Implementation Of Sliding Mode Control Research Articles

FPGA Implementation of Sliding Mode Control and Proportional-Integral-Derivative Controllers for a DC–DC Buck Converter

DC–DC buck converters have been designed by incorporating different control stages to drive the switches. Among the most commonly used controllers, the sliding mode control (SMC) and proportional-integral-derivative (PID) controller have shown advantages in accomplishing fast slew rate, reducing settling time and mitigating overshoot. The proposed work introduces the implementation of both SMC and PID controllers by using the field-programmable gate array (FPGA) device. The FPGA is chosen to exploit its main advantage for fast verification and prototyping of the controllers. In this manner, a DC–DC buck converter is emulated on an FPGA by applying an explicit multi-step numerical method. The SMC controller is synthesized into the FPGA by using a signum function, and the PID is synthesized by applying the difference quotient method to approximate the derivative action, and the second-order Adams–Bashforth method to approximate the integral action. The FPGA synthesis of the converter and controllers is performed by designing digital blocks using computer arithmetic of 32 and 64 bits, in fixed-point format. The experimental results are shown on an oscilloscope by using a digital-to-analog converter to observe the voltage regulation generated by the SMC and PID controllers on the DC–DC buck converter.

Performance Comparison of a DC–DC Boost Converter With Conventional and Non-linear SMC Controller in Dual Loop Structure

Generally, the control system confronts various control techniques in the dual-loop control concept. Most of the studies deal with two different controllers in their loops, which increases the problem of designing two distinct procedures with lengthened calculations. In this article, different control techniques like conventional proportional integral (PI), proportional integral derivative (PID), and nonlinear sliding mode control (SMC) have been discussed, and the implementation of SMC in the Dual loop control of a DC–DC Boost converter is presented. The converter’s dynamic behavior is observed by driving their analytical equations. The effective controller for the proposed converter is ascertained by their comparative analysis. The proposed concept is validated with MATLAB/Simulink and a hardware prototype. The controller’s response is compared for various disturbances. Here, dual-loop SMC is put forward in both loops and its competence is confirmed with a minimal settling period of 0.005 sec and a percentage overshoot of 0.2% during the startup conditions, whereas during the line disturbances a minimum peak time of 0.0001 sec is achieved with a settling time of 0.025 sec. Additionally, a nil percentage overshoot and a settling time of 0.02 sec with a 0.001 sec peak time are attained during the load variations. Furthermore, a settling time of 0.01 sec and a percentage overshoot of 0.8% is reached during the reference voltage variations. From the numerical analysis, it is contemplated that an appropriate selection of SMC controllers in both the outer and inner loop results in optimal performance of the converter during the closed loop operation. Finally, the SMC + SMC controller exhibits superior controlling action compared to PI + PI and PID + PID controllers.

Cascade sliding mode control implementation in photovoltaic power supply for camping-car applications

A cascade proportional integral sliding mode control for a two-stage interleaved boost converter (2IBC) serving as a reliable supplementary power source for camping-car applications is reported. Unlike the active fault-tolerant control approaches used for interleaved boost converters, which require controller reconfiguration, the proposed control scheme is passive fault-tolerant and does not require reconfiguration in the event of a faulty stage. The 2IBC model is analyzed together with the most important parasitic parameters, then, the averaged state-space model is derived to implement the control scheme. The appropriate linear cascade control is determined by using the small-signal equivalent model and improving the robustness and dynamic performance, thereby a proportional integrator controller is replaced by a sliding mode controller. The prototype system uses a signal processor and a low-power solar panel. The control code is generated by a PSIM software and loaded to the via a code composer tool. The experimental results validate the control design and demonstrate the efficiency of the proposed control scheme. In addition, the proposed controller ensures the continuity of service in the event of a faulty stage by verifying the reliability of the power supply.

Real-Time Implementation of Sliding Mode Controller for Standalone Microgrid Systems for Voltage and Frequency Stabilization

Real-Time Implementation of Sliding Mode Controller for Standalone Microgrid Systems for Voltage and Frequency Stabilization

A Comparative Study: The Precision of CNC Machines Using a Sliding Mode Controller (SMC) and a Wi-Fi ESP32

Computerized numerical control (CNC) is one example of advances in automated machine technology. CNC can fulfil high precision and complex product specifications. Industrial CNC milling is still expensive regarding the hardware and software required to operate it. As a result, CNC milling machines are only used by large companies, with only a few mid-sized industries using them. It makes it impossible for medium enterprises to compete with large industries in terms of quality and output. This research aims to develop a CNC that uses an offline Wi-Fi controller based on ESP32 as an application that supports CNC machine work processes for use in small and medium enterprises. In an experiment, the precision of a CNC milling machine equipped with a sliding mode controller (SMC) controller was compared with that of a CNC machine equipped with an ESP-32 Wi-Fi controller. The CNC milling process with SMC control exceeds the tolerance limits in three dimensions based on the results of ten tests, namely length, width, and height or depth. Six values, two in each dimension of length, width, and height or depth, exceeded tolerance limits due to the CNC milling machine's ESP32 Wi-Fi control. Therefore, the CNC with SMC control is more accurate than the ESP32 Wi-Fi control because there are fewer failures with the former. This research has been carried out and provides input for the implementation of SMC, which can be considered in the CNC milling process.

Robust Control Design of a Human Heart Rate System for Cardiac Rehabilitation Exercise

Automatic, precise, and accurate heart rate control during treadmill exercise is an interesting topic among researchers. The human heart is a highly nonlinear system. Conventional control techniques are not sufficient and it is difficult to accurately model the human heart. Two different robust controllers were designed for this nonlinear system. Firstly, sliding mode control (SMC) was implemented; SMC is robust against parametric uncertainties and external disturbance but its robustness is not guaranteed during the reaching phase, especially in heart rate control, and implementation of SMC requires the linear parameters of the system (human heart rate model). In this research, the signal compression method (SCM) was used for approximately linearized modeling of the human heart rate. The extraction of the human heart rate model using SCM requires experiment and computation. Furthermore, it was observed in this research that SCM is not a precise method. Therefore, integral sliding mode control (ISMC) was designed and implemented to overcome these difficulties. By introducing an auxiliary sliding surface, the reaching phase and effect of the perturbation on an actual sliding surface were eliminated; furthermore, implementation of ISMC does not require the linear parameters of the system. Simulations were performed in MATLAB/Simulink and experiments were conducted in a hospital. Six clinical subjects participated in this experiment. Both forms of control logic were implemented during the desired heart rate tracking test. Results showed that the desired heart rate tracking of ISMC is better than that of SMC. The tracking error of ISMC is smaller than that of SMC. However, ISMC control output has chattering, which needs to be reduced.

Sliding Mode Control in Power Converters and Drives: A Review

Sliding mode control (SMC) has been studied since the 1950s and widely used in practical applications due to its insensitivity to matched disturbances. The aim of this paper is to present a review of SMC describing the key developments and examining the new trends and challenges for its application to power electronic systems. The fundamental theory of SMC is briefly reviewed and the key technical problems associated with the implementation of SMC to power converters and drives, such chattering phenomenon and variable switching frequency, are discussed and analyzed. The recent developments in SMC systems, future challenges and perspectives of SMC for power converters are discussed.

Barrier function-based adaptive nonsingular sliding mode control of disturbed nonlinear systems: A linear matrix inequality approach

In this study, a novel barrier function-based adaptive non-singular terminal sliding mode control methodology is suggested for robust stability of disturbed nonlinear systems. It is proved that the barrier function-based control method can force the state trajectories to converge to a region near origin in the finite time. A sufficient criterion is derived using Lyapunov stability theorem and linear matrix inequalities (LMIs) to satisfy the asymptotic stability of state trajectories. In addition, the design eliminates the necessity to have any knowledge about the upper bounds of external disturbances; a common requirement in sliding mode control implementation. The stability analysis verifies that the system states, under the designed control scheme, can asymptotically converge to a pre-defined region. Lastly, simulation studies are presented to confirm the efficacy and robustness of proposed approach.

Sliding mode control of a servo system in LabVIEW: Comparing different control methods

AbstractThe main contribution of this paper is to present the efficiency of LabVIEW in simulating and controlling a servo system with conventional methods (PI and PID control), as well as sliding mode control (SMC). The control of an actual system with LabVIEW and NI hardware provides an efficient implementation platform, using both LabVIEW’s graphical programming and the text-based m-file language MathScript RT. Both programming environments and the connection to NI hardware are relatively easy to use, therefore, ideal for education. The graphical “coding” can help novice users to see through their algorithms. However, the mathematical background of sliding mode control is difficult compared to conventional PID control; the SMC implementation for practical uses can be quite simple, as the presented example demonstrates. The first didactic step is a simulation with the Control Design and Simulation, as well as MathScript RT Modules. Then a myRIO Student Embedded Device is used to control a real servo system. LabVIEW code can be compiled to run on computers, (soft) real-time targets, and FPGAs (hard real-time targets), so students can easily and quickly step up to real industrial measurement and control problems without the need to learn new programming environments.

Fixed-frequency implementation of sliding-mode controllers for photovoltaic systems

Traditional implementation of sliding-mode controllers, based on hysteresis comparators, exhibits variable switching frequency. Such a condition makes it difficult to select the semiconductor devices, design the passive elements of dc/dc converters, and design the sensing filters usually adopted for removing the switching noise from currents and voltages. Those problems are always present in photovoltaic systems based on variable-frequency sliding-mode controllers. Therefore, this paper proposes an implementation methodology for sliding-mode controllers providing constant switching frequency, which is aimed for grid-connected photovoltaic applications. The proposed solution does not compromise the power production of the PV system, hence it provides the same PV power in comparison with the classical variable-frequency implementation. Finally, the performance and correct operation of the fixed-frequency implementation are demonstrated using both simulation and experimental results.

Robust Speed Control of PMSM Using Sliding Mode Control (SMC)—A Review

Permanent magnet synchronous motors (PMSMs) are known as highly efficient motors and are slowly replacing induction motors in diverse industries. PMSM systems are nonlinear and consist of time-varying parameters with high-order complex dynamics. High performance applications of PMSMs require their speed controllers to provide a fast response, precise tracking, small overshoot and strong disturbance rejection ability. Sliding mode control (SMC) is well known as a robust control method for systems with parameter variations and external disturbances. This paper investigates the current status of implementation of sliding mode control speed control of PMSMs. Our aim is to highlight various designs of sliding surface and composite controller designs with SMC implementation, which purpose is to improve controller’s robustness and/or to reduce SMC chattering. SMC enhancement using fractional order sliding surface design is elaborated and verified by simulation results presented. Remarkable features as well as disadvantages of previous works are summarized. Ideas on possible future works are also discussed, which emphasize on current gaps in this area of research.

Real-time implementation of SMC–PID for Magnetic Levitation System

Magnetic levitation is significant in almost all arenas of engineering. This principle is used to levitate objects such as a bullet train, flywheel, etc. This paper presents an experimental set-up of Magnetic Levitation System (MLS) in which a ball is levitated to a desired position and is sustained at a desired level for a stipulated time. The ball position is measured using an optoelectronic sensor and a controller is used to determine the time span of the ball at desired heights. To achieve this, a Sliding Mode Controller (SMC) is designed in such a way so as to regulate the current, which in turn controls the position through an electromagnet. Real-time observations of such ball positions have been recorded and compared to those of conventional PID (Proportional Integral Derivative) and robust SMC. Disturbance rejection, servo operation and set point tracking have also been tested and verified for the same. The outcome of such results processed through MATLAB proves that SMC’s performance is predominant over other controllers.

Implicit Euler Implementation of Twisting Controller and Super-Twisting Observer without Numerical Chattering: Precise Quasi-Static MEMS Mirrors Control

The quasi-static operations of MEMS mirror are very sensitive to undesired oscillations due to its very low damping. It has been shown that closed-loop control can be superior to reduce those oscillations than open-loop control in the literature. For the closed-loop control, the conventional way of implementing sliding mode control (SMC) algorithm is forward Euler method, which results in numerical chattering in the control input and output. This paper proposes an implicit Euler implementation scheme of super twisting observer and twisting control for a commercial MEMS mirror actuated by an electrostatic staggered vertical comb (SVC) drive structure. The famous super-twisting algorithm is used as an observer and twisting SMC is used as a controller. Both are discretized by an implicit Euler integration method, and their implementation algorithms are provided. Simulations verify that, as compared to traditional sliding mode control implementation, the proposed scheme reduces the chattering both in trajectory tracking output and control input in presence of model uncertainties and external disturbances. The comparison demonstrates the potential applications of the proposed scheme in industrial applications in terms of feasibility and performance.

Sliding-Mode Control of Distributed Maximum Power Point Tracking Converters Featuring Overvoltage Protection

In Photovoltaic (PV) systems with Distributed Maximum Power Point Tracking (DMPPT) architecture each panel is connected to a DC/DC converter, whose outputs are connected in series to feed a grid-connected inverter. The series-connection forces the output voltage of those converters to be proportional to the converter’ output power; therefore, under mismatched conditions, the output voltage of a highly-irradiated converter may exceed the rating (safe) value, causing an overvoltage condition that could damage the converter. This paper proposes a sliding-mode controller (SMC) acting on each converter to regulate both the input and output voltages, hence avoiding the overvoltage condition under partial shading. The proposed control strategy has two operation modes: maximum power point tracking (MPPT) and Protection. In MPPT mode the SMC imposes to the PV panel the voltage reference defined by an MPPT technique. The Protection mode is activated when the output voltage reaches the safety limit, and the SMC regulates the converter’ output voltage to avoid overvoltage condition. The SMC has a bilinear sliding surface designed to provide a soft transition between both MPPT and Protection modes. The SMC analysis, parameters design and implementation are presented in detail. Moreover, simulation and experimental results illustrate the performance and applicability of the proposed solution.

Fuzzy sliding-mode control with low pass filter to reduce chattering effect: an experimental validation on Quanser SRIP

Stabilization of a single rotary inverted pendulum (SRIP) system is a benchmark nonlinear control problem. Inherent instability of SRIP in upright position and the presence of modelling uncertainty pose a challenge for control engineers. Sliding-mode control (SMC) is the most widely accepted robust control technique. Various versions of SMCs to stabilize SRIP have been reported in literature. Advantages of SMC come at the cost of chattering of input, which inhibits its usage in many practical applications. Several works have been done to reduce the chattering in SMC. Application of fuzzy logic in SMC to reduce chattering has been analysed extensively in the literature. Even though implementation of fuzzy SMC (FSMC) in theory/simulations completely eliminates chattering, practical implementation of FSMC does not reduce chattering to zero. In this paper, a filtered FSMC is proposed, which filters the high frequency component in the system input. Experimental results of SMC, FSMC and a fuzzy sliding-mode controller with filter (FSMCF) are given in this paper. Results indicate that filtering the output of FSMCF reduces the chattering effect in the system without affecting the closed loop dynamics.

Adaptive fuzzy sliding mode control for redundant manipulators with varying payload

Purpose This paper aims to present an adaptive fuzzy sliding mode controller with nonlinear observer (AFSMCO) for the redundant robotic manipulator handling a varying payload to achieve a precise trajectory tracking in the task space. This approach could be applied to solve the problems caused by the dynamic effect of the varying payload to robotic system caused by model uncertainties. Design/methodology/approach First, a suitable observer using the recursive algorithm is presented for an accurate estimation of external disturbances caused by a variable payload. Second, the adaptive fuzzy logic is designed to approximate the parameters of the sliding mode controller combined with nonlinear observer (SMCO) to avoid chattering in real time. Moreover, Lyapunov theory is applied to guarantee the stability of the proposed closed-loop robotic system. Finally, the effectiveness of the proposed control approach and theoretical discussion are proved by simulation results on a seven-link robot and demonstrated by a humanoid robot platform. Findings The varying payload leads to large variations in the dynamics of the manipulator and the tracking error. To achieve high-precision position tracking, nonlinear observer was introduced to feed into the sliding mode control (SMC) which had improved the ability to resist the external disturbance. In addition, the chattering caused by the SMC was eliminated by recursively approximating the switching gain with the usage of adaptive fuzzy logic. Therefore, a distributed control strategy solves the problems of an SMC implementation in improving its tracking performance and eliminating the chattering of the system control. Originality/value The AFSMCO is proposed for the first time and used to control the redundant robotic manipulator that handles the varying payload. The proposed control algorithm possesses better robustness and higher precision for the trajectory tracking than classical SMC.

ROBUST VIBRATION CONTROL OF WIND-EXCITED HIGHRISE BUILDING STRUCTURES

A robust filtered sliding mode control (SMC) approach is presented for vibration control of wind-excited highrise building structures. Rather than using a Lyapunov-function based control design, an alternative way is provided to find the control force based on the equivalent control force principle to obtain the control force. A low pass filter is properly selected to remove the high-frequency components of the control force while retaining the structural stability. The performance of the proposed filtered SMC is evaluated by application to a wind-excited 76-story building benchmark problem equipped with an active tuned mass damper (ATMD) on the roof. Due to the elimination of high-frequency part of the control force, the structure, sensors, actuators, and dampers are all less excited, and consequently their response is reduced compared with the unfiltered SMC approach. In addition, the required control forces are reduced which means a reduction in the size of actuators, thus making their implementation more practical. It is shown the proposed method is more robust to structural stiffness uncertainties compared with the linear quadratic Gaussian (LQG) algorithm and another implementation of SMC.

Practical Realization of Scalar Optimization Function of Shielded Metal Arc Welding Process

Welders in large numbers are engaged in manual shielded metal arc welding (SMAW) process to make mechanical joints in metals. Inputs to the process have multiple origin and specified joint characteristics are wide. Welder and controller are two active elements involved in the process. Modern welding controllers have greatly simplified the role of welders in making good quality joints. However, in that process of technological evolution, essential aspects such as health hazards and welder friendliness have not been paid due attention. Process efficiency is also poor. The present article details, with detailed practical implementations, the extended role of power electronics controller with the help of selective use of sliding mode control (SMC) ideas for achieving conflict free multi-objective optimization program of the process. Traditional structure switching has been completely avoided for implementation of SMC.

Design and Implementation of Sliding Mode Controller using Coefficient Diagram Method for a nonlinear process

Design and Implementation of Sliding Mode Controller using Coefficient Diagram Method for a nonlinear process

Neural network-based adaptive sliding mode control for uncertain non-linear MIMO systems

The purpose of this paper is the design of neural network-based adaptive sliding mode controller (NASMC) for uncertain unknown MIMO non-linear systems. A special architecture adaptive neural network, with hyperbolic tangent activation functions, is used to emulate the equivalent and switching control terms of the classic sliding mode controller (SMC). The bounded motion of the system around the sliding surface and the stability of the global system, in the sense that all signals remain bounded, are guaranteed. Unlike other works, this is not a combination of neural networks and SMC approaches, but a new implementation of adaptive SMC using multiple neural networks approach, with special architecture. A two-link robot example and its simulation results are presented to illustrate the proposed approach.