de montrer que lae controleurs lineaires classiques n'assurent pas l'éfficacite requise, surtout lorsque I'actionneur du système hydraulique fonctionne a charge maximala. En deuxieme lieu, la variation des paramètres hydrauliques du systeme, en fonction de la pression et de la temperature, ainsi que son effet sur la degradation de l'efficacité du controleur, est étudiée. En consequence, il est conclu qu'une stratégie de commande adaptative est necessaire afin de mettre a jour le controleur avec la variation des parametres. En effet, la backstepping adaptatif indirect est employe : d'abord, parce qu'il parmet I'identification des valeurs reelles des parametres du systeme; ensuite, il permet en même temps de profiter de la robustesse et de la stabilite qu'offre le backstapping. Les resultats experimentaux a ce niveau sont compares a ceux d'un controleur backstapping non-adaptadf applique au même banc d'essai, dans les mêmes conditions. L'efficacité de I'approche proposee, en termes de stabilite garantie et erreur de poursuite negligeable, en presence de parametres variables, est bien demontree. La troisieme et dernière étape, étudie la commande d'une suspension active electrohydraulique, basee sur une combinaison de backstapping et de forwarding. Le modele mathematique d'une suspension active electrohydrauliqua peut etre classifie parmi les systemes entrelaces. Ceci signifie que le modele d'etat est forme d'equations en 'feedback' et en 'feedforward'. Par consequent, le backstapping et la forwarding forment une strategie de commande appropriee pour stabiliser ce type de systemes. L'avantage ultime de cetta derniere est qu'elle ne laisse aucune dynamique interne, contrairement a d'autres strategies. II sera demontre, que le backstapping combine avec la forwarding est une stratégie de commande propice pour compenser l'effet des perturbations routières sur la stabilite des vehicules. Les resultats sont compares a ceux d'un PID classique et d'un controlaur par mode de glissement, pour prouver que la controleur propose surpasse une gamme de controleurs existants, pour une gamme de perturbations

Modelling of an electro-hydraulic actutor using extended adaptive distance gap statistic approach

The existence of high degree of non-linearity in Electro-Hydraulic Actuator (EHA) system has imposed a challenging task in developing its model so that effective control algorithm can be proposed. In general, there are two modelling approaches available for EHA system, which are the dynamic equation modelling method and the system identification modelling method. Both approaches have disadvantages, where the dynamic equation modelling is hard to apply and some parameters are difficult to obtain, while the system identification method is less accurate when the system’s nature is complicated with wide variety of parameters, nonlinearity and uncertainties. This thesis presents a new modelling procedure of an EHA system by using fuzzy approach. Two sets of input variables are obtained, where the first set of variables are selected based on mathematical modelling of the EHA system. The reduction of input dimension is done by the Principal Component Analysis (PCA) method for the second set of input variables. A new gap statistic with a new within-cluster dispersion calculation is proposed by introducing an adaptive distance norm in distance calculation. The new gap statistic applies Gustafson Kessel (GK) clustering algorithm to obtain the optimal number of cluster of each input. GK clustering algorithm also provides the location and characteristic of every cluster detected. The information of input variables, number of clusters, cluster’s locations and characteristics, and fuzzy rules are used to generate initial Fuzzy Inference System (FIS) with Takagi-Sugeno type. The initial FIS is trained using Adaptive Network Fuzzy Inference System (ANFIS) hybrid training algorithm with an identification data set. The ANFIS EHA model and ANFIS PCA model obtained using proposed modelling procedure, have shown the ability to accurately estimate EHA system’s performance at 99.58% and 99.11% best fitting accuracy compared to conventional linear Autoregressive with External Input (ARX) model at 94.97%. The models validation result on different data sets also suggests high accuracy in ANFIS EHA and ANFIS PCA model compared to ARX model