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

Model Identification And Controller Design For An Electro-Pneumatic Actuator System With Dead Zone Compensation

Pneumatic actuator system is inexpensive, high power to weight ratio, cleanliness and ease of maintenance make it’s a choice compared to hydraulic actuator and electromagnetic actuator. Nonetheless, the steady state error of the system is high due to the dead zone of the valve. In this paper, an Auto-Regressive with External Input (ARX) model structure is chosen to represent the pneumatic actuator system. The recursive least square method is used to estimate the model parameters. The pole-assignment controller is then developed for position tracking. To cater the problem of high in steady state error, the dead zone compensation is added to the system. The dead zone controller was designed based on the inverse dead zone model and the dead zone compensation designed based on the desired error. The proposed method is then experimentally with varies load and compares with Nonlinear PID controller. The result shows that the proposed controller reduced the overshoot and steady state error of the pneumatic actuator system to no overshoot and 0.025mm respectively. Index terms: System identification, recursive least square, ARX, dead zone compensator, pneumatic actuato

Adaptive sliding mode control with disturbance observer for a class of electro-hydraulic actuator system

Position tracking control has become one of the most popular studies in the control of Electro-Hydraulic Actuator (EHA) systems. However, it deals with highly nonlinear behaviours, uncertainties and external disturbances, which significantly affect the control performance. In the class of nonlinear robust control, Sliding Mode Control (SMC) has become an effective approach for systems experiencing these issues due to its discontinuous nature. But, employing SMC as a stand-alone controller may not be effective for EHA systems with time-varying external disturbance, and integration is needed. Hence, the objective of this study is to formulate and implement a robust SMC in adaptive control form integrated with Nonlinear Disturbance Observer (NDO) to guarantee robustness, position tracking accuracy, and smoothness of the control actions to an EHA system in the presence of uncertainties and disturbances. The EHA system was modelled as a nonlinear system which contains nonlinearities, uncertainties and disturbances. The SMC was developed in integration with NDO, in which switching gain of the SMC is designed to be adaptive on the bounds of uncertainties and disturbances, and updated by the NDO through an adaptation mechanism. Stability of the SMC and the NDO are guaranteed by the Lyapunov function candidate. Simulation and experimental results show that capability of the integrated controller to improve the smoothness of the control actions is as good as the stand-alone adaptive SMC with varying boundary layers technique. Also, it is capable to maintain the tracking accuracy about 25% better than the stand-alone SMC. Integration of the NDO into the SMC offers a better compromise between position tracking accuracy and control actions smoothness in position tracking control technique based-SMC

Improved Third Order PID Sliding Mode Controller for Electrohydraulic Actuator Tracking Control

An electrohydraulic actuator (EHA) system is a combination of hydraulic systems and electrical systems which can produce a rapid response, high power-to-weight ratio, and large stiffness. Nevertheless, the EHA system has nonlinear behaviors and modeling uncertainties such as frictions, internal and external leakages, and parametric uncertainties, which lead to significant challenges in controller design for trajectory tracking. Therefore, this paper presents the design of an intelligent adaptive sliding mode proportional integral and derivative (SMCPID) controller, which is the main contribution toward the development of effective control on a third-order model of a double-acting EHA system for trajectory tracking, which significantly reduces chattering under noise disturbance. The sliding mode controller (SMC) is created by utilizing the exponential rule and the Lyapunov theorem to ensure closed-loop stability. The chattering in the SMC controller has been significantly decreased by substituting the modified sigmoid function for the signum function. Particle swarm optimization (PSO) was used to lower the total of absolute errors to adjust the controller. In order to demonstrate the efficacy of the SMCPID controller, the results for trajectory tracking and noise disturbance rejection were compared to those obtained using the proportional integral and derivative (PID), the proportional and derivative (PD), and the sliding mode proportional and derivative (SMCPD) controllers, respectively. In conclusion, the results of the extensive research given have indicated that the SMCPID controller outperforms the PD, PID, and SMCPD controllers in terms of overall performance.

Design of Lyapunov based nonlinear velocity control of electrohydraulic velocity servo systems

Razvoj regulacijskog sustava hidrauličkog pogona u procesu centrifugalnog lijevanja čelika zahtijeva točan pozicijski i vremenski odaziv sustava, kako bi se što preciznije izlio lijev. U okviru preliminarnih istraživanja razmatrana je dinamička analiza i regulacija elektrohidrauličkog brzinskog servosustava, kod koje nastupaju nelinearnosti prouzrokovane hidrauličkim tokom i unutrašnjim trenjem. Nelinearnosti i nesigurnosti u dinamičkim karakteristikama otežavaju postizanje visokih zahtjeva po stabilizaciji upotrebom konvencionalnih regulatora. Prikazana su dva različita primjera nelinearnog konstruiranja regulatora, prvi kod kojeg je postignuta linearizacija povratnim ciklusom, i drugi primjer linearizacije povratnim korakom. Uporabom oba regulatora postignuta je učinkovita stabilizacija u bilo kojoj radnoj točki sustava. Isto tako ostvaren je i bolji uvid u dinamičke karakteristike sustava što daje dodatnu vrijednost spomenutom regulatoru. Rezultati su potvrđeni računarskom simulacijom uporabom nelinearnog matematičkog modela sustava.Development of a hydraulically driven process of steel centrifugal die casting industry requires accurate response of position in time. In the frame of preliminary investigations the analysis and control of electrohydraulic velocity servo system is considered in the presence of flow nonlinearities and internal friction. The nonlinear and uncertainty characteristics make the conventional controller not yield to the system high requirements. Two different nonlinear design procedures are employed: feedback linearization and backstepping. It is shown that both these techniques can be successfully used to stabilize any chosen operating point of the system. Additionally, invaluable new insights are gained about the dynamics of the system under consideration. This illustrates that the true potential of constructive nonlinear design lies far beyond the mere task of achieving a desired control objective. All derived results are validated by computer simulation of the nonlinear mathematical model of the system

Model-Based Control Design of an EHA Position Control Based on Multicriteria Optimization

For the control of dynamic systems such as an Electro-Hydraulic Actuator (EHA), there is a need to optimize the control based on simulations, since a prototype or a physical system is usually not available during system design. In consequence, no system identification can be performed. Therefore, it is unclear how well a simulation model of an EHA can be used for multicriteria optimization of the position control due to the uncertain model quality. To evaluate the suitability for control optimization, the EHA is modeled and parameterized as a grey-box model using existing parameters independent of test bench experiments. A method for multi-objective optimization of a controller is used to optimize the position control of the EHA. Finally, the step responses are compared with the test bench. The evaluation of the step responses for different loads and control parameters shows similar behavior between the simulation model and the physical system on the test bench, although the essential phenomena could not be reproduced. This means that the model quality achieved by modeling is suitable as an indication for the optimization of the control by simulation without a physical system

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