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Adaptive Control
Published in Jitendra R. Raol, Ramakalyan Ayyagari, Control Systems, 2020
Jitendra R. Raol, Ramakalyan Ayyagari
A sliding model control (SMC) provides robustness against parameter variations and disturbances, and it is a special class of the variable structure systems (VSSs). The main aspect of SMC is that in a (small) neighborhood of a specified switching manifold (usually some curved surface), the velocity vector of the controlled state trajectories always points toward this manifold. This motion is induced by disruptive/discontinuous control actions in the form of switching control operations. For an ideal sliding mode (SM), the system state should satisfy the dynamic equation that governs the sliding mode for all the time. This would require infinite switching operations to ensure the SM. Several interesting problems of SMC are: (i) chattering, (ii) the effects of unmodeled dynamics, (iii) handling of disturbances/uncertainties, (iv) adaptive learning, and (v) enhancing of robustness [14]. One important aim of the recent SMC research is to make it more intelligent, and this leads to the introduction of intelligent agents, via soft computing (SC) into SMC paradigms.
Soft Computing Methodologies in Sliding Mode Control
Published in Bogdan M. Wilamowski, J. David Irwin, Control and Mechatronics, 2018
Sliding mode control (SMC) is a special class of the variable structure systems (VSSs) [34], which has been studied extensively for over 50 years and widely used in practical applications due to its simplicity and robustness against parameter variations and disturbances [35,46]. The essence of SMC is that in a vicinity of a prescribed switching manifold, the velocity vector of the controlled state trajectories always points toward the switching manifold. Such motion is induced by imposing disruptive (discontinuous) control actions, commonly in the form of switching control strategies. An ideal sliding mode exists only when the system state satisfies the dynamic equation that governs the sliding mode for all time. This requires an infinite switching in general to ensure the sliding motion. For details about the fundamentals of SMC, readers are referred to Chapter 13 [27] of this handbook.
Methods in Motion Control
Published in Tarik Uzunović, Asif Šabanović, Motion Control of Functionally Related Systems, 2020
Tarik Uzunović, Asif Šabanović
For a few decades, sliding mode control (SMC) has attracted significant interest of researchers and application engineers, mostly due to its simple implementation and good performance. A comprehensive overview of the SMC application in motion control systems is given in [81]. The main feature of the systems with sliding modes is constraint of the system motion in a manifold. Such a motion can appear in systems where control switches between distinct values. Since a different system structure is associated with each of the control values, such systems are called variable structure systems (VSSs). The analysis and design of the systems with sliding modes are discussed in detail in books [14, 28, 70, 71]. A significant portion of the literature on variable structure systems with sliding modes is dedicated to application in electromechanical systems. For example, book [68] is entirely dedicated to that subject. The reader is advised to consider this book as a reference. SMC was very frequently applied for position tracking control of robotic manipulators. The main idea is to construct a manifold in such a way that motion on the manifold implies that the manipulator is tracking the reference position. The first set-point sliding mode controller for robotic manipulators was proposed by Young in 1978 [89]. The control strategy was designed and tested for a two-joint manipulator in a hybrid simulation. As a conclusion, the author stated that the variable structure approach is applicable to the manipulator controller design. This approach was after that often used in position tracking control (and of course in positioning control) for robotic manipulators; discussion and examples of these applications are given in [23, 53]. In addition to the position tracking control, the force control is also discussed in the literature, as an example of SMC application to robotic manipulators, and it is done for both constrained and unconstrained systems. The main idea is the same as for the position tracking, only the manifold description changes. Force control strategies for robotic manipulators with SMC application are discussed in [85, 60, 15, 83]. In the work [69], SMC-based design of the path tracking algorithm for a mobile robot is presented. The authors propose SMC to enforce that a mobile robot tracks a specified gradient. The sliding manifold is designed in such a way that motion on the manifold means that the robot’s velocity vector has the specified magnitude and the vector is directed as the specified gradient. A similar approach is given in [21], where SMC is utilized to track the gradient of an artificial potential field. There are many other applications of SMC to motion control systems, with marine vessel control [9], vehicle steering control [6], and control of under-actuated systems [57] being some of them.
Design and Validation of Fractional-Order Control Scheme for DC Servomotor via Internal Model Control Approach
Published in IETE Technical Review, 2019
The DC servomotor has been used as a classical control example for nearly half a century because it is a standard second-order system with stable characteristics (i.e. speed-torque characteristics are well suited with most mechanical loads) and has high industrial applicability (particularly in performance drives of rolling mills, machine tools, traction, robotics, etc.). Many control ideas have been developed and illustrated for this system, such as pulse width modulation and thyristor based control [1,2], variable structure system control [3,4], optimal control based on Pontryagin's minimum principle [5], H∞ control [6], minimum energy point-to-point motion planning control [7], adaptive control [8], neural network [9,10], Fuzzy PID [11], feedback linearization scheme [12], estimation of distribution scheme [13], disturbance observer scheme [14], model predictive control [15,16], model-free control [17], algebraic derivation estimation-based control [18], integral retarded algorithm [19], stability boundary locus [20] and reduced modeling [21] based PID tunings and many more.
Performance analysis of dynamic voltage restorer using modified sliding mode control
Published in International Journal of Electronics Letters, 2019
Neelam Kassarwani, Jyoti Ohri, Alka Singh
SMC based on variable structure system is the exceptional case of a hybrid dynamical system in which the system flows through the continuous state space and also moves through various distinct and discontinuous control modes. SMC enables to observe the system dynamics and stability of higher order non-linear system through first-order sliding surface around the switching line. This stamps SMC a variable structured, non-linear and stochastically featured control method based on state-feedback control law. SMC being variable structured control method-based method has earned the honour of robust control to get the desired response of the closed loop system.