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Sliding Mode Control Approaches for Robust Control of Quadruple Tank System
Published in Mangey Ram, Mathematics in Engineering Sciences, 2019
Dipesh Shah, Dhruv Patel, Axaykumar Mehta
With rapid advancement in control technology in recent years, sliding mode controller (SMC) has received much attention in process applications due to its robust properties and simple structure. SMC is a nonlinear control technique preferred for the systems where the performance depends on model uncertainties and external disturbances. Various researchers [14–19] have tried to design SMCs for controlling the liquid level of coupled and quadruple tank system in the presence of matched and unmatched disturbances. The sliding mode control involves the design of sliding surface and reaching law. Presently, constant-rate, power-rate, and exponential reaching laws are widely used in continuous-time domain to derive the sliding mode control, as they provide faster convergence in the presence of model uncertainties and disturbances.
Conventional and Intelligent Control
Published in Clarence W. de Silva, Intelligent Control, 2018
This sliding-mode controller satisfies Equation (8), but has drawbacks arising from the sgn(s) function. Specifically, very high switching frequencies can result when the control effort is significant. This is usually the case in the presence of large modeling errors and disturbances. High-frequency switching control can lead to the excitation of high-frequency modes in the plant. It can also lead to chattering problems. This problem can be reduced if the signum function in Equation (9) is replaced by a saturation function, with a boundary layer ±ϕ, as shown in Figure 6. In this manner, any switching that would have occurred within the boundary layer would be filtered out. Furthermore, the switching transitions would be much less severe. Clearly, the advantages of sliding mode control include robustness against factors such as nonlinearity, model uncertainties, disturbances, and parameter variations.
Power Converters
Published in Vadim Utkin, Jürgen Guldner, Jingxin Shi, Sliding Mode Control in Electro-Mechanical Systems, 2017
Vadim Utkin, Jürgen Guldner, Jingxin Shi
For circuits controlled by switching devices, in which the control variable can take only values from a discrete set, it is natural to consider sliding mode strategies to synthesize the switching policy, from both a technological and a theoretical point of view. In the past, the method of statespace averaging has been widely used to analyze DC/DC converters. In the state-space averaging method, the linear circuit models and the statespace equation are identified for each of the possible switch positions of the converter during the switching period. These state-space equations are then averaged over the switching period, leading to a low-frequency equivalent model of the converter. The low-frequency model thus obtained may be linearized to apply linear control theory to design feedback compensators. In essence, state-space averaging provides a method of low-frequency characterization of converters such that frequency domain design approaches may be applied. Sliding mode control theory belongs to the category of time domain techniques and can be used to characterize the system under both small signal and large signal conditions. Sliding mode control uses state feedback and sets up directly the desired closed-loop response in time domain or in terms of differential equations. The most important feature of the sliding mode approach is the low sensitivity to system parameter variations.
Novel resilient compensator design for FDI attack mitigation on AGC system
Published in International Journal of Modelling and Simulation, 2023
For smooth operation, it is important to not only detect an attack but also mitigate the effect of an attack on AGC. In other words, the attacked signal cannot be just ignored because all signals are essential in calculating the ACE in different system areas. One way of mitigation is to estimate the attacked signal and subtract it from the collected signals to mitigate the attack. This mitigation technique has been reported in [18] where Kalman filter is used for FDI-attack estimation. In Section 3.2.1, the said mitigation technique is applied using GESO for estimating the FDI attack. In Section 3.2.2, a novel technique utilizing a sliding mode compensator is proposed to recompense for FDI attacks in AGC systems regardless of the effect of AGC nonlinearities and disturbances. It is well known that sliding mode control is a powerful design technique when dealing with uncertain systems as it is insensitive to disturbances and parameter uncertainties.
Practical torque sensorless super-twisting control of manipulators based on a novel integral non-singular fast terminal sliding mode with fixed-time convergence
Published in Advanced Robotics, 2023
Mohammad Yazdani, Soheil Ganjefar
The reason for chattering in the sliding mode control is using the sign function in the switching part of the control law. In this research, a super twisting algorithm is used, which is one of the most powerful and well-known higher-order sliding mode algorithms. In higher-order sliding modes, the control discontinuity is limited in the higher-order derivatives, and the control signal given to the system is continuous. Due to the existence of a discontinuous function under the integral in the structure of the super-twisting algorithm, a correct selection of its gains must be made to obtain a chattering-free control signal. The switching part of control law, based on a super twisting algorithm, is considered as follows: where and so that to satisfy finite-time convergence condition of the super-twisting algorithm must be for .
Stability and stabilisation of switched time-varying delay systems: a multiple discontinuous Lyapunov function approach
Published in International Journal of Systems Science, 2020
Mohammad Mahdi Saberi, Iman Zamani
Since the 1950s, sliding mode control has proven to be an effective robust control scheme for nonlinear systems and imperfectly modelled systems. In the past decade, sliding mode control has been successfully applied to a variety of practical engineering systems such as robot manipulators, aircraft, spacecraft, underwater vehicles, electrical motors, power systems, and automotive engines (Azar & Zhu, 2015; Utkin et al., 2017). The main idea of sliding mode control is to utilise a discontinuous control to force the system state trajectories to some predefined sliding surfaces on which the system has desired properties such as stability, disturbance rejection capability, and tracking ability (Shtessel et al., 2014). Many significant results have been reported for this kind of control scheme. To express a few, in particular, sliding mode control has been investigated for uncertain systems (Ginoya et al., 2014), stochastic systems (Wu et al., 2017), Markovian jump systems (Li et al., 2016) and singular systems (Wang et al., 2018). There are some papers which have presented sliding mode control for the continuous-time switched system (Wu et al., 2011; Wu & Lam, 2008; Yin et al., 2017a), and discrete-time switched system (Su et al., 2017; Su et al., 2018), but switching signal with MDADT property, time-varying delay, and consisting unstable subsystems have not been fully investigated.