A practical approach to adaptive sliding mode control

This paper is concerned with the development of a practical approach to the design of adaptive sliding mode controllers. The objective is to define an adaptive control law that presents some desired advantages such as non overestimation of the disturbance input, cancellation of the chattering phenomenon, zero overshooting response, avoid control saturation and simplicity of algorithm tuning. In this practical approach a solution is provided that uses both, adaptive sliding surfaces and adaptive control gains so the proposed controller is able to manage input disturbances with bounded derivatives.Agencia Estatal de Investigación | Ref. DPI2017-84259-C2-2-RMinisterio de Economía y Competitividad | Ref. PTQ-14-07366Ministerio de Economía y Competitividad | Ref. DPI2016-79278-C2-2-

Design And Analysis Of Super Twisting Sliding Mode Control For Machine Tools

High demands of precision on machine tools are hardly cope by using existing classic control algorithms. This paper focuses on the design, analysis and validation of a super twisting sliding mode controller on a single axis direct drive positioning system for improved tracking performances. The second order positioning system parameters were determined using input and output of measured data. Effects of two gain parameters in control algorithm on the quality of the control input and tracking error were analysed experimentally. The gain parameters were selected based on magnitude reduction in chattering during practical application. The performance of tuned super twisting sliding mode controller was compared with a traditional sliding mode controller using sigmoidlike function. Results showed that super twisting sliding mode controller reduced the chattering effect and improved the performance of system in terms of tracking error by 16.5%

Second Order Sliding Mode Control For Direct Drive Positioning System

Second order sliding mode control is known for the ability to suppress chattering effect, often being associated with the implementation of a traditional sliding mode controller. The purpose of this paper is to demonstrate and compare the ability of super twisting sliding mode control to suppress chattering as well as to improve tracking performances against the traditional sliding mode controller. Both controllers were designed, numerically analysed and experimentally validated on a second order single-input single output system direct drive single axis positioning table. A continuous Kalman-Bucy filter was applied to estimate the velocity signal to further improve the overall tracking performance. Results showed that super twisting sliding mode controller was able to successfully suppress chattering effect by smoothening the control input through integration action to form a continuous function, thus dampening the effect of high frequency switching. The effectiveness of this control algorithm would promote its application in real-time application as it provides better control performance as compared to the standard sliding mode controlle

Backstepping integral sliding mode control of an electromechanical system

The aim of this paper is to design a backstepping integral sliding mode controller (BISMC) for speed control of an electromechanical system under uncertainties and disturbances. An integral dynamic is included in traditional sliding surface to improve chattering and steadystate error in tracking a reference signal when parametric uncertainties and disturbances exist. Design and stability of the closed-loop system is realized by Lyapunov criterion in a step by step procedure. Experimental results of the proposed BISMC are compared with those of the traditional sliding mode controller (SMC). The proposed BISMC achieves reasonable tracking performance and exhibits more robust performance concerning parametric uncertainties and disturbances than the traditional SMC

Cascade Control of PM DC Drives Via Second-Order Sliding-Mode Technique

Abstract-This paper presents a novel scheme for the speed/ position control of permanent-magnet (PM) dc motor drives. A cascade-control scheme, based on multiple instances of a secondorder sliding-mode-control (2-SMC) algorithm, is suggested, which provides accurate tracking performance under large uncertainty about the motor and load parameters. The overall control scheme is composed of three main blocks: 1) a 2-SMC-based velocity observer which uses only position measurements; 2) a 2-SMC-based velocity control loop that provides a reference command current; and 3) a 2-SMC-based current control loop generating the reference voltage. The proposed scheme has been implemented and tested experimentally on a commercial PM dc motor drive. The experimental results confirm the precise and robust performance and the ease of tuning and implementation, featured by the proposed scheme. Index Terms-Cascade control, dc motor drives, second-order sliding-mode (2-SM) control (2-SMC), SM differentiators

Finite-Time Second-Order Sliding Mode Controllers for Spacecraft Attitude Tracking

The attitude tracking control problem of a spacecraft nonlinear system with external disturbances and inertia uncertainties is studied. Two robust attitude tracking controllers based on finite-time second-order sliding mode control schemes are proposed to solve this problem. For the first controller, smooth super twisting control is applied to quaternion-based spacecraft-attitude-tracking maneuvers. The second controller is developed by adding linear correction terms to the first super twisting control algorithm in order to improve the dynamic performance of the closed-loop system. Both controllers are continuous and, therefore, chattering free. The concepts of a strong Lyapunov function are employed to ensure a finite-time convergence property of the proposed controllers. Theoretical analysis shows that the resulting control laws have strong robustness and disturbance attenuation ability. Numerical simulations are also given to demonstrate the performance of the proposed control laws

Retrofit Control to Prevent ASD Nuisance Tripping Due to Power Quality Problems

Since the onset of automation, industry has relied on adjustable speed drives to accurately control the speed of motors. Recent advances have increased the number of adjustable speed drives hitting the market. The proper operation of the speed drives requires electrical supply with relatively high power quality which is not the case in most industrial facilities. Power quality problems such as harmonic, sag, swell, flicker, and unbalance can trip the speed drive with a wrong message, which is referred as a premature tripping. Although the power quality problems can be mitigated by using custom power devices, they are bulky and costly. Moreover, they themselves might adversely affect the operation of the adjustable speed drive. A comprehensive study done in this thesis presents the overlooked effect of the custom power devices on the speed drive stability. It is found that the speed drive system might trip due to its interaction with custom power devices. Obviously, it is vital to increase ASD immunity to premature tripping because of poor power quality or custom power. This thesis offers fast, efficient and robust algorithms to achieve this immunity by retrofitting the ASD control unit and integrating the power conditioning function with the adjustable speed drive. Therefore, the power quality problem is mitigated and the drive system performance is significantly enhamced. Such integration requires the modification of the control unit by considering various elements such as envelope tracking, phase-locked loop, symmetrical component extraction, and the controller. Simple but robust and fast algorithms are proposed for such elements based on a newly developed energy operator algorithm. The developed energy operator and the developed algorithms overcome the drawbacks of the existing algorithms

Second-Order Sliding-Mode Control of DC Drives

One of the most recent topics in variable-structure systems theory is represented by the second-order sliding-mode control (2-SMC) methodology. This approach guarantees the same robustness and dynamic performance of traditional first-order SMC algorithms, and, at the same time, attenuates the chattering phenomenon, which is the main drawback in the actual implementation of this technique. In the present paper, a recently-proposed 2-SMC algorithm is used to synthesize a robust dc-drive control system which does not require current feedback and demands only rough information about the actual motor parameters. Stability and performance are analyzed, and an experimental comparison with a proportional–integral-based control scheme is reported