Development of dynamic model of a 7DOF hydraulically actuated tele-operated robot for decommissioning applications

In this paper the problem of system integration and dynamic modeling of a hydraulically actuated manipulator with seven degrees of freedom, i.e. HydroLek HLK-7W is investigated. The arm is fitted on Multi-Arm mobile Robot System for Nuclear Decommissioning (MARS-ND) applications purposes. This is a step forward with respect to the previous works where only kinematics of the robot was taking into account. As the decommissioning robot has to perform precise and complex tasks autonomously using effective model-based nonlinear control algorithms having an accurate dynamic model of the arm which is reliable enough to predict the behavior of the manipulator under different operating conditions would be crucial. To this end the symbolic, and numerical model of the dynamic of robot is developed and a first attempt for model validation and tuning the parameters of the model is taken forward

Controller design of hydraulic actuator system using self-tuning and model reference adaptive control

Nowadays, hydraulic actuator system has become a major drive system in industrial sector especially when involving motion control or position tracking applications. However, due to its natural behaviour which is highly nonlinear, associated with many uncertainties and having parameters that change with timevariation, handling and controlling a hydraulic actuator system is a challenging task. The purpose of this study is to model and to design a controller for hydraulic actuator system. Thus, in order to develop a system that meets the desired performance such as a highly-accurate trajectory tracking, a special knowledge about the system togather with a suitable modelling and control design for the system is mandatory. In this research, Self-tuning Controller using Generalized Minimum Variance Control Strategy and Model Reference Adaptive Controller using Gradient Method has been designed to improve the performance of hydraulic actuator system. System Identification technique with the aid of System Identification Toolbox in MATLAB is used to estimate the mathematical model of the system. System Identification is chosen because it only requires a set of input and output data without the prior knowledge about the system, in order to obtain the system’s transfer function. Auto Regressive with exogeneous input (ARX) model was selected as system’s model structure and the best model among ARX orders was selected based on the analysed result of fitting percentage, loss function and Akaike’s Final Prediction Error. The obtained model was then used to develop the controller for hydraulic actuator system. The output performance was analysed and it has been shown that the output of controlled system successfully tracked the given input signal for both simulation and experimental modes. It has also been observed that Model Reference Adaptive Controller using Gradient Method demonstrates a better output performance compared to Self-tuning Controller using Generalized Minimum Variance Control Strategy in terms of having a minimum phase lagging and a better transient response in terms of rise time, settling time and steady state error

Robusno upravljanje elektrohidrauličkog servosustava primjenom metode povratnog koraka

Tema ovog diplomskog rada je robusno upravljanje elektrohidrauličkog servosustava primjenom metode povratnog koraka (eng. backstepping). Cilj ovog rada je dobivanje matematičkog modela koji opisuje dinamiku elektrohidrauličkog sustava upravljanog nelinearnim backstepping regulatorom. U radu je opisan elektrohidraulički sustav i njegove komponente te je izveden matematički model nelinearnog sustava i opisana je metoda povratnog koraka (eng. backstepping control) robusnog nelinearnog upravljanja kao i primjena na elektrohidrauličkom servosustavu. Simulacija je napravljena u programskog paketu Matlab (Simulink). Na ulaz simulacijskog modela dovode se pobudni signali različitog oblika i prati se odziv sustava. Referentni signal izveden je kao napon (-10 V do +10 V) koji predstavlja položaj klipa cilindra (0 ÷ 300 mm) a na temelju regulacijskog odstupanja regulator pratit referenti signal. Kada je dobiveno zadovoljavajuće ponašanje modela napravljen je eksperiment na laboratorijskom postavu elektrohidrauličkog sustava gdje je uspoređen klasični PID regulatora s regulatorom povratnog koraka

Internal Leakage Fault Detection and Tolerant Control of Single-Rod Hydraulic Actuators

The integration of internal leakage fault detection and tolerant control for single-rod hydraulic actuators is present in this paper. Fault detection is a potential technique to provide efficient condition monitoring and/or preventive maintenance, and fault tolerant control is a critical method to improve the safety and reliability of hydraulic servo systems. Based on quadratic Lyapunov functions, a performance-oriented fault detection method is proposed, which has a simple structure and is prone to implement in practice. The main feature is that, when a prescribed performance index is satisfied (even a slight fault has occurred), there is no fault alarmed; otherwise (i.e., a severe fault has occurred), the fault is detected and then a fault tolerant controller is activated. The proposed tolerant controller, which is based on the parameter adaptive methodology, is also prone to realize, and the learning mechanism is simple since only the internal leakage is considered in parameter adaptation and thus the persistent exciting (PE) condition is easily satisfied. After the activation of the fault tolerant controller, the control performance is gradually recovered. Simulation results on a hydraulic servo system with both abrupt and incipient internal leakage fault demonstrate the effectiveness of the proposed fault detection and tolerant control method

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