Adaptive Sliding Mode Control Based on Uncertainty and Disturbance Estimator

This paper presents an original adaptive sliding mode control strategy for a class of nonlinear systems on the basis of uncertainty and disturbance estimator. The nonlinear systems can be with parametric uncertainties as well as unmatched uncertainties and external disturbances. The novel adaptive sliding mode control has several advantages over traditional sliding mode control method. Firstly, discontinuous sign function does not exist in the proposed adaptive sliding mode controller, and it is not replaced by saturation function or similar approximation functions as well. Therefore, chattering is avoided in essence, and the chattering avoidance is not at the cost of reducing the robustness of the closed-loop systems. Secondly, the uncertainties do not need to satisfy matching condition and the bounds of uncertainties are not required to be unknown. Thirdly, it is proved that the closed-loop systems have robustness to parameter uncertainties as well as unmatched model uncertainties and external disturbances. The robust stability is analyzed from a second-order linear time invariant system to a nonlinear system gradually. Simulation on a pendulum system with motor dynamics verifies the effectiveness of the proposed method

Development of Novel Compound Controllers to Reduce Chattering of Sliding Mode Control

The robotics and dynamic systems constantly encountered with disturbances such as micro electro mechanical systems (MEMS) gyroscope under disturbances result in mechanical coupling terms between two axes, friction forces in exoskeleton robot joints, and unmodelled dynamics of robot manipulator. Sliding mode control (SMC) is a robust controller. The main drawback of the sliding mode controller is that it produces high-frequency control signals, which leads to chattering. The research objective is to reduce chattering, improve robustness, and increase trajectory tracking of SMC. In this research, we developed controllers for three different dynamic systems: (i) MEMS, (ii) an Exoskeleton type robot, and (iii) a 2 DOF robot manipulator. We proposed three sliding mode control methods such as robust sliding mode control (RSMC), new sliding mode control (NSMC), and fractional sliding mode control (FSMC). These controllers were applied on MEMS gyroscope, Exoskeleton robot, and robot manipulator. The performance of the three proposed sliding mode controllers was compared with conventional sliding mode control (CSMC). The simulation results verified that FSMC exhibits better performance in chattering reduction, faster convergence, finite-time convergence, robustness, and trajectory tracking compared to RSMC, CSMC, and NSFC. Also, the tracking performance of NSMC was compared with CSMC experimentally, which demonstrated better performance of the NSMC controller

Applied mechatronics: Designing a sliding mode controller for active suspension system

The suspension system is referred to as the set of springs, shock absorbers, and linkages that connect the car to the wheel system. The main purpose of the suspension system is to provide comfort for the passengers, which is created by reducing the effects of road bumpiness. It is worth noting that reducing the effects of such vibrations also diminishes the noise and undesirable sound as well as the effects of fatigue on mechanical parts of the vehicle. Due to the importance of the abovementioned issues, the objective of this article is to reduce such vibrations on the car by implementing an active control method on the suspension system. For this purpose, a conventional first-order sliding mode controller has been designed for stochastic control of the quarter-car model. It is noteworthy that this controller has a significant ability to overcome the stochastic effects, uncertainty, and deal with nonlinear factors. To design a controller, the governing dynamical equation of the quarter-car system has been presented by considering the nonlinear terms in the springs and shock absorber, as well as taking into account the uncertainty factors in the system and the actuator. The design process of the sliding mode controller has been presented and its stability has been investigated in terms of the Lyapunov stability. In the current research, road surface variations are considered as Gaussian white noise. The dynamical system behavior for controlled and uncontrolled situations has been simulated and the extracted results have been presented. Besides, the effects of existing uncertainty in the suspension system and actuator have been evaluated and controller robustness has been checked. Also, the obtained quantitative and qualitative compressions have been presented. Moreover, the effect of controller parameters on the basin of attraction set and its extensiveness has been assessed. The achieved results have indicated the good performance and significant robustness of the designed controller to stabilize the suspension system and mitigate the effects of road bumpiness in the presence of uncertainty and noise factors

Proceedings of the International Micro Air Vehicles Conference and Flight Competition 2017 (IMAV 2017)

The IMAV 2017 conference has been held at ISAE-SUPAERO, Toulouse, France from Sept. 18 to Sept. 21, 2017. More than 250 participants coming from 30 different countries worldwide have presented their latest research activities in the field of drones. 38 papers have been presented during the conference including various topics such as Aerodynamics, Aeroacoustics, Propulsion, Autopilots, Sensors, Communication systems, Mission planning techniques, Artificial Intelligence, Human-machine cooperation as applied to drones

Wind Turbine Reliability Improvement by Fault Tolerant Control

This thesis investigates wind turbine reliability improvement, utilizing model-based fault tolerant control, so that the wind turbine continues to operate satisfactorily with the same performance index in the presence of faults as in fault-free situations. Numerical simulations are conducted on the wind turbine bench mark model associated with the considered faults and comparison is made between the performance of the proposed controllers and industrial controllers illustrating the superiority of the proposed ones

Modeling control and simulation of a prototype wind turbine using S4WT

Wind energy is a renewable and sustainable kind of energy that is becoming increasingly important in the last decades. The technologies converting wind energy into usable forms of electricity are developed as alternatives to traditional power plants that rely on fossil fuels. The smallest wind turbines are used for applications such as battery charging or auxiliary power on boats; while large grid-connected wind turbines are designed to generate commercial electricity. This thesis focuses on modeling, control and simulation of a 500 KW prototype wind turbine that is being developed in the context of the MILRES (National Wind Energy Systems) Project in Turkey. Aerodynamic, mechanical, and electrical models are built in both Samcef for Wind Turbines (S4WT) and Matlab/Simulink environments. S4WT enables to choose each of the turbine components to be used in the composition of prototype wind turbine model, to design their characteristics and the way in which they are connected together and to analyze the behavior of the prototype model. The standard components (tower, bedplate, rotor, rotor shaft, gearbox, generator and coupling shaft) have been used compatible with the IEC 61400-1 in S4WT to perform the simulations. The dynamic equations of aerodynamic, mechanical and electrical models are also modeled in Matlab/Simulink environment. The main control purpose of the wind turbines is to maximize energy efficiency. However, the turbine must also be protected from excessive loads at different wind speeds. To achieve this goal, generated power curve should be close to the ideal power curve that depicts the optimum energy gathering from the wind depending on the wind speed. The prototype wind turbine is designed to have a nominal power of 500 KW at a nominal wind speed of around 11 m/s. Ideal power curve has two operating regions: Partial load operating region and full load operating region. Partial load operating region has wind speeds lower than the nominal wind speed and full load operating region has wind speeds above the nominal wind speed. The pitch and torque controllers are used to achieve an actual power curve that is very close to the ideal one. A pitch function and a standard PI controller with gain scheduling have been used to control the pitch angle of the blades to limit the power at the full load operating region in S4WT environment. In Matlab/Simulink environment, a simple Proportional (P) controller is used for the pitch controller. The generator torque which consists of an optimal mode gain method is employed in S4WT environment. A sliding mode controller (SMC) is utilized in Matlab/Simulink environment for controlling the torque. Torque controllers which are designed in both environments are used to control the power at both partial and full load operating regions. Kaimal turbulence model has been used to generate realistic wind profiles in TurbSim that can be integrated with S4WT. The performance analysis of 500 KW wind turbine prototype is done for both the partial load and full load operating regions under the power production scenario in S4WT environment. A similar analysis is also carried out in Matlab/Simulink environment using the models and controllers developed in this environment. The prototype turbine is tested under several other scenarios including start up, emergency stop, shut down and parked in S4WT. Simulation results both in S4WT and Matlab are quite successful