Salim Hadj Saïd

High gain observer based on-line rotor and stator resistances estimation for IMs

One of the main challenging issues in induction motor drives is the lack of knowledge about the actual values of some critical parameters, such as rotor and stator resistances which are subject to large variations during operation. Such problem is difficult to resolve due to the strong interconnection between states and parameters in the nonlinear motor model, besides the unavailability of both rotor flux and load torque. In the spirit to accurately follow the on-line machine variables, this paper focuses on the simultaneous estimation of internal states and time varying parameters. Especially, a new identification scheme for rotor resistance and/or stator resistance is introduced. In the aim of decoupling the unknown electrical parameters, we adopt a mild change of coordinates that allows to easily design a two-stage of high gain observer. The simplicity of presented procedures and the efficiently for real time computation constitute both main features of the proposed approach. Moreover, possible exploitation of our algorithm in the fault detection issue is discussed through a simulation of an abrupt rotor short-circuit.

Model-based Predictive and Backstepping controllers for a state coupled four-tank system with bounded control inputs: A comparative study

Abstract This paper investigates the problem of global tracking control design for a state coupled four-tank liquid level system with bounded control inputs. For this MIMO system׳s dynamics, motivated by a desire to provide precise liquid level control, two radically different control approaches are presented and compared: the nonlinear generalized predictive control (NGPC) and the Backstepping control. First, an analytical solution of the NGPC is developed based on the nominal model. Then, a nonlinear Backstepping controller is designed in order to ensure globally asymptotical stabilization for this nonlinear system. To ensure a suitable basis for their comparison, the two different control methods are designed and verified with the same test setup under the control input saturation imposed by the system’s actuators. To highlight the efficiency and applicability of the proposed control schemes, simulation as well as experimental results are provided and discussed.

Observer-Based Backstepping Controller for a State-Coupled Two-Tank System

ABSTRACT This paper addresses the nonlinear control design problem for a state-coupled two-tank liquid level system. For this systems dynamics, motivated by a desire to provide precise and economic liquid level control, a new output feedback control scheme is developed. In the proposed approach, a robust controller based on backstepping strategy is designed in order to ensure globally asymptotically stabilisation for a particular class of second-order nonlinear systems. Moreover, a model-based backstepping controller combined with a high gain observer is designed for the two-tank, liquid level system. Only one sensor is available to measure the liquid level in the bottom tank and the other processs state is assumed unavailable. The observer converges in a finite time and leads to good estimate of the liquid level in the top tank as well as a good track of the liquid level in the bottom tank with the reference trajectory. To highlight the efficiency and applicability of the proposed control scheme, a comparison with proportional plus integral plus derivative controller as well as a simulation and experimental results are provided.

A set of observers design to a quadruple tank process

In this paper, quadruple tank process is exploited to study different type of nonlinear observer. Indeed, from the physical model of the process, and with liquid levels measurement in the bottom of two tanks, we search to reconstruct liquid levels of the two upper ones. Three approaches are analyzed namely extended Kalman filter (EKF), high gain observer (HGO) and high gain-extended Kalman filter (HG-EKF). The behavior of estimated state, in the presence of disturbance, are provided to appropriate the feature of every observer.

Predictive and Backstepping Control of Double Tank Process: A Comparative Study

ABSTRACT This paper addresses the nonlinear control design problem for a state-coupled two-tank liquid-level system. For this systems dynamics, motivated by a desire to provide precise liquid-level control, two radically different control approaches are presented and compared: the model predictive control and the backstepping control. In the first proposed approach, a model-based predictive controller is designed for the two-tank liquid-level system that ensures exponentially stabilization for a particular class of second-order nonlinear system. Moreover, a robust controller based on a backstepping strategy is designed in order to ensure globally asymptotically stabilization for another particular class of second-order nonlinear systems. To ensure a suitable basis for their comparison, two different control methods are designed and verified with the same test setup. To highlight the efficiency and applicability of the proposed control schemes, theoretical comparisons as well as experimental results are provided and discussed.

Output feedback predictive control for hydrographic process

This paper introduces a new output feedback control scheme, which combine nonlinear generalized predictive control (NGPC) with a high gain observer (HGO). We consider the input affine nonlinear MIMO class of systems, that include the model of our hydrographic process. Indeed, from the liquid levels measurements in both bottoms tanks, we reconstruct the levels of both upper ones, and we use them in the state feedback control loop. The predictive control law synthesized is an explicit continuous solution of optimization problem, it arise from receding horizon index minimization. As it is known, to deal with the separation principle requirement, we need to lead the system in the new state coordinate and to impose control constraints. This last can inherently taking into account by the predictive controller, when we reformulate control law through the on-line solution of quadratic programming (QP) problem.

Generalized predictive control for a coupled four tank MIMO system using a continuous-discrete time observer

This paper deals with the problem of the observer based control design for a coupled four-tank liquid level system. For this MIMO systems dynamics, motivated by a desire to provide precise and sensorless liquid level control, a nonlinear predictive controller based on a continuous-discrete observer is presented. First, an analytical solution from the model predictive control (MPC) technique is developed for a particular class of nonlinear MIMO systems and its corresponding exponential stability is proven. Then, a high gain observer that runs in continuous-time with an output error correction time that is updated in a mixed continuous-discrete fashion is designed in order to estimate the liquid levels in the two upper tanks. The effectiveness of the designed control schemes are validated by two tests; The first one is maintaining a constant level in the first bottom tank while making the level in the second bottom tank to follow a sinusoidal reference signal. The second test is more difficult and it is made using two trapezoidal reference signals in order to see the decoupling performance of the systems outputs. Simulation and experimental results validate the objective of the paper.

FPGA implementation of high gain observer for induction machine using Simulink HDL coder

This paper focus on the implementation in Field Programmable Gate Arrays (FPGA) of high gain observer (HGO) applied to induction machine. We use the evaluated board Spartant3E with Xc3s500 FPGA for this purpose. The three phases supply and its corresponding pulse width modulation (PWM) are softly generated. Then, with only the both stator currents measurements, an estimation of rotor flux, mechanical speed achieved. Due to the limitation resources of Xc3s500, we have choice a reduced size format of the internals variables as well as the software algorithm can give an acceptable signals with moderate ripples. We have highlight different ways to obtain the implementation of complex functions inherent of the HGO. With the flexibility of our method, other algorithm related to observation or advanced control law can easily embedded into the FPGA.

Backstepping control for a quadruple tank process based on adaptive observer

This paper is about control of hydrographic process. A new output control scheme is developed, which combine a nonlinear backstepping control with an adaptive high gain observer. We consider the nonlinear MIMO class of systems, which include the model of our hydrographic process. The main objective is to automate the control of pumps for a successful and safe manner in order to keeps the levels of the bottoms tanks to specific references. Only two sensors are available to measure the liquid level in both bottom tanks and the other processs states and some parameters are assumed unavailable. An adaptive high gain observer is used as solution for estimating conjointly liquid levels for high tanks and system parameters. Thereafter, the estimate variables are incorporated in the Backstepping controller in order to generate the control signal for both motopump that ensuring the tracking objective.

Observer-based Backstepping liquid level controller for a quadruple tank process

This paper deals with the design of a nonlinear sensorless controller for a quadruple tank process. So to provide an economic liquid level control, a novel output feedback control scheme is developed. In the proposed approach, a model-based Backstepping controller combined with a second order sliding mode observer is designed for the four-tank liquid levels system. In fact, only two sensors are used to measure the liquid levels in the two bottom tanks and the other processs states are assumed unavailable. The nonlinear Backstepping controller is synthesized in order to ensure globally asymptotical stabilization for this nonlinear system. The super twisting observer converges in a finite time. It leads to a good estimation of the liquid levels in the two top tanks. A good track of the liquid level in the bottom tank with the reference trajectory is achieved by the proposed controller. To highlight the applicability and the efficiency of the proposed control scheme, simulation results are provided and discussed.